Modified Algorithm Using Total Count for Calculating Myocardial Washout Rate in Single-Photon Emission Computerized Tomography

Hideyuki Miyauchi; Ryohei Ono; Takashi Iimori; Koichi Sawada; Keisuke Hoshi; Ken-Ichi Hirano; Yoshio Kobayashi

doi:10.17996/anc.22-00172

Modified Algorithm Using Total Count for Calculating Myocardial Washout Rate in Single-Photon Emission Computerized Tomography

Ann Nucl Cardiol. 2023;9(1):19-25. doi: 10.17996/anc.22-00172. Epub 2023 Oct 31.

Authors

Hideyuki Miyauchi¹, Ryohei Ono¹, Takashi Iimori², Koichi Sawada², Keisuke Hoshi³, Ken-Ichi Hirano⁴, Yoshio Kobayashi¹

Affiliations

¹ Department of Cardiovascular Medicine, Chiba University Graduate School of Medicine, Chiba, Japan.
² Department of Radiology, Chiba University Hospital, Chiba, Japan.
³ Department of Pediatrics, The University of Tokyo Hospital, Tokyo, Japan.
⁴ Laboratory of Cardiovascular Disease, Novel, Non-invasive, and Nutritional Therapeutics (CNT) and Triglyceride Research Center (TGRC), Department of Triglyceride Science, Graduate School of Medicine, Osaka University, Osaka, Japan.

Abstract

Background: The arithmetic mean of washout rate (WR) (namely, AMWR) of each segment is a commonly used algorithm for calculating WR from a polar map in single-photon emission computerized tomography (SPECT). However, in this algorithm, uneven radiotracer uptake among segments affects WR calculation. To solve this possible issue, we formulated a modified algorithm for calculating WR based on the total count (namely, TCWR). Methods: The WR of iodine-123-β-methyl-p-iodophenylpentadecanoic acid (BMIPP) was calculated using TCWR and AMWR, and WR values using TCWR and AMWR were compared by disease. Participants included those without cardiovascular diseases (normal), those with CD36 deficiency, triglyceride deposit cardiomyovasculopathy (TGCV), TGCV with old myocardial infarction (OMI), and non-TGCV with OMI. Results: WR values using TCWR and AMWR did not differ significantly in the following groups: normal, 27.4±8.5 and 27.3±8.5% (p=0.97); CD36 deficiency, -3.2±6.5 and -4.1±7.4% (p=0.81); TGCV, 2.4±6.3 and 2.2±6.3% (p=0.93); and TGCV with OMI, -0.9±7.6 and -3.7±8.4% (p=0.32). However, AMWR showed a lower WR than TCWR in non-TGCV with OMI (4.8±8.7 and 18.9±6.7%, p=0.0008). Conclusions: TCWR is suitable for calculating WR using SPECT polar maps even in cases with heterogeneous radiotracer uptake, such as OMIs. TCWR may be applied to measuring the WR of radiopharmaceuticals other than BMIPP in investigating the pathophysiology of heart diseases.

Keywords: CD36 deficiency; Iodine-123-β-methyl-p-iodophenylpentadecanoic acid (BMIPP); Myocardial infarction; Single-photon emission computerized tomography (SPECT); Triglyceride deposit cardiomyovasculopathy (TGCV); Washout rate.