@MASTERSTHESIS\{IMM2013-06553,
    author       = "M. Ghafory",
    title        = "{2D} patient setup verification in {MRI-}only radiotherapy versus current {CT-}based verification",
    year         = "2013",
    school       = "Technical University of Denmark, {DTU} Compute, {E-}mail: compute@compute.dtu.dk",
    address      = "Matematiktorvet, Building 303{-B,} {DK-}2800 Kgs. Lyngby, Denmark",
    type         = "",
    note         = "{DTU} supervisor: Rasmus Larsen, rlar@dtu.dk, {DTU} Compute",
    url          = "http://www.compute.dtu.dk/English.aspx",
    abstract     = "Radiation therapy (RT) is one of the most common treatment method for cancer patients. The purpose of {RT} is to cure the patient through ionizing radiation. This requires a treatment planning process with high accuracy. The current treatment planning is based on a computed tomography (CT) scan which contains information about the electron densities, which are required for dose calculation. The {CT} scan is also important for {2D} patient setup verification. {RT} based on magnetic resonance imaging (MRI) has proved advantages compared to the {CT} due to e.g. better delineation of tumour volume and organ at risks. The aim of this study is to investigate the possibility of using {MRI} for {2D} patient setup verification.
Data from four palliative patients receiving cranial {RT} was used in this study. The patients were scanned with 1 Tesla open {MRI-}system and {MRI} ultrashort echo-time (UTE) sequence scans were required. The Markov random field (MRF) segmentation method was used to classify each {MRI} {UTE} sequence data into air, soft tissue and bone and created a substituted {CT} (sCT) scans. sCT bone digital reconstructed radiographs (DRRs) were generated from the sCT scans and {CT} bone DRRs were generated from the planning {CT} scans. Manual match of OBIs on both {CT} DRRs and sCT DRRs were performed in Offine Review Eclipse V.10 (Varian Medical System). A {2D} lateral and frontal match was performed by ve radiation therapists (RTTs). A statistical evaluation was made of whether there is a significant difference in {2D} patient setup verification when performing matching on sCT generated DRRs as compared to {CT} generated DRRs.
The {MRF} segmentation facilitated creating sCT scan and generated bone DRRs.
A significant difference between the sCT and {CT} generated DRRs was seen in longitudinal (lateral) direction, vertical direction and pitch (rotation) when performing {2D} lateral match. For the frontal match a significant difference was observed in rnt (rotation) whereas longitudinal (front) and lateral directions were non-significant.
This study showed that treatment planning solely based on {MRI} is a feasible alternative to current {CT} based on treatment planning due to {2D} setup verification."
}