Photon-counting computed tomography thermometry via material decomposition and machine learning

Thermal ablation procedures,such as high intensity focused ultrasound and radiofrequency ablation,are often used to eliminate tumors by minimally invasively heating a focal region.For this task,real-time 3D temperature visualization is key to target the diseased tissues while minimizing damage to the surroundings.Current computed tomography(CT)thermometry is based on energy-integrated CT,tissue-specific experimental data,and linear relationships between attenuation and temperature.In this paper,we develop a novel approach using photon-counting CT for material decomposition and a neural network to predict temperature based on thermal characteristics of base materials and spectral tomographic measurements of a volume of interest.In our feasibility study,distilled water,50 mmol/L CaCl2,and 600 mmol/L CaCl2 are chosen as the base materials.Their attenuations are measured in four discrete energy bins at various temperatures.The neural network trained on the experimental data achieves a mean absolute error of 3.97°C and 1.80°C on 300 mmol/L CaCl2 and a milk-based protein shake respectively.These experimental results indicate that our approach is promising for handling non-linear thermal properties for materials that are similar or dis-similar to our base materials.

Coronary Artery Anomalies Detected by Multi-Detector Computed Tomography: A Single Centre Experience

Background: Coronary artery anomalies (CAA) prevalence represents less than 1% of congenital heart diseases. It includes anomalies in origin, course, and termination. Its detection has been easier with advances in imaging techniques using multi-detector computed tomography (MDCT). MDCT helps not only detection of the anomalous origin, but it allows delineation of the course and termination of the arteries, differentiation between benign and malignant courses, and guiding therapeutic interventions. Results: There were consecutive patients with a low-to-intermediate probability of coronary artery disease scanned with 128 MDCT. Each patient underwent a non-contrast prospective gating acquisition for coronary calcium scoring followed by contrast-enhanced helical retrospective gated scans for the detection of coronary artery origin, course, termination, and detection of concomitant atherosclerosis. We scanned 1000 patients with a mean age of 57.5 ± 8.3, and 68% were males. Thirty-two anomalies were noted (3.2%) including;nineteen (1.9%) anomalous origin from the opposite sinus, three (0.3%) anomalous left coronary arteries from the pulmonary artery (ALCAPA), one (0.1%) super dominant left anterior descending artery (LAD) giving origin to the posterior descending artery (PDA), three single coronary arteries (0.3%)in which the left main (LM) and right coronary arteries were originating with a common stem from the right coronary sinus (RCS)and the LM took a pre-pulmonic course. Along with six (0.6%) dual LAD including five (0.5%) patients with type I (short LAD and long diagonal), there was one (0.1%) type 4 with an extra LAD originating from the RCS with a pre-pulmonic course. Conclusions: MDCT allows easy detection of coronary anomalies with high spatial resolution and overcomes limitations in conventional invasive coronary angiography. Based on our study we recommend the use of MDCT as an efficient and feasible modality for the diagnosis of coronary anomalies once this pathology is clinically suspected.

Rectal cancer staging: Multidetector-row computed tomography diagnostic accuracy in assessment of mesorectal fascia invasion

AIM: To assess the diagnostic accuracy of multidetectorrow computed tomography(MDCT) as compared with conventional magnetic resonance imaging(MRI), in identifying mesorectal fascia(MRF) invasion in rectal cancer patients.METHODS: Ninety-one patients with biopsy proven rectal adenocarcinoma referred for thoracic and abdominal CT staging were enrolled in this study. The contrast-enhanced MDCT scans were performed on a 256 row scanner(ICT, Philips) with the following acquisition parameters: tube voltage 120 KV, tube current 150-300 m As. Imaging data were reviewed as axial and as multiplanar reconstructions(MPRs) images along the rectal tumor axis. MRI study, performed on 1.5 T with dedicated phased array multicoil, included multiplanar T2 and axial T1 sequences and diffusion weighted images(DWI). Axial and MPR CT images independently were compared to MRI and MRF involvement was determined. Diagnostic accuracy of both modalities was compared and statistically analyzed.RESULTS: According to MRI, the MRF was involved in 51 patients and not involved in 40 patients. DWI allowed to recognize the tumor as a focal mass with high signal intensity on high b-value images, compared with the signal of the normal adjacent rectal wall or with the lower tissue signal intensity background. The number of patients correctly staged by the native axial CT images was 71 out of 91(41 with involved MRF; 30 with not involved MRF), while by using the MPR 80 patients were correctly staged(45 with involved MRF; 35 with not involved MRF). Local tumor staging suggested by MDCT agreed with those of MRI, obtaining for CT axial images sensitivity and specificity of 80.4% and 75%, positive predictive value(PPV) 80.4%, negative predictive value(NPV) 75% and accuracy 78%; while performing MPR the sensitivity and specificity increased to 88% and 87.5%, PPV was 90%, NPV 85.36% and accuracy 88%. MPR images showed higher diagnostic accuracy, in terms of MRF involvement, than native axial images, as compared to the reference magnetic resonance images. The difference in accuracy was statistically significant(P = 0.02). CONCLUSION: New generation CT scanner, using high resolution MPR images, represents a reliable diagnostic tool in assessment of loco-regional and whole body staging of advanced rectal cancer, especially in patients with MRI contraindications.

Multi-detector computed tomography imaging of large airway pathology:A pictorial review

The tracheobronchial tree is a musculo-cartilagenous framework which acts as a conduit to aerate the lungs and consequently the entire body. A large spectrum of pathological conditions can involve the trachea and bronchial airways. These may be congenital anomalies, infections, post-intubation airway injuries, foreign body aspiration or neoplasms involving the airway. Appropriate management of airway disease requires an early and accurate diagnosis. In this pictorial essay review, we will comprehensively describe the various airway pathologies and their imaging findings by multi-detector computed tomography.

Relation between Epicardial Adipose Tissue Thickness Assessed by Multidetector Computed Tomography and Significance of Coronary Artery Disease

Objective: To evaluate the relation between epicardial adipose tissue (EAT) thickness and also pericoronary fat assessed by Multidetector Computed Tomography (MDCT) with both calcium score and significance of coronary artery disease. Background: Epicardial adipose tissue (the visceral fat of the heart present under the visceral layer of the pericardium) has the same origin of abdominal visceral fat, which is known to be strongly related to the development of coronary artery atherosclerosis. Multidetector CT (MDCT) provides an accurate and reproducible quantification of EAT due to its high spatial and temporal resolution. Patients and Methods: The current study included 70 patients with low-intermediate probability of coronary artery disease. All patients were subjected to 256 Multidetectors CT to assess EAT thickness, the mean thickness of the pericoronary fat surrounding the three coronary arteries and coronary calcium score. Also coronary CT angiography was done and patients were then divided into 3 groups according to significance of coronary atherosclerosis: Group 1: No atherosclerosis (20 patients), Group 2: Non obstructive atherosclerosis (luminal narrowing less than 50% in diameter) (25 patients), Group3: Obstructive atherosclerosis (luminal narrowing ≥ 50%) (25 patients). Results: The mean EAT thickness and the mean pericoronary fat thickness were significantly higher in patients with obstructive coronary artery disease (CAD) with stenosis > 50% (group 3) compared to other groups with normal coronaries or non obstructive (CAD). ROC curve was used to define the best cut off value of the thickness of both EAT and pericoronary fat in predicting the obstructive CAD group which was ≥7.2 and 12.6 mm for epicardial and pericoronary fat respectively. Also there is a positive correlation between both epicardial adipose tissue and pericoronary fat thickness and the coronary calcium score. Conclusion: EAT thickness and pericoronary fat thickness can be used in predicting the significance of coronary artery disease.

Diagnosis of Congenital Aortic Arch Anomalies in Chinese Children by Multi-Detector Computed Tomography Angiography

Summary： The purpose of this study was to evaluate the value of multi-detector computed tomography （MDCT） angiography for the diagnosis of congenital aortic arch anomalies and present the radiological images of congenital aortic arch anomalies in Chinese children. MDCT angiography and transthoracic echocardiography （TTE） were applied for the diagnosis of congenital aortic arch anomalies in 362 Chi- nese children between May 2006 and December 2011 （age ranges from 5 days to 12 years; mean age, 3.3 years）. Surgery and/or catheter angiography （CA） were conducted in all patients to confirm the final diagnosis. In the 362 Chinese children with congenital heart anomalies, congenital aortic arch anomalies were definitely diagnosed in 198 children and 164 children ruled out by operation and/or （CA）. Among the 198 children with anomalies, coarctation of aorta （CoA）, interruption of aortic arch （IAA）, fight aor- tic arch, aberrant right subclavian artery and double aortic arch were diagnosed in 134, 32, 20, 10 and 2 children respectively, and there were 6 cases with uncommon congenital aortic arch anomalies： 2 had double aortic arch including 1 with five branches of the aortic arch, 2 had isolation of the right sub- clavian artery with two patent ductus arteriosus （PDA）, 1 had an isolation of the common carotid artery with a PDA, and 1 had double PDA with a single ventricle and pulmonary artery atresia. Among the 32 children with IAA, 28 were of type A, and 4 were of type B. The diagnostic sensitivity, specificity and accuracy of MDCT angiography for congenital aortic arch anomaiies were 100% （198/198）, 98% （161/164） and 99% （359/362）, respectively. The diagnostic sensitivity, specificity and accuracy of TTE were 92% （182/198）, 81% （133/164） and 87% （315/362）, respectively. In conclusion, MDCT angiogra- phy is a reliable, noninvasive imaging technique for the diagnosis of congenital aortic arch anomalies in children. Sometimes, even more information can be obtained from this technique than from conven- tional angiography.

Scattering correction method for panel detector based cone beam computed tomography system

A scattering correction method for a panel detector based cone beam computed tomography system is presented. First, the x-ray spectrum of the system is acquired by using the Monte Carlo simulation method. Secondly, scattered photon distribution is calculated and stored as correction matrixes by using the Monte Carlo simulation method according to scanned objects and computed tomography system specialties. Thirdly, scattered photons are removed from projection data by correction matrixes. A comparison of reconstruction image between before and after scattering correction demonstrates that the scattering correction method is effective for the panel detector based cone beam computed tomography system.

A spontaneous strangulated transomental hernia: Prospective and retrospective multi-detector computed tomography findings

Transomental hernias are among the rarest type of all internal hernias which overall account for less than 6% of small bowel obstructions. Most transomental hernias occurring in adults are either iatrogenic or post-traumatic. More rarely, a spontaneous herniation of small bowel loops may result from senile atrophy of the omentum. We report a case of an 86-year-old male who presented with signs and symptoms of small bowel obstruction but had no past surgical or traumatic abdominal history. At contrast-enhanced multi-detector row computed tomography(CT), a cluster of fluid-filled dilated small bowel loops could be appreciated in the left flank, with associated signs of bowel wall ischemia. Swirling of the mesenteric vessels could also be appreciated and CT findings were prospectively considered consistent with a strangulated small bowel volvulus. At laparotomy, no derotation had to be performed but up to 100 cm of gangrenous small bowel loops had to be resected because of a transomental hernia through a small defect in the left part of the greater omentum. Retrospective reading of CT images was performed and findings suggestive of transomental herniation could then be appreciated.

Multidetector computed tomography of temporomandibular joint: A road less travelled

This article reviews the imaging anatomy of temporomandibular joint(TMJ), describes the technique of multi-detector computed tomography(MDCT) of the TMJ, and describes in detail various osseous pathologic afflictions affecting the joint. Traumatic injuries affecting the mandibular condyle are most common, followed by joint ankylosis as a sequel to arthritis. The congenital anomalies are less frequent, hemifacial microsomia being the most commonly encountered anomaly involving the TMJ. Neoplastic afflictions of TMJ are distinctly uncommon, osteochondroma being one of the most common lesions. MDCT enables comprehensive evaluation of osseous afflictions of TMJ, and is a valuable tool for surgical planning. Sagittal, coronal and 3D reformatted images well depict osseous TMJ lesions, and their relationship to adjacent structures.

Multi-Detector Row Computed Tomography Urography (MDCTU) in the Evaluation of Microscopic Hematuria in Adults

Multi-detector row computed tomography urography (MDCTU) becomes the imaging modality of choice for evaluation of the kidneys and urinary tract. The aim of this study was to discuss and illustrate the role of MDCTU, on a 32-row CT scanner in the evaluation a variety of entities that were frequently associated with microscopic hematuria in adults. This prospective cohort study was performed in the period of August 2013 to October 2014. Fifty positive participants to microscopic hematuria were examined at the radiology department of Alnilin Diagnostic Medical Center and Antalya Medical Center. Computed tomography urography (CTU) scanning was performed using two powerful performances, high speed multi-detector row on 32-row CT scanners (Siemens Healthcare Global, Somatom Emotion Duo Eco). Statistical analysis was done through the standard Statistical Package for the Social Sciences (SPSS Inc., Chicago, IL, USA) version 15 for windows. MDCTU established the correct cause of microscopic hematuria in (44;88%) of participants. In (6;12%) of participants, no cause of hematuria was identified based on the standard of references. The causes of hematuria in (41;82%) participants were diseases in the upper urinary tract, while urinary bladder neoplasms (2;4%) and diverticulum (1;2%) were the causes of hematuria (3;6%) in the lower urinary tract. Thirty two-row MDCTU scanner demonstrated satisfactory results in the investigation of microscopic hematuria, being able to demonstrate a wide spectrum of diseases affecting the urinary tract is the main advantage of the technique.

Predictive Factors of the Presence and Number of Noncalcified Coronary Plaque in Japanese Patients with Zero Coronary Artery Calcium Score Using 64-Slice Multi-Detector Computed Tomography

Background: Factors that can predict the presence and number of noncalcified coronary plaques (NCP) in Japanese patients with zero coronary artery calcium scores (CACS) essentially remain undefined. Methods and Results: We assessed independent predictors of the presence and number of segments with NCP in 111 Japanese patients with zero CACS who underwent 64-slice multi-detector computed tomography at our hospital. Thirty five patients (32%) had NCP, and 24 patients (22%) had ≥ 2 NCPs. Multiple logistic regression analysis revealed that significant predictors for the presence of NCP were age (odds ratio [OR]: 1.06, 95% confidence interval [CI] 1.01 - 1.11, p = 0.021), male (OR: 3.61, 95% CI 1.40 - 9.35, p = 0.008) and diabetes mellitus (OR: 3.10, 95% CI 1.02 - 9.45, p = 0.046), and those for the presence of ≥ 2 NCPs were age (OR: 1.08, 95% CI 1.02 - 1.15, p = 0.007) and a current smoking habit (OR: 5.09, 95% CI 1.00 - 25.74, p = 0.049). Multiple linear regression analysis identified advanced age, male gender and diabetes mellitus as independent predictors of the number of NCPs. A novel score calculated from the above four predictors showed moderate accuracy for a diagnosis of NCP and ≥ 2 NCPs, with areas under receiver operating curves of 0.738 and 0.736, respectively. Conclusions: Male Japanese patients with zero CACS, advanced age, diabetes mellitus and a current smoking habit might have NCPs.

High-resolution computed tomography in patients with atypical 'cardiac' chest pain: a study investigating patients at 10-year cardiovascular risks defined by the Framingham and PROCAM scores

Background and objective Atypical 'cardiac' chest pain (ACCP) is not usually caused by myocardial ischaemia. Current noninvasive investigations for these symptoms are not yet as accurate as invasive coronary angiography. The latest 64-row multi-detector computed tomography (MDCT) technology is non-invasive, has high specificity and negative predictive values for the detection of significant coronary disease. Our aim was to investigate if this modality can provide more information in the assessment of outpatients with ACCP in addition to established cardiovascular risk scores. Methods Seventy consecutive patients presenting to the outpatient clinic with ACCP underwent 64-row MDCT scan of the coronary arteries. They were categorized into low, medium or high risk groups based upon the Framingham and PROCAM scores. We defined a clinically abnormal MDCT scan as coronary stenosis =50% or calcium score ＞400 Agatston. Results Fifty-three (75.7%) patients did not have clinically abnormal scans. Framingham score classified 43 patients as low-risk while PROCAM classified 59 patients as low-risk. MDCT scans were abnormal for 18.6% and 22.0% of the respective low-risk group of patients. For patients with medium-to-high risk, 33.3% and 36.4% of Framingham and PROCAM patient groups respectively had abnormal MDCT scans. Conclusion MDCT adds valuable information in the assessment of patients with ACCP by identifying a significant proportion of patients categorized as low-risk to have underlying significant coronary stenosis and coronary calcification by established cardiovascular risk scores.

Hi'CT:a pixel sensor-based device for ion tomography

Carbon ions,commonly referred to as particle therapy,have become increasingly popular in the last decade.Accurately predicting the range of ions in tissues is important for the precise delivery of doses in heavy-ion radiotherapy.Range uncertainty is currently the largest contributor to dose uncertainty in normal tissues,leading to the use of safety margins in treatment planning.One potential method is the direct relative stopping measurement(RSP)with ions.Heavy-ion CT(Hi′CT),a compact segmented full digital tomography detector using monolithic active pixel sensors,was designed and evaluated using a 430 MeV/u high-energy carbon ion pencil beam in Geant4.The precise position of the individual carbon ion track can be recorded and reconstructed using a 30μm×30μm small pixel pitch size.Two types of customized image reconstruction algorithms were developed,and their performances were evaluated using three different modules of CAT-PHAN 600-series phantoms.The RSP measurement accuracy of the tracking algorithm for different types of materials in the CTP404 module was less than 1%.In terms of spatial resolution,the tracking algorithm could achieve a 20%modulation transfer function normalization value of CTP528 imaging results at 5 lp/cm,which is significantly better than that of the fast imaging algorithm(3 lp/cm).The density resolution obtained using the tracking algorithm of the customized CTP515 was approximately 10.5%.In conclusion,a compact digital Hi'CT system was designed,and its nominal performance was evaluated in a simulation.The RSP resolution and image quality provide potential feasibility for scanning most parts of an adult body or pediatric patient,particularly for head and neck tumor treatment.

宽体探测器CT血管造影与超声心动图对小儿先天性心脏病的诊断效能

目的探讨宽体探测器CT血管造影(computer tomography angiography,CTA)与超声心动图(ultrasound cardiogram,UCG)在小儿先天性心脏病(congenital heart disease,CHD)的诊断效能。方法回顾性分析2019-08/2023-09月作者医院收治的65例疑似CHD患儿的影像学资料,所有患儿均行心脏CTA及UCG检查。对两种检查方式的图像质量进行主观评价并比较其差异;以手术或数字减影血管造影(digital subtraction angiography,DSA)为“金标准”,对比两种检查方式在诊断CHD的灵敏度、特异度、阳性预测值、阴性预测值及准确率的差异,并应用Kappa检验比较与“金标准”结果的一致性;采用受试者工作特征(receiver operating characteristic,ROC)曲线分析两种检查方式对小儿CHD的诊断效能。结果CTA诊断小儿CHD心外畸形图像质量主观评分明显高于UCG,二者比较差异具有统计学意义(P<0.05),心内畸形图像质量主观评分二者比较差异无统计学意义(P>0.05)。两名医师对图像质量主观评分的一致性较好(κ=0.802)。CTA、UCG诊断小儿CHD心内畸形准确率比较差异无统计学意义(P>0.05);CTA诊断小儿CHD心外畸形准确率为96.43%,显著高于UCG 50.00%,组间比较差异具有统计学意义(P<0.05)。CTA诊断小儿CHD的灵敏度、特异度、阳性预测值、阴性预测值及准确率分别为90.00%、60.00%、96.43%、33.33%及87.69%,与手术或DSA结果一致性较好(κ=0.766);UCG诊断CHD的灵敏度、特异度、阳性预测值、阴性预测值及准确率分别为83.33%、20.00%、92.59%、9.09%及79.81%,与手术或DSA结果一致性一般(κ=0.522)。CTA、UCG两种检查方式诊断小儿CHD的灵敏度、特异度、阴性预测值及准确率差异比较均有统计学意义(P均<0.05)。ROC曲线分析结果显示,CTA与UCG诊断小儿CHD的曲线下面积(area under the cure,AUC)分别为0.853和0.773,二者比较差异有统计学意义(P<0.05)。结论宽体探测器CTA在小儿CHD心外畸形方面的诊断效能优于UCG,而在心内畸形方面稍差,因此建议二者联合检查,诊断价值更高。

光子计数探测器CT脂肪定量准确性和稳定性的体模研究

目的 旨在探讨光子计数探测器(PCD)-CT在不同扫描方案下进行脂肪定量的准确性及辐射剂量水平。方法 构建11个不同脂肪浓度的体模[真实脂肪分数(FF)为0%、2.5%、5%、10%、15%、20%、25%、30%、40%、50%和100%]。采用3种扫描模式(横断面扫描、常规螺旋扫描和大螺距螺旋扫描)、4种管电压[90、120、140和锡过滤(Sn)100 kV]和3种水平的影像质量(IQ,20、40和80)的参数组合方式完成36种扫描方案的PCD-CT扫描。记录每种扫描方案重建影像的CT剂量指数(CTDIvol)。以120 kV-IQ80的常规螺旋扫描方案作为参考,将所有方案扫描获得的CT值通过线性回归方程转换为FF值。采用组内相关系数(ICC)和Bland-Altman分析进行准确性和一致性评估,使用单向重复测量方差分析对PCD-CT衍生的FF进行比较分析。结果 PCD-CT在所有扫描方案下获得的FF的一致性和准确性结果优异[ICC>0.9(范围:0.929~0.998,P<0.017)]。通过PCD-CT获得的FF与真实FF值之间的均方根误差(RMSE)范围为1.0%~5.0%,其中120 kV-IQ20大螺距扫描的RMSE值最低(1.0%)。120 kV-IQ20和120kV-IQ80常规螺旋扫描偏倚值最低(平均值分别为1.19%和1.23%)。36种扫描方案的辐射剂量范围为0.09~1.45m Gy。结论 PCD-CT在多种扫描方案下进行脂肪定量均具有较高的准确性。此外,PCD-CT具有在超低辐射剂量下进行准确脂肪定量的潜力。

光子计数探测器技术应用进展

光子计数探测器(PCD)是一种用于检测X射线光子的装置,能够将光子能量直接转化为电信号,从而实现对光子的计数和测量。基于PCD的能谱CT技术(PCD-CT)可以提供额外的能谱成像信息,改善成像质量,同时降低辐射剂量。相较于能量积分探测器(EID),PCD具有能量转换效率高、成像质量好、结构设计精巧、应用范围广等优势,在超低剂量CT、特定病症检验及工业检测中具有广阔的应用前景。综述PCD-CT在能谱CT成像中的应用,为其在临床医疗诊断与工业应用提供有益参考。

对比剂分次团注联合能量成像获得CTU和CTA联合成像的应用研究

目的:探讨对比剂分次团注结合双层探测器光谱CT 50 keV虚拟单能量图像(VMI),在CT泌尿系成像(CTU)与主动脉CTA联合成像中的应用价值。方法:收集2024年3月至4月在首都医科大学附属北京同仁医院Philips IQon双层探测器光谱CT行CTU检查患者32例为试验组。使用对比剂分次团注及团注追踪技术;扫描后重建常规120 kVp混合能量图像为A1组;光谱重建获得50 keV VMI为A2组。收集2023年12月至2024年3月间在相同设备行CTU检查患者32例为对照组,使用对比剂分离团注技术及团注追踪技术;扫描后重建常规120 kVp混合能量图像为B组。客观评价包括:比较3组腹主动脉、双侧肾动脉的CT值、对比噪声比(CNR)、信噪比(SNR);比较输尿管起始部平均CT值和中下部平均CT值,并采用Kruskal-Wallis检验,采用Nemenyi检验进行两两比较。试验组与对照组的有效辐射剂量比较采用Wilcoxon检验。主观评价由两名高年资影像医师分别对3组CTA及CTU图像进行4分法和3分法评价,两名医师主观评分的一致性采用Kappa检验。结果:客观评价指标中,A2组分别与A1组和B组比较,均有统计学差异;A1组与B组仅双侧肾动脉SNR有统计学差异。两组有效辐射剂量有统计学差异,试验组较对照组降低15.1%。3组CTA、CTU图像主观评价无统计学差异;两名医师对CTA图像评分结果一致性非常好,对CTU图像评分结果一致性好。结论:利用对比剂分次团注行CTU检查时,获得泌尿系及主动脉同时显影的融合图像,不仅具有明确的解剖关系及相同的图像质量,而且降低有效辐射剂量;光谱重建获得的50 keV虚拟单能量图像,优化CTU及CTA图像质量,具有临床价值。

宽体探测器CT不同扫描模式在甲状腺检查中的应用

目的:探讨宽体探测器CT轴扫与螺旋扫描对甲状腺图像质量及辐射剂量的影响。方法:将90例患者随机分为A、B、C 3组,每组各30例,A、B组采用轴扫,C组采用螺旋扫描。增强扫描时,A、C组在阈值触发3 s后扫描,B组在阈值触发4 s后扫描,其余扫描参数均相同。对3组图像的动、静脉期正常甲状腺组织、颈总动脉、颈内静脉、胸锁乳突肌的CT值、噪声值(SD)及空气噪声值,以及曝光时间、容积剂量指数(CTDIvol)、剂量长度乘积(DLP)、有效剂量(ED)、图像SNR和CNR进行客观统计分析,并对图像的整体图像质量、伪影进行主观评价。结果:轴扫较螺旋扫描曝光时间、CTDIvol、DLP、ED均明显减少(均P<0.001)。图像质量方面,A组动脉期甲状腺CT值较C组低(P'<0.017),B组与C组差异无统计学意义(P'>0.017);3组图像中甲状腺组织的SD值、SNR、CNR差异均无统计学意义(均P'>0.017)。主观评价方面,A组动脉期整体图像质量评分较C组低(P=0.045),B组与C组差异无统计学意义,余动静脉期3组图像在整体图像质量与伪影评分差异均无统计学意义(均P>0.05)。结论:应用宽体探测器CT轴扫对甲状腺进行扫描,相较螺旋扫描可明显减少曝光时间,降低辐射剂量,图像质量差异无统计学意义;适当延迟增强扫描动脉期起始时间,组织强化效果更明显,图像质量更佳。

不同管电压对超高分辨光子计数探测器CT评估冠状动脉支架的影响:一项体模研究

目的 探讨不同管电压对超高分辨光子计数探测器CT(PCD-CT)评估冠状动脉支架的影响。方法 选取6枚直径约3 mm的不同材质的冠状动脉支架,置入人造模拟冠状动脉血管内,分别采用140 kV和120 kV管电压以相对于扫描设备z轴0°和90°方向对支架行超高分辨PCD-CT扫描。通过不同的扫描和重建参数组合完成144组影像数据的采集。对全部影像进行主观评分及客观影像质量评价。客观影像评价包括支架腔内衰减增加比率(SAIR)、支架的边缘上升距离(ERD)和支架内径。采用Cohen’s Kappa检验评估影像质量主观评分的观察者间一致性。采用配对t检验或Wilcoxon检验比较2种管电压下0°和90°方向支架的影像质量指标。采用多因素广义线性混合效应模型分析高管电压(140 kV)对冠状动脉支架影像定性定量评估的影响。结果 对于0°方向支架,120 kV和140 kV管电压下扫描获得的冠状动脉支架影像的影像质量主观评分、SAIR值、ERD值及支架内径差异均无统计学意义(均P>0.05)。对于90°方向支架,140 kV相比120 kV管电压下的支架影像具有更高的SAIR值、更低的ERD值及更大的支架内径(均P<0.05)。对于0°和90°方向支架,140 kV均可增加SAIR值(均P<0.05);而对于90°方向支架,140 kV还能提高支架内直径测量值,减小ERD值(均P<0.05)。结论 140 kV相较120 kV管电压可降低超高分辨PCD-CT上的冠状动脉支架硬化线束伪影。当冠状动脉支架相对于z轴的角度增加,高管电压可进一步增加支架锐利度及支架内径。但高管电压可增加辐射剂量,临床应用中仍需综合评估。

光谱CT碘定量评估肾肿瘤患者分肾功能

目的:探究利用光谱计算机体层成像(computed tomography,CT)碘定量评估肾肿瘤患者分肾功能的潜在临床应用价值。方法:回顾并分析50例2周内先后行光谱CT肾脏多期增强及核素肾动态显像的肾肿瘤患者。光谱CT肾脏多期增强扫描采用标准的腹部3期增强方案。手动勾画光谱CT参数肾脏体积(volume,V)、平均CT值(Hounsfield unit,HU)、平均碘浓度值(iodine concentration,IC),并将平均IC与肾脏体积相乘得到碘对比剂累积量K值,同时使用简化的Patlak方程计算得到分肾CT清除率。根据99m锝-二亚乙基三胺五乙酸(^(99m)Tc-diethylene triaminepentaacetic acid,^(99m)Tc-DTPA)肾动态显像盖茨法肾小球滤过率(Gates glomerular filtration rate,Gates GFR)参考值,将100个肾脏分为分肾功能正常组(Gates GFR≥40 mL/min)、分肾功能受损组(Gates GFR<40 mL/min)两组。采用Kruskal-Wallis H检验比较两组间光谱CT各参数的差异,并将各参数与肾动态显像所得Gates GFR进行Spearman相关性分析。绘制受试者工作特征(receiver operating characteristic,ROC)曲线得出分肾CT清除率区分分肾功能正常和分肾功能受损的最佳诊断阈值。结果:光谱CT所得肾脏体积V、动脉期平均CT值HU(t1)、静脉期平均CT值HU(t2)、动脉期平均碘浓度值IC(t1)、静脉期平均碘浓度值IC(t2)、动脉期肾脏碘对比剂累积量K(t1)、静脉肾脏期碘对比剂累积量K(t2)及分肾CT清除率两组之间的差异均有统计学意义(Z/t=-4.459、2.815、-3.313、2.611、-3.609、-4.395、-5.637、-5.815,均P<0.05);并且上述各参数均与GFR相关(r=0.489、0.339、0.481、0.361、0.531、0.590、0.724、0.740,均P<0.001)。区分分肾功能正常与受损的碘定量分肾CT清除率界值为543 mg。结论:光谱CT各参数均可反映分肾功能,其中光谱CT碘定量分肾CT清除率与Gates GFR相关性最高并能区分肾功能是否受损,具有潜在的临床应用价值。