Comparison of the image-derived radioactivity and blood-sample radioactivity for estimating the clinical indicators of the efficacy of boron neutron capture therapy (BNCT): 4-borono-2-18F-fluoro-phenylalanine (FBPA) PET study.

Ikuko Mochida,Kayako Isohashi,Mitsuaki Tatsumi,Tadashi Watabe,Genki Horitsugi,Hiroki Kato,Eku Shimosegawa,Keiko Matsunaga,Yasukazu Kanai,Jun Hatazawa,Sadahiro Naka

doi:10.1186/s13550-016-0230-7

Abstract

BackgroundIn boron neutron capture therapy (BNCT), positron emission tomography (PET) with 4-borono-2-18F-fluoro-phenylalanine (FBPA) is the only method to estimate an accumulation of 10B to target tumor and surrounding normal tissue after administering 10B carrier of L-paraboronophenylalanine and to search the indication of BNCT for individual patient. Absolute concentration of 10B in tumor has been estimated by multiplying 10B concentration in blood during BNCT by tumor to blood radioactivity (T/B) ratio derived from FBPA PET. However, the method to measure blood radioactivity either by blood sampling or image data has not been standardized. We compared image-derived blood radioactivity of FBPA with blood sampling data and studied appropriate timing and location for measuring image-derived blood counts.MethodsWe obtained 7 repeated whole-body PET scans in five healthy subjects. Arterialized venous blood samples were obtained from the antecubital vein, heated in a heating blanket. Time-activity curves (TACs) of image-derived blood radioactivity were obtained using volumes of interest (VOIs) over ascending aorta, aortic arch, pulmonary artery, left and right ventricles, inferior vena cava, and abdominal aorta. Image-derived blood radioactivity was compared with those measured by blood sampling data in each location.ResultsBoth the TACs of blood sampling radioactivity in each subject, and the TACs of image-derived blood radioactivity showed a peak within 5 min after the tracer injection, and promptly decreased soon thereafter. Linear relationship was found between blood sampling radioactivity and image-derived blood radioactivity in all the VOIs at any timing of data sampling (p < 0.001). Image-derived radioactivity measured in the left and right ventricles 30 min after injection showed high correlation with blood radioactivity. Image-derived blood radioactivity was lower than blood sampling radioactivity data by 20 %. Reduction of blood radioactivity of FBPA in left ventricle after 30 min of FBPA injection was minimal.ConclusionWe conclude that the image-derived T/B ratio can be reliably used by setting the VOI on the left ventricle at 30 min after FBPA administration and correcting for underestimation due to partial volume effect and reduction of FBPA blood radioactivity.

Highlights

In boron neutron capture therapy (BNCT), positron emission tomography (PET) with 4-borono-2-18F-fluorophenylalanine (FBPA) is the only method to estimate an accumulation of 10B to target tumor and surrounding normal tissue after administering 10B carrier of L-paraboronophenylalanine and to search the indication of BNCT for individual patient
We conclude that the image-derived to blood radioactivity (T/B) ratio can be reliably used by setting the volumes of interest (VOIs) on the left ventricle at 30 min after FBPA administration and correcting for underestimation due to partial volume effect and reduction of FBPA blood radioactivity
BNCT was effective in patients with inoperable, locally advanced brain tumors, head and neck cancers and melanomas, even in those with tumor recurrence at previously irradiated sites [3,4,5]

Summary

Introduction

In boron neutron capture therapy (BNCT), positron emission tomography (PET) with 4-borono-2-18F-fluorophenylalanine (FBPA) is the only method to estimate an accumulation of 10B to target tumor and surrounding normal tissue after administering 10B carrier of L-paraboronophenylalanine and to search the indication of BNCT for individual patient. Absolute concentration of 10B in tumor has been estimated by multiplying 10B concentration in blood during BNCT by tumor to blood radioactivity (T/B) ratio derived from FBPA PET. The method to measure blood radioactivity either by blood sampling or image data has not been standardized. We compared image-derived blood radioactivity of FBPA with blood sampling data and studied appropriate timing and location for measuring image-derived blood counts. Boron neutron capture therapy (BNCT) requires selective delivery of 10B-containing drug to the tumor and irradiation of the tumor with neutrons.

Methods

Results

Discussion

Conclusion