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

Abstract

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%.

Fig 1.

Concentration-time curve. Peak enhancement: maximal concentration of contrast agent with time: Peak = $\underset{t}{\max }$ C(t). Time-to-peak enhancement: the time needed for the contrast agent to reach its maximum concentration: TTP = arg $\underset{t}{\max }$ C(t). Wash-in: initial upslope of the concentration-time curve (slope from the end of the baseline to the peak of the curve). Washout: down-slope of the concentration time curve (negative slope from the peak to the last acquisition time point). ΔSI indicates change in signal intensity.

Fig 2.

A 68-year-old woman with primary hyperparathyroidism (parathyroid hormone =120 pg/mL, Ca²⁺ = 11.2 mg/dL). Axial arterial phase contrast-enhanced image from MR perfusion demonstrates a PTA (arrow) in the right tracheoesophageal groove. Contrast-time curve analysis from ROIs placed over the PTA (arrow), thyroid gland, and a jugulodigastric lymph node shows significantly faster TTP and higher wash-in and washout values in the PTA compared with the thyroid gland and cervical lymph node. PTA: TTP, 37 seconds; wash-in, 7.8; washout, 0.58. Thyroid: TTP, 42 seconds; wash-in, 5.4 washout, 0.46. Lymph node: TTP, 60 seconds; wash-in, 4.8; washout, 0.29.

Fig 3.

ROC analysis with the AUC for each imaging biomarker and best combined AUC for PTA-versus-lymph node and PTA-versus-thyroid gland is shown.

Fig 4.

A 47-year-old woman with primary hyperparathyroidism (parathyroid hormone = 164 pg/mL, Ca²⁺ = 10.8 mg/dL). Axial arterial phase contrast-enhanced image from MR perfusion data demonstrates a PTA (arrow) in the left tracheoesophageal groove. Contrast-time curve analysis from ROIs placed over the PTA, thyroid gland, and a cervical lymph node shows significantly faster TTP and higher wash-in and significant washout values in the PTA compared with the thyroid gland and cervical lymph node. PTA: TTP, 30 seconds; wash-in, 5.6; washout, 0.64 Thyroid: TTP, 38 seconds; wash-in, 3.8 seconds; washout, 0.43 seconds. Lymph node: TTP, 62 seconds; wash-in, 2.9; washout, 0.23.