How to Perform 4D CT for Parathyroid Localization

Abstract

Introduction: Four-dimensional CT (4D CT) can be used in the setting of hyperparathyroidism to localize parathyroid adenomas. In particular, 4D CT can help differentiate an adenoma from common decoys to localize ectopic lesions and identify multigland disease. The purpose of this video was to provide an introduction and general overview of this imaging modality for clinicians who treat patients with hyperparathyroidism. Materials and Methods: Imaging is performed with a 64-detector row CT scanner (Philips, Andover, MA) with the following specifications: 180 to 400 mA, 120 kV, and 180 mm field of view. To minimize the radiation dose, coverage is customized from the mandible to the aorticopulmonary window. The patient is situated in the supine position with the shoulders retracted caudally within the limits of patient comfort. The patient is passed through the scanner for the initial precontrast imaging phase. Contrast is subsequently delivered through a 20-gauge cannula in the antecubital vein. We administered 75 mg of iohexol 300 followed by a saline chaser. For patients with normal cardiac output, we used a bolus tracking technique. Additional images are obtained after 30 and 90 seconds following contrast administration. Results: There is a characteristic appearance of parathyroid glands on 4D CT imaging: low attenuation on precontrast images, peak in enhancement in the arterial phase (30 seconds), and then washout of contrast material from the arterial to venous phase (90 seconds).1 4D CT offers improved sensitivity for localization of parathyroid adenomas compared to scintigraphy in all its varieties.2,3 In addition, 4D CT demonstrates a lower radiation burden (12.4 vs 18.0 mSv) compared to dual-phase SPECT-CT sestamibi at our institution. Conclusions: In coordination with high-resolution ultrasonography performed by an experienced practitioner, 4D CT can be used to localize parathyroid adenomas with excellent sensitivity and an unparalleled degree of anatomic detail. In addition, 4D CT offers the potential benefit of decreased radiation exposure compared to scintigraphy. 4D CT may be recommended as either the first- or second-line procedure for the localization of parathyroid adenomas. No competing financial interests exist. Runtime of video: 8 mins 49 secs