Orlandi Ester, Zonca Giancarlo, Pignoli Emanuele, Stucchi Claudio, Borroni Marta, Collini Paola, Cantù Giulio, Casali Paolo G, Grosso Federica, Cerrotta Annamaria, Fallai Carlo, Olmi Patrizia
Department of Radiation Oncology I, Istituto Nazionale per lo Studio e la Cura dei Tumori, Milan, Italy.
Tumori. 2007 Jan-Feb;93(1):45-52. doi: 10.1177/030089160709300109.
In vivo and phantom dosimetry is reported to estimate the fetal dose and evaluate the effectiveness of a special shielding device to reduce fetal exposure in a woman undergoing postoperative radiation therapy for synovial oral cavity sarcoma at the 30th week of pregnancy.
In vivo measurements were performed by placing thermoluminescent dosimeters on 3 points for fetal dose estimation: uterine fundus, umbilicus and pubis. A Rando anthropomorphic phantom was used to simulate radiotherapy. We also performed off-axis dose measurements for wedged beams to estimate the dose contribution of this accessory used in the treatment.
The special shielding device reduced the fetal dose by 70% on average, despite the presence of wedges, which increased the dose by a factor of about 2.5. Before delivery the patient received 48 Gy, and from the in vivo measurements a fetal dose of 8.5, 1.7 and 0.7 cGy was estimated to the uterine fundus, umbilicus and pubis, respectively.
Pre-treatment simulation in the same irradiation conditions is the only reliable approach to predict the fetal dose. By using a special shielding device, radiotherapy can be optimized while keeping the fetal exposure below the risk of deterministic damage.
