Localization of parathyroid adenomas using 11C-methionine positron emission tomography

BACKGROUND AND AIM: In symptomatic hyperparathyroidism, pre-surgical localization of the suspected site of adenoma is desirable. All widely available techniques may have difficulty in localizing the site. The aim of this study was to determine whether 11C-methionine positron emission tomography (PET) could accurately localize parathyroid adenomas in patients in whom conventional imaging had failed. PATIENTS AND METHODS: Fifty-one patients presenting with hyperparathyroidism, and in whom other imaging techniques had failed to definitely identify the site of adenoma, were reviewed retrospectively after 11C-methionine PET scanning. Patients were followed up by surgical histology, or clinically if surgery was not performed. RESULTS: 11C-Methionine PET scanning was found to have a sensitivity of 83%, a specificity of 100% and an accuracy of 88% in successfully locating parathyroid adenomas. Most false negatives were due to adenomas in the lower mediastinum that was outside the area of scanning. CONCLUSIONS: 11C-Methionine PET is a reliable and highly accurate technique for localizing parathyroid adenomas in patients in whom conventional imaging techniques have failed. It is necessary to image to the level of the lower mediastinum.     

A hidden parathyroid adenoma behind a thyroid autonomous nodule causing multiple brown tumors: advantages of tomography imaging over planar imaging

A 56-year-old man who had diffuse bone pain and weight loss for 1 year underwent FDG PET/CT and a dual-tracer, dual-phase parathyroid imaging. The FDG PET/CT scan showed foci of increased metabolism in several bones and the stomach, which were proven histologically as brown tumor and gastritis. The planar images of parathyroid imaging revealed only thyroid nodule, whereas the tomographic imaging demonstrated both the thyroid and the parathyroid adenomas, which were confirmed by surgical pathology.     

Dual Pathologies of Parathyroid Adenoma and Papillary Thyroid Cancer on Fluorocholine and Fluorodeoxyglucose PET/CT

¹⁸F-Fluorocholine (FCH) PET/CT is evolving as a functional imaging modality for the preoperative imaging of abnormal parathyroid tissue(s) helping to localize eutopic and ectopic parathyroid tissue and limit the extent of surgery. FCH PET/CT may show incidental uptake in various thyroid lesions necessitating further evaluation, whereas the role of ¹⁸F-fluorodeoxyglucose (FDG) PET/CT in the detection of incidental thyroid nodules is well documented. The case of a middle-aged woman with dual pathology of parathyroid adenoma and papillary thyroid cancer detected on FCH and FDG PET/CT is presented.     

Multi-modality parathyroid imaging: A shifting paradigm

The goal of parathyroid imaging in hyperparathyroidism is not diagnosis, rather it is the localization of the cause of hyperparathyroidism for planning the best therapeutic approach. Hence, the role of imaging to accurately and precisely localize the abnormal parathyroid tissue is more important than ever to facilitate minimally invasive parathyroidectomy over bilateral neck exploration. The common causes include solitary parathyroid adenoma, multiple parathyroid adenomas, parathyroid hyperplasi...     

Parathyroid adenomas and hyperplasia. Dual radionuclide scintigraphy and bone densitometry studies

Dual radionuclide imaging of the neck (Tc-99m pertechnetate and TI-201 thallous chloride) was performed in 22 patients with chemical evidence of hyperparathyroidism (elevated blood calcium and parathormone [PTH] levels). Of these, 19 of 22 had localization of a TI-201 "excess" area on radiothallium-radiotechnetium subtraction images. In 13 patients who have had operative confirmation at this writing, the dual radionuclide imaging was positive in 12 (12/13 = 92.3%). One patient had two parathyroid adenomas, both of which were seen on the images; thus, overall detection was 13 out of 14 or 92.8%. The parathyroid adenomas visualized weighed from 0.06 to 3.0 g; the one not detected weighed 0.25 g. In three patients with parathyroid hyperplasia secondary to renal disease, the subtraction imaging detected eight of 12 glands (66.7%). The forearm bone mineral content and bone density were determined in eight patients with parathyroid adenomas; results were abnormally low in five of these eight. One of the three patients with secondary hyperparathyroidism had an abnormally low radial bone mass. The combination of dual radionuclide imaging and radial bone mass determination may present a useful approach in both localizing abnormal parathyroid tissue and in examining its functional consequences.     

Co-existent parathyroid adenoma and thyroid carcinoma. Nonspecificity of dual tracer parathyroid imaging for parathyroid lesions

Dual tracer parathyroid imaging (DTPI) using Tc-99m and TI-201 has a reported sensitivity of 92% for the detection of parathyroid adenomas. A patient with biopsy-proven parathyroid adenoma as well as papillary thyroid carcinoma is presented. To date, this is the first such case ever to be reported and implies that DTPI, although a sensitive diagnostic modality for parathyroid adenoma detection, is not specific. The diagnosis of primary hyperparathyroidism has recently been established more frequently than in the past due to detection of elevated serum calcium levels on routine blood samples, relatively sensitive parathormone (PTH) assays, and noninvasive imaging modalities such as nuclear medicine, CT scanning, and ultrasonography. At our institution, we have successfully detected the location of parathyroid adenomas in many cases, using the dual tracer method with TI-201 and Tc-99m, confirmed at surgery. We present a case of primary hyperparathyroidism in which two distinct lesions were detected by nuclear imaging: one lesion was proven at surgery to be a parathyroid adenoma, while the other represented thyroid carcinoma.     

I-131 metaiodobenzylguanidine uptake in a parathyroid adenoma

We describe a patient with multicentric small bowel carcinoids, severe hypertension, primary hyperparathyroidism, and multiple parathyroid adenomas. Intense uptake of I-131 metaiodobenzylguanidine (MIBG) occurred in a parathyroid adenoma. There was no biochemical evidence of catecholamine secretion by the tumor but elevated serum levels of parathyroid hormone were demonstrated. We suspect that occasional parathyroid adenomas, like other APUDomas, may give false positive results when MIBG imaging is used to search for pheochromocytomas. This observation supports the inclusion of the parathyroid chief cells in the amine precursor uptake and decarboxylation (APUD) cell system.     

Localization of ectopic parathyroid glands using technetium-99m sestamibi imaging: Comparison with magnetic resonance and computed tomographic imaging

The aim of the study was to compare the accuracy of technetium-99m sestamibi imaging for localization of ectopic parathyroid glands in patients with hyperparathyroidism with that of magnetic resonance (MR) and computed tomographic (CT) imaging. Eleven patients with primary (n=3) or secondary (n=8) hyperparathyroidism were studied with^99mTc sestamibi parathyroid imaging CT and MR imaging. Images of the neck were acquired at 10 min and 2–3 after tracer injection. The three patients with primary hyperparathyroidism and five patients with secondary hyperparathyroidism underwent parathyroidectomy. The ectopic glands were confirmed by histopathological examination of the resected specimens. In respect of 20 parathyroid glands in the eight patients explored surgically, the sensitivity and specificity of sestamibi imaging were 70% (14/20) and 88%, respectively, those of CT, 40% (8/20) and 88%, and those of MR imaging, 60% (12/20) and 88%. Of these patients, three had parathyroid adenomas while five had hyperplasia (17 glands). Sestamibi imaging localized eight ectopic parathyroid glands, which were surgically confirmed (six were located in the thymus and two in the mediastinum). In one patient explored surgically, the ectopic gland was located outside the field of the MR coil. Although the remaining three cases of secondary hyperparathyroidism were not confirmed surgically, these patients demonstrated sestamibi uptake in five parathyroid glands, including three ectopic glands. MR images demonstrated abnormal parathyroid glands in the same regions as sestamibi imaging. Our data indicate that^99mTc-sestamibi imaging should be used initially to localize the ectopic parathyroid glands in patients with hyperparathyroidism for anatomical guidance prior to MR or CT imaging.     

Parathyroid adenoma screening efficacies of different imaging tools and factors affecting the success rates

PurposeWe aimed to compare the efficacy of three different parathyroid adenoma screening tools—high-resolution ultrasonography (USG), technetium Tc 99m-methoxyisobutylisonitrile (MIBI) parathyroid scintigraphy, and magnetic resonance imaging (MRI)—and we evaluated the factors affecting the detection success rates.MethodsParathyroid imaging was evaluated by USG, double-phase 99mTc-MIBI parathyroid scintigraphy, and cervical MRI in patients with hyperparathyroidism (n=39).ResultsAmong the 39 patients, USG, parathyroid scintigraphy, and MRI correctly identified 35 adenomas (89.7%), 28 adenomas (71.8%), and 26 adenomas (66.7%), respectively. Positive predictive values for USG (34/35), scintigraphy (27/28), and cervical MR (26/26) imaging were 97.1%, 96%, and 100%, respectively. Parathyroid adenomas were detected with 92.3% (36/39) certainty when both USG and scintigraphy modalities were applied together. Minimally invasive parathyroidectomy under local anesthesia with unilateral incision was successfully performed in 24 (61.5%) patients.ConclusionsMinimally invasive surgery for parathyroid adenomas has been developed and has equal success with traditional surgery. However, accurate localization of adenomas should be obtained prior to surgery. In this study, ultrasound was found to be effective in localizing adenomas for successful surgery. Adding other imaging modalities does not improve localizing the parathyroid adenomas.     

Hepatic adenomatosis may mimic metastatic lesions of liver with 18F-FDG PET/CT

Hepatic adenomatosis is an uncommon benign neoplasm, with the presence of multiple adenomas (generally more than 4) within the liver. A 52-year-old woman presented with multiple (>10) solid liver lesions detected with abdominal ultrasonography and verified with magnetic resonance imaging (MRI). Subsequently, F-18 FDG PET/CT demonstrated increased uptake in these lesions. Histology revealed hepatic adenomatosis. F-18 FDG PET/CT cannot reliably differentiate hepatic adenomas from malignant processes on the basis of uptake.     

Dual isotope parathyroid imaging

Eleven patients who had clinical and biochemical evidence of primary hyperparathyroidism were studied using dual isotope technetium-thallium parathyroid subtraction imaging. The parathyroid scans correctly identified all surgically proven parathyroid adenomas. Three abnormal foci also were identified that were not parathyroid adenomas. These were caused by adenocarcinoma metastatic to a lymph node, primary papillary carcinoma of the thyroid, and parathyroid hyperplasia. This report also demonstrates the importance of surgically examining all abnormal sites of uptake.     

Detection and localization of parathyroid adenomas in patients with hyperparathyroidism using a single radionuclide imaging procedure with technetium-99m-sestamibi (double-phase study)

Dual radionuclide imaging using a combination of 201Tl with either 99mTcO4- or 123I is recognized as a useful procedure in the preoperative localization of parathyroid adenomas. Recently, 99mTc-sestamibi (MIBI) has been introduced for myocardial perfusion imaging as an alternative to 201Tl. The purpose of this prospective study was to evaluate parathyroid scan using early and late imaging following MIBI injection. Twenty-three patients (21 F, 2 M, mean age: 57 yr) with a clinical and biologic diagnosis of hyperparathyroidism were submitted to a MIBI study prior to surgical exploration of the neck. Cervico-thoracic planar imaging (anterior view, 10 min/view) was performed at 15 min and at 2-3 hr after an intravenous injection of 20-25 mCi of MIBI. A positive MIBI scan for parathyroid adenoma was defined as an area of increased focal uptake which persisted on late imaging, contrary to the uptake in the normal thyroid tissue which progressively decreases over time (differential washout). Surgical exploration of the neck, performed between 1 day and 72 days (average: 16 days) after the MIBI study, showed a parathyroid adenoma in 21 patients and hyperplasia in two patients. MIBI scan correctly detected and localized 19/21 adenomas (90%). In conclusion, parathyroid imaging using a single radionuclide with MIBI (early and late study with differential washout analysis) is a promising procedure in the preoperative detection and localization of parathyroid adenomas in patients with primary hyperparathyroidism.     

Pituitary adenoma detected on FDG positron emission tomography in a patient with mucosa-associated lymphoid tissue lymphoma

A 52-year-old woman with a history of treated non-Hodgkin's lymphoma, B-cell type, was examined for a right eyelid mass proved on excision to be a mucosa-associated lymphoid tissue lymphoma. She was referred for F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) imaging of the whole body, including the brain, to identify the possible presence or recurrence of lymphoma. The FDG-PET images revealed focal marked FDG uptake in the pituitary gland but no evidence of abnormal metabolic sites in the rest of the body, including the orbital regions. Magnetic resonance imaging and computed tomography confirmed a 1.8 x 1.5 cm intrasellar mass. Surgery was performed, and histologic examination revealed a nonfunctional adenoma that was negative for leukocyte common antigen staining, an antigen that is positive in lymphoma but negative in pituitary adenoma. This case provides evidence for avid uptake of FDG on PET imaging of pituitary adenomas.     

三发性甲状旁腺功能亢进伴巨大甲状旁腺腺瘤99Tcm-MIBI SPECT/CT显像一例

笔者报道了1例三发性甲状旁腺功能亢进（HPT）伴巨大甲状旁腺腺瘤的99Tcm-MIBI SPECT/CT显像病例。从临床症状、实验室检查及影像学检查结果综合分析了该病的特点,通过文献复习加深了对三发性HPT的认识。三发性HPT常见于慢性肾功能不全的透析患者,其甲状旁腺长期受到低血钙的刺激,部分组织增生后转变为具有自主分泌功能的腺瘤,其发病率较低,内科治疗效果欠佳,及时进行99Tcm-MIBI SPECT/CT显像可以进一步定性、定位,利于为患者选择更为合适的治疗方案。     

Parathyroid scintigraphy: comparison of technetium-99m methoxyisobutylisonitrile and technetium-99m tetrofosmin studies

We report the preliminary results of a prospective study demonstrating tetrofosmin uptake in surgically and histologically proven parathyroid adenomas. In ten patients with primary chronic hyperparathyroidism, parathyroid imaging was performed using (1) technetium-99m methoxyisobutylisonitrile (MIBI) and (2)^99mTc-1,2-bis(bis(2-ethoxyethyl)phosphino)ethane (tetrofosmin) within a time interval of 3–5 days. Both tracers correctly identified the parathyroid adenomas by focal prolonged tracer retention. On visual inspection image contrast was generally higher with MIBI than with tetrofosmin in all the patients studied. Tetrofosmin showed a slower elimination from the parathyroid adenomas than MIBI in six of the ten cases. Our preliminary results show that tetrofosmin, like MIBI, as a feasible, sensitive tracer for parathyroid scintigraphy. For routine use, the rapid kit preparation without heating and the lower radiation dose to the patient make tetrofosmin an alternative tracer for parathyroid scintigraphy. Further evaluation is needed to determine which of the two tracers is the more sensitive for the detection of parathyroid adenomas, and which tracer properties better reflect the degree of endocrine activity.[/p]     

Pre-operative Localization of Parathyroid Adenomas: A Comparison of Power and Colour Doppler Ultrasonography with Nuclear Medicine Scintigraphy

AIM: To compare power and colour Doppler ultrasonography (US) with nuclear medicine scintigraphy (NM) in the preoperative localization of parathyroid adenomas in patients with primary hyperparathyroidism (PHPT). MATERIALS AND METHODS: Thirty-one patients with biochemical evidence of PHPT underwent pre-operative US and NM for parathyroid adenoma localization. Both studies were interpreted independently without prior knowledge of the other study's findings. All patients had surgical removal of the parathyroid adenoma utilizing standard neck exploration or minimally invasive unilateral surgical techniques with rapid serum assay of circulating parathyroid hormone levels. RESULTS: All patients had single parathyroid adenomas at surgery. Prospective sensitivities for US, NM and both studies combined were 65%, 68%, and 74%, respectively, with a positive predictive value of 100% each. The adenoma was localized by only one imaging modality in 16% of cases. CONCLUSIONS: US and NM provide complementary roles in the pre-operative localization of parathyroid adenomas in patients with PHPT.     

Comparison of pinhole and SPECT 99mTc-MIBI imaging in primary hyperparathyroidism

OBJECTIVE: This study aims to compare dual tracer, dual phase pinhole technetium-99m labelled 2-methoxyisobutylisonitrile (Tc-MIBI) imaging (including oblique imaging), with single photon emission computed tomography (SPECT) and dual phase planar Tc-MIBI images, and combined SPECT, dual phase planar Tc-MIBI images and anterior pinhole thyroid images for the localization of parathyroid adenomas in the neck in primary hyperparathyroidism. METHODS: Sixty-two patients underwent Tc-MIBI dual phase, anterior and anterior oblique pinhole images of the neck, anterior planar images of the neck and chest and early phase neck/chest SPECT followed by [Tc] pertechnetate anterior and anterior oblique pinhole thyroid images. Images were reviewed by consensus in three combinations - dual phase anterior and anterior oblique pinhole Tc-MIBI images and pinhole thyroid images; SPECT and dual phase planar Tc-MIBI images and combined SPECT, dual phase planar Tc-MIBI images and anterior pinhole thyroid images. RESULTS: For 52 parathyroid adenomas in 50 patients, the sensitivity of dual phase anterior and anterior oblique pinhole Tc-images and pinhole thyroid images was 81%. Significantly lower sensitivities were observed with SPECT and dual phase planar Tc-MIBI images (54%, P=0.0005) and combined SPECT, dual phase planar Tc-MIBI images and anterior pinhole thyroid images (65%, P=0.0209). The positive predictive value for all imaging combinations was 88-92%. CONCLUSION: Dual phase anterior and anterior oblique pinhole Tc-MIBI images and pinhole thyroid images are significantly more sensitive than imaging combinations that included SPECT and remains the optimal imaging protocol for the localization of parathyroid adenomas in the neck in primary hyperparathyroidism.     

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.     

<Superscript>18</Superscript>F-Fluorocholine PET/CT in the assessment of primary hyperparathyroidism compared with <Superscript>99m</Superscript>Tc-MIBI or <Superscript>99m</Superscript>Tc-tetrofosmin SPECT/CT: a prospective dual-centre study in 100 patients

Purpose

In this prospective study we compared the accuracy of ¹⁸F-fluorocholine PET/CT with that of ^99mTc-MIBI or^99mTc-tetrofosmin SPECT/CT in the preoperative detection of parathyroid adenoma in patients with primary hyperparathyroidism. We also assessed the value of semiquantitative parameters in differentiating between parathyroid hyperplasia and adenoma.

Methods

Both ¹⁸F-fluorocholine PET/CT and ^99mTc-MIBI/tetrofosmin SPECT/CT were performed in 100 consecutive patients with biochemical evidence of primary hyperparathyroidism. At least one abnormal focus on either ¹⁸F-fluorocholine or ^99mTc-MIBI/tetrofosmin corresponding to a parathyroid gland or ectopic parathyroid tissue was considered as a positive finding. In 76 patients with positive findings on at least one imaging modality, surgical exploration was performed within 6 months, and the results were related to histopathological findings and clinical and laboratory findings at 3–6 months as the standard of truth. In 24 patients, no surgery was performed: in 18 patients with positive imaging findings surgery was refused or considered risky, and in 6 patients imaging was negative. Therefore, data from 82 patients (76 undergoing surgery, 6 without surgery) in whom the standard of truth criteria were met, were used in the final analysis.

Results

All patients showed biochemical evidence of primary hyperparathyroidism with a mean serum calcium level of 2.78?±?0.34 mmol/l and parathormone (PTH) level of 196.5?±?236.4 pg/ml. The study results in 76 patients with verified histopathology and 3 patients with negative imaging findings were analysed. Three of six patients with negative imaging showed normalized serum PTH and calcium levels on laboratory follow-up at 3 and 6 months, and the results were considered true negative. In a patient-based analysis, the detection rate with ¹⁸F-fluorocholine PET/CT was 93% (76/82), but was only 61% (50/82) with ^99mTc-MIBI/tetrofosmin SPECT/CT. In a lesion-based analysis, the sensitivity, specificity, positive predictive value, negative predictive value and overall accuracy of ¹⁸F-fluorocholine PET/CT in the detection of parathyroid adenoma were 93.7%, 96.0%, 90.2%, 97.4% and 95.3%, respectively, and of ^99mTc-MIBI/tetrofosmin SPECT/CT were 60.8%, 98.5%, 94.1%, 86.3% and 87.7%, respectively. Although ¹⁸F-fluorocholine PET-positive adenomatous lesions showed higher SUVmax values than the hyperplastic glands (6.80?±?3.78 vs. 4.53?±?0.40) in the semiquantitative analysis, the difference was not significant (p?=?0.236). The mean size (measured as the length of the greatest dimension) and weight of adenomas were 15.9?±?7.6 mm (median 15 mm, range 1–40 mm) and 1.71?±?1.86 g (median 1 g, range: 0.25–9 g), respectively. Among the analysed parameters including serum calcium and PTH and the size and weight of parathyroid adenomas, size was significantly different between patients with negative ^99mTc-MIBI/tetrofosmin SPECT/CT and those with positive ^99mTc-MIBI/tetrofosmin SPECT/CT (mean size 13.4?±?7.6 mm vs. 16.9?±?7.4 mm, respectively; p?=?0.042).

Conclusion

In this prospective study, ¹⁸F-fluorocholine PET/CT showed promise as a functional imaging modality, being clearly superior to ^99mTc-MIBI/tetrofosmin SPECT/CT, especially in the detection and localization of small parathyroid adenomas in patients with primary hyperparathyroidism. SUVmax was higher in parathyroid adenomas than in hyperplasia. However, further evaluation of this modality is needed.

     

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.