Effect of electron contamination on in vivo dosimetry for lung block shielding during TBI

Our institution performs in vivo verification measurement for each of our total body irradiation (TBI) patients with optically stimulated luminescent dosimeters (OSLD). The lung block verification measurements were commonly higher than expected. The aim of this work is to understand this discrepancy...

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Bibliographic Details
Published in:Journal of applied clinical medical physics 2016-05, Vol.17 (3), p.486-491
Main Authors: Narayanasamy, Ganesh, Cruz, Wilbert, Saenz, Daniel L., Stathakis, Sotirios, Papanikolaou, Niko, Kirby, Neil
Format: Article
Language:English
Subjects:
Calibration
Dosimetry
electron contamination
Electrons
Equipment Contamination
Expected values
Geometry
Humans
In Vivo Dosimetry - methods
Lung - radiation effects
lung block
OSLD
Radiation Dosage
Radiation Measurements
Radiation Protection
Radiotherapy Planning, Computer-Assisted - methods
Radiotherapy, Intensity-Modulated - methods
Skin
TBI
Thermoluminescent Dosimetry
Whole-Body Irradiation
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Summary:Our institution performs in vivo verification measurement for each of our total body irradiation (TBI) patients with optically stimulated luminescent dosimeters (OSLD). The lung block verification measurements were commonly higher than expected. The aim of this work is to understand this discrepancy and improve the accuracy of these lung block verification measurements. Initially, the thickness of the lung block was increased to provide adequate lung sparing. Further tests revealed the increase was due to electron contamination dose emanating from the lung block. The thickness of the bolus material covering the OSLD behind the lung block was increased to offset the electron contamination. In addition, the distance from the lung block to the dosimeter was evaluated for its effect on the OSLD reading and found to be clinically insignificant over the range of variability in our clinic. The results show that the improved TBI treatment technique provides for better accuracy of measured dose in vivo and consistency of patient setup. PACS number(s): 87.53.Bn, 87.53.Kn, 87.55.N‐, 87.55.Qr
ISSN:1526-9914
1526-9914
DOI:10.1120/jacmp.v17i3.6128