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CT of the sacroiliac joints. Dosimetry and optimal settings for a high-resolution technique
J Damilakis1, P Prassopoulos, K Perisinakis
1Department of Medical Physics, University of Crete, Faculty of Medicine, Iraklion, Greece.
Purpose:
The aim was to select an optimal technique for low-dose high-resolution CT of the sacroiliac joints (SJ).
Material And Methods:
Dose measurements were performed on a Rando anthropomorphic phantom using thermoluminescence dosimeters for 4 CT protocols and 2 conventional radiography protocols used for SJ evaluation. Six available reconstruction algorithms were tested on CT protocols using 285-665 mAs and 120 or 130 kVp settings and noncontiguous 1.5-mm-thin sections with 3.5-mm intervals. Settings with optimum performance on phantom tests were also applied in a series of 10 patients with SJ arthropathies.
Results:
A CT protocol using 120 kVp/175 mA/2.9 s/1.5-mm slice thickness/5-mm table increment implied the lower radiation dose among all examination protocols tested and provided high image quality of the SJ. A reconstruction algorithm yielding images of improved spatial resolution with acceptable noise was selected.
Conclusion:
A high spatial frequency reconstruction algorithm, and 120 kVp and 508 mAs were considered optimal for a low-dose CT examination of the SJ that employed narrow (1.5 mm) slice images with interspacing.