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Updated: Mar 17, 2026
Stereotactic Radiosurgery for Gynecologic Cancer
Published on: April 17, 2012
Dose-volume histogram analysis of composite EQD2 dose distributions using the central shielding technique in cervical
Tomoaki Tamaki1, Shin-Ei Noda2, Tatsuya Ohno2
1Department 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.
Purpose:
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.
Methods And Materials:
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.
Results:
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.
Conclusion:
The dose contributions of CS were variable but not negligible when analyzing the total doses delivered to the HR-CTV.
