Accuracy and definitive interpretation of preoperative technetium 99m sestamibi imaging based on the discipline of the reader

Highly specific preoperative selection of solitary parathyroid adenoma cases in primary hyperparathyroidism by quantitative image analysis of the early-phase Technetium-99m sestamibi scan

INTRODUCTION

Highly specific preoperative localizing test is required to select patients for minimally invasive parathyroidectomy (MIP) in lieu of traditional four-gland exploration. We hypothesized that Tc-99m sestamibi scan interpretation incorporating numerical measurements on the degree of asymmetrical activity from bilateral thyroid beds can be useful in localizing single adenoma for MIP.

METHODS

We devised a quantitative interpretation method for Tc-99m sestamibi scan based on the numerically graded asymmetrical activity on early phase. The numerical ratio value of each scan was obtained by dividing the number of counts from symmetrically drawn regions of interest (ROI) over bilateral thyroid beds. The final pathology and clinical outcome of 109 patients were used to perform receiver operating curve (ROC) analysis.

RESULTS

Receiver operating curve analysis revealed the area under the curve (AUC) was calculated to be 0.71 (P = 0.0032), validating this method as a diagnostic tool. The optimal cut-off point for the ratio value with maximal combined sensitivity and specificity was found with corresponding sensitivity of 67.9% (56.5-77.2%, 95% CI) and specificity of 75.0% (52.8-91.8%, 95% CI). An additional higher cut-off with higher specificity with minimal possible sacrifice on sensitivity was also selected, yielding sensitivity of 28.6% (18.8-38.6%, 95% CI) and specificity of 90.0% (69.6-98.8%, 95% CI).

CONCLUSIONS

Our results demonstrated that the more asymmetrical activity on the initial phase, the more successful it is to localize a single parathyroid adenoma on sestamibi scans. Using early-phase Tc-99m sestamibi scan only, we were able to select patients for minimally invasive parathyroidectomy with 90% specificity.

Outcomes for minimally invasive parathyroidectomy: widening inclusion criteria based on preoperative imaging results

BACKGROUND

Primary hyperparathyroidism is caused by a single adenoma in at least 80% of cases. Minimally invasive parathyroidectomy (MIP) has overtaken bilateral neck exploration as the gold standard for treatment in cases with adequate preoperative localization. There is evidence that, following careful review of preoperative imaging by the surgeon, increasing numbers of patients can successfully undergo MIP.

METHODS

We conducted a retrospective review of 225 consecutive cases performed by a single surgeon. Outcomes for patients with disease reported as localized by radiologists and nuclear medicine physicians using sestamibi and ultrasound were compared with patients with negative or indeterminate localization studies, in which the surgeon reviewed the sestamibi, performed an ultrasound study and identified likely single adenomas and planned MIP.

RESULTS

One hundred and sixty patients with radiologist-localized disease and an additional 29 patients with surgeon-localized disease underwent MIP. The surgeon-localized group had higher rates of conversion to bilateral neck exploration (21% compared with 4%, P = 0.004), but rates of failure to cure were comparable between the two groups (4.3% compared with 2.8%).

CONCLUSION

Careful review of preoperative sestamibi and ultrasound studies by an experienced surgeon can increase the number of patients that can successfully undergo MIP for the treatment of primary hyperparathyroidism. Offering MIP to these patients does not result in increased rates of failure or recurrence.

Improved localization of sestamibi imaging at high-volume centers

OBJECTIVES/HYPOTHESIS

Sestamibi imaging can provide critical information regarding the location of suspected parathyroid adenomas. However, this modality can be challenging to perform and interpret reliably. The impact of experience on the localizing efficacy of sestamibi scanning was assessed.

STUDY DESIGN

Prospective analysis of a consecutive series of patients undergoing parathyroidectomy was undertaken after institutional review board approval was obtained.

METHODS

Patients undergoing parathyroid surgery from October 2003 through June 2011 were considered. Inclusion criteria represented primary surgery for primary hyperparathyroidism, in which a single adenoma was excised and cure obtained. Sestamibi scan results, performed at our institution and at outside imaging centers, were compared to intraoperative findings.

RESULTS

There were 389 parathyroidectomies performed; 188 patients met inclusion criteria. Fifty-four patients had sestamibi scans performed at outside institutions; 36 (67%) were localizing and 18 (33%) were nonlocalizing. Among localizing studies, half identified the correct quadrant and half recognized the correct side. At our institution, 147 patients underwent sestamibi imaging; 121 (82%) localized and 26 (18%) did not. Among localizing studies, the correct quadrant was reported in 64% and the correct side in 36%. Of the 147 scans performed at our institution, 13 represented repeat scans of patients with nonlocalizing outside scans. All 13 of these localized; six identified the correct quadrant and seven the side of the adenoma.

CONCLUSIONS

A high volume of experience may improve the yield of sestamibi imaging. Repeating this study at a high-volume center when it was nonlocalizing elsewhere may provide useful additional information.

Technetium-99m sestamibi imaging: are the results dependent on the reviewer?

BACKGROUND

Minimally invasive parathyroidectomy (MIP) is dependent upon accurate preoperative parathyroid localization. We hypothesized that surgeon recognition of subtle differences in radiotracer accumulation would increase the sensitivity of technetium-99m sestamibi imaging and result in more frequent use of MIP.

METHODS

Technetium-99m sestamibi scans completed at our institution for patients who underwent resection of a solitary parathyroid adenoma were reviewed by a surgeon and a radiologist who were blinded to patient identifying information, prior scan interpretation, and results of the operation. For each scan, the reviewer determined whether there was abnormal radiotracer accumulation and documented its location. Results were correlated with outcome of operation and final pathology. Blinded interpretations of the surgeon and radiologist were compared to each other and to the original radiologic interpretation.

RESULTS

From 1994 to 2009, 274 patients with primary hyperparathyroidism (HPT) had sestamibi imaging prior to parathyroidectomy; 149 patients with a single adenoma underwent curative parathyroidectomy and had scans available for review. Seventeen radiologists who reviewed an average of 11 ± 14 scans (range = 1-61) completed the original interpretations of the sestamibi imaging. Sensitivity of sestamibi imaging was 86% for the blinded surgeon compared to 75% for the blinded radiologist and 69% for the original radiologists (P < 0.05). There was no difference in the false positive rates (blinded surgeon = 5%, blinded radiologist = 5%, original radiologists = 5%, P > 0.05).

CONCLUSION

Radiologists were less likely to call a scan positive. Surgeon recognition of subtle anatomic asymmetry increases the sensitivity of sestamibi imaging and successful completion of MIP.