Superimposed double parathyroid adenoma on Tc-99m MIBI imaging: the value of oblique images

Preoperative Dual-Phase Parathyroid Imaging With Tc-99m-Sestamibi

BACKGROUND

Previously, we have found that the additional use of a pinhole collimator in parathyroid scintigraphy resulted in a decrease in the number of incorrect side localizations and an increase in reproducibility compared with that of using a parallel-hole collimator alone.

PURPOSE

The aim was to investigate whether the addition of anterior oblique views to parathyroid scintigraphy (PS) with a pinhole collimator could further enhance the diagnostic ability and reproducibility. The level of preoperative parathyroid hormone (PTH) as a potential predictor of the usefulness of the supplementary views was also studied.

METHOD AND MATERIAL

Forty-seven patients with primary hyperparathyroidism (HPT) underwent dual-phase PS using a combined protocol with parallel-hole and pinhole collimators. The pinhole collimator was used in the anterior as well as right and left anterior oblique positions. Thyroid pertechnetate scans were undertaken in the same positions. Two observers assessed the images independently.

RESULTS

By adding oblique views, the gain in correct side localization occurred in all cases but one was seen in patients with rapid washout. The level of PTH could not predict these patients. The observer agreement on correct side localizations rose significantly from 81% to 94%.

CONCLUSION

The addition of oblique views to the imaging protocol using the pinhole collimator for parathyroid and thyroid scintigraphy in primary HPT results in an increase in observer agreement and the number of correct side localizations in patients with rapid washout of MIBI. The preoperative level of PTH cannot, however, predict these patients.

How to localize parathyroid tumors in primary hyperparathyroidism?

The management of primary hyperparathyroidism (PHPT) has dramatically changed in the last 5 yr. Many more patients now undergo focused, limited or minimally invasive parathyroidectomy instead of traditional bilateral neck exploration. This change has taken place because of the improved accuracy of pre-operative localizing studies in selecting patients who have single-gland parathyroid disease (single adenoma) and can therefore have a minimally invasive parathyroidectomy. Sestamibi scanning followed by ultrasound, magnetic resonance imaging (MRI) and computed tomography (CT) scans are most accurate for localizing parathyroid tumors in patients with PHPT. Selective venous catheterization for PTH levels is useful when other localizing studies are negative or discordant in patients with persistent or recurrent PHPT. The routine use of one or more localizing studies commonly identifies the parathyroid tumor in patients with single-gland disease; but if localizing studies are negative or discordant, patients should have intra-operative PTH levels monitored or have a bilateral neck exploration to ensure a high rate of biochemical cure.

Intraoperative parathyroid hormone measurement during minimally invasive parathyroidectomy: does it "value-add" to decision-making?

BACKGROUND

Routine use of intraoperative parathyroid hormone levels (IOPTH) during minimally invasive parathyroidectomy (MIP) has been challenged simply because the test works best when needed least, ie, once a solitary adenoma has been resected, and is less accurate with multiple gland disease. It has also been shown not to be cost-effective. The aim of this study was to determine if IOPTH "value-added" to decision-making during MIP.

STUDY DESIGN

The study group comprised 100 consecutive patients with sporadic hyperparathyroidism and an unequivocally positive sestamibi scan who were undergoing MIP in our unit from June 2004 until October 2005, from whom blood was collected for parathyroid hormone measurement preoperatively, preexcision, and at 10 and 30 minutes postremoval. No action was taken on the results of the test.

RESULTS

Ninety-eight patients were cured by MIP alone. Two patients had persistent hyperparathyroidism, one of whom was cured with subsequent open reexploration and removal of a second adenoma, and the other remains hypercalcemic despite additional open neck exploration. IOPTH in both patients failed to fall in retrospect, only the first would have been cured by conversion at the time of operation. The value-added accuracy of IOPTH was really only 1%. In an additional nine patients, IOPTH at 10 minutes had failed to fall by > 50% from the highest level, those patients (9%) would have been subjected to an unnecessary conversion on the basis of a false-negative result.

CONCLUSIONS

IOPTH does not substantially value-add to decision-making during MIP. Most patients will be cured with appropriate selection for MIP based on preoperative localization studies.