A COMPARISON OF 10 MHZ ULTRASOUND AND 201-THALLIUM 99M-TECHNETIUM SUBTRACTION SCANNING IN PRIMARY HYPERPARATHYROIDISM

Both high resolution (10 MHz) ultrasound and 201-thallium/99m-techneti um subtraction scanning (Tl/Tc) were carried out preoperatively in 25 patients with primary hyperparathyroidism. Operative findings were the standard against which these two imaging methodologies were compared. Tl/Tc scanning showed a sensitivity of 42% and a specificity of 97%. By comparison, sensitivity of ultrasound was 38% and specificity 89%. Both techniques were positive together in nine instances and correctly localized the parathyroid adenoma in eight of these. In 44% of cases, however, both methods together failed to localize any abnormal parath yroid tissue. The ability of these modalities to localize abnormal par athyroid tissue correctly tended to vary with gland size. Where both u ltrasound and Tl/Tc scans were negative, median gland size was smaller at 170 mg (range 50-2,500 mg), compared with where Tl/Tc scanning was correct (750 mg, 150-6,820 mg, P<0.03), ultrasound was correct (960 m g, 100-6,820 mg; P<0.03) and both techniques together were correct (98 0 mg, 600-6,820 mg; P = 0.002). These results suggest that neither Tl/ Tc scanning or ultrasound has sufficient sensitivity or specificity to be used routinely in the preoperative evaluation of patients with pri mary hyperparathyroidism.