title: MRI thresholds for discrimination between normal and mild temporomandibular joint involvement in juvenile idiopathic arthritis.
abstract: BACKGROUND
  Currently there is no consensus agreement on the degree of enhancement in normal temporomandibular joints (TMJ) in children, which makes it difficult for clinicians to distinguish between the presence/absence of mild synovitis. Quantitative measurements of synovial and condylar enhancement may be useful additions to current qualitative methods on early MRI diagnosis and follow up of TMJ involvement in JIA. The purpose of the study is to establish thresholds/tendencies for quantitative measures that enable distinction between mild TMJ involvement and normal TMJ appearance based on the degree of synovial and bone marrow enhancement in JIA patients.
  
  
  METHODS
  TMJ MRI examinations in 67 children with JIA and in 24 non-rheumatologic children who underwent MRI for neurologic/orbit indications were retrospectively assessed. As a priori determined TMJs of JIA patients were categorized into three groups by experienced staff radiologists based on the degree of synovial and condylar enhancement: no active disease (rheumatologic control), mild and moderate/severe findings. The signal intensity (SI) of the synovial tissue around each condyle and of the bone marrow was measured to calculate the enhancement ratio (ER) and relative SI change. The ER was calculated using signal to noise ratios, while relative SI change was calculated using signal intensities alone. Quantitative measurements of synovial and condylar enhancement of TMJs with mild or moderate/severe findings were compared with the rheumatologic and non-rheumatologic controls.
  
  
  RESULTS
  Mean ER values were significantly different between the TMJs without active disease and those with mild and moderate/severe synovial enhancement, with highest values in the moderate/severe group (P < 0.0001). Similar findings were seen for condylar enhancement with P < 0.005. Relative SI change was unable to differentiate TMJs with mild synovitis from the two controls (P > 0.10). 27/60 (45%) TMJs without active disease had osteochondral changes. 8/40 (20%) TMJs in the mild group did not demonstrate any synovial thickening.
  
  
  CONCLUSIONS
  Quantitative signal to noise ratios of TMJ synovial and condylar enhancement generate thresholds/tendencies, which offer additional information to differentiate mild synovitis from normal TMJs in JIA patients. Osteochondral changes and synovial thickening may not be reliable indicators of active TMJ involvement and should be differentiated from synovial enhancement.
authors.affiliation: Department of Radiology, Ohio State University Wexner Medical Center, 410 West 10th Ave, Columbus, OH, 43210, USA. grace.ma@osumc.edu.
authors.forename: Grace Mang Yuet
authors.initials: GM
authors.lastname: Ma
authors.affiliation: Department of Diagnostic Imaging, The Hospital for Sick Children, 555 University Avenue, Toronto, ON, M5G1X8, Canada. afsaneh.amirabadi@sickkids.ca.
authors.forename: Afsaneh
authors.initials: A
authors.lastname: Amirabadi
authors.affiliation: Department of Diagnostic Imaging, Hospital Sant Joan de Deu, Passeig Sant Joan de Déu, 2, 08950 Esplugues de Llobregat, Barcelona, Spain. emilioinarejos@gmail.com.
authors.forename: Emilio
authors.initials: E
authors.lastname: Inarejos
authors.affiliation: Department of Diagnostic Imaging, The Hospital for Sick Children, 555 University Avenue, Toronto, ON, M5G1X8, Canada. mirkamal.tolend@sickkids.ca.
authors.forename: Mirkamal
authors.initials: M
authors.lastname: Tolend
authors.affiliation: Department of Diagnostic Imaging, The Hospital for Sick Children, 555 University Avenue, Toronto, ON, M5G1X8, Canada. jennifer.stimec@sickkids.ca.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Stimec
authors.affiliation: Department of Family and Community Medicine, University of Toronto, 500 University Ave, Toronto, ON, M5G 1V7, Canada. rahim.moineddin@utoronto.ca.
authors.forename: Rahim
authors.initials: R
authors.lastname: Moineddin
authors.affiliation: Department of Rheumatology, The Hospital for Sick Children, 555 University Avenue, Toronto, ON, M5G1X8, Canada. Lynn.Spiegel@sickkids.ca.
authors.forename: Lynn
authors.initials: L
authors.lastname: Spiegel
authors.affiliation: Department of Diagnostic Imaging, The Hospital for Sick Children, 555 University Avenue, Toronto, ON, M5G1X8, Canada. andrea.doria@sickkids.ca.
authors.forename: Andrea S
authors.initials: AS
authors.lastname: Doria
mesh_terms: D000293:Adolescent; D001171:Arthritis, Juvenile / Q000150:complications / Q000175:diagnosis* / Q000473:pathology; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D013704:Temporomandibular Joint / Q000033:anatomy & histology / Q000473:pathology; D013705:Temporomandibular Joint Disorders / Q000175:diagnosis* / Q000209:etiology / Q000473:pathology