Percentage arterial enhancement: An objective index for accurate identification of parathyroid adenoma/hyperplasia in primary hyperparathyroidism.

BACKGROUND: Radiation exposure to neck by four-dimensional computerized tomography (4DCT) is relatively high and limits its use as a first-line investigation in evaluation of primary hyperparathyroidism (PHPT). Radiation exposure can be reduced by restricting the number of CT phases. Our aim was to study the performance of 4DCT in cohort of surgery-naïve PHPT patients, and to evaluate percentage enhancement as an objective radiological index to discriminate parathyroid lesions (adenoma/hyperplasia) from thyroid tissue and lymph nodes. MATERIALS AND METHOD: Retrospective study of 49 PHPT patients {(44 single-gland diseases (SGD) and five multiple-gland disease (MGD)} who underwent 4DCT (unenhanced, early arterial, early venous and delayed venous phase) pre-operatively. Two radiologists who were blinded to surgical location of parathyroid lesions examined the scans. Attenuation values were recorded for parathyroid lesions (n=50), thyroid gland (n=50) and lymph nodes (n=12) in different phases. Percentage enhancement for different phases was calculated as "(HU in a specific enhanced phase-HU in unenhanced phase)/HU in unenhanced phase" ×100. RESULTS: Inter-rater reliability between the two radiologists was 0.83 (Cohen's kappa). In SGD, sensitivity and PPV were 93.18% and 98.8% for lateralization, and 89.77% and 95.18% for quadrant localization, respectively. In MGD, 4DCT showed 50% sensitivity and 100% PPV. Percentage arterial enhancement showed highest area under curve (AUC=0.992) for differentiation of parathyroid lesions from thyroid tissue and lymph nodes. A cut-off value of 128.9% showed 95.8% sensitivity and 100% specificity for the identification of parathyroid lesions. CONCLUSIONS: We propose that percentage arterial enhancement can be used as an objective radiological index for accurate identification of parathyroid adenoma/hyperplasia.

Dual-phase computed tomography for localization of parathyroid lesions in children and adolescents with primary hyperparathyroidism.

BACKGROUND: Childhood and adolescent primary hyperparathyroidism (PHPT) is a rare disease caused by single adenomas in 65-94% of patients. In this patient group, there is no data on computed tomography (CT) for pre-operative parathyroid localization that may facilitate focused parathyroidectomy. METHODS: Two radiologists reviewed dual-phase (nonenhanced and arterial) CT images of twenty-three operated children and adolescents [20:single-gland disease(SGD), 3:multi-glandular disease(MGD)] with proven histopathological PHPT. Percentage arterial enhancement (PAE) was calculated as [100*{arterial-phase Hounsfield unit (HU)-nonenhanced phase HU}/nonenhanced HU] of the parathyroid lesion(s), thyroid, and lymph node. RESULTS: Dual-phase CT lateralized 100%, localized to the correct quadrant/site 85% SGD (including 3/3 ectopic), and identified 1/3 MGD. PAE (cutoff ≥ 112.3%) was sensitive (91.3%) and specific (99.5%) in distinguishing parathyroid lesions from local mimics (P<0.001). The average effective dose was 3.16±1.01mSv, comparable to the planar/single photon emission CT (SPECT) Technetium 99m(Tc)-sestamibi and choline positron emission tomography (PET)/CT scans. Solid-cystic morphology identified in 4 patients harboring pathogenic germline variants (3:CDC73, 1:CASR) may serve as a radiological clue to molecular diagnosis. Nineteen out of 20 (95%) patients with SGD who had undergone single gland resection based on pre-operative CT findings were in remission over a median follow-up of 18 months. CONCLUSION: As most children/adolescents with PHPT have SGD, dual-phase CT protocols which reduce the effective radiation dose with high localization sensitivity for single parathyroid lesions may be a sustainable pre-operative imaging modality in this patient group.

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.

Radiological differentiation of phaeochromocytoma from other malignant adrenal masses: importance of wash-in characteristics on multiphase CECT.

Rationale and introduction: To evaluate the computerised tomography (CT) characteristics of phaeochromocytoma (PCC) that differentiate them from other non-benign adrenal masses such as adrenocortical carcinoma (ACC), primary adrenal lymphoma (PAL) and adrenal metastases (AM). Methods: This retrospective study was conducted at a tertiary health care institute from Western India. Patients presented between January 2013 and August 2016 with histological diagnosis of PCC or other non-benign adrenal mass having adequate reviewable imaging data comprising all four CECT phases were included. Results: The study cohort consisted of 72 adrenal masses from 66 patients (33 PCC, 22 ACC, 4 PAL, 13 AM). Unlike other masses, majority of PCC (25/33) showed peak enhancement in early arterial phase (EAP). PCC had significantly higher attenuation in EAP and early venous phase (EVP), and higher calculated percentage arterial enhancement (PAE) and percentage venous enhancement (PVE) than other adrenal masses (P < 0.001). For diagnosis of PCC with 100% specificity, PAE value ≥100% and EAP attenuation ≥100 HU had 78.8 and 63.6% sensitivity respectively. ACC were significantly larger in size as compared to PCC and metastasis. The adreniform shape was exclusively found in PAL (two out of four) and AM (4 out of 13). None of the enhancement, wash-in or washout characteristics were discriminatory among ACC, PAL and AM. Conclusion: Peak enhancement in EAP, PAE value ≥100% and EAP attenuation ≥100 HU differentiate PCC from other malignant adrenal masses with high specificity.