title: Dose-volume histogram analysis of composite EQD2 dose distributions using the central shielding technique in cervical cancer radiotherapy.
abstract: To analyze the dose-volume histogram of the central shielding technique for cervical cancer radiotherapy by computing the composite three-dimensional EQD2 dose distributions of external-beam radiotherapy plus intracavitary brachytherapy.
  
  
  
  On a phantom, three patterns of high-risk clinical target volume (HR-CTV) with right-left diameters of 3, 4, and 5 cm were created using clinical data. Four patterns of combinations of whole-pelvis irradiation plus "pelvis irradiation using the central shielding technique" (CS) (shielding width, 3 or 4 cm) were created: 20 Gy/10 fractions + 30 Gy/15 fractions, 30 Gy/15 fractions + 20 Gy/10 fractions, 40 Gy/20 fractions + 10 Gy/5 fractions, and 50 Gy/25 fractions + 0 Gy. The intracavitary brachytherapy plan was set as 24 Gy/4 fractions prescribed to the Point A. The HR-CTV D90/D98 and modeled bladder/rectum D2cc were computed using the composite EQD2 dose distributions of all the treatment combinations.
  
  
  
  If appropriate combinations of the treatment plans were selected on the basis of the CS doses and the HR-CTV sizes, the D90/D98 of HR-CTV 3 cm, HR-CTV 4 cm, and HR-CTV 5 cm were 89.7 Gy/80.6 Gy, 77.3 Gy/72.0 Gy, and 73.0 Gy/69.2 Gy in the case of CS width 3 cm, respectively; and 86.2 Gy/76.0 Gy, 73.3 Gy/67.6 Gy, and 70.9 Gy/67.1 Gy in the case of CS width 4 cm, respectively. The contributions of CS to the HR-CTV D90/bladder D2cc/rectum D2cc values were 24-56%/28-32%/9% of the CS plan doses for shielding width of 3 cm and were 13-35%/11-16%/5-6% for shielding width of 4 cm.
  
  
  
  The dose contributions of CS were variable but not negligible when analyzing the total doses delivered to the HR-CTV.
authors.affiliation: Department of Radiation Oncology, Fukushima Medical University, Fukushima, Japan; Department of Radiation Oncology, Gunma University Graduate School of Medicine, Gunma, Japan; Department of Radiation Oncology, Saitama Medical University International Medical Center, Saitama, Japan. Electronic address: tamakit@fmu.ac.jp.
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Tamaki
authors.affiliation: Department of Radiation Oncology, Gunma University Graduate School of Medicine, Gunma, Japan.
authors.forename: Shin-Ei
authors.initials: SE
authors.lastname: Noda
authors.affiliation: Department of Radiation Oncology, Gunma University Graduate School of Medicine, Gunma, Japan.
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Ohno
authors.affiliation: Department of Radiation Oncology, Saitama Medical University International Medical Center, Saitama, Japan.
authors.forename: Yu
authors.initials: Y
authors.lastname: Kumazaki
authors.affiliation: Department of Radiation Oncology, Saitama Medical University International Medical Center, Saitama, Japan.
authors.forename: Shingo
authors.initials: S
authors.lastname: Kato
authors.affiliation: Department of Radiation Oncology, Gunma University Graduate School of Medicine, Gunma, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Nakano
mesh_terms: D001918:Brachytherapy / Q000379:methods; D005260:Female; D006801:Humans; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D012007:Rectum; D001743:Urinary Bladder; D002583:Uterine Cervical Neoplasms / Q000532:radiotherapy*
keywords: Central shielding technique; Cervical cancer; External-beam radiotherapy; Intracavitary brachytherapy; Whole-pelvis irradiation