Preoperative Localization of Parathyroid Adenomas Using 4-Dimensional Computed Tomography: A Pictorial Essay

How has the diagnostic approach to parathyroid localization techniques evolved in the past decade? Insights from a single-center experience

The standardization of preoperative imaging in primary hyperparathyroidism is one of the current challenges of endocrine surgery. A correct localization of the hypersecretory gland by neck ultrasound and 99mTc-sestamibi (MIBI) scintigraphy are not sufficiently sensitive in some cases. In recent years, CT-4D, 18F-Fluorocholine PET/CT, and radio-guided parathyroidectomy have come into common use. The aim of this study is to evaluate the performance of 18F-Fluorocholine PET/CT after prior negative or discordant first-line imaging in patients with primary hyperparathyroidism undergoing parathyroid surgery. Monocentric observational study on patients affected by pHPT undergoing surgery from July 2009 to April 2024 at the Division of General Surgery, Cattinara Teaching Hospital of Trieste. Preoperative, intra-operative, and follow-up data were collected. The imaging methods used were neck ultrasound, 99mTc-sestamibi (MIBI) scintigraphy, and 18F-Fluorocholine PET/CT (since 2018). 172 patients were included. As first radiologic examination, neck ultrasound (US) was performed in 140 cases and 99mTc-sestamibi (MIBI) scintigraphy in 162. Ultrasound and/or scintigraphy imaging were sufficient for the identification of the gland in 127 patients (73.8%), while in 45 patients (26.2%), the localization was defined with other techniques. Particularly, three patients with negative or discordant first-line imaging underwent neck 4D-CT scan who was useful for parathyroid localization all cases (100%). Only one patient received a neck magnetic resonance (MRI) and resulted positive for preoperative localization. Starting in 2018, 29 out of 45 patients underwent 18F-FCH PET/CT yielding a positive result in 29 patients (100%). In other 16 cases (before the introduction of PET/CT in our preoperative imaging study), the preoperative localization was inconclusive and bilateral neck exploration (BNE) was necessary. The sample was homogeneous in terms of age, anthropometric characteristics, and preoperative biochemical parameters. Male/female ratio was 1:5.1. In the intra-operative site, in the cases of exclusive PET/CT positivity, in 28 cases (96.5%), a diagnostic agreement was confirmed, and the gland was macroscopically smaller or normal in size. The combination of ultrasound and MIBI scintigraphy remains the preferred imaging approach for preoperative studies of pHPT. If secondary imaging is required, 18F -FCH PET/CT stands out as the most advantageous option due to its ability to provide anatomical and functional specificity. FCH PET/CT resulted an effective imaging modality with the highest sensitivity of the available imaging techniques for localizing the hyperfunctioning parathyroid gland. Therefore, this method can be recommended in patients showing negative or inconclusive results in the conventional diagnostic imaging.

Frequency and characteristics of ectopic parathyroid adenomas in a cohort of patients referred for 18 F-fluorocholine PET/CT

AIM

This article aimed to study the frequency and characteristics of ectopic/intrathyroidal parathyroid adenomas in patients referred for 18 F-fluorocholine PET/computed tomography (CT).

PATIENTS AND METHODS

From 11 June 2015 to 15 January 2024, 729 patients were studied. Recorded patient variables included hyperparathyroidism type, sex, age, presence of symptoms, renal involvement, bone involvement, parathyroid hormone (PTH), and serum calcium, phosphate, and vitamin D as well as 24-h urine calcium excretion. PET/CT results were also collected. In case of parathyroidectomy, the weight of the adenomas was recorded. Continuous variables were expressed as mean ± SD. Differences were evaluated with Mann-Whitney U -tests or two-sample t -tests, when appropriate. P -values ≤0.05 were considered statistically significant.

RESULTS

PET/CT showed no adenoma in 163 (22%), adenoma in 451 (62%), hyperplasia/multiglandular disease in 32 (4%), and equivocal results in 83 (11%) patients. A total of 6/729 (1%) adenomas were located intrathyroidally and 16/729 (2%) had an ectopic location. Patients with ectopic/intrathyroidal adenoma showed significantly higher serum PTH levels than patients with no visualization of adenoma on PET. The mean mass of the adenoma was 1 ± 2.3 g in patients with orthotopic adenomas versus 2.7 ± 3.3 g in patients with ectopic/intrathyroidal adenomas; however, this was not significantly different ( P  = 0.09).

CONCLUSION

In the presented cohort, the frequency of ectopic/intrathyroidal parathyroid adenomas was 3%. No significant difference in weight was found between orthotopic and ectopic/intrathyroidal parathyroid adenomas.

Persistence of primary hyperparathyroidism: a single-center experience

BACKGROUND

Parathyroidectomy is the only definitive treatment for primary hyperparathyroidism (PHPT). Precise localization of abnormal glands is a key to a successful surgery. Most patients are expected to be successfully treated with focused parathyroidectomy. However, this approach is associated with a risk of existing multiglandular disease which may lead to the postoperative persistence of PHPT.

METHODS

Eight hundred ten patients who underwent an initial surgery for PHPT at SPBU Hospital in 2017-2018 were included in the study. Preoperative imaging results were evaluated. Multivariate logistic regressions were calculated to estimate predictive values of preoperative data for the risk of postoperative persistence and risk of MGD.

RESULTS

Multiglandular disease was found to be a leading cause of persistent hyperparathyroidism. An anamnesis of thyroid surgery was found to be a significant risk factor for the persistence of hyperparathyroidism. The rate of persistence did not differ significantly between groups with bilateral neck exploration and focused parathyroidectomy. Age, sex, body mass index as well as negative results of preoperative US, MIBI, and 4D CT were not independently associated with a higher risk of MGD. All preoperative imaging modalities showed from low to moderate sensitivity for the detection of MGD. The frequency of cases of a missed second adenoma did not differ significantly between patients with concordant and discordant preoperative data. There were 7 cases with previously unsuspected second adenomas found solely due to bilateral neck exploration.

CONCLUSIONS

None of the combination of preoperative visualization modalities was able to rule out the MGD and reliably identify patients for focused parathyroidectomy. Additional preoperative visualization failed to improve overall results. Bilateral neck exploration appeared to have a slight benefit for the patients with concordant preoperative imaging results.

Acute Pancreatitis as the Index Manifestation of Parathyroid Adenoma

Acute pancreatitis is one of the most common clinical emergencies encountered in our day-to-day practice. Although gallstones are the most common cause worldwide, alcohol consumption remains the leading cause of acute pancreatitis in the Indian population. We report a rare case of parathyroid adenoma, which presented with acute pancreatitis as its initial manifestation in an elderly patient. A 65-year-old gentleman with acute abdominal pain, distension, and obstipation, underwent emergency laparotomy in view of acute intestinal obstruction and was found to have acute pancreatitis intra-operatively. On post-operative evaluation, his serum calcium was >14 mg/dl and serum parathormone (PTH) was >2,000 pg/ml. Single-photon emission computed tomography (SPECT) and technetium (Tc-99m) sestamibi scintigraphy revealed a right inferior parathyroid adenoma, which was surgically excised, following which the patient made an uneventful recovery. Hypercalcemia induced by hyperparathyroidism causes auto-activation of pancreatic enzymes within the pancreatic parenchyma and is also believed to cause pancreatic duct obstruction by calcium deposition, thus causing pancreatitis. Radionucleotide scan, in addition to contrast-enhanced computed tomography, can help in localizing the lesion causing hyperparathyroidism. Appropriate resuscitation and stabilization with anti-hypercalcemic measures, including hydration and forced calciuresis, followed by surgery form the mainstay of treatment in patients with primary hyperparathyroidism. Patients with acute pancreatitis without a history of gallstone disease or alcohol intake should be evaluated for other rare causes. Early diagnosis and prompt treatment of the underlying condition can prevent the recurrence of pancreatitis.

4D-CT facilitates focused parathyroidectomy in patients with primary hyperparathyroidism by maintaining a high negative-predictive value for uninvolved quadrants

INTRODUCTION

Improved preoperative localization facilitates minimally invasive parathyroidectomy for removal of parathyroid lesions therefore preventing an invasive bilateral neck exploration. As 4D-CT has emerged, its high specificity has helped with preoperative parathyroid lesion localization. A high negative predictive value (NPV) would serve to further confirm parathyroid lesion localization and limit unnecessary surgical exploration. This study's objective was to determine the NPV of preoperative 4D-CT and its facilitation of minimally invasive parathyroidectomy.

METHODS

A retrospective review was compiled for patients undergoing parathyroidectomy for primary hyperparathyroidism with a preoperative 4D-CT. Included patients were sorted into various groups for comparison: those with 4D-CT localizing to a single lesion, localizing to multiple lesions, and those with nonlocalizing findings; multiple hypercellular parathyroid gland versus single gland findings; extent of surgical exploration; lesion location; and patients with concomitant thyroid nodules. Negative predictive value was calculated and used to quantify the ability for 4D-CT to rule out biochemically significant parathyroid lesions.

RESULTS

In our review of 68 patients: sensitivity was 81.3%, specificity was 95.5%, positive predictive value was 87.1%, and negative predictive value was 93.3%. 86% had a single localizing 4D-CT, 7% had a non-localizing 4D-CT, and 7% had a multiple quadrant localizing 4D-CT. NPV for single and multi-localizing 4D-CT were 96.8% and 88.9%, respectively.

CONCLUSION

Preoperative 4D-CT has a high negative predictive value (93.3%), suggesting in the majority of cases, a quadrant with no 4D-CT radiographic findings suspicious for parathyroid is unlikely to harbor biochemically significant parathyroid lesions.

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.

Accuracy of 2-Phase Parathyroid CT for the Preoperative Localization of Parathyroid Adenomas in Primary Hyperparathyroidism

BACKGROUND AND PURPOSE

Minimally invasive parathyroidectomy requires accurate preoperative localization of suspected adenomas, and multiphase CT allows adenoma characterization while providing detailed anatomic information. The purpose of this study was to assess the feasibility of a protocol using only arterial and venous phases to localize pathologic glands in patients with primary hyperparathyroidism.

MATERIALS AND METHODS

We identified 278 patients with primary hyperparathyroidism who had undergone 2-phase CT with surgical cure. All scans were read prospectively by board-certified neuroradiologists. A neuroradiology fellow retrospectively reviewed images and reports and classified suspected adenomas on the basis of anatomic location. Accuracy was determined by comparing imaging results with surgical findings. The ability of 2-phase CT to localize adenomas to 1 of 4 neck quadrants and lateralize them to the correct side was assessed. Accuracy of identifying multigland disease was also evaluated.

RESULTS

In patients with single-gland disease, the sensitivity and specificity of 2-phase CT to correctly localize the quadrant were 55.4% and 85.9%, respectively. The sensitivity and specificity of correct lateralization were 78.8% and 67.8%, respectively. The sensitivity and specificity to identify multigland disease were 22.9% and 79.5%, respectively.

CONCLUSIONS

While the 2-phase CT protocol in this study demonstrates lower accuracy compared with reports of other techniques, its lower radiation compared with 3- and 4-phase techniques may make it a feasible alternative for preoperative parathyroid localization. Further prospective studies are needed to identify patients for whom this technique is most suitable.

Preoperative 4D CT Localization of Nonlocalizing Parathyroid Adenomas by Ultrasound and SPECT-CT

Objective

To evaluate 4-dimensional (4D) computed tomography (CT) for the localization of parathyroid adenomas previously considered nonlocalizing on ultrasound and single-photon emission CT with CT scanning (SPECT-CT). To measure radiation exposure associated with 4D-CT and compared it with SPECT-CT.

Study Design

Case series with chart review.

Setting

University tertiary hospital.

Subjects and Methods

Nineteen adults with primary hyperparathyroidism who underwent preoperative 4D CT from November 2013 through July 2014 after nonlocalizing preoperative ultrasound and technetium-99m SPECT-CT scans. Sensitivity, specificity, predictive values, and accuracy of 4D CT were evaluated.

Results

Nineteen patients (16 women and 3 men) were included with a mean age of 66 years (range, 39-80 years). Mean preoperative parathyroid hormone level was 108.5 pg/mL (range, 59.3-220.9 pg/mL), and mean weight of the excised gland was 350 mg (range, 83-797 mg). 4D CT sensitivity and specificity for localization to the patient’s correct side of the neck were 84.2% and 81.8%, respectively; accuracy was 82.9%. The sensitivity for localizing adenomas to the correct quadrant was 76.5% and 91.5%, respectively; accuracy was 88.2%. 4D CT radiation exposure was significantly less than the radiation associated with SPECT-CT (13.8 vs 18.4 mSv, P = 0.04).

Conclusion

4D CT localizes parathyroid adenomas with relatively high sensitivity and specificity and allows for the localization of some adenomas not observed on other sestamibi-based scans. 4D CT was also associated with less radiation exposure when compared with SPECT-CT based on our study protocol. 4D CT may be considered as first- or second-line imaging for localizing parathyroid adenomas in the setting of primary hyperparathyroidism.