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A CT calibration method based on the polybinary tissue model for radiotherapy treatment planning.
Nobuyuki Kanematsu1, Naruhiro Matsufuji, Ryosuke Kohno
1Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-Ku, Chiba 263-8555, Japan. nkanemat@nirs.go.jp
Physics in Medicine and Biology
|May 14, 2003
Summary
A new method calibrates CT numbers to effective density for radiotherapy, achieving 1% accuracy using tissue substitutes. This simplifies treatment planning, especially for heavy charged particle therapy.
Area of Science:
- Medical Physics
- Radiotherapy Physics
Background:
- Accurate effective density determination is crucial for radiotherapy treatment planning.
- Current methods for relating CT numbers to density can lack precision for advanced therapies.
Purpose of the Study:
- To develop a method for establishing the relationship between CT number and effective density for therapeutic radiation applications.
- To achieve high calibration accuracy for radiotherapy treatment planning.
Main Methods:
- Approximating body tissues as mixtures of muscle, air, fat, and bone.
- Using CT scans of tissue substitutes: water, air, ethanol, and potassium phosphate solution.
- Applying simple and specific corrections for non-equivalencies between substitutes and actual tissues.
Main Results:
- A calibration accuracy of 1% was achieved for the CT number-effective density relationship.
- The method was tested with biological materials, demonstrating its efficacy.
- The proposed method offers accuracy, simplicity, and specificity.
Conclusions:
- The developed method provides a reliable and accurate calibration for radiotherapy treatment planning.
- This approach is particularly suitable for heavy charged particle therapy.
- The method meets the requirements for a standard in radiotherapy.