Annals of nuclear cardiology最新文献

The International Study of Comparative Health Effectiveness with Medical and Invasive Approaches (ISCHEMIA) trial has had a great impact on the management of chronic coronary artery disease (CAD). One of the implications of this trial is the importance of close patient follow-up. To improve patient prognosis, evaluation of the residual extent of ischemia after treatment may be important because several studies have shown a close relationship between residual ischemia and cardiac events. For this assessment, myocardial perfusion single-photon emission computed tomography (MPS) has been utilized and is almost the only modality. Among the participants in the ISCHEMIA trial, more than 10% were excluded due to the absence of obstructive CAD. The pathophysiology of ischemia without non-obstructive coronary artery disease (INOCA) is gaining recognition; however, diagnosis is difficult, except for the assessment of myocardial flow reserve (MFR). Myocardial perfusion positron emission tomography (PET) is the most common modality for noninvasive evaluation of MFR; however, its availability in Japan is limited. For a breakthrough in this situation, a novel gamma camera with a cadmium zinc telluride (CZT) semiconductor might be one of the solutions that enables the evaluation of MFR with a commercially available perfusion tracer, similar to PET. Another solution is a novel PET tracer with a longer half-life. Clinical trials with ¹⁸F labeled perfusion agents have been initiated in Japan, and in a few years, delivery of this perfusion tracer will result in more frequent and easier assessment of MFR.

Machine learning has become popular in clinical practice, and the amount of research that uses artificial intelligence is rapidly increasing. In contrast to conventional statistical and rule-based methods, machine learning creates algorithms based only on combinations of input and output databases. Basic understanding of the internal workings of artificial intelligence, its structures and need for appropriate databases, as well as its strengths and weaknesses is important for efficient machine learning application. The cardiological applications of machine learning include diagnosing coronary artery diseases and heart failure, and examples are addressed herein. A preliminary application of machine learning to a ¹²³I-metaiodobenzylguanidine-based risk model appears promising, and further studies using similar approaches are anticipated. Nuclear medicine physicians and cardiologists should play key roles in developing machine learning-based methods to ensure practical and reliable decisions.

Purpose: Heart-type fatty acid binding protein (H-FABP) is primary transporter of free fatty acid and plays an important role in myocardial metabolism, which is characterized by high specificity and rapid appearance under ischemic condition. The objective of this study was to clarify the usefulness of imaging study of targeting H-FABP appearance using radio-labeled antibody, and correlation with myocardial fatty acid metabolism and perfusion in acute reperfusion ischemia. Method: Wistar rats were allotted to sham-operated control group (sham; n=4), ischemia non-reperfused group (IG; n=5), and ischemia-reperfusion group (RG; n=5). Ligation of left coronary artery (LCA) was performed for IG and RG. 20 min of ischemia was followed by 60min of reperfusion for RG. ¹²⁵I labeled anti H-FABP antibody (anti H-FABP), BMIPP and ^99mTc-sestamibi (MIBI) was injected intravenously. Multi-tracer digital autoradiogram was performed using µ-imager^®. The ratio of radioactivity in LCA related (culprit) area to the inferior (remote) area (target uptake ratio=TUR) was generated. Results: In sham group, no visually detectable accumulation was observed for the anti H-FABP image, and TUR_MIBI and TUR_BMIPP were equivalent to 1. In IG, TUR_MIBI and TUR_BMIPP were remarkably low (0.12±0.01, 0.24±0.07). In RG, TUR_MIBI was significantly lower (0.20±0.03, p<0.05 vs. other groups). However, TUR_BMIPP was significantly higher (2.78±1.28, p<0.05) compared to the sham and IG, whereas anti H-FABP showed markedly higher ratio in the reperfused area compared to the sham and IG (3.43±0.73 vs. 0.31±0.13 and 1.09±0.07 for IG and sham; p<0.05, and <0.01, respectively). Conclusion: Anti H-FABP accumulated specifically in reperfused area under acute ischemia, and it accorded to the area where fatty acid metabolism was activated. This study has shown the future potential for clinical application in vivo imaging of acute coronary syndrome.

The Japanese Circulation Society (JCS) 2021 guideline on radiation safety in cardiology was updated based on the eight best practices for myocardial perfusion single-photon emission computed tomography myocardial perfusion imaging (SPECT-MPI), which was determined by panels of international atomic energy agency (IAEA) nuclear cardiology protocols cross-sectional study (INCAPS). Although the guideline recommends to avoid too much ²⁰¹Tl or ²⁰¹Tl/^99mTc dual-isotope protocol, the utilization rate of ²⁰¹Tl for SPECT-MPI in Japan is considerably high compared to other countries. In Japan, protocols using ^99mTc should be appropriately promoted based on the guideline to reduce radiation exposure in SPECT-MPI. Among the eight practices, stress-only imaging is considered to be a useful strategy that contributes to a significant reduction in radiation exposure, and hybrid assessment in combination with rest computed tomography (CT)-MPI is one of the practical application methods.

Background: Recent advances in cardiac modalities contribute to the guidelines on the diagnosis of cardiac sarcoidosis (CS) updated by the Japanese Circulation Society. The multicenter registry, Japanese Cardiac Sarcoidosis Prognostic (J-CASP) study tried to reveal recent trends of diagnosis and outcomes in CS patients and to validate the non-invasive diagnostic approach, including cardiac ¹⁸F-fluorodeoxyglucose (FDG) study. Methods/results: Databases from 12 hospitals consisting of 231 CS patients (mean age, 64 years; female, 65%; LV ejection fraction, 47%) diagnosed by the guidelines with FDG positron emission tomography (PET) study were integrated to compile clinical information on the diagnostic criteria and outcomes. Cardiac ¹⁸F-FDG uptake and magnetic resonance imaging (CMR) was positive identically in the histology-proven and clinically-diagnosed groups. The histology-proven group more frequently had reduce LV ejection fraction, myocardial perfusion abnormality and low-grade electrocardiogram (ECG) abnormality (P=0.003 to 0.016) than did the clinical group. During a 45-month period, the histology-proven group more frequently underwent appropriate implantable cardioverter-defibrillator (ICD) treatment (14% versus 4%, P=0.013) and new electronic device implantation (30% versus 12%, P=0.007) than did clinical group, respectively. There, however, was no difference in all-cause or cardiac mortality or in new hospitalization due to heart failure progression between them. Conclusion: The J-CASP registry demonstrated the rationale and clinical efficacies of non-invasive approach using advanced cardiac imaging modalities in the diagnosis of CS even when histological data were available.

Since Agatston et al. first reported quantification of the coronary artery calcification score (CACS) in 1990, discussion of its clinical significance and use in diagnostic management has continued. Recent papers have reported the relationship between CACS and myocardial perfusion single photon emission computed tomography (SPECT: MPS) and its combined diagnostic value. When interpreting CACS results, it should be noted that the frequency of significant ischemia detected by MPS, likelihood of coronary artery disease (CAD), and event rate gradually increased from mild to moderate CACS (1-400). At present, high CACS is considered to be moderately consistent with abnormal MPS, and abnormal CACS in normal MPS may contribute to CAD risk stratification. However, it should be noted that CACS=0 does not completely exclude CAD, which is particularly important when using CACS as a gatekeeper for MPS. Both stand-alone computed tomography (CT) scanner and hybrid SPECT-CT scanner are available for combined risk stratification of CACS and MPS in addition to improvement of image quality with attenuation correction.

Background: There is no phantom for image quality test in magnetic resonance imaging combined with positron emission tomography systems (PET/MRI systems). In MRI, radioactive water phantom containing 2-deoxy-2-[F-18] fluoro-D-glucose (¹⁸F-FDG) cannot be used due to the dielectric effect. Even for phantoms filled with MR-available solutions, the source current of the RF coil is strongly disturbed as the diameter of the phantom increases. Stable MR images require proper phantom size and solution selection. Previous reports have not provided these details. Other than that, few existing phantoms evaluate negative signals such as N-13 ammonia (¹³N-NH₃). We created a phantom for PET/MRI system for image quality test. Methods: The phantom for the PET/MRI system was assembled in two portions. One portion is a signal part containing ¹⁸F-FDG radioactive water. The other portion is filled with polyvinyl alcohol glue to construct MRI image to generate µ-map. The glue part is allowed to rewrite the table position overlaps with the first layer, and attenuation correction is performed. Signals are set as positive (4 times and twice higher than background radioactivity) and negative (no radioactivity) columns with different sizes (15 mm φ and 7 mm φ). The PET images with X-ray computed tomography-based attenuation correction (CT-AC) and MRI-AC were evaluated by %-contrasts, variation and uniformity. Results: The %-contrasts of the positive shallow signals with PET/magnetic resonance (MR) and PET/CT were 41.8% and 45.4%, respectively. And it of the positive deep signals with PET/MR and PET/CT were 40.7% and 44.9%. On the other hand, the %-contrasts of the negative shallow signals with PET/MR and PET/CT were 62.3% and 65.6%, respectively. And it of the negative deep signals with PET/MR and PET/CT were 60.7% and 63.7%. Moreover, the % Nj index of uniformity was 2.0% on PET/MRI images and 0.34% on PET/CT images. For negative signals that assume a decrease in myocardial blood flow, The image quality of MR-AC was almost the same as that of CT-AC. Consistency between the images after CT-AC and MR-AC correction were confirmed, and in particular, a stable MR-AC µ-map was obtained in the phantom study. Conclusion: The suggested prototype phantom for generating µ-map is reasonable and useful for evaluating PET/MRI image quality, based on the present standard.

Background: Triglyceride deposit cardiomyovasculopathy (TGCV) is a rare intractable cardiovascular disorder (Orphanet ORPHAcode: 565612) in which defective intracellular lipolysis results in heart failure and coronary artery disease. Myocardial scintigraphy with ¹²³I-β-methyl-p-iodophenylpentadecanoic acid (BMIPP) is useful to evaluate myocardial TG metabolism; its washout rate (WR) reflects myocardial lipolysis. This study reports the effects of CNT-01 (tricaprin), a developing orphan drug to facilitate lipolysis, on BMIPP-WR in patients with TGCV. Methods: An investigator-initiated, multicenter, randomized, double-blind exploratory, trial (Phase IIa) was conducted (UMIN000035403). Seventeen patients with idiopathic TGCV were orally administered 1.5 g/day of CNT-01 or placebo for 8 weeks. Endpoints included delta BMIPP-WR and clinical parameters such as 6-minwalk distance and TGCV severity score. Results: During the protocol, delta BMIPP-WRs were -0.26±3.28 and 7.08±3.28% (95% confidence intervals, -7.36 to 6.84 and -0.01 to 14.18) in the placebo and CNT-01 groups, respectively. The baseline-adjusted difference of delta BMIPP-WR between the two groups was significant (p=0.035) after one patient was excluded from the placebo group because of pseudonormalization of BMIPP-WR related to coronary bypass graft stenosis. Clinical parameters did not show significant changes. Conclusions: This study proved the mechanism of CNT-01 to improve myocardial lipolysis in TGCV, as demonstrated by BMIPP scintigraphy.