Improved preoperative planning for directed parathyroidectomy with 4-dimensional computed tomography

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.

ACR Appropriateness Criteria® Parathyroid Adenoma

Hyperparathyroidism is defined as excessive parathyroid hormone production. The diagnosis is made through biochemical testing, in which imaging has no role. However, imaging is appropriate for preoperative parathyroid gland localization with the intent of surgical cure. Imaging is particularly useful in the setting of primary hyperparathyroidism whereby accurate localization of a single parathyroid adenoma can facilitate minimally invasive parathyroidectomy. Imaging can also be useful to localize ectopic or supernumerary parathyroid glands and detail anatomy, which may impact surgery. This document summarizes the literature and provides imaging recommendations for hyperparathyroidism including primary hyperparathyroidism, recurrent or persistent primary hyperparathyroidism after parathyroid surgery, secondary hyperparathyroidism, and tertiary hyperparathyroidism. Recommendations include ultrasound, CT neck without and with contrast, and nuclear medicine parathyroid scans. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

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.

Four-dimensional computed tomography (4D-CT) for preoperative parathyroid localization: A good study but are we using it?

BACKGROUND

Four-dimensional computed tomography (4D-CT) scan to localize abnormal parathyroid glands is diagnostically superior to ultrasound (US) and sestamibi. The implementation of 4D-CT imaging is unknown.

METHODS

The Collaborative Endocrine Surgery Quality Improvement Program (CESQIP) database from 2014 to 2018 was utilized. Patients with hyperparathyroidism undergoing an initial operation were included. The rate of US, sestamibi and 4D-CT performance was calculated for the entire study population, and for each institution.

RESULTS

7,959 patients were included. In 311(3.9%) patients, no preoperative imaging was recorded. Of patients with imaging, US was performed in 6,872(86.3%), sestamibi in 5,094(64.0%), and 4D-CT in 1,630(20.4%). The combination of US and sestamibi was most frequent (3,855, 48.4%). Institutional rates of 4D-CT performance varied from 0.1% to 88.7%.

CONCLUSIONS

Of the imaging modalities, 4D-CT was utilized least frequently and with greatest variability. Given the high accuracy of 4D-CT, efforts to reduce this variation may improve overall preoperative localization in patients with hyperparathyroidism.

The use of computed tomography as a first-line imaging modality in patients with primary hyperparathyroidism

BACKGROUND

The success of minimally invasive parathyroidectomy (MIP) relies on accurate localization of the abnormal parathyroid glands. Concordant findings on ultrasound (US) and ^99mTc-scintigraphy (sestamibi) are currently considered the 'gold standard'. Computed tomography (CT) has also recently been used in preoperative planning. We sought to assess the accuracy of CT for localization of abnormal parathyroid glands in such patients.

METHODS

An audit of 75 patients with primary hyperparathyroidism (PHPT) who underwent neck US and CT between 2017 and 2019 at our center as their first-line imaging.

RESULTS

All 75 patients underwent US and CT and 54 (72.0%) also had sestamibi. CT alone identified a potential target in all patients, of which the location was correct in 63 (84.0%). The overall combined sensitivity of US and CT was 88% (95% CI 78-94) and was higher than the combined sensitivity of US and sestamibi (65% [95% CI 53-76]; p < 0.001). Twenty-one patients (28.0%) had an ectopic gland, and the sensitivity of US and CT was 86% (95% CI 64-96) versus US and sestamibi (57% [95% CI 34-77]; p = 0.016). For adenomas < 1.0 g (n = 36; 48%), the accuracy of CT was 81% (95% CI 64-91) compared with 62% (95% CI 44-77) for US and sestamibi (p = 0.04). The correct preoperative diagnosis of multiglandular disease (n = 9; 12%) seemed to be the most difficult, with similar accuracy for US and sestamibi (40% [95% CI 14-73]) and US and CT (50% [95% CI 20-80]) (p > 0.99).

CONCLUSION

The combination of US and CT was able to correctly identify the location of the abnormal parathyroid in 88% of patients and, in comparison with US and sestamibi, had better diagnostic accuracy, especially for smaller and ectopic adenomas. This finding suggests that US and CT could be considered as a first-line imaging modality in patients with PHPT considered for MIP.

Parathyroid Surgery: What Radiologists Need to Know

Surgical intervention remains the mainstay of treatment of hyperparathyroidism and provides the highest chance at cure. After the disease is confirmed by biochemical testing, surgeons must use a combination of patient clinical history and radiographic imaging to determine the most appropriate surgical strategy. Through either minimally invasive parathyroidectomy or bilateral cervical exploration, surgeons provide high rates of cure for hyperparathyroidism with low rates of persistence or recurrence.

Direct Comparison of Preoperative Imaging Modalities for Localization of Primary Hyperparathyroidism: A Systematic Review and Network Meta-analysis

Importance

Accurate preoperative localization of primary hyperparathyroidism (pHPT) is an important and challenging issue for a successful parathyroidectomy. Although new imaging modalities have been introduced during the past decade, direct comparative studies on advanced imaging techniques are limited.

Objective

To compare the performance of different preoperative imaging modalities for the localization of pHPT by performing a network meta-analysis (NMA).

Data Sources

PubMed, Embase, and the Cochrane Library were searched from the earliest available indexing date through September 28, 2020.

Study Selection

The inclusion criteria were diagnostic tests with sensitivities of 2 or more different preoperative imaging modalities for the same indivduals.

Data Extraction and Synthesis

Two researchers independently reviewed the literature according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses extension statement of health care intervention guidelines for network meta-analyses.

Main Outcomes and Measures

After classifying various imaging modalities into 8 representative imaging categories, the pooled estimation between the odds ratio and 95% credible intervals (CrIs) was calculated in the sensitivity for localization of pHPT. The surface under the cumulative ranking curve (SUCRA) values were obtained to calculate the probability of each imaging modality being the most effective diagnostic method.

Results

A total of 8495 patients from 119 direct comparative studies using 2 or more imaging modalities for localization of pHPT were included. The sensitivity of choline positron emission tomography and computed tomography (PET-CT) was significantly higher than that of technetium 99m sestamibi single-photon emission computed tomography (MIBI SPECT) in both patient-based and lesion-based analyses (patient-based analysis: odds ratio, 5.22; 95% CrI, 2.36-11.80; lesion-based analysis: odds ratio, 17.70; 95% CrI, 5.79-60.10). Among 8 representative imaging modality categories, choline PET-CT showed the highest SUCRA value in both patient-based and lesion-based analyses. In patient-based analysis after 2010, choline PET-CT showed the highest SUCRA value, followed by the CT category, although MIBI SPECT had the highest SUCRA value in analysis before 2009.

Conclusions and Relevance

The results from this network meta-analysis suggest that choline PET-CT showed the best performance in both patient-based and lesion-based analyses and that choline PET-CT would be the best preoperative imaging modality for localization of pHPT.

Recurrence after successful parathyroidectomy-Who should we worry about?

BACKGROUND

Preventing cervical reoperations is important-especially after parathyroidectomy. We sought to examine early predictors of recurrence of primary hyperparathyroidism after surgical cure.

METHODS

Adult patients with sporadic primary hyperparathyroidism treated with parathyroidectomy between September 1, 1997, and September 1, 2019, with confirmed eucalcemia at 6 months postoperatively were identified. Recurrence was defined as hypercalcemia (>10.2 mg/dL) with an elevated or nonsuppressed parathyroid hormone level on subsequent follow-up.

RESULTS

Parathyroidectomy was performed in 522 patients (median age, 62.1 years, 77% female) with the majority undergoing planned minimally invasive parathyroidectomy (85.4%, n = 446). After a median follow-up of 30.9 months, 13 patients (2.5%) recurred (median time to recurrence 50.2 months, interquartile range 27.9-66.5), all of whom underwent planned minimally invasive parathyroidectomy (n = 13/446, 2.9%). Recurrence was more common in those with higher (but still normal) 6-month calcium (10.1 vs 9.3 mg/dL, P < .001) or parathyroid hormone values (64 vs 46 pg/mL, P < .01). Multivariate analysis revealed that age >66.5 years, calcium ≥9.8mg/dL and parathyroid hormone ≥80 pg/mL at 6 months were associated with increased risk of recurrence. In addition, the presence of at least 1 preoperative imaging study that conflicted with intraoperative findings among minimally invasive parathyroidectomy patients (n = 446) was associated with increased risk of recurrence (hazard ratio 4.93, 95% confidence interval 1.25-16.53, P = .016).

CONCLUSION

Recurrence of sporadic primary hyperparathyroidism after initial surgical cure in the era of minimally invasive parathyroidectomy is 2.5%. Identification of those at risk for recurrence using 6-month serum calcium ≥9.8 mg/dL, parathyroid hormone ≥80 pg/mL, and/or potentially conflicting localization studies may inform surveillance strategies.

Rapid intraoperative perfusion assessment of parathyroid adenomas with ICG using a wide-field portable hand-held fluorescence imaging system

BACKGROUND

Fluorescence angiography (FA) using indocyanine green dye (ICG) has recently been introduced for real-time identification of parathyroid adenomas. However, time to peak fluorescence has not yet been critically evaluated.

METHODS

This was a retrospective review of parathyroidectomies with ICG FA over a one-year period.

RESULTS

There were 66 patients with average age of 64 years. The average time to initial fluorescence was 26.7 s and to peak fluorescence was 38.0 s. The time to saline flush administration significantly correlated with times to initial and peak fluorescence (p < .0001). The rate of in-situ fluorescence was 97%. The rates of suspected adenoma detection were 69% for sestamibi scan, 71% for ultrasound, and 96% for CT scan. Imaging was discordant in 13 cases (20%), with the adenoma located on the opposite side of the neck in 4 cases.

CONCLUSIONS

ICG FA is a rapid and effective adjunct for the intraoperative identification of parathyroid adenomas.

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.

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.

Implementation of a 4-dimensional computed tomography protocol for parathyroid adenoma localization

PURPOSE

To present the results of our implementation of a four-dimensional computed tomography- (4DCT) based parathyroid localization protocol for primary hyperparathyroidism at a safety net hospital.

METHODS

We performed a retrospective review of all patients who underwent parathyroidectomy for primary hyperparathyroidism at Elmhurst Hospital Center from June 2016 - September 2019. Patients treated prior to the implementation of 4DCT during October 2018 served as historical controls for comparison. Imaging-related costs and hospital charges were obtained from the Radiology Department for each patient.

RESULTS

Forty-two patients underwent parathyroid surgery during the study period. Twenty patients had undergone 4DCT while 22 had nuclear medicine studies with or without ultrasonography. The sensitivity and specificity of 4DCT was 90.4% and 100% respectively, compared to 63% and 93.7% for nuclear imaging studies and 41% and 95% for ultrasound. The mean number of glands explored was significantly less in the 4DCT group, 1.8 ± 1.19 versus 2.77 ± 1.26 (p = 0.01). There was no increase in infrastructure or personnel costs associated with 4DCT implementation.

CONCLUSIONS

4DCT represents an increasingly common imaging modality for pre-operative parathyroid localization. Here we demonstrate that 4DCT is associated with a reduction in the number of glands explored and enables minimally invasive parathyroid surgery. 4DCT is a cost-effective and clinically sound localization study for parathyroid localization in an urban safety-net hospital.

Multimodality Imaging Review of Multiple Endocrine Neoplasia

OBJECTIVE. The purpose of this article is to review the clinical manifestations, endocrine tumors types, and multimodality diagnostic tools available to physicians involved in the management of patients with multiple endocrine neoplasia (MEN) syndrome, in addition to discussing relevant imaging findings and appropriate imaging follow-up. CONCLUSION. Thorough knowledge of the spectrum of tumors associated with MEN gene mutations aids in the screening, diagnostic workup, and posttreatment monitoring of patients with MEN-related gene mutations.

Diagnostic Role of Four-Dimensional Computed Tomography for Preoperative Parathyroid Localization in Patients with Primary Hyperparathyroidism: A Systematic Review and Meta-Analysis

We sought to systematically evaluate diagnostic performance of four-dimensional computed tomography (4D-CT) in the localization of hyperfunctioning parathyroid glands (HPGs) in patients with primary hyperparathyroidism (pHPT). We calculated the pooled sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), and diagnostic odds ratios (DOR) of 4D-CT on a per-lesion level, as well as pooled sensitivity and positive predictive value (PPV) on a per-patient level with 95% confidence intervals (CIs). Additionally, we plotted summary receiver operating characteristic (SROC) curves and evaluated the areas under the curves (AUC). A total of 16 studies were included in the analysis. Their pooled sensitivity, specificity, PLR, NLR, and DOR of 4D-CT on per-lesion level were 75% (95%CI: 66–82%), 85% (95%CI: 50–97%), 4.9 (95%CI: 1.1–21.3), 0.30 (95%CI: 0.19–0.45), and 17 (95%CI: 3–100), respectively, with an AUC of 81% (95%CI: 77–84%). We also observed heterogeneity in sensitivity (I² = 79%) and specificity (I² = 94.7%), and obtained a pooled sensitivity of 81% (95%CI: 70–90%) with heterogeneity of 81.9% (p < 0.001) and PPV of 91% (95%CI: 82–98%) with heterogeneity of 80.8% (p < 0.001), based on a per-patient level. Overall, 4D-CT showed moderate sensitivity and specificity for preoperative localization of HPG(s) in patients with pHPT. The diagnostic performance may improve with 4D-CT’s promotion to first-line use on a lesion-based level, further research is needed to confirm the results.

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.

Usefulness of the Wisconsin and CaPTHUS indices for predicting multiglandular disease in patients with primary hyperparathyroidism in a southern European population

Background

Focused parathyroidectomy is a safe technique for the treatment of primary hyperparathyroidism. The CaPTHUS score and the Wisconsin index are preoperative diagnostic tools designed to distinguish between single- and multigland disease. The aim of the study is to evaluate the usefulness of these models for predicting multiglandular disease in a European population.

Methods

Retrospective review of a database of patients operated upon for primary hyperparathyroidism at a referral center. The sensitivity, specificity, positive and negative predictive values, and reliability of both scores for the prediction of multiglandular disease, were calculated. Receiver operating characteristic (ROC) curves were constructed to assess the sensitivity and specificity of CaPTHUS score and Wisconsin Index for predicting single-gland disease. A level of P<0.05 was accepted as significant.

Results

Two hundred and eighty-one patients who underwent successful surgery from January 2001 to December 2018 were included. Single-gland disease was detected in 92.5%, and 73.7% had a CaPTHUS score of ≥3. The sensitivity, specificity, positive and negative predictive values of this model for predicting single-gland disease with a score of ≥3 were 76.9%, 66.7%, 96.6%, and 18.9% respectively. The area under the curve value of the CaPTHUS score for predicting single-gland disease was 0.74. A Wisconsin Index >2,000 and an excised gland weight above one gram presented a positive predictive value for single-gland disease of 92.5%.

Conclusions

Despite the good performance of both scales, the established cut-off points did not definitively rule out parathyroid multiglandular disease in our population. In cases with a minimal suspicion of this condition, additional intraoperative techniques must be used, or bilateral neck explorations should be performed.

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.

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.

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.

Accuracy of 4-Dimensional Computed Tomography for Localization in Primary Hyperparathyroidism

BACKGROUND

The etiology of primary hyperparathyroidism (PHP) is single-gland adenoma in most patients. Imaging localization of single-gland disease allows for a focused operation. We sought to determine the accuracy of imaging for localizing a solitary parathyroid adenoma.

METHODS

A single-institution retrospective review was performed of adult patients with PHP undergoing parathyroidectomy from January 2017 through December 2018. Surgeon-performed ultrasound (US), four-dimensional computed tomography (4DCT), and sestamibi were assessed for localization of a parathyroid adenoma yielding a single-gland parathyroidectomy. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were calculated for each imaging modality.

RESULTS

One hundred fifty-four patients underwent parathyroidectomy for PHP during the study period, with 100 patients meeting inclusion criteria with a mean age of 61.1 (SD 10) y and 80% women. Mean calcium was 11.1 mg/dL (SD 0.7) and mean PTH was 116 pg/mL (SD 66). All 100 patients had surgeon-performed US with 17 localized, 51 patients had 4DCT with 41 (80%) localized, and 69 patients had sestamibi with 53 (77%) localized. Eighty-two patients underwent successful unilateral parathyroidectomy, 18 required bilateral neck exploration. US was the most specific imaging modality at 94%. Accuracy of imaging localization was 32% for US, 70% for sestamibi, and 86% for 4DCT.

CONCLUSIONS

Surgeon-performed US is a highly specific imaging modality for preoperative localization of solitary parathyroid adenoma in patients with PHP. 4DCT is the most accurate imaging localization study and should be considered for patients with a nonlocalized US.

A Simple Formula to Estimate Parathyroid Weight on 4D-CT, Predict Pathologic Weight, and Diagnose Parathyroid Adenoma in Patients with Primary Hyperparathyroidism

BACKGROUND AND PURPOSE

Parathyroid gland weight is a clinically relevant parameter used to diagnose parathyroid adenomas intraoperatively. We evaluated the accuracy of a formula to estimate parathyroid weight on preoperative 4D-CT.

MATERIALS AND METHODS

A single-institution retrospective study was performed in patients with primary hyperparathyroidism who underwent 4D-CT between January 2013 and December 2014 with subsequent parathyroidectomy and surgical cure. All patients had correct localization of a solitary parathyroid adenoma. The longest 3 dimensions of all identified parathyroid glands were measured on CT, and weight was estimated using the formula: weight_4D-CT (mg) = 1 mg/mm³ × Length (mm) × Width (mm) × Height (mm) × π/6. We correlated weight_4D-CT with pathology specimen weight (weight_pathology). Using receiver operating characteristic analysis, we estimated the performance of weight_4D-CT to discriminate a parathyroid adenoma from normal glands on 4D-CT and determined the optimal threshold based on the Youden index.

RESULTS

One hundred sixteen patients (85 women, 31 men) were evaluated. Weight_4D-CT was shown to be strongly correlated with weight_pathology as demonstrated by Spearman ρ = 0.73 (P < .01), concordance correlation coefficient = 0.92 (95% CI, 0.89-0.94), and Cronbach α = 0.96. The performance of weight_4D-CT for the diagnosis of parathyroid adenoma was excellent, with an area under the curve of 0.955 (95% CI, 0.925-0.985; P < .001). Based on the Youden index, the optimal threshold was >50 mg, with a sensitivity of 96.7% and a specificity of 95.7%.

CONCLUSIONS

Radiologists can accurately estimate parathyroid adenoma weight on 4D-CT. This metric is highly correlated with pathologic weight, and a threshold cutoff of >50 mg can be used to distinguish parathyroid adenoma from normal glands.

Parathyroid 4D CT: What the Surgeon Wants to Know

Parathyroid four-dimensional (4D) CT is an increasingly used and powerful tool for preoperative localization of abnormal parathyroid tissue in the setting of primary hyperparathyroidism. Accurate and precise localization of a single adenoma facilitates minimally invasive parathyroidectomy, and localization of multiglandular disease aids bilateral neck exploration. However, many radiologists find the interpretation of these examinations to be an intimidating challenge. The authors review parathyroid 4D CT findings of typical and atypical parathyroid lesions and provide illustrative examples. Relevant anatomy, embryology, and operative considerations with which the radiologist should be familiar to provide clinically useful image interpretations are also discussed. The most important 4D CT information to the surgeon includes the number, size, and specific location of candidate parathyroid lesions with respect to relevant surgical landmarks; the radiologist's opinion and confidence level regarding what each candidate lesion represents; and the presence or absence of ectopic or supernumerary parathyroid tissue, concurrent thyroid pathologic conditions, and arterial anomalies associated with a nonrecurrent laryngeal nerve. The authors provide the radiologist with an accessible and practical approach to performing and interpreting parathyroid 4D CT images, detail what the surgeon really wants to know from the radiologist and why, and provide an accompanying structured report outlining the key information to be addressed. By accurately reporting and concisely addressing the key information the surgeon desires from a parathyroid 4D CT examination, the radiologist substantially impacts patient care by enabling the surgeon to develop and execute the best possible operative plan for each patient. ^©RSNA, 2020.

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.

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.

Distinguishing Recurrent Thyroid Cancer from Residual Nonmalignant Thyroid Tissue Using Multiphasic Multidetector CT

BACKGROUND AND PURPOSE

During thyroidectomy incomplete resection of the thyroid gland may occur. This complicates the imaging surveillance of these patients as residual thyroid needs to be distinguished from local recurrence. Therefore, the purpose of this study was to determine if multiphasic multi-detector computed tomography (4D-MDCT) can differentiate residual nonmalignant thyroid tissue and recurrent thyroid carcinoma after thyroidectomy.

MATERIALS AND METHODS

In this retrospective study, Hounsfield unit values on multiphasic multidetector CT in precontrast, arterial (25 seconds), venous (55 seconds), and delayed (85 seconds) phases were compared in 29 lesions of recurrent thyroid cancer, 29 with normal thyroid, and 29 with diseased thyroid (thyroiditis/multinodular thyroid). The comparison of Hounsfield unit values among lesion types by phase was performed using ANOVA. The performance of Hounsfield unit values to predict recurrence was evaluated by logistic regression and receiver operating characteristic analysis.

RESULTS

All 3 tissue types had near-parallel enhancement characteristics, with a wash-in-washout pattern. Statistically different Hounsfield unit density was noted between the recurrence (lowest Hounsfield unit), diseased (intermediate Hounsfield unit), and normal (highest Hounsfield unit) thyroid groups throughout all 4 phases (P < .001 for each group and in each phase). Dichotomized recurrence-versus-diseased/normal thyroid tissue with univariate logistic regression analysis demonstrated that the area under the receiver operating characteristic curve for differentiating benign from malignant thyroid for the various phases of enhancement was greatest in the precontrast phase at 0.983 (95% CI, 0.954-1), with a cutoff value of ≤62 (sensitivity/specificity, 0.966/0.983) followed by the arterial phase.

CONCLUSIONS

Recurrent thyroid carcinoma can be distinguished from residual nonmalignant thyroid tissue using multiphasic multidetector CT with high accuracy. The maximum information for discrimination is in the precontrast images, then the arterial phase. An optimal clinical protocol could be built from any number of phases but should include a precontrast phase.

Preoperative parathyroid localization does not improve surgical outcomes for patients with primary hyperparathyroidism

BACKGROUND

Most patients with primary hyperparathyroidism undergo localization prior to operation with variable success. Therefore, in this study we investigated the safety of parathyroidectomy without imaging.

METHODS

A prospective database of 2057 surgical patients with primary hyperparathyroidism from 2001 to 2019 was reviewed. Patients were categorized by use of preoperative imaging (ultrasound, sestamibi, CT scan), pathology, and cure.

RESULTS

1879 (91%) patients underwent preoperative imaging. CT scan was the most sensitive study (92%), though specificity was only 64%. Patients with imaging were older, had higher pre- and postoperative calcium, more likely to undergo unilateral exploration and have an adenoma (p < 0.001-0.038). No differences were seen in nerve injury (<1%), postoperative hypocalcemia (<1%), or cure rate.

CONCLUSIONS

While localization may lead to minimally-invasive operations, we observed no differences in postoperative complications or cure rates in the hands of an experienced surgeon. Therefore, preoperative parathyroid localization does not improve outcomes for hyperparathyroidism and can be ordered sparingly.

Preoperative and Intraoperative Methods of Parathyroid Gland Localization and the Diagnosis of Parathyroid Adenomas

Accurate pre-operative determination of parathyroid glands localization is critical in the selection of minimally invasive parathyroidectomy as a surgical treatment approach in patients with primary hyperparathyroidism (PHPT). Its importance cannot be overemphasized as it helps to minimize the harmful side effects associated with damage to the parathyroid glands such as in hypocalcemia, severe hemorrhage or recurrent laryngeal nerve dysfunction. Preoperative and intraoperative methods decrease the incidence of mistakenly injuring the parathyroid glands and allow for the timely diagnosis of various abnormalities, including parathyroid adenomas. This article reviews 139 studies conducted between 1970 and 2020 (49 years). Studies that were reviewed focused on several techniques including application of carbon nanoparticles, carbon nanoparticles with technetium sestamibi (99m Tc-MIBI), Raman spectroscopy, near-infrared autofluorescence, dynamic optical contrast imaging, laser speckle contrast imaging, shear wave elastography, and indocyanine green to test their potential in providing proper parathyroid glands' localization. Apart from reviewing the aforementioned techniques, this study focused on the applications that helped in the detection of parathyroid adenomas. Results suggest that applying all the reviewed techniques significantly improves the possibility of providing proper localization of parathyroid glands, and the application of indocyanine green has proven to be the 'ideal' approach for the diagnosis of parathyroid adenomas.

A case of intrathyroid parathyroid tumor that was difficult to diagnose by ultrasonography

Background

With advances in diagnostic imaging such as ultrasonography (US), computed tomography (CT), and ^99mTc-MIBI-sestamibi (MIBI) scintigraphy, localized diagnosis of hyperparathyroidism (pHPT) has become possible with considerable accuracy. However, even with the use of these imaging techniques, since intrathyroid parathyroid tumors exist as a mass within the thyroid, it is often difficult to distinguish from thyroid masses. Although there have been various reports on US images of intraparathyroid tumors, we experienced a case with US images that were distinct from previous reports. Herein we present a case of an intrathyroid parathyroid adenoma (IPA) that was difficult to diagnose, with a main focus on US images.

Case presentation

A 53-year-old man with a diagnosis of hyperparathyroidism was referred to our department in December 2018. Ultrasonography revealed a tumor that was located in the inferior pole of the right lobe of the thyroid gland and no parathyroid mass was observed. The tumor had an irregular round shape and showed heterogeneous hyperechogenicity with a defined margin, but within it, there were a few irregular and hypoechogenic area with unclear margins, while the tumor had a mosaic appearance at first glance. Although ^99mTc-MIBI scintigraphy showed accumulation at the same location in delayed phase, it was difficult to determine the presence of a parathyroid tumor on the image. The patient underwent an operation on April 2019 and the tumor could not be identified on both naked eye and palpation. We used US intraoperatively to define the location and resected the tumor. A parathyroid adenoma was diagnosed by frozen section and the final diagnosis was an intrathyroid parathyroid adenoma.

Conclusion

We experienced an IPA presenting an US image that was atypical and has previously not been reported. IPA has no established US image to confirm the diagnosis and even with the use of other imaging techniques, a definitive diagnosis often cannot be established. Thus, our recommendation based on the current situation is that operation with intraoperative diagnosis using frozen section should be conducted if hypercalcemia and high I-PTH are observed and when localization sites in MIBI and US coincide.

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.

Diagnostic value of four-dimensional computed tomography and four-dimensional magnetic resonance imaging in primary hyperparathyroidism when first-line imaging was inadequate

INTRODUCTION

Accurate localisation of the abnormal hyperfunctioning gland with preoperative imaging has a critical role in parathyroid surgery to obtain a successful outcome. This study aimed to evaluate the diagnostic performance of second-line imaging and their contribution to the treatment success in primary hyperparathyroidism when the first-line methods were negative or discordant.

METHODS

Among the patients who underwent parathyroidectomy due to primary hyperparathyroidism, 33 who underwent four-dimensional computed tomography and/or four-dimensional magnetic resonance imaging because of negative or discordant first-line imaging results were included. Persistent and recurrent cases were excluded.

RESULTS

The majority of the patients were female (84.8%) and the mean age was 59.2 years. Seventeen patients had four-dimensional computed tomography and 25 had four-dimensional magnetic resonance imaging, respectively. Four-dimensional computed tomography and four-dimensional magnetic resonance imaging localised the culprit gland successfully in 52.9% and 84%, respectively. Twenty-five patients in whom single adenoma was detected underwent focused parathyroidectomy. The culprit gland was solitary in 32 cases and one patient had double adenoma. Normocalcaemia was achieved in all cases. Among the 29 patients who completed their postoperative sixth month success rate was 100%.

CONCLUSION

Four-dimensional magnetic resonance imaging had high accuracy with fast dynamic imaging in detecting parathyroid adenomas. When the first-line imaging methods were negative or inconclusive, four-dimensional magnetic resonance imaging should be considered primarily since it is cost effective in Turkey and emits no radiation.

Multiphase Iodine Contrast-Enhanced SPECT/CT Outperforms Nonenhanced SPECT/CT for Preoperative Localization of Small Parathyroid Adenomas

PURPOSE

The aim of this study was to assess the value of intravenously contrast-enhanced CT in conjunction with Tc-MIBI SPECT for preoperative localization of parathyroid adenoma.

METHODS

One hundred ninety-two patients with primary hyperparathyroidism were enrolled in the study between May 2015 and May 2017. The patients underwent a preoperative "one-stop shop" examination with Tc-MIBI SPECT/CT by using dual time-point (10 and 90 minutes) protocol and both nonenhanced CT and contrast-enhanced CT acquisition in the arterial and venous phase, 35 and 75 seconds, respectively, after contrast medium injection start. For 149 patients, the imaging results could be correlated to those at surgery and histopathology.

RESULTS

The median adenoma weight was 330 mg. The addition of contrast-enhanced CT increased the sensitivity from 81.1% to 89.9% (P = 0.003). The specificity of nonenhanced SPECT/CT was similar to contrast-enhanced CT (96.1% vs 97.9%; P = 0.077). For patients with uniglandular disease (n = 140, 94.0%), the sensitivity increased from 86.4% to 93.6% (P = 0.021) and the specificity from 96.2% to 97.9% (P = 0.118) by adding contrast-enhanced CT. In patients with multiglandular disease (n = 9, 6.0%), adding contrast-enhanced CT improved detection sensitivity from 42.1% to 63.2%. However, these patients were few and significance was not reached (P = 0.125).

CONCLUSIONS

In this cohort, with generally small parathyroid adenomas, the sensitivity in preoperative localization was greatly improved by adding contrast-enhanced CT to Tc-MIBI SPECT/CT.

Atypical presentations of parathyroid gland pathology: A pictorial review

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Adenoma, carcinoma and hyperplasia cause parathyroid gland enlargement.

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Mimics include thyroid nodules and cystic structures in the head and neck.

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Enlarged parathyroid glands can enhance variably following contrast administration.

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Hyperparathyroidism can present acutely with respiratory compromise.

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Syndromic associations.

Primary hyperparathyroidism is associated with significant morbidity and mortality. It is in this day and age, an eminently treatable condition which relies heavily on preoperative imaging to localise enlarged parathyroid glands. The imaging appearances of parathyroid gland enlargement are varied; this paper seeks to address some of its more unusual manifestations with an emphasis on its atypical enhancement patterns, mimics and associations. An enlarged glands may also present as an ‘incidentaloma’ in head and neck imaging performed for entirely different indications, or as part of sporadic or familial syndrome. Radiologists are in a good position to expedite the relevant investigations and curative treatment, and knowledge of the spectrum of imaging appearances is crucial.

Microvascular clamp technique as a reversible simulation of parathyroid gland excision

INTRODUCTION

This study demonstrates the effectiveness of a microvascular clamp to simulate parathyroid adenoma excision with respect to intraoperative parathyroid hormone (ioPTH) changes in vivo.

METHODS

Cases in which microvascular clamps were employed intraoperatively in conjunction with intraoperative parathyroid hormone(ioPTH) assays were reviewed. ioPTH values were recorded throughout these procedures to assess the efficacy and reversibility of tissue ischemia using microvascular clamps.

RESULTS

Application of a microvascular clamp across the vascular pedicle of a parathyroid adenoma resulted in a significant ioPTH drop in 95% of cases (N = 20). Removal of the clamp resulted in complete or partial rebound of ioPTH in 90% of cases (N = 20).

CONCLUSION

The use of a microvascular clamp to temporarily occlude a parathyroid gland's vascular pedicle is an effective simulation of gland excision with respect to ioPTH changes. Rebound of ioPTH levels after clamp removal demonstrates that this technique is generally reversible.

LEVEL OF EVIDENCE

2b, Retrospective cohort study.

Practice Patterns in Parathyroid Surgery: A Survey of Asia-Pacific Parathyroid Surgeons

BACKGROUND

Practice variations exist amongst parathyroid surgeons depending on their expertise and resources. Our study aims to elucidate the choice of surgical techniques and adjuncts used in parathyroid surgery by surgeons in the Asia-Pacific region.

METHODS

A 25-question online survey was sent to members of five endocrine surgery associations. Questions covered training background, practice environment and preferred techniques in parathyroid surgery. Respondents were divided into three regions: Australia/New Zealand, South/South East Asia and East Asia, and responses were analysed according to region, specialty, case volume and years in practice.

RESULTS

One hundred ninety-six surgeons returned the questionnaire. Most surgeons (98%) routinely perform preoperative imaging, with 75% preferring dual imaging with ^99mTcsestamibi and ultrasound. Ten per cent of surgeons use parathyroid 4DCT as first-line imaging, more commonly in East Asia (p = 0.038). Minimally invasive parathyroidectomy is the favoured technique of choice (97%). Most surgeons reporting robotic or endoscopic approaches are from East Asia. Rapid intraoperative parathyroid hormone is accessible to just under half of the surgeons but less available in Australian/New Zealand (p < 0.001). The use of intraoperative neuromonitoring is not commonly used, even less so amongst Asian surgeons (p = 0.048) and surgeons with low case load (p = 0.013).

CONCLUSION

Dual localisation techniques are the preferred choice of investigations in preparation for parathyroid surgery, with minimally invasive surgery without neuromonitoring the preferred approach. Use of adjuncts is sporadic and limited to certain centres.

Imaging of brown tumours: a pictorial review

Brown tumours do not represent neoplastic process, but they are focal bony lesions due to bone remodelling from either primary or secondary hyperparathyroidism. Their incidence is also low. The current literature on brown tumour is mainly in the form of case reports that focus on single affected sites. This pictorial review describes the full imaging workup and pathway of suspected brown tumour in the setting of both primary and secondary hyperparathyroidism. It aims to illustrate the management strategy to aid both clinicians and radiologists in suspected cases of brown tumour. We highlight the complementary roles that different imaging modalities can play in different settings including the importance of parathyroid ultrasound, ^99mTc-sestamibi scintigraphy and SPECT/CT in the localisation of the parathyroid adenoma. We present cases with full clinical and imaging workup in both the acute and chronic setting and scenarios that require exclusion of primary and secondary bone malignancies.

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.

Parathyroid Computed Tomography Angiography: Early Experience with a Novel Imaging Technique in Primary Hyperparathyroidism

Objectives

To describe parathyroid computed tomography angiography (PCTA), determine its accuracy, and, as a secondary objective, calculate its mean radiation dosimetry.

Study Design

Retrospective chart review of patients who underwent parathyroidectomy for primary hyperparathyroidism from 2007 to 2015.

Setting

Single-center tertiary care academic military hospital.

Subjects and Methods

PCTA is a 2-phase computed tomography imaging technique that uses individualized timing of contrast infusion and novel patient positioning to accurately identify parathyroid adenomas. Consecutive patients who underwent parathyroidectomy for primary hyperparathyroidism from 2007 to 2015 were reviewed; 55% of patients were women. The mean age was 50.9 years (range, 26-68 years). Sensitivity and specificity were calculated as well as mean radiation dosimetry and timing of contrast.

Results

A total of 108 procedures were performed during the study period. Twenty-one patients undergoing 22 PCTAs after prior sestamibi scans were nonlocalizing or equivocal. In this group, there were 15 true-positive, 3 false-positive, 4 true-negative, and 0 false-negative PCTAs. This represents a sensitivity of 100% (95% CI, 74.7%-100%) and a specificity of 57% (95% CI, 20%-88%). The mean calculated radiation dose was 5.15 mSv. In the most recent studies, a mean dose of 4.1 mSv was calculated. The ideal time of image acquisition contrast administration varied from 20 to 30 seconds after contrast infusion.

Conclusions

PCTA is a new technique in anatomic imaging for hyperparathyroidism. In a single-center, single-radiologist retrospective study, it demonstrates excellent accuracy for patients with parathyroid adenomas that are otherwise difficult to localize preoperatively. Preliminary experience suggests that its use may be indicated as a primary imaging modality in the future.

Role of advanced magnetic resonance imaging in the assessment of malignancies of the mediastinum

In the new era of functional magnetic resonance imaging (MRI), the utility of chest MRI is increasing exponentially due to several advances, including absence of ionizing radiation, excellent tissue contrast and high capability for lesion characterization and treatment monitoring. The application of several of these diagnostic weapons in a multiparametric fashion enables to better characterize thymic epithelial tumors and other mediastinal tumoral lesions, accurate assessment of the invasion of adjacent structures and detection of pathologic lymph nodes and metastasis. Also, “do not touch lesions” could be identified with the associated impact in the management of those patients. One of the hot-spots of the multiparametric chest MR is its ability to detect with acuity early response to treatment in patients with mediastinal malignant neoplasms. This has been related with higher rates of overall survival and progression free survival. Therefore, in this review we will analyze the current functional imaging techniques available (¹⁸F-Fluorodeoxiglucose positron emission tomography/computed tomography, diffusion-weighted imaging, dynamic contrast-enhanced MRI, diffusion tensor imaging and MR spectroscopy) for the evaluation of mediastinal lesions, with a focus in their correct acquisition and post-processing. Also, to review the clinical applications of these techniques in the diagnostic approach of benign and malignant conditions of the mediastinum.

Diagnostic Performance of 4D CT and Sestamibi SPECT/CT in Localizing Parathyroid Adenomas in Primary Hyperparathyroidism

Background There currently is no consensus on the optimal localization procedure and imaging protocol for parathyroid adenoma. Parathyroid four-dimensional (4D) CT has emerged as a promising method for preoperative localization. Purpose To evaluate the diagnostic performance of parathyroid 4D CT and technetium 99m-sestamibi (hereafter, referred to as sestamibi) SPECT/CT in preoperative localization in patients with primary hyperparathyroidism. Materials and Methods This was a single-institution retrospective study of patients with primary hyperparathyroidism who underwent a combined imaging protocol of sestamibi SPECT/CT and 4D CT (noncontrast, contrast agent-enhanced, arterial, and delayed venous phases) acquired in a single setting from February 2013 to May 2016, with subsequent parathyroidectomy within 6 months. Reference standard for correct localization was on the basis of location denoted on operative reports, with pathologic confirmation of parathyroid adenoma or hyperplasia. By using a four-quadrant analysis, sensitivity, specificity, and area under the curve (AUC) for localization of the hyperfunctioning parathyroid gland or glands at sestamibi SPECT/CT and 4D CT were compared, per modality and in combination. Results Four hundred patients (319 women, 81 men; mean age, 61 years ± 14 [standard deviation]) were evaluated. Similar diagnostic performance was found in both combined 4D CT with sestamibi SPECT/CT and 4D CT alone (area under the curve [AUC], 0.88 [95% CI: 0.86, 0.90] and 0.87 [95% CI: 0.85, 0.90], respectively; P = .82). Both modalities outperformed sestamibi SPECT/CT (AUC, 0.78; 95% CI: 0.76, 0.81; P < .001). Four-dimensional CT showed higher sensitivity than did sestamibi SPECT/CT (sensitivity, 79.3% [414 of 522] vs 58.0% [303 of 522], respectively; P < .001). In a subset analysis, 4D CT had higher sensitivity than sestamibi SPECT/CT in patients with single-gland disease (sensitivity, 92.5% [297 of 321] vs 75.1% [241 of 321], respectively; P < .001) and with multigland disease (sensitivity, 58.2% [117 of 201] vs 30.8% [62 of 201], respectively; P < .001). Conclusion Four-dimensional CT provided superior preoperative localization compared with sestamibi SPECT/CT in patients with single and multigland disease. The combination of the two modalities did not improve diagnostic performance compared with four-dimensional CT alone. © RSNA, 2019 Online supplemental material is available for this article. See also the editorial by Sinha and Oates in this issue.