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KMID : 1164220100220020145
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Journal of Korean Society for Radiotherapeutic Technology
2010 Volume.22 No. 2 p.145 ~ p.153
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How to Determine the Moving Target Exactly Considering Target Size and Respiratory Motion: A Phantom Study
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Kim Min-Su
Back Geum-Mun
Kim Dae-Sup
Kang Tae-Young
Hong Dong-Ki
Kwon Kyung-Tae
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Abstract
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Purpose: To accurately define internal target volume (ITV) for treatment of moving target considering tumor size and respiratory motion, we quantitatively investigated volume of target volume delineated on CT images from helical CT and 4D CT scans.
Materials and Methods: CT images for a 1D moving phantom with diameters of 1.5, 3, and 6 cm, acryl spheres were acquired using a LightSpeed RT¹? CT simulator. To analyze effect of tumor motion on target delineation, the CT image of the phantoms with various moving distances of 1~4 cm, and respiratory periods of 3~6 seconds, were acquired. For investigating the accuracy of the target trajectory, volume ratio of the target volumes delineated on CT images to expected volumes calculated with diameters of spherical phantom and moving distance were compared.
Results: Ratio for the diameter of 1, 5, 3, and 6 cm targets were 32±14%, 45±14%, 58±13% and , respectively, in the all cases. As to 4DCT, RatioMIP were 98±8%, 97±5% and 95±1% respectively.
Conclusion: The target volumes delineated on MIP images well represented the target trajectory, in comparison to those from helical CT. Target volume delineation on MIP images might be reasonable especially for treatment of early stage lung cancer, with meticulous attention to small size target, large respiratory motion, and fast breathing.
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KEYWORD
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target size, 4D CT, MIP, respiratory period
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