Biological factors influencing parathyroid localization

Primary Hyperparathyroidism: Outcomes of Repeated Imaging After Initial Negative Radiological Localization

BACKGROUND

Radiological localization imaging aids in the identification of abnormal parathyroid glands resulting in primary hyperparathyroidism (PHPT), thereby facilitating minimally invasive parathyroid surgery. Sometimes initial imaging may fail to identify the abnormal gland and imaging may therefore be repeated. This study explored patient outcomes of repeated parathyroid localization imaging, after initial negative gland localization, at a United Kingdom institution.

METHODOLOGY

Data was retrospectively collected and analyzed for patients with PHPT undergoing repeated imaging during a five-year period (2015-2020). The total number of episodes of scanning, types of scans performed, the time interval between scans and the imaging success of gland localization were recorded. We explored the reasons for repeated imaging and attempted to identify any factors that might predict subsequent positive radiological localization.

RESULTS

A total of 45 patients were identified who underwent repeated localizing imaging after first localizing imaging was negative. Of these, 39 did not undergo surgery despite repeat imaging being undertaken; 11 out of these 39 patients (28%) had subsequent positive localization scans. Again, a large proportion of patients were managed conservatively, despite the repeated sets of imaging being done. Patients undergoing three or four sets of repetitive imaging did not have imaging or surgical success.

CONCLUSION

A streamlined parathyroid pathway should be followed whereby patients should be triaged for suitability for surgery prior to repeated imaging. A second set of scans should be offered when patients are unsuitable for conservative management and are willing and fit to undergo surgery. There is no merit to repeating imaging more than twice.

Use of dual energy computed tomography versus conventional techniques for preoperative localization in primary hyperparathyroidism: Effect of preoperative calcium and parathyroid hormone levels

BACKGROUND

We aimed to investigate the association of preoperative calcium and parathyroid hormone (PTH) levels with sensitivity and accuracy of dual energy computed tomography (DECT), single-photon emission CT with ^99mTc-sestamibi (CT-MIBI), and ultrasound (US) for pre-operative localization primary hyperparathyroid (PHP) patients.

METHODS

Patients undergoing parathyroidectomy for PHP at a tertiary care facility who underwent DECT, CT-MIBI and US between 2012 and 2021 were stratified by preoperative calcium and PTH levels.

RESULTS

Of 278 patients, those with high calcium and PTH levels had a higher sensitivity and accuracy with DECT (87.7%, 85.2%) compared to CT-MIBI (82.3%, 79.0%), and US (61.7%, 53.1%). DECT was more sensitive and accurate than other preoperative localization techniques in subgroups with normal PTH (DECT sensitivity 60.9%, accuracy 52.1%) and normal calcium levels (41.7%, 33.3%).

CONCLUSION

Preoperative calcium and PTH were associated with sensitivity and accuracy of pre-operative localization in PHP. DECT was sensitive and accurate for preoperative localization compared to other first-line imaging techniques.

An essential practice summary of the new EANM guidelines for parathyroid imaging

Parathyroid imaging is essential for the detection and localization of hyperfunctioning parathyroid tissue in patients with primary hyperparathyroidism (pHPT). Surgical treatment of pHPT mainly consists of minimally invasive parathyroidectomy (MIP), as a single adenoma represents the most common cause of this endocrine disorder. Successful surgery requires an experienced surgeon and relies on the correct preoperative detection and localization of hyperfunctioning parathyroid glands. Failure to preoperatively identify the culprit parathyroid gland by imaging may entail a more invasive surgical approach, including bilateral open neck exploration, with higher morbidity compared to minimally invasive parathyroidectomy. Parathyroid imaging may be also useful before surgery in case of secondary hyperparathyroidism (sHPT) or hereditary disorders (MEN 1, 2, 4) as it enables correct localization of typically located parathyroid glands, detection of ectopic as well as supernumerary glands. It is now accepted by most surgeons experienced in parathyroid surgery that preoperative imaging plays a key role in their patients' management. Recently, the European Association of Nuclear Medicine (EANM) issued an updated version of its Guidelines on parathyroid imaging. Its aim is to precise the role and the advantages and drawbacks of the various imaging modalities proposed or well established in the preoperative imaging strategy. It also aims to favor high performance in indicating, performing, and interpreting those examinations. The objective of the present article is to offer a summary of those recent EANM Guidelines and their originality among other Guidelines in this domain issued by societies of nuclear medicine physicians or other disciplines.

Quantitative analysis in parathyroid adenoma scintigraphy

OBJECTIVE

Surgery is the only curative treatment for primary hyperparathyroidism. Parathyroid scintigraphy is one method used to preoperatively localize the lesion. We examined time-related changes in radiopharmaceutical uptake in parathyroid adenomas (PTAs) and thyroid gland by quantitative single-photon-emission computed tomography (SPECT) imaging to assess differences between rapid and delayed washout patterns.

PATIENTS AND METHODS

The study group consisted of 35 histologically verified PTAs after radio-guided surgery extirpation in 33 patients with primary hyperparathyroidism. Patients underwent a three-phase SPECT/CT study of the neck and upper thorax post 99mTc-methoxyisobutylisonitrile (MIBI) injection. Images were reconstructed using a proprietary ordered-subset-conjugate-gradient-maximization algorithm (Siemens xSPECT Quant). PTAs were divided into those with a rapid (group A) and those with a slow (group B) washout pattern. SUVmax values of PTAs and thyroid gland tissue at 10, 90 and 180 min post 99mTc-MIBI injection were recorded and statistically assessed. Retention indexes related to the early examination were calculated for PTA and thyroid gland (RI-PTA and RI-TG).

RESULTS

There were 11 PTAs in group A and 24 in group B. Significant between-group differences in PTA SUVmax and PTA/thyroid gland ratios were observed only at 180 min postinjection (P = 0.0297, P = 0.0222, respectively). RI-PTAs differed significantly at 90 and 180 min postinjection (P = 0.0298, P = 0.0431). No differences in PTA volumes, thyroid gland SUVmax values or RI-TG were observed between the groups.

CONCLUSION

PTAs with rapid and slow washout patterns have different characteristics on quantitative analysis in later phases. No significant differences in directly measurable quantitative values (SUVmax, PTA/thyroid gland ratio) at the early stages of multi-phase examination were observed.

Clinicopathological variables that correlate with sestamibi positivity in uniglandular parathyroid disease: a retrospective analysis of 378 parathyroid adenomas

PURPOSE

Technetium-99 m sestamibi parathyroid scintigraphy (MIBI scan) has been used to localize abnormal glands in patients with primary hyperparathyroidism to guide parathyroidectomy. This series aimed to identify the biochemical and histopathological correlates of MIBI scan findings in patients with parathyroid adenoma.

METHODS

A total of 378 patients with histologically and biochemically proven parathyroid adenoma were included. The results of MIBI scan, histopathological (gland volume and weight, oxyphil cell ratio), biochemical (blood and 24 h urine calcium, creatinine, glomerular filtration rate, parathormone, alkaline phosphate, and vitamin D3) variables were recorded. A positive uptake on the MIBI scan referred to a localized adenoma. Among histological variables, a cutoff of 30% was applied to define parathyroid adenomas with low (≤ 30%) and high (> 30%) oxyphil cell content. Statistical analyses were performed to assess the relationship among variables.

RESULTS

MIBI scan localized the adenoma in 306 patients. Parathyroid gland volume and weight, and oxyphil ratio were significantly higher in the MIBI scan-positive group. Among the biochemical variables, only PTH was found to be significantly increased in the MIBI scan-positive group. Binary logistic regression models identified statistically significant cutoffs for the gland volume (1700 mm³), gland weight (1.3 g) and PTH levels (170 pg/mL) that can be used to predict the MIBI scan positivity.

CONCLUSION

In addition to PTH levels, this series underscored the impact of cellular composition along with the parathyroid gland volume and weight, both of which correlate with sestamibi positivity in patients with benign uniglandular parathyroid disease.

Dual-tracer radionuclide imaging in hyperparathyroidism: thallium-201 parathyroid scintigraphy revisited

OBJECTIVES

Tc-sestamibi is the current radiopharmaceutical of choice for the localization of hyperactive lesions of the parathyroid glands in patients with hyperparathyroidism. However, there are multiple factors that adversely affect the accumulation and retention Tc-sestamibi in the hyperfunctioning parathyroid tissue, resulting in a false-negative scan. The objective of this study was to investigate the possibility of an incremental diagnostic role of thallium-201 parathyroid scintigraphy in patients with presumably false-negative Tc-sestamibi scan results.

PATIENTS AND METHODS

The study comprised of 22 patients including 16 with primary hyperparathyroidism (PHPT) and 6 with secondary hyperparathyroidism where Tc-sestambi scan was initially negative, inconclusive or where additional lesions were suspected on the single-photon computed tomography/computed tomography (SPECT/CT) scan with the CT component identifying lesion(s) without significant Tc-sestamibi uptake.

RESULTS

The results of our study show that in 22 patients (5 male, 17 female; age range 26-81; median age 53.4) further imaging with thallium-201 SPECT/CT scan showed 46.5% additional lesions in patients with hyperparathyroidism caused by an adenomatous or hyperplastic parathyroid lesion. In patients with PHPT caused by an adenomatous or hyperplastic parathyroid lesion, further imaging with thallium-201 showed 59% additional hyperactive parathyroid lesions. In patients with secondary hyperparathyroidism, further imaging with thallium-201 SPECT/CT showed additional 33.3% hyperplastic parathyroid lesions.

CONCLUSION

The results of this pilot study strongly advocate a role for thallium parathyroid SPECT/CT imaging in patients with primary and secondary hyperparathyroidism where the initial Tc-sestamibi scan is deemed to be false-negative in the presence of biochemical hyperparathyroidism.

The EANM practice guidelines for parathyroid imaging

INTRODUCTION

Nuclear medicine parathyroid imaging is important in the identification of hyperfunctioning parathyroid glands in primary hyperparathyroidism (pHPT), but it may be also valuable before surgical treatment in secondary hyperparathyroidism (sHPT). Parathyroid radionuclide imaging with scintigraphy or positron emission tomography (PET) is a highly sensitive procedure for the assessment of the presence and number of hyperfunctioning parathyroid glands, located either at typical sites or ectopically. The treatment of pHPT is mostly directed toward minimally invasive parathyroidectomy, especially in cases with a single adenoma. In experienced hands, successful surgery depends mainly on the exact preoperative localization of one or more hyperfunctioning parathyroid adenomas. Failure to preoperatively identify the hyperfunctioning parathyroid gland challenges minimally invasive parathyroidectomy and might require bilateral open neck exploration.

METHODS

Over a decade has now passed since the European Association of Nuclear Medicine (EANM) issued the first edition of the guideline on parathyroid imaging, and a number of new insights and techniques have been developed since. The aim of the present document is to provide state-of-the-art guidelines for nuclear medicine physicians performing parathyroid scintigraphy, single-photon emission computed tomography/computed tomography (SPECT/CT), positron emission tomography/computed tomography (PET/CT), and positron emission tomography/magnetic resonance imaging (PET/MRI) in patients with pHPT, as well as in those with sHPT.

CONCLUSION

These guidelines are written and authorized by the EANM to promote optimal parathyroid imaging. They will assist nuclear medicine physicians in the detection and correct localization of hyperfunctioning parathyroid lesions.

The value of parathyroid scintigraphy on lesion detection in patients with normocalcemic primary hyperparathyroidism

OBJECTIVE

Primary hyperparathyroidism (PHPT) is one of the most frequent endocrine diseases. Most of the patients with PHPT are asymptomatic, and only 20% of them become symptomatic with increasing levels of calcium. It has been reported that normocalcemic primary hyperparathyroidism (NPHPT) may be the incipient period of PHPT where calcium (Ca) levels are in normal range, and it may advance to overt PHPT. Early diagnosis of PHPT is important in order to prevent its complications. In this retrospective study, we aimed to evaluate the role of 99mTc-MIBI parathyroid scintigraphy on lesion detection in patients with NPHPT.

MATERIAL AND METHODS

The parathyroid scintigraphy database was reviewed retrospectively in patients with PHPT. 117 patients who underwent 99mTc-MIBI scintigraphy were recruited to the study. Serum calcium level above 10.5mg/dl was considered as hypercalcemia.

RESULTS

A total of 117 patients' (female/male:98/19) mean serum PTH levels (mean±SD) were 149±97 pg/ml in normocalcemic group (Ca:9.6±0.6mg/dL, n:38) and 189±135 pg/ml in hypercalcemic group (Ca:11.4±0.6mg/dL, n:79) (p:0.072). The sex and ages were not different between the scintigraphy positive and negative groups, but the lesion detection rates with parathyroid scintigraphy were 42% in normocalcemic group and 81% in hypercalcemic group (p<0.0001).

CONCLUSIONS

Several factors including serum Ca, the imaging protocol, existence of multiglandular disease, the size and MIBI biokinetics of the adenoma may influence lesion detectability in parathyroid scintigraphy. Although high serum Ca level is an important parameter in predicting its success, parathyroid scintigraphy remains a valuable diagnostic method even in patients with NPHPT.

Factors That Affect the Sensitivity of Imaging Modalities in Primary Hyperparathyroidism

BACKGROUND

Cervical ultrasound, 99mTc-sestamibi single-photon emission computed tomography/computed tomography (99mTc-MIBI SPECT/CT), and cervical CT are routinely used in preoperative localization of primary hyperparathyroidism (PHPT). However, false-negative imaging results are also frequently encountered in clinical practice. Exploring the factors that affect the sensitivity of these imaging modalities is important for the surgical management of PHPT patients.

METHODS

Clinical data of 352 PHPT patients hospitalized in our center from January 2011 to December 2015 were retrospectively collected to evaluate the sensitivity of 3 imaging modalities in the preoperative localization of parathyroid lesions. The ROC curve analysis was used to explore the clinical factors affecting the sensitivity of localization, and the cut-point(s) of related factors were determined.

RESULTS

99mTc-MIBI SPECT/CT has the highest sensitivity among the localization modalities commonly used, reaching 91.1% (86.0%-94.8%). When the lengths of parathyroid lesions were ≤1.3 cm, the sensitivity of neck ultrasonography significantly decreased, while the sensitivity of 99mTc-MIBI SPECT/CT decreased with parathyroid lesions ≤1.3 cm or serum PTH≤252 pg/ml. 99mTc-MIBI SPECT/CT was less effective in localizing the hyperplasia lesions. Neck ultrasonography combined with 99mTc-MIBI SPECT/CT can effectively improve the accuracy of preoperative localization of parathyroid lesions to 96.2% (92.7%-98.1%).

CONCLUSIONS

Small parathyroid lesion and mild elevation of serum PTH would reduce the accuracy of parathyroid localization in PHPT patients.

Will 18F-fluorocholine PET/CT replace other methods of preoperative parathyroid imaging?

INTRODUCTION

Primary hyperparathyroidism (PHPT) is a common endocrine disorder usually due to hyperfunctioning parathyroid glands (HPs). Surgical removal of the HPs is the main treatment for PHPT, making the correct detection and localization of HPs crucial to guiding targeted and minimally invasive surgical treatment in patients with PHPT. To date, different imaging methods have been used to detect and localize HPs, including radiology, nuclear medicine, and hybrid techniques.

METHODS

The present work discusses the role and value of different imaging methods in PHPT and, particularly, evaluates the potential role of ¹⁸F-fluorcholine PET/CT as a "one-stop-shop" method for preoperative parathyroid localization in patients with PHPT.

DISCUSSION

Cervical ultrasound (US) and parathyroid scintigraphy using ^99mTc-MIBI are the most commonly employed methods in clinical practice. More recently, four-dimensional computed tomography (4D CT) and positron emission tomography (PET) with radiolabeled choline have emerged as useful alternatives in cases of negative or discordant findings from first-line imaging methods.

CONCLUSIONS

Due to the excellent diagnostic performance of radiolabeled choline PET/CT and the low radiation burden, this technique seems to be an ideal candidate to substitute current imaging procedures including US, MIBI scintigraphy, 4D CT and MRI and perform a fast and reliable "one-stop-shop" preoperative localization of HP in patients with PHPT, including challenging cases of postoperative persistent/recurrent disease.

Causes of false negatives in technetium-99 m methoxyisobutylisonitrile scintigraphy for hyperparathyroidism: influence of size and cysts in parathyroid lesions

OBJECTIVE

The aim of this study was to elucidate the causes of false-negative cases of technetium-99 m methoxyisobutylisonitrile scintigraphy (MIBI) for hyperparathyroidism.

METHODS

Consecutive MIBI examinations performed in 154 patients between April 2011 and March 2017 were retrospectively reviewed. Sensitivities of MIBI, CT and US were calculated. The effects of serum calcium, phosphorus, PTH, weight of parathyroid lesions, use of NSAIDs and Ca-channel blocker (CCB), presence of cyst in parathyroid lesions, and a number of lesions observed by MIBI were investigated.

RESULTS

Seventy-nine patients (21 men and 58 women), ranging from 18 to 88 years of age (mean ± SD: 57.6 ± 15.3 years), who underwent parathyroidectomy, were included. MIBI and preoperative US were performed in the 79 patients and single-phase parenchymal contrast-enhanced CT (CE-CT) was performed in 55 patients. A total of 120 parathyroid proliferative nodules were detected by MIBI and US, and 92 lesions were detected by CE-CT. In the lesion base, MIBI detected 82 out of the 120 lesions (sensitivity = 68.3%), US detected 103 out of the 120 lesions (sensitivity = 85.8%), CE-CT detected 63 out of the 92 lesions (sensitivity = 68.5%), and MIBI plus CE-CT detected 72 of the 92 lesions (sensitivity = 78.3%). A significant difference in the sensitivity was found between US and MIBI (P < 0.01), and between US and CT (P < 0.01). In the patient base, MIBI detected 67 out of the 79 patients (sensitivity = 84.8%), US detected 74 out of the 79 patients (sensitivity = 93.7%), CE-CT detected 45 out of the 55 patients (sensitivity = 81.8%), and MIBI plus CE-CT detected 52 out of the 55 patients (sensitivity = 94.5%). No significant difference was observed in any of the comparisons. A significant difference was observed in lesion weight (P < 0.01), single or multiple lesions (P = 0.02), and presence of cyst (P < 0.01) between the MIBI false-negative (n = 38) and the true-positive groups (n = 82).

CONCLUSION

The presence of cyst in parathyroid proliferative lesions as well as small size and multiple number of parathyroid lesions contribute to false negative in parathyroid MIBI scan.

VEGFR-2 is downregulated in sestamibi-negative parathyroid adenomas

BACKGROUND

The purpose of this study was to determine the expression profile of several biomarkers in sestamibi-positive (n = 23) and sestamibi-negative (n = 6) parathyroid adenomas.

METHODS

A tissue microarray of parathyroid adenomas from 29 patients was constructed and slides were stained for several proteins involved in angiogenesis, inflammation, cell adhesion, cell cycle, apoptosis, and with markers of the sonic hedgehog, mTOR, Forkhead box O and WNT signal transduction pathways. Protein expression was determined using an image-analysis software (Spectrum Plus©, 38 Aperio).

RESULTS

Protein expression analysis revealed that the vascular endothelial growth factor receptor 2 (VEGFR2) score was significantly higher in the sestamibi-positive cohort compared to sestamibi-negative adenomas (P = .038). Other proteins were not differentially expressed between sestamibi-positive and sestamibi-negative adenomas.

CONCLUSION

It is hypothesized that VEGFR-2 overexpression in parathyroid adenomas increases vascular permeability resulting in a higher uptake of sestamibi.

Comparison of hyperparathyroidism types and utility of dual radiopharmaceutical acquisition with Tc99m sestamibi and 123I for localization of rapid washout parathyroid adenomas

Tc99m-sestamibi dual-time imaging is a standard tool for localization of adenomas/hyperplasia in hyperparathyroidism. We investigated the degree and causes of localization failure among different types of hyperparathyroidism. Pre-operative parathyroid hormone levels and size of the gland were major determinants of Tc99m-sestamibi positivity; ¹²³I scan may be helpful in localization failures.

INTRODUCTION

Tc99m-sestamibi dual-time imaging is a standard tool for localization of adenomas/hyperplasia in hyperparathyroidism. However, parathyroid adenomas/hyperplasia has been reported to washout as fast as normal thyroid tissue ("rapid washout") which may lead to diagnostic failure. We aimed to evaluate the determinants of rapid washout and to determine the role of subtraction imaging for detection of parathyroid adenomas/hyperplasia with rapid washout.

METHODS

Retrospective analysis of patients with hyperparathyroidism who have undergone Tc99m-sestamibi dual-time imaging and parathyroid surgery. Rapid washout was correlated to the type of hyperparathyroidism in surgically confirmed cases. Biochemical and pathological data were reviewed.

RESULTS

A total of 135 hyperparathyroidism patients met the inclusion criteria. Ninety-six (72%), 29 (21%), and 10 (7%) had primary, secondary, and tertiary hyperparathyroidisms, respectively. Rapid washout was identified in 28/87 glands (32%), 14/53 glands (26%), and 1/16 glands (6%) with primary, secondary, and tertiary hyperparathyroidisms, respectively. Glands that were positive on late-phase Tc99m-sestamibi scans were significantly large being 1.7 (IQR 1.4-2.3) vs. 1.45 (IQR 1-2) cm (p = 0.003). High parathyroid hormone levels (PTH) were associated with early-phase Tc99m-sestamibi positivity in both primary (p = 0.01) and secondary hyperparathyroidism (p = 0.03) but not with last phase (p = 0.11, p = 0.37, respectively). Correlative imaging with subtraction scintigraphy was positive in 14/16 (87.5%) parathyroid adenomas.

CONCLUSION

Pre-operative PTH levels and size of the gland were major determinants of Tc99m-sestamibi positivity on early-phase Tc99m-sestamibi scans, whereas size is an independent predictor of late-phase Tc99m-sestamibi positivity. Subtraction scintigraphy might be a useful tool in suspected cases of rapid washout adenomas/hyperplasia.

Influence of single photon emission computed tomography (SPECT) reconstruction algorithm on diagnostic accuracy of parathyroid scintigraphy: Comparison of iterative reconstruction with filtered backprojection

Background & objectives:

Preoperative localization of parathyroid lesions is essential for improving the results in patients with primary hyperparathyroidism. The purpose of this study was to evaluate retrospectively the value of technetium-99m (Tc-99m) methoxyisobutylisonitrile (MIBI) single photon emission computed tomography (SPECT) and to compare the diagnostic accuracy of iterative reconstruction (IR) and filtered backprojection (FBP) reconstruction algorithms about localization of parathyroid lesions.

Methods:

Forty four patients with primary hyperparathyroidism, in whom histopathological correlation could be performed, were included in the study. Dual-phase Tc-99m parathyroid scintigraphy was performed 20 and 120 min after injection of 740 MBq Tc-99m MIBI in all patients. Tomographic images were acquired 120 min after the administration of radiopharmaceutical. The SPECT data were evaluated using an IR as well as a FBP algorithm. In 23 of 44 patients, SPECT acquisitions were performed in 64×64 matrix; in the remaining 21 patients, tomographic data were collected in 128×128 matrix. The imaging results were compared with pathological findings and sensitivities of both reconstruction algorithms, and planar views were calculated.

Results:

Using planar MIBI scans, abnormal parathyroid glands were correctly localized in 75 per cent of the cases. Sensitivity increased to 77 per cent using SPECT with FBP and to 84 per cent with IR. When the sensitivities were calculated according to the acquisition matrix, these were 95 per cent (20/21) and 85 per cent (18/21) for IR and FBP, respectively in patients in whom 128×128 matrix was used. The sensitivities were lower in patients who were imaged with 64×64 matrix; these were calculated as 74 per cent (17/23) and 70 per cent (16/23) with IR and FBP, respectively.

Interpretation & conclusions:

Our findings showed that compared to planar scintigraphy, Tc-99m MIBI SPECT was more sensitive diagnostic modality in the detection of abnormal parathyroid tissues. Image quality and sensitivity may be improved further when larger matrices with IR are used instead of FBP algorithm.

Dual-phase 99mTc-MIBI imaging and the expressions of P-gp, GST-π, and MRP1 in hyperparathyroidism

Objective

The aim of this study was to further elucidate the mechanisms of dual-phase technetium-99m methoxyisobutylisonitrile (^99mTc-MIBI) parathyroid imaging by exploring the association between early uptake results (EUR), delayed uptake results (DUR), and the retention index (RI) in dual-phase ^99mTc-MIBI parathyroid imaging and P glycoprotein (P-gp), multidrug resistance-associated protein 1 (MRP1), and glutathione S-transferase-π (GST-π) expression in hyperparathyroidism (HPT).

Patients and methods

Preoperative dual-phase (early and delayed) ^99mTc-MIBI imaging was performed on 74 patients undergoing parathyroidectomy for HPT. EUR, DUR, and RI were calculated. P-gp, MRP1, and GST-π expressions were assessed using immunohistochemistry in resected tissue from HPT and control patients. The association between P-gp, MRP1, and GST-π expressions and EUR, DUR, and RI in HPT was evaluated.

Results

The positive rate of dual-phase ^99mT c-MIBI imaging was 91.89% (68/74) and the false-negative rate was 8.11% (6/74). P-gp and GST-π expressions were higher in tissues resected from control compared with HPT patients (47.37 and 81.5%, P<0.05); there was no difference in MRP1. EUR were associated with P-gp and GST-π expressions, and DUR were associated with MRP1 expression. There was a significant difference in MRP1 expression between RI greater than or equal to 0 and RI less than 0. There was no relationship between the sensitivity of dual-phase ^99mTc-MIBI imaging and P-gp, MRP1, and GST-π expressions in resected parathyroid tissue. The six false-negative HPT cases consisted of three P-gp (−)/MRP1 (−) tissues, three P-gp (−)/GST-π (−) tissues, and four MRP1 (−)/GST-π (−) tissues.

Conclusion

As P-gp and GST-π expressions were higher in tissues resected from control compared with HPT patients, ^99mTc-MIBI may wash out faster from normal parathyroid tissue surrounding the lesion compared with the lesion itself, facilitating detection.

A case report of mediastinal ectopic parathyroid adenoma presented as parathyroid crisis localized by SPECT/CT

INTRODUCTION

Parathyroid crisis due to ectopic parathyroid adenomas can pose diagnostic and management challenges, since it is quite rare in clinical practice.

CLINICAL FINDINGS/PATIENT CONCERNS

A 67-year-old Chinese male presented as a parathyroid crisis due to an ectopic mediastinal parathyroid adenoma with his serum calcium and PTH markedly increased in short time. An ultrasonography and computed tomography (CT) scan of the neck did not reveal any parathyroid adenoma. Thoracic CT detected a contrast-enhanced mass in the mediastinum. Although the ectopic location is difficult to appreciate on anterior planar technetium-99m-sestamibi scintigraphy views but has been accurately localized with single photon-emission computed tomography/computed tomography. After fluid resuscitation, loop diuretic, and calcitonin treatment, a thoracoscope surgery was performed. The histopathology of the mediastinal nodule was consistent with a parathyroid adenoma. Hypocalcemia due to hungry bone syndrome occurred after surgery and was resolved quickly with large-dose calcium and calcitriol supplementation. He is asymptomatic and has normal serum calcium and PTH levels on regular follow-up.

DIAGNOSES

The ultrasonography, CT, sestamibi, and single photon-emission computed tomography/computed tomography provide limited sensitivity in the detecting ectopic parathyroid adenomas alone. The combination of these techniques has incremental value in localizing ectopic parathyroid adenomas over either technique alone.

CONCLUSION

Any parathyroid crisis without parathyroid adenoma in the neck should alert physicians to search for ectopic locations through combination of imaging techniques.

Molecular pathways associated with transcriptional alterations in hyperparathyroidism

Hyperparathyroidism is characterized by the oversecretion of parathyroid hormone biochemically and increased cell proliferation histologically. Primary and secondary hyperparathyroidism exhibit distinct pathophysiology but share certain common microscopic features. The present study performed the first genome-wide expression analysis directly comparing the expression profile of primary and secondary hyperparathyroidism. Microarray gene expression analyses were performed in parathyroid tissues from 2 primary hyperparathyroidism patients and 3 secondary hyperparathyroidism patients. Unsupervised hierarchical clustering analysis identified two natural subgroups containing different types of hyperparathyroidism. Combined with additional data extracted from a publicly available database, a meta-signature was constructed to represent an intersection of two sets of differential expression profile. Multiple pathways were identified that are aberrantly regulated in hyperparathyroidism. In primary hyperparathyroidism, dysregulated pathways included cell adhesion molecules, peroxisome proliferator-activated receptor signaling pathway, and neuroactive ligand-receptor interaction. Pathways implicated in secondary hyperparathyroidism included tryptophan metabolism, tight junctions, renin-angiotensin system, steroid hormone biosynthesis, and O-glycan biosynthesis. The present study demonstrates that different pathophysiology is associated with differential gene profiling in hyperparathyroidism. Several pathways are involved in parathyroid dysregulation and may be future targets for therapeutic intervention.

A comparison between 11C-methionine PET/CT and MIBI SPECT/CT for localization of parathyroid adenomas/hyperplasia

OBJECTIVE

The purpose of this study was to compare the sensitivity of single-photon emission computed tomography/computed tomography (SPECT/CT) using 99mTc-sestamibi (MIBI) with that of PET/CT using 11C-methionine (MET) for localization of parathyroid adenomas/hyperplasia in primary hyperparathyroidism.

MATERIALS AND METHODS

Twenty-three patients with primary hyperparathyroidism were analyzed. Fifteen patients underwent surgery, and the remaining eight did not, but these patients were clinically diagnosed as having primary hyperparathyroidism. Patients underwent both MET PET/CT and MIBI SPECT/CT scanning. The sensitivities of both modalities were evaluated on a per-patient basis, and on a per-lesion basis for parathyroid lesions detected by surgery. The size of the parathyroid adenoma/hyperplasia and serum intact parathyroid hormone levels were compared with the results of each of the two modalities.

RESULTS

Per-patient sensitivities of MET PET/CT and MIBI SPECT/CT were 65 and 61%, respectively. Per-lesion sensitivities of MET PET/CT and MIBI SPECT/CT were 91 and 73% for histologically confirmed adenomas and 30 and 30% for hyperplastic glands, respectively. No significant differences were observed between the two modalities. The size of uptake-positive lesions was significantly larger than that of uptake-negative lesions in both modalities. Intact parathyroid hormone levels showed no significant difference between uptake-positive and uptake-negative patients in both modalities.

CONCLUSION

The sensitivities of MET PET/CT and MIBI SPECT/CT were comparable. MET PET/CT has a complementary role in localizing parathyroid adenomas/hyperplasia when MIBI SPECT/CT is inconclusive.

Radiographic evaluation of non-localizing parathyroid adenomas

PURPOSE

Patients with primary hyperparathyroidism routinely undergo preoperative imaging to localize the abnormal gland to facilitate a guided parathyroidectomy. These techniques include neck ultrasound (US), dual phase planar technetium-99m ((99m)TC) sestamibi (MIBI) scans, single photon emission computed tomography (SPECT), combined SPECT/CT, and four dimensional CT scans (4D CT). Despite appropriate preoperative imaging, non-localization of abnormal glands does occur. This study aims to determine whether non-localization is the result of radiologic interpretive error or a representation of a subset of truly non-localizing parathyroid adenomas.

MATERIALS AND METHODS

A retrospective study was performed; two senior radiologists reinterpreted the preoperative imaging (US and MIBI scans) of 30 patients with initially non-localizing studies. All patients underwent parathyroidectomy for primary hyperparathyroidism at a tertiary referral center. Both radiologists were blinded to the scores of his colleague. The results were compared for inter-reader reliability using Cohen's kappa test.

RESULTS

Twenty-nine of thirty nuclear studies were found to be negative on reinterpretation. The readers agreed in 86.67% of their observations, with a kappa (κ) value of 0.706 (SE=±0.131, 95% confidence interval for κ =0.449-0.962). One of eighteen ultrasounds had positive localizations on reexamination, however, the inter-observer agreement was only 55.6%, with a kappa value of 0.351 (SE=±0.139, and 95% confidence interval for κ =0.080-0.623). Overall, no statistically significant difference in preoperative and retrospective interpretation was found.

CONCLUSION

This study identifies a subset of parathyroid adenomas that do not localize on preoperative imaging despite sound radiographic evaluation.

Evaluation of conventional imaging techniques on preoperative localization in primary hyperparathyroidism

We aimed to evaluate the diagnostic and preoperative localization capacity of 99mTc methoxyisobutylnitrile (MIBI) parathyroid scintigraphy and ultrasonography (USG) in enlarged parathyroid glands in the primary hyperparathyroidism (pHPT) as well as the relationship between the success rate of these techniques and biochemical values. In this study, we retrospectively evaluated 39 patients with clinical and biological evidence of pHPT who referred to the university hospital for MIBI parathyroid scintigraphy. Patients were examined with USG and double-phase MIBI parathyroid scintigraphy for the detection of enlarged parathyroid glands. Preoperative serum intact parathyroid hormone (iPTH) levels, calcium (Ca), phosphate and alkaline phosphatase measurements were obtained. A total of 45 parathyroid lesions in 39 patients were reviewed. Thirty-four patients had a single adenoma and 5 patients with multi-gland disease had 11 abnormal parathyroid glands including three adenomas, whereas the remaining 8 glands showed hyperplasia. The overall sensitivities of MIBI parathyroid scintigraphy, USG and combined techniques were 85.3%, 72.5% and 90.4%, respectively; the positive predictive values (PPV) were 89.7%, 85.2% and 92.6%, respectively. The most successful approach for detection of enlarged parathyroid glands in hyperparathyroidism is the concurrent application of USG and MIBI parathyroid scintigraphy modalities. The concomitancy of thyroid diseases decreases the sensitivity of both MIBI parathyroid scintigraphy and USG in enlarged parathyroid glands.

The relationship between technetium-99m-methoxyisobutyl isonitrile parathyroid scintigraphy and hormonal and biochemical markers in suspicion of primary hyperparathyroidism

OBJECTIVE

Technetium-99m-methoxyisobutyl isonitrile (Tc-99m MIBI) has been widely used to evaluate hyperfunctioning autonomous parathyroid glands in patients with elevated intact parathyroid hormone (iPTH) and/or calcium (Ca) level. The aim of this study was to evaluate the relationship between Tc-99m MIBI parathyroid scintigraphy and hormonal and biochemical markers in suspicion of primary hyperparathyroidism (PHPT).

MATERIAL AND METHODS

Dual-phase Tc-99m MIBI parathyroid scintigraphy and total serum iPTH, Ca, phosphorus (P) and albumin measurements were performed in 60 patients (52 females, 8 males; mean age, 59.38±12.51 years; range, 34 to 86 years) with suspicion of PHPT.

RESULTS

The iPTH median level was 160.3 pg/mL (47.8 to 782.6). Thirty-five of the patients had surgical resection of hyperfunctioning parathyroid glands. Of the 35 patients, parathyroid gland pathology was detected in 30 patients using scintigraphic examination. Tc-99m MIBI parathyroid scintigraphy was negative in 30 patients. The iPTH, Ca and P levels were significantly different between in the Tc-99m MIBI positive group and the negative group, respectively: For iPTH, 202.1 (47.8-782.6) pg/mL versus 111.6 (80.1-373) pg/mL; p<0.001. For Ca, 11.7±1.15 mg/dL versus 10.3±1.05 mg/dL; p<0.001 and for P levels, 2.46±0.62 mg/dL versus 3.40±0.70 mg/dL; p<0.001). There was no significant difference in serum albumin levels between the MIBI positive and MIBI negative groups (4.25±0.27 g/dL versus 4.25±0.41 g/dL; p>0.05). Tc-99m MIBI parathyroid scintigraphy showed good correlation with iPTH level and histopathological diagnosis. Sensitivity and specificity was found 83.3% and 76.7%, respectively at the level of iPTH>147.7pg/mL.

CONCLUSION

Tc-99m MIBI parathyroid scintigraphy is most likely to produce identification and localization of a parathyroid adenoma when both iPTH and Ca are elevated as well as decreased P levels.

CONFLICT OF INTEREST

None declared.

Thyroid diseases cause mismatch between MIBI scan and neck ultrasound in the diagnosis of hyperfunctioning parathyroids: usefulness of FNA-PTH assay

DESIGN

To evaluate the efficacy of the main tools in the diagnostic localization of hyperfunctioning parathyroids (HP) in primary hyperparathyroidism (pHPT) with concomitant thyroid diseases.

METHODS

Forty-three patients with pHPT associated with nodular goiter (NG, n=32) and/or autoimmune thyroid diseases (AITDs, n=11) for a total of 63 neck lesions were considered. Sixteen patients displaying HP (16 lesions), unequivocally localized by sestaMIBI scintigraphy (MIBI) and neck ultrasound (US) (group I), were compared with 27 patients (47 neck lesions) displaying equivocal parathyroid localization (group II). In all cases, neck US, MIBI scan, cytology, and parathyroid hormone assay in fine-needle aspiration washout fluid (FNA-PTH) were performed. All patients finally underwent surgery.

RESULTS

According to histological examination, high FNA-PTH values (>103 pg/ml) correctly identified all HP in both groups of patients (100% of sensitivity and specificity). Both MIBI and US correctly identified all HP only in group I patients; in contrast, four patterns of mismatch between these techniques were observed in group II patients, leading to low diagnostic performances of neck US (71.4% sensitivity and 78.9% specificity) and of MIBI scan (35.7% sensitivity and 42.1% specificity). The latter was due to both false-negative (mainly in AITD) and false-positive (mainly in NG) scan images.

CONCLUSIONS

Coexistent thyroid diseases are responsible for mismatch between MIBI and US images resulting in equivocal HP localization. In these cases, FNA-PTH resulted in the most accurate tool to identify HP. However, although safe, it should be advised only to patients with uncertain HP localization.

Differential findings of tc-99m sestamibi dual-phase parathyroid scintigraphy between benign and malignant parathyroid lesions in patients with primary hyperparathyroidism

PURPOSE

This study aimed to investigate the differential findings in clinical and biochemical features, and Tc-99m sestamibi (MIBI) dual-phase parathyroid scintigraphy for malignant and benign parathyroid lesions in patients with primary hyperparathyroidism.

METHODS

Subjects were 102 parathyroid lesions from 91 patients with primary hyperparathyroidism. Scintigraphic findings included radioactivity grade, uptake pattern, uptake contour, lesion size on early and delayed images, and degree of washout. Clinical and biochemical features were also evaluated. Histopathology confirmed the final diagnosis for all the patients.

RESULTS

Final diagnoses were 94 benign parathyroid lesions and 8 parathyroid carcinomas. The patients with parathyroid carcinoma were significantly older (p = 0.002) and had significantly higher serum parathyroid hormone concentrations than those with benign parathyroid lesions (p < 0.001). All malignant parathyroid lesions showed intense radioactivity similar to or greater than the submandibular gland activity on delayed images (p = 0.007), and little radioactivity difference between early and delayed images (p = 0.012). The cancer incidence for parathyroid lesions with both intense radioactivity and no washout was 17.0% (8/47). When parathyroid lesions with all of the above-mentioned findings were regarded as malignant, the cancer incidence significantly increased from 17.0% to 33.3% (8/24, p < 0.001).

CONCLUSION

For Tc-99m MIBI dual-phase parathyroid scintigraphy, uptake grade on delayed images and washout were significantly useful diagnostic criteria for differentiating benign from malignant parathyroid lesions, along with age and parathyroid hormone serum concentration.

Minimally invasive parathyroidectomy: benefits and requirements of localization, diagnosis, and intraoperative PTH monitoring. long-term results

BACKGROUND

Surgery is the only curative treatment for primary hyperparathyroidism. Initial parathyroidectomy procedures fail due to ectopic gland location and unappreciated multigland disease.

METHODS

An evidence-based literature review was performed,which surveyed all human studies in PubMed, searching for parathyroidectomy in humans between 1990 and 2009. Between 10 and 30% of patients have multigland disease caused by double adenomas or hyperplasia. Use of preoperative imaging studies and intraoperative PTH monitoring helps parathyroid surgeons overcome these obstacles.

RESULTS

Sestamibi nuclear scan and neck ultrasound identify 70-80% of abnormal glands in patients with single adenomas. The sensitivity of ultrasound or sestamibi to identify all abnormal glands in patients with multigland disease is extremely low. Intraoperative PTH monitoring should be utilized in all patients who undergo neck exploration for primary hyperparathyroidism to reduce failures due to multigland disease. Blood samples should be drawn from peripheral veins only and a postresection level 10-15 min after gland removal should have a >50%decrease from baseline preoperative levels, and also must go to the normal range for the PTH assay being used.

CONCLUSIONS

Contemporary prospective studies (level of evidence III/IV) show that by combining preoperative imaging and IOPTH it is possible to maximize performance of successful outpatient minimally invasive parathyroidectomy.

Imaging of parathyroid glands

Preoperative imaging studies have an important role in facilitating successful localization of adenomas for surgeons. Their use has increased and parallels the recent growth of minimally invasive parathyroidectomy. Based on findings that scintigraphy is reported to have the highest accuracy for localization of adenomas when compared with anatomic imaging techniques, this article discusses the current role and limitations of imaging, with a focus on scintigraphy, in the evaluation of patients before surgery for hyperparathyroidism.

Determinants of Tc-99m sestamibi SPECT scan sensitivity in primary hyperparathyroidism

BACKGROUND

The aim of this study was to evaluate the influence of patient and adenoma characteristics on (99m)Tc-methoxy isobutyl isonitrile (MIBI) scan performance in individuals diagnosed with primary hyperparathyroidism (PHP).

METHODS

Records of patients undergoing parathyroidectomy for PHP over 6 years at a single center were reviewed.

RESULTS

The overall true-positive (TP) rate for (99m)Tc-MIBI scans was 56%. Adenomas sized 1.9 to 3.5 cm were more likely to have TP scans than 0.3-cm to 1.8-cm adenomas (74% vs 40%, P < .001). Preoperative ionized calcium levels between 1.49 and 1.72 mmol/L were more likely to have TPs than levels between 1.27 and 1.48 mmol/L (65% vs 47%, P < .05). No single class of medication was shown to significantly effect TP rates. A decrease in TP rate was observed for larger adenomas in patients on >or=1 medication (74% vs 65%, P = .05).

CONCLUSIONS

In PHP, (99m)Tc-MIBI scan positivity is most related to adenoma size and preoperative ionized calcium level.

Failed Switching off in the MIBI-Parathyroid Scintigraphy in a Dialyzed Patient with Secondary Hyperparathyroidism Responsive to Cinacalcet Therapy

The aims of your case report is to show the predictivity of (99m)Tc-sestamibi (MIBI) scintigraphy and doppler ultrasound imaging on secondary hyperparathyroidism (SHPT) in a patient responsive to calcimimetic treatment. Moreover, it has been reported that calcimimetic has great potential in reducing the volume of the parathyroid gland. On the other hand, the MIBI scintigraphy is considered a crucial diagnostic procedure to monitor the response to therapy in terms of turnover and cellular metabolism; whereas, ultrasound to monitor the volume variation in response to treatment. It is described the case of a 73-year-old man on hemodialysis from 1995 for ESRD. Within 2 years the patient gradually developed SHPT with progressively increased iPTH up to 1,000 rhog/ml. The ultrasound, highlighted the presence of two parathyroid hyperplasia, confirmed by scintigraphy, showing focal increase uptake of sestamibi in the same anatomical areas. As a result of the patient's refusal to perform a parathyroidectomy, cinacalcet, was administered (65 mg overage daily dose). After a year of treatment, there was a striking decrease of iPTH (from 1300 to 57 rhog/ml, -95%); but, on the contrary to expectations, this positive metabolic outcome, was not followed by parathyroid changes in ultrasound and scintigraphic findings.

Parathyroid scintigraphy in patients with primary hyperparathyroidism: 99mTc sestamibi SPECT and SPECT/CT

The clinical diagnosis of primary hyperparathyroidism is based largely on serum laboratory test results, as patients often are asymptomatic. Surgery, often with bilateral exploration of the neck, has been considered the definitive treatment for symptomatic disease. However, given that approximately 90% of cases are due to a single parathyroid adenoma, a better treatment may be the selective surgical excision of the hyperfunctioning parathyroid gland after its preoperative identification and localization at radiologic imaging. Scintigraphy and ultrasonography are the imaging modalities most often used for preoperative localization. Various scintigraphic protocols may be used in the clinical setting: Single-phase dual-isotope subtraction imaging, dual-phase single-isotope imaging, or a combination of the two may be used to obtain planar or tomographic views. Single photon emission computed tomography (SPECT) with the use of technetium-99m ((99m)Tc) sestamibi as the radiotracer, especially when combined with x-ray-based computed tomography (CT), is particularly helpful for preoperative localization: The three-dimensional functional information from SPECT is fused with the anatomic information obtained from CT. In addition, knowledge of the anatomy and embryologic development of the parathyroid glands and the pathophysiology of primary hyperparathyroidism aid in the identification and localization of hyperfunctioning glands.

Factors contributing to negative parathyroid localization: an analysis of 1000 patients

BACKGROUND

Localizing studies are the key for determining the optimal surgical strategy in patients with primary hyperparathyroidism (HP). Most of the data in the literature are retrospective in nature and from analysis on a per patient basis. This is a prospective study looking at the characteristics of the patient and the gland that determine the likelihood of an abnormal parathyroid to be detected by ultrasonography (US) and sestamibi scan (MIBI).

METHODS

This is a prospective analysis of 1000 consecutive patients with HP who underwent parathyroidectomy at a tertiary care center. The study group included HP with single gland disease (63%), double adenoma (15%), as well as hyperplasia (15%), familial HP (2%), and secondary/tertiary HP (6%). All patients underwent surgeon-performed neck US followed by MIBI scan. Univariate logistic regression and multivariate analyses were performed on pre- and intraoperative variables.

RESULTS

A total of 1845 abnormal glands were analyzed. Overall, US was superior to MIBI for the detection of abnormal glands in all subgroups. On multivariate analysis, body mass index (BMI), gland size, and gland volume were the statistically significant independent factors predicting detection by both US and MIBI in primary HP. The sensitivity of US was better for single gland disease than for multigland disease in primary HP, but the sensitivity of MIBI was similar in both groups. For a given size, hyperplastic glands in primary HP imaged less well with US and MIBI than in familial or secondary/tertiary HP.

CONCLUSION

This prospective study demonstrates that BMI and gland size independently predict accurate detection of abnormal parathyroid glands by US and MIBI in sporadic primary HP. Understanding the factors that affect the accuracy of parathyroid localization tests will allow the surgeon to develop a successful surgical strategy in a given patient.

P-glycoprotein expression is associated with sestamibi washout in primary hyperparathyroidism

Background

The detection of parathyroid adenomas by 99mTc-labelled hexakis 2-methoxyisobutyl isonitrile (sestamibi) scintigraphy is influenced by several factors, including tumour size and serum level of parathyroid hormone (PTH). This study examined the relationship between sestamibi accumulation and multidrug resistance (MDR)-related P-glycoprotein (P-gp) expression in a large series of surgically excised parathyroid tumours.

Methods

Seventy-eight patients underwent dual-phase sestamibi imaging before parathyroidectomy. Expression of P-gp within tumour cells was assessed by immunohistochemistry. Tumour size was measured and the ellipsoid volume calculated. Scan results were analysed in relation to preoperative serum levels of calcium and PTH, P-gp expression and tumour volume.

Results

Sixty-four of the 78 sestamibi scans were positive and 14 negative. Smaller adenomas (less than 0·5 cm3) were more likely to be sestamibi negative than larger lesions (P = 0·006). Ten of 14 adenomas with negative imaging showed strong P-gp membrane positivity and 45 of 64 lesions with a positive scan did not show P-gp membrane expression, indicating a significant association between high P-gp membrane immunoreactivity and negative sestamibi result (P = 0·006).

Conclusion

These data suggest an association between P-gp membrane expression and false-negative sestamibi scan result. Inhibition of the P-gp transmembrane pump using MDR modulators may therefore improve the sensitivity of sestamibi scintigraphy.

Dobutamine modulated Tc-99m MIBI scintigraphy in secondary hyperparathyroidism in uremic patients

The aim of this study was to determine if low-dose dobutamine infusion can enhance Tc-99m methoxy isobutyl isonitrile (MIBI) uptake of hyperfunctioning parathyroid glands of patients with secondary hyperparathyroidism (SHP). We studied 24 patients with chronic renal failure and SHP. Median age of the sample was 47.5 years. A single-tracer, double-phase technique was performed, acquiring planar images of the neck and thorax after the injection of 740 to 1110 MBq (20-30 mCi) of Tc-99m MIBI. After 2 to 7 days, the study was repeated after the infusion of low-dose dobutamine of 2.0 microg . kg . min for 60 minutes. The scan was considered positive for hyperfunctioning parathyroid tissue when an area of increased uptake that persisted on late imaging was found. Parathyroid-to-thyroid count rates (PT/T) were calculated for each abnormal focus. Hyperplasic parathyroid tissue was confirmed in 12 of 24 patients who underwent neck surgery whereas the remaining group had persistent or worsening disease, verified by clinical follow-up between 6 and 25 months after the nuclear studies (median: 12 months). An MIBI baseline study was positive in 21 of 24 patients (87%), whereas the dobutamine study was positive in all patients. Thirty-five abnormal foci were seen on baseline MIBI studies and 43 on dobutamine scans (1.46 +/- 1.02 vs. 1.79 +/- 0.88, mean +/- SD, respectively, P = 0.043). Dobutamine PT/T ratios were significantly higher than those from the baseline study (1.49 +/- 0.30 vs. 1.38 +/- 0.28, mean +/- SD, respectively, P = 0.0002, n = 43). We concluded that low-dose dobutamine Tc-99m MIBI scintigraphy has the potential of enhancing tracer uptake and retention in patients with SHP.

Diagnosis of a case of ectopic parathyroid adenoma on the early image of 99mTc-MIBI scintigram

We report the case of a 64-year-old woman who had a severe hypercalcemia. Serum calcium, intact parathyroid hormone (PTH), 1alpha, 25 (OH)(2 )vitamin D(3) levels were all elevated, and serum phosphorus level was decreased, which were all consistent with primary hyperparathyroidism (PHPT). (201)Tl/(99m)Tc subtraction scintigraphy failed to detect any abnormal accumulation in the neck and chest, while (99m)Tc-MIBI scintigraphy demonstrated the focal accumulation of increased radiotracer uptake in the mediastinum only on the early image, but not on the delayed image. Neck and chest computerized tomography scanning showed a small nodule at the retrosternal region, and a selective venous sampling study of the intact PTH suggested PTH production from the nodule. Together with the observation of the early image of (99m)Tc-MIBI scintigraphy, it was diagnosed that the patient had an ectopic parathyroid adenoma. Video-assisted thoracic surgery was performed. A 15-mm diameter mass, visualized by an intravenous infusion of methylene blue, was excited. The histopathology was consistent with the parathyroid adenoma. The adenoma was composed of mainly chief cells and rarely oxyphil cells. The absence of oxyphil cells would explain the lack of (99m)Tc-MIBI retention on late-phase imaging in our case. Even without uptake on the delayed image of (99m)Tc-MIBI scintigram, the early image was available for the localization of an ectopic parathyroid adenoma.

Hypermethylation of adenosine triphosphate-binding cassette transporter genes in primary hyperparathyroidism and its effect on sestamibi imaging

CONTEXT

Retention of technetium-(99m)-sestamibi ((99m)Tc-sestamibi) by parathyroid adenomas appears to be due to the loss of at least one membrane transporter, multidrug resistance 1 (MDR1), and possibly another, multidrug resistance-associated protein 1 (MRP1).

OBJECTIVE

The objective was to determine whether hypermethylation of either gene plays a role in their expression and (99m)Tc-sestamibi retention.

DESIGN

This was a retrospective study on a convenience sample of paraffin-embedded parathyroid glands.

SETTING

The study was performed at the John Wayne Cancer Institute at Saint John's Health Center (Santa Monica, CA).

PATIENTS

Forty-eight patients with primary hyperparathyroidism and five patients without parathyroid disease undergoing thyroid surgery provided 27 adenomatous, 10 hyperplastic, and 16 normal parathyroid glands.

INTERVENTION

We performed immunohistochemistry, real-time quantitative RT-PCR, and methylation-specific PCR for MDR1 and MRP1 on archival parathyroid tissue and correlated these results with the patient's (99m)Tc-sestamibi scan.

MAIN OUTCOME MEASURE

The main outcome measure was to determine whether hypermethylation of the genes for either transporter is associated with loss of their expression and with a positive (99m)Tc-sestamibi scan.

RESULTS

The MDR1 gene was methylated in none of 12 normal glands, 19 of 27 adenomas, and three of 10 hyperplastic glands. Methylation of the MRP1 gene was uncommon (five of 48 tested glands). Methylation of the gene affected the transcript level only for MDR1. Among all glands, hypermethylation for MDR1 was more likely in (99m)Tc-sestamibi-positive scans (P < 0.001).

CONCLUSION

In parathyroid tissue, hypermethylation of the MDR1 gene decreases its expression and is associated with increased detection of parathyroid adenomas by (99m)Tc-sestamibi parathyroid scans.

Two-phase scintigraphy with technetium 99m–sestamibi in patients with hyperparathyroidism due to chronic renal failure

BACKGROUND

The objective of the current study was to study different functional and anatomic features of the hyperplastic gland and clinical and biochemical characteristics of renal hyperparathyroidism (HPT) patients and their relationship with the scintigraphic detection of parathyroid glands.

METHODS

A retrospective study was performed of 40 patients with chronic renal failure (CRF) who underwent cervical surgery for HPT. Weight, histology, and localization of hyperplastic glands were recorded. Parathyroid cell proliferation was assessed by percentage of S-phase cells. Double-phase scintigraphy with technetium 99m-sestamibi and serum parathyroid intact hormone (PTHi), creatinine, calcium, and phosphate levels were performed.

RESULTS

Detection of hyperplastic parathyroid glands by 99mTc-sestamibi scintigraphy was associated with the weight and inferior localization of the glands. The functionality of the glands as reflected in serum PTHi and phosphorus levels was associated with the number of glands detected.

CONCLUSION

Double-phase 99mTc-sestamibi scintigraphy is of limited usefulness in patients with renal HPT. Detection of hyperplastic parathyroid glands in patients with CRF depends on the weight and inferior localization of the glands. Serum PTHi, phosphorus and creatine levels are associated with the number of glands detected by means of 99mTc-sestamibi scintigraphy.

Parathyroid imaging: how good is it and how should it be done?

Hypersecretion of parathormone in primary hyperparathyroidism is common, occurring in approximately 1 in 500 women and 1 in 2,000 men per year in their fifth to seventh decades of life. This has been suggested from the literature to be primarily the result of a parathyroid adenoma (80-85% of cases), hyperplasia involving more than 1 gland, usually with all 4 glands being involved (10-15% of cases), or the result, albeit rarely, of parathyroid carcinoma (0.5-1% of cases). Surgical removal of the hypersecreting gland is the primary treatment; this procedure is best performed by a skilled surgeon who would normally find the abnormality in 95% of cases. Imaging, however, should be used to identify the site of abnormality, potentially reducing inpatient stay and improving the patient experience. Functional imaging of parathyroid tissue using thallium was introduced in the 1980s but has largely been superceded by the use of (99m)Tc-labeled isonitriles. The optimum techniques have used (99m)Tc-sestamibi with subtraction imaging or washout imaging. A recent systematic review reported the percentage sensitivity (95% confidence intervals) for sestamibi in the identification of solitary adenomas as 88.44 (87.48-89.40), multigland hyperplasia 44.46 (41.13-47.8), double adenomas 29.95 (-2.19 to 62.09), and carcinoma 33 (33). This review does not separate the washout and subtraction techniques. The subtraction technique using (99m)Tc-sestamibi and (123)I is the optimal technique enabling the site to be related to the thyroid tissue when the parathyroid gland is in the neck in a normal position. If there is an equivocal scan then confirmation with high resolution ultrasound should be used. With ectopic glands, the combined use of single-photon emission computed tomography may then provide anatomical information to enable localization of the functional abnormality. In patients who have had surgical exploration by an experienced parathyroid surgeon in a unit with an experienced nuclear medicine team and negative sestamibi imaging, it is reasonable to image the patient with (11)C methionine. It is debatable whether patients with a high likelihood of secondary hyperparathyroidism should be imaged. The only possible justification for this is to exclude an ectopic site. There is no substitute for an experienced surgeon and an experienced imaging unit to provide a parathyroid service.

Preoperative Dual-Phase Parathyroid Imaging With Tc-99m-Sestamibi

BACKGROUND

Previously, we have found that the additional use of a pinhole collimator in parathyroid scintigraphy resulted in a decrease in the number of incorrect side localizations and an increase in reproducibility compared with that of using a parallel-hole collimator alone.

PURPOSE

The aim was to investigate whether the addition of anterior oblique views to parathyroid scintigraphy (PS) with a pinhole collimator could further enhance the diagnostic ability and reproducibility. The level of preoperative parathyroid hormone (PTH) as a potential predictor of the usefulness of the supplementary views was also studied.

METHOD AND MATERIAL

Forty-seven patients with primary hyperparathyroidism (HPT) underwent dual-phase PS using a combined protocol with parallel-hole and pinhole collimators. The pinhole collimator was used in the anterior as well as right and left anterior oblique positions. Thyroid pertechnetate scans were undertaken in the same positions. Two observers assessed the images independently.

RESULTS

By adding oblique views, the gain in correct side localization occurred in all cases but one was seen in patients with rapid washout. The level of PTH could not predict these patients. The observer agreement on correct side localizations rose significantly from 81% to 94%.

CONCLUSION

The addition of oblique views to the imaging protocol using the pinhole collimator for parathyroid and thyroid scintigraphy in primary HPT results in an increase in observer agreement and the number of correct side localizations in patients with rapid washout of MIBI. The preoperative level of PTH cannot, however, predict these patients.

Intrathyroidal Parathyroid Carcinoma as Cause of Hypercalcemia and Pitfall of Localization Techniques: Clinical and Biologic Features

OBJECTIVE

To describe an unusual case of intrathyroidal parathyroid carcinoma (PC), which was retrospectively diagnosed in a woman who underwent surgical treatment of a recurrent nodular goiter.

METHODS

We report the clinical and biologic features of an intrathyroidal PC, discuss the challenges with distinguishing PC from parathyroid adenoma, and review the related literature.

RESULTS

A 67-year-old woman sought medical attention for dysphagia attributable to the recurrence of a normal functioning multinodular goiter. Thyroid ultrasonography disclosed a 3-cm solid inferior nodule. Because she refused surgical treatment and a trial of levothyroxine was unsuccessful, periodic follow-up examinations were scheduled. At 1-year follow-up, hypercalcemia (12.1 to 12.6 mg/dL) and low phosphorus levels (2.0 to 2.3 mg/dL) were found, and parathyroid hormone (PTH) levels were profoundly increased (481 to 721 pg/mL). Neck ultrasonography showed a large hypoechogenic solid nodule, not clearly cleaved from the right thyroid lobe, which was possibly compatible with an enlarged parathyroid gland; however, a sestamibi scan was negative. During total thyroidectomy, intraoperative frozen sections of the intrathyroid nodule were compatible with nodular goiter with cellular pleomorphism. Final histologic examination showed cellular nests with nuclear pleomorphism and invasive behavior into the thyroid tissue and likely into the vessels, in conjunction with immunohistochemical negativity for thyroglobulin and strong positivity for PTH. These findings were highly suggestive of and supported the diagnosis of PC. Postoperatively, calcium levels normalized, and PTH values declined considerably but remained slightly increased. Vitamin D supplementation helped normalize the PTH levels. The patient has undergone follow-up for 5 years and has shown no morphologic or biochemical signs of tumor recurrence.

CONCLUSION

PC is a rare entity but should be suspected in patients with hypercalcemia, substantially increased PTH levels, and a neck mass. In such patients, techniques such as sestamibi scanning may fail to localize the neoplasm. Surgical treatment remains the preferred technique for an optimal outcome of the disease. Nevertheless, lifelong follow-up is necessary.