Safety and efficacy of oral ivabradine as a heart rate-reducing agent in patients undergoing CT coronary angiography

Objective

To investigate the role of oral ivabradine as a heart rate reducing agent in patients undergoing CT coronary angiography (CTCA). Despite the routine use of β-blockers prior to CTCA studies, it is not uncommon to have patients with heart rates persistently above the target range of 65 bpm. Ivabradine is a selective inhibitor of the I_f current, which primarily contributes to sinus node pacemaker activity, and has no significant direct cardiovascular effects such as reduction of blood pressure, cardiac contractility or impairment of cardiac conduction.

Methods

We investigated 100 consecutive patients who had been referred for CTCA for the evaluation of suspected coronary artery disease (CAD). Patients were randomised to receive either of the following two pre-medication protocols: oral metorprolol or oral ivabradine.

Results

Ivabradine was significantly more effective than metorprolol in lowering the heart rate; the mean percentage reduction in heart rate with ivabradine vs metorpolol was 23.89+6.95% vs 15.20+4.50%, respectively (p=0.0001). Metoprolol significantly lowered both systolic and diastolic blood pressure while ivabradine did not. The requirement of additional doses to achieve a target heart rate of <65 beats per min was also significantly more frequent with metoprolol.

Conclusion

Ivabradine is a potentially attractive alternative to currently used drugs for reduction of heart rate in patients undergoing CTCA.Since the introduction of CT coronary angiography (CTCA) as a non-invasive tool for coronary artery imaging, its clinical utility has been established in various studies [1-3]. However, the presence of motion artefacts often prevents optimal reconstruction of individual coronary arteries, prompting use of pharmacological interventions (primarily β-blockers) during scanning to enhance image quality [4,5]. A target heart rate of 65 beats per min (bpm) or less provides optimum image quality in most cases [6,7]. Though calcium channel-blockers have also been used as alternatives to β-blockers [8], there still exists a subset of patients in whom the administration of these rate-lowering drugs may be hazardous (e.g. those with baseline blood pressure <100–110 mmHg, severe left ventricular dysfunction, peripheral vascular disease or severe obstructive airway disease). Moreover, despite the routine use of β-blockers prior to CTCA studies, it is not uncommon to have patients with heart rates persistently above the target range of 65 bpm [9-11].There is a clear need for assessment of the potential role of alternative rate-lowering drugs in patients undergoing CTCA. Ivabradine, a novel heart rate-lowering agent, is a selective and specific inhibitor of the I_f current, which is one of the most important ionic currents for regulating pacemaker activity in the sinoatrial (SA) node [12-14]. This is primarily a mixed Na⁺–K⁺ inward current activated by hyperpolarisation and modulated by the autonomic nervous system, and ivabradine acts by selectively inhibiting the pacemaker I_f current and slowing the diastolic depolarisation slope of SA node cells, reducing both resting and exercise heart rate. Moreover, ivabradine inhibits the I_f current at concentrations that do not affect other cardiac ionic currents, resulting in a lack of haemodynamic effects such as reduction of blood pressure or cardiac contractility, which is often a limitation with β-blockers. It has a good safety profile without any effects on atrioventricular conduction, corrected QT interval and peripheral vasomotion, and there is no rebound effect with drug cessation or tolerance with prolonged use.We investigated the safety and efficacy of oral ivabradine as a heart rate-lowering agent in patients undergoing CTCA at our institute. The aims of the study were (1) to assess the efficacy of ivabradine in achieving adequate heart rate control (defined as target heart rate <65 bpm), (2) to compare the differences (if any) between ivabradine and the β-blocker metoprolol in achieving target heart rate prior to CTCA and (3) to compare any difference in numbers of patients requiring additional doses of drugs prior to achieving the target heart rate.     

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.     

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.     

The effect of adaptive iterative dose reduction on image quality in 320-detector row CT coronary angiography

Objective

To evaluate the effect of adaptive iterative dose reduction (AIDR) on image noise and image quality as compared with standard filtered back projection (FBP) in 320-detector row CT coronary angiography (CTCA).

Methods

50 patients (14 females, mean age 68±9 years) who underwent CTCA (100 kV or 120 kV, 400–580 mA) within a single heartbeat were enrolled. Studies were reconstructed with FBP and subsequently AIDR. Image noise, vessel contrast and contrast-to-noise ratio (CNR) in the coronary arteries were evaluated. Overall image quality for coronary arteries was assessed using a five-point scale (1, non-diagnostic; 5, excellent).

Results

All the examinations were performed in a single heartbeat. Image noise in the aorta was significantly lower in data sets reconstructed with AIDR than in those reconstructed with FBP (21.4±3.1 HU vs 36.9±4.5 HU; p<0.001). No significant differences were observed between FBP and AIDR for the mean vessel contrast (HU) in the proximal coronary arteries. Consequently, CNRs in the proximal coronary arteries were higher in the AIDR group than in the FBP group (p<0.001). The mean image quality score was improved by AIDR (3.75±0.38 vs 4.24±0.38; p<0.001).

Conclusion

The use of AIDR reduces image noise and improves image quality in 320-detector row CTCA.CT coronary angiography (CTCA) is a robust non-invasive imaging modality with high spatial and temporal resolution that enables accurate diagnosis or exclusion of coronary artery disease [1-4]. However, CTCA usually exposes the patient to a substantial amount of radiation (9.4–21.4 mSv) [5-7]. Therefore, several scanning techniques, such as ECG-based tube current modulation, prospective ECG triggering and reduced tube voltage scanning, have been developed to reduce the patient''s radiation exposure [6-8]. Reductions of the tube current also lead to lower radiation exposure, as the tube current correlates to dose in a linear fashion. However, lower radiation leads to an increase in CT image noise because the current reconstruction method, filtered back projection (FBP), is unable to consistently generate diagnostic-quality images with reduced tube currents [9].Recently, the adaptive iterative dose reduction technique has been developed as a new reconstruction algorithm to improve image noise [10-12], and has already been shown to reduce the radiation dose in clinical practice [13-16]. Adaptive iterative dose reduction (AIDR) developed for CT by Toshiba Medical Systems Corporation is a modified iterative reconstruction technique in which the original high-noise image undergoes a number of reconstructions that reduce image noise until the resultant image displays the desired noise level. This technique is expected to reduce the radiation dose for a similar noise level to FBP.To our knowledge, no study has evaluated the quality of CT images using AIDR. The purpose of this study was to evaluate the effect of AIDR regarding image noise and image quality in comparison with FBP, using the same raw data set for both FBP and AIDR, in 320-detector row CTCA.     

Comparison between the image quality of multisegment and halfscan reconstructions of non-invasive CT coronary angiography

The purpose of this study was to compare the image quality of multisegment and halfscan reconstructions of multislice computed tomography (MSCT) coronary angiography. 126 patients with suspected coronary artery disease and uninfluenced heart rates were examined by 16-slice CT before they underwent invasive coronary angiography. Multisegment and halfscan reconstructions were performed in all patients, and subjective image quality, overall vessel length, vessel length free of motion artefacts and contrast-to-noise ratios (CNRs) were compared for both techniques. The diagnostic accuracy of both approaches was compared with the results of invasive coronary angiography. Overall image quality scores of multisegment reconstruction were superior to those of halfscan reconstruction (13.3±2.1 vs 11.9±2.9; p<0.001). Multisegment reconstruction depicted significantly longer overall coronary vessel lengths (p<0.001) and larger vessel proportions free of motion artefacts in three of the four main coronary arteries. CNRs in the left main, left anterior descending and left circumflex coronary arteries were significantly higher when multisegment reconstruction was used (p<0.001). Overall accuracy was higher for multisegment reconstruction compared with halfscan reconstruction (87% vs 62%). In conclusion, multisegment reconstruction significantly improves image quality and diagnostic accuracy of MSCT coronary angiography compared with standard halfscan reconstruction, resulting in vessel lengths depicted free of motion comparable to those of CT performed in patients given β-blockers to lower heart rates.Non-invasive coronary angiography is an alternative approach to conventional coronary angiography in patients with suspected coronary artery disease (CAD) with high clinical [1–4] and economic [5] relevance. Recently, multislice computed tomography (MSCT) has developed into the most reliable non-invasive method for imaging of the whole coronary artery tree [6]. The susceptibility of MSCT to motion artefacts can only be overcome by systematic pre-scan β-blockade to lower heart rates to target values below 65 beats per minute (bpm). Recent studies have shown that β-blocker administration is necessary even on 64-slice scanners [4, 7–11]. Motion artefacts result from a relatively long acquisition window, which is determined by the gantry rotation time in standard halfscan reconstruction. In contrast, multisegment reconstruction [12] reduces the acquisition time by using up to four different segments from up to four consecutive heart beats [13]. In this way, an acquisition window as short as one-eighth of the gantry rotation time can be achieved [14]. In a small retrospective study of 34 patients with suspected CAD, multisegment reconstruction showed superior image quality and diagnostic accuracy compared with halfscan reconstruction. Based on these results, it was suggested that there is no need for β-blocker administration when multisegment reconstruction is used [15]. However, a recently published subgroup analysis of patients with different heart rates showed that image quality and diagnostic performance of multisegment reconstruction varied with heart rate [16]. Therefore, the use of β-blockers was recommended in patients with heart rates above 75 bpm when using multisegment reconstruction.In this study, we analysed prospectively the overall image quality and diagnostic accuracy of multisegment reconstruction compared with halfscan reconstruction in a large consecutive group of patients with uninfluenced heart rates to determine whether systematic β-blockade is needed.     

Iron overload: accuracy of in-phase and out-of-phase MRI as a quick method to evaluate liver iron load in haematological malignancies and chronic liver disease

Objectives

The purpose of this prospective study was to evaluate the accuracy of in-phase and out-of-phase imaging to assess hepatic iron concentration in patients with haematological malignancies and chronic liver disease.

Methods

MRI-based hepatic iron concentration (M-HIC, μmol g^–1) was used as a reference standard. 42 patients suspected of having iron overload and 12 control subjects underwent 1.5 T in- and out-of-phase and M-HIC liver imaging. Two methods, semi-quantitative visual grading made by two independent readers and quantitative relative signal intensity (rSI) grading from the signal intensity differences of in-phase and out-of-phase images, were used. Statistical analyses were performed using the Spearman and Kruskal–Wallis tests, receiver operator curves and κ coefficients.

Results

The correlations between M-HIC and visual gradings of Reader 1 (r=0.9534, p<0.0001) and Reader 2 (r=0.9456, p<0.0001) were higher than the correlations of the rSI method (r=0.7719, p<0.0001). There was excellent agreement between the readers (weighted κ=0.9619). Both visual grading and rSI were similar in detecting liver iron overload: rSI had 84.85% sensitivity and 100% specificity; visual grading had 85% sensitivity and 100% specificity. The differences between the grades of visual grading were significant (p<0.0001) and the method was able to distinguish different degrees of iron overload at the threshold of 151 μmol g^–1 with 100% positive predictive value and negative predictive value.

Conclusion

Detection and grading of liver iron can be performed reliably with in-phase and out-of-phase imaging. Liver fat is a potential pitfall, which limits the use of rSI.Iron overload is a clinically recognised condition with variety of aetiologies and clinical manifestations [1-4]. Liver iron concentration correlates closely with the total body iron stores [5]. The excess iron accumulates mainly in the liver and the progressive accumulation of toxic iron can lead to organ failure if untreated [2,4]. Several diseases causing iron overload, such as transfusion-dependent anaemia, haematological malignancies, thalassaemia, haemochromatosis and chronic liver disease, result in a large number of patients with a potentially treatable iron overload [1,2,4].Several quantitative MRI methods for iron overload measurement by multiple sequences have been established, such as proportional signal intensity (SI) methods and proton transverse relaxation rates (R₂, R₂*) [4,6,7]. A gradient echo liver-to-muscle SI-based algorithm [8] has been widely validated and used for quantitative liver iron measurement [8-11]. MRI-based hepatic iron concentration (M-HIC, μmol g^–1 liver dry weight) with corresponding R₂* [9] can be calculated with this method which is a directly proportional linear iron indicator, virtually independent of the fat fraction, as the echo times are taken in-phase [8,9]. This method showed a high accuracy in calibrations with the biochemical analysis of liver biopsies (3–375 μmol g^–1) of 174 patients. The mean difference of 0.8 μmol g^–1 (95% confidence interval of –6.3 to 7.9) between this method and the biochemical analysis is quite similar [8] to the intra-individual variability found in histological samples [12].The quantitative MRI methods are based on progressive SI decay, with the longer echo times due to relaxing properties of iron. Interestingly, this iron-induced effect is seen in MR images with multiple echoes [4,6-11], but also in dual-echo images, namely in-phase and out-of-phase imaging [13,14]. In-phase and out-of-phase imaging has become a routine part of liver MRI, performed initially for liver fat detection [6,13,15]. Quite recently some investigators have noticed an alternative approach of the sequence to detect liver iron overload due to the more pronounced SI decrease on in-phase images with the longer echo time [13,14]. Yet, to our knowledge, this is the first prospective study evaluating the accuracy of in-phase and out-of-phase imaging to assess hepatic iron concentration.The purpose of the study was to evaluate the capability and accuracy of dual-echo in-phase and out-of-phase imaging to assess hepatic iron concentration at 1.5 T in patients with haematological malignancies and chronic liver disease. MRI-based hepatic iron concentration (M-HIC, μmol g^–1) was used as a reference standard [8,9].     

Prognostic factors associated with a subchondral insufficiency fracture of the femoral head

Objective

The aim of this study was to identify the risk factors associated with the prognosis of a subchondral insufficiency fracture of the femoral head (SIF).

Methods

Between June 2002 and July 2009, 25 patients diagnosed with SIF were included in this study. Sequential radiographs were evaluated for the progression of collapse. Clinical profiles, including age, body mass index, follow-up period and Singh’s index, were documented. The morphological characteristics of the low-intensity band on T₁ weighted MRI were also examined with regards to four factors: band length, band thickness, the length of the weight-bearing portion and the band length ratio (defined as the proportion of the band length to the weight-bearing portion of the femoral head in the slice through the femoral head centre).

Results

Radiographically, a progression of collapse was observed in 15 of 25 (60.0%) patients. The band length in patients with progression of collapse [22.5 mm; 95% confidence interval (CI) 17.7, 27.3] was significantly larger than in patients without a progression of collapse (13.4 mm; 95% CI 7.6, 19.3; p<0.05). The band length ratio in patients with progression of collapse (59.8%; 95% CI 50.8, 68.9) was also significantly higher than in patients without a progression of collapse (40.9%; 95% CI 29.8, 52.0; p<0.05). No significant differences were present in the other values.

Conclusion

These results indicate that the band length and the band length ratio might be predictive for the progression of collapse in SIF.Subchondral insufficiency fractures of the femoral head (SIF) often occur in osteoporotic elderly patients [1-9]. Patients usually suffer from acute hip pain without any obvious antecedent trauma. Radiologically, a subchondral fracture is seen primarily in the superolateral portion of the femoral head [4,5,10]. T₁ weighted MRI reveal a very low-intensity band in the subchondral area of the femoral head, which tends to be irregular, disconnected and convex to the articular surface [2,4,5,7,9,11]. This low-intensity band in SIF was histologically proven to correspond with the fracture line and associated repair tissue [5,9]. Some cases of SIF resolve after conservative treatment [5,11-14]; other cases progress until collapse, thereby requiring surgical treatment [4-10,15]. The prognosis of SIF patients remains unclear.The current study investigated the risk factors that influence the prognosis of SIF based on the progression to collapse.     

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.     

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.     

Correlation between computerised findings and Newman's scaling on vascularity using power Doppler ultrasonography imaging and its predictive value in patients with plantar fasciitis

Objectives

The purpose of this study was to correlate findings on small vessel vascularity between computerised findings and Newman''s scaling using power Doppler ultrasonography (PDU) imaging and its predictive value in patients with plantar fasciitis.

Methods

PDU was performed on 44 patients (age range 30–66 years; mean age 48 years) with plantar fasciitis and 46 healthy subjects (age range 18–61 years; mean age 36 years). The vascularity was quantified using ultrasound images by a customised software program and graded by Newman''s grading scale. Vascular index (VI) was calculated from the software program as the ratio of the number of colour pixels to the total number of pixels within a standardised selected area of proximal plantar fascia. The 46 healthy subjects were examined on 2 occasions 7–10 days apart, and 18 of them were assessed by 2 examiners. Statistical analyses were performed using intraclass correlation coefficient and linear regression analysis.

Results

Good correlation was found between the averaged VI ratios and Newman''s qualitative scale (ρ = 0.70; p<0.001). Intratester and intertester reliability were 0.89 and 0.61, respectively. Furthermore, higher VI was correlated with less reduction in pain after physiotherapeutic intervention.

Conclusions

The computerised VI not only has a high level of concordance with the Newman grading scale but is also reliable in reflecting the vascularity of proximal plantar fascia, and can predict pain reduction after intervention. This index can be used to characterise the changes in vascularity of patients with plantar fasciitis, and it may also be helpful for evaluating treatment and monitoring the progress after intervention in future studies.Plantar fasciitis is the most common cause of heel pain, and about 2 000 000 patients in the USA receive treatment every year because of this condition [1]. Besides mechanical loading, vascular disturbance with consequent metabolic impairment and hypoxia is thought to play an important role [2]. Indeed, fibrovascular hyperplasia and vascular proliferation were observed from microscopic specimens obtained from operative resection [3-5]. Walther et al [6] were the first group to evaluate plantar fascia vascularity non-invasively using power Doppler ultrasonography (PDU).PDU is one of the colour flow imaging techniques that encodes the amplitude of the power spectral density of the Doppler signals [7]. This method has been used to assess soft-tissue vascularity and treatment efficacy with a variety of musculoskeletal and related problems. Changes in vascularity in synovial tissues in patients with rheumatoid arthritis [8-11], osteoarthritis [12,13], tendinopathy [6,14-21] and plantar fasciitis [6] have been reported. Modulation in vascularity was observed in patients with tendinopathy after a course of intervention [14-21]. Most of these studies used the Newman''s grading scale to grade the tissue vascularity [19-21]. This qualitative grading for the PDU images had high correlation with the histopathological grading of vascularity of the synovial membrane in patients with arthritis [11]. Nevertheless, Newman''s grading system may not be objective and sensitive enough to differentiate subtle vascularity changes.Recently, computerised methods were used to quantify tissue vascularity with ultrasonography. Tissue vascularity was quantified by computing a vascular index (VI), which is calculated as the ratio of the number of colour pixels to the total number of pixels within the region of interest in patients with soft-tissue problems [8,9,11,17]. Note that most of these studies were conducted using colour Doppler ultrasonography. In this connection, PDU is superior to frequency-based colour Doppler ultrasonography, especially in tissues with low blood flow, such as the plantar fascia [6,22,23]. Ying et al [24] reported the feasibility of computerised quantification of vascularity in thyroid tissues with PDU. We were interested in evaluating whether the computerised quantification of vascularity could be applied on musculoskeletal tissue, such as the plantar fascia. Therefore, the purpose of the present study was to correlate the computerised VI and Newman''s qualitative grading scale in quantifying plantar fascia vascularity using PDU, to evaluate the intra- and intertester reliability of the computerised quantitative method and its predictive ability of recovery in patients with plantar fasciitis. Proximal plantar fascia, which is the most commonly affected area in individuals with plantar fasciitis, according to clinical examination [25,26] and previous B-mode ultrasonography [26-28], was chosen as the target testing area.     

Quality assurance of dynamic parameters in volumetric modulated arc therapy

Objectives

The purpose of this study was to demonstrate quality assurance checks for accuracy of gantry speed and position, dose rate and multileaf collimator (MLC) speed and position for a volumetric modulated arc treatment (VMAT) modality (Synergy® S; Elekta, Stockholm, Sweden), and to check that all the necessary variables and parameters were synchronous.

Methods

Three tests (for gantry position–dose delivery synchronisation, gantry speed–dose delivery synchronisation and MLC leaf speed and positions) were performed.

Results

The average error in gantry position was 0.5° and the average difference was 3 MU for a linear and a parabolic relationship between gantry position and delivered dose. In the third part of this test (sawtooth variation), the maximum difference was 9.3 MU, with a gantry position difference of 1.2°. In the sweeping field method test, a linear relationship was observed between recorded doses and distance from the central axis, as expected. In the open field method, errors were encountered at the beginning and at the end of the delivery arc, termed the “beginning” and “end” errors. For MLC position verification, the maximum error was −2.46 mm and the mean error was 0.0153 ±0.4668 mm, and 3.4% of leaves analysed showed errors of >±1 mm.

Conclusion

This experiment demonstrates that the variables and parameters of the Synergy® S are synchronous and that the system is suitable for delivering VMAT using a dynamic MLC.The concept of volumetric modulated arc therapy (VMAT) has been described in many studies [1-5]. VMAT is a system for intensity-modulated radiotherapy treatment (IMRT) delivery that achieves high dose conformity by optimising the dose rate, gantry speed and leaf positions of the dynamic multileaf collimator (MLC) [6]. One study [5] demonstrated quality assurance (QA) checks using dynamic MLC controller log files (Dynalog) for VMAT systems such as RapidArc® (Varian Medical Systems Inc., Palo Alto, CA). It is assumed that the actual delivery process is truly represented in the log files [6]. The major disadvantage of this method is that Dynalog files need to be validated against an independent system. The electronic portal imaging device (EPID) is a dependable system when corrections are made for systematic tilts and shifts [7,8] and when image sagging due to gantry angle [9] has been taken into account. A significant number of researchers have investigated MLC QA by film or EPID [7-13] to measure the accuracy of the MLC controller independently and ensure that the MLC edge positions agree with the radiation field edges to within 0.3 mm [14]. EPID measurements are highly reproducible, with a standard deviation of <0.1 mm for individual leaf/collimator positions and <0.05 mm for a 10×10 cm² field [7]. Few studies [15-17] have demonstrated commissioning, QA and patient-specific QA for VMAT using both the RapidArc and the Synergy® S (Elekta, Stockholm, Sweden) systems. The purpose of this study was to demonstrate QA checks for accuracy of gantry speed and position, dose rate, MLC leaf speed and MLC position, and to ensure that all the necessary variables and parameters were synchronous. These simple tests were designed to fulfil the requirements and limits recommended by the American Association of Physicists in Medicine (AAPM) for the clinical implementation of IMRT [18] and a recent recommendation by AAPM task group 142 (TG-142) [19] for the QA of medical accelerators.     

Beam angle manipulation to reduce cardiac dose during breast radiotherapy

Objective

Standard tangential radiotherapy techniques after breast conservative surgery (BCS) often results in the irradiation of the tip of the left ventricle and the left anterior descending coronary artery (LAD), potentially increasing cardiovascular morbidity. The importance of minimising radiation dose to these structures has attracted increased interest in recent years. We tested a hypothesis that in some cases, by manipulating beam angles and accepting lower-than-prescribed doses of radiation in small parts of the breast distant from the surgical excision site, significant cardiac sparing can be achieved compared with more standard plans.

Methods

A sample of 12 consecutive patients undergoing radiotherapy after left-sided BCS was studied. All patients were planned with a 6 MV tangential beam, beam angles were manipulated carefully and if necessary lower doses were given to small parts of the breast distant from the surgical excision site to minimise cardiac irradiation (“institutional” plan). Separate “hypothetical standard” plans were generated for seven patients using set field margins that met published guidelines.

Results

In seven patients, the institutional plans resulted in lower doses to the LAD and myocardium than the hypothetical standard plans. In the other five patients, LAD and myocardial doses were deemed minimal using the hypothetical standard plan, which in these patients corresponded to the institutional plan (the patients were actually treated using the institutional plans).

Conclusion

Much attention has been devoted to ways of minimising cardiac radiation dose. This small sample demonstrates that careful manipulation of beam angles can often be a simple, but effective technique to achieve this.Late cardiovascular morbidity associated with breast irradiation has received considerable attention recently, especially as diagnostic and therapeutic advances have translated into improvements in long-term survival [1].Most invasive breast cancers are discovered at an early localised stage and can be treated with breast conservation surgery (BCS) and adjuvant radiotherapy with equivalent survival rates to mastectomy [2-4]. Whole-breast radiation therapy conventionally uses tangential beam arrangements, which include the entire breast, a portion of the chest wall and some contents of the anterior thoracic cavity. In left-sided breast irradiation, the field can include a significant volume of the heart. The mean cardiac dose from left-sided breast irradiation can be two or three times that of right-sided breast irradiation. In women treated in the 1950s to 1990s, it has been estimated that the mean cardiac dose was 0.9–14 Gy and 0.4–6 Gy for left and right breast/chest wall irradiation, respectively [5]. Using 6 MV tangential radiotherapy, the mean cardiac doses were 4.7 Gy and 1.5 Gy, and the mean left anterior descending coronary artery (LAD) doses were 21.9 Gy and 1.4 Gy for left and right breast irradiation, respectively [5].In a meta-analysis by the Early Breast Cancer Trialists'' Collaborative Group that included 78 randomised trials of breast or chest wall irradiation after surgery, there was an excess of non-breast cancer deaths owing to heart disease and lung cancer [6]. A population study showed that the cardiac mortality is 25% higher among women treated for left-sided breast tumours than those treated for right-sided tumours 15 years after treatment [7]. In another study of women irradiated between 1973 and 1982, the cardiac mortality ratio (left vs right breast cancer) was 1.42 after 10–14 years and 1.58 after 15 years [8].Cardiovascular toxicity associated with radiation includes coronary artery disease, valvular disease, chronic pericardial disease, arrhythmia and conduction disturbances, and cardiomyopathy [9,10]. The exact mechanism of radiation-related heart disease and the threshold dose at which damage to the heart caused by radiation occurs is still unclear, which stresses the importance of striving to minimise the dose to the heart and the volume irradiated whenever possible. A review of some of the experiments investigating coronary artery disease after radiation has suggested that radiation increases myocardial infarction (MI) frequency by interacting with the pathological pathway of age-related coronary artery atherosclerosis resulting in accelerated atherosclerosis [10]. Radiation could also increase lethality of age-related MI by reducing the heart''s tolerance to acute infarctions as a result of microvascular myocardial damage [10].There is a correlation between cardiac perfusion defects and the volume of irradiated left ventricle; the defects becoming evident when 6% of the ventricle is irradiated by greater than 23–25 Gy [11]. A cardiac catheterisation study showed that there was an excess of cardiac stress test abnormalities among left-side irradiated patients; these were located in the anterior heart, which is most at risk in the tangential field and with 85% of abnormalities occur as stenoses of the LAD [12]. In a study of 50 patients treated with left tangential irradiation, the mean heart dose was 2.3 Gy and the mean LAD dose was 7.6 Gy [13]. A dosimetric study of 20 patients who had left-sided breast radiotherapy found that standard tangential radiotherapy resulted in a mean dose of 2.9 Gy to the heart, 12.05 Gy to the proximal LAD, 31.52 Gy to the distal LAD and a V₃₀ (the volume receiving more than 30 Gy) of 23.09±28.37% for the proximal LAD and 45.43±42.5% for the distal LAD [14].As patients with early breast cancer have an increasingly good prognosis, consideration of long-term effects such as cardiac toxicity and resulting complications is necessary when planning post-operative radiotherapy. It usually takes 10 years for radiation-related coronary artery disease and cardiac deaths to become apparent after breast irradiation [15]. However, it has been highlighted that delineation of anatomical subregions of the irradiated heart and LAD is challenging because it is difficult to accurately visualise these structures using current imaging modalities used in treatment planning [16].Since the 1970s, it has been estimated that left chest wall/breast tangential radiotherapy-associated heart dose has reduced from 14 Gy with 250 kV to 4.7 Gy with cobalt-60, to 2.3 Gy with CT planned 6 MV photons [13,17]. However, with the increased use of anthracyclines, taxanes and trastuzumab there may be a potential increase in cardiac toxicity in the future. The literature review on radiation dose–volume effect on the heart did not show a clear quantitative dose and/or volume dependence for cardiac toxicity owing to scarcity of data [16]. As mentioned previously, this highlights the importance of minimising both the dose to these structures and the volume being irradiated as much as possible. There has been considerable interest in developing modern technology for radiotherapy planning to avoid excess cardiac irradiation, by modulation of the dose around organs at risk (OAR) using intensity modulated radiotherapy (IMRT) [18,19], IMRT with simultaneously integrated boost [20], placement of heart blocks [21] and deep inspiratory breath-holding (DIBH) and gated techniques [22-25]. Beam angle modulation remains a very simple, and, up until now, rather neglected way of achieving this outcome.We hypothesised that in some cases, in comparison with “standard” plans, beam angle manipulation to reduce the dose to the LAD and the heart, while accepting lower-than-prescribed doses in small parts of the breast distant from the site of surgical excision, could lead to significant cardiac and LAD sparing without compromising the dose delivered to the “high-risk” part of the breast. This was done using dose–volume histograms (DVHs) of breast tissue, myocardium and LAD, taken from actually used plans, and “hypothetical standard” plans (see Methods and Materials for definition) in a series of our patients.     

Application of prospective ECG-triggered dual-source CT coronary angiography for infants and children with coronary artery aneurysms due to Kawasaki disease

Objectives

The aim of this study was to prospectively evaluate the initial application and value of prospective electrocardiogram (ECG)-triggered dual-source CT coronary angiography (DSCTCA) in the diagnosis of infants and children with coronary artery aneurysms due to Kawasaki disease.

Methods

19 children [12 males; mean age 13.47 months, range 3 months to 5 years; mean heart rate 112 beats per minute (bpm), range 83–141 bpm] underwent prospective ECG-triggered DSCTCA with free breathing. Subjective image quality was assessed on a five-point scale (1, excellent; 5, non-diagnostic) by two blinded observers. The location, number and size of each aneurysm were observed and compared with those of transthoracic echocardiography (TTE) performed within 1 week. Interobserver agreement concerning the subjective image quality was evaluated with Cohen''s κ-test. Bland–Altman analysis was used to evaluate the agreement on measurements (diameter and length of aneurysms) between DSCTCA and TTE. The average effective dose required for DSCTCA was calculated for all children.

Results

All interobserver agreement for subjective image quality assessment was excellent (κ=0.87). The mean±standard deviation (SD) aneurysm diameter with DSCTCA was 0.76±0.36 cm and with TTE was 0.76±0.39 cm. The mean±SD aneurysm length with DSCTCA was 2.06±1.35 cm and with TTE was 2.00±1.22 cm. The Bland–Altman plot for agreement between DSCTCA and TTE measurements showed good agreement. The mean effective dose was 0.36±0.06 mSv.

Conclusion

As an alternative diagnostic modality, prospective ECG-triggered DSCTCA with excellent image quality and low radiation exposure has been proved useful for diagnosing infants and children with coronary artery aneurysms due to Kawasaki disease.

Advances in knowledge

Prospective ECG–triggered DSCTCA for infants and children allows rapid, accurate assessment of coronary aneurysms due to Kawasaki diseases, compared with TTE.Kawasaki disease (KD), also known as mucocutaneous lymph node syndrome, is an autoimmune vasculitis in which the small and medium vessels throughout the body become inflamed [1,2]. It predominantly occurs in infants and children (younger than 5 years old). It affects many organ systems; injury, such as aneurysm, dilation, ectasia, stenosis and embolism, to the heart is rare but serious, and fatal myocardial infarction can be induced in untreated cases [3-6]. It is crucial to detect coronary artery lesions at an early stage [7]. Diagnosis of KD is based on clinical signs, symptoms and laboratory findings, but no specific laboratory test exists and it is hard to establish the diagnosis, especially in the early course [8].Recently, multidetector CT, especially the advent of dual-source CT, has provided improved spatial and temporal resolution; moreover, multiple techniques on dose reduction have been applied in children. Electrocardiogram (ECG)-gated scans, especially retrospective ECG-gated scans, have been used to evaluate coronary artery lesions in children with KD [2,9]. The high radiation dose required remains the main concern [10]; even though dose-saving methods including low tube potential, tube current modulation and body size-adapted CT protocols have been adopted, the effective radiation dose is still high at up to 2.17–3.14 mSv [11-13].Recently, prospective ECG-triggered scans were considered to be the most promising approach for dose reduction as they were used in the assessment of cardiovascular deformities in children with congenital heart disease [14-17]; however, no further studies have been reported on the application of prospective ECG-triggered CT angiography in children with KD.The aim of this study was to evaluate the initial application of prospective ECG-triggered dual-source CT coronary angiography (DSCTCA) in infants and children with coronary artery aneurysms due to KD.     

320-detector row CT coronary angiography: effects of heart rate and heart rate variability on image quality, diagnostic accuracy and radiation exposure

Objectives

To evaluate the effects of heart rate and heart rate variability on image quality, patient dose and diagnostic accuracy of 320-detector row CT.

Methods

94 patients were prospectively enrolled. Heart rate was defined as the mean value of different intervals elapsing between two consecutive R waves in an electrocardiogram (R–R intervals) and the heart rate variability was calculated as the standard deviation from the average heart rate. The image quality was evaluated by four grades, according to motion artefacts (“step artefacts” and “blurring artefacts”). The diagnostic accuracy was analysed in 43 patients who were scheduled for invasive coronary angiography (ICA). The coeffects of heart rate and heart rate variability on image quality, radiation dose and diagnostic accuracy were evaluated by multivariate regression.

Results

The mean image quality score was 1.2±0.5 and the mean effective dose was 14.8±9.8 mSv. The results showed that heart rate (74.0±11.2 beats per minute) was the single factor influencing image quality (p<0.001) and radiation dose (p<0.001), while heart rate variability (3.7±4.6) had no significant effect on them (p=0.16 and p=0.47, respectively). For 43 patients who underwent ICA, heart rate and heart rate variability showed no influence on the accuracy (p=0.17 and p=0.12, respectively). Overall sensitivity was 97.4% (37/38), specificity was 99.4% (351/353), positive predictive value was 94.9% (37/39) and negative predictive value was 99.7% (351/352).

Conclusion

320-detector row CT, with improved longitudinal coverage of detector, resolves step artefact and high patient dose caused by irregular heart rate. However, it is still recommended to control heart rate to a lower level to eliminate blurring artefact and radiation dose.As the clinical application of 4-detector CT to scan the coronary arteries by a non-invasive procedure, CT coronary angiography has emerged as an attractive, diagnostic modality for detecting coronary artery disease. However, motion artefact by rapid movement throughout the cardiac cycle and blooming artefact caused by calcified plaque represent the major challenges for artefact-free coronary CT angiography. Generally, “step artefacts” and “blurring artefacts” are two kinds of motion artefact influencing the quality of coronary artery image. To improve image quality, CT scanners with higher spatial resolution, temporal resolution and wider detector array were developed.The Discovery™ CT750 HD (GE Healthcare, Waukesha, WI) improves spatial resolution and decreased calcium blooming artefact significantly [1]. Dual-source CT (DSCT), with two X-ray sources and a temporal resolution of 83 ms, has improved blurring artefacts caused by high heart rate (HR) [2-4]. Nevertheless, as the coverage of the detectors is limited, step artefacts caused by heart rate variability (HRv) is still an inverse factor influencing the image quality [2,3]. Just as the improved temporal resolution should resolve the problem of high HR, the longitudinal coverage of the detector should be expanded further to resolve the influence of HRv [5-8]. 320-detector row dynamic volume CT (DVCT) can cover the whole heart within one heartbeat, which enables DVCT to have the potential to resolve the impact of HRv [9].A previous study has shown that DVCT reliably provides high diagnostic accuracy without HR control [9]. The aim of our study was to evaluate the influence of degree of HR and HRv on image quality, radiation dose and diagnostic accuracy in patients undergoing DVCT.     

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.     

Diagnostic quality of 50 and 100 μm computed radiography compared with screen-film mammography in operative breast specimens

Objective

To compare reader ratings of the clinical diagnostic quality of 50 and 100 μm computed radiography (CR) systems with screen–film mammography (SFM) in operative specimens.

Methods

Mammograms of 57 fresh operative breast specimens were analysed by 10 readers. Exposures were made with identical position and compression with three mammographic systems (Fuji 100CR, 50CR and SFM). Images were anonymised and readers blinded to the CR system used. A five-point comparative scoring system (−2 to +2) was used to assess seven quality criteria and overall diagnostic value. Statistical analysis was subsequently performed of reader ratings (n=16 925).

Results

For most quality criteria, both CR systems were rated as equivalent to or better than SFM. The CR systems were significantly better at demonstrating skin edge and background tissue (p<1×10⁻⁵). Microcalcification was best demonstrated on the CR50 system (p<1×10⁻⁵). The overall diagnostic value of both CR systems was rated as being as good as or better than SFM (p<1×10⁻⁵).

Conclusion

In this clinical setting, the overall diagnostic performance of both CR systems was as good as or better than SFM, with the CR50 system performing better than the CR100.There are currently three technologies widely available for diagnostic mammography: screen–film mammography (SFM) and two forms of large-field digital mammography [1]. The use of the term full-field digital mammography (FFDM) varies in the published literature and has been applied to both computed radiography (CR) and direct digital radiography (DR). Small-field digital mammography (SFDM) is mainly used for imaging during stereotactic biopsy [2].The advantages of digital mammography over SFM include: improved sensitivity in dense breast tissue, reduced radiation dose, the ability to manipulate images for review, and digital storage and retrieval methods [3]. CR was the earliest digital system in use. Imaging cassettes contain a re-useable photostimulable phosphor, replacing the traditional screen–film cassettes, and are then transferred to a laser reader. DR has an in-built detector and reader. Digital mammography has a lower spatial resolution than SFM, but has a very high contrast resolution. This allows the overall resolution of digital mammography to be at least equivalent to SFM [4-8], even when viewing calcification smaller than the pixel size [9]. Some CR systems have not met the quality standards of a number of governing bodies for mammography, including the European Network of Reference Assessment Centres (EUREF) and the NHS Breast Screening Programme (NHSBSP) [10,11]. This is related to the resolution achievable with 100 µm cassettes [12]. It is now known that CR systems using 50 µm cassettes can provide improved resolution, at an acceptable mean glandular dose, and have been approved for screening by the NHSBSP [13-15].Phantom studies indicate that the resolution and performance of DR are greater than those of CR [16,17], but have limitations. Although there are many clinical studies comparing the performance of DR and SFM [4-7,9,18-26], there are fewer that compare CR with SFM or DR [8,25,27-32]. We sought a method to compare the clinical diagnostic quality of two types of CR technology with that of SFM. We chose to study surgical specimens of breast tissue, which, although not absolutely comparable to in vivo mammography, allows realistic testing of image quality. In addition, multiple exposures can be obtained in reproducible conditions without irradiating the patient.     

MRI features of serous oligocystic adenoma of the pancreas: differentiation from mucinous cystic neoplasm of the pancreas

Objectives

The purpose of this study was to describe the MRI features of the benign pancreatic neoplasm serous oligocystic adenoma (SOA) that differ from those of mucinous cystic neoplasm (MCN), a neoplasm with the potential for malignant degeneration.

Methods

Seven patients with SOA (seven women; mean age 36.6 years) and eight patients with MCN (eight women: mean age 39.9 years) were included. Several imaging features were reviewed: mass size, location, shape, wall thickness, cyst configuration (Type I, unilocular; Type II, multiple clustered cyst; Type III, cyst with internal septation) and signal intensity of the lesion with heterogeneity.

Results

SOA lesions were smaller (3.4 cm) than those of MCN (9.3 cm) (p=0.023). The commonest lesion shape was lobulated (85.7%) for SOA, but oval (50.0%) or lobulated (37.5%) for MCN (p=0.015). The most common cyst configuration was Type II (85.7%) for SOA and Type III (75.0%) for MCN (p=0.008). Heterogeneity of each locule in T₁ weighted images was visible in all cases of MCN, but in no case for SOA (p=0.004).

Conclusion

SOA could be differentiated from MCN by identifying the imaging features of lobulated contour with multiple clustered cyst configurations and homogeneity of each locule in T₁ weighted MR images.Serous oligocystic adenoma (SOA) is a recently described rare, benign pancreatic neoplasm and a morphological variant of serous microcystic adenoma, because it contains six or fewer cysts and the cysts are large (>2 cm) [1,2]. Pathologically, SOA is a benign pancreatic neoplasm composed of a few relatively large cysts uniformly lined with glycogen-rich cuboidal epithelial cells [3]. According to the World Health Organization classification, SOA is a subgroup of pancreatic serous cystic tumours and the term SOA is a synonym for macrocystic serous cystadenoma [3,4].The CT and MRI features of SOA of the pancreas are documented [2]. On CT and MRI, SOA typically appears as a small unilocular or bilocular cyst (<5 cm) with a thin wall (<2 mm) that lacks mural nodules or calcifications [2]. Because the cystic spaces are >2 cm, SOA images can be mistaken for mucinous cystic neoplasm (MCN), pseudocyst or intraductal papillary mucinous tumour [2,5-7]. It is very difficult to differentiate SOA from MCN by clinical and radiological features [2,6,8,9]. SOA does not require resection unless it causes symptoms, but MCN should be resected because of a potential for malignant degeneration [5,7,8]. Endoscopic ultrasound and cyst fluid aspiration have a role in distinguishing mucinous and serous lesions, but it is an invasive procedure with a risk of complications such as pancreatitis [10]. Therefore, it is clinically valuable to determine characteristic imaging findings that can distinguish SOA from MCN.Recently, Kim et al [6] and Cohen-Scali et al [5] described characteristic CT findings that can be used to differentiate SOA from MCN. MRI can demonstrate septa within a lesion with greater sensitivity than CT; therefore, MRI provides a better evaluation of tissue characteristics than CT [1,11]. However, few studies have described the MRI features of SOA [1,2]. The purpose of this study was to describe the differences in the MRI features of SOA and MCN in the pancreas.     

Contrast-enhanced ultrasonography of hepatocellular carcinoma: correlation between quantitative parameters and histological grading

Objective

The quantitative parameters in the contrast-enhanced ultrasonography time–intensity curve of hepatocellular carcinoma (HCC) were studied to explore their possible implication for histological grading of HCC.

Methods

A total of 130 HCC patients (115 males and 15 females; age: 48.13±11.00 years) were studied using contrast-enhanced ultrasonography time–intensity curve and histological pathology. The quantification software Sonoliver® (TomTec Imaging Systems, Unterschleissheim, Germany) was applied to derive time–intensity curves of regions of interest in the interior of HCCs and in reference. Quantitative parameters of 115 patients were successfully obtained, including maximum of intensity (IMAX), rise time (RT), time to peak (TTP), rise slope (RS) and washout time (WT). Histological grading of HCC was performed using haematoxylin–eosin staining, and monoclonal antibodies specific for smooth muscle actin were used to observe unpaired arteries (UAs).

Results

There were significant differences among WTs in the three differentiated HCC groups (p<0.05). However, there were no significant differences among RT, TTP, RS and IMAX in the differentiated HCC groups. Moreover, the number of UAs in the differentiated HCC groups showed no statistical significance.

Conclusion

WT plays an important role in predicting well, moderately and poorly differentiated HCC.The majority of hepatocellular carcinomas (HCCs) develop through multistep hepatocarcinogenesis [1]. Various types of hepatocellular nodules are seen in cirrhotic livers. The International Working Party of the World Congress of Gastroenterology classifies hepatocellular nodules into six types: regenerative nodules, low-grade dysplastic nodules, high-grade dysplastic nodules, well-differentiated HCC, moderately differentiated HCC and poorly differentiated HCC. The histopathological grades and types constitute well-established prognostic factors [2]. Thus, early diagnosis and confirmation of the type of hepatocellular nodules present and cellular differentiation before treatment are important.Although definite differentiation among HCC by imaging is usually impossible, the relationship between tumour cellular differentiation and image findings has been studied using contrast-enhanced (CE) CT, CEMRI and CE ultrasonography (CEUS). Tumour pathological differentiation correlates well with image findings [,3−8].Dynamic CEUS during the past decade has noticeably improved the detection and characterisation of focal liver lesions [9]. A previous study showed that CEUS and spiral CT provided a similar diagnostic accuracy in the characterisation of focal liver lesion [10]. The appearance of HCC on CEUS has also been described well. Current low-mechanical-index techniques for CEUS using second-generation microbubble agents have advantages in characterising HCC, including real-time demonstration of continuous haemodynamic changes in both the liver and hepatocellular nodules. Some studies postulated that variations of enhancement patterns may be related to the pathological function of HCC [,5−8]. Moderately differentiated HCCs generally show classic enhancement features, with presence of hypervascularity in the arterial phase and washout during the portal phase, whereas well and poorly differentiated tumours account for most atypical variations in the arterial phase and portal venous phase [7].Reports assessing hepatocellular nodules have been based on visual analysis, despite the disadvantages of interobserver variability and low reproducibility of results. Although quantitative analysis CEUS perfusion provides more objective, reliable and reproducible results [11], the time–intensity curve (TIC) of CEUS has been obtained by quantification software for offline analysis [,12−14], from which a series of semi-quantitative perfusion parameters is extracted and analysed. An analysis of the parameters of TIC in HCC has proven the correlation of CEUS with unpaired arteries (UAs) in HCC [14]. In the present study, we compare the quantitative parameters in CEUS and UAs in different pathological gradings of HCCs to explore their possible implication for histological grading of HCC.     

Hepatocellular carcinoma in cirrhotic patients at multidetector CT: hepatic venous phase versus delayed phase for the detection of tumour washout

Objectives

Our aim was to compare retrospectively hepatic venous and delayed phase images for the detection of tumour washout during multiphasic multidetector row CT (MDCT) of the liver in patients with hepatocellular carcinoma (HCC).

Methods

30 cirrhotic patients underwent multiphasic MDCT in the 90 days before liver transplantation. MDCT was performed before contrast medium administration and during hepatic arterial hepatic venous and delayed phases, images were obtained at 12, 55 and 120 s after trigger threshold. Two radiologists qualitatively evaluated images for lesion attenuation. Tumour washout was evaluated subjectively and objectively. Tumour-to-liver contrast (TLC) was measured for all pathologically proven HCCs.

Results

48 HCCs were detected at MDCT. 46 of the 48 tumours (96%) appeared as either hyper- or isoattenuating during the hepatic arterial phase subjective washout was present in 15 HCCs (33%) during the hepatic venous phase and in 35 (76%) during the delayed phase (p<0.001, McNemar’s test). Objective washout was present in 30 of the 46 HCCs (65%) during the hepatic venous phase and in 42 of the HCCs (91%) during the delayed phase (p=0.001). The delayed phase yielded significantly higher mean TLC absolute values compared with the hepatic venous phase (−16.1±10.8 HU vs −10.5±10.2 HU; p<0.001).

Conclusions

The delayed phase is superior to the hepatic venous phase for detection of tumour washout of pathologically proven HCC in cirrhotic patients.Multiphasic contrast-enhanced multidetector row CT (MDCT) plays a pivotal role in the diagnostic work-up of cirrhotic patients, who are at increased risk of developing hepatocellular carcinoma (HCC) [1]. Increased enhancement of the tumour compared with the surrounding liver parenchyma during the hepatic arterial phase is the cornerstone for the diagnosis of HCC at multiphasic MDCT [1,2]. However, a variety of entities—dysplastic nodules [3], confluent hepatic fibrosis [4], non-tumourous arterioportal shunts [5] and haemangioma [6]—can also manifest with increased arterial enhancement and thus mimic HCC, particularly if they are smaller than 2 cm in diameter.Tumour washout, i.e. hypoattenuation relative to the adjacent hepatic parenchyma during the hepatic venous or delayed phase, has been recognised as a strong predictor of HCC [7,8]. This sign has been included, along with the presence of hypervascularity, in the latest American Association for the Study of Liver Diseases (AASLD) guidelines for the diagnosis of HCC at multiphasic MDCT, MRI or contrast-enhanced ultrasonography [1]. Although it is well known that tumour enhancement is best visualised during the late hepatic arterial phase [9,10], there is no consensus regarding the correct timing for the detection of tumour washout at multiphasic MDCT of the liver. Most commonly, the hepatic arterial phase is followed by the hepatic venous phase, acquired 60–70 s after injection of contrast material [9-12]. In addition, a delayed phase, acquired from 2–10 min after contrast material injection, can follow the hepatic venous phase [13-20] or can occur alone after the hepatic arterial phase [21-23]. Regardless of the phase sequence chosen, to the best of our knowledge, no study has yet compared the hepatic venous and delayed phases for the detection of tumour washout in patients with HCC. The purpose of our study was to compare retrospectively the hepatic venous and delayed phases for the detection of tumour washout during multiphasic MDCT of the liver in patients with HCC who underwent liver transplantation.