CT of the sacroiliac joints. Dosimetry and optimal settings for a high-resolution technique.
OBJECTIVE
The aim was to select an optimal technique for low-dose high-resolution CT of the sacroiliac joints (SJ).


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.


CONCLUSIONS
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.
Damilakis
J
J
Department of Medical Physics, University of Crete, Faculty of Medicine, Iraklion, Greece.
Prassopoulos
P
P
Perisinakis
K
K
Faflia
C
C
Gourtsoyiannis
N
N
D000465:Algorithms; D016477:Artifacts; D005374:Filtration / Q000295:instrumentation; D006801:Humans; D019047:Phantoms, Imaging / Q000706:statistics & numerical data; D011829:Radiation Dosage; D012446:Sacroiliac Joint / Q000000981:diagnostic imaging*; D013819:Thermoluminescent Dosimetry / Q000295:instrumentation; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods* / Q000706:statistics & numerical data