Abstract
A multiple‐slit collimator (MSC) design was introduced for scatter reduction in cone‐beam computed tomography (CBCT). Unlike most other collimators, the open and closed septa of the proposed MSC are placed in an equi‐angular interval on a circular track of the central sagittal plane. Therefore, one gantry rotation provides only the half of necessary dataset and two gantry rotations are needed to obtain full information. During the first gantry rotation, the MSC position relative to the source is fixed. For the second rotation, the MSC is rotated by the equi‐angle interval. We assume signals under the closed septa are totally attributed to scatter radiation. Then, scatter contributions under open septa are determined by interpolating them.Monte Carlo (MC) simulations for two virtual phantoms (one with a simple geometry and the other with two heterogeneities simulating the bone and the lung) were performed to evaluate the effectiveness of the system. Using the method developed, we could obtain images with significant scatter reduction. Contrast ratio (CR) improvement factors were 1.165 in a 2D projection view, and 1.210 and 1.223 at the central and peripheral slice of the reconstructed CBCT image of the simple geometry phantom.This preliminary study demonstrated that the proposed MSC, together with the imaging process technique, had a great potential to reduce scatter contribution in CBCT. Further studies will be performed to investigate the effect of various factors, such as reducing the detector size, increasing the number of history of MC simulation, and including many structures with different densities.PACS number: 87.57.C
Highlights
Image-guided radiation therapy (IGRT) is a state-of-the-art treatment method that utilizes various imaging techniques to precisely deliver the intended dose to the treatment target
It was demonstrated that compensation filters, so-called bowtie filters, could reduce scatter and patient dose by compensating for the variation of attenuation through different patient body parts.[8,9] In several scatter correction algorithms, scatter correction factors were obtained from pre-acquired 2D scatter fluence maps and applied to each projection in cone-beam CT (CBCT) to reduce scatter effect.[10,11,12] A few studies showed the use of air gap and/or an antiscatter grid was very practical.[13,14,15] By increasing the patient-to-detector distance and using a grid, a fair amount of scatter radiation was reduced
We propose a static multiple-slit system for the scatter reduction of CBCT
Summary
Image-guided radiation therapy (IGRT) is a state-of-the-art treatment method that utilizes various imaging techniques to precisely deliver the intended dose to the treatment target. One of the most widely used imaging techniques for IGRT is cone-beam CT (CBCT), in which a volumetric image set is reconstructed using many projected radiographic images under conebeam geometry.[1,2,3,4,5]. The increased amount of scatter radiations due to the large projection field size of cone-beam geometry reduces image contrast, increases image noise, and generates artifacts in reconstructed 3D images.[6,7]. Its advantage was limited by the geometric dullness of the slit edges in mammography imaging
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