Babic S, Battista J, Jordan K. Three-dimensional dose verification for intensity-modulated radiation therapy in the radiological physics centre head-and-neck phantom using optical computed tomography scans of ferrous xylenol-orange gel dosimeters.
Int J Radiat Oncol Biol Phys 2008;
70:1281-91. [PMID:
18313533 DOI:
10.1016/j.ijrobp.2007.11.032]
[Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2007] [Revised: 11/14/2007] [Accepted: 11/14/2007] [Indexed: 01/27/2023]
Abstract
PURPOSE
To extend the Radiological Physics Centre (RPC) intensity-modulated radiation therapy dose verification protocol to three dimensions using optical computed tomography (CT) scans of ferrous xylenol-orange (FX) gels.
METHODS AND MATERIALS
The dosimetry insert in the RPC head-and-neck phantom was replaced with an FX cylindrical gel dosimeter. Two gels were calibrated, independently irradiated with 6-MV X-ray beams and scanned using laser and cone-beam (Vista) optical CT, respectively. For matching dose slices, measured dose distributions were compared with Pinnacle3 computed distributions.
RESULTS
Within high-dose regions and low gradients, doses measured using laser CT were 2% to 3% less than the computed dose, whereas with cone-beam CT they were 4% to 5% less. Inside the central 90% of the gel cylinder diameter, the fraction of voxels satisfying the two-dimensional gamma analysis (5% dose difference, 3-mm distance to agreement) with laser-beam- and cone-beam-measured dose distributions were 98.4% and 99.0%, respectively. A three-dimensional gamma analysis with cone-beam data revealed that 96.7% of voxels within the central 90% gel volume satisfied the above criteria. Within the axial and sagittal planes through the primary planning target volume (PTV), computed and measured doses using GAFChromicEBT film (RPC measured) and cone-beam scanned FX gel generally agreed. At equivalent points in the planning target volumes, computed, thermoluminescent dosimeter (RPC-measured), and gel point doses agreed to within 5.1% in absolute dose.
CONCLUSIONS
Laser and cone-beam CT yield comparable dose distributions in high-dose regions. The RPC head phantom and optical CT-scanned FX gels can be used for accurate intensity-modulated radiation therapy dose verification in three dimensions.
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