title: Validation of automatic joint space width measurements in hand radiographs in rheumatoid arthritis.
abstract: Computerized methods promise quick, objective, and sensitive tools to quantify progression of radiological damage in rheumatoid arthritis (RA). Measurement of joint space width (JSW) in finger and wrist joints with these systems performed comparable to the Sharp-van der Heijde score (SHS). A next step toward clinical use, validation of precision and accuracy in hand joints with minimal damage, is described with a close scrutiny of sources of error. A recently developed system to measure metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints was validated in consecutive hand images of RA patients. To assess the impact of image acquisition, measurements on radiographs from a multicenter trial and from a recent prospective cohort in a single hospital were compared. Precision of the system was tested by comparing the joint space in mm in pairs of subsequent images with a short interval without progression of SHS. In case of incorrect measurements, the source of error was analyzed with a review by human experts. Accuracy was assessed by comparison with reported measurements with other systems. In the two series of radiographs, the system could automatically locate and measure 1003/1088 (92.2%) and 1143/1200 (95.3%) individual joints, respectively. In joints with a normal SHS, the average (SD) size of MCP joints was [Formula: see text] and [Formula: see text] in the two series of radiographs, and of PIP joints [Formula: see text] and [Formula: see text]. The difference in JSW between two serial radiographs with an interval of 6 to 12 months and unchanged SHS was [Formula: see text], indicating very good precision. Errors occurred more often in radiographs from the multicenter cohort than in a more recent series from a single hospital. Detailed analysis of the 55/1125 (4.9%) measurements that had a discrepant paired measurement revealed that variation in the process of image acquisition (exposure in 15% and repositioning in 57%) was a more frequent source of error than incorrect delineation by the software (25%). Various steps in the validation of an automated measurement system for JSW of MCP and PIP joints are described. The use of serial radiographs from different sources, with a short interval and limited damage, is helpful to detect sources of error. Image acquisition, in particular repositioning, is a dominant source of error.
authors.affiliation: University of Twente , MIRA Institute for Biomedical Technology and Technical Medicine, Drienerlolaan 5, 7522 NB, Enschede, The Netherlands.
authors.forename: Olga
authors.initials: O
authors.lastname: Schenk
authors.affiliation: University Medical Center Utrecht, Image Sciences Institute, Heidelberglaan 100, 3584 CX, Utrecht, The Netherlands; University Medical Center Utrecht, Department of Rheumatology and Clinical Immunology, Heidelberglaan 100, 3584 CX, Utrecht, The Netherlands.
authors.forename: Yinghe
authors.initials: Y
authors.lastname: Huo
authors.affiliation: University Medical Center Utrecht , Image Sciences Institute, Heidelberglaan 100, 3584 CX, Utrecht, The Netherlands.
authors.forename: Koen L
authors.initials: KL
authors.lastname: Vincken
authors.affiliation: Department of Rheumatology , Medisch Spectrum Twente, Koningsplein 1, 7512 KZ, Enschede, The Netherlands.
authors.forename: Mart A
authors.initials: MA
authors.lastname: van de Laar
authors.affiliation: Department of Rheumatology , Medisch Spectrum Twente, Koningsplein 1, 7512 KZ, Enschede, The Netherlands.
authors.forename: Ina H H
authors.initials: IH
authors.lastname: Kuper
authors.affiliation: University of Twente , MIRA Institute for Biomedical Technology and Technical Medicine, Drienerlolaan 5, 7522 NB, Enschede, The Netherlands.
authors.forename: Kees C H
authors.initials: KC
authors.lastname: Slump
authors.affiliation: University Medical Center Utrecht , Department of Rheumatology and Clinical Immunology, Heidelberglaan 100, 3584 CX, Utrecht, The Netherlands.
authors.forename: Floris P J G
authors.initials: FP
authors.lastname: Lafeber
authors.affiliation: Department of Rheumatology , Ziekenhuisgroep Twente, Geerdinksweg 141, 7555 DL, Hengelo, The Netherlands.
authors.forename: Hein J
authors.initials: HJ
authors.lastname: Bernelot Moens
keywords: automated measurements; computer assisted measurements; image analysis; rheumatoid arthritis