64-slice computed tomography assessment of coronary artery stents: a phantom study

Purpose: To compare the use of a new 64-slice computed tomography (CT) scanner with 16-slice CT in the visualization of coronary artery stent lumen.

Material and Methods: Eight different coronary artery stents, each with a diameter of 3 mm, were placed in a static chest phantom. The phantom was positioned in the CT gantry at an angle of 0° and 45° towards the z-axis and examined with both a 64-slice and a 16-slice CT scanner. Effective slice thickness was 0.6 mm with 64-slice CT and 1 mm with 16-slice CT. A reconstruction increment of 0.3 mm was applied in both scanners. Image quality was assessed visually using a 5-point grading scale. Stent diameters were measured and compared using paired Wilcoxon tests.

Results: Artificial lumen reduction was significantly less with 64-slice than with 16-slice CT. Average visible stent lumen was 53.4% using 64-slice CT and 47.5% with 16-slice MSCT. Most severe artifacts were seen in stents with radiopaque markers. Using 64-slice CT, image noise increased by approximately 30% due to thinner slice thickness.

Conclusion: Improved spatial resolution of 64-slice CT resulted in superior assessment of coronary artery stent lumen compared to 16-slice CT. However, a relevant part of the stent lumen is still not assessable with multi-slice CT.     

成人三房心:64层CT诊断价值

目的：评价64层CT在成人三房心中的诊断价值。方法：回顾性分析自2009年2月～2010年3月我院64层CT冠状动脉检查病例,发现三房心6例,男5例,女1例,年龄45～71岁,完全型1例,不完全型5例。采用多种CT图像重组技术包括容积再现（VR）、容积密度投影（VIP）、多平面重组（MPR）和最大密度投影（MIP）等对心脏结构和冠状动脉进行分析。结果：CT可以清晰地显示心房内的异常隔膜和隔膜孔以及肺静脉和心房的连接、有无梗阻,显示并发的心脏畸形及冠状动脉血管。结论：64层CT是诊断成人三房心的有效影像学技术。     

The impact of scan length on the exposure levels in 16- and 64-row multidetector computed tomography: a phantom study

RATIONALE AND OBJECTIVES: Higher patient exposure levels have been reported for 64-row multidetector computed tomography (MDCT) compared to 16-row MDCT. The objective of this study was to make a thorough comparison by evaluating the impact of scan length on the exposure levels at 16-row MDCT and 64-row MDCT. MATERIALS AND METHODS: Dose-length product (DLP) values were determined to compare exposure levels in 16- and 64-row MDCT. This phantom study does not deal with a possible reduction in image quality induced by an increase in scattered radiation in 64-row MDCT compared to 16-row MDCT. RESULTS: The exposure levels of 64-row MDCT (scan slice thickness, 0.5 mm) are up to 18% lower than those of 16-row MDCT at slice thickness 0.5 mm when scanning an object larger than 12.3 cm. At this value, the plots of the 16- and 64-row DLP values versus scan length cross. The DLP curves of 1- and 2-mm slice thickness 16-row MDCT are in closer resemblance to those of 0.5-mm 64-row MDCT. The respective exposure levels of 1- and 2-mm slice thickness 16-row MDCT exceed those of 0.5-mm 64-row MDCT by up to 4% and 3%, with intersections of 30 and 25 cm, respectively. CONCLUSION: Lower effective doses are obtained in 64-row MDCT compared to 16-row MDCT (0.5-mm slice thickness) provided that scan length exceeds 12.3, 30, and 25 cm, for 16-row MDCT slice thickness of 0.5, 1, and 2 mm, respectively. Reduced effective dosage in 64-row MDCT compared to 16-row MDCT has not been demonstrated before. Differences in object size may thus explain discrepancies between previous studies with regard to the exposure levels at 64-slice CT compared to 16-slice CT.     

Variability of repeated coronary artery calcium scoring and radiation Dose on 64- and 16-slice computed tomography by prospective electrocardiographically-triggered axial and retrospective electrocardiographically-gated spiral computed tomography: a phantom study

RATIONALE AND OBJECTIVES: We sought to compare coronary artery calcium (CAC) scores, the variability and radiation doses on 64- and 16-slice computed tomography (CT) scanners by both prospective electrocardiographically (ECG)-triggered and retrospective ECG-gated scans. MATERIALS AND METHODS: Coronary artery models (n = 3) with different plaque CT densities (approximately 240 Hounsfield units [HU], approximately 600 HU, and approximately 1000 HU) of four sizes (1, 3, 5, and 10 mm in length) on a cardiac phantom were scanned three times in five heart rate sequences. The tube current-time products were set to almost the same on all four protocols (32.7 mAs for 64-slice prospective and retrospective scans, 33.3 mAs for 16-slice prospective and retrospective scans). Slice thickness was set to 2.5 mm to keep the radiation dose low. Overlapping reconstruction with a 1.25-mm increment was applied on the retrospective ECG-gated scan. RESULTS: The CAC scores were not different between the four protocols (one-factor analysis of variance: Agatston, P = .32; volume, P = .19; and mass, P = .09). Two-factor factorial analysis of variance test revealed that the interscan variability was different between protocols (P < .01) and scoring algorithms (P < .01). The average variability of Agatston/volume/mass scoring and effective doses were as follows: 64-slice prospective scan: 16%/15%/11% and 0.5 mSv; 64-slice retrospective scan: 11%/11%/8% and 3.7 mSv; 16-slice prospective scan: 20%/18%/13% and 0.6 mSv; and 16-slice retrospective scan: 16%/15%/11% and 2.9 to 3.5 mSv (depending on the pitch). CONCLUSION: Retrospective ECG-gated 64-slice CT showed the lowest variability. Prospective ECG-triggered 64-slice CT, with low radiation dose, shows low variability on CAC scoring comparable to retrospective ECG-gated 16-slice CT.     

Gated cardiac imaging of the aortic valve on 64-slice multidetector row computed tomography: preliminary observations

PURPOSE: To conduct a pilot study to determine the feasibility of evaluating aortic valve morphology and motion on electrocardiogram-gated 64-slice cardiac MDCT. METHODS: Four-dimensional images of the aortic valve were reviewed in 20 consecutive patients who underwent computed tomography (CT) coronary angiography. A consensus reading of 3 readers was performed of valve visibility, number of leaflets, valve motion, and calcification. Visibility of the valve leaflets and visualization of opening and closing of the valve leaflets were graded as well seen or suboptimally seen. The number of valve leaflets (3 or 2) and presence of valvular calcification were noted. RESULTS: The aortic valve was well seen in all 20 patients. Three leaflets were identified in all cases, and no calcifications were seen. Valve movement with opening and closure of the leaflets during the cardiac cycle was also well seen in all cases. CONCLUSIONS: Visualization of the aortic valve and valvular motion during the cardiac cycle is feasible on CT studies performed for coronary angiography. CT has a potential role in the assessment of aortic valvular pathology.     

Acute abdomen: Added diagnostic value of coronal reformations with 64-slice multidetector row computed tomography

RATIONALE AND OBJECTIVES: We sought to assess retrospectively the added value of coronal reformations from isotropic voxels obtained with 64-slice multidetector row computed tomography (CT) of the acute abdomen. MATERIALS AND METHODS: This retrospective study was approved by the institutional review board and informed consent was waived. Multidetector helical 64-section CT (section thickness, 0.6 mm; pitch 1.75; table speed 35 mm/sec) was performed in 100 patients (60 women and 40 men; age range, 9-/+85 years; mean age, 45.2 years) with acute nontraumatic abdominal pain who had been referred from the emergency department. Axial images were reconstructed with 5-mm-thick sections at 5-mm intervals. The second data set was reformatted coronally, with 3-mm-thick sections at 3-mm intervals. Four independent, blinded readers with various level of training interpreted first the axial scans alone and then followed immediately by the coronal scans. Confidence in the visualization of anatomy and pathology was scored on a 5-point scale. The final diagnosis was determined by surgical and pathologic reports and by clinical follow-up in those who did not undergo surgery. RESULTS: Based upon the individual patient's clinical history and other comorbid factors, 92 patients received intravenous contrast and 90 patients received oral contrast. In 45 patients, no CT abnormalities were detected for an explanation of the abdominal pain. Mean sensitivity and specificity of axial CT alone were 92.5% and 91%, respectively. No significant differences in sensitivity and specificity were observed for the use of combined axial and coronal images. For the most inexperienced reader, the coronal reformations were helpful in 95% of cases, while for the most experienced reader, the coronal reformations were helpful in 35% of the cases. The coronal images were deemed helpful in an average of 62.3% of the cases for the four readers. However, diagnosing subtle pathology in the abdominal wall was difficult on coronal reformations alone. Overall, coronal reformations improved diagnostic confidence and interobserver agreement over axial images alone for visualization of normal abdominal structures and in the diagnosis of abdominal pathology. CONCLUSION: Axial and coronal reformations of 64-section multidetector row CT have equal sensitivity and specificity for the diagnosis of acute abdominal pathology. However, coronal reformations improved the diagnostic confidence for all readers but most significantly for the least experienced. Therefore, radiology departments with residents should consider routinely generating coronal images in patients with acute abdominal pain.     

Evaluation of cardiac function and myocardial viability with 16- and 64-slice multidetector computed tomography

Retrospectively ECG-gated MDCT shows a high correlation and acceptable agreement of left-ventricular functional parameters compared to MR imaging. Thus, in addition to the non-invasive evaluation of coronary arteries, further important additional information of left-ventricular functional parameters with clinical and prognostic relevance can be achieved by one single MDCT examination. For assessment of myocardial viability, low-dose CT late enhancement scanning is feasible, and preliminary results look promising. CT late enhancement adds valuable diagnostic information on the haemodynamical significance of coronary stenoses or prior to interventional procedures.     

Evaluation of cardiac function and myocardial viability with 16- and 64-slice multidetector computed tomography

Retrospectively ECG-gated MDCT shows a high correlation and acceptable agreement of left-ventricular functional parameters compared to MR imaging. Thus, in addition to the non-invasive evaluation of coronary arteries, further important additional information of left-ventricular functional parameters with clinical and prognostic relevance can be achieved by one single MDCT examination. For assessment of myocardial viability, low-dose CT late enhancement scanning is feasible, and preliminary results look promising. CT late enhancement adds valuable diagnostic information on the haemodynamical significance of coronary stenoses or prior to interventional procedures.     

Comparison of whole-body 64-slice multidetector computed tomography and conventional radiography in staging of multiple myeloma

This study compares the sensitivity of whole-body multidetector CT (MDCT) and conventional radiography (CR) in the staging of multiple myeloma (MM). Twenty-nine patients with MM underwent a staging examination both by MDCT and CR. CT examination was performed with a collimation of 64×0.6 mm, a tube potential of 100 kVp, an effective tube current-time product of 100 mAs and automatic dose modulation as low-dose protocol. Number, size and diagnostic confidence of osteolytic lesions were determined and compared. The effective dose of MDCT and CR was assessed. Using MDCT, the detection of osteolysis was increased seven-fold concerning the spine. Ninety-seven lesions in 18 patients were detected exclusively by MDCT. The detection rate concerning the spine, pelvic skeleton and thoracic cage was significantly higher (p≤0.001), and diagnostic confidence was increased by MDCT (p<0.02) compared to CR. Therapy was changed after MDCT in 18.2% of the patients with a clinical suspicion of progressive disease. The estimated effective dose of MDCT (4.8 mSv) and CR (1.7 mSv) was comparable. In conclusion, MDCT has a significantly higher sensitivity and reliability in the detection of osteolysis than CR and can be recommended as standard imaging method in the staging of MM.     

MSCT检查对阴性阑尾切除率的影响

目的：通过前瞻性观察研究评估MSCT检查对急性阑尾疑诊患者阴性阑尾切除率的影响。方法：78例急性阑尾炎临床疑诊患者纳入研究。由急诊科医师根据临床资料（包括实验室检查）结合Alvarado评分做出临床诊断,分为两组：临床典型组（Alvarado评分≥7分）和临床不典型组（Alvarado评分〈7分）。所有患者均行MSCT检查,由放射科医师做出CT诊断。治疗方案由外科医师综合参考临床与CT诊断结果后制定,最终诊断以手术病理和临床随访为准。计算临床与CT诊断的阴阳性结果及相关评价指标,并进行统计学处理。结果：MSCT检查的各个评价指标（准确度94.9%,敏感度95.6%,特异度93.9%,阳性预测值95.6%,阴性预测值93.9%,阳性似然比15.8,阴性似然比0.05）均明显优于临床诊断。78例患者中,35例属临床表现典型组,其中9例（25.7%）证实为急性阑尾炎阴性,此9例患者MSCT诊断结果全为阴性。结论：术前MSCT检查可明显降低急性阑尾疑诊患者的阴性阑尾切除率,避免不必要的剖腹探查。     

Calcium score of small coronary calcifications on multidetector computed tomography: Results from a static phantom study

Introduction

Multi detector computed tomography (MDCT) underestimates the coronary calcium score as compared to electron beam tomography (EBT). Therefore clinical risk stratification based on MDCT calcium scoring may be inaccurate. The aim of this study was to assess the feasibility of a new phantom which enables establishment of a calcium scoring protocol for MDCT that yields a calcium score comparable to the EBT values and to the physical mass.

Materials and methods

A phantom containing 100 small calcifications ranging from 0.5 to 2.0 mm was scanned on EBT using a standard coronary calcium protocol. In addition, the phantom was scanned on a 320-row MDCT scanner using different scanning, reconstruction and scoring parameters (tube voltage 80–135 kV, slice thickness 0.5–3.0 mm, reconstruction kernel FC11–FC15 and threshold 110–150 HU). The Agatston and mass score of both modalities was compared and the influence of the parameters was assessed.

Results

On EBT the Agatston and mass scores were between 0 and 20, and 0 and 3 mg, respectively. On MDCT the Agatston and mass scores were between 0 and 20, and 0 and 4 mg, respectively. All parameters showed an influence on the calcium score. The Agatston score on MDCT differed 52% between the 80 and 135 kV, 65% between 0.5 and 3.0 mm and 48% between FC11 and FC15. More calcifications were detected with a lower tube voltage, a smaller slice thickness, a sharper kernel and a lower threshold. Based on these observations an acquisition protocol with a tube voltage of 100 kV and two reconstructions protocols were defined with a FC12 reconstruction kernel; one with a slice thickness of 3.0 mm and a one with a slice thickness of 0.5 mm. This protocol yielded an Agatston score as close to the EBT as possible, but also a mass score as close to the physical phantom value as possible, respectively.

Conclusion

With the new phantom one acquisition protocol and two reconstruction protocols can be defined which produces Agatston scores comparable to EBT values and to the physical mass.     

Noninvasive coronary angiography using 64-slice spiral computed tomography in an unselected patient collective: effect of heart rate, heart rate variability and coronary calcifications on image quality and diagnostic accuracy

OBJECTIVE: The aim of this study was to assess the impact of heart rate, heart rate variability and calcification on image quality and diagnostic accuracy in an unselected patient collective. SUBJECTS AND METHODS: One hundred and two consecutive patients with known or suspected coronary artery disease underwent both 64-MSCT and invasive coronary angiography. Image quality (IQ) was assessed by independent observers using a 4-point scale from excellent (1) to non-diagnostic (4). Accuracy of MSCT regarding detection or exclusion of significant stenosis (>50%) was evaluated on a per segment basis in a modified AHA 13-segment model. Effects of heart rate, heart rate variability, calcification and body mass index (BMI) on IQ and accuracy were evaluated by multivariate regression. IQ and accuracy were further analysed in subgroups of significant predictor variables and simple regression performed to calculate thresholds for adequate IQ. RESULTS: Mean heart rate was 68.2+/-13.3 bpm, mean heart rate variability 11.5+/-16.0 beats per CT-examination (bpct) and median Agatston score 226.5. Average IQ score was 2+/-0.6 whilst diagnostic quality was obtained in 89% of segments. Overall sensitivity, specificity, PPV or NPV was 91.2%, 99.2%, 95.3% or 98.3%. According to multivariate regression, overall IQ was significantly related to heart rate and calcification (P=0.0038; P<0.0001). The effect of heart rate variability was limited to IQ of RCA segments (P=0.018); BMI was not related to IQ (P=0.52). Calcification was the only predictor variable with significant effect on the number of non-diagnostic segments (P<0.0001). In a multivariate regression, calcification was also the single factor with impact on diagnostic accuracy (P=0.0049). CONCLUSION: Whilst heart rate, heart rate variability and calcification all show an inverse correlation to IQ, severe calcium burden remains the single factor with translation of such effect into decrease of diagnostic accuracy.     

64-slice multidetector computed tomography (MDCT) for detection of aortic regurgitation and quantification of severity

BACKGROUND: Recent advances in 64-slice multidetector computed tomography (MDCT) provide an opportunity to assess coronary artery disease, left ventricular function and, potentially, valvular heart disease. OBJECTIVE: To determine the ability of 64-MDCT to both detect and to quantify the severity of aortic regurgitation (AR), as compared with transthoracic echocardiography (TTE). METHODS: We evaluated a total of 64 patients (43 males, mean age 63+/-11 years), 30 with varying severities of AR as assessed by TTE and 34 matched controls. The severity of AR by TTE was determined using the vena contracta, the ratio of jet to left ventricular outflow tract (LVOT) height, and the ratio of the jet to LVOT cross-sectional area. AR by MDCT was defined as a lack of coaptation of the aortic valve leaflets in diastole and, if detected, the maximum anatomic aortic regurgitant orifice was determined. RESULTS: All 34 control patients without AR were correctly identified by MDCT. There were 14 patients with mild AR, 10 with moderate AR, and 6 with severe AR by TTE. Of these patients, MDCT correctly identified 21 patients with AR (sensitivity 70%, specificity 100%, positive predictive value [PPV] 100%, and negative predictive value [NPV] 79%). Anatomic regurgitant orifice area measured by MDCT correlated well with the TTE-derived vena contracta (r=0.79, P<0.001), ratio of jet to LVOT height (r=0.79, P<0.001), and ratio of jet to LVOT cross-sectional area (r=0.75, P<0.001). CONCLUSIONS: Direct planimetric measurement of the aortic valve anatomic regurgitant orifice area on 64-MDCT provides an accurate, noninvasive technique for detecting and quantifying AR.     

Influence of heart rate and temporal resolution on left-ventricular volumes in cardiac multislice spiral computed tomography: a phantom study

PURPOSE: We sought to investigate the influence of heart rate and temporal resolution on the assessment of left-ventricular (LV) function with multislice spiral computed tomography (CT). MATERIAL AND METHODS: A dynamic cardiac phantom was repeatedly scanned with a 64-slice CT scanner using a standardized scan protocol (64 x 0.6 mm, 120kV, 770mAs(eff), 330 milliseconds rotation time) at different simulated heart rates, ranging from 40 to 140 beats per minute. Images were reconstructed with an algorithm utilizing data from 1 to 4 cardiac cycles (RR intervals). Ejection fraction (EF), end-systolic, end-diastolic, and stroke volume as well as cardiac output were calculated. Results of the measurements were compared with the real volumes of the phantom. Interscan and intraobserver variability were calculated. RESULTS: Using a monosegmental reconstruction algorithm, the temporal resolution was fixed to 165 milliseconds. With bi-, tri-, and quad-segmental image reconstruction, mean temporal resolution was 128.3 +/- 33.2 milliseconds, 103.3 +/- 49.2 milliseconds, and 87.8 +/- 81.5 milliseconds, respectively. Multisegmental image reconstruction resulted in a lower deviation when comparing measured and real volumes. Using mono-, bi-, tri-, and quad-segmental image reconstruction, the percent deviation between measured and real values for EF was 8.2%, 4.5%, 3.3%, and 3.4%, respectively. Applying multisegmental image reconstruction with improved temporal resolution the deviation decreased with increasing heart rate when compared with mono-segmental image reconstruction. Interscan and intraobserver variability for EF were 1.1% and 1.9%, respectively. CONCLUSION: Enhanced temporal resolution improves the quantification of LV volumes in cardiac multislice spiral CT, enabling reliable assessment of LV volumes even at increased heart rates.     

64层螺旋CT尿路成像与静脉尿路造影对照分析

目的探讨64层螺旋CT尿路成像(CTU)与静脉尿路造影(IVU)对泌尿系病变的应用价值。方法 130例临床疑诊泌尿系病变的患者,先进行IVU,再行64层螺旋CT尿路成像检查,通过工作站进行多种后处理,比较两者结果。结果 IVU诊断正常3例,诊断泌尿系结石95例,其中肾结石50例,输尿管结石44例,膀胱结石1例,输尿管外压病变2例,泌尿系畸形6例,肿瘤7例,感染性病变1例。CTU诊断正常2例,诊断泌尿系结石106例,其中肾结石60例,输尿管结石45例,膀胱结石1例,外压病变4例,泌尿系畸形9例,肿瘤20例,感染性病变17例。对于泌尿系结石、畸形的诊断两种方法无统计学差异(P>0.05),对于泌尿系肿瘤、感染的诊断两者有统计学差异(P<0.05)。结论 64层螺旋CT通过多种后处理方法,既可全景显示泌尿系的形态结构,也可观察局部病变细节,对泌尿系各种疾病的诊断有重要的临床价值;而对于泌尿系单纯结石性梗阻亦可采用IVU。     

Quantitative evaluation of coronary arterial stenosis using 16-slice multidetector-row computed tomography: preliminary evaluation of phantom study

OBJECTIVE: The purpose of this study is to consider the possibility of quantitative evaluation of coronary arterial stenosis by using 16-slice multidetector-row computed tomography (MDCT). METHODS: Simulated coronary arteries were prepared, which consist of 5-mm-diameter acryl tubes with contrast media (270 HU). Simulated stenoses of known density (-33 HU) were created in each coronary artery (25%, 50%, and 75%). Cardiac pulsating with 0, 50, 65, 85, and 105 beats per minute (bpm) was performed. Multiplanar reformation images for each coronary artery were created. Percent stenosis was calculated using the width middle value of boundary part of the arteries. RESULTS: The stenoses were depicted in all heart rates. Average percent stenosis +/- standard deviation was 27.4 +/- 3.6%, 45.8 +/- 2.6%, and 69.4 +/- 2.7%, respectively. For each percent stenosis, there was a significant difference (P < 0.05). CONCLUSION: Sixteen-slice MDCT has a potential for noninvasive quantitative evaluation of stenosis in coronary arteries.     

Radioanatomical study of a true tracheal bronchus using multidetector computed tomography

Purpose  

True tracheal bronchus (TTB) is a rare anomaly in which a lobar or segmental ectopic bronchus arises from the trachea. We examined the frequency and multidetector computed tomography (MDCT) appearances of TTB.     

Assessment of coronary artery stent patency and restenosis using 64-slice computed tomography

RATIONALE AND OBJECTIVES: Restenosis remains a major limitation of coronary catheter-based stent placement. Therefore, a reliable noninvasive diagnostic method for the evaluation of stented coronary arteries would be highly desirable. Our aim was to evaluate the diagnostic accuracy of high-resolution 64-slice computed tomography (64SCT) in a pilot study for the assessment of the lumen of coronary artery stents. MATERIALS AND METHODS: Twenty-five patients underwent 64SCT of the coronary arteries and quantitative x-ray coronary angiography (QCA) after coronary artery stent placement. 64SCT coronary angiography was performed with the following parameters: spatial resolution = 0.4 x 0.4 x 0.4 mm; temporal resolution = 83-165 milliseconds; contrast agent = 80 mL at a flow rate of 5 mL/second; retrospective electrocardiogram gating. The 64SCT scans were evaluated for image quality and for the presence of significant in-stent and peri-stent (proximal and distal) stenoses. Determinations were made of the sensitivity, specificity, diagnostic accuracy, and positive and negative predictive values (PPV and NPV) of 64SCT for the detection or exclusion of stenoses. RESULTS: A total of 46 stents were evaluated, of which 45 (98%) were of diagnostic image quality. Significant in-stent restenosis or occlusion was detected on QCA in 8/45 cases (>/=50% stenosis = 6; occlusion = 2). The sensitivity, specificity, accuracy, PPV, and NPV of 64SCT for the detection of significant in-stent disease was 75%, 92%, 89%, 67%, and 94%, respectively. Both occluded coronary artery stents were correctly identified. The sensitivity, specificity, and accuracy values of 64SCT for the detection of significant proximal peri-stent stenoses were 75%, 95%, and 93%, respectively, whereas the values for detection of significant distal peri-stent stenoses were 67%, 85%, and 84%, respectively. CONCLUSION: The high spatial and temporal resolution of 64SCT may permit improved assessment of stent occlusion and peri-stent disease, although detection of in-stent stenosis remains difficult.