Zero Time‐to‐Echo Imaging of the Hand and Wrist in Rheumatoid Arthritis Patients

BACKGROUND: Zero time-to-echo (ZTE) imaging allows for signal acquisition from tissues with extremely short T2* relaxation times, enabling the generation of computed tomography (CT)-like images through gray-scale inversion. PURPOSE: To assess the usefulness of adding ZTE imaging to conventional MRI for the detection of hand and wrist bone erosions in rheumatoid arthritis (RA) patients, using CT as the reference method. STUDY TYPE: Prospective. SUBJECTS: Fifteen patients with RA (4 male and 11 female; mean age, 61.8 ± 15.5 years) participated in this study. FIELD STRENGTH/SEQUENCE: 3-T, T1-weighted image (fast spin echo), T2-weighted image (fast spin echo), ZTE imaging (gradient echo). ASSESSMENT: Three radiologists independently evaluated bone erosions on plain radiography, conventional MRI, and ZTE imaging using a four-point scale (0 = normal; 1 = discrete erosion; 2 ≤ 50% of joint surface involvement; 3 ≥ 50%). Bone erosion was defined as a sharply delineated juxta-articular lesion with a cortical defect. A total of 25 anatomical sites per hand and wrist were assessed, including the distal radius and ulna, eight carpal bones, metacarpal bases, and proximal and distal aspects of the metacarpophalangeal joints. CT was interpreted by a musculoskeletal radiologist and served as the reference standard. STATISTICAL TESTS: Diagnostic performance (sensitivity and specificity) was compared with the McNemar test, and interobserver variability was assessed using Fleiss κ statistics. p values less than 0.01 were considered significant. RESULTS: The sensitivity and specificity of plain radiography, conventional MRI, and ZTE were 40.6/98.9%, 72.6/94.6%, and 95.9/97.6%, respectively. Interobserver agreement on bone erosion assessment was excellent for ZTE imaging (κ value of 0.822) but fair for plain radiography (κ value of 0.427) and good for conventional MRI (κ value of 0.711). DATA CONCLUSIONS: ZTE imaging can provide reliable bone erosion assessment in RA patients. TECHNICAL EFFICACY: Stage 2.