99Tcm sestamibi--a new agent for parathyroid imaging

Parathyroid imaging using 99Tcm sestamibi has been carried out prior to surgery in five patients with hyperparathyroidism and the results compared with a standard preoperative localization technique using 201Tl (thallous chloride). The 99Tcm sestamibi correctly localized all abnormal glands and showed higher parathyroid to thyroid uptake in three of four parathyroid adenomas. Both agents showed localization in a thyroid adenoma. The higher uptake of sestambi and better imaging properties of its 99Tcm radiolabel means that the agent may replace thallium for routine preoperative parathyroid localization.

Minimally invasive parathyroidectomy facilitated by intraoperative nuclear mapping

BACKGROUND

The inability to predict the location and number of diseased parathyroid glands has precluded the wide acceptance of unilateral neck exploration for primary hyperparathyroidism. We used intraoperative nuclear mapping in patients identified by sestamibi scanning to have a single adenoma in hopes of minimizing operative intervention while maintaining the efficacy of a full exploration.

METHODS

Fifteen consecutive patients with primary hyperparathyroidism underwent technetium 99m-labeled sestamibi scanning 3.0 +/- 0.1 hours before operation. Placement of the initial 2.0 cm incision and all dissection were guided by quantitative gamma counting in four neck quadrants with an 11 mm Neoprobe. Ex vivo radioactivity was determined for parathyroid glands, fat, and lymph nodes. Potential radiation hazards were assessed.

RESULTS

Intraoperative nuclear mapping discriminated between 14 solitary adenomas and one patient with four-gland hyperplasia that was not predicted on preoperative sestamibi scanning. Removal of the adenoma resulted in a decline in radioactivity in that quadrant (p < 0.001) and the entire neck (p < 0.05), with equalization of all neck quadrants. Ex vivo counts always identified parathyroid tissue (p < 0.0001 versus fat and lymph node). Adenomas were located in 19 +/- 1.7 minutes through a 2.3 +/- 0.1 cm incision. No significant radiation hazard existed, and no special handling of the specimen was required (0.06 +/- 0.01 mR/hr).

CONCLUSIONS

Intraoperative nuclear mapping complements sestamibi scanning to help distinguish single-gland from multigland disease. This technique allows for a minimally invasive operation under local anesthesia in a true outpatient setting.

Improved preoperative planning for directed parathyroidectomy with 4-dimensional computed tomography

BACKGROUND

Four-dimensional computed tomography (4D-CT) provides both functional and highly detailed anatomic information about parathyroid tumors. The purpose of this study was to compare 4D-CT with sestamibi imaging and ultrasonography as methods for the accurate preoperative localization of hyperfunctioning parathyroid glands before parathyroidectomy.

METHODS

A study of 75 patients with primary hyperparathyroidism was performed at a tertiary-care institution. Sestamibi imaging, ultrasonography, and 4D-CT were performed on each patient preoperatively. Results of the imaging studies were compared with operative findings, pathologic data, and biochemical measurements to assess the sensitivity and specificity of each of the imaging modalities.

RESULTS

4D-CT demonstrated improved sensitivity (88%) over sestamibi imaging (65%) and ultrasonography (57%), when the imaging studies were used to localize (lateralize) hyperfunctioning parathyroid glands to 1 side of the neck. Moreover, when used to localize parathyroid tumors to the correct quadrant of the neck (ie, right inferior, right superior, left inferior, or left superior), the sensitivity of 4D-CT (70%) was significantly higher than sestamibi imaging (33%) and ultrasonography (29%).

CONCLUSION

4D-CT provides significantly greater sensitivity than sestamibi imaging and ultrasonography for precise (quadrant) localization of hyperfunctioning parathyroid glands. This allows improved preoperative planning, particularly for the case of reoperation. In addition to the data that are provided, we present a novel classification scheme for use in parathyroid localization.

Outpatient minimally invasive parathyroidectomy: a combination of sestamibi-SPECT localization, cervical block anesthesia, and intraoperative parathyroid hormone assay

BACKGROUND

Despite the high cure rate and low morbidity of bilateral neck exploration for primary hyperparathyroidism, there is a movement toward minimizing the process in terms of incision, cost, extent of exploration, and length of hospital stay, while maintaining excellent outcomes.

METHODS

Between March and November 1998, 33 patients with primary hyperparathyroidism underwent minimally invasive parathyroidectomy. All had preoperative sestamibi-SPECT scans suggesting a single adenoma, underwent anterior cervical block anesthesia by the surgeon, and were explored through a 1- to 4-cm incision. Intraoperative parathyroid hormone assays were performed before and 5 to 10 minutes after parathyroid resection. Outcomes were compared with those of 184 consecutive patients who underwent bilateral parathyroid exploration under general anesthesia by the same surgeon between August 1990 and May 1996.

RESULTS

The mean age of the patients undergoing minimally invasive parathyroidectomy was 61 +/- 2 years, and 24 of the 33 patients were women. Thirty (91%) had resection of a single adenoma under regional anesthesia; 26 of these were done as outpatient procedures. Three patients underwent conversion to general anesthesia for bilateral exploration and were found to have multigland disease (two double adenomas, one hyperplasia). All 33 patients were normocalcemic postoperatively. There was no morbidity. When the minimally invasive parathyroidectomy and bilateral parathyroid exploration groups were compared, they were found to be similar with respect to age, preoperative calcium and parathyroid hormone levels, cause of primary hyperparathyroidism, weight of resected glands, cure rates, and morbidity. However, the minimally invasive parathyroidectomy group had a significantly shorter length of hospital stay (0.3 +/- 0.2 vs 1.8 +/- 0.1 days, P < .001) and lower costs ($3174 +/- $386 vs $6328 +/- $292, P < .001).

CONCLUSIONS

Minimally invasive parathyroidectomy is a safe, cost-effective alternative to bilateral exploration and may be the procedure of choice for select patients with primary hyperparathyroidism.

Comparison of SPECT/CT, SPECT, and planar imaging with single- and dual-phase (99m)Tc-sestamibi parathyroid scintigraphy

Various methodologies for (99m)Tc-sestamibi parathyroid scintigraphy are in clinical use. There are few direct comparisons between the different methods and even less evidence supporting the superiority of one over another. Some reports suggest that SPECT is superior to planar imaging. The addition of CT to SPECT may further improve parathyroid adenoma localization. The purpose of our investigation was to compare hybrid SPECT/CT, SPECT, and planar imaging and to determine whether dual-phase imaging is advantageous for the 3 methodologies.

METHODS

Scintigraphy was performed on 110 patients with primary hyperparathyroidism and no prior neck surgery. Of these, 98 had single adenomas and are the subject of this review. Planar imaging and SPECT/CT were performed at 15 min and 2 h after injection. Six image sets (early and delayed planar imaging, SPECT, and SPECT/CT) and combinations of the 2 image sets were reviewed for adenoma localization at 13 possible sites. Each review was scored for location and certainty of focus by 2 reviewer groups. Surgical location served as the standard. Sensitivity, specificity, area under the curve, positive predictive value, negative predictive value, and kappa-values were determined for each method.

RESULTS

The overall kappa-coefficient (certainty of adenoma focus) between reading groups was 0.68 (95% confidence interval, 0.66-0.70). The highest values were for dual-phase studies that included SPECT/CT. Dual-phase planar imaging, SPECT, and SPECT/CT were statistically significantly superior to single-phase early or delayed imaging in sensitivity, area under the curve, and positive predictive value. Neither single-phase nor dual-phase SPECT was statistically superior to dual-phase planar imaging. Early-phase SPECT/CT in combination with any delayed imaging method was superior to dual-phase planar imaging or SPECT for sensitivity, area under the curve, and positive predictive value.

CONCLUSION

Early SPECT/CT in combination with any delayed imaging method was statistically significantly superior to any single- or dual-phase planar or SPECT study for parathyroid adenoma localization. Localization with dual-phase acquisition was more accurate than with single-phase (99m)Tc-sestamibi scintigraphy for planar imaging, SPECT, and SPECT/CT.

A new approach to parathyroidectomy

OBJECTIVE

To decrease the operative time for parathyroidectomy in patients with hypercalcemic (primary) hyperparathyroid disease, a combination of preoperative localization of a parathyroid tumor with an effective nuclear scan (scintigram) and intraoperative monitoring of parathyroid hormone (quick parathyroid hormone measurement) to ensure excision of all hyperfunctioning tissue was studied.

SUMMARY BACKGROUND DATA

For many years, persistent hypercalcemia after parathyroidectomy (3% to 10%) has been constant and is usually due to the surgeon's failure to remove all hyperfunctioning glands. A marked decrease in parathormone level after excision of a single large gland predicts operative success and a return to normal calcium levels. Conversely, persistent high levels of parathyroid hormone indicate excess secretion by another gland(s) and the need for further exploration. Recently Tc-99m-sestamibi (MIBI) scintigraphy was shown to be more effective in localizing parathyroid tumors than previous methods. A combination of both techniques could be useful to the surgeon if they improve the operative success rate and are cost-effective.

METHODS

Parathyroidectomy was performed on 18 patients with primary hyperparathyroid disease, with tumors localized by MIBI scintigrams. When excision of the identified parathyroid gland was accomplished, the operation was terminated and quick parathyroid hormone was measured to confirm that all hyperfunctioning tissue was removed.

RESULTS

Sixteen patients with positive results of scintigram had successful parathyroidectomies confirmed by quick parathyroid hormone measurement with a cervical approach. Two patients with mediastinal tumors localized by MIBI scintigraphy could not be resected using this approach. One false-positive/false-negative scintigram was obtained. Compared with patients having parathyroidectomy without localization and hormone monitoring, the average operative time was shortened from 90 to 36 minutes.

CONCLUSIONS

Localization and successful excision of parathyroid tumors with confirmation that no other hyperfunctioning glands were present by quick parathyroid hormone monitoring can predict a return to normal calcium levels and a decrease in operative time in parathyroidectomy.

One hundred consecutive minimally invasive parathyroid explorations

OBJECTIVE

To review the outcomes of 100 consecutive minimally invasive parathyroid explorations.

SUMMARY BACKGROUND DATA

Minimally invasive parathyroidectomy (MIP) has challenged the traditional approach of bilateral neck exploration for patients with primary hyperparathyroidism. Most patients with primary hyperparathyroidism have a single adenoma that when resected results in cure. It therefore appears logical to perform a directed approach to adenoma extirpation. MIP involves high-quality sestamibi images obtained with single photon emission computed tomography to localize enlarged parathyroid glands in three dimensions, limited exploration after surgeon-administered cervical block anesthesia, rapid intraoperative parathyroid hormone assay to confirm the adequacy of resection, and discharge within 1 to 3 hours of surgery.

METHODS

MIP was offered to 100 selected consecutive patients during an 18-month period beginning in March 1998.

RESULTS

Ninety-two cases were accomplished under cervical block anesthesia and 89 of these on an ambulatory basis. The cure rate was 100%, and there were no long-term complications. The mean hospital charge for MIP was less than 40% of that associated with traditional exploration.

CONCLUSIONS

Outpatient MIP appears to be the procedure of choice for most patients with primary hyperparathyroidism.

Cost-effectiveness of preoperative sestamibi scan for primary hyperparathyroidism is dependent solely upon the surgeon's choice of operative procedure

BACKGROUND

In 1991, a National Institutes of Health Consensus Panel stated that preoperative localization for primary hyperparathyroidism is not cost effective. Since then, the sestamibi scan has been applied to parathyroid disease with excellent results, even allowing unilateral exploration under local anesthesia.

STUDY DESIGN

A metaanalysis of the English literature over the past 10 years was performed to determine the collective sensitivity and specificity of sestamibi scanning to establish its utility in directing a unilateral procedure. The cost effectiveness of scanning all patients with sporadic primary hyperparathyroidism was examined by determining the costs of seven operative technique-dependent variables that could be reduced with a limited procedure.

RESULTS

The average sensitivity and specificity of sestamibi were 90.7% and 98.8%, respectively, indicating its ability to guide an accurate unilateral exploration. The analysis of 6,331 patients showed that 87% had solitary adenomas. An average cost savings of $650 was demonstrated for a unilateral operation, which could be realized in as many as 90% (sestamibi sensitivity) of those with solitary adenomas.

CONCLUSIONS

A preoperative sestamibi scan is specific enough in identifying solitary adenomas to allow unilateral exploration with a < 1% failure rate. The sensitivity of this scan suggests that 78% of all patients with sporadic primary hyperparathyroidism (90% of the 87% with solitary adenomas) are candidates for unilateral exploration. This rate is significantly higher than the 51% rate at which scanning all patients becomes cost effective.

Ultrasound of thyroid, parathyroid glands and neck lymph nodes

In the past 15 years high-frequency B-mode sonography and colour-power Doppler have become the most important and most widely employed imaging modalities for the study of the neck, in particular for thyroid gland, parathyroids and lymph nodes. Sonography allows not only the detection but often also the characterization of the diseases of these organs, distinguishing benign from malignant lesions with high sensitivity and specificity, which could be further improved by the employ of ultrasound contrast agents and harmonic imaging. Although no single sonographic criterion is specific for benign or malignant nature of the lesions, the combination of different signs can be markedly helpful to speed up the diagnostic process. Fine-needle aspiration biopsy (FNAB) remains the most accurate modality for the definitive assessment of thyroid gland nodules and of any doubtful case of nodal disease. In association with clinical findings and serum levels of parathormone, FNAB has specificity close to 100% for the characterization of parathyroid adenomas. A combined approach with sonography and FNAB is generally highly effective.

Effect of minimally invasive radioguided parathyroidectomy on efficacy, length of stay, and costs in the management of primary hyperparathyroidism

OBJECTIVE

To compare the first 20 patients who underwent minimally invasive radioguided parathyroidectomies (MIRPs) performed at the authors' institution with 20 similar patients who underwent a more conventional surgical approach for primary hyperparathyroidism.

SUMMARY BACKGROUND DATA

The technique of parathyroidectomy has traditionally involved a bilateral exploration of the neck with the intent of visualizing four parathyroid glands and resecting enlarged parathyroid glands. Parathyroid scanning using radioisotopes has evolved and now can localize adenomas in 80% to 90% of patients. MIRP combines parathyroid scanning with a hand-held intraoperative detector that guides the surgeon to the adenoma.

METHODS

Forty patients with documented primary hyperparathyroidism who underwent surgery by a single surgeon between January 1998 and May 1999 were included in this study. Twenty of these patients underwent MIRP. The technique involved injecting 20 mCi technetium-99m sestamibi 2 hours before surgery and performing a parathyroid scan. If the scan was considered positive for a single adenoma, patients were taken to the operating room and given the choice of either general anesthesia or intravenous sedation with local anesthesia. Using an incision of 4 cm or less, the dissection down to the adenoma was guided by the Navigator miniature hand-held probe. An additional 20 patients who underwent more conventional bilateral or unilateral neck exploration were chosen to match the MIRP patient population. Both groups included four patients undergoing repeat surgery for persistent or recurrent primary hyperparathyroidism and one patient with multiple endocrine neoplasia type 1 syndrome. Patient demographics, preoperative calcium and parathyroid hormone levels, operative time, total time in the operating room, time in the recovery room, complications, hospital charges for the operating room, and total hospital charges were analyzed.

RESULTS

There were no differences in patient demographics, presenting symptoms, or preoperative calcium level between patients undergoing the standard procedure versus MIRP. Operative time, total time in the operating room, operative charges, and total hospital charges were significantly reduced in the MIRP group. All 40 patients were cured of primary hyperparathyroidism. There were no recurrent laryngeal nerve injures in either group. The mean length of stay in the standard group was 1. 35 days; in the MIRP group, 65% of patients were discharged within 5 hours after surgery.

CONCLUSIONS

The MIRP technique resulted in excellent cure rates for primary hyperparathyroidism while simultaneously decreasing operative time and hospital stays. These resulted in significant cost reductions without compromising patient safety. The technique may significantly change the management of primary hyperparathyroidism.

Prospective evaluation of delayed technetium-99m sestamibi SPECT scintigraphy for preoperative localization of primary hyperparathyroidism

BACKGROUND

Delayed technetium-99m sestamibi single photon emission computed tomography (SPECT) scans were prospectively analyzed in a large series of patients with primary hyperparathyroidism.

METHODS

Three hundred thirty-eight patients underwent sestamibi-SPECT and were explored. Prospective data included preoperative demographics, clinical, sestamibi, and operative findings, laboratory values, and pathologic and follow-up laboratory results from all patients.

RESULTS

Between 1994 and 2000, 287 unexplored patients (85%) and 51 re-explored patients (15%) participated. The abnormal parathyroid glands excised from 336 of 338 patients included 299 single adenomas (88%) and 23 double adenomas (7%), and 14 patients had multigland hyperplasia (4%). Sestamibi SPECT correctly lateralized 349 of 400 abnormal parathyroid glands, with an overall sensitivity of 87%, an accuracy of 94%, and a positive predictive value of 86%. Precise localization occurred in 82% of the abnormal parathyroid glands. Sestamibi sensitivity was similar in unexplored (87%) and reoperative (92%) cases; two hundred eighty-six of 299 (96%) solitary adenomas, 38 of 46 (83%) double adenomas, but only 25 of 55 (45%) hyperplastic glands were identified. The mean weight of the true-positive glands (1252 +/- 1980 mg) was greater than that of the false-negative glands (297 +/- 286 mg) (P <.005). Three patients had persistent primary hyperparathyroidism, in spite of the excision of sestamibi-identified lesions in 2 cases. Follow-up indicated curative resection in 99% of the unexplored cases and 94% of the remedial cases.

CONCLUSIONS

Sestamibi SPECT is highly accurate for the localization of parathyroid adenomas in unexplored and re-explored cases, where it is often the only imaging required. Its sensitivity is limited in multiglandular disease.

Ultrasonography for preoperative localization of enlarged parathyroid glands in primary hyperparathyroidism: comparison with (99m)technetium sestamibi scintigraphy

OBJECTIVE

To determine the utility of ultrasonography for the preoperative localization of enlarged parathyroid glands in primary hyperparathyroidism, and to compare this method with (99m)technetium sestamibi scintigraphy.

DESIGN

The results of ultrasonography for localization of enlarged parathyroid glands were determined in 120 consecutive patients with primary hyperparathyroidism and compared with findings at surgery (n = 86) and with the results of (99m)technetium sestamibi scintigraphy (n = 99).

PATIENTS

All patients had biochemically documented primary hyperparathyroidism based on elevated serum calcium and 'intact' parathyroid hormone measured by immunoassay. Patients with prior parathyroid surgery or secondary hyperparathyroidism were excluded.

MEASUREMENTS

High-resolution ultrasonography was performed by a single observer. (99m)Technetium sestamibi scintigraphy was performed using early and delayed (2-h) views, and correlated with simultaneous thyroidal 123I uptake in most patients.

RESULTS

Ultrasonography detected putative enlarged parathyroid glands in 92 of 120 unselected patients (77%). It correctly predicted surgical findings in 64 of 86 patients undergoing surgery (74%), including 61 of 72 patients with solitary eutopic parathyroid adenomas (84%), but only two of eight patients with solitary ectopic adenomas, and only one of six patients with multigland parathyroid disease. Sestamibi scintigraphy was positive in 87 of 99 unselected patients (88%), a higher proportion than ultrasonography (P < 0.05), reflecting superior sensitivity for the detection of ectopic parathyroid adenomas. For 74 patients undergoing parathyroid surgery who underwent both imaging tests there was no statistically significant difference between ultrasonography and sestamibi scintigraphy in ability to correctly predict surgical findings (74%vs. 82%, respectively) or in positive predictive value (93%vs. 90%, respectively). However, sestamibi scintigraphy was clearly more sensitive for ectopic parathyroid adenomas, providing correct localization in 8/8 cases. When one test was negative, testing with the second method was usually positive, improving the likelihood of a positive result to 98% when both tests were employed.

CONCLUSIONS

Ultrasonography can be a sensitive and accurate method for preoperative localization of enlarged parathyroid glands in primary hyperparathyroidism, comparable in overall utility to sestamibi scintigraphy. These results suggest that a strategy of initial testing with one or the other method, followed by the alternate imaging test if the first test is negative, would provide correct parathyroid imaging in most patients without prior parathyroid surgery.

The 20% rule: a simple, instantaneous radioactivity measurement defines cure and allows elimination of frozen sections and hormone assays during parathyroidectomy

BACKGROUND

Although primary hyperparathyroidism is a physiologic disease, surgeons rely on anatomical characteristics (gross and histologic) to determine appropriate operative decisions. After the development of radioguided parathyroidectomy, we hypothesized that the amount of radioactivity contained within resected tissue would be the only information needed to establish the nature of the tissue and to determine a cure for the disease.

METHODS

A total of 1290 tissue specimens were obtained from 345 patients who had sporadic primary hyperparathyroidism. Ex-vivo radioactivity, in counts per second, was measured in parathyroid and other tissues within 3.5 hours of sestamibi injection. Background radioactivity was measured after tissue excision, and ratios were calculated.

RESULTS

Lymph nodes, normal parathyroids, and fat never contained more than 2.2% of background radioactivity, whereas thyroid and hyperplastic parathyroids contained 5.5% and 7.5%, respectively, and never more than 16%. In contrast, adenomas contained 59% +/- 9% of background radioactivity (P < .000001 vs all other tissues), with a range of 18% to 136%.

CONCLUSIONS

Radioactive ratios are an instantaneous measure of metabolic activity, thereby determining parathyroid function. Any excised tissue containing more than 20% of background radioactivity in a patient with a positive sestamibi scan result is a solitary parathyroid adenoma. This alleviates the need to identify other glands, obtain frozen sections, or measure serum parathyroid hormone levels intraoperatively.

Radionuclide imaging of the parathyroid glands

The parathyroid glands, which usually are situated behind the thyroid gland, secrete parathyroid hormone, or PTH, which helps maintain calcium homeostasis. Primary hyperparathyroidism results from excess parathyroid hormone secretion. In secondary hyperparathyroidism, the normal PTH effect on bone calcium release is lost. Serum PTH rises, causing generalized hyperplasia. In tertiary hyperparathyroidism, a complication of secondary hyperparathyroidism, normal feedback mechanisms governing PTH secretion are lost, parathyroid gland sensitivity to PTH decreases, and the threshold for inhibiting PTH secretion increases. 99mTc sestamibi, or MIBI, the current radionuclide study of choice for preoperative parathyroid localization, can be performed in various ways. The "single-isotope, double-phase technique" is based on the fact that MIBI washes out more rapidly from the thyroid than from abnormal parathyroid tissue. However, not all parathyroid lesions retain MIBI and not all thyroid tissue washes out quickly, and subtraction imaging is helpful. Many MIBI avid thyroid lesions also accumulate pertechnetate and iodine, and subtraction reduces false positives. Single-photon emission computed tomography provides information for localizing parathyroid lesions, differentiating thyroid from parathyroid lesions, and detecting and localizing ectopic parathyroid lesions. The most frequent cause of false-positive MIBI results is the solid thyroid nodule. Other causes include thyroid carcinoma, lymphoma, and lymphadenopathy. False-negative results occur because of several factors. Lesion size is important. Cellular function also may be important. Parathyroid tissue that expresses P-glycoprotein does not accumulate MIBI. Parathyroid adenomas that express either P-glycoprotein or the multidrug resistance related protein MRP are less likely to accumulate MIBI. MIBI scintigraphy is less sensitive for detecting hyperplastic parathyroid glands. In secondary hyperparathyroidism, MIBI uptake is more closely related to cell cycle than to gland size. Mitochondria-rich oxyphil cells presumably account for MIBI uptake in parathyroid lesions. Fewer oxyphil cells, and hence fewer mitochondria, may explain both lower uptake and rapid washout of MIBI from some lesions. MIBI is also less sensitive for detecting multigland disease than solitary gland disease.

Technetium 99m-MIBI-SPECT: A highly sensitive diagnostic tool for localization of parathyroid adenomas

BACKGROUND

The aim of this study was to assess the value of technetium 99m-MIBI scintigraphy using the single photon emission computed tomography (SPECT) technique for preoperative localization of smaller (</= 1 g) parathyroid adenomas.

METHODS

A total of 92 patients (34 men, 58 women; mean age, 60 +/- 13 years) with an established diagnosis of primary hyperparathyroidism and nondiagnostic ultrasonography (inclusion criteria) were scanned preoperatively. After a thyroid examination to check for other possible radionuclide-accumulating thyroid diseases, a planar technetium 99m-pertechnetate/technetium 99m-MIBI subtraction scintigraphy (15 minutes post injection) and tomographic images (120 minutes post injection) were acquired after intravenous injection of 740 MBq of technetium 99m-MIBI and using a 3-head gamma camera (Picker Prism 3000). Sensitivity was defined by the ability to predict the correct site of a parathyroid adenoma.

RESULTS

All patients had parathyroid adenomas </= 1 g (53 patients, 0.5 -1.0 g; 39 patients, < 0.5 g). Correct localization of parathyroid adenomas to one side or the other was achieved in 87% of the patients using planar technetium 99m-pertechnetate/technetium 99m-MIBI subtraction scintigraphy. Sensitivity was increased to 95% by supplementary use of the SPECT technique and a 3-D display (volume-rendered reprojection for visualization). There was technetium 99m-MIBI accumulation in 11 benign thyroid nodes, but none of the healthy parathyroid glands were shown on the scan.

CONCLUSIONS

This study indicates that technetium 99m-MIBI parathyroid scintigraphy is a sensitive and specific tool for topographic localization even of small parathyroid adenomas, especially with the use of SPECT. This method could help to improve the efficiency of parathyroidectomy (eg, by making unilateral exploration sufficient).

Does intraoperative quick parathyroid hormone assay improve the results of parathyroidectomy?

Preoperative sestamibi (MIBI) and ultrasonography (US) are used to localize parathyroid tumors in patients with primary hyperparathyroidism (pHPT). The intraoperative quick PTH assay (qPTH) has been recommended to determine whether all hyperfunctioning parathyroid tissue has been removed. We questioned whether qPTH improves the results of parathyroidectomy in patients with pHPT. We analyzed 115 unselected patients with pHPT without a family history or multiple endocrine neoplasia but who had undergone parathyroidectomy. All 115 patients had successful operations without complications. Of these patients, 88 (77%) had solitary adenomas, 13 had double adenomas, 1 had triple adenomas, 12 had hyperplasia, and 1 had carcinoma. Overall, MIBI was correct in 72% (76/106), US in 49% (49/99), and qPTH in 80% (92/115). For preoperative studies showing a single tumor, MIBI was correct in 83% (73/88), US was correct in 71% (45/63), and combined MIBI and US were correct in 95% (37/39). Adding qPTH in this subgroup did not improve the successful focused approach: 70% for MIBI, 65% for US, and 87% for combined MIBI and US. However, adding qPTH improved the overall success of parathyroidectomy (MIBI 92%, US 86%, combined MIBI and US 97%), but at the cost of unnecessary further exploration (MIBI 13%, US 6%, combined MIBI and US 8%). We conclude that when the same solitary tumor is identified by both MIBI and US, a focused exploration can be done with a 95% success rate. Adding qPTH to MIBI or US can improve the success rate but at a significant cost. General exploration of all parathyroid glands, however, has the highest success rate (100%).

Minimally invasive radioguided parathyroidectomy in the reoperative neck

BACKGROUND

Operations for hyperparathyroidism (HPT) in a previously operated neck present a significant challenge and carry much higher morbidity rates than first-time operations. Our extensive experience with minimally invasive radioguided parathyroidectomy (MIRP) for first-time surgery for HPT has shown this method to be a directed approach to the offending adenoma, suggesting that the technique could be used to minimize reoperative neck surgery as well.

METHODS

Over an 11-month period 24 consecutive patients with primary HPT who had undergone at least one previous neck operation were referred for re-exploration. All patients underwent preoperative sestamibi scanning; 21 localized sufficiently to undergo MIRP.

RESULTS

All patients were cured after reoperation. Eighteen patients underwent MIRP under local anesthesia as outpatients; 3 MIRPs were done under general anesthesia. Average total operative time was 44 minutes, average incision length was 3.0 cm +/- 0.2 cm. Nineteen of the procedures were completed without any frozen sections. There were no complications.

CONCLUSION

MIRP is extremely effective in patients with HPT who have undergone previous neck exploration for parathyroid or thyroid disease. The technique allows for such a directed dissection that smaller incisions and local anesthesia in an outpatient setting are routine.

Sestamibi parathyroid imaging

Since the introduction of technetium-99m (99mTc) sestamibi (hexakis-2-methoxyisobutyl isonitrile) as a parathyroid imaging agent in 1989, many investigators using several different imaging protocols have reported uniformly excellent results for localization of parathyroid adenomas. Exact localization of hyperplastic parathyroid glands has not met with as much success. However, the results of multiple comparative studies suggest that the diagnostic utility of sestamibi protocols equals or exceeds other noninvasive, nonscintigraphic imaging strategies, including high-resolution ultrasound, computed tomography, and magnetic resonance imaging. Two different, but not necessarily mutually exclusive imaging strategies have been used: subtraction imaging using iodine-123 (123I) or 99mTc sodium pertechnetate as the thyroid agent, and sestamibi dual-phase imaging, which takes advantage of differential washout of sestamibi from thyroid and parathyroid tissue. Sestamibi subtraction imaging has been shown to have greater sensitivity for abnormal parathyroid glands compared with thallium-201 subtraction imaging using pooled data, 87% versus 71%, respectively. Dual-phase sestamibi imaging protocols are much more variable in their conduct and have a much greater variability in sensitivity, 43% to 91%, but with a pooled sensitivity of 73%. Data suggest that dual phase techniques are at least as sensitive, and in optimized protocols, superior to, thallium-201 subtraction techniques. This superiority is attributed to the favorable washout kinetics of sestamibi and the superior imaging characteristics of the 99mTc label. Specificity and positive predictive value for both sestamibi techniques are very high, typically greater than 90% and at least equal to thallium-subtraction protocols, although specificity may be slightly lower for sestamibi subtraction techniques. Therefore, sestamibi protocols are the scintigraphic procedure of choice for parathyroid imaging. Dual-phase sestamibi protocols are more robust and lend themselves to single photon emission computer tomography (SPECT) imaging, and may be followed sequentially by subtraction techniques if results are inconclusive. Despite the excellent results of sestamibi parathyroid imaging, it is unclear whether this accuracy can compete with the even better success of an experienced surgeon in initial surgeries for hyperparathyroidism, and routine preoperative imaging before initial surgery is still controversial. However, sestamibi parathyroid imaging is an excellent addition to a correlative imaging approach in reoperations for persistent and recurrent hyperparathyroidism.

Mediastinal parathyroid tumors: experience with 38 tumors requiring mediastinotomy for removal

Most hyperfunctioning parathyroid tumors situated in the mediastinum can be removed by means of a cervical approach. However, a few tumors, because of their location deep in the chest, require mediastinotomy for removal. These tumors are probably derived from parathyroid glands that have developed from the third branchial pouch. Between 1942 and 1980, 38 such tumors were removed at the Mayo Clinic, using a sternum-splitting procedure. With one exception, the patients had undergone previous parathyroid exploration, Almost all of the patients had significant complications of primary hyperparathyroidism (HPT). Thirty-seven patients (97%) were cured after removal of their mediastinal parathyroid tumors, but postoperative chest complications were encountered in eight patients (21%), and eight have permanent hypoparathyroidism. Six patients had selective arteriography, two had selective thyroid venous sampling and parathyroid hormone assay, and 13 had mediastinal computed tomography in an attempt to localize tumors before operation. The anatomic locations of the tumors at operation were variable, but the vast majority (68%) were in or near the thymus.

Technetium-99m-MIBI SPECT/CT in Primary Hyperparathyroidism

The novel trend toward focused parathyroidectomy requires precise preoperative localization of the parathyroid adenoma in patients with primary hyperparathyroidism (PHPT). The present study evaluated the impact of hybrid single photon emission computed tomography/computed tomography (SPECT/CT), using 99mTc-sestamibi (MIBI), on the surgical management of these patients. In a retrospective study of 36 patients with PHPT, SPECT/CT was undertaken when planar 99mTc-MIBI scintigraphy was negative or when an ill-defined focus in the neck or an ectopic site on planar views was visualized. Imaging data were compared with intraoperative findings, and the incremental value of SPECT/CT to lesion localization and surgical procedure was assessed. Three patients with both negative planar and SPECT/CT studies subsequently underwent bilateral neck exploration, with multiglandular hyperplasia diagnosed in two patients and a parathyroid adenoma in one. Of 33 patients with a positive MIBI study, parathyroid adenoma was confined to the neck in 23 patients and to the lower neck-mediastinum in 10. SPECT/CT facilitated the surgical exploration of all 10 ectopic parathyroid adenomas and 4 of 23 cervical parathyroid adenomas, the latter four either at reexploration or in patients with nonvisualization of the thyroid after thyroidectomy. SPECT/CT contributed to the localization of parathyroid adenomas in patients with PHPT and to planning the surgical exploration in 14 of 36 (39%) patients, predominantly those with ectopic parathyroid adenomas or who had distorted neck anatomy.

Values of ultrasonography, sestamibi scintigraphy, and intraoperative measurement of 1-84 PTH for unilateral neck exploration of primary hyperparathyroidism

Unilateral neck exploration (UNE) is a controversial approach to the treatment of primary hyperparathyroidism (PHP), and most surgeons favor bilateral neck exploration. The aim of this study was to assess the value of ultrasonography, sestamibi scintigraphy, and intraoperative measurement of urinary cyclic AMP (UcAMP) or 1-84 PTH in 200 patients undergoing unilateral neck exploration under local anesthesia. Conditions for UNE were (1) a presumed solitary adenoma detected by ultrasonography, (2) no thyroid disease, and (3) no family history of PHP or multiple endocrine neoplasia. Patient's consent was obtained for conversion to bilateral exploration according to surgical and biologic findings. Sensitivity of ultrasonography was 92.5%. Sestamibi scintigraphy, performed in 70 patients, was less sensitive than ultrasonography (80%). Persistent PHP was accurately detected by intraoperative measurement of UcAMP or 1-84 PTH in all cases. At follow-up, 96.0% of the patients were cured either after unilateral neck exploration only (90.5%), or after conversion into bilateral exploration. Ultrasonography and intraoperative measurement of 1-84 PTH allow unilateral neck exploration with excellent results in a selected group of patients with PHP.

Advantages of combined technetium-99m-sestamibi scintigraphy and high-resolution ultrasonography in parathyroid localization: comparative study in 91 patients with primary hyperparathyroidism

OBJECTIVE

To evaluate the usefulness of the combination of Tc-sestamibi/Tc-pertechnetate subtraction scintigraphy (SS) and high-resolution neck ultrasonography (US) in patients with primary hyperparathyroidism (pHPT) undergoing parathyroidectomy.

DESIGN AND METHODS

Ninety-one patients with proved pHPT were studied, excluding patients with persistent or recurrent disease. There were 65 (71.4%) women and 26 (28.6%) men, with a median age of 59 years (range 18-78 years). All patients underwent both SS and US prior to surgery, and the results were compared with operative and histological findings. The intraoperative quick-parathyroid hormone assay was available for 52 (57.1%) patients. When multiglandular disease was found, both SS and US were considered truly positive only when at least two enlarged parathyroid (PT) glands had been localized.

RESULTS

Eighty-three (91.2%) solitary PT adenomas and three (3.3%) carcinomas were found. Moreover, two (2.2%) patients had a double adenoma and three (3.3%) patients had diffuse PT hyperplasia. The overall sensitivity of combined SS+US was 94.5% (86.8% and 80.4% for SS and US respectively). There was a significant (P<0.05, Student's t-test) difference in size between the PT glands correctly identified and undetected by SS, whereas the site of the removed PT tumors significantly (P<0.05, Fisher exact test) influenced only the US sensitivity.

CONCLUSIONS

When the preoperative localization of the PT glands is chosen, the combination of SS and US represents a reliable noninvasive localization technique and should be considered for use in each patient with pHPT undergoing surgery.

Radioguided parathyroidectomy is equally effective for both adenomatous and hyperplastic glands

OBJECTIVE

To determine the utility of radioguided parathyroidectomy for patients with hyperparathyroidism, we studied the properties of 180 resected, hyperfunctioning parathyroid glands.

SUMMARY AND BACKGROUND DATA

Radioguided resection of hyperfunctioning parathyroid glands has been shown to be technically feasible in patients with parathyroid adenomas. Radioguided excision may obviate the need for intraoperative frozen section because excised parathyroid adenomas uniformly have radionuclide ex vivo counts >20% of background. The feasibility and applicability of radioguided techniques for patients with parathyroid hyperplasia are unclear.

METHODS

Between March 2001 and September 2002, 102 patients underwent neck exploration for primary (n = 77) and secondary/tertiary (n = 25) hyperparathyroidism. All patients received an injection of 10 mCi of Tc-99m sestamibi the day of surgery. Using a gamma probe, intraoperative scanning was performed, looking for in vivo radionuclide counts > background to localize abnormal parathyroid glands. After excision, radionuclide counts of each ex vivo parathyroid gland were determined and expressed as a percentage of background counts.RESULTS Although patients with single adenomas had higher mean background radionuclide counts, the average in vivo counts of all enlarged glands were higher than background. Notably, in vivo counts did not differ between adenomatous and hyperplastic glands, suggesting equal sensitivity for intraoperative gamma detection. Ectopically located glands were identified in 22 cases and all were accurately localized using the gamma probe. Postresection, mean ex vivo radionuclide counts were highest in the single parathyroid adenomas and lowest in hyperplastic glands. Importantly, in all hyperplastic glands, the ex vivo counts were >20%.

CONCLUSIONS

In patients with hyperparathyroidism, radioguided surgery is a sensitive adjunct for the intraoperative localization of both adenomatous and hyperplastic glands. In this series, all 180 enlarged parathyroids were located with the gamma probe. We have also shown that the ">20% rule" for ex vivo counts not only applies to parathyroid adenomas but also to hyperplastic glands. Therefore, radioguided resection is equally effective and informative for both adenomatous and hyperplastic glands.

Localization of parathyroid adenomas in patients who have undergone surgery. Part I. Noninvasive imaging methods

The authors evaluated computed tomography (CT), ultrasound (US), technetium/thallium scintigraphy, and magnetic resonance (MR) imaging as localization procedures in 53 patients with proved parathyroid adenomas and previous unsuccessful parathyroid surgery. CT had the highest overall sensitivity (47%), followed by US (36%) and scintigraphy (27%). There is still too little data to assess MR imaging. Adenoma size affected the sensitivity of CT, scintigraphy, and MR imaging but not US. When all three studies were used, at least one study depicted a lesion in 78% of patients, but definitive localization (two positive studies) was achieved in only 31%.

Location of parathyroid adenomas by thallium-201 and technetium-99m subtraction scanning

Solitary parathyroid adenomas were correctly located before surgery in 20 out of 21 cases by using 201mT1 and 99mTc in a subtraction technique. The technique was not useful in identifying hyperplastic parathyroid glands. The technique is recommended as a useful procedure before surgery for primary hyperparathyroidism.