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 Nikon D7000, 20mm lens, f/2.8, 400ISO
• Used camera control pro 2 app
• Image of ruler taken at sheet for pixels to mm conversion
• 5 images taken at each collimator size with 1 background image each.
• Change exposure time until near max saturation - get's best bit depth
• View data analysis here

First run

With scintillator sheet
Collimator Size (mm)	Exposure (s)	Image	Comments
5	30
7.5	20
10	15
12.5	10
15	8
20	8
25	6
30	6
35	5
40	4
50	3
60	3

No scintillator sheet
Collimator Size (mm)	Exposure (s)	Image	Comments
60	3		Can see green discolouration caused by previous irradiations. Blocks must have been rotated by 90 when re-assembling

Second run
Replaced plastic blocks from first run with new un-irradiated plastic blocks, but using same green scintillator sheet.

With scintillator sheet
Collimator Size (mm)	Exposure (s)	Image	Comments
5	30
7.5	20
10	15
12.5	10
15	8
20	8
25	6
30	6
35	5
40	4
50	3
60	3		Green discolouration probably from scintillator sheet. Rotated by 90 when re-assembling blocks and sheet

No scintillator sheet
Collimator Size (mm)	Exposure (s)	Image	Comments
5	30
7.5	20
10	15
12.5	10
15	8
20	8
25	6
30	6
35	5
40	4
50	3
60	3