Dosimetric verification of helical tomotherapy for total scalp irradiation

Journal Article · Sat Nov 15 04:00:00 EST 2008 · Medical Physics

DOI:https://doi.org/10.1118/1.2996288· OSTI ID:22095255

Hardcastle, Nicholas; Soisson, Emilie; Metcalfe, Peter; Rosenfeld, Anatoly B.; Tome, Wolfgang A. ^[1]

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1. Departments of Human Oncology and Medical Physics, University of Wisconsin, Madison, Wisconsin 53792 and Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW (Australia)

Total scalp irradiation is a treatment technique used for a variety of superficial malignancies. Helical tomotherapy is an effective technique used for total scalp irradiation. Recent published work has shown the TomoTherapy planning system to overestimate the superficial dose. In this study, the superficial doses for a helical tomotherapy total scalp irradiation have been measured on an anthropomorphic phantom using radiochromic and radiographic film as well as a new skin dosimeter, the MOSkin. The superficial dose was found to be accurately calculated by the TomoTherapy planning system. This is in contrast to recent reports, probably due to a combination of the smaller dose grid resolution used in planning and this particular treatment primarily consisting of beamlets tangential to the scalp. The superficial dose was found to increase from 33.6 to 41.2 Gy and 36.0 to 42.0 Gy over the first 2 mm depth in the phantom in selected regions of the PTV, measured with radiochromic film. The prescription dose was 40 Gy. The superficial dose was at the prescription dose or higher in some regions due to the bolus effect of the thermoplastic head mask and the head rest used to aid treatment setup. It is suggested that to achieve the prescription dose at the surface ({<=}2 mm depth) bolus or a custom thermoplastic helmet is used.

• OSTI ID: 22095255
• Journal Information: Medical Physics, Journal Name: Medical Physics Journal Issue: 11 Vol. 35; ISSN 0094-2405; ISSN MPHYA6
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
COMPUTERIZED TOMOGRAPHY
CT-GUIDED RADIOTHERAPY
DOSEMETERS
EXTERNAL IRRADIATION
HEAD
NEOPLASMS
PHANTOMS
PLANNING
RADIATION DOSES
SKIN
THERMOPLASTICS
VERIFICATION