全脊柱MR成像9例失败原因分析

目的:探讨全脊柱MR成像中因体位设计、参数设置、病人配合等因素造成全眷柱MR成像失败的原因及其解决方法.方法:采用GE SIGNA双梯度HDx 1.5-T磁共振成像系统,专用8通道全脊柱相控阵线圈,GE AW4.3图像后处理工作站,拼接处理软件pasting 1.1.利用自动移床技术一次定位分两段扫描,即颈胸段和胸腰骶段;将矢状位、冠状位扫描图像传至后处理工作站,通过pasting 1.1软件将上下两段同一序列图像分别进行自动的无缝隙拼接生成全脊柱图像.结果:79例中全脊柱MR成像失败9例;其中4例因体位设计不当或在两序列扫描间歇期由于患者左右移动,使得脊髓正中面不能拼接在一幅图像中;有3例因上下两段的层数、扫描起始位置不一致或扫描定位时定位线偏转了一定角度,使得全脊柱图像序列中有几幅只有上段或只有下段原始扫描图像;有1例因下段扫描野过小使得全脊柱图像序列中胸12椎体层面信息缺失;还有1例因扫描下段T2W1像时患者向上移动了一段距离,使得全脊柱图像T2WI序列中颈1-腰5只有22个椎体显示.其余70例均获得准确、直观的全椎管内脊髓及椎体结构的影像.结论:要获得高质量的全脊柱MR成像,必须选择正确的扫描参数,体位设计时要求操作者有足够的细心和耐心一次性摆好体位,还要和患者有良好的沟通以便取得患者最好的配合.     

BLADE技术在3.0T磁共振克服关节扫描中运动伪影上的临床应用

目的:探讨在3.0T磁共振成像过程中,刀锋伪影较正(BLADE)技术在克服关节扫描中运动伪影方面的的的临床应用.方法:20例行四肢关节MR扫描检查的患者(肩关节10例,腕关节10例),在常规行T2WI常规扫描中出现不同程度的运动伪影,然后引入BLADE技术,扫描T2WI.,以能否清晰显示韧带肌腱而无重影为标准,对比常规序列扫描来评价BLADE技术在消除关节扫描过程中图像运动伪影方面的价值.结果:常规T2扫描出现运动伪影,用BLADE技术序列扫描出来的图像运动伪影消失,对比度明显提高.结论:应用BLADE技术进行扫描可以有效消除病人细微运动造成的运动伪影,获得高分辨率无伪影具有临床诊断价值的理想的图像.     

MRI对卵巢成熟畸胎瘤术前诊断初步探讨

目的:探讨MRI对卵巢成熟畸胎瘤术前诊断价值及手术方式选择的指导意义.方法:回顾性分析经妇科手术治疗、病理诊断为卵巢成熟畸胎瘤58例,术前均行MRI扫描.采用自旋回波(SE)序列、快速自旋回波(FSE)序列、压脂序列、DWI序列扫描.常规行矢状面、横断面及冠状面扫描.结果:(1)病变位于右侧卵巢30例,左侧卵巢28例,双侧卵巢3例.(2)病变大小为1.2-16.7cm,边缘较清晰,形态多为类圆形.(3)病变为囊性或囊实性.其内成分多样,MRI信号显示混杂,脂肪成分MRI上T1W、T2W为双高信号,脂肪抑制序列为低信号;牙齿、毛发、软骨、纤维成分T1W、T2W为双低信号;肌肉、神经成分T1W、T2W为等信号.(4)病变小于10 cm,其内脂肪成分较多,无腹腔镜手术禁忌症患者行腹腔镜卵巢畸胎瘤切除术;病变大于10 cm,钙化、毛发等实性成分较少时,能耐受膀胱截石位,行阴式卵巢畸胎瘤切除术;病变大于15 cm,或病变较小但以钙化、牙齿、毛发等实行性成分为主,怀疑恶性卵巢畸胎瘤或者不能判断病变性质时行传统方式开腹卵巢畸胎瘤切除术.结论:MRI能较好显示卵巢畸胎瘤内部结构及成分,在临床手术术式选择方面具有指导意义.     

应用KV-CBCT分析鼻咽癌调强放射治疗的摆位误差

目的:应用KV-CBCT分析鼻咽癌调强放射治疗时的摆位误差,为鼻咽癌调强放射治疗计划设计时CTV外扩PTV边界的大小提供参考。方法:选取30例IMRT的鼻咽癌患者,治疗过程中每周一次应用KV-CBCT采集患者治疗前的CT图像,将所得图像与定位CT图像进行匹配,分别测定X、Y、Z轴三个方向的摆位误差。结果:30例患者共拍摄168次KV-CBCT,获得168组摆位误差结果,群体摆位误差分别为X轴-0.15±1.43 mm,Y轴0.20±1.58 mm,Z轴-0.21±1.65 mm;根据Van Herk公式计算得到各方向的CTV-PTV外放边界值X、Y、Z轴分别为3.1 mm、3.3 mm和3.4 mm。结论:应用KV-CBCT影像系统可实时测量摆位误差并在线进行纠正,减小摆位误差,为CTV-PTV外放边界提供参考。     

磁共振水成像对脊柱疾病诊断中的应用价值

目的:探讨磁共振水成像技术对脊柱疾病诊断的应用价值。方法:采用快速高级自旋回波(FASE)、重T2WI及脂肪抑制序列对300例病人检查行磁共振椎管水成像(MRmyelography,MRM)。结果:MRM显示正常25例,MRM异常275例,清楚显示原发病变与邻近脊髓腔、脊髓、神经根的相关关系。结论:MRM具有无创伤、无辐射、速度快,不需对比剂,患者易接受的特点。MRM与常规MRI图像结合可获得全面、客观的病变信息,MRM图像可取代X线脊髓造影和CT脊髓造影。     

饲料脂肪水平对大菱鲆幼鱼TOR信号通路的影响

研究旨在探究饲料脂肪水平对大菱鲆(Scophthalmus maximus)幼鱼雷帕霉素受体(TOR)信号通路的影响。以大菱鲆幼鱼[初始体重(8.6±0.01) g]为实验对象, 配制脂肪水平分别为11.69% (适宜脂肪组)和16.58% (高脂组)的2种等氮饲料在室内循环水系统中进行投喂实验, 养殖周期为97d。结果显示: (1)饲料脂肪水平升高对大菱鲆幼鱼存活和特定生长率(SGR)无显著影响(P>0.05)。(2)与适宜脂肪组相比, 肝脏中TOR和4EBP1 mRNA水平在高脂组上调(P<0.05)而4EBP2 mRNA水平在高脂组下调(P<0.05)。此外, 与适宜脂肪组相比, 肌肉中TOR和4EBP1 mRNA水平在高脂组下调(P<0.05)而4EBP2 mRNA水平在高脂组无显著变化。(3)饲料脂肪水平显著影响AKT、TOR和4EBPs磷酸化水平。肝脏中p-AKT (T308和S473)/AKT、p-mTOR(S2448)/mTOR和p-4EBP1 (T37/46)/4EBP1在高脂组显著高于适宜脂肪组,而p-p70S6K (T389)/p70S6K在高脂组显著低于适宜脂肪组。肌肉中p-AKT (S473)/AKT、p-mTOR (S2448)/mTOR和p-4EBP1 (T37/46)/4EBP1在高脂组显著低于适宜脂肪组,而p-p70S6K (T389)/p70S6K在高脂组显著高于适宜脂肪组。结果表明: 大菱鲆幼鱼肝脏和肌肉TOR、4EBP1和4EBP2的mRNA表达量与AKT、TOR、4EBP1和p70 S6K磷酸化受到饲料脂肪水平调控, 饲料脂肪水平升高, 激活了肝脏TOR信号通路, 同时肌肉TOR信号通路受到部分抑制。     

肝癌自发性破裂出血的MRI诊断

目的:探讨肝癌自发性破裂出血的MRI图像特征。方法:对6例经手术或肝动脉血管造影确诊为原发性肝癌破裂出血患者的MR图像进行回顾性分析,总结其临床特点及MRI图像特征。结果:6例患者均行MR平扫及增强扫描,肝被膜下出血4例,腹腔内出血2例。出血表现为T1WI呈高或等信号,T2WI呈高或低信号,5例可清晰显示肿瘤破口。结论:MR诊断肝癌自发性破裂出血及时、准确,T1WI及延迟扫描冠状位图像对诊断有定性意义。     

MR 脑图像海马自动分割法在AD 早期诊断中的应用研究

目的:研究磁共振(Magnetic resonance,MR)脑图像中海马的自动分割方法及海马的形态学分析方法,为阿尔茨海默病(Alzheimer’s disease,AD)的早期诊断提供依据。方法:对20例AD患者和60名正常对照者行MRI T1 WI 3D容积扫描,建立海马的三维主动表观模型,并以此模型对每个个体脑部磁共振图像上的海马进行自动识别和三维分割,分别建立正常对照组和AD组的海马统计形状模型,比较AD组与正常对照组间海马形状的差异性。结果:海马三维分割方法与手动分割方法在海马体积测量上无统计学差别(P>0.05);AD患者海马头部发生萎缩(P<0.05)。结论:基于主动表观模型的MR脑图像海马自动识别和三维分割法是准确可靠的;海马头部萎缩可作为AD诊断的依据之一。     

脂筏与T细胞信号转导

抗原提呈细胞将抗原加工处理后通过MHCⅠ/MHCⅡ类分子提呈供T细胞识别。TCR对抗原的识别引起一系列下游信号事件的发生,最终使T细胞激活,但对TCR复合物结合抗原后引起胞内区磷酸化的早期事件机制还不是很清楚。最近的研究揭示脂筏参与了这一早期信号事件的发生。脂筏是一种膜脂双层内含有的特殊微区,T细胞膜表面参与T细胞激活的各种关键信号分子都定位于脂筏。T细胞激活过程中脂筏通过聚集和重分配形成一个信号转导的平台。     

CT和MRI鉴定腹膜后间隙脂肪肉瘤与组织病理学特征相关

本研究选取2012年1月至2018年1月在我院治疗的腹膜后间隙脂肪肉瘤患者33例,分析患者术前CT、MRI图像及术后病理结果,旨在探讨不同类型腹膜后间隙脂肪肉瘤病理学及影像学特征。研究结果表明:33例患者中术后病理诊断为高分化脂肪肉瘤19例,去分化脂肪肉瘤7例,黏液性脂肪肉瘤7例;不同病理分型脂肪肉瘤病灶大小比较差异无统计学意义(p>0.05);高分化脂肪肉瘤其CT密度同皮下脂肪,CT值-10～-110 Hu,肿瘤内可见不规则增厚的间隔;去分化脂肪肉瘤部分区域呈脂肪密度(CT值-70～30 Hu),部分区域呈软组织肿块(CT值为30～50 Hu);黏液性脂肪肉瘤CT密度接近水,增强扫描时肿块呈网状、片状、延迟强化,CT值20～40 Hu;高分化脂肪肉瘤MRI信号同皮下脂肪;黏液性脂肪肉瘤MRI呈长T1,长T2信号,与水相似;CT和MRI诊断腹膜后间隙脂肪瘤准确率分别为69.70%和73.33%,差异比较无统计学意义(p>0.05)。本研究得出初步结论,不同病理类型腹膜后间隙脂肪肉瘤的CT、MRI表现有所差异;CT和MRI术前诊断腹膜后间隙脂肪肉瘤准确性相似。     

In vivo NMR detection of diet-induced changes in adipose tissue composition

We introduce an in vivo spectroscopic method to assess the effects of diet on fatty acid composition of the predominant chemical constituent of adipocytes in mice. To do this, we make use of a nonlinear NMR signal that, unlike a standard NMR signal, is intrinsically insensitive to local magnetic field inhomogeneities and which naturally suppresses the large water signal from nonfatty tissues. Our method yields fat composition information from fat depots distributed over large sample volumes in a single experiment, without requiring the use of tedious shimming procedures, voxel selection, or water suppression. Our results suggest that this method can reveal clear differences in adipose tissue composition of mice fed a standard chow diet compared with mice fed a diet rich in polyunsaturated fatty acids. With further developments this method could be used to obtain information on human lipid composition noninvasively and to track changes in lipid composition induced by diet intervention, pharmaceutical drugs, and exercise.     

Impact of 3.0 T Cardiac MR Imaging Using Dual-Source Parallel Radiofrequency Transmission with Patient-Adaptive B1 Shimming

Objectives

To prospectively evaluate the impact of 3.0 T Cardiac MR imaging using dual-source parallel radiofrequency (RF) transmission with patient-adaptive B1 shimming compared with single-source RF transmission in the RF homogeneity, image contrast and image quality.

Methods

The study was approved by the local institutional review board, and all subjects provided written informed consent. Fourteen healthy volunteers were examined at 3.0 T MR, with both the conventional single-source and the new dual-source RF transmission. B1 calibrations (RF shimming) of the heart region were performed to acquire a percent of the prescribed flip angle (FA) of B1 maps, which were used for quantitative assessment of RF homogeneity. Contrast ratios (CRs) between ventricular blood pool and septum were calculated on balanced-turbo field echo (B-TFE) cine images. The off-resonance artifacts of cine images were blindly assessed by two radiologists according to a 4-point grading-scale.

Results

A significantly lower mean coefficients of variance of the achieved FA with dual-source revealed better RF homogeneity compared to single-source (P = 0.0094). Dual-source RF shimming significantly increased the CRs (P<0.05) and reduced the off-resonance artifacts of B-TFE cine images (P<0.05). Inter-observer agreement for the off-resonance artifacts of B-TFE cine images was good to excellent (k >0.65).

Conclusions

Dual-source parallel RF transmission significantly improves the RF homogeneity, increases image contrast and reduces image artifacts of cardiac B-TFE images compared to single-source mode. This may be of value in reducing the observer-dependence of cardiac MR images and enhancing diagnostic confidence for clinical practice using CMR at 3.0 T.     

宝石能谱CT GSI成像和常规成像在上腹部应用价值的对比研究

目的:探讨宝石能谱CT GSI扫描模式在上腹部检查中降低辐射剂量和优化图像质量的可行性及应用价值。方法:选择2016年9月至2016年12月期间我院40例拟行上腹部三期增强的患者,根据扫描模式将患者分为A组和B组,每组20例。A组患者采用宝石能谱CT常规扫描模式行螺旋扫描,管电压120 Kvp及自动毫安管电流,确定NI值为10。B组患者采用GSI模式行三期增强扫描收集门脉期图像。回顾性自适应统计迭代重建(ASIR)70kev单能量图像,应用ASIR Review工具收集0到100%ASIR的CT值、噪声值,计算图像信号噪声比(SNR)。记录各组剂量报告中CT剂量容积指数(CTDI vol)及剂量长度乘积(DLP),并计算有效剂量(ED),采用图像质量主观评分对图像进行评价。结果:B组CT值、噪声值及SNR均高于A组(P0.05),B组CTDIvol、DLP和ED均显著低于A组(P0.05);随着ASIR升高,SNR升高,但是图像质量主观评分先升高后降低。当ASIR为50%时,图像质量最高,不同ASIR的CT值、噪声值之间的差异无统计学意义(P0.05)。结论:宝石能谱CT GSI扫描模式的效果明显优于螺旋扫描,同时在降低图像噪声的前提下选择50%ASIR,可保障图像质量。     

Semiautomatic extraction of cortical thickness and diaphyseal curvature from CT scans

The understanding of locomotor patterns, activity schemes, and biological variations has been enhanced by the study of the geometrical properties and cortical bone thickness of the long bones measured using CT scan cross‐sections. With the development of scanning procedures, the internal architecture of the long bones can be explored along the entire diaphysis. Recently, several methods that map cortical thickness along the whole femoral diaphysis have been developed. Precise homology is vital for statistical examination of the data; however, the repeatability of these methods is unknown and some do not account for the curvature of the bones. We have designed a semiautomatic workflow that improves the morphometric analysis of cortical thickness, including robust data acquisition with minimal user interaction and considering the bone curvature. The proposed algorithm also performs automatic landmark refinement and rigid registration on the extracted morphometric maps of the cortical thickness. Because our algorithm automatically reslices the diaphysis into 100 cross‐sections along the medial axis and uses an adaptive thresholding method, it is usable on CT scans that contain soft tissues as well as on bones that have not been oriented specifically prior to scanning. Our approach exhibits considerable robustness to error in user‐supplied landmarks, suppresses distortion caused by the curvature of the bones, and calculates the curvature of the medial axis.     

Diagnostic quality assessment of compressed SENSE accelerated magnetic resonance images in standard neuroimaging protocol: Choosing the right acceleration

PurposeTo investigate the impact of compressed sensing – sensitivity encoding (CS-SENSE) acceleration factor on the diagnostic quality of magnetic resonance images within standard brain protocol.MethodsThree routine clinical neuroimaging sequences were chosen for this study due to their long acquisition time: T2-weighted turbo spin echo (TSE), fluid - attenuated inversion recovery (FLAIR), and 3D time of flight (TOF). Fully sampled reference scans and multiple prospectively 2x to 5x undersampled CS scans were acquired. Retrospectively, undersampled scans were compared to fully sampled scans and visually assessed for image quality and diagnostic quality by three independent radiologists.ResultsImages obtained with CS-SENSE accelerated acquisition were of diagnostically acceptable quality at up to 3x acceleration for T2 TSE (average qualitative score 3.53 on a 4-point scale, with the acquisition time reduction of 64%), up to 2x for FLAIR (average qualitative score 3.27, with the acquisition time reduction of 43%) and 4x acceleration for 3D TOF sequence (average qualitative score 3.13, with the acquisition time reduction of 73%). There were no substantial differences between the readers’ diagnostic quality scores (p > 0.05).ConclusionsCS-SENSE accelerated T2 TSE, FLAIR, and 3D TOF sequences of the brain show image quality similar to that of conventional acquisitions with reduced acquisition time. CS-SENSE can moderately reduce scan time, providing many benefits without losing the image quality.     

Semantic Focusing Allows Fully Automated Single-Layer Slide Scanning of Cervical Cytology Slides

Liquid-based cytology (LBC) in conjunction with Whole-Slide Imaging (WSI) enables the objective and sensitive and quantitative evaluation of biomarkers in cytology. However, the complex three-dimensional distribution of cells on LBC slides requires manual focusing, long scanning-times, and multi-layer scanning. Here, we present a solution that overcomes these limitations in two steps: first, we make sure that focus points are only set on cells. Secondly, we check the total slide focus quality. From a first analysis we detected that superficial dust can be separated from the cell layer (thin layer of cells on the glass slide) itself. Then we analyzed 2,295 individual focus points from 51 LBC slides stained for p16 and Ki67. Using the number of edges in a focus point image, specific color values and size-inclusion filters, focus points detecting cells could be distinguished from focus points on artifacts (accuracy 98.6%). Sharpness as total focus quality of a virtual LBC slide is computed from 5 sharpness features. We trained a multi-parameter SVM classifier on 1,600 images. On an independent validation set of 3,232 cell images we achieved an accuracy of 94.8% for classifying images as focused. Our results show that single-layer scanning of LBC slides is possible and how it can be achieved. We assembled focus point analysis and sharpness classification into a fully automatic, iterative workflow, free of user intervention, which performs repetitive slide scanning as necessary. On 400 LBC slides we achieved a scanning-time of 13.9±10.1 min with 29.1±15.5 focus points. In summary, the integration of semantic focus information into whole-slide imaging allows automatic high-quality imaging of LBC slides and subsequent biomarker analysis.     

Elimination of biological and physical artifacts in abdomen and brain computed tomography procedures using filtering techniques

IntroductionMedical images are usually affected by biological and physical artifacts or noise, which reduces image quality and hence poses difficulties in visual analysis, interpretation and thus requires higher doses and increased radiographs repetition rate.ObjectivesThis study aims at assessing image quality during CT abdomen and brain examinations using filtering techniques as well as estimating the radiogenic risk associated with CT abdomen and brain examinations.Materials and MethodsThe data were collected from the Radiology Department at Royal Care International (RCI) Hospital, Khartoum, Sudan. The study included 100 abdominal CT images and 100 brain CT images selected from adult patients. Filters applied are namely: Mean filter, Gaussian filter, Median filter and Minimum filter. In this study, image quality after denoising is measured based on the Mean Squared Error (MSE), Peak Signal-to-Noise Ratio (PSNR), and the Structural Similarity Index Metric (SSIM).ResultsThe results show that the images quality parameters become higher after applications of filters. Median filter showed improved image quality as interpreted by the measured parameters: PSNR and SSIM, and it is thus considered as a better filter for removing the noise from all other applied filters.DiscussionThe noise removed by the different filters applied to the CT images resulted in enhancing high quality images thereby effectively revealing the important details of the images without increasing the patients’ risks from higher doses.ConclusionsFiltering and image reconstruction techniques not only reduce the dose and thus the radiation risks, but also enhances high quality imaging which allows better diagnosis.     

Visualizing the Prostate Gland by MR Imaging in Young and Old Mice

Purpose

Prostate imaging requires optimization in young and old mouse models. We tested which MR sequences and field strengths best depict the prostate gland in young and old mice; and, whether prostate MR signal, size, and architecture change with age.

Technique

Magnetic resonance imaging (MRI) of the prostate of young (2 months) and old (18 months) male nude mice (n = 6) was performed at 4.7 and 7 T and SCID mice (n = 6) at 7 T field strengths, using T1, fat suppressed T1, DWI, T2, fat suppressed T2, as well as T2-based- and proton density-based Dixon “water only” sequences. Images were ranked for best overall sequence for prostate visualization, prostate delineation, and quality of fat suppression. Prostate volume and signal characteristics were compared and histology was performed.

Results

T2-based-Dixon “water only” images ranked best overall for prostate visualization and delineation as well as fat suppression (n = 6, P<0.001) at both 4.7 T and 7 T in nude and 7T in SCID mice. Evaluated in nude mice, T2-based Dixon “water only” had greater prostate CNR and lower fat SNR at 7 T than 4.7 T (P<0.001). Prostate volume was less in older than younger mice (n = 6, P<0.02 nude mice; n = 6, P<0.002 SCID mice). Prostate T2 FSE as well as proton density-based and T2-based-Dixon “water only” signal intensity was higher in younger than older mice (P<0.001 nude mice; P<0.01 SCID mice) both at 4.7 and 7 T. This corresponded to an increase in glandular hyperplasia in older mice by histology (P<0.01, n = 6).

Conclusion

T2-based Dixon “water only” images best depict the mouse prostate in young and old nude mice at 4.7 and 7 T. The mouse prostate decreases in size with age. The decrease in T2 and T2-based Dixon “water only” signal with age corresponds with glandular hyperplasia. Findings suggest age should be an important determinant when choosing models of prostate biology and disease.     

Left ventricular strain and peak systolic velocity: responses to controlled changes in load and contractility, explored in a porcine model

ABSTRACT: BACKGROUND: Tissue velocity echocardiography is increasingly used to evaluate global and regional cardiac function. Previous studies have suggested that the quantitative measurements obtained during ejection are reliable indices of contractility, though their load-sensitivity has been studied in different settings, but still remains a matter of controversy. We sought to characterize the effects of acute load change (both preload and afterload) and change in inotropic state on peak systolic velocity and strain as a measure of LV contractility. METHODS: Thirteen anesthetized juvenile pigs were studied, using direct measurement of left ventricular pressure and volume and transthoracic echocardiography. Transient inflation of a vena cava balloon catheter produced controlled load alterations. At least eight consecutive beats in the sequence were analyzed with tissue velocity echocardiography during the load alteration and analyzed for change in peak systolic velocities and strain during same contractile status with a controlled load alteration. Two pharmacological inotropic interventions were also included to generate several myocardial contractile conditions in each animal. RESULTS: Peak systolic velocities reflected the drug-induced changes in contractility in both radial and longitudinal axis. During the acute load change, the peak systolic velocities remain stable when derived from signal in the longitudinal axis and from the radial axis. The peak systolic velocity parameter demonstrated no strong relation to either load or inotropic intervention, that is, it remained unchanged when load was systematically and progressively varied (peak systolic velocity, longitudinal axis, control group beat 1- 5.72 +/- 1.36 with beat 8- 6.49 +/- 1.28 cm/sec, 95% confidence interval), with the single exception of the negative inotropic intervention group where peak systolic velocity decreased a small amount during load reduction (beat 1- 3.98 +/- 0.92 with beat 8- 2.72 +/- 0.89 cm/sec). Systolic strain, however, showed a clear degree of load-dependence. CONCLUSIONS: Peak systolic velocity appears to be load-independent as tested by beat-to-beat load reduction, while peak systolic strain appears to be load-dependent in this model. Peak systolic velocity, in a controlled experimental model where successive beats during load alteration are assessed, has a strong relation to contractility. Peak systolic velocity, but not peak strain rate, is largely independent of load, in this model. More study is needed to confirm this finding in the clinical setting.     

Image quality for radiotherapy CT simulators with different scanner bore size

PurposeWe compare image quality parameters derived from phantom images taken on three commercially available radiotherapy CT simulators. To make an unbiased evaluation, we assured images were obtained with the same surface dose measured using XR-QA2 model GafChromic™ film placed at the imaging phantom surface for all three CT-simulators.MethodsRadiotherapy CT simulators GE LS 16, Philips Brilliance Big Bore, and Toshiba Aquilion LB were compared in terms of spatial resolution, low contrast detectability, image uniformity, and contrast to noise ratio using CATPHAN-504 phantom, scanned with Head and Pelvis protocols. Dose was measured at phantom surface, with CT scans repeated until doses on all scanners were within 2%.ResultsIn terms of spatial resolution, the GE simulator appears slightly better, while Philips CT images are superior in terms of SNR for both scanning protocols. The CNR results show that Philips CT images appear to be better, except for high Z material, while Toshiba appears to fit in between the two simulators.ConclusionsWhile the image quality parameters for three RT CT simulators show comparable results, the scanner bore size is of vital importance in various radiotherapy applications. Since the image quality is a function of a large number of confounding parameters, any loss in image quality due to scanner bore size could be compensated by the appropriate choice of scanning parameters, including the exposure and by balancing between the additional imaging dose to the patient and high image quality required in highly conformal RT techniques.