Clinical value of early-phase 99mTc-MIBI SPECT in rapid washout parathyroid adenomas.

OBJECTIVE

Parathyroid adenomas with rapid tracer washout may be missed on delayed-phase technetium-99m-sestamibi (99mTc-MIBI) imaging, potentially leading to false-negative localization. This retrospective single-center study evaluated the clinical value of early-phase single photon emission computed tomography (SPECT) compared with delayed-phase SPECT in detecting rapid washout parathyroid adenomas, particularly in centers without access to SPECT/computed tomography (CT), and assessed whether this washout pattern could be predicted by biochemical parameters.

SUBJECTS AND

METHODS

Eighteen patients with surgically and histopathologically confirmed parathyroid adenomas who underwent dual-phase 99mTc-MIBI SPECT imaging were included. Early-phase and delayed-phase SPECT images were independently reviewed by two experienced nuclear medicine physicians. Lesion detection rates were compared using McNemar's test, interobserver agreement was assessed using Cohen's kappa coefficient, and preoperative biochemical parameters were compared between adenomas detected only on early-phase imaging and those visible on delayed-phase imaging.

RESULTS

Early-phase SPECT enabled detection of all surgically confirmed adenomas, whereas delayed-phase SPECT failed to identify 8 of 18 lesions (44%) due to rapid tracer washout, with a statistically significant difference between the two phases (P<0.01). No significant differences were observed in preoperative biochemical parameters between rapid washout and persistent uptake groups, indicating that early washout could not be reliably predicted clinically. Despite localization being achieved using SPECT without CT correlation, postoperative parathyroid hormone levels normalized in all patients, confirming surgical success. Interobserver agreement was excellent for both imaging phases (κ=1.00).

CONCLUSION

These findings indicate that early-phase 99mTc-MIBI SPECT significantly improves detection of rapid washout parathyroid adenomas and, as this pattern cannot be anticipated biochemically, its routine inclusion represents a simple and cost-effective strategy with direct relevance for routine clinical practice in centers without SPECT/CT.