Medical Physics Department
Projects from when I was an undergraduate student at UW-Madison as a member of the Medical Physics Department
Four Dimentional - Digital Subtaction Angiogrophy (4D-DSA)
Quantitative Analysis of Artifacts in Volumetric DSA: the Relative Contributions of Beam Hardening and Scatter to Vessel Dropout Behind Highly Attenuating Structures
In this work the cause of angle dependent vessel dropout in 4D-DSA was investigated. Using monte carlo ray casting simulations, scattering artifacts were found to be the predominate cause of signal loss.
(a) Arrows indicate the portion of the vessel that experiences contrast degradation. (a) 4D-DSA reconstruction of an aneurysm in the carotid artery with no signal loss. (b) 4D-DSA volume reconstructed using a projection in which dental implants are interfering with the signal from the aneurysm. (c) A projection image after digital subtraction at the same view angle as image (b). Some of the anatomy is visible due to a slight misregistration and one can clearly observe that the dental implants are causing the loss of vessel contrast.
Poster SPIE 2014 [Download]
Scatter Correction of Vessel Dropout Behind Highly Attenuating Structures in 4D-DSA
In this work we designed and implemented a correction which uses a threshold to locate vasculature where signal loss will likely be observed and then increases the signal for those projections, correcting the vessel dropout.
Flow chart of algorithem
Poster SPIE 2015 [Download]
Fluence Feild Modulations (FFM) using Digital Beam Attenuators (DBA)
2D-Dyamic fluid Bowtie Attenuators
Fluence field modulation (FFM) allows for improved image quality and dose reduction, in this work the use of highly attenuating fluids for FFM is proposed. Potential fluids are selected and compared through computations which determine the required pathlength and pressure for liquids and gases respectively. A prototype frame work for the mechanical modulation is then designed and 3D printed.
Diagram of proposed actuation scheme.
Image or prototype
James Hermus and Timothy P. Szczykutowicz. 2D-Dynamic Fluid Bowtie Attenuators. Journal of Medical Imaging (JMI) 3(1) 2016 [Link]
Realization of fluence field modulated CT on a clinical TomoTherapy megavoltage CT system
In this work an Accuray TomoTherapy radiation therapy (RT) system was used to preform fluence field modulation in the form of volume of interest imaging (VOI). Images with 30% of the dose outs side the VOI were possible. This work could be immediately implemented for radiation therapy patients to decrease dose to healthy tissue during preoperative alignment CTs.
On the left a phantom was used to demonstrate high resolution with in a VOI while distributing a 30% lower dose to the rest of the phantom. The image on the right shows the dose map of the phantom.
Timothy P. Szczykutowicz and James Hermus. Fluence field modulated CT on a clinical TomoTherapy Radiation Therapy Machine. (Talk). SPIE Medical Imaging Conference 9412-28 2015 [Link]