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Title: SU-G-JeP4-13: Continuous Intra-Fractional Monitoring of the Prostate Using Dynamic KV Collimation and Tube Current Modulation

Abstract

Purpose: The focus of this work is to improve the available kV image quality for continuous intra-fraction monitoring of the prostate. This is investigated using a novel blade collimation system enabling modulated volume-of-interest (VOI) imaging of prostate fiducial markers. Methods: A four-blade dynamic kV collimator was used to track a VOI during gantry rotation. Planar image quality was investigated as a function of collimator dimension, while maintaining the same dose to isocenter, for a 22.2 cm diameter cylindrical water phantom with a 9 mm diameter bone insert. A sample prostate anatomy was defined in the planning system, including three fiducial markers within the CTV. The VOI margin around each marker was set to be 2σ of the population covariance matrix characterizing prostate motion. DRRs were used to calculate the kV attenuation for each VOI as a function of angle. The optimal marker and tube current were determined using kV attenuation. Monte Carlo simulations were used to calculate the imaging dose to the phantom and MV scatter dose to the imaging panel. Results: Preliminary measurements show an increase in CNR by a factor of 1.3 with the VOI method, when decreasing from an 6×6 to 2×2 cm{sup 2} field. Attenuation calculationsmore » show a change in kV fluence at the detector by a factor of 21.6 with fiducial optimization; resultant tube current modulation increases maximum dose by a factor of 1.4 compared to no modulation. MV scatter contribution to the kV detector changes by approximately a factor of two over a complete gantry rotation. Conclusion: The dynamic collimation system allows single fiducial marker tracking at a very low dose, with reduction of scatter and improvement of image quality, compared to imaging the entire prostate. The approach is compatible with tube current modulation, which enables consistent image quality throughout the range of gantry rotation. This project was funded by Varian Medical Systems.« less

Authors:
 [1];  [1];  [2]
  1. Dalhousie Unviersity, Halifax, Nova Scotia (Canada)
  2. (Canada)
Publication Date:
OSTI Identifier:
22649462
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 43; Journal Issue: 6; Other Information: (c) 2016 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; 61 RADIATION PROTECTION AND DOSIMETRY; ATTENUATION; BIOMEDICAL RADIOGRAPHY; COLLIMATORS; COMPUTERIZED SIMULATION; FIDUCIAL MARKERS; IMAGES; MODULATION; MONITORING; MONTE CARLO METHOD; PARTICLE TRACKS; PROSTATE; RADIATION DOSES

Citation Formats

Parsons, D, Robar, J, and Nova Scotia Health Authority, Halifax, NS. SU-G-JeP4-13: Continuous Intra-Fractional Monitoring of the Prostate Using Dynamic KV Collimation and Tube Current Modulation. United States: N. p., 2016. Web. doi:10.1118/1.4957123.
Parsons, D, Robar, J, & Nova Scotia Health Authority, Halifax, NS. SU-G-JeP4-13: Continuous Intra-Fractional Monitoring of the Prostate Using Dynamic KV Collimation and Tube Current Modulation. United States. doi:10.1118/1.4957123.
Parsons, D, Robar, J, and Nova Scotia Health Authority, Halifax, NS. Wed . "SU-G-JeP4-13: Continuous Intra-Fractional Monitoring of the Prostate Using Dynamic KV Collimation and Tube Current Modulation". United States. doi:10.1118/1.4957123.
@article{osti_22649462,
title = {SU-G-JeP4-13: Continuous Intra-Fractional Monitoring of the Prostate Using Dynamic KV Collimation and Tube Current Modulation},
author = {Parsons, D and Robar, J and Nova Scotia Health Authority, Halifax, NS},
abstractNote = {Purpose: The focus of this work is to improve the available kV image quality for continuous intra-fraction monitoring of the prostate. This is investigated using a novel blade collimation system enabling modulated volume-of-interest (VOI) imaging of prostate fiducial markers. Methods: A four-blade dynamic kV collimator was used to track a VOI during gantry rotation. Planar image quality was investigated as a function of collimator dimension, while maintaining the same dose to isocenter, for a 22.2 cm diameter cylindrical water phantom with a 9 mm diameter bone insert. A sample prostate anatomy was defined in the planning system, including three fiducial markers within the CTV. The VOI margin around each marker was set to be 2σ of the population covariance matrix characterizing prostate motion. DRRs were used to calculate the kV attenuation for each VOI as a function of angle. The optimal marker and tube current were determined using kV attenuation. Monte Carlo simulations were used to calculate the imaging dose to the phantom and MV scatter dose to the imaging panel. Results: Preliminary measurements show an increase in CNR by a factor of 1.3 with the VOI method, when decreasing from an 6×6 to 2×2 cm{sup 2} field. Attenuation calculations show a change in kV fluence at the detector by a factor of 21.6 with fiducial optimization; resultant tube current modulation increases maximum dose by a factor of 1.4 compared to no modulation. MV scatter contribution to the kV detector changes by approximately a factor of two over a complete gantry rotation. Conclusion: The dynamic collimation system allows single fiducial marker tracking at a very low dose, with reduction of scatter and improvement of image quality, compared to imaging the entire prostate. The approach is compatible with tube current modulation, which enables consistent image quality throughout the range of gantry rotation. This project was funded by Varian Medical Systems.},
doi = {10.1118/1.4957123},
journal = {Medical Physics},
number = 6,
volume = 43,
place = {United States},
year = {Wed Jun 15 00:00:00 EDT 2016},
month = {Wed Jun 15 00:00:00 EDT 2016}
}