心脏专用碲化镉锌相机的相关临床应用新进展

在评估缺血性心脏病的无创性方法中,SPECT心肌灌注显像（MPI）是大家公认的显像方法,但MPI受到一些因素的影响,如组织不均一性导致的衰减、扫描时间长、辐射等。近年来出现的心脏专用碲化镉锌（CZT）相机越来越受到人们的广泛关注,该设备有先进的CZT探测器、采集方法及重建算法。心脏专用CZT相机的计数率、空间分辨率和能量分辨率较传统SPECT显著提高。该文就心脏专用CZT相机的相关临床应用进展进行综述。     

碲锌镉心脏专用SPECT的临床应用进展

心肌灌注显像在已知或可疑冠状动脉疾病患者的诊疗过程中发挥着重要作用，应用碲锌镉探测器的心脏专用SPECT的分辨率和灵敏度均得到提高，达到了降低显像剂剂量、缩短采集时间、改善图像质量和扩展临床应用范围等目的。笔者对碲锌镉心脏专用SPECT的临床应用进展进行综述。     

伽玛相机型SPECT的验收及质量控制

伽玛相机型SPECT的验收及质量控制是很有必要的,其测试性能指标包括:空间分辨率,固有均匀性,能量分辨率,线性,计数率效应,多窗空间重合性,系统灵敏度,γ相机/准直器均匀性,旋转中心,探头运动轨迹中心与旋转中心的重合性,x、y轴的增益等。     

高分辨及通用型准直器,哪种适合于SPECT?

对于SPECT研究工作来说,准直器的选择是一个重要的问题.提高了分辨率使测量的准确性增加的同时,不可避免地导致灵敏性下降,使精确度降低.为了选择理想的准直器,结合使用平滑型及清晰型两类重建滤波器,作者对市售的通用型和高分辨准直器进行了比较.结果:对于脑显像来说(用HMPAO,555MBq),用通用型准直器计数约140Kc,用高分辨型准直器计数约80Kc.应用高分辨准直器,经最清晰滤波或最平滑滤波,噪声分别为38%及11%;而用通用型准直器的噪声分别为28%及8%.用Jaszczak模型所采集的结果表明,用高分辨准直器经Parzen滤波     

探测距离对SPECT断层分辨率的影响

目的探讨探测距离对SPECT断层分辨率的影响.方法采用内置不同直径的圆柱体(冷区)的自制黑箱模型.设定不同探测距离对模型进行360°采集,并对所采集的20组原始资料进行重建处理,观察重建后模型图像.结果配置低能高分辨准直器,探头旋转半径≤18cm时,及配置低能通用准直器,探头旋转半径为15cm时,重建结果可分辨出直径10mm柱型模型,余重建结果均达不到此分辨效果.结论探测距离愈小,分辨率愈高;反之,则分辨率下降.     

SPECT图像重建方法对Hoffmann模型图像质量的影响

目的探讨SPECT显像不同断层重建方法对Hoffmann模型图像质量的影响。方法采用放射性线源及Hoffmann模型,进行SPECT配平行孔低能高分辨准直器断层采集。对线源图像和Hoffmann模型图像均用滤波反投影（FBP）法和有序子集最大期望值迭代（OSEM）法进行断层重建。对线源重建图像计算2种重建算法的半高宽（FWHM）值,视觉评价2种方法重建的Hoffmann模型图像,并比较2种重建方法的重建时间和模型特定感兴趣区（ROI）。采用SPSS15．0软件,2种重建方法的脑叶及基底节ROI与小脑ROI计数比值行两独立样本t检验。结果平行孔低能高分辨准直器采集的线源断层图像经FBP法和OSEM法重建,FWHM值分别为18．77mm,12．62mm。OSEM法重建所得Hoffmann模型总的图像质量、基底节区的显示以及核团分辨程度均优于FBP法。FBP法和OSEM法重建时间分别为80s和100s,均在临床允许范围之内。OSEM迭代与FBP法脑叶及基底节ROI与小脑ROI比值差异无统计学意义（t=-0．332,P=0．750）。结论在现有软硬件技术条件下,平行孔低能高分辨准直器配合OSEM法优于FBP法,可获得空间分辨率和图像质量较好的Hoffmann模型重建图像。     

符合线路SPECT 3D采集的可行性研究

目的 分析符合线路SPECT（GE Millennium VH with Hawkeye）三维（3D）采集的可行性.方法 采用充满^18F溶液的圆柱体模型,用符合线路SPECT仪对模型分别行用隔栅（二维,2D）和没有隔栅的探头护板（3D）2种方式图像采集.首先进行X线透射扫描约10 min,获得横断层透射影像,然后进行符合探测采集10 min,获得发射扫描数据.根据横断层透射影像生成非均匀衰减校正图,用有序子集最大期望值迭代法（OSEM）加衰减校正进行发射影像重建.对获得的模型横断面图像进行处理,得到对比度、均匀性、空间分辨率、符合计数率等指标.结果 与2D采集相比,3D采集的单光子计数率提高2倍以上,符合计数率提高4倍以上,其“热区”对比度有所降低,但幅度较小,均匀性降低29%,空间分辨率差异无显著性.结论 3D符合采集可减少临床采集时间,其图像质量在正常剂量条件下与2D采集相比无明显降低,但在低剂量条件下,3D图像质量优于2D图像.     

移动校正对CZT SPECT心肌血流定量显像影响的初步研究

目的:探讨移动校正(MC)对碲锌镉SPECT(CZT SPECT)心肌血流(MBF)和心肌血流储备(MFR)计算值的影响。方法:回顾性收集2019年6月至2019年8月于泰达国际心血管病医院行动态CZT SPECT心肌灌注显像(MPI)的可疑或确诊冠状动脉粥样硬化性心脏病(简称冠心病)患者28例[男10例,女18例,年...     

小动物SPECT的应用和进展

小动物SPECT是实验科学向临床科学过渡的重要工具,已广泛应用在临床前新药研发、人类生理和疾病实验动物模型的研究中.随着硬件技术和图像重建算法的进展,小动物SPECT的系统灵敏度、空间分辨率和定量准确性都得到了明显提高.与小动物PET相比,小动物SPECT在研究的适应性、放射性药物来源的便利性及研究成本上具有更大优势,在一段时间内仍将是疾病临床前分子影像研究的重要手段之一.     

用~(99)Tc~m-tetrofosm in和~(18)F-FDG校正SPECT评价心肌灌注和存活能力

目的 :心肌灌注 -代谢不匹配主要由 PET检测。近来 ,将1 8F-氟代脱氧葡萄糖 (1 8F- FDG)与 99Tcm标记的灌注示踪剂相结合 ,用双同位素同时采集 (DISA) SPECT来检测灌注 -代谢不匹配心肌 ,便可提供与 PET等同的临床信息。此研究用99Tcm- tetrofosmin和 1 8F- FDG DISA SPECT显像评价心肌灌注和存活能力时交互校正的用途。方法 :选择 18例冠状动脉疾病病人 (14男 ,4女 ,平均 6 4岁 ) ,注入 740 MBq99Tcm - tetrofosmin后 ,用双探头、低能高分辨准直器进行 SPECT研究 ;采集完后 ,口服 75 g葡萄糖 ,再静脉注入 1 8F- FDG 370…     

Physical attributes, limitations, and future potential for PET and SPECT

Advances in SPECT and PET imaging hardware, software, and radiotracers are vastly improving the non-invasive evaluation of myocardial perfusion and function. In contrast to traditional dual-headed, sodium iodide crystal and photomultiplier cameras with mechanical collimators, new SPECT camera designs utilize novel, collimators, and solid-state detectors that convert photons directly to electrical signals. These cameras simultaneously collect data from as many as 76 small detectors narrowly focused on the heart. New noise regularization and resolution recovery/noise reduction reconstruction software interprets emitted counts more efficiently and thus more effectively discriminates between useful signals and noise. As a result, shorter acquisition times and/or lower tracer doses produce higher quality SPECT images than were possible before. PET perfusion imaging has benefitted from the introduction of novel detectors that now allow true 3D imaging, new radiopharmaceuticals, and precise attenuation correction (AC). These developments have resulted in perfusion images with higher spatial and contrast resolution that may be acquired in shorter protocols and/or with less patient radiation exposure than traditional SPECT. Hybrid SPECT/CT and PET/CT cameras utilize transmission computed tomographic (CT) scans for AC, and offer the additional clinical advantages of evaluating coronary calcium, myocardial anatomy (including non-invasive CT angiography), myocardial function, and myocardial perfusion in a single imaging procedure.     

Performance of cardiac cadmium-zinc-telluride gamma camera imaging in coronary artery disease: a review from the cardiovascular committee of the European Association of Nuclear Medicine (EANM)

The trade-off between resolution and count sensitivity dominates the performance of standard gamma cameras and dictates the need for relatively high doses of radioactivity of the used radiopharmaceuticals in order to limit image acquisition duration. The introduction of cadmium-zinc-telluride (CZT)-based cameras may overcome some of the limitations against conventional gamma cameras. CZT cameras used for the evaluation of myocardial perfusion have been shown to have a higher count sensitivity compared to conventional single photon emission computed tomography (SPECT) techniques. CZT image quality is further improved by the development of a dedicated three-dimensional iterative reconstruction algorithm, based on maximum likelihood expectation maximization (MLEM), which corrects for the loss in spatial resolution due to line response function of the collimator. All these innovations significantly reduce imaging time and result in a lower patient’s radiation exposure compared with standard SPECT. To guide current and possible future users of the CZT technique for myocardial perfusion imaging, the Cardiovascular Committee of the European Association of Nuclear Medicine, starting from the experience of its members, has decided to examine the current literature regarding procedures and clinical data on CZT cameras. The committee hereby aims 1) to identify the main acquisitions protocols; 2) to evaluate the diagnostic and prognostic value of CZT derived myocardial perfusion, and finally 3) to determine the impact of CZT on radiation exposure.     

Appropriate collimators in a small animal SPECT scanner with CZT detector

Objective

Almost all small animal SPECT is performed with pinhole collimators (PH), including single-PH (SPH) and multi-PH (MPH). In the clinical study, not only PH but also parallel-hole collimator (PAH) is often used in planar and SPECT imaging. However, there have been no comparative studies on image quality with various collimators on the small animal imaging. This study compared the basic characteristics of PH and PAH in small animal imaging.

Methods

Performance of planar and SPECT images was evaluated using ^99mTcO₄ ^? and SPH, MPH and PAH with low energy and high resolution on the SPECT/CT scanner FX3200. We measured sensitivity, resolution, concentration linearity and uniformity. Planar imaging of mice with ^99mTc-labeled mercaptoacetyltriglycine (^99mTc-MAG₃) was performed using SPH and PAH. SPECT imaging with ^99mTc-methylene diphosphonate (^99mTc-MDP) was performed using all collimators.

Results

With SPH, MPH and PAH, sensitivity was 43.5, 211.2 and 926.5 cps/MBq, respectively, and spatial resolution was 0.60/0.56, non/0.96, 5.20/5.34 mm full-width half maximum (planar/SPECT), respectively. There were marked correlations between the radioactivity counts on images and radioactivity with all collimators. Values of % standard deviation on planar imaging showed small differences between the SPH and PAH, while the values were the smallest on SPECT imaging with MPH. On imaging of mice, SPH yielded high-quality ^99mTc-MAG₃-planar images when compared with PAH. MPH yielded sharper ^99mTc-MDP-SPECT images than SPH and PAH.

Conclusions

The characteristics of PH and PAH differed on small animal imaging. Although sensitivity was higher with PAH, PH showed higher resolution. Among the PH collimators, SPH was more appropriate for planar imaging, and MPH was more suitable for SPECT imaging in a small animal imaging scanner with CZT detector.     

Impact of a new ultrafast CZT SPECT camera for myocardial perfusion imaging: fewer equivocal results and lower radiation dose

Purpose  

The new ultrafast cardiac single photon emission computed tomography (SPECT) cameras with cadmium-zinc-telluride (CZT)-based detectors are faster and produce higher quality images as compared to conventional SPECT cameras. We assessed the need for additional imaging, total imaging time, tracer dose and 1-year outcome between patients scanned with the CZT camera and a conventional SPECT camera.     

SPECT instrumentation: performance, lesion detection, and recent innovations

The use of a gamma camera for single photon emission computed tomography (SPECT) imaging places greater demand on camera performance than does planar imaging, since camera specifications that are adequate for planar imaging may produce serious image artifacts in SPECT. Manufacturers have responded to the challenge with improvements in both hardware and software, but the user must pay careful attention to quality control procedures. Field nonuniformity is caused mainly by spatial distortion, which may vary during rotation; some cameras incorporate a means of automatically correcting for angular changes. The purpose of performing SPECT is to improve lesion detection, ie, to improve contrast, which is influenced by many factors. Attenuation corrections may be applied either before or after reconstruction. For Tc-99m an attenuation coefficient less than that for water, ie, either 0.11 or 0.12, would appear to give better results; the visual appearance is improved but the effect on contrast is minimal. Scattered photons are the major cause of loss of contrast in SPECT images. Recent developments in on-line energy corrections allow the use of narrower photopeak windows as well as asymmetric energy windows. Offpeak energy windows have demonstrated significant improvements in contrast; however, the increase in nonuniformity can cause artifacts which may limit their use. Simultaneous collection of separate images, one in the photopeak region and the other in the scatter region (92 to 125 keV) may enable a transaxial scatter image to be subtracted from the transaxial photopeak image. This may permit quantification of the true radioactivity distribution. New collimator designs introduced to improve SPECT resolution include cast collimators which can be made with more uniform hole construction than the lead-foil type; for brain imaging, long bore parallel hole and converging fan beam collimators as well as astigmatic collimators which converge in both planes with different lines of focus. Some of these improve both sensitivity and resolution compared to parallel hole collimators. Noncircular orbits have also been introduced in order to improve resolution, but their use presents many problems which require careful monitoring. Transaxial multicrystal systems have been developed over many years, but have not been widely used, primarily because of their inherent complexity, high costs, and limited applicability. Some of these drawbacks may be overcome by a new type of SPECT camera currently under development by several different groups.(ABSTRACT TRUNCATED AT 400 WORDS)     

Comparison of low- and medium-energy collimators for SPECT imaging with iodine-123-labeled antibodies

The planar and single photon emission computed tomography (SPECT) imaging performance of two low-energy and one medium-energy collimators has been compared for 123I(p,5n). Septal penetration in the low-energy collimators affected the planar uniformity and sensitivity and made the usual uniformity correction methods inappropriate. SPECT uniformity and resolution were also distorted by these artifacts induced in the planar images obtained with the low-energy collimators. The planar and SPECT images of a SPECT phantom contradicted the spatial resolution measurements made with a line source in air. The medium-energy collimator is recommended for imaging 123I(p,5n)-labeled antibodies in patients, particularly when quantitation is required.     

Advances in preclinical SPECT instrumentation

Preclinical SPECT of rodents is both in demand and very demanding. The need for high spatial resolution in combination with good sensitivity has given rise to considerable innovation in the areas of detectors, collimation, acquisition geometry, and image reconstruction. Some of the developments described herein are beginning to carry over into clinical imaging as well.     

Sensitivity, resolution and image quality with a multi-head SPECT camera.

This investigation sought to determine which collimation factors were most important in providing superior image quality with a three-headed SPECT device. The relationship between sensitivity, resolution and SPECT image quality was studied. Two different sets of parallel-hole collimators were used. The ultrahigh-resolution collimators have higher spatial resolution (8.9 versus 11.0 mm), but only 55% of the sensitivity of the high-resolution collimators. A phantom with hot rods was imaged with both collimator sets. Observers compared images with the ultrahigh-resolution collimators to images of varying counts with the high-resolution collimators and determined which high-resolution images matched the ultrahigh-resolution images in image quality. Eleven patient studies were acquired with both collimator sets for equal time, and observers chose which image set they preferred. Transverse images of brain and liver studies were simulated with varying resolution and counts and subjectively compared. The phantom study indicated that the improvement in resolution led to image quality comparable to increasing the number of counts by a factor of 2.5 to 3.4. The clinical studies showed that the ultrahigh-resolution collimators were preferred in a large majority of the cases. These trends were also seen in the simulation study. These results confirm that higher resolution collimators should be used with multihead SPECT devices. The improvement in resolution more than compensates for the loss in sensitivity, leading to an overall improvement in image quality.