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Radiation Treatment Management for Young and Pregnant Female Patients Using Photons From Gamma Knife Perfexion and Varian TrueBeam LINAC

E Kendall

E Kendall*, Y Chen , K Hibbitts , O Algan , L Muller , S Ahmad , University of Oklahoma Health Sciences Center, Oklahoma City, OK


SU-I-GPD-T-487 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: A young girl with brain arteriovenous malformation at the left temporal lobe was planned to be treated using photons from Gamma Knife Perfexion with a prescription dose of 23 Gy to the 50% isodose line; and a pregnant woman with intracranial ependymoma was planned also to be treated using 6 MV photons from Varian TrueBeam LINAC with a prescription dose of 54 Gy delivered in 30 fractions. The objective of this study is to determine the dose to ovaries of the girl and to the fetus (8-12 weeks gestation age) of the woman to ensure patient safety against radiation treatment.

Methods: A RANDO phantom was used to mimic patient body scatter for both cases. For Perfexion, six thermoluminescent dosimeters (TLDs) were placed inside the phantom, 70 cm away from the treatment isocenter. Measurements were made with a 10 minute beam-on time at a dose rate of 2.893 Gy/min to the isocenter. For TrueBeam, two treatment plans (a 3-arc and a 2-arc) delivering prescription dose were used for phantom irradiation. Five TLDs were placed inside the phantom for each plan. Doses to the umbilicus, mid-uterus, and symphysis were measured.

Results: The mean dose to the TLDs was 0.019 cGy (range 0.012-0.031 cGy) for the Perfexion phantom measurement. For the 3-arc phantom plan the umbilicus, mid-uterus, and symphysis doses were 0.2 cGy, 0.1 cGy, 0.1 cGy, respectively. The doses for 2-arc plans were less than 0.1 cGy. The midline doses for the umbilicus and mid-uterus for both plans were less than 0.3 and 0.2 cGy, respectively.

Conclusion: On the basis of the measured doses to the ovaries and fetus of the phantom, the decision was made to treat those two patients as planned.

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