Author: Tianliang Gu 👨🔬
Affiliation: UT Health Science Center at Houston 🌍
Purpose:
In Nuclear Regulatory Commission guide 8.39 on releasing patients administered radioactive material, the dose is calculated assuming both the source and receiver are points. This point model should be a good approximation if the source and receiver are at a large distance. It may need some correction when the source and receiver distance is at the same range as the geometrical dimensions of the source or the receiver. The purpose of this study is to estimate the dose difference between non point and point models.
Methods:
We modeled the source as a solid cylinder where the radionuclide was evenly distributed. Most of the radiation on the receiver is along the surface close to the source. To simplify the calculation, we model that part of the receiver’s surface as a line and the longitudinal directions of source and receiver are parallel. The dose for the cylinder-line model is numerically calculated with an average adult height of 66 inches and waist circumference of 39 inches at various source to receiver distances.
Results:
When the surface to surface distance between two adults is 6 inches, the dose calculated using the non point model is about 40% of that calculated using a point model. For surface to surface distance at 3 feet, the dose from the non point model is about 80% to that from a point source. For long distance above 6 feet, the non point source model results are close to that of the point source model.
Conclusion:
When the source and receiver are at a close distance, the dose calculated using point model is lower than that from a point model. The method in the study is useful to estimate the dose in case the released patient may have a close contact with others.