Effects of computed tomography slice thickness on clinical target volume and dose in intensity-modulated radiotherapy for chest cancer based on different reconstruction methods(PDF)
《中国医学物理学杂志》[ISSN:1005-202X/CN:44-1351/R]
- Issue:
- 2018年第3期
- Page:
- 249-255
- Research Field:
- 医学放射物理
- Publishing date:
Info
- Title:
- Effects of computed tomography slice thickness on clinical target volume and dose in intensity-modulated radiotherapy for chest cancer based on different reconstruction methods
- Author(s):
- HE Ya’nan; LUO Huanli; JIN Fu; YANG Dingyi; HUANG Luo
- Chongqing Cancer Institute & Hospital & Cancer Center, Chongqing 400030, China
- Keywords:
- ; chest tumor; computed tomography slice thickness; image reconstruction; intensity-modulated radiotherapy; organs-at-risk
- PACS:
- R737.9；R815.2
- DOI:
- DOI:10.3969/j.issn.1005-202X.2018.03.001
- Abstract:
- Objective To evaluate the effects of different computed tomography (CT) slice thicknesses on the volume and dose of target areas and organs-at-risk of patients with chest cancer based on two different reconstruction methods. Methods Eleven patients with chest cancer (mainly, esophagus cancer, lung cancer and breast cancer) were enrolled in the study. The CT images with 2 mm slice thickness (2-CT) were transferred to Eclipse 10.0 treatment planning system. The images with different slice thicknesses (4, 6, 8 and 10 mm), namely 4-CT, 6-CT, 8-CT and 10-CT, were reconstructed by two methods. In Method 1, the largest target layer was taken as the starting layer, while in Method 2, the metal marker layer was treated as the starting layer. The target areas and organs-at-risk were delineated on 2-CT images and then were copied slice by slice on CT images with different slice thicknesses. Similarly, intensity-modulated radiotherapy (IMRT) plans were developed on the 2-CT images and then were copied on the other CT images. The target volume and doses were computed independently for each image. The results on 2-CT images were chosen as the reference standard. Results The target volume in two reconstruction methods was gradually increasing with the increase of slice thickness. When the target area was 1.3 cm3, the volume deviation on 10-CT images in two methods was up to 84.62% and the deviation on 8-CT images was 38.46% (Method 1) and 84.62% (Method 2). For the target volume of 30-100 cm3, the volume changes in Method 1 were significantly smaller than that in Method 2; for target volume larger than 100 cm3, the deviation was trivial, without being increasing with the increase of slice thickness. The changes in radiation conformal index (CI) were gradually larger as the thickness increased. The changes in CI of small targets (<30 cm3) were particularly significant on 8-CT image (6.56% and 13.18% for Method 1 and Method 2, respectively) and 10-CT image (13.60% and 11.18% for Method 1 and Method 2, respectively) and that for larger targets with 30-100 cm3 were 1.29%-3.03% (Method 1) and 1.34%-5.42% (Method 2). Both the variation tendency of CI in Method 1 and Method 2 was less than 1.38%. Nevertheless, the difference of HI between two methods was not obvious. The changes of HI were larger on 8-CT image (12.95% and 16.15% for Method 1 and Method 2, respectively) and 10-CT image (17.42% and 15.43% for Method 1 and Method 2, respectively). The minimum dose, average dose of spinal cord, the V5, V30 of lung, and the V30, V40 of heart in IMRT were significantly affected by CT slice thickness (P<0.05). Conclusion In the IMRT for chest cancer, the reconstruction method based on the largest target layer is superior to that based on the metal marker layer. Meanwhile, the study provides some reference for improving the existing CT scanning process.
Last Update: 2018-03-21