Optimal reconstruction interval in dual source CT coronary angiography: a single-center experience in 285 patients

PURPOSE

We aimed to evaluate the visibility of coronary arteries and bypass-grafts in patients who underwent dual source computed tomography (DSCT) angiography without heart rate (HR) control and to determine optimal intervals for image reconstruction.

MATERIALS AND METHODS

A total of 285 consecutive cases who underwent coronary (n=255) and bypass-graft (n=30) DSCT angiography at our institution were identified retrospectively. Patients with atrial fibrillation were excluded. Ten datasets in 10% increments were reconstructed in all patients. On each dataset, the visibility of coronary arteries was evaluated using the 15-segment American Heart Association classification by two radiologists in consensus.

RESULTS

Mean HR was 76±16.3 bpm, (range, 46–127 bpm). All coronary segments could be visualized in 277 patients (97.19%). On a segment-basis, 4265 of 4275 (99.77%) coronary artery segments were visible. All segments of 56 bypass-grafts in 30 patients were visible (100%). Total mean segment visibility scores of all coronary arteries were highest at 70%, 40%, and 30% intervals for all HRs. The optimal reconstruction intervals to visualize the segments of all three coronary arteries in descending order were 70%, 60%, 80%, and 30% intervals in patients with a mean HR <70 bpm; 40%, 70%, and 30% intervals in patients with a mean HR 70–100 bpm; and 40%, 50%, and 30% in patients with a mean HR >100 bpm.

CONCLUSION

Without beta-blocker administration, DSCT coronary angiography offers excellent visibility of vascular segments using both end-systolic and mid-late diastolic reconstructions at HRs up to 100 bpm, and only end-systolic reconstructions at HRs over 100 bpm.Improvements in computed tomography (CT) scanning technology throughout the last decade have resulted in widespread acceptance of contrast-enhanced multidetector CT (MDCT) coronary angiography as a reliable modality for noninvasive evaluation of the coronary arteries (1). Having a high negative predictive value, MDCT coronary angiography is considered particularly beneficial in patients with low to intermediate pretest probability for coronary artery disease (CAD) by reliably excluding coronary artery stenosis and therefore, preventing unnecessary invasive angiography (2, 3).Small dimensions and continuous rapid motions of coronary arteries make their visualization by CT challenging. Thus, excellent spatial and temporal resolution is required for adequate imaging of coronary arteries. Initial reports using a 4-detector row MDCT were promising in selected patients with low heart rates (HRs) (4–6); however, image quality was not sufficient for assessment in up to 29% of the coronary segments. With the introduction of 16- and 64-row MDCT, major improvements of image quality were achieved, with adequate visualization of up to 97% of coronary segments (7–9). Since, image quality deteriorates with increasing HRs even with 64-slice MDCT scanners (10, 11), it has been common in clinical practice to use HR-modulating beta-blockers to achieve better diagnostic quality. In 2005, dual source CT (DSCT) system equipped with two sets of X-ray tubes and corresponding detectors mounted onto the gantry with an angular offset of 90° was introduced (12). Using half-scan reconstruction algorithms, this system provides high temporal resolution (83 milliseconds [ms]) that corresponds to a quarter gantry rotation time. Preliminary studies without use of beta-blocker premedication have shown that DSCT coronary angiography provides good image quality of coronary arteries even at a relatively high HR (13, 14). Subsequent studies with relatively small patient populations confirmed these findings with diagnostic image quality in 97.8% of coronary artery segments (15, 16).Achievement of good image quality with DSCT coronary angiography is highly dependent upon selecting the optimal reconstruction interval for evaluation. Previous publications indicate a relationship between optimal reconstruction window and HR with mid- to end-diastolic reconstructions providing better image quality at low HRs, whereas at faster HRs, end-systolic reconstructions will often provide the dataset with the least motion artifact (17–19). However, some of these prior studies were based on relatively small patient samples, and in some, the entire R-R interval was not evaluated. Detection of optimal reconstruction interval is also important for the purpose of radiation dose reduction. Since DSCT scanners are equipped with electrocardiogram (ECG)-based tube current modulation, the width and timing of the ECG pulsing window, during which the full tube current is given, can be manually selected by the operator with the tube current outside the pulsing window decreased to 20% or 4% of the nominal tube current and thus, significantly reducing the radiation dose up to 40% (20).We aimed to evaluate the visibility of coronary arteries and bypass-grafts in patients who underwent DSCT angiography without HR control and to determine optimal intervals for image reconstruction.     

Impact of biplane versus single-plane imaging on radiation dose,contrast load and procedural time in coronary angioplasty

Coronary angioplasties can be performed with either single-plane or biplane imaging techniques. The aim of this study was to determine whether biplane imaging, in comparison to single-plane imaging, reduces radiation dose and contrast load and shortens procedural time during (i) primary and elective coronary angioplasty procedures, (ii) angioplasty to the main vascular territories and (iii) procedures performed by operators with various levels of experience. This prospective observational study included a total of 504 primary and elective single-vessel coronary angioplasty procedures utilising either biplane or single-plane imaging. Radiographic and clinical parameters were collected from clinical reports and examination protocols. Radiation dose was measured by a dose–area–product (DAP) meter intrinsic to the angiography system. Our results showed that biplane imaging delivered a significantly greater radiation dose (181.4±121.0 Gycm²) than single-plane imaging (133.6±92.8 Gycm², p<0.0001). The difference was independent of case type (primary or elective) (p = 0.862), vascular territory (p = 0.519) and operator experience (p = 0.903). No significant difference was found in contrast load between biplane (166.8±62.9 ml) and single-plane imaging (176.8±66.0 ml) (p = 0.302). This non-significant difference was independent of case type (p = 0.551), vascular territory (p = 0.308) and operator experience (p = 0.304). Procedures performed with biplane imaging were significantly longer (55.3±27.8 min) than those with single-plane (48.9±24.2 min, p = 0.010) and, similarly, were not dependent on case type (p = 0.226), vascular territory (p = 0.642) or operator experience (p = 0.094). Biplane imaging resulted in a greater radiation dose and a longer procedural time and delivered a non-significant reduction in contrast load than single-plane imaging. These findings did not support the commonly perceived advantages of using biplane imaging in single-vessel coronary interventional procedures.The use of biplane imaging during diagnostic coronary angiography and coronary interventions has been reported to reduce the total contrast load to the patient compared with single-plane imaging [1–8]. Additionally, acquiring two simultaneous images from two orthogonal planes has been reported to be more efficient than single-plane imaging [2, 8–11]. However, there are conflicting reports as to whether the radiation dose to the patient differs between biplane and single-plane imaging during coronary studies [3, 10, 11].Biplane imaging allows two cineangiography runs to be recorded simultaneously with a single injection of contrast. With single-plane imaging, however, the same information can be acquired only by carrying out the two cineangiography runs serially with two separate injections of contrast [1, 2, 8, 10]. Biplane imaging enables the operator to visualise the target lesion in orthogonal planes simultaneously and was presumed to be more efficient than single-plane imaging, particularly in difficult procedures [1, 4, 9, 12]. Accordingly, examinations would become faster, use of fluoroscopy would be reduced, fewer cineangiography runs would be required and the average radiation dose to the patient would be comparatively lower than in the case of procedures performed with single-plane imaging. The contrast load with biplane imaging was also expected to be significantly reduced [3, 4, 11].These perceived advantages of biplane imaging have led to recommendations for its use in paediatric and adult cardiac catheter laboratories [1, 4, 5, 10, 12, 13]. A previous study comparing biplane and single-plane imaging in 1156 diagnostic coronary angiography procedures found a small, but notable, reduction in contrast load accompanied by significantly longer table times and screening times with biplane imaging, although radiation dose was not examined [14].Contrast-induced nephropathy (CIN) is a complication associated with prolonged hospitalisation and development of end-stage renal failure [15]. Patients with pre-existing renal disease, diabetes, congestive heart failure or older age are at the greatest risk in developing CIN [16–18]. These high-risk patients have a calculated incidence of CIN ranging from 10% to 30% [4, 18–20]. Pre-hydration is the primary intervention for preventing contrast nephropathy [18], but is not possible in the setting of emergency (primary) angioplasty procedures. The total contrast load during interventional procedures has been established as an independent predictor of CIN and could be effectively controlled by the operator during primary angioplasty cases [18, 21, 22]. Biplane imaging is commonly employed to minimise the contrast load, especially in patients with renal impairment and those who require primary coronary angioplasty procedures [1, 6, 7, 18, 23].Numerous studies have found that the radiation dose varies significantly according to tube angulations, particularly in the combination of steep left anterior oblique (LAO) with cranial or caudal angulations [24–27]. However, there are no published data on whether the radiation dose with biplane or single-plane imaging during coronary angioplasty differs between the three vascular territories: right coronary artery (RCA), left anterior descending (LAD) and left circumflex/intermediate (LCX). Furthermore, interventional cardiac procedures are operator dependent [28–30]. Hence, it was postulated that senior cardiologists would be more familiar with biplane equipment and thereby more able to reduce radiation dose, contrast load and procedural time than less experienced operators. To our knowledge, no studies have been published that compare the impact of biplane and single-plane imaging in coronary angioplasty procedures.The aims of this study were to determine whether biplane imaging reduces both contrast load and radiation dosage and shortens procedural time in patients undergoing primary or elective coronary angioplasty compared with single-plane imaging. We also investigated if there was a significant difference in radiation dose, contrast load and procedural time between biplane and single-plane imaging during coronary angioplasty in the three main vascular territories (RCA, LAD and LCX) and in procedures performed by operators with various levels of experience.     

Optimisation of coronary angiography exposures requires a multifactorial approach and careful procedural definition

Objective:

This study investigates the factors associated with higher doses for both single-plane and biplane procedures and establishes centre-specific 75th percentile levels.

Methods:

602 patients undergoing coronary angiography in a large hospital at Sydney were recruited to the study, and causal agents for high radiation doses were investigated: gender, procedural complexity, severity of coronary artery disease, presence of coronary bypass grafts, entry approach (radial or femoral), level of operator experience; and a single-plane or a biplane imaging system was employed.

Results:

The 75th percentile levels were calculated. The results demonstrated that, for both systems, higher exposures were associated with patients who were male (p<0.001), had coronary vessel disease (p<0.001) and had a history of coronary bypass grafts (p<0.001). In addition, for biplane systems, procedural complexity (p<0.001), types of entry approach (p<0.001) and levels of operator experience (p<0.001) significantly impacted upon the dose. Biplane examinations recorded higher doses than single-plane procedures (p<0.001) and the inclusion of left-sided ventriculography contributed to the overall dose by up to 10%.

Conclusion:

The 75th percentile levels in this study represent the tentative reference levels and are 48.9, 44.2 and 56 Gy cm² for all exposures, single-plane- and biplane-specific exposures, respectively, and compare favourably with the diagnostic reference level values established elsewhere internationally, with only the UK and Irish data being lower.

Advances in knowledge:

Specific agents have been identified for dose-reducing strategies and the importance of operator training is highlighted. The assumption that biplane procedures may reduce the patient dose should be treated with caution.Diagnostic coronary angiography is regarded as an essential imaging and therapeutic tool, given the high incidence of cardiovascular disease in Australia, with 18% of Australians having chronic cardiovascular disease [1,2]. It is the most common invasive cardiac procedure and is used for both the initial diagnosis of coronary artery disease (CAD) and the follow-up examinations of patients after coronary interventional procedures, coronary bypass surgery or cardiac transplantation [3,4]. It is a standardised procedure that involves several cine-fluorographic series of the right and left coronary artery systems, with or without a left ventriculogram [5].Recently, the rapid increase in the frequency of diagnostic coronary angiography procedures has prompted radiation protection concerns [6], and studies have been performed to determine patient radiation doses in a number of countries [1,3,5,7]. The radiation dose of diagnostic coronary angiography is often presented in the form of a diagnostic reference level (DRL) [8], which is established at the 75th percentile dose–area product (DAP) value of the distributions of doses observed for a particular examination [9]. The main purpose of DRLs is to facilitate the optimisation of the radiation dose for a particular type of examination by identifying practices with unnecessarily high patient doses [8] and serving as a benchmark for the comparison of radiation dose among countries [10].Diagnostic coronary angiography can be performed using single-plane and biplane imaging systems. Biplane diagnostic coronary angiography enables two cine-angiography runs to be recorded simultaneously from two orthogonal planes during a single injection of contrast medium [11]. Single-plane diagnostic coronary angiography views the individual in one plane (with one X-ray tube) and acquires patient depth information by altering the tube position between X-ray exposures [11].In terms of clinical usage, biplane diagnostic coronary angiography has been reported to be more efficient than single-plane diagnostic coronary angiography [11]. Biplane imaging should be faster, employ reduced fluoroscopy time, require fewer cine-angiography runs and therefore involve lower average radiation dose to the patient than that of single-plane imaging, prompting recommendations for its use in paediatric examinations [11]. Despite these advantages, other researchers have suggested that biplane diagnostic coronary angiography is complicated and requires longer set-ups that can result in increased radiation exposure to both the operator and the patients [7,12–14].The aim of this study is to address the current biplane imaging debate by examining radiation doses in a large metropolitan teaching hospital in Sydney, NSW, Australia. It will also explore the impact that a number of patients and procedural factors have on dose, such as gender, procedural complexity, severity of CAD, presence of coronary artery bypass grafts, types of entry approach and levels of operator experience. The baseline radiation dose for diagnostic coronary angiography will be provided and compared with published DRLs.     

Dose and image quality comparison between prospectively gated axial and retrospectively gated helical coronary CT angiography

Objective

Our aim was to compare image quality, coronary segment assessability and radiation dose in prospectively gated axial (PGA) coronary CT angiography (CTA) and conventional retrospectively gated helical (RGH) coronary CTA.

Methods

Institutional review committee approval and informed consent were obtained. RGH CTA was performed in 41 consecutive patients (33 males, 8 females; mean age 52.6 years), then the PGA CTA technique was evaluated in 41 additional patients (24 males, 17 females; mean age 57.3 years) all with a pre-scan heart rate of ≤70 beats per minute (bpm). Two radiologists, blinded to clinical information, independently scored subjective image quality on a five-point ordinal scale.

Results

The mean effective dose in the PGA group was 4.7±0.9 mSv, representing a 69% dose reduction compared with the RGH CTA group (15.1±1.9 mSv, p<0.001). The mean segmental image quality score was significantly higher in the PGA group (3.4 vs 3.2) than in the RGH CTA group (p<0.005). The percentage of assessable segments was 98.1% in the PGA group and 97.3% in the RGH group (p = 0.610).

Conclusion

PGA CTA offers a significant reduction in radiation dose compared with RGH CTA, with comparable image quality for patients with heart rates below 70 bpm.Rapid advances in multidetector CT (MDCT) technology have enabled non-invasive coronary angiography with high diagnostic accuracy [1–4]. However, the potential radiation risks associated with standard retrospectively gated helical (RGH) techniques for MDCT-based coronary CT angiography (CTA) have become a concern [5, 6]. Reported radiation doses from coronary CTA have ranged from 11 to 27 mSv [1, 7–10]: nearly 2–4 times the radiation dose attributed to typical invasive diagnostic angiography [11, 12]. Consequently, reducing cardiac CT doses to levels as low as reasonably achievable has become a major issue. A new prospectively gated axial (PGA) acquisition protocol has recently been introduced [13] to reduce the radiation dose by scanning only the mid-diastolic phase [8–10] of the cardiac cycle. The acquisition is based on a prospective electrocardiogram (ECG)-triggered sequential axial acquisition mode in opposition to the standard retrospectively gated continuous helical acquisition. Our aim was to compare image quality and radiation dose of PGA-based coronary CTA with the standard helical mode on a 64-channel CT.     

Embolisation of the right gastric artery in patients undergoing hepatic arterial infusion chemotherapy using two possible approach routes

We used a retrospective non-randomised study to investigate the clinical effect of selective embolisation of the right gastric artery before hepatic arterial infusion chemotherapy (HAIC) using a port-catheter system. We evaluated whether the hepatic artery or the left gastric artery is the better approach for selecting the right gastric artery. A total of 367 patients (244 men and 123 women; mean age, 64.1 years) with unresectable advanced liver cancer underwent percutaneous implantation of a port-catheter system. In 294 of these patients, right gastric arterial embolisation with microcoils was attempted before placement of the port-catheter system to prevent gastric mucosal lesions. Approach was either through the hepatic artery (175 patients) or through the left gastric artery (119 patients), with success rates in catheterising the right gastric artery of 78.3% and 77.3%, respectively. If the attempt was unsuccessful, the catheter was redirected to the alternative approach, which increased the final success rate to 96.3%. Only seven patients experienced gastroduodenal mucosal lesions acutely after HAIC, as revealed by endoscopy. Embolisation of the right gastric artery is a feasible procedure that can reduce the incidence of gastric mucosal lesions associated with HAIC. Approach through either the hepatic artery or the left gastric artery is equally acceptable.Long-term hepatic arterial infusion chemotherapy (HAIC) via an implanted port-catheter system is a treatment option for patients with unresectable advanced liver cancer [1, 2]. In the past, such catheter placement was done by surgical laparotomy under general anaesthesia [3–6], an invasive procedure. However, recent advances in interventional techniques allow the implantation of port-catheter systems percutaneously under local anaesthesia [7–14].A frequent complication is reactive gastric or duodenal mucosal lesions, which result from chemical irritation caused by infusion of chemotherapeutic agents into adjacent organs through arteries originating from the common hepatic artery [15–24]. One such complication is a gastric mucosal lesion caused by inflow of chemotherapeutic agents into the right gastric artery [15–24]. To prevent this complication, the efficacy of selectively embolising the right gastric artery with coils at the time of implantation of the port-catheter system has been noted [21, 25–27].In many cases, however, the right gastric artery is slender and angulated, with anatomical variations [26, 28–31]. Hence, it is occasionally difficult to insert a catheter selectively into the right gastric artery by antegrade catheterisation via the site of the hepatic artery. This is the approach most commonly used by interventional radiologists. Failure to embolise the right gastric artery can result [26]. As an alternative method, a retrograde approach to the right gastric artery via the left gastric artery has been introduced [32, 33].Because HAIC with an implanted port-catheter system is performed in a relatively large number of cases in our institution, we have many opportunities to embolise the right gastric artery using both approaches. The aim of the present retrospective non-randomised study, which included a large number of subjects, was to evaluate the usefulness of right gastric arterial embolisation and to determine whether the antegrade or retrograde approach is more useful.     

Cardiac MR enables diagnosis in 90% of patients with acute chest pain,elevated biomarkers and unobstructed coronary arteries

Objective:

To assess the diagnostic value of cardiac MRI (CMR) in patients with acute chest pain, elevated cardiac enzymes and a negative coronary angiogram.

Methods:

This study included a total of 125 patients treated in the chest pain unit during a 39-month period. Each included patient underwent MRI within a median of 3 days after cardiac catheterization. The MRI protocol comprised cine, oedema-sensitive and late gadolinium-enhancement imaging. The standard of reference was a consensus diagnosis based on clinical follow-up and the synopsis of all clinical, laboratory and imaging data.

Results:

MRI revealed a multitude of diagnoses, including ischaemic cardiomyopathy (CM), dilated CM, myocarditis, Takotsubo CM, hypertensive heart disease, hypertrophic CM, cardiac amyloidosis and non-compaction CM. MRI-based diagnoses were the same as the final reference diagnoses in 113/125 patients (90%), with the two diagnoses differing in only 12/125 patients. In two patients, no final diagnosis could be established.

Conclusion:

CMR performed early after the onset of symptoms revealed a broad spectrum of diseases. CMR delivered a correct final diagnosis in 90% of patients with acute chest pain, elevated cardiac enzymes and a negative coronary angiogram.

Advances in knowledge:

Diagnosing patients with acute coronary syndrome but unobstructed coronary arteries remains a challenge for cardiologists. CMR performed early after catheterization reveals a broad spectrum of diseases with only a simple and quick examination protocol, and there is a high concordance between MRI-based diagnoses and final reference diagnoses.Acute coronary syndrome (ACS) is a common working diagnosis in emergency and chest pain units worldwide. Acute chest pain is the cardinal symptom of an ACS, but clinical findings vary among patients, ranging from mild discomfort to severe cardiac arrhythmias and sudden cardiac death. Among all patients admitted to a hospital with acute chest pain, only 30% receive a final diagnosis of ACS.¹ This is reasonable owing to the multitude of differential diagnoses for troponin-positive acute chest pain ranging from ST-elevation myocardial infarction to non-cardiac aetiologies, such as pulmonary embolism and sepsis.^2,3In addition to the examination of clinical signs and symptoms, electrocardiogram (ECG) diagnostics and troponin measurements are routinely used in ACS evaluation. Standard 12-lead ECG is a key diagnostic tool for determining which patients with suspected acute myocardial infarction should be directed to the angiography suite.⁴ However, while ST elevations may indicate myocardial infarction, they can also be owing to other serious conditions, including pericarditis, myocarditis, cardiomyopathy (CM) and congestive heart failure. Moreover, ACS can be present even without ECG changes, for example, in cases of non-ST-elevation myocardial infarction (NSTEMI) or unstable angina pectoris.^3–5Cardiac troponin measurement, especially with implementation of highly sensitive assays, plays a central role in establishing a diagnosis and stratifying risk in patients with ACS.^6,7 However, aetiological diagnosis remains challenging in cases of troponin-positive acute chest pain with either normal coronary arteries or non-flow-limiting coronary artery disease. There are many possible responsible entities, such as clot lysis and recanalization of an acute thrombotic obstruction, coronary thromboembolism, acute myocarditis, apical ballooning syndrome, coronary vasospasm, inherited thrombophilia, non-ischaemic cardiomyopathies and non-cardiac aetiologies.^3,8Cardiac MRI (CMR) does not yet have a well-established role in patients with suspected ACS and is not part of the routine clinical work-up described in the current guidelines of the European Society of Cardiology.⁹ However, increasing evidence suggests that CMR may provide incremental diagnostic value in these patients.^10–13 We have adopted CMR in the diagnostic work-up of patients with suspected ACS.The present study aimed to investigate the diagnostic value of CMR in patients with suspected ACS. As a standard of reference, we used a consensus-based final diagnosis established using clinical follow-up of up to 3 months after admission and the synopsis of all clinical, laboratory and imaging findings.     

Evaluation of CT coronary artery angiography with 320-row detector CT in a high-risk population

Objectives

The aim of this article was to prospectively evaluate the accuracy and radiation dose of 320-detector row dynamic volume CT (DVCT) for the detection of coronary artery disease (CAD) in a high-risk population.

Methods

60 patients with a high risk of CAD underwent DVCT without preceding heart rate control and also underwent invasive coronary angiography (ICA), which served as the standard reference.

Results

On a per segment analysis, overall sensitivity was 95.3%, specificity was 97.6%, positive predictive value was 90.6%, negative predictive value was 98.8% and Youden index was 0.93. In both heart rate subgroups, diagnostic accuracy for the assessment of coronary artery stenosis was similar. The accuracy of the subgroup with an Agatston score ≥100 was lower than that for patients with an Agatston score <100. However, the difference between DVCT and ICA results was not significant (p=0.08). The mean estimated effective dose of CT was 12.5±9.4 mSv. In those patients with heart rates less than 70 beats per minute (bpm), the mean radiation exposure of DVCT was 5.2±0.9 mSv. The effective radiation dose was significantly lower than that of ICA (14.1±5.9 mSv) (p<0.001). When the heart rate was >70 bpm, a significantly higher dose was delivered to patients with DVCT (22.6±5.2 mSv, p<0.001) than with ICA (15.0±5.3 mSv, p<0.001).

Conclusion

DVCT reliably provides high diagnostic accuracy without heart rate/rhythm control. However, from a dosimetric point of view, it is recommended that heart rate should be controlled to <70 bpm to decrease radiation dose.The small diameter of the coronary segments, their complex three-dimensional geometry and their rapid movement throughout the cardiac cycle represent the major challenges for artefact-free coronary CT angiography (CTA). With each scanner generation, motion artefacts re-appear as a major cause of image quality degradation during coronary CTA [1-10]. Coronary CTA studies of each coronary artery with four-multidetector CT (MDCT) at a gantry rotation time of 500 ms had significantly decreased image quality with increasing mean heart rates [3]. Using 16-MDCT at a gantry rotation time of 420 ms, Hoffmann et al [2] found a significant negative correlation between overall image quality and mean heart rate. Even using 64-section CT, with its gantry rotation speed of 330 ms, elevated and irregular heart beats were found to cause relevant degradation of image quality [1,4,9,11]. Using dual-source CT (DSCT) with an increased temporal resolution of 83 ms, there was no significant correlation between mean heart rate and the overall image quality for any coronary segment or for any individual coronary artery. Nonetheless, irregular heart rates still slightly affect the image quality of non-invasive coronary angiography, even with DSCT [10,12].The 320-detector row dynamic volume CT (DVCT) is characterised by 320 slice detectors with a thickness of 0.5 mm and gantry rotation time of 350 ms. With a wide coverage of 16 cm in the z-axis, the whole heart can be covered within one cardiac cycle. Theoretically, DVCT makes it possible to scan patients with an irregular heart rate without “stair-step” artefacts. At the same time, DVCT avoids the overlapping rotations of helical CT, and the application of prospective echocardiogram (ECG) gating has become more feasible. Recent studies of DVCT have mainly been based on a low heart rate [13-17]. Few studies have investigated the diagnostic accuracy in higher heart rates and arrhythmia. Our purpose was to systematically evaluate the diagnostic accuracy and exposure dose of DVCT in a high-risk population with high and irregular heart rates.     

Troponin-positive chest pain with unobstructed coronary arteries: definitive differential diagnosis using cardiac MRI

Objective

The purpose of this study was to assess the outcome of cardiac MRI (CMRI) with late gadolinium enhancement (LGE) at outpatient follow-up in a consecutive series of patients with troponin-positive chest pain but unobstructed coronary arteries at the index admission.

Methods

The study group comprised 91 consecutive patients who presented to our institution with cardiac chest pain, elevated troponin I and unobstructed coronary arteries on coronary angiography. All patients underwent an outpatient CMRI with LGE imaging in order to establish a definitive diagnosis.

Results

The average time from coronary angiography to LGE-CMRI was 2 months. 73% of patients had no abnormality on their LGE-CMRI, 16% of patients had patchy late enhancement consistent with myocarditis and 11% had focal subendocardial or full thickness late enhancement consistent with myocardial infarction. There were no deaths in this cohort during a mean follow-up of 21 months.

Conclusion

LGE-CMRI is a useful tool for establishing whether such patients have definitive evidence of non-ST-segment elevation myocardial infarction (NSTEMI), and can make an important contribution to the long-term management strategy of these patients as an inappropriate diagnosis of NSTEMI carries important medical, social and financial implications.Chest pain is one of the commonest indications for acute hospital admission in the UK [1]. A history of cardiac-sounding chest pain stimulates a series of investigations including electrocardiography (ECG) recordings and cardiac biomarkers as part of risk stratification [2]. A large body of evidence has demonstrated that, in patients with troponin-positive non-ST-segment elevation myocardial infarction (NSTEMI), early revascularisation is associated with a significant reduction in the rates of major adverse cardiac events (MACE) [3,4]. Current American and European guidelines recommend early angiography and revascularisation in this population. For this reason the vast majority of patients presenting with troponin-positive chest pain undergo coronary angiography with a view to revascularisation on the index admission.However, while the commonest reason for this presentation is NSTEMI due to atherosclerotic plaque rupture, there are other potential aetiologies, which include myocarditis or arrhythmia (particularly in the context of impaired left ventricular systolic function). Up to 10% of patients referred for angiography with troponin-positive chest pain have unobstructed coronary arteries [5,6]. This cohort of patients presents a diagnostic dilemma and as a result their subsequent management is heterogeneous. National and international guidelines lead us to an apparent diagnosis of NSTEMI [2,7] for patients presenting in this fashion. Given that it is possible for plaque rupture to occur at the site of a “non-obstructive” stenosis, which is generally defined as <50% by visual assessment on angiography, the finding of non-obstructed coronary arteries does not fully exclude the diagnosis of NSTEMI. By contrast, in many such cases, the true reason for admission may not be NSTEMI, with a differential diagnosis of myopericarditis most often considered. The management strategy adopted for this cohort of patients is variable. Many such patients are committed to post-myocantial infarction (MI) secondary prevention treatment for presumed NSTEMI and retain this diagnostic label. This in turn carries important potential implications for lifestyle outcomes, such as driving as well as insurance and job applications.The development of late gadolinium enhancement (LGE) cardiac MRI (CMRI) provides a sensitive and specific tool for the detection of even small amounts of myocardial damage [8]. This group and others have previously described the application of CMRI for differentiation of myocardial damage due to coronary occlusion or inflammation [9-11]. Furthermore, the clinical implications of detecting no LGE in such patients is uncertain as the underlying cause for the troponin release remains unexplained.The aim of this study was to assess the outcome of LGE-CMRI at outpatient follow-up in a consecutive series of patients who had presented to this regional cardiac centre with troponin-positive chest pain but who had no obstructive coronary artery disease at angiography on the index admission. We also sought to identify the relative proportions of patients with (a) no LGE, (b) LGE typical of MI and (c) patchy LGE typical of myocarditis in the largest cohort of such patients reported so far.     

Cross-sectional area measurement of the coronary arteries using CT angiography at the level of the bifurcation: is there a relationship?

PURPOSE

Our aim was to determine whether there is a correlation between cross-sectional areas of the left main coronary artery (LMCA), left anterior descending artery (LAD), and circumflex artery (CX) in normal cases using coronary CT angiography.

METHOD

Examinations of 180 patients (119 men and 61 women) were selected among 2248 consecutive coronary CT angiography studies. Cross-sectional areas of LMCA, LAD, and CX were measured at the level of bifurcation. Correlation between age, height, and body mass index and coronary artery cross-sectional areas was investigated and possibility of formulating a correlation between the cross-sectional areas of LMCA, LAD, and CX was explored.

RESULTS

Mean cross-sectional areas of LMCA, LAD, and CX were found as 17.4±3.9 mm², 12.5±3.1 mm², and 10.5±3.0 mm², respectively. While cross-sectional areas of LMCA and LAD were significantly larger in men, no significant difference was found between the sectional areas of CX in men and women. A multiple regression analysis was conducted to elucidate the relationship between the cross-sectional areas of LMCA LAD, and CX. Our analysis showed that the relationship between LMCA, LAD, and CX cross-sectional areas can be formulated as follows: LMCA=3.870 + 0.718×LAD + 0.434×CX.

CONCLUSION

There is a correlation between the cross-sectional areas of LMCA, LAD, and CX at the level of bifurcation, and this correlation can be expressed with a formula.Coronary artery disease is the leading cause of death worldwide. Thus, coronary artery imaging is one of the most commonly used diagnostic methods. Recently, coronary computed tomography angiography (CCTA) has become another widely used method in coronary artery imaging since it is a noninvasive technique that is easy to perform (1, 2).One of the major advantages of CCTA is that it allows for the measurement of not only two-dimensional diameters but also cross-sectional areas of the vascular structures. Thus, it is possible to calculate the degree of narrowing caused by atherosclerotic plaques in case of obstruction. It is also possible to predict the symptoms that may arise in a patient in relation to the obstruction and determine the treatment that can be performed using CT angiography.Atherosclerotic plaques are commonly seen adjacent to vascular bifurcations (3, 4). Left main coronary artery (LMCA) length is variable, and it is shorter in comparison with other main coronary arteries. Therefore, atherosclerotic plaques can occupy the whole vessel in some cases. In such cases, it is difficult to determine the degree of narrowing caused by the plaque since it is not possible to understand the reference artery diameter. Similarly, normal dimensions of the arteries might not be understood in cases of plaque build-up that occupy the long segment starting from the left anterior descending artery (LAD) and circumflex artery (CX) origin. Recently developed multidetector computed tomography (MDCT) technology provides valuable information in terms of understanding three-dimensional anatomy of coronary bifurcation and measuring the angle and vessel cross-sectional area (5, 6). This information is considerably important for the diagnosis and treatment of bifurcation lesions.Some studies aimed to elucidate the correlation between the diameters of coronary arteries at bifurcation levels using Murray’s law or Finet’s formula (7, 8). However, no study aiming to evaluate the relationship between the cross-sectional areas of the coronary arteries at the level of LMCA bifurcation is found to date. In this study, we aimed to investigate whether there is a correlation between LMCA, CX, and LAD cross-sectional areas in normal cases and explore the possibility of explaining the relationship with a formula, which may then be used to estimate the reference cross-sectional area of a stenosed coronary artery when the other two arteries are normal.     

Primary vaginal cancer: role of MRI in diagnosis,staging and treatment

Primary carcinoma of the vagina is rare, accounting for 1–3% of all gynaecological malignancies. MRI has an increasing role in diagnosis, staging, treatment and assessment of complications in gynaecologic malignancy. In this review, we illustrate the utility of MRI in patients with primary vaginal cancer and highlight key aspects of staging, treatment, recurrence and complications.The incidence of primary vaginal cancer increases with age, with approximately 50% of patients presenting at age greater than 70 years and 20% greater than 80 years.¹ Around 2890 patients are currently diagnosed with vaginal carcinoma in the USA each year, and almost 30% die of the disease.² The precursor for vaginal cancer, vaginal intraepithelial neoplasia (VAIN) and invasive vaginal cancer is strongly associated with human papillomavirus (HPV) infection (93%).^3,4 In situ and invasive vaginal cancer share many of the same risk factors as cervical cancer, such as tobacco use, younger age at coitarche, HPV and multiple sexual partners.^5–7 In fact, higher rates of vaginal cancer are observed in patients with a previous diagnosis of cervical cancer or cervical intraepithelial neoplasia.^7,8As is true for other gynaecologic malignancies, vaginal cancer diagnosis and staging rely primarily on clinical evaluation by the International Federation of Gynecology and Obstetrics (FIGO).⁹ Pelvic examination continues to be the most important tool for evaluating local extent of disease, but this method alone is limited in its ability to detect lymphadenopathy and the extent of tumour infiltration. Hence, FIGO encourages the use of imaging. Fluorine-18 fludeoxyglucose-positron emission tomography (¹⁸F-FDG-PET), a standard imaging tool for staging and follow-up in cervical cancer, can also be used for vaginal tumours, with improved sensitivity for nodal involvement compared to CT alone.¹⁰ In addition to staging for nodal and distant disease, CT [simulation with three dimensional (3D) conformations] is particularly useful for treatment planning and delivery of external beam radiation. MRI, with its excellent soft tissue resolution, is commonly used in gynaecologic malignancies and has been shown to be accurate in diagnosis, local staging and spread of disease in vaginal cancer.^11,12 While no formal studies are available for vaginal cancer, in cervical cancer MRI actually alters the stage in almost 30% of patients.^13–15Treatment planning in primary vaginal cancer is complex and requires a detailed understanding of the extent of disease. Because vaginal cancer is rare, treatment plans remain less well defined, often individualized and extrapolated from institutional experience and outcomes in cervical cancer.^1,16–19 There is an increasing trend towards organ preservation and treatment strategies based on combined external beam radiation and brachytherapy, often with concurrent chemotherapy,^14,20,21 surgery being reserved for those with in situ or very early-stage disease.²² Increasing utilization of MR may provide superior delineation of tumour volume, both for initial staging and follow-up, to allow for better treatment planning.²³     

Detection of ischaemic myocardial lesions with coronary CT angiography and adenosine-stress dynamic perfusion imaging using a 128-slice dual-source CT: diagnostic performance in comparison with cardiac MRI

Objective:

We assessed the diagnostic performance of adenosine-stress dynamic CT perfusion (ASDCTP) imaging and coronary CT angiography (CCTA) for the detection of ischaemic myocardial lesions using 128-slice dual-source CT compared with that of 1.5 T cardiac MRI.

Methods:

This prospective study included 33 patients (61±8 years, 82% male) with suspected coronary artery diseases who underwent ASDCTP imaging and adenosine-stress cardiac MRI. Two investigators independently evaluated ASDCTP images in correlation with significant coronary stenosis on CCTA using two different thresholds of 50% and 70% diameter stenosis. Hypoattenuated myocardial lesions on ASDCTP associated with significant coronary stenoses on CCTA were regarded as true perfusion defects. All estimates of diagnostic performance were calculated and compared with those of cardiac MRI.

Results:

With use of a threshold of 50% diameter stenosis on CCTA, the diagnostic estimates per-myocardial segment were as follows: sensitivity, 81% [95% confidence interval (CI): 70–92%]; specificity, 94% (95% CI: 92–96%); and accuracy 93% (95% CI: 91–95%). With use of a threshold of 70%, the diagnostic estimates were as follows: sensitivity, 48% (95% CI: 34–62%); specificity, 99% (95% CI: 98–100%); and accuracy, 94% (95% CI: 92–96%).

Conclusion:

Dynamic CTP using 128-slice dual-source CT enables the assessment of the physiological significance of coronary artery lesions with high diagnostic accuracy in patients with clinically suspected coronary artery disease.

Advances in knowledge:

Combined CCTA and ASDCTP yielded high accuracy in the detection of perfusion defects regardless of the threshold of significant coronary stenosis.It is important to evaluate not only anatomical information about coronary arteries but also physiological information about myocardial perfusion for the precise assessment of coronary artery disease (CAD) [1]. Myocardial perfusion imaging (MPI) can provide haemodynamic information during exercise-induced or pharmacological stress. Single-photon emission tomography (SPECT), cardiac MRI or positron emission tomography (PET) has been extensively used for MPI [2,3]. Moreover, a normal MPI determined using these techniques carries an excellent prognosis with a low rate of cardiac events [4–6].SPECT and PET are limited in their ability to evaluate coronary artery morphology and cardiac structures. By contrast, CT MPI with coronary CT angiography (CCTA) can evaluate not only anatomical structure, including coronary artery morphology, but also myocardial perfusion status. Although radiation dose associated with CT perfusion (CTP) is a concern, recent studies have shown that exposure to radiation can be reduced using different techniques, such as high-pitch helical scan of static CTP, half-scan duration of dynamic CTP and anatomical tube current modulation [7,8]. SPECT is more frequently used than MRI as a reference standard for evaluating the diagnostic accuracy of CTP. However, Jaarsma et al [9] reported that both cardiac MRI and PET showed a significantly higher diagnostic accuracy than SPECT for detection of obstructive CAD. Among several techniques of CTP, adenosine-stress dynamic CTP (ASDCTP) using 128-slice dual-source CT (DSCT) has the advantages of quantitative analysis of myocardial blood flow (MBF) and the use of dynamic data sets [10–14]. There have been 2 previous studies of dynamic CTP using stress perfusion MRI as the reference standard [13,15], but these reports enrolled only 10 patients in the study arm evaluating dynamic CTP.The purpose of this study was to evaluate the diagnostic performance of ASDCTP using a 128-slice DSCT for the detection of myocardial perfusion defects compared with adenosine-stress cardiac MRI.     

320-detector CT coronary angiography with prospective and retrospective electrocardiogram gating in a single heartbeat: comparison of image quality and radiation dose

Objectives

To compare the image quality, radiation dose and diagnostic accuracy of 320-detector CT coronary angiography with prospective and retrospective electrocardiogram (ECG) gating in a single heartbeat.

Methods

Two independent reviewers separately scored image quality of coronary artery segment for 480 cardiac CT studies in a prospective group and a retrospective group (240 patients with a heart rate <65 beats per minute in each group). The two groups matched well for clinical characteristics and CT parameters. There was good agreement for image quality scores of coronary artery segment between the independent reviewers (κ = 0.73). Of the 7023 coronary artery segments, the image quality scores of the prospective group and retrospective group were not significantly different (p>0.05). The mean radiation dose was 10.0±3.5 mSv (range 6.2–21.6 mSv) for prospective ECG gating at 65–85% of R–R interval (the interval between the R-wave of one heartbeat to the R-wave of the next). The mean radiation dose for retrospective ECG-triggered modulated scans was 23.2±3.4 mSv (range 17–27.4 mSv). The mean radiation dose was 57% lower for prospective gating than for retrospective gating (p<0.01).

Results

Compared with coronary angiography, the results for prospective vs retrospective ECG gating were 92% vs 90% for sensitivity (p = 0.23), 89% vs 91% for specificity (p = 0.19), 90% vs 93% for positive predictive value (p = 0.25) and 92% vs 95% for negative predictive value (p = 0.21) for lesions with ≥50% stenosis, respectively.

Conclusion

320-detector CT coronary angiography performed with prospective ECG gating has similar subjective image quality scores, but a 57% lower radiation dose than retrospective ECG gating in a single heartbeat.Cardiovascular disease is the leading cause of morbidity and mortality in the West [1]. Early detection of coronary artery disease (CAD) is of vital importance as timely treatment may significantly reduce morbidity and mortality. Although invasive coronary angiography (CAG) remains the standard of reference for the evaluation of CAD, multidetector CT angiography (CTA) has recently emerged as a robust imaging modality for the non-invasive evaluation of CAD [1-7]. Advances in CTA technology have led to continuous improvements in image quality, as well as a reduction in radiation dose and contrast material [8-10]. Recently, 320-detector CT systems were introduced, with enhanced craniocaudal volume coverage when compared with 64-detector systems. With 16 cm anatomical coverage (0.5 mm×320 detectors), this new generation of CT scanners allows image acquisition of the entire heart within a single gantry rotation and one heartbeat. As detector arrays have evolved to expand coverage in the z-axis, the application of prospective electrocardiogram (ECG) gating has become feasible. Prospective ECG gating protocols with 64-detector systems have been shown to provide a substantial decrease in overall radiation dose to patients, although with some limitations with regard to temporal resolution and artefacts [4]. Dynamic volume 320-detector CT, with full cardiac coverage in one gantry rotation, can now provide prospective ECG gating cardiac images without some of the previous limitations. Specifically, dynamic volume CT provides significant improvements with regard to image quality, temporal uniformity and reduction of artefacts, as well as improvements in patient safety, with a reduction in radiation and contrast doses [6,7,9,10].The image quality, radiation dose and diagnostic accuracy of 320-detector CT with prospective and retrospective ECG gating have not been reported previously. Therefore, the purpose of our study was to compare the image quality, patient radiation dose and diagnostic accuracy of 320-detector CT with prospective and retrospective ECG gating.     

Detection of myocardial perfusion abnormalities: standard dual-source coronary computed tomography angiography versus rest/stress technetium-99m single-photo emission CT

We compared coronary dual-source computed tomography angiography (corDSCTA) with technetium-99m single-photon emission computed tomography (SPECT) for the detection of myocardial perfusion abnormalities. Fifty-five consecutive patients underwent both gated myocardial perfusion SPECT and corDSCTA, the latter during a single arterial-phase injection of contrast agent. The perfusion defects visualised by corDSCTA correlated with the findings of rest/stress SPECT. Abnormal findings on stress SPECT, which were due to either ischaemia or infarct, were found in 24 patients. In comparison to SPECT at rest, corDSCTA detected perfusion defects with a sensitivity and specificity of 100% and 78%, respectively. Compared to SPECT at stress, the sensitivity and specificity values of corDSCTA were 83.3% and 90.3%, respectively. On corDSCTA , the average attenuation values of perfusion defects that corresponded to chronic infarcts (−8.5±22.2 HU) were significantly lower (p = 0.002) than those of non-infarct-related perfusion defects (43.1±17.5 HU). Using rest/stress SPECT is the gold standard for the diagnosis of myocardial ischaemia, corDSCTA was able to diagnose ischaemic disease (defined as the presence of high-grade stenotic CAD (≥50% luminal narrowing)) with a sensitivity and specificity of 59% and 89%, respectively, in patients with no known history of myocardial infarction (n = 4). Thus, corDSCTA may serve as a diagnostic tool for the detection of perfusion abnormalities (first) visualised by SPECT. There appears to be a limited correlation between coronary stenotic disease and SPECT findings.Coronary artery disease (CAD) is one of the leading causes of morbidity and mortality in developed countries. During the progression of atherosclerosis, the coronary artery wall undergoes pathological changes with build-up of plaque and subsequent luminal narrowing resulting in impaired blood supply to the myocardium. The focus of perfusion imaging is the detection of pathological changes in myocardial perfusion. At present, various perfusion imaging techniques are in clinical use, including nuclear medicine modalities such as single-photon emission computed tomography (SPECT), positron emission tomography (PET) and cardiac perfusion MRI.Rest/stress myocardial perfusion SPECT imaging is a non-invasive modality that is widely used to evaluate patients with suspected CAD. Compared with conventional coronary angiography, myocardial perfusion SPECT has demonstrated sensitivities and specificities of 82–98% and 44–91%, respectively, for the detection of CAD [1, 2]. SPECT findings such as the extent, severity and reversibility of perfusion defects have shown to be valuable for the prediction of future cardiovascular events [3]. In the absence of morphological correlation, however, SPECT is limited in allocating perfusion defects to their determining coronary lesion, which is a major precondition for accurate therapy planning [4]. As a consequence, invasive conventional coronary angiography (CCA) is often performed in cases of abnormal or equivocal SPECT findings [5]. To avoid a missed diagnosis of significant CAD, many patients whose SPECT findings are equivocal undergo further tests, the majority of which have negative results. It has been estimated that these negative evaluations cost $10–13 billion per year in the United States alone [6].Since the advent of multidetector computed tomography (MDCT) scanners with their greatly improved spatial and temporal resolutions, coronary CT angiography (CCTA) has been gradually evolving as a promising non-invasive method for the assessment of CAD that is less costly than invasive coronary catheter angiography. Recent studies using 64-slice MDCT to diagnose patients with CAD showed sensitivity and specificity values of 96–98% and 84–93%, respectively [7–9]. Importantly, the combined results from a number of studies have demonstrated a mean per-patient negative predictive value of 97%. According to a recent study, the accuracy of 64-slice MDTA was comparable to that of stress nuclear perfusion imaging (SPECT) in the detection and exclusion of acute coronary syndrome in patients with chest pain [10]. Furthermore, MDCT has expanded its application beyond coronary angiography towards a more comprehensive evaluation of cardiovascular disease, including the evaluation of cardiac function, valvular disease [11], congenital abnormalities [12] and myocardial viability [13, 14]. Precise grading of stenotic CAD by CCTA is made difficult or even impossible in heavily calcified vascular segments because of blooming artefacts [15], and the diagnostic accuracy of this method is therefore limited, particularly in patients who have advanced calcified atherosclerosis, e.g. patients with end-stage diabetic disease. For that reason, additional diagnostic information to predict the haemodynamic relevance of stenotic CAD is desirable.A few studies have assessed the potential of cardiac CT imaging for the detection of myocardial perfusion abnormalities. Animal studies have shown that myocardial perfusion can be depicted by looking at the differences between rest and stress imaging [16]. Furthermore, dynamic CT data acquisition has been used in attempts to calculate myocardial perfusion reserve. These experimental approaches have limitations, however, including restricted ventricular coverage, high image noise, artefacts and increased radiation exposure owing to multiple CT data acquisitions. Recently, a new generation of dual-source CT (DSCT) scanners has been introduced. DSCT scanners are equipped with two X-ray tubes and two corresponding detectors mounted on the rotating gantry with an angular offset of 90°. The reconstruction of a single cross-sectional image of the heart requires the acquisition of data over a rotation of approximately 180°. Therefore, with DSCT systems, a one-quarter rotation of the gantry is sufficient for image reconstruction when both tubes and detectors are operated simultaneously. With a gantry rotation time of 330 ms, DSCT allows image acquisition with an effective scan time of 83 ms. This technology allows bisection of temporal resolution for cardiac CT scans compared with the most recent 64-slice CT scanners, obviating the need to administer beta blockers to reduce heart rate [17]. Coronary dual-source computed tomography angiography (corDSCTA) data sets are typically acquired during a single breath-hold period of 6–10 s. A bolus administration of iodinated contrast agent is given at a flow rate of 5 ml s⁻¹.Besides visualising the coronary arteries, corDSCTA can simultaneously provide information on blood volume distribution that is based on an early arterial myocardial contrast phase. The primary aim of this study is to evaluate the performance of corDSCTA in the detection of myocardial perfusion abnormalities in comparison with rest/stress technetium-99m SPECT, which served as the gold standard. A secondary objective was to assess the potential value of corDSCTA for the detection of chronic myocardial infarcts based on the measurement of attenuation values within areas of hypoperfused myocardium (perfusion defects). A third objective was to correlate the presence of high-grade coronary disease (≥50% luminal narrowing) as determined by corDSCTA with perfusion defects on rest/stress SPECT.     

Accessory or additional renal arteries show no relevant effects on the width of the upper urinary tract: a 64-slice multidetector CT study in 1072 patients with 2132 kidneys

Objective

The aim of this study was to find out on an unselected patient group whether crossing vessels have an influence on the width of the renal pelvis and what independent predictors of these target variables exist.

Methods

In this cross-sectional study, 1072 patients with arterially contrasted CT scans were included. The 2132 kidneys were supplied by 2736 arteries.

Results

On the right side, there were 293 additional and accessory arteries in 286 patients, and on the left side there were 304 in 271 patients. 154 renal pelves were more than 15 mm wide. The greatest independent factor for hydronephrosis on one side was hydronephrosis on the contralateral side (p<0.0001 each). Independent predictors for the width of the renal pelvis on the right side were the width of the renal pelvis on the left, female gender, increasing age and height; for the left side, predictors were the width of the renal pelvis on the right, concrements, parapelvic cysts and great rotation of the upper pole of the kidney to dorsal. Crossing vessels had no influence on the development of hydronephrosis. Only anterior crossing vessels on the right side are associated with widening of the renal pelvis by 1 mm, without making it possible to identify the vessel as an independent factor in multivariate regression models.

Conclusion

The width of the renal pelvis on the contralateral side is the strongest independent predictor for hydronephrosis and the width of the renal pelvis. There is no link between crossing vessels and the width of the renal pelvis.Obstructions of the ureteropelvic junction (UPJ) can be caused by intrinsic or extrinsic factors [1]. Although there are no studies of this to date, crossing the UPJ by an aberrant crossing vessel is considered the most important [2] of the extrinsic factors [3]. Crossing vessels, which are thought to cause from 40% to over 50% of the extrinsic UPJ obstructions in adults [4, 5], are located ventral more often than dorsal to the UPJ. These are usually normal vessels of the lower pole segment [4, 6–9], which can be divided into additional renal arteries arising from the aorta, and accessoric renal arteries arising from branches of the aorta [10, 11]. The primary surgical therapy of choice is endoscopic endopyelotomy [12]. The success rate of 89–90% [12, 13] is thought to be noticeably poorer in patients with crossing vessels [12, 13]; however, this is not undisputed [14, 15]. Be that as it may, to prevent bleeding complications it is necessary to be familiar with the vascular situation around the UPJ prior to the procedure [3, 16–18]. CT angiography is used for this purpose, as it is highly accurate, quick to perform and shows all relevant anatomical structures in relation to one another [3, 19, 20]. The objective of this study was to determine whether or not there are vascular morphological patterns or other factors that influence the width of the renal collecting system, regardless of the definitions of hydronephrosis.     

Towards clinical assessment of velopharyngeal closure using MRI: evaluation of real-time MRI sequences at 1.5 and 3 T

Objective

The objective of this study was to demonstrate soft palate MRI at 1.5 and 3 T with high temporal resolution on clinical scanners.

Methods

Six volunteers were imaged while speaking, using both four real-time steady-state free-precession (SSFP) sequences at 3 T and four balanced SSFP (bSSFP) at 1.5 T. Temporal resolution was 9–20 frames s⁻¹ (fps), spatial resolution 1.6×1.6×10.0–2.7×2.7×10.0 mm³. Simultaneous audio was recorded. Signal-to-noise ratio (SNR), palate thickness and image quality score (1–4, non-diagnostic–excellent) were evaluated.

Results

SNR was higher at 3 T than 1.5 T in the relaxed palate (nasal breathing position) and reduced in the elevated palate at 3 T, but not 1.5 T. Image quality was not significantly different between field strengths or sequences (p=NS). At 3 T, 40% acquisitions scored 2 and 56% scored 3. Most 1.5 T acquisitions scored 1 (19%) or 4 (46%). Image quality was more dependent on subject or field than sequence. SNR in static images was highest with 1.9×1.9×10.0 mm³ resolution (10 fps) and measured palate thickness was similar (p=NS) to that at the highest resolution (1.6×1.6×10.0 mm³). SNR in intensity–time plots through the soft palate was highest with 2.7×2.7×10.0 mm³ resolution (20 fps).

Conclusions

At 3 T, SSFP images are of a reliable quality, but 1.5 T bSSFP images are often better. For geometric measurements, temporal should be traded for spatial resolution (1.9×1.9×10.0 mm³, 10 fps). For assessment of motion, temporal should be prioritised over spatial resolution (2.7×2.7×10.0 mm³, 20 fps).

Advances in knowledge

Diagnostic quality real-time soft palate MRI is possible using clinical scanners and optimised protocols have been developed. 3 T SSFP imaging is reliable, but 1.5 T bSSFP often produces better images.Approximately 450 babies born in the UK every year have an orofacial cleft [1], the majority of which include the palate [2]. While a cleft palate is commonly repaired surgically at around 6 months [3], residual velopharyngeal insufficiencies require follow-up surgery in 15–50% of cases [4]. This residual defect results in an incomplete closure of the velopharyngeal port, which in turns leads to hypernasal speech. Assessment of velopharyngeal closure in speech therapy is commonly performed using X-ray videofluoroscopy or nasendoscopy [5,6]. While nasendoscopy is only minimally invasive, it may be uncomfortable and provides only an en face view of the velopharyngeal port. In contrast, X-ray videofluoroscopy is non-invasive and produces an image which is a projection of the target anatomy. Additional information may be obtained from projections at multiple angles [5,7], but anatomical structures may overlie each other. Furthermore, soft tissue contrast, such as that from the soft palate, is poor, although it may be improved using a barium contrast agent coating [8] at the expense of making the procedure more invasive and unpleasant. Arguably the greatest drawback of X-ray videofluoroscopy is the associated ionising radiation dose, which carries increased risk in paediatric patients [9].An increasing number of research studies have used MRI to image the soft palate [10-13] and upper vocal tract [14-17]. In contrast to X-ray videofluoroscopy and nasendoscopy, MRI provides tomographic images in any plane with flexible tissue contrast. As a result, MRI has been used to obtain images of the musculature of the palate at rest and during sustained phonation [10,18,19]. It has also been used to image the whole vocal tract at rest or during sustained phonation [20-27] and with a single mid-sagittal image dynamically during speech [13,15-17,28-35].For assessment of velopharyngeal closure, dynamic imaging with sufficient temporal resolution and simultaneous audio recording is required. Audio recording during imaging is complicated by the loud noise of the MRI scanner, and both the safety risk and image degradation caused by using an electronic microphone within the magnet. As a result, optical fibre-based equipment with noise cancellation algorithms must be used [36].In order to fully resolve soft palate motion, Narayanan et al [30] suggested that a minimum temporal resolution of 20 frames s⁻¹ (fps) is required. A similar conclusion was reached by Bae et al [13], based on measurements of soft palate motion extracted from X-ray videofluoroscopy. Using segmented MRI, Inoue et al [35] demonstrated that changes in the velar position that were evident at acquired frame rates of 33 fps were not observed at 8 fps. However, MRI is traditionally seen as a slow imaging modality and achieving sufficient temporal resolution at an acceptable spatial resolution is challenging. Furthermore, as the soft palate is bordered on both sides by air, the associated changes in magnetic susceptibility at the interfaces make images prone to related artefacts.Dynamic MRI of the vocal tract has been performed using both segmented [17,33,37] and real-time acquisitions [13,15,16,28,31,38]. Segmented acquisitions [39] acquire only a fraction of the k-space data required for each image during one repetition of the test phrase and, hence, require multiple identical repetitions. While these segmented techniques permit high temporal and spatial resolutions [35], they require reproducible production of the same phrase up to 256 times [34], leading to subject fatigue. Differences between repeats of up to 95 ms in the onset of speech following a trigger have also been demonstrated [36].In contrast to segmented techniques, real-time dynamic methods permit imaging of natural speech, but require extremely rapid acquisition and often advanced reconstruction methods. The turbo spin echo (TSE) zoom technique [40] has been used to perform real-time MRI of the vocal tract [29,31] and is available as a clinical tool. The zoom technique excites a reduced field of view in the phase encode direction, hence allowing a smaller acquisition matrix and shorter scan for a constant spatial resolution. While such spin echo-based techniques are less susceptible to magnetic field inhomogeneity related signal dropout artefacts than other sequences, the frame rates achieved with these sequences are limited to 6 fps [31]. Gradient echo-based techniques have also been used to achieve similar temporal resolution [12,41,42] in the upper vocal tract, but are often used at much higher frame rates in other MRI applications such as cardiac imaging [43,44]. A number of gradient echo sequence variants exist. Fast low-angle shot (FLASH) type sequences [45] spoil any remaining transverse magnetisation at the end of every sequence repetition (TR). In contrast, steady-state free-precession (SSFP) sequences are not spoiled [46] and the remaining transverse magnetisation is used in the next TR to improve the signal-to-noise ratio (SNR), but renders the images sensitive to signal loss in the presence of motion. Balanced SSFP (bSSFP) sequences include additional gradients to bring the transverse magnetisation completely back into phase at the end of every TR [47,48]. The result is that bSSFP sequences have high SNR and are less sensitive to motion than SSFP sequences, but are more sensitive to field inhomogeneities, which cause bands of signal dropout.Both TSE and the gradient echo techniques discussed here sample in a rectilinear or Cartesian fashion, where one line of k-space is sampled in each echo. However, for real-time speech imaging, the highest acquired frame rates have been achieved by sampling k-space along a spiral trajectory [15,16,30,49]. While spiral imaging is an efficient way to sample k-space and is motion-resilient, it is prone to artefacts, particularly blurring caused by magnetic field inhomogeneities and off-resonance protons (i.e. fat) [50]. Recently, one group successfully used spiral imaging with multiple saturation bands and an alternating echo time (TE) to achieve an acquired real-time frame rate of 22 fps [13,16]. The saturation bands were used to allow a small field of view to be imaged without aliasing artefacts. The alternating TE was used to generate dynamic field maps which were incorporated into the reconstruction to compensate for magnetic field inhomogeneities. However, such advanced acquisition and reconstruction techniques are only available in a small number of research centres.The aim of this work is to optimise and demonstrate high-temporal-resolution real-time sequences available on routine clinical MRI scanners for assessment of soft palate motion and velopharyngeal closure. Consequently, radial and spiral acquisitions were excluded and the work focuses on Cartesian gradient echo sequences with parallel imaging techniques. As more clinical MRI departments now have 3 T scanners, imaging was performed at both 1.5 and 3 T to enable comparisons. At each field strength, we optimised sequences and implemented four combinations of spatial and temporal resolution in six subjects with simultaneous audio recordings.     

Reduction of the total injection volume of contrast material with a short injection duration in 64-detector row CT coronary angiography

The ability of short injection duration of contrast material to reduce the total injection volume in 64-detector row CT coronary angiography was investigated. 45 patients were divided into three groups: (i) those receiving 0.8 ml kg^–1 of contrast material (350 mgI ml^–1) injected with a fixed duration of 14 s (Group A; n _ 16); (ii) those receiving 0.8 ml kg^–1 of contrast material injected with a fixed duration of 10 s (Group B; n _ 15); and (iii) those receiving 0.7 ml kg^–1 of contrast material injected with a fixed duration of 10 s (Group C; n _ 14). All patients then received 20 ml of saline. Contrast densities of the ascending aorta and proximal and distal coronary arteries were assessed where vessel diameters were >2.0 mm. The mean enhancement value in the ascending aorta for Group B was significantly higher than that for Groups A and C (p<0.05), whereas there was no significant difference between Groups A and C. All enhancement values in the coronary arteries were higher than 250 Hounsfield units. The mean enhancement value for each coronary artery in Group B was significantly higher than that for Group A (p<0.05), whereas there was no significant difference between Groups A and C. In conclusion, a short injection duration allows a reduction in the total volume of contrast material from 0.8 ml kg^–1 to 0.7 ml kg^–1 while a steady contrast enhancement is maintained in the ascending aorta and coronary arteries.CT coronary angiography has become a standard tool for the non-invasive assessment of coronary arteries in the past few years [1–4]. In particular, the improved spatial and temporal resolution and short data acquisition period of 64-detector row CT has led to a further improvement in image quality [5].In CT coronary angiography, high and consistent vascular enhancement is a prerequisite for sufficient evaluation [6–9]. As the coronary arteries are branches of the ascending aorta, enhancement of the ascending aorta plays a major role in the enhancement of the coronary arteries. Recently, it has been reported that aortic enhancement is closely related to injection duration when the contrast material dose is determined according to patient weight, and that a shorter injection duration contributes to higher aortic enhancement [10, 11]. To our knowledge, only a few studies have evaluated the optimal dose of contrast material on the basis of patient weight for a steady vessel enhancement in coronary CT examinations [9]. The purpose of this study is to investigate, on the basis of patient weight, whether it is possible to decrease the total injection volume of contrast material by shortening injection duration while maintaining adequate coronary vessel enhancement in 64-detector row CT coronary angiography.     

Obscure gastrointestinal bleeding: diagnostic performance of 64-section multiphase CT enterography and CT angiography compared with capsule endoscopy

Objective:

To compare the diagnostic capabilities between capsule endoscopy (CE) and multislice CT (MSCT) enterography in combination with MSCT angiography for assessment of obscure gastrointestinal bleeding (OGIB).

Methods:

A total of 127 patients with OGIB were looked at in this study. 82 patients (aged 42.7 ± 19.1 years; 34 males) were assigned to receive MSCT diagnosis and 67 patients to (aged 53.9 ± 16.2 years; 28 males) receive CE diagnosis. Among them, 22 patients (aged 54.1 ± 19.1 years; 12 males) received both examinations. Oral isotonic mannitol and intramuscular injection of anisodamine were performed; non-ionic contrast (iopromide, 370 mg I ml⁻¹) was intravenously administered; and then multiphase scanning was conducted at arterial, small intestinal and portal venous phases in MSCT. The results were compared with findings of reference standards including double balloon enteroscopy, digital subtraction angiography, intraoperative pathological examination and/or clinical diagnosis.

Results:

Administration of anisodamine markedly increased the satisfaction rate of bowel filling (94.67% vs 28.57%; p < 0.001) but not the diagnostic yield (p = 0.293) of MSCT. Compared with MSCT, CE showed an improved overall diagnostic yield (68.66% vs 47.56%; p = 0.010), which was also observed in overt bleeding patients (i.e. patients with continued passage of visible blood) (76.19% vs 51.02%; p = 0.013) and in patients aged younger than 40 years of age (85% vs 51.28%; p = 0.024). However, CE had similar positive rates to MSCT (p > 0.05). Among the 22 cases in whom both examinations were conducted, CE showed no significantly different diagnostic capability compared with MSCT (p = 0.4597).

Conclusion:

Both CE and MSCT are safe and effective diagnostic methods for OGIB.

Advances in knowledge:

CE is preferred for overt bleeding or patients aged younger than 40 years. The combined use of CE and MSCT is recommended in OGIB diagnosis.Obscure gastrointestinal bleeding (OGIB), which accounts for approximately 5% of all gastrointestinal haemorrhage cases,¹ is defined as persistent or recurring gastrointestinal bleeding without an obvious aetiology after gastroduodenoscopy and colonoscopy.^2,3 Based on the presence or absence of clinically evident bleeding, OGIB could be divided into occult (no visible blood) and overt (continued passage of visible blood, such as haematemesis, melaena or haematochezia) bleeding.^3,4 OGIB frequently occurs in the small bowel and is caused by small bowel diseases such as intestinal erosions, ulcers, vascular anomaly, gastrointestinal tumours and inflammatory bowel and parasitic diseases.^5,6Multiple diagnostic techniques have been developed to elucidate the causes of OGIB. Among them, two non-invasive technologies, capsule endoscopy (CE) and multislice CT (MSCT) markedly improved the ability to determine the causes of OGIB by allowing the visualization of the gastrointestinal tract.^2,3,6 CE is able to obtain direct visualization of mucosal surface of the entire small intestine.^4,7,8 However, capsule retention remains a major risk of CE diagnosis.^4,9–11 In addition, the visual field restriction limits the value of CE in diagnosis of umbilicate or extraluminal lesions, since the small bowel is difficult to evaluate owing to its large length and tortuous course.^4,10 Conversely, MSCT, including MSCT angiography (MSCTA), MSCT enteroclysis and MSCT enterography (MSCTE), has full capacity to depict the extraintestinal lesions, owing to the combination of the advantages of enteral volume challenge with the ability of cross-sectional imaging.^4,12 Yet, substantial patient radiation exposure is one of the major disadvantages of MSCT diagnosis.^3,13 Careful preparation is also needed before examination.¹⁴ Considering that both CE and MSCT have advantages and disadvantages, a limited number of published data have compared the two diagnostic tools in patients with OGIB.^4,6,15–17 However, most of these studies did not refer to MSCTA, and apparently different results were obtained owing to the advancement of the two technologies. Thus, an updated and comprehensive comparison is required.Hence, we compared the diagnostic capability of MSCTE in combination with MSCTA with CE in patients suffering from OGIB. In this study, MSCTE and MSCTA technologies performed with a 64-slice spiral CT scanner were combined by non-contrast-enhanced scanning after oral administration of a neutral enteric contrast material (isotonic mannitol, 2.5%) and the intramuscular injection of anisodamine to restrain enterocinesia, and the following multiphase scanning at arterial, small intestinal and portal venous phases followed the intravenous infusion of non-ionic iodinated contrast material (iopromide, 370 mg I ml⁻¹). In addition, the influences of the clinical bleeding pattern and age on the diagnostic capability were also investigated.     

Radiation dose and cancer risk in retrospectively and prospectively ECG-gated coronary angiography using 64-slice multidetector CT

This study aimed to estimate the radiation dose and cancer risk to adults in England, the USA and Hong Kong associated with retrospectively and prospectively electrocardiogram (ECG)-gated coronary computed tomography angiography (CTA) using currently practised protocols in Hong Kong. The doses were simulated using the ImPACT spreadsheet. For retrospectively ECG-gated CTA with pitches of 0.2, 0.22 and 0.24, the effective doses were 27.7, 23.6 and 20.7 mSv, respectively, for males and 23.6, 20.0 and 18.8 mSv, respectively, for females. For prospectively ECG-gated CTA, the effective dose was 3.7 mSv for both males and females. A table of lifetime attributable risks (LAR) of cancer incidence was set up for the English population for the purpose of estimating cancer risk induced by low-dose radiation exposure, as previously reported for US and Hong Kong populations. From the tables, the LAR of cancer incidence for a representative 50-year-old subject was calculated for retrospectively ECG-gated CTA to be 0.112% and 0.227% for English males and females, respectively, 0.103% and 0.228% for US males and females, respectively, and was comparatively higher at 0.137% and 0.370% for Hong Kong males and females, respectively; for prospectively ECG-gated CTA, the corresponding values were calculated to be 0.014% and 0.035% for English males and females, respectively, and 0.013% and 0.036% for US males and females, respectively, and again were higher at 0.017% and 0.060% for Hong Kong males and females, respectively. Our study shows that prospectively ECG-gated CTA reduces radiation dose and cancer risks by up to 87% compared with retrospectively ECG-gated CTA.Conventional coronary angiography is the gold standard for assessing the heart and coronary arteries, owing to its excellent spatial and temporal resolution; however, the procedure is invasive and can cause serious complications, such as thromboembolism and arterial dissection. Non-invasive imaging methods such as computed tomography angiography (CTA) can therefore be advantageous [1–4]. Applications of coronary artery CTA have, in the past, been limited by problems such as cardiac motion, respiratory motion and the small size of coronary arteries. However, technological advances with multidetector CT (MDCT) scanners have enhanced the spatial and temporal resolution achievable by CTA. Moreover, applying electrocardiogram (ECG)-gated technology, the data at diastole during each cardiac cycle can be selected and used for image reconstruction, thereby minimising motion artefacts [5]. There are two kinds of ECG-gating technologies: retrospective ECG gating and prospective ECG gating [5, 6]. For retrospective ECG gating, data are acquired during the entire cardiac cycle and only some of the data (data at the diastolic phase) are used for image reconstruction. To obtain sufficient raw data, data oversampling is used with a low pitch, which, in turn, depends on the patient''s heart rate. For prospective ECG gating, initially the mean duration of a cardiac cycle is averaged over multiple heart cycles. The trigger, a predefined time-point in each subsequent cardiac cycle, is used to initiate a sequential axial scan during diastole. The acquisition time for one axial position is about 250–500 ms. All data acquired in prospectively ECG-gated scans are used for image reconstruction.With the advent of MDCT for coronary CTA, however, radiation dose has become an important issue to be considered [7, 8]. The doses reported from coronary CTA may be even higher than for conventional angiography [9]. Using retrospectively ECG-gated CTA, doses to the organs exposed directly to X-rays are especially high: up to 114 mSv for oesophagus, 80 mSv for breast and 91 mSv for lung [10]. Recently, cancer risks from CTA, the major detriment associated with radiation exposure, have been reported in the literature [10–12]. These studies estimated lifetime cancer incidence to be up to 0.2% and 0.7% for patients undergoing coronary CTA on 16- and 64-slice CT scanners, respectively [10, 12]. Moreover, a lifetime incidence of up to 0.5% and 0.4% was reported specifically for breast and lung cancer, respectively [11]. Doses from prospectively ECG-gated CTA have been reported and were found to be much lower than those for retrospectively ECG-gated CTA [13, 14].This study investigated the radiation dose from retrospectively and prospectively ECG-gated coronary CTA on 64-slice MDCT and compared the associated cancer risk imparted to adults in England, the USA and Hong Kong. Comparisons were based on the principles introduced by the Biological Effects of Ionizing Radiation (BEIR) Committee of the National Research Council in its seventh report (BEIR VII report) [15].     

Association of pericardial fat volume with coronary atherosclerotic disease assessed by CT angiography

Objective:

To investigate the association of pericardial fat volume (PFV) with coronary artery disease (CAD) in patients with intermediate pre-test probability of ischaemic heart disease assessed by coronary CT angiography.

Methods:

From a total of 115 consecutive Iraqi patients who underwent 64-multislice multidetector CT angiography examinations, only 74 patients (females, 38% and males, 68%) with a mean age of 54 ± 8 years were found to be eligible for statistical analysis. The patients were divided into two groups according to the median value of PFV (above and below 100 ml).

Results:

The median value of PFV in our study was 100 ml (range, 17–319 ml). A significant association was observed between high PFV and significant coronary artery stenosis (p = 0.005), between high PFV and significant left circumflex stenosis (p = 0.021) and between high PFV and the presence of coronary plaque (p = 0.005). Whereas there was no significant correlation between high PFV and coronary calcium score (p = 0.188), between high PFV and number of diseased coronary vessels (p > 0.3), and between high PFV and body weight and body mass index.

Conclusion:

Increased PFV is strongly associated with the presence and severity of CAD.

Advances in knowledge:

Our study highlights the role of pericardial fat as an emerging biomarker in cardiovascular risk assessment and supports its association with the magnitude of CAD.Pericardial fat is an adipose tissue surrounding the heart, with anatomic proximity to the epicardial coronary arteries. Several studies^1–5 show growing evidence that pericardial adipose tissue may be associated with increased left ventricular mass, metabolic syndrome, endothelial dysfunction, insulin resistance and the presence of coronary artery disease (CAD) via local secretion of numerous pro-inflammatory hormones and cytokines.Coronary CT angiography is a non-invasive method that has been used for cardiovascular risk stratification based on the presence and severity of coronary calcium and atherosclerotic plaque with a reported sensitivity of 94–95% and specificity of 82%. Pericardial fat volume (PFV) can be assessed by direct measurement that depends on the detection of the thin pericardium or as a component of heart-level thoracic fat volume.^6,7Pericardial fat has been found to have a higher lipolysis and lipogenesis activity than that of other fat tissues with a strong correlation between PFV and triglyceride concentration in the myocardium.⁸Furthermore, recent data have shown that PFV assessed by CT angiography is significantly associated with severe coronary stenosis, plaque burden even in asymptomatic individuals, high-risk plaque features and an increased risk of future cardiac events.^9–11The aim of this study was to investigate the association of PFV with CAD, cardiac risk factors and calcium scoring index in patients with an intermediate pre-test probability of ischaemic heart disease assessed by coronary CT angiography.