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Journal of Cancer Research and... 2018The aim of this study is to evaluate the dose rate and energy dependency of methacrylic acid gelatin tetrakis (hydroxymethyl) phosphonium chloride (MAGAT) gel in...
AIMS
The aim of this study is to evaluate the dose rate and energy dependency of methacrylic acid gelatin tetrakis (hydroxymethyl) phosphonium chloride (MAGAT) gel in unflattened photon beam using X-ray computed tomography (CT) and ultraviolet (UV)-visible spectroscopy.
MATERIALS AND METHODS
MAGAT gel was prepared and it was exposed to 6 MV flattened and unflattened beams. The dose selected for irradiation was ranging from 3 to 15 Gy with an increment of 3 Gy. The dose rate dependency of the gel was investigated by exposing the gel to three different dose rates of 250, 500, and 1500 cGy/min for flattening filter free (FFF). To verify the energy dependency of the gel, it was exposed by both FFF and flattening filter (FF) for constant dose rate (250 cGy/min) and different energy (6 and 10 MV X-ray photons). The exposed gels were scanned by X-ray CT and UV-visible spectrophotometer.
RESULTS
The change in dose sensitivity observed over the dose rate from 250 cGy/min to 1500 cGy/min was 58.00% and 57.89% using a UV-visible spectrophotometer and X-ray CT analysis method. Energy dependency was evaluated with respect to dose sensitivity and the variation between 6 MV FF and FFF photon beams was found to be 2.20% and 2.21% using UV-visible spectrophotometer analysis and X-ray CT, respectively. Similarly, the variation noticed with 10 MV FF and FFF was 2.30% using UV-visible spectrophotometer analysis and 2.22% using X-ray CT analysis.
CONCLUSIONS
The results clearly show that the MAGAT gel was highly dose rate-dependent and less dependent on energy. The beam quality variation between FF and FFF was less. The similar results obtained using X-ray CT scanner and UV-visible spectrophotometer indicate that this study can be recommended for polymer gel scanning procedure.
Topics: Gelatin; Humans; Methacrylates; Organophosphorus Compounds; Photons; Radiation; Radiation Dosage; Radiometry
PubMed: 29516908
DOI: 10.4103/0973-1482.191033 -
International Journal of Molecular... Oct 2022FLASH radiotherapy, or the delivery of a dose at an ultra-high dose rate (>40 Gy/s), has recently emerged as a promising tool to enhance the therapeutic index in cancer... (Review)
Review
FLASH radiotherapy, or the delivery of a dose at an ultra-high dose rate (>40 Gy/s), has recently emerged as a promising tool to enhance the therapeutic index in cancer treatment. The remarkable sparing of normal tissues and equivalent tumor control by FLASH irradiation compared to conventional dose rate irradiation—the FLASH effect—has already been demonstrated in several preclinical models and even in a first patient with T-cell cutaneous lymphoma. However, the biological mechanisms responsible for the differential effect produced by FLASH irradiation in normal and cancer cells remain to be elucidated. This is of great importance because a good understanding of the underlying radiobiological mechanisms and characterization of the specific beam parameters is required for a successful clinical translation of FLASH radiotherapy. In this review, we summarize the FLASH investigations performed so far and critically evaluate the current hypotheses explaining the FLASH effect, including oxygen depletion, the production of reactive oxygen species, and an altered immune response. We also propose a new theory that assumes an important role of mitochondria in mediating the normal tissue and tumor response to FLASH dose rates.
Topics: Humans; Radiotherapy Dosage; Reactive Oxygen Species; Neoplasms; Oxygen
PubMed: 36292961
DOI: 10.3390/ijms232012109 -
International Journal of Radiation... Sep 2016To analyze the dose rate influence in hyper-radiosensitivity (HRS) of human melanoma cells to very low doses of fast neutrons and to compare to the behaviour of normal...
PURPOSE
To analyze the dose rate influence in hyper-radiosensitivity (HRS) of human melanoma cells to very low doses of fast neutrons and to compare to the behaviour of normal human skin fibroblasts.
MATERIALS AND METHODS
We explored different neutron dose rates as well as possible implication of DNA double-strand breaks (DSB), apoptosis, and energy-provider adenosine-triphosphate (ATP) levels during HRS.
RESULTS
HRS in melanoma cells appears only at a very low dose rate (VLDR), while a high dose rate (HDR) induces an initial cell-radioresistance (ICRR). HRS does not seem to be due either to DSB or to apoptosis. Both phenomena (HRS and ICRR) appear to be related to ATP availability for triggering cell repair. Fibroblast survival after neutron irradiation is also dose rate-dependent but without HRS.
CONCLUSIONS
Melanoma cells or fibroblasts exert their own survival behaviour at very low doses of neutrons, suggesting that in some cases there is a differential between cancer and normal cells radiation responses. Only the survival of fibroblasts at HDR fits the linear no-threshold model. This new insight into human cell responses to very low doses of neutrons, concerns natural radiations, surroundings of accelerators, proton-therapy devices, flights at high altitude. Furthermore, ATP inhibitors could increase HRS during high-linear energy transfer (high-LET) irradiation.
Topics: Apoptosis; Cell Line, Tumor; Cell Survival; Computer Simulation; Dose Fractionation, Radiation; Dose-Response Relationship, Radiation; Fibroblasts; Humans; Melanoma; Models, Biological; Neutrons; Radiation Tolerance
PubMed: 27258624
DOI: 10.1080/09553002.2016.1186300 -
Brachytherapy 2013To present recommendations for the use of brachytherapy (BT) in patients with soft tissue sarcoma (STS). (Review)
Review
PURPOSE
To present recommendations for the use of brachytherapy (BT) in patients with soft tissue sarcoma (STS).
METHODS
A group of practitioners with expertise and experience in sarcoma BT formulated recommendations for BT in STS based on clinical experience and literature review.
RESULTS
The indications for adjuvant BT are discussed. There is no consensus on the use of BT alone or in combination with external beam radiation therapy (EBRT), but factors that influence the selection of this modality include tumor grade and size, prior surgeries, and tumor recurrence. Low-dose-rate, high-dose-rate, and pulsed-dose-rate radiation are all acceptable BT modalities to use for STS. Recommendations are made for patient selection, techniques, dose rates, and dosages. Outcome data and toxicity data are reviewed.
CONCLUSIONS
BT is a useful component of the treatment of STS. The advantages of BT are the targeted dose distribution, low integral dose, and short treatment times. Ultimately the clinician should select the modality or combination of modalities that are most familiar to the treatment team and suitable to the patient.
Topics: Brachytherapy; Consensus; Humans; Practice Guidelines as Topic; Radiotherapy Dosage; Sarcoma; Societies, Medical; United States
PubMed: 23434220
DOI: 10.1016/j.brachy.2012.12.002 -
Scientific Reports Nov 2020In the long term, Cs is probably the most biologically important agent released in many accidental (or malicious) radiation disasters. It can enter the food chain, and...
In the long term, Cs is probably the most biologically important agent released in many accidental (or malicious) radiation disasters. It can enter the food chain, and be consumed, or, if present in the environment (e.g. from fallout), can provide external irradiation over prolonged times. In either case, due to the high penetration of the energetic γ rays emitted by Cs, the individual will be exposed to a low dose rate, uniform, whole body, irradiation. The VADER (VAriable Dose-rate External Cs irradiatoR) allows modeling these exposures, bypassing many of the problems inherent in internal emitter studies. Making use of discarded Cs brachytherapy seeds, the VADER can provide varying low dose rate irradiations at dose rates of 0.1 to 1.2 Gy/day. The VADER includes a mouse "hotel", designed to allow long term simultaneous residency of up to 15 mice. Two source platters containing ~ 250 mCi each of Cs brachytherapy seeds are mounted above and below the "hotel" and can be moved under computer control to provide constant low dose rate or a varying dose rate mimicking Cs biokinetics in mouse or man. We present the VADER design and characterization of its performance over 18 months of use.
Topics: Animals; Brachytherapy; Cesium Radioisotopes; Equipment Design; Gamma Rays; Mice; Mice, Inbred C57BL; Radiation Dosage; Whole-Body Irradiation
PubMed: 33199728
DOI: 10.1038/s41598-020-76941-2 -
Journal of Biomedical Physics &... Apr 2022The dose values obtained from procedures of diagnostic radiology are relatively low. To accurately and precisely measure the dose values in this dose range, it is...
BACKGROUND
The dose values obtained from procedures of diagnostic radiology are relatively low. To accurately and precisely measure the dose values in this dose range, it is necessary to know the characteristics of dosimeters.
OBJECTIVE
The aim of this study was to evaluate several thermoluminescent characteristics of GR-200, TLD-700H and TLD-100 for low dose measurement.
MATERIAL AND METHODS
In this experimental study, linearity, repeatability, dose rate and photon energy dependence of different TLD materials were investigated in a 0.05-10 mGy range dose. It is noteworthy that the data obtained from TLD-100 were considered as reference and the data obtained from two other types of TLDs were compared with them.
RESULTS
For all three types of TLD materials, there are linear relations between absorbed dose values to TLDs and their responses. TLD-100 and TLD-700H have very low sensitivity than GR-200. For GR-200 and TLD-100, the coefficients of variation values (%) are 3.00% and 2.01%, respectively, that these values are within the tolerance limit (<7.5%). However, this value for TLD-700H is 10.85% which it is more than the reported tolerance limit. Furthermore, remarkable effects of dose rate and photon energy dependence on the responses of GR-200 are not observed in a 0.5-4 mGy dose range; nevertheless, remarkable effects of dose rate and photon energy dependence on the responses of TLD-100 and TLD-700H are found in this dose range.
CONCLUSION
The evaluated thermoluminescent characteristics for GR-200 are better than two other types of TLDs (TLD-100 and TLD-700H) for low dose values.
PubMed: 35433523
DOI: 10.31661/jbpe.v0i0.1247 -
Current Issues in Molecular Biology Aug 2023The output constancy of the accelerator used for boron neutron capture therapy (BNCT) is essential to ensuring anti-tumor efficacy and safety. BNCT as currently...
The output constancy of the accelerator used for boron neutron capture therapy (BNCT) is essential to ensuring anti-tumor efficacy and safety. BNCT as currently practiced requires a wide variety of beam quality assessments to ensure that RBE dose errors are maintained within 5%. However, the necessity of maintaining a constant beam dose rate has not been fully discussed. We therefore clarified the effect of different physical dose rates of the accelerator BNCT on biological effects. SAS and A172 cells exposed to B-boronophenylalanine were irradiated using a neutron beam (normal operating current, 100 μA) at the Aomori Quantum Science Center. Thermal neutron flux was attenuated to 50.0 ± 0.96% under 50 μA irradiation compared to that under 100 μA irradiation. Cells were given physical doses of 1.67 and 3.36 Gy at 30 and 60 mC, respectively, and survival was significantly increased after 50 μA irradiation for both cell types ( = 0.0052 for SAS; = 0.046 for A172, for 60 mC). Differences in accelerator BNCT beam dose rates have non-negligible effects on biological effects. Dose rate fluctuations and differences should not be easily permitted to obtain consistent biological effects.
PubMed: 37754225
DOI: 10.3390/cimb45090441 -
Dose-response : a Publication of... 2021This work concerns study of self-absorption factor (SAF) and dose rate constants of zirconium-89 (Zr) for the purpose of radiation protection in positron emission...
This work concerns study of self-absorption factor (SAF) and dose rate constants of zirconium-89 (Zr) for the purpose of radiation protection in positron emission tomography (PET) and to compare them with those of F-deoxyglucose (F-FDG). We analyzed the emitted energy spectra by F and Zr through anthropomorphic phantom and calculated the absorbed energy using Monte Carlo method. The dose rate constants for both radionuclides were estimated with 2 different fluence-to-effective dose conversion coefficients. Our estimated SAF value of 0.65 for F agreed with the recommendation of the American Association of Physicists in Medicine (AAPM). The SAF for Zr was in the range of 0.61-0.66 depending on the biodistribution. Using the fluence-to-effective dose conversion coefficients recommended jointly by the American National Standards Institute and the American Nuclear Society (ANSI/ANS), the dose rate at 1 m from the patient for F was 0.143 μSv·MBq·hr, which is consistent with the AAPM recommendation, while that for Zr was 0.154 μSv·MBq·hr. With the conversion coefficients currently recommended by the International Committee on Radiological Protection (ICRP), the dose rate estimates were lowered by 2.8% and 2.6% for Zr and F, respectively. Also, we observed that the AAPM derived dose is an overestimation near the patient, compared to our simulations, which can be explained by the biodistribution nature and the assumption of the point source. Thus, we proposed new radiation protection factors for Zr radionuclide.
PubMed: 34290574
DOI: 10.1177/15593258211028467 -
European Review For Medical and... 2014Tumor necrosis might be a consequence of innate sensitivity of tumor cells to changed dosage instead of the increased dosage of chemotherapeutics in the treatment of... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
Tumor necrosis might be a consequence of innate sensitivity of tumor cells to changed dosage instead of the increased dosage of chemotherapeutics in the treatment of osteosarcoma patients.
AIM
To explore whether dose-intensive regimen was a better treatment method than dose-control chemotherapy for high-grade osteosarcoma patients.
MATERIALS AND METHODS
The data of the included studies was analyzed by random-effects model when there was heterogeneity, otherwise by fixed-effects method. Meta-analysis outcomes were calculated as risk ratio (RR) and 95% confidence interval (CI) for 5-year disease free survival rate, 5-year overall survival, local recurrence rate, good histological response rate and Limb salvage rate.
RESULTS
Five studies involving 1434 patients with high-grade osteosarcoma were included. All the included studies were inadequate in the information about randomization and blinding method. The meta-analysis showed that there was no significant difference between the dose-intensive group and the dose control group in 5-year disease free survival rate (RR: 1.08, 95% CI: 0.96-1.21), 5-year overall survival rate (RR: 1.07, 95% CI: 0.98-1.17), good histological response rate (RR: 1.08, 95% CI: 0.82-1.43), limb salvage rate (RR: 0.97, 95% CI: 0.93-1.02). However, the local recurrence rate (RR: 0.65, 95% CI: 0.46- 0.92) and the 5-year disease free survival rate of the good and poor histological response (RR: 1.57, 95% CI: 1.36- 1.82) were significantly different.
CONCLUSIONS
Dose-intensive regimen might not be a preferred treatment for all of the high-grade osteosarcoma patients. Although there were advantages in dose-intensive regimen, appropriate dosage of chemotherapy should be considered in clinical cases.
Topics: Antineoplastic Combined Chemotherapy Protocols; Bone Neoplasms; Chi-Square Distribution; Disease-Free Survival; Drug Administration Schedule; Humans; Limb Salvage; Necrosis; Neoplasm Grading; Neoplasm Recurrence, Local; Odds Ratio; Osteosarcoma; Risk Factors; Time Factors; Treatment Outcome
PubMed: 24867518
DOI: No ID Found -
Dose-response : a Publication of... 2019Dose rate is one of the most varied experimental parameters in radiation biology research. In this study, effects of dose rates on the radiation responses of 2 different...
Dose rate is one of the most varied experimental parameters in radiation biology research. In this study, effects of dose rates on the radiation responses of 2 different types of human epithelium-derived cells, immortalized keratinocytes (HaCaT), and colorectal cancer cells (HCT116 p53 and HCT116 p53) were systematically studied. Cells were γ-irradiated at one of the 4 dose rates (24.6, 109, 564, and 1168 mGy/min) to a total dose of 0.5 to 2 Gy. Clonogenic survival and mitochondrial membrane potential (MMP) were measured to assess the levels of reproductive cell death and damage to mitochondrial physiology, respectively. It was found that clonogenic survival was similar at all 4 tested dose rates in the 3 cell lines. The loss of MMP occurred at all tested dose rates in all 3 cell lines except for one case where the MMP increased in HCT116 p53cells after exposure to 0.5 Gy at 24.6 mGy/min. In HCT116 cells, the loss of MMP was the most severe at high dose/dose rate combination exposure and when p53 was expressed. In contrast, no effect in dose rate was observed with HaCaT cells as the reduction level of MMP was similar at the tested dose rates.
PubMed: 31210757
DOI: 10.1177/1559325819852508