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A Novel Algorithm for the Reconstruction of an Entrance Beam Fluence from Treatment Exit Patient Portal Dosimetry Images

Sperling, Nicholas Niven
http://rave.ohiolink.edu/etdc/view?acc_num=toledo1384521982

Abstract Details

2013, Doctor of Philosophy, University of Toledo, Physics.
The problem of determining the in vivo dosimetry for patients undergoing radiation treatment has been an area of interest since the development of the field. Most methods which have found clinical acceptance work by use of a proxy dosimeter, e.g.: glass rods, using radiophotoluminescence; thermoluminescent dosimeters (TLD), typically CaF or LiF; Metal Oxide Silicon Field Effect Transistor (MOSFET) dosimeters, using threshold voltage shift; Optically Stimulated Luminescent Dosimeters (OSLD), composed of Carbon doped Aluminum Dioxide crystals; RadioChromic film, using leuko-dye polymers; Silicon Diode dosimeters, typically p-type; and ion chambers. More recent methods employ Electronic Portal Image Devices (EPID), or dosimeter arrays, for entrance or exit beam fluence determination. The difficulty with the proxy in vivo dosimetery methods is the requirement that they be placed at the particular location where the dose is to be determined. This precludes measurements across the entire patient volume. These methods are best suited where the dose at a particular location is required. The more recent methods of in vivo dosimetry make use of detector arrays and reconstruction techniques to determine dose throughout the patient volume. One method uses an array of ion chambers located upstream of the patient. This requires a special hardware device and places an additional attenuator in the beam path, which may not be desirable. A final approach is to use the existing EPID, which is part of most modern linear accelerators, to image the patient using the treatment beam. Methods exist to deconvolve the detector function of the EPID using a series of weighted exponentials (1). Additionally, this method has been extended to determine in vivo dosimetry. The method developed here employs the use of EPID images and an iterative deconvolution algorithm to reconstruct the impinging primary beam fluence on the patient. This primary fluence may then be employed to determine dose through the entire patient volume. The method requires patient specific information, including a CT for deconvolution/dose reconstruction. With the large-scale adoption of Cone Beam CT (CBCT) systems on modern linear accelerators, a treatment time CT is readily available for use in this deconvolution and in dose representation.
E. Parsai, PhD (Committee Chair)
Diana Shvydka, PhD (Committee Member)
Michael Dennis, PhD (Committee Member)
Thomas Kvale, PhD (Committee Member)
Krishna Reddy, PhD, MD (Committee Member)
229 p.
Physics
Medical Physics; EPID; Portal Dosimetry

Recommended Citations

Citations

  • Sperling, N. N. (2013). A Novel Algorithm for the Reconstruction of an Entrance Beam Fluence from Treatment Exit Patient Portal Dosimetry Images [Doctoral dissertation, University of Toledo]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1384521982

    APA Style (7th edition)

  • Sperling, Nicholas. A Novel Algorithm for the Reconstruction of an Entrance Beam Fluence from Treatment Exit Patient Portal Dosimetry Images. 2013. University of Toledo, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=toledo1384521982.

    MLA Style (8th edition)

  • Sperling, Nicholas. "A Novel Algorithm for the Reconstruction of an Entrance Beam Fluence from Treatment Exit Patient Portal Dosimetry Images." Doctoral dissertation, University of Toledo, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1384521982

    Chicago Manual of Style (17th edition)

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© 2013, all rights reserved.
This open access ETD is published by University of Toledo and OhioLINK.