心肌灌注显像常见伪影分析

伪影是造成心肌灌注显像出现假阳性的主要原因之一，有必要对造成伪影的因素、伪影的表现形式和校正方法进行系统、全面的认识。心肌灌注显像中的伪影主要可归结为：与检测仪器有关的伪影，与病人因素有关的伪影，与图像处理有关的伪影，以及与非冠状动脉疾病有关的伪影等。     

衰减校正技术在SPECT心肌灌注显像中的应用分析

心肌灌注显像（MPI）的伪影对其图像质量以及图像的判别产生较大影响,造成假阳性率较高。目前针对软组织衰减所造成的伪影主要有以下2类校正技术,非X射线校正法（如变换体位采集、门控采集和固体153Gd线源穿透式采集）和CT衰减校正法。明确2种方法的应用范围及其优缺点,使临床医师在阅片中对伪影有正确的分析判断,从而提高诊断的准确率。     

心肌显像病人所致伪影的辨析及其对策研究

重点介绍了在心肌灌注显像过程中,由于病人因素导致的位移、膈肌衰减和肝脏放射性聚集等所产生的伪影的表现和校正方法。     

心肌显像病人所致伪影的辨析及其对策研究

重点介绍了心肌灌注显像过程中，由于病人因素导致的位移、膈肌衰减和肝脏放射性聚集等所产生的伪影的表现和校正方法。     

心肌灌注显像中位移伪影的辨析

目的 探讨心肌灌注显像时位移伪影的影像学特征、不同轴向、发生位移起始点和帧数与伪影的相关性。方法 在心肌显像过程中依次沿x,y和z轴方向,分别在不同起始点,对不同帧数作一定距离的位移。其图像与正常对照比较判断有无伪影。结果作多因素分析。结果 轻度位移伪影的特征为：x轴位移表现为下壁突出的结节状热区;y轴位移表现为间隔和侧壁呈对称分布的热区;z轴位移表现为前壁的局部热区;这些表现仅见于短轴像上。重度伪影表现为“三角形”分布的壁内热区以及典型的“双三角形”改变。位移距离相同,方向相反,伪影的“冷”“热”分布的壁内热区以及典型的“双三角形”改变。位移距离相同,方向相反,伪影的“冷”“热”区位置相反。伪影与位移帧数和轴向有关,与起始点无关。结论 不同轴向位移伪影各有特征。移动帧数和y轴位移对伪影产生的影响最大。     

18F-FDG PET/CT伪影和不常见生理性摄取分析

目的 探讨^18F-脱氧葡萄糖（FDG）PET/CT显像各种伪影的影像学表现及其产生的原理.方法 回顾性分析^18F-FDG PET/CT检查患者的图像,根据伪影产生的原因进行分类,同时对临床不常见的生理性摄取进行分析.结果 伪影分为自身因素和设备技术因素伪影,自身因素所致伪影中以呼吸运动伪影和高密度物质伪影最为常见;设备因素伪影中以截断伪影、注射点外漏和放射性污染最为常见.不常见的生理性摄取包括：子宫内膜摄取、乳腺摄取和脂肪摄取.结论 PET显像伪影影像学表现可分为“热区”或“冷区”.不常见的生理性摄取主要表现为“热区”.伪影产生原因中以CT应用于PET显像后物理学因素多见.不常见的生理性摄取与检查技术有关.     

SPECT心脏影像的伪影识别与校正技术

ＳＰＥＣＴ心肌显像中由于光子散射、衰减、患者移动、以及仪器与采样因素产生图像伪影，本文系统介绍了各种伪影的机理、识别和校正方法     

SPECT心脏影像的伪影识别与校正技术

ＳＰＥＣＴ心肌显像中由于光子散射、衰减、患者移动、以及仪器与采样因素产生图像伪影，本文系统介绍了各种伪影的机理、识别和校正方法。     

心肌灌注断层显像的质量保证

心脏核医学中应用最广泛的是心肌灌注显像 ,其主要用于诊断心肌缺血、心肌梗死 ,判断心肌存活、预后及危险性分级 ,监测冠心病治疗效果及冠状动脉再狭窄等。获得高质量心肌灌注显像的关键是受检者准备、显像方案选择、采集和处理的整个过程进行严格的质量控制 ,在此前提下 ,仍疑有伪影 ,可进行校正。在此笔者介绍用西门子ORBITER 75 0 0型SPECT仪行心肌灌注断层显像时质量保证的经验和体会。一、显像准备1.审阅检查申请单 ,选择显像方式。①接到心肌灌注显像申请单后 ,首先看检查目的和病史摘要等 ,了解受检者的心血管病史和循环、呼吸系统检查情况 ,包括基本生命体征。病史中须特别注意受检者的指征、用药、症状、心脏危险因素、预诊断及治疗方案[1 ] 。对申请单内容不详者 ,及时询问受检者或与申请医生联系。如受检者以前曾做过心肌灌注显像 ,嘱其检查时把结果带来以利于阅片时比较。②确定显像剂及显像方式。普通受检者一般选择99Tcm 甲氧基异丁基异腈 (MIBI)心肌灌注断层显像 ,连续 2个上午检查 ,对时间紧者亦可选择一日法2 0 1 Tl心肌灌注显像。如以诊断心肌缺血为目的 ,首选2 0 1 Tl,也可用两日法99T...     

心脏移动校正技术在心肌灌注断层显像中的应用

心肌灌注断层显像过程中患者身体移动会造成心脏移动 ,出现移动伪影 ,影响显像结果。笔者采用心脏移动校正技术对心肌灌注断层显像数据进行校正 ,比较有无移动时校正前后的放射性分布异常的差异 ,并探讨其在临床应用中的价值。资料与方法1.临床资料。随机抽取 1998年 9月～ 2 0 0 0年 4月在我科行心肌灌注断层显像者 71例 ,在“电影方式 (Ｃｉｎｅｍｏｄｅ)”下观察分析 ,以数据采集过程中有无心脏呈头足方向 (ｙ方向 )的移动而分为移动组及非移动组。非移动组 37例 ,男 2 1例 ,女 16例 ,年龄 38～ 73岁 (平均 5 7 8岁 ) ;移动组 34例 ,男 2…     

Optimization of spiral‐based pulse sequences for first‐pass myocardial perfusion imaging

Although spiral trajectories have multiple attractive features such as their isotropic resolution, acquisition efficiency, and robustness to motion, there has been limited application of these techniques to first‐pass perfusion imaging because of potential off‐resonance and inconsistent data artifacts. Spiral trajectories may also be less sensitive to dark‐rim artifacts that are caused, at least in part, by cardiac motion. By careful consideration of the spiral trajectory readout duration, flip angle strategy, and image reconstruction strategy, spiral artifacts can be abated to create high‐quality first‐pass myocardial perfusion images with high signal‐to‐noise ratio. The goal of this article was to design interleaved spiral pulse sequences for first‐pass myocardial perfusion imaging and to evaluate them clinically for image quality and the presence of dark‐rim, blurring, and dropout artifacts. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.     

Myocardial first pass perfusion imaging with gadobutrol: impact of parallel imaging algorithms on image quality and signal behavior

OBJECTIVE: To implement parallel imaging algorithms in fast gradient recalled echo sequences for myocardial perfusion imaging and evaluate image quality, signal-to-noise ratio (SNR), contrast-enhancement ratio (CER), and semiquantitative perfusion parameters. MATERIALS AND METHODS: In 20 volunteers, myocardial perfusion imaging with gadobutrol was performed at rest using an accelerated TurboFLASH sequence (TR 2.3 milliseconds, TE 0.93 milliseconds, flip angle [FA] 15 degrees) with GRAPPA, R=2. A nonaccelerated TurboFLASH sequence with similar scan parameters served as standard of reference. Artifacts were assessed qualitatively. SNR, CER, and CNR were calculated and semiquantitative perfusion parameters were determined from fitted SI-time curves. RESULTS: Phantom measurements yielded significant higher SNR for nonaccelerated images (P<0.001). CER was equal; differences in CNR were statistically nonsignificant. The evaluation of semiquantitative perfusion parameters yielded significantly higher peak signal intensities in nonaccelerated images (P<0.001). Differences in maximum upslope were statistically nonsignificant. A qualitative examination of all images for artifacts by 2 board-certified radiologists yielded a significant reduction in dark rim artifacts with GRAPPA, R=2 (P<0.001). CONCLUSIONS: The application of GRAPPA with an acceleration factor of R=2 leads to a significant reduction of dark rim artifacts in fast gradient recalled echo sequences.     

The diagnostic and prognostic value of ECG-gated SPECT myocardial perfusion imaging.

Since the development of gated SPECT imaging approximately 10 y ago, this technique is now almost universally used as an adjunct for radionuclide perfusion imaging, enabling the assessment of perfusion along with determination of regional and global left ventricular function in the same examination. The gated SPECT determination of the left ventricular ejection fraction and volumes has been extensively validated. Additionally, this method allows for the improved identification of soft-tissue artifacts and enhances the detection of multivessel coronary artery disease. Furthermore, gated SPECT provides powerful information for the risk assessment of patients with known or suspected coronary artery disease and aids in the assessment of myocardial viability. Gated SPECT imaging has clearly become an integral part of radionuclide myocardial perfusion imaging.     

Myocardial first pass perfusion: steady-state free precession versus spoiled gradient echo and segmented echo planar imaging.

The imaging sequences used in first pass (FP) perfusion to date have important limitations in contrast-to-noise ratio (CNR), temporal and spatial resolution, and myocardial coverage. As a result, controversy exists about optimal imaging strategies for FP myocardial perfusion. Since imaging performance varies from subject to subject, it is difficult to form conclusions without direct comparison of different sequences in the same subject. The purpose of this study was to directly compare the saturation recovery SSFP technique to other more commonly used myocardial first pass perfusion techniques, namely spoiled GRE and segmented EPI. Differences in signal-to-noise ratio (SNR), CNR, relative maximal upslope (RMU) of signal amplitude, and artifacts at comparable temporal and spatial resolution among the three sequences were investigated in computer simulation, contrast agent doped phantoms, and 16 volunteers. The results demonstrate that SSFP perfusion images exhibit an improvement of approximately 77% in SNR and 23% in CNR over spoiled GRE and 85% SNR and 50% CNR over segmented EPI. Mean RMU was similar between SSFP and spoiled GRE, but there was a 58% increase in RMU with SSFP versus segmented EPI.     

High-resolution myocardial perfusion imaging at 3 T: comparison to 1.5 T in healthy volunteers

The purpose of this study was to evaluate high-resolution (HR) myocardial first-pass perfusion in healthy volunteers at 3 T compared to a typical clinical imaging protocol at 1.5 T, with respect to overall image quality and the presence of subendocardial dark rim artifacts. Myocardial first-pass rest perfusion studies were performed at both field strengths using a T1-weighted saturation-recovery segmented k-space gradient-echo sequence combined with parallel imaging (Gd-DTPA 0.05 mmol/kg). Twenty-six healthy volunteers underwent (1) a HR perfusion scan at 3 T(pixel size 3.78 mm²) and (2) a standard perfusion approach at 1.5 T(pixel size 9.86 mm²). The contrast enhancement ratio (CER) and overall image quality (4-point grading scale: 4: excellent; 1: non-diagnostic) were assessed, and a semiquantitative analysis of dark rim artifacts was performed for all studies. CER was slightly higher (1.31 ± 0.32 vs. 1.14 ± 0.34; p<0.01), overall image quality was significantly improved (3.03 ± 0.43 vs. 2.37 ± 0.39; p<0.01), and the number of dark rim artifacts (139 ± 2.09 vs. 243 ± 2.33; p<0.01) was significantly reduced for HR perfusion imaging at 3 T compared to the standard approach at 1.5 T. HR myocardial rest perfusion at 3 T is superior to the typical clinical perfusion protocol performed at 1.5 T with respect to the overall image quality and presence of subendocardial dark rim artifacts.     

Comparison of three accelerated pulse sequences for semiquantitative myocardial perfusion imaging using sensitivity encoding incorporating temporal filtering (TSENSE)

PURPOSE: To investigate the parallel acquisition technique sensitivity encoding incorporating temporal filtering (TSENSE) with three saturation-recovery (SR) prepared pulse sequences (SR turbo fast low-angle shot [SR-TurboFLASH], SR true fast imaging with steady precession [SR-TrueFISP], and SR-prepared segmented echo-planar-imaging [SR-segEPI]) for semiquantitative first-pass myocardial perfusion imaging. MATERIALS AND METHODS: In blood- and tissue-equivalent phantoms the relationship between signal intensity (SI) and contrast-medium concentration was evaluated for the three pulse sequences. In volunteers, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and normalized upslopes (NUS) were calculated from signal-time curves (STC). Moreover, artifacts, image noise, and overall image quality were qualitatively evaluated. RESULTS: Phantom data showed a 40% increased linear range of the relation between SI and contrast-medium concentration with TSENSE. In volunteers, TSENSE introduced significantly residual artifacts and loss in SNR and CNR. No differences were found for NUS values with TSENSE. SR-TrueFISP yielded highest SNR, CNR, and quality scores. However, in SR-True-FISP images, dark-banding artifacts were most pronounced. NUS values obtained with SR-TrueFISP were significantly higher and with SR-segEPI significantly lower than with SR-TurboFLASH. CONCLUSION: Semiquantitative myocardial perfusion imaging can significantly benefit from TSENSE due to shorter acquisition times and increased linearity of the pulse sequences. Among the three pulse sequences tested, SR-TrueFISP yielded best image quality. SR-segEPI proved to be an interesting alternative due to shorter acquisition times, higher linearity and fewer dark-banding artifacts.     

Quantitative myocardial perfusion imaging using different autocalibrated parallel acquisition techniques

PURPOSE: To compare three different autocalibrated parallel acquisition techniques (PAT) for quantitative and semiquantitative myocardial perfusion imaging. MATERIALS AND METHODS: Seven healthy volunteers underwent myocardial first-pass perfusion imaging at rest using an SR-TrueFISP pulse sequence without PAT and while using GRAPPA, mSENSE, and TSENSE. signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), normalized upslopes (NUS), and myocardial blood flow (MBF) were calculated. Artifacts, image noise, and overall image quality were qualitatively assessed. Furthermore, the relation between signal intensity (SI) and contrast medium (CM) concentration was determined in phantoms. RESULTS: Using PAT the linear range of the SR-TrueFISP sequence was increased about 40%. All three PAT methods introduced significant loss in SNR and CNR. GRAPPA yielded slightly better values then mSENSE and TSENSE. Both SENSE techniques introduced significantly residual aliasing artifacts. Image noise was increased with all three PAT methods. However, overall image quality was reduced only with mSENSE. Even though GRAPPA yielded smaller NUS values than non-PAT, mSENSE, and TSENSE, no differences were found in MBF between all applied techniques. CONCLUSION: Quantitative and semiquantitative myocardial perfusion imaging can benefit from PAT due to shorter acquisition times and increased linearity of the pulse sequence. GRAPPA and TSENSE turned out to be well suited for quantitative myocardial perfusion imaging.     

Assessment of myocardial perfusion with real-time myocardial contrast echocardiography: Methodology and clinical applications

Real-time myocardial contrast perfusion imaging (RTMCI) with echocardiography is a promising technique for evaluation of patients with known or suspected coronary artery disease. The technique is based on the utilization of small (<10 mum) microbubbles, which are capable of crossing the pulmonary circulation after intravenous injection. Unlike radioactive isotopes, which are taken actively or diffuse passively in the myocytes, myocardial contrast agents remain extracellularly in the capillaries and present a measure of the myocardial capillary blood volume and microvascular integrity. RTMCI has been shown to be a safe and feasible method for the assessment of myocardial perfusion at rest and with pharmacologic stress. Recent studies have shown the value of RTMCI with dobutamine stress in improving overall and regional detection of coronary artery disease and detecting of abnormalities at submaximal stress, therefore improving sensitivity in patients who are unable to achieve the target heart rate. The advantages of the technique include the ability to assess perfusion at bedside in one setting, simultaneous assessment of myocardial function, shorter imaging time, no need for ionizing irradiation, immediate availability of the results, and the ability to determine the ischemic threshold. Recent studies have shown that RTMCI improves the prognostic utility of standard dobutamine stress in addition to wall motion analysis. Patients with normal perfusion had a better outcome than those with normal wall motion. The combination of abnormal wall motion and perfusion identified patients at greatest risk of death and nonfatal myocardial infarction. Perfusion abnormalities were also shown to predict short-term cardiac events in patients presenting to the emergency department with chest pain and no ST-segment elevation. Refinement of imaging techniques is expected to improve the specificity of RTMCI, particularly in differentiating true perfusion defects from artifacts. This review will discuss the physiologic basis, methodology, clinical utility, and limitations of RTMCI in the assessment of patients with known or suspected coronary artery disease.     

Value of attenuation correction on ECG-gated SPECT myocardial perfusion imaging related to body mass index

BACKGROUND: Obesity is a growing problem in the United States, and attenuation artifacts are more prevalent in this patient group. This study evaluated the impact of attenuation correction in patients with a high body mass index (BMI). METHODS AND RESULTS: Three readers interpreted gated attenuation-corrected and non-attenuation-corrected rest/stress technetium 99m sestamibi myocardial perfusion imaging results in 116 patients (BMI <30, n = 60; BMI > or =30, n = 56) who had coronary angiography no more than 60 days after imaging. Readers were blinded to all clinical information and as to whether myocardial perfusion imaging was attenuation-corrected or non-attenuation-corrected. Sensitivity, specificity, and accuracy for detection of coronary artery disease of 70% or greater for attenuation-corrected versus non-attenuation-corrected single photon emission computed tomography (SPECT) were 86% versus 89%, 79% versus 50%, and 84% versus 79%, respectively. Sensitivity, specificity, and accuracy for attenuation-corrected versus non-attenuation-corrected SPECT for patients with BMI less than 30 were 90% versus 90%, 82% versus 64%, and 88% versus 85%, respectively. For BMI of 30 or greater, the results were 82% versus 87%, 76% versus 41%, and 80% versus 73%, respectively. There was a significant difference in specificity overall ( P = .02) and for the category of BMI of 30 or greater ( P = .03). CONCLUSIONS: This study demonstrates that electrocardiography-gated attenuation-corrected Tc-99m sestamibi SPECT myocardial perfusion imaging improves specificity compared with electrocardiography-gated non-attenuation-corrected SPECT myocardial perfusion imaging, especially in patients with BMI of 30 or greater.