SAT0550 SPINAL AND PELVIC MDCT USING “iDose5” ITERATIVE RECONSTRUCTION ALGORITHM IN PATIENTS WITH PSORIATIC SPONDYLOARTHRITIS: DIAGNOSTIC CAPABILITIES AND IMAGE QUALITY IN RELATION TO RADIATION EXPOSURE

Background:Psoriatic spondyloarthritis (PsSpA) is an inflammatory arthritis related to psoriasis, whereas a large number of patients may have persistent inflammation developing gradual and in some cases extensive joint involvement of the axial skeleton.Conventional radiographs (CRs) have been used for the detection of structural damage (syndesmophyte formation, paravertebral ossification, sacroiliitis, ankyloses and erosions), facilitating as an important measure of efficacy of various therapies. However overlapping of anatomic structures of pelvis and spine as well as limited capabilities to visualize soft tissue have led to the development of newer imaging technologies (1). Multidetector CT technology (MDCT), it is now possible to perform low dose CT (ldCT) of the entire vertebral column, viewed in multiple planes and without overprojection with a low radiation dose. (2) Still, the capabilities of ldCT algorithms in the diagnosis and progression of PsSpA has not been fully explored.Objectives:The aim of this study is to examine the effect of “iDose5” iterative reconstruction algorithm on radiation dose, diagnostic capabilities and image quality in spine-pelvis (S-P) CT scanning compared with CRs, in detection of findings suggestive of PsSpA.Methods:Thirty-nine patients with PsSpA (26 females and 13 males, age range: 23 to 70 years old) were prospectively studied with “iDose5” CT of spine and pelvis on a 64-row MDCT scanner. Multiplannar reformats followed. All patients satisfied the Psoriatic Arthritis (CASPAR) classification criteria and had undergone standard AP and lateral CRs of the cervical, thoracic and lumbar spine and AP radiographs of the pelvis within one months of the iDose CT. Twenty-five patients underwent, additional MR imaging (MRI) of the same anatomic areas. Written consent was obtained from all patients. Two musculoskeletal radiologists read and scored CT scans and CRs in consensus, according to the PASRI criteria and the CTSS score. CT image quality and effective dose for CT and radiographs were assessed.All data were analyzed using SPSS 24.0 statistical software.Results:CT revealed erosions and ankyloses of the sacroiliac joints, fusion of the posterior elements of vertebra especially in the thoracic spine, enthesophytes, not seen with CRs, in 26 patients (p<0,05).Level of diagnostic confidence was higher when interpreting CT compared to CRs, in cases of erosions and ankyloses, in 35 patients (p<0,05).CT was slightly superior in the detection and characterization of syndesmophytes, enthesopathy and calcifications.Effective dose for “i-Dose 5” CT was 1.20 ± 0.26 mSv and for CR =1.07 ± 0.21 mSv. The difference was not statistically significant (p=0.588).Conclusion:iDose CT of spine and pelvis at an effective dose, lower than previously published, seems to perform better than radiographs in the detection of structural changes of PsSpA. Further studies are needed to document the capabilities of iDose CT for the imaging assessment of PsSpA in daily clinical practice.References:[1]Baraliakos Χ, et al (2009)The Natural Course of Radiographic Progression in Ankylosing Spondylitis — Evidence for Major Individual Variations in a Large Proportion of Patients The Journal of Rheumatology May, 36 (5) 997-1002[2]de Koning A et, al (2018) Low-dose CT detects more progression of bone formation in comparison to conventional radiography in patients with ankylosing spondylitis: results from the SIAS cohort. Ann Rheum Dis.;77(2):293-299.Disclosure of Interests:None declared