Parathyroid imaging

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.

Preoperative Localization of Parathyroid Adenomas with Technetium-99m Methoxyisobutylisonitrile Imaging: Relationship with P-Glycoprotein Expression, Oxyphilic Cell Content, and Tumoral Tissue Volume

In addition to tumor size, it has been suggested that P-glycoprotein (P-gp) expression and/or oxyphilic cell content in parathyroid adenomas has an important influence on the results of technetium 99m methoxyisobutylisonitrile (Tc-99m MIBI) parathyroid imaging.

AIM

In this study, we compared the results of MIBI parathyroid imaging and immunohistochemical analysis (IHA) of P-gp expression, oxyphilic cell content, and tumoral tissue volume in parathyroid adenomas. We also evaluated the relationship between MIBI and ultrasound (US) results, operation findings, serum biochemical values.

MATERIALS AND METHODS

Forty (40) patients (36 female and 4 male; mean age, 53.2 +/- 8.16 years) with hyperparathyroidism who had undergone surgery were included in this study. Preoperatively, "double phase" parathyroid scintigraphy with Tc-99m MIBI (including imaging of the neck and mediastinum) was performed in all patients. Thirty-two (32) of the patients had also neck US. Serum parathormon (PTH), calcium (Ca), phosphorus (P), and alkaline phosphatase (ALP) levels were measured preoperatively. In resected parathyroid tissues, P-gp expression and percentage of oxyphilic cell content were analyzed with IHA in 34 patients.

RESULTS

Three (3) of the resected parathyroid tissues were hyperplastic parathyroid tissue, whereas 31 of the tissues were parathyroid adenoma (mean volume, 1.99 +/- 1.93 mL). In Tc-99m MIBI parathyroid scintigraphy, 70% of the parathyroid adenoma/hyperplastic parathyroid tissue was detected in correct localization; at US, this rate was 46.8%. According to the resected parathyroid tissue localization at surgery, sensitivity, accuracy, positive predictive value, and prevalence in scintigraphy were 82.3%, 70%, 82.3%, and 85%, respectively. Those were 60%, 46.8%, 68.2%, and 78.1% for US, respectively. No significant correlation and no concordance was found between MIBI and US results (kappa, -0.103, r = -0.11; p: 0.53). Interestingly, significant correlation was found between tumoral volume and ALP level (r = 0.42; p = 0.010) and between PTH and ALP levels (r = 0.72; p < 0.001). Significant correlation was also found between patient age and tumoral volume (r =-0.37; p = 0.02) and between PTH and serum Ca levels (r = 0.32; p = 0.04). In 23 of 34 patients in whom histopathological examination was done MIBI was positive and in 13 of these patients (56.5%), P-gp expression was positive. When the histopathological results and MIBI results were compared, there was no significant correlation and concordance between P-gp expression (kappa = 0.09, r = 0.10; p = 0.54), oxyphilic cell content (r = -0.17; p = 0.33), and tumoral tissue volume (r = -0.14; p = 0.38). In 12 of 19 patients (63%) who had parathyroid tissue < 1 mL and in 15 of 24 patients (62.5%) who had oxyphilic cell content < 10%, lesions were also detected correctly with MIBI scintigraphy.

CONCLUSIONS

Present study results suggest that MIBI scintigraphy was clearly superior to US as a diagnostic tool. However, P-gp expression, oxyphilic cell content, and tumoral volume may have not a main effect on MIBI parathyroid scintigraphy results in parathyroid adenoma.

Ultrasound of the thyroid and parathyroid glands

Ultrasound plays a prominent role in the management of thyroid disease and parathyroid adenomas. It can detect clinically impalpable thyroid nodules and characterize them as cystic, solid, or complex. Determining that a nodule is definitively benign or malignant is difficult, and so when indicated an ultrasound-guided fine-needle aspiration can be performed. In the follow-up of patients with thyroid cancer, ultrasound can be used alone or in conjunction with computed tomography (CT)/magnetic resonance imaging (MRI) to detect recurrent disease. Recurrences can be confirmed using ultrasound to guide fine-needle aspirations. To locate parathyroid adenomas, ultrasound is often used in conjunction with sestamibi scanning. If both studies agree on the location of the adenoma, the surgeon can perform focused surgery for its removal. In patients in whom the studies do not agree or in whom they do not detect the adenoma, further evaluation with CT or more preferably MRI is indicated.

[99m-Tc sestamibi scintigraphy in primary hyperparathyroidism. Importance of lateral projections using a pin-hole collimator]

99mTc-Sestamibi double-phase scintigraphy has been improved with digital and tomographic procedures as well as additional projections. Since two years ago, we have introduced additional early lateral views of neck to the conventional double-phase scintigraphy. We have tried to give anatomic data about the depth of the adenomas and to evaluate the possibility of obviating the late images of the double-phase study.

METHOD

Two observers reviewed 50 studies performed for primary hyperparathyroidism in two different ways. The first one reviewed only conventional double-phase studies and the second one, with the additional report of the lateral views.

RESULTS

in 32/50 patients (64 %) the report of the additional lateral views and the conventional early views was enough to diagnose parathyroid adenomas. No additional lesions were observed in the late views. These views did not provide any additional useful data and could have been obviated. Four ectopic adenomas were found, 1 mediastinal and 3 in paraesophagic area; three intrathyroidal focus; all of these atypical lesions were identified by lateral pinhole views.

CONCLUSION

The performance of additional lateral projections of the parathyroids supplies additional information to the surgeon on the depth of the lesion in atypical sites and would have made it possible to obviate the late phase in more than half of the patients since this did not supply additional information to that of the early images that had reached a diagnosis.

Thallium-201-chloride scintigraphy in staging and monitoring radiotherapy response in follicular lymphoma patients

PURPOSE

To study thallium-201-chloride scintigraphy (201Tl-S) in staging and monitoring response after radiotherapy in follicular lymphoma (FL) patients.

PATIENTS AND METHODS

Forty-one consecutive and unselected FL patients were examined by 'Conventional Standard Staging' (CSS) procedures (history and physical examination, ultrasound, CT scans, biopsies and fine needle aspiration cytology) prior to irradiation. Eight standardized potentially affected lymphoma localizations (neck, axilla, mediastinum, spleen, paraaortic, parailiac, femoral and extranodal) per patient were separately studied, resulting in the investigation of 328 localizations. Thirty minutes after the intravenous administration of a tracer dose of 150 MBq thallium-201-chloride total body images were made, immediately followed by single photon emission computed tomography acquisition. All lymphoma localizations were subsequently irradiated. Patients were re-examined after a median of 4 weeks (range 3-6 weeks) by all CSS modalities and 201Tl-S. Diagnostic performance was evaluated both per site and per patient, both in the diagnostic phase of the study as well as in the post-treatment re-evaluation phase.

RESULTS

In staging, 201Tl-S was positive in 82 of the 129 initial positive regions by CSS (64%). This percentage increased to 70% when eliminating upper abdominal lymph nodes from the analysis. In 24 patients all lesions were visualized by 201Tl-S, in 11 patients some but not all lesions were detected. In six patients none of the lesions were detected by 201Tl-S. In four patients, four additional lesions were initially found by 201Tl-S only. After irradiation, 83 of the total 86 positive regions reached a complete or partial remission by CSS. Eighty-one of these were also diagnosed as remission by 201Tl-S and two as stable disease. In 31 out of 35 patients (89%; 95% CI: 73-97%) the overall response in all irradiated sites was identical by 201Tl-S and CSS. Only two patients, in remission on CSS modalities, showed stable disease on 201Tl-S, while two others were diagnosed as CR by CSS and PR by 201Tl-S.

CONCLUSIONS

201Tl-S has limited additional value in staging FL patients, since only two-thirds of all localizations are detected. However, 201Tl-S is accurate in monitoring radiation treatment response in FL patients. If an FL patient with a positive 201Tl-S at diagnosis is treated by irradiation, the treatment response can be reliably ascertained by only performing a 201Tl-S.

Parathyroid imaging: preoperative localization

The role of parathyroid localization is as a preoperative localization procedure. This is becoming increasingly important with the trend towards limited surgical approaches. Although there are a variety of methods used to identify the site of parathyroid adenomas, 99mTc sestamibi is at present the agent of choice. Debate continues as to whether imaging is best performed using a subtraction technique or delayed imaging/dual phase technique. There is also discussion as to which collimator to use and whether surgery should be directed by the combined use of ultrasound and radionuclide imaging. These areas are discussed within this review. The technique of choice is a subtraction 99mTc sestamibi scan of the neck using a pinhole collimator. This should be combined with a mediastinal view using a parallel hole collimator. There is sufficient evidence to suggest that combining subtraction imaging with high resolution ultrasound will improve the sensitivity and give greater information to the surgeon.

Size and P-glycoprotein expression limit 99mTc-tetrofosmin uptake in parathyroid adenomas

The purpose of this study was to retrospectively evaluate (99m)Tc-tetrofosmin (Tc-TF) uptake in large parathyroid adenomas and to compare the results with their expression of multidrug resistance (MDR)-mediated, 170 kDa, P-glycoprotein (Pgp). Twenty patients with large parathyroid adenomas (larger than 1.5 g), who had undergone early and delayed (10 min and 2 h) Tc-TF parathyroid imaging before operation, were enrolled in this retrospective study. Immunohistochemical analyses were performed on multiple, non-consecutive sections of the 20 parathyroid adenomas and 40 normal control specimens (20 normal parathyroid glands and 16 normal thyroid specimens) to detect Pgp expression. Tc-TF parathyroid imaging accurately localized 17 large parathyroid adenomas, but not the remaining three. The 17 parathyroid adenomas with significant Tc-TF uptake in delayed (2 h) parathyroid images revealed negative Pgp expression, but the three adenomas without significant Tc-TF uptake, as well as 20 normal parathyroid glands and 20 normal thyroid specimens, revealed positive Pgp expression. Therefore, not only the size, but also the expression of Pgp, limited the sensitivity of Tc-TF parathyroid imaging to localize parathyroid adenomas before operation.

Using technetium 99m tetrofosmin parathyroid imaging to detect parathyroid adenoma and its relation to P-glycoprotein expression

BACKGROUND

The purpose of this study was to retrospectively evaluate technetium 99m tetrofosmin (Tc-TF) uptake in parathyroid adenomas and compare the results with their expression of multidrug resistance-mediated 170-kDa P-glycoprotein (Pgp).

METHODS

Twenty patients with larger parathyroid adenomas (> 1.5 g) and the other 40 patients with smaller parathyroid adenomas (0.5-1.5 g) underwent early and delayed (10-minute and 2-hour) Tc-TF parathyroid imaging before operation. In this retrospective study, immunohistochemical analyses were performed on multiple nonconsecutive sections of the 40 parathyroid adenomas and 40 normal control specimens (20 normal parathyroid glands and 20 normal thyroid specimens) to detect Pgp expression.

RESULTS

The Tc-TF parathyroid image accurately localized 17 larger and 16 smaller parathyroid adenomas, but not the remaining 3 larger and 4 smaller adenomas. The 17 larger and 16 smaller parathyroid adenomas with significant Tc-TF uptake on the delayed 2-hour parathyroid images revealed negative Pgp expression, but the 3 larger and 4 smaller adenomas without significant Tc-TF uptake, as well as 20 normal parathyroid glands and 20 normal thyroid specimens, revealed positive Pgp expression.

CONCLUSIONS

Not only the size of parathyroid adenomas, but Pgp expression also limited the sensitivity of Tc-TF parathyroid image to localize parathyroid adenomas before the operation.

Detecting parathyroid adenoma using technetium-99m tetrofosmin: comparison with P-glycoprotein and multidrug resistance related protein expression--a preliminary report

The aim of this study was to investigate the relationships among technetium-99m tetrofosmin (Tc-TF) accumulation in parathyroid adenoma and the expression of P-glycoprotein (Pgp) or multidrug resistance related protein (MRP). Before operation, 33 patients with parathyroid adenomas (larger than 1.5 gm) were studied with parathyroid scintigraphy 10 minutes and 2 hours after intravenous injection of Tc-TF before operation. Immunohistochemical analyses (IHA) were performed on multiple nonconsecutive sections of operative parathyroid specimens to detect Pgp or MRP expression. According to the results of IHA, the 33 parathyroid adenomas were separated into four groups: (1) 2 adenomas with both positive Pgp and positive MRP expression, (2) 1 adenomas with positive Pgp but negative MRP expression, (3) 2 adenomas with negative Pgp but positive MRP expression, and (4) 28 adenomas with both negative Pgp and negative MRP expression. All of 28 adenomas in the group 4 could be detected by Tc-TF parathyroid imaging. All of 5 adenomas in the groups 1 to 3 could not be detected by TcTF parathyroid imaging (p < 0.05). Not only the size of parathyroid adenomas, but also significant Pgp or MRP expression limited the sensitivity of Tc-TF parathyroid imaging to localize parathyroid adenomas before operation.

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

PURPOSE

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Correlation between P-glycoprotein (P-gp) expression in parathyroid and Tc-99m MIBI parathyroid image findings

The major factor to influence localization of parathyroid adenomas is tumor size. P-glycoprotein (P-gp) expression in parathyroid adenomas has been considered to be an another possible factor to influence localization of parathyroid adenomas because false-negative studies have been reported with large tumors and true-positives reported with very small tumors in previous studies. The aim of this study was to characterize Tc-99m MIBI uptake and retention by parathyroid adenomas and to correlate this with cell surface expression of P-gp. Sixteen patients with parathyroid adenoma (larger than 1.5 gm) underwent dual-phase (10min and 2hr) Tc-99m MIBI parathyroid image immediately before parathyroid exploration. Tissues were obtained from normal and abnormal parathyroid glands and from the thyroid gland. Immunohistochemistry (IHC) was obtained with monoclonal antibodies to identify P-gp expression in all tissues. All of the 16 parathyroid adenomas and 32 normal control specimens (16 normal parathyroid and 16 normal thyroid specimens) were submitted for P-gp detection by IHC. The dual-phase Tc-99m MIBI parathyroid image accurately localized 14 parathyroid adenomas, but not the remaining 2 adenomas. The 14 parathyroid adenomas with significant Tc-99m MIBI uptake in delayed 2hr images revealed negative P-gp expression, but the 2 adenomas without significant Tc-99m MIBI uptake, as well as normal parathyroid and normal thyroid specimens, revealed positive P-gp expression when evaluated by IHC. Not only the size of parathyroid adenomas, but also significant P-gp expression limited the sensitivity of dual-phase Tc-99m MIBI parathyroid image to localize parathyroid adenomas before operation.

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.

Ultrasonography of the parathyroid glands as an aid in differentiation of acute and chronic renal failure in dogs

OBJECTIVE

To evaluate whether determination of parathyroid gland size by use of ultrasonography is helpful in differentiating acute renal failure (ARF) from chronic renal failure (CRF) in dogs.

DESIGN

Prospective study.

ANIMALS

20 dogs with renal failure in which serum creatinine concentration was at least 5 times the upper reference limit. Seven dogs had ARF, and 13 dogs had CRF. Twenty-three healthy dogs were used as controls.

PROCEDURE

Dogs were positioned in dorsal recumbency for ultrasonographic examination of the ventral portion of the neck, A 10-MHz linear-array high-resolution transducer was used. The size of the parathyroid gland was determined by measuring the maximal length of the gland on the screen when it was imaged in longitudinal section. For comparison among groups, the longest linear dimension of any of the parathyroid glands of each dog was used.

RESULTS

Size of the parathyroid glands in the control dogs varied from 2.0 to 4.6 mm (median, 3.3 mm). In the dogs with ARF, gland size ranged from 2.4 to 4.0 mm (median, 2.7), which was not significantly different from controls. In dogs with CRF, the glands were more distinctly demarcated from the surrounding thyroid tissue, than those of controls and dogs with ARF. Sizes ranged from 3.9 to 8.1 mm (median, 5.7 mm), which was significantly larger, compared with controls and dogs with ARF.

CONCLUSIONS AND CLINICAL RELEVANCE

In dogs with severe azotemia, ultrasonographic examination of the parathyroid glands was helpful in differentiating ARF from CRF Size of the parathyroid glands appeared to be related to body weight.

Ultrasound evaluation of the parathyroid glands in two hypercalcemic cats

Two parathyroid masses were identified using ultrasound in two hypercalcemic cats. The masses were identified as parathyroid adenomas on surgical biopsy. Both parathyroid masses contained hypoechoic regions with distal acoustic enhancement. Both masses were greater than 1.0 cm in diameter.

The usefulness of Tc-99m tetrofosmin scintigraphy in the diagnosis and localization of hyperfunctioning parathyroid glands

PURPOSE

The aim of the work was to study the diagnostic value of Tc-99m tetrofosmin to localize anomalous parathyroid glands in patients with hyperparathyroid disease.

METHODS

We studied 31 patients, 19 with primary and 12 with secondary hyperparathyroid disease. Five of these patients were renal graft recipients. All patients underwent surgery. Each patient was injected with 555 to 740 MBq (15 to 20 mCi) Tc-99m tetrofosmin. Subsequently, radionuclide images were acquired 15 and 120 minutes after injection using a low-energy, all-purpose, parallel-hole collimator. Pertechnetate thyroid scintigraphy was obtained in nine cases (24 to 48 h later) when the thyroid activity made it difficult to identify the parathyroid glands.

RESULTS

All cases showed tracer uptake as early as 15 minutes after injection. In the group of patients with primary hyperparathyroid disease, 15 showed focal uptake in a parathyroid gland, and surgery revealed an adenoma in the same location. In one patient with hyperplasia, scintigraphy identified only two of four diseased glands. In the three remaining cases, scintigraphy showed focal uptake in the lower parathyroid gland, whereas at surgery the abnormal gland was located in the upper pole. In the secondary hyperparathyroidism group, seven patients showed diffuse tracer uptake in two or more glands, and histologic analysis confirmed hyperplasia in all of them. Five cases showed focal uptake, with three evaluated after surgery (uptake in the only remaining gland); one of them was a renal graft recipient, and the remaining patient had chronic renal failure and was receiving hemodialysis.

CONCLUSIONS

Our results suggest that Tc-99m tetrofosmin may be a suitable tracer for preoperative detection and screening of anomalous parathyroid glands. The earlier images at 15 minutes were better than those at 120 minutes. Tc-99m tetrofosmin is cleared more slowly from the normal thyroid than is Tc-99m sestamibi, and both of these tracers may give better results than the old pertechnetate TI-201 subtraction technique.

Double-phase Tc-99m sestamibi scintigraphy in the preoperative location of lesions causing hyperparathyroidism

Hyperparathyroidism (HPT) is one of the most prevalent endocrine diseases, for which the only effective treatment is surgery. The use of imaging techniques in the preoperative localization of the hyperfunctioning glands is the subject of controversy. The purpose of this paper is to assess the use of double-phase scintigraphy with Tc-99m sestamibi in the localization of lesions causing HPT. We used scintigraphy to preoperatively examine 41 patients, 31 of whom had primary HPT and 10 with secondary HPT. We acquired two anterior view planar images of the neck and chest 10 minutes and 3 hours after injection of Tc-99m sestamibi. Final diagnosis, determined with biopsy, was adenoma in 26 patients, 24 of whom had a positive scintigraphic study (sensitivity 92%), with only two false negative results. In the 14 cases of parathyroid hyperplasia, scintigraphy was also positive, and 62% (30/48) of the excised glands were identified by Tc-99m sestamibi. The radioisotope study was of particular interest in the six patients who previously had undergone surgery, since all the studies were positive; in two patients, additional diseased glands were located in the neck, and an ectopic adenoma was found in the remaining four patients. A fifth ectopic lesion was also sestamibi-positive and, in this case, the scintigraphic result was a direct indication for mediastinal surgery. There were no false positive results, even in patients with multinodular goiter. We conclude that, due to its high sensitivity and the ease with which it is performed, double-phase scintigraphy with Tc-99m sestamibi is the preferred technique for the preoperative localization of diseased glands in patients with HPT, especially in cases of parathyroid adenoma, including those with aberrant location. Its use is of particular interest in patients who previously have undergone surgery.

Technical report: double-phase technetium-99m-sestamibi parathyroid imaging with an in-field photopenic marker for better mapping

The author introduces a photopenic marker that was used to delineate better anatomic mapping in a double-phase technetium-99m-sestamibi parathyroid imaging. This home-marker was placed on a patient within the imaging field to increase reproducibility of the images: early versus delayed images.

Intraoperative nuclear guidance in benign hyperparathyroidism and parathyroid cancer

The success of parathyroid surgery is determined by the identification and removal of all hyperactive parathyroid tissue. Ectopic location of parathyroid tumours and fibrosis due to previous operations can cause failure of parathyroidectomy. Parathyroid tumours accumulate and retain 2-methoxyisobutylisonitrile (MIBI) labelled with technetium-99m. This study assesses the value of intra-operative localization of parathyroid tumours using a hand-held gamma detector in patients with hyperparathyroidism and parathyroid cancer. Twenty patients undergoing their first operations for hyperparathyroidism, 15 patients undergoing reoperations for either persistent or recurrent hyperparathyroidism and two patients with parathyroid cancer were studied. Radioactivity in the neck and the mediastinum was recorded by a gamma detector after administration of 370 MBq 99m Tc-MIBI. Surgical findings and postoperative serum levels of calcium were documented. The sensitivity of the gamma detector in identifying parathyroid tumours was 90.5% in first parathyroidectomies, 88.9% in reoperations for either persistent or recurrent hyperparathyroidism and 100% in parathyroid cancer. One false-positive result was due to a thyroid nodule. Hypercalcaemia ceased in all but one patient postoperatively. It is concluded that employment of the gamma detector is to be advocated in first parathyroidectomies when a parathyroid tumour cannot be discovered, in reoperations for either persistent or recurrent hyperparathyroidism and in surgery for parathyroid cancer.

Localization of a parathyroid adenoma by the addition of pinhole imaging to Tc-99m sestamibi dual-phase scintigraphy. Report of a case and review of experience

Scintigraphy using Tc-99m has been shown to be highly sensitive in localizing abnormal parathyroid glands in patients with hyperparathyroidism. False-negative studies most often are attributed to glandular size or location. The authors report a case of negative parathyroid imaging using standard dual-phase technique, which was converted to a positive study by the addition of a pinhole view. During a 1-year period, the authors systematically added an anterior-pinhole image of the neck to all equivocal or negative Tc-99m studies. Five of 19 patient studies were pinhole-image positive and standard-image negative or equivocal. In selected patients undergoing Tc-99m scintigraphy for hyperparathyroidism, the addition of a pinhole view may enhance study sensitivity and the confidence in interpretation.

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.

Pin-hole collimator, parallax, and the localization of mediastinal parathyroid adenoma

A parathyroid adenoma was wrongly localized by pinhole Tc-99m sestamibl scintigraphy to the anterior mediastinum near a lower pole of the thyroid gland. After a failed surgical attempt to resect the adenoma, the patient was re-imaged with a parallel-hole collimator and SPECT. The adenoma was found to be near the heart, anterior to the carina. The pinhole findings were replicated using a phantom and measurements obtained from a CT of the chest. By placing the pinhole collimator at the sternal notch level, the lesion was correctly located deep in the chest. Moving the pinhole collimator cephalad or tilting the collimator toward the feet, maneuvers sometimes needed to clear the chest in large patients, projected the lesion closer to the sternal notch. Scintigraphy with a parallel-hole collimator is recommended and SPECT should be considered when the lesion is located below the sternal notch and when a lesion is not detected, despite the clinical and biochemical diagnosis of hyperparathyroidism.