Spiral computed tomography phase-space source model in the BEAMnrc/EGSnrc Monte Carlo system: implementation and validation
| Autor: | Indrin J. Chetty, Sangroh Kim, Terry T. Yoshizumi, Fang-Fang Yin |
|---|---|
| Rok vydání: | 2013 |
| Předmět: |
Physics
Film Dosimetry Radiological and Ultrasound Technology business.industry Equivalent dose Monte Carlo method Isocenter Models Theoretical Imaging phantom Spiral computed tomography Optics Mockup Computer graphics (images) Radiology Nuclear Medicine and imaging Tomography business Monte Carlo Method Tomography Spiral Computed Spiral |
| Zdroj: | Physics in Medicine and Biology. 58:2609-2624 |
| ISSN: | 1361-6560 0031-9155 |
| DOI: | 10.1088/0031-9155/58/8/2609 |
| Popis: | Currently, the BEAMnrc/EGSnrc Monte Carlo (MC) system does not provide a spiral CT source model for the simulation of spiral CT scanning. We developed and validated a spiral CT phase-space source model in the BEAMnrc/EGSnrc system. The spiral phase-space source model was implemented in the DOSXYZnrc user code of the BEAMnrc/EGSnrc system by analyzing the geometry of spiral CT scan-scan range, initial angle, rotational direction, pitch, slice thickness, etc. Table movement was simulated by changing the coordinates of the isocenter as a function of beam angles. Some parameters such as pitch, slice thickness and translation per rotation were also incorporated into the model to make the new phase-space source model, designed specifically for spiral CT scan simulations. The source model was hard-coded by modifying the 'ISource = 8: Phase-Space Source Incident from Multiple Directions' in the srcxyznrc.mortran and dosxyznrc.mortran files in the DOSXYZnrc user code. In order to verify the implementation, spiral CT scans were simulated in a CT dose index phantom using the validated x-ray tube model of a commercial CT simulator for both the original multi-direction source (ISOURCE = 8) and the new phase-space source model in the DOSXYZnrc system. Then the acquired 2D and 3D dose distributions were analyzed with respect to the input parameters for various pitch values. In addition, surface-dose profiles were also measured for a patient CT scan protocol using radiochromic film and were compared with the MC simulations. The new phase-space source model was found to simulate the spiral CT scanning in a single simulation run accurately. It also produced the equivalent dose distribution of the ISOURCE = 8 model for the same CT scan parameters. The MC-simulated surface profiles were well matched to the film measurement overall within 10%. The new spiral CT phase-space source model was implemented in the BEAMnrc/EGSnrc system. This work will be beneficial in estimating the spiral CT scan dose in the BEAMnrc/EGSnrc system. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
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