Kamalesh Majumdar1

MR and CT scan had equal sensitivity and specificity in the diagnosis and determination of staging of sacroiliitis in all stages of involvements of bones and joints. There was no significant mentionable difference between CT scan and MR study in the determination of bone changes like erosion, sclerosis or inflammation.
To compare the value and usefulness of CT scan and MR imaging studies in the diagnosis of sacroiliitis1 in all stages of the disease in ethnic Bengalis among West Bengal population.
Total of 45 patients attending in the outpatient department and admitted in the indoor ward of a teaching medical college in West Bengal (KPC Medical College and Hospital, Jadavpur, West Bengal) with clinical diagnosis of sacroiliitis of any stage were selected. Detail histories of the condition of the patients were taken and thorough physical examination was done. All pathological investigations2 reports were collected. In some patients, there was no previous investigation report. In those cases, fresh tests were done. Then, all reports were assessed separately for each patient. In next step, the patients were imaged and evaluated by MRI using T1, T2, STIR, two-dimensional T2* FLASH and after intravenous contrast, T1 fat saturated sequence on a GE 3.0 Tesla system.
Then, CT scan evaluation of the sacroiliac joints of the same patient were done using GE 16-slice multidetector system in the supine position with a 20° cranial gantry tilt to obtain sections through both the cartilaginous and ligamentous portions of the joints.
Findings of both the methods were charted in a tabulated form and compared with each other for the same patient. Then, statistical evaluation was done and p values were considered.
In total, 26 patients were diagnosed to have sacroiliitis by CT scan and 31 patients were diagnosed to have sacroiliitis by MRI study.
MR and CT had equal sensitivity and specificity in the diagnosis of sacroiliitis. There was no significant difference between CT and MR in the determination of erosion or sclerosis.
However, active inflammation3 in the bone and joint space change including acute arthritis can only be diagnosed by MRI study. Contrast-enhanced MRI is also an added advantage because postcontrast MRI study did give many extra information, which were not available with CT alone.
Both MRI and CT are equally useful in the diagnosis of sacroiliitis. Bone marrow oedema and enhancement that cannot be shown by CT can only be visualised by MRI (plain or contrast enhanced). Absence of ionising radiation is another advantage in MRI. However, easy availability and cost of investigation are also important factor to consider.