Abstract
A Monte Carlo simulation was used to study imaging and dosimetric characteristics of a novel design of megavoltage (MV) X-ray detectors for radiotherapy applications. The new design uses Cerenkov effect to convert X-ray energy absorbed in optical fibres into light for MV X-ray imaging. The proposed detector consists of a matrix of optical fibres aligned with the incident X rays and coupled to an active matrix flat-panel imager (AMFPI) for image readout. Properties, such as modulation transfer function, detection quantum efficiency (DQE), and energy response of the detector, were investigated. It has been shown that the proposed detector can have a zero-frequency DQE more than an order of magnitude higher than that of current electronic portal imaging device (EPID) systems and yet a spatial resolution comparable to that of video-based EPIDs. The proposed detector is also less sensitive to scattered X rays from patients than current EPIDs.
Highlights
Radiation therapy is widely used today to treat patients with tumors [1]
We investigate the feasibility of the new design (i.e., CPID) using Monte Carlo simulation
We investigated the CPID response in absence of a patient as well as the response in presence of a “patient”
Summary
Radiation therapy is widely used today to treat patients with tumors [1]. Megavoltage (MV) X-ray beams generated from a linear accelerator are commonly used to deliver the prescribed radiation dose to the tumor while minimizing the dose to the surrounding healthy tissues. One of the main challenges with this approach is that the imaging dose currently required to achieve sufficient soft tissue contrast to visualize and delineate a soft tissue target; for example, the prostate is prohibitively large for daily verification. This is due to the poor X-ray absorption, that is, low quantum efficiency (QE) of the EPID used. For most EPIDs developed so far, the QE is typically on the order of 2–4% at 6 MV as compared to the theoretical limit of 100% [5] This is because the total combined thickness of the energy conversion layer and the metal buildup in most EPIDs is only ∼2 mm. A significant increase of QE is required in order to reduce the dose currently required to visualize and delineate the prostate using MV-CBCT
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