兔脑CTP低剂量扫描联合迭代重建的可行性研究

目的:评价联合迭代重建技术(iDose4)的低剂量兔脑CT灌注成像参数的准确性及图像质量.方法:将60只成年雄性新西兰白兔随机均分为3组进行CT灌注成像,扫描参数:常规剂量组(RD)为80 kV、100 mAs、FBP,低剂量组(LD)为80 kV、50 mAs、iDose4和层级3),超低剂量组(ULD)为80kV、25mAs、iDose4和层级5.测量各组兔脑的灌注参数值(包括脑血流量CBF、脑血容量CBV、平均通过时间MTT、达峰时间TTP)并计算有效辐射剂量.对3组灌注图像质量进行评估和比较,包括图像噪声、脑实质信噪比(SNR)和图像质量评分.结果:共有54只兔脑CT灌注扫描成功,其中RD组16只,LD组20只,ULD组18只.三组的有效剂量分别为:RD组3.47 mSv,LD组1.53 mSv,ULD组0.75 mSv;与RD组比较,LD组和ULD组的有效辐射剂量分别下降55.9％和78.3％.各项灌注参数值(CBF、CBV、MTT和TTP)在三组间差异均无统计学意义(P＞0.05).图像噪声和脑实质SNR在三组间差异无统计学意义(P＞0.05).图像质量主观评分:ULD组低于RD组,差异有统计学意义(P=0.006);LD组与RD组,ULD组与LD组间差异无统计学差异(P＞0.05).两位观察者对图像质量主观评价结果的一致性中等(Kappa=0.471,P＜0.01).结论:通过联合不同层级的迭代重建技术,低剂量和超低剂量兔脑CT灌注成像可获得准确的灌注参数值以及可接受的图像质量.     

CT低剂量联合迭代算法在输尿管结石诊断中的应用

目的 探讨CT低剂量联合迭代算法在输尿管结石诊断中的应用价值.方法 90例输尿管结石患者在首次检查均应用常规剂量扫描(120 kV,400 mAs),采用滤波反投影算法(FBP)薄层重组,保守治疗后结石未排出.复查CT应用低剂量扫描随机分为3组(A组:120 kV,200 mAs;B组:120 kV,150 mAs;C组:120 kV,100 mAs)后分别行6级迭代算法薄层重组.由2名放射医师采用双盲法读片并对图像质量做主观评分,记录CT容积剂量指数(CTDIvol)、剂量长度乘积(DLP),计算辐射有效剂量(ED);测量图像的客观噪声值,计算信噪比,测量结石CT值及最大长径,记录结石检出数.结果 常规组:CTDIvol(23.51±0.79) mGy,DLP(1166.38±52.78)mGy·cm,ED(17.50±0.79)mSv;A组:CTDIvol(11.78±0.38) mGy,DLP(584.68±25.47) mGy· cm,ED(8.77±0.38) mSv;B组:CTDIvol(8.34±0.13)mGy,DLP(462.87±24.76) mGy· em,ED(6.94±0.37)mSv;C组:CTDIvol(5.47±0.21) mGy,DLP(268.20±19.03)mGy·cm,ED(4.02±0.29) mSv;各组低剂量迭代算法重组的iDose l ～6图像结石检出数、结石CT值及大小与常规剂量比较差异无统计学意义(P＞0.05);A组低剂量迭代算法重组的iDose4图像噪声(SD)、信噪比(SNR)及iDose 4—6图像质量主观评分与常规剂量比较差异无统计学意义(P＞0.05);B组低剂量迭代算法重建的iDose6图像噪声、信噪比及图像质量主观评分与常规剂量比较差异无统计学意义(P＞0.05);C组低剂量迭代算法重建的iDose l～6各组图像噪声、信噪比及图像质量主观评分与常规剂量比较差异有统计学意义(P＜0.05).结论 CT低剂量扫描联合迭代算法诊断输尿管结石是可行的,可以在不影响图像质量的前提下明显减低辐射剂量.管电压120 kV情况下,在iDose6水平管电流150mAs为最低临界扫描参数.     

双下肢动脉CT血管成像不同剂量扫描方法的影像质量比较

目的 探索双下肢动脉CT血管成像(CTA)低剂量扫描的不同方法的差异,以及双下肢动脉CTA低剂量扫瞄三维处理(VR)图像的质量与血管CT值及标准差SD的关系。方法 选取行双下肢动脉CTA检查的受检者90例。用随机数字表法分成3组,常规剂量组、120 kV和80 mAs组、100 kV和130 mAs组,每组30例。图像进行容积再现三维成像(VR)处理后,按优、良、差 3个等级进行评定,对3组进行图像质量等级比较。测量CT值及标准差SD值,与VR 图像质量等级关系进行受试者操作特性曲线(ROC)分析。结果 常规剂量组(120 kV,150 mAs)、120 kV,80 mAs组和100 kV,130 mAs组VR图像等级为优的分别为93.3%、86.6%和96.6%。SD值与双下肢动脉CTA的VR图像的质量相关性分析ROC曲线下面积为0.9078,CT值与双下肢动脉CTA的VR图像的质量相关性分析ROC曲线下面积为0.9116。结论 双下肢动脉CTA低剂量扫描切实可行,100 kV和130 mAs组的图像质量优于120 kV和80 mAs组。     

低剂量脑CT灌注成像联合IMR的图像质量评价

目的 探讨低剂量脑CT灌注成像(CTPI)联合全模型迭代重组(IMR)技术临床应用的可行性.方法 收集因临床怀疑急性脑梗死行脑CTPI检查的患者80例.A组35例, B组45例.A、B组分别采用80 kV,150 mAs+传统滤波反投影(FBP)及80 kV,30 mAs+IMR重建.选取A、B 组脑灌注正常的一侧脑各30侧.比较2组图像主观评分、有效剂量(ED)和阿尔伯塔脑卒中计划早期CT评分层面2(ASPECTS2)水平大脑中动脉供血区灰白质的CT值、图像噪声(SD)、信噪比(SNR)、对比噪声比(CNR)以及灌注参数值.结果 A、B 2组ED分别为2.52、0.50 mSv;2组灰白质的灌注参数、CT值、SD,CNR,灰质SNR及主观评分之间无明显统计学差异(P>0.05);2组白质SNR存在明显统计学差异(P<0.05).结论 IMR联合30 mAs的CTPI在保证图像质量和灌注参数稳定的前提下明显降低辐射剂量.     

头颈部256层CTA低剂量扫描的临床研究

目的 探讨头颈部256层CTA低剂量扫描的可行性.方法 将84例行头颈部CTA检查的成人(体质指数(BMI) ＜22.9 kg/m2)随机分为常规剂量组(400 mAs组)、300 mAs组和200 mAs组,每组28例,均采用Phil-ips 256层CT扫描,3组管电压均为120kV,管电流分别为400 mAs、300 mAs和200 mAs,对照分析3组的图像质量及辐射剂量.结果 3组主观图像质量评分及颈总动脉(CCA)与基底动脉(BA)平均CT值比较差异无统计学意义(P＞0.05).200 mAs组的背景噪声(N)明显高于常规剂量组和300 mAs组(P＜0.05),信噪比(SNR)明显降低(P＜0.05).3组的CT剂量指数(CTDIvd)和剂量长度乘积(DLP)随管电流降低而逐步降低(P＜0.05).结论 头颈部256层CTA检查管电压120 kV、管电流300 mAs时的图像质量好、辐射剂量较低,可作为最佳扫描参数.     

双低技术在iCT全脑灌注成像中的应用研究

目的探讨80kV低管电压及低管电流在iCT全脑灌注成像(CTP)中的可行性。方法 60例全脑CTP检查者,管电压均为80kV,按照不同管电流分为3组,A组(50mAs),B组(100mAs),C组(150mAs),每组20例。记录各组的辐射剂量,比较分析每例颞叶白质、尾状核头的灌注参数[脑血容量(CBV)、脑血流量(CBF)、平均通过时间(MTT)及达峰时间(TTP)]、图像客观指标[CT值、噪声(SD)、信噪比(SNR)、对比噪声比(CNR)]及主观评分。结果 A～C组的有效剂量(ED)分别为1.10mSv、2.21mSv、3.31mSv;3组颞叶白质的CBV、MTT存在统计学差异(P0.05),颞叶白质的CBF、TTP及尾状核头的各灌注参数均无显著差异(P0.05);3组图像质量客观指标、主观评分比较均有统计学差异(P0.05);B组与C组的灌注参数及图像质量均无显著差异(P0.05)。结论 80kV低管电压联合100mAs低管电流行全脑CTP扫描可行性较好,不仅对灌注参数和图像质量没有显著影响,而且还显著降低了辐射剂量。     

多层螺旋CT颈部血管造影低剂量扫描的初步研究

目的 探讨多层螺旋CT颈部血管造影(CTA)低剂量扫描的可行性和合理性.资料与方法 将常规行颈部CTA检查的患者60例随机分为A、B、C三组,每组20例.在其他扫描参数不变的情况下,A组采用常规剂量250 mAs、B组采用150 mAs、C组采用100 mAs条件行CTA扫描.以图像显示解剖结构及病变的情况为主要指标,比较B、C两种低剂量组扫描所得图像质昔与常规剂量A组扫描图像质量的差异.结果 当mA值由常规250mAs降低至150 mAs和100 mAs时,CT剂量加权指数(CTDI)由16.7 mGy分别降至10.0 mGy和6.7 mGy,下降40.1%和59.8%;剂量长度积(DLP)由(564.6±32.5)mGy分别降至(336.2±24.5)mGy和(204.3±33.7)mGy,下降40.5%和63.8%.B、c组与A组比较,剂量差异均有统计学意义(P<0.01);而B组图像质量与A组比较,差异无统计学意义(P>0.05);C组图像质量与A组比较,差异有统计学意义(P<0.05).结论 150 mAs町作为颈部CTA低剂量扫描的最佳mA值,适当降低管电流是一种切实可行的降低辐射剂量的CTA扫描方法.     

多层螺旋CT肺部低剂量与常规剂量检查的放射剂量评估

目的比较多层螺旋CT肺部低剂量与常规剂量检查的X线辐射剂量,为低剂量多层螺旋CT普查早期肺癌提供剂量参数. 资料与方法肺部低剂量与常规剂量多层螺旋CT扫描共54例.其中,低剂量扫描24例,扫描参数为:120 kV,20 mAs,准直器4×5 mm,重建层厚8 mm,床速30 mm/周,螺距为7,扫描时间0.5 s/周;常规剂量扫描30例,扫描参数为:120 kV,90 mAs,准直器4×5 mm,重建层厚8 mm,床速30 mm/周,螺距为7,扫描时间0.5 s/周.观察并计算两种扫描剂量的权重CT剂量指数(CTDIw),有效mAs,总mAs,剂量长度乘积(DLP)及有效辐射剂量. 结果肺部低剂量扫描的CTDIw为1.38 mGy,是常规剂量扫描(6.21 mGy)的22.2%;低剂量扫描的DLP为44 mGy*cm,明显低于常规剂量扫描的189 mGy*cm(P＜0.01);低剂量扫描的总mAs为459,是常规剂量扫描(1 308)的35.1%;低剂量扫描的X线最大有效辐射剂量为0.9 mSv,明显低于常规剂量扫描的4.2 mSv(P＜0.01). 结论多层螺旋CT肺部低剂量扫描(20 mAs)的有效辐射剂量为常规剂量扫描的21.4%,适用于高危人群普查早期肺癌.     

肺部低剂量CT体检中的价值探讨

目的探讨体检中肺部低剂量CT应用价值,为临床检查辐射剂量选择提供参考。方法对228例患者采用随机抽样方法分为常规剂量组(114例)和低剂量组(114例),分别采用肺部常规剂量CT扫描(扫描参数:130kV,50mAs,层厚6mm)和肺部低剂量CT扫描(扫描参数:130kV,15mAs,层厚6mm),对两组患者图像质量和扫描辐射量进行比较。结果两组CT扫描图像质量无明显区别;低剂量组CTDIvol1.64m,DLP及辐射剂量均显著优于常规剂量组,差异有统计学意义(P<0.05)。结论肺部低剂量CT用于体检可在减少辐射剂量的同时保证图像质量,具有一定临床价值。     

256 CT低管电压联合迭代重组技术在头颈部CT血管成像中的应用

目的 探讨低管电压(80 kV)联合迭代重组技术在头颈部CT血管成像(CTA)扫描中对图像质量、辐射剂量的影响.方法 将75例临床需要行头颈部CTA检查的患者随机编入A、B、C三组,每组25例.A组为常规剂量扫描,参数为120 kV、300 mAs,经滤波反投影(FBP)重组;B、C组为低剂量扫描,管电流和管电压分别为120kV、180 mAs,80 kV、180 mAs,采用iDose4迭代重组.对比分析CT图像质量,包括动脉强化值、对比噪声比(CNR)、图像质量评分及辐射剂量.计量资料采用配对t检验两两比较,图像质量评分采用非参数x2检验进行统计分析.结果 (1)图像质量主观评分:A组3分1例,4分24例;B组3分2例,4分23例;C组3分5例,4分20例;统计学分析无差异(P＞0.05).(2)A、B两组主动脉弓、颈总动脉、颈内动脉及大脑中动脉的动脉强化CT值统计无明显差异(P＞0.05);C组的CT动脉强化值高于A组(P＜0.05).(3)C组的背景噪声[(12.5±1.9)HU]高于A组[(9.0±1.6)HU](P＜0.05);两组的CNR分别为(49.2±9.4)、(43.0±12.6),无统计学差异(P＞0.05).(4)A、B、C组的剂量长度乘积(DLP)分别为(925.1±48.5)、(571.4±24.2)、(164.1±7.0)mGy·cm;辐射有效剂量(ED)分别为(2.87±0.15)、(1.77±0.08)、(0.51±0.02) mSv,均有统计学意义(P＜0.05),C组较A组辐射剂量明显降低,约82.3％.结论 256 CT头颈部CTA采用低管电压(80 kV)联合迭代重组技术能提供满足临床诊断要求的图像,同时明显降低辐射剂量.     

Computed tomography of the bowel: A prospective comparison study between four techniques

Objectives

The major objective was to prospectively compare the grade of bowel distension obtained with four different computed tomography (CT) techniques dedicated for the examination of the small intestine (CT enteroclysis [CTE] and enterography [CTe]), of the colon (CT with water enema [CT-WE]), or both (CTe with water enema [CTe-WE]). The secondary objective was to assess patients’ tolerance toward each CT protocol.

Materials and methods

Recruitment was designed to obtain four groups of the same number of patients (30). Each group corresponded to a specific CT technique, for a total of 120 consecutive outpatients (65 male and 55 female, mean age 51.09 ± 13.36 years).CTE was performed after injection of methylcellulose through a nasojejunal tube, while in the CTe protocol a polyethylene glycol electrolyte solution was orally administered to patients prior to the CT acquisition. In the CT-WE protocol intraluminal contrast (water) was administered only by a rectal enema, while CTe-WE technique included both a rectal water enema and oral ingestion of neutral contrast material to obtain a simultaneous distension of small and large bowel.CT studies were reviewed in consensus by two gastrointestinal radiologists who performed a quantitative and qualitative analysis of bowel distension on a per segment basis. The presence and type of adverse effects were recorded.

Results

CTE provided the best distension of jejunal loops (median diameter 27 mm, range 17–32 mm) when compared to all the other techniques (p < 0.0001). The frequency of patients with an adequate distension of the terminal ileum was not significantly different among the four groups (p = 0.0608). At both quantitative and qualitative analysis CT-WE and CTe-WE determined a greater and more consistent luminal filling of the large intestine than that provided by both CTE and CTe (p < 0.0001 for all colonic segments). Adverse effects were more frequent in patients belonging to the CTE group (p < 0.0028).

Conclusions

CTE allows an optimal distension of jejunal loops, but it is the most uncomfortable CT protocol. When performing CT-WE, an adequate retrograde distension of the terminal ileum was provided in a particularly high percentage of patients. CTe-WE provides a simultaneous optimal distension of both small and large bowel.     

Value of contrast enhanced CT scanning in the non-trauma emergency room patient

Summary To determine the value of performing contrast CT in addition to non-contrast CT in the evaluation of acute non-traumatic central nervous system disorders, we retrospectively reviewed 322 cases originating from the emergency room at our institution. The most common indication for scanning was seizure activity (34% of total), followed by headache (30%), focal neurological deficit (10%), and altered mental status (8%). 75% of the noncontrast scans were normal. The contrast-enhanced scan revealed abnormalities not evident on the non-contrast scan in only three of these cases, and the information did not alter patient management. We concluded that in the acute setting, if a non-contrast CT is normal, a contrast study is usually unnecessary. Therefore, given the additional risks of contrast infusion, the contrast study, if needed, is generally best obtained at a later date, after more careful evaluation of the patient's history and medical records. If the non-contrast CT scan is abnormal, a contrast enhanced CT scan may be beneficial, but, again, is often not needed to direct acute patient management.     

A model for temporal resolution of multidetector computed tomography of coronary arteries in relation to rotation time, heart rate and reconstruction algorithm

A model is presented that describes the image quality of coronary arteries with multidetector computer tomography. The results are discussed in the context of rotation time of the scanner, heart rate, and number of sectors used in the acquisition process. The blurring of the coronary arteries was calculated for heart rates between 50 and 100 bpm for rotation times of 420, 370, and 330 ms, and one-, two-, three-, and four-sector acquisition modes and irregular coronary artery movement is included. The model predicts optimal timing within the RR cycle of 45±3% (RCA), 44±4% and 74±6% (LCX), and 35±4% and 76±5% (LAD). The optimal timing shows a negative linear dependency on heart rate and increases with the number of sectors used. The RCA blurring decreases from 0.98 cm for 420 ms, one-sector mode to 0.27 cm for 330 ms, four-sector mode. The corresponding values are 0.81 cm and 0.29 cm for LCX and 0.42 cm and 0.17 cm for LAD. The number of sectors used in a multisector reconstruction and the timing within the cardiac cycle should be adjusted to the specific coronary artery that has to be imaged. Irregular coronary artery movement of 1.5 mm justifies the statement that no more than two sectors should be used in multisector acquisition processes in order to improve temporal resolution in cardiac MDCT.     

Timing of exposure in angiographic computed tomography

Visualization of heart chambers or the abdominal arterial phase on one of two CT-scans was achieved in 89.4% of 169 injections (91 patients) using only 30 ml of contrast medium (370 mg iodine/ml), when the start of scanning was accurately timed at predicted bolus peak concentration. Normal arrival times and numer of transit cycles to the bolus concentration maximum in the right (RV) and left ventricle (LV) after injection of a small radionuclide bolus of technetium-99 m were related to the patient's heart rate (HR) in a group of 200 patients. For the RV, mean arrival times varied significantly between 2.31 (HR: 90–109 beats per minute) and 3.46 seconds (HR: 50–59 beats per minute), mean number of transit cycles between 4.1 and 3.5. For the LV, mean arrival times varied significantly between 6.92 (HR: 90–109 beats per minute) and 11.37 seconds (HR: 50–59 beats per minute), and the mean number of transit cycles between 11.5 and 10.7. Washout from the LV lasted between an average of 9.2 (HR: 90–109 beats per minute) and 8.5 cycles (HR: 50–59 beats per minute). Contrary to actual transit times, there was no significant difference in the number of transit heart cycles for heart rates between 60 and 109 beats per minute, so that to determine the scan starting time, the patient's cycle length (60 divided by heart rate) had only to be multiplied by the corresponding normal value of transit cycles, i.e., four for the RV, 11 for the LV, and 13 for the abdominal arteries. By applying the estimated values, the result was negative on two successive scans in only 10.6% because of failure in coordination on the part of the operators or bolus transit delays (due to severe heart failure, severe lung disease, recent thoracotomy, or small veins disease). With automatic triggering of the scanner by a timer and injector and with a flush of saline after injection, results can be further improved. Radionuclide studies supported by grant of the Internal Department of the Government of the Federal Republic of Germany     

Multiplanar display of spiral CT data of the pulmonary hila in patients with lung cancer : Preliminary observations

Spiral or helical computed tomography (CT)-generated multiplanar reconstructions were used in the radio-logical assessment of the pulmonary hila in patients with central lung cancer. Twelve patients with non-small-cell lung cancer and hilar abnormalities were examined with contrast-enhanced spiral CT. Studies were performed on a Siemens Somatom S or Plus-S scanner using either a 24- or 32-second spiral. The study volume was from the arch of the aorta to the inferior pulmonary veins done in a single breath-hold, using 4-mm collimation, and reconstructed at 2-mm intervals. We assessed the quality of vascular enhancement and of multiplanar reconstructions. Bronchoscopic, surgical, and pathological findings were correlated. Excellent vascular opacification and good-quality reconstructions were obtained in all patients. No interscan motion was detected. No problems were encountered with the breathholding technique or in the reconstruction of images, even in patients with poor respiratory function. Multiplanar reconstructions were useful for the evaluation of mediastinal including vascular and airways invasion, for optimal definition of lymph node groups, for the planning of bronchoscopically guided biopsy, as well as for endobronchoscopic laser coagulation therapy and surgical treatment. Spiral CT-generated multiplanar reconstructions of the hila are helpful for staging, solving problems, guiding bronchoscopy, and planning surgery. Even patients with limited respiratory reserve can successfully complete the examination.     

胸壁病变的计算机X线摄影和CT检查

目的：探讨胸壁病变的计算机Ｘ线摄影（ＣＲ）和ＣＴ表现及其诊断价值,提高对胸壁病变的认识。材料和方法：回顾分析经手术病理、穿刺细胞学检查或临床随访资料证实的３９例ＣＲ和ＣＴ资料。结果：感染组１２例中（包括化脓性感染４例,胸壁结核８例）,ＣＲ准确诊断４例,ＣＴ诊断１１例;软组织肿瘤组１６例中（包括脂肪瘤７例,纤维肉瘤４例,血管瘤、神经纤维瘤、恶性纤维组织细胞瘤、侵袭性纤维瘤病和脂肪肉瘤各１例）,ＣＲ准确诊断３例,ＣＴ诊断１４例;骨肿瘤和肿瘤样病变组１１例中（包括骨纤维异常增殖症７例,软骨瘤２例,多发性骨髓瘤和骨嗜酸性肉芽肿各１例）,ＣＲ准确诊断８例,ＣＴ诊断１０例。结论：ＣＲ简便,能诊断大多数胸壁骨性病变。ＣＴ对各种胸壁病变尤其是软组织病变的诊断较ＣＲ明显优越,对鉴别胸壁肿瘤的良恶性有肯定作用,但仍有一定限制。     

Study on motion artifacts in coronary arteries with an anthropomorphic moving heart phantom on an ECG-gated multidetector computed tomography unit

Acquisition time plays a key role in the quality of cardiac multidetector computed tomography (MDCT) and is directly related to the rotation time of the scanner. The purpose of this study is to examine the influence of heart rate and a multisector reconstruction algorithm on the image quality of coronary arteries of an anthropomorphic adjustable moving heart phantom on an ECG-gated MDCT unit. The heart phantom and a coronary artery phantom were used on a MDCT unit with a rotation time of 500 ms. The movement of the heart was determined by analysis of the images taken at different phases. The results indicate that the movement of the coronary arteries on the heart phantom is comparable to that in a clinical setting. The influence of the heart rate on image quality and artifacts was determined by analysis of several heart rates between 40 and 80 bpm where the movement of the heart was synchronized using a retrospective ECG-gated acquisition protocol. The resulting reformatted volume rendering images of the moving heart and the coronary arteries were qualitatively compared as a result of the heart rate. The evaluation was performed on three independent series by two independent radiologists for the image quality of the coronary arteries and the presence of artifacts. The evaluation shows that at heart rates above 50 bpm the influence of motion artifacts in the coronary arteries becomes apparent. In addition the influence of a dedicated multisector reconstruction technique on image quality was determined. The results show that the image quality of the coronary arteries is not only related to the heart rate and that the influence of the multisector reconstruction technique becomes significant above 70 bpm. Therefore, this study proves that from the actual acquisition time per heart cycle one cannot determine an actual acquisition time, but only a mathematical acquisition time.     

Computed tomography of intrathecal thorotrast

Summary Thorotrast is distributed in the cerebral subarachnoid space in a distinctive manner. Computed tomography is an excellent method for demonstrating this distribution.     

Asymmetry of the renal nephrograms on CT: Significance of the unilateral prolonged cortical nephrogram

The normal renal nephrogram as seen on contrast-enhanced computed tomography (CT) is reviewed, and the etiologies and diagnostic significance of the asymmetric renal nephrograms, characterized by a unilateral prolonged cortical nephrogram, are discussed.