Whole-body lymphoscintigraphy using transmission scans

Objective: Our objective was to show the advantages of performing whole-body lymphoscintigraphy using transmission sources. This technique should decrease scanning time, help locate the sentinel lymph node, and decrease radiation exposure to the technologist. Methods: Twenty patients with proven melanoma received 18.5 MBq (0.5 mCi) filtered (0.22 μm) ^99mTc-sulfur colloid in a 0.2-mL volume, administered as multiple intradermal or subcutaneous injections around the known melanoma lesion or scar. All 20 patients underwent serial static imaging immediately after the injection, along with whole-body scanning after the static imaging. The static emission images were acquired for 5 min and the transmission images for 1 min using a 256 × 256 matrix. The whole-body transmission scans were acquired after the whole-body emission scans. The transmission scans were obtained with the same parameters as the emission scans, with the addition of placement of a ⁵⁷Co sheet source on one of the detectors of the large-field-of -view dual-head camera. The planar static axial images (transmission, emission) were compared with the whole-body images (transmission, emission) to determine whether the same number of lymph nodes was visualized with each technique. Posterior outlines were obtained through computer manipulation of anterior transmission images. Results: In all 20 patients, the number of lymph nodes seen on the static images was the same as that seen on the whole-body emission and transmission images. The whole-body emission and transmission scanning time was an average of 30 min less than the time required to acquire the serial static images. Conclusion: The anatomic location of the sentinel lymph node is seen more easily on whole-body images, both anterior transmission and posterior transmission, than on planar static images. Whole-body emission and transmission imaging decreased scanning time and thus improved patient comfort and throughput. Technologists received less radiation exposure when handling the ⁵⁷Co source only twice during whole-body imaging, as opposed to several times during static imaging.