Radiotherapy/Experimental Runs/2020-02-04

Second experimental measurements with Cyberknife at Birmingham. Green scintillator thin sheet measurements only.

Setup

Schematic

Pre-data Taking Information and Notes

• Phantom
  • 200mmx200mmx2mm blue scintillator sheet polystyrene base
  • sandwiched by two 200mmx200mmx50mm polystyrene clear plastic blocks
• 565mm from lens to centre
• Check camera in focus with ruler on the sheet
• Ruler in focus at sheet
• Scintillator blocks aligned to laser cross hairs
• 785 mm source to surface distance suitable for output factor/PDD/profile measurements.
• Wooden box is covered with black cloth
• Camera height adjusted with wooden plates
• Top surfaces of plastic blocks and sheet aligned with paper underneath

Data Taking

• All images taken with
  • Canon EOS 1100D
  • 18-55mm lens
  • f/5
  • 200ISO
  • 30s exposure
• Beam turned on for a given amount of time within the 30s exposure
• This is noted in monitor units, with the beam having constant 1000MU/minute

• Used EOS utility app for controlling camera
• Image of ruler taken at sheet for pixels to mm conversion
• 3 images taken at each collimator size with 1 background image each.

Collimator Size (mm)	Monitor Units	With sheet	No sheet
5	400
7.5	400
10	400
12.5	400
15	400
20	400
25	300
30	300
35	250
40	250
50	150
60	150

Before and after irradiation

Green discolouration observed after irradiation. Only present when the lights are on