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Tomotherapy for Craniospinal Irradiation: Dosimetric Comparison between Techniques

使用螺旋光子刀對全腦及脊髓照射:不同技術之劑量學比較

摘要


Purpose: The aim of this study is to compare dosimetric parameters of TomoTherapy (Tomo) and 3D conformal radiotherapy (3D CRT) for craniospinal irradiation (CSI). Materials & Methods: Three patients requiring CSI treatments were enrolled. All patients were adult males and treated in the supine position. Computed tomography (CT) scans with 10mm slice thickness were acquired for both the 3D CRT and Tomo plans. The prescribed dosage of the planning target volume (PTV) was 32 Gy. Dose homogeneity index (DHI), conformal index (CI), and physical parameters were used to compare the differences between the two treatment modalities. Results: The V95% (volume of receiving at least 95% of prescribed dose) of planning target volume-brain (PTV-B) was 100% for six plans. The mean V95% of planning target volume-spine (PTV-S) were 98.7% and 100% for 3D CRT and Tomo plans, respectively. The mean Dmax (maximal dose) of PTV-B was higher on 3D CRT than on Tomo (37.4 Gy/117% vs. 33.6 Gy/105%). The mean Dmax of PTV-S on 3D CRT was much higher than that on Tomo (50.8 Gy/159% vs. 33 Gy/103%). The mean DHI of PTV-B showed significant differences between CRT (1.17) and Tomo (1 .05), p= 0.009. The dose distribution of PTV-S planned by Tomo was more homogenous than that planned by 3D CRT (mean DHI 1.03 vs. 1.59, p= 0.0047). There were no significant differences in the mean CI of PTV-B on CRT (0.76) and Tomo (0.74), p> 0.05. The mean CI of PTV-S of Tomo was better than that of 3D CRT (0.47 vs. 0.2, p< 0.05). There were decreases in all Dmax of organs at risk (OARs) in the Tomo group except for bilateral kidneys (Tomo vs. 3D CRT: 14.8 Gy vs. 3.8 Gy). Conclusion: Tomo is simpler than linear accelerator for CSI because there is no junction between treatment fields. The dosimetric parameters of DHI and CI are superior in the Tomo group. Decreased OAR dose via Tomo may be helpful for minimizing the long-term latent effect.

並列摘要


Purpose: The aim of this study is to compare dosimetric parameters of TomoTherapy (Tomo) and 3D conformal radiotherapy (3D CRT) for craniospinal irradiation (CSI). Materials & Methods: Three patients requiring CSI treatments were enrolled. All patients were adult males and treated in the supine position. Computed tomography (CT) scans with 10mm slice thickness were acquired for both the 3D CRT and Tomo plans. The prescribed dosage of the planning target volume (PTV) was 32 Gy. Dose homogeneity index (DHI), conformal index (CI), and physical parameters were used to compare the differences between the two treatment modalities. Results: The V95% (volume of receiving at least 95% of prescribed dose) of planning target volume-brain (PTV-B) was 100% for six plans. The mean V95% of planning target volume-spine (PTV-S) were 98.7% and 100% for 3D CRT and Tomo plans, respectively. The mean Dmax (maximal dose) of PTV-B was higher on 3D CRT than on Tomo (37.4 Gy/117% vs. 33.6 Gy/105%). The mean Dmax of PTV-S on 3D CRT was much higher than that on Tomo (50.8 Gy/159% vs. 33 Gy/103%). The mean DHI of PTV-B showed significant differences between CRT (1.17) and Tomo (1 .05), p= 0.009. The dose distribution of PTV-S planned by Tomo was more homogenous than that planned by 3D CRT (mean DHI 1.03 vs. 1.59, p= 0.0047). There were no significant differences in the mean CI of PTV-B on CRT (0.76) and Tomo (0.74), p> 0.05. The mean CI of PTV-S of Tomo was better than that of 3D CRT (0.47 vs. 0.2, p< 0.05). There were decreases in all Dmax of organs at risk (OARs) in the Tomo group except for bilateral kidneys (Tomo vs. 3D CRT: 14.8 Gy vs. 3.8 Gy). Conclusion: Tomo is simpler than linear accelerator for CSI because there is no junction between treatment fields. The dosimetric parameters of DHI and CI are superior in the Tomo group. Decreased OAR dose via Tomo may be helpful for minimizing the long-term latent effect.

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