Parathyroid localization with modified 4D-computed tomography and ultrasonography for patients with primary hyperparathyroidism

Accuracy of Four-Dimensional Computed Tomography and Different Imaging Modalities in Primary Hyperparathyroidism

Background This study aimed to compare the accuracy of different imaging modalities in the preoperative localization of parathyroid pathology in primary hyperparathyroidism. Methodology This prospective study enrolled 70 patients who were biochemically diagnosed with primary hyperparathyroidism between 2021 and 2022 at our center. Patients underwent scanning using three imaging modalities, namely, Tc99m sestamibi scan (sestamibi), parathyroid ultrasonography, and four-dimensional computed tomography (4DCT). A descriptive analysis was performed to determine and compare the respective localizing sensitivities. Results The most common site of parathyroid adenoma (PA) was the left inferior parathyroid gland, seen in 28 (40%) patients. Three patients had false-positive imaging studies with no parathyroid pathology identified surgically or on histological examination. The median levels of parathyroid hormone decreased significantly (p < 0.001) after the surgery, with a median of 24.3 (1.90-121). Furthermore, 4DCT accomplished a sensitivity of 97.14% for diagnosing the side and 94.03% for overall localization of PA. This sensitivity was superior to the sensitivity of ultrasonography and sestamibi scan to detect the side and quadrant of the adenoma. 4DCT was significantly higher in sensitivity when compared to the combination of ultrasound and sestamibi (p < 0.001). Conclusions 4DCT yielded the highest sensitivity in localizing parathyroid pathology from the imaging modalities studied with the lowest false-negative rate. Using ultrasound with 4DCT could be the most cost-effective combination for detecting primary hyperparathyroidism.

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

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

An Assessment of Enhancement Patterns in Abnormal Parathyroid Glands on Three-Phase CT Imaging

Background Four-dimensional computed tomography (4DCT) is increasingly used in the investigation of primary hyperparathyroidism. The objective of this study was to identify and analyse the usefulness of different enhancement patterns on 4DCT to improve its sensitivity. Methodology Retrospective data were collected on 100 glands. A consultant head and neck radiologist measured the Hounsfield units (HU) of the parathyroid gland and surrounding normal thyroid tissue in the pre-contrast, arterial and venous phases. Each gland was grouped according to the enhancement pattern, and the percentage change in HU was also calculated between the three phases. Results Thirty-five parathyroid glands demonstrated enhancement higher than the thyroid gland in the arterial phase and lower in the delayed phase and were placed into group A. Four parathyroid glands demonstrated enhancement higher than the thyroid gland in the arterial phase and also higher in the delayed phase and were placed into group B. Fifty-nine parathyroid glands demonstrated enhancement lower than the thyroid gland in the arterial phase and also lower in the delayed phase and were placed into group C. Two parathyroid glands demonstrated enhancement lower than the thyroid gland in the arterial phase and higher in the delayed phase and were placed into group D. Conclusions This study demonstrated that the classically described enhancement pattern of the parathyroid gland is not always present or the most frequent, thereby showing that the enhancement pattern cannot be relied upon in isolation. Instead, a thorough understanding of anatomy, embryology and possible ectopic gland locations is essential.

Percentage arterial enhancement on 2D CT in the diagnosis of primary hyperparathyroidism: A prospective validation study and potential pitfalls

BACKGROUND

Parathyroid lesions are identified by subjective enhancement and washout patterns on computed tomography (CT). We have previously proposed "percentage arterial enhancement" (PAE) as an objective index and now aim to validate its performance prospectively.

METHODS

Dual-phase CT was performed in 40 consecutive primary hyperparathyroidism patients. PAE was calculated as [{arterial phase Hounsfield unit (HU)-unenhanced phase HU}/unenhanced phase HU] × 100. PAE > 128.9% was considered parathyroid.

RESULTS

PAE had 94.2% sensitivity, 100% positive predictive value (PPV) in lateralization, and sensitivity and PPV of 93.9% in quadrant localization of single-gland disease. PAE failed to identify two lesions: an intrathyroidal parathyroid carcinoma in the background of multinodular goiter and another lower enhancing cystic parathyroid adenoma. PAE had 60% sensitivity, and 100% PPV to identify multigland disease. The mean effective dose was 2.74 mSV.

CONCLUSIONS

PAE is a specific CT index for parathyroid lesions with less radiation exposure. Areas of caution include intrathyroidal and cystic lesions.

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

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

Assessment of 4DCT imaging findings of parathyroid adenomas in correlation with biochemical and histopathological findings

PURPOSE

To assess polar vessel presence and enhancement 4DCT imaging and their relation with biochemical and histopathological features.

METHODS

Patients with primary hyperparathyroidism and preoperative 4DCT imaging were screened retrospectively and those with histopathologically proven diagnosis of PA were included. Biochemical findings, densitometric measurements (HU_precontrast, HU_arterial, HU_venous, HU_wash-in, HU_wash-out, HU_retained) and CT_volume of PA on 4DCT, presence of a polar vessel (PV), and histopathological features were recorded. Correlations between serum PTH, calcium levels and densitometric measurements of PA on 4DCT were investigated. Differences between subgroups created according to PV presence were also evaluated.

RESULTS

Thirty-nine patients were enrolled (F/M = 32/7, median age = 57, interquartile range = 50-62 years). In all patients, serum PTH levels positively correlated with CT_volume (r = 0.398, p = 0.012) but negatively correlated with HU_arterial (r = - 0.366; p = 0.022), HU_venous (r = - 0.452; p = 0.004) and HU_retained (r = - 0.421; p = 0.008). In PV (-) PAs, PTH levels were positively correlated with CT_volume (r = 0.608, p ≤ 0.002) and negatively with HU_arterial (r = - 0.449, p ≤ 0.028), HU_venous (r = - 0.560, p = 0.004), HU_wash-in (r = - 0.460, p = 0.024), and HU_retained (r = - 0.539, p = 0.007). No correlation between PTH levels and densitometric measurements was found in PV (+) PAs. HU_wash-in and HU_wash-out were significantly higher in PV (+) PAs compared to PV (-) PAs (p = 0.021 and p = 0.033, respectively). Histopathologic features revealed no difference according to the presence of PV.

CONCLUSION

PTH levels might have an association with imaging findings of PAs, especially when categorized with respect to PV presence. PTH levels were negatively correlated with degree of enhancement in PV (-) PAs. Therefore, radiologists should be aware that in patients with high serum PTH levels and without a discernible PV, PA might be difficult to localize.

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.

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.

Utility of intraoperative digital scintigraphy in radioguided parathyroidectomy

BACKGROUND

Intraoperative scintigraphy (IoS) has been proposed as a tool for real-time intraoperative decision-making regarding parathyroid adenoma localization and confirmation of excision.

METHODS

Retrospective review of patients who underwent minimally invasive parathyroidectomies with scintigraphy performed intraoperatively. Preoperative neck ultrasound, 4D computed tomography, as well as intraoperative parathyroid hormone (IOPTH) and gamma probe measurements were conducted per standard practice. IoS images were obtained prior to and following parathyroid excision. Cases were reviewed to determine accuracy of IoS for localizing parathyroid pathology and confirming successful excision.

RESULTS

Fifty-six cases met the inclusion criteria. Twenty-nine patients (51.8%) showed confirmation of excision of an abnormal gland on post-excision IoS. There were no significant differences in IOPTH reduction and postoperative laboratory values between patients with IoS-identified resolution and those without IoS-identified resolution.

CONCLUSIONS

With low accuracy in correctly localizing abnormal glands and confirming their excision, there is no appreciable benefit of IoS at this time.

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.

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.

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.

A rural perspective on minimally invasive parathyroidectomy: optimal preoperative imaging and patient outcomes

BACKGROUND

Our retrospective review of prospectively collected data evaluated the efficacy of minimally invasive parathyroidectomy (MIP) and compared preoperative imaging modalities in a rural referral centre.

METHODS

Patients with a diagnosis of primary hyperparathyroidism underwent surgeon-performed ultrasound (SUS) and technetium-99 m sestamibi (MIBI). Radiologist-performed ultrasound (RUS) was sought when the diagnosis remained in doubt. Four-dimensional computed tomography (4DCT) first replaced RUS in mid-2014, then MIBI as a frontline modality in 2015. MIP was conducted if possible and bilateral neck exploration (BNE) when localization remained doubtful. Treatment was evaluated by histopathology and serum parathyroid hormone and calcium levels at 6 weeks.

RESULTS

A total of 122 of 165 (73.9%) glands were removed by MIP and 43 of 165 (26.1%) by BNE. Of 15 cases with non-localizing preoperative investigations, one patient had a negative BNE. A total of 160 of 165 (97.0%) patients underwent a successful operation, with five (3.0%) suffering persistent post-operative hypercalcaemia. SUS had a sensitivity of 79.4% (131/165) and a positive predictive value (PPV) of 97.0% (131/135). MIBI had a sensitivity of 60.0% (81/135) and a PPV of 95.3% (81/85). RUS produced a sensitivity of 65.5% (76/116) and PPV of 98.7% (76/77). When used as a second-line modality, 4DCT had a sensitivity of 76.9% (10/13) and PPV of 100%. The sensitivity and PPV were 85.7% (18/21) and 94.7% (18/19) after 4DCT's promotion to first-line use.

CONCLUSION

MIP can be safely performed in rural centres of adequate volume. We recommend that operations be guided by SUS with routine use of an adjunctive modality. Our study has seen 4DCT replace MIBI in this regard.

Evaluation of the radiation dose exposure and associated cancer risks in patients having preoperative parathyroid localization

OBJECTIVE The study aimed to evaluate the total effective and organ absorbed radiation doses associated with three- and four-phase parathyroid computed tomography (CT) and sestamibi scans used for the preoperative localisation of parathyroid adenomas in a cohort of patients with primary hyperparathyroidism at a single institution. We aimed to assess the risk of cancer incidence for the organs demonstrating the highest absorbed doses for the different imaging techniques, and more specifically determine the risk for our cohort of patients. METHODS Fifty patients with primary hyperparathyroidism had both multiphase CT and sestamibi scans. The Imaging Performance Assessment of CT Scanners (ImPACT) calculator was used to estimate the patient-effective and organ-absorbed radiations doses for all the CT examinations. For sestamibi scans, the US Nuclear Regulatory Commission NUREG/CR-6345 publication was used to estimate the dose for each patient. The attributable risks of cancer were calculated using the Health Protection Agency HPA-CRCE-028 publication. RESULTS The mean patient total effective doses were 15.9% ± 2.8 mSv, 20.2% ± 2.8  mSv and 5.6 ± 0.24 mSv for three-phase CT, four-phase CT and sestamibi examinations, respectively. In our cohort, the highest attributable lifetime risk was for lung cancer (0.03%) after multiphase CT. This compared with a tenfold lower risk for thyroid cancer (0.003%). After sestamibi, the highest risk was for colon cancer (0.06%). CONCLUSIONS Multiphase CT is associated with a higher radiation dose and thus a higher potential risk of cancer, but this risk is low in the older population that constituted the majority of our cohort.

Multiparametric ultrasonography and ultrasound elastography in the differentiation of parathyroid lesions from ectopic thyroid lesions or lymphadenopathies

To evaluate the accuracy of ultrasound elastography with Elastoscan^TM Core Index in the differential diagnosis of parathyroid lesions from ectopic thyroid nodules and lymph nodes. Seventy nine patients with repeatedly high levels of circulating intact parathyroid hormone, normal vitamin D and renal function tests, with an ultrasound scan showing a neck lesion, sharply demarcated from the thyroid lobules, were consecutively enrolled. Ultrasound with and without Color Doppler and ultrasound elastography were performed before histological examination. All ultrasound features, vascularization and ultrasound elastography diagnostic performance were assessed using ROC curves. Histological examination confirmed 47 parathyroid lesions, 18 thyroid ectopic nodules and 14 reactive lymph nodes. In distinguishing parathyroid from thyroid nodules, shape had a 100 % sensitivity (95 % CI 92.4-100) and 50 % specificity (95 % CI 37.2-64.7), cleavage had a 85.1 % sensitivity (95 % CI 72.3-92.6) and 77.8 % specificity (95 % CI 65.1-88) while peripheral vascularization had a sensitivity of 91.5 (95 % CI 79.6-97.6) and specificity of 72.2 (95 % CI 46.5-90.3). An Elastoscan^TM Core Indexof 1.28 was 46 % sensitive (95 % CI 33.4-58.7) and 77 % specific (95 % CI 66.2-89.1) in discriminating parathyroid lesions from thyroid nodules. An Elastoscan^TM Core Index of 1.0 was 78 % sensitive (95 % CI 65.1-88) and 71 % specific (95 % CI 56-81.3) in discriminating parathyroid lesions from lymph nodes (p = 0.045). An Elastoscan^TM Core Index greater than 2.58 had a 100 % sensitivity (95 % CI 43.8-100) and 95.4 % specificity (95 % CI 38.3-99.7) in discriminating malignant from benign parathyroid nodules. Elastoscan^TM Core Index was significantly higher in thyroid nodules than in reactive lymph nodes (1.18 ± 0.62, p = 0.008). The ultrasound features of cleavage and peripheral vascularization help to differentiate parathyroid from thyroid nodules. Elastoscan^TM Core Index can improve ultrasound discrimination of parathyroid lesions from lymph nodes. The Elastoscan^TM Core Index is significantly higher in malignant than in benign parathyroid lesions.

Ectopic mediastinal parathyroid adenoma localized with four-dimensional CT: a case report

We present a case of an ectopic mediastinal parathyroid adenoma in a 58-year-old male patient. We show how different imaging modalities were successfully used to reach a diagnosis. We particularly focus on the role of four-dimensional CT scan in preoperative localization of ectopic adenomas and discuss how diverse imaging modalities can be integrated in the workup of ectopic parathyroid adenomas.

Clinical efficacy of 2-phase versus 4-phase computed tomography for localization in primary hyperparathyroidism

BACKGROUND

Four-dimensional computed tomography is being used increasingly for localization of abnormal glands in primary hyperparathyroidism. We hypothesized that compared with traditional 4-phase imaging, 2-phase imaging would halve the radiation dose without compromising parathyroid localization and clinical outcomes.

METHODS

A transition from 4-phase to 2-phase imaging was instituted between 2009 and 2010. A pre-post analysis was performed on patients undergoing operative treatment with a parathyroid protocol computed tomography, and relevant data were correlated with operative findings. Sensitivity, positive predictive value, technical success, and cure rates were calculated. The Fisher exact test or χ(2) test assessed the significance of 2-phase and 4-phase imaging and operative findings.

RESULTS

Twenty-seven patients had traditional four-dimensional computed tomography and 35 had modified 2-phase computed tomography. Effective radiation doses were 6.8 mSy for 2-phase and 14 mSv for 4-phase. Four-phase computed tomography had a sensitivity and positive predictive value of 93% and 96%, respectively. Two-phase computed tomography had a comparable sensitivity and positive predictive value of 97% and 94%, respectively. Eight patients with discordant imaging had an average parathyroid weight of 240 g compared with 1,300 g for all patients. Technical surgical success (90% for 4-phase computed tomography versus 91% 2-phase computed tomography) and normocalcemia rates at 6 months (88% for both) did not differ between computed tomography protocols. Computed tomography correctly predicted multiglandular disease and localization for reoperations in 88% and 90% of cases, respectively, with no difference by computed tomography protocol.

CONCLUSION

With regard to surgical outcomes and localization, 2-phase parathyroid computed tomography is equivalent to 4-phase for parathyroid localization, including small adenomas, reoperative cases, and multiglandular disease. Two-phase parathyroid computed tomography for operative planning should be considered to avoid unnecessary radiation exposure.

Effect of tumor volume on the enhancement pattern of parathyroid adenoma on parathyroid four-dimensional CT

INTRODUCTION

The purpose of this study is to assess the effect of tumor volume on the enhancement pattern of parathyroid adenoma (PTA) on four-dimensional computed tomography (4D-CT).

METHODS

We analyzed the enhancement patterns of PTA on four-phase 4D-CT in 44 patients. Dependency of the changes of Hounsfield unit values (ΔHU) on the tumor volumes and clinical characteristics was evaluated using linear regression analyses. In addition, an unpaired t test was used to compare ΔHU of PTAs between PTA volume ≥1 cm(3) and <1 cm(3), thyroid gland, and lymph node.

RESULTS

PTA volume based on CT was the strongest factor on the ΔHUPre to Arterial and ΔHUArterial to Venous and ΔHUArterial to Delayed (R (2) = 0.34, 0.25, and 0.32, respectively, P < 0.001 for both). PTA ≥1 cm(3) had statistically significant greater enhancement between the unenhanced phase and the arterial phase than PTA <1 cm(3) (mean values ± standard deviations (SDs) of ΔHUPre to Arterial, 102.7 ± 33.7 and 57.5 ± 28.8, respectively, P < 0.001). PTA ≥1 cm(3) showed an early washout pattern on the venous phase, whereas PTA <1 cm(3) showed a progressive enhancement pattern on the venous phase (mean values ± SDs of ΔHUArterial to Venous, -13.2 ± 31.6 and 14.4 ± 32.7, respectively; P = 0.009).

CONCLUSION

The enhancement pattern of PTA on 4D-CT is variable with respect to PTA volume based on CT. Therefore, the enhancement pattern of PTA on 4D-CT requires careful interpretation concerning the tumor volume, especially in cases of PTA <1 cm(3).

Preoperative ¹¹C-methionine PET/CT enables focused parathyroidectomy in MIBI-SPECT negative parathyroid adenoma

BACKGROUND

Precise preoperative localization is essential for focussed parathyroidectomy. The imaging standard consists of cervical ultrasonography (cUS) and (99m)Tc-MIBI-SPECT (MIBI-SPECT). (11)C-methionine positron emission tomography/computed tomography (Met-PET/CT) is a promising method for localizing parathyroid adenomas. The objective of our study was to elucidate whether additional Met-PET/CT increases the rate of focussed parathyroidectomy.

METHODS

Fourteen patients with primary hyperparathyroidism (HPT) and three patients with tertiary HPT underwent cUS and MIBI-SPECT. Met-PET/CT was carried out in patients with negative MIBI results. Subsequent surgical strategy was adapted according to imaging results.

RESULTS

cUS localized a single parathyroid adenoma in 10/17 patients (59 %), while MIBI-SPECT/CT identified 11/17 single adenomas (65 %). In the remaining six patients, Met-PET/CT identified five single adenomas. This step-up approach correctly identified single adenomas in 16/17 patients (94 %).

CONCLUSION

Met-PET/CT raises the rate of correctly localized single parathyroid adenomas in patients with negative cUS and MIBI-SPECT/CT and increases the number of focussed surgical approaches.

Dynamic 4D MRI for Characterization of Parathyroid Adenomas: Multiparametric Analysis

BACKGROUND AND PURPOSE

The hypervascular nature of parathyroid adenomas can be explored by proper dynamic imaging to narrow the target lesions for surgical exploration. The purpose of this study was to establish MR perfusion characteristics of parathyroid adenomas to differentiate them from their mimics, such as subjacent thyroid tissue and cervical lymph nodes.

MATERIALS AND METHODS

Preoperative high-spatial and -temporal resolution dynamic 4D contrast-enhanced MR imaging in 30 patients with surgically proved parathyroid adenomas was evaluated retrospectively. Using coregistered images, we placed ROIs over the parathyroid adenoma, thyroid gland, and a cervical lymph node (jugulodigastric) to obtain peak enhancement, time-to-peak, wash-in, and washout in each patient. Data were analyzed by logistic regression and analysis of variance. Receiver operating characteristic analysis was performed to determine the optimal parameters for determination of parathyroid adenomas versus thyroid tissue and cervical lymph nodes.

RESULTS

Parathyroid adenomas showed significantly (P < .05) faster time-to-peak, higher wash-in, and higher washout compared with cervical lymph nodes and significantly (P < .05) higher peak enhancement, faster time-to-peak, higher wash-in, and higher washout compared with thyroid tissue. Logistic regression analysis indicated significant contribution from time-to-peak (P = .02), wash-in (P = .03), and washout (P = .008) for differentiation of parathyroid adenomas from thyroid and cervical lymph nodes. Using receiver operating characteristic analysis, we obtained the best diagnostic accuracy from a combination of time-to-peak/wash-in/washout in the differentiation of parathyroid adenomas versus lymph nodes (area under the curve, 0.96; sensitivity/specificity, 88%/90%) and in distinguishing parathyroid adenomas versus thyroid tissue (area under the curve, 0.96; sensitivity/specificity, 91%/95%).

CONCLUSIONS

Dynamic 4D contrast-enhanced MR imaging can be used to exploit the hypervascular nature of parathyroid adenomas. Multiparametric MR perfusion can distinguish parathyroid adenomas from subjacent thyroid tissue or lymph nodes with diagnostic accuracies of 96%.

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.

Incidental thyroid nodules in patients with primary hyperparathyroidism

BACKGROUND

It is desirable to detect neoplastic thyroid disease before proceeding with surgical therapy for hyperparathyroidism so that both conditions can be treated with a single operation.

METHODS

Between March 1998 and June 2009, 227 patients with primary hyperparathyroidism were treated with surgical therapy. Of these, 217 were evaluated preoperatively with a modified 4-dimensional CT and ultrasonography. The medical records of these patients were reviewed in order to document the incidence and significance of thyroid pathology in this cohort of patients.

RESULTS

Thyroid nodules were identified in 159 of the 217 patients (73.3%). Nine of 217 patients (4.1%) were treated with either a partial or a total thyroidectomy at the time of parathyroidectomy. Three of these patients had papillary thyroid carcinoma, 1 had a Hurthle cell carcinoma, and 1 had an incidental micropapillary thyroid carcinoma.

CONCLUSION

The rate of clinically significant thyroid malignancy in patients undergoing surgical treatment of primary hyperparathyroidism was 1.8%.

Lifetime Attributable Risk of Cancer From Radiation Exposure During Parathyroid Imaging: Comparison of 4D CT and Parathyroid Scintigraphy

OBJECTIVE

The purpose of this study is to measure the organ doses and effective dose (ED) for parathyroid 4D CT and scintigraphy and to estimate the lifetime attributable risk of cancer incidence associated with imaging.

MATERIALS AND METHODS

Organ radiation doses for 4D CT and scintigraphy were measured on the basis of imaging with our institution's protocols. An anthropomorphic phantom with metal oxide semiconductor field effect transistor detectors was scanned to measure CT organ dose. Organ doses from the radionuclide were based on International Commission for Radiological Protection report 80. ED was calculated for 4D CT and scintigraphy and was used to estimate the lifetime attributable risk of cancer incidence for patients differing in age and sex with the approach established by the Biologic Effects of Ionizing Radiation VII report. A 55-year-old woman was selected as the standard patient according to the demographics of patients with primary hyperparathyroidism.

RESULTS

Organs receiving the highest radiation dose from 4D CT were the thyroid (150.6 mGy) and salivary glands (137.8 mGy). For scintigraphy, the highest organ doses were to the colon (41.5 mGy), gallbladder (39.8 mGy), and kidneys (32.3 mGy). The ED was 28 mSv for 4D CT, compared with 12 mSv for scintigraphy. In the exposed standard patient, the lifetime attributable risk for cancer incidence was 193 cancers/100,000 patients for 4D CT and 68 cancers/100,000 patients for scintigraphy. Given a baseline lifetime incidence of cancer of 46,300 cancers/100,000 patients, imaging results in an increase in lifetime incidence of cancer over baseline of 0.52% for 4D CT and 0.19% for scintigraphy.

CONCLUSION

The ED of 4D CT is more than double that of scintigraphy, but both studies cause negligible increases in lifetime risk of cancer. Clinicians should not allow concern for radiation-induced cancer to influence decisions regarding workup in older patients.

Is Intraoperative Parathyroid Hormone Monitoring Warranted in Cases of 4D-CT/Ultrasound Localized Single Adenomas?

Objective

To analyze the utility of intraoperative parathyroid hormone (IOPTH) monitoring for patients with primary hyperparathyroidism who had evidence of single-gland disease on preoperative imaging with modified 4-dimensional computed tomography that was done in conjunction with ultrasonography (Mod 4D-CT/US).

Study Design

Case series with chart review.

Setting

Tertiary care university medical center.

Subjects and Methods

Patients were drawn from consecutive directed parathyroidectomies performed between December 2001 and June 2013 by the senior authors. All patients had primary hyperparathyroidism and underwent a Mod 4D-CT/US study that showed findings on both studies that were consistent with a single adenoma. The modified Miami criteria were used for IOPTH monitoring (parathyroid hormone decrease by >50% and into the normal range).

Results

Of 356 patients who underwent parathyroid surgery, 206 had a single gland localized on the Mod 4D-CT and the US studies. IOPTH monitoring was used in 172 cases, of which 169 had adequate clinical follow-up to assess the surgical outcome. Twenty-one patients (12.4%) had IOPTH values that did not meet modified Miami criteria after removal of one gland, of which 7 were found to have multigland disease (4.1%). Three patients (1.8%) had persistent primary hyperparathyroidism despite an IOPTH that met modified Miami criteria.

Conclusions

Although IOPTH monitoring correctly identifies a small percentage of patients with multigland disease, some patients will be subjected to unnecessary neck explorations that can result in difficult intraoperative decisions, such as whether to remove normal or equivocal-sized glands when they are encountered.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

KEY POINTS

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

The utility of 4-dimensional computed tomography for preoperative localization of primary hyperparathyroidism in patients not localized by sestamibi or ultrasonography

BACKGROUND

To determine the sensitivity and clinical application of 4-dimensional computed tomography (4D CT) for the localization of patients with primary hyperparathyroidism when ultrasonography (US) and sestamibi scans (STS) are negative.

METHODS

We compiled a database of 872 patients with primary hyperparathyroidism who underwent parathyroid operation by a single surgeon from January 2003 to September 2013. Seventy-three patients who failed to have positive localization by US or STS were identified. Thirty-six underwent operation without a preoperative 4D CT, and 37 underwent operation after 4D CT.

RESULTS

In patients not localized by US or STS, 4D CT was 89% sensitive in localizing an abnormal parathyroid gland when reviewed blindly by a radiologist specializing in endocrine localization studies, yielding a positive likelihood ratio of 0.89 and positive predictive value of 74%. Sensitivity, positive likelihood ratio, and positive predictive value for correct gland lateralization were 93%, 0.93, and 80%. The average size of parathyroid glands removed after preoperative localization by 4D CT was 404 mg and 0.57 cm3 (SD = 280, 0.64), compared with 259 mg and 0.39 cm3 (SD = 166, 0.21) in patients not localized by 4D CT. A focused, unilateral exploration was performed in 38% of patients with preoperative localization by 4D CT compared with 19% of patients without 4D CT (χ2 = 3.0, P = .041).

CONCLUSION

4D CT provided a positive localization in a clinically substantial number of patients not able to be localized by US or STS, which enabled an increased rate of successful, focused, unilateral operations compared with patients who did not undergo a 4D CT.

Endocrine scintigraphy with hybrid SPECT/CT

Nuclear medicine imaging of endocrine disorders takes advantage of unique cellular properties of endocrine organs and tissues that can be depicted by targeted radiopharmaceuticals. Detailed functional maps of biodistributions of radiopharmaceutical uptake can be displayed in three-dimensional tomographic formats, using single photon emission computed tomography (CT) that can now be directly combined with simultaneously acquired cross-sectional anatomic maps derived from CT. The integration of function depicted by scintigraphy and anatomy with CT has synergistically improved the efficacy of nuclear medicine imaging across a broad spectrum of clinical applications, which include some of the oldest imaging studies of endocrine dysfunction.

Dynamic CT for parathyroid disease: are multiple phases necessary?

BACKGROUND AND PURPOSE

A 4D CT protocol for detection of parathyroid lesions involves obtaining unenhanced, arterial, early, and delayed venous phase images. The aim of the study was to determine the ideal combination of phases that would minimize radiation dose without sacrificing diagnostic accuracy.

MATERIALS AND METHODS

With institutional review board approval, the records of 29 patients with primary hyperparathyroidism who had undergone surgical exploration were reviewed. Four neuroradiologists who were blinded to the surgical outcome reviewed the imaging studies in 5 combinations (unenhanced and arterial phase; unenhanced, arterial, and early venous; all 4 phases; arterial alone; arterial and early venous phases) with an interval of at least 7 days between each review. The accuracy of interpretation in lateralizing an abnormality to the side of the neck (right, left, ectopic) and localizing it to a quadrant in the neck (right or left upper, right or left lower) was evaluated.

RESULTS

The lateralization and localization accuracy (90.5% and 91.5%, respectively) of the arterial phase alone was comparable with the other combinations of phases. There was no statistically significant difference among the different combinations of phases in their ability to lateralize or localize adenomas to a quadrant (P = .976 and .996, respectively).

CONCLUSIONS

Assessment of a small group of patients shows that adequate diagnostic accuracy for parathyroid adenoma localization may be achievable by obtaining arterial phase images alone. If this outcome can be validated prospectively in a larger group of patients, then the radiation dose can potentially be reduced to one-fourth of what would otherwise be administered.

How to perform parathyroid 4D CT: tips and traps for technique and interpretation

Parathyroid four-dimensional (4D) computed tomography (CT) is an imaging technique for preoperative localization of parathyroid adenomas that involves multidetector CT image acquisition during two or more contrast enhancement phases. Four-dimensional CT offers an alternative or additional tool in the evaluation of primary hyperparathyroidism. The purpose of this article is to describe the 4D CT technique and provide a practical guide to the radiologist for imaging interpretation. The article will discuss the rationale for imaging, approach to interpretation, imaging findings, and pitfalls.

Discriminating parathyroid adenoma from local mimics by using inherent tissue attenuation and vascular information obtained with four-dimensional CT: formulation of a multinomial logistic regression model

PURPOSE

To identify a set of parameters, which are based on tissue enhancement and native iodine content obtained from a standardized triple-phase four-dimensional (4D) computed tomographic (CT) scan, that define a multinomial logistic regression model that discriminates between parathyroid adenoma (PTA) and thyroid nodules or lymph nodes.

MATERIALS AND METHODS

Informed consent was waived by the institutional review board for this retrospective HIPAA-compliant study. Electronic medical records were reviewed for 102 patients with hyperparathyroidism who underwent triple-phase 4D CT and parathyroid surgery resulting in pathologically proved removal of adenoma from July 2010 through December 2011. Hounsfield units were measured in PTA, thyroid, lymph nodes, and aorta and were used to determine seven parameters characterizing tissue contrast enhancement. These were used as covariates in 10 multinomial logistic regression models. Three models with one covariate, four models with two covariates, and three models with three covariates were investigated. Receiver operating characteristic (ROC) analysis was performed to determine how well each model discriminated between adenoma and nonadenomatous tissues. Statistical differences between the areas under the ROC curves (AUCs) for each model pair were calculated, as well as sensitivity, specificity, accuracy, negative predictive value, and positive predictive value.

RESULTS

A total of 120 lesions were found; 112 (93.3%) lesions were weighed, and mean and median weights were 589 and 335 mg, respectively. The three-covariate models were significantly identical (P > .65), with largest AUC of 0.9913 ± 0.0037 (standard error), accuracy of 96.9%, and sensitivity, specificity, negative predictive value, and positive predictive value of 94.3%, 98.3%, 97.1%, and 96.7%, respectively. The one- and two-covariate models were significantly less accurate (P < .043).

CONCLUSION

A three-covariate multinomial logistic model derived from a triple-phase 4D CT scan can accurately provide the probability that tissue is PTA and performs significantly better than models using one or two covariates.

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

Accurate preoperative localization is the key to successful parathyroid surgery in the era of minimally invasive parathyroid surgery. This article presents and discusses the embryologic basis of parathyroid gland and ectopic location and different imaging modalities helpful in diagnosing and localizing parathyroid adenomas and/or hyperplasia. We also aim to review the current surgical concepts in treatment of parathyroid adenomas and/or hyperplasia, the utility of 4-dimensional computed tomography for accurate preoperative localization of hyperfunctioning parathyroid glands, imaging classification of adenomas and/or hyperplasia, and, finally, present some of the limitations of 4-dimensional computed tomography.

4D-CT for preoperative localization of abnormal parathyroid glands in patients with hyperparathyroidism: accuracy and ability to stratify patients by unilateral versus bilateral disease in surgery-naive and re-exploration patients

BACKGROUND AND PURPOSE

4D-CT is an emerging technique that uses high-resolution images, multiplanar reformats, and perfusion characteristics to identify abnormal parathyroid glands in patients with hyperparathyroidism. This study evaluates the accuracy of 4D-CT for localization and lateralization of abnormal parathyroid glands in preoperative planning for minimally invasive parathyroidectomy vs bilateral neck exploration at a tertiary referral center.

MATERIALS AND METHODS

Radiology, pathology, and operative reports were retrospectively reviewed for 208 patients with hyperparathyroidism who underwent 4D-CT and parathyroid surgery between May 2008 and January 2012. 4D-CT performance in localizing side and site was determined by use of surgical and pathologic findings as a reference.

RESULTS

Of 208 patients, 155 underwent initial surgery and 53 underwent re-exploration parathyroid surgery. No lesions were found in 8 patients (3.8%). A total of 284 lesions were found in 200 patients; 233 were correctly localized by 4D-CT (82.0%). Of the 200 patients with parathyroid lesions, 146 underwent unilateral and 54 bilateral neck exploration. 4D-CT correctly identified unilateral vs bilateral disease in 179 (89.5%) of 200. 4D-CT correctly localized parathyroid lesions in 126 of the unilateral cases (86.3%). In the re-exploration cohort, 4D-CT correctly identified unilateral vs bilateral disease in 46 (95.8%) of 48. There was no statistically significant difference in subgroups stratified by surgery type (primary or subsequent) and number of scan phases (3 or 4) (P > .56).

CONCLUSIONS

4D-CT leverages modern high-resolution CT scanning and dynamic contrast enhancement to localize abnormal parathyroid glands in patients with hyperparathyroidism of any cause and can be used for planning minimally invasive parathyroidectomy vs bilateral neck exploration.

Preoperative localization strategies for primary hyperparathyroidism: an economic analysis

BACKGROUND

Strategies for localizing parathyroid pathology preoperatively vary in cost and accuracy. Our purpose was to compute and compare comprehensive costs associated with common localization strategies.

METHODS

A decision-analytic model was developed to evaluate comprehensive, short-term costs of parathyroid localization strategies for patients with primary hyperparathyroidism. Eight strategies were compared. Probabilities of accurate localization were extracted from the literature, and costs associated with each strategy were based on 2011 Medicare reimbursement schedules. Differential cost considerations included outpatient versus inpatient surgeries, operative time, and costs of imaging. Sensitivity analyses were performed to determine effects of variability in key model parameters upon model results.

RESULTS

Ultrasound (US) followed by 4D-CT was the least expensive strategy ($5,901), followed by US alone ($6,028), and 4D-CT alone ($6,110). Strategies including sestamibi (SM) were more expensive, with associated expenditures of up to $6,329 for contemporaneous US and SM. Four-gland, bilateral neck exploration (BNE) was the most expensive strategy ($6,824). Differences in cost were dependent upon differences in the sensitivity of each strategy for detecting single-gland disease, which determined the proportion of patients able to undergo outpatient minimally invasive parathyroidectomy. In sensitivity analysis, US alone was preferred over US followed by 4D-CT only when both the sensitivity of US alone for detecting an adenoma was ≥ 94 %, and the sensitivity of 4D-CT following negative US was ≤ 39 %. 4D-CT alone was the least costly strategy when US sensitivity was ≤ 31 %.

CONCLUSIONS

Among commonly used strategies for preoperative localization of parathyroid pathology, US followed by selective 4D-CT is the least expensive.

Imaging techniques in parathyroid surgery for primary hyperparathyroidism

As more patients present with the incidental diagnosis of primary hyperparathyroidism due to biochemical screening, treatment guidelines have been developed for the treatment of hyperparathyroidism. Management of primary hyperparathyroidism has evolved in recent years, with considerable interest in minimally invasive approaches. Successful localization of the diseased gland(s) by nuclear imaging and anatomical studies, along with rapid intraoperative parathyroid hormone assay, has allowed for focused and minimally invasive surgical approaches. Patients in whom the localization studies have identified single-gland adenoma or unilateral disease are candidates for such focused approaches instead of the traditional approach of bilateral exploration. These imaging techniques have also been critical in the successful management of patients with persistent or recurrent disease.

Parathyroid lesions: characterization with dual-phase arterial and venous enhanced CT of the neck

This clinical report describes the enhancement characteristics of hypersecreting parathyroid lesions on dual-phase neck CT. We retrospectively analyzed the enhancement characteristics of 5 pathologically confirmed PTH-secreting lesions on dual-phase CT examinations. Attenuation values were measured for PTH-secreting lesions, vascular structures (CCA and IJV), and soft tissue structures (thyroid gland, jugulodigastric lymph node, and submandibular gland). From the attenuation values, "relative enhancement washout percentage" and "tissue-vascular ratio" were calculated and compared. All lesions decreased in attenuation from arterial to venous phase, while the mean attenuation values of other soft tissue structures increased. A high relative enhancement washout percentage was correlated with parathyroid lesions (P < .006). The tissue-CCA ratio and tissue-IJV ratio for PTH-secreting lesions in the arterial phase were statistically significantly higher compared with soft tissue structures (P < .05). If these results are validated in future larger studies, noncontrast and delayed venous phases of 4D-CT could be eliminated to markedly reduce radiation exposure.

Localization of Small Parathyroid Adenomas Using Modified 4-Dimensional Computed Tomography/Ultrasound

Objective. To investigate whether parathyroid gland weight has an impact on the accuracy of preoperative localization of parathyroid adenomas with modified 4 dimensional computed tomography/ultrasound. And to determine if the weight of parathyroid adenomas can be calculated accurately based on the dimensions of the gland on the CT images.

Study Design. Case series with chart review.

Setting. Tertiary care hospital.

Subjects and Methods. One hundred forty-two patients who had a preoperative modified 4-dimensional computed tomography/ultrasound and underwent parathyroidectomy for hyperparathyroidism due to a parathyroid adenoma between 1998 and 2009. Charts were reviewed to identify (1) the sensitivity and specificity for localization of parathyroid adenomas according to gland weight and (2) correlation between preoperative estimate of parathyroid weight and the surgical weight of the parathyroid gland.

Results. Modified 4-dimensional computed tomography/ultrasound displayed 92% sensitivity for localizing adenomas weighing <150 mg to the correct side of the neck (95% confidence interval [CI], 65%-99%), 100% sensitivity for glands weighing 150 to 500 mg (95%-100%), and 98% sensitivity for glands weighing >500 mg (92%-100%). For localization to the correct quadrant of the neck, sensitivity was 75% (95% CI, 47%-91%) for glands weighing <150 mg, 89% (79%-95%) for those weighing 150 to 500 mg, and 94% (85%-97%) for glands weighing >500 mg. A positive correlation was seen between the preoperative weight estimate based on imaging and the operative weight of the gland, with a Pearson correlation coefficient of 0.96.

Conclusion. Modified 4-dimensional computed tomography/ultrasound can closely predict the weight of parathyroid glands preoperatively and has good sensitivity for localization of adenomas, even in glands weighing less than 150 mg.