Keisuke Kiso

Recommendations for (18)F-fluorodeoxyglucose positron emission tomography imaging for cardiac sarcoidosis: Japanese Society of Nuclear Cardiology recommendations.

Sarcoidosis is a systemic granulomatous disease that forms epithelioid cell granuloma (accompanied by infiltration of inflammatory cells) without caseous necrosis in organs throughout the body, including the lungs, lymph nodes, skin, eyes, heart, and muscles. Generally there is a good prognosis for spontaneous resolution of sarcoidosis; however, for cardiac-involvement sarcoidosis, the prognosis is extremely poor, and careful management is required. The most common cause of death from sarcoidosis is cardiac complications of the disease, and therefore early detection and treatment of these are very important in the management of cardiac-involvement sarcoidosis. Guidelines for the diagnosis of cardiac sarcoidosis were first published by Hiraga et al. [1] in 1992 (Table 1). These guidelines were modified by the joint committee of the Japan Society of Sarcoidosis and Other Granulomatous Disorders and the Japanese College of Cardiology in 2006 (Table 2) [2]. These modified guidelines stipulate the following: a histopathological or clinical diagnosis of sarcoidosis in organs other than the heart is essential, and the following cases should be diagnosed as cardiac sarcoidosis: (1) cases histopathologically diagnosed as positive for cardiac sarcoidosis on the basis of myocardial biopsy (histopathologically diagnosed group) and (2) cases with clinical findings indicating characteristic cardiac abnormalities including principal and secondary signs and symptoms (clinically diagnosed group) (Tables 1, 2). In the histopathologically diagnosed group, the positivity rate for detection of cardiac sarcoidosis may be low owing to sampling errors in myocardial biopsy. Hence, in actual clinical settings, the number of cases in the clinically diagnosed group is higher than in the histopathologically diagnosed group. Upon diagnosis of cardiac sarcoidosis, it is important to determine the disease activity to develop a treatment strategy, assess severity, predict prognosis, and Committee for diagnosis of cardiac sarcoidosis using 18F-FDG PET, Japanese Society of Nuclear Cardiology.

Lung perfused blood volume images with dual-energy computed tomography for chronic thromboembolic pulmonary hypertension: correlation to scintigraphy with single-photon emission computed tomography.

Objective: The purpose of this study was to evaluate the feasibility and diagnostic utility of lung perfused blood volume (LPBV) images generated by dual-energy computed tomography (CT), as compared with pulmonary perfusion scintigraphy, for patients with chronic thromboembolic pulmonary hypertension. Methods: Patients (n = 51) with chronic pulmonary thromboembolic embolism were examined by dual-source CT in dual-energy mode. Lung perfused blood volume images were generated by analysis of the iodine content of the lung parenchyma using dual-energy data. Pulmonary perfusion defects were evaluated on a segment-by-segment basis in images obtained by both LPBV and pulmonary scintigraphy. Findings suggestive of chronic thromboembolic pulmonary hypertension in CT pulmonary angiography were analyzed. Results: All examinations were acquired without complications, and the contrast enhancement of the pulmonary artery was sufficient for diagnosis of vascular thromboses. In the LPBV images, in 76 (8.3%) of 918 segments, it was difficult to assess perfusion because of artifacts. The agreement between the 2 modalities was good (&kgr; = 0.70). The sensitivity of LPBV in detecting perfusion defects was 96%; the specificity was 76%; the positive predictive value was 94%, and the negative predictive value was 29%. Conclusions: Lung perfused blood volume imaging by dual-energy CT is feasible for the evaluation of pulmonary perfusion and is comparable to pulmonary scintigraphy. It is possible to evaluate vessels and pulmonary perfusion with CT pulmonary angiography and LPBV images and to assess pulmonary perfusion more definitively in diagnosing chronic pulmonary thromboembolic embolism.

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.

Transient constrictive pericarditis diagnosed by cardiac magnetic resonance, 67Ga scintigraphy, and positron emission tomography

Constrictive pericarditis occurs following pericardial fibrosis and often leads to refractory right side heart failure. Surgical relief is often required for correction of hemodynamic abnormalities. Two recent reports described a transient form of constrictive pericarditis that resolved without surgical intervention. In this case, we present representative images of transient constrictive pericarditis detected by late gadolinium enhancement of cardiac magnetic resonance, 67Ga scintigraphy, and 18FDG positron emission tomography before and after corticosteroid therapy. This is the first demonstration of the utility of imaging modalities in the diagnosis of transient constrictive pericarditis, and we document radiologic changes in pericardial inflammation after medical therapy.

Breath-hold CT attenuation correction for quantitative cardiac SPECT

BackgroundAttenuation correction of a single photon emission computed tomography (SPECT) image is possible using computed tomography (CT)-based attenuation maps with hybrid SPECT/CT. CT attenuation maps acquired during breath holding can be misaligned with SPECT, generating artifacts in the reconstructed images. The purpose of this study was to investigate the effects of respiratory phase during breath-hold CT acquisition on attenuation correction of cardiac SPECT imaging.MethodsA series of 201Tl-emission and 99mTc-based transmission computed tomography (TCT) scans was carried out along with CT-attenuation scans on 11 young normal volunteers using a hybrid SPECT/CT scanner. The CT scans were performed at three respiratory phases: end-inspiration (INS), end-expiration (EXP), and the midpoint (MID) between these phases. Using alignment parameters between attenuation maps and SPECT images without attenuation or scatter corrections, quantitative SPECT images were reconstructed, including corrections for attenuation and scatter. Regional radioactivity concentrations normalized by the subjects’ weights were compared between CT- and TCT-based attenuation correction techniques.ResultsSPECT images with CT attenuation maps at the EXP phase showed significant differences in regional weight-normalized radioactivity concentrations relative to the images using the other attenuation maps (p < 0.05), as well as systematic positive bias errors, compared to TCT-based images for all myocardial segments, 5.7% ± 2.7% (1.9% to 10.0%). No significant differences in regional weight-normalized radioactivity concentrations were observed between images with CT attenuation maps at MID and INS phases or between these and the TCT-based images, but regional tendencies were found: for anterior to anterolateral segment, positive bias of 5.0% ± 2.2% (1.3% to 8.1%) and 5.6% ± 1.9% (2.6% to 8.5%) and for inferior to inferoseptal segment, negative bias of −5.3% ± 2.6% (−9.1% to −1.7%) and −4.6% ± 2.5% (−8.8% to −1.5%) for the MID and INS phases, respectively.ConclusionsUse of breath-hold CT attenuation maps at INS and MID phases for attenuation and scatter corrections demonstrated accurate quantitative images that would prove beneficial in cardiac SPECT/CT studies.

Usefulness of Nuclear Medicine: “PET/SPECT Imaging” for Management of Recipients after Heart Transplantation

Heart transplantation(HTx)in Japan started in 1992 after putting the Organ Transplant Law into force. Even after the amendment of this law in 2010, numbers of HTx performed in Japan has been much less than other countries, however, the outcome of HTx in Japan is much superior to that of international registry. For the management after HTx, surveillance of acute cellular rejection, cardiac allograft vasculopathy(CAV), infections, renal dysfunction, malignancies is essential. Nuclear medicine, such as myocardial perfusion imaging, Ga scintigraphy, F-FDG PET, etc., has been utilized for detection of these rejections and complications, adding to other modalities. Moreover, re-innervation from denervated heart is unique phenomenon which is observed in HTx recipients. For the evaluation of re-innervation in transplanted heart, I-metaiodobenzylguanidine (MIBG), which is the analogue of norepinephrine, has been utilized. Then, several reports described that the degree of re-innervation was related to sympathetic functional recovery, such as responses of the heart rate and contractile function to exercise. As described above, nuclear medicine has contributed to recipient9s care and management after HTx. However, invasive techniques, such as endomyocardial biopsy, coronary angiography, etc., have played a major role in management of recipients, because of high reliability for detection of rejections and complications, compared with other non-invasive modalities. So, we professional of imaging diagnosis have to keep on challenging to offer securer and easier care to HTx recipients.

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.

Criteria for the addition of prone imaging to myocardial perfusion single-photon emission computed tomography for inferior wall

Objective Myocardial perfusion single-photon emission computed tomography (SPECT) is occasionally suspected to generate images that represent either ischemia or infarction for the inferior wall [right coronary artery (RCA) disease] or attenuation artifacts because of the diaphragm. We often encounter this. The application of prone imaging is advantageous in the differentiation of RCA disease because of attenuation artifacts. If decreased accumulation of radioisotopes is observed at the site with either RCA disease or attenuation artifacts, then a criterion that enables the addition of prone imaging should be implemented. Then, we evaluated sites where RCA disease and attenuation artifacts would likely appear and investigated the threshold of decreased accumulation that enables utilization of prone imaging. Patients and methods The patients in this study were divided into two groups: group A (20 patients) suspected to have attenuation artifacts because of the diaphragm and group B (14 patients) with RCA disease. Additional evaluation by prone imaging was performed in all patients. We utilized a 20-segment quantitative perfusion SPECT polar map in the supine and prone positions to compare the percentage increase in 201Thallium chloride (201Tl) in both groups. We then investigated the percent uptake (%uptake) value of decreased accumulation in the inferior wall for the addition of prone imaging. Results The highest %uptake was present in segments 3, 4, 5, and 10 in group A after the prone imaging. Detection of attenuation artifacts from the diaphragm was easy in segments 3, 4, 5, and 10, and we set the %uptake threshold at 62, 61, 71, and 76%, respectively, in the supine position for the addition of prone imaging. Conclusion A decrease of the %uptake in segments 3, 4, 5, and 10 after supine imaging is presumed to result from attenuation artifact or RCA disease. We established evaluation criteria for the addition of prone imaging in patients with decreased accumulation in the inferior wall during supine imaging.

Optimal injected dose ratio of a very rapid 1-day protocol of myocardial perfusion imaging with cadmium–zinc–telluride single-photon emission tomography: simulation and phantom study

Objective Cadmium–zinc–telluride detectors enable shorter acquisition durations in myocardial perfusion imaging (MPI), but the time interval of sequential scanning is still unchanged in clinical practice. We designed a very rapid 1-day protocol of MPI using cadmium–zinc–telluride single-photon emission tomography and evaluated the optimal dose ratio between two scanning acquisitions by means of simulations and phantom experiments. Methods We intended to perform a 1-day MPI within 140 min and simulate radioactivities in the second scan under various injected dose ratios. To apply this, a cardiac phantom was scanned with various radioactivities and scans were compared with a reference scan with the ideal tracer concentrations. Results In the stress-first protocol, the dose ratio 1 : 5 was enough to show the same regional percentage uptake compared with the reference. However, in the rest-first protocol, the regional percentage uptakes were higher than those of the reference image even with a 1 : 6 dose ratio. Conclusion The injected dose ratio 1 : 5 is optimal in a stress-first rapid 1-day protocol. The rest-first protocol is not appropriate because a dose ratio greater than 1 : 6 is required to withdraw shine-through artifacts.

Comparison between prone and upright imaging of the inferior wall using 201TlCl myocardial perfusion single photon emission computed tomography

Because it suppresses attenuation artifacts from the diaphragm, prone SPECT is suitable for evaluating the cardiac inferior wall. A solid-state dedicated cardiac camera allows upright imaging, which can also be used to avoid attenuation artifacts from the diaphragm. We compared prone and upright imaging for inferior wall evaluation using 201TlCl myocardial perfusion SPECT (MPS). Methods: The study targeted 45 patients. The prone imaging group included 23 subjects who underwent additional prone imaging because supine imaging indicated that the inferior wall had reduced uptake. The upright imaging group included 22 subjects who, in the past, had shown reduced uptake in the inferior wall during supine imaging. Using the MPS stress images and analysis software, we created a polar map showing the incorporation of the radioisotope throughout the whole of the myocardium; this polar map was then classified into 17 segments. The percentage uptake ratios of the inferior/anterior wall were calculated for the prone and upright acquisitions. These ratios were used as the ratio of percentage uptake in each segment of the anterior wall to percentage uptake in each segment of the inferior wall. In addition, 6 reviewers visually evaluated the uniformity within the inferior wall for both the prone and the upright imaging. Results: There was a significant difference in percentage uptake ratios between the prone and upright images in segments 4/1 (basal inferior/basal anterior; P < 0.05), 11/12 (mid inferolateral/mid anterolateral; P < 0.001), and 15/13 (apical inferior/apical anterior; P < 0.05). There were no significant differences between the prone and upright images in visual evaluations of uniformity within the inferior wall. Conclusion: In comparison with upright imaging, prone imaging has a higher rate of suppression of attenuation artifacts from the diaphragm. However, this difference does not seem to affect the images visually. Therefore, upright and prone imaging can be used interchangeably to evaluate the inferior wall.