The dose penumbra of a custom‐made shield used in hemibody skin electron irradiation

Abstract

We report our technique for hemibody skin electron irradiation with a custom‐made plywood shield. The technique is similar to our clinical total skin electron irradiation (TSEI), performed with a six‐pair dual field (Stanford technique) at an extended source‐to‐skin distance (SSD) of 377 cm, with the addition of a plywood shield placed at 50 cm from the patient. The shield is made of three layers of standard 5/8” thick plywood (total thickness of 4.75 cm) that are clamped securely on an adjustable‐height stand. Gafchromic EBT3 films were used in assessing the shield's transmission factor and the extent of the dose penumbra region for two different shield‐phantom gaps. The shield transmission factor was found to be about 10%. The width of the penumbra (80%‐to‐20% dose falloff) was measured to be 12 cm for a 50 cm shield‐phantom gap, and reduced slightly to 10 cm for a 35 cm shield‐phantom gap. In vivo dosimetry of a real case confirmed the expected shielded area dose.PACS number(s): 87.53.Bn

Development and Evaluation of a Thimble-Like Head Bolus Shield for Hemi-Body Electron Beam Irradiation Technique

“…However, the HBI technique primarily uses photon beams with collimators because electron shielding is extremely complicated owing to the electron scattering effect and X-ray contamination [8]. Several studies have been conducted on hemi-body electron beam irradiation (HBIe -) using lead, aluminum, or plywood plates [9][10][11]; however, they all reported significantly wide penumbra at the shield boundary. Furthermore, a previous study on electron shielding has investigated the effect of surrounding the organs-atrisk with low-Z materials, such as wax bolus [12].…”