Planar and tomographic imaging dosimetry comparing to develop a new radiopharmaceutical for melanoma therapy

Sarah Soriano,Sérgio Souza,Thiago Barboza,Lidia De Sá

doi:10.15392/bjrs.v8i2.1191

Abstract

This work aims to compare SPECT (Single Photon Emission Tomography Computed) and planar modalities as the most efficient methodology to perform dosimetry by molecular imaging. Twenty-one male C57BL6 mice induced with murine melanoma cell line B16-F10, administered 131I-Ixolaris were used for melanoma therapy. The procedures applied to them followed the standards described for the use of experimental animals, duly approved by the National Council for Animal Experimentation Control (CONCEA from Federal University of Rio de Janeiro. The accumulated activities were obtained in order to estimate the absorbed doses in each organ. Mass and metabolic differences between mice and humans were considered and used to extrapolate data acquired at different scales. From the dose factors provided by the MIRDOSE software, the absorbed doses in the target organs irradiated by the source organs were calculated and, finally, the effective dose was estimated. From the Student's t-hypothesis test performed in the accumulated activity, absorbed dose and S-factor quantities, there is no statistically significant difference between performing the image dosimetry from SPECT and planar acquired images.

Highlights

Technological innovation associated new radiopharmaceuticals developments contribute to recent diagnostic and therapeutic tools
Dosimetry is an integral and fundamental part of preclinical studies and can be performed semi-quantitatively, where relative measurements are compared with healthy regions; physiological quantification, such as perfusion or glucose metabolism; and absolute quantification, which was the main focus of this work, that is, the measurement of the true concentration of activity in a volume of interest [2]
Single Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET) produces images that represent the threedimensional distribution of radioactivity

Summary

Introduction

Technological innovation associated new radiopharmaceuticals developments contribute to recent diagnostic and therapeutic tools. Molecular imaging is based on the tracer principle, where a tiny amount of a radiopharmaceutical is introduced into the body to monitor the physiological function of the patient. Planar scintigraphy is used extensively in clinical practice because it offers the advantage of fast, large area acquisition at relatively low cost [4]. The limitation of this technique is the lack of information about the spatial distribution of radioactivity in the body. Single Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET) produces images that represent the threedimensional distribution of radioactivity. There are some factors to consider such as system sensitivity and resolution, dead time and attenuation, scatter and partial volume effects, voluntary and involuntary patient movement, kinetic differences, and radiopharmaceutical bladder filling [5]

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