A new method with high sensitivity and specificity for localization of abnormal parathyroid glands

Comparison and histopathological correlation of three parathyroid imaging methods in a population with a high prevalence of concomitant thyroid diseases

The aim of this prospective study was to evaluate the diagnostic utility of a technetium-99m sestamibi dual-phase protocol enhanced by single-photon emission tomography (SPET) and semiquantitative analysis in comparison to established preoperative staging procedures in patients with primary hyperparathyroidism. Twenty-eight (50%) out of 56 patients had superimposed thyroid disease, and 12 patients had previously undergone neck surgery. Visual and semiquantitative analysis of planar 99mTc-sestamibi dual-phase imaging, SPET of the delayed phase, ultrasonography, and thallium-201 chloride-technetium-99m pertechnetate subtraction scintigraphy was further correlated with the histopathological examination of the surgical specimens. 99mTc-sestamibi dual-phase imaging achieved the highest sensitivity for side localization and precise localization compared with 201Tl-99mTc subtraction scintigraphy and ultrasonography, but the differences reached statistical significance only in comparison to ultrasonsography. Semiquantitative analysis did not enhance sensitivity. Adenoma detection by 99mTc-sestamibi dual-phase imaging was only correlated to serum calcium levels and osteocalcin, not to cell density or oxyphil cell count (SPET yielded additional information for the exact topographical localization of the parathyroid tumour in 22 (39%) patients with superimposed thyroid disease or previous neck surgery but did not enhance the overall detection rate.

A prospective trial evaluating a standard approach to reoperation for missed parathyroid adenoma

OBJECTIVES

The authors evaluate the results of preoperative imaging protocols and surgical re-exploration in a series of patients with missed parathyroid adenomas after failed procedures for primary hyperparathyroidism.

BACKGROUND

The success rate is lower and the complication rate is increased in patients undergoing reoperation for primary hyperparathyroidism compared with initial procedures. Scarring and distortion of tissue planes plus the potential for ectopic gland location leads to this worsened outcome.

METHODS

Two hundred eighty-eight consecutive patients with persistent/recurrent hyperparathyroidism were treated at a single institution after a failed procedure or procedures at outside institutions. Two hundred twenty-two of these patients (77%) were believed to have a missed single adenoma, and these patients underwent 228 operations and 227 preoperative work-ups. Preoperative evaluation consisted of a combination of four noninvasive imaging studies--neck ultrasound, nuclear medicine scan, neck and mediastinal computed tomography scan, and neck and mediastinal magnetic resonance imaging. Based on the noninvasive testing alone, 27% patients underwent surgery whereas the other patients underwent invasive studies, including selective angiography (58%), selective venous sampling for parathyroid hormone (43%), or percutaneous aspiration of suspicious lesions (15%).

RESULTS

Abnormal parathyroid adenomas were found in 209 of 222 initial procedures and 6 of 6 second procedures, with an overall success rate in terms of resolution of hypercalcemia in 97% (215/222) of patients. The single most common site of missed adenoma glands was in the tracheal-esophageal groove in the posterior superior mediastinum (27%). The most common ectopic sites for parathyroid adenomas are thymus (17%), intrathyroidal (10%), undescended glands (8.6%), carotid sheath (3.6%), and the retroesophageal space (3.2%). The most sensitive and specific noninvasive imaging test is the sestamibi subtraction scan, with 67% true-positive and no false-positive results. The rate of true-positive and false-positive results for ultrasound, computed tomography, magnetic resonance imaging, and technetium thallium scans were 48%/21%, 52%/16%, 48%/14% and 42%/8%, respectively. The incidence of injury to the recurrent laryngeal nerve was 1.3%.

CONCLUSIONS

A single missed parathyroid adenoma is the most common cause for a failed initial parathyroid operation. Appropriate use of preoperative imaging tests and knowledge of the potential location or parathyroid adenomas can lead to very high cure rates with minimal morbidity.

Comparison of Tc-99m MIBI and TI-201/Tc-99m pertechnetate for diagnosis of primary hyperparathyroidism

The purpose of this study was to directly compare the efficacy of Tc-99m MIBI with TI-201/Tc-99m pertechnetate scintigraphy for localizing parathyroid adenomas in patients with primary hyperparathyroidism. Of 21 patients suspected of having primary hyperparathyroidism who had undergone both studies, 14 had subsequent surgery and pathologic correlation. Based on the surgical and pathologic results, Tc-99m MIBI yielded 13 true-positive and 1 false-negative result. Thallium-201/ Tc-99m pertechnetate imaging yielded eight true-positive, four false-negative, and two nondiagnostic studies because of lack of Tc-99m pertechnetate uptake from thyroid hormone suppression. In conclusion, Tc-99m MIBI scintigraphy is an accurate method for localizing parathyroid adenomas in patients with primary hyperparathyroidism and the results suggest that it is superior to using TI-201/Tc-99m pertechnetate.

Parathyroidectomy in the west Midlands

A retrospective audit was made of 101 patients undergoing parathyroidectomy, performed by 20 general surgeons in the West Midlands region during 1992. The mean number of cases per surgeon was five; nine surgeons performed fewer than three parathyroidectomies. Some 57 patients had primary hyperparathyroidism. Only seven were diagnosed by general practitioners and referral was invariably to a non-endocrine physician. Delay between diagnosis and surgical referral exceeded 2 years in 12 patients. Four patients (7 per cent) with primary hyperparathyroidism remained hypercalcaemic after first exploration; all were operated on by surgeons who performed fewer than four parathyroidectomies per year. Minor complications occurred in 32 per cent of patients. All 44 patients with renal hyperparathyroidism were treated in specialist units where diagnosis and treatment were expeditious; parathyroidectomy was successful in 41. Hyperparathyroidism should be managed in specialized units and by surgeons who perform parathyroidectomy frequently. A heightened awareness of primary hyperparathyroidism is required at primary care level.

Technetium99m-sestamibi scanning before initial neck exploration in patients with primary hyperparathyroidism

Technetium99m (Tc) sestamibi(mibi) has been proposed as an alternative to the standard radionuclide imaging technique of thallium 201 chloride-99mTc pertechnetate subtraction scan (TTS) in patients with primary hyperparathyroidism. In the present study, mibi was evaluated as an alternative to TTS in 37 patients who had either mibi-99mTc pertechnetate subtraction scans, mibi-iodine123 (I) subtraction scans or mibi single isotope washout scans. There were 30 females and 7 males with an average age of 57 years (range, 27-78 years). Parathyroid adenomas were found in 35 patients and hyperplasia in 2. Twenty-eight mibi scans were positive and 25 of these correctly localized the parathyroid abnormality for a sensitivity of 68% (25 of 37) and a positive predictive value of 89% (25 of 28). There were 3 false-positives (8%) and 9 false-negatives (25%). The scan was not helpful in either patient with parathyroid gland hyperplasia. Mibi-123I subtraction was the most accurate scan and was diagnostic clinically in all 7 patients studied. Mibi scans were significantly more likely to identify inferior rather than superior adenomas (P = 0.01). Twenty-seven of the 37 patients also had a TTS which was correct in only 37% of cases while the mibi scan was correct in 68% (P = 0.02). However, routine use of nuclear scanning with mibi was still not supported by these data. Further clinical evaluation of various techniques may improve accuracy. Since mibi was significantly more accurate than TTS, it should be considered preferentially when radionuclide imaging is used in patients with recurrent hyperparathyroidism.

Thallium-technetium-subtraction scintigraphy in secondary hyperparathyroidism

Between 1983 and 1992 thallium-technetium subtraction scintigraphy (TTS) was performed on 74 patients with clinical and biochemical evidence of hyperparathyroidism. Twenty-five of the 53 investigations since 1988 were conducted on patients with renal failure with a suspicion of secondary hyperparathyroidism. In a retrospective study we have evaluated radioisotope scintigraphy for patients with adenoma and for renal failure patients with possible parathyroid hyperplasia. Thirty of 74 patients underwent neck exploration. Scintigraphy detected 17 of 24 parathyroid adenomas (sensitivity 71%). In contrast, in six renal patients who came to operation, scintigraphy localised only 5 of 20 hyperplastic parathyroid glands (sensitivity 25%) and in one renal patient we localised a parathyroid adenoma. A review of the literature shows low detection rates for hyperplasia by TTS to be a common observation. Based on these findings a rational approach is offered for parathyroid localisation in renal patients prior to neck exploration.

Localization of parathyroid enlargement: experience with technetium-99m methoxyisobutylisonitrile and thallium-201 scintigraphy, ultrasonography and computed tomography

Technetium-99m methoxyisobutylisonitrile (MIBI), like thallium-201, has recently been introduced as a myocardial perfusion agent and is now also showing very promising results in parathyroid scintigraphy. The results of 201Tl/99mTc-pertechnetate and 99mTc-MIBI/99mTc-pertechnetate subtraction scintigraphy, ultrasonography and computed tomography are presented in a series of 43 patients operated on for hyperparathyroidism. All four imaging modalities were confirmed to be reliable, scintigraphy being the most accurate. Sensitivities ranged from 81% to 95%, that of 99mTc-MIBI being the highest. Moreover this tracer, which has more favourable physical and also biochemical properties, yielded images of superior quality. This allowed localization of the lesion by visual inspection only in as many as 86% of the patients with positive 99mTc-MIBI/99MTc-pertechnetate subtraction scintigraphy. We believe that the higher sensitivity, superior image quality and lower cost of 99mTc-MIBI imaging will make 99mTc-MIBI the new radiopharmaceutical of choice for parathyroid scintigraphy (when one take into account the stability of labelling with large activities it is possible to perform three or four cardiac studies together with one parathyroid scintigraphic examination using one lyophilized vial).

Localization of hyperfunctioning parathyroid glands by means of thallium-201 and iodine-131 subtraction scintigraphy in patients with primary and secondary hyperparathyroidism

The accuracy of the preoperative localization of hyperfunctioning parathyroid glands by subtraction scintigraphy with 201Tl and 131I was evaluated by comparison with the operative findings. The subjects were 67 consecutive patients with hyperparathyroidism (HPT), including 24 with primary and 43 with secondary HPT. In primary HPT, surgery revealed 26 adenomas weighing 0.26-15.80 g (mean +/- SD; 3.01 +/- 3.04 g). Two patients had double adenomas. Scintigraphy correctly localized 25/26 adenomas (96.2%) in primary HPT for a sensitivity, specificity, and accuracy of 96.2%, 98.5%, and 97.9%, respectively. In secondary HPT, 163 hyperplastic glands weighing 0.03-5.08 g (0.85 +/- 0.93 g) were found. Scintigraphy correctly localized 79 glands (48.5%) weighing 0.03-5.08 g (1.19 +/- 1.10 g), but 84 glands (51.5%) weighing 0.04-2.70 g (0.51 +/- 0.50 g) were not detected. Thus, the sensitivity, specificity, and accuracy of scintigraphy were respectively 48.5%, 100%, and 51.2%, in secondary HPT. These results show that scintigraphy with 201Tl and 131I can be used to locate abnormal parathyroid glands with an efficacy equal to or better than that of the conventional methods with 201Tl and 99mTc or 201Tl and 123I.

Comparison of imaging methods for localization of parathyroid tumors

Preoperative localization of parathyroid tumors by computed tomography (CT), thallium-201/technetium-99m pertechnetate subtraction scintigraphy (Tl-201/Tc-99m), ultrasonography (US), and magnetic resonance imaging (MRI) was compared in patients with hyperparathyroidism (HPT) to examine the characteristics of each method. A total of 87 patients with HPT were divided into two groups according to the time when they were examined. Patients in group I were examined before MRI had been introduced in our hospital, and a 2.5-MHz transducer probe was used for US. Those in group II were examined by MRI and US using a 7.5-MHz transducer probe. Group I included 45 patients (36 with primary hyperparathyroidism [PHPT] and 9 with secondary hyperparathyroidism [SHPT]), and group II included 42 patients (15 with PHPT and 27 with SHPT). In both PHPT and SHPT and SHPT of group I and PHPT of group II, there was no significant difference in detection rates between all diagnostic methods. In patients with SHPT in group II, the detection rate was significantly higher for CT than for Tl-201/Tc-99m and MRI (both p less than 0.01), and for US than for Tl-201/Tc-99m (p less than 0.01). In both groups I and II, the detection rate of each study method was significantly higher in patients with PHPT than in those with SHPT (all p less than 0.01). Compared with group I, the rate was significantly improved in group II, in both types of patients. Regarding the location of the parathyroid tumor, the detection rate of CT was significantly higher for upper parathyroid glands than for lower glands, whereas that of US and Tl-201/Tc-99m was significantly higher for lower glands. The detection rate sharply increased when the tumor weight reached 250 mg (CT, US) or 1,000 mg (Tl-201/Tc-99m, MRI).

A five year audit of the role of parathyroid hormone assays and thallium-technetium isotope subtraction scanning in the preoperative investigation of primary hyperparathyroidism

An audit has been performed of the value of parathyroid hormone assays and thallium-technetium isotope scanning in the pre-operative investigation of 67 hypercalcaemic patients referred for surgery over a 5 year period. Parathyroid hormone assay by region-specific technique was found to have a diagnostic sensitivity of 75% (n = 52) whilst the more recent assay for the intact molecule was 97% sensitive (n = 34). Thallium-technetium isotope scanning was only 64% sensitive overall (n = 59), due in part to the small size of adenomata now being referred for surgery. This study confirms the role of the intact parathyroid hormone assay but questions that of thallium-technetium isotope scanning in standard protocols of investigation for hypercalcaemia.

Preoperative localization of parathyroid tumours does not reduce operating time

Accurate preoperative localization of abnormal parathyroid glands might be expected to result in a reduction in operating time. To test this hypothesis the duration of surgery was recorded in a consecutive series of 50 patients who underwent neck exploration after preoperative localization by thallium-201 and technetium-99m subtraction scanning and were found to have parathyroid tumours. A total of 34 patients had accurate localization by the scan, and these patients had a median operating time of 90 min. When the tumour had not been localized before operation, the median operating time was not significantly different (80 min). Accurate preoperative localization of parathyroid tumours does not reduce operating time.

Scintigraphic localization of ectopic parathyroid lesions with thallium-201

Six consecutive patients with ectopic parathyroid lesions were studied by preoperative thallium-technetium scintigraphy. Ectopic lesions were accurately localized in 5 of 6 patients. Four of five lesions deep in the superior mediastinum, and 1 in the superior carotid sheath, were correctly identified. Ectopic lesions in 4 of 5 patients, who had previously undergone unsuccessful exploration, were correctly localized. In 1 previously unoperated patient, a mediastinal lesion was identified by preoperative scintigraphy. In 2 patients, deep mediastinal exploration via manubriotomy was successfully conducted without confirmation by "invasive" intravascular procedures. There were no false-positive studies. Lesions identified weighed from 185 mg to 9 g and were from 1.1 to 3.0 cm in size. Scintigraphy is particularly effective for demonstration of ectopic parathyroid tissue, because the absence of thyroid tissue in the mediastinum or superior cervical region permits appreciation of areas of abnormal thallium uptake unobscured by uptake in adjacent thyroid tissue. We conclude that ectopic parathyroid tissue may be accurately identified by thallium-technetium scintigraphy without confirmation by invasive intravascular studies.

Parathyroid imaging by Tc/Tl scintigraphy

Between 1983 and 1988, a total of 224 99mTc/201Tl subtraction parathyroid scintigraphy studies were performed in 214 patients (136 women, 78 men, average age 50, +/- 15 years) with clinical and biochemical signs of hyperparathyroidism. Of the 214 patients, 113 underwent surgical exploration, and 127 benign parathyroid lesions were found, 48 of which were correctly localized by scintigraphy (sensitivity 38%). We detected 30 of 71 adenomas (42%) and 18 of 56 hyperplastic glands (32%). Additionally, the scans localized 2 of 6 parathyroid carcinomas in 5 patients. Overall, 83 parathyroid lesions were missed. There was no significant difference in size between detected and missed lesions. Previous neck surgery (65 of 113 patients) was not a significant detriment to scan sensitivity; but correct detection did depend upon the anatomic site of the lesion: 39% (n = 109) were detected in the typical site, 44% (n = 9) intrathyroidal, and 11% (n = 9) in the anterior and/or superior mediastinum. In conclusion, these results show only limited value for this 99mTc/201Tl subtraction scintigraphy protocol as the initial procedure for localization of abnormal parathyroid tissue prior to surgical exploration.

Comparison of techniques for thallium-201-technetium-99m parathyroid imaging

It is impracticable to compare the variety of techniques advocated for thallium-technetium (Tl-Tc) subtraction parathyroid imaging by repeated studies in patients. We therefore carried out studies using a phantom assembly to simulate thyroid and parathyroid in the neck, containing activities of 99Tcm and 201Tl similar to those likely to be present in patient imaging. An initial study of imaging protocol confirmed that correction for scatter from 99Tcm in the 201Tl window usefully improved the image. After making a preliminary selection of gamma cameras and collimators it was found that the GE Maxicamera 400T just visualized the 0.3 g "parathyroid" in a 5 min image with the pinhole collimator and 6 mm insert (A). It performed slightly less well with the HR converging collimator (B) and only marginally better with the 4 mm insert (C), but this is unduly slow unless it is placed close enough to limit the field of view unacceptably. The Siemens Orbiter 75 ZLC with special thyroid collimator (D) gave results similar to (A), is convenient for positioning the patient and is very suitable for parathyroid imaging.

Accuracy and cost-effectiveness of preoperative isotope and ultrasound imaging in primary hyperparathyroidism

A total of 54 patients underwent surgical exploration for primary hyperparathyroidism from 1980 to 1988. Beginning in November 1984 nearly all patients were evaluated with preoperative radionuclide and ultrasound imaging studies. Ultrasound correctly localized 76% of the adenomas removed at surgery, whereas the success rate with radionuclide imaging was 74%. Localization of hyperplastic glands was less successful with the use of either technique. Correct preoperative localization studies in cases of single adenoma reduced the operative time an average of 32 minutes when compared with those cases with no localization studies. Cost-effectiveness was studied based on current charges for operating room time, anesthesia, and the preoperative localization studies. An average cost savings of $124 per case was achieved when results of both localization studies were correct. These localization studies are quick, noninvasive, relatively inexpensive, and associated with no morbidity. Because it is possible to reduce operative time and overall costs, we recommend that radionuclide and ultrasound studies be routinely used in patients with primary hyperparathyroidism.

Improvement of parathyroid Tl-Tc scintigraphy by using a new image subtraction method

Forty five thallium-technetium parathyroid scans were performed preoperatively in patients with a high suspicion of parathyroid adenoma or hyperplasia. The patients were imaged after sequential IV injection of 201Tl-thallous chloride (74 MBq) and 99mTc-pertechnetate (222 MBq) using a gamma camera with a pinhole collimator. According to surgical findings, the prevalence of parathyroid abnormalities was 42/45: single (34 patients) and double (1 patient) adenomas, hyperplasia (7 patients, 16 hyperplastic glands). Three methods of analysis of scintigraphic images were compared. Method one was the visual comparison of the thallium and the technetium images. Method two used the subtraction image obtained after normalisation. Method three used a new image comparison method which performs the geometric and gray level registrations of the two images and generates the image of the significant differences. Three observers were involved in the evaluation procedures. Surgery and histological examinations were taken as the gold standard. Results show that the sensitivity is increased by applying method three. The interobserver reproducibility of the results is also higher for method three. We conclude that an adequate image subtraction technique significantly increases the diagnostic value of parathyroid scintigraphy.

Parathyroid imaging: its current status and future role

The management of autonomous (primary or tertiary) hyperparathyroidism is controversial for two important reasons: (1) Diagnosis of primary or tertiary hyperparathyroidism (as distinct from reactive or secondary hyperparathyroidism) has been revolutionized in the past 20 years as a result of routine inclusion of serum calcium concentration assays in serum multiautomated analysis, now obtained routinely for both hospitalized as well as ambulatory patients. The prevalence of primary hyperparathyroidism in the general population has appeared to rise as a consequence of this assay and the enhanced detection of this disease. This situation has confused the management of hyperparathyroidism since most patients now present with asymptomatic disease, and the need for surgical treatment is controversial in asymptomatic individuals. (2) Primary hyperparathyroidism usually is caused by hypersecretion of parathyroid hormone by an autonomously functioning parathyroid adenoma. In a small percentage of cases, multigland hyperplasia is present. In experienced hands, surgical removal of an adenoma within the thyroid bed cures the hyperparathyroidism 90% to 95% of the time, without performance of a preoperative procedure to localize the adenoma. Approximately 10% of parathyroid tissue is ectopic in location, however. Furthermore, approximately two thirds of "missed" adenomas are within the thyroid bed. Reexploration in the event of a failed operation therefore is not an uncommon occurrence. Parathyroid localization procedures clearly are indicated in patients with primary hyperparathyroidism who have evidence of persistent disease after a failed attempt at surgical cure. In patients first presenting with primary hyperparathyroidism, the need for a localization procedure is less clear, since surgery appears to be successful much of the time without it. Regardless of the nature of the above controversies, surgery for autonomous hyperparathyroidism continues, and localization procedures become more popular. Preoperative localization procedures such as angiography and venography with venous sampling for parathormone are cumbersome and invasive. Noninvasive tests to localize the parathyroid glands have emerged in the past 10 years, including dual tracer radionuclide scintigraphy with 201-thallous chloride and 99m-technetium pertechnetate, high-resolution computer tomography, and fine parts ultrasonography. Dual tracer scintigraphy with thallium and technetium is reported to have a localization sensitivity of 70%-90%. False-negative studies occur primarily in patients with small adenomatous or hyperplastic glands.(ABSTRACT TRUNCATED AT 400 WORDS)

Technetium-thallium scintiscanning for localization of parathyroid adenomas and hyperplasia. A reappraisal

The dual tracer nuclear scintiscan using technetium and thallium to localize enlarged or ectopic parathyroid tissue has been reported to be highly accurate and efficacious. Fourteen previous series reporting results of the technique have been compiled from the literature and analyzed. This analysis has revealed a total of 317 surgically confirmed scan results with a low false-positive rate (17 of 317 scans), a sensitivity rate of 82 percent, and an overall accuracy rate of 78 percent. Forty-five patients from five Portland area hospitals have been retrospectively studied. They had a total of 49 preoperative scans. In our experience with the scan, a higher false-positive rate (4 of 45 scans), a sensitivity rate of 78 percent, and an overall accuracy rate of 73 percent were noted. The scan's effectiveness in acknowledged areas of difficulty in parathyroid surgery, such as patients with ectopic adenomas, hyperplastic glands, and those with previous neck explorations, has been analyzed. We conclude that the scan is a useful preoperative localization tool, especially in patients with ectopic adenomas or with persistent hypercalcemia after neck exploration. However, it is less accurate than initially reported in complex patients, and additional localization techniques are frequently required.

How to recognize and treat parathyroid carcinoma

Parathyroid carcinoma is a rare tumor and its clinical course is variable. Differentiation of patients with parathyroid carcinoma from those with parathyroid adenoma is often difficult both preoperatively and at operation. For good results, the surgeon must recognize this disorder and perform an en bloc resection at the initial surgery. A neck dissection is necessary only when there is evidence of regional node metastases. After surgery, periodic follow-up of the serum calcium and iPTH levels is essential. When hypercalcemia recurs or the serum iPTH increases, localization studies with the use of thallium-201 scanning help detect local recurrence and regional lymph node metastases, but unfortunately, this method often fails to localize pulmonary metastases. Chest radiographs and CT scanning are useful for delineating pulmonary metastases. A wide excision of locally recurrent tumor, an en bloc radical neck dissection and mediastinum dissection for lymphatic metastases, and an aggressive surgical resection of lung metastases are recommended. Although these operations are rarely curative, they usually offer definite palliation of the marked hypercalcemia, often for a considerable period. Drugs to lower the serum calcium level and systemic chemotherapy are currently of only limited benefit, and radiation therapy is generally ineffective.

Technical aspects of magnetic resonance imaging in parathyroid gland lesions

Two patients with primary hyperparathyroidism were examined before parathyroid surgery with magnetic resonance imaging at 0.35 tesla in order to analyse optimal methods of visualization. Two large parathyroid glands in the neck had long transverse relaxation times which rendered them clearly visible in T2-weighted images as structures of a signal intensity higher than that of the surrounding. Large parathyroid lesions may thus be easily detected by magnetic resonance imaging provided proper examination parameters are employed.

Nuclear scanning in the diagnosis and localization of parathyroid adenomas

Technetium-thallium nuclear scanning was performed in 17 patients whose clinical and biochemical findings were suggestive of the presence of hyperparathyroidism. An adenoma was located by scanning in 12 patients. Ten of these 12 patients underwent surgery; the scan had located the adenoma correctly in all these patients. One patient with a negative result of a scan examination subsequently had an adenoma removed at operation. Thyroid pathology interfered with the interpretation of the scan. This technique is recommended as a useful preoperative procedure for the detection of parathyroid adenomas, and its role in the rapid evaluation of hypercalcaemia seems promising. A prospective study to compare the sensitivity and specificity of this technique with computerized tomographic scanning and ultrasound is warranted.

Thallium-pertechnetate subtraction scintigraphy: a quantitative comparison between adenomatous and hyperplastic parathyroid glands

In a prospective study of 201Tl-99mTc subtraction scintigraphy, 61 hyperparathyroid patients were investigated prior to neck exploration. At surgery, 46 adenomatous and 28 hyperplastic parathyroid glands were excised. We examined the relationship between the pathological category of these glands, their mass, uptake of 201Tl thallous chloride, and the frequency of true-positive and false-negative scintigraphic findings. The variation of sensitivity with parathyroid mass was found to be similar for both adenomatous and hyperplastic glands, with a detection threshold that lay in the range 0.3-0.8 g. The higher overall sensitivity for the detection of adenomas (85%) compared with hyperplasias (44%) was due to the smaller mean weight of the latter. When the parathyroid uptake of thallium was quantified scintigraphically, the practical detection limit of subtraction scanning was found to be an uptake of 0.015%. For glands greater than 1.5 g in weight, uptake increased linearly with mass, and specific uptakes were within the range 0.01-0.04%/g. Below lg, certain small glands had much higher specific uptakes, up to 0.2%/g. The range of specific uptakes found was similar for both adenomatous and hyperplastic categories. Multinodular or diffuse goitre was a cause of failure in 10% of investigations. In a further 5%, a solitary thyroid nodule gave rise to a false-positive result.

Paradoxical technetium-thallium subtraction scan in a case of parathyroid adenoma

A technetium-thallium (99mTcO4-201Tl) subtraction scan was performed in a patient with clinical and biological evidence of hyperparathyroidism. The 201Tl image indicated a normal thyroid gland. The 99mTcO4 image revealed a left inferior thyroidal extension with an intense and transient focus corresponding to an ultrasonographic nodule. The transient character of the focus was not explicable in terms of vascular kinetics. A supplementary scintigram using 123I confirmed the presence of an inferior extension of the thyroid, but no increased uptake was found. A nodule weighing 250 mg containing a parathyroid adenoma surrounded by normal thyroidal tissue was excised at the focus site. Biological serum levels returned to normal after the operation. It is concluded that the analysis of 99mTcO4 dynamic data could improve the accuracy of parathyroid subtraction scintigraphy.

Reoperation for persistent and recurrent hyperparathyroidism

As a consequence of an experience with 175 patients undergoing reoperation for persistent or recurrent hyperparathyroidism, the authors have evolved an approach to management. The emphasis is on the confirmation of the diagnosis; the critical evaluation of invasive and noninvasive localization tests, techniques of intraoperative assessment as to the adequacy of the reexploration; the avoidance of postoperative complications; the treatment with cryopreserved autografts of persistent hypocalcemia. With this approach, the authors have had a success rate of greater than 90% for reexploration in patients with persistent and recurrent hyperparathyroidism.