scholarly journals Hydrogels for Three-Dimensional Ionizing-Radiation Dosimetry

Gels ◽  
2021 ◽  
Vol 7 (2) ◽  
pp. 74
Author(s):  
Maurizio Marrale ◽  
Francesco d’Errico
Keyword(s):  
Radiation Dosimetry ◽  
Optical Tomography ◽  
Absorbed Dose ◽  
Acceptance Testing ◽  
Proton Relaxation ◽  
Polyacrylamide Gels ◽  
Relaxation Rates ◽  
Ferrous Ions ◽  
Radiation Quality ◽  
Radiation Induced

Radiation-sensitive gels are among the most recent and promising developments for radiation therapy (RT) dosimetry. RT dosimetry has the twofold goal of ensuring the quality of the treatment and the radiation protection of the patient. Benchmark dosimetry for acceptance testing and commissioning of RT systems is still based on ionization chambers. However, even the smallest chambers cannot resolve the steep dose gradients of up to 30–50% per mm generated with the most advanced techniques. While a multitude of systems based, e.g., on luminescence, silicon diodes and radiochromic materials have been developed, they do not allow the truly continuous 3D dose measurements offered by radiation-sensitive gels. The gels are tissue equivalent, so they also serve as phantoms, and their response is largely independent of radiation quality and dose rate. Some of them are infused with ferrous sulfate and rely on the radiation-induced oxidation of ferrous ions to ferric ions (Fricke-gels). Other formulations consist of monomers dispersed in a gelatinous medium (Polyacrylamide gels) and rely on radiation-induced polymerization, which creates a stable polymer structure. In both gel types, irradiation causes changes in proton relaxation rates that are proportional to locally absorbed dose and can be imaged using magnetic resonance imaging (MRI). Changes in color and/or opacification of the gels also occur upon irradiation, allowing the use of optical tomography techniques. In this work, we review both Fricke and polyacrylamide gels with emphasis on their chemical and physical properties and on their applications for radiation dosimetry.

scholarly journals Biodistribution and internal radiation dosimetry of a companion diagnostic radiopharmaceutical, [68Ga]PSMA-11, in subcutaneous prostate cancer xenograft model mice

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Su Bin Kim ◽  
In Ho Song ◽  
Yoo Sung Song ◽  
Byung Chul Lee ◽  
Arun Gupta ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Radiation Dosimetry ◽  
Xenograft Model ◽  
Absorbed Dose ◽  
Patient Specific ◽  
Internal Radiation ◽  
Washout Phase ◽  
Heterogeneous Tissue ◽  
Organ Level ◽  
Reported Data

Abstract[68Ga]PSMA-11 is a prostate-specific membrane antigen (PSMA)-targeting radiopharmaceutical for diagnostic PET imaging. Its application can be extended to targeted radionuclide therapy (TRT). In this study, we characterize the biodistribution and pharmacokinetics of [68Ga]PSMA-11 in PSMA-positive and negative (22Rv1 and PC3, respectively) tumor-bearing mice and subsequently estimated its internal radiation dosimetry via voxel-level dosimetry using a dedicated Monte Carlo simulation to evaluate the absorbed dose in the tumor directly. Consequently, this approach overcomes the drawbacks of the conventional organ-level (or phantom-based) method. The kidneys and urinary bladder both showed substantial accumulation of [68Ga]PSMA-11 without exhibiting a washout phase during the study. For the tumor, a peak concentration of 4.5 ± 0.7 %ID/g occurred 90 min after [68Ga]PSMA-11 injection. The voxel- and organ-level methods both determined that the highest absorbed dose occurred in the kidneys (0.209 ± 0.005 Gy/MBq and 0.492 ± 0.059 Gy/MBq, respectively). Using voxel-level dosimetry, the absorbed dose in the tumor was estimated as 0.024 ± 0.003 Gy/MBq. The biodistribution and pharmacokinetics of [68Ga]PSMA-11 in various organs of subcutaneous prostate cancer xenograft model mice were consistent with reported data for prostate cancer patients. Therefore, our data supports the use of voxel-level dosimetry in TRT to deliver personalized dosimetry considering patient-specific heterogeneous tissue compositions and activity distributions.

scholarly journals EANM position paper on the role of radiobiology in nuclear medicine

2021 ◽  
Author(s):  
An Aerts ◽  
Uta Eberlein ◽  
Sören Holm ◽  
Roland Hustinx ◽  
Mark Konijnenberg ◽  
...  
Keyword(s):  
Nuclear Medicine ◽  
Absorbed Dose ◽  
Added Value ◽  
External Irradiation ◽  
Executive Summary ◽  
Dose Rates ◽  
Biological Responses ◽  
Medical Physicists ◽  
Radiation Induced

Executive SummaryWith an increasing variety of radiopharmaceuticals for diagnostic or therapeutic nuclear medicine as valuable diagnostic or treatment option, radiobiology plays an important role in supporting optimizations. This comprises particularly safety and efficacy of radionuclide therapies, specifically tailored to each patient. As absorbed dose rates and absorbed dose distributions in space and time are very different between external irradiation and systemic radionuclide exposure, distinct radiation-induced biological responses are expected in nuclear medicine, which need to be explored. This calls for a dedicated nuclear medicine radiobiology. Radiobiology findings and absorbed dose measurements will enable an improved estimation and prediction of efficacy and adverse effects. Moreover, a better understanding on the fundamental biological mechanisms underlying tumor and normal tissue responses will help to identify predictive and prognostic biomarkers as well as biomarkers for treatment follow-up. In addition, radiobiology can form the basis for the development of radiosensitizing strategies and radioprotectant agents. Thus, EANM believes that, beyond in vitro and preclinical evaluations, radiobiology will bring important added value to clinical studies and to clinical teams. Therefore, EANM strongly supports active collaboration between radiochemists, radiopharmacists, radiobiologists, medical physicists, and physicians to foster research toward precision nuclear medicine.

Dosimetry of High-Energy Photon Beams Based on Standards of Absorbed Dose to Water: Abstract

2001 ◽  
Vol 1 (1) ◽  
pp. 8-8 ◽  
Author(s):  
K. Hohlfeld ◽  
P. Andreo ◽  
O. Mattsson ◽  
J. P. Simoen
Keyword(s):  
Reference Conditions ◽  
International Comparisons ◽  
Absorbed Dose ◽  
High Energy ◽  
National Standards ◽  
Photon Radiation ◽  
Photon Beams ◽  
Radiation Induced ◽  
Absorbed Dose To Water ◽  
Primary Standards

This report examines the methods by which absorbed dose to water can be determined for photon radiations with maximum energies from approximately 1 MeV to 50 MeV, the beam qualities most commonly used for radiation therapy. The report is primarily concerned with methods of measurement for photon radiation, but many aspects are also relevant to the dosimetry of other therapeutic beams (high-energy electrons, protons, etc.). It deals with methods that are sufficiently precise and well established to be incorporated into the dosimetric measurement chain as primary standards (i.e., methods based on ionisation, radiation-induced chemical changes, and calorimetry using either graphite or water). The report discusses the primary dose standards used in several national standards laboratories and reviews the international comparisons that have been made. The report also describes the reference conditions that are suitable for establishing primary standards and provides a formalism for determining absorbed dose, including a discussion of correction factors needed under conditions other than those used to calibrate an instrument at the standards laboratory.

Free radicals and food irradiation

1995 ◽  
Vol 61 ◽  
pp. 247-258 ◽  
Author(s):  
"N.J.F. Dodd
Keyword(s):  
Free Radicals ◽  
Radiation Dosimetry ◽  
Food Poisoning ◽  
Food Irradiation ◽  
Specific Method ◽  
Naturally Occurring ◽  
Spin Resonance ◽  
Radiation Induced ◽  
Calcified Tissues ◽  
Control Insect

Ionizing radiation can be used to control insect and microbial infestation of foodstuffs, inhibit sprouting, delay ripening and reduce the dangers from food-poisoning bacteria. Irradiation produces free radicals, most of which decay rapidly, although some are more persistent. These latter radicals can be detected and characterized by electron spin resonance (ESR). In bone and other calcified tissues, the radiation-induced radicals are distinguishable from naturally occurring radicals, and their stability makes them ideal for radiation dosimetry. The radicals induced in plant material, such as seeds and dried spices, are generally indistinguishable from the endogenous radicals and decay over a period of days or weeks. However, in many of these materials, a radiation-specific radical can be detected at low concentration, thereby permitting identification of irradiated samples, although precluding accurate dosimetry. ESR, although not universally applicable, currently provides the most specific method for the detection of irradiated food.

OSL in NaCl vs. TL in LiF for absorbed dose measurements and radiation quality assessment in the photon energy range 20 keV to 1.3 MeV

2018 ◽  
Vol 112 ◽  
pp. 11-15 ◽  
Author(s):  
Maria Christiansson ◽  
Christian Bernhardsson ◽  
Therése Geber-Bergstrand ◽  
Sören Mattsson ◽  
Christopher L. Rääf
Keyword(s):  
Energy Range ◽  
Quality Assessment ◽  
Photon Energy ◽  
Absorbed Dose ◽  
Photon Energy Range ◽  
Radiation Quality ◽  
Dose Measurements

Temperature- and pH-dependence of proton relaxation rates in rat liver tissue

1995 ◽  
Vol 13 (3) ◽  
pp. 429-440 ◽  
Author(s):  
E. Moser ◽  
E. Winklmayr ◽  
P. Holzmüller ◽  
M. Krssak
Keyword(s):  
Rat Liver ◽  
Liver Tissue ◽  
Ph Dependence ◽  
Proton Relaxation ◽  
Relaxation Rates

RADIATION-INDUCED GENOMIC INSTABILITY: RADIATION QUALITY AND DOSE RESPONSE

2003 ◽  
Vol 85 (1) ◽  
pp. 23-29 ◽  
Author(s):  
Leslie E. Smith ◽  
Shruti Nagar ◽  
Grace J. Kim ◽  
William F. Morgan
Keyword(s):  
Genomic Instability ◽  
Dose Response ◽  
Radiation Quality ◽  
Radiation Induced

scholarly journals A comparison of in-air and in-water calibration of a dosimetry system used for radiation dose assessment in cancer therapy

2010 ◽  
Vol 25 (1) ◽  
pp. 51-54 ◽  
Author(s):  
Waheed Arshed ◽  
Khalid Mahmood ◽  
Ikramullah Qazi ◽  
Asad Ullah ◽  
Perveen Akhter ◽  
...  
Keyword(s):  
Radiation Dosimetry ◽  
Absorbed Dose ◽  
Dose Assessment ◽  
Dose Delivery ◽  
Air Kerma ◽  
Tissue Equivalent ◽  
Dosimetry System ◽  
Irradiation Geometry ◽  
Radiation Dose Assessment ◽  
Absorbed Dose To Water

An accurate calibration of the therapy level radiation dosimetry system has a pivotal role in the accuracy of dose delivery to cancer patients. The two methods used for obtaining a tissue equivalent calibration of the system: air kerma calibration and its conversion to a tissue equivalent value (absorbed dose to water) and direct calibration of the system in a water phantom, have been compared for identical irradiation geometry. It was found that the deviation between the two methods remained within a range of 0% to ?1.7% for the PTW UNIDOS dosimetry system. This means that although the recommended method is in-water calibration, under exceptional circumstances, in-air calibration may be used as well.

scholarly journals Spectrophotometric Study of ?-Irradiated PM-355

2009 ◽  
Vol 6 (3) ◽  
pp. 584-589
Author(s):  
Baghdad Science Journal
Keyword(s):  
Absorption Spectra ◽  
Calibration Curve ◽  
Linear Relation ◽  
Response Curve ◽  
Energy Gap ◽  
Linear Part ◽  
Absorbed Dose ◽  
Spectrophotometric Study ◽  
High Dose ◽  
Radiation Induced

The aim of the present work is concerned with the effect of ?-irradiation on PM-355 with absorbed dose of (30-160Mrad) range. This polymer is evaluated spectrophotometrically for use as high dose dosimeters. The absorption spectra of irradiated samples showed radiation induced absorption changes. There is an increment in absorption proportional with absorbed dose. This increment is attributed to interfaces traps which, are formed by irradiation. Calibration curve was drawn .The linear relation was found in calibration curve, and dosimeter range was determined from the linear part. The linearity in response curve suggested that PM-355 could be used as dosimeter within (30-160Mrad) rang. Energy gap shift was used as a second tool to determine the dosimeter range. It was found that PM-355 energy gap systematically decreasing with absorbed dose, and it could be used as a second tool to determine the dosimeter range.

Molecular Reorientation of Methanol in Mixtures with Carbon Tetrachloride

1992 ◽  
Vol 47 (7-8) ◽  
pp. 857-864 ◽  
Author(s):  
M. D. Zeidler ◽  
D. S. Gill ◽  
M. D. Zeidler
Keyword(s):  
Carbon Tetrachloride ◽  
Composition Dependence ◽  
Nmr Relaxation ◽  
Dipolar Interaction ◽  
Coupling Constants ◽  
Proton Relaxation ◽  
Relaxation Rates ◽  
Molecular Reorientation ◽  
Quadrupole Coupling ◽  
Interaction Contribution

Abstract Proton and oxygen-17 nmr relaxation rates of CD317OH as well as deuteron nmr relaxation rates of CH3OD were measured in mixtures with carbon tetrachloride at different compositions and temperatures. By varying the 170-content different contributions to the proton relaxation rate could be separated and from the 17O-H dipolar interaction contribution the correlation time τ2OH of the OH bond was determined. Using these correlation times the composition dependence of the deuterium and oxygen-17 quadrupole coupling constants of methanol was derived. A strong variation of the coupling constants over the measured composition range is evident

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