Value of 123I-subtraction and single-photon emission computed tomography in addition to planar 99mTc-MIBI scintigraphy before parathyroid surgery

The purpose of this study was to find out if single-photon emission computed tomography (SPECT) and 123I-subtraction can enhance the findings of 99mTc-methoxyisobutylisonitrile (MIBI) scintigraphy for the preoperative localization of parathyroid (PT) tumors. Among the 111 consecutive patients who underwent preoperative planar 99mTc-MIBI scintigraphy for hyperparathyroidism (HPT), 64 underwent delayed SPECT, and 17 underwent 123I-subtraction. Two independent blinded experts scored the topographical localization, diagnostic confidence, and impact of each diagnostic modality on the surgical strategy. For adenomas, 99mTc-MIBI scintigraphy had a sensitivity of 77% with a positive predictive value (PPV) of 83%. SPECT did not affect the sensitivity or PPV, but it increased the diagnostic confidence and changed the surgical strategy in 21% of the patients. 123I-subtraction increased the sensitivity from 64% to 82%, but decreased the PPV from 88% to 82%. In hyperplastic glands, 99mTc-MIBI scintigraphy had a sensitivity of 47% and a PPV of 95%. When 99mTc-MIBI scintigraphy was combined with SPECT and 123I-subtraction, the results were 44%/10% and 52%/92%, respectively. Both SPECT and 123I-subtraction decreased the diagnostic confidence. Adding SPECT to 99mTc-MIBI scintigraphy improved the surgical decision for parathyroid adenomas. The addition of 123I-subtraction was of limited value. For hyperplastic glands, 99mTc-MIBI scintigraphy was relatively ineffective, even with the addition of SPECT or 123I-subtraction. (author)