Fusion SPECT/CT boosts detection of parathyroid adenomas

The diagnostic shortcomings of technetium-99m-sestamibi SPECT and multislice CT for the detection of parathyroid adenomas largely disappears when images from the two modalities are combined using postacquisition fusion software.

Dr. Peter Kovacs, a radiology researcher at the Medical University of Innsbruck in Austria, found that the fusion technique substantially improves sensitivity and specificity for identifying either typical or ectopic parathyroid adenomas. Results from 43 patients examined with four- or 16-slice CT and dual-head Tc-99m-MIBI SPECT were compared with surgical findings.

Postprocedural image fusion was performed on a Medtronics Treon system and Cranial 4 software.

For adenomas found in the typical position for the presentation of such disease, images merged by postprocessing fusion generated sensitivity and specificity rates of 82% and 93%, respectively, compared with 71% sensitivity and 67% specificity for SPECT alone and 76% sensitivity and 96% specificity for CT alone. When the results of the separate SPECT and CT findings concurred, 100% sensitivity and 100% specificity were reported for the fused images.

Ectopic parathyroid adenoma is inherently harder to find than typical parathyroid disease because of lesion migration. However, fusion again outperformed SPECT and CT alone for the diagnosis of the ectopic form of this cancer. The sensitivity and specificity of fusion SPECT/CT were 69% and 80%, respectively, compared with 41% sensitivity and specificity for SPECT alone and 59% sensitivity and 91% specificity for CT alone.

Again, the accuracy rates were highest when the individual findings from SPECT and CT concurred.

The takeaway lesson from this study is not that SPECT/CT should set a new standard for diagnostic accuracy in parathyroid cancer, Kovacs said, but that fusion software combining the imaging results from the two modalities should be preferred, at least in this limited setting.