Visualization of lower extremity lymphedema in the same cohort using 99mTc-human serum albumin and 99mTc-phytate lymphoscintigraphy with SPECT-CT.

Lymphoscintigraphy with single-photon emission computed tomography (SPECT-CT) is useful in diagnosing lymphedema. However, there are multiple timings, techniques, and tracers utilized worldwide without any comparison. We examined and compared the image clarity with two different radiotracers, 99mTc human serum albumin (HSA) and 99mTc phytate (phytate), in the same patients. The study retrospectivity examined 46 limbs of 36 patients who underwent lymphoscintigraphy using HSA and phytate from January 2013 to September 2018. Tracer accumulation in the lymph nodes, linear pattern (LP), and dermal backflow (DBF) were qualitatively analyzed; contrast-to-noise ratios (CNR) of DBF and standardized uptake value ratio (SUVR) of LP were also quantitatively analyzed. Neither lymph node accumulation nor DBF identification showed significant difference. However, a significant difference was observed between the LP identification of the unaffected (p<0.001) and affected sides (p<0.001). On quantitative evaluation, CNR and SUVR of LP was significantly higher with HSA than with phytate (p<0.001). SUVR of LP was also significantly higher with HSA than with phytate in both unaffected (p=0.002) and affected (p=0.005) sides. Overall, images acquired with HSA were clearer than that with phytate, and the identification of LP was particularly better with HSA than with phytate. Thus, lymphoscintigraphy using HSA is preferred over phytate for both diagnosis and evaluation of disease severity and surgical site selection.