Mathews Fish

Myocardial Perfusion Imaging with a Solid-State Camera: Simulation of a Very Low Dose Imaging Protocol

High-sensitivity dedicated cardiac camera systems provide an opportunity to lower the injected doses for SPECT myocardial perfusion imaging (MPI), but the exact limits for lowering doses have not been determined. List-mode data acquisition allows for reconstruction of various fractions of acquired counts, enabling a simulation of gradually lower administered dose. We aimed to determine the feasibility of very low dose MPI by exploring the minimal count level in the myocardium required for accurate MPI. Methods: Seventy-nine patients were studied (mean body mass index, 30.0 ± 6.6; range, 20.2–54.0 kg/m2) who underwent 1-d standard-dose 99mTc-sestamibi exercise or adenosine rest–stress MPI for clinical indications using a cadmium-zinc-telluride dedicated cardiac camera. The imaging time was 14 min, with averaged 803 ± 200 MBq (21.7 ± 5.4 mCi) of 99mTc injected at stress. To simulate clinical scans with a lower dose at that imaging time we reframed the list-mode raw data. Accordingly, 6 stress-equivalent datasets were reconstructed containing various count fractions of the original scan. Automated quantitative perfusion and gated SPECT software was used to quantify total perfusion deficit (TPD) and ejection fraction for all 553 datasets (7 × 79). The minimal acceptable left ventricular region counts were determined on the basis of a previous report with repeatability of same-day, same-injection Anger camera studies. Pearson correlation coefficients and the SD of differences in TPD for all scans were calculated. Results: The correlations of quantitative perfusion and function analysis were excellent for both global and regional analysis between original scans and all simulated low-count scans (all r ≥ 0.95, P < 0.0001). The minimal acceptable counts were determined to be 1.0 million for the left ventricular region. At this count level, the SD of differences was 1.7% for TPD and 4.2% for ejection fraction. This count level would correspond to a 92.5-MBq (2.5-mCi) injected dose for the 14-min acquisition or 125.8-MBq (3.4-mCi) injected dose for the 10-min acquisition. Conclusion: 1.0 million counts appear to be sufficient to produce myocardial images that agree well with 8.0-million-count images on quantitative perfusion and function parameters. With a dedicated cardiac camera, these images can be obtained over 10 min with an effective radiation dose of less than 1 mSv without significant sacrifice of accuracy.

Comparison of Image Quality, Myocardial Perfusion, and Left Ventricular Function Between Standard Imaging and Single-Injection Ultra-Low-Dose Imaging Using a High-Efficiency SPECT Camera: The MILLISIEVERT Study

SPECT myocardial perfusion imaging plays a central role in coronary artery disease diagnosis, but concerns exist regarding its radiation burden. Compared with standard Anger SPECT (A-SPECT) cameras, new high-efficiency (HE) cameras with specialized collimators and solid-state cadmium-zinc-telluride detectors offer potential to maintain image quality (IQ), while reducing administered activity and thus radiation dose to patients. No previous study has compared IQ, interpretation, total perfusion deficit (TPD), or ejection fraction (EF) in patients receiving both ultra-low-dose (ULD) imaging on an HE SPECT camera and standard low-dose (SLD) A-SPECT imaging. Methods: We compared ULD HE SPECT with SLD A-SPECT imaging by dividing the rest dose in 101 patients at 3 sites scheduled to undergo clinical A-SPECT myocardial perfusion imaging using a same day rest–stress 99mTc protocol. Patients underwent HE SPECT imaging after an initial approximately 130-MBq (3.5 mCi) dose and SLD-A-SPECT imaging after the remainder of the planned dose. Images were scored visually by 2 masked readers for IQ and summed rest score. TPD and EF were assessed quantitatively. Results: Mean activity was 134 MBq (3.62 mCi) for ULD HE SPECT (effective dose, 1.15 mSv) and 278 MBq (7.50 mCi, 2.39 mSv) for SLD A-SPECT. Overall IQ was superior for ULD HE SPECT (P < 0.0001), with twice as many studies graded excellent quality. Extracardiac activity and overall perfusion assessment were similar. Between-method correlations were high for summed rest score (r = 0.87), TPD (r = 0.91), and EF (r = 0.88). Conclusion: ULD HE SPECT rest imaging correlates highly with SLD A-SPECT. It has improved image quality, comparable extracardiac activity, and achieves radiation dose reduction to 1 mSv for a single injection.

Quantitative myocardial-perfusion SPECT: Comparison of three state-of-the-art software packages

BackgroundWe almed to compare the automation and diagnostic performance in the detection of coronary artery disease (CAD) of the 4DMSPECT (4DM), Emory Cardiac Toolbox (EMO), and QPS systems for automated quantification of myocardial perfusion.Methods and ResultsWe studied 328 patients referred for rest/stress Tc-99m sestamibi imaging, 140 low-likelihood patients and 188 with angiography. Contours were corrected when necessary. All other processing was fully automated. A 17-segment analysis was performed, and a summed stress score (SSS) ≥4 was considered abnormal. The average SSSs (±SD) for 4DM, EMO, and QPS were 10.5±9.4, 11.1±8.3, and 10.1±8.9 respectively (P=.02 for QPS versus EMO). The receiver operator characteristics areas-under-the-curve for the detection of CAD (±SEM) were 0.84±0.03, 0.76±0.04, and 0.88±0.03 for 4DM, EMO, and QPS, respectively (P=.001 for QPS versus EMO, and P=.03 for 4DM versus EMO), Normalcy rate was higher for QPS and 4DM versus EMO, at 91% and 94% versus 77%, respectively (P=.02). Sensitivity was higher for QPS (87%) versus 4DM (80%) (P=.045). Specificity was higher for QPS (71%) versus EMO (49%) (P=.01). The accuracy rate was higher for QPS versus 4DM and EMO, at 83% versus 77% and 76%, respectively, (P=.05).ConclusionsThere are differences in myocardial-perfusion quantification, diagnostic performance, and degree of automation of software packages.

Comparison of Fully Automated Computer Analysis and Visual Scoring for Detection of Coronary Artery Disease from Myocardial Perfusion SPECT in a Large Population

We compared the performance of fully automated quantification of attenuation-corrected (AC) and noncorrected (NC) myocardial perfusion SPECT (MPS) with the corresponding performance of experienced readers for detection of coronary artery disease (CAD). Methods: Rest–stress 99mTc-sestamibi MPS studies (n = 995; 650 consecutive cases with coronary angiography and 345 with likelihood of CAD < 5%) were obtained by MPS with AC. The total perfusion deficit (TPD) for AC and NC data was compared with the visual summed stress and rest scores of 2 experienced readers. Visual reads were performed in 4 consecutive steps with the following information progressively revealed: NC data, AC + NC data, computer results, and all clinical information. Results: The diagnostic accuracy of TPD for detection of CAD was similar to both readers (NC: 82% vs. 84%; AC: 86% vs. 85%–87%; P = not significant) with the exception of the second reader when clinical information was used (89%, P < 0.05). The receiver-operating-characteristic area under the curve (ROC AUC) for TPD was significantly better than visual reads for NC (0.91 vs. 0.87 and 0.89, P < 0.01) and AC (0.92 vs. 0.90, P < 0.01), and it was comparable to visual reads incorporating all clinical information. The per-vessel accuracy of TPD was superior to one reader for NC (81% vs. 77%, P < 0.05) and AC (83% vs. 78%, P < 0.05) and equivalent to the second reader (NC, 79%; and AC, 81%). The per-vessel ROC AUC for NC (0.83) and AC (0.84) for TPD was better than that for the first reader (0.78–0.80, P < 0.01) and comparable to that of the second reader (0.82–0.84, P = not significant) for all steps. Conclusion: For detection of ≥70% stenoses based on angiographic criteria, a fully automated computer analysis of NC and AC MPS data is equivalent for per-patient and can be superior for per-vessel analysis, when compared with expert analysis.

Automated Quality Control for Segmentation of Myocardial Perfusion SPECT

Left ventricular (LV) segmentation, including accurate assignment of LV contours, is essential for the quantitative assessment of myocardial perfusion SPECT (MPS). Two major types of segmentation failures are observed in clinical practices: incorrect LV shape determination and incorrect valve-plane (VP) positioning. We have developed a technique to automatically detect these failures for both nongated and gated studies. Methods: A standard Cedars-Sinai perfusion SPECT (quantitative perfusion SPECT [QPS]) algorithm was applied to derive LV contours in 318 consecutive 99mTc-sestamibi rest/stress MPS studies consisting of stress/rest scans with or without attenuation correction and gated stress/rest images (1,903 scans total). Two numeric parameters, shape quality control (SQC) and valve-plane quality control, were derived to categorize the respective contour segmentation failures. The results were compared with the visual classification of automatic contour adequacy by 3 experienced observers. Results: The overall success of automatic LV segmentation in the 1,903 scans ranged from 66% on nongated images (incorrect shape, 8%; incorrect VP, 26%) to 87% on gated images (incorrect shape, 3%; incorrect VP, 10%). The overall interobserver agreement for visual classification of automatic LV segmentation was 61% for nongated scans and 80% for gated images; the agreement between gray-scale and color-scale display for these scans was 86% and 91%, respectively. To improve the reliability of visual evaluation as a reference, the cases with intra- and interobserver discrepancies were excluded, and the remaining 1,277 datasets were considered (101 with incorrect LV shape and 102 with incorrect VP position). For the SQC, the receiver-operating-characteristic area under the curve (ROC-AUC) was 1.0 ± 0.00 for the overall dataset, with an optimal sensitivity of 100% and a specificity of 98%. The ROC-AUC was 1.0 in all specific datasets. The algorithm was also able to detect the VP position errors: VP overshooting with ROC-AUC, 0.91 ± 0.01; sensitivity, 100%; and specificity, 70%; and VP undershooting with ROC-AUC, 0.96 ± 0.01; sensitivity, 100%; and specificity, 70%. Conclusion: A new automated method for quality control of LV MPS contours has been developed and shows high accuracy for the detection of failures in LV segmentation with a variety of acquisition protocols. This technique may lead to an improvement in the objective, automated quantitative analysis of MPS.

Quantitative Diagnostic Performance of Myocardial Perfusion SPECT with Attenuation Correction in Women

Attenuation correction (AC) for myocardial perfusion SPECT (MPS) had not been evaluated separately in women despite specific considerations in this group because of breast photon attenuation. We aimed to evaluate the performance of AC in women by using automated quantitative analysis of MPS to avoid any bias. Methods: Consecutive female patients—134 with a low likelihood (LLk) of coronary artery disease (CAD) and 114 with coronary angiography performed within less than 3 mo of MPS—who were referred for rest–stress electrocardiography-gated 99mTc-sestamibi MPS with AC were considered. Imaging data were evaluated for contour quality control. An additional 50 LLk studies in women were used to create equivalent normal limits for studies with AC and with no correction (NC). An experienced technologist unaware of the angiography and other results performed the contour quality control. All other processing was performed in a fully automated manner. Quantitative analysis was performed with the Cedars-Sinai myocardial perfusion analysis package. All automated segmental analyses were performed with the 17-segment, 5-point American Heart Association model. Summed stress scores (SSS) of ≥3 were considered abnormal. Results: CAD (≥70% stenosis) was present in 69 of 114 patients (60%). The normalcy rates were 93% for both NC and AC studies. The SSS for patients with CAD and without CAD for NC versus AC were 10.0 ± 9.0 (mean ± SD) versus 10.2 ± 8.5 and 1.6 ± 2.3 versus 1.8 ± 2.5, respectively; P was not significant (NS) for all comparisons of NC versus AC. The SSS for LLk patients for NC versus AC were 0.51 ± 1.0 versus 0.6 ± 1.1, respectively; P was NS. The specificity for both NC and AC was 73%. The sensitivities for NC and AC were 80% and 81%, respectively, and the accuracies for NC and AC were 77% and 78%, respectively; P was NS for both comparisons. Conclusion: There are no significant diagnostic differences between automated quantitative MPS analyses performed in studies processed with and without AC in women.

Quantitation of left ventricular ejection fraction reserve from early gated regadenoson stress Tc-99m high-efficiency SPECT.

BackgroundEjection fraction (EF) reserve has been found to be a useful adjunct for identifying high risk coronary artery disease in cardiac positron emission tomography (PET). We aimed to evaluate EF reserve obtained from technetium-99m sestamibi (Tc-99m) high-efficiency (HE) SPECT.MethodsFifty patients (mean age 69 years) undergoing regadenoson same-day rest (8-11 mCi)/stress (32-42 mCi) Tc-99m gated HE SPECT were enrolled. Stress imaging was started 1 minute after sequential intravenous regadenoson .4 mg and Tc-99m injections, and was composed of five 2 minutes supine gated acquisitions followed by two 4 minutes supine and upright images. Ischemic total perfusion deficit (ITPD) ≥5 % was considered as significant ischemia.ResultsSignificantly lower mean EF reserve was obtained in the 5th and 9th minute after regadenoson bolus in patients with significant ischemia vs patients without (5th minute: −4.2 ± 4.6% vs 1.3 ± 6.6%, P = .006; 9th minute: −2.7 ± 4.8% vs 2.0 ± 6.6%, P = .03).ConclusionsNegative EF reserve obtained between 5th and 9th minutes of regadenoson stress demonstrated best concordance with significant ischemia and may be a promising tool for detection of transient ischemic functional changes with Tc-99m HE-SPECT.Spanish AbstractAntecedentesSe ha encontrado que la reserva de la Fracción de Eyección (FE) en la tomografía de emisión de positrones cardiaca (PET, positron emission tomography por sus siglas en ingles) es una herramienta útil adicional en la identificación de pacientes con enfermedad arterial coronaria de alto riesgo. Nuestro objetivo fue evaluar la reserva de la FE obtenida por SPECT de alta eficiencia (AE) con Tecnecio-99m (Tc-99m) sestamibi.MétodosCincuenta pacientes (edad promedio 69 años) a quienes se les realizo un SPECT de AE con Tc‐99m sincronizado con el electrocardiograma en un solo día reposo (8-11mCi)/estrés 32-42mCi) con regadenoson fueron incluidos La adquisición de las imágenes de estrés se inicio un minuto después de la administración secuencial intravenosa de regadenoson .4mg y Tc-99m, compuesta de 5 adquisiciones sincronizadas con el electrocardiograma de 2 minutos cada una en supino seguidas de dos adquisiciones de 4 minutos cada una en supino y sentado. Un defecto total de perfusión isquémico (DTPI) ≥5% fue considerado como isquemia significativa.ResultadosEl promedio obtenido de la Reserva de la FE fue significativamente menor en los minutos 5to y 9no posterior al bolo de regadenoson en pacientes con isquemia significativa comparados con pacientes sin isquemia (5to minuto: −4.2 ± 4.6% vs 1.3 ± 6.6%, p= 0.006; 9no minuto: −2.7 ± 4.8% vs 2.0 ± 6.6%, p = 0.03).ConclusionesUna Reserva de la FE negativa obtenida en los minutos 5to y 9no del estrés con regadenoson demostró una mejor concordancia con la presencia de isquemia significativa y podría ser un herramienta promisoria para la detección de cambios funcionales isquémicos transitorios con un estudio SPECT de AE con Tc-99m.Chinese Abstract背景对于心脏PET显像, 射血分数 (EF) 储备 已成为评判高风险冠心病的有效辅助手段。本文旨在评价采用Tc-99m甲氧基异丁基异睛显影剂和高能SPECT测定EF储备的可行性。方法入选55行类伽腺苷一日法静息 (8-11mCi) /负荷 (32-42mCi) 门控高能SPECT显像的患者, 平均年龄为69岁。在连续静脉注射类伽腺苷 (0.4mg) 和Tc-99m一分钟后开始负荷图像的采集。负荷图像包括5个2分钟的仰卧位门控采集和后续2个分别为仰卧位和直立位的4分钟门控采集。总灌注缺损≧5%为显著缺血。结果注射类伽腺苷后, 显著缺血患者的平均EF储备在第5和第9分钟时较无缺血患者显著降低 (第5分钟: −4.2 ± 4.6% vs. 1.3 ± 6.6%, p = 0.006; 第9分钟: −2.7 ± 4.8% vs. 2.0 ± 6.6%, p=0.03)。结论在类伽腺苷负荷时, 第5至9分钟测得的EF储备负值与显著缺血的一致性最佳, 这很可能成为Tc-99m高能SPECT检测一过性心肌缺血伴随的心功能改变的有效手段。

Direct Quantification of Left Ventricular Motion and Thickening Changes Using Rest–Stress Myocardial Perfusion SPECT

Changes in myocardial wall motion and thickening during myocardial perfusion SPECT are typically assessed separately from gated studies for the presence of stress-induced functional abnormalities. We sought to develop and validate a novel approach for automatic quantification of rest–stress myocardial motion and thickening changes (MTCs). Methods: Endocardial surfaces at the end-diastolic and end-systolic frames for rest–stress studies were registered automatically to each other by matching ventricular surfaces. Myocardial MTCs were computed, and normal limits of change were determined as the mean and SD for each polar sample. Normal limits were used to quantify the MTCs for each map, and the accumulated sample values were used for abnormality assessments in segmental regions. A hybrid method was devised by combining the total perfusion deficit (TPD) and MTC for each vessel territory. Normal limits were obtained from 100 subjects with low likelihood of coronary artery disease. For validation, 623 subjects with correlating invasive angiography were studied. All subjects underwent a rest–stress 99mTc-sestamibi exercise or adenosine test and coronary angiography within 3 months of myocardial perfusion SPECT. All MTC and TPD measurements were derived automatically. The diagnostic accuracy for detection of coronary artery disease for MTC plus TPD was compared with TPD alone. Results: Segmental normal values were between −1.3 and −4.1 mm for motion change and between −30.1% and −9.8% for thickening change. MTC combined with TPD achieved 61% sensitivity for 3-vessel-disease (3VD), 63% for 2-vessel-disease (2VD), and 90% for 1-vessel-disease (1VD) detection, compared with 32% for 3VD (P < 0.0001), 53% for 2VD (P < 0.001), and 90% for 1VD (P = 1.0) detection using the TPD-alone method. The specificity for the combined method was 71% for 3VD, 72% for 2VD, and 47% for 1VD detection versus 90% for 3VD (P < 0.0001), 80% for 2VD (P < 0.001), and 50% for 1VD detection (P = 0.0625) for the TPD-alone method. The accuracy of 3VD detection by MTC plus TPD was higher (69%) than the accuracy of TPD plus change in ejection fraction (63%) (P < 0.004). Conclusion: We established normal limits and a novel method for computation of regional functional changes between the rest and poststress studies. Compared with TPD alone, the combination of TPD with MTC improved the sensitivity for the detection of 3VD and 2VD.

Improved Quantification and Normal Limits for Myocardial Perfusion Stress–Rest Change

We aimed to improve the quantification of myocardial perfusion stress–rest changes in myocardial perfusion SPECT (MPS) studies for the optimal automatic detection of ischemia and coronary artery disease (CAD). Methods: Rest–stress 99mTc MPS studies (997 cases; 651 consecutive cases with correlating angiography and 346 cases with less than 5% likelihood (low likelihood [LLK]) of CAD) were analyzed. Normal limits for stress–rest changes were derived from additional LLK patients (40 women, 40 men). We computed the global stress–rest change (C-SR) by integrating direct stress–rest changes for each polar map pixel. Additionally, stress–rest change and total perfusion deficit (TPD) at stress were combined in 1 variable (C-TPD) for the optimal detection of CAD. Results: The area under the receiver-operating-characteristic curve (AUC) for C-SR (0.92) was larger than that for stress TPD–rest TPD (0.88) for the identification of stenosis of 70% or more (P < 0.0001). AUC (0.94) and sensitivity (90%) for C-TPD were higher than those for stress TPD (0.91 and 83%, respectively) (P < 0.0001), whereas specificity remained the same (81%). Conclusion: C-SR and C-TPD provide higher diagnostic performance than difference between stress and rest TPD or stress hypoperfusion analysis.

“Same-Patient Processing” for multiple cardiac SPECT studies. 1. Improving LV segmentation accuracy

ObjectivesThis paper describes a novel approach (same-patient processing, or SPP) aimed at improving left ventricular segmentation accuracy in patients with multiple SPECT studies, and evaluates its performance compared to conventional processing in a large population of 962 patients undergoing rest and stress electrocardiography-gated SPECT MPI, for a total of 5,772 image datasets (6 per patient).MethodsEach dataset was independently processed using a standard algorithm, and a shape quality control score (SQC) was produced for every segmentation. Datasets with a SQC score higher than a specific threshold, suggesting algorithmic failure, were automatically reprocessed with the SPP-modified algorithm, which incorporates knowledge of the segmentation mask location in the other datasets belonging to the same patient. Experienced operators blinded as to whether datasets had been processed based on the standard or SPP approach assessed segmentation success/failure for each dataset.ResultsThe SPP approach reduced segmentation failures from 219/5772 (3.8%) to 42/5772 (0.7%) overall, with particular improvements in attenuation corrected (AC) datasets with high extra-cardiac activity (from 100/962 (10.4%) to 12/962 (1.4%) for rest AC, and from 41/962 (4.3%) to 9/962 (0.9%) for stress AC). The number of patients who had at least one of their 6 datasets affected by segmentation failure decreased from 141/962 (14.7%) to 14/962 (1.7%) using the SPP approach.ConclusionWhenever multiple image datasets for the same patient exist and need to be processed, it is possible to deal with the images as a group rather than individually. The same-patient processing approach can be implemented automatically, and may substantially reduce the need for manual reprocessing due to cardiac segmentation failure.