Prognosis of stress-only SPECT myocardial perfusion imaging with prone imaging

Background

Stress-only single-photon emission computed tomography myocardial perfusion imaging (SO SPECT MPI) is associated with similarly benign prognosis as stress-rest SPECT MPI. However, previous studies have used attenuation correction rather than prone imaging to increase the rate of SO studies.

Objectives

To assess the prognosis of SO SPECT MPI performed with prone imaging.

Methods

We performed a retrospective cohort analysis of all patients who underwent a Tc-99m gated SPECT MPI over a 58-month period.

Results

Two thousand four hundred and sixty five patients were followed up. Of them, 1114 (45.2%) patients had a SO supine test, 388 (15.7%) underwent a SO supine and prone test, and the remaining 963 (39.1%) patients underwent a full stress-rest SPECT MPI. There was a similar annual mortality rate between the SO supine/prone group (1.3%), the SO supine (1.5%), and the stress-rest (1.5%) group (P = 0.47). Patients in the stress-rest group were significantly more likely to suffer from myocardial infarction (MI) as compared to the other two groups with an annual rate of 0.7% as compared to 0.4% (P = 0.049).

Conclusions

Normal supine-prone SO SPECT MPI is associated with a similarly benign prognosis as stress-rest SPECT MPI. The adjunction of prone imaging to the stress supine significantly increases the rate of SO SPECT MPI

     

Prognostic implications of combined prone and supine acquisitions in patients with equivocal or abnormal supine myocardial perfusion SPECT.

Although acquisition of (99m)Tc-sestamibi myocardial perfusion SPECT (MPS) with the patient in the prone position is commonly used to minimize attenuation artifacts, the impact of combined prone and supine imaging on the prognostic evaluation of coronary artery disease (CAD) has not been determined. The prognostic implications of MPS obtained in both prone and supine positions in patients with perfusion defects on supine MPS were evaluated. METHODS: We studied 3,834 patients who were monitored for 24.2 +/- 6.0 mo after rest (201)Tl/stress (99m)Tc-sestamibi MPS acquired during 1994-1995, when prone acquisition was performed only in patients with inferior wall perfusion defects that might represent attenuation or motion artifact. RESULTS: During follow-up, there were 132 hard events (cardiac death or myocardial infarction) and 375 total events (hard events or late myocardial revascularization). Overall, patients who underwent prone and supine acquisitions had similar characteristics to those who underwent supine-only imaging, with the exception of being more commonly male. In multivariable analysis, there were similar independent predictors for hard events and total events; the type of acquisition (prone and supine or supine-only) was not a significant predictor of either of these outcome events. After risk adjustment, the predicted event rates were nearly identical for patients undergoing prone and supine compared with supine-only studies. Both observed and predicted hard event rates of patients with normal prone and supine versus supine-only imaging were very low (observed, 0.7%/y and 0.5%/y, respectively; predicted, 1.5% over 24 mo for both). There was no reduction in the higher rates of events associated with abnormal scan results with the combination of prone and supine imaging. CONCLUSION: Patients with inferior wall defects on supine MPS that are not present on prone MPS have a low risk of subsequent cardiac events, similar to that of patients with normal supine-only studies.     

SPECT myocardial perfusion imaging with prone-only acquisitions: correlation with coronary angiography

Background  Recent evidence suggests that combining supine and prone acquisitions during stress-gated SPECT myocardial perfusion imaging (MPS) improves detection of obstructive coronary artery disease (CAD), though the additional imaging time required may not be feasible in routine clinical practice. MPS with prone-only acquisitions is occasionally performed in many laboratories, though little is known about the ability of modern MPS with prone-only acquisitions to detect obstructive CAD. Our goal was to assess the ability of MPS with prone-only acquisitions to detect obstructive CAD as determined by coronary angiography. Methods and Results  We studied 386 patients referred for MPS with either recent coronary angiography or a low pretest likelihood of coronary artery disease. All rest and stress images were obtained exclusively in the prone position. The sensitivity of prone-only MPS was 88% for detecting ≥50% coronary artery stenosis and 92% for detecting ≥70% coronary artery stenosis as determined by coronary angiography. Normalcy rate for prone-only MPS in patients with low probability for CAD was 95%, and normalcy rates did not significantly differ among coronary artery distributions. Conclusions  The findings of this study suggest that MPS using prone-only acquisitions is a reasonable diagnostic option for the detection of ischemia due to obstructive coronary artery disease.     

Quantitative assessment of myocardial perfusion abnormality on SPECT myocardial perfusion imaging is more reproducible than expert visual analysis

Background  Current guidelines of Food and Drug Administration for the evaluation of SPECT myocardial perfusion imaging (MPI) in clinical trials recommend independent visual interpretation by multiple experts. Few studies have addressed whether quantitative SPECT MPI assessment would be more reproducible for this application. Methods and Results  We studied 31 patients (age 68 ± 13, 25 male) with abnormal stress MPI who underwent repeat exercise (n = 11) or adenosine (n = 20) MPI within 9-22 months (mean 14.9 ± 3.8 months) and had no interval revascularization or myocardial infarction and no change in symptoms, stress type, rest or stress ECG, or clinical response to stress on the second study. Visual interpretation per FDA Guidance used 17-segment, 5-point scoring by two independent expert readers with overread of discordance by a third expert, and percent myocardium abnormal was derived from normalized summed scores. The quantitative magnitude of perfusion abnormality was assessed by the total perfusion deficit (TPD), expressing stress, rest, and ischemic perfusion abnormality. High linear correlations were observed between visual and quantitative size of stress, rest, and ischemic defects (R = 0.94, 0.92, 0.84). Correlations of two tests were higher by quantitative than by visual methods for stress (R = 0.97 vs R = 0.91, P = 0.03) and rest defects (R = 0.94 vs R = 0.82, P = 0.03), respectively, and statistically similar for ischemic defects (R = 0.84 vs R = 0.70, P = ns). Conclusions  In stable patients having serial SPECT MPI, quantification is more reproducible than visual for magnitude of perfusion abnormality, suggesting its superiority for use in randomized clinical trials and monitoring the effects of therapy in an individual patient. See related editorial, doi: This study was presented in part at the Society of Nuclear Medicine 55th Annual Meeting, New Orleans, Louisiana, June 14-18, 2008.     

Automatic and visual reproducibility of perfusion and function measures for myocardial perfusion SPECT

Background  

We define the repeatability coefficients (RC) of key quantitative and visual perfusion and function parameters that can be derived by the QGS/QPS automated software and by expert visual observer from gated myocardial perfusion SPECT (MPS) scans.     

Combined supine and prone quantitative myocardial perfusion SPECT: method development and clinical validation in patients with no known coronary artery disease.

Acquisition in the prone position has been demonstrated to improve the specificity of visually analyzed myocardial perfusion SPECT (MPS) for detecting coronary artery disease (CAD). However, the diagnostic value of prone imaging alone or combined acquisition has not been previously described using quantitative analysis. METHODS: A total of 649 patients referred for MPS comprised the study population. Separate supine and prone normal limits were derived from 40 males and 40 females with a low likelihood (LLk) of CAD using a 3 average-deviation cutoff for all pixels on the polar map. These limits were applied to the test population of 369 consecutive patients (65% males; age, 65 +/- 13 y; 49% exercise stress) without known CAD who had diagnostic coronary angiography within 3 mo of MPS. Total perfusion deficit (TPD), defined as a product of defect extent and severity scores, was obtained for supine (S-TPD), prone (P-TPD), and combined supine-prone datasets (C-TPD). The angiographic group was randomly divided into 2 groups for deriving and validating optimal diagnostic cutoffs. Normalcy rates were validated in 2 additional groups of consecutive LLk patients: unselected patients (n = 100) and patients with body mass index >30 (n = 100). RESULTS: C-TPD had a larger area under the receiver-operating-characteristic (ROC) curve than S-TPD or P-TPD for identification of stenosis >or=70% (0.86, 0.88, and 0.90 for S-TPD, P-TPD, and C-TPD, respectively; P < 0.05). In the validation group, sensitivity for P-TPD was lower than for S- or C-TPD (P < 0.05). C-TPD yielded higher specificity than S-TPD and a trend toward higher specificity than P-TPD (65%, 83%, and 86% for S-, P-, and C-TPD, respectively, P < 0.001; vs. S-TPD and P = 0.06 vs. P-TPD). Normalcy rates for C-TPD were higher than for S-TPD in obese LLk patients (78% vs. 95%, P < 0.001). CONCLUSION: Combined supine-prone quantification significantly improves the area under the ROC curve and specificity of MPS in the identification of obstructive CAD compared with quantification of supine MPS alone.     

Challenges for measurement of myocardial perfusion and perfusion reserve by SPECT imaging

Conclusions  The present study by Storto et al¹ provides additional evidence that quantitative estimates of myocardial perfusion and perfusion reserve can be derived from SPECT myocardial perfusion images by use of equipment, tracers, and techniques that are available in most nuclear cardiology laboratories. Additional clinical studies are needed to optimize the methods used to derive the quantitative estimates of perfusion and perfusion reserve from the SPECT imaging studies and, ultimately, to determine the applicability of these measurements to the daily practice of nuclear cardiology.     

Early post-stress pulmonary uptake of 99mTc tetrofosmin during exercise (SPECT) myocardial perfusion imaging: correlation with haemodynamic, perfusion and function parameters

OBJECTIVE: To test the association of early post-stress lung/heart ratio (LHR) of 99mTc tetrofosmin radioactivity with gated-SPECT findings and angiographic results. METHODS: We studied 158 consecutive patients, with stress/rest 99mTc tetrofosmin myocardial SPECT and coronary angiography. Rest scans were obtained as gated SPECT and the left ventricular ejection fraction and end diastolic volume were calculated. To evaluate myocardial ischaemia, we calculated the summed stress score, summed rest score and summed difference score indices. For the LHR calculation, we acquired an anterior image, 4-6 min after radiotracer injection at stress; LHR was defined as mean counts/pixel in the lung region of interest divided by the mean counts/pixel in the myocardial region of interest. RESULTS: An early post-stress LHR value of 0.500 was defined as the upper normal limit. The most significant correlation (P<0.001) was observed among early post-stress LHR, summed stress score and the number of stenosed vessels. The incidence of multi-vessel coronary artery disease in the subgroup of patients with increased values of early post-stress LHR, was significantly higher than in the normal group (81% vs. 42%, P<0.001). There was a significant difference (P<0.001) of the early post-stress LHR value between patients with normal coronary arteries or one-vessel disease and patients with multi-vessel disease. Early post-stress LHR was an independent predictor of multi-vessel coronary artery disease (coefficient 1.85, SD 0.16, P<0.001), with an incremental value for its identification. CONCLUSIONS: Our results suggest that early post-stress 99mTc tetrofosmin LHR appears to be a useful index of extensive myocardial ischaemia dysfunction and multi-vessel coronary artery disease.     

Recent developments and future prospects of SPECT myocardial perfusion imaging

Myocardial perfusion SPECT imaging is the most commonly performed functional imaging for assessment of coronary artery disease. High diagnostic accuracy and incremental prognostic value are the major benefits while suboptimal spatial resolution and significant radiation exposure are the main limitations. Its ability to detect hemodynamic significance of lesions seen on multidetector CT angiogram (MDCTA) has paved the path for a successful marriage between anatomical and functional imaging modalities in the form of hybrid SPECT/MDCTA system. In recent years, there have been enormous efforts by industry and academia to develop new SPECT imaging systems with better sensitivity, resolution, compact design and new reconstruction algorithms with ability to improve image quality and resolution. Furthermore, expected arrival of Tc-99m-labeled deoxyglucose in next few years would further strengthen the role of SPECT in imaging hibernating myocardium. In view of these developments, it seems that SPECT would enjoy its pivotal role in spite of major threat to be replaced by fluorine-18-labeled positron emission tomography perfusion and glucose metabolism imaging agents.     

IQ·SPECT、碲锌镉探测器SPECT和传统SPECT在心肌灌注显像中的应用分析

IQ·SPECT与碲锌镉（CZT）探测器SPECT是心肌灌注显像新技术,与传统SPECT相比,具有灵敏度和空间分辨率高、采集时间短、注射显像剂剂量少及辐射剂量低等优点。与传统SPECT不同（低能高分辨率平行孔准直器）,IQ·SPECT使用SMART-ROOM准直器及心脏为焦点的采集模式,提高了灵敏度;CZT探测器SPECT的探测器为半导体,取代了传统NaI晶体探测器,提高了能量分辨率、空间分辨率、灵敏度及信噪比等,并可定量分析心肌血流储备。笔者主要对三者的成像原理、性能参数及临床应用进行综述。     

Quantification of myocardial perfusion SPECT using freeware package (cardioBull)

Objective  

We have developed freeware package for automatically quantifying myocardial perfusion and ¹²³I-labeled radiopharmaceutical single-photon emission computed tomography (SPECT), which is called “cardioBull”. We aim to evaluate diagnostic performance of the detection of coronary artery disease (CAD) on the developed software in comparison with commercially available software package [Quantitative Perfusion SPECT (QPS)].