Cardiofocal collimators for gated single-photon emission tomographic myocardial perfusion imaging

Cardiofocal collimators (CFCs) are more sensitive than parallel-hole collimators (PHCs) of the same resolution because the rays converge in the centre of the field of view. After reconstruction a useful field of view with a 10 cm radius in which both sensitivity and resolution are homogeneous is obtained. In this article the feasibility and accuracy of gated single-photon emission tomographic (gated SPET) myocardial perfusion imaging using a triple-head camera equipped with CFC, is evaluated. Twenty patients with a history of myocardial infarction were studied. SPET myocardial perfusion images, gated in eight time bins, were acquired in a random sequence with a PHC and a CFC for each patient. Imaging was started 60 min after the injection of 925 MBq of technetium-99m tetrofosmin at rest. Ninety-six projections over 360° were acquired, with 32 stops of 40 s for the PHC and 20 s for the CFC in order to obtain similar count densities. The extent (EXT) and severity (SEV) of perfusion defects were quantified on polar maps using the non-gated data. Left ventricular volumes [end-diastolic volume (EDV), end-systolic volume (ESV)] and ejection fraction (LVEF) were calculated from gated data using the Cedars-Sinai program. In 17 of 20 patients the complete left ventricle was positioned within the useful field of view of the CFC. The results in respect of perfusion, volumes and ejection fraction were almost identical to those obtained with the PHC. The mean difference±SD between the CFC and the PHC was −2.30±7.16 (% of LV area) for EXT, −0.48±2.90 for SEV (arbitrary units), −1,50±5.25 (ml) for EDV and 0.53±4.10 (%) for LVEF. The largest differences in EXT and LV volumes were observed in patients in whom a part of the LV was not positioned within the useful field of view. We conclude that, for the majority of patients, identical information with regard to both perfusion and function can be derived from gated SPET myocardial perfusion studies obtained with PHCs or with CFCs. Because of the greater sensitivity, however, a much shorter acquisition time is required with CFCs. Received 7 May and in revised form 31 August 1997     

门控断层显像在心肌灌注断层显像中的应用

使用门控心肌断层显像不但减低了心脏搏动产生的图像边缘模糊,提高了对心肌缺血诊断的灵敏度和特异性,而且通过傅立叶变换和图像边缘识别技术等图像处理技术,可以在一次采集的信息基础上同时获得心脏的心肌血流灌注、心肌活力、室壁运动、射血功能和收缩协调性等参数,提高了核素心脏检查的价值,为临床准确判断患者的心脏状况,选择治疗方案,预后及疗效评价提供了更可靠的数据。本文就其近年来的临床应用进行综述。     

Influence of arrhythmias on gated SPECT myocardial perfusion and function quantification.

Despite the importance of R-wave gating myocardial perfusion tomography for ventricular function assessment, neither prevalence of gating errors nor their influence on quantified cardiac parameters has been studied. METHODS: Arrhythmia-induced anomalies in curves of counts versus projection angle for each R-wave segment were detected visually and algorithmically. Arrhythmia prevalence was tabulated for 379 patients (group 1) with prospective coronary artery disease (mean age 63+/-13 y, 47% male). Myocardial counts were analyzed from all reconstructed cinematic midventricular slices to assess arrhythmia effects on percentage of systolic count increase, generally assumed to equal percentage of wall thickening. In a separate retrospective analysis of 41 patients (group 2), with coronary artery disease (mean age 64+/-12 y, 68% male) having no significant arrhythmias, 36 of whom also underwent equilibrium radionuclide angiography, original projection data were altered to simulate arrhythmia-induced aberrant count patterns to evaluate effects on ventricular function and perfusion measurements. RESULTS: Group 1 patients consisted of 26% without gating errors, 32% with count losses only in the last R-wave interval due to inconsistent transient increase of heart rate, 24% with count decreases in several late intervals due to consistently variable rates, 8% with early interval count increases paired with late interval count decreases due to ectopic beats and 9% with erratic count changes due to atrial fibrillation. Observed count patterns were strongly associated (P < 10(-3)) with arrhythmias detected by electrocardiogram monitoring. In group 2 simulations, ventricular volumes changed by only 2%+/-9% and ejection fraction (EF) by only 1%+/-4% from control values and correlated linearly (r> or = 0.96) with control values for all simulated arrhythmias. SPECT and equilibrium radionuclide angiography EFs correlated similarly (r = 0.85-0.89) for control and all simulations. Percentage changes from control in perfusion defect extent and severity were larger than processing reproducibility limits, the largest change being for atrial fibrillation. Control wall thickening was 38%+/-17%, significantly lower (P < 10(-6)) than for simulated arrhythmias, reflecting similar observations for group 1 patients. CONCLUSION: Even though ventricular volumes and EFs were affected minimally by arrhythmias, both perfusion analysis and wall thickening were compromised. Consequently, quality assurance of gating may be critically important for obtaining accurate quantified parameters.     

肌聚糖病的99Tc^m—MIBI门控心肌灌注断层显像评价

目的探讨99Tc^m一MIBIG—MPI评价肌聚糖病患者心肌受损的价值。方法临床、分子病理确诊的肌聚糖病患者8例（男3例,女5例,年龄10—30岁）、对照者4名均接受99TcmMIBIG—MPI。原始数据按常规处理成断层图像,再应用定量门控分析软件（QGS）进行左室功能定量分析。采用将左心室分为7个节段、20个亚段的5分制（0—4分）半定量方法,用于评估心肌受损的程度。结果8例患者99Tcm-MIBIG—MPI阳性7例。7例阳性患者140个心肌亚段中共检出59个亚段异常。按病变累及室壁节段（7个节段）分为：单一室壁节段异常1例,2个室壁节段异常2例,3个及3个以上室壁节段异常、病灶呈散在性分布4例。8例肌聚糖患者中5例患者左心室扩大,其中3例左室射血分数为（43．1±2．8）％。结论99Tcm-MIBIG—MPI能直观探测肌聚糖病患者的心肌损害,可作为肌聚糖病患者心肌损害早期诊断和远期随访的辅助诊断方法。     

Scatter and attenuation correction changes interpretation of gated myocardial perfusion imaging

Attenuation correction may improve the diagnostic accuracy of myocardial perfusion imaging (MPI). However, few studies have dealt with the clinical consequences for reporting. We compared routine reports based on scatter-corrected MPI (MPI-routine) with consensus readings of scatter-corrected (MPI-scatter) and scatter plus attenuation-corrected studies (MPI-attenuation) to investigate the impact of attenuation correction on reporting. One hundred consecutive stable angina patients (including 55 men) were investigated in a ^99mTc-sestamibi 2-day gated protocol with scatter and attenuation correction. With MPI-routine, 53 patients had normal perfusion and 47 abnormal perfusion, compared to 62 and 38 with MPI-attenuation, and 54 and 46, respectively, with MPI-scatter. Agreement between MPI-routine and MPI-attenuation with respect to overall diagnosis (normal/abnormal perfusion) was 89% (kappa=0.78) compared to 95% (kappa=0.90) between MPI-routine and MPI-scatter. With MPI-attenuation, the overall routine diagnosis changed in 11 patients, of which ten cases were judged normal after scatter plus attenuation correction. The majority of the normalised studies were among patients with apparently single-vessel RCA disease as judged from MPI. Agreement rates with regard to normal, reversible or irreversible defects between MPI-attenuation and MPI-routine for the LAD, LCX and RCA territories were 88%, 97% and 85%, respectively, without significant sex differences. In conclusion, attenuation correction caused a change in diagnosis in approximately 10% of the patients, corresponding to one-fifth of the abnormal studies. In all but one case, the shift was from abnormal to normal, mostly because of a different interpretation in the RCA territory.This work was presented in part (as a poster) at the 6th International Conference of Nuclear Cardiology, Florence, Italy, April 29, 2003     

Prospective multicenter evaluation of rapid, gated SPECT myocardial perfusion upright imaging

Background  A novel three-dimensional (3D) iterative image reconstruction method (3D-OSEM) has been developed that in phantom studies yielded comparable image quality at one half the imaging time. In this study, we compared standard (STD) and rapid (nSPEED) protocols for diagnostic quality of images and quantitation of end-diastolic volume (EDV), end-systolic volume (ESV), left ventricular ejection fraction (LVEF), and perfusion defect severity. Methods  At 11 US community centers, 448 patients prospectively underwent rest–stress-gated SPECT imaging using Tc-99m-labeled agent. The difference in quality and diagnostic equivalence of STD and nSPEED images were blindly evaluated by three experts. Defect intensity was quantitated as %normal in the three coronary artery territories. Results  Studies were abnormal in 40% of patients. In 98.7% of stress and 98% of rest images, the nSPEED image quality was identical to or better than the STD images. nSPEED images were diagnostically equivalent to the STD in 444/448 (99%) patients. A high correlation was observed between nSPEED and STD studies for measurement of EDV (Y = 0.957X, R ² = 0.99), ESV (Y = 0.962X, R ² = 0.99), and LVEF (Y = 1.005X, R ² = 0.96). STD and nSPEED studies were not significantly different (P = ns) for quantitative perfusion defect severity. Conclusion  Rapid, gated rest–stress myocardial perfusion upright SPECT imaging may be achieved without compromising perfusion and function information. Financial support for this study was partly provided by Digirad Corporation, Poway, CA.     

定量门控心肌显像评价局部室壁运动

目的　探讨定量门控99Tcm 甲氧基异丁基异腈 (MIBI)、2 0 1 Tl和99Tcm tetrofosmin心肌显像评价局部室壁运动的可靠性。方法　对 30 1例左室功能受检者行门控99Tcm MIBI(n =15 8)、2 0 1 Tl(n =113)和99Tcm tetrofosmin(n=30 )心肌显像 ,采用QGSPECT程序评价左室总体和各区域局部室壁运动。并与二维超声心动图进行比较。结果　①左室总体局部室壁运动 :定量门控99Tcm MIBI心肌显像评价室壁运动与超声心动图的结果基本符合 (Kappa =0 6 3,P <0 0 1) ,定量门控2 0 1 Tl(Kappa =0 5 2 ,P <0 0 1)和99Tcm tetrofosmin(Kappa =0 5 4 ,P <0 0 1)心肌显像评价室壁运动与超声心动图的结果中等符合。②左室各区域局部室壁运动 :定量门控99Tcm MIBI和99Tcm tetrofosmin心肌显像能较准确评价左室前壁、前侧壁、后侧壁、下壁、前间壁、后间壁和后壁局部室壁运动 (Kappa =0 4 6～ 0 89,P <0 0 1) ;而定量门控2 0 1 Tl心肌显像只能较准确评价左室前壁、下壁和后壁局部室壁运动 (Kappa=0 6 5～ 0 72 ,P <0 0 1) ,其侧壁和间壁的可靠性低于前者 (Kappa =0 2 7～ 0 39)。结论　定量门控99Tcm MIBI、2 0 1 Tl和99Tcm tetro fosmin心肌显像能较准确评价局部室壁运动。     

门控心肌显像和心血池显像联合检测左心室功能

目的应用99mTC-MIBI门控心肌显像和心血池显像来评价左心室功能.方法30例受检者,静脉注射99mTc-MIBI后,用SPECT行常规体位平面心肌显像,观察分析室壁运动和左心室收缩分数(LVCF).结果99mTc-MI3I门控心肌显像能清楚区分室壁边缘,在判断室壁运动上与心血池显像的完全符合节段达66%.用象素数表现左心室腔面积大小所计算的左心室收缩分数(LVCF)与左心室射血分数(LVEF)明显相关(r=0.09,P＜0.01).结论99mTc-MIBI门控心肌显像和心血池显像在冠心病的检查中具有重要价值,可作为常规检查之一应用于临床.     

Effect of perfusion pattern and imaging sequence on gated perfusion SPECT evaluation of myocardial stunning.

The aim of this study was to determine the effect of perfusion defect and imaging sequence on the evaluation of myocardial stunning with gated perfusion SPECT. METHODS: A dynamic mathematic cardiac torso phantom was used to create 100 gated SPECT simulations (50 stress-rest and 50 rest-stress sequences) with a wide range of perfusion defects. No segmental wall motion abnormalities were created. After generating projection images, 2 additional acquisitions were simulated by thresholding the projected data to 25% and 75% of the maximum. Finally, gated SPECT projections were grouped by 2s to generate 2 series of phantoms corresponding to stress-rest and rest-stress imaging sequences. For each sequence, the first dataset was the 25% thresholded gated SPECT. Both 75% thresholded and 100% signal intensity were used as a second dataset. Each simulated gated SPECT image differed from others in the extent of myocardial scar or ischemia, but all had the same end-diastolic volume (EDV) (125 mL), end-systolic volume (ESV) (48 mL), and ejection fraction (EF) (62%). Left ventricular perfusion and function were each assessed using validated software. RESULTS: Mean stress EDV was decreased when compared with rest-simulated data (111 +/- 4.7 and 112.4 +/- 4.8 mL, respectively; P < or = 0.05), and mean stress ESV was increased when compared with rest-simulated data (44 +/- 4.2 and 42.7 +/- 4 mL, respectively; P < 0.02). The resulting mean stress EF was decreased in the same comparison (60.3% +/- 3.1% and 62% +/- 2.7%, respectively; P = 0.0001). After multivariate analysis, the difference between stress and rest EF was significantly influenced by myocardial infarction (P = 0.0027), severe extent of myocardial ischemia (P = 0.0017), and imaging sequence (P < 0.0001). A > or =5% decrease in EF on stress SPECT (i.e., myocardial stunning) was significantly associated with the stress-rest sequence (chi(2) = 26; P < 0.0001). CONCLUSION: Perfusion defects and imaging sequence had significant effects on the evaluation of myocardial stunning using gated perfusion SPECT.     

Improved perfusion quantification in FAIR imaging by offset correction.

Perfusion quantification using pulsed arterial spin labeling has been shown to be sensitive to the RF pulse slice profiles. Therefore, in Flow-sensitive Alternating-Inversion Recovery (FAIR) imaging the slice selective (ss) inversion slab is usually three to four times thicker than the imaging slice. However, this reduces perfusion sensitivity due to the increased transit delay of the incoming blood with unperturbed spins. In the present article, the dependence of the magnetization on the RF pulse slice profiles is inspected both theoretically and experimentally. A perfusion quantification model is presented that allows the use of thinner ss inversion slabs by taking into account the offset of RF slice profiles between ss and nonselective inversion slabs. This model was tested in both phantom and human studies. Magn Reson Med 46:193-197, 2001.     

CT血管成像检出心肌桥患者的^99Tc^m—MIBI门控心肌显像研究

目的探讨^99Tc^m-MIBI G-MPI对冠状动脉CT血管成像（CTA）检出心肌桥（MB）患者的临床价值。方法对象为62例（MB患者45例,对照组17例）经CTA（64排CT）检查并接受^99Tc^m-MIBIG-MPI的患者,分析其心肌灌注、室壁运动和左心室功能。所有患者行静息显像,其中17例MB患者和9例对照行运动负荷G-MPI。组间率的比较用,检验或确切概率法,计量资料用t检验比较差异。结果运动负荷和静息心肌显像对MB患者的心肌缺血和（或）灌注异常的阳性检出率分别为（1）门控半定量法：64．7％（11／17）、42．2％（19／45）;（2）目测法：41．2％（7／17）、22．2％（10／45）,静息门控半定量法和目测法的阳性检出率差异有统计学意义（P=0．035）。静息显像对不同位置[近段0／7、中段19．4％（6／31）、远段4／7]和深度[表浅型16．7％（7／42）、纵深型3／3]MB的心肌灌注异常阳性检出率差异有统计学意义（x2=7．086,P〈0．05;P=0．008）。门控半定量法评价17例（有负荷显像结果）MB中可逆性缺血、固定缺血和混合性缺血分别占35．3％、23．5％和5．9％;室壁运动和室壁增厚率类型总积分反向分布异常、可逆性异常、固定异常所占百分比分别是23．5％、23．5％、11．8％和35．3％、29．4％、5．9％。不论静息相还是运动负荷相,MB组和对照组间LVEF和高峰充盈率差异均无统计学意义（t=-0．564～1．292,P均〉0．05）。结论^99Tc^m -MIBIG—MPI对CTA检出的MB患者的心肌缺血和（或）灌注异常及左心室功能状况评价有一定价值。     

99Tcm-替曲膦与99Tcm-MIBI门控心肌灌注显像的对比研究

目的 对比99Tcm-替曲膦(TF)和99Tcm-MIBI G-MPI的左室心肌灌注及左室心功能参数结果,探讨99 Tcm-TF能否作为临床G-MPI常规显像剂.方法 99Tcm标记TF和MIBI并进行放化纯测定.选取2011年12月至2012年5月间既往健康、排除严重心律不齐及临床拟诊为心肌炎、心肌病的112例受试者(研究经医院伦理委员会批准,患者签署知情同意书),采用简单随机抽样法将其随机分成2组,分别行一日法99Tcm-TF(47例,运动负荷状态下注射显像剂370 MBq,静息状态下注射显像剂740 MBq)G-MPI和两日法99Tcm-MIBI(65例,注射剂量均为555 MBq)G-MPI,所有受试者均于1周内行CAG和UCG检查.利用Cedars定量门控SPECT(QGS)软件获得左室心功能参数,包括LVEF、EDV、ESV、峰充盈率(PFR)、峰射血率(PER)及相位标准差(SD).采用SPSS 17.0软件进行x2检验、两独立样本r检验、配对r检验及直线相关分析.结果 99 Tcm-TF和99Tcm-MIBI放化纯分别为(97.5±0.4)％和(99.1±0.2)％.与CAG结果对比,99Tcm-MIBI心肌灌注结果符合率为90.5％(57/63),99Tcm-TF为88.9％(40/45),两者差异无统计学意义(x2=0.389,P＞0.05).99Tcm-TF和99Tcm-MIBIG-MPI获得的左室心功能参数差异也无统计学意义[LVEF:(62.60±±13.56)％与(60.52±7.08)％,r=0.940;EDV:(103.31±17.29) ml与(98.52±19.37) ml,t=1.348;ESV:(41.73±12.69) ml与(46.05±10.81) ml,t=0.851;PER:(2.73±0.67) EDV/s与(2.61±1.04) EDV/s,t =0.725;PFR:(2.13±0.80) EDV/s与(2.07±1.09) EDV/s,t=0.339;相位SD:(5.58±4.16).与(5.97±4.64).,t=0.450,均P＞0.05].两者G-MPI获得的左室心功能参数与UCG结果差异无统计学意义[LVEF:(61.39±10.28)％与(62.13±8.51)％,t=0.991;EDV:(100.50±18.61) ml与(101.70±18.34) ml,t=1.806;ESV:(44.25±11.77) ml与(43.94±11.28)ml,t=0.658;均P＞0.05],且与UCG结果呈正相关(r=0.673、0.710和0.452,均P＜0.05).结论 99Tcm-TF可作为G-MPI显像剂常规用于临床,同时评价左室心肌灌注情况和左室功能.     

门控心肌灌注显像相位分析及其临床应用进展

在门控心肌灌注显像（GMPI）中采用相位分析获得简单的参数值来评估左室机械不同步性具有简便和可重复等优势,同时,其也受到多种因素的影响。GMPI相位分析的应用前景广阔,其研究和应用的主要方向包括心脏再同步化治疗、其他多种心脏疾病的早期诊断、帮助制定临床决策以及预测疾病的临床结局等。笔者对GMPI相位分析及其临床应用进展进行综述。     

Analysis of apical remodeling in gated myocardial perfusion SPECT imaging in ischemic cardiomyopathy

Background  A divergent pattern (DP) of the left ventricle (LV) is an expression of apical remodeling in myocardial perfusion gated single-photon emission computed tomography (SPECT) of patients with ischemic cardiomyopathy (ICM). Methods and Results  We consecutively studied 156 patients (mean age, 63 years; 24 women) with ICM (LV ejection fraction, ≤40%) using gated SPECT and technetium-labeled agents. Apical remodeling was considered to exist when a DP was observed. Apical remodeling was noted in 30% of patients, all of whom had a history of anterior myocardial infarction. A divergent pattern was observed more frequently in younger patients and in those with ST-segment elevation on their electrocardiograms. The longer the interval between the infarction and the performance of gated SPECT, the more prevalent were the LV dilatation and DP. A divergent pattern was associated with cardiac death and heart failure only in patients with scintigraphic criteria for myocardial viability. Conclusions  A divergent pattern in gated SPECT, as an expression of apical remodeling, can be observed in up to a third of patients with ICM, all with a history of anterior infarction. The longer the time between the infarction and the gated SPECT, the more prevalent the LV dilatation becomes. Apical remodeling is a variable predicts mortality in patients with scintigraphic criteria for viability. This study was partially funded by grants from Fundación Carolina (Madrid, Spain) and the Redes Temáticas de Investigación Cooperativa. Instituto Carlos III (Red C03/01, red temática de entermedades cardiovasculares [RECAVA] (Madrid, Spain).     

Comparison of three commercially available softwares for measuring left ventricular perfusion and function by gated SPECT myocardial perfusion imaging

Background

The three softwares, Quantitative Perfusion SPECT (QPS), Emory Cardiac Toolbox, and 4 Dimension-Myocardial SPECT (4DM) are widely used with myocardial perfusion imaging (MPI) to determine perfusion defect size (PDS) and left ventricular (LV) function. There are limited data on the degree of agreement between these methods in quantifying the LV perfusion pattern and function.

Methods and Results

In 120 consecutive patients who had abnormal regadenoson SPECT MPI with a visually derived summed stress score ≥4, the correlation between the softwares for measurements of PDS, reversible, and fixed defects was poor to fair (Spearman’s ρ = 0.18-0.72). Overall, estimation of defect size was smaller by QPS and larger by 4DM. There was discordance among the softwares in 62% of the cases in defining PDS as small/moderate/large. The correlation between the softwares was better for measuring LVEF, volumes and mass (ρ = 0.84-0.97), and discrepant results for defining normal/mild-moderate/severe LV systolic dysfunction were prevalent in 28% of the patients.

Conclusion

There are significant differences between the softwares in measuring PDS as well as LV function, and more importantly in defining small, moderate, or large ischemic burden. These results suggest the necessity of using the same software when assessing interval changes by serial imaging.     

门控SPECT心肌灌注显像评估急性心肌梗死患者心肌挽救量的研究进展

急性心肌梗死（AMI）患者经皮冠状动脉介入治疗（PCI）的目的在于尽可能地挽救濒死心肌。心肌挽救量（MS）与患者能否获益密切相关,在PCI的疗效评估及预后判断中具有重要价值。评价MS需明确初始心肌危险区面积（AAR）和心肌最终梗死面积（FIS）,二者之差即为MS。通过急诊时和PCI后2次99Tcm-甲氧基异丁基异腈门控SPECT心肌灌注显像（GSMPI）可分别定量AAR和FIS,从而获得MS,结果客观、准确,其临床价值在早期的大样本研究中已得到肯定。但在急诊时行GSMPI受到很多限制,致使AAR较难获得。近年来有学者提出的新显像方案,仅通过PCI后早期行1次GSMPI即可测定AAR,替代了2次显像法计算得到MS,其可行性及在临床中的实用价值显著提高。同时,新显像方案也扩展了核素GSMPI在AMI诊疗中的应用范围,为AMI患者的危险度分层提供了补充信息。笔者拟对GSMPI评估AMI患者MS的新显像方案的机制、应用价值、优势及发展前景作一综述。