Karen Margaret Horton MD, Abstract Co-Author: Research support, Siemens AG Advisory Board, Siemens AG Research support, General Electric Company Advisory Board, General Electric Company

Sameer Ahmed BS, Abstract Co-Author: Nothing to Disclose

Atif Zaheer MD, Abstract Co-Author: Nothing to Disclose

Salina Doris Tsai MD, Abstract Co-Author: Nothing to Disclose

Pamela Tecce Johnson MD, Presenter: Nothing to Disclose

Elliot K. Fishman MD, Abstract Co-Author: Research support, Siemens AG Advisory Board, Siemens AG Research support, General Electric Company Advisory Board, General Electric Company Co-founder, HipGraphics, Inc

Hong C. Lai MPH, Abstract Co-Author: Nothing to Disclose

To determine the prevalence of unsuspected thyroid nodules on MDCT of the chest, in a population of adult outpatients imaged for indications other than thyroid disease.

3077 consecutive adult outpatient's IV contrast enhanced 16- and 64-MDCT scans of the chest were reviewed retrospectively, to identify unsuspected thyroid nodules. Exclusion criteria included history of thyroid cancer, known thyroid nodules or thyroid disease and risk factors for thyroid cancer, as evidenced by their medical records. One of 9 radiologists recorded number of nodules, location and bidirectional measurement of largest nodule, as well as amount of thyroid visualized on the chest CT. Presence of nodule was correlated with age, gender, race and percentage of thyroid imaged.

Included were 2510 subjects, 1288 men (51.3%) and 1222 (48.7%) women. Mean age was 59.3 years (range 18 - 94 years). Women more frequently had 1 nodule (206/1222 or 16.86% of women vs. 181/1288 or 14.1 % of men) and multiple nodules (167/1222 or 13.7% of women and 75/1288 or 5.8% of men) (p<.0001). There was a significant difference in the mean age of patients with no nodules (57.8 years), 1 nodule (62.4 years) and multiple nodules (66.2 years) (p<0.05). No association was shown with race (p=0.56). One or more nodules were identified in 629 subjects (25.1%). More than half of these subjects had 1 nodule (61.5%, 387/629). Mean maximum diameter was 8.56 mm (standard deviation 6.43 mm, range 1-62 mm). Most nodules were < 1 cm (426 or 67.8%), as opposed to 1 cm or greater (202 or 32.2%). The entire thyroid gland was imaged in 55.3% (1389/2510), more than half of the thyroid gland was imaged in 36.9% (925/2510) and less than half in 7.8% (196/2510). Of the patients who had the entire thyroid imaged (N=1389), nodules were identified in 352 (25.3%), compared to 277/1121 (24.7%) whose thyroid was only partially imaged. Presence of a nodule was not associated with percentage of thyroid imaged (p=0.72).

In this series of adult outpatients, the prevalence of unsuspected thyroid nodules on contrast-enhanced chest CT was 25%. The presence of a nodule was significantly associated with female gender and increasing age.

By recognizing the frequency of incidental thyroid nodules, the radiologist will better appreciate why a standard approach and reporting of these lesions is so critical.

Horton, K, Ahmed, S, Zaheer, A, Tsai, S, Johnson, P, Fishman, E, Lai, H, Prevalence of Unsuspected Thyroid Lesions on IV Contrast-enhanced 64 MDCT of the Thorax.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9000911.html