Details

Autor(en) / Beteiligte

• Kumakura, Yoshitaka
• Shimizu, Yuji
• Ichikawa, Kenichi
• Kaneoya, Yuya
• Nomura, Kyoichi

Titel

An RI angiographic approach to estimate cardiac blood pool contribution to heart ROI radioactivity of planar ^sup 123^I-MIBG myocardial scintigraphy

Ist Teil von

• The Journal of nuclear medicine (1978), 2018-05, Vol.59, p.1572

Ort / Verlag

New York: Society of Nuclear Medicine

Erscheinungsjahr

2018

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• Objectives: Planar myocardial scintigraphy with 123I-meta-iodobenzylguanidine (MIBG) is a useful clinical tool to evaluate impaired sympathetic innervation, which can be frequently caused by Parkinson’s disease and Lewy body dementia. The myocardial accumulation of MIBG is semi-quantified from count rates of two ROIs placed on heart (H) and referential mediastinum (M). The heart ROI is obviously contaminated by extra-myocardial radioactivity, mainly originated from the cardiac pool of whole blood. In this preliminary study, we estimated contribution ratio of the cardiac pool to the heart ROI count rates for 26 consecutive patients. An RI angiography immediately after bolus injection of MIBG was carried out for the estimation. We hypothesized that the heart ROI count rates of female patients could be underestimated, compared with those of male patients, due to breast attenuation. Methods: All the 26 patients (mean age 71.5; 14 males and 12 females) were examined with a GE Discovery NM630 SPECT scanner. We implemented a two-min RI angiographic study consisting of 30 frames per minute. Assuming that the first pass bolus of MIBG (111MBq) travels through the HM ROIs to the level of aortic arch, we calculated areas under the curve (AUCs) of the HM ROI TACs up to four seconds after the bolus passage exhibiting a maximum heart ROI count rate. To calculate TACs of the cardiac blood pool, the mediastinum TACs can be rescaled by the individual AUC ratios of heart to mediastinum (RAUC). Results: Body mass index (BMI) was not significantly different between the gender subgroups. The mean BMI (SD) was 22.0 (1.0) for males, and 23.9 (0.8) for females. No significant correlation was found between the AUC ratios and the BMIs of 26 patients with and without gender stratification. The mean RAUC was 1.05 (0.07) for males and 0.89 (0.04) for females, presenting an approximately 15% difference that was statistically significant (P=0.038, one-tailed unpaired t test). Conclusion: The additional RI angiography study of MIBG can readily be part of routine planar imaging practice for investigation of myocardial catecholamine innervation. In this small cohort study, BMIs was not a good predictor of blood pool radioactivity fractions to correct contaminated heart ROI count rates. Although breast attenuation is individually variable, we conclude that the heart ROI radioactivity of the female group might be underestimated compared with that of the male group. Based on the RAUC results, subtracting mediastinum ROI radioactivity multiplied by unity seems to be reasonably valid. However, it might be another source of underestimation of specific myocardial MIBG accumulation for the patients with low RAUC.