Diagnosis of hyperparathyroidism

AIM: To preoperatively localize enlarged parathyroid glands in patients with hyperparathyroidism (HPT). METHODS: Besides clinical and biochemical workup, high-resolution ultrasonography (US) is the most commonly used imaging method.Additionally,Tc-99m-MIBI scintigraphy in subtraction or biphasic technique, computed tomography (CT) and magnetic resonance imaging (MRI) are used. RESULTS: US fails to detect a minimum of 10% of enlarged parathyroid glands,most commonly due to ectopic location, or difficult examination conditions, such as nodular goiter or previous surgery. If attempted US localization is unsuccessful, multiphase scintigraphy, using Tc-99m-sestamibi, can help to locate ectopic adenomas in the mediastinum. With SPECT, ademomas can be found which escape detection on planar scans due to their small size.With combined use of US and scintigraphy, a correct localization of parathyroid adenomas is possible in up to 90%. CT and MRI are of limited value due to their low specificity. CONCLUSION: For newly diagnosed hyperparathyroidism, high-resolution US is the method of choice for localizing parathyroid adenomas.If ultrasound fails to detect a lesion, Tc-99m-MIBI scintigraphy is recommended. In patients scheduled for re-operation for recurrent or persistent HPT, a preoperative detection of a parathyroid adenoma should be attempted whenever possible, in order to minimize the extent of surgery. The role of CT or MRI is mainly to help to better anatomically localize a suspected adenoma previously detected with scintigraphy.     

MRI及99Tcm-MIBI显像对甲状旁腺机能亢进症的诊断价值

目的：评价MRI及^99Tcm-甲氧基异丁基异腈（MIBI）显像在原发性甲状旁腺机能亢进症（PHT）中检出病理性腺体的临床价值。方法：25例经手术证实的PHT患者实行了术前定位MRI检查，若甲状旁腺部位发现可凝软组织肿物，其信号高于周围正常甲状腺，则认为是病理性甲状旁腺，其中23例同时进行了双时相99Tcm-MIBI显像，如早期相出现放射性浓聚区且延迟相持续存在则考虑为异常甲状旁腺，MRI和99Tcm-MIBI显像阅片结果与病理检查结果对照。结果：术中共发现39个异常甲状旁腺，包括19个腺瘤（18例），19个增生（6例）和1个上皮细胞癌（1例），MRI和99Tcm-MIBI显像对检出病理性腺体的准确性分别为84．1％和85．0％,但前者灵敏度（74．4％）高于后者（67．6％），而后者的特异性（97．8％）高于前者（91．8％），两种方法联合应用准确性提高到91．3％，灵敏度为91．2％，特异性为91．3％，结论：99Tcm-MIBI显像可作为继B超检查之后的首选术前定位检查法，但最理想的最联合应用MIR和99Tcm-MIBI显像。     

Preoperative localization and radioguided parathyroid surgery.

Clinical or subclinical hyperparathyroidism is one of the most common endocrine disorders. Excessive secretion of parathyroid hormone is most frequently caused by an adenoma of >or=1 parathyroid gland. Unsuccessful surgery with persistent hyperparathyroidism, due to inadequate preoperative or intraoperative localization, may be observed in about 10% of patients. The conventional surgical approach is bilateral neck exploration, whereas minimally invasive parathyroidectomy (MIP) has been made possible by the introduction of (99m)Tc-sestamibi scintigraphy for preoperative localization of parathyroid adenomas. In MIP, the incision is small, dissection is minimal, postoperative pain is less, and hospital stay is shorter. Localization imaging techniques include ultrasonography, CT, MRI, and scintigraphy. Parathyroid scintigraphy with (99m)Tc-sestamibi is based on longer retention of the tracer in parathyroid than in thyroid tissue. Because of the frequent association of parathyroid adenomas with nodular goiter, the optimal imaging combination is (99m)Tc-sestamibi scintigraphy and ultrasonography. Different protocols are used for (99m)Tc-sestamibi parathyroid scintigraphy, depending on the institutional logistics and experience (classical dual-phase scintigraphy, various subtraction techniques in combination with radioiodine or (99m)Tc-pertechnetate). MIP is greatly aided by intraoperative guidance with a gamma-probe, based on in vivo radioactivity counting after injection of (99m)Tc-sestamibi. Different protocols used for gamma-probe-guided MIP are based on different timing and doses of tracer injected. Gamma-probe-guided MIP is a very attractive surgical approach to treat patients with primary hyperparathyroidism due to a solitary parathyroid adenoma. The procedure is technically easy, safe, with a low morbidity rate, and has better cosmetic results and lower overall cost than conventional bilateral neck exploration. Specific guidelines should be followed when selecting patients for gamma-probe-guided MIP.     

Dynamic 4D MRI for Characterization of Parathyroid Adenomas: Multiparametric Analysis

BACKGROUND AND PURPOSE:The hypervascular nature of parathyroid adenomas can be explored by proper dynamic imaging to narrow the target lesions for surgical exploration. The purpose of this study was to establish MR perfusion characteristics of parathyroid adenomas to differentiate them from their mimics, such as subjacent thyroid tissue and cervical lymph nodes.MATERIALS AND METHODS:Preoperative high-spatial and -temporal resolution dynamic 4D contrast-enhanced MR imaging in 30 patients with surgically proved parathyroid adenomas was evaluated retrospectively. Using coregistered images, we placed ROIs over the parathyroid adenoma, thyroid gland, and a cervical lymph node (jugulodigastric) to obtain peak enhancement, time-to-peak, wash-in, and washout in each patient. Data were analyzed by logistic regression and analysis of variance. Receiver operating characteristic analysis was performed to determine the optimal parameters for determination of parathyroid adenomas versus thyroid tissue and cervical lymph nodes.RESULTS:Parathyroid adenomas showed significantly (P < .05) faster time-to-peak, higher wash-in, and higher washout compared with cervical lymph nodes and significantly (P < .05) higher peak enhancement, faster time-to-peak, higher wash-in, and higher washout compared with thyroid tissue. Logistic regression analysis indicated significant contribution from time-to-peak (P = .02), wash-in (P = .03), and washout (P = .008) for differentiation of parathyroid adenomas from thyroid and cervical lymph nodes. Using receiver operating characteristic analysis, we obtained the best diagnostic accuracy from a combination of time-to-peak/wash-in/washout in the differentiation of parathyroid adenomas versus lymph nodes (area under the curve, 0.96; sensitivity/specificity, 88%/90%) and in distinguishing parathyroid adenomas versus thyroid tissue (area under the curve, 0.96; sensitivity/specificity, 91%/95%).CONCLUSIONS:Dynamic 4D contrast-enhanced MR imaging can be used to exploit the hypervascular nature of parathyroid adenomas. Multiparametric MR perfusion can distinguish parathyroid adenomas from subjacent thyroid tissue or lymph nodes with diagnostic accuracies of 96%.

Single parathyroid adenoma (PTA) is the most common cause of primary hyperparathyroidism, accounting for approximately 80%–90% of all cases.¹ Definitive treatment requires surgical excision, and preoperative localization with imaging is commonly used to decrease the size of surgical incisions and complication rates.²Imaging has been increasingly used for preoperative detection of parathyroid adenomas. While sonography and technetium Tc99m sestamibi scintigraphy have often been used as first-line imaging to localize PTA, these tests are often inconclusive. This situation has led to the development of multiphasic CT (4D CT), which identifies PTAs through their hypervascular perfusion pattern compared with lymph nodes and the thyroid gland. 4D CT has shown superior accuracy compared with scintigraphy,³ though the radiation dose remains as high as 5.56–10.4 mSv.^4–6MR imaging is an attractive alternative to both scintigraphy and 4D CT due to the lack of radiation and has been used for the evaluation of PTAs with some success,^7–9 though not with the same effectiveness as 4D CT. Traditional technical limitations to localizing PTAs with MR imaging have recently been addressed with modern MR imaging technology. These include limited spatial and temporal resolution for multiphase dynamic contrast-enhanced MR imaging over a large FOV required for parathyroid imaging. This limitation can be addressed by the use of fast imaging tools such as time-resolved imaging with stochastic trajectories (TWIST)¹⁰ and improved parallel imaging techniques such as controlled aliasing in parallel imaging results in higher acceleration (CAIPIRINHA).¹¹ The second limitation is inhomogeneity of fat suppression in the neck required for detection of small parathyroid adenomas. The Dixon fat-suppression technique¹² can dramatically improve this shortcoming.¹³In this study by using a modified dynamic contrast-enhanced sequence with incorporation of a TWIST-CAIPIRINHA combination and the Dixon fat saturation technique, we sought to describe MR perfusion characteristics of PTAs in a cohort of patients with pathology-proved PTA. We hypothesized that MR perfusion biomarkers can differentiate PTA from PTA mimics, such as subjacent thyroid gland and cervical lymph nodes.     

Parathyroid imaging: comparison of double-tracer (T1-201, Tc-99m) scintigraphy and high-resolution US

Parathyroid scintigraphy using a double-tracer (T1-201, Tc-99m) subtraction technique depicted 17 of 23 (74%) parathyroid adenomas in patients with and without previous neck operations. High-resolution (10-MHz) ultrasound (US) depicted 18 (78%) of these adenomas. Average tumor size depicted by US was 17 X 10 X 8 mm (excluding a giant adenoma) and 19 X 10 X 9 mm by scintigraphy. Alone, neither modality was particularly sensitive in the depiction of primary hyperplasia of the parathyroid glands, but combined techniques were more effective than the use of a single modality. With both US and T1-201 scintigraphy, only two of 23 cases of parathyroid adenoma in the neck were missed, and none of the eight cases of secondary hyperplasia were missed. In 11 patients who had previously undergone neck surgery, parathyroid tumors were identified in eight by either US or double-tracer scintigraphy. Preoperative parathyroid imaging with double-tracer scintigraphy and high-resolution US is suggested for patients with hyperparathyroidism, particularly in those patients who have had previous parathyroid surgery.     

The spectrum of positive scan patterns in parathyroid scintigraphy

Parathyroid scintigraphy provides the clinician treating primary hyperparathyroidism with valuable information regarding the presence and location of parathyroid adenomas. In dual-phase imaging of the parathyroid glands, a widely employed technique that exploits the radiotracer washout characteristics of parathyroid adenomas, images are typically obtained at 20 minutes after administration of the radiotracer (Tc-99m sestamibi or Tc-99m tetrofosmin) and again at 2 hours after injection. Additional imaging of the thyroid is frequently performed to localize thyroid tissue, using Tc-99m pertechnetate or iodine-123.A positive examination can display one of several different patterns; a focus of increased radiotracer activity representing a parathyroid adenoma may be detected on the initial images, on the delayed images, or both. On the thyroid scan, the parathyroid adenoma (if it is discernible) may appear as a cold defect or a persistently hot focus. In our retrospective review of 148 consecutive patients over a 2-year period, 74 examinations were positive and had pathologic confirmation. These examinations were divided into 4 patterns: I (hot focus seen on initial and delayed images, and not on thyroid scan), II (hot focus seen only in initial images), III (hot focus seen only on delayed images), and IV (hot focus seen on initial, delayed and thyroid scan images). Results were as follows: pattern I, 88% (65/74); pattern II, 7% (5/74); pattern III, 3% (2/74); and pattern IV, 3% (2/74).Parathyroid adenomas produce several different patterns on dual-phase scintigraphy. To interpret the examination correctly, it is important for the radiologist to be aware of these patterns of positivity.     

Neck ultrasonography as preoperative localization of primary hyperparathyroidism with an additional role of detecting thyroid malignancy

Objective

To evaluate and compare the diagnostic performances of high-resolution ultrasonography and ^99mTc-sestamibi scintigraphy for the preoperative localization of abnormal parathyroid glands and to evaluate the ability of US for additional diagnostic roles in detecting thyroid malignancy in patients with pHPT.

Materials and methods

Preoperative localization images of 115 parathyroid adenomas from high-resolution ultrasonography (US) and ^99mTc-sestamibi scintigraphy (SS) were studied from 105 patients, who had undergone parathyroidectomy. Sensitivity, accuracy, and positive predictive value were calculated for the identification of adenomas in lesions and patients for both US and SS, respectively, and US and SS diagnostic performances were compared using generalized estimating equation.

Results

Preoperative imaging by both modalities localized 105 (93.8%) of the 112 parathyroid lesions confirmed at surgery and histology. Sensitivity, accuracy, and positive predictive value were 93.1% and 92.2%, 90.4% and 89.5%, and 96.9% and 96.9% by US and SS, respectively, without any statistically significant differences (P = 0.796, 0.796, 0.879). US found incidental thyroid nodules in 47 patients (47/107, 43.9%), and 7 patients (7/107, 6.5%) were confirmed to have malignancy based on pathology results (all had papillary thyroid carcinoma).

Conclusion

Neck ultrasonography and ^99mTc-sestamibi scintigraphy are complementary methods of the preoperative localization of parathyroid adenomas. Neck ultrasounds add an additional thyroid gland evaluation, and can be useful in the detection of incidental thyroid gland lesions, especially malignant nodules.     

Comparison between 99mTc-tetrofosmin/pertechnetate subtraction scintigraphy and 99mTc-tetrofosmin SPECT for preoperative localization of parathyroid adenoma in an endemic goiter area

RATIONALE AND OBJECTIVES: Technetium-99m-((99m)Tc-) tetrofosmin, a cationic, lipophilic complex like (99m)Tc-sestamibi, has proved to be a potential tracer for parathyroid scintigraphy despite some differences in washout behavior from the thyroid gland. Previous results comparing a double-phase technique with single-proton emission computed tomography (SPECT) or with subtraction techniques demonstrated a high detection rate, especially when SPECT and subtraction techniques were used, whereas the double-phase protocol revealed only moderate results. In this study, a direct comparison was made between (99m)Tc-tetrofosmin/pertechnetate subtraction and SPECT to elucidate the optimal protocol for tetrofosmin parathyroid imaging. METHODS: Twenty-three patients who were biochemically suspected of parathyroid adenoma or hyperplasia due to primary or tertiary hyperparathyroidism were included in our study. In all patients, serum calcium, phosphate, and intact parathormone levels were analyzed in a single blood sample before (99m)Tc-tetrofosmin/pertechnetate subtraction scintigraphy and SPECT. Ultrasound of the neck was performed in all patients to exclude false-positive results due to thyroid adenomas. All patients underwent parathyroidectomy with intraoperative revision of all parathyroid glands, and the histological results were compared with preoperative findings. RESULTS: Both imaging modalities, ie, subtraction scintigraphy and SPECT, correctly identified 20 of 23 (87%) histologically confirmed adenomas preoperatively. The positive predictive value was calculated to be 95% and 100%, respectively, for these two methods. Subtraction scintigraphy and SPECT showed concordant results in 19 patients (18 positive, 1 false-negative) and discordant results in 4 patients (2 positive with subtraction, 2 with SPECT). The combined use of subtraction scintigraphy and SPECT techniques revealed a sensitivity of 95.7% (22/23) and a positive predictive value of 95%. The whole procedure can be performed in less than 90 minutes per patient. Whereas subtraction scintigraphy tended to show more false-positive retentions due to thyroid adenomas, the interpretation of SPECT may be difficult in small adenomas with missing thyroid/parathyroid differential washout. CONCLUSIONS: Both imaging modalities, subtraction scintigraphy with pertechnetate and SPECT, are highly sensitive methods for parathyroid adenoma localization with (99m)Tc-tetrofosmin. However, our study did demonstrate that a combination of both modalities can further improve the diagnostic accuracy. Especially in an endemic goiter area, additional ultrasound may be required to avoid false-positive results due to thyroid adenomas.     

Preoperative Localization of Parathyroid Adenomas Using 4-Dimensional Computed Tomography: A Pictorial Essay

Accurate preoperative localization is the key to successful parathyroid surgery in the era of minimally invasive parathyroid surgery. This article presents and discusses the embryologic basis of parathyroid gland and ectopic location and different imaging modalities helpful in diagnosing and localizing parathyroid adenomas and/or hyperplasia. We also aim to review the current surgical concepts in treatment of parathyroid adenomas and/or hyperplasia, the utility of 4-dimensional computed tomography for accurate preoperative localization of hyperfunctioning parathyroid glands, imaging classification of adenomas and/or hyperplasia, and, finally, present some of the limitations of 4-dimensional computed tomography.     

Hyperparathyroidism: A comparison of sestamibi scintigraphy,mri, and ultrasonography

For patients with persistent or recurrent hyperpara-thyroldism, parathyroid imaging is indicated to confirm the presence of abnormal parathyroid gland(s) and identify their location. These imaging techniques are being modified constantly and newer methods have been developed. Sestamibi scintigraphy, MRI and sonography were compared in 23 patients with persistent or recurrent hyperparathyroidism. Preoperative 99m-Technetium Sestamibi (MIBI), MRI and ultraaono-graphic (US) studies of 23 patients with 25 histopatho-logically confirmed abnormal parathyroid glands were compared, using independent prospective interpretations. All patients had been operated upon previously for hyperparthytroidism. Accuracy of various combinations of MRI. MIBI, and US also were calculated. The results are shown for all abnormal glands (n = 25): sensitivities and accuracies were 88 and 84% for MRI. 80 and 80% for MIBI. and 58 and 44% for US. For only parathyroid adenomas (n = 18). sensitivities and accuracies were 89 and 89% for MRI, 94 and 94% for MIBI. and 58 and 39% for US. Finally, for parathyroid hyperplasla (n = 7 glands in five patients), sensitivities and accuracies were 83 and 71% for MRI. 43 and 43% for MIBI, and 57 and 57% for US. Either MIBI or MRI results were significantly better for detecting abnormal parathyroid glands than US (P <0.01), but MRI and MIBI were not statistically different. Combining MRI and MIBI produced a combined accuracy of 92%, whereas combining either of these tests with US did not improve on the accuracy of either test alone. In conclusion, for patients with persistent or recurrent hyperparathyroidism, MRI and MIBI are equally accurate for detecting abnormal parathyroid glands, and the combination of both tests may be more accurate than either test alone.     

Pre-operative localisation of hyperfunctional parathyroid tissue with <Superscript>11</Superscript>C-methionine PET

Purpose Previous studies have shown high sensitivity of positron emission tomography (PET) with ¹¹C-methionine in the pre-operative localisation of parathyroid adenoma and hyperplasia. Nonetheless, in secondary and tertiary hyperparathyroidism (HPT) and in patients with recurrent disease, pre-operative localisation of adenomatous (PTA) or hyperplastic tissue is still a problem with all available methods. The aim of this study was to define the optimal imaging protocol and to compare the diagnostic value of ¹¹C-methionine PET and ^99mTc-methoxyisobutylisonitrile (MIBI) single-photon emission computed tomography (SPECT): in particular, we wished to define the benefit of ¹¹C-methionine in those patients with inconclusive or negative conventional imaging.Methods Thirty highly pre-selected patients with HPT were enrolled. Sixteen patients had primary HPT, 12 patients had secondary HPT, and two patients had recurrences of parathyroid carcinomas. All patients had ultrasound of the neck, dual-phase scintigraphy with ^99mTc-MIBI and PET with ¹¹C-methionine. SUV_parathyroid/SUV_{cervical soft tissue} (target-to-background) and SUV_{parathyroid tissue}/SUV_{thyroid tissue} (target-to-non-target) ratios were calculated. After surgery, histology of specimens was obtained in all patients but one.Results In 12 patients with secondary or tertiary HPT, 36 hyperplastic parathyroid glands were histologically verified. Twenty-five of 36 lesions (69%) were detected with ¹¹C-methionine PET and 17 (47%) with ^99mTc-MIBI scintigraphy. PET studies were positive in 17/18 (94%) cases in which HPT was related to adenomas or carcinomas. ^99mTc-MIBI scintigraphy/SPECT yielded pathological lesions in 9/18 cases (50%). All eight atypical localisations of parathyroid glands were detected with PET but only six of the eight were detected with ^99mTc-MIBI scintigraphy/SPECT. In 10/11 patients with recurrent HPT and non-diagnostic scintigraphy/SPECT, hyperfunctional parathyroid tissue was identified with ¹¹C-methionine PET. The highest SUV_parathyroid/SUV_{cervical soft tissue} ratio was found 10 min, and the highest SUV_{parathyroid tissue}/SUV_{thyroid tissue} ratio 40 min post injection. In three patients clear delineation of hyperfunctional tissue was only achieved after 40 min post injection.Conclusion ¹¹C-methionine PET is a clinically useful method in highly pre-selected patients with recurrent primary HPT as well as in secondary and tertiary HPT if ultrasound and ^99mTc-MIBI SPECT are inconclusive or negative. PET imaging of atypical PTA localisations is more accurate than conventional scintigraphy. In order to achieve optimal contrast of parathyroid glands versus thyroid tissue and adjacent soft tissue, imaging at both 10 min and 40 min is recommended.     

Optimization of peroperative procedures

Minimally invasive radio-guided surgery (MIRS) of parathyroid adenomas has been favoured by three main factors. One is the significant improvements achieved in preoperative localizing imaging, particularly with sestamibi scintigraphy. Another is the availability of intra-operative quick parathyroid hormone measurement, and finally the increase in availability of the intra-operative gamma probes in many surgical centres especially those performing sentinel node biopsy. In contrast with the traditional wide bilateral neck exploration (BNE), MIRS requires strict inclusion criteria: 1) high probability of a solitary parathyroid adenoma, 2) a significant sestamibi uptake in the parathyroid adenoma, 3) absence of a concomitant thyroid nodular disease, 4) no family history of familial hyperparathyroidism (HPT) of multiple endocrine neoplasia, 5) no previous neck irradiation. Following these criteria about 60-70% of all primary HPT patients are suitable for a MIRS. Two main protocols for MIRS have been proposed. The single day, imaging and surgery, protocol is based on the injection of a 740 MBq dose of 99mTc sestamibi with the purpose of obtaining scintigraphic imaging and then MIRS within 3 hours from radio-tracer injection. An alternative is for imaging to be performed a few days before surgery, with a further small administered activity of 37MBq of 99mTc sestamibi injected intravenously in the operating theatre a few minutes before commencing the intervention for the purpose of MIRS only. The latter protocol allows both better planning of operating theatre scheduling and reduction of the radiation exposure to the surgical staff. The main advantages of MIRS in respect to the traditional BNE include less surgical trauma, a shorter duration of anaesthesia and surgery, a shorter hospital stay with the possibility of same-day discharge, less post-surgical pain with improved cosmetic results and lower costs. Moreover, MIRS has proven to be a safe technique with a low morbidity rate and a cure rate higher than 95% in patients with primary HPT.     

Role of Tc-99m sestamibi scintigraphy in the diagnosis and surgical decision-making process in primary hyperparathyroid disease

PURPOSE: Ultrasound (US) and scintigraphy are used most frequently of all the available imaging techniques for the preoperative evaluation of patients with possible primary hyperparathyroid disease. The aim of this study was to assess the value of dual-phase Tc-99m MIBI scintigraphy compared with US in the detection of adenomatous or hyperplastic glands and in the surgical decision-making process for patients with a biochemical diagnosis of primary hyperparathyroid disease. METHODS: Ninety-seven patients with increased levels of parathyroid hormone and calcium, and at least 6 months' follow-up after US and scintigraphy, were examined retrospectively to assess the influence of the diagnostic work-up on the therapeutic decision of the referring clinicians and to evaluate the sensitivity of these diagnostic tools in the surgically treated patients. Forty-eight patients underwent surgery. RESULTS: Parathyroid adenomas were found in 43 patients and hyperplasia in 1, whereas 4 patients had no evidence at surgery. The sensitivity and specificity rates were 84.4% and 95.9% for scintigraphy, and 66.6% and 98.6% for US, respectively. Of the 49 nonsurgically treated patients, 35 had negative results with both MIBI and US; only 3 had positive findings with both imaging methods. Patients treated conservatively had significantly lower parathyroid hormone and serum calcium levels than did the patients who had surgery. CONCLUSIONS: The data suggest that the high sensitivity of dual-phase MIBI scintigraphy can improve the detection of hyperfunctioning parathyroid glands. Furthermore, despite the controversy surrounding the use of imaging methods in the preoperative assessment of primary hyperparathyroid disease, these data suggest that the decision of the clinician to order surgery for a patient with a moderate increase of serum PTH level may be influenced by the results of the imaging methods.     

Hyperparathyroidism: comparison of MR imaging with radionuclide scanning

Twenty-three patients with hyperparathyroidism were evaluated preoperatively with magnetic resonance (MR) imaging. Twenty patients also underwent thallium-201/technetium-99m scintigraphy. Of 22 patients with primary hyperparathyroidism, 12 had persistent or recurrent disease. One had secondary hyperparathyroidism due to end-stage renal disease. MR imaging allowed accurate localization of abnormal parathyroid glands in 64% evaluated prospectively and 82% evaluated retrospectively. Scintigraphy allowed localization of 60% evaluated prospectively and 70% retrospectively. The two imaging modalities together allowed detection of 68% evaluated prospectively and 91% retrospectively. MR imaging allowed detection of two of five mediastinal adenomas evaluated prospectively and four of five retrospectively. In patients who underwent both imaging studies, MR was more successful in those with previous neck surgery (73% evaluated prospectively and 91% retrospectively) than in those with no prior surgery (57% prospectively and 71% retrospectively). Scintigraphy allowed accurate localization in 64% evaluated prospectively and 64% retrospectively in patients with previous surgery versus 57% prospectively and 86% retrospectively in patients with no prior neck surgery. Four false-positive results were obtained with MR imaging and three with scintigraphy. MR imaging was useful for parathyroid localization in patients with hyperparathyroidism, particularly in patients requiring additional surgery.     

MRI,CT, sonography and thallium-technetium subtraction scintigraphy for the detection of parathyroid disease: a four-year experience

Sonography, subtraction scintigraphy, computed tomography and MRI were compared in 100 patients who had surgery 105 times for hyperparathyroidism (HPT). Surgical and pathological data were available for all operations. A total of 105 MR, 77 CT, 84 sonograms and 70 subtraction scintigrams were performed. The ability of the imaging modalities, individually and in combination, to detect HPT, histology, size, concomitant thyroid disease and location of the diseased glands has been evaluated. For primary HPT, sensitivity ranged from 68% for MRI to 40% for scintigraphy but was much lower for tertiary HPT with all modalities. The ability to identify diseased glands was strongly size dependent for all methods. If patients had had previous neck surgery, the most sensitive methods were MRI and scintigraphy and this also held true for patients with concomitant thyroid disease and ectopically located glands.The findings presented suggest that while sonography may be the only imaging examiantion warranted in newly diagnosed parathyroid disease, recurrent disease should be examined pre-operatively with MRI and possibly subtraction scintigraphy. Correspondence to: G. K. von Schulthess     

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.     

2009 EANM parathyroid guidelines

The present guidelines were issued by the Parathyroid Task Group of the European Association of Nuclear Medicine. The main focus was imaging of primary hyperparathyroidism. Dual-tracer and single-tracer parathyroid scintigraphy protocols were discussed as well as the various modalities of image acquisition. Primary hyperparathyroidism is an endocrine disorder with high prevalence, typically caused by a solitary parathyroid adenoma, less frequently (about 15%) by multiple parathyroid gland disease (MGD) and rarely (1%) by parathyroid carcinoma. Patients with MGD may have a double adenoma or hyperplasia of three or all four parathyroid glands. Conventional surgery has consisted in routine bilateral neck exploration. The current trend is toward minimally invasive surgery. In this new era, the success of targeted parathyroid surgery depends not only on an experienced surgeon, but also on a sensitive and accurate imaging technique. Recognizing MGD is the major challenge for pre-operative imaging, in order to not direct a patient towards inappropriate minimal surgery. Scintigraphy should also report on thyroid nodules that may cause confusion with a parathyroid adenoma or require concurrent surgical resection. The two main reasons for failed surgery are ectopic glands and undetected MGD. Imaging is mandatory before re-operation, and scintigraphy results should be confirmed with a second imaging technique (usually US for a neck focus, CT or MRI for a mediastinal focus). Hybrid SPECT/CT instruments should be most helpful in this setting. SPECT/CT has a major role for obtaining anatomical details on ectopic foci. However, its use as a routine procedure before target surgery is still investigational. Preliminary data suggest that SPECT/CT has lower sensitivity in the neck area compared to pinhole imaging. Additional radiation to the patient should also be considered. The guidelines also discuss aspects related to radio-guided surgery of hyperparathyroidism and imaging of chronic kidney disease patients with secondary hyperparathyroidism.     

Incremental diagnostic value of preoperative 99mTc-MIBI SPECT in patients with a parathyroid adenoma.

The purpose of this prospective study was to evaluate the diagnostic value of early parathyroid SPECT combined with quantitative analysis as compared with planar imaging in patients undergoing minimally invasive radioguided surgery. METHODS: A total of 52 consecutive patients with primary hyperparathyroidism underwent planar and SPECT parathyroid scintigraphy 2-5 d before surgery. Each patient had a single-tracer dual-phase technique using (99m)Tc-methoxyisobutylisonitrile ((99m)Tc-MIBI) and a double-tracer subtraction technique using a delayed (99m)Tc-pertechnetate scan. Immediately after the first (99m)Tc-MIBI planar image, a SPECT study was acquired. Before radioguided parathyroidectomy, each patient was reinjected with (99m)Tc-MIBI. Serum calcium levels were available for all patents before surgery and at 8 and 24 h after surgery. Serum parathyroid hormone (PTH) levels were also available for all patients. Quantitative analysis was performed using the average count ratio of parathyroid to left thyroid lobe, right thyroid lobe, and maximum thyroid activity. All patients had histopathologic examination of the removed glands. RESULTS: The average time for radioguided surgery was 30 min (range, 20-40 min). Postsurgical calcium levels correlated significantly with the adenoma weight (r = 0.5; P = 0.016). Combined planar scintigraphy correctly identified 41 adenomas (79%). SPECT increased the sensitivity to 96%. SPECT was superior to planar imaging in 9 patients, mainly in patients with ectopic adenomas or with multinodular goiters. Gland size did not affect significantly the detectability of SPECT. (99m)Tc-MIBI retention was noted in only 31 adenomas (60%). The average uptake ratios of parathyroid counts to the left lobe, right lobe, and maximum thyroid activity were 1.20 +/- 0.42, 1.29 +/- 0.45, and 0.84 +/- 0.35, respectively. The latter ratio was significantly correlated with PTH levels before surgery (r = 0.408; P = 0.04). CONCLUSION: Our data indicate that early preoperative SPECT in patients with primary hyperparathyroidism is essential for accurate localization of parathyroid adenomas and for the selection of patients who are candidates for minimally invasive radioguided surgery. Planar parathyroid imaging is less sensitive compared with SPECT, and washout kinetics of (99m)Tc-MIBI are unreliable in the dual-phase technique. Patients with higher presurgical PTH levels may especially benefit from radioguided surgery.     

Parathyroid scintigraphy.

Parathyroid scintigraphy, first proposed in the seventies, has developed an irreplaceable role in the preoperative location of enlarged parathyroid tissues. The contribution of Ferlin, who in the early eighties proposed the use of the potassium analogue 201Thallium and subtraction scintigraphy to obviate thyroid tissue interference was especially important. At the present time, this imaging modality, is widely accepted for the preoperative localization of parathyroid adenomas owing to its high accuracy and reproducibility. Various modified acquisition and processing protocols have been reported and 201Thallium still continues to be used, but other radiopharmaceuticals, such as 99mTc-methoxyisobutyl isonitrile (99mTc-MIBI) and 99mTc-tetrofosmin are now often preferred, especially because of the more favourable physical properties of the Technetium labelling. In some cases, thyroid subtraction scintigraphy can be replaced by dual phase 99mTc-methoxyisobutyl isonitrile acquisition. There is also an increasing interest in SPECT studies, which have the potential to more accurately locate the sites of adenomas and allow for detection of smaller lesions, which further increases total sensitivity and accuracy of the technique.     

Diagnostic performance of planar scintigraphy using 99mTc-MIBI in patients with secondary hyperparathyroidism: a meta-analysis

Objective

Parathyroid scintigraphy using ^99mTc-MIBI is not currently considered a valuable diagnostic tool for the localization of involved glands in patients with secondary hyperparathyroidism (SHPT). However, published data about its diagnostic accuracy are discordant and a meta-analysis about this topic is still lacking. The aim of our study is to meta-analyze the published data about the diagnostic performance of ^99mTc-MIBI parathyroid scintigraphy in patients with SHPT.

Methods

A comprehensive computer literature search of studies published in PubMed/MEDLINE, Scopus and Embase databases through September 2011 and regarding the diagnostic accuracy of ^99mTc-MIBI parathyroid scintigraphy in patients with SHPT was carried out. Only articles in English language in which at least 10 patients with SHPT underwent planar ^99mTc-MIBI parathyroid scintigraphy were selected. Pooled sensitivity, pooled specificity and area under the ROC curve on a per lesion-based analysis were calculated to measure the diagnostic accuracy of ^99mTc-MIBI parathyroid scintigraphy in SHPT patients.

Results

Twenty-four studies comprising 471 patients were included in this meta-analysis. The pooled sensitivity and specificity of ^99mTc-MIBI parathyroid scintigraphy in detecting hyperplastic glands in SHPT patients were 58?% [95?% confidence interval (95?% CI) 52?C65?%] and 93?% (95?% CI 85?C100?%), respectively, on a per lesion-based analysis. Area under ROC curve was 0.75.

Conclusions

In patients with SHPT and diffuse or nodular hyperplasia, planar parathyroid scintigraphy using ^99mTc-MIBI has demonstrated an inadequate diagnostic accuracy. Therefore, it should not be considered as a first-line diagnostic imaging method in the pre-surgical detection of hyperplastic parathyroid glands.