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

Comparison of parathyroid scintigraphy findings in pediatric and adult patients with secondary hyperparathyroidism

OBJECTIVES

Secondary hyperparathyroidism (sHPT) is a compensatory complication of chronic kidney disease. The aim of this study was to compare PS findings in pediatric and adult patients with sHPT.

METHODS

This study included 50 pediatric and 50 adult patients with sHPT. Parathyroid scintigraphy was performed with Tc-99m sestamibi. After radiopharmaceutical injection, early-phase (15 min) and late-phase (60-90 min) images were acquired. Planar images were interpreted visually for the presence / number of active foci compatible with a parathyroid lesion, the presence and degree of uptake in skeletal structures, and the degree of thyroid sestamibi uptake. Parathyroid surgery was performed in 21 pediatric and 28 adult patients.

RESULTS

Serum PTH and ALP values were significantly higher in pediatric than in adult patients ( P < 0.05 for each). In operated patients, on a lesion-based analysis, the sensitivity of PS in pediatric and adult patients were 40% and 71%, respectively. A nonlocalizing scan was observed in 24% of pediatric patients. Pediatric patients had a higher incidence of reduced thyroid sestamibi uptake (42% versus 2%). Skeletal sestamibi uptake was detected in 40% of pediatric and 30% of adult patients and the degree of uptake was higher in pediatric patients.

CONCLUSIONS

The results revealed more significant changes in the biochemical profile of pediatric compared with adult patients with sHPT. The sensitivity of PS was lower, and the likelihood of a nonlocalizing scan was higher in pediatric patients. The results may also suggest more severe skeletal findings in pediatric patients. Reduced thyroid sestamibi uptake in children needs further evaluation.

Parathyroid Imaging

Primary hyperparathyroidism (1° HPT) is a relatively common endocrine disorder usually caused by autonomous secretion of parathormone by one or several parathyroid adenomas. 1° HPT causing hypercalcemia, kidney stones and/or osteoporosis should be treated whenever possible by parathyroidectomy. Accurate preoperative location of parathyroid adenomas is crucial for surgery planning, mostly when performing minimally invasive surgery. Cervical ultrasonography (US) is usually performed to localize parathyroid adenomas as a first intention, followed by 99mTc- sestamibi scintigraphy with SPECT/CT whenever possible. 4D-CT is a possible alternative to 99mTc- sestamibi scintigraphy. Recently, 18F-fluorocholine positron emission tomography/computed tomography (18F-FCH PET/CT) has made its way in the clinics as it is the most sensitive method for parathyroid adenoma detection. It can eventually be combined to 4D-CT to increase its diagnostic performance, although this results in higher dose exposure to the patient. Other forms of hyperparathyroidism consist in secondary (2° HPT) and tertiary hyperparathyroidism (3° HPT). As parathyroidectomy is not usually part of the management of patients with 2° HPT, parathyroid imaging is not routinely performed in these patients. In patients with 3° HPT, total or subtotal parathyroidectomy is often performed. Localization of hyperfunctional glands is an important aid to surgery planning. As 18F-FCH PET/CT is the most sensitive modality in multigland disease, it is the preferred imaging technic in 3° HPT patients, although its cost and availability may limit its widespread use in this setting.

Update on Preoperative Parathyroid Localization in Primary Hyperparathyroidism

Parathyroidectomy is the treatment of choice for primary hyperparathyroidism when the clinical criteria are met. Although bilateral neck exploration is traditionally the standard method for surgery, minimally invasive parathyroidectomy (MIP), or focused parathyroidectomy, has been widely accepted with comparable curative outcomes. For successful MIP, accurate preoperative localization of parathyroid lesions is essential. However, no consensus exists on the optimal approach for localization. Currently, ultrasonography and technetium-99m-sestamibi-single photon emission computed tomography/computed tomography are widely accepted in most cases. However, exact localization cannot always be achieved, especially in cases with multiglandular disease, ectopic glands, recurrent disease, and normocalcemic primary hyperparathyroidism. Therefore, new modalities for preoperative localization have been developed and evaluated. Positron emission tomography/computed tomography and parathyroid venous sampling have demonstrated improvements in sensitivity and accuracy. Both anatomical and functional information can be obtained by combining these methods. As each approach has its advantages and disadvantages, the localization study should be deliberately chosen based on each patient's clinical profile, costs, radiation exposure, and the availability of experienced experts. In this review, we summarize various methods for the localization of hyperfunctioning parathyroid tissues in primary hyperparathyroidism.

Usefulness of 99mTc-SESTAMIBI Scintigraphy in Persistent Hyperparathyroidism after Kidney Transplant

Purpose

^99mTc-labeled sestamibi scintigraphy combined with single-photon emission computed tomography (SPECT) has a high positive predictive value for localizing hyperfunctioning parathyroid lesions in primary hyperparathyroidism (pHPT) but relatively low sensitivity and specificity in secondary hyperparathyroidism (sHPT) and tertiary hyperparathyroidism (tHPT). The purpose of this study is to investigate the usefulness of ^99mTc-sestamibi scintigraphy in persistent hyperparathyroidism after kidney transplant (KT).

Methods

Retrospectively evaluated 50 patients who received parathyroidectomy after KT at a single medical center. The parathyroid lesion with the highest sestamibi uptake intensity of a patient was graded from 0 to 3. Uptake intensity was analyzed in correlation with parathyroid hormone (PTH), calcium, ionized calcium, phosphorus, and vitamin D.

Results

Per-patient analysis, 43 patients had hyperplasia, 6 patients had adenomas, and 1 patient had a carcinoma. Only 3 patients with hyperplasia did not demonstrate any sestamibi uptake in the parathyroid scans. Out of the 148 pathologically confirmed parathyroid lesions, SPECT/CT images were able to identify 89 lesions (60%) and planar images of 71 lesions (48%). The average of sestamibi uptake intensity was mild at grade 1.6. Uptake intensity showed a positive correlation with parathyroid hormone (PTH) level but not with phosphorus, calcium, ionized calcium, or vitamin D levels. The largest lesion showed a high positive predictive value, especially in lesions with a diameter over 1.0 cm.

Conclusions

Regardless of relatively low and less discrete uptake in KT patients, it well depicts the largest and the most hyperfunctioning lesion.

Semi-quantitative analysis of 99mTc-sestamibi retention level for preoperative differential diagnosis of parathyroid carcinoma

Background

To investigate the role of ^99mTc-labeled sestamibi (^99mTc-MIBI) retention level in the assessment of malignant potential of parathyroid lesions.

Methods

Twenty patients with parathyroid carcinomas and forty controls with benign parathyroid lesions who underwent preoperatively ^99mTc-MIBI dual-phase planar and SPECT/CT imaging were retrospectively enrolled in this study. The mean and peak of retention index (RI_mean and RI_peak) were measured for evaluating the retention level of ^99mTc-MIBI in the parathyroid lesions. Diagnostic accuracies of RI for differentiating malignant parathyroid lesions from benign ones were assessed by receiver operating characteristic analyses (area under the curve; AUC).

Results

RI_peak (AUC =0.87, P<0.001) and RI_mean (AUC =0.78, P<0.001) showed significant difference between the malignant and benign lesions. The diagnostic sensitivity, specificity, positive and negative predictive values, accuracy of RI_peak were respectively 80.0%, 85.0%, 72.7%, 89.5% and 83.3% when its cutoff value was -19.03%. In addition, the level of serum parathyroid hormone (PTH) slightly correlated with RI_peak (r=0.260, P=0.044) or RI_mean (r=0.281, P=0.029).

Conclusions

Parathyroid carcinomas have higher retention level of ^99mTc-MIBI than benign parathyroid lesions. RI_peak may contribute to preoperative differential diagnosis of parathyroid carcinoma.

99mTc-MIBI Uptake in a Benign Thymic Cyst

A 34-year-old man with end-stage renal failure status post rejection of a deceased donor kidney transplant presented with bone pain in the setting of elevated serum parathyroid hormone and calcium levels. A Tc-MIBI SPECT/CT was performed before planned subtotal parathyroidectomy. SPECT/CT imaging revealed a 1.9-cm anterior mediastinal lesion with radiotracer uptake on both the immediate and delayed images. Surgical pathology of the lesion showed a benign thymic cyst with no parathyroid component.

Comparison between technetium-99m methoxyisobutylisonitrile scintigraphy and ultrasound in the diagnosis of parathyroid adenoma and parathyroid hyperplasia

Objective

The aim of this study was to evaluate the value of technetium-99m methoxyisobutylisonitrile (^99mTc-MIBI) imaging and ultrasound in preoperative localization of parathyroid adenoma (PA) and parathyroid hyperplasia (PH).

Participants and methods

A retrospective study of ^99mTc-MIBI double-phase scintigraphy (DPS) was performed in 187 hyperparathyroidism cases with pathologically diagnosed PA or PH. Of these patients, 167 cases underwent ultrasound, and 146 cases underwent ^99mTc-MIBI single-photon emission computed tomography/computed tomography (SPECT/CT). The sensitivity and diagnostic accuracy of ultrasound, ^99mTc-MIBI DPS, and SPECT/CT were compared between PA and PH. Differences in ^99mTc-MIBI DPS, serum parathyroid hormone (PTH), serum calcium and phosphorus, as well as the weight and longest diameter of lesion between PA and PH were also compared.

Results

As per patient-based analysis, the sensitivity of ultrasound, ^99mTc-MIBI DPS, and SPECT/CT was 90.70% (39/43), 95.56% (43/45), and 100.00% (30/30), respectively, for PA, and 93.55% (116/124), 90.85% (129/142), and 93.10% (108/116), respectively, for PH. There were no significant differences in sensitivity of these three imaging methods between PA and PH. However, per lesion-based analysis, the accuracy of ultrasound, ^99mTc-MIBI DPS, and SPECT/CT in detecting PA was 78.43% (40/51), 86.79% (46/53) and 96.88% (31/32), respectively, and the accuracy of ^99mTc-MIBI DPS was higher than that of ultrasound (χ²=6.507, P=0.011), and for PH, it was 49.69% (160/322), 40.71% (171/420), and 43.80% (152/347), respectively. The accuracy of ultrasound was higher than that of ^99mTc-MIBI DPS (χ²=5.940, P=0.015). The accuracy of a combination of all three examinations of ultrasound+^99mTc-MIBI DPS, ultrasound+^99mTc-MIBI SPECT/CT, ^99mTc-MIBI DPS+SPECT/CT, and ultrasound+^99mTc-MIBI DPS+^99mTc-MIBI SPECT/CT was 51.51% (154/299), 53.85% (161/299), 50.17% (150/299), and 54.18% (162/299), respectively, which was higher than that of ultrasound (χ²=5.273, P=0.022; χ²=8.226, P=0.004; χ²=3.880, P=0.049; χ²=8.702, P=0.003, respectively). Serum levels of PTH and phosphorus were lower in patients with PA than in patients with PH (P<0.001), and serum calcium level, the weight, and the longest diameter of lesion and early uptake rate of ^99mTc-MIBI DPS were higher in patients with PA than in patients with PH (P<0.01). Serum PTH level is often less than 1000 pg/ml in PA, but usually more than 1000 pg/ml in PH.

Conclusion

Ultrasound, ^99mTc-MIBI DPS, and SPECT/CT all have a higher value in the diagnosis of PA than PH. ^99mTc-MIBI SPECT/CT should be optimal for detecting PA, and early SPECT/CT scan might be better than delayed scan. Compared with ^99mTc-MIBI DPS and SPECT/CT, ultrasound has a slight advantage in localization of PH lesions. The combination of ultrasound and ^99mTc-MIBI DPS or SPECT/CT imaging could improve the accuracy in localization of PH lesions and should be considered as the first-line method for detecting PH.

MIBI scintigraphy of parathyroid adenomas: correlation with biochemical and histological markers

PURPOSE

In this study, we tested the hypothesis that MIBI-positive and MIBI-negative adenomas of parathyroid glands (APGs) have distinct biochemical and histological markers that could help differentiate MIBI-positive from MIBI-negative APGs.

PATIENTS AND METHODS

40 patients with 41 APGs were included in the study. Patients were enrolled in the study after MIBI scintigraphy examinations had been carried out. Biochemical analyses included serum levels of calcium (Ca), intact parathyroid hormone (iPTH), and 25-hydroxyvitamin D3 (25-OH-D3). All patients had neck ultrasound and MIBI examinations. After surgical resection the APGs were examined histologically.

RESULTS

In each of 39 patients one APG could be confirmed by histology, and in one patient, two contralateral APGs were identified. MIBI studies were positive in 73 % and negative in 27 % of the APGs. False-positive cases were not observed. MIBI-negative APGs were only present in patients with iPTH values below 150 pg/ml. In 82 % of MIBI negative studies oxyphilic cells were absent, and this cell type was present in only 18 % of MIBI negative cases (p < 0.001). Regarding cysts within the APGs, no differences were demonstrated between MIBI positive or negative studies (p = 0.32). Fat cells were seen in none of the MIBI -negative studies and in only 3 % of MIBI positive studies (p = 0.08).

CONCLUSIONS

For APGs, MIBI positivity correlates with serum iPTH concentration. The absence of oxyphilic cells with large numbers of mitochondria in APGs contributes to MIBI negativity, probably because of the reduced binding sites for the radiotracer.

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.

Biochemical and pathologic factors affecting technetium-99m-methoxyisobutylisonitrile imaging results in patients with primary hyperparathyroidism

OBJECTIVE

Technetium 99 m methoxyisobutylisonitrile (Tc-99m MIBI) scintigraphy represents the most commonly utilized imaging modality for the detection of the diseased gland in patients with primary hyperparathyroidism (PHPT). In this study, we aimed to identify potential biological factors with an impact on MIBI sensitivity.

METHODS

A total of 147 patients with surgically confirmed parathyroid adenomas were assessed retrospectively. Data including medical history, biochemical and hormonal measurements, cervical US, Tc-99m MIBI scans as well as pathology reports were retrieved and recorded.

RESULTS

Of the 147 patients, there were a total of 77, 39, and 31 cases with a positive, negative, and suspicious parathyroid adenoma on Tc-99m MIBI scan, respectively. Serum calcium (Ca), parathyroid hormone (PTH) and 25 (OH) D levels were comparable among MIBI positive and negative patients [Ca: 11.5 ± 0.9 vs 11.3 ± 0.9 mg/dL (P = 0.42); PTH: 216 (146-347) vs 194 (140-317) pg/mL (P = 0.45); 25(OH)D: 8.4 (5.7-18.2) vs 10.0 (4.7-23.3) ng/mL (P = 0.64), respectively]. P-glycoprotein (P-gp) staining was negative in both groups. Also, pathological examination of tissue preparations revealed no difference in terms of the volume of the adenomas, incidence of cystic adenomas, cell-type dominance (oxyphilic cell), percent fat, and Ki-67 ratio in MIBI positive and negative groups. The rate of hyalinization was 13% in MIBI positive and 28% in MIBI negative subjects, the difference being statistically significant (P = 0.04).

CONCLUSION

Presence of hyalinization in parathyroid adenomas was found to be negatively correlated with MIBI scan results.

The effect of regadenoson on the integrity of the human blood-brain barrier, a pilot study

Regadenoson is an FDA approved adenosine receptor agonist which increases blood-brain barrier (BBB) permeability in rodents. Regadenoson is used clinically for pharmacologic cardiac stress testing using SPECT or CT imaging agents that do not cross an intact BBB. This study was conducted to determine if standard doses of regadenoson transiently disrupt the human BBB allowing higher concentrations of systemically administered imaging agents to enter the brain. Patients without known intracranial disease undergoing clinically indicated pharmacologic cardiac stress tests were eligible for this study. They received regadenoson (0.4 mg) followed by brain imaging with either ^99mTc-sestamibi for SPECT or visipaque for CT imaging. Pre- and post-regadenoson penetration of imaging agents into brain were quantified [SPECT: radioactive counts, CT: Hounsfield units (HU)] and compared using a matched-pairs t-test. Twelve patients (33% male, median 60 yo) were accrued: 7 SPECT and 5 CT. No significant differences were noted in pre- and post-regadenoson values using mean radionuclide counts (726 vs. 757) or HU (29 vs. 30). While animal studies have demonstrated that regadenoson transiently increases the permeability of the BBB to dextran and temozolomide, we were unable to document changes in the penetration of contrast agents in humans with intact BBB using the FDA approved doses of regadenoson for cardiac evaluation. Further studies are needed exploring alternate regadenoson dosing, schedules, and studies in patients with brain tumors; as transiently disrupting the BBB to improve drug entry into the brain is critical to improving the care of patients with CNS malignancies.

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.

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.

Clinical utility of ultrasound and 99mTc sestamibi SPECT/CT for preoperative localization of parathyroid adenoma in patients with primary hyperparathyroidism

AIM

To evaluate the accuracy of ultrasound and parathyroid scintigraphy using single photon-emission computed tomography/computed tomography (SPECT/CT) for the preoperative localization of solitary parathyroid adenomas in patients with primary hyperparathyroidism who would be suitable for minimally invasive parathyroid surgery.

MATERIALS AND METHODS

Retrospective study of 63 consecutive patients with biochemical evidence of primary hyperparathyroidism referred for preoperative localization of parathyroid adenoma that proceeded to surgery in the same institution. All patients underwent high-resolution ultrasound and Technetium-99m sestamibi scintigraphy with planar and SPECT/CT imaging. The accuracy of preoperative imaging was compared to surgical and histological findings as the reference standard.

RESULTS

Fifty-nine patients had solitary parathyroid adenomas, three patients had multiglandular hyperplasia, and one patient had multiple parathyroid adenomas confirmed at surgery and histology. Thirty-five solitary parathyroid adenomas were identified preoperatively with ultrasound (64%) and 53 with SPECT-CT (90%). Concordant ultrasound and SPECT/CT findings were found in 35 cases (59%). An additional three adenomas were found with ultrasound alone and 18 adenomas with SPECT/CT alone. Fifty-one of the 56 adenomas localized using combined ultrasound and SPECT/CT were found at the expected sites during surgery. Combined ultrasound and SPECT/CT has an overall sensitivity of 95% and accuracy of 91% for the preoperative localization of solitary parathyroid adenomas.

CONCLUSIONS

The combination of ultrasound and SPECT/CT has incremental value in accurately localizing solitary parathyroid adenomas over either technique alone, and allows selection of patients with primary hyperparathyroidism who would be suitable for minimally invasive surgery.

Synchronous parathyroid adenoma and thyroid papillary carcinoma: a case report

A 51-year-old female patient presented with atypical chest pain, laryngo-oesophageal reflux, increased levels of serum calcium and parathyroid hormone. Ultrasonography showed a multinodular goiter with a prominent solid nodule in the lower left thyroid lobe and a solid hypoechoic nodule outside this area.

Tc99m-sestamibi parathyroid scintigraphy was performed to investigate a primary hyperparathyroidism, revealing an area with increased uptake in the lower left thyroid lobe and another area with marked uptake lower than this level. Thyroid scintigraphy with 99mTc showed a cold nodule of the left lower pole. FNA of the thyroid nodule was positive for papillary carcinoma later verified by postoperative histopathology.

This case underlines the need for a clinical high index of suspicion for synchronous hyperparathyroidism and thyroid cancer.