RADTH Imaging Guidelines

• PTV margin: based on confidence of the treatment technique's set up to be stable / reproducible

  • good immobilization is key: externally and internally
• Image Modality: based on what we need to see to accurately localize the target volume

  • MV images: use EPI, often done as BEV image
  • KV/KV images: use OBI, orthogonal images for field positioning / target localizing
  • CBCT: use OBI, 3D representation of patient's body
• Prostate:

  • PTV margin = 0.6 cm
  • Imaging = CBCT
  • shift action level = apply all shifts
  • image repeat action level = 0.6 cm
• Prostate Bed

  • PTV margin = 1 cm
  • Imaging = KV / KV
  • shift action level = 0.5 cm
  • image repeat action level = 1 cm
• Bladder:

  • PTV margin = 1.5 - 2 cm
  • Imaging = CBCT
  • shift action level = 0.5 cm
  • image repeat action level = 1 cm
• Cervix / Endometrium:

  • PTV margin = CTV +0.7 cm
  • Imaging = CBCT
  • shift action level = 0.3 cm
  • image repeat action level = 0.6 cm
• Esophagus / Stomach / Pancreas:

  • PTV margin = 0.5 - 1 cm
  • Imaging = KV / KV
  • shift action level = 0.5 cm
  • image repeat action level = 1 cm
• Anal Canal

  • PTV margin = 0.5 - 1 cm
  • Imaging = CBCT
  • shift action level = 0.3 cm
  • image repeat action level = 0.6 cm
• Rectum:

  • PTV margin = 1 cm or (0.5 - 1 cm)
  • Imaging = KV / KV or (CBCT)
  • shift action level = 0.5 cm or (0.3 cm)
  • image repeat action level = 1 cm or (0.6 cm)
• CBCT Prostate Procedure:

  → automatch to bone:

  • set ROI to include:
  • sacrum, pubic symphysis, femoral heads, pelvis
  • within scanned CBCT area (no black parts outside)
  • exclude: femur shaft
• CBCT Prostate Procedure:

  → automatch to soft tissue:

  • set ROI to include:
  • CTV + rectum
  • within scanned CBCT area (no black parts outside)
  • exclude: small bowel + rectal gas
• Evaluating pre treatment prep for prostate CBCT:

  • bladder:
  • at least 2 / 3 as full as simulated bladder (on mid plane sagittal)
  • rectum:
  • < 4 cm
  • no more than 2 cm greater than simulated rectum
  • does not displace more than 1 / 3 of prostate