UNIFORM DOSE COMPENSATION USING FIELD WITHIN A FIELD TECHNIQUE IN T-SHAPED IRRADIATION FOR ESOPHAGEAL CANCER

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Other Title
  • 食道癌に対するＴ字照射における画一的線量分布補正―重複照射野法（ｆｉｅｌｄ　ｗｉｔｈｉｎ　ａ　ｆｉｅｌｄ　ｔｅｃｈｎｉｑｕｅ）の応用―
  • 重複照射野法 (field within a field technique) の応用

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Abstract

Purpose: We devised a uniform compensation method to improve dose distribution using the field within a field technique in T-shaped irradiation for esophageal cancer. Material and Method: Isodose curves and dose volume histograms (DVH) of the esophagus in the treatment volume were examined in ten patients treated for esophageal cancers. For the DVH analysis, the prescription dose was 40 Gy to the center of the treatment volume, and the volume ratio of the esophagus receiving within ± 5% of the prescription dose (38-42 Gy) was regarded as an index of dose homogeneity (V ± 5%). Result: The peak dose in the conventional antero-posterior opposed fields irradiation existed at the clavicular level, and the 90% isodose curve crossing the esophagus almost corresponded to the top level of the aortic arch. When 40 Gy is irradiated, the maximum dose of the esophagus and V ± 5% were 45.55 ± 0.55 Gy and 59.7 ± 13.2% respectively. The dose distribution of the esophagus became relatively homogeneous when a 10% dose was added using the field within a field technique to the area under the bottom level of the aortic arch, and the maximum dose and V ± 5% were 42.53 ± 0.94 Gy and 91.7 ± 7.1 %respectively. Conclusion: A 10% and more overdose area existed at the clavicular level in the conventional antero-posterior opposed fields irradiation. A relatively homogeneous dose distribution could be obtained using the field within a field technique.

Journal

  • The Journal of JASTRO

    The Journal of JASTRO 15 (2), 85-88, 2003

    Japanese Society for Therapeutic Radiology and Oncology

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