Device for providing a radiation treatment

The present relates to a device for providing a radiation treatment to a patient comprising :- an electron source for providing a beam of electrons, and- a linear accelerator for accelerating said beam until a predetermined energy, and - a beam delivery module for delivering the accelerated beam from said linear accelerator toward the patient to treat a target volume with a radiation dose, The device further comprises intensity modulation means configured to modulate the distribution of the radiation dose in the target volume according to a predetermined pattern.The pattern is determined to match the dimensions of a target volume of at least about 50 cm3, and/or a target volume located at least about 5 cm deep in the tissue of the patient with said radiation dose,The radiation dose distributed is up to about 20 Gy delivered during an overall treatment time less than about 50 ms

Dose- and Volume-Limiting Late Toxicity of FLASH Radiotherapy in Cats with Squamous Cell Carcinoma of the Nasal Planum and in Mini Pigs

Purpose: The FLASH effect is characterized by normal tissue sparing without compromising tumor control. Although demonstrated in various preclinical models, safe translation of FLASH-radiotherapy stands to benefit from larger vertebrate animal models. Based on prior results, we designed a randomized phase III trial to investigate the FLASH effect in cat patients with spontaneous tumors. In parallel, the sparing capacity of FLASH-radiotherapy was studied on mini pigs by using large field irradiation. Experimental Design: Cats with T1-T2, N0 carcinomas of the nasal planum were randomly assigned to two arms of electron irradiation: arm 1 was the standard of care (SoC) and used 10 × 4.8 Gy (90% isodose); arm 2 used 1 × 30 Gy (90% isodose) FLASH. Mini pigs were irradiated using applicators of increasing size and a single surface dose of 31 Gy FLASH. Results: In cats, acute side effects were mild and similar in both arms. The trial was prematurely interrupted due to maxillary bone necrosis, which occurred 9 to 15 months after radiotherapy in 3 of 7 cats treated with FLASH-radiotherapy (43%), as compared with 0 of 9 cats treated with SoC. All cats were tumor-free at 1 year in both arms, with one cat progressing later in each arm. In pigs, no acute toxicity was recorded, but severe late skin necrosis occurred in a volume-dependent manner (7–9 months), which later resolved. Conclusions: The reported outcomes point to the caveats of translating single-high-dose FLASH-radiotherapy and emphasizes the need for caution and further investigations. See related commentary by Maity and Koumenis, p. 363

REMOTE - Medical physics of ultra-high dose rate electron beams

The dose delivered to tissues induces a specific biological effect (i.e. normal tissue sparing associated with sustained tumor control) when ultra-high dose rates (UHDR; &gt; ~40 Gy/s in average) are used. That effect is called the FLASH effect. Biological experiments were performed on prototype or experimental devices where specific dosimetric procedures had to be developed and validated to reach a reasonable accuracy, because, as an example, no metrological traceability is established for such UHDR beams. Alongside the challenging work to provide adequate beams and correct dose data reporting for pre-clinical experiments, further developments are necessary to produce a large homogeneous beam compatible with clinical requirements. Moreover, an important prerequisite for the use of UHDR for clinical treatments is obviously the safety and reliability of UHDR devices. I will present the characteristics of available devices as well as potential future machines for the clinical transfer, particularly for deep seated tumors, and describe the challenges that we will face for the safe transfer of that promising technique to patients. Short bio: Raphaël Moeckli completed his MSc degree in Ecole Polytechnique Fédérale de Lausanne and his PhD in medical imaging at the University of Lausanne in 2001. He is certified Swiss medical physicists since 1999, head of the radiation therapy group in Institute of Radiation Physics and head physicist in the Radio-Oncology Department in CHUV Lausanne since 2001. He is associate professor in Lausanne University since 2021. His main fields of research are FLASH therapy, tomotherapy and multicriteria optimisation. He is and has been director and experts for various national and international PhD thesis juries. He has published more than 80 papers in peer-reviewed journal. He is past president of the Swiss Society of Radiobiology and Medical Physics and he has been active in different working groups having issued Swiss recommendations about good practice in radiation therapy. He has been member of different scientific committees of ESTRO meetings as well as other Swiss and international meetings.</p

Variability of a peripheral dose among various linac geometries for second cancer risk assessment.

Second cancer risk assessment for radiotherapy is controversial due to the large uncertainties of the dose-response relationship. This could be improved by a better assessment of the peripheral doses to healthy organs in future epidemiological studies. In this framework, we developed a simple Monte Carlo (MC) model of the Siemens Primus 6 MV linac for both open and wedged fields that we then validated with dose profiles measured in a water tank up to 30 cm from the central axis. The differences between the measured and calculated doses were comparable to other more complex MC models and never exceeded 50%. We then compared our simple MC model with the peripheral dose profiles of five different linacs with different collimation systems. We found that the peripheral dose between two linacs could differ up to a factor of 9 for small fields (5 × 5 cm(2)) and up to a factor of 10 for wedged fields. Considering that an uncertainty of 50% in dose estimation could be acceptable in the context of risk assessment, the MC model can be used as a generic model for large open fields (≥10 × 10 cm(2)) only. The uncertainties in peripheral doses should be considered in future epidemiological studies when designing the width of the dose bins to stratify the risk as a function of the dose

Clinical evaluation of a novel optimization algorithm for cyberknife IRIS-based treatment plans

Purpose: To report on the clinical implementation of the VOLOTMoptimization algorithm for SRS/SBRT treatments and its dosimetric comparison with the previous Sequential Optimization (SO) algorithm. Materials and methods: Forty patients treated for brain, spine, prostate and lung tumors, and planned with the SO algorithm were re-planned with VOLOTM. Comparison involved target coverage, conformity, gradient and homogeneity indexes (CN, GI and HI) and specifc indicators of dose to OARs. Plans were also compared in terms of number of nodes, beams, MU and delivery time. All dose distributions designed with VOLOTM were validated via ionisation chamber measurements. Results: The following statistically signifcant dosimetric differences were observed. VOLOTM was superior in terms of target coverage for prostate (99% vs 96%) and spine (92% vs 81%), GI for brain (4.41 vs 4.76), CN for brain (0.77 vs 0.72), and for brain and urethra dose sparing. SO gave better results for GI for prostate (3.67 vs 4.05) and maximum dose to brain stem. VOLOTM showed a steeper peripheral dose fall-off for brain and lung cases; SO was superior for prostate and spine cases. Overall, the number of nodes, beams and MU were reduced with VOLOTM up to 36%, 14% and 31%, respectively. The average reduction of delivery time was 20% (ranging from 8% for brain to 30% for prostate). The mean 1D dose measurement deviation from calculation was –0.2% (range –1.3–1.7%). 2D dose measurements returned a mean distance-to-agreement of 0.8±0.8 mm and a mean dose difference of 0.6±1.0%. Conclusions: VOLOTM optimization algorithm provided clinically acceptable dose distributions, most of the time better than SO. The treatment time was signifcantly reduced up to 30%. The peripheral dose fall-off increased for large collimator sizes. The verifcation measurements proved its clinical implementation