Calculation of organ doses from breast cancer radiotherapy: a Monte Carlo study

Abstract

The current study aimed to: a) utilize Monte Carlo simulation methods for the assessment of radiation doses imparted to all organs at risk to develop secondary radiation induced cancer, for patients undergoing radiotherapy for breast cancer; and b) evaluate the effect of breast size on dose to organs outside the irradiation field. A simulated linear accelerator model was generated. The in‐field accuracy of the simulated photon beam properties was verified against percentage depth dose (PDD) and dose profile measurements on an actual water phantom. Off‐axis dose calculations were verified with thermoluminescent dosimetry (TLD) measurements on a humanoid physical phantom. An anthropomorphic mathematical phantom was used to simulate breast cancer radiotherapy with medial and lateral fields. The effect of breast size on the calculated organ dose was investigated. Local differences between measured and calculated PDDs and dose profiles did not exceed 2% for the points at depths beyond the depth of maximum dose and the plateau region of the profile, respectively. For the penumbral regions of the dose profiles, the distance to agreement (DTA) did not exceed 2 mm. The mean difference between calculated out‐of‐field doses and TLD measurements was 11.4%±5.9%. The calculated doses to peripheral organs ranged from 2.32 cGy up to 161.41 cGy depending on breast size and thus the field dimensions applied, as well as the proximity of the organs to the primary beam. An increase to the therapeutic field area by 50% to account for the large breast led to a mean organ dose elevation by up to 85.2% for lateral exposure. The contralateral breast dose ranged between 1.4% and 1.6% of the prescribed dose to the tumor. Breast size affects dose deposition substantially.PACS numbers: 87.10.rt, 87.56.bd, 87.53.Bn, 87.55.K‐, 87.55.ne, 87.56.jf, 87.56.J‐

Cancer risk estimates from radiation therapy for heterotopic ossification prophylaxis after total hip arthroplasty

“…A sufficient number of source electrons was used during radiation therapy simulations in order to ensure statistical errors below 7%. 12 The organ dose values corresponded to a typical adult patient undergoing hip irradiation. Possible deviations from these typical somatometric characteristics might result in unknown errors in the prediction of the organ dose.…”

“…12 The model consisted of the main beam modifying parts such as the bremstrahlung target, primary and secondary collimators, flattening filter and flattening filter holder. All structural shielding components of the head were also simulated by the model.…”

“…In-field and out-of-field radiation doses calculated by the Monte Carlo model were found to be in a very good agreement with direct dose measurements performed in a water tank (RFA-300, Scanditronix Wellhofer, Upasla, Sweden) and in a Rando anthropomorphic phantom (Alderson Research Labs, Stanford, CA), respectively. 12 An androgynous mathematical phantom was produced by a commercially available software package (Body Builder, White Rock Science, Los Alamos, New Mexico) and implemented into the Monte Carlo environment. The produced phantom was based on the descriptions obtained by Cristy and Eckerman report.…”

Evaluation of surface dose outside the treatment area for five breast cancer irradiation modalities using thermo-luminescent dosimeters

“…Several papers are published on the evaluation of peripheral and organ doses due to breast cancer radiotherapy; among those the in vivo and phantom measurements using thermo-luminescent dosimeters (TLDs), a computerized Monte Carlo (MC) technique using a mathematical phantom, and several commercial treatment planning software (TPS). [30][31][32][33] Their results vary from method to method, i.e., the peripheral dose difference between TPS and MC was reported up to 70%, 34 while the mean difference between MC out-of-field doses and TLD measurements was found 11.4% ± 5.9%. 30 The percent difference between the TPS and TLD measurement skin doses was found in the range from -15% to 44%.…”

“…[30][31][32][33] Their results vary from method to method, i.e., the peripheral dose difference between TPS and MC was reported up to 70%, 34 while the mean difference between MC out-of-field doses and TLD measurements was found 11.4% ± 5.9%. 30 The percent difference between the TPS and TLD measurement skin doses was found in the range from -15% to 44%. 35 The peripheral doses at 20cm away from the target area was found 2.52 cGy and 2.07 cGy using TLDs in LINAC and tomotherapy delivery correspondingly, for a planning target volume (PTV) dose of 200 cGy.…”