Body outlining using Tc-99m filled flood source for lymphoscintigraphy imaging

  Introduction: In the current study, we evaluated the feasibility of body outlining using Tc-99m filled flood source for lymphoscintigraphy imaging. Methods: 80 patients were included in the study. Sentinel node mapping was done using Tc-99m Antimony sulfide colloid. For outlining the body a Tc-99m filled flood source was used which was placed behind or lateral to the patients for Anterior and lateral images respectively. The flood source was filled with 0.5 mCi, 1 mCi, 2 mCi, and 5 mCi for 10, 47, 10, and 3 patients respectively. The quality of outline images was assessed by two nuclear medicine specialists independently. Radiation exposure to the patients was also evaluated using thermoluminescent dosimeter (TLD-100).   Results: The quality of body contour images were good in images taken by 1, 2, and 5 mCi filled flood source. However the quality of images was poor in 8 out of 10 lymphoscintigraphies taken by 0.5 mCi filled flood source. The measured dose rate from the Tc-99m flood source was 1.07 ± 0.04 µSv/MBq/hr (39 ± 1.5 µSv/mCi/hr) or 3.25 µSv for 5 min acquisition times. Conclusion: Body outlining is feasible with Tc-99m filled flood source. To assure high quality, at least 1 mCi of Tc-99m pertechnetate should be used for filling the source. This technique can be very useful especially when Co-57 is not available or has decayed. The need to prepare the flood source for each patient and difficulty in handling the source especially for the lateral views are the major limitations.