Four-channel multidetector CT in facial fractures: do we need 2 x 0.5 mm collimation?
OBJECTIVE
Our aim was to optimize acquisition protocols and multiplanar reformation algorithms for the evaluation of facial fractures using multidetector CT (MDCT) and to determine whether 2 x 0.5 mm collimation is necessary.


METHODS
A cadaveric head with artificial blunt facial trauma was examined using a four-channel MDCT scanner. The influence of acquisition parameters (collimation, 2 x 0.5 mm, 4 x 1 mm, 4 x 2.5 mm; tube current, 120 mAs, 90 mAs, 60 mAs), image reconstruction algorithms (standard vs ultra-high-resolution modes; reconstructed slice thicknesses, 0.5 mm, 1 mm, 3 mm; increment, 0.3 mm, 0.6 mm, 1.5 mm), and reformation algorithms (slice thicknesses, 0.5 mm, 1 mm, 3 mm; overlap, 0.5 mm, 1 mm, 3 mm) on detectability of facial fractures in multiplanar reformations with MDCT was analyzed.


RESULTS
Fracture detection was significantly higher with thin multiplanar reformations (0.5 and 0.5 mm, 1 and 0.5 mm, and 1 and 1 mm) (p < or = 0.014) acquired with 2 x 0.5 mm collimation (p < or = 0.046) in ultra-high-resolution mode (p < 0.0005) with 120 mAs (p < or = 0.025). Interobserver variability showed very good agreement (kappa > or = 0.942). Non-ultra-high-resolution mode, lower milliampere-seconds, and thick multiplanar reformations (3 and 0.5 mm, 3 and 1 mm, and 3 and 0.5 mm) showed significantly decreased fracture detectability.


CONCLUSIONS
Although thin multiplanar reformations obtained from thin collimation (2 x 0.5 mm) are statistically superior for the detection of subtle fractures, 4 x 1 mm collimation is sufficient for routine diagnostic evaluation. Ultra-high-resolution mode with 120 mAs is mandatory for detection of clinically relevant fractures.
Philipp
Marcel O
MO
Department of Radiology, Division of Surgery, University of Vienna Medical School, General Hospital Vienna, Waehringer Guertel 18-20, Austria.
Funovics
Martin A
MA
Mann
Frederick A
FA
Herneth
Andreas M
AM
Fuchsjaeger
Michael H
MH
Grabenwoeger
Florian
F
Lechner
Gerhard
G
Metz
Viktor M
VM
D000368:Aged; D000465:Algorithms; D005147:Facial Bones / Q000000981:diagnostic imaging* / Q000293:injuries*; D005151:Facial Injuries / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D015588:Observer Variation; D012680:Sensitivity and Specificity; D012887:Skull Fractures / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed; D015599:Trauma Severity Indices