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Annals of the ICRP Oct 2018For stochastic effects such as cancer, linear-quadratic models of dose are often used to extrapolate from the experience of the Japanese atomic bomb survivors to... (Review)
Review
For stochastic effects such as cancer, linear-quadratic models of dose are often used to extrapolate from the experience of the Japanese atomic bomb survivors to estimate risks from low doses and low dose rates. The low dose extrapolation factor (LDEF), which consists of the ratio of the low dose slope (as derived via fitting a linear-quadratic model) to the slope of the straight line fitted to a specific dose range, is used to derive the degree of overestimation (if LDEF > 1) or underestimation (if LDEF < 1) of low dose risk by linear extrapolation from effects at higher doses. Likewise, a dose rate extrapolation factor (DREF) can be defined, consisting of the ratio of the low dose slopes at high and low dose rates. This paper reviews a variety of human and animal data for cancer and non-cancer endpoints to assess evidence for curvature in the dose response (i.e. LDEF) and modifications of the dose response by dose rate (i.e. DREF). The JANUS mouse data imply that LDEF is approximately 0.2-0.8 and DREF is approximately 1.2-2.3 for many tumours following gamma exposure, with corresponding figures of approximately 0.1-0.9 and 0.0-0.2 following neutron exposure. This paper also cursorily reviews human data which allow direct estimates of low dose and low dose rate risk.
Topics: Animals; Dose-Response Relationship, Radiation; Humans; Mice; Neoplasms, Radiation-Induced; Radiation Dosage; Risk
PubMed: 29652168
DOI: 10.1177/0146645318756235 -
Cancer Radiotherapie : Journal de La... Oct 2014Since February 2014, it is no longer possible to use low-dose rate 192 iridium wires due to the end of industrial production of IRF1 and IRF2 sources. The Brachytherapy... (Comparative Study)
Comparative Study Review
Since February 2014, it is no longer possible to use low-dose rate 192 iridium wires due to the end of industrial production of IRF1 and IRF2 sources. The Brachytherapy Group of the French society of radiation oncology (GC-SFRO) has recommended switching from iridium wires to after-loading machines. Two types of after-loading machines are currently available, based on the dose rate used: pulsed-dose rate or high-dose rate. In this article, we propose a comparative analysis between pulsed-dose rate and high-dose rate brachytherapy, based on biological, technological, organizational and financial considerations.
Topics: Automation; Brachytherapy; Clinical Trials as Topic; Cost-Benefit Analysis; Dose-Response Relationship, Radiation; Facility Design and Construction; Humans; Iridium Radioisotopes; Neoplasms; Patient Acceptance of Health Care; Patient Isolation; Patients' Rooms; Radiation Oncology; Radiation Protection; Radiotherapy Dosage; Time Factors; Treatment Outcome
PubMed: 25195117
DOI: 10.1016/j.canrad.2014.07.156 -
Medical Physics Jun 2022Silicon diodes are often the detector of choice for relative dose measurements, particularly in the context of radiotherapy involving small photon beams. However, a...
PURPOSE
Silicon diodes are often the detector of choice for relative dose measurements, particularly in the context of radiotherapy involving small photon beams. However, a major drawback lies in their dose-rate dependency. Although ionization chambers are often too large for small field output factor (OF) measurements, they are valuable instruments to provide reliable percent-depth dose (PDD) curves in reference beams. The aim of this work is to propose a practical and accurate method for the characterization of silicon diode dose-rate dependence correction factors using ionization chamber measurements as a reference.
METHODS
The robustness of ionization chambers for PDD measurements is used to quantify the dose-rate dependency of a diode detector. A mathematical formalism, which exploits the error induced in percent-depth ionization (PDI) curves for diodes by their dose-rate dependency, is developed to derive a dose-rate correction factor applicable to diode relative measurements. The method is based on the definition of the recombination correction factor given in the addendum to TG 51 and is applied to experimental measurements performed on a CyberKnife M6 radiotherapy unit using a PTW 60012 diode detector. A measurement-based validation is provided by comparing corrected PDI curves to measurements performed with a PTW 60019 diamond detector, which does not exhibit dose-rate dependence.
RESULTS
Results of dose-rate correction factors for PDI curves, off-axis ratios (OARs), tissue-phantom ratios, and small field OFs are coherent with the expected behavior of silicon diode detectors. For all considered setups and field sizes, the maximum correction and the maximum impact of the uncertainties induced by the correction are obtained for OARs for the 60 mm collimator, with a correction of 2.5% and an uncertainty of 0.34%. For OFs, corrections range from 0.33% to 0.82% for all field sizes considered, and increase with the reduction of the field size. Comparison of PDI curves corrected for dose-rate and for in-depth beam quality variations illustrates excellent agreement with measurements performed using the diamond detector.
CONCLUSION
The proposed method allows the efficient and precise correction of the dose-rate dependence of silicon diode detectors in the context of clinical relative dosimetry.
Topics: Diamond; Phantoms, Imaging; Radiometry; Radiotherapy Dosage; Silicon; Uncertainty
PubMed: 35315526
DOI: 10.1002/mp.15628 -
Cancer Reports (Hoboken, N.J.) Jan 2022High-dose-rate brachytherapy (HDR BRT) has been enjoying rapid acceptance as a treatment modality offered to selected prostate cancer patients devoid of risk group,... (Review)
Review
BACKGROUND
High-dose-rate brachytherapy (HDR BRT) has been enjoying rapid acceptance as a treatment modality offered to selected prostate cancer patients devoid of risk group, employed either in monotherapy setting or combined with external beam radiation therapy (EBRT) and is currently one of the most active clinical research areas.
RECENT FINDINGS
This review encompasses all the current evidence to support the use of HDR BRT in various clinical scenario and shines light to the HDR BRT rationale, as an ultimately conformal dose delivery method enabling safe dose escalation to the prostate.
CONCLUSION
Valid long-term data, both in regard to the oncologic outcomes and toxicity profile, support the current clinical indication spectrum of HDR BRT. At the same time, this serves as solid, rigid ground for emerging therapeutic applications, allowing the technique to remain in the spotlight alongside stereotactic radiosurgery.
Topics: Brachytherapy; Dose Fractionation, Radiation; Humans; Male; Prostatic Neoplasms
PubMed: 34164950
DOI: 10.1002/cnr2.1450 -
Scientific Reports Apr 2022Reproductive sterility is the basis of the sterile insect technique (SIT) and essential for its success in the field. Numerous factors that influence dose-response in...
Reproductive sterility is the basis of the sterile insect technique (SIT) and essential for its success in the field. Numerous factors that influence dose-response in insects have been identified. However, historically the radiation dose administered has been considered a constant. Efforts aiming to standardize protocols for mosquito irradiation found that, despite carefully controlling many variable factors, there was still an unknown element responsible for differences in expected sterility levels of insects irradiated with the same dose and handling protocols. Thus, together with previous inconclusive investigations, the question arose whether dose really equals dose in terms of biological response, no matter the rate at which the dose is administered. Interestingly, the dose rate effects studied in human nuclear medicine indicated that dose rate could alter dose-response in mammalian cells. Here, we conducted experiments to better understand the interaction of dose and dose rate to assess the effects in irradiated mosquitoes. Our findings suggest that not only does dose rate alter irradiation-induced effects, but that the interaction is not linear and may change with dose. We speculate that the recombination of reactive oxygen species (ROS) in treatments with moderate to high dose rates might minimize indirect radiation-induced effects in mosquitoes and decrease sterility levels, unless dose along with its direct effects is increased. Together with further studies to identify an optimum match of dose and dose rate, these results could assist in the development of improved methods for the production of high-quality sterile mosquitoes to enhance the efficiency of SIT programs.
Topics: Animals; Humans; Infertility; Insecta; Mammals; Pupa; Radiation Dosage
PubMed: 35422488
DOI: 10.1038/s41598-022-10027-z -
Frontiers in Oncology 2022To evaluate the plan quality and robustness of both dose and dose rate of proton pencil beam scanning (PBS) transmission FLASH delivery in lung cancer treatment.
PURPOSES
To evaluate the plan quality and robustness of both dose and dose rate of proton pencil beam scanning (PBS) transmission FLASH delivery in lung cancer treatment.
METHODS AND MATERIALS
An in-house FLASH planning platform was used to optimize 10 lung cancer patients previously consecutively treated with proton stereotactic body radiation therapy (SBRT) to receive 3 and 5 transmission beams (Trx-3fds and Trx-5fds, respectively) to 34 Gy in a single fraction. Perturbation scenarios (n=12) for setup and range uncertainties (5 mm and 3.5%) were introduced, and dose-volume histogram and dose-rate-volume histogram bands were generated. Conventional proton SBRT clinical plans were used as a reference. RTOG 0915 dose metrics and 40 Gy/s dose rate coverage (V) were used to assess the dose and dose rate robustness.
RESULTS
Trx-5fds yields a comparable iCTV D of 105.3%, whereas Trx-3fds resulted in inferior D of 111.9% to the clinical SBRT plans with D of 105.6% (p<0.05). Both Trx-5fds and Trx-3fds plans had slightly worse dose metrics to organs at risk than SBRT plans. Trx-5fds achieved superior dosimetry robustness for iCTV, esophagus, and spinal cord doses than both Trx-3fds and conventional SBRT plans. There was no significant difference in dose rate robustness for V coverage between Trx-3fds and Trx-5fds. Dose rate distribution has similar distributions to the dose when perturbation exists.
CONCLUSION
Transmission plans yield overall modestly inferior plan quality compared to the conventional proton SBRT plans but provide improved robustness and the potential for a toxicity-sparing FLASH effect. By using more beams (5- versus 3-field), both dose and dose rate robustness for transmission plans can be achieved.
PubMed: 36059710
DOI: 10.3389/fonc.2022.970602 -
Chemico-biological Interactions Mar 2019The goal of this manuscript is to define the role of dose rate and dose protraction on the induction of biological changes at all levels of biological organization. Both... (Review)
Review
The goal of this manuscript is to define the role of dose rate and dose protraction on the induction of biological changes at all levels of biological organization. Both total dose and the time frame over which it is delivered are important as the body has great capacity to repair all types of biological damage. The importance of dose rate has been recognized almost from the time that radiation was discovered and has been included in radiation standards as a Dose, Dose Rate, Effectiveness Factor (DDREF) and a Dose Rate Effectiveness Factor (DREF). This manuscript will evaluate the role of dose rate at the molecular, cellular, tissue, experimental animals and humans to demonstrate that dose rate is an important variable in estimating radiation cancer risk and other biological effects. The impact of low-dose rates on the Linear-No-Threshold Hypothesis (LNTH) will be reviewed since if the LNTH is not valid it is not possible to calculate a single value for a DDREF or DREF. Finally, extensive human experience is briefly reviewed to show that the radiation risks are not underestimated and that radiation at environmental levels has limited impact on total human cancer risk.
Topics: Animals; Dose-Response Relationship, Radiation; Humans; Linear Models; Models, Statistical; Neoplasms, Radiation-Induced; Radiation Dosage; Risk Assessment
PubMed: 30763551
DOI: 10.1016/j.cbi.2018.12.007 -
Cancer Radiotherapie : Journal de La... Oct 2017Based on recent, important publications on the impact of brachytherapy in the management of prostate cancer, we analysed already validated indications and the "under... (Review)
Review
Based on recent, important publications on the impact of brachytherapy in the management of prostate cancer, we analysed already validated indications and the "under investigations" use of brachytherapy. Published studies (MEDLINE), randomized trials and recommendations were reviewed, as well as Delphi consensus when available. While low-dose rate brachytherapy remains a standard of care for low-risk eligible patients, three randomized trials are now available to consider that combination of external beam radiation therapy with brachytherapy boost (low- or high-dose rate) appears as a recommended treatment for intermediate and high-risk patients. Other indications of prostate brachytherapy (monotherapy and salvage) remain under evaluation. For low-risk patients with good urinary status, low-dose rate brachytherapy alone should be offered. For low-intermediate risk prostate cancer, low-dose rate brachytherapy alone may be offered as monotherapy, while for high-intermediate risk prostate cancer, a combination of external beam radiation therapy (with or without androgen deprivation therapy) plus brachytherapy boost (low- or high-dose rate) should be offered to eligible patients. For patients with high-risk prostate cancer receiving external beam radiation therapy and androgen deprivation therapy, brachytherapy boost (low- or high-dose rate) should be offered to eligible patients. High-dose rate brachytherapy as monotherapy (single dose for low-risk/multifractionated for intermediate and high-risk) must be explored under clinical investigations, as well as salvage brachytherapy for local recurrence.
Topics: Biomedical Research; Brachytherapy; Forecasting; Humans; Male; Prostatic Neoplasms
PubMed: 28847460
DOI: 10.1016/j.canrad.2017.06.009 -
Medical Physics Jun 2023Conformality has been a key requirement in radiation therapy for cancer to minimize normal tissue toxicity while maintaining tumor control. Since 2014, there has been... (Review)
Review
Conformality has been a key requirement in radiation therapy for cancer to minimize normal tissue toxicity while maintaining tumor control. Since 2014, there has been great interest in ultra-high dose rate (UHDR), "FLASH," radiation therapy to enhance this therapeutic window. In multiple pre-clinical studies, it was seen that normal tissue demonstrated less damage due to radiation of various modalities when the same dose was delivered at ultra-high mean dose rates exceeding ∼40 Gy/s while tumor control remained indifferent to changes in dose rate. The scientific community has large-scale interdisciplinary studies to investigate this potentially breakthrough technique to enhance treatment options for cancer. FLASH studies have been performed using a number of modalities and delivery techniques for many pre-clinical models. There have been several studies reporting evidence of the FLASH effect as well as technological developments relating to UHDR studies. There is sustained interest and motivation for this topic as well as many questions that are yet to be answered. We provide a short overview to highlight some of the major work and challenges to advance research in FLASH radiotherapy.
Topics: Humans; Neoplasms; Motivation; Radiotherapy Dosage
PubMed: 36758965
DOI: 10.1002/mp.16271 -
Radiation Protection Dosimetry Apr 2018The literature describing the experimental investigations of possible dose-rate effects in the thermoluminescence (TL) of LiF:Mg,Ti (Harshaw) is reviewed. The total lack... (Review)
Review
The literature describing the experimental investigations of possible dose-rate effects in the thermoluminescence (TL) of LiF:Mg,Ti (Harshaw) is reviewed. The total lack of glow curve analysis, coupled with inclusion of all or part of the high temperature TL and absence of parallel measurements of possible dose-rate effects in the irradiation stage severely limit the scientific and technical level of the experiments. In addition, the experimental procedures are far from sufficient to warrant any conclusion concerning the presence or absence of dose-rate effects in the TL of LiF:Mg,Ti. This decision is contrary to the widely held belief that there are no dose-rate effects in the TL of LiF:Mg,Ti. In addition, the literature on dose-rate effects in the optical absorption (irradiation stage) of LiF is reviewed and is found contradictory. No dose-rate studies have been carried out on optical absorption in LiF:Mg,Ti. Kinetic simulations demonstrating the possibility, even likelihood, of dose-rate effects are also reviewed. Dose-rate effects are shown to be likely due to competition between excitation and recombination in the irradiation stage. Some other possible mechanisms involving multiple charge carrier trapping are suggested. Further definitive experiments are sorely needed, but the interested researcher should beware, it is not an easy task.
Topics: Dose-Response Relationship, Radiation; Fluorides; Lithium Compounds; Magnesium Compounds; Radiation Dosage; Thermoluminescent Dosimetry; Titanium
PubMed: 29145646
DOI: 10.1093/rpd/ncx248