Comparison between measurements of dose rate in the vicinity of a point source and a flat source of 3600 MBQ iodine-131

Introduction In nuclear medicine, whenever radiation calculations must be made in the vicinity of a source of iode131, is regularly asks the difference between point source and plane. Using two different detectors measurements were made. They show differences in the vicinity of sources. Materials and methods Two detectors were used: GM Nardeux type and type Victoreen ionization chamber with two radioactive sources iode131 of 3600 MBq. A point source of 1 ml in a bottle and a flat source in a phantom of 53 × 42 cm 2 . For each source and each detector measurements were performed for distances from 0.1 to 3 m. Results There was no significant difference between the two detectors. We observed that there are differences between the two types of sources for distances less than 1 m. For example at 25 cm 1500 mSv/ h for the source plane and 2200 mSv/h for the point source that is 50% more. Conclusion Less than 1 m there is a difference between a measurement in the vicinity of a point source and a flat source for the same radioactivity. From 1 m, and considering that this is the area of radiation protection, the values for the two types of sources are identical.