Preoperative contrast-enhanced MRI of the parathyroid glands in hyperparathyroidism

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.

The added value of non-contrast 3-Tesla MRI for the pre-operative localization of hyperparathyroidism

OBJECTIVE

We investigated the efficacy of non-contrast 3-Tesla MR imaging added to the combination of sestamibi with^99mTc (MIBI) scintigraphy and Ultrasonography (US) for the pre-operative localization of Primary Hyperparathyroidism (PHPT) lesions.

METHODS

A total of 34 parathyroid glands, including nine normal glands, were examined with MIBI, US, and non-contrast 3-Tesla MRI. MRI was performed with the acquisition of T1- and T2-weighted images and fat-suppressed T2-weighted images. We calculated the sensitivities of MIBI, US, and the 'additional' MRI, with knowledge of the former two modalities' results.

RESULTS

For the diagnosis of PHPT lesions, the sensitivity values of MIBI, US, and additional MRI were 88.0% (22/25), 84.0% (21/25), and 92.0% (23/25), respectively. Normal glands were not visualized with any modality (0/9). One lesion was detected neither with US nor MRI, but only with MIBI, with the limitation that MIBI represented no more than laterality. The two glands not identified in MRI were 4 mm and 6 mm in their size, which are within the range of normal gland's size. Two lesions were not detected with US or MIBI but were visualized with the additional MRI, which indicated that the MRI contributed an 8.0% (2/25) improvement of sensitivity, compared from that of US. Fat-suppressed T2-weighted images were useful in the identification of parathyroid lesions, as these images helped to differentiate between the lesion and the adjacent tissue.

CONCLUSION

Additional non-contrast 3-Tesla MRI was a useful adjunctive tool for localization of PHPT, which improved the sensitivity of the pre-operative localization of PHPT lesions. Fat-suppressed T2-weighted images contributed to their identification.

LEVEL VI

Evidence from a single descriptive or qualitative study.

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.

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.

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.

Pediatric hyperparathyroidism: review and imaging update

Hyperparathyroidism, due to increased secretion of parathyroid hormones, may be primary, secondary or tertiary. Most pediatric patients with sporadic primary hyperparathyroidism will be symptomatic, presenting with either end-organ damage or nonspecific symptoms. In younger patients with primary hyperparathyroidism, there is a higher prevalence of familial hyperparathyroidism including germline inactivating mutations of the calcium-sensing receptor genes that result in either neonatal severe hyperparathyroidism or familial hypocalciuric hypercalcemia. Parathyroid scintigraphy and ultrasound are complementary, first-line imaging modalities for localizing hyperfunctioning parathyroid glands. Second-line imaging modalities are multiphase computed tomography (CT) and magnetic resonance imaging. In pediatrics, multiphase CT protocols should be adjusted to optimize radiation dose. Although, the role of these imaging modalities is better established in preoperative localization of hyperfunctioning parathyroid glands in primary hyperparathyroidism, the same principles apply in secondary and tertiary hyperparathyroidism. In this manuscript, we will review the embryology, anatomy, pathophysiology and preoperative localization of parathyroid glands as well as several subtypes of primary familial hyperparathyroidism. While most of the recent imaging literature centers on adults, we will focus on the issues that are pertinent and applicable to pediatrics.

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.

Comparison of 4DMRI and 4DCT for the preoperative evaluation of patients with primary hyperparathyroidism

BACKGROUND

Minimally invasive parathyroid surgery is the standard of care in patients with Primary Hyperparathyroidism (PHPT) which requires accurate preoperative localization. Of all the available imaging modalities, 4DCT is considered the best modality for localization, however it entails the risk of ionizing radiation. To circumvent this 4DMRI was evaluated for parathyroid lesion localization.

PURPOSE

To evaluate and compare the accuracy of 4DCT and 4DMRI in the localization of parathyroid Lesions.

MATERIALS AND METHODS

In this ethically approved observational diagnostic study, 135 patients (age range: 10-75 years, male: female ratio - 1:2.1) with clinically and biochemically suspected PHPT were recruited. Of these, 56 patients underwent both 4DCT and 4DMRI. Six patients with positive imaging who didn't undergo surgery were excluded. A total of 50 patients with 61 proven parathyroid lesions were included for analysis. 48 patients had surgical and histopathological findings for the confirmation of imaging findings.

RESULTS

Both 4DCT and 4DMRI correctly detected 59/61 lesions in 48 patients. There was one false positive and two true negatives. In addition, 2 (3.22 %) lesions which were not detected by 4DCT and 4DMRI were found on surgery. The sensitivity of both 4DCT and 4DMRI was 96.7 %; specificity was 66.6 % and accuracy was 95.2 %.

CONCLUSION

4DMRI and 4DCT had similar accuracy for the detection of parathyroid lesions. However, 4DMRI has the advantage of lack of exposure to ionizing radiation, which can be beneficial in younger patients.

Imaging and choosing the right patients for transoral endoscopic parathyroidectomy vestibular approach

Advances in imaging for preoperative localization have propelled the widespread adoption of minimally invasive/focused parathyroidectomy in primary hyperparathyroidism. Though it is performed through a relatively small incision, studies have shown that the presence of a neck scar increases attentional bias towards the neck resulting in compromised quality of life. Transoral endoscopic parathyroidectomy vestibular approach (TOEPVA) eliminates a neck scar. While indications for TOEPVA are the same as that of minimally invasive open parathyroidectomy, confident preoperative localization of the parathyroid with a surgeon performed ultrasound along with concordant localization with SPECT CT is an essential prerequisite before offering patients this approach for parathyroidectomy. Early data has demonstrated the feasibility and safety of this approach.

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.

Surgical implications of recent modalities for parathyroid imaging

Clinical or subclinical primary hyperparathyroidism (PHPT) is one of the most common endocrine disorders in the world. Parathyroidectomy is the treatment of choice in symptomatic patients, stabilizing the progression of complications caused by the destruction activity of parathyroid hormone (PTH). Parathyroid surgical techniques have evolved over the years from bilateral neck exploration, to minimally invasive single parathyroid gland exploration, to minimally invasive video-assisted parathyroidectomy. Localization of the abnormal parathyroid gland before surgery is crucial for the operation to be effective. Increased incidences of reoperations of the parathyroid glands and the rapid development of minimally invasive methods led to the development of new localization techniques. The noninvasive studies include ultrasound (US), computed tomography (CT), magnetic resonance (MR) and ^99mTc-methoxyisobutylisonitrile (MIBI) scintigraphy combined with single-photon emission CT (SPECT/CT). Among the latest technologies, the four-dimensional (4D)-CT scan, positron emission tomography (PET)/CT and PET/MR are very promising, and are going to have surgical implications in the future.

American Head and Neck Society Endocrine Surgery Section update on parathyroid imaging for surgical candidates with primary hyperparathyroidism

Health care consumer organizations and insurance companies increasingly are scrutinizing value when considering reimbursement policies for medical interventions. Recently, members of several American Academy of Otolaryngology-Head & Neck Surgery (AAO-HNS) committees worked closely with one insurance company to refine reimbursement policies for preoperative localization imaging in patients undergoing surgery for primary hyperparathyroidism. This endeavor led to an AAO-HNS parathyroid imaging consensus statement (https://www.entnet.org/content/parathyroid-imaging). The American Head and Neck Society Endocrine Surgery Section gathered an expert panel of authors to delineate imaging options for preoperative evaluation of surgical candidates with primary hyperparathyroidism. We review herein the current literature for preoperative parathyroid localization imaging, with discussion of efficacy, cost, and overall value. We recommend that planar sestamibi imaging, single photon emission computed tomography (SPECT), SPECT/CT, CT neck/mediastinum with contrast, MRI, and four dimensional CT (4D-CT) may be used in conjunction with high-resolution neck ultrasound to preoperatively localize pathologic parathyroid glands. PubMed literature on parathyroid imaging was reviewed through February 1, 2019.

The diagnostic value of 4D MRI at 3T for the localization of parathyroid adenomas

PURPOSE

The aim of this study was to assess the feasibility of four-dimensional magnetic resonance imaging (4D MRI) at 3 T for the localization of parathyroid adenomas.

MATERIALS AND METHODS

Preoperative 4D MRI scans, encompassing dynamic contrast-enhanced (DCE) sequences and non-contrast enhanced (non-CE) sequences, including a T2-weighted multipoint Dixon (T2-mDixon) sequence, with in-phase, out-phase, and water-only images, were evaluated retrospectively in 41 patients with surgically proven parathyroid lesions. Two readers who were blinded to the surgical findings independently reviewed the images in two sessions (non-CE sequences alone and non-CE + DCE sequences). The MRI localization of the suspected adenoma in each session and the consensus interpretation of the MRI images, were compared with the surgical results and interobserver agreement was assessed.

RESULTS

By interpreting the non-CE sequences alone, reader 1 correctly localized 34 parathyroid lesions (sensitivity 81.0%, positive predictive value (PPV) 87.2%), and reader 2 correctly localized 34 parathyroid lesions (sensitivity 81.0%, PPV 91.9%). With the addition of DCE sequences, reader 1 correctly identified 35 parathyroid lesions (sensitivity 83.3%, PPV 87.5%), while reader 2 correctly identified 36 parathyroid lesions (sensitivity 85.7%, PPV 92.3%). Overall, MRI detected 38 parathyroid lesions (sensitivity 90.5%, PPV 95.0%). Interobserver agreement was slightly superior in non-CE + DCE sequences compared to non-CE sequences alone (ĸ = 0.796 vs. ĸ = 0.738).

CONCLUSION

4D MRI with DCE sequencing is a reliable method for the localization of parathyroid adenomas.

Feasibility of Hyperfunctioning Parathyroid Gland Localization Using [18F]fluciclovine PET/CT

PURPOSE

To evaluate the ability of anti-1-amino-3-anti-1-amino-3-[¹⁸F]fluorocyclobutane-1-carboxylic acid ([¹⁸F]fluciclovine) positron emission tomography/X-ray computed tomography (PET/CT) in comparison to Technetium-99m 2-methoxy isobutyl isonitrile ([^99mTc]sestamibi) single-photon emission computed tomography/CT (SPECT/CT) for the localization of hyperfunctioning parathyroid glands in patients with hyperparathyroidism.

PROCEDURES

Four patients with hyperparathyroidism underwent 60-minutes sequential neck and thorax PET/CT after [¹⁸F]fluciclovine (352 ± 28 MBq) injection. Lesion uptake and target-to-background ratios (TBR) were compared with [^99mTc]sestamibi (798 ± 27 MBq) SPECT/CT in the same patient.

RESULTS

Both techniques detected 4/5 hyperfunctioning parathyroid glands identified at surgery. The highest [¹⁸F]fluciclovine uptake and TBRs were at 5-9 min with rapid washout. [^99mTc]sestamibi had significantly higher TBRs compared with [¹⁸F]fluciclovine (5-9 min) for blood pool (10.9 ± 4.7 vs 1.3 ± 0.6; p < 0.01) and reference muscle backgrounds (5.8 ± 3.0 vs 1.7 ± 0.6; p < 0.01), with non-significant trend for thyroid tissue background (1.3 ± 0.5 vs 1.1 ± 0.5; p = 0.73).

CONCLUSION

Hyperfunctioning parathyroid glands can be detected on [¹⁸F]fluciclovine PET/CT at early imaging, but conspicuity (TBR) is better with [^99mTc]sestamibi. [¹⁸F]fluciclovine PET/CT does not seem promising in the detection of hyperfunctioning parathyroid glands.

Update in Parathyroid Imaging

Primary hyperparathyroidism (PHPT) is characterized by excessive, dysregulated production of parathyroid hormone (PTH) by 1 or more abnormal parathyroid glands. Minimally invasive surgical techniques have created a need for more precise localization of the parathyroid lesion by imaging. A variety of imaging protocols and techniques have been used for this purpose, but no one modality is clearly superior. Nuclear medicine scintigraphy and ultrasound imaging are established modalities, although multiphase or 4-dimensional computed tomography is an emerging modality with several advantages. This review provides a background regarding PHPT and key anatomy, and discusses these alternative parathyroid imaging modalities with updates.

18F Fluorocholine PET/MR Imaging in Patients with Primary Hyperparathyroidism and Inconclusive Conventional Imaging: A Prospective Pilot Study

Purpose To investigate the performance of flourine 18 (¹⁸F) fluorocholine (FCH) positron emission tomography (PET)/magnetic resonance (MR) imaging in patients with hyperparathyroidism and nonlocalized disease who have negative or inconclusive results at ultrasonography (US) and technetium 99m (^99mTc) sestamibi scintigraphy. Materials and Methods This study was approved by the institutional review board. Between May and December 2015, 10 patients (mean age, 70.4 years; range, 58-82 years) with biochemical primary hyperparathyroidism and inconclusive results at US and ^99mTc sestamibi scintigraphy were prospectively enrolled. All patients gave informed consent. Directly after administration of 3 MBq/kg of FCH, PET imaging was performed, followed by T1- and T2-weighted MR imaging before and after gadolinium enhancement. Intraoperative localization and histologic results were the reference standard for calculating sensitivity and positive predictive value. The Wilcoxon rank test was used to calculate the mean difference in maximum standardized uptake value (SUV_max) between abnormal parathyroid uptake and physiologic thyroid uptake. The Wilcoxon rank-sum test was performed. Results MR imaging alone showed true-positive lesions in five patients and a false-positive lesion in one patient. FCH PET/MR imaging allowed correct localization of nine of 10 adenomas (90% sensitivity), without any false-positive results (100% positive predictive value). One patient had four-gland hyperplasia, of which three hyperplastic glands were not localized. The median SUV_max of the nine preoperatively identified adenomas was 4.9 (interquartile range, 2.45-7.35), which was significantly higher than the SUV, 2.7 (interquartile range, 1.6-3.8), of the thyroid (P = .008). Conclusion FCH PET/MR imaging allowed localization of adenomas with high accuracy when conventional imaging results were inconclusive and provided detailed anatomic information. More patients must be examined to confirm our initial results, and the accuracy of FCH PET/MR imaging for localization of glands in patients with four-gland hyperplasia remains to be investigated. ^© RSNA, 2017.

Performance of magnetic resonance imaging in the evaluation of first-time and reoperative primary hyperparathyroidism

BACKGROUND

Preoperative imaging in patients with primary hyperparathyroidism and a previous parathyroid operation is essential; however, performance of conventional imaging is poor in this subgroup. Magnetic resonance imaging appears to be a good alternative, though overall evidence remains scarce. We retrospectively investigated the performance of magnetic resonance imaging in patients with and without a previous parathyroid operation, with a separate comparison for dynamic gadolinium-enhanced magnetic resonance imaging.

METHODS

All patients undergoing magnetic resonance imaging prior to parathyroidectomy for primary hyperparathyroidism (first time or recurrent) between January 2000 and August 2015 at a high-volume, tertiary care, referral center for endocrine operations were included. We compared the sensitivity and positive predictive value of magnetic resonance imaging with conventional ultrasound and sestamibi on a per-lesion level.

RESULTS

A total of 3,450 patients underwent parathyroidectomy, of which 84 patients with recurrent (n = 10) or persistent (n = 74) disease and 41 patients with a primary operation were included. Magnetic resonance imaging had a sensitivity and positive predictive value of 79.9% and 84.7%, respectively, and performance was good in both patients with and without a previous parathyroid operation. Adding magnetic resonance imaging to the combination of ultrasound and sestamibi resulted in a significant increase in sensitivity from 75.2% to 91.5%. Dynamic magnetic resonance imaging produced excellent results in the reoperative group, with sensitivity and a positive predictive value of 90.1%.

CONCLUSION

Technologic advances have enabled faster and more accurate magnetic resonance imaging protocols, making magnetic resonance imaging an excellent alternative modality without associated ionizing radiation. Our study shows that the sensitivity of multimodality imaging for parathyroid adenomas improved significantly with the use of conventional and dynamic magnetic resonance imaging, even in the case of recurrent or persistent disease.

Imaging of the parathyroid glands in primary hyperparathyroidism

Primary hyperparathyroidism (PHPT) is one of the most frequent endocrine diseases worldwide. Surgery is the only potentially curable option for patients with this disorder, even though in asymptomatic patients 50 years of age or older without end organ complications, a conservative treatment may be a possible alternative. Bilateral neck exploration under general anaesthesia has been the standard for the definitive treatment. However, significant improvements in preoperative imaging, together with the implementation of rapid parathyroid hormone determination, have determined an increased implementation of focused, minimally invasive surgical approach. Surgeons prefer to have a localization study before an operation (both in the classical scenario and in the minimally invasive procedure). They are not satisfied by having been referred a patient with just a biochemical diagnosis of PHPT. Imaging studies must not be utilized to make the diagnosis of PHPT. They should be obtained to both assist in determining disease etiology and to guide operative procedures together with the nuclear medicine doctor and, most importantly, with the surgeon. On the contrary, apart from minimally invasive procedures in which localization procedures are an obligate choice, some surgeons believe that literature on parathyroidectomy over the past two decades reveals a bias towards localization. Therefore, surgical expertise is more important than the search for abnormal parathyroid glands.

MR appearance of parathyroid adenomas at 3 T in patients with primary hyperparathyroidism: what radiologists need to know for pre-operative localization

OBJECTIVES

To identify frequent MRI features of parathyroid adenomas (PTAs) in patients with primary hyperparathyroidism (PHPT) using a fast protocol with a 3 T magnet.

METHODS

Thirty-eight patients with PHPT underwent a 3 T-MR. All patients had positive US and Tc-99 sestamibi, for a total number of 46 PTAs. T2-weighted IDEAL-FSE and T1 IDEAL-sequences, before and after contrast, were performed. Five features of PTAs were recognised: hyperintensity, homogeneous or "marbled" appearance and elongated morphology on T2-sequences; cleavage plane from thyroid gland on T2-outphase; rapid enhancement in post-contrast T1. Image quality for T2-weighted IDEAL FSE and usefulness for IDEAL post-contrast T1-weighted and T2-outphase sequences were also graded.

RESULTS

PTAs were hyperintense in T2-sequences in 44/46 (95.7%), "marbled" in 30/46 (65.2%) and elongated in 38/46 (82.6%) patients. Cleavage plane was observed in 36/46 (78.3%), and rapid enhancement in 20/46 (43.5%) patients. T2-sequences showed both excellent fat suppression and image quality (average scores of 3.2 and 3.1). T2-outphase images demonstrated to be quite useful (score 2.8), whereas, post-contrast T1 images showed a lower degree of utility (score 2.4).

CONCLUSIONS

A fast protocol with 3.0-T MRI, recognising most common features of PTAs, may be used as a second-line method in the preoperative detection of PTAs.

KEY POINTS

3 T MRI protocol based on T2-weighted IDEAL FSE sequences was used. T2-hyperintensity and elongated morphology are common features of PTAs. 3 T MRI could be used in the preoperative detection of PTAs.

Radioguided Parathyroidectomy with Portable Mini Gamma-Camera for the Treatment of Primary Hyperparathyroidism

Background. A proper localisation of pathological parathyroid glands is essential for a minimally invasive approach in the surgical treatment of primary hyperparathyroidism (PHP). The recent introduction of portable mini gamma-cameras (pMGCs) enabled intraoperative scintigraphic scanning. The aim of our study is to evaluate the efficacy of this new method and compare it with the preoperative localisation surveys. Methods. 20 patients were studied; they were evaluated preoperatively by neck ultrasound and (99mm)Tc-sestaMIBI-scintigraphy and intraoperatively with the pMGC IP Guardian 2. The results obtained from the three evaluations were compared. Results. The pMGC presented a sensitivity of 95%, a specificity of 98.89%, and a diagnostic accuracy of 98.18%, which were higher than those of preoperative ultrasound (sensitivity 55%; specificity 95%; diagnostic accuracy 87%) and scintigraphy with (99mm)Tc-sestaMIBI (sensitivity 73.68%; specificity 96.05%; diagnostic accuracy 91.58%). Conclusions. The pMGC can be used effectively as an intraoperative method to find the correct location of the pathological parathyroid glands. The pMGC is more reliable than the currently used preoperative and intraoperative localisation techniques.

Clinical review: Parathyroid localization and implications for clinical management

CLINICAL CONTEXT

The prevalence of hyperparathyroidism, especially primary hyperparathyroidism, has increased in recent decades due to improvements in diagnostic techniques with a corresponding surge in parathyroid surgery, leading to the development of focused, minimally invasive surgical approaches. Focused parathyroidectomy is predicated on preoperative localization of suspected parathyroid pathology. As a result, there has been a proliferation of parathyroid imaging modalities and protocols, resulting in confusion about their indications and applications.

EVIDENCE ACQUISITION

Bibliographies from clinical trials and review articles published since 2000 were reviewed and supplemented with targeted searches using biomedical databases. We also employed our extensive clinical experience.

EVIDENCE SYNTHESIS

The best-studied modalities for parathyroid localization are nuclear scintigraphy and sonography and are widely applied as initial studies. Multiple variations exist, and several additional noninvasive imaging techniques, such as computed tomography and magnetic resonance, are described. The exquisite anatomical detail of 4-dimensional computed tomography must be balanced with significant radiation exposure to the thyroid gland. Invasive venous PTH sampling and parathyroid arteriography have important roles in remedial cases. Due to considerable heterogeneity in imaging, multidisciplinary collaboration between endocrinologists, surgeons, and radiologists is beneficial.

CONCLUSIONS

Parathyroid localization is indicated in surgical candidates. Crucial considerations when selecting an imaging study include availability, cost, radiation exposure, local expertise, and accuracy. Additional factors include the patient's anticipated pathology and whether it is de novo or refractory disease. An approach to imaging for patients with primary hyperparathyroidism is presented.

Primary hyperparathyroidism: imaging to pathology

The aim of this review is to describe the multimodal imaging (ultrasound, magnetic resonance, computed tomography, and nuclear medicine) of primary hyperparathyroidism and its correlation to the pathological findings. In the last decades, imaging science has progressed a great deal. Accurate preoperative localization of the involved glands is essential for surgical success.

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

PURPOSE

We aimed to compare the efficacy of three different parathyroid adenoma screening tools--high-resolution ultrasonography (USG), technetium Tc 99m-methoxyisobutylisonitrile (MIBI) parathyroid scintigraphy, and magnetic resonance imaging (MRI)--and we evaluated the factors affecting the detection success rates.

METHODS

Parathyroid imaging was evaluated by USG, double-phase 99mTc-MIBI parathyroid scintigraphy, and cervical MRI in patients with hyperparathyroidism (n=39).

RESULTS

Among the 39 patients, USG, parathyroid scintigraphy, and MRI correctly identified 35 adenomas (89.7%), 28 adenomas (71.8%), and 26 adenomas (66.7%), respectively. Positive predictive values for USG (34/35), scintigraphy (27/28), and cervical MR (26/26) imaging were 97.1%, 96%, and 100%, respectively. Parathyroid adenomas were detected with 92.3% (36/39) certainty when both USG and scintigraphy modalities were applied together. Minimally invasive parathyroidectomy under local anesthesia with unilateral incision was successfully performed in 24 (61.5%) patients.

CONCLUSIONS

Minimally invasive surgery for parathyroid adenomas has been developed and has equal success with traditional surgery. However, accurate localization of adenomas should be obtained prior to surgery. In this study, ultrasound was found to be effective in localizing adenomas for successful surgery. Adding other imaging modalities does not improve localizing the parathyroid adenomas.

Bilateral retropharyngeal parathyroid hyperplasia detected with 4D multidetector row CT

We present a case of bilateral retropharyngeal parathyroid hyperplasia detected with 4D-CT in a patient with persistent primary hyperparathyroidism and failed neck exploration. We discuss the embryologic basis of ectopic retropharyngeal parathyroid adenomas and hyperplasia and the utility of 4D-CT in their localization for surgical planning.

Parathyroid imaging: technique and role in the preoperative evaluation of primary hyperparathyroidism

OBJECTIVE

This article discusses the commonly used techniques for imaging the parathyroid glands and their role in the preoperative evaluation of patients with primary hyperparathyroidism.

CONCLUSION

The importance of sonography and sestamibi scintigraphy in the preoperative evaluation of patients with primary hyperthyroidism has increased with the adoption of minimally invasive parathyroidectomy techniques at most medical centers. When the results of these studies are concordant, the cure rates of minimally invasive surgery equal those of traditional bilateral neck exploration.

Parathyroid sonography: imaging and intervention

This article reviews the role of high-resolution sonography as an imaging modality for the diagnosis and treatment of patients with parathyroid disease. Included is a discussion of sonographic anatomy and technique, disease processes of the parathyroid glands and their sonographic appearances, preoperative imaging, and the use of sonography as a guide for diagnostic and therapeutic intervention in parathyroid disease.

A review of contrast media research in 1999-2000

Contrast media research published during the years 1999 and 2000 is reviewed in this article, in terms of relevance to developments within the field of diagnostic radiology. The primary focus is on publications from the journal Investigative Radiology, which publishes much of the clinical and laboratory research performed in this field. The journals Radiology and the American Journal of Roentgenology are dominant in the field of diagnostic radiology and together publish more than 10 times the number of articles as appear each year in Investigative Radiology. However, in 1999 for example, these two journals together published fewer articles than did Investigative Radiology alone that concerned basic (animal) research with contrast media. Thirty-six percent of the articles in Investigative Radiology in 1999 had a primary focus on contrast media and 18% on basic (animal) research with contrast media. To make this review more complete, articles from other major journals are cited and discussed, as needed, to provide supplemental information in the few areas not well covered by articles in Investigative Radiology. The safety of contrast media is always an important topic and research continues to be performed in this area, both to explore fundamental issues regarding iodinated contrast media and also to establish the overall safety profile of new magnetic resonance (MR) and ultrasound agents. In regard to preclinical investigations, most of the work performed in the last 2 years has been with MR and ultrasound. In MR, research efforts continue to be focused on the development of targeted agents. In ultrasound, research efforts are split between studies looking at new imaging methods and early studies of targeted agents. In regard to the clinical application of contrast media, the published literature continues to be dominated by MR. Investigations include the study of disease in clinical trials and in animal models. A large number of studies continue to be published in regard to new techniques and applications within the field of contrast-enhanced magnetic resonance angiography. This field represents the single, largest new clinical application of contrast media in MR to emerge in the last decade. New clinical research continues to be published regarding the use of contrast media in computed tomography (CT), ultrasound, and x-ray angiography. The introduction of spiral CT (together with the multidetector scanners) has led to greater utilization of this modality, as well as intravenous iodinated contrast media. The number of publications regarding clinical applications of intravenously injected ultrasound contrast agents remains low, with the high expectations in regard to growth (in terms of number of exams using contrast) of the last decade yet to be fulfilled.