Gamma camera calibrations for the Italian multicentre study for lesion dosimetry in 223Ra therapy of bone metastases.

Abstract

PURPOSE:

The aim was to calibrate gamma cameras in the framework of the Italian multicentre study for lesion dosimetry in 223Ra therapy of bone metastases. Equipments of several manufacturers and different models were used.

METHODS:

Eleven gamma cameras (3/8- and 5/8-inch crystal) were used, acquiring planar static images with double-peak (82 and 154keV, 20% wide) and MEGP collimator. The sensitivity was measured in air, varying source-detector distance and source size. Transmission curves were measured, calculating the parameters used for attenuation/scatter correction with the pseudo-extrapolation number method, and assessing their variations with the source size.

RESULTS:

Values of the calibration factor (geometric mean of both detector sensitivities) ranged from 41.1 to 113.9cps/MBq. For the smallest source (diameter of 3.5cm), the calibration factor decrease ranged from -30% to -4%, highlighting the importance of partial volume effects according to the equipment involved. The sensitivity variation with the source-detector distance, with respect to the 15cm-value, reached 10% (in absolute value) in the range 5-30cm, but fixing the distance between the two heads, the calibration factor variation with the distance from the midline was within 3.6%. Appreciable variation of the transmission curves with the source size were observed, examining the results obtained with six gamma cameras.

CONCLUSION:

Assessments of sensitivity and transmission curve variations with source size should be regularly implemented in calibration procedures. The results of this study represent a useful compendium to check the obtained calibrations for dosimetric purposes.

• Authors: Massimiliano Pacilio, Bartolomeo Cassano, Rosanna Pellegrini, Elisabetta Di Castro, Alessandra Zorz, Giuseppe De Vincentis, Guido Ventroni, Lucio Mango, Stefano Giancola, Mahila Ferrari, Marta Cremonesi, Claudia Bianchi, Giorgio Virotta, Claudia Carbonini, Patrizia Cesana, Cristian Fulcheri, Valentina Reggioli, Alessandra Ricci, Edoardo Trevisiol, Silvia Anglesio, Roberto Pani
• Journal: Physica medica : PM : an international journal devoted to the applications of physics to medicine and biology : official journal of the Italian Association of Biomedical Physics (AIFB) (Phys Med) Vol. 41 Pg. 117-123 (Sep 2017) ISSN: 1724-191X [Electronic] Italy
• PMID: 28457786 (Publication Type: Journal Article, Multicenter Study)
• Copyright: Copyright © 2017 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Topics

• Bone Neoplasms (radiotherapy)
• Calibration
• Gamma Cameras
• Humans
• Italy
• Radiometry (standards)