模体大小对CBCT图像剂量计算的影响

目的：锥形束CT（CBCT）使用宽束X-射线,探测板获取的信号受散射线的影响很大。该文对扫描模体大小及散射体积对CBCT重建图像HU值及剂量计算的影响进行研究。方法：在Elekta Synergy-XVICBCT系统中对不同深度及散射体积的均匀水模和非均匀密度参考模体扫描,并测量感兴趣区域的HU值;建立考虑和不考虑散射的两组HU-物理密度曲线应用于水模及头颈部仿真模体CBCT图像进行剂量计算,与常规CT图像（FBCT）计算结果比较。结果：均匀水模CBCT图像的HU值随水模深度增加先增大后略有减少,随纵轴散射长度增加而减少,变化幅度最大均接近10%。随散射长度增加,非均匀密度参考模体CBCT图像的高密度组织的HU值减少而低密度组织HU值增加,对1.609 g/cm3致密度骨最大减少约1422 HU。均匀水模和头颈部仿真模体CBCT图像使用考虑散射的HU-物理密度修正曲线计算与FBCT图像比较结果为：点绝对剂量（cGy/MU）最大偏差小于1.5%,等剂量线偏差小于2 mm~3 mm,2%/2 mm DTA指数的通过率平均大于97%,明显优于不做散射修正的结果。结论：Elekta Synergy-XVI系统获取CBCT图像的HU值受扫描模体的几何大小及散射体积影响很大,应选择与扫描患者近似几何大小及人体组织等效的HU-密度校准模体。考虑模体大小及散射修正的头颈部模体CBCT图像用于剂量计算能满足临床要求。     

一种高性能静态医用计算机断层成像装置

传统医用螺旋CT利用滑环旋转射线源和探测器采集全角度数据。由于受离心加速度及高压绝缘材料的应力等因素限制,其转速已接近物理极限,且高速旋转会导致机架结构不稳定,带来安全隐患,影响成像质量。为解决以上问题,本研究提出一种静态CT系统,采用高速脉冲切换的分布式射线源,无需任何物理运动即可采集全角度投影数据。该系统设计包括成像、结构和控制三部分。通过扫描20 cm水模、体模Catphan500和人体体模、生物组织验证系统性能和成像稳定性。结果显示,静态CT扫描系统在10 ms内,在体模测试中获取的图像可达到验收标准,其中,空间分辨率的测试结果高于正常指标3倍;在人体组织扫描测试中图像质量的合格率大于98%。该静态CT系统各项图像性能指标良好,可满足临床需求。     

基于体模的DSA类CT图像质量研究

目的 在血管造影（DSA）设备上,通过对等效性能的人体仿真体模进行类CT成像,分析DSA中的类CT的图像质量,为DSA设备中类CT图像质量评估提供基础。方法 分别在配置相同的西门子dTA DSA设备上和飞利浦FD20 DSA设备上,利用仿真头颅体模Kyoto Kagaku PBU-60和自制小孔体模进行类CT成像,对采集到的数据进行低对比度、空间均匀性等分析,并进行体模一致性分析。结果 这2台设备均能清晰地呈现头模内部血管结构、走行,以及相应的组织结构等信息,对于自制的体模2台设备的低对比度均为0.2 %,场均匀性2.624 07 Hu 和2.489 75 Hu。结论 这2台设备的类CT图像质量指标,包括噪声、低对比度、场均匀性等均符合检测要求,对DSA设备的类CT图像质量控制工作的开展具有一定的实际意义。     

非均匀体模与人体对钴—60γ射线等效性的对比测试研究报告

非均匀人体组织等效辐照体模(简称非均匀体模或体模)的各种组织材料的等效性已由四川大学核物理专业采用能谱测量法测试验证,但制作成型后,是否仍具有与真实人体相似的辐照等效性,尚需进一步研究证实。体模的X光照片及CT扫描图象照片与真人照片的     

基于组织等效3D打印的多模椎骨体模设计

目的:设计一种基于影像建模、组织等效和3D打印技术的多模态椎骨骨折影像学仿真体模。方法:采集1例健康人腰椎影像样本的腰椎段CT影像序列,将原始DICOM图像导入Mimics交互式的医学影像控制系统软件进行椎骨、肾脏和软组织的三维重建,在重建模型中构建"一"字缝、"Y"字缝的椎骨峡部骨折模型。使用3D打印和组织等效技术打印等X线吸收密度的椎骨骨折模型,经CT、数字X线摄影(DR)多模成像,对模型CT值进行评估,验证体模仿真程度。结果:所获得的椎骨骨折体模在CT、DR下成像清晰,组织X线吸收系数等效于真实人体组织。结论:基于3D打印技术的多模态椎骨骨折体模可在CT和DR影像下获得,并可应用于有限元生物力学分析。模体制做成本低廉且快速,组织等效参数符合正常人体参数范围,能够有效仿真3种不同类型的椎骨峡部裂骨折等人体腹部病变。     

辐照仿真人体模型三维建模及装配原理与方法

辐照仿真人体模型是放射治疗和空间辐照研究的重要装备,实现其数字化建模,提高制造精度和仿真程度是仿真假人研究的重点和难点之一。以"成都剂量体模"(CDP)的序列CT切片集为源数据,运用MATLAB软件,通过图像预处理、图像提取等数字图像处理技术获得人体器官的点云数据;在CATIA软件Digitized Shape Editor模块中处理点云数据得到肝脏、肺、肾和胃等主要器官和组织的三维实体模型;以人体骨骼为基础建立人体器官装配坐标系;根据器官的"局部坐标系原点"、"标志点"和"特征点"与人体骨骼的相对位置,确定器官在人体器官装配坐标系中的坐标;利用Pro/E软件完成人体主要器官(异形体零件)装配。实验证明利用该方法建立的三维辐照仿真假人数字化模型与CDP具有较高的等效程度,为人体参数化设计奠定了理论基础,能够满足辐照仿真假人数字化生产的要求。     

干水组织等效材料的辐射特性和热力学特性研究

从1895年伦琴发现X射线以来,X线射被最先应用于医学领域,许多医学家和实验物理学家不断努力,试图利用所谓组织等效材料(tissue eguivalent matevials)来复制射线在体内外的相似效应。1906年奥地利放射学家Kienboch最早提出一定厚度的铝箔与肌肉组织辐射效应相似的观点。随着科学技术的发展和核技术在工农医领域广泛的应用,到八十年代初辐射等效材料已形成五大系列(固体、水、液体、凝胶、粉剂)160余种,而液体和凝胶材料占30％,展现了人体组织替代物和仿真人体模型诱人的发展前景。新近国际辐射剂量单位和测量委员会(ICRU)组织替代物和体模专门委员会主席D、R、White指出“随着现代医疗照射设备和技术的进步,将需要更多的仿真体模和组织替代物材料,放射物理工作者应把研究和制备这些体模和材料视为自己的光荣职责”。     

基于3D打印技术构建仿真儿童CT增强腹部体模的测试研究

目的:本研究构建仿真的儿童CT增强腹部体模,并验证其解剖结构的CT衰减特性与正常儿童腹部增强CT图像质量比较。方法:基于3D打印直写成型技术,将聚氨酯和三(2-氯乙基)磷酸酯(TCEP)作为混合的打印材料。使用不同浓度的TCEP(0%～60%)混合材料,在不同管电压下(80～120 kV),评价TCEP混合材料浓度和CT值的线性关系。根据患者CT影像数据设计并打印仿真动脉期儿童CT增强腹部体模。体模在CT下重复3次扫描以评估数据一致性。将仿真CT图像与正常儿童的CT图像比较,对肝脏、腹主动脉、肾皮质、脾脏和肌肉的CT值、图像噪声、对比噪声比(CNR)进行计算和客观评价。采用5分制,由两个放射科医生对图像质量进行主观评价。结果:在不同的管电压下,TCEP浓度变化和CT值之间都存在良好的线性关系(P0.001, r=0.99)。除了腹主动脉,仿真体模各解剖结构CT值与正常儿童一致(P0.05)。肝脏、肾皮质和脾脏的体模图像比正常儿童的图像有更高的CNR值(7.08±0.83 vs 5.50±0.48、14.18±2.48vs10.67±1.05、11.84±1.69 vs 8.78±0.53)。仿真体模CT图像噪声相比于正常儿童基本一致[(12.3±1.47)HU vs (13.7±1.5)HU]。但主观图像质量评分略低(4.35±0.17 vs 4.72±0.17、4.50±0.16 vs 4.65±0.12)。结论:研究证明通过3D打印直写成型技术构建仿真体模具有可行性,且图像质量和一致性良好。仿真的儿童CT体模能模拟不同患者体型的组织衰减特性,可用于优化CT剂量和重建算法。     

动态心脏体模在心脏计算机断层扫描成像质量控制中的应用

论述了动态心脏体模作为计算机断层扫描（CT）设备心脏成像质量评价与质量保证工具的重要性;介绍了当前几类动态心脏体模在心脏CT成像质量控制中的应用进展,包括运动型、功能型和仿真型动态心脏体模。分析了现有动态心脏体模在解剖结构、组织材料和运动特性的不足,并提出利用等效材料制作四腔室心脏体模和基于容积-时间曲线控制模拟心脏全周期运动的可行性,以探究研制一种“结构仿生、运动仿真”动态心脏体模的可行性,从而为建立心脏CT成像质量定量评价标准提供理论依据和技术支撑。     

基于3D打印的医学三维重构软件系统的精度研究

为研究Arigin 3D Pro医学三维重构软件的精度和稳定性,制作3种形状的CT体模和球形的MRI体模作为实体模型。选取3种CT设备和1种MRI设备对制作的实体模型进行数据扫描,选择重构经验不同的3名操作者使用Arigin 3D Pro医学三维重构软件进行重构,每次重构均使用Geomagic Wrap测量3次参数,并用游标卡尺测量实体模型参数。结果表明,重构的三维模型与实体模型的相对误差占实体模型的0.09%～1.28%,该软件可对不同品牌的CT、MRI扫描数据进行处理,一致性指标ICC为0.930,具有通用性。同一操作者多次重构相同模型的组内误差占实体模型的0.56%～0.82%,不同操作者重构的三维模型存在组间差异,重构经验越少,差异越大。通过Catphan体模对Arigin 3D Pro医学三维重构软件的定量评价,表明该软件重构的模型精度准确性较高,稳定性较好。     

Effect of motion on tracer activity determination in CT attenuation corrected PET images: a lung phantom study

Respiratory motion is known to affect the quantitation of 18FDG uptake in lung lesions. The aim of the study was to investigate the magnitude of errors in tracer activity determination due to motion, and its dependence upon CT attenuation at different phases of the motion cycle. To estimate these errors we have compared maximum activity concentrations determined from PET/CT images of a lung phantom at rest and under simulated respiratory motion. The NEMA 2001 IEC body phantom, containing six hollow spheres with diameters 37, 28, 22, 17, 13, and 10 mm, was used in this study. To mimic lung tissue density, the phantom (excluding spheres) was filled with low density polystyrene beads and water. The phantom spheres were filled with 18FDG solution setting the target-to-background activity concentration ratio at 8:1. PET/CT data were acquired with the phantom at rest, and while it was undergoing periodic motion along the longitudinal axis of the scanner with a range of displacement being 2 cm, and a period of 5 s. The phantom at rest and in motion was scanned using manufacturer provided standard helical/clinical protocol, a helical CT scan followed by a PET emission scan. The moving phantom was also scanned using a 4D-CT protocol that provides volume image sets at different phases of the motion cycle. To estimate the effect of motion on quantitation of activities in six spheres, we have examined the activity concentration data for (a) the stationary phantom, (b) the phantom undergoing simulated respiratory motion, and (c) a moving phantom acquired with PET/4D-CT protocol in which attenuation correction was performed with CT images acquired at different phases of motion cycle. The data for the phantom at rest and in motion acquired with the standard helical/clinical protocol showed that the activity concentration in the spheres can be underestimated by as much as 75%, depending on the sphere diameter. We have also demonstrated that fluctuations in sphere's activity concentration from one PET/CT scan to another acquired with standard helical/clinical protocol can arise as a consequence of spatial mismatch between the sphere's location in PET emission and the CT data.     

The development of a xenon/computed tomography cerebral blood flow quality assurance phantom

A simple, easy to use, quality assurance and performance test phantom was developed for the xenon/computed tomography (CT) cerebral blood flow method. The phantom combines an inhalation system which allows for the simulation of xenon buildup or washout in the arterial blood as well as a multisection translatable cylinder in which several sections can be scanned during a preselected protocol to simulate the CT enhancement in brain tissue during a study. The phantom and scanning protocol are described and their use is demonstrated. The results compare favorably to the theoretically expected fast, intermediate, and slow "flow" values designed into the phantom.     

A Monte Carlo based method to estimate radiation dose from multidetector CT (MDCT): cylindrical and anthropomorphic phantoms

The purpose of this work was to extend the verification of Monte Carlo based methods for estimating radiation dose in computed tomography (CT) exams beyond a single CT scanner to a multidetector CT (MDCT) scanner, and from cylindrical CTDI phantom measurements to both cylindrical and physical anthropomorphic phantoms. Both cylindrical and physical anthropomorphic phantoms were scanned on an MDCT under the specified conditions. A pencil ionization chamber was used to record exposure for the cylindrical phantom, while MOSFET (metal oxide semiconductor field effect transistor) detectors were used to record exposure at the surface of the anthropomorphic phantom. Reference measurements were made in air at isocentre using the pencil ionization chamber under the specified conditions. Detailed Monte Carlo models were developed for the MDCT scanner to describe the x-ray source (spectra, bowtie filter, etc) and geometry factors (distance from focal spot to isocentre, source movement due to axial or helical scanning, etc). Models for the cylindrical (CTDI) phantoms were available from the previous work. For the anthropomorphic phantom, CT image data were used to create a detailed voxelized model of the phantom's geometry. Anthropomorphic phantom material compositions were provided by the manufacturer. A simulation of the physical scan was performed using the mathematical models of the scanner, phantom and specified scan parameters. Tallies were recorded at specific voxel locations corresponding to the MOSFET physical measurements. Simulations of air scans were performed to obtain normalization factors to convert results to absolute dose values. For the CTDI body (32 cm) phantom, measurements and simulation results agreed to within 3.5% across all conditions. For the anthropomorphic phantom, measured surface dose values from a contiguous axial scan showed significant variation and ranged from 8 mGy/100 mAs to 16 mGy/100 mAs. Results from helical scans of overlapping pitch (0.9375) and extended pitch (1.375) were also obtained. Comparisons between the MOSFET measurements and the absolute dose value derived from the Monte Carlo simulations demonstrate agreement in terms of absolute dose values as well as the spatially varying characteristics. This work demonstrates the ability to extend models from a single detector scanner using cylindrical phantoms to an MDCT scanner using both cylindrical and anthropomorphic phantoms. Future work will be extended to voxelized patient models of different sizes and to other MDCT scanners.     

Influence of phantom diameter,kVp and scan mode upon computed tomography dose index

The computed tomography (CT) radiation dose to pediatric patients has received considerable attention recently. Moreover, it is important to be able to determine CT radiation doses for various patient sizes ranging from infants to large adults. The current AAPM protocol only measures CT radiation dose using a 16 cm acrylic phantom to represent an adult head and a 32 cm acrylic phantom to represent an adult body. The goal of this paper is to study the dependence of the computed tomography dose index (CTDI) upon the size of the phantom, the kVp selected and the scan mode employed. Our measurements were done on phantom sizes ranging from 6 cm to 32 cm. The x-ray tube potential ranged from 80 to 140 kVp. The scan modes utilized for the measurements included: consecutive axial scans, single-slice helical scans with variable pitch and multislice helical scans with variable pitch. The results were consolidated into simplified equations which related the phantom diameter and kVp to the measured CTDI. Some generalizations were made about the relationship between the scan modes of the various CT units to the measured radiation doses. The CTDI appears to be an exponential function of phantom diameter. For the same kVp and mAs, the radiation doses for smaller phantoms are much greater than for larger sizes. The derived relationship can be used to estimate the radiation doses for a variety of scan conditions and modes from measurements with the two standard reference phantoms. A method was also given for converting axial CT dose measurements to appropriate MSAD values for helical CT scans.     

DoseLab软件检测CT图像噪声的程序改进及应用分析

目的:对DoseLab软件进行程序改进,增加检测CT图像噪声的功能,对改进的程序进行测试分析。方法:首先,通过使用圆的内接多边形顶点位置计算公式,得到圆内接正三十二边形顶点坐标值。然后,在DoseLab软件Catphan 504模体CTP486模块的图像分析程序中,添加一个正三十二边形的感兴趣区（ROI）,用于检测CT图像噪声。选取2018年每月由西门子CT模拟机日常质量检测（DQC）程序得到的水模体两个层面（S3和S4）的CT图像,对DoseLab改进程序进行测试。对DoseLab改进程序和DQC程序得到的CT图像噪声数据,进行统计分析和比较研究。结果:根据公式计算得到了半径4 cm圆的内接正三十二边形的32个顶点的坐标值,该多边形ROI的面积为49.94 cm2。计算DoseLab改进程序和DQC程序得到的CT图像噪声的差异（ΔN）。在120 kV情形,S3和S4层的ΔN值分别为（0.06±0.07） HU和（0.03±0.09） HU;在140 kV情形,S3和S4层的ΔN值分别为（0.10±0.09） HU和（0.08±0.09） HU。结论:通过添加正三十二边形ROI得到的DoseLab改进程序,可以自动分析水模体和Catphan模体,得到CT图像噪声数据。     

Hybrid computational phantoms of the male and female newborn patient: NURBS-based whole-body models

Anthropomorphic computational phantoms are computer models of the human body for use in the evaluation of dose distributions resulting from either internal or external radiation sources. Currently, two classes of computational phantoms have been developed and widely utilized for organ dose assessment: (1) stylized phantoms and (2) voxel phantoms which describe the human anatomy via mathematical surface equations or 3D voxel matrices, respectively. Although stylized phantoms based on mathematical equations can be very flexible in regard to making changes in organ position and geometrical shape, they are limited in their ability to fully capture the anatomic complexities of human internal anatomy. In turn, voxel phantoms have been developed through image-based segmentation and correspondingly provide much better anatomical realism in comparison to simpler stylized phantoms. However, they themselves are limited in defining organs presented in low contrast within either magnetic resonance or computed tomography images-the two major sources in voxel phantom construction. By definition, voxel phantoms are typically constructed via segmentation of transaxial images, and thus while fine anatomic features are seen in this viewing plane, slice-to-slice discontinuities become apparent in viewing the anatomy of voxel phantoms in the sagittal or coronal planes. This study introduces the concept of a hybrid computational newborn phantom that takes full advantage of the best features of both its stylized and voxel counterparts: flexibility in phantom alterations and anatomic realism. Non-uniform rational B-spline (NURBS) surfaces, a mathematical modeling tool traditionally applied to graphical animation studies, was adopted to replace the limited mathematical surface equations of stylized phantoms. A previously developed whole-body voxel phantom of the newborn female was utilized as a realistic anatomical framework for hybrid phantom construction. The construction of a hybrid phantom is performed in three steps: polygonization of the voxel phantom, organ modeling via NURBS surfaces and phantom voxelization. Two 3D graphic tools, 3D-DOCTOR and Rhinoceros, were utilized to polygonize the newborn voxel phantom and generate NURBS surfaces, while an in-house MATLAB code was used to voxelize the resulting NURBS model into a final computational phantom ready for use in Monte Carlo radiation transport calculations. A total of 126 anatomical organ and tissue models, including 38 skeletal sites and 31 cartilage sites, were described within the hybrid phantom using either NURBS or polygon surfaces. A male hybrid newborn phantom was constructed following the development of the female phantom through the replacement of female-specific organs with male-specific organs. The outer body contour and internal anatomy of the NURBS-based phantoms were adjusted to match anthropometric and reference newborn data reported by the International Commission on Radiological Protection in their Publication 89. The voxelization process was designed to accurately convert NURBS models to a voxel phantom with minimum volumetric change. A sensitivity study was additionally performed to better understand how the meshing tolerance and voxel resolution would affect volumetric changes between the hybrid-NURBS and hybrid-voxel phantoms. The male and female hybrid-NURBS phantoms were constructed in a manner so that all internal organs approached their ICRP reference masses to within 1%, with the exception of the skin (-6.5% relative error) and brain (-15.4% relative error). Both hybrid-voxel phantoms were constructed with an isotropic voxel resolution of 0.663 mm--equivalent to the ICRP 89 reference thickness of the newborn skin (dermis and epidermis). Hybrid-NURBS phantoms used to create their voxel counterpart retain the non-uniform scalability of stylized phantoms, while maintaining the anatomic realism of segmented voxel phantoms with respect to organ shape, depth and inter-organ positioning.     

低剂量迭代重建技术在放疗定位图像中的应用

目的:探讨新型低剂量迭代重建技术应用于放疗定位图像的可行性。方法:基于体模的实验数据,对CT辐射剂量进行分析。对CT值、低对比度分辨率、噪声、均匀性以及几何畸变各项质量评价参数进行定量的分析。对仿真体模进行迭代重建技术扫描重建,并在放射治疗计划系统中对仿真体模进行模拟剂量计算,分析感兴趣体积的绝对剂量和平面内剂量的Gamma通过率。结果:低剂量迭代重建技术能够在保证图像质量的同时减少约60%的CT扫描辐射剂量。当管电压保持不变时,低剂量迭代重建技术对TPS剂量计算的准确性的影响可以忽略不计,感兴趣体积剂量最大差异0.6%,面剂量的Gamma通过率优于99.82%。低剂量迭代重建技术对图像低对比度分辨率有一定影响,需要进一步结合临床影像进行分析。结论:低剂量迭代重建技术可以应用于放疗定位图像中,但是需要注意图像特性和某些图像质量的改变,建议与PET-CT、超声、核磁等检查手段结合综合考虑确定靶区范围。 【关键词】低剂量迭代重建;放射治疗;定位图像     

Effective dose efficiency: an application-specific metric of quality and dose for digital radiography

The detective quantum efficiency (DQE) and the effective DQE (eDQE) are relevant metrics of image quality for digital radiography detectors and systems, respectively. The current study further extends the eDQE methodology to technique optimization using a new metric of the effective dose efficiency (eDE), reflecting both the image quality as well as the effective dose (ED) attributes of the imaging system. Using phantoms representing pediatric, adult and large adult body habitus, image quality measurements were made at 80, 100, 120 and 140 kVp using the standard eDQE protocol and exposures. ED was computed using Monte Carlo methods. The eDE was then computed as a ratio of image quality to ED for each of the phantom/spectral conditions. The eDQE and eDE results showed the same trends across tube potential with 80 kVp yielding the highest values and 120 kVp yielding the lowest. The eDE results for the pediatric phantom were markedly lower than the results for the adult phantom at spatial frequencies lower than 1.2-1.7 mm(-1), primarily due to a correspondingly higher value of ED per entrance exposure. The relative performance for the adult and large adult phantoms was generally comparable but affected by kVps. The eDE results for the large adult configuration were lower than the eDE results for the adult phantom, across all spatial frequencies (120 and 140 kVp) and at spatial frequencies greater than 1.0 mm(-1) (80 and 100 kVp). Demonstrated for chest radiography, the eDE shows promise as an application-specific metric of imaging performance, reflective of body habitus and radiographic technique, with utility for radiography protocol assessment and optimization.     

Monte Carlo simulations in CT for the study of the surface air kerma and energy imparted to phantoms of varying size and position

A Monte Carlo computational model of CT has been developed and used to investigate the effect of various physical factors on the surface air kerma length product, the peak surface air kerma, the air kerma length product within a phantom and the energy imparted. The factors investigated were the bow-tie filter and the size, shape and position of a phantom which simulates the patient. The calculations show that the surface air kerma length product and the maximum surface air kerma are mainly dependent on phantom position and decrease along the vertical axis of the CT plane as the phantom surface moves away from the isocentre along this axis. As a result, measurements using standard body dosimetry phantoms may underestimate the skin dose for real patients. This result is specially important for CT fluoroscopic procedures: for an adult patient the peak skin dose can be 37% higher than that estimated with a standard measurement on the body AAPM (American Association of Physicists in Medicine) phantom. The results also show that the energy imparted to a phantom is mainly influenced by phantom size and is nearly independent of phantom position (within 3%) and shape (up to 5% variation). However, variations of up to 30% were found for the air kerma to regions within the AAPM body phantom when it is moved vertically. This highlights the importance of calculating doses to organs taking into account their size and position within the gantry.     

Abdominal aortic aneurysm and stent graft phantom manufactured by medical rapid prototyping

A novel human aorta phantom built by medical rapid prototypingfor use in computed tomography (CT) scanning is described. The phantom contained a stent graft that was deployed internally to mimic a repaired aortic aneurysm. The phantom was produced to allow assessment of the CT appearance of a stent graft inside an aorta using the new virtual intravascular endoscopy image presentation technique. The stent graft utilized contained suprarenal components (metalfixation struts), and these were placed with these struts covering the renal artery ostia. The phantom was filled with iodinated contrast medium at a concentration that produced a density similar to that found in normal CT angiographic scanning. The model was scanned at a variety of slice thicknesses, pitch and image reconstruction intervals. Visualization of the stent suprarenal components in relation to the renal artery ostia is shown and the overestimation of stent wire strut diameter demonstrated.