Coronary computed tomography angiography using prospective electrocardiography-gated axial scans with 64-detector computed tomography: evaluation of stair-step artifacts and padding time

Purpose  

We compared stair-step artifacts and radiation dose between prospective electrocardiography (ECG)-gated coronary computed tomography angiography (prospective CCTA) and retrospective CCTA using 64-detector CT and determined the optimal padding time (PT) for prospective CCTA.     

Feasibility of contrast material volume reduction in coronary artery imaging using 320-slice volume CT

Objective  

To assess reduced volumes of contrast agent on image quality for coronary computed tomography angiography (CCTA) by using single-beat cardiac imaging with 320-slice CT.     

Effect of low tube kV on radiation dose and image quality in retrospective ECG-gated coronary CT angiography

IntroductionCoronary computed tomography angiography (CCTA) has emerged as a useful diagnostic imaging modality in the assessment of coronary artery disease. However, the potential risks due to exposure to ionizing radiation associated with CCTA have raised concerns.ObjectivesCCTA can be done with low dose technique to reduce radiation exposure, without compromise of image quality or diagnostic capabilities.Material and methodsForty patients referred for CCTA were examined with low kV (100 kV for patients ?85–61 kg and 80 kV for patients ?60 kg). The dose length product (DLP) were compared with other group (40 patients) with comparable body weight, scan length and acquisition parameters. The second group was selected from PACS database, for which CCTA was done with standard 120 kV.ResultsThere was considerable reduction of radiation dose about 40% with 100 kV and 60% with 80 kV compared to standard 120 kV CCTA protocols with preserved image quality.ConclusionThe use of lower tube voltage leads to significant reduction in radiation exposure in CCTA. Image quality in non-obese patients is not negatively influenced.     

Diagnostic performance of free-breathing coronary computed tomography angiography without heart rate control using 16-cm z-coverage CT with motion-correction algorithm

ObjectivesTo evaluate the feasibility of coronary computed tomography angiography (CCTA) in patients with free-breathing using 16-cm z-coverage CT with motion correction algorithm.Methods616 patients underwent CCTA without heart rate control. 325 examinations were performed during breath-holding (group A), and the remaining 291 were performed during free-breathing (group B). The image quality scores were defined as 1 (excellent), 2 (good), 3 (adequate), and 4 (poor). 22 patients in group A and 24 in group B underwent invasive coronary angiography (ICA) after CCTA within two weeks. The image quality score, diagnostic accuracy using ICA as reference, signal-to-noise ratio (SNR), and effective dose (ED) were compared between the two groups.ResultsMean heart rate during scanning was 70.8 ± 13.8 bpm in group A and 70.7 ± 13.2 bpm in group B (P = .950). No significant differences were observed in SNR and image quality score (1.49 ± 0.62 vs. 1.53 ± 0.67; P = .647) between the breath-holding and free-breathing groups. ED (1.99 ± 0.83 mSv vs. 2.01 ± 0.88 mSv) was not significantly different between the two groups (P = .975). In a segment-based analysis, the sensitivity, specificity and diagnostic accuracy in the detection of coronary stenosis of more than 50% were 82.1%, 96.8% and 92.2%, respectively in the breath-holding group and 82.2%, 96.6% and 92.2%, respectively in the free-breathing group with no significant differences for these parameters between the two groups.ConclusionsCCTA for patients without heart rate control and during free-breathing using 16-cm z-coverage CT with motion correction algorithm showed no significant difference in image quality and diagnostic performance compared with CCTA during breath-holding.     

Reduction of cardiac motion artifact in step-and-shoot coronary CT angiography with third-generation as compared with second-generation dual-source CT scanners

PURPOSEWe aimed to compare the effects of misregistration (stair-step artifact) occurrence during coronary computed tomography angiography (CCTA) using third- and second-generation dual-source computed tomography (DSCT) scanners.METHODSCCTA was performed in consecutive patients with suspected coronary heart disease. Patients were randomly assigned to two groups and imaged using a third-generation (n=68; group A) or second-generation (n=63; group B) DSCT scanner. Heart rate (HR), heart rate variability (HRV), the number of acquisition steps required, and the anatomical cardiac length of each patient were recorded and compared between the two groups. Qualitative interpretation and analyses were scored with respect to subjective image quality and misregistration (stair-step artifact) by two interpreters. Cohen’s kappa was used to evaluate the consistency between the observers.RESULTSAll CCTA images (100%) on both DSCT scanners yielded satisfactory image quality, with a subjective image quality score of 4.21±0.17. The consistency between the two observers with respect to misregistration and subjective scores were good (κ= 0.91 and 0.92, respectively). Both the number of acquisition steps required and the scan length of each patient in group A differed significantly (p < 0.001) from those in group B; there were significantly fewer artifacts in group A than in group B (p < 0.001). Misregistration artifacts did not correlate with the HRs or HRVs between two required acquisition steps (p > 0.20).CONCLUSIONAs compared with second-generation DSCT, the reduced number of acquisition steps required and the shorter scan length in third-generation DSCT reduced the occurrence of misregistration artifacts in CCTA images.

Coronary computed tomography angiography (CCTA) has gained widespread acceptance as the first choice for noninvasive assessment of a wide variety of cardiac diseases, as it has strong negative-predictive value and is effective in ruling out coronary artery disease in symptomatic patients, particularly those with intermediate risk (1). However, despite recent advances in cardiac computed tomography (CT) technologies, such as faster gantry rotation and an increased number of detector rows, CCTA images remain vulnerable to a number of artifacts due to patient- and technique-specific causes. Artifacts in cardiac CT may cause image degradation and interference in diagnosis (2–4), leading to either underdiagnosis or overtreatment, both of which are associated with increased patient morbidity and mortality (5).Misregistration (stair-step) artifact, a type of cardiac motion artifact, appears when the heart is not in an identical position during consecutive heartbeats, because of arrhythmias (5). Avoiding misregistration artifacts between adjacent acquisition steps remains a challenge in step-and-shoot CCTA (6). Numerous studies have investigated step-and-shoot CCTA with different types of CT scanners. A previous study investigated misregistration artifacts with a 64-slice single-source CT (7), another study investigated image quality obtained with 128-slice dual-source CT (DSCT) (8), while yet another study investigated the effect of heart rate (HR) and heart rate variability (HRV) on image quality when using a 256-slice CT scanner (6). Most guidelines state that decreasing the mean HR and HRV is the most important factor for minimizing cardiac motion artifacts (9, 10), including misregistration artifacts. However, it is not clear whether the incidence of misregistration artifacts would be similar in the new-generation DSCT scanners, with their faster gantry speed and increased Z-coverage.Hence, the aim of this study was to investigate the frequency of occurrence of misregistration artifacts in step-and-shoot CCTA with a third-generation DSCT scanner, as compared with that of a second-generation DSCT scanner.     

Consistency of quantitative analysis of coronary computed tomography angiography

BackgroundThe present study aimed to assess the reliability and reproducibility of coronary computed tomography angiography (CCTA) for the serial quantitative assessment of plaque volume.MethodsPatients who underwent repeated CCTA scans within 90 days were retrospectively screened and enrolled. Clinical data and CCTA imaging data were collected. Paired CCTA scans were analyzed using the quantitative method by separate observers blinded to the other paired CCTA scans. Results were compared between the index CCTA and follow-up CCTA.ResultsPaired CT scans of 95 patients (61 ± 13 years; 56.8% men) with same tube voltages (kVp) at both CCTAs and 24 patients (57 ± 19 years; 48.3% men) with different kVp at two CCTAs were analyzed. In patients with same kVp at both CCTAs, there were no difference in PV and PVs of each components in per-segment analysis and per-lesion analysis (all p > 0.05). In per-lesion analysis of CCTAs from patients who used different kVp between two CCTAs, lesion length, area and diameter stenosis, and PVs were not different between index and follow-up CCTAs (all p > 0.05). Segment length and PV were also showed no difference between two serial CCTAs in per-segment analysis.ConclusionWe showed the reproducibility and reliability of quantitative analysis of CCTA for assessment of coronary plaques. CCTA can be applied for the serial quantitative assessment of coronary artery disease progression, regardless of differences in the image acquisition protocol.     

Trends in radiation protection in CT: Present and future status

With the introduction of modern multislice scanner generations, computed tomography (CT) has emerged as a useful tool for evaluation of the coronary arteries. A common application of coronary CT angiography (CCTA) is the examination of patients with intermediate pretest probability for obstructive coronary artery disease. Despite the widespread use of cardiac CT examinations in clinical practice, concern remains about the exposure to ionizing radiation and its potential hazards. Therefore, radiation dose and strategies for dose reduction have become an important focus of interest. Several smaller analyses have shown an effective radiation dose between 6.4 and 27.8 mSv for spiral CCTA image acquisition. The international Prospective Multicenter Study On RadiaTion Dose Estimates Of Cardiac CT AngIOgraphy I (PROTECTION I) study, the largest observational study on radiation dose estimates of cardiac CT so far, determined radiation dose estimates of CCTA, as well as the effect of different strategies to reduce dose in clinical practice. The median dose-length-product of 1965 CCTA examinations was 885 mGy × cm, which corresponds to a median estimated effective radiation dose of 12 mSv. However, a large variation in dose between study sites was observed, indicating a large potential to reduce dose for individual sites. Several dose-saving scanning techniques and algorithms have been developed. This article discusses these strategies as well as their effect on radiation dose and image quality. Because the contrast-enhanced CT angiography is the largest part of the total study dose, the following described strategies focus on radiation dose reduction for CCTA image acquisition.     

Impaired left ventricular function has a detrimental effect on image quality in multi-detector row CT coronary angiography

AIM: To determine whether there is a relationship between left ventricular (LV) haemodynamic parameters, circulation times, and arterial contrast opacification that might affect the image quality of computed tomography (CT) coronary angiography. METHODS: Thirty-six patients were included in the study: 18 with cardiomyopathy (CM) and LV dilatation of suspected ischaemic aetiology [age 57.9+/-13.7 years, range 30-77 years; 14 male, four female; body mass index (BMI)=27.7+/-4.5, range 25.5-31.8] and 18 controls (age 62.3+/-9.4 years, range 47-89 years; 10 male, eight female; BMI 27.8+/-6.6; range 19.2-33.6). Coronary artery image quality was assessed using a three-point visual scale; contrast medium circulation times, aortic root contrast attenuation, and LV functional parameters were studied. RESULTS: Visually reduced contrast opacification impaired image quality more often in the CM group than the control group (27.4 versus 5.1%). A total of 55.6% CM patients had a contrast transit time ranging from 30-75 s; the number of "unassessable" segments increased with increasing transit time conforming to a fitted quadratic model (R2=0.74). The relationship between LV ejection fraction and contrast attenuation may also conform to a quadratic model (R2=0.71). CONCLUSION: LV haemodynamics influence coronary artery opacification using cardiac CT, and users imaging this subgroup must do so with the knowledge of this potential pitfall. The results indicate the need for further studies examining CT protocols in this clinical subgroup.     

Tools of the trade for CTA: MDCT scanners and contrast medium injection protocols

The introduction of multi-detector row computed tomography (MDCT) scanners in 1998 ushered in new advances in CT angiography (CTA). The subsequent expansion of MDCT scanner capabilities, coupled with advances in understanding of contrast medium (CM) dynamics, has further improved the clinical availability and consistency of CTA. We will review recent advances in CT scanner technology and discuss early CM dynamics. Specifically, we describe an approach tailored to the available scanner technology and to patient size aimed at providing consistently robust CTA studies across all vascular territories. A rational method to design combined CTA scan/injection protocols to facilitate this goal will be described. Our current experience with a simplified protocol for CTA with 64-MDCT will also be explained.     

Interpretability of coronary CT angiography performed with a novel whole-heart coverage high-definition CT scanner in 300 consecutive patients with coronary artery bypass grafts

AimsCoronary CT angiography (CCTA) is an accurate non-invasive tool for the evaluation of coronary artery bypass graft (CABG). However, inability to sustain a long breath-hold, high heart rate (HR) and atrial fibrillation may affect image quality. Moreover, radiation exposure is still a matter of some concern. A scanner combining 0.23-mm spatial resolution, new iterative reconstruction and fast gantry rotation time has been recently introduced in the clinical field. The aims of our study were to evaluate interpretability, radiation exposure and diagnostic accuracy of CCTA performed with the latest generation of cardiac-CT scanners compared to invasive coronary angiography (ICA) in the assessment of bypass grafts, and non-grafted and post-anastomotic native coronary arteries.Methods and resultsWe prospectively enrolled 300 patients undergoing clinically indicated CCTA with a 16-cm z-axis coverage, 256-detector rows, and 0.28-sec gantry rotation time scanner. Coronary artery and graft interpretability, image quality and effective dose (ED) were assessed in all patients and diagnostic accuracy was evaluated in a subgroup of 100 patients who underwent ICA.Mean HR during the scan was 69.6 ± 10.8. Sinus rhythm was present in 118 patients with HR < 75 bpm and in 112 patients with HR ≥ 75 bpm, while 70 patients had atrial fibrillation. CABG interpretability was 100%. Compared to ICA, CCTA was able to correctly detecting occlusions or significant stenoses of all CABG segments. Overall interpretability of native coronary segments was 95.6%. Sensitivity, specificity, positive predictive value, negative predictive value and accuracy of coronary arteries were 98.3%, 97.4%, 93.1%, 99.3% and 96.5%, respectively. The diagnostic accuracy in a patient based analysis was 95.2%. Mean ED was 3.14 ± 1.7 mSv.ConclusionsThe novel whole-heart coverage CT scanner allows to evaluating CABG and native coronary arteries with excellent interpretability and low radiation exposure even in the presence of unfavorable heart rhythm.     

Feasible scan timing for 320-row coronary CT angiography generated by the time to peak in the ascending aorta

PurposeA 320-row CT scanner can briefly scan the entire heart. Therefore, the feasible scan timing is required. The aim of this study was to propose a refined method for feasible scan timing for coronary CT angiography (CCTA) using a time-density curve of the ascending aorta (AAo).MethodsOne-hundred and twenty-nine patients were prospectively enrolled. All patients were performed test-bolus method. For the initial 65 patients, the scan timing was determined as a 3.0 s delay at the peak time in the AAo, which was defined as the conventional protocol (COV-P). For the next 64 patients, a scan timing of 1.0, 3.0, or 5.0 s delay was determined according to the interval from the contrast media arrival to peak time in the AAo, which was defined as the arrival to peak protocol (AP-P). The optimal scan timing was identified by the measurement of CT number in the left atrium, left ventricle, AAo, and descending aorta. The coronary enhancement and heterogeneity were compared between the two protocols.ResultsThe optimal scan timing was significantly higher in the AP-P than in the COV-P (85.9% vs. 61.5%, p = 0.0017). The CT number in the left circumflex artery (LCX) was significantly higher in the AP-P than the COV-P (344.5 Hounsfield units vs. 316.3 Hounsfield units, p = 0.0484). The heterogeneous index of the LCX was significantly greater for the COV-P than the AP-P (−36.8 vs. –25.8, p = 0.0028).ConclusionsThe AP-P can be used to determine the optimal scan timing for CCTA and contributes to stable coronary enhancement.     

64层螺旋CT心脏检查对比剂注射方案的优化

目的：探讨64层螺旋CT心脏检查中应用三时相一次扫描获得理想的冠状动脉图像、心脏形态和功能分析的对比剂优化注射方案。方法：将326例患者以不同注射方案随机分成5组：方案A,30例,单期注射,仅团注80～90ml对比剂。方案B30例,双期注射,团注60～80ml对比剂后于第二时相注射30ml生理盐水。方案C、D、E共266例,均行三期注射。其中,方案C 92例;方案D 83例;方案E91例。第一时相团注50～60ml对比剂,第二时相分别以不同比率（方案C 50％,方案D 40％,方案E 30％）注射30～40ml对比剂-生理盐水混合液,第三时相注射30ml生理盐水。分别测量升主动脉根部、同层面胸主动脉、主肺动脉、左心室及右心室的CT值,计算心室腔-心室壁的对比噪声比（CNR）。比较不同对比剂注射方案冠状动脉各级分支显示情况及右心室内对比剂均匀性。结果：CNR左心室各组间差异无统计学意义（P〉0．05）;CNR右心室各组间有显著性差异（P〈0．01）,C组CNR右心室明显高于其他各组（P〈0．01）。左心室、升主动脉根部和降主动脉的平均CT值差异无统计学意义（P〉0．05）;主肺动脉和右心室的平均CT值有显著性差异（P〈0．01）,其中,右心室CT值C组高于其他各组（P〈0．01）。各组在冠状动脉的显示方面无统计学意义（P〉0．05）。右心室的均匀性各组间存在显著性差异（P〈0．01）,C组优于A、B、D组（P〈0．05）,与E组间差别无明显统计学意义（P〉0．05）。结论：应用三时相注射方案,先团注50～60ml对比剂（第一时相）,再以50％的比率注射30～40ml对比剂-生理盐水混合液（第二时相）,随后注射30ml生理盐水（第三时相）,一次扫描不仅可以在清晰显示冠状动脉的同时行心脏形态和功能分析,而且减少了对比剂的用量,可以为临床冠心病的筛查提供相应的综合?     

Feasibility of extracellular volume fraction calculation using myocardial CT delayed enhancement with low contrast media administration

BackgroundMyocardial extracellular volume fraction (ECV) derived from CT delayed enhancement (CTDE) may allow assessment of diffuse myocardial fibrosis. However, the amount of contrast medium required for ECV estimation has not been established. Since ECV estimation by CT is typically performed in combination with coronary CT angiography (CCTA) in clinical settings, we aimed to investigate whether reliable ECV estimation is possible using the contrast dose optimized for CCTA without additional contrast administration.MethodsTwenty patients with known or suspected coronary artery disease who underwent CTDE with a dual-source scanner using two protocols (Protocols A and B) within 2 years were retrospectively enrolled. In Protocol A, CTDE was obtained with 0.84 ml/kg of iopamidol (370 mgI/ml) injected for CCTA. In Protocol B, stress CT perfusion imaging, which requires 40 ml of contrast medium, was added to Protocol A. ECV values calculated from the two protocols were compared.ResultsDespite the different contrast doses, no significant difference in mean myocardial ECV was seen between Protocols A and B at the patient level (28.7 ± 4.3% vs. 28.7 ± 4.4%, respectively, P = 0.868). Excellent correlations in ECV were seen between the two protocols (r = 0.942, P < 0.001). Bland-Altman analysis showed slight bias (+0.06%), within a 95% limit of agreement of −2.9% and 3.0%. The coefficient of variation was 5.2%.ConclusionReliable ECV estimation can be achieved with the contrast doses optimized for CCTA. Despite the differing contrast administration schemes and doses, ECV values calculated from the two protocols showed excellent agreement, indicating the robustness of ECV estimation by CT.     

Safety, efficacy, and indications of beta-adrenergic receptor blockade to reduce heart rate prior to coronary CT angiography

For selected indications, coronary computed tomographic (CT) angiography is an established clinical technology for evaluation in patients suspected of having or known to have coronary artery disease. In coronary CT angiography, image quality is highly dependent on heart rate, with heart rate reduction to less than 60 beats per minute being important for both image quality and radiation dose reduction, especially when single-source CT scanners are used. β-Blockers are the first-line option for short-term reduction of heart rate prior to coronary CT angiography. In recent years, multiple β-blocker administration protocols with oral and/or intravenous application have been proposed. This review article provides an overview of the indications, efficacy, and safety of β-blockade protocols prior to coronary CT angiography with respect to different scanner techniques. Moreover, implications for radiation exposure and left ventricular function analysis are discussed.     

Saline chasing technique with dual-syringe injector systems for multi-detector row computed tomographic angiography: rationale, indications, and protocols

Computed tomography (CT) technology has significantly changed over the last two decades. The advent of multi-detector row CT (MDCT) has resulted in rapid acquisition times and improved z-axis resolution that paved the way for CT angiography. With MDCT technology, CT angiography has become more dependent upon optimal vessel opacification and, consequently, contrast administration protocols have had to evolve. We examine the use of intravenous contrast from a historical perspective and discuss the latest methodologies, such as saline chasing techniques, that optimize the contrast bolus with CT angiography.     

Comprehensive morphologic and functional imaging of heart transplant patients: first experience with dynamic perfusion CT

Objectives

We aimed to assess the diagnostic performance of a combined protocol with coronary computed tomography angiography (CCTA) and stress CT perfusion imaging (CTP) in heart transplant patients for comprehensive morphological and functional imaging.

Methods

In this prospective study, 13 patients undergoing routine follow-up 8±6 years after heart transplantation underwent CCTA and dynamic adenosine stress CTP using a third-generation dual-source CT scanner, cardiac magnetic resonance (MR) adenosine stress perfusion imaging at 1.5 T, and catheter coronary angiography. In CCTA stenoses >50% luminal diameter narrowing were noted. Myocardial perfusion deficits were documented in CTP and MR. Quantitative myocardial blood flow (MBF) was calculated with CTP. Left ventricular ejection fraction was determined on cardiac MR cine images. Radiation doses of CT were determined.

Results

One of the 13 patients had to be excluded because of severe motion artifacts. CCTA identified three patients with stenosis >50%, which were confirmed with catheter coronary angiography. CTP showed four patients with stress-induced myocardial hypoperfusion, which were confirmed by MR stress perfusion imaging. Quantitative analysis of global MBF showed lower mean values as compared to known reference values (MBF under stress 125.5 ± 34.5 ml/100 ml/min). Average left ventricular ejection fraction was preserved (56 ± 5%).

Conclusions

In heart transplant patients, a comprehensive CT protocol for the assessment of morphology and function including CCTA and CTP showed good concordance to results from MR perfusion imaging and catheter coronary angiography.

Key Points

? Stress CT perfusion imaging enables the detection of myocardial ischemia ? CT myocardial perfusion imaging can be combined with coronary computed tomography angiography ? Combining perfusion and coronary CT imaging is accurate in heart transplant patients ? CT myocardial perfusion imaging can be performed at a reasonable radiation dose

     

Maintaining image quality and reducing dose in prospectively-triggered CT coronary angiography: A systematic review of the use of iterative reconstruction

IntroductionCoronary computed tomography angiography (CCTA) is a reliable, minimally invasive technique used in the diagnosis and characterisation of coronary artery disease. Within this modality iterative reconstruction has the potential to maintain image quality whilst reducing radiation dose.MethodsA priori search terms and inclusion/exclusion criteria were developed.ResultsThree studies were included in the review which analysed a total of 227 participants. As CTDI_vol decreased there was no significant change in objective image quality, although some subjective image quality scores decreased.DiscussionThe decrease of subjective image quality scores may be explained as a reaction to the difference in image appearance of the iterative reconstruction images; a potential reduction in dynamic range; and the number of scorers used.ConclusionIterative reconstruction can be utilized as a tool to significantly reduce patients' exposure to ionising radiation; however there may be implications for radiologists/cardiologist in the interpretation of these images.     

Multi-detector row CT coronary angiography in patients with cardiomyopathy -- initial single-centre experience

AIMS: To evaluate the diagnostic accuracy of computed tomography (CT) in assessing haemodynamically significant coronary artery stenoses in patients with cardiomyopathy (CM). SUBJECTS AND METHODS: Eighteen patients with CM were approached to undergo CT coronary angiography to evaluate the use of this technique for investigating the presence of significant coronary artery disease (CAD), and also to compare the findings with catheter angiography. RESULTS: On a segment-by-segment analysis the sensitivity, specificity, positive and negative predictive values in the CM group were 66.7, 96.5, 40 and 98.8%, respectively, with 100% accuracy in "whole-patient terms". CONCLUSION: Non-invasive, 16-detector row CT coronary angiography in patients with presumed CM would seem to be a useful clinical tool for the exclusion of significant coronary artery disease. However, the presence of suboptimal contrast opacification in this patient group means that the implication of these results must be interpreted with caution.     

Prognostic value of CT myocardial perfusion imaging and CT-derived fractional flow reserve for major adverse cardiac events in patients with coronary artery disease

ObjectivesThe purpose of this study was to analyze the prognostic value of dynamic CT perfusion imaging (CTP) and CT derived fractional flow reserve (CT-FFR) for major adverse cardiac events (MACE).Methods81 patients from 4 institutions underwent coronary computed tomography angiography (CCTA) with dynamic CTP imaging and CT-FFR analysis. Patients were followed-up at 6, 12, and 18 months after imaging. MACE were defined as cardiac death, nonfatal myocardial infarction, unstable angina requiring hospitalization, or revascularization. CT-FFR was computed for each major coronary artery using an artificial intelligence-based application. CTP studies were analyzed per vessel territory using an index myocardial blood flow, the ratio between territory and global MBF. The prognostic value of CCTA, CT-FFR, and CTP was investigated with a univariate and multivariate Cox proportional hazards regression model.Results243 vessels in 81 patients were interrogated by CCTA with CT-FFR and 243 vessel territories (1296 segments) were evaluated with dynamic CTP imaging. Of the 81 patients, 25 (31%) experienced MACE during follow-up. In univariate analysis, a positive index-MBF resulted in the largest risk for MACE (HR 11.4) compared to CCTA (HR 2.6) and CT-FFR (HR 4.6). In multivariate analysis, including clinical factors, CCTA, CT-FFR, and index-MBF, only index-MBF significantly contributed to the risk of MACE (HR 10.1), unlike CCTA (HR 1.2) and CT-FFR (HR 2.2).ConclusionOur study provides initial evidence that dynamic CTP alone has the highest prognostic value for MACE compared to CCTA and CT-FFR individually or a combination of the three, independent of clinical risk factors.     

The combined application of the contrast-to-noise index and 80 kVp for cardiac CTA scanning before atrial fibrillation ablation reduces radiation dose exposure

IntroductionTo compare the radiation dose, diagnostic accuracy, and the resultant ablation procedures using 80 and 120-kVp cardiac computed tomography angiography (CCTA) protocols with the same contrast-to-noise ratio in patients scheduled for atrial fibrillation (AF) ablation.MethodsThis retrospective study was performed following institutional review board approval. We divided 140 consecutive patients who had undergone CCTA using a 64-MDCT scanner into two equal groups. Standard deviation (SD) of the CT number was set at 25 Hounsfield units (HU) for the 120-kVp protocol. To facilitate a reduction in radiation dose it was set at 40 HU for the 80 kVp protocol. We compared the two protocols with respect to the radiation dose, the diagnostic accuracy for detecting left atrial appendage (LAA) thrombi, matching for surface registration, and the resultant ablation procedures.ResultsAt 120 kVp, the dose length product (DLP) was 2.2 times that at 80 kVp (1269.0 vs 559.0 mGy cm, p < 0.01). The diagnostic accuracy for thrombus detection was 100% using both protocols. There was no difference between the two protocols with respect to matching for surface registration. The protocols did not differ with respect to the subsequent time required for the ablation procedures and the ablation fluoroscopy time, and the radiation dose (p = 0.54, 0.33, and 0.32, respectively).ConclusionFor the same CNR, the DLP at 80 kVp (559.0 mGy cm) was 56% of that delivered at 120 kVp (1269.0 mGy cm). There was no reduction in diagnostic accuracy.Implications for practiceMaintaining CNR allows for a reduction in the radiation dose without reducing the image quality.