Optimized image acquisition parameters for imaging radioactive iodine-125 seed implantation for cancer treatment

Using nuclear medicine imaging, we explored suitable acquisition window parameters for assessing the distribution of iodine-125 radioactive seed implantation.

We studied 30 patients with various tumors (21 of which were liver cancers) who had received iodine-125 radioactive seed implantation and had undergone whole-body scintigraphy. Scintigraphy images were acquired at a magnification of 1.0 in a 1024×256 matrix and at a scan speed of 25cm/min. Energy peaks were set to 29keV or 35keV, and energy window widths were set to 20%, 50%, 70% and 100%, the image data were divided into eight groups. After image processing under the same conditions, the eight groups of whole-body scintigraphy images were assessed by three experienced nuclear medicine physicians. Two acceptable groups of images were selected from the eight groups of images for each patient. The regions of interest (ROI) of iodine-125, background and whole-body scintigraphy images were outlined to calculate the iodine-125 to background ratio of the radioactive counts and the iodine-125 to whole-body scintigraphy ratio of the radioactive counts.

Through subjective evaluation by three physicians, the percentages of acceptable images of groups 2, 3 and 7 were more than 50%, with group 2 showing the highest percentage. Furthermore, no statistical significant difference was found in the iodine-125 seed target/background ratio and iodine-125 seed target/whole-body scintigraphy ratio among the three groups (P>0.05).

The parameters to yield high-quality images of iodine-125 radioactive seed were chosen to be an energy peak of 29keV, an energy window width of 50% and a scan speed of 25cm/min.