Quantitative analysis of intra-fractional variation in CT-based image guided brachytherapy for cervical cancer patients

Yuya Miyasaka, Noriyuki Kadoya, Kengo Ito, Rei Umezawa, Masaki Kubozono, Takaya Yamamoto, Yujiro Nakajima, Masahide Saito, Yoshiki Takayama, Kenji Nemoto, Takeo Iwai, Keiichi Jingu

Research output: Contribution to journalArticlepeer-review

Abstract

We quantified intra-fractional dose variation and organ movement during CT-based 3D-image guided brachytherapy (3D-IGBT) in cervical cancer patients. Fifteen patients who underwent CT-based 3D-IGBT were studied. For all patients, pre-delivery CT for treatment planning after applicator insertion and post-delivery CT after dose delivery without changing the applicator position were acquired. Pre- and post-delivery CT were rigidly fused by matching the inserted applicator and planned dose on pre-delivery CT (pre-delivery dose) was mapped on post-delivery CT (post-delivery dose). D2, D1, and D0.1 cm3 of the rectum and bladder were compared between pre- and post-delivery doses with contours on each CT image. Organ movement and deformation was evaluated using deformation vector fields calculated by deformable image registration between pre- and post-delivery CT. We also evaluated dose variation and DVF between with and without a catheter to control filling. Differences in all DVH parameters were <±3% in physical dose and ± 5% in EQD2. However, a > 15% dose difference was found in 13.8% of the fractions in rectum D2 cm3 and in 11.1% of those in bladder D2 cm3. The mean value of DVF for bladder was larger than that of rectum, especially for the superior-inferior (S-I) direction. Insertion catheters in bladder reduced mean dose and DVF variation compared with that of without catheters. In fraction groups with large dose increasing, DVF in the S-I direction was significantly larger than that of other fraction groups. Our results indicated that preparation is needed to reduce changes in the S-I direction affect dose variation.

Original languageEnglish
Pages (from-to)164-172
Number of pages9
JournalPhysica Medica
Volume73
DOIs
Publication statusPublished - 2020 May

Keywords

  • CT-based 3D-IGBT
  • Cervical cancer
  • Deformable image registration
  • Deformation vector field
  • Intra-fractional variation

ASJC Scopus subject areas

  • Biophysics
  • Radiology Nuclear Medicine and imaging
  • Physics and Astronomy(all)

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