Keith Evan Schubert

Baylor University | BU · Department of Electrical & Computer Engineering

Objective. Alternating electric fields (AEF) therapy is a treatment modality for patients with glioblastoma. Tumor characteristics such as size, location, and extent of peritumoral edema may affect the AEF strength and distribution. We evaluated the sensitivity of the AEFs in a realistic 3D rat glioma model with respect to these properties. Approac...

Objective. Application of alternating electrical fields (AEFs) in the kHz range is an established treatment modality for primary and recurrent GBM. Preclinical studies would enable innovations in treatment monitoring and efficacy, which could then be translated to benefit patients. We present a practical translational process converting image-based...

Objective: To propose a mathematical model for applying Ionization Detail (ID), the detailed spatial distribution of ionization along a particle track, to proton and ion beam radiotherapy treatment planning (RTP). Approach: Our model provides for selection of preferred ID parameters (Ip) for RTP, that associate closest to biological effects. Clu...

Protons have advantageous dose distributions and are increasingly used in cancer therapy. At the depth of the Bragg peak range, protons produce a mixed radiation field consisting of low- and high-linear energy transfer (LET) components, the latter of which is characterized by an increased ionization density on the microscopic scale associated with...

italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Alternating projection onto convex sets (POCS) provides an iterative procedure to find a signal that satisfies two or more convex constraints when the sets intersect. For nonintersecting constraints, the method of simultaneous projections produces a mi...

We have previously defined synchronization (Gomez, E. and K. Schubert 2011) as a relation between the times at which a pair of events can happen, and introduced an algebra that covers all possible relations for such pairs. In this work we introduce the synchronization matrix, to make it easier to calculate the properties and results of $N$ event sy...

Exposing cancer cells to alternating electric fields of frequency 100-300 kHz and strength 1-4 V/cm has been shown to significantly reduce cancer growth in cell culture and in human patients. This form of anti-cancer therapy is more commonly referred to as tumor treating fields (TTFields), a novel treatment modality that has been approved by the U....

Alternating projection onto convex sets (POCS) provides an iterative procedure to find a signal that satisfies two or more convex constraints when the sets intersect. For nonintersecting constraints, the method of simultaneous projections produces a minimum mean square error (MSE) solution. In certain cases, a minimax solution is more desirable. Ge...

italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Goal: To enhance endovascular navigation using surgical guidewires and the use of ionizing radiation, we demonstrate a method for ultrasonic localization of wires with diameters less than the wavelength of ultrasound in the medium. Methods: Nitinol w...

Proton computed tomography (pCT) is an image modality that will improve treatment planning for patients receiving proton radiation therapy compared with the current treatment techniques, which are based on X-ray CT. Reconstruction of a pCT image requires solving a large and sparse system of linear equations, which should be accomplished within a fe...

We summarize recent results and ongoing activities in mathematical algorithms and computer science methods related to proton computed tomography (pCT) and intensity-modulated particle therapy (IMPT) treatment planning. Proton therapy necessitates a high level of delivery accuracy to exploit the selective targeting imparted by the Bragg peak. For th...

We summarize recent results and ongoing activities in mathematical algorithms and computer science methods related to proton computed tomography (pCT) and intensity-modulated particle therapy (IMPT) treatment planning. Proton therapy necessitates a high level of delivery accuracy to exploit the selective targeting imparted by the Bragg peak. For th...

Proton CT (pCT) is a promising new imaging technique that can reconstruct relative stopping power (RSP) more accurately than x-ray CT in each cubic millimeter voxel of the patient. This, in turn, will result in better proton range accuracy and, therefore, smaller planned tumor volumes (PTV). The hardware description and some reconstructed images ha...

Robust methods, such as Tikhonov regularization and Bounded data uncertainty, have been used extensively in relatively small problems involving dense matrices for many decades, but have not been used in large-scale iterative methods for image reconstruction in particle imaging until recently. In this case, robust methods may allow more accurate rec...

Microbial life permeates Earth's critical zone and has likely inhabited nearly all our planet's surface and near subsurface since before the beginning of the sedimentary rock record. Given the vast time that Earth has been teeming with life, do astrobiologists truly understand what geological features untouched by biological processes would look li...

Previous work showed that total variation superiorization (TVS) improves reconstructed image quality in proton computed tomography (pCT). The structure of the TVS algorithm has evolved since then and this work investigated if this new algorithmic structure provides additional benefits to pCT image quality. Structural and parametric changes introduc...

Low-dose Proton Computed Tomography (pCT) is an evolving imaging modality that is used in proton therapy planning which addresses the range uncertainty problem. The goal of pCT is generating a 3D map of Relative Stopping Power (RSP) measurements with high accuracy within clinically required time frames. Generating accurate RSP values within the sho...

Proton computed tomography (pCT) has recently seen considerable research interest as a means of reducing range uncertainties in proton therapy, by reconstructing directly relative stopping power to water (RSP). Recent detector developments have permitted the development of two list-mode pCT scanner prototypes based on broad (passively scattered) pr...

In this study, we expand upon the biogeography of biological soil crusts (BSCs) and provide molecular insights into the microbial community and biochemical dynamics along the vertical BSC column structure, and across a transect of increasing BSC surface coverage in the central Mojave Desert, CA, United States. Next generation sequencing reveals a b...

This simulation study presents the application of fluence field modulated computed tomography (FFMCT), initially developed for x-ray CT, to proton computed tomography (pCT). By using pencil beam (PB) scanning, fluence modulated pCT (FMpCT) may achieve variable image quality in a pCT image and imaging dose reduction. Three virtual phantoms, a unifo...

We are exploring low-dose proton radiography and computed tomography (pCT) as techniques to improve the accuracy of proton treatment planning and to provide artifact-free images for verification and adaptive therapy at the time of treatment. Here we report on comprehensive beam test results with our prototype pCT head scanner. The detector system a...

We propose a definition of parallel state, derive a phase space from this state, and calculate the entropy of states and full executions using combinatorial analysis. A main contribution of this work is the introduction of an experimentally measurable phase space, which we then use to analyze execution states, ensembles of states, and ensembles of...

We report on the operation and performance tests of a preclinical head scanner developed for proton computed tomography (pCT). After extensive preclinical testing, pCT is intended to be employed in support of proton therapy treatment planning and pre-treatment verification in patients undergoing particle-beam therapy. In order to assess the perform...

We report on the design, fabrication, and first tests of a tomographic scanner developed for proton computed tomography (pCT) of head-sized objects. After extensive preclinical testing, pCT is intended to be employed in support of proton therapy treatment planning and pre-treatment verification in patients undergoing particle-beam therapy. The scan...

Presentation at Astrobiology Sciences Conference 2015, Chicago

Image registration techniques based on anatomical features can serve to automate patient alignment for intracranial radiosurgery procedures in an effort to improve the accuracy and efficiency of the alignment process as well as potentially eliminate the need for implanted fiducial markers. To explore this option, four two-dimensional (2D) image reg...

A device for determining or measuring temporomandibular joint positions and movements of a patient. A method for determining or measuring one or more than one temporomandibular joint position or movement of a patient. A method of diagnosing a condition or disease of a temporomandibular joint of a patient.

Proton radiography has applications in patient alignment and verification procedures for proton beam radiation therapy. In this paper, we report an experiment which used 200 MeV protons to generate proton energy-loss and scattering radiographs of a hand phantom. The experiment used the first-generation proton computed tomography (CT) scanner protot...

Proton computed tomography (pCT) is a novel imaging modality developed for patients receiving proton radiation therapy. The purpose of this work was to investigate hull-detection algorithms used for preconditioning of the large and sparse linear system of equations that needs to be solved for pCT image reconstruction. The hull-detection algorithms...

Proton computed tomography (pCT) is an image modality that will improve treatment planning for patients receiving proton radiation therapy compared with the current treatment techniques, which are based on X-ray CT. Reconstruction of a pCT image requires solving a large and sparse system of linear equations, which should be accomplished within a fe...

This paper considers how to determine the boundary of an object by comparing two methods: space carving (SC) and filtered back-projection (FBP). Determination of the boundary is an important first step in proton CT. The boundary is used to set up the large sparse linear system of equations, which are then solved to determine the relative stopping p...

Accurate navigation on the moon, Mars, or any other astronomical body is essential to scientific investi-gation. The research presented in this paper covers the constellation design of a Lunar Global Positioning System (GPS) using the CubeSat platform. Since CubeSats have significantly smaller dimensions than most current satellites, their associat...

The use of microbial fuel cells to detect anaer-obes and power experiments in remote extreme environments is examined by a team of scientists and student teachers in a joint venture of the California State University system and NASA Ames. The economic viability of carbon fiber electrodes is tested by comparing their performance to graphite rods, wh...

In the search for life on Mars and other extraterrestrial bodies or in our attempts to identify biological traces in the most ancient rock record of Earth, one of the biggest problems facing us is how to recognize life or the remains of ancient life in a context very different from our planet's modern biological examples. Specific chemistries or bi...

In the search for life on Mars and other extraterrestrial bodies or in our attempts to identify biological traces in the most ancient rock record of Earth, one of the biggest problems facing us is how to recognize life or the remains of ancient life in a context very different from our planet's modern biological examples. Specific chemistries or bi...

Modern multiprocessor architectures have exacerbated problems of coordinating access to shared data, in particular as regards to the possibility of deadlock. For example semaphores, one of the most basic synchronization primitives, present difficulties. Djikstra defined semaphores to solve the problem of mutual exclusion. Practical implementation o...

Modern multiprocessor architectures have exacerbated problems of coordinating access to shared data, in particular as regards to the possibility of deadlock. For example semaphores, one of the most basic synchronization primitives, present difficulties. Djikstra defined semaphores to solve the problem of mutual exclusion. Practical implementation o...

Proton computed tomography (pCT) is an imaging modality that is based on tracking individual protons as they traverse the object to be imaged. Proton-by-proton tracking is necessary due to the effects of multiple Coulomb scattering (MCS), a process that deviates the proton path from a striaght line. If optimal spatial resolution is to be achieved,...

Currently proton dose calculations rely on X-ray computed tomography (CT), which limits their accuracy due to the physical interaction differences of protons and X-rays. To gain the maximum benefit from proton therapy, proton computed tomography (pCT) offers the opportunity to more accurately plan proton doses and to verify the correct proton beam...

An accurate system matrix is required for quantitative proton CT (pCT) image reconstruction with iterative projection algorithms. The system matrix is composed of chord lengths of individual proton path intersections with reconstruction pixels. In previous work, reconstructions were performed assuming constant intersection chord lengths, which led...

In the search for life on Mars and other extraterrestrial bodies, one of the biggest problems facing us is, how do we recognize life or the remains of ancient life when we find it? We will need to recognize residual patterns left by life. One approach to recognizing these kinds of patterns is look at patterns created and left by life in extreme env...

The research conducted is intended to enhance the way we view and study our solar system and others, by allowing scientists of astronomy, physics, and computer science to accurately simulate celestial systems. The Extensible Simulator organizes individual groups of celestial bodies, calculates their positions, graphically visualizes their movement...

Determination of the Bragg peak position in proton therapy requires accurate knowledge of the electron density and ratio of effective atomic number and mass (Z/A) of the body tissues traversed. While the Z/A ratio is fairly constant for human tissues, the density of tissues varies significantly. One possibility to obtain accurate electron density i...

The limited spatial resolution in proton computed tomography (pCT) in comparison to x-ray CT is related to multiple Coulomb scattering (MCS) within the imaged object. The current generation pCT design utilizes silicon detectors that measure the position and direction of individual protons prior to and post-traversing the patient to maximize the kno...

Targeting of brain tumors or diseased brain tissues with neurosurgical instruments or ra- diosurgery beams requires magnetic resonance image (MRI) sets with high spatial resolution. In recent years, the spatial resolution of MRI scanners has in- creased considerably with the introduction of high- fleld (3T) technology. As a result, isotropic submil...

Monitoring of the target position relative to the beam delivery system is a crucial requirement for creating small functional lesions in the brain with any radiosurgery modality. We have studied the performance of an optoelectronic localization system for monitoring brain lesioning with narrow proton beams. The system consists of three high-resolut...

Bioinformatics in general and bioimaging in particular are characterized by large, often distributed datastores. Datastores involve more than just a database, as relational databases cannot, for example, store and protect an image. This paper examines the effects of network performance on a bioimaging datas-tore when it is locally connected, LAN co...

This paper discusses the correction of MR images to submillimeter accuracy needed for functional radiosurgery. MR images experience non-linear distortion due to the mag-netic field, which becomes more of a problem for newer ma-chines with larger bores and stronger magnetic fields. This paper models the distortion correction parameters using a spher...

A new system for functional proton radiosurgery has been proposed. The goal of the system is to target specific brain areas with high doses of proton beams with submillimeter ac- curacy. High-energy proton beams have exquisitely sharp lat- eral penumbra and are, therefore, ideal for functional radio- surgery. Localizing the anatomical target with a...

We present advanced technology developments in space networking achieved under the Interplanetary Network Directorate Information Technology Program. Progress has been made in three primary areas: (1) distributed on-board scheduling as it applies to ...