ABSTRACT
Dwell location accuracy can be assessed by running the radioactive source into a catheter to a predetermined position. e dierence between the actual and intended source position quanties dwell location accuracy. Although there are many techniques that can be used to accomplish this test, the most direct will dene the intended position using the same x-ray markers used to identify potential source positions during the treatment planning process and the actual source positions using x-ray lm. For example, a typical approach would x a clear catheter to a piece of GafChromic EBT lm (International Specialty Products, Wayne, NJ), insert a strand of x-ray markers, and label with pen on the lm the location of three markers. A treatment run will then be initiated in which the HDR unit has been instructed to run the source out to the previously dened locations. By comparing the centers of the resulting exposure spots on the lm with the previously identied pen marks, an average dwell location error can be calculated (Figure 83.1).
