Reduction in x-ray scatter and radiation dose for volume-of-interest (VOI) cone-beam breast CT--a phantom study.
With volume-of-interest (VOI) cone-beam computed tomography (CBCT) imaging, one set of projection images are acquired with the VOI collimator at a regular or high exposure level and the second set of projection images are acquired without the collimator at a reduced exposure level. The high exposure VOI scan data inside the VOI and the low exposure full-field scan data outside the VOI are then combined together to generate composite projection images for image reconstruction. To investigate and quantify scatter reduction, dose saving and image quality improvement in VOI CBCT imaging, a flat panel detector-based bench-top experimental CBCT system was built to measure the dose, the scatter-to-primary ratio (SPR), the image contrast, noise level, the contrast-to-noise ratio (CNR) and the figure of merit (FOM) in the CBCT reconstructed images for two polycarbonate cylinders simulating the small and the large phantoms. The results showed that, compared to the full field CBCT technique, radiation doses for the VOI CBCT technique were reduced by a factor of 1.20 and 1.36 for the small and the large phantoms at the phantom center, respectively, and from 2.7 to 3.0 on the edge of the phantom, respectively. Inside the VOI, the SPRs were substantially reduced by a factor of 6.6 and 10.3 for the small and the large phantoms, the contrast signals were improved by a factor of 1.35 and 1.8, and the noise levels were increased by a factor of 1.27 and 1.6, respectively. As a result, the CNRs were improved by a factor of 1.06 and 1.13 for the small and the large phantoms and the FOM improved by a factor of 1.4 and 1.7, respectively.
Department of Imaging Physics, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA. chaolai@di.mdacc.tmc.edu
Chao-Jen
CJ
Lai
Lingyun
L
Chen
Huojun
H
Zhang
Xinming
X
Liu
Yuncheng
Y
Zhong
Youtao
Y
Shen
Tao
T
Han
Shuaiping
S
Ge
Ying
Y
Yi
Tianpeng
T
Wang
Wei T
WT
Yang
Gary J
GJ
Whitman
Chris C
CC
Shaw
D000465:Algorithms; D001940:Breast / Q000473:pathology; D001943:Breast Neoplasms / Q000532:radiotherapy; D002138:Calibration; D004867:Equipment Design; D005260:Female; D006801:Humans; D008327:Mammography / Q000379:methods; D015233:Models, Statistical; D009010:Monte Carlo Method; D019047:Phantoms, Imaging; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D012542:Scattering, Radiation; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014965:X-Rays