Parathyroid Four-Dimensional Computed Tomography: Evaluation of Radiation Dose Exposure During Preoperative Localization of Parathyroid Tumors in Primary Hyperparathyroidism

Primary Hyperparathyroidism: Part One: Evaluation

Primary hyperparathyroidism (PHPT) is a disorder characterized by the autonomous overproduction of parathyroid hormone (PTH) that leads to hypercalcemia, multiple clinical sequelae, and heterogenous presentation. Whether PHPT is caused by a single benign adenoma (85%), multiglandular disease (15%), or parathyroid carcinoma (1%), surgery is the definitive treatment.

Four-dimensional computed tomography as first-line imaging in primary hyperparathyroidism, a retrospective comparison to conventional imaging in a predominantly single adenoma population

BACKGROUND

To determine the use of four-dimensional CT as first-line imaging compared to the traditional combination of ultrasound and [99mTc]Tc-Sestamibi SPECT.

MATERIALS AND METHODS

Retrospective review of preoperative imaging in patients with primary hyperparathyroidism, who underwent parathyroidectomy between 2012 and 2021. In one group, the combination ultrasound and [99mTc]Tc-Sestamibi SPECT was used as first-line imaging (n = 54), in the other group four-dimensional CT was the first-line imaging modality (n = 51). Sensitivity and positive predictive value were calculated on patient, lateralisation and localisation level. The need for additional imaging was also assessed for both groups.

RESULTS

Four-dimensional CT had a significantly higher sensitivity compared to the combination of ultrasound/[99mTc]Tc-Sestamibi SPECT on patient and localisation level (70.6% vs. 51.9%, p = 0.049 and 60.8% vs. 35.2%, p = 0.009 respectively). Sensitivity for lateralisation also appeared higher, but did not reach significance (62.7% vs. 44.4%, p = 0.060). Positive predictive value was not significantly higher for four-dimensional CT compared to ultrasound and [99mTc]Tc-Sestamibi SPECT (88.9% vs. 85.7% for lateralisation and 86.1% vs. 67.9% for localisation respectively). Additional imaging was required in 14 patients with four-dimensional CT as first-line imaging (27.4%) consisting of 2 ultrasound/[99mTc]Tc-Sestamibi SPECT and 13 [18F]fluorocholine PET/CT, compared to 24 patients with ultrasound/[99mTc]Tc-Sestamibi SPECT as first-line imaging (44.4%), requiring 22 four-dimensional CT and 9 [18F]fluorocholine PET/CT.

CONCLUSIONS

Four-dimensional CT as the sole first-line parathyroid imaging modality had higher sensitivity than the combination of ultrasound and [99mTc]Tc-Sestamibi SPECT, therefore requiring fewer additional procedures. Although the most costly, [18F]fluorocholine PET/CT was the most effective technique to localise parathyroid adenoma in case all other imaging was negative.

Four-Dimensional Computed Tomography for Parathyroid Adenoma Localization: A Pre-Operative Imaging Protocol

OBJECTIVE

Primary hyperparathyroidism (PHPT) affects approximately 0.86% of the population, with surgical resection as the treatment of choice. A 4D computed tomography (CT) is a highly effective tool in localizing parathyroid adenomas; however, there is currently no defined role for 4D CT when stratified against ultrasonography (USG) and nuclear medicine Technetium Sestamibi SPECT/CT (SES) imaging.

STUDY DESIGN

Retrospective Study.

SETTING

University Hospital.

METHODS

All patients who underwent parathyroidectomy for PHPT between 2014 and 2019 at a single institution were reviewed. Patients who had a 4D CT were included. We compared outcomes of 4D CT as a second line imaging modality to those of USG and SES as first line modalities. An imaging algorithm was proposed based on these findings.

RESULTS

There were 84 patients identified who had a 4D CT after unsuccessful first line imaging. A 4D CT localized parathyroid adenoma to the correct quadrant in 64% of cases, and to the correct laterality in 75% of cases. Obese patients had significantly lower rates of adenoma localization with USG (33.4%), compared to non-obese patients (67.5%; P = .006). In determining multigland disease the sensitivity of 4D CT was 86%, while the specificity was 87%.

CONCLUSIONS

A 4D CT has impressive rates of accurate localization of parathyroid adenomas; however due to the radiation exposure involved, it should remain a second line imaging modality. PHPT patients should first be evaluated with USG, with 4D CT used if this is unsuccessful and patients are greater than 40 years old, have a high BMI, or are having revision surgery.

Head-to-head comparison of [11C]methionine PET, [11C]choline PET, and 4-dimensional CT as second-line scans for detection of parathyroid adenomas in primary hyperparathyroidism

PURPOSE

Accurate preoperative localization is imperative to guide surgery in primary hyperparathyroidism (pHPT). It remains unclear which second-line imaging technique is most effective after negative first-line imaging. In this study, we compare the diagnostic effectiveness of [11C]methionine PET/CT, [11C]choline PET/CT, and four dimensional (4D)-CT head-to-head in patients with pHPT, to explore which of these imaging techniques to use as a second-line scan.

METHODS

We conducted a powered, prospective, blinded cohort study in patients with biochemically proven pHPT and prior negative or discordant first-line imaging consisting of ultrasonography and 99mTc-sestamibi. All patients underwent [11C]methionine PET/CT, [11C]choline PET/CT, and 4D-CT. At first, all scans were interpreted by a nuclear medicine physician, and a radiologist who were blinded from patient data and all imaging results. Next, a non-blinded scan reading was performed. The scan results were correlated with surgical and histopathological findings. Serum calcium values at least 6 months after surgery were used as gold standard for curation of HPT.

RESULTS

A total of 32 patients were included in the study. With blinded evaluation, [11C]choline PET/CT was positive in 28 patients (88%), [11C]methionine PET/CT in 23 (72%), and 4D-CT in 15 patients (47%), respectively. In total, 30 patients have undergone surgery and 32 parathyroid lesions were histologically confirmed as parathyroid adenomas. Based on the blinded evaluation, lesion-based sensitivity of [11C]choline PET/CT, [11C]methionine PET/CT, and 4D-CT was respectively 85%, 67%, and 39%. The sensitivity of [11C]choline PET/CT differed significantly from that of [11C]methionine PET/CT and 4D-CT (p = 0.031 and p < 0.0005, respectively).

CONCLUSION

In the setting of pHPT with negative first-line imaging, [11C]choline PET/CT is superior to [11C]methionine PET/CT and 4D-CT in localizing parathyroid adenomas, allowing correct localization in 85% of adenomas. Further studies are needed to determine cost-benefit and efficacy of these scans, including the timing of these scans as first- or second-line imaging techniques.

Radiation-Related Thyroid Cancer

Radiation is an environmental factor that elevates the risk of developing thyroid cancer. Actual and possible scenarios of exposures to external and internal radiation are multiple and diverse. This article reviews radiation doses to the thyroid and corresponding cancer risks due to planned, existing, and emergency exposure situations, and medical, public, and occupational categories of exposures. Any exposure scenario may deliver a range of doses to the thyroid, and the risk for cancer is addressed along with modifying factors. The consequences of the Chornobyl and Fukushima nuclear power plant accidents are described, summarizing the information on thyroid cancer epidemiology, treatment, and prognosis, clinicopathological characteristics, and genetic alterations. The Chornobyl thyroid cancers have evolved in time: becoming less aggressive and driver shifting from fusions to point mutations. A comparison of thyroid cancers from the 2 areas reveals numerous differences that cumulatively suggest the low probability of the radiogenic nature of thyroid cancers in Fukushima. In view of continuing usage of different sources of radiation in various settings, the possible ways of reducing thyroid cancer risk from exposures are considered. For external exposures, reasonable measures are generally in line with the As Low As Reasonably Achievable principle, while for internal irradiation from radioactive iodine, thyroid blocking with stable iodine may be recommended in addition to other measures in case of anticipated exposures from a nuclear reactor accident. Finally, the perspectives of studies of radiation effects on the thyroid are discussed from the epidemiological, basic science, and clinical points of view.

Diagnostic Performance of Magnetic Resonance Imaging for Parathyroid Localization of Primary Hyperparathyroidism: A Systematic Review

Accurate preoperative localization is crucial for successful minimally invasive parathyroidectomy in primary hyperparathyroidism (PHPT). Preoperative localization can be challenging in patients with recurrent and/or multigland disease (MGD). This has led clinicians to investigate multiple imaging techniques, most of which are associated with radiation exposure. Magnetic resonance imaging (MRI) offers ionizing radiation-free and accurate imaging, making it an attractive alternative imaging modality. The objective of this systematic review is to provide an overview of the diagnostic performance of MRI in the localization of PHPT. PubMed and Embase libraries were searched from 1 January 2000 to 31 March 2023. Studies were included that investigated MRI techniques for the localization of PHPT. The exclusion criteria were (1) secondary/tertiary hyperparathyroidism, (2) studies that provided no diagnostic performance values, (3) studies published before 2000, and (4) studies using 0.5 Tesla MRI scanners. Twenty-four articles were included in the systematic review, with a total of 1127 patients with PHPT. In 14 studies investigating conventional MRI for PHPT localization, sensitivities varied between 39.1% and 94.3%. When employing more advanced MRI protocols like 4D MRI for PHPT localization in 11 studies, sensitivities ranged from 55.6% to 100%. The combination of MR imaging with functional techniques such as 18F-FCH-PET/MRI yielded the highest diagnostic accuracy, with sensitivities ranging from 84.2% to 100% in five studies. Despite the limitations of the available evidence, the results of this review indicate that the combination of MR imaging with functional imaging techniques such as 18F-FCH-PET/MRI yielded the highest diagnostic accuracy. Further research on emerging MR imaging modalities, such as 4D MRI and PET/MRI, is warranted, as MRI exposes patients to minimal or no ionizing radiation compared to other imaging modalities.

Role of four-dimensional computer tomography (4D-CT) in non-localising and discordant first-line imaging in primary hyperparathyroidism

BACKGROUND

Accurate preoperative localisation of parathyroid adenoma is imperative for the success of minimally invasive parathyroidectomy (MIP).

OBJECTIVE

Our study aimed to evaluate the role of four-dimensional computer tomography (4D-CT) scan as an imaging modality in patients with failed and discordant localisation reported in the first-line imaging modalities (ultrasonography and 99mTc-MIBI-SPECT/CT).

METHODS

This is a prospective cohort study performed at a university teaching centre from March 2013 to July 2021. All patients with primary hyperparathyroidism who had failed localisation by ultrasonography and 99mTc-MIBI-SPECT/CT (SpCT), or discordance between them, had 4D-CT performed in this study.

RESULTS

One hundred and two sporadic cases of pHPT with failed/discordant first-line imaging had 4D-CT imaging prior to parathyroidectomy. In 102 patients, 105 parathyroid adenomas were reported on histopathology. 4D-CT was able to localise 78% of them to the correct side and 64% to the correct quadrant in 102 patients, as compared with US (correct side 21%, correct quadrant 16%) and 99mTc-MIBI-SPECT/CT (correct side 36%, correct quadrant 31%). 4D-CT had a sensitivity, precision, accuracy and F1 score for correct quadrant localisation as 79%, 81%, 66% and 80%; and for correct side localisation as 82%, 98%, 80% and 89%, respectively. 4D-CT was able to identify three ectopic adenomas (two in superior mediastinum and one in the oesophageal wall) which were not detected on US or SpCT.

CONCLUSION

4D-CT was found to be sensitive and accurate in preoperative localising of the diseased parathyroid glands after failed/discordant US and SpCT. This led to more patients being offered MIP as the primary surgery and improved operative outcomes.

A contemporary analysis of the pre- and intraoperative recognition of multigland parathyroid disease

BACKGROUND

Despite advances in biochemical and radiological identification of parathyroid gland enlargement, primary hyperparathyroidism (PHPT) due to sporadic multigland parathyroid disease (MGPD) remains a perioperative diagnostic dilemma. Failure to recognise MGPD pre- or intraoperatively may negatively impact surgical cure rates and result in persistent PHPT and ongoing patient morbidity.

METHODS

We have conducted a comprehensive review of published literature in attempt to determine factors that could aid in reliably diagnosing sporadic MGPD pre- or intraoperatively. We discuss preoperative clinical features and examine pre- and intraoperative biochemical and imaging findings concentrating on those areas that give practicing surgeons and the wider multi-disciplinary endocrine team indications that a patient has MGDP. This could alter surgical strategy.

CONCLUSION

Biochemistry can provide diagnosis of PHPT but cannot reliably discriminate parathyroid pathology. Histopathology can aid diagnosis between MGPD and adenoma, but histological appearance can overlap. Multiple negative imaging modalities indicate that MGPD may be more likely than a single parathyroid adenoma, but the gold standard for diagnosis is still intraoperative identification during BNE. MGPD remains a difficult disease to both diagnose and treat.

Diagnostic Value of Four-Dimensional Dynamic Computed Tomography for Primary Hyperparathyroidism in Patients with Low Baseline Parathyroid Hormone Levels

Low baseline levels of parathyroid hormone (PTH) are associated with a higher rate of multiglandular disease, lower localization rates of preoperative imaging modalities, and a higher rate of unsuccessful minimally invasive parathyroidectomies. The objective of this study is to assess the diagnostic value of four-dimensional dynamic computed tomography (4D-CT) in localizing primary hyperparathyroidism (pHPT) in patients with low baseline PTH levels, compared to patients with high baseline PTH levels. Patients with pHPT who received a 4D-CT scan as part of their standard diagnostic evaluation were divided into two groups based on the following criteria: (1) preoperative PTH levels less than 100 pg/mL and (2) patients with preoperative PTH levels greater than 100 pg/mL. All patients underwent parathyroidectomy based on 4D-CT findings, with intraoperative parathyroid hormone monitoring. The lesion-based sensitivity of 4D-CT was 88% in patients with low baseline PTH levels and 94.7% in patients with high baseline PTH levels (p = 0.33). However, the success rate of image-guided resection based on 4D-CT findings was 71.4% in the low baseline PTH group compared to 90.6% in the high baseline PTH group (p = 0.06). Our study demonstrated that 4D-CT has a high lesion-based sensitivity in patients with pHPT and low baseline PTH levels but led to a relatively low rate of successful image-guided resection in patients with low baseline PTH levels. Therefore, it is important to exercise increased caution during 4D-CT-guided surgical exploration of patients with low baseline PTH levels to ensure successful surgical resection of all parathyroid lesions.

Can virtual non-contrast imaging replace true non-contrast imaging in multiphase scanning of the neck region?

Background

Dual-energy computed tomography (DECT) is an advanced imaging method that enables reconstruction of virtual non-contrast (VNC) images from a contrast-enhanced acquisition. This has the potential to reduce radiation exposure by eliminating the need for a true non-contrast (TNC) phase.

Purpose

The purpose is to evaluate the feasibility of VNC images in the neck region.

Materials and methods

A total of 100 patients underwent a DECT scan as part of diagnostic workup of primary hyperparathyroidism. VNC images were reconstructed from 30 s (arterial) and 50 s (venous) post-contrast scans. Regions of interest (ROIs) were placed in thyroid tissue, lymph node, carotid artery, jugular vein, fat, and sternocleidomastoid muscle. Mean densities of all anatomical structures were compared between VNC and TNC images.

Results

For all anatomical structures except the thyroid gland, the difference in mean density between TNC and VNC images was less than 15 HU. The mean difference in density between TNC and VNC images of the thyroid was 53.2 HU (95% CI 46.8; 59.6, p = <0.001).

Conclusion

This study demonstrated an acceptable agreement in density between true non-contrast and virtual non-contrast images for most anatomical structures in the neck region. Therefore, VNC images may have the potential to replace TNC images in the neck. However, due to significant differences in CT density of thyroid tissue, true non-contrast imaging cannot be directly substituted by virtual non-contrast imaging when examining the thyroid and its surrounding tissue.

Role of 18Fluorocholine Positron Emission Tomography/Computed Tomography in the Localization of Culprit Lesions in Patients of Persistent/Recurrent Primary Hyperparathyroidism: A Prospective Study in COVID Times

Introduction

Recurrent/persistent primary hyperparathyroidism in patients who have undergone previous parathyroidectomy is a challenging condition. Imaging is important for localizing the parathyroid adenoma for re-exploration and 18F-Fluorocholine (18F-FCH) positron emission tomography/computed tomography (PET/CT) seems ideal for this purpose.

Aim

This prospective study attempted to ascertain the utility of 18F-FCH PET/CT as an investigation in preoperative localization of abnormal parathyroid tissue in recurrent/persistent primary hyperparathyroidism while comparing it with 99mTc-Sestamibi dual-phase scintigraphy with early single-photon emission CT (SPECT)/CT and neck ultrasonography (USG).

Methods

Twenty patients with biochemical features of recurrent/persistent primary hyperparathyroidism were enrolled into this study. They underwent neck USG, 99mTc-Sestamibi dual-phase scintigraphy with early SPECT/CT and 18F-FCH PET/CT for localization of parathyroid lesions. Six patients underwent surgical resection of the detected lesions, 3 were awaiting surgery, and 11 were managed conservatively. One patient died due to COVID.

Results

The calculated positive predictive values on a per-lesion basis of neck USG, 99mTc-sestamibi scintigraphy and early SPECT/CT and 18F-FCH PET/CT in the cohort of the 5 operated patients were 75% (3/4), 71.4% (5/7), and 71.4% (5/7), respectively. On a per-patient basis, the lesion detection rate was 100% for 99mTc-sestamibi scan and FCH PET (5/5) and 80% on neck USG (4/5).

Conclusion

18F-FCH PET/CT is a highly accurate imaging modality for the detection of parathyroid lesions in patients with recurrent/persistent primary hyperparathyroidism.

18F-fluorocholine PET/MRI versus ultrasound and sestamibi for the localization of parathyroid adenomas

PURPOSE

Accurate preoperative localization is imperative to facilitate a minimally invasive parathyroidectomy (MIP) in primary hyperparathyroidism (pHPT). This study aims to compare the diagnostic value of standard-of-care localization techniques (ultrasound [US] and 99mTechnetium (99mTc) -sestamibi scintigraphy) to [F-18]-fluorocholine positron emission tomography/magnetic resonance imaging (FCH-PET/MRI) to determine the additional clinical usefulness of PET/MRI in a Canadian cohort.

METHODS

We conducted a prospective, appropriately powered, study to compare the diagnostic value of -FCH PET/MRI to that of the US and 99mTc-sestamibi scintigraphy for localization of parathyroid adenomas in a patient with pHPT. The primary outcome was the per-lesion sensitivity and positive predictive value (PPV) of FCH-PET/MRI, US, and 99mTc-sestamibi scintigraphy. Intraoperative surgeon localization, parathormone levels, and histopathological findings were used as reference standards.

RESULTS

Forty-one patients underwent FCH-PET/MRI of which 36 patients had parathyroidectomy. In these 36 patients, 41 parathyroid lesions were histologically confirmed as adenomas or hyperplastic glands. Per-lesion sensitivity of FCH-PET/MRI was 82.9% and of US and 99mTc-sestamibi scintigraphy combined at 50.0%, respectively. The sensitivity of FCH-PET/MRI was superior to that of US and 99mTc-sestamibi scintigraphy (p = 0.002). In the 19 patients in whom both US and 99mTc-sestamibi scintigraphy were negative, PET/MRI correctly identified the parathyroid adenoma in 13 patients (68%).

CONCLUSIONS

FCH-PET/MRI is a highly accurate imaging modality for localization of parathyroid adenomas in a tertiary center in North America. It is a superior functional imaging modality to 99mTc-sestamibi scintigraphy alone and more sensitive for localization of parathyroid lesions than US and 99mTc-sestamibi scintigraphy combined. This imaging modality could become the most valuable preoperative localization study given its superior performance in localizing parathyroid adenomas.

Multi-modality parathyroid imaging: A shifting paradigm

The goal of parathyroid imaging in hyperparathyroidism is not diagnosis, rather it is the localization of the cause of hyperparathyroidism for planning the best therapeutic approach. Hence, the role of imaging to accurately and precisely localize the abnormal parathyroid tissue is more important than ever to facilitate minimally invasive parathyroidectomy over bilateral neck exploration. The common causes include solitary parathyroid adenoma, multiple parathyroid adenomas, parathyroid hyperplasia and parathyroid carcinoma. It is highly imperative for the radiologist to be cautious of the mimics of parathyroid lesions like thyroid nodules and lymph nodes and be able to differentiate them on imaging. The various imaging modalities available include high resolution ultrasound of the neck, nuclear imaging studies, four-dimensional computed tomography (4D CT) and magnetic resonance imaging. Contrast enhanced ultrasound is a novel technique which has been recently added to the armamentarium to differentiate between parathyroid adenomas and its mimics. Through this review article we wish to review the imaging features of parathyroid lesions on various imaging modalities and present an algorithm to guide their radiological differentiation from mimics.

Dual-phase computed tomography for localization of parathyroid lesions in children and adolescents with primary hyperparathyroidism

BACKGROUND

Childhood and adolescent primary hyperparathyroidism (PHPT) is a rare disease caused by single adenomas in 65-94% of patients. In this patient group, there is no data on computed tomography (CT) for pre-operative parathyroid localization that may facilitate focused parathyroidectomy.

METHODS

Two radiologists reviewed dual-phase (nonenhanced and arterial) CT images of twenty-three operated children and adolescents [20:single-gland disease(SGD), 3:multi-glandular disease(MGD)] with proven histopathological PHPT. Percentage arterial enhancement (PAE) was calculated as [100*{arterial-phase Hounsfield unit (HU)-nonenhanced phase HU}/nonenhanced HU] of the parathyroid lesion(s), thyroid, and lymph node.

RESULTS

Dual-phase CT lateralized 100%, localized to the correct quadrant/site 85% SGD (including 3/3 ectopic), and identified 1/3 MGD. PAE (cutoff ≥ 112.3%) was sensitive (91.3%) and specific (99.5%) in distinguishing parathyroid lesions from local mimics (P<0.001). The average effective dose was 3.16±1.01mSv, comparable to the planar/single photon emission CT (SPECT) Technetium 99m(Tc)-sestamibi and choline positron emission tomography (PET)/CT scans. Solid-cystic morphology identified in 4 patients harboring pathogenic germline variants (3:CDC73, 1:CASR) may serve as a radiological clue to molecular diagnosis. Nineteen out of 20 (95%) patients with SGD who had undergone single gland resection based on pre-operative CT findings were in remission over a median follow-up of 18 months.

CONCLUSION

As most children/adolescents with PHPT have SGD, dual-phase CT protocols which reduce the effective radiation dose with high localization sensitivity for single parathyroid lesions may be a sustainable pre-operative imaging modality in this patient group.

Localization Strategy Prior to Radiofrequency Ablation for Primary and Secondary Hyperparathyroidism

Objective: Preoperative localization in patients with primary or secondary hyperparathyroidism before radiofrequency ablation (RFA) is crucial. There is currently a lack of consensus regarding imaging protocol. Evaluating the diagnostic performance of ultrasound, four-dimensional computed tomography (4D-CT), and technetium 99m-sestamibi single-photon-emission-computed tomography/computed tomography (SPECT/CT) is necessary for RFA of hyperparathyroidism. Methods: This retrospective study recruited patients with primary or secondary hyperparathyroidism who underwent ultrasound, 4D-CT, and SPECT/CT before RFA at a single institution. The sensitivity, accuracy, and receiver operating characteristic curve analysis were used to evaluate the diagnostic performance of the imaging modalities. Results: A total of 33 patients underwent RFA for hyperparathyroidism (8 patients with primary hyperparathyroidism, 25 patients with secondary hyperparathyroidism). Ultrasound had the highest sensitivity (0.953) and accuracy (0.943), while 4D-CT had higher sensitivity and accuracy than SPECT/CT (sensitivity/accuracy, 4D-CT vs. SPECT/CT: 0.929/0.920 vs. 0.741/0.716). Combined ultrasound with 4D-CT and the three combined modalities achieved equivalent, and the highest, diagnostic performance (sensitivity 1.000, accuracy 0.989). The lesion length and volume were important predictors of the diagnostic performance of 4D-CT and SPECT/CT (area under curve of length in 4D-CT/volume in 4D-CT/length in SPECT/volume in SPECT: 0.895/0.834/0.767/0.761). Conclusion: Combined ultrasound with 4D-CT provides optimal preoperative localization prior to RFA in patients with primary or secondary hyperparathyroidism. The length and volume of parathyroid lesions are determinative of the diagnostic performance of 4D-CT and SPECT/CT.

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.

The Diagnostic Value of Contrast Enhanced Ultrasound for Localization of Parathyroid Lesions in Primary Hyperparathyroidism: Comparison With Color Doppler Ultrasound: Comparison With Color Doppler Ultrasound

OBJECTIVES

Preoperative localization of pathological parathyroid glands with imaging is essential for focused unilateral neck exploration and minimally invasive techniques. Recently published studies suggested that contrast-enhanced ultrasonography (CEUS) had high accuracy in the localization of hyperfunctioning parathyroid glands, with a general increase in the sensitivity as compared to conventional sonography. The purpose of this study was to determine the usefulness of CEUS in the localization of parathyroid lesions relating to surgical and histopathological data, in comparison to color Doppler ultrasound (CDUS), in the same series of patients.

METHODS

Records of 142 patients who underwent parathyroidectomy were retrospectively examined comparing imaging and intraoperative/histopathologic findings.

RESULTS

The overall sensitivity of CEUS was 77.6% compared with 74.6% for CDUS, although no significative differences were found (P = .516). Conversely, CDUS has shown higher sensitivity than CEUS in the group of patients with associated thyroid pathology but there was no statistical difference (P = .529). The sensitivity for detection of multiple adenomas was the same for both procedures.

CONCLUSIONS

We found no significative superior sensitivity of CEUS also in case of concomitant thyroid pathology and multiple glands disease.

Surgical Aspects of Primary Hyperparathyroidism

Parathyroidectomy (PTX) is the treatment of choice for symptomatic primary hyperparathyroidism (PHPT). It is also the treatment of choice in asymptomatic PHPT with evidence for target organ involvement. This review updates surgical aspects of PHPT and proposes the following definitions based on international expert consensus: selective PTX (and reasons for conversion to an extended procedure), bilateral neck exploration for non-localized or multigland disease, subtotal PTX, total PTX with immediate or delayed autotransplantation, and transcervical thymectomy and extended en bloc PTX for parathyroid carcinoma. The systematic literature reviews discussed covered (i) the use of intraoperative PTH (ioPTH) for localized single-gland disease and (ii) the management of low BMD after PTX. Updates based on prospective observational studies are presented concerning PTX for multigland disease and hereditary PHPT syndromes, histopathology, intraoperative adjuncts, localization techniques, perioperative management, "reoperative" surgery and volume/outcome data. Postoperative complications are few and uncommon (<3%) in centers performing over 40 PTXs per year. This review is the first global consensus about surgery in PHPT and reflects the current practice in leading endocrine surgery units worldwide. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

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.

Relative Perfusion Differences between Parathyroid Adenomas and the Thyroid on Multiphase 4DCT

A multiphase 4DCT technique can be useful for the detection of parathyroid adenomas. Up to 16 different phases can be obtained without significant increase of exposure dose using wide beam axial scanning. This technique also allows for the calculation of perfusion parameters in suspected lesions. We present data on 19 patients with histologically proven parathyroid adenomas. We find a strong correlation between 2 perfusion parameters when comparing parathyroid adenomas and thyroid tissue: parathyroid adenomas show a 55% increase in blood flow (BF) (p < 0.001) and a 50% increase in blood volume (BV) (p < 0.001) as compared to normal thyroid tissue. The analysis of the ROC curve for the different perfusion parameters demonstrates a significantly high area under the curve for BF and BV, confirming these two perfusion parameters to be a possible discriminating tool to discern between parathyroid adenomas and thyroid tissue. These findings can help to discern parathyroid from thyroid tissue and may aid in the detection of parathyroid adenomas.

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.

Preoperative Imaging with [18F]-Fluorocholine PET/CT in Primary Hyperparathyroidism

Primary hyperparathyroidism (pHPT) is a common endocrine disorder due to hyperfunctioning parathyroid glands. To date, the only curing therapy is surgical removal of the dysfunctional gland, making correct detection and localization crucial in order to perform a minimally invasive parathyroidectomy. ¹⁸F-Fluorocholine positron emission tomography/computed tomography (¹⁸F-FCH PET/CT) has shown promising results for the detection of pHPT, suggesting superiority over conventional imaging with ultrasounds or scintigraphy. A total of 33 patients with pHPT who had negative or equivocal findings in conventional imaging received ¹⁸F-FCH PET/CT preoperatively and were retrospectively included. A pathological hyperfunctional parathyroid gland was diagnosed in 24 cases (positive PET, 72.7%), 4 cases showed equivocal choline uptake (equivocal PET, 12.1%), and in 5 cases, no enhanced choline uptake was evident (negative PET, 15.2%). Twelve of the twenty-four detected adenoma patients underwent surgery, and in all cases, a pathological parathyroid adenoma was resected at the site detected by PET/CT. Two of the six patients without pathological choline uptake who received a parathyroidectomy revealed no evidence of parathyroid adenoma tissue in the histopathological evaluation. This retrospective study analyzes ¹⁸F-FCH PET/CT in a challenging patient cohort with pHPT and negative or equivocal conventional imaging results and supports the use of ¹⁸F-FCH for the diagnosis of hyperfunctional parathyroid tissue, especially in this patient setting, with a 100% true positive and true negative detection rate. Our study further demonstrates the importance of ¹⁸F-FCH PET/CT for successful surgical guidance.

Organs' absorbed dose and comparison of different methods for effective dose calculation in computed tomography of parathyroid glands

Objective:To estimate organs' absorbed dose from the two-phase CT of parathyroid glands, effective dose (ED) based on three different methods, and compare the dose values with those reported by other published protocols.Methods:Volumetric-computed-tomography-dose-index (CTDIvol), dose-length-product (DLP), and the corresponding scan length during each phase of a parathyroid protocol were recorded, for seventy-six patients. One k-factor, and two different k-factors for the neck and chest area were used to estimate the ED from DLP. A Monte Carlo software, VirtualDoseCT, was also used for the estimation of organs' absorbed dose and ED.Results:Two-phase parathyroid CT resulted in a mean ED of 3.93 mSv, 4.29 mSv and 4.21 mSv according to the one k-factor, two k-factors, and VirtualDoseCT methods, respectively. The two k-factors method resulted in a slight overestimation of 1.9% in total ED compared to VirtualDoseCT. No statistically significant difference was found in ED values between these methods (Wilcoxon test, p>0.05), except for female patients in the pre-contrast phase. The organs inside the SFOV received the following doses: thymus 23.3 mGy, lungs 11.5 mGy, oesophagus 9.2 mGy, thyroid 6.9 mGy, and breast 6.3 mGy. The ED and organs' dose (OD) values were significantly lower in the pre-contrast than in the arterial phase (Wilcoxon test, p<0.001). A statistically significant difference was observed between male and female patients for the pre-contrast phase (Mann-Whitney test, p<0.05), regarding the ED values obtained with the two k-factors method and VirtualDoseCT software.Conclusions:The two k-factors method could be applied for the ED estimation in clinical practice, if appropriate software is not available. An extensive range of ED values derived from the literature, mainly depending on the acquisition protocol parameters and the estimation method.

Contemporary Multimodality Imaging of Primary Hyperparathyroidism

Primary hyperparathyroidism (PHPT) is a disorder characterized by hypercalcemia and an elevated or inappropriately normal parathyroid hormone level. Classic features include bone pain, fractures, renal impairment, nephrolithiasis, and mental disturbance. However, most cases of PHPT are now asymptomatic at diagnosis or associated with nonspecific neurocognitive changes. The most frequent cause of PHPT is a solitary adenoma that secretes parathyroid hormone without the normal suppressive effect of serum calcium. A smaller number of cases can be attributed to multigland disease. Parathyroidectomy is curative and is considered for nearly all affected patients. Although PHPT is primarily a clinical and biochemical diagnosis, imaging is key to the localization of adenomas, which can lie in conventional locations adjacent to the thyroid gland or less commonly at ectopic sites in the neck and mediastinum. In addition, accurate localization facilitates the use of a minimally invasive or targeted surgical approach. Frequently used localization techniques include US, parathyroid scintigraphy, and four-dimensional CT. Second- and third-line modalities such as MRI, PET/CT, and selective venous sampling with or without parathyroid arteriography can increase confidence before surgery. These localization techniques, along with the associated technical aspects, relative advantages, and drawbacks, are described. Local expertise, patient factors, and surgeon preference are important considerations when determining the type and sequence of investigation. A multimodality approach is ultimately desirable, particularly in challenging scenarios such as multigland disease, localization of ectopic adenomas, and persistent or recurrent PHPT. Online supplemental material is available for this article. ^©RSNA, 2022.

Parathyroid venous sampling for the preoperative localisation of parathyroid adenoma in patients with primary hyperparathyroidism

Preoperative localisation studies are essential for parathyroidectomy in patients with primary hyperparathyroidism. If the location of abnormal parathyroid glands cannot be identified through non-invasive studies, parathyroid venous sampling (PVS) may be employed. In this study, we evaluated the utility of preoperative PVS in parathyroid surgery. Patients with primary hyperparathyroidism who underwent preoperative PVS at Severance Hospital between January 2015 and June 2020 were identified. Patients for whom the results of non-invasive imaging studies were inconsistent or negative underwent PVS. The results of PVS were compared with operative findings and pathologic results. For 14 patients, the results of preoperative ultrasonography and ^99mTc-sestamibi single-photon emission computed tomography (SPECT) were negative; for 20 patients, either the result of only one test was positive, or the results of the two tests were inconsistent. With respect to the lateralisation of diseased adenoma, the results of PVS and pathological examination were inconsistent only for one patient in either group (total: 2/34 patients). This study showed that PVS could be used effectively for preoperative localisation in patients with primary hyperparathyroidism in whom the location of diseased parathyroid glands cannot be determined through non-invasive image studies.

Parathyroid Imaging: Past, Present, and Future

The goal of parathyroid imaging is to identify all sources of excess parathyroid hormone secretion pre-operatively. A variety of imaging approaches have been evaluated and utilized over the years for this purpose. Ultrasound relies solely on structural features and is without radiation, however is limited to superficial evaluation. 4DCT and 4DMRI provide enhancement characteristics in addition to structural features and dynamic enhancement has been investigated as a way to better distinguish parathyroid from adjacent structures. It is important to recognize that 4DCT provides valuable information however results in much higher radiation dose to the thyroid gland than the other available examinations, and therefore the optimal number of phases is an area of controversy. Single-photon scintigraphy with 99mTc-Sestamibi, or dual tracer 99mTc-pertechnetate and 99mTc-sestamibi with or without SPECT or SPECT/CT is part of the standard of care in many centers with availability and expertise in nuclear medicine. This molecular imaging approach detects cellular physiology such as mitochondria content found in parathyroid adenomas. Combining structural imaging such as CT or MRI with molecular imaging in a hybrid approach allows the ability to obtain robust structural and functional information in one examination. Hybrid PET/CT is widely available and provides improved imaging and quantification over SPECT or SPECT/CT. Emerging PET imaging techniques, such as 18F-Fluorocholine, have the exciting potential to reinvent parathyroid imaging. PET/MRI may be particularly well suited to parathyroid imaging, where available, because of the ability to perform dynamic contrast-enhanced imaging and co-registered 18F-Fluorocholine PET imaging simultaneously with low radiation dose to the thyroid. A targeted agent specific for a parathyroid tissue biomarker remains to be identified.

DOSIMETRIC EVALUATION OF THE TWO-PHASE COMPUTED TOMOGRAPHY IN PARATHYROID GLANDS IMAGING

This study evaluates the patient radiation dose from the two-phase protocols of two different computed tomography (CT) systems and compares this with that delivered by the other similar protocols previously published. Two hundred and fourteen patients with primary hyperparathyroidism were included in the study with a two-phase CT scan between 2008 and 2020 by using a Toshiba Aquilion Prime 80 and a GE Light Speed 16. The standard 'neck' or a modified 'parathyroid' protocol was used. The patient dose was evaluated in terms of volumetric computed tomography dose index (CTDIvol), dose length product (DLP) and effective dose (ED) per acquisition protocol and CT system. CTDIvol and DLP were recorded retrospectively, while the ED was calculated based on DLP and an appropriate conversion coefficient. Comparisons of patient dose between the two protocols and two CT systems and the corresponding published values were established. A significantly lower patient dose (40.2-43.2%) than the GE system (p < 0.0001) resulted from the Toshiba system. The 'parathyroid' protocol resulted in a 6.5-9.6% lower patient dose than the standard 'neck' protocol. Compared with the literature, the lowest ED value (3.6 mSv) was observed since this protocol consists of a lowered tube voltage of 100 kVp, a reduced scan length for the pre-contrast phase and implementation of an iterative reconstruction algorithm.

Clinical adaptation of auxiliary methods and multidisciplinary approach to changing trends in parathyroid surgery

To examine the effects of multidisciplinary approach and adjunct methods, on the surgical strategy, complications and treatment success of parathyroid surgery.Patients, who were operated for primary hyperparathyroidism (n = 411) at our institution between 2012 and 2019 were reviewed retrospectively. Preoperative imaging studies, surgical method, additional diagnostic methods used during surgery, frozen section results, and histopathology findings, complications, persistence, and recurrence were examined.Localization was determined by first-line examinations in 79.9% (n = 348). Four-dimensional computed tomography was used with an 83.3% success rate. Lateralization success for angiographic selective venous sampling was 80.3% and exact localization success was 65.1%. Bilateral neck exploration was performed in 10.6% (n = 37) of the patients, and in the remaining 89.4% (n = 311), minimally invasive parathyroidectomy (MIP) was performed. While the complication rate was higher in the bilateral neck exploration group (P = .019), persistence and recurrence rates were similar between 2 groups. During the study period, annual case volume increased from 9 cases to 103 cases (P < .001) and the rate of MIP increased from 44.4% to 92.8% over the years (P < .001).Effective use of adjunct techniques has increased the rates of MIP. The multidisciplinary approach has also provided low complication rates with the increasing number of cases.

High-frequency Multiphase 4DCT for the Detection of Parathyroid Adenomas: A Pictorial Essay

4-Dimensional computed tomography (4DCT) for the detection of (an) enlarged parathyroid(s) is a commonly performed examination in the management of primary hyperparathyroidism. In our center, we introduced a high-frequency multiphase 4DCT protocol obtaining 16 phases, including 11 different arterial phases. Exposure to this multiphase 4DCT technique is similar to that for classic helical 4DCT. In this pictorial essay we reconstructed our multiphase 4DCT series in the manner of a classic helical 4DCT and compare both techniques. We illustrate how multiphase 4DCT may aid in the detection of parathyroid adenomas. We found 17 out of 19 lesions demonstrating a type A pattern of enhancement, therefore suggesting this pattern could be more prevalent than previously thought. Some parathyroid adenomas may be mistaken for enlarged lymph nodes using classic 4DCT whereas high-frequency multiphase 4DCT can detect a temporary rise in enhancement, thus suggesting the lesions in question to be of parathyroid origin. Smaller lesions may prove more obvious as the difference in enhancement between parathyroid and thyroid can become more prominent.

Detectability of 18F-choline PET/MR in primary hyperparathyroidism

PURPOSE

We aimed to evaluate the power of 18F-fluorocholine (FCH) positron emission tomography/magnetic resonance (PET/MR) imaging in unlocalized primary hyperparathyroidism.

METHODS

Thirty-four patients were included. In 17/34 patients, PET/MR was performed immediately after a negative 18F-FCH PET/CT. Sensitivity, specificity, positive and negative predictive values were calculated for MR only (blinded to PET data) and PET only (blinded to MR data) findings.

RESULTS

18F-FCH PET/MR was positive in 26/34 (76%) patients. PET/MR was also positive in 12/17 (71%) patients with a negative PET/CT. Among 11/34 (32%) patients where 18F-FCH PET-only and MR-only results were discordant, MR was false positive in 7/11 patients (3/7 of the lesions were not 18F-FCH avid and in 4/7 of them PET and MRI pointed different locations. Postoperative histopathology revealed that 18F-FCH-positive ones were true positives). Sensitivity, specificity, PPV, NPV and accuracy of neck MR evaluated blinded to PET data were 80%, 50%, 70%, 64% and 68%, respectively, and all were calculated as 100% for PET/MR.

CONCLUSION

18F-FCH PET/MR is very effective in preoperative localization of parathyroid adenomas even if 18F-FCH PET/CT is negative. Neck MR alone is insufficient in detecting parathyroid adenomas but PET/MR combination helps in precise localisation.

Assessment and Comparison of 18F-Fluorocholine PET and 99mTc-Sestamibi Scans in Identifying Parathyroid Adenomas: A Metaanalysis

Hyperparathyroidism is an endocrine disorder caused by one or more hyperfunctioning parathyroid glands. Current imaging consisting of ultrasound and 99mTc-sestamibi is imprecise, making localization difficult. 18F-fluorocholine (18F-FCH) PET has recently shown promise in presurgical localization of parathyroid adenomas. The primary aim of this study was to summarize the sensitivities and specificities of studies using 18F-FCH PET to localize hyperparathyroidism. A secondary aim was to summarize a subset of studies in which 99mTc-sestamibi scans were also used and to compare the performance of the 2 modalities. Methods: We searched the MEDLINE and EMBASE databases following the PRISMA (Preferred Reporting Items for Systematic Review and Metaanalysis) statement. Quality was assessed using the QUADAS-2 tool (Quality Assessment of Diagnostic Accuracy Studies). Twenty studies were included for quantitative assessment in our metaanalysis. A random-effects model and a hierarchic summary receiver-operating-characteristic model was used to summarize the sensitivity of 18F-FCH PET in detecting abnormal parathyroid adenomas. We used the same methodology to assess sensitivity of 99mTc-sestamibi, as a comparison to 18F-FCH PET. Results:18F-FCH PET had a high sensitivity, 0.97 (range, 0.96-0.98), for the detection of abnormal parathyroid adenomas. In the subpopulation for which both 18F-FCH and 99mTc-sestamibi were reported, 18F-FCH also had a higher sensitivity, 0.96 (0.94-0.98), than the 0.54 (0.29-0.79) reported for 99mTc-sestamibi (P < 0.001). Conclusion:18F-FCH PET demonstrates high localization accuracy in patients with hyperparathyroidism. This metaanalysis supports the use of 18F-FCH over 99mTc-sestamibi in patients with 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.

4DCT Scanning Technique for Primary Hyperparathyroidism: A Scoping Review

Objective

4DCT for the detection of (an) enlarged parathyroid(s) is a commonly performed examination in the management of primary hyperparathyroidism. Protocols are often institution-specific; this review aims to summarize the different protocols and explore the reported sensitivity and specificity of different 4DCT protocols as well as the associated dose.

Materials and Methods

A literature study was independently conducted by two radiologists from April 2020 until May 2020 using the Medical Literature Analysis and Retrieval System Online (MEDLINE) database. Articles were screened and assessed for eligibility. From eligible studies, data were extracted to summarize different parameters of the scanning protocol and observed diagnostic attributes.

Results

A total of 51 articles were included and 56 scanning protocols were identified. Most protocols use three (n = 25) or four different phases (n = 23). Almost all authors include noncontrast enhanced imaging and an arterial phase. Arterial images are usually obtained 25–30 s after administration of contrast, and less agreement exists concerning the timing of the venous phase(s). A mean contrast bolus of 100 mL is administered at 3-4 mL/s. Bolus tracking is not often used (n = 3). A wide range of effective doses are reported, up to 28 mSv. A mean sensitivity of 81.5% and a mean specificity of 86% are reported.

Conclusion

Many different 4DCT scanning protocols for the detection of parathyroid adenomas exist in the literature. The number of phases does not appear to affect sensitivity or specificity. A triphasic approach, however, seems preferable, as three patterns of enhancement of parathyroid adenomas are described. Bolus tracking could help to reduce the variability of enhancement. Sensitivity and specificity also do not appear to be affected by other scan parameters like tube voltage or tube current. To keep the effective dose within limits, scanning at a lower fixed tube current seems preferable. Lowering tube voltage from 120 kV to 100 kV may yield similar image contrast but would also help lower the dose.

Three-phase four-dimensional computed tomography as a first-line investigation in primary hyperparathyroidism

INTRODUCTION

Parathyroid computed tomography using multiple phases (four-dimensional computed tomography (4DCT) for parathyroid localization was first described in 2006. Since its inception, there has been variable uptake of this technique due to inconsistency of results between institutions and perceived higher radiation dose than technetium-99 sestamibi scans (MIBI). 4DCT has been the primary imaging modality for parathyroid localization at our institution since 2013.

METHODS

A retrospective study of surgically managed patients with primary hyperparathyroidism who had preoperative localization with 4DCT from 2013-2018 was performed.

RESULTS

A total of 353 patients were included for analysis. The positive predictive value (PPV) of our three-phase 4DCT protocol was 93.3%, sensitivity (localized) 85.2% with a 5.8% false-positive rate and 13.9% false-negative (non-localizing) rate when reported by a head and neck radiologist (HNR). Calculated effective dose varied from 4.5 to 8.9mSV. On multivariable logistic regression, reporting by an experienced HNR (P < 0.001) and gland weight > 200 mg (P = 0.002) were significant for higher accuracy, lower false positives and false negatives.

CONCLUSION

A first-line three-phase 4DCT protocol for primary hyperparathyroidism is an accurate technique providing precise anatomical localization of abnormal parathyroid glands, particularly when performed by a specialist HNR. In our practise, it provides the best rate of detection and superior anatomical localization needed for minimally invasive parathyroid surgery, compared to other commonly used localization techniques. It also avoids the need for four gland exploration in the majority of patients with primary hyperparathyroidism.

Detection of parathyroid adenomas with multiphase 4DCT: towards a true four-dimensional technique

Background

Four-dimensional computed tomography (4DCT) is a commonly performed examination in the management of primary hyperparathyroidism, combining three-dimensional imaging with enhancement over time as the fourth dimension. We propose a novel technique consisting of 16 different contrast phases instead of three or four different phases. The main aim of this study was to ascertain whether this protocol allows the detection of parathyroid adenomas within dose limits. Our secondary aim was to examine the enhancement of parathyroid lesions over time.

Methods

For this prospective study, we included 15 patients with primary hyperparathyroidism and a positive ultrasound prior to surgery. We performed 4DCT with 16 different phases: an unenhanced phase followed by 11 consecutive arterial phases and 4 venous phases. Continuous axial scanning centered on the thyroid was performed over a fixed 8 cm or 16 cm coverage volume after the start of contrast administration.

Results

In all patients, an enlarged parathyroid lesion was demonstrated, and the mean lesion size was 13.6 mm. The mean peak arterial enhancement for parathyroid lesions was 384 Hounsfield units (HU) compared to 333 HU for the normal thyroid. No significant difference could be found. The time to peak (TTP) was significantly earlier for parathyroid adenomas than for normal thyroid tissue: 30.8 s versus 32.3 s (p value 0.008). The mean slope of increase (MSI) of the enhancement curve was significantly steeper than that of normal thyroid tissue: 29.8% versus 22.2% (p value 0.012). The mean dose length product was 890.7 mGy cm with a calculated effective dose of 6.7 mSv.

Conclusion

Our 4DCT protocol may allow better visualization of the pattern of enhancement of parathyroid lesions, as enhancement over time curves can be drawn. In this way, wash-in and wash-out of contrast in suspected lesions can be readily demonstrated. Motion artifacts are less problematic as multiple phases are available. Exposure to our proposed 4DCT technique is comparable to that for classic helical 4DCT. Careful selection of parameters (lowering kV and SNR) can help to further reduce the dose.

Preoperative Localization for Primary Hyperparathyroidism: A Clinical Review

With increasing use of minimally invasive parathyroidectomy (PTx) over traditional bilateral neck exploration in patients with primary hyperparathyroidism (PHPT), accurate preoperative localization has become more important to enable a successful surgical outcome. Traditional imaging techniques such as ultrasound (US) and sestamibi scintigraphy (MIBI) and newer techniques such as parathyroid four-dimension computed tomography (4D-CT), positron emission tomography (PET), and magnetic resonance imaging (MRI) are available for the clinician to detect the diseased gland(s) in the preoperative workup. Invasive parathyroid venous sampling may be useful in certain circumstances such as persistent or recurrent PHPT. We review the diagnostic performance of these imaging modalities in preoperative localization and discuss the advantages and weaknesses of these techniques. US and MIBI are established techniques commonly utilized as first-line modalities. 4D-CT has excellent diagnostic performance and is increasingly performed in first-line setting and as an adjunct to US and MIBI. PET and MRI are emerging adjunct modalities when localization has been equivocal or failed. Since no evidence-based guidelines are yet available for the optimal imaging strategy, clinicians should be familiar with the range and advancement of these techniques. Choice of imaging modality should be individualized to the patient with consideration for efficacy, expertise, and availability of such techniques in clinical practice.

Comparing the diagnostic accuracy of 4D CT and 99mTc-MIBI SPECT/CT for localizing hyperfunctioning parathyroid glands: a systematic review and meta-analysis

PURPOSE

To compare the diagnostic accuracy of dual-phase 99mTc-MIBI single photon emission computed tomography/computed tomography (SPECT/CT) and 4D CT for the localization of hyperfunctioning parathyroid glands, a systematic review and meta-analysis was performed. Whether 4D CT combined to SPECT/CT [contrast-enhanced (CE)-SPECT/CT] had a better diagnostic performance than SPECT/CT alone in this scenario was also evaluated.

MATERIAL AND METHODS

PubMed and Embase databases were searched for eligible studies. To reduce interstudy heterogeneity, only studies with clear head-to-head comparison were included. Publication bias was assessed by the Deeks funnel plot. The pooled sensitivity, specificity and the area under the curve (AUC) for 4D CT, SPECT/CT and CE-SPECT/CT were determined by random-effect analysis, respectively.

RESULTS

Nine studies met the inclusion criteria, with a total of 911 participants. The sensitivity and specificity of 4D CT were 0.85 [95% confidence interval (CI), 0.69-0.94] and 0.93 (95% CI, 0.88-0.96), whereas the sensitivity and specificity for SPECT/CT were 0.68 (95% CI, 0.51-0.82; P = 0.048 compared with 4D CT) and 0.98 (95% CI, 0.95-0.99; P = 0.014 compared with 4D CT), respectively. CE-SPECT/CT is comparable to SPECT/CT in specificity and AUC, but it may improve the sensitivity (although there was a lack of statistical difference, 0.87 vs. 0.78; P = 0.125).

CONCLUSION

Although 4D CT shows comparable AUC and borderline better sensitivity than SPECT/CT, its clinical application is confined by relatively low specificity and high radiation exposure. CE-SPECT/CT may improve the sensitivity without compromising the specificity and AUC of SPECT/CT.

Single Gland, Ectopic Location: Adenomas are Common Causes of Primary Hyperparathyroidism in Children and Adolescents

BACKGROUND

Primary hyperparathyroidism (PHPT) in children and adolescents is uncommon. Data-driven guidelines for management in pediatric patients are limited.

METHODS

We performed a retrospective cohort analysis of all patients (1997-2017) with PHPT ≤ 21 years of age who underwent parathyroidectomy at three institutions. Clinical and demographic variables were analyzed. Primary operative outcome was cure (normocalcemia > 6 months after surgery); secondary outcome was operative success (intraoperative parathyroid hormone decrease of ≥ 50%).

RESULTS

We identified 86 patients with a median age of 17 years (IQR: 14, 19); 64% (n = 55) were female. The mean preoperative serum calcium was 11.7 mg/dL, median parathyroid hormone (PTH) was 110 pg/mL, and median urine calcium was 4.1 mg/kg/24 h. Preoperatively, sestamibi scan localized in 41/71 patients (58%); neck ultrasound localized in 19/44 (43%). The most common pathology at surgery was a single ectopic parathyroid adenoma in 71% (n = 61). A high incidence of ectopic adenomas (25%, n = 22) was observed, most commonly intrathymic (n = 13), followed by tracheoesophageal groove (n = 5), carotid sheath (n = 2), and intrathyroidal (n = 2). Of 56 patients with retrievable data > 6 months postoperatively, cure was achieved in 55 of 56 patients (98%). One patient who presented to us with parathyromatosis require subsequent reoperation.

CONCLUSION

In this multi-institutional series of PHPT in children and adolescents, the majority were sporadic PHPT and were due to a single adenoma. We observed a high incidence of ectopic parathyroid adenomas, most commonly intrathymic. Given the high risk for ectopic adenoma in pediatric patients, parathyroid surgery in children and adolescents should be performed by experienced surgeons.

Pre-operative imaging workup for surgical intervention in primary hyperparathyroidism: A tertiary referral center experience

PURPOSE

Preoperative imaging in patients with primary hyperparathyroidism provides important localization information, allowing the surgeon to perform a focused surgery. However there are no evidence-based guidelines suggesting which preoperative imaging should be used, resulting in a risk of excessive prescription of exams and waste of economic resources. The main purpose of this study was to describe our experience on the performance of various imaging techniques for the preoperative localization of abnormal parathyroid gland/s, with a focus on the sensitivity and specificity of each technique. Secondly, we carried out an analysis of the cost utility of each technique in order to determine the most clinical and cost-effective combination of localization studies.

MATERIALS AND METHODS

Records of 336 patients who underwent parathyroidectomy were retrospectively examined comparing imaging and intraoperative/histopathologic findings to evaluate the accuracy in parathyroid detection of each imaging technique. Costs were determined by regional health system reimbursement.

RESULTS

We found that the sensitivity of color Doppler US was significantly higher than SPECT (p 0,023), while the sensitivity of 4D-CT was significantly better than US (p 0,029) and SPECT (p 0,0002).

CONCLUSIONS

In experienced hands color Doppler US is a highly sensitive technique especially in patients with no thyroid diseases. In patients with concomitant thyroid pathology, the combination of US and 4D-CT represents a reliable localization technique.

Performance of F-18 Fluorocholine PET/CT for Detection of Hyperfunctioning Parathyroid Tissue in Patients with Elevated Parathyroid Hormone Levels and Negative or Discrepant Results in conventional Imaging

Objective

Our aim was to assess the diagnostic performance of F-18 fluorocholine (FCH) positron emission tomography/computed tomography (PET/CT) in detecting hyperfunctioning parathyroid tissue (HPT) in patients with elevated parathyroid hormone levels with negative or inconclusive conventional imaging results and to compare the findings with those obtained using technetium-99m sestamibi (MIBI) scintigraphy and neck ultrasonography (US).

Materials and Methods

Images of 105 patients with hyperparathyroidism who underwent FCH PET/CT, dual-phase MIBI parathyroid scintigraphy (median interval: 42 days), and neck US were retrospectively analyzed. The gold standard was histopathological findings for 81 patients who underwent parathyroidectomy and clinical follow-up findings in the remaining 24 patients. Sensitivities, positive predictive values (PPVs), and accuracies were calculated for all imaging modalities.

Results

Among the 81 patients who underwent parathyroidectomy, either parathyroid adenoma (n = 64), hyperplasia (n = 9), neoplasia (n = 4), or both parathyroid adenoma and hyperplasia (n = 1) were detected, except 3 patients who did not show HPT. Of the 24 (23%) patients who were followed-up without operation, 22 (92%) showed persistent hyperparathyroidism. FCH PET/CT showed significantly higher sensitivity than MIBI scintigraphy and US in detection of HPT (p < 0.01). Sensitivity, PPV, and accuracy of FCH PET/CT were 94.1% (95/101), 97.9% (95/97), and 92.4% (97/105), respectively. The corresponding values for MIBI scintigraphy and US were 45.1% (46/102), 97.9% (46/47), and 45.7% (48/105) and 44.1% (45/102), 93.8% (45/48), and 42.9% (45/105), respectively. Among the 35 patients showing negative MIBI scintigraphy and neck US findings, 30 (86%) showed positive results on FCH PET/CT. FCH PET/CT could demonstrate ectopic locations of HPT in 11 patients whereas MIBI and US showed positive findings in only 6 and 3 patients, respectively.

Conclusion

FCH PET/CT is an effective imaging modality for detection of HPT with the highest sensitivity among the available imaging techniques. Therefore, FCH PET/CT can be recommended especially for patients who show negative or inconclusive results on conventional imaging.

Evaluation of an optimal cutoff of parathyroid venous sampling gradient for localizing primary hyperparathyroidism

INTRODUCTION

Parathyroid venous sampling (PVS) has been reported to be a useful adjunctive test in localizing lesions in elusive cases of primary hyperparathyroidism (PHPT). Conventional cutoff (twofold) is now widely being used, but optimal cutoff threshold for PVS gradient based on discriminatory performance remains unclear.

MATERIALS AND METHODS

Among a total of 197 consecutive patients (mean age 58.2 years, female 74.6%) with PHPT who underwent parathyroidectomy at a tertiary center between 2012 and 2018, we retrospectively analyzed 59 subjects who underwent PVS for persistent or recurrent disease after previous parathyroidectomy, or for equivocal or negative results from conventional imaging modalities including ultrasonography (US) and Tc^99m-Sestamibi SPECT-CT (MIBI). True parathyroid lesions were confirmed by combination of surgical, pathological findings, and intraoperative parathyroid hormone (PTH) changes. Optimal PVS cutoff were determined by receiver-operating characteristics (ROC) analysis with Youden and Liu method.

RESULTS

Compared to subjects who did not require PVS, PVS group tends to have lower PTH (119.8 pg/mL vs 133.7 pg/mL, p = 0.075). A total of 79 culprit parathyroid lesions (left 40; right 39) from 59 patients (left 24; right 26; bilateral 9) were confirmed by surgery. The optimal cutoff for PVS gradient was estimated as 1.5-fold gradient (1.5 ×) with sensitivity of 61.8% and specificity of 84%. When 1.5 × cutoff was applied, PVS improved the discrimination for true parathyroid lesions substantially based on area under ROC (0.892 to 0.942, p < 0.001) when added to US and MIBI.

CONCLUSION

Our findings suggest that PVS with cutoff threshold 1.5 × can provide useful complementary information for pre-operative localization in selected cases.

18F-choline PET/4D CT in hyperparathyroidism: correlation between biochemical data and study parameters

BACKGROUND

Hyperparathyroidism (HPT) is characterised by increased levels of parathyroid hormone (HPT), surgical excision being the only definitive curative option. After establishing the need for surgery, it is essential to identify the parathyroid glands in the preoperative period to use a minimally invasive approach. Negativity and / or discrepancy in first-line studies (ultrasound and Tc-99m MIBI parathyroid scintigraphy) require more accurate images to reduce the likelihood of bilateral cervical exploration or reintervention.

OBJECTIVES

a) To demonstrate the sensitivity of ¹⁸F-fluorocholine (¹⁸F-choline) positron emission tomography (PET)/4D computed tomography (4D CT) in HPT. b) To check whether there is a correlation between calcaemia and preoperative PTH versus size and early and late SUVmax (Standardized Uptake Value) of the gland, determined by ¹⁸F-choline PET/4D CT and c) to study the behaviour of parathyroid lesions with intravenous contrast (IV).

MATERIAL AND METHODS

A total of 28 patients were included between 2016 and 2019 in a single institution. Prospective observational cohort study. Correlations were analysed using Pearson's coefficient for variables with normal distribution and Spearman (rho) for those with non-normal distribution. Anatomopathological analysis was the benchmark standard to determine sensitivity was. A p<.05 was interpreted as significant. STATA 13 software was used.

RESULTS

Of the 28 patients who underwent ¹⁸F-choline PET/4D CT, 18 were operated. Of the 26 lesions diagnosed by ¹⁸F-choline PET/4D CT as suggestive of parathyroid lesions, 23 corresponded to glandular disease (adenoma or hyperplasia) establishing a sensitivity of 88.5%. There was a correlation between the patient's preoperative PTH and the maximum size of the gland on ¹⁸F-choline PET/4D CT. (Spearman=.66; p=.0014). The parathyroid lesions showed, in addition to IV contrast enhancement, distinctive behavioural characteristics identified as highly suggestive.

CONCLUSIONS

18F-choline PET/CT 4D is an anatomical and functional study with high sensitivity in patients with HPT with negative or discrepant first-line studies. Preoperative PTH showed a correlation with maximum gland size on ¹⁸F-choline PET/CT 4D. Parathyroid lesions behave in a highly suggestive way and are enhanced by IV contrast.

Pediatric parathyroid disease

Parathyroid glands are critical for calcium and phosphate homeostasis. Parathyroid disease is relatively rare in the pediatric population, but there are some important pediatric-specific considerations and conditions. This article reviews parathyroid physiology, disorders of hyper- and hypo- function, operative management, and uniquely pediatric diagnoses such as neonatal severe hyperparathyroidism. Advances in preoperative imaging, intra-operative gland identification, and management of post-thyroidectomy hypocalcemia are also presented in detail. This article combines a review of fundamentals with recent advances in care, emphasizing pediatric-specific publications.

4D-Dynamic Contrast-Enhanced MRI for Preoperative Localization in Patients with Primary Hyperparathyroidism

BACKGROUND AND PURPOSE

Our aim was to test the hypothesis that our recently introduced 4D-dynamic contrast-enhanced MR imaging with high spatial and temporal resolution has equivalent accuracy to 4D-CT for preoperative gland localization in primary hyperparathyroidism without requiring exposure to ionizing radiation.

MATERIALS AND METHODS

Inclusion criteria were the following: 1) confirmed biochemical diagnosis of primary hyperparathyroidism, 2) preoperative 4D-dynamic contrast-enhanced MR imaging, and 3) surgical cure with >50% decrease in serum parathyroid hormone intraoperatively. 4D-dynamic contrast-enhanced studies were reviewed independently by 2 neuroradiologists to identify the side, quadrant, and number of abnormal glands, and compared with surgical and pathologic results.

RESULTS

Fifty-four patients met the inclusion criteria: 37 had single-gland disease, and 17, multigland disease (9 with double-gland hyperplasia; 3 with 3-gland hyperplasia; and 5 with 4-gland hyperplasia). Interobserver agreement (κ) for the side (right versus left) was 0.92 for single-gland disease and 0.70 for multigland disease. Interobserver agreement for the quadrant (superior versus inferior) was 0.70 for single-gland disease and 0.69 for multigland disease. For single-gland disease, the gland was correctly located in 34/37 (92%) patients, with correct identification of the side in 37/37 (100%) and the quadrant in 34/37 (92%) patients. For multigland disease, the glands were correctly located in 35/47 (74%) patients, with correct identification of the side in 35/47 (74%) and the quadrant in 36/47 (77%).

CONCLUSIONS

The proposed high spatial and temporal resolution 4D-dynamic contrast-enhanced MR imaging provides excellent diagnostic performance for preoperative localization in primary hyperparathyroidism, with correct gland localization of 92% for single-gland disease and 74% in multigland disease, superior to 4D-CT studies.

Surgery versus Imaging in Non-Localizing Primary Hyperparathyroidism: A Cost-Effectiveness Model

OBJECTIVE

To determine whether advanced imaging is cost-effective compared to primary bilateral neck exploration in the management of non-localizing primary hyperparathyroidism.

STUDY DESIGN

Cost-effectiveness analysis.

METHODS

Cost-effectiveness analysis based on decision tree model and available Medicare financial data using data from 347 consecutive patients having parathyroidectomy for primary hyperparathyroidism with either 1) positive, concordant ultrasound and sestamibi or 2) negative sestamibi and negative ultrasound.

RESULTS

Bilateral neck exploration (BNE) costs $9578 and has a success rate of 97.3%. Single photon emission computed tomography (SPECT) + minimally invasive parathyroidectomy (MIP) was modeled to have a total cost of $8197 with a success rate of 98.6%. SPECT/computed tomography (CT) + MIP was modeled to have a total cost of $8271 and a 98.9% success rate. Four-dimensional (4D)-CT + MIP was modeled to cost $8146 with a success rate of 99%. Incremental cost-effectiveness ratios (IECR) (as compared to BNE) were -536.1, -605.5, and -701.6 ($/percent cure rate) for SPECT, SPECT/CT, and 4D-CT respectively. One-way sensitivity analyses demonstrate the change in IECR and cut-off points (IECR = 0) for four major variables.

CONCLUSIONS

In patients with non-localizing primary hyperparathyroidism, advanced imaging is associated with cost-savings compared to routine bilateral neck exploration. Increased cost-savings were predicted with increased imaging accuracy and decreased imaging costs. Increasing time for BNE or decreasing time for MIP were associated with increased cost savings.

LEVEL OF EVIDENCE

III Laryngoscope, 2020.