Background Magnetic resonance (MR) imaging allows to visualize inflammatory lesions of psoriatic arthritis (PsA). However, evaluation of the small joints of the hands remains a challenge. CT has a high spatial resolution, therefore it is suitable to evaluate small structures. In spite of this advantage, CT usage in inflammatory arthritis has been limited because of its poor contrast resolution. However, iodine map, the amount of iodine distribution in each voxel, can be created by the so-called three material decomposition from imaging data obtained with Dual-Energy CT (DE-CT)1). Because DE-CT with iodine map has both high spatial resolution and high iodine contrast resolution, we hypothesized this technic can be useful in evaluation of inflammatory lesions of PsA
Objectives To assess the feasibility of DE-CT with iodine map in the evaluation of hand PsA
Methods Materials were 16 (11 male 5 female) consecutive psoriasis patients with finger joint symptoms. All patients fulfilled CASPER criteria. The Patients were scheduled for both contrast enhanced DE-CT and contrast enhanced MR imaging within 1 month. There was no therapeutic intervention between 2 examinations. Images were evaluated by 2 radiologists independently under blinded to clinical data and other images. For evaluation of both DE-CT and MR imaging, we modified the OMERACT Psoriatic Arthritis Magnetic Resonance Imaging Scoring System (PsAMRIS)2). For inflammatory lesions (synovitis, flexor tenosynovitis, and extensor peritendinitis) graded as 0–3 and bone erosion graded as 0–10, inter-reader agreement was calculated with using weighted κ. For other inflammatory lesion (periarticular inflammation) and structural change (bone proliferation), which were scored as grade 0–1, inter-reader agreement was calculated with using κ. With using consensus score, sensitivity and specificity of DE-CT for inflammatory lesions were calculated with MR imaging as gold standard. As for structural changes, we used DE-CT as gold standard and calculated sensitivity and specificity of MR imaging.
Results Inter-reader agreement of inflammatory lesions were good or very good (weighted κ=0.83 and κ=0.75 in DE-CT, weighted κ=0.81 and κ=0.87 in MR imaging). Although inter-reader agreement of MR imaging for bone proliferation was moderate (κ=0.44), it was good (weighted κ=0.77) for bone erosion. Inter-reader agreement of CT for structural changes were good (κ=0.66) for bone proliferation and very good (weighted κ=0.84) for bone erosion. Sensitivity and specificity of DE-CT for inflammatory lesions were 0.78 and 0.87. However, DE-CT detected 134 various inflammatory lesions which were not observed on MR imaging, out of 1120 evaluated inflammatory items. Of these 134 lesion, 69% (93/134) was located in the DIP joints. About structural changes, MR imaging had poor sensitivity (0.30) and high specificity (0.99).
Conclusions DE-CT with iodine map has found to be a useful new imaging modality to evaluate PsA of hands, and may have higher detection capability of small joint inflammatory lesions compared with MR imaging.
Kuno H, et al. Radiology 2012: 265; 488–496.
Ostergaard M, et al. J Rheum 2009: 36; 1816–1824.
Disclosure of Interest None declared