Dynamic fluence field modulation in computed tomography using multiple aperture devices.

Dynamic fluence field modulation in computed tomography using multiple aperture devices.
Phys Med Biol. 2019 Apr 02;:
Authors: Gang GJ, Mao A, Wang W, Siewerdsen JH, Mathews A, Kawamoto S, Levinson R, Stayman JW
Abstract
A novel beam filter consisting of multiple aperture devices (MADs) has been developed for dynamic fluence field modulation (FFM) in CT. Each MAD achieves spatial modulation of x-ray through fine-scale, highly attenuating tungsten bars of varying widths and spacings. Moir\'e patterns produced by relative motions between two MADs provide versatile classes of modulation profiles. The dual-MAD filter can be designed to achieve specific classes of target profiles. The designed filter was manufactured through a laser-sintering process and integrated to an experimental imaging system that enables linear actuation of the MADs. Dynamic FFM was achieved through a combination of beam shape modulation (by relative MAD motion) and amplitude modulation (by view-dependent mAs). To correct for gains associated with the MADs, we developed an algorithm to account for possible focal spot changes during/between scans and spectral effects introduced by the MADs. We performed FFM designs for phantoms following two imaging objectives: 1) to achieve minimum mean variance in filtered backprojection (FBP) reconstruction, and 2) to flatten the fluence behind the phantom. Comparisons with conventional FFM strategies involving a static bowtie an...

Source: Physics in Medicine and Biology - April 1, 2019 Category: Physics Authors: Gang GJ, Mao A, Wang W, Siewerdsen JH, Mathews A, Kawamoto S, Levinson R, Stayman JW Tags: Phys Med Biol Source Type: research