Visualisation and diagnostic utility for cardiovascular diseases using Biparametric Heatmap in iodine-123-beta-methyl-p-iodophenyl-pentadecanoic acid scintigraphy

Abstract Background In nuclear medicine, tracer uptake and washout rate (WR) are established indices for differentiating cardiovascular diseases (CVDs). WR is calculated as: WR = (Early Count − Radioactive-Decay-Corrected Late Count) / Early Count × 100 (%). Combining tracer uptake and WR offers a more comprehensive understanding of myocardial pathology, potentially improving diagnostic accuracy. Iodine-123-β-methyl-p-iodophenyl-pentadecanoic acid (BMIPP) is a radiotracer reflecting fatty acid and triglyceride metabolism in cardiomyocytes, providing insights into myocardial energy utilisation. Various CVDs exhibit characteristic BMIPP uptake and WR patterns during scintigraphy. For example, CD36 deficiency shows low uptake and low WR; in old myocardial infarction (OMI), regions with defective uptake have markedly decreased WR; triglyceride deposit cardiomyovasculopathy (TGCV) demonstrates preserved uptake but decreased WR; and mitochondrial cardiomyopathy (MC) exhibits enhanced BMIPP uptake. Tracer uptake and WR have conventionally been displayed on separate polar maps, requiring physicians to cognitively combine both parameters. Integrating them into a single image allows physicians to understand cardiac pathology more comprehensively and accurately. Purpose We developed a technique called Biparametric Heatmap (BH) to visualise various CVDs and enhance diagnostic accuracy by integrating uptake and WR into a single image. Methods A two-dimensional colour scale called Biparametric Heatscale was devised, with the horizontal axis representing early image counts (uptake) and the vertical axis representing WR (Figure 1). The count axis ranged from 50 to the mean plus two standard deviations specific to each case; counts over 400 were assigned the colour yellow. The WR window was set between –20% and 30%. Each coordinate pair of count and WR corresponded to a specific colour, facilitating intuitive visualisation of combined data. The resulting BH was displayed as a Polar Map representing the left ventricle. BH was evaluated in normal cases, TGCV, TGCV with OMI, non-TGCV patients with OMI, CD36 deficiency, and MC. Results In normal cases, BH showed an overall light blue, indicating sufficient counts and normal WR. In TGCV, BH displayed an overall purple, reflecting sufficient early counts but markedly decreased WR. In TGCV with OMI, BH showed purple in the TGCV myocardium and blue in the OMI region. In non-TGCV patients with OMI, BH presented light blue in normal regions and blue in OMI regions, reflecting decreased counts in infarcted areas. In CD36 deficiency, BH demonstrated an overall blue corresponding to low uptake and low WR, indicating impaired fatty acid metabolism. In MC, BH showed an overall yellow, indicating enhanced BMIPP uptake (Figure 2). Conclusion BH effectively visualises diverse cardiovascular diseases, demonstrating significant potential to enhance diagnostic precision in clinical practice.Figure 1 Figure 2