Using Cherenkov imaging to monitor the match line between photon and electron radiation therapy fields on biological tissue phantoms

Application of Cherenkov radiation in tumor imaging and treatment

Cherenkov radiation (CR) is the characteristic blue glow that is generated during radiotherapy or radioisotope decay. Its distribution and intensity naturally reflect the actual dose and field of radiotherapy and the location of radioisotope imaging agents in vivo. Therefore, CR can represent a potential in situ light source for radiotherapy monitoring and radioisotope-based tumor imaging. When used in combination with new imaging techniques, molecular probes or nanomedicine, CR imaging exhibits unique advantages (accuracy, low cost, convenience and fast) in tumor radiotherapy monitoring and imaging. Furthermore, photosensitive nanomaterials can be used for CR photodynamic therapy, providing new approaches for integrating tumor imaging and treatment. Here the authors review the latest developments in the use of CR in tumor research and discuss current challenges and new directions for future studies.

The Measurement of the Surface Dose in Regular and Small Radiation Therapy Fields Using Cherenkov Imaging

Purpose: The aim of this study is to measure the output factor (OF) and profile of surface dose in regular and small radiation therapy fields using Cherenkov imaging (CI). Methods: A medical linear accelerator (linac) was employed to generate radiation fields, including regular open photon field (ROPF), regular wedge photon field (RWPF), regular electron field (REF) and small photon field (SPF). The photon beams consisted of two filter modes including flattening filter (FF) and flattening filter free (FFF). All fields were delivered to a solid water phantom. Cherenkov light was captured using a charge-coupled device system during phantom irradiation. The OF and profile of surface dose measured by CI were compared with those determined by film measurement, ionization chamber measurement and treatment planning system calculation in order to examine the feasibility of measuring surface dose OF and profile using CI. Results: The discrepancy between surface dose OF measured by CI and that determined by other methods is less than 6% in ROPFs with size less than 10 × 10 cm², REFs with size less than 10 × 10 cm², and SPFs except for 1 × 1 cm² field. In the flat profile region, the discrepancy between surface dose profile measured by CI and that determined by other methods is less than 4% in REFs and less than 3% in ROPFs, RWPFs, and SPFs except for 1 × 1 cm2 field. The discrepancy of the surface dose profile is in compliance with the recommendation by IAEA TRS 430 reports. The discrepancy between field width measured by CI and that determined by film measurement is equal to or less than 2 mm, which is within the tolerance recommend by the guidelines of linac quality assurance in regular open FF photon fields, SPFs, and REFs with cone size of 10 × 10 cm² in area. Conclusion: CI can be used to quantitatively measure the OF and profile of surface dose. It is feasible to use CI to measure the surface dose profile and field width in regular open FF photon fields and SPFs except for 1 × 1 cm² field.