The Monte Carlo method was used to study perturbations of single I-125 seed dose distributions created by the presence of one or three neighboring seeds for the case of seeds immersed in a water phantom. Perturbation factors were determined within the geometric shadow of neighboring seeds for two-seed designs, four-seed spacings, and several choices of dose point. The results were compared to dose estimates obtained by the simple superposition of single-seed data for one- and two-plane implants. Some significant differences were found.
Quantitative conjugate-view external counting techniques were applied to estimate the radiation dose to the liver, spleen, and metaphyseal growth complexes (distal femur and proximal tibia) for ten pediatric patients undergoing gallium-67 scanning procedures. The effective half-life of Ga 67 in these organs was approximately 78 hours. The dose per unit of administered activity for the liver and spleen was between 0.3 and 4.0 rad/mCi (0.08 to 1.08 Gy/GBq) and 0.5 and 7.0 rad/mCi (0.13 to 1.89 Gy/GBq), respectively. For the metaphyseal growth plates, the range was 2.3 to 14.3 rad/mCi (0.62 to 3.86 Gy/GBq).
Many of the newer X‐ray machines are equipped with electronic means to provide dose–area product (DAP) information. For machines without that ability, an alternative method is to record radiation on a film that can handle a large amount of cumulative exposure. The use of GafChromic XR Type R film was investigated for this purpose by placing it at the X‐ray tube assembly to record the radiation in interventional radiological procedures. Dose‐area product was determined with a reflective densitometer and then with a flatbed scanner. Precisions were demonstrated to be 5% and 2%, respectively. In a comparison with the machine‐recorded DAP, a regression analysis showed the validity of both techniques for values less than 1200 Gy‐cm2.PACS numbers: 87.52.Df, 87.66.Cd
The Monte Carlo method was used to investigate the dose distribution around a 3M Company model 6711 125I seed immersed in a water phantom. Dose rate per unit activity data are presented as a matrix of 63 points surrounding the seed. Relative dose data are presented graphically for two mutually perpendicular directions and compared with the corresponding data for the only other 125I seed currently available, the 3M Company model 6702 125I seed. The 6711 relative dose distribution decreases more rapidly with distance from the seed than does the 6702 relative dose distribution. Uncertainties in the 6711 seed dose distribution produced by end-weld thickness variations were investigated and found to be substantial at certain points.
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