scholarly journals Basic Properties of a New Polymer Gel for 3D-Dosimetry at High Dose-Rates Typical for FFF Irradiation Based on Dithiothreitol and Methacrylic Acid (MAGADIT): Sensitivity, Range, Reproducibility, Accuracy, Dose Rate Effect and Impact of Oxygen Scavenger

Polymers ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 1717 ◽  
Author(s):  
Muzafar Khan ◽  
Gerd Heilemann ◽  
Wolfgang Lechner ◽  
Dietmar Georg ◽  
Andreas Georg Berg
Keyword(s):  
Ascorbic Acid ◽  
Radiation Therapy ◽  
Dose Rate ◽  
Methacrylic Acid ◽  
Polymer Gels ◽  
High Dose ◽  
Polymer Gel ◽  
Oxygen Scavenger ◽  
Dose Rates ◽  
Dose Rate Effect

The photon induced radical-initiated polymerization in polymer gels can be used for high-resolution tissue equivalent dosimeters in quality control of radiation therapy. The dose (D) distribution in radiation therapy can be measured as a change of the physical measurement parameter T2 using T2-weighted magnetic resonance imaging. The detection by T2 is relying on the local change of the molecular mobility due to local polymerization initiated by radicals generated by the ionizing radiation. The dosimetric signals R2 = 1/T2 of many of the current polymer gels are dose-rate dependent, which reduces the reliability of the gel for clinical use. A novel gel dosimeter, based on methacrylic acid, gelatin and the newly added dithiothreitol (MAGADIT) as an oxygen-scavenger was analyzed for basic properties, such as sensitivity, reproducibility, accuracy and dose-rate dependence. Dithiothreitol features no toxic classification with a difference to THPC and offers a stronger negative redox-potential than ascorbic acid. Polymer gels with three different concentration levels of dithiothreitol were irradiated with a preclinical research X-ray unit and MR-scanned (T2) for quantitative dosimetry after calibration. The polymer gel with the lowest concentration of the oxygen scavenger was about factor 3 more sensitive to dose as compared to the gel with the highest concentration. The dose sensitivity (α = ∆R2/∆D) of MAGADIT gels was significantly dependent on the applied dose rate D ˙ (≈48% reduction between D ˙ = 0.6 Gy/min and D ˙ = 4 Gy/min). However, this undesirable dose-rate effect reduced between 4–8 Gy/min (≈23%) and almost disappeared in the high dose-rate range (8 ≤   D ˙ ≤   12 Gy/min) used in flattening-filter-free (FFF) irradiations. The dose response varied for different samples within one manufacturing batch within 3%–6% (reproducibility). The accuracy ranged between 3.5% and 7.9%. The impact of the dose rate on the spatial integrity is demonstrated in the example of a linear accelerator (LINAC) small sized 5 × 10 mm2 10 MV photon field. For MAGADIT the maximum shift in the flanks in this field is limited to about 0.8 mm at a FFF dose rate of 15 Gy/min. Dose rate sensitive polymer gels likely perform better at high dose rates; MAGADIT exhibits a slightly improved performance compared to the reference normoxic polymer gel methacrylic and ascorbic acid in gelatin initiated by copper (MAGIC) using ascorbic acid.

scholarly journals Serum Metabolomic Alterations Associated with Cesium-137 Internal Emitter Delivered in Various Dose Rates

Metabolites ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 270
Author(s):  
Heng-Hong Li ◽  
Yun-Tien Lin ◽  
Evagelia C. Laiakis ◽  
Maryam Goudarzi ◽  
Waylon Weber ◽  
...  
Keyword(s):  
Dose Rate ◽  
Cumulative Dose ◽  
Low Dose ◽  
Biological Effects ◽  
Serum Samples ◽  
Dose Rates ◽  
Sphingosine 1 Phosphate ◽  
Cesium 137 ◽  
Dose Rate Effect ◽  
Medium Dose

Our laboratory and others have use radiation metabolomics to assess responses in order to develop biomarkers reflecting exposure and level of injury. To expand the types of exposure and compare to previously published results, metabolomic analysis has been carried out using serum samples from mice exposed to 137Cs internal emitters. Animals were injected intraperitoneally with 137CsCl solutions of varying radioactivity, and the absorbed doses were calculated. To determine the dose rate effect, serum samples were collected at 2, 3, 5, 7, and 14 days after injection. Based on the time for each group receiving the cumulative dose of 4 Gy, the dose rate for each group was determined. The dose rates analyzed were 0.16 Gy/day (low), 0.69 Gy/day (medium), and 1.25 Gy/day (high). The results indicated that at a cumulative dose of 4 Gy, the low dose rate group had the least number of statistically significantly differential spectral features. Some identified metabolites showed common changes for different dose rates. For example, significantly altered levels of oleamide and sphingosine 1-phosphate were seen in all three groups. On the other hand, the intensity of three amino acids, Isoleucine, Phenylalanine and Arginine, significantly decreased only in the medium dose rate group. These findings have the potential to be used in assessing the exposure and the biological effects of internal emitters.

PET Image-guided Dose Escalation in High-dose Rate Radiation Therapy

2010 ◽  
Vol 78 (3) ◽  
pp. S415
Author(s):  
E.K. Lee ◽  
F. Yuan ◽  
A. Templeton ◽  
R. Yao ◽  
J.C. Chu
Keyword(s):  
Radiation Therapy ◽  
Dose Rate ◽  
Dose Escalation ◽  
High Dose Rate ◽  
High Dose ◽  
Image Guided

scholarly journals Back to the Future: Very High-Energy Electrons (VHEEs) and Their Potential Application in Radiation Therapy

Cancers ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 4942
Author(s):  
Maria Grazia Ronga ◽  
Marco Cavallone ◽  
Annalisa Patriarca ◽  
Amelia Maia Leite ◽  
Pierre Loap ◽  
...  
Keyword(s):  
Radiation Therapy ◽  
Current Knowledge ◽  
High Energy ◽  
High Dose Rate ◽  
Point Of View ◽  
High Dose ◽  
Dose Rates ◽  
High Energy Electrons ◽  
Very High Energy ◽  
Very High

The development of innovative approaches that would reduce the sensitivity of healthy tissues to irradiation while maintaining the efficacy of the treatment on the tumor is of crucial importance for the progress of the efficacy of radiotherapy. Recent methodological developments and innovations, such as scanned beams, ultra-high dose rates, and very high-energy electrons, which may be simultaneously available on new accelerators, would allow for possible radiobiological advantages of very short pulses of ultra-high dose rate (FLASH) therapy for radiation therapy to be considered. In particular, very high-energy electron (VHEE) radiotherapy, in the energy range of 100 to 250 MeV, first proposed in the 2000s, would be particularly interesting both from a ballistic and biological point of view for the establishment of this new type of irradiation technique. In this review, we examine and summarize the current knowledge on VHEE radiotherapy and provide a synthesis of the studies that have been published on various experimental and simulation works. We will also consider the potential for VHEE therapy to be translated into clinical contexts.

scholarly journals Implementation of High Dose Rate Brachytherapy in Cancer Treatment

2021 ◽  
Vol 1 (3) ◽  
pp. 77-106
Author(s):  
Amir Shahabaz ◽  
Muhammad Afzal
Keyword(s):  
Radiation Therapy ◽  
Side Effects ◽  
Dose Rate ◽  
Radiation Source ◽  
Cancer Recurrence ◽  
High Dose Rate ◽  
High Dose ◽  
Hdr Brachytherapy ◽  
Short Treatment ◽  
High Dose Rate Brachytherapy

A technique of radiation therapy delivery in which the radioactive sources are placed very close or even inside the target volume is called Brachytherapy (BT). Brachytherapy is a type of radiation therapy. It destroys cancer cells by making it hard for them to multiply. In this technique, a radiation source is placed directly into or near a tumour. High dose-rate brachytherapy is also known as HDR brachytherapy, or temporary brachytherapy. It is a type of internal radiotherapy. HDR was developed to reduce the risk of cancer recurrence while shortening the amount of time it takes to get radiation treatment. HDR also limits the dose of radiation (associated side effects) to surrounding normal tissue. The important benefits of HDR brachytherapy include extremely precise radiation therapy delivered internally, used alone or after surgery to help prevent cancer recurrence, convenient treatments that are usually pain-free, and a reduction in the risk of common short- and long-term side effects. Currently, tumour dose, as well as doses of the surrounding normal structures, can be evaluated accurately, and high-dose-rate brachytherapy enables three-dimensional image guidance. The biological disadvantages of high-dose-rate were overcome by fractional irradiation. In the definitive radiation therapy of cervical cancer, high-dose-rate brachytherapy is most necessary. Most patients feel little discomfort during brachytherapy. There is no residual radioactivity when the treatment is completed. A patient may be able to go home shortly after the procedure, resuming his normal activities with few restrictions. An advantage of brachytherapy is to deliver a high dose to the tumour during treatment and save the surrounding normal tissues. High-dose-rate (HDR) brachytherapy has great promise with respect to proper case selection and delivery technique because it eliminates radiation exposure, can be performed on an outpatient basis and allows short treatment times. Additionally, by varying the dwell time at each dwell position, the use of a single-stepping source allows optimization of dose distribution. As the short treatment times do not allow any time for correction of errors, and mistakes can result in harm to patients, so the treatments must be executed carefully by using HDR brachytherapy. Refinements will occur primarily in the integration of imaging (computed tomography, magnetic resonance imaging, intraoperative ultrasonography) and optimization of dose distribution and it is expected that the use of HDR brachytherapy will greatly expand over the next decade. Various factors in the development of well-controlled randomized trials addressing issues of efficacy, quality of life, toxicity and costs-versus-benefits will ultimately define the role of HDR brachytherapy in the therapeutic armamentarium. Surrounding healthy tissues are not affected by the radiation due to the ability to target radiation therapy at high dose rates directly to the tumour. Treatment to be delivered as an outpatient in as few as one to five sessions is also allowed by this targeted high dose approach. HDR brachytherapy is the most precision radiation therapy, even better than carbon ion therapy. At the time of invasive placement of the radiation source into the tumour area, brachytherapy requires the skills and techniques of radiation oncologists.

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