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Po‐Poster ‐ 01: A bench‐top megavoltage CT scanner
Author(s) -
Tu D,
Monajemi T,
Rickey D,
Fallone B,
Rathee S
Publication year - 2005
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.2030980
Subject(s) - detector , optics , scanner , detective quantum efficiency , tomotherapy , scintillator , physics , linear particle accelerator , data acquisition , nuclear medicine , beam (structure) , image quality , computer science , medicine , artificial intelligence , image (mathematics) , operating system , radiation therapy
The purpose of this project was to design, fabricate and test the data acquisition timing control, precision rotary stage control, and analog data multiplexer unit for a prototype megavoltage computed tomography (MVCT) detector. An 80‐element prototype detector array is made with CdWO 4(element size 0.275 × 0.8 × 1 cm 3 ) scintillators and photodiodes on an arc (radius of 110 cm). In addition to designing and fabricating an in‐house data acquisition system (front‐end integrators, data multiplexer unit, and timing control), a precision rotary stage and its control are added to create a third generation MVCT scanner. Data acquisition is synchronized with radiation pulses from a linac. Response of detector as a function of dose rate was studied by varying the source to detector distance. A narrow slit beam, at five locations, was used to measure the pre‐sampled MTF . Detector signal in open beam was measured for a number of radiation pulses to use the periodogram method for NPS estimation. Using the measured MTF, NPS , and photon fluence impinging on detector, DQE was calculated. Detector response is linear as a function of dose rate, however shows a non‐linear component while measuring the attenuation by solid water due to the polyenergetic spectrum. Beam‐hardening correction is necessary before image reconstruction. MTF at the Nyquist frequency (0.16 mm −1 ) is 0.48. Zero‐frequency DQE in 6 MV at 21% is higher than any experimental MVCT detector. The basic performance of the prototype detector is satisfactory for producing reasonable low contrast resolution in MVCT images with low dose.