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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-22 2:38 |
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Conference: Bucharest University Faculty of Physics 2013 Meeting
Section: Biophysics; Medical Physics
Title:
Hip prosthesis metal induced artifacts influence in prostate cancer
VMAT treatment planning
Authors:
Mihai Daniel Suditu (1,2), Daniela Adam (2),Răducu Popa (1,2), Violeta Ciocaltei (2), Gabriel Rîcu (2), Cristian Barbu (2)
Affiliation:
(1)Faculty of Physics, University of Bucharest
(2)Amethyst Radiology Therapeutic Center, Bucharest
E-mail
suditu.mihai@yahoo.com
Keywords:
metal induced artifacts, dose distribution, volumetric modulated arc therapy
Abstract:
In modern radiation therapy techniques dose calculation is essential for a precise radiation treatment plans and this accuracy depends upon anatomic and tissue electron density information. The presence of metal in the scanned volume by an X-ray CT scanner causes metal induced artifacts that influence tissue associated CT numbers and introduce errors in the dose distribution calculation. Also, in radiation therapy, metal induced artifacts on the CT images can affect the delineation of the interest anatomical structures like target volumes and organs at risk. To evaluate how the metal induced artifacts affect the treatment planning process, three patients with prostate cancer and hip prosthesis implants were selected and the corresponding CT images sets in original form and reconstructed using the Metal Artifact Reduction algorithm (O-MAR) were used for target volume and organs at risk delineation and dose calculation. Volumetric modulated arc therapy (VMAT) plans were generated using three images data sets for each patient: uncorrected images, corrected images with O-MAR and images were the regions with artifacts were modified by overriding density with a uniform value. The plans generated for corrected images with O-MAR was selected as reference plan and then this was projected on the last images sets and recalculated.
In the delineation process suboptimal image quality may cause the omission of a portion of the target volume or inadvertent delineation of normal structures causing serious errors. Dosimetric differences revealed between original, O-MAR corrected CT scans and corrected images by overriding density in artifacts regions can be substantial. Even if mean dose differences between corrected and uncorrected cases are small, significant hot/cold local regions are observed when CT to electron density table equates MAR-affected regions to density near air and sometimes significant underdosing can occur.
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