Parathyroid Imaging

Trends in using intraoperative parathyroid hormone monitoring during parathyroidectomy: Protocol and rationale for a cross-sectional survey study of North American surgeons

Hyperparathyroidism is a common endocrine disorder that occurs secondary to abnormal parathyroid gland functioning. Depending on the type of hyperparathyroidism, surgical extirpation of hyperfunctioning parathyroid glands can be considered for disease cure. Intraoperative parathyroid hormone (IOPTH) monitoring improves outcomes in patients undergoing surgery for primary hyperparathyroidism, but studies are needed to characterize its institutional adoption and its role in surgery for secondary and tertiary hyperparathyroidism, as these entities can be difficult to cure. Hence, we will perform a cross-sectional survey study of surgeon rationale, operational details, and barriers associated with IOPTH monitoring adoption across North America. We will utilize a convenience sampling technique to distribute an online survey to head and neck surgeons and endocrine surgeons across North America. This survey will be distributed via email to three North American professional societies (i.e., Canadian Society for Otolaryngologists-Head and Neck Surgeons, American Head and Neck Society, and American Association of Endocrine Surgeons). The survey will consist of 30 multiple choice questions that are divided into three concepts: (1) participant demographics and training details, (2) details of surgical adjuncts during parathyroidectomy, and (3) barriers to adoption of IOPTH. Descriptive analyses and multiple logistic regression will be used to evaluate the impact of demographic, institutional, and training variables on the use of IOPTH monitoring in surgery for all types of hyperparathyroidism and barriers to IOPTH monitoring adoption. Ethics approval was obtained by the Hamilton Integrated Research Ethics Board (2024-17173-GRA). These findings will characterize surgeon and institutional practices with regards to IOPTH monitoring during parathyroid surgery and will inform future trials aimed to optimize the use of IOPTH monitoring in secondary and tertiary hyperparathyroidism.

Normocalcemic primary hyperparathyroidism: From pathophysiology to clinical management

Normocalcemic primary hyperparathyroidism (NPHPT), a variant of primary hyperparathyroidism (PHPT) characterized by persistently elevated parathyroid hormone (PTH) levels and normal serum calcium, has gained recognition as a substantial subset of PHPT cases. Despite its increasing prevalence, the precise pathophysiology and natural progression of NPHPT remain enigmatic. This in-depth literature review explores recent advancements in our understanding of NPHPT, encompassing pathophysiology, clinical presentation, diagnostic approaches, medical and surgical management options. By synthesizing this wealth of information, this review aims to contribute to a more nuanced and informed approach to the treatment of patients grappling with NPHPT. As our understanding of the condition continues to evolve, the knowledge gathered from this review has the potential to significantly enhance the quality of care and outcomes for individuals afflicted with NPHPT, ultimately improving their overall well-being and prognosis.

Ectopic parathyroid adenoma on sternocleidomastoid muscle: a case report

A 54-year-old woman was admitted to the hospital with a left neck mass. Enhanced CT and ultrasound examinations revealed a lesion in the left sternocleidomastoid muscle. The patient undergone right thyroid lobe resection 8 years ago. Interestingly, the lesion on the sternocleidomastoid muscle, along with the left lobe of the patient's thyroid, visually appears to form a displaced and complete thyroid in the early Tc-99m-MIBI parathyroid scintigraphy. Combined with Tc-99m-MIBI scintigraphy and abnormal PTH and blood calcium levels, the consideration was given to the lesion in the sternocleidomastoid muscle as an ectopic parathyroid adenoma. Subsequent surgical pathology confirmed this suspicion.

Preoperative localization of water clear cell giant parathyroid adenoma: A case report

Primary hyperparathyroidism commonly results from a solitary parathyroid adenoma. A water clear cell parathyroid adenoma represents a rare histological variant. This report presents the challenges of preoperative detection of a giant parathyroid adenoma, which was of the water clear cell variant. A case of severe hypercalcemia in a patient without clinical symptoms and equivocal findings on standard imaging modalities, in which the use of [11C]C-Methionine PET/CT facilitated the preoperative detection of a giant parathyroid adenoma. Histopathological examination confirmed the diagnosis of a water clear cell giant parathyroid adenoma following surgical excision. These findings highlight the significance of advanced imaging techniques in the detection and management of a rare form of parathyroid adenoma.

The Parathyroid Gland: An Overall Review of the Hidden Organ for Radiologists

Parathyroid glands are small endocrine glands that regulate calcium metabolism by producing parathyroid hormone (PTH). These are located at the back of the thyroid gland. Typically, four glands comprise the parathyroid glands, although their numbers may vary among individuals. Parathyroid diseases are related to parathyroid gland dysfunction and can be caused by problems with the parathyroid gland itself or abnormal serum calcium levels arising from renal disease. In recent years, as comprehensive health checkups have become more common, abnormal serum calcium levels are often found incidentally in blood tests, after which several additional tests, including a PTH test, ultrasonography (US), technetium-99m sestamibi parathyroid scan, single-photon-emission CT (SPECT)/CT, four-dimensional CT (4D-CT), and PET/CT, are performed for further evaluation. However, the parathyroid gland remains an organ less familiar to radiologists. Therefore, the normal anatomy, pathophysiology, imaging, and clinical findings of the parathyroid gland and its associated diseases are discussed here.

Comparing accuracy of machine learning approaches to identifying parathyroid adenomas: Lessons and new directions

PURPOSE

The purpose of this investigation is to understand the accuracy of machine learning techniques to detect biopsy-proven adenomas from similar appearing lymph nodes and factors that influence accuracy by comparing support vector machine (SVM) and bidirectional Long short-term memory (Bi-LSTM) analyses. This will provide greater insight into how these tools could integrate multidimensional data and aid the detection of parathyroid adenomas consistently and accurately.

METHODS

Ninety-nine patients were identified; 93 4D-CTs of patients with pathology-proven parathyroid adenomas were reviewed; 94 parathyroid adenomas and 112 lymph nodes were analyzed. A 2D slice through the lesions in each phase was used to perform sequence classification with ResNet50 as the pre-trained network to construct the Bi-LSTM model, and the mean enhancement curves were used to form an SVM model. The model characteristics and accuracy were calculated for the training and validation data sets.

RESULTS

On the training data, the area under the curve (AUC) of the Bi-LSTM was 0.99, while the SVM was 0.95 and statistically significant on the DeLong test. The overall accuracy of the Bi-LSTM on the validation data set was 92 %, while the SVM was 88 %. The accuracy for parathyroid adenomas specifically was 93 % for the Bi-LSTM and 83 % for the SVM model.

CONCLUSION

Enhancement characteristics are a distinguishing feature that accurately identifies parathyroid adenomas alone. The Bi-LSTM performs statistically better in identifying parathyroid adenomas than the SVM analysis when using both morphologic and enhancement information to distinguish between parathyroid adenomas and lymph nodes.

SUMMARY STATEMENT

The Bi-LSTM more accurately identifies parathyroid adenomas than the SVM analysis, which uses both morphologic and enhancement information to distinguish between parathyroid adenomas and lymph nodes, performs statistically better.

Differentiating pathologic parathyroid glands from thyroid nodules on neck ultrasound: the PARATH-US cross-sectional study

Background

Neck ultrasound (US) is a widely used and accessible operator-dependent technique that helps characterize thyroid nodules and pathologic parathyroid glands (PPGs). However, thyroid nodules may sometimes be confused with PPGs. PARATH-US study aims at identifying US characteristics to differentiate PPGs from thyroid nodules, as there is no study, at present, which directly compares the US features of these two common neoplasms.

Methods

PARATH-US is a single-center study that was conducted at a tertiary referral center, including consecutive lesions from patients undergoing neck US examination from 2016 to 2022.

Findings

176 PPGs (158 patients: serum calcium levels 2.91 [IQR 2.74-3.05] mmol/L, PTH levels 173 [112-296] ng/L) were compared to 232 size- and volume-matched thyroid nodules (204 age- and sex-matched patients). The morphologic patterns, echoic content and vascular status were all different between PPGs and thyroid neoplasms (p < 0.01 for all comparisons). The combined parameters maximally discriminated PPGs from thyroid nodules (OR, 7.6; 95% CI: 3.4, 17.1, p < 0.0001). When applying risk stratification systems developed for thyroid malignancies, 58-63% of PPGs were classified as high-risk lesions. Parathyroid adenomas had larger sizes and volumes than hyperplasias (p = 0.013 and p = 0.029). Serum calcium and PTH levels were significantly correlated with PPG size and volume (p < 0.0001 for all comparisons).

Interpretation

We demonstrate the presence of distinct US characteristics in PPGs, which help differentiate them from thyroid nodules. When mistaken for thyroid nodules, PPGs bear high-risk US features. When dealing with high-risk cervical lesions detected on US, a PPG should be suspected, and an assessment of calcium levels recommended to avoid unnecessary invasive procedures.

Funding

CYTO-TRAIN, C2022DOSRH053, funded by the French Regional Health Agency.

Parathyroid carcinoma: Current management and outcomes – A systematic review

OBJECTIVE

Parathyroid carcinoma is rarely encountered in clinical practice. When faced with this clinical challenge, there is currently a paucity of evidence available for the optimal management of patients with parathyroid carcinoma. This systematic review synthesizes the available literature to evaluate the optimal management approach, thus providing guidance for future management.

METHODS

A systematic review was conducted according to PRISMA guidelines using Ovid MEDLINE, EMBASE, and PubMed databases for studies, published in English, reporting on parathyroid carcinoma. Full text of potentially eligible articles were reviewed by two authors independently and eligible studies selected. Treatment options and associated outcomes were evaluated. Descriptive statistics were used to describe pooled patient cohorts.

RESULTS

3203 articles were initially identified using the search criteria with 59 full-text articles then screened for eligibility. Seven articles, all retrospective studies, concerning 2307 patients (median 224/study). Parathyroidectomy alone was the most frequently utilised surgical approach across all studies, followed by en-bloc resection (with adjacent thyroid and/or nodal tissue). There was no difference in post-operative morbidity, mortality or survival between surgical approaches (p < 0.005). Patients who underwent either form of surgery had longer overall survival than those managed non-operatively (p < 0.005).

CONCLUSION

Surgical resection is the optimal treatment of parathyroid carcinoma. However there remains no consensus on the optimal extent of surgery, and as such future randomised prospective studies are necessary to evaluate the effects of different surgical approaches on morbidity, mortality and oncologic outcomes. Following resection, long-term surveillance with PTH is advised.

The magic mirror: a novel intraoperative monitoring method for parathyroid glands

The accurate detection of parathyroid glands (PGs) during surgery is of great significance in thyroidectomy and parathyroidectomy, which protects the function of normal PGs to prevent postoperative hypoparathyroidism and the thorough removal of parathyroid lesions. Existing conventional imaging techniques have certain limitations in the real-time exploration of PGs. In recent years, a new, real-time, and non-invasive imaging system known as the near-infrared autofluorescence (NIRAF) imaging system has been developed to detect PGs. Several studies have confirmed that this system has a high parathyroid recognition rate and can reduce the occurrence of transient hypoparathyroidism after surgery. The NIRAF imaging system, like a magic mirror, can monitor the PGs during surgery in real time, thus providing great support for surgeries. In addition, the NIRAF imaging system can evaluate the blood supply of PGs by utilizing indocyanine green (ICG) to guide surgical strategies. The NIRAF imaging system and ICG complement each other to protect normal parathyroid function and reduce postoperative complications. This article reviews the effectiveness of the NIRAF imaging system in thyroidectomies and parathyroidectomies and briefly discusses some existing problems and prospects for the future.

Giant Parathyroid Tumor: Parathyroid Adenoma versus Parathyroid Carcinoma

Parathyroid adenoma is the most common cause of primary hyperparathyroidism (PHPT). We present the preoperative detection of a giant parathyroid adenoma (GPA) using (^99mTc)-sestamibi parathyroid scintigraphy in a patient presenting with severely elevated parathyroid hormone, hypercalcemia, hypophosphatemia, and vitamin D insufficiency. The patient complained of cerebral symptoms and intermittent abdominal discomfort without constipation. After surgical removal of the hyperactive parathyroid gland and D vitamin supplementation, all blood tests were normalized. The clinical and paraclinical characteristics of GPA may raise the suspicion of parathyroid carcinoma, but not absolutely in this case.

Application value of contrast-enhanced ultrasound in preoperative localization of microwave ablation for primary hyperparathyroidism

BACKGROUND

Ultrasonography (US) and ^99m Technetium-sestamibi scintigraphy (^99m Tc-MIBI) are currently first-line imaging modalities to localize parathyroid adenomas with sensitivities of 80% and 84%, respectively. Therefore, finding other modalities to further improve the diagnostic accuracy for preoperative localization is critically needed.

PURPOSE

To evaluate the application value of contrast-enhanced ultrasound (CEUS) in the preoperative localization of microwave ablation (MWA) for primary hyperparathyroidism (PHPT).

METHODS

Between December 2012 and May 2021, 100 PHPT patients (34 males and 66 females; mean age, 56.31 ± 13.43 years; age range, 25-85 years) with 130 suspected parathyroid nodules were enrolled. US, CEUS, and ^99m Tc-MIBI were performed for the localization of pathological parathyroid glands. All patients were performed MWA under ultrasound guidance. All the suspected parathyroid nodules underwent core needle biopsy under ultrasound guidance during MWA to confirm the pathology. The diagnostic performance of all the imaging tests was analyzed in comparison with the pathological results.

RESULTS

A total of 130 nodules suspected to be of parathyroid origin from preoperative localization images were confirmed by pathological results, of which 116 were of parathyroid origin, and 14 were not of parathyroid origin. The sensitivity, specificity, accuracy, and the area under receiver operating characteristic curve of CEUS in the localization of pathological parathyroid glands were 100%, 92.86%, 99.23%, and 0.964, which were significantly higher than those of US (93.10%, 42.86%, 87.69%, and 0.680) and ^99m Tc-MIBI (81.90%, 42.86%, 77.69%, and 0.624) (p < 0.05). The sensitivity and accuracy of CEUS were 100% and 97.22%, which were higher than those of ^99m Tc-MIBI (65.62% and 63.89%) or US (75.00% and 72.22%) in patients with multiple parathyroid glands (p < 0.05). For smaller parathyroid adenomas (≤2 cm in diameter), the sensitivities of CEUS in locating hyperfunctioning parathyroid glands were 100%, which was significantly higher than that of ^99m Tc-MIBI (73.68% and 84.31%, p < 0.05).

CONCLUSIONS

CEUS is a valuable preoperative localization method for PHPT patients performed MWA, especially for the patients with smaller pathological parathyroid gland and multiple glandular lesions.

Primary hyperparathyroidism: Disease of diverse genetic, symptomatic, and biochemical phenotypes

Genetic, symptomatic, and biochemical heterogeneity of patients with primary hyperparathyroidism (PHPT) has become apparent in recent years. An in-depth, evidence-based review of the phenotypes of PHPT was conducted. This review was intended to provide the resulting information to surgeons who operate on patients with hyperparathyroidism. This review revealed that the once relatively clear distinction between familial and sporadic PHPT has become more challenging by the finding of various germline mutations in patients with seemingly sporadic PHPT. On the one hand, the genetic and clinical characteristics of some syndromes in which PHPT is an important component are now better understood. On the other hand, knowledge is emerging about novel syndromes, such as the rare multiple endocrine neoplasia type IV (MEN4), in which PHPT occurs frequently. It also revealed that, currently, the classical array of symptoms of PHPT is seen rarely upon initial presentation for evaluation. More common are nonspecific, nonclassical symptoms and signs of PHPT. In areas of the world where serum calcium levels are checked routinely, most patients today are "asymptomatic" and they are diagnosed after an incidental finding of hypercalcemia; however, some of them have subclinical involvement of bones and kidneys, which is demonstrated on radiographs, ultrasound, and modern imaging techniques. Last, the review points out that there are three distinct biochemical phenotypes of PHPT. The classical phenotype in which calcium and parathyroid hormone levels are both elevated, and other disease presentations in which the serum levels of calcium or intact parathyroid hormone are normal. Today several, distinct phenotypes of the disease can be identified, and they have implications in the diagnostic evaluation and treatment of patients, as well as possible screening of relatives.

Primary Hyperparathyroidism – A Contemporary Picture Based on 100 Patients from the Last Decade

Primary hyperparathyroidism (PHPT) is an endocrine disease, the clinical picture of which has slowly shifted to milder and asymptomatic forms during the last decades.

Objective

to describe the clinical presentation and the main laboratory and imaging findings in a group of patients with PHPT diagnosed during the last 10 years.

Materials and Methods

This was a retrospective cross-sectional study with data review from the database of a tertiary endocrine clinic from the last 10 years. Secondary causes for elevated PTH were excluded. The major clinical symptoms and signs of hypercalcemia/HPT were reviewed as well as concomitant diseases and medications. Serum calcium (total, albumin-corrected and ionized; sCa, corrCa, iCa+), phosphates (P), magnesium, creatinine, alkaline phosphatase, beta-crosslinks were measured. The intact parathyroid hormone (iPTH) and 25(OH)-vitamin D were determined by electro-hemi-luminescence (Elecsys, Roche Diagnostics). 24-hour urinary probes for calcium and phosphate were collected. Neck ultrasound (US) was used as the localization study of choice. Almost half of the participants underwent fine-needle aspiration biopsy (FNAB) with cytology and needle-washouts for iPTH. One fourth of the patients were assessed by Single-Photon Emission Tomography (SPECT-CT). Data on bone density (from DXA), fractures and renal stones (from renal US) were collected.

Results

One hundred patients met the study criteria – 95 were women. Most of them were in their 5th and 6th decades. The median corrected sCa was 2.73 mmol/l, iCa+ – 1.39 mmol/l, P – 0.88 mmol/l, iPTH – 14.5 pmol/l and 25(OH)D – 54.0 nmol/l. Normal sCa was registered in 20 participants (20%), while normal sP – in 67.0%. The neck US located single lesions (parathyroid adenoma) in 81% – behind or below the left inferior pole of the thyroid gland in 33 cases (33%) and contra-laterally in another 33%. FNAB of the suspicious lesion had been performed in 51% of the study subjects. The cytology confirmed the presence of parathyroid cells in 22 cases (43.1%), Bethesda II thyroid nodules in 21 cases (41.2%), Bethesda III nodules in 2 cases (3.9%) and insufficient samples (Bethesda I) in 5 cases (9.8%). SPECT-CT from 27 patients identified a suspicious left parathyroid in 11 cases, a right one – in 6 cases, as well as three ectopic locations. BMD data were available in 66 female patients and showed a higher prevalence of osteoporosis than in the general age-matched population; fractures, however, were not more frequent. Data from renal ultrasound were available in 77% and revealed chronic pyelonephritis without stones in 8 patients and renal stone disease – in 37 patients.

Conclusion

To our knowledge, this study is the first of its kind in our country during the last two decades. Mild to moderate hypercalcemia was very common, although most patients were oligoor asymptomatic. Renal and bone involvement were surprisingly frequent, with reduced eGFR and low bone mass being more prevalent than in the general population. The most typical location was a single parathyroid lesion within the lower glands. The use of SPECT-CT seems to decline and is replaced by US-guided FNAB with needle washout measurements of iPTH and cytological examination. Although the general picture of PHPT is shifting towards milder and asymptomatic (and probably earlier) forms of the disease, the classical clinical presentation can still be found in everyday practice.

Imaging features of hypercalcemia: A primer for emergency radiologists

Hypercalcemia is a marker for a wide variety of underlying etiologies, and its presentation in the emergency setting may be asymptomatic, incidental, or a primary complaint with associated symptoms and physical exam findings. While the workup is initially driven through serum laboratory testing, imaging plays an important role in diagnosis and post-treatment follow up. This review covers multiple common and uncommon etiologies of hypercalcemia, details their underlying mechanisms, and identifies the most important associated imaging findings. It is important for radiologists to be familiar with these etiologies and imaging findings, particularly in the emergency setting since hypercalcemia may represent the only significant laboratory abnormality associated with the presenting condition. Furthermore, the radiologist's interpretation of a study may be directly influenced by knowing about a patient's hypercalcemia.

Institutional characterisation of water clear cell parathyroid adenoma: a rare entity often unrecognised by TC-99m-sestamibi scintigraphy

Parathyroid lesions exhibiting a water clear cell morphology are exceedingly rare manifestations in primary hyperparathyroidism (PHPT), and the phenomenon has been reported both for uniglandular (water clear cell adenoma; WCCA) and multiglandular disease (water clear cell hyperplasia; WCCH). In all, only 24 previous descriptions of WCCA exist in the literature. Herein, we present seven cases with water clear cell morphology (6 WCCAs and 1 case of WCCH) in an institutional series of approximately 4000 parathyroid lesions spanning 29 years in a tertiary centre setting. Major histological attributes and clinical parameters associated with this morphological subtype were reviewed, and a literature search was conducted. WCCA and WCHH exhibited an institutional prevalence of 0.15% and 0.025%, respectively. All cases displayed histological hallmarks of water clear cell morphology, with cells exhibiting abundant cytoplasm filled with vacuoles. Atypical findings or unequivocal evidence of invasive behaviour were not observed. The gender distribution was 6:1 (F:M), patients were generally symptomatic with mild hypercalcaemia, and the median age at surgery was 53 years (range 38-78). The preoperative localisation was inconclusive in four of seven, and neck exploration of all four glands was undertaken in five cases. The excised WCCAs exhibited an average weight of 1215 mg, markedly higher than conventional adenomas, and all patients were cured of PHPT following parathyroidectomy. Interestingly, previous reports mirror our observations that these lesions often are large, in relation to their sizes biochemically fairly indolent, and indecisively localised using scintigraphy, providing correlations of possible clinical value when pre-operatively assessing these rare lesions.