Laleh Daftaribesheli MD, Presenter: Nothing to Disclose

Emad Ahmadi MD, Abstract Co-Author: Nothing to Disclose

Omid Khalilzadeh MD, MPH, Abstract Co-Author: Nothing to Disclose

Rajiv Gupta PhD, MD, Abstract Co-Author: Nothing to Disclose

Compared to thyroid, parathyroid is hypothesized to uptake more amounts of iodine after iodine contrast injection, and to have more rapid iodine washout in delayed images. The aim of this study was to ease the distinction of parathyroid from thyroid gland in CT images by comparing the changes of iodine content in these two glands over time after iodine contrast injection. Using dual-energy CT, we also aimed to minimize radiation exposure by eliminating the pre-contrast phase.

We retrospectively studied seven CT angiograms of head and neck that had been performed for vascular assessment of patients. The imaging protocol included iodine contrast injection followed by one post-contrast dual-energy CT image and one delayed image after injection. We defined regions of interest over parathyroid and thyroid gland, computed the iodine content in these regions using dual-energy CT post-processing software, and subtracted the iodine content in delayed image from that of the post-contrast image. This iodine content change was then compared between thyroid and parathyroid glands.

Our study includes 5 males and 2 females with the mean age of 67. Our analysis showed that the iodine content decrease from post-injection to delayed image was 6.2 ± 1.8 for parathyroid gland, and it was 2.1 ± 2.1 for the thyroid gland. The figure shows the changes of iodine content over time in both parathyroid and thyroid glands, as well as the defined regions of interest for two representative cases.

Using a two-phase dual energy CT scan (post-contrast and delayed phase), parathyroid tissue can be distinguished from thyroid gland based on the pattern of iodine content changes between the phases.

Difference between iodine content of post-contrast image and delayed post-contrast image in the parathyroid and thyroid tissue might enable clinicians to differentiate the two tissues reliably. Distinction of parathyroid from thyroid tissues in dual-energy CT images might be facilitated by superimposing computed images on the CT image that are encoded based on changes of iodine content from post-injection to delayed-phase images.

Daftaribesheli, L, Ahmadi, E, Khalilzadeh, O, Gupta, R, Application of the Dual Energy CT Scan for Differentiation of Parathyroid Gland from Thyroid Gland Based on Enhancement Characteristics.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14018995.html