Abstract
BackgroundTo evaluate the dose-effect relations for myocardial metabolic disorders after mediastinal radiotherapy (RT) by performing iodine-123 β-methyl-iodophenyl pentadecanoic acid (I-123 BMIPP) scintigraphy.MethodsBetween 2011 and 2012, we performed I-123 BMIPP scintigraphy for patients with esophageal cancer before and six months after curative mediastinal RT. Single photon emission computed tomography (SPECT) images of pre-RT and post-RT were registered into RT dose distributions. The myocardium was contoured, and the regional RT dose was calculated. Normalization is required to compare pre- and post-RT SPECT images because the uptake pattern is changed due to the breathing level. Normalization was applied on the mean of SPECT counts in regions of the myocardium receiving less than 5 Gy. Relative values in each dose region (interval of 5 Gy) were calculated on the basis of this normalization for each patient. The reduction in the percent of relative values was calculated.ResultsFive patients were enrolled in this study. None of the patients had a past history of cardiac disease. The left ventricle was partially involved in RT fields in all patients. The patients received RT with median total doses of 60-66 Gy for the primary tumor and metastatic lymph nodes. Concomitant chemotherapy consisting of cisplatin or nedaplatin and 5-fluorouracil with RT was performed in 4 patients. All patients had reduced uptake corresponding to RT fields. Dose-effect relations for reduced uptake tended to be observed at 6 months after RT with mean decreases of 8.96% in regions at 10-15 Gy, 12.6% in regions at 20-25 Gy, 15.6% in regions at 30-35 Gy, 19.0% in regions at 40-45 Gy and 16.0% in regions at 50-55 Gy.ConclusionsDose-effect relations for myocardial metabolic disorders tended to be observed. We may need to make an effort to reduce high-dose mediastinal RT to the myocardium in RT planning.
Highlights
To evaluate the dose-effect relations for myocardial metabolic disorders after mediastinal radiotherapy (RT) by performing iodine-123 β-methyl-iodophenyl pentadecanoic acid (I-123 Iodine-123 β-methyl-iodophenyl pentadecanoic acid (BMIPP)) scintigraphy
We reported that reduced uptake corresponding to RT fields was observed mainly in the base of the left ventricle by using scintigraphy with iodine-123 β-methyliodophenyl pentadecanoic acid (I-123 BMIPP), which is a branched fatty acid analogue that enters myocardial cells and can show the degree of myocardial fatty acid metabolism [12]
I-123 BMIPP scintigraphy Single photon emission computed tomography (SPECT) imaging was performed 20 minutes after intravenous administration of 111 MBq of I-123 BMIPP (Cardiodine® Injectable, provided by Nihon Mediphysics Co, Sendai, Japan), using a dual-detector gamma camera combined with computed tomography (CT) (Symvia T2, Siemens, Hoffman Estates, IL)
Summary
To evaluate the dose-effect relations for myocardial metabolic disorders after mediastinal radiotherapy (RT) by performing iodine-123 β-methyl-iodophenyl pentadecanoic acid (I-123 BMIPP) scintigraphy. We reported that reduced uptake (myocardial metabolic disorder) corresponding to RT fields was observed mainly in the base of the left ventricle by using scintigraphy with iodine-123 β-methyliodophenyl pentadecanoic acid (I-123 BMIPP), which is a branched fatty acid analogue that enters myocardial cells and can show the degree of myocardial fatty acid metabolism [12]. The purpose of the present study was to evaluate myocardial metabolic disorders corresponding to RT fields by performing I-123 BMIPP scintigraphy before and after mediastinal RT. We evaluated the dose-effect relations for reduced uptake. We report these results as a pilot study
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