title: Fast high-resolution 3D segmented echo planar imaging for dose mapping using a superheated emulsion chamber.
abstract: The superheated emulsion chamber (SEC) consists of superheated droplets of halocarbons in an aqueous gel. The gel resides in a pressure chamber. Brachytherapy sources can be implanted in the SEC for radiation dosimetry studies. Upon irradiation by ionizing radiation, the metastable droplets vaporize to form microbubbles. MRI can be used to determine the distribution of bubbles following irradiation of the SEC. In order to generate sufficient statistical accuracy in the determination of dose distributions around brachytherapy sources, it is necessary to use hundreds of irradiation cycles. Susceptibility-weighted images provide contrast between the gel and the vapor microbubbles. This article describes a 3D, blipped, double-sampled, segmented echo-planar imaging technique for rapidly imaging the SEC at 650 microm isotropic 3D resolution in about 2 min. This method was used with a pressure cycling SEC to acquire hundreds of images in several hours. Results are presented showing the 2D dose distribution generated by an (125)I source as measured in the SEC using this new imaging method.
authors.affiliation: Department of Radiology & Pediatrics, Children's Hospital Medical Center, Imaging Research Center, 3333 Burnet Avenue, Cincinnati, OH 45229-3030, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Lamba
authors.forename: Scott K
authors.initials: SK
authors.lastname: Holland
authors.forename: Vincent
authors.initials: V
authors.lastname: Schmithorst
authors.forename: Bernard
authors.initials: B
authors.lastname: Dardzinski
authors.forename: Francesco
authors.initials: F
authors.lastname: d'Errico
authors.forename: Ravinder
authors.initials: R
authors.lastname: Nath
mesh_terms: D001918:Brachytherapy / Q000295:instrumentation / Q000379:methods*; D017352:Echo-Planar Imaging / Q000379:methods*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D009369:Neoplasms / Q000532:radiotherapy; D011874:Radiometry / Q000379:methods