LhARA radiobiology; meeting: 27Nov25; 14:00 BST

ZOOM: ​https://imperial-ac-uk.zoom.us/j/98220889714?pwd=SM90vOF7BKSXoU3mD9q7OwBQo4IVB3.1

Attended: EM, JMcG, CW, DA, AFr, TP, AG, MB, MH, JP, RW, CD

Meeting Notes

1. Minutes and actions:

2. Laser: RW
   

• RW: Explanation of the laser problem and the fix
  • That problem seems permanently fixed.

3. RCF: AFR, DA, CD
   

• Calibration
  • Rotation Issue
  • Rotating the films in the scanner can cause a ~30% change to the mean dose in a particular case. More generally causes a substantial difference.
  • Can combat by rotating the films each time we scan and always selecting the orientation that gives the highest mean pixel count
• Calculating Dose per Shot, Variation and Dose delivered to Cells
  • From RCF, average dose per shot of 0.61±0.25Gy (More data to be analysed)
  • Hard to spot a variation day to day
  • Variation in one showed a change after 8 films had been irradiated. Need to analyse the shots to get a better understanding of what this is
    • Robbie's suggestion is a defocussing laser spot effect
• Flatness and Uniformity of Dose
  • Average CV: 15.1±2.5%
  • Average Flatness in X: 26.4±5.5%
  • Average Flatness in Y: 29.6±4.7%
  • Beam is too non-uniform still
• Sim comparison
  • CV: 17%
  • Moving the Copper closer would bring CV down to 9% and the mean dose would also fall by 45%
• Slides

4. Bio: EM, JP
   
   • Dry run seeding density test has worked: Slides
   • Marie/Rosh are going to check colonies on Friday/Monday and make executive decision on staining days
   • Test the temperature of the incubator, as it seems too warm
   • Incubator water dried out, Rosh has refilled (some indication the plates were drying out ~50% - check how much as only 3ml was added. Could top up with fresh media)

• Josie sent cell pellets over to Marie/Rosh - will comets be performed? Concern is the “time point” due to the time spent on ice post-IR

• Wait for staining (& analysis?) of current clonogenics before irradiating more cells
• If no survival in the control plates is seen, procedure needs evaluating as dry run was ok
• Issues for running cells next week: Cells/Mylar dishes/lids need to be taken from Birmingham - discussions regarding specific ideal days and people availability are needed
• Next run - do comparable experiments with Marie/Rosh and the X-ray source and possibly add RCF to base of the cell dish.
  • Discussion of faster cell analysis techniques such as western blot
  • Use IF to get an idea of hotspots in the cell dish?

5. Future:
   

• Current Problems:
  • Clear Communication of Requirements
  • RCF to Dose Procedure
    • Alfredo and Diaza are piecing together a protocol document to standardise how we complete this procedure
    • The rotation issue is taken into account
    • Diaza in favour of scanning at lower resolution to speed it up
  • Uniformity not good enough
    • Place the Copper scatterer closer
    • Results need to analysed
  • Shot-to-shot variation
    • Include a piece of RCF in front of the cells (Ideally delaminated but not possible to calibrate before the next visit)
      • Need to sim what the LET would be for our energy range into the cells with the RCF in place
    • Longer-term investigate an on-beam diagnostic
    • Another option is to find a correlation between the RCF mean dose and one of the laser diagnostics that the team already gathers

• Discussion of when to use the rollover days
  • Plan to use Wednesday, Thursday and Friday next week
  • If good, then use the 3 days to do more cell irradiations
    • Emma will send the dishes up tomorrow
  • If not work on more beam diagnostics and improving it to complete cell irradiations, tackling either uniformity or shot-to-shot variation

• IPAC abstract submission?
  • No takers and a belief that we should wait until we have a slam dunk result
  • Note: LhARA will have a general submission that will mention PoPLaR
• Book a longer discussion to analyse all the results and define a plan for the future
  • Not discussed

6. DoNM

• 11th Dec

7. AoB

• Congratulations Dr Melia!!!
• pic

Summary of actions required

Short-Term

• MB: Evaluate the cells
• EM: Send the cell dishes to SCAPA if required and decide on the shot plan
• CD, RW, EM, CW ...: Plan what to run if cells not required. Lay out a clear aim for the rollover days.
• CD, TP: Evaluate LET in the cells with the RCF in front
• CD, AFr: Complete analysis of RCF with Error Calculation
• AFr, DA: Write out RCF procedure document
• TP: Test orientation of calibration RCF in scanner at Birmingham
• CD: Send shot results to Robbie to help find the cause of variation after 8 films irradiated

Long-Term

• ALL: Organise a longer meeting discussion post rollover days
• RW, CD: Study correlation between laser diagnostics and mean dose
• EM, JMcG: Write up summary of PoPLaR Phase 2
• KL: Investigate other on-beam diagnostics
• CD, JMcG: Investigate how to achieve uniformity without scatterer in place

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