TL-201-CHLORIDE UPTAKE RATIOS IN DIFFERENTIATING BENIGN FROM MALIGNANT LESIONS - RECOMMENDATIONS FOR RATIO CALCULATIONS AND INTERPRETATION

Thallium-201 (Tl-201) chloride ratios have been used to differentiate benign from malignant lesions in bones and soft tissues, brain, breast , lungs and thyroid. Different values of these ratios have been report ed by various authors. The need to standardize the methods for calcula ting thallium ratios is discussed in this paper. The difference betwee n calculating the ratios using planar and single photon emission tomog raphy (SPET) images is presented in two patients who had metastatic bo ne lesions to the lower femoral condyle from non-Hodgkin's lymphoma an d to the iliac bone from breast carcinoma. In our experience, it is mo re reliable to calculate the thallium ratios from SPET images whenever possible.