The does rate at a distance of 120cm from the center of a brachytherapy source t

Question

The does rate at a distance of 120cm from the center of a brachytherapy source transport container is 2 mR/hr. The dose rate at a distance of 30cm from its center is _____ mR/hr A. 18 B. 28 C. 32 D. 64 E. 84 A batch of I-125 seeds is ordered so that the activity will be 0.48 mCi/seed on the day of the prostate implant. If the seeds arrive 5 days before the implant, the expected activity on receipt is _____mCi/seed. A. 0.45 B. 0.51 C. 0.55 D. 0.57 E. 0.59 An anisotropy correction is used in I-125 seed brachytherapy calculations to account for: A. Absorption in adjacent seeds. B. Decay of activity between the date of source calibration and the date of implantation. C. Reduction in average dose rate due to self absorption along the seed-axis. D. Conversion between different units of activity. Pd-103 is favored over I-125 for permanent breast implants because: A. The half-life is shorter B. The time taken to deliver 90% of the total dose is longer C. The initial dose rate is lower D. The initial activity is lower E. All of the above. An Ir-192 HDR unit has an activity of 8.6 Ci on May 2. The treatment time for a vaginal cylinder is 300 seconds. If the treatment time for a similar treatment is not to exceed 10 minutes, the source must be changed on: A. July 15 B. June 23 C. July 1 D. August 5

Explanation / Answer

Inverse Square Law is given by

I1D12=I2D22

plug the values

2x120x120=I2x30x30

C)) I2=32

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