The Value of Three-Dimensional Radiotherapy Planning in Advanced Carcinoma of the Urinary Bladder Based on Computed Tomography

Larsen, Lisbeth; Engelholm, Svend Aage

doi:10.3109/02841869409121778

Cited by 12 publications

(1 citation statement)

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“…14 No. 1 February 2002 more accurately [1,2]. However, some uncertainties from the intra-treatment organ movement and the daily setup error still deserve attention to overcome [3,4].…”

Section: Introductionmentioning

confidence: 99%

Model Analysis of Respiration-Related Dosimetric Change During Radiotherapy

Chen

Cheng

et al. 2002

Biomed. Eng. Appl. Basis Commun.

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To estimate the respiration-induced dosimetric change at beam edge during a beam-on interval of radiotherapy, by the integration of a mathematical model for organ motion and a modeled beam profile. A method is proposed which incorporated the effects of intra-treatment organ motion due to breathing on the dosimetric change for the treatment of liver cancer. The basic algorithm was to assume the motion of infra-abdominal organs was predominantly in the superior-inferior (S-I) direction. The starting phase was defined as the mid-phase at exhale, to reproduce the same situation of computed tomography simulation for liver cancer. The S-I extent of motion was defined as 1.5cm. The period of a breathing cycle was defined as 4.2 seconds. The shape parameter of the respiratory model was defined as 3. The radiation dose of 100 cGy given with the rate of 300 MU/minute was designed for the model analysis. The position at the beam edge as a function of time could be parameterized for a 10cm x 10cm field with a setup of SAD 100cm. The dose profiles of both 6MV and 18MV photons were applied for the dosimetric calculation of the beam-edge point during the dynamic movement in a beam-on time interval of radiotherapy. The point doses at the superior beam edge for 6MV photons and18MV photons during a beam-one interval of 22.8 seconds were 73.5% and 77.2% of the isocenter dose, respectively. The point doses at the inferior beam edge for the two energies were 31.2% and 32.4%, respectively. There were 147-154% dose increase for superior beam edge and 62.4-64.8% dose decrease for inferior beam edge, as compared to the 50% isocenter dose with the static dose distribution. It is simple and feasible to use the mathematical model to estimate the dosimetric change of the intra-abdominal organ motion from respiration. The impact of respiration on the dosimetric difference deserves more attention in the prescription of radiation treatment. Further measurement of the exact organ motion during the real treatment is warranted to optimize the model.

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“…14 No. 1 February 2002 more accurately [1,2]. However, some uncertainties from the intra-treatment organ movement and the daily setup error still deserve attention to overcome [3,4].…”

Section: Introductionmentioning

confidence: 99%