Radiotherapy/Experimental Runs/2020-02-04

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

Setup

Schematic

Photos of setup

(Inside pelicase, outside pelicase, collimators, through pelicase window)

Pre-data Taking Information and Notes

• Used 200mmx200mmx2mm green scintillator sheet polystyrene base sandwiched by two 200mmx200mmx50mm polystyrene clear plastic blocks
• 53cm from lens to sheet
• Check camera in focus with ruler on the sheet
• Near/Far limit of focus 49.4cm 57.1cm calculated using https://dofmaster.com/dofjs.html
• Pelicase on couch
• Scintillator blocks aligned to laser cross hairs
• 785 mm source to surface distance suitable for output factor/PDD/profile measurements.
• Room lights out and pelicase window open.
• Check optical axis aligned with top surface using crosshair in the image analysis.
• Arrived at hospital at 11am, finished data taking at 5pm

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.

With scintillator sheet
Collimator Size (mm)	Monitor Units	Image	Comments
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

No scintillator sheet
Collimator Size (mm)	Monitor Units	Image	Comments
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