Dosimetry for FLASH Radiotherapy: A Review of Tools and the Role of Radioluminescence and Cherenkov Emission

Ashraf, Mudasir; Rahman, Mahbubur; Zhang, Rongxiao; Williams, Benjamin B.; Gladstone, David J.; Pogue, Brian W.; Brůža, Petr

doi:10.3389/fphy.2020.00328

Cited by 110 publications

(151 citation statements)

References 140 publications

(179 reference statements)

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“…The ideal situation, with the electron beam impinging along the normal towards a flat surface of a homogeneous tissue, was not fulfilled in the treatments, which may have led to degrading of the dose distribution estimated to be less than 10%. Ion-chambers, which are the standard real time dosimeter in conventional radiotherapy, experience a large drop in ion collection efficiency at the ultra-high dose rates associated with FLASH radiation (24)(25)(26), making them imprecise and impractical for real time dose measurements. Therefore, the Farmer-type ion-chamber used in the current setup was functioning solely as an output monitor.…”

Section: Patient Nomentioning

confidence: 99%

Establishment and Initial Experience of Clinical FLASH Radiotherapy in Canine Cancer Patients

Konradsson

Arendt

Jensen³

et al. 2021

Front. Oncol.

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FLASH radiotherapy has emerged as a treatment technique with great potential to increase the differential effect between normal tissue toxicity and tumor response compared to conventional radiotherapy. To evaluate the feasibility of FLASH radiotherapy in a relevant clinical setting, we have commenced a feasibility and safety study of FLASH radiotherapy in canine cancer patients with spontaneous superficial solid tumors or microscopic residual disease, using the electron beam of our modified clinical linear accelerator. The setup for FLASH radiotherapy was established using a short electron applicator with a nominal source-to-surface distance of 70 cm and custom-made Cerrobend blocks for collimation. The beam was characterized by measuring dose profiles and depth dose curves for various field sizes. Ten canine cancer patients were included in this initial study; seven patients with nine solid superficial tumors and three patients with microscopic disease. The administered dose ranged from 15 to 35 Gy. To ensure correct delivery of the prescribed dose, film measurements were performed prior to and during treatment, and a Farmer-type ion-chamber was used for monitoring. Treatments were found to be feasible, with partial response, complete response or stable disease recorded in 11/13 irradiated tumors. Adverse events observed at follow-up ranging from 3-6 months were mild and consisted of local alopecia, leukotricia, dry desquamation, mild erythema or swelling. One patient receiving a 35 Gy dose to the nasal planum, had a grade 3 skin adverse event. Dosimetric procedures, safety and an efficient clincal workflow for FLASH radiotherapy was established. The experience from this initial study will be used as a basis for a veterinary phase I/II clinical trial with more specific patient inclusion selection, and subsequently for human trials.

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Section: Patient Nomentioning

confidence: 99%

Establishment and Initial Experience of Clinical FLASH Radiotherapy in Canine Cancer Patients

Konradsson

Arendt

Jensen³

et al. 2021

Front. Oncol.

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“…Other dose-rate independent dosimeters that have been employed for the measurement of ultrahigh dose-rate beams are the PTW microdiamond, the LYNX 2D scintillator the TLD-100 and the Methyl Viologen ( 44 ). A comprehensive review of dosimeters for FLASH including charge-based, chemicals and luminescence detectors has been presented recently ( 49 ) with interesting figures of merit in a spider chart diagram for each of them, underlying the importance of the luminescence methods for resolution in time and additional performances on measuring Oxygen tension and LET.…”

Section: Biology: Revisiting Radiation Biology To Improve Healthy Tismentioning

confidence: 99%

Biological and Mechanical Synergies to Deal With Proton Therapy Pitfalls: Minibeams, FLASH, Arcs, and Gantryless Rooms

et al. 2021

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Proton therapy has advantages and pitfalls comparing with photon therapy in radiation therapy. Among the limitations of protons in clinical practice we can selectively mention: uncertainties in range, lateral penumbra, deposition of higher LET outside the target, entrance dose, dose in the beam path, dose constraints in critical organs close to the target volume, organ movements and cost. In this review, we combine proposals under study to mitigate those pitfalls by using individually or in combination: (a) biological approaches of beam management in time (very high dose rate “FLASH” irradiations in the order of 100 Gy/s) and (b) modulation in space (a combination of mini-beams of millimetric extent), together with mechanical approaches such as (c) rotational techniques (optimized in partial arcs) and, in an effort to reduce cost, (d) gantry-less delivery systems. In some cases, these proposals are synergic (e.g., FLASH and minibeams), in others they are hardly compatible (mini-beam and rotation). Fixed lines have been used in pioneer centers, or for specific indications (ophthalmic, radiosurgery,…), they logically evolved to isocentric gantries. The present proposals to produce fixed lines are somewhat controversial. Rotational techniques, minibeams and FLASH in proton therapy are making their way, with an increasing degree of complexity in these three approaches, but with a high interest in the basic science and clinical communities. All of them must be proven in clinical applications.

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“…4 Unfortunately, high average and instantaneous dose rates and high doses per pulse make dosimetry for FLASH exceptionally challenging. [5][6][7][8][9][10][11][12] Most conventional dosimeters either show significant dependence on dose rate at high dose rate conditions or fail to provide any temporal information. Generally, detectors can be divided into three main categories based on the underlying physical mechanism governing the detector's response to radiation: (a) charge, (b) chemical, and (c) luminescence.…”

Section: Introductionmentioning

confidence: 99%

“…This novel modality has garnered considerable interest and was recently used to treat the first human patient 4 . Unfortunately, high average and instantaneous dose rates and high doses per pulse make dosimetry for FLASH exceptionally challenging 5–12 . Most conventional dosimeters either show significant dependence on dose rate at high dose rate conditions or fail to provide any temporal information.…”

Section: Introductionmentioning

confidence: 99%

Technical Note: Single‐pulse beam characterization for FLASH‐RT using optical imaging in a water tank

et al. 2021

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High dose rate conditions, coupled with problems related to small field dosimetry, make dose characterization for FLASH-RT challenging. Most conventional dosimeters show significant dependence on dose rate at ultra-high dose rate conditions or fail to provide sufficiently fast temporal data for pulse to pulse dosimetry. Here fast 2D imaging of radioluminescence from a water and quinine phantom was tested for dosimetry of individual 4 μs linac pulses. Methods: A modified clinical linac delivered an electron FLASH beam of >50 Gy/s to clinical isocenter. This modification removed the x-ray target and flattening filter, leading to a beam that was symmetric and gaussian, as verified with GafChromic EBT-XD film. Lateral projected 2D dose distributions for each linac pulse were imaged in a quinine-doped water tank using a gated intensified camera, and an inverse Abel transform reconstruction provided 3D images for on-axis depth dose values. A total of 20 pulses were delivered with a 10 MeV, 1.5 cm circular beam, and beam with jaws wide open (40 × 40 cm 2 ), and a 3D dose distribution was recovered for each pulse. Beam output was analyzed on a pulse by pulse basis. Results: The R p , D max , and the R 50 measured with film and optical methods agreed to within 1 mm for the 1.5 cm circular beam and the beam with jaws wide open. Cross beam profiles for both beams agreed with film data with >95% passing rate (2%/2 mm gamma criteria). The optical central axis depth dose agreed with film data, except for near the surface. A temporal pulse analysis revealed a ramp-up period where the dose per pulse increased for the first few pulses and then stabilized. Conclusions: Optical imaging of radioluminescence was presented as a valuable tool for establishing a baseline for the recently initiated electron FLASH beam at our institution.

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Dosimetry for FLASH Radiotherapy: A Review of Tools and the Role of Radioluminescence and Cherenkov Emission

Cited by 110 publications

References 140 publications

Establishment and Initial Experience of Clinical FLASH Radiotherapy in Canine Cancer Patients

Establishment and Initial Experience of Clinical FLASH Radiotherapy in Canine Cancer Patients

Biological and Mechanical Synergies to Deal With Proton Therapy Pitfalls: Minibeams, FLASH, Arcs, and Gantryless Rooms

Technical Note: Single‐pulse beam characterization for FLASH‐RT using optical imaging in a water tank

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