Affiliations: Medical Physics Section, Department of Radiology,
University of Minnesota, Minneapolis, MN, USA
Note: [] Corresponding author: Jie Zhang, Ph.D, Department of Radiology,
University of Minnesota, B271 Mayo, MMC 292 Mayo 8292, 420 Delaware St SE,
Minneapolis, MN 55455, USA. Tel.: +1 612 624 8183; Fax: +1 612 626 1951;
E-mail: [email protected]
Abstract: This study compared patient dose and image quality of a mobile
O-arm™ cone beam imaging system in the 3D scan
acquisition mode to those of a 64 slice Computed Tomography (CT) imaging
system. The investigation included patient dose, scattered radiation, and image
quality measurements. The patient dose was measured using a 0.6cc Farmer ion
chamber and 30cm long Computed Tomography (CT) head and body
polymethylmethacrylate (PMMA) phantoms. The results show that under identical
radiographic techniques (kVp, mAs, etc.) and with the same scan length, the
O-arm™ in 3D scan acquisition mode delivers
approximately half the radiation dose of a 64 slice CT scanner. Scattered
radiation was measured at several locations around the O-arm™, at 1 m, 2 m and 3 m distances in 3D CT scan acquisition mode
with a RadCal 10 × 5–180 pancake ion chamber using a
30 cm long CT body phantom as the source of scatter. Similar measurements were
made in a 64 slice CT scanner. The data demonstrate that scattered radiation
from the O-arm™ to personnel involved in a clinical
procedure is comparable to that from a 64 slice CT scanner. Image quality was
compared by exposing a CATPHAN phantom to comparable doses in both the
O-arm™ and the CT scanner. The resultant images were
then evaluated for modulation transfer function (MTF), high-contrast spatial
resolution, and low contrast sensitivity for clinical application purpose. The
O-arm™ shows comparable high contrast to the CT
(7 lp/cm vs. 8 lp/cm). The low contrast in the O-arm™
is not visible due to fixed pattern noise. For image guided
surgery applications where the location of a structure is emphasized over a
survey of all image details, the O-arm™ has some
advantages due to wide radiation beam coverage and lower patient dose. The
image quality of the O-arm™ needs significant
improvement for other clinical applications where high image quality is
desired.
