Edwin H.G. Oei MD, PhD, Presenter: Nothing to Disclose

J. H. J. M. Bessems MD, Abstract Co-Author: Nothing to Disclose

Dieuiwke Schiphof PhD, Abstract Co-Author: Nothing to Disclose

Abida Zahra Ginai MD, PhD, Abstract Co-Author: Nothing to Disclose

Jan Heeringa MD, PhD, Abstract Co-Author: Nothing to Disclose

Gabriel P. Krestin MD, PhD, Abstract Co-Author: Consultant, General Electric Company Research Grant, General Electric Company Research Grant, Bayer AG Research Grant, Siemens AG Speakers Bureau Siemens AG

Albert Hofman MD, PhD, Abstract Co-Author: Nothing to Disclose

Meike Willemijn Vernooij MD, Abstract Co-Author: Nothing to Disclose

Sita Bierma-Zeinstra PhD, Abstract Co-Author: Nothing to Disclose

MRI of the knee is increasingly applied in population-based studies, particularly on osteoarthritis (OA). Little is known on incidental knee MRI findings in an unselected ageing population. Our purpose was to describe the prevalence and clinical relevance of incidental findings on knee MRI in females of the Rotterdam Study, an ongoing open population-based study of middle-aged and elderly.

891 female participants aged 45-60 (mean 55) from the Rotterdam Study underwent MRI of both knees (1.5 T scanner (GE)) independent of OA status. All participants gave written informed consent, including a section on incidental findings. Incidental findings were assessed by trained researchers, reviewed with an experienced musculoskeletal radiologist and classified into findings that did or did not require referral, based on clinical relevance, expected health benefit and evidence based therapeutic consequences. Age-related changes were not considered findings that needed referral because these were primary study outcomes. In accordance with informed consent, findings that required referral were reported to participants and their GP.

In 1782 MRI scans we identified 54 incidental findings (3.0%) in 52 participants, 17 of which (1.0%) in 17 participants required referral: 16 lesions suspicious of a chondroid lesion with uncertain benign characteristics and 1 large atypical cystic intraosseous abnormality. In all referrals, additional dynamic contrast-enhanced MRI was performed. Although this did neither demonstrate malignant tumor characteristics nor necessitated specific treatment in any, all referred participants are still followed-up clinically and radiologically. Among findings that did not require referral were 37 chondroid lesions in 35 participants with unequivocal benign features (central metadiaphysial lesion <1cm without endosteal scalloping).

Our findings suggest that in the general middle-aged female population incidental findings are present in 3% of knee MR scans. While referral and additional MRI was deemed necessary in 1% of MRIs, this demonstrated that incidental findings virtually all consist of chondroid tumors with low suspicion of high tumor grade.

Incidental findings are present on 3% of knee MRI scans in the general middle-aged female population and virtually all consist of chondroid tumors with low suspicion of high tumor grade.

Oei, E, Bessems, J, Schiphof, D, Ginai, A, Heeringa, J, Krestin, G, Hofman, A, Vernooij, M, Bierma-Zeinstra, S, Incidental Findings and Their Clinical Relevance Magnetic Resonance Imaging (MRI) of the Knee in an Open Population-based Study of Middle-aged Females.  Radiological Society of North America 2013 Scientific Assembly and Annual Meeting, December 1 - December 6, 2013 ,Chicago IL. http://archive.rsna.org/2013/13017570.html