In vitro evaluation of coronary stents and in-stent stenosis using a dynamic cardiac phantom and a 64-detector row CT scanner

Introduction

The aim of the study was to examine the ability of a 64-slice MDCT to detect in-stent stenoses in an ex vivo model of coronary stents.

Methods

Five different stents (Liberté?, Boston Scientific; Driver^®, Medtronic; Multi-Link Vision^®, Guidant; Taxus^® Express^®, Boston Scientific; Cypher^®, Cordis) were examined using a dynamic cardiac phantom. The stents were pulled over a vessel model that consists of a polymer tube with diameters of 3.0, 3.5, and 4.0 mm and four different degrees of stenoses (0%; 30%; 50%; 70–80%). This model was moved with a rate of 60 bpm to mimic cardiac motion. To assess the degree of artificial signal reduction (artificial reduction of attenuation (ARA)) by the different stents, attenuation values were measured in the vessel outside the stent, and in the non-stenotic vessel inside the stent. Furthermore the grade of stenosis was assessed by two clinical observers.

Results

Highest ARA was found for the Cypher^® Stent (35 HU), whereas the Liberté? Stent presented the lowest ARA (16 HU). Depending on the stent and the vessel diameter, up to 87.5% of the stenoses were correctly diagnosed. In the 3.0 and 3.5 mm vessels, a nonstenotic or low-grade stenotic vessel was diagnosed as intermediate or high-grade stenosis in 22.5%, whereas in the 4.0 mm vessels, this kind of overestimation did not occur. A 50% stenosis was diagnosed as a 30% stenosis in 30%. On the other hand, highgrade stenoses were underestimated in only 10%. On a fourpoint scale, the average deviation from the real grade of stenosis was 0.21 for the Liberté? stent, 0.54 for the Taxus^® Express^® stent, 0.29 for Driver^® stent, 0.62 for the Multi-Link Vision^® stent, and 0.37 for the Cypher? stent.

Conclusions

In a dynamic cardiac phantom model, high grade stenoses in vessels with a diameter of 4 mm could be reliably detected irrespective of the stent type used in this study. Vice versa, high grade stenoses (≥50%) could only be ruled out with certainty in vessels with a diameter of 4 mm. In smaller vessels, the ability to correctly diagnose high-grade stenoses was dependent on the type of stent and the imaging artifacts associated with it.

     

320排宽探测器CT评估儿童先天性心脏病术后心功能

目的 探讨320排宽探测器CT评估儿童先天性心脏病（CHD）术后心功能的可行性。方法 对25例CHD术后患儿以320排宽探测器CT和3.0T MR设备进行扫描，分别利用相应心功能分析软件测量左右心室射血分数（EF）、舒张末期容积指数（EDVI）、收缩末期容积指数（ESVI）、每搏输出量指数（SVI）和心指数（CI），分析320排宽探测器CT与MRI测量结果的相关性和可重复性。结果 CT测得左右心室EF、EDVI、ESVI、SVI、CI与MRI相应指标差异均无统计学意义（P均>0.05）且均具有良好相关性（r=0.62~0.97，P均<0.05）；CT所测各指标均值均高于MRI；CT各心功能测量值重复性良好（ICC=0.85~0.98，P均<0.05），左心室容量指标（EDVI、ESVI、SVI、CI）的重复性好于右心室。结论 320排宽探测器CT可用于评价CHD术后患儿心功能，对无法接受MR检查者具有重要价值。     

Coronary CT angiography using the second-generation 320-detector row CT: assessment of image quality and radiation dose in various heart rates compared with the first-generation scanner

To assess the image quality and radiation dose reduction in various heart rates in coronary CT angiography using the second-generation 320-detector row CT compared with the first-generation CT. Ninety-six patients were retrospectively included. The first 48 patients underwent coronary CT angiography with the first-generation 320-detector row CT, while the last 48 patients underwent with the second-generation CT. Subjective image quality was graded using a 4-point scale (4, excellent; 1, unable to evaluate). Image noise and contrast-to-noise ratio were also analyzed. Subgroup analysis was performed based on the heart rate. The mean effective dose was derived from the dose length product multiplied by a conversion coefficient for the chest (κ = 0.014 mSv × mGy^?1 × cm^?1). The overall subjective image quality score showed no significant difference (3.66 vs 3.69, respectively, p = 0.25). The image quality score of the second-generation group tended to be higher than that of the first-generation group in the 66- to 75-bpm subgroup (3.36 vs 3.53, respectively, p = 0.07). No significant difference was observed in image noise and contrast-to-noise ratio. The overall radiation dose reduced by 24 % (3.3 vs 2.5 mSv, respectively, p = 0.03), and the reduction was substantial in patients with higher heart rate (66- to 75-bpm, 4.3 vs 2.2 mSv, respectively, p = 0.009; >75 bpm, 8.2 vs 3.7 mSv, respectively, p = 0.005). The second-generation 320-detector row CT could maintain the image quality while reducing the radiation dose in coronary CT angiography. The dose reduction was larger in patients with higher heart rate.     

256层螺旋CT大范围心电门控扫描的冠状动脉成像质量评价

目的：探讨256层螺旋CT大范围心电门控扫描胸腹部血管联合成像对冠状动脉成像质量的评价.方法：对34例因胸痛就诊的患者用256层螺旋CT行大范围心电门控扫描检查,检查完成后,进行冠状动脉图像重建,并与常规CT冠脉扫描的图像进行比较.结果：行大范围心电门控扫描检查组的冠状动脉图像质量优良率为89.7％ （456/508）,能够满足诊断要求的为95.5％（485/508）,常规冠状动脉扫描组中,图像质量优良率为89.8％（460/512）,能够满足诊断要求的为96.3％ （489/512）.两组的图像优良率无明显差异（χ2=1.072,P=-0.192）.结论：256层螺旋CT大范围心电门控扫描能够满足冠状动脉成像的要求,具有较高的临床应用价值.     

Comparison of aortic root dimension changes during cardiac cycle between the patients with and without aortic valve calcification using ECG-gated 64-slice and dual-source 256-slice computed tomography scanners: results of a multicenter study

With advent of transcatheter aortic valve implantation, using multislice computed tomography (MSCT) to provide detailed data about aortic root has become more crucial. We compared aortic dimension changes during cardiac cycle in patients with and without aortic valve calcification and evaluated its correlation with aortic valve calcium score in former group. Fifty-two patients with and 52 subjects without aortic valve calcification underwent coronary MSCT using two 64-slice and a dual-source 256-slice CT scanners. Aortic root dimensions were measured in both systolic and diastolic phases. Changes in annular maximum diameter (D_max), minimum diameter (D_min), cross sectional area and perimeter, three diameters of sinuses of Valsalva (V_a, V_b and V_c), sinotubular junction maximum (STJ_max) and minimum (STJ_min) diameters between systolic and diastolic phases (systole minus diastole) were ?0.59 mm, ?0.05 mm, ?2.53 mm², ?1.48 mm, +0.91 mm, +1.08 mm, +0.42 mm, +0.63 mm, +0.40 mm and in those without aortic calcification –0.33 mm, 0.00 mm, ?6.92 mm², ?0.41 mm, +0.30 mm, +0.38 mm, +0.61 mm, +0.33 mm, +0.20 mm in patients with aortic calcification, respectively. Apart from two diameters in sinuses of Valsalva (V_a and V_b), changes in all other diameters of aortic root during cardiac cycle were not significantly different between the two groups. Furthermore, in patients with aortic calcification, no significant correlation was detected between changes in nearly all aortic root dimensions during cardiac cycle and aortic valve calcium score or location of calcification (annular, commissural or both).     

Prediction of coronary artery plaque progression and potential rupture from 320-detector row prospectively ECG-gated single heart beat CT angiography: Lattice Boltzmann evaluation of endothelial shear stress

Advances in MDCT will extend coronary CTA beyond the morphology data provided by systems that use 64 or fewer detector rows. Newer coronary CTA technology such as prospective ECG-gating will also enable lower dose examinations. Since the current standard of care for coronary diagnoses is catheterization, CT will continue to be benchmarked against catheterization reference points, in particular temporal resolution, spatial resolution, radiation dose, and volume coverage. This article focuses on single heart beat cardiac acquisitions enabled by 320-detector row CT. Imaging with this system can now be performed with patient radiation doses comparable to catheterization. The high image quality, excellent contrast opacification, and absence of stair-step artifact provide the potential to evaluate endothelial shear stress (ESS) noninvasively with CT. Low ESS is known to lead to the development and progression of atherosclerotic plaque culminating in high-risk vulnerable plaque likely to rupture and cause an acute coronary event. The magnitude of local low ESS, in combination with the local remodeling response and the severity of systemic risk factors, determines the natural history of each plaque. This paper describes the steps required to derive an ESS map from 320-detector row CT data using the Lattice Boltzmann method to include the complex geometry of the coronary arterial tree. This approach diminishes the limitations of other computational fluid dynamics methods to properly evaluate multiple coronary arteries, including the complex geometry of coronary bifurcations where lesions tend to develop.     

多层螺旋CT对活体肾移植供体术前综合评价的初步研究

目的评价MSCT在活体肾供体术前综合评价中的价值。方法11例供体术前进行了MSCT三期增强扫描,均进行VR及MIP重组,观察肾实质、肾动脉、肾静脉以及集尿系统,并与9例手术结果进行对照分析。结果MSCTA显示23支肾动脉,包括左肾副动脉1例;23支肾静脉,包括1例左双肾静脉;23支肾盂输尿管,包括1例右侧双肾盂双输尿管。此外,还检出副肝静脉2例,脾动脉瘤1例。2例放弃手术,1例因肾血管原因,1例为乙肝病毒携带者;9例手术结果与MSCT所见完全吻合,准确率为100%。结论MSCT作为术前活体肾供体的一站式检查技术,有重要的临床应用价值。     

320排CT可变螺距采集技术在经导管主动脉瓣置换术术前评估中的应用

目的:探讨CT可变螺距(VHP)采集技术在大范围主动脉及主动脉瓣膜成像中的应用价值。方法:回顾性分析我院2016年1月至2018年4月经导管主动脉瓣置换术(TAVR)术前扫描CTA患者54例(实验组),采用东芝320排CT,扫描范围从胸廓入口扫描至股骨中段水平;胸廓入口至心底采用小螺距心电门控,心底至股骨中段水平采用大螺距非心电门控扫描模式;管电压120 kV,智能管电流,层厚/间距0.5/0.3 mm,对比剂90～100 mL,流速4～5 mL/s;分别重建30%、40%、75%时相。对照组32例患者采用大范围全门控扫描方案,扫描范围、扫描条件、重建参数、对比剂用量均与实验组相同。结果:53例屏气好的患者扫描均获得了成功,1例患者因屏气能力太差导致扫描失败。回顾性心电门控可以很好地获得主动脉瓣瓣膜的图像,并可以观察冠状动脉狭窄情况;大范围非心电门控扫描可获得所有的外周血管入路。结论:VHP技术适用于TAVR术前评估,一次扫描可完成大范围全主动脉的扫描,对比剂使用少,且可观察瓣膜及冠状动脉;缺点是屏气要求高,心电门控时只能采用全门控,辐射剂量较高。     

Optimization of acquisition and contrast injection protocol for C-arm CT imaging in transcatheter aortic valve implantation: initial experience in a swine model

To determine the optimal C-arm computed tomography (CT) protocol for transcatheter aortic valve implantation (TAVI) in swine. In 6 swine, C-arm CT was performed using 5-s ungated acquisition during sinus rhythm with aortic root (Method 1) or peripheral (Method 2) injection, and during rapid ventricular pacing with root injection (Method 3). Additionally, 24-s ECG-gated acquisitions were performed during sinus rhythm with root (Method 4) or peripheral (Method 5) injection. Aortic root enhancement, presence of artifacts and contrast volumes were compared for all methods. Aortic root measurements were also compared between C-arm CT and multidetector-row computed tomography (MDCT). The best C-arm CT image set was identified and used to predict optimal angiographic projection angles during TAVI; predictions were compared to those from MDCT. Methods 1, 3, 4, and 5 yielded sufficient root enhancement with mild or moderate artifacts and aortic annulus, sinotubular junction, and mid-ascending aorta diameters similar to MDCT. Ungated C-arm CT (Methods 1, 3) required less contrast than ECG-gated C-arm CT (Methods 4, 5). Method 3 was optimal yielding images with high attenuation, few artifacts (2.0), and root measurements similar to MDCT using minimal contrast (36 mL). Predicted angiographic projections from Method 3 were similar to MDCT. Ungated C-arm CT during rapid pacing with aortic root injection required minimal contrast, yielded high attenuation and few artifacts, and aortic root measurements and predicted angiographic planes similar to those from MDCT.     

CT angiography for evaluation of coronary artery disease in inner-city outpatients: an initial prospective comparison with stress myocardial perfusion imaging

To evaluate the utility of CT coronary angiography (CTA) for demonstrating coronary artery disease in inner-city outpatients, we prospectively compared CTA with stress SPECT myocardial perfusion imaging in an ethnically diverse, gender balanced population. All patients gave written informed consent for this IRB approved, HIPAA compliant study. Sixty-one patients completed both CTA and SPECT. About 67% were ethnic minorities, 51% were women. A stenosis of ≥70% on CTA was considered positive. Results were compared with perfusion defects on SPECT and correlated with clinical endpoints (hospital admissions, cardiovascular events, coronary interventions and deaths). CTA and SPECT data were compared with results of coronary angiography, when performed. There was moderate global agreement of 79% (48/61) between CTA and SPECT, κ = 0.483 (SE ± 0.13, P = 0.0001). With SPECT as the reference standard, CTA had sensitivity of 73% (11/15), specificity of 80% (37/46), negative predictive value of 90% (37/41) and positive predictive value of 55% (11/20). Positive SPECT was associated with positive CTA, (P < 0.0001, OR = 22). Eleven (18%) underwent subsequent cardiac catheterization, which was positive in 91% (10/11). CTA and SPECT had positive predictive values of 90 and 83% compared with catheterization. This study lends preliminary evidence to support to the utility of CTA as an alternative modality for the evaluation of CAD in an ethnically diverse, gender balanced inner-city outpatient population. Similar to more homogenous groups, CTA had a high negative predictive value and demonstrated disease occult to SPECT. Further study is necessary to evaluate the impact of CTA on patient outcomes.     

Triple rule-out acute chest pain evaluation using a 320-row-detector volume CT: a comparison of the wide-volume and helical modes

The purpose of this study was to investigate the image quality and radiation dose of triple rule-out computed tomography (TROCT) using a 320-row-detector volume CT system to compare the wide-volume and helical modes of this CT system. Sixty-four patients with noncritical chest pain were allocated to one of 2 groups according to the type of CT examination mode used. Group 1 patients were examined using the wide-volume (non-spiral) mode and group 2 patients were examined using the 160-detector row helical mode, with the same contrast injection protocol in both methods [biphasic injection protocol; injection rate of 4 ml/s, median volume, 70 ml (range 65–100 ml)]. Attenuations of the pulmonary trunk, ascending aorta, and coronary arteries were measured in Hounsfield units; a subjective overall patient-based image quality score of 1–3 was awarded to each study. Effective doses, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. Average effective dose was significantly lower in group 1 than group 2 (9.7 ± 5.1 vs. 16 ± 5.9 mSv, P < 0.001). The mean attenuation of the main pulmonary trunk was significantly higher in group 1 than group 2 (P = 0.04) and mean attenuations in other vessels were not significant different. SNR and CNR were not significantly different between the groups. The proportion of diagnostic image qualities for chest CT angiography (CTA) was similar between the groups (93.5 vs. 93.9 %). In coronary CTA, group 1 showed a higher proportion of diagnostic image qualities than group 2 (100 vs. 87.9 %). The use of wide-volume mode of 320-detector CT reduces the overall effective radiation dose and results in similar attenuation and image quality for TROCT as compared with the helical mode.     

Improvement of in-stent lumen measurement accuracy with new High-Definition CT in a phantom model: comparison with conventional 64-detector row CT

The purpose of this study was to evaluate improvement of measurement accuracy of in-stent lumen using coronary stent phantoms on new High-Definition CT (HDCT) compared with conventional 64 detector-row CT (MDCT). To estimate the spatial resolution, a high-resolution insert of CATPHAN (The Phantom Laboratory, NY, USA) was scanned by both HDCT (Discovery CT750 HD) and MDCT (LightSpeed VCT). Also, we developed six types of stent phantom, which have 2.5- and 3.0-mm-diameter with three different types of stents (Velocity: Johnson & Johnson, Driver: Medtronic, Multilink-Rx: Guidant). A 50% stenotic segment made of acrylic resin was built at the center inside the stent. Those coronary vessel phantoms were made of acrylic resin and filled with diluted Iodine (350 HU in 120 kVp), and each stent was fixed inside of those vessels. Those phantoms in water-filled tank were scanned on both HDCT and MDCT. The luminal diameter obtained using digital calipers at five different points and the mean luminal diameter (MLD) were calculated. The underestimate ratio (UR) and △UR was defined as follows: UR = [True diameter of stent—MLD]/True diameter of stent; △UR = [MLD at HDCT—MLD at MDCT]/True diameter of stent. The spatial resolution was estimated to be 0.71 mm on MDCT and 0.50 mm on HDCT. At the non-stenotic segments, the △URs were 11.6% (Velocity), 16.4% (Driver) and 7.2% (Multilink) for the 2.5-mm stents, and 14.0% (Velocity), 16.3% (Driver) and 13.3% (Multilink) for the 3.0-mm stents. At the stenotic segment, the △URs were 23.2% (Velocity), 8.0% (Driver) and 13.6% (Multilink) for the 2.5-mm stents, and 20.0% (Velocity), 14.7% (Driver) and 15.3% (Multilink) for the 3.0-mm stents. Superior spatial resolution of HDCT could be promising for more accurate measurement of in-stent diameter.     

Surgical management of aortic and mitral valve disease: an overview

This paper examines aortic and mitral valve disease. It considers how nurses can treat patients with these conditions and provide support and education to help them understand their disease and the risks and benefits of surgery. Nurses also have a role in secondary prevention and in helping patients adapt to living with a prosthetic valve.     

Evaluation of complex congenital heart disease with prospective ECG-gated cardiac CT in a single heartbeat at low tube voltage (70 kV) and adaptive statistical iterative reconstruction in infants: a single center experience

The International Journal of Cardiovascular Imaging - The purpose of this study is to evaluate the radiation dose, image quality, and diagnostic accuracy of prospective ECG-gated cardiac CT at...     

Prospective versus retrospective ECG-gated 64-detector coronary CT angiography for evaluation of coronary artery bypass graft patency: comparison of image quality,radiation dose and diagnostic accuracy

We aimed to evaluate image quality, radiation dose and diagnostic accuracy of coronary CT angiography (CCTA) with a prospectively gated transverse-axial scan (PGT) compared with a retrospectively gated helical scan (RGH), using a 64-slice scanner in patients who underwent coronary artery bypass graft (CABG). Of the 131 consecutive patients that underwent CABG using 64-slice multidetector row computed tomography during 2008, patients with heart rate (HR) of <75 beats/minute (bpm), and HR variation <10 bpm were included in the study. PGT was performed on 39 patients with 93 grafts, with RGH performed on 43 patients with 102 grafts. Image quality (1: excellent—4: poor) and estimated radiation dose were compared between the two groups. Of these, a total of 64 segments in 26 patients were subjected to invasive coronary angiography (ICA) for clinical reasons. Diagnostic accuracy of CCTA for evaluation of graft was performed between the two groups with ICA as a reference standard in terms of significant stenosis (≥ 50% of luminal stenosis). The image quality was not statistically different in the two groups. Mean effective radiation dose was 6.5 mSv in PGT-group, which was significantly lower than that in the RGH-group (21.2 mSv; P < 0.001). There was no statistically significant difference in diagnostic accuracy between the two groups (PGT-group versus RGH-group; 93.1% versus 91.4%). PGT can achieve dose reductions of up to 70% compared to RGH while maintaining image quality and high diagnostic accuracy in patients undergoing CABG.     

CT predictors of post-procedural aortic regurgitation in patients referred for transcatheter aortic valve implantation: an analysis of 105 patients

Cardiac computed tomography (CT) allows accurate and detailed analysis of the anatomy of the aortic root and valve, including quantification of calcium. We evaluated the correlation between different CT parameters and the degree of post-procedural aortic regurgitation (AR) after transcatheter aortic valve implantation (TAVI) using the balloon-expandable Edwards Sapien prosthesis. Pre-intervention contrast-enhanced dual source CT data sets of 105 consecutive patients (48 males, mean age 81 ± 6 years, mean logEuroSCORE 34 ± 13 %) with symptomatic severe aortic valve stenosis referred for TAVI using the Edwards Sapien prosthesis (Edwards lifesciences, Inc., CA, USA) were analysed. The degrees of aortic valve commissural calcification and annular calcification were visually assessed on a scale from 0 to 3. Furthermore, the degree of aortic valve calcification as quantified by the Agatston score, aortic annulus eccentricity, aortic diameter at the level of the sinus of valsalva and at the sinotubular junction were assessed. Early post-procedural AR was assessed using aortography. Significant AR was defined as angiographic AR of at least moderate degree (AR ≥ 2). Visual assessment of the degree of aortic annular calcification as well as the Agatston score of aortic valve calcium correlated weakly, yet significantly with the degree of post-procedural AR (r = 0.31 and 0.24, p = 0.001 and 0.013, respectively). Compared to patients with AR < 2, patients with AR ≥ 2 showed more severe calcification of the aortic annulus (mean visual scores 1.9 ± 0.6 vs. 1.5 ± 0.6, p = 0.003) as well as higher aortic valve Agatston scores (1,517 ± 861 vs. 1,062 ± 688, p = 0.005). Visual score for commissural calcification did not differ significantly between both groups (mean scores 2.4 ± 0.5 vs. 2.5 ± 0.5, respectively, p = 0.117). No significant correlation was observed between the degree of AR and commissural calcification, aortic annulus eccentricity index or aortic diameters. The extent of aortic valve annular calcification, but not of commissural calcification, predicts significant post-procedural AR in patients referred for TAVI using the balloon-expandable Edwards Sapiens prosthesis.     

A hybrid approach for quantification of aortic valve stenosis using cardiac magnetic resonance imaging and echocardiography:

Summary We replaced Dopplerderived stroke volume in the continuity equation (method A) by either right heart catheterizationderived stroke volume (method B) or cardiovascular magnetic resonance–derived stroke volume (method C) to calculate aortic valve area in 20 consecutive patients with moderate or severe aortic stenosis. Comparison of both hybrid methods (methods B and C) by Bland–Altman analysis showed a mean difference near zero, a spread within two standard deviations and very similar limits of agreement. More importantly, all patients were classified into the same category of severity by both methods.     

Subclavian artery stenosis masquerading as prosthetic aortic stenosis: a potential source of confusion in Doppler evaluation of aortic valve disease.

In this case report we describe a patient with a prosthetic aortic valve in whom a high-velocity signal from a right subclavian artery stenosis initially was mistaken for the aortic jet signal. Differences in the shapes of the jets obtained from an apical and right supraclavicular position suggested different origins of these two high-velocity systolic signals. Correct identification of the origin of each signal was possible with pulsed Doppler recordings of the subclavian artery and high pulse-repetition-frequency pulsed Doppler interrogation of the aortic valve.