(Sunday, 7/29/2018) 3:00 PM - 6:00 PM
Room: Exhibit Hall
Purpose: For Mycosis Fungoides treatment, due to the curvature of the patient’s body and self-shielding, certain regions of the body like the scalp, perineum and the soles of the feet do not get the adequate prescribed dose. This study investigates if there is a relationship between patient height and delivered dose to the scalp when using a modified Stanford technique.
Methods: Six Nanodots- OSLDs were placed at regular intervals around the crown of a head phantom and one OSLD at the vertex. Location of the OSLD placement was selected by locating the point of maximum dose on a radiochromic film strip that was placed over the scalp of the head phantom from left to right ear (See Fig.1). Measurements were made with the head phantom at heights of 160cm, 170cm and 180cm. The phantom was placed at our TSET treatment geometry at a SSD of 322cm, using acrylic spoiler, and dual fields at gantry angles of 72 and 108 degrees. High dose rate 9MeV electron beam was used to deliver 200cGy. Doses to the OSLD locations were read using a microSTARii (Landauer system, Glenwood, Il).
Results: The mean dose distribution around the crown of head decreases from 214.6cGy to 194.7cGy with increase in height, from 160cm to 180cm. Dose to the vertex decreased from 218cGy to 138.2cGy with the same increase in height. There was an increase in standard deviation and coefficient of variability with increasing height.
Conclusion: There is greater variation of dose distribution and a decrease in dose to the scalp with increase in height of the patient. There is a decrease of dose to the vertex with increases in height. In certain cases a boost to the scalp/ vertex may not be necessary depending on the height of the patient.
Keywords
Electron Therapy, Dose Uniformity, Surface Dose
Taxonomy
TH- External beam- electrons: dose measurement
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