Tokuo Kasai

Normal values and standardization of parameters in nuclear cardiology: Japanese Society of Nuclear Medicine working group database

As a 2-year project of the Japanese Society of Nuclear Medicine working group activity, normal myocardial imaging databases were accumulated and summarized. Stress-rest with gated and non-gated image sets were accumulated for myocardial perfusion imaging and could be used for perfusion defect scoring and normal left ventricular (LV) function analysis. For single-photon emission computed tomography (SPECT) with multi-focal collimator design, databases of supine and prone positions and computed tomography (CT)-based attenuation correction were created. The CT-based correction provided similar perfusion patterns between genders. In phase analysis of gated myocardial perfusion SPECT, a new approach for analyzing dyssynchrony, normal ranges of parameters for phase bandwidth, standard deviation and entropy were determined in four software programs. Although the results were not interchangeable, dependency on gender, ejection fraction and volumes were common characteristics of these parameters. Standardization of 123I-MIBG sympathetic imaging was performed regarding heart-to-mediastinum ratio (HMR) using a calibration phantom method. The HMRs from any collimator types could be converted to the value with medium-energy comparable collimators. Appropriate quantification based on common normal databases and standard technology could play a pivotal role for clinical practice and researches.

F-18 fluorodeoxyglucose uptake in atherosclerotic plaque in the mediastinum mimicking malignancy: another potential for error.

Atherosclerosis is an inflammatory process accumulating numerous inflammatory cells such as macrophages and lymphocytes. This cellular infiltrate has a high metabolic demand, which can be reflected on F-18 FDG positron emission tomographic (PET) imaging. The FDG uptake in atherosclerotic vessels is usually distinguishable as a result of its linear and continuous appearance and mild level of activity. However, occasionally, atherosclerotic plaques present themselves as focal “hot spots,” which can be easily misinterpreted as malignancy. This report emphasizes atherosclerotic plaques as a potential pitfall while interpreting FDG scans. It also highlights the importance of radiographic correlation to avoid such an error.

Prognostic study of cardiac and renal events in Japanese patients with chronic kidney disease and cardiovascular risk using myocardial perfusion SPECT : J-ACCESS 3 study design

Cardiovascular disease is the leading cause of morbidity and mortality in patients with chronic kidney disease. Recent studies have indicated that the incidence of cardiovascular disease increases inversely with estimated glomerular filtration rate. Although coronary angiography is considered the gold standard for detecting coronary artery disease, contrast‐induced nephropathy or cholesterol microembolization remain serious problems; therefore, a method of detecting coronary artery disease without renal deterioration is desirable. From this viewpoint, stress myocardial perfusion single photon emission computed tomography (SPECT) might be useful for patients with chronic kidney disease. We recently performed the Japanese Assessment of Cardiac Events and Survival Study by Quantitative Gated SPECT (J‐ACCESS) investigating patients with suspected or extant coronary artery disease and the J‐ACCESS 2 study of patients with diabetes. The findings from these studies showed that SPECT can detect coronary artery disease and help to predict future cardiac events. Thus, we proposed a multicenter, prospective cohort study called “J‐ACCESS 3” in patients with chronic kidney disease and cardiovascular risk. The study aimed at predicting cardiovascular and renal events based on myocardial perfusion imaging and clinical backgrounds. We began enrolling patients in J‐ACCESS 3 at 74 facilities from April 2009 and will continue to do so until 31 March 2010, with the aim of having a cohort of 800 patients. These will be followed up for three years. The primary endpoints will be cardiac death and sudden death. The secondary endpoints will comprise any cardiovascular or renal events. This study will be completed in 2013. Here, we describe the design of the J‐ACCESS 3 study.

Impact of gating errors with electrocardiography gated myocardial perfusion SPECT

Case history and clinical course. A 72-year-old man with tongue carcinoma was admitted to undergo a surgical treatment. He was a smoker and had a complaint of shortness of breath. He was referred for stress testing so that he could be cleared for surgery. After the intravenous administration of 325 MBq technetium 99m sestamibi at rest and 1088 MBq during stress, single photon emission computed tomography (SPECT) of the heart was performed over 180° in 32 steps in a 64 64 matrix by use of a dual-head gamma camera (Optima; GE Medical Systems, Milwaukee, Wis) equipped with low-energy high-resolution collimators. Gated SPECT images with 8 frames per R-R interval were acquired 30 minutes after the stress completion. Filtered backprojection was used for image reconstruction. The baseline electrocardiogram showed normal sinus rhythm and tall T waves (Figure 1). The patient achieved more than 85% of his predicted maximal heart rate. He had no chest pain, and no ST-segment changes were detected. There was no patient motion during the acquisition. Perfusion was normal on both of the stress and rest images. The gated SPECT images revealed diffuse hypokinesis and no wall thickening. The time-volume curve (TVC) obtained by use of QGS software (Cedars-Sinai, Los Angeles, Calif) showed virtually a straight line (Figure 2). The left ventricular ejection fraction (LVEF) was calculated as 16.3% by QGS. However, normal wall motion was demonstrated subsequently by echocardiography, and LVEF was estimated to be 68%. The patient was considered to be at low risk for surgery and subsequently underwent the procedure without any perioperative events. Discussion. Myocardial perfusion SPECT plays an important role in assessing cardiac risk for noncardiac surgery. 1 Moreover, gating has improved diagnostic accuracy for detecting ischemia 2 nd has brought about an incremental predictive value for prognosis. 3 However, gating errors may occur with gated SPECT. These errors sometimes render the study suboptimal, especially for evaluation of wall motion, wall thickening, and calculation of LVEF. According to the reports of Nichols et al, left ventricular volumes and LVEFs are affected minimally by arrhythmias; however, wall thickening is more prone to be underestimated. Even if there are no arrhythmias, cardiac cycle variations may cause artifacts. With marked arrhythmias, gating errors may produce perfusion abnormalities. 4,6 In the present case, no arrhythmias or perfusion defects were detected. However, no significant contraction or thickening was demonstrated. A similar gating error has been reported for equilibrium radionuclide angiocardiography (ERNA). 7 With tall T waves, the R-T phase and T-R phase are regarded as two “cardiac cycles.” The first cardiac cycle, the R-T phase, consists of systole. The subsequent cardiac cycle, the T-R phase, consists predominantly of diastole. When the TVC is generated by summation of these phases, the R-T phase makes up the downsloping curve and the T-R phase makes up the upsloping curve. Because the R-T phase and T-R phase are regarded as identical cardiac cycles, the final TVC is produced essentially as a flat line (Figure 3A). Other potential errors also have been reported for ERNA. 7 First, with bigeminy or pulsus alter nans, the computer may erroneously select an R-R interval involving two entire cardiac cycles, detecting only the tallest R waves. When the original R wave is selected as a trigger, the TVC will show a “down-up” shape. If the premature beat or alternans beat appears before end systole of the original cycle, the TVC will be U-shaped. If it appears after end systole of the original cycle, the TVC will be W-shaped (Figure 3 B-1). If the premature beat or alternans beat is selected as a trigger, the TVC will be inverted (Figure 3 B-2). Second, if the T wave is tall and its amplitude is greater than the R wave, the T wave may trigger the electrocardiographic (ECG) gate. Although the gating interval will correspond in length to the R-R interval, the TVC will also be inverted (Figure 3C). From the Division of Nuclear Medicine, Department of Radiology, a

Prognostic impact of reducing myocardial ischemia identified using ECG-gated myocardial perfusion SPECT in Japanese patients with coronary artery disease: J-ACCESS 4 study

AIM Whether myocardial ischemia identified using myocardial perfusion imaging (MPI) can be an alternative target of coronary revascularization to reduce the incidence of cardiac events remains unclear. METHODS AND RESULTS This multicenter, prospective cohort study aimed to clarify the prognostic impact of reducing myocardial ischemia. Among 494 registered patients with possible or definite coronary artery disease (CAD), 298 underwent initial pharmacological stress 99mTc-tetrofosmin MPI before, and eight months after revascularization or medical therapy, and were followed up for at least one year. Among these, 114 with at least 5% ischemia at initial MPI were investigated. The primary endpoints were cardiac death, non-fatal myocardial infarction and hospitalization for heart failure. Ischemia was reduced ≥5% in 92 patients. Coronary revascularization reduced ischemia (n = 89) more effectively than medical therapy (n = 25). Post-stress cardiac function also improved after coronary revascularization. Ejection fraction significantly improved at stress (61.0% ± 10.7% vs. 65.4% ± 11.3%; p < 0.001) but not at rest (67.1% ± 11.3% vs. 68.3% ± 11.6%; p = 0.144), among patients who underwent revascularization. Rates of coronary revascularization and cardiac events among the 114 patients were significantly higher (13.6%, p = 0.035) and lower (1.1% p = 0.0053), respectively, in patients with, than without ≥5% ischemia reduction. Moreover, patients with complete resolution of ischemia at the time of the second MPI had a significantly better prognosis. CONCLUSIONS Reducing ischemia by ≥5% and the complete resolution of ischemia could improve the prognosis of patients with stable CAD.