The diagnostic utility of dual phase Tc-99m sestamibi parathyroid imaging

Interpretation of 99mTc sestamibi parathyroid SPECT scan is improved when read by the surgeon and nuclear medicine physician together

OBJECTIVE

Parathyroid gland localization and lateralization are important before surgery, particularly for minimally invasive parathyroidectomy (MIP) and recurrent hyperparathyroidism. We hypothesized that readings of Tc sestamibi scans with single photon emission computed tomography (SPECT) by a surgeon and nuclear medicine physician together (NMP+S) compared to a nuclear medicine physician alone (NMP alone) might affect scan interpretation accuracy.

METHODS

Between May 1999 and December 2002, 127 hyperparathyroid patients had preoperative localization with sestamibi SPECT. Scans were prospectively interpreted by an endocrine surgeon and nuclear medicine physician attending together (NMP+S) and a nuclear medicine physician attending alone (NMP alone). These readings were compared to intra-operative findings, which served as the 'gold standard'.

RESULTS

There were 120 patients with primary hyperparathyroidism (55 underwent MIP) and seven with secondary or tertiary hyperparathyroidism; seven patients had recurrent hyperparathyroidism. Of 127 patients, 83 had single adenomas; 27, double adenomas; 15, hyperplasia; one, MENIIA; and one, parathyroid cancer. Sensitivity and positive predictive values were 58.6% and 67.4% for NMP alone compared to 81.9% and 70.0% for NMP+S. The overall accuracy of correct localization was 45.7% vs. 60.6% (P<0.01) and of correct lateralization was 69.3% vs. 80.3% (P<0.01) for NMP alone versus NMP+S respectively. The most common finding interpreted incorrectly by NMP alone and correctly by NMP+S was an ectopic superior parathyroid adenoma in the inferior position. Ninety-eight per cent of patients were cured of their hyperparathyroidism.

CONCLUSIONS

Parathyroid sestamibi SPECT scan interpretation by an endocrine surgeon reading with a nuclear medicine attending resulted in improved accuracy of gland localization and lateralization compared to a nuclear medicine attending reading alone. This improvement may be due to increased awareness of clinical factors and head-and-neck anatomy.

A systematic review of the diagnosis and treatment of primary hyperparathyroidism from 1995 to 2003

OBJECTIVE

To systematically review the current preoperative diagnostic modalities, surgical treatments, and glandular pathologies associated with primary hyperparathyroidism.

STUDY DESIGN

A systematic literature review.

RESULTS

Of the 20,225 cases of primary hyperparathyroidism reported, solitary adenomas (SA), multiple gland hyperplasia disease (MGHD), double adenomas (DA), and parathyroid carcinomas (CAR) occurred in 88.90%, 5.74%, 4.14%, and 0.74% of cases respectively. Tc 99m -sestamibi and ultrasound were 88.44% and 78.55% sensitive, respectively, for SA, 44.46% and 34.86% for MGHD, and 29.95% and 16.20% for DA, respectively. Postoperative normocalcemia was achieved in 96.66%, 95.25%, and 97.69% of patients offered minimally invasive radio-guided parathyroidectomy (MIRP), unilateral, and bilateral neck exploration (BNE). Intraoperative PTH assays (IOPTH) were helpful in approximately 60% of bilateral neck exploration conversion (BNEC) surgeries.

CONCLUSION

The overall prevalence of multiple gland disease (MGD and DA) was lower than often suggested by conventional wisdom. Furthermore, preoperative imaging was less accurate than it is often perceived for accurately imaging MGD. MIRP and UNE were more successful in achieving normocalcemia than is typically quoted. IOPTH was a helpful but not "fool-proof" adjunct in parathyroid exploration surgery.

SIGNIFICANCE

These results support a greater role for the treatment of primary hyperparathyroidism using less invasive approaches. EMB rating: B-3.

Increased sensitivity and confidence of SPECT over planar imaging in dual-phase sestamibi for parathyroid adenoma detection

PURPOSE OF REPORT: To determine the usefulness of SPECT imaging over planar imaging for the detection of parathyroid adenomas using dual-phase Tc-99m sestamibi.

MATERIALS AND METHODS

The records of patients referred for dual-phase sestamibi scintigraphy for detection of parathyroid adenomas were reviewed retrospectively. The images were reviewed blindly and planar images were compared with SPECT. The imaging results were compared with the operative results to determine the sensitivity, accuracy of localization, and confidence of the reporting radiologist.

RESULTS

The records of 37 patients were reviewed. Sensitivity was 62% for planar imaging and 73% for SPECT. There was one false positive. The side of the adenoma was correctly identified in all other patients. Confidence of detection was higher for SPECT than for planar imaging.

CONCLUSION

SPECT imaging increased the sensitivity and confidence of the detection of parathyroid adenomas. The results indicate that SPECT should be used for all preoperative parathyroid localization.

Management of primary hyperthyroidism: toward minimal access surgery

Fifteen years ago, bilateral exploration of the neck was dogma in parathyroid surgery. Now, less invasive procedures can be used to target lesions identified by new tests such as dual-phase Sestamibi scanning or intraoperative documentation of parathyroid hormone (PTH) level changes after removal of a parathyroid gland. A hand-held gamma probe can be used for intraoperative detection of high-uptake lesions, and video-assisted endoscopic surgery has been used successfully. With these new techniques, surgical exploration can be confined to one side of the neck through smaller incisions associated with better cosmetic results. The operating time is reduced, and in some cases the procedure can be done under local anesthesia. The objective of this article is to describe recent changes in the management of parathyroid adenoma requiring surgery.

Preoperative evaluation of parathyroid lesions in patients with concomitant thyroid disease: role of high resolution ultrasonography and dual phase technetium 99m sestamibi scintigraphy

The aim of this study was to evaluate the sensitivity and usefulness of high resolution ultrasonography (US) and dual phase technetium-99m sestamibi (Tc-MIBI) scintigraphy in the preoperative localization of parathyroid lesions in patients with or without thyroid disease and to define the impact of the presence of thyroid disease on these methods. Preoperative US and scintigraphy were performed on 52 patients with primary hyperparathyroidism. Age, gender, preoperative parathyroid hormone level, serum calcium level, serum phosphate level, diameter, location, associated with thyroid abnormality, and results of parathyroid exploration were determined in all patients. The results of US and Tc-MIBI imaging were analyzed and compared with surgical and histopathologic findings. At surgery, 56 parathyroid lesions were found in 52 patients (9 men, 43 women), the parathyroid lesion was solitary (47 adenomas, two hyperplasias), in 2 patients double adenomas were present, in 1 patient three glands was affected by hyperplasia. Twenty-seven patients had concomitant thyroid disease. The overall sensitivity of US and Tc-MIBI scintigraphy was 84% and 73%, respectively. In patients without thyroid disease, the sensitivity of these techniques was 90% and 75%, respectively. In patients with thyroid disease, the sensitivity was 78% and 70%, respectively. In patients with thyroid disease, the combined sensitivity of these techniques was 89%. These results allow the conclusion that, in experienced hands, US is a highly sensitive technique. Especially in patients with no thyroid pathology and typical located gland, US alone should be used as a first step for preoperative localization of parathyroid lesions. When negative, Tc-MIBI scintigraphy is suggested. In patients with concomitant thyroid disease, the combination of US and Tc-MIBI scintigraphy represents a reliable localization technique.

Enhanced Scintigraphic Protocol Required for Optimal Preoperative Localization Before Targeted Minimally Invasive Parathyroidectomy

At our tertiary care institution, a targeted minimally invasive parathyroidectomy (MIP) is the preferred surgical procedure for primary hyperparathyroidism. Similar to unilateral neck exploration (UNE), preoperative scintigraphic localization of the adenoma in relation to the midline is required. However, in contrast to the abbreviated standard incision for UNE, 2 distinct incision sites, 1 medial and 1 lateral, are available on each side with MIP. The incision site is ultimately chosen based on scintigraphic determination of the adenoma's vascular origin to facilitate ligation and removal. Unfortunately, the scintigraphic location of a parathyroid adenoma does not necessarily reflect the site of its vascular origin. We reviewed our database to identify factors that accurately predict the site of vascular origin of parathyroid adenomas. A retrospective chart review was performed on 125 patients who underwent Tc-99m sestamibi scintigraphy and parathyroidectomy. Scintigraphic localization, surgical findings, and histopathology were recorded. Preoperative image interpretations that were discordant with operative findings were independently reviewed. Scintigraphy identified the presence of an adenoma in 105 of 118 patients (89%) with primary hyperparathyroidism. In 17 of the 105 cases (16%), the scintigraphic interpretation did not accurately reflect the site of superior or inferior vascular origin seen at surgery. In many discordant cases, anterior images were insufficient for determining the vascular origin. The posterior displacement of an adenoma in relation to the thyroid on early lateral images was often critical in determining the superior or inferior vascular origin. Scintigraphic determination of the superior or inferior vascular origin of a parathyroid adenoma directs incision placement for MIP. Imaging protocols should include early lateral images when localizing parathyroid adenomas before minimally invasive parathyroidectomy.

Experienced Scintigraphers Contribute to Success of Minimally Invasive Parathyroidectomy by Skilled Endocrine Surgeons

Minimally invasive parathyroidectomy (MIP) has become the preferred surgical treatment for selected patients diagnosed with primary hyperparathyroidism (PHPT) at our tertiary-care center. Preoperative scintigraphy establishes the position of a parathyroid adenoma, dictates the incision site, and can minimize incision size and consequent tissue dissection. We reviewed our database and sought to identify factors that led to discordant preoperative imaging and operative findings and to assess the effect of experience on these findings. A retrospective review was performed on all patients with biochemically proven PHPT who underwent Tc-99m sestamibi scintigraphy and surgical intervention. Patient demographics, date of surgical intervention, scintigraphic localization, surgical findings, pre- and postoperative biochemical markers, histopathology, coexisting thyroid pathology, and 6-month follow up were recorded. Preoperative images that were discordant with operative findings were independently reviewed. Parathyroid scintigraphy was performed on 125 consecutive patients for PHPT between November 1999 and January 2002. Seventy-six patients had MIPs, 35 had standard cervical explorations, 11 had MIPs that were converted to standard cervical explorations, and three had surgery directed to an ectopic location. At 6-month follow-up 98.4 per cent were cured. Preoperative imaging and surgical findings were ipsilateral and concordant in 105 of 118 (89%) patients with parathyroid adenoma. The anatomic origin of an adenoma was predicted in only 83 of 118 (68%) patients. Most of the inaccurate scintigraphy readings occurred during the first 13 of the 26 months that MIPs were performed at our institution. Only two discordant cases occurred during the last 9 months of this period. Biochemical markers, prior neck operation, and concomitant thyroid pathology had no correlation with imaging sensitivity. Scintigraphic interpretation of smaller adenomas was less reliable; discordant cases were more common in small adenomas. Communication between endocrine surgeons and nuclear medicine physicians about the MIP technique and anatomic orientation of adenomas led to better scintigraphic localization as experience increased. Now that MIP by skilled endocrine surgeons is becoming the favored treatment for PHPT experienced nuclear medicine physicians may be the most important factor to achieve maximum success.

Preoperative parathyroid localization: correlating false-negative technetium 99m sestamibi scans with parathyroid disease

OBJECTIVE/HYPOTHESIS

The recent trend toward minimally invasive directed parathyroid surgery has increased the surgeon's reliance on preoperative parathyroid localization. Technetium Tc 99m sestamibi scanning is generally viewed as the gold standard for preoperative localization, with reported sensitivities of 75% to 100% and specificities of 75% to 90%. However, in each reported series there exists a group of patients in whom preoperative localization is either equivocal or negative.

STUDY DESIGN

We focused on a subset of patients from our parathyroid database with false-negative sestamibi (MIBI) scans, in an attempt to elucidate features that could affect these studies. We identified 20 patients with negative preoperative scans and confirmed parathyroid disease. We compared them with 22 consecutive patients with positive scans, correlating the following variables: patient age, gender, concomitant thyroid disease (Hashimoto's thyroiditis, papillary thyroid carcinoma, thyroid adenoma), preoperative parathyroid hormone values, location and number of enlarged parathyroid glands, parathyroid weight, and the relative proportion of chief cells, clear cells, oxyphil cells, and adipose tissue.

METHODS

Retrospective chart review of clinicopathological and radiological findings.

RESULTS

We found that patients with false-negative scans were more likely to have an enlarged parathyroid containing a high proportion of clear cells (P =.01). A trend was seen (P =.1) correlating increased parathyroid fat content and false-negative scans. Conversely, positive preoperative scans were more likely to be associated with a higher percentage of oxyphil cells (P =.02). Univariate analysis for other variables, as well as logistic regression analysis, did not achieve statistical significance.

CONCLUSIONS

To date, the present study is the largest clinicopathological review of patients with false-negative sestamibi scans. Technetium Tc 99m uptake correlates with parathyroid oxyphil cell content, and false-negative scans can occur with parathyroid glands containing predominantly clear cells.

Presurgical localization of abnormal parathyroid glands using a single injection of Tc-99m sestamibi: comparison of high-resolution parallel-hole and pinhole collimators, and interobserver and intraobserver variation

PURPOSE

Scintigraphy using Tc-99m sestamibi is sensitive in localizing abnormal parathyroid glands in patients with hyperparathyroid disease (HPT). Various methods have been described to increase the sensitivity of the single-tracer technique, such as SPECT, factor analysis of dynamic structures, and use of a pinhole collimator, but often the gain in sensitivity is accompanied by a loss of specificity.

PURPOSE

In this study, the authors compared the sensitivity and specificity of side localization of the diseased gland(s) using the double-phase single-tracer method performed with and without the addition of a pinhole collimator in the early and late phases of imaging. The combined high-resolution parallel-hole and pinhole collimator imaging protocol was further validated by investigation of interobserver and intraobserver variation.

MATERIALS AND METHODS

Forty-seven patients with primary HPT and 16 patients with secondary HPT examined from 1996 to 1999 with the Tc-99m sestamibi double-phase technique and who had subsequent surgery formed the basis of the study. Their histologic and follow-up data were also factored into this analysis. Tc-99m sestamibi (750 to 900 MBq; 18.9 to 24.3 mCi) was injected. Ten-minute neck and mediastinum images acquiring 1,000 K counts were obtained with the high-resolution parallel-hole collimator, and a neck image containing 500 K counts was obtained with the pinhole collimator. Two to three hours later, the same parallel-hole and pinhole collimator images were obtained that had the same acquisition time as the early images. Two observers who were nuclear medicine specialists independently viewed all the parallel-hole scintigrams and afterward all parallel-hole and pinhole scintigrams two times.

RESULTS

Thirty-eight (81%) of the patients with primary HPT had a single adenoma. The sensitivity and specificity for the correct side of localization were 54% and 89%, respectively, using the high-resolution parallel-hole collimator, and 88% and 77%, respectively, with the addition of the pinhole collimator in all patients with primary HPT. In patients with secondary HPT, the sensitivity and specificity for localization of the correct side were 58% and 100%, respectively, using the high-resolution parallel-hole collimator, and 85% and 100%, respectively, with the addition of the pinhole collimator. The interobserver agreement was acceptable, with an overall agreement of 84% and a kappa value of 0.67. The intraobserver agreement was even better, with an overall agreement of 88% and 90% and kappa values of 0.76 and 0.79 for the two observers.

CONCLUSIONS

Sensitivity is increased considerably when the pinhole collimator is added to the imaging protocol of parathyroid scintigraphy in patients with primary or secondary HPT. A loss of specificity occurred only in patients with primary HPT. The precision of the combined approach is very high.

Optimal pinhole techniques for preoperative localization with Tc-99m MIBI for primary hyperparathyroidism

PURPOSE

Technetium-99m-labeled 2-methoxyisobutylisonitrile (Tc-99m MIBI) has been used extensively to localize parathyroid adenomas before operation. Imaging techniques vary widely, and the aim of this study was to determine the optimal time of delayed imaging and the value of routine correlative pertechnetate thyroid imaging.

MATERIALS AND METHODS

In this study, preoperative parathyroid localization was performed using pinhole anterior and oblique images (15 minutes and 2 and 4 hours after injection) with correlative pertechnetate thyroid images. Ninety-seven patients underwent dual- or triple-phase Tc-99m MIBI imaging and correlative pertechnetate thyroid imaging before surgery. Two nuclear medicine physicians blinded to the surgical findings interpreted all available images and various Tc-99m MIBI image combinations at 15 minutes alone; 15 minutes and 2 hours, 15 minutes and 4 hours; and 15 minutes and 2 and 4 hours each with and without correlative pertechnetate thyroid imaging.

RESULTS

Ninety parathyroid adenomas were detected in 86 patients. The optimal results were achieved with 15-minute and 2- and 4-hour Tc-99m-MIBI images, with correlative thyroid scans resulting in a sensitivity rate of 88%. Fifteen-minute and 2-hour Tc-99m-MIBI images and correlative thyroid scans and 15-minute and 4-hour Tc-99m MIBI images and correlative thyroid scans produced similar results (sensitivity rate, 86% and 83%, respectively; P = not significant). Compared with all Tc-99m MIBI image combinations alone, the addition of the routine correlative thyroid scan significantly improved sensitivity and also improved reporter confidence in 45% of studies.

CONCLUSIONS

Of the pinhole techniques compared, 15-minute and 2-hour Tc-99m MIBI images with correlative thyroid scanning may be the preferred imaging protocol, because this yields results similar to imaging for as long as 4 hours after injection in a shorter, more logistically acceptable imaging time.

An Analysis of Sestamibi-Positive versus -Negative Patients with Primary Hyperparathyroidism

We performed this study to evaluate two patient groups with primary hyperparathyroidism depending on whether their abnormal gland(s) could be preoperatively imaged with sestamibi. Patients with primary hyperparathyroidism evaluated by preoperative sestamibi examination from January 1999 to June 2000 were divided into two groups depending on the ability of sestamibi to localize their disease. Records were reviewed to determine pre- and postoperative biochemical data, weight of the excised glands, and total operating room time. When the sestamibi imaging was positive a minimally invasive parathyroidectomy was performed; however, when sestamibi scanning was negative patients underwent a formal bilateral neck exploration. All 40 patients in the sestamibi-positive group and 17 of 18 patients in the sestamibi-negative group were cured of their primary hyperparathyroidism as a result of surgery. Sestamibi scanning with a minimally invasive parathyroidectomy shortens operating room time and is most effective when adenomas are large. The results of this study suggest that strategies to preoperatively increase the activity of adenomas may improve the sensitivity of sestamibi scan localization of parathyroid adenomas.

Dual phase 99m-technetium Sestamibi imaging with single photon emission computed tomography in primary hyperparathyroidism: influence on surgery

The purposes of this study were to determine the positive and negative predictive values of 99m Technetium (99mTc) Sestamibi dual phase imaging with single photon emission computed tomography (SPECT) for parathyroid adenomata or hyperplasia and the effect of preoperative localization on duration of surgery. We reviewed 33 adults (14 men, 19 women; mean age 53 years) with newly diagnosed primary hyperparathyroidism who underwent neck exploration. The duration of surgery for this cohort was compared with a group of historical controls (n = 53) who underwent surgery without preoperative SPECT. At surgery, there were 21 adenomata (including one carcinoma), 10 patients with hyperplasia and two with no pathology detected. The positive predictive values (PPV) for adenomata and hyperplasia were 95% and 100%, respectively. The negative predictive values (NPV) for these entities were 67% and 22%, respectively. The mean weight of adenomata detected was 3.4 g (range 0.2-17 g). Mean duration of surgery was 112.6 min as compared with 113 min in the historical controls (P = not significant). We conclude that 99mTc Sestamibi dual phase imaging with SPECT has an excellent PPV for parathyroid adenomata and hyperplasia, but does not contribute to reduced duration of surgery in patients undergoing neck exploration for the first time. The NPV is low, suggesting that a negative result does not exclude an adenoma or hyperplasia.

Efficacy of preoperative dual-phase sestamibi scanning in hyperparathyroidism

PURPOSE

The objective of this article is to evaluate our experience with sestamibi scanning in patients with primary and secondary hyperparathyroidism.

PATIENTS AND METHODS

A retrospective review of patients referred to the radiology department at the University of Kansas Medical Center for parathyroid studies between January 1, 1993, and August 1, 1998, was done. Patients included in the study were those who underwent both dual-phase technetium (Tc-99m) sestamibi scanning and subsequent parathyroidectomy at our institution (n = 34). Twenty-six patients had primary hyperparathyroidism and 8 patients had secondary hyperparathyroidism. Fifteen had previous history of neck exploration.

RESULTS

Sensitivity of sestamibi scans in detection of all abnormal pathology in cases of primary hyperparathyroidism was 60% overall. Among the subset of adenoma cases, sensitivity was 82% (14/17). Among cases of primary parathyroid hyperplasia, no scan correctly localized all abnormal glands; however 60% (3/5) showed localization of at least one hyperplastic gland. Of the 2 patients with parathyroid carcinoma, in only one case was there evidence of sestamibi retention in the correct thyroid lobe. In patients with secondary hyperparathyroidism, sestamibi scanning was successful in identifying all hyperplastic tissue in only one case (sensitivity 13%). In 7 of the 8 cases of secondary hyperparathyroidism, the scan localized at least one hyperplastic gland.

CONCLUSION

Sestamibi scanning is useful in the localization of abnormal pathology in cases of primary hyperparathyroidism, especially adenomas. In cases of hyperplasia, whether attributable to primary or secondary hyperparathyroidism, sestamibi imaging is less successful.

Double-phase parathyroid scintigraphy in dogs using technetium-99M-sestamibi

The purpose of this study was to evaluate the utility of double-phase parathyroid scintigraphy using 99mTc-sestamibi for detecting and localizing hyperfunctioning parathyroid glands in hypercalcemic dogs. Fifteen hypercalcemic dogs that underwent parathyroid scintigraphy were included in this study: 3 dogs with hypercalcemia of malignancy, and 12 dogs with hyperfunctioning parathyroid tissue (parathyroid adenoma or parathyroid hyperplasia). The presence of parathyroid adenoma or parathyroid hyperplasia was documented by histopathologic examination. In 3 dogs with hypercalcemia of malignancy, parathyroid scintigraphy was negative for hyperfunctioning parathyroid tissue and the scans were classified as true negative. Parathyroid scintigraphy correctly identified the presence and location of hyperfunctioning parathyroid tissue in only 1 of 6 dogs with a parathyroid adenoma. False positive and false negative results occurred in dogs with parathyroid adenomas. Parathyroid scintigraphy failed to detect hyperfunctioning parathyroid tissue in 5 of 6 dogs with parathyroid hyperplasia and were classified as false negative. False positive results were obtained in the remaining dog with parathyroid hyperplasia. Sensitivity of parathyroid scintigraphy for detecting and localizing hyperfunctioning parathyroid tissue was 11%, specificity was 50%, and overall accuracy was 27%. Positive and negative predictive value were 25% and 27%, respectively. Sensitivity for detection of parathyroid adenomas was 25%, and sensitivity for detection of hyperplastic glands was 0 %. Results of this study indicate that double-phase parathyroid scintigraphy does not appear to have acceptable accuracy in detecting hyperfunctioning parathyroid glands in dogs. Due to the poor sensitivity and specificity of the technique in dogs, parathyroid scintigraphy is not recommended for definitive identification of abnormal parathyroid glands as the cause of hypercalcemia in dogs.