Machine learning for proton path tracking in proton computed tomography.

A Machine Learning approach to the problem of calculating the proton paths inside a scanned object in proton Computed Tomography is presented. The method is developed in order to mitigate the loss in both spatial resolution and quantitative integrity of the reconstructed images caused by multiple Coulomb scattering of protons traversing the matter. Two Machine Learning models were used: a forward neural network (NN) and the XGBoost method.

Molière maximum likelihood proton path estimation approximated by cubic Bézier curve for scatter corrected proton CT reconstruction.

A maximum likelihood approach to the problem of calculating the proton paths inside the scanned object in proton computed tomography is presented. Molière theory is used for the first time to derive a physical model that describes proton multiple Coulomb scattering, avoiding the need for the Gaussian approximation currently used. To enable this, the proposed method approximates proton paths with cubic Bézier curves and subsequently maximizes the path likelihood through parametric optimization, based on the Molière model.

Impact of flat panel-imager veiling glare on scatter-estimation accuracy and image quality of a commercial on-board cone-beam CT imaging system.

Purpose: The purposes of this study is to measure the low frequency drop (LFD) of the modulation transfer function (MTF), associated with the long tails of the detector point spread function (PSF) of an on-board flat panel imager and study its impact on cone-beam CT (CBCT) image quality and scatter measurement accuracy.

Methods: Two different experimental methods were used to characterize LFD and its associated PSF of a Varian OBI flat-panel detector system: the edge response function (ERF) method and the disk transfer function (DTF) method. PSF was estimated by fitting parametric models to these measurements for four values of the applied voltage (kVp).

SU-E-J-21: An Intercomparison of Imaging Performance of Two Linac-Mounted Imaging Systems Used in Radiation Therapy: TrueBeam and Trilogy.

Purpose: To evaluate and compare the performance of the imaging systems of two linear accelerators, used in radiation therapy. The study includes the following imaging components: electronic portal imaging device (EPID), kilovoltage projection imaging and kilovoltage cone-beam CT.

Method And Materials: The imaging systems mounted on the Varian Trilogy (Varian Medical Systems) and Varian TrueBeam, were evaluated.

Bow-tie wobble artifact: effect of source assembly motion on cone-beam CT.

Purpose: To investigate the cause of a bow-tie wobble artifact (BWA) discovered on Varian OBI CBCT images and to develop practical correction strategies.

Method And Materials: The dependence of the BWA on phantom geometry, phantom position, specific system, and reconstruction algorithm was investigated. Simulations were conducted to study the dependence of the BWA on scatter and beam hardening corrections.

Monte Carlo evaluation of scatter mitigation strategies in cone-beam CT.

Purpose: To investigate the efficacy of two widely used scatter mitigation methods: antiscatter grids (ASGs) and beam modulating with bowtie filters (BTFs), in combination with subtractive scatter correction or zeroth order normalization phantom calibration, for improving image noise, contrast, contrast-to-noise ratio (CNR), and image uniformity for on-board cone-beam CT (CBCT) imaging systems used for image-guided radiation therapy.

Methods: PTRAN Monte Carlo CBCT x-ray projections of head and pelvic phantoms were calculated for combinations of beam-modulation and scatter rejection methods and images were reconstructed by in-house developed software. In addition, a simple one-dimensional analytic model was developed to predict scatter-to-primary ratio (SPR) and CNR as a function of cylindrical phantom thickness, ASG transmission, and beam modulation with bow-tie filters.

Size-selective protein adsorption to polystyrene surfaces by self-assembled grafted poly(ethylene glycols) with varied chain lengths.

We report about the surface modification of polystyrene (PSt) with photoreactive alpha-4-azidobenzoyl-omega-methoxy poly(ethylene glycol)s (ABMPEG) of three different molecular weights (MWs of approximately 2, approximately 5, and approximately 10 kg/mol) and with two poly(ethylene glycol)/poly(propylene glycol) triblock copolymers (PEG-PPG-PEG) of about identical PEG/PPG ratio (80/20, w/w) and MW(PEG) of approximately 3 and approximately 6 kg/mol, all via adsorption from aqueous solutions. For ABMPEGs, an additional UV irradiation was used for photografting to the PSt. Contact angle (CA) and atomic force microscopy data revealed pronounced differences of the hydrophilicity/hydrophobicity and topography of the surfaces as a function of PEG type and concentration used for the modification.

An integrated research tool for X-ray imaging simulation.

This paper presents a software simulation package of the entire X-ray projection radiography process including beam generation, absorber structure and composition, irradiation set up, radiation transport through the absorbing medium, image formation and dose calculation. Phantoms are created as composite objects from geometrical or voxelized primitives and can be subjected to simulated irradiation process. The acquired projection images represent the two-dimensional spatial distribution of the energy absorbed in the detector and are formed at any geometry, taking into account energy spectrum, beam geometry and detector response.

A software data generator for radiographic imaging investigations.

A software data generation tool, intended to be used in radiographic applications, has been developed. The application integrates a phantom design module and an imaging simulator. Phantoms can be described as a set of either geometrical objects or voxels, or contours drawn on multiple tomographic slices.

Monte Carlo simulation of the radiographic imaging procedure for electronically designed phantoms.

This paper presents a software simulation package of the entire X-ray projection radiography process including beam generation, absorber structure and composition, irradiation set up, radiation transport through the absorbing medium and image formation. This software tool is an augmented version of a previously presented system with expanded range of application by the implementation of Monte Carlo approach for the simulation of the radiation interaction at the absorber and the detector. Phantoms are created as composite objects from geometrical or voxelized primitives and can be subjected to simulated irradiation process.