In vivo dosimetry for single-fraction targeted intraoperative radiotherapy (TARGIT) for breast cancer.
OBJECTIVE
In vivo dosimetry provides an independent check of delivered dose and gives confidence in the introduction or consistency of radiotherapy techniques. Single-fraction intraoperative radiotherapy of the breast can be performed with the Intrabeam compact, mobile 50 kV x-ray source (Carl Zeiss Surgical, Oberkochen, Germany). Thermoluminescent dosimeters (TLDs) can be used to estimate skin doses during these treatments.


METHODS
Measurements of skin doses were taken using TLDs for 72 patients over 3 years of clinical treatments. Phantom studies were also undertaken to assess the uncertainties resulting from changes in beam quality and backscatter conditions in vivo.


RESULTS
The mean measured skin dose was 2.9 ± 1.6 Gy, with 11% of readings higher than the prescription dose of 6 Gy, but none of these patients showed increased complications. Uncertainties due to beam hardening and backscatter reduction were small compared with overall accuracy.


CONCLUSIONS
TLDs are a useful and effective method to measure in vivo skin doses in intraoperative radiotherapy and are recommended for the initial validation or any modification to the delivery of this technique. They are also an effective tool to show consistent and safe delivery on a more frequent basis or to determine doses to other critical structures as required.
Department of Radiotherapy Physics, Royal Free Hospital, University College London, London, United Kingdom. davideaton@nhs.net
David J
DJ
Eaton
Bronagh
B
Best
Chris
C
Brew-Graves
Stephen
S
Duck
Tabasom
T
Ghaus
Regina
R
Gonzalez
Katharine
K
Pigott
Claire
C
Reynolds
Norman R
NR
Williams
Mohammed R S
MR
Keshtgar
D001943:Breast Neoplasms / Q000532:radiotherapy* / Q000601:surgery; D005260:Female; D006801:Humans; D007430:Intraoperative Care / Q000379:methods; D019047:Phantoms, Imaging; D011879:Radiotherapy Dosage; D012867:Skin / Q000528:radiation effects*; D013819:Thermoluminescent Dosimetry / Q000295:instrumentation / Q000379:methods*