M Rahman¹*, MR Ashraf^1,2, R Zhang^1,3,4, X Cao⁵, D Gladstone^1,3,4, L Jarvis^3,4, J Hoopes^1,3,4,6, B Pogue^1,4,6, P Bruza¹, (1) Thayer School of Engineering, Dartmouth College, Hanover, NH, (2) Department of Radiation Oncology, Stanford University, Stanford, CA, (3) Department of Medicine, Radiation Oncology, Geisel School of Medicine, Dartmouth College, Hanover NH, (4) Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, NH,(5) School of Life Science and Technology, Xidian University, Xi'an, China, (6) Department of Surgery, Geisel School of Medicine, Dartmouth College, Hanover NH

• 
  M Rahman

• 
  
• 
  
• 
  
• 
  
• 
  
• 
  
• 
  

(Saturday, 3/26/2022)   [Central Time (GMT-5)]

Purpose: A fast-imaging technique was developed for the first in vivo Cherenkov emission imaging from an ultra-high dose rate (UHDR) electron beam source at single pulse (360 Hz) submillimeter resolution for beam delivery monitoring.

Methods: A CMOS camera, gated to the UHDR LINAC, imaged the Cherenkov emission profiles pulse by pulse passively during the irradiation of mice on their limbs and intestinal region and a tissue equivalent phantom. An intensifier’s effect on image quality was investigated considering signal to noise and spatial resolution. Pulse by pulse and cumulative Cherenkov emission profiles were quantified spatially and temporally.

Results: An intensifier improved the emission profile’s signal to noise ratio from 15 to 280, with reduced spatial resolution. The profile extended beyond the treatment field edge due to the lateral scattering of the electrons and optical photons in tissue. The CMOS camera with an intensifier detected the changes of ~3mm in Cherenkov emission profile due to expiration and inspiration during the murine respiratory cycle. The intensified camera’s submillimeter resolution facilitates accurate detection of beam parameters (i.e. output, shift, full width half max, symmetry and flatness).

Conclusion: This fast-imaging technique can be utilized for in vivo intrafraction monitoring of FLASH patient treatments at single pulse resolution. It can display delivery differences during respiration, and variability in the delivered treatment’s surface profile, which may be perturbed from the intended UHDR treatment more for pencil beam scanning systems. The technique may leverage the Cherenkov emission surface profile to gate the treatment via respiratory gating systems under FLASH conditions while considering beam parameters such as per pulse output or beam steering consistency during delivery.

Funding Support, Disclosures, and Conflict of Interest: This work was supported by seed funding (Norris Cotton Cancer Center core grant P30 CA023108 and Thayer School of Engineering), Department of Medicine SEAM Award from DHMC and Geisel School of Medicine, and NIH grant R01 EB024498. Brian Pogue is cofounder and Mahbubur Rahman is an employee of DoseOptics LLC.

ePosters

• 174-60670-16021654-182589-1873635082.pdf (M Rahman)

Keywords

Electron Therapy, In Vivo Dosimetry, Image Guidance

Taxonomy

TH- External Beam- Electrons: Development (new technology and techniques)

Contact Email