Four-dimensional computed tomography protocol for preoperative evaluation of the parathyroid glands and its correlations with other imaging methods: a pictorial essay

Abstract

Parathyroid adenoma is the most common cause of primary hyperparathyroidism. Advances in surgical techniques have made it possible to excise only the affected parathyroid gland in most cases. Imaging examinations play a fundamental role in the preoperative planning of parathyroidectomy. To localize the parathyroid glands, imaging tests such as scintigraphy, ultrasound, and, more recently, four-dimensional computed tomography (4D CT). The aim of this pictorial review was to illustrate the use of the 4D CT protocol in cases of parathyroid adenoma and to determine how well it correlates with other imaging methods, in order to improve understanding of the 4D CT method.

Keywords: Adenoma/diagnostic imaging; Four-dimensional computed tomography/methods; Hyperparathyroidism/surgery; Parathyroid neoplasms/diagnostic imaging.

Figure 1

Normal 4D CT protocol. A: Unenhanced image showing hyperattenuating thyroid tissue (rectangle) in relation to adjacent lymph node (circle). B: Image acquired in the arterial phase, showing the absence of significant enhancement of the nodule (circle) and adjacent thyroid tissue (rectangle). C: Image acquired in the venous phase.

Figure 2

Parathyroid adenoma evaluated with the 4D CT protocol. A: Note the area of hypoattenuation (circle) adjacent to the lower third of the thyroid gland (rectangle), which is hyperattenuating in relation to adjacent structures. B: Contrast-enhanced image showing avid enhancement of the nodule (circle) in the arterial phase. C: Note the contrast wash-out in the late phase (circle).

Figure 3

Parathyroid adenoma evaluated with the 4D CT protocol, shown in different reconstructions. A: Image of a hyperattenuating lymph node in the arterial phase, showing avid contrast enhancement (circle). In larger lesions such as this one, enhancement is not always homogeneous. B: Image showing the nodule (rectangle) in the sagittal plane. C: Image showing the nodule (rectangle) in the coronal plane.

Figure 4

Examples of ectopic parathyroid adenomas. Mediastinal adenoma, adjacent to the aortic arch (circle). A: Unenhanced CT scan (in a patient with a history of an allergic reaction to contrast agents). B: Correlation of the case shown in A with 99mTc-sestamibi scintigraphy, showing that uptake of the radiopharmaceutical persisted (circle) at two hours after administration. C: Unenhanced CT scan of a retropharyngeal adenoma that is difficult to delimit because of the adjacent structures. D: Contrast-enhanced CT scan of the case shown in C, showing a nodule with intense contrast enhancement (circle). A biopsy of the lesion confirmed the diagnosis of ectopic parathyroid adenoma.

Figure 5

Correlation of 4D CT with 99mTc-sestamibi scintigraphy and with SPECT/CT for evaluation of the parathyroid glands. A: 4D CT in the arterial phase showing an area of avid enhancement (circle) adjacent to the common carotid artery and the lower pole of the right thyroid lobe. B,C: 99mTc-sestamibi scintigraphy acquired at 15 min and 2 h after administration, showing persistence of the radiotracer adjacent to the lower pole of the right thyroid lobe (circle). D: SPECT/CT showing uptake of the radiopharmaceutical (marker) by the adenoma.

Figure 6

Parathyroid adenoma. A: Contrast-enhanced CT scan acquired in the arterial phase, showing a nodule with avid enhancement (circle) in the left thyroid bed. B: Contrast-enhanced coronal CT scan acquired in the arterial phase, showing a polar vessel (between the red lines) feeding a nodule with avid enhancement (blue asterisk). C: Correlation with ultrasound; color Doppler showing a hypoechoic area in the left thyroid bed (circle), as well as the polar feeding vessel (red asterisks).