Stress-only imaging in patients with prior SPECT MPI: A simulation study

Objectives  

The aim of this study was to determine if omitting the repeat resting scan in patients who had prior single-photon emission computed tomography myocardial perfusion imaging (SPECT MPI) would have an impact on the interpretation of the stress test.     

Detecting changes in serial myocardial perfusion SPECT: A simulation study

BACKGROUND: New algorithms were evaluated for their efficacy in detecting and quantifying serial changes in myocardial perfusion from single photon emission computed tomography (SPECT). METHODS AND RESULTS: We generated 72 simulations with various left ventricular positions, sizes, count rates, and perfusion defect severities using the nonuniform rational B-splines (NURBs)-based CArdiac Torso (NCAT) phantom. Images were automatically aligned by use of both full linear and rigid transformations and quantified for perfusion by use of the CEqual program. Changes within a given perfusion defect were compared by use of a Student t test before and after registration. Registration approaches were compared by use of receiver operating characteristic analysis. Changes of 5% were not detected well in single patients with or without alignment. Changes of 10% and 15% could be detected with false-positive rates of 15% and 10%, respectively, in single studies if alignment was performed before perfusion analysis. Alignment also reduced the number of studies necessary to demonstrate a significant perfusion change (P < .05) in groups of patients by about half. CONCLUSION: Comparison of mean uptake by t values in SPECT perfusion defects can be used to detect 10% and greater differences in serial perfusion studies of single patients. Image alignment is necessary to optimize automatic detection of perfusion changes in both single patients and groups of patients.     

Fractional flow reserve and myocardial viability as assessed by SPECT perfusion scintigraphy in patients with prior myocardial infarction

Background

In patients with previous myocardial infarction (MI), assessment of myocardial viability and physiological significance of coronary artery stenoses are essential for appropriate guidance of revascularization. The aim of the study was to evaluate the relation between fractional flow reserve (FFR) and myocardial viability as assessed by gated SPECT MIBI perfusion scintigraphy in patients with previous MI undergoing elective PCI.

Methods

The study population consisted of 26 patients (mean age 55 ± 7 years; 21 male) with a previous MI and a significant coronary stenosis in a single infarct-related coronary vessel for which PCI was being performed. In all patients, FFR was evaluated before and immediately after PCI. SPECT imaging was done before and 3 ± 1 months after PCI. A region representing the MI was considered viable if MIBI uptake was ≥55% of the normal region. Improvement in perfusion after revascularization was considered achieved if perfusion abnormalities decreased by 5% or more and there was a decrease in segmental score of ≥1 in three segments in PCI-related vascular territory.

Results

Extent of perfusion abnormalities decreased from 32 ± 16% to 27 ± 19% after PCI (P < .001). In patients with myocardial viability in comparison to patients with no viability, there was significant difference in FFR before PCI (.57 ± .14 vs .76 ± .12, P = .002), despite almost the same values of diameter stenosis of infarct-related artery (63 ± 8% vs 64 ± 3%, respectively, P = .572). In addition, FFR prior to PCI was related to improvement in perfusion abnormalities after revascularization (P = .047), as well as with peak activity of creatine-kinase measured during previous MI (r = .56, P = .005).

Conclusion

Lower values of FFR before angioplasty are associated with myocardial viability and functional improvement as assessed by SPECT perfusion scintigraphy.     

Role of carbonated water technique to enhance Tc-99m tetrofosmin myocardial perfusion imaging by reducing subdiaphragmatic artefacts

Annals of Nuclear Medicine - Myocardial perfusion imaging (MPI) with single-photon emission computed tomography (SPECT) is confounded by the extracardiac artefacts cause by hepatobiliary clearance...     

Prognostic value of automated vs visual analysis for adenosine stress myocardial perfusion SPECT in patients without prior coronary artery disease: A case-control study

Purpose

We aimed to evaluate the prognostic value of automated quantitative hypoperfusion parameters derived from adenosine stress myocardial perfusion SPECT (MPS) for predicting sudden or cardiac death (CD) in case-controlled patients with suspected coronary artery disease (CAD).

Methods

We considered patients with available adenosine stress Tc-99m sestamibi MPS scans and follow-up information. 81 CD patients from a registry of 428 patients documented by the National Death Index were directly matched in a retrospective case-control design to patients without CD by key clinical parameters (age by deciles, gender, no early revascularization, pre-test likelihood categories, diabetes, and chest pain symptoms). Multivariable analysis of stress MPS total perfusion deficit (STPD) and major clinical confounders were used as predictors of CD. Visual 17-segment summed stress segmental scores (VSSS) obtained by an expert reader, were compared to STPD.

Results

CD patients had higher stress hypoperfusion measures compared to controls [STPD: 7.0% vs 3.6% (P < .05), VSSS: 5.3 vs 2.1 (P < .05)]. By univariate analysis, STPD and VSSS have similar predictive power (the areas under receiver operator characteristics curves: STPD = 0.64, VSSS = 0.63; Kaplan-Meier models: χ² = 7.59, P = .0059 for STPD and χ² = 11.10, P = .0009 for VSSS). The multiple Cox proportional hazards regression models with continuous perfusion measures showed that STPD had similar power to normalized VSSS as a predictor for CD (χ² = 4.92; P = .027) vs (χ² = 8.90; P = .003).

Conclusions

Quantitative analysis is comparable to expert visual scoring in predicting CD in a case-controlled study.     

Risk stratification of patients with prior myocardial infarction and advanced left ventricular dysfunction by gated myocardial perfusion SPECT imaging

Background. The Multicenter Automatic Defibrillator Implantation Trial II (MADIT-II) has shown that the prophylactic implantable cardiac defibrillator improves the survival rate of patients with prior myocardial infarction and advanced left ventricular (LV) dysfunction. However, a more accurate noninvasive predictor should be found to identify subgroups at high risk, one that would allow implantable cardiac defibrillator therapy to be directed specifically to the patients who would benefit most. Methods and Results. To elucidate whether technetium 99m tetrofosmin electrocardiogram-gated single photon emission computed tomography (SPECT) imaging at rest can determine the risk of arrhythmic death, 106 patients who met the MADIT-II criteria (LV ejection fraction ≤0.3, myocardial infarction τ;1 month earlier, and no sustained ventricular tachyarrhythmia) were recruited from a pool of 4628 consecutive patients who had undergone resting Tc-99m tetrofosmin SPECT imaging. By use of the endpoints of lethal arrhythmic events, which included documentation of sustained ventricular tachycardia, ventricular fibrillation, or diagnosis of sudden cardiac death, we performed follow-up for a mean of 30 months. Lethal arrhythmic events occurred in 14 patients. Patients with lethal arrhythmic events had a lower LV ejection fraction, greater LV end-systolic and end-diastolic volume indices, and a greater perfusion defect volume than the remaining patients. By receiver operating characteristic curve analysis, myocardial defect volume was the strongest predictor for the development of lethal arrhythmic events. Conclusion. Our results confirm that perfusion defect volume by Tc-99m tetrofosmin scintigraphy is the most pivotal predictor of the future occurrence of lethal arrhythmic events and of sudden cardiac death. Tc-99m tetrofosmin SPECT images may assist in identifying subsets of patients with a greater likelihood of arrhythmic death among patients with LV dysfunction.     

体位改变对SPECT心肌显像中左室下壁衰减校正的价值

目的 探讨右侧卧位（RL）和俯卧位采集对^99Tc^m－甲氧基异丁基异腈（MIBI）心肌显像左室下壁衰减校正的价值。方法 对31例正常者进行了仰卧位、RL和俯卧位^99Tc^m-MIBI静息心肌显像。在靶心图上测定各区域像素平均计数,在断面图上对下壁显示断层形态和扫描过程中位移情况进行分级,在不同体位间进行比较。结果 （1）仰卧位有58．1％的下壁显示不全,体位变化后88．9％有不同程度的改善。（2）俯卧位和RL对于下壁的形态显示和计数均优于仰卧位。（3）各种体位间位移差异无显著性。结论 俯卧位和RL可使下壁衰减得以校正,计数和断层明显改善,且前者更好。     

心肌灌注断层显像与运动心电图ST段移位检测心肌缺血部位比较

目的　探讨运动心肌灌注断层显像与运动心电图ST段移位检测心肌缺血部位的一致性。方法　心肌灌注异常和ST段移位患者 3 0 2例 ,将ST段移位所在心肌部位与灌注异常部位进行相关性比较。结果　 40例ST段抬高的患者常有心绞痛史 ,并且易为运动诱发 ,运动持续时间较短(P <0 .0 5 )。ST段压低的部位与灌注异常的部位之间存在弱一致性 (Κ =0 .3 6,P <0 .0 1) ;左前降支(LAD)支配节段的灌注异常最常伴有前壁ST段压低 (χ2 =60 6.5 ,P <0 .0 5 ) ;ST段抬高与心肌灌注异常在病变定位上完全一致 (Κ =1.0 0 ,P <0 .0 1)。结论　ST段压低与灌注异常的定位一致性差 ,而ST段抬高则与灌注异常定位显著一致。     

A novel approach to multipinhole SPECT for myocardial perfusion imaging.

Myocardial perfusion imaging with SPECT remains critically important for diagnosing, assessing, and evaluating treatment of coronary artery disease. However, conventional rotational SPECT suffers from prolonged study times because of relatively low detection efficiency. We therefore have investigated a multipinhole collimator that could improve the detection efficiency in cardiac SPECT by a factor 5, while providing image quality comparable to standard rotational SPECT techniques using parallel-hole collimation. METHODS: We have measured the spatial resolution and efficiency of a 9-pinhole and a parallel-hole collimator mounted to a standard nuclear medicine gamma-camera as a function of distance from the collimator with a point source array. The efficiency was derived by integrating the detected counts, and the spatial resolution was determined from the full width at half maximum of the detected point spread function. In addition, we generated and reconstructed projection data of a 9-pinhole collimator from a digital heart phantom with a basal lesion. We simulated 3 scenarios: single view from left anterior, 2 views from left anterior and left lateral; and 4 views that include the 2 previous views and left lateral and anterior views. RESULTS: We found that the spatial resolution of the 9-pinhole collimator with 8-mm diameter pinholes was 30% poorer than that for the parallel-hole collimator, whereas the detection efficiency was increased by >10-fold. This predicts that a 9-pinhole collimator having the same spatial resolution as a parallel-hole collimator will have 5 times greater efficiency. Reconstructed data from 1 angular view of the 9-pinhole collimator showed the expected loss of spatial resolution in the longitudinal direction with reduced resolution of the basal lesion. In addition, the tomograms showed distortions in the apical region. In contrast, the reconstructed data from 2 and 4 views of the 9-pinhole collimator demonstrated good lesion definition and also produced images describing the shape and size of the heart more accurately. CONCLUSION: Our results indicate that myocardial multipinhole tomography with 2 or more views offers an image quality and spatial resolution comparable with current rotational SPECT techniques, but with the advantage of a 5-fold increase in efficiency.     

Consideration of perfusion reserve in viability assessment by myocardial Tl-201 rest-redistribution SPECT: A quantitative study with dual-isotope SPECT

BACKGROUND: To optimize the use of thallium 201 rest-redistribution study in Tl-201/technetium 99m sestamibi dual-isotope single photon emission computed tomography (SPECT), the predictability of Tl-201 rest-redistribution for viable myocardium was examined according to the degree of perfusion reserve. METHODS AND RESULTS: Twenty patients with both unstable angina and left ventricular dysfunction were enrolled. Tl-201 rest-dipyridamole stress Tc-99m sestamibi gated SPECT/Tl-201 24-hour redistribution SPECT was performed before and 3 months after coronary artery bypass grafting. Through use of a 20-segment model, segmental stress perfusion, rest perfusion, and systolic thickening were quantified on gated SPECT by means of automatic quantitation software. Perfusion was expressed as the average percentage of maximal radioactivity uptake. To represent perfusion reserve, the perfusion difference score (PDS) was defined as rest perfusion minus stress perfusion. A low PDS indicated little or no inducible ischemia, and a high PDS indicated inducible ischemia. In dysfunctional myocardium, viability was defined by the improvement of thickening after coronary artery bypass grafting. The overall predictability of Tl-201 redistribution for viability was 0.709 of the area under the curve (AUC) in receiver operating characteristic analysis. With a cutoff of 7, predictability was significantly better in the low PDS group (AUC = 0.785) than in the high PDS group (AUC = 0.582). CONCLUSIONS: The predictability of Tl-201 rest-redistribution for viability differs according to perfusion reserve. It was more reliable for dysfunctional myocardium with persistent perfusion decrease. On the basis of the continuum hypothesis of chronic stunning and hibernation, we suggest that dysfunctional myocardium with persistent perfusion decrease should be assessed by Tl-201 redistribution SPECT.     

Stress-only SPECT myocardial perfusion imaging: A review

Myocardial perfusion imaging (MPI) has enjoyed considerable success for decades due to its diagnostic accuracy and wealth of prognostic data. Despite this success several limitations such as lengthy protocols and radiation exposure remain. Advancements to address these shortcomings include abbreviated stress-only MPI (SO MPI) protocols, PET and both hardware and software methods to reduce radiation exposure and time. SO MPI has advantages in protocol time and radiation reduction with a wealth of supporting data in terms of diagnostic validity and prognostic value. Newer technologies such as attenuation correction, and advanced camera technologies have enabled SO MPI to be more efficient in reducing the time of acquisition and radiation dose and improving accuracy. This review examines the literature available, regarding accuracy, patient outcomes, implementation strategies, and newer developments associated with SO MPI.     

Incidental detection of breast cancer during Tl-201 myocardial SPECT study

A case of left breast cancer which was detected incidentally by Tl-201 SPECT performed to evaluate the status of myocardial perfusion, is reported. Both stress and redistribution Tl-201 SPECT clearly delineated the tumor. It was confirmed later as scirrhous carcinoma of the breast.     

SPECT心肌灌注显像对糖尿病心肌缺血损伤的研究

近年来糖尿病和冠心病发病率逐年增高,糖尿病可使患者患动脉粥样硬化和心血管疾患尤其是冠心病的危险性大大增加。糖尿病患者总死亡率的75%与冠心病有直接关系。SPECT心肌灌注显像可早期发现糖尿病患者中潜在的心肌缺血患者,对糖尿病患者进行危险度分级、预后和疗效判断,为临床制定治疗方案提供重要依据。     

Preliminary evaluation of the effect of an attenuation correction method in myocardial perfusion SPECT

We propose a method to assess an attenuation correction method in myocardial perfusion SPECT. Three types of images are obtained: one resulting from a classic acquisition and filtered back-projection (classic), and those resulting from acquisition with a transmission source and an iterative reconstruction, with (music) or without (hybrid) the attenuation correction factored in to compare the three types of images and classify them as normal or abnormal, a three dimensional inter-patient quantitative comparison method was used. Differences were computed as fractions of the myocardial volume in which density differences are significant by population standards. In 7 cases the cumulative difference between prone and supine in hybrid images was 124 and 45 in music images. In 10 cases the cumulative difference between classic vs music images was 279, and between classic and hybrid 86. The AC changed 4/12 cases from abnormal to normal. The attenuation correction effect was concentrated on the septal and inferior walls, but neither exclusively nor evenly among patients. The attenuation correction effectively minimizes attenuation effects by a factor of 2.7, due to a correction of at least 69%. The correction has a small but substantial effect on the results.     

Quantitative gated myocardial SPECT: effect of collimation on left-ventricular ejection fraction

OBJECTIVE: Left-ventricular ejection fraction (LVEF) can be computed from gated myocardial perfusion SPECT studies using quantitative algorithms. The purpose of this study was to compare the LVEF obtained using the conventional high-resolution parallel-hole collimator (HRC) to the Cardiofocal collimator (CFC) (Siemens Medical Systems, Hoffman Estates, IL) using a quantitative LVEF program. METHODS: Thirty-four patients (15 men, 19 women; mean age = 62 y) had either treadmill or pharmacological stress testing with 25-30 mCi 99mTc sestamibi injected at peak stress. Conventional gated SPECT imaging was performed approximately 30 min poststress, first with the HRC collimator, then with the CFC, using the same acquisition parameters on a single-head gamma camera. Traditional (TRAD) determination of LVEF using planar gated blood pool and/or cardiac catherization also was obtained for each patient. RESULTS: The correlation in LVEF between the CFC and HRC acquisitions was excellent, r = 0.99. The correlation between CFC and TRAD LVEF was good, r = 0.95, as was the HRC and TRAD correlation, r = 0.97. The mean LVEF value for HRC was slightly less than TRAD (54% vs. 55.4%), while the CFC mean LVEF was higher (62% vs. 55.4%). Although CFC LVEF correlated well with HRC, mean LVEF value using CFC was higher than HRC. CONCLUSION: The choice of collimator may alter the LVEF obtained from gated SPECT perfusion studies.     

The effect of beta-blockers on the diagnostic accuracy of vasodilator pharmacologic SPECT myocardial perfusion imaging

Background  The effect of beta (β) blockers on the accuracy, particularly the sensitivity, of vasodilator radionuclide myocardial perfusion imaging (MPI) is not entirely clear. This study aimed to further assess the effect of β-blockers on the ability of MPI to identify significant and high-risk coronary artery disease (CAD). Methods and Results  For 555 patients who underwent vasodilator MPI and had coronary angiography within 90 days, global and per-vessel sensitivities and specificities were calculated, and were found to be similar between patients taking β-blockers and those who were not. β-blockers did not decrease the ability to detect patients with multivessel disease. Summed stress scores and summed rest scores were likewise similar in both groups. To account in part for catheterization referral bias and the potential of false-negative MPI studies in patients receiving β-blockers, survival analysis was performed on 2646 patients with normal MPI studies who did not undergo cardiac catheterization and failed to demonstrate significant mortality difference related to the taking of β-blockers. Conclusions  β-blocker therapy does not diminish the ability of vasodilator stress MPI to detect clinically significant CAD, nor hide the mortality risk of patients with normal studies not referred for catheterization. Presented in part at the American Society of Nuclear Cardiology 9th Scientific Session, September 2004, New York, NY.     

Collection conditions of ECG-gated myocardial SPECT

In ECG-gated myocardial SPECT, we evaluated the effects of data acquisition and imaging conditions on the parameters of left ventricular cardiac function by a phantom experiments and in patients (n = 50) and normal controls (n = 15). Data acquisition was performed under the following conditions: (1) matrix size, 64 x 64 or 128 x 128; R-R interval, 8 or 6 frames; (3) presence or absence of attenuation and scatter corrections; and (4) changes in the accumulation rate of the radioactive tracer (information content) in the myocardium. When the matrix size was 64 x 64 and an R-R interval was divided into 8 frames, end-diastolic volume (EDV), end-systolic volume (ESV), and ejection fraction (EF) were 98.30 +/- 13.74 ml, 44.20 +/- 7.45 ml, and 54.91 +/- 2.84%, respectively, for normal controls. These values were slightly lower than those under other conditions. When attenuation and scatter corrections were not performed, the values of the above parameters were even lower. In patients with high accumulation of the radioactive tracer in the liver affecting the myocardial area, the cardiac function parameters were markedly decreased. In phantom experiments in which a decreased accumulation of the radioactive tracer was assumed, the left ventricular volume increased.     

A comparison of the image quality of full-time myocardial perfusion SPECT vs wide beam reconstruction half-time and half-dose SPECT

Objectives

Wide Beam Reconstruction (WBR) (UltraSPECT, Ltd) uses resolution recovery and noise modeling to cope with decreased SPECT count statistics. Because WBR processing reconstructs half the usual SPECT count statistics, we postulate that image quality equivalent to a full-time acquisition can be achieved in either half the time or with half the radiopharmaceutical activity.

Methods

In 156 consecutive patients (pts) rest and 8-frame gated post-stress myocardial perfusion SPECT was performed following 333-444 and 1184-1480 MBq (9-12 and 32-40 mCi) Tc-99m sestamibi injections, respectively, with full-time (rest = 14 min; stress = 12.3 min) acquisitions processed with OSEM and also separate “half-time” acquisitions processed with WBR. A subsequent group of 160 consecutive pts matched in gender, weight, and chest circumference received “half-dose” rest and stress injections 214.6 ± 22.2 and 647.5 ± 92.5 MBq (5.8 ± 0.6 and 17.5 ± 2.5 mCi) with full-time SPECT acquisitions. Image quality (1 = poor to 5 = excellent) was judged by myocardial count density and uniformity, endocardial edge definition, perfusion defect delineation, right ventricular visualization, and background noise.

Results

Mean image quality for rest, stress, and post-stress gated images were 3.6 ± 0.7, 3.8 ± 0.7, and 3.9 ± 1.0, respectively, for “full-time OSEM; 3.7 ± 0.8, 4.0 ± 0.7, and 4.8 ± 0.4 for “half-time” WBR; and 4.3 ± 0.8, 4.6 ± 0.6, and 4.7 ± 0.6 for “half-dose” WBR. “Half-time” and “half-dose” WBR image quality were both superior to standard full-time OSEM (P’s < .001). There was no significant difference between the summed stress and rest scores for “full-time” OSEM vs “half-time” WBR in 82 patients with perfusion defects.

Conclusions

Both “half-time” and “half-dose” WBR provide myocardial perfusion SPECT quality superior to full-time OSEM, with an associated decrease in scan acquisition time and patient radiation exposure, respectively.