Four-dimensional Computed Tomography Imaging in Primary Hyperparathyroidism: Multireader Multicase Study of Both Neuroradiologists and General Radiologists of Imaging Approaches With Less Phases.

Objective: Primary hyperparathyroidism (PHPT) is commonly caused by parathyroid adenomas (PAs), and four-dimensional computed tomography (4DCT) is increasingly used for localising PAs due to its high sensitivity and specificity. However, the relative high radiation dose of 4DCT may limit its widespread use as first line imaging in some settings. A reduced phase protocol and enhancement maps, which highlight relative enhancement differences between the nonenhanced and arterial phases, have been proposed as ways to reduce radiation exposure without compromising diagnostic accuracy. This study aims to assess whether reduced 4DCT protocols can maintain diagnostic performance and if the enhancement map can further assist in adenoma localisation.

Methods: This retrospective study included 27 PHPT patients, with both single and double adenomas, and some ectopic cases and 3 secondary HPT patients. Five-phase combinations derived from our institution's 4-phase protocol were evaluated using a multireader, multicase approach involving experienced neuroradiologists and general radiologists. The phases tested included combinations of nonenhanced, arterial, venous, and delayed venous phases. An enhancement map was introduced as one of the phases. Readers were asked to identify adenomas and assign confidence levels. Performance metrics, including sensitivity, specificity, and area under the curve (AUC), were calculated, and noninferiority tests compared the results to the current 4-phase protocol.

Results: Sensitivity of the total group was between 0.64 and 0.70 with a specificity between 0.94 and 0.97. AUC were between 0.80 and 0.84. All reduced phase combinations were noninferior to the 4-phase protocol. Neuroradiologists achieved noninferior results with 1-phase to 3-phase protocols, while general radiologists required at least 3-phases. The enhancement map did not improve sensitivity or specificity, although readers found it useful as a supplementary tool for identifying lesions. Artefacts, especially in ectopic locations, reduced its effectiveness.

Conclusions: This study supports the use of reduced 4DCT protocols for PHPT. A 1-phase or 2-phase protocol is recommended for experienced radiologists, while a 3-phase protocol is suitable for less experienced radiologists.