Dosimetrical Aspect of CT Simulation Role in Radiation Therapy Planning
Background: The dose distribution is affected by tissue inhomogeneities and purpose of this article is a dosimetric evaluation of corrective role of computerized tomographic (CT) data in radiotherapy treatment planning (RTP) for different parts of the body.
Method & materials: 54 cases of head&neck, pelvis, abdomen and breast cancers were included. All of them were imaged with same CT Scan. Each case was planned without and with CT-based density correction by a two dimensional ALFARD RTP system. Analysis of dosimetric parameters was done for with and without inhomogeneity corrections based on effective path length method. Dosimetric parameters are dose uniformity (Te), average (Davg), minimum (Dmin) and maximum (Dmax) doses for both the planning target volumes and organs at risk.
Results: Typical results of the mean differences (MD) between corrected and non-corrected dose parameters in TV’s were shown below.
Conclusion: Present study showed the role of CTS for dosimetric corrections. However, findings confirm that CT correction for density variation shows different improvements for different parts of the body. In some parts, if correction not applied, the dose deviations can be out of tolerance limits defined by standards for tumors and normal tissues.
KeywordsRadiotherapy planning density correction target volume organ at risk CT planning
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