Irradiation Of Biological Material Research Articles

First clinical experience following the consensus guide for calibrating a proton stopping power ratio curve in a new proton centre

Background and PurposeThis work introduces the first assessment of CT calibration following the ESTRO’s consensus guidelines and validating the HLUT through the irradiation of biological material. MethodsTwo electron density phantoms were scanned with two CT scanners using two CT scan energies. The stopping power ratio (SPR) and mass density (MD) HLUTs for different CT scan energies were derived using Schneider’s and ESTRO’s methods. The comparison metric in this work is based on the Water-Equivalent Thickness (WET) difference between the treatment planning system and biological irradiation measurement. The SPR HLUTs were compared between the two calibration methods. To assess the accuracy of using MD HLUT for dose calculation in the treatment planning system, MD vs SPR HLUT was compared. Lastly, the feasibility of using a single SPR HLUT to replace two different energy CT scans was explored. ResultsThe results show a WET difference of less than 3.5% except for the result in the Bone region between Schneider’s and ESTRO’s methods. Comparing MD and SPR HLUT, the results from MD HLUT show less than a 3.5% difference except for the Bone region. However, the SPR HLUT shows a lower mean absolute percentage difference as compared to MD HLUT between the measured and calculated WET difference. Lastly, it is possible to use a single SPR HLUT for two different CT scan energies since both WET differences are within 3.5%. ConclusionThis is the first report on calibrating an HLUT following the ESTRO’s guidelines. While our result shows incremental improvement in range uncertainty using the ESTRO’s guideline, the prescriptional approach of the guideline does promote harmonization of CT calibration protocols between different centres.

The effects of N-acetylcysteine on radiotherapy-induced small intestinal damage in rats.

Some six million cancer patients currently receive radiotherapy. Radiotherapy eliminates cancer cells by accelerating their death. However, radiotherapy is not selective, and it therefore harms healthy tissues around cancerous tissue. The latest studies have shown that the irradiation of biological materials causes a rapid increase in reactive oxygen species (ROS) in the tissue as a result of exposure of the target molecule to direct and indirect ionization. N-acetylcysteine (NAC) is an antioxidant that permits the elimination of free oxygen radicals and that contributes to glutathione synthesis. Our study, therefore, examined the effects of radiation resulting from radiotherapy on the small intestine at the molecular level, and prospectively considered the potential protective characteristics of NAC against gastrointestinal syndrome resulting from radiotherapy.

Complete-active-space second-order perturbation theory (CASPT2//CASSCF) study of the dissociative electron attachment in canonical DNA nucleobases caused by low-energy electrons (0-3 eV).

Low-energy (0-3 eV) ballistic electrons originated during the irradiation of biological material can interact with DNA/RNA nucleobases yielding transient-anion species which undergo decompositions. Since the discovery that these reactions can eventually lead to strand breaking of the DNA chains, great efforts have been dedicated to their study. The main fragmentation at the 0-3 eV energy range is the ejection of a hydrogen atom from the specific nitrogen positions. In the present study, the methodological approach introduced in a previous work on uracil [I. González-Ramírez et al., J. Chem. Theory Comput. 8, 2769-2776 (2012)] is employed to study the DNA canonical nucleobases fragmentations of N-H bonds induced by low-energy electrons. The approach is based on minimum energy path and linear interpolation of internal coordinates computations along the N-H dissociation channels carried out at the complete-active-space self-consistent field//complete-active-space second-order perturbation theory level. On the basis of the calculated theoretical quantities, new assignations for the adenine and cytosine anion yield curves are provided. In addition, the π1 (-) and π2 (-) states of the pyrimidine nucleobases are expected to produce the temporary anions at electron energies close to 1 and 2 eV, respectively. Finally, the present theoretical results do not allow to discard neither the dipole-bound nor the valence-bound mechanisms in the range of energies explored, suggesting that both possibilities may coexist in the experiments carried out with the isolated nucleobases.

Dosimetry in radiobiological studies with the heavy ion beam of the Warsaw cyclotron

The aim of this study was to verify various dosimetry methods in the irradiation of biological materials with a 12C ion beam at the Heavy Ion Laboratory of the University of Warsaw. To this end the number of ions hitting the cell nucleus, calculated on the basis of the Si-detector system used in the set-up, was compared with the number of ion tracks counted in irradiated Solid State Nuclear Track Detectors and with the number of ion tracks detected in irradiated Chinese Hamster Ovary cells processed for the γ-H2AX assay. Tests results were self-consistent and confirmed that the system serves its dosimetric purpose.

The masking model: a possible explanation for various effects of near-UV radiation.

Abstract— A general model is proposed to explain certain phenomena observed upon the near‐UV irradiation of biological materials. The model states that the ratio of two action spectra (e.g. in the presence or absence of histidine) does not accurately portray the absorption spectrum of the underlying chromophore. Rather, such a ratio is dictated by the relative amounts of two photoproducts. Both photoproducts are induced most efficiently at or below 300 nm. One photoproduct, sensitive to the presence of the variable agent (e.g. histidine), has a broader production spectrum than the other, which is induced independently of the variable agent. The first photoproduct is quantitatively more important at shorter wavelengths while the second dominates at longer wavelengths. An equation has been derived which defines the model in mathematical terms. Such a model might explain: (1) increased phage and bacterial inactivation in the presence of sublethal hydrogen peroxide concentrations; (2) the discrepancy between the inactivation action spectrum and absorption spectrum of psoralen; (3) histidine protection of transforming DNA inactivation; (4) phage T7 inactivation; (5) bacterial inactivation under anoxic conditions; (6) inactivation of DNA repair enzymes; and (7) photomutagenesis at low fiuence rates.

The long-time reactor irradiation of biological material at reduced temperature

When biological material in closed quartz ampoules is irradiated gaseous reaction products are formed as a result of radiation damage and thermal decomposition. The pressure thus created in the ampoules puts a limit to the time of irradiation or the sample mass and thereby to the detection limit of neutron activation analysis. The investigation will show how the internal pressure of the ampoules is reduced by cooling the sample containers in a nitrogen bath during irradiation so that a number of trace elements also in fresh biological material can be detected by means of neutron activation analysis with long-time irradiation. It will further contain a methodical study of the mechanical strength of quartz ampoules used as sample containers and the change in sample temperature using different sample containers and cooling through different media. The results of two irradiation studies of biological material in the low temperature irradiation unit of the reactor Melusine of the CENG Grenoble will be discussed.

Mitotic delay in irradiated roots of Vicia faba: the effect of oxygen.

IT is well known that the presence of oxygen during the irradiation of biological materials by X- or gamma-rays usually increases the amount of radiation damage. At the cellular level a considerable amount of quantitative data exists on the effect of oxygen, given during irradiation, on the yield of chromosome aberrations1, but little information is available concerning the influence of oxygen on the amount of mitotic inhibition. Early work on the fall in mitotic index values of broad bean root tips2 and the more recent studies on mitotic rates of Chortophaga neuroblasts3 and Tradescantia microspores4 have all indicated that the degree of mitotic inhibition is dependent on the amount of oxygen present during irradiation.

The Production of High Intensity Ultrasonics at Megacycle Frequencies

An apparatus is described for the generation of high-power ultrasonics at frequencies in the megacycle per second region using a piezo-electric generator. The use of transmission plates and various focusing devices have been investigated and beams of high intensity unfocused ultrasonics have been generated and measured by a calorimetric method up to a maximum intensity of 55 W./sq.cm. The factor limiting the power output was shown to be the dielectric strength of the transformer oil used. The apparatus was developed for the irradiation of biological material with a uniform intensity of ultrasonics over an area of a few square centimetres.

Irradiation of Biological Materials by High Energy Roentgen Rays and Cathode Rays

In this work roentgen rays and cathode rays of several million-volts energy have been applied to an investigation of their biological, photo-chemical, and germicidal effects, particularly as they are related to the processing of foods and biological materials. A constant-potential electrostatic generator, together with an acceleration tube, was used to produce continuous streams of electrons with homo-geneous and controllable energy. [R. J. Van de Graaff, K. T. Compton, and L. C. Van Atta, Phys. Rev. 43, 149 (1943).] These high energy electrons were utilized both for the production of penetrating roentgen rays and for the direct irradiation of materials. The mechanism of the biological action of both roentgen rays and cathode rays is discussed, as well as the energy considerations in their application to various absorbers. The companion paper [C. G. Dunn, W. L. Campbell, H. Fram, and A. Hutchins, J. App. Phys. 19, 605 (1948)] reports on measurements of the lethal action of these radiations on a wide variety of micro-organisms and also on the effect of the radiations on enzymes, vitamins, and certain whole food products. Both investigations have been conducted cooperatively by the Departments of Electrical Engineering and Food Technology at the Massachusetts Institute of Technology. The systematic and quantitative study of the effects of roentgen and cathode rays on various elementary forms of living matter is regarded as an essential prelude to their possible widespread application to the preservation of foods and the sterilization of various biological materials. It was realized that the mechanisms of biological action of high energy roentgen rays and cathode rays are similar and depend closely upon the ionization energy absorbed per gram of material. The studies were begun with roentgen rays since these were immediately available and permitted quantitative measurement of the energy absorbed in the biological materials. Later, the water-cooled gold x-ray target was replaced with an aluminum cathode-ray window, and corresponding studies were begun on the direct application of high energy electrons to these materials. During the period of these biological studies the x-ray source was also used in a daily clinical program of deep cancer therapy under the medical direction of Dr. Richard Dresser and also in the investigation of the physical properties of high energy radiations. [R. Dresser, Radiology, in publication.]

Die Wirkung von Adenin und Urazil auf das Wachstum vonB. coli commune

The growth ofBacterium coli commune in culture-medium afterFriedlein containing glucose was controled by photometry. Addition of uracil hastens the growth slightly, addition of adenin delays it. The curve of growth with adenin shows two maxima similarly as the primary and secundary effect after irradiation of biological material by ultrashort rays. As known the irradiation of nucleic-acids sets in partial freedom purins and pyrimidins. These are changed again by intense irradiation. The news products of irradiation have probably also biological influences.

Recovery Function of Irradiated Tissues: A Theoretical and Experimental Study

A discussion of the function of recovery of irradiated tissues must be based on a dear understanding of the relation between physically measured radiation quantities and observable biological effects and also upon a dear concept of what the terms damage and injury, recovery and repair of tissues represent physically, chemically, and biologically. These matters are here considered under four main headings: I. Quantitative relations between physical measurements and observable changes from irradiation of biological materials. II. Radiation effects on cells and tissues. III. Tissue injury and recovery equilibrium. IV. Biological action rate and cell-killing curves for various tissues. I. Quantitative Relations between Physical Measurements and Observable Changes Resulting from Irradiation of Biological Materials A. Definitions. (a) The Absorption Law: A homogeneous beam having the physical intensity I0, absorbed in a material of thickness x, will emerge with the intensity Ix, and this process expressed in symbols is found experimentally to be represented by In this equation, µ is the constant characteristic of the absorbing substance and the radiation. It indicates the percentage decrease of the radiation in one unit thickness of absorbing material. A heterogeneous beam is reduced in intensity in a more complex manner. The diminution found experimentally is represented by the expression, In this equation µ is the absorption coefficient, η is the heterogeneity coefficient which changes with increasing depths as the radiation is additionally filtered and homogenized in the absorbing material, and the effective absorption coefficient is given by (−µ + 2η) (1). (b) Ionization Measurements: The intensity of a radiation is generally estimated by counting the number of ions produced. The charges of the ions are measured as electrostatic units, each of which represents 2.1 × 109 ions per second. A radiation intensity which produces in 1 second of time in 1 milliliter of air, under standard conditions, 2.1 × 109 ions per second, is called the roentgen (r). Obviously, the number of ions produced in an ionization chamber depends on the fraction k of the beam that is absorbed in the air of the chamber and the constant b indicating the amount of work required to separate an electron from an atom, thereby creating one pair of ions (2). If i is the ionization current then measured, we have the equation The value of k is fixed in the definition of the roentgen and is easily determined experimentally. The value of b is determined for air as 35 volts; its value for liquids, solids, and tissues is not known but is probably much larger. The number of ions, therefore, produced in other media is different from the number of ions produced in air; from the values measured with a small ionization chamber at various depths in a medium other than air, no conclusions can be drawn as to the absorption or ionization produced in that medium.