Development and validation of SCAISS, a tool for semi-automated quantification of sacroilitis by magnetic resonance in spondyloarthritis

Abstract

To develop a semi-automated method to quantify inflammation in sacroiliac (SI) joints by measuring bone marrow edema (BME) on MRI. The SCAISS was designed as an image-processing software. Validation followed: (1) three readers evaluated SI images of 23 patients with axial SpA and various levels of BME severity with the SCAISS, and two non-automated methods, SPARCC and Berlin; (2) 20 readers evaluated 12 patients images, also with the three methods; (3) 203 readers evaluated 12 patient images with the Berlin and the SCAISS. Convergent validity, reliability and feasibility were estimated in the first two steps and reliability was confirmed with the third. The interobserver reliability (ICC and 95% CI) in the three observers' study was similar across methods: SCAISS = 0.770 (0.580-0.889); Berlin = 0.725 (0.537-0.860); and SPARCC = 0.824 (0.671-0.916). In the 20 observers' study, ICC was: SCAISS = 0.801 (0.653-0.927); Berlin = 0.702 (0.518-0.882); and SPARCC = 0.790 (0.623-0.923). In the 203 observers' study, ICC were: SCAISS = 0.810 (0.675-0.930), and Berlin = 0.636 (0.458-0.843). SCAISS showed good convergent validity (r with SPARCC = 0.760). Median time (interquartile range) employed in the reading procedure was 28 (27) seconds for the SCAISS, 14 (9) for the Berlin score, and 94 (68) for the SPARCC. The SCAISS permits a valid, reliable, and fast calculation of overall BME lesion at the SI joint on MRI images not dependent on readers' experience.

The semi-automated algorithm for the detection of bone marrow oedema lesions in patients with axial spondyloarthritis

“…MRI of sacroiliac joints performed in our centre consists of 18-22 slices (for slice thickness equal to 3 mm) and the joint space is visible on approximately 8-12 slices. In consequence, an analysis time of the whole MRI examination of one patient is up to 10 s for our technique, which is faster than median analysis time of Zarco et al method-28 s [5]. Processing time reduction for the second method of reference signal calculation is a result of an identical average reference signal intensity and its standard deviation for all tested pixels.…”

“…In the second case, the risk of the diagnostic mistake is high, as only well-marginated, highly hyperintense part of a change might draw the attention of the evaluating radiologist, and hence the magnitude of the lesion would be underestimated. The second problem was solved by Zarco et al tool which was invented for the semi-automated detection of bone marrow oedema borders and further lesions scoring [5]. The concept of this software is completely different from ours, as it requires the mouse-click within the suspected change to detect its actual borders, basing on predetermined tolerance range.…”

“…The majority of existing solutions focuses on the evaluation of some features of such diseases as rheumatoid arthritis (RA) and osteoarthritis (OA). Regarding axSpA, only one tool has been developed, which enables for the semi-automated quantification of active sacroiliitis in MRI [5]. However, the primary drawback of this method is that it requires manual selection of lesions (software only detects their contours) and does not detect lesions missed by the observer [5].…”

“…Regarding axSpA, only one tool has been developed, which enables for the semi-automated quantification of active sacroiliitis in MRI [5]. However, the primary drawback of this method is that it requires manual selection of lesions (software only detects their contours) and does not detect lesions missed by the observer [5]. So far, any software allowing for the detection of bone marrow oedema lesions in MRI, which do not require their manual selection, has not been designed yet, even though the need is large [6].…”

Ab1077 validation of a Simplified Spanish Tool for Semi-Automatic Quantification of Sacroiliac Inflammation by Magnetic Resonance in Spondyloarthritis (S- Scaiss).

“…Almodovar 1 , P. Zarco-Montejo 2 , A. Bueno 3 , L. M. Molinero 4 on behalf of SCAISS Study Group. 1 Hospital Universitario Fundación Alcorcón,Madrid.,Rheumatology Department.,Madrid,Spain;2 Hospital Universitario Fundación Alcorcón,Madrid.,Rheumatology Unit,Madrid,Spain;3 Hospital Universitario Fundación Alcorcón,Radiology Department,Madrid,Spain;4 ALCE ingeniería,Madrid,Spain Background: With the objective to improve quantification of sacroiliitis maintaining a practical perspective, our group developed SCAISS, a semi-automated method to measure bone marrow edema (BME) in MR images from sacroiliac (SI) joints, combining semi-axial and semi-coronal slices [1]. The 2009 ASAS definition of active sacroiliitis was based on standard semi-coronal slices only, perpendicular semi-axial slices being considered but optional [2].…”