Tissue Kerma Research Articles

ORGAN AND EFFECTIVE DOSE COEFFICIENTS FOR CRANIAL AND CAUDAL IRRADIATION GEOMETRIES: NEUTRONS.

With the introduction of new recommendations of the International Commission on Radiological Protection (ICRP) in Publication 103, the methodology for determining the protection quantity, effective dose, has been modified. The modifications include changes to the defined organs and tissues, the associated tissue weighting factors, radiation weighting factors and the introduction of reference sex-specific computational phantoms. Computations of equivalent doses in organs and tissues are now performed in both the male and female phantoms and the sex-averaged values used to determine the effective dose. Dose coefficients based on the ICRP 103 recommendations were reported in ICRP Publication 116, the revision of ICRP Publication 74 and ICRU Publication 57. The coefficients were determined for the following irradiation geometries: anterior-posterior (AP), posterior-anterior (PA), right and left lateral (RLAT and LLAT), rotational (ROT) and isotropic (ISO). In this work, the methodology of ICRP Publication 116 was used to compute dose coefficients for photon irradiation of the body with parallel beams directed upward from below the feet (caudal) and directed downward from above the head (cranial). These geometries may be encountered in the workplace from personnel standing on contaminated surfaces or volumes and from overhead sources. Calculations of organ and tissue kerma and absorbed doses for caudal and cranial exposures to photons ranging in energy from 10 keV to 10 GeV have been performed using the MCNP6.1 radiation transport code and the adult reference phantoms of ICRP Publication 110. As with calculations reported in ICRP 116, the effects of charged-particle transport are evident when compared with values obtained by using the kerma approximation. At lower energies the effective dose per particle fluence for cranial and caudal exposures is less than AP orientations while above ∼30 MeV the cranial and caudal values are greater.

REFERENCE NEUTRON FIELDS IN CALIBRATION LABORATORY; SIMPLE DOSIMETRIC PARAMETERS AND THEIR CHANGES IN TIME.

The calibration laboratory revises periodically the dosimetric properties of its calibration fields. For reference neutron fields based on radionuclide sources, it is due to presence of isotopic impurities in the source ingredients. Consequently, in long term, the admixtures and their decay products become significant. Neglecting the impact of such effect leads to inconsistencies between the neutron emission rate observed during the measurements and the emission rate derived from the decay curve of the main isotope. In the Radiation Protection Measurements Laboratory at the National Centre for Nuclear Research the neutron fields of the bare sources of 252Cf, 241AmBe and 239PuBe have been examined for nearly 30 years, regularly, in fixed geometry. Additionally, at the particular point of a calibration bench, determination of neutron fluence rate, ambient dose equivalent rate and its scattered component, total neutron and gamma dose rate, gamma to total dose ratio, radiation quality factor and total tissue kerma are occasionally determined. In this article, we would like to present recently achieved results and their comparison with the measurement data formerly presented. The growth of the neutron emission of 239PuBe source, as well as discrepancies between the decay curves of relevant isotopes and the emission rate of 252Cf and 241AmBe will be presented.

Measurement of the gamma-ray energy spectrum of the educational Kinki University Reactor (UTR-KINKI)

The gamma-ray energy spectrum of the Kinki University Reactor (UTR-KINKI) was estimated from Ge detector measurements combined with Monte Carlo N-particle transport criticality calculations. The gamma rays mainly originated from prompt fission components, although small amounts of gamma rays from (n,γ) reactions, fission product gamma rays, and activation gamma rays were detected. The averaged gamma-ray tissue kerma rate in the irradiation port during UTR-KINKI operation at 1W was calculated as 10.5cGy/h based on the estimated gamma-ray energy spectrum. This value is consistent with a previous measurement with paired ionization chambers and a tissue equivalent gas proportional counter. This result demonstrates the reliability of the estimated gamma-ray energy spectrum.

ORGAN AND EFFECTIVE DOSE COEFFICIENTS FOR CRANIAL AND CAUDAL IRRADIATION GEOMETRIES: PHOTONS

With the introduction of new recommendations of the International Commission on Radiological Protection (ICRP) in Publication 103, the methodology for determining the protection quantity, effective dose, has been modified. The modifications include changes to the defined organs and tissues, the associated tissue weighting factors, radiation weighting factors and the introduction of reference sex-specific computational phantoms. Computations of equivalent doses in organs and tissues are now performed in both the male and female phantoms and the sex-averaged values used to determine the effective dose. Dose coefficients based on the ICRP 103 recommendations were reported in ICRP Publication 116, the revision of ICRP Publication 74 and ICRU Publication 57. The coefficients were determined for the following irradiation geometries: anterior-posterior (AP), posterior-anterior (PA), right and left lateral (RLAT and LLAT), rotational (ROT) and isotropic (ISO). In this work, the methodology of ICRP Publication 116 was used to compute dose coefficients for photon irradiation of the body with parallel beams directed upward from below the feet (caudal) and directed downward from above the head (cranial). These geometries may be encountered in the workplace from personnel standing on contaminated surfaces or volumes and from overhead sources. Calculations of organ and tissue kerma and absorbed doses for caudal and cranial exposures to photons ranging in energy from 10 keV to 10 GeV have been performed using the MCNP6.1 radiation transport code and the adult reference phantoms of ICRP Publication 110. As with calculations reported in ICRP 116, the effects of charged-particle transport are evident when compared with values obtained by using the kerma approximation. At lower energies the effective dose per particle fluence for cranial and caudal exposures is less than AP orientations while above ∼30 MeV the cranial and caudal values are greater.

Electron paramagnetic resonance radiation dose assessment in fingernails of the victim exposed to high dose as result of an accident.

In this paper, we report results of radiation dose measurements in fingernails of a worker who sustained a radiation injury to his right thumb while using 130 kVp X-ray for nondestructive testing. Clinically estimated absorbed dose was about 20-25 Gy. Electron paramagnetic resonance (EPR) dose assessment was independently carried out by two laboratories, the Naval Dosimetry Center (NDC) and French Institut de Radioprotection et de Sûreté Nucléaire (IRSN). The laboratories used different equipments and protocols to estimate doses in the same fingernail samples. NDC used an X-band transportable EPR spectrometer, e-scan produced by Bruker BioSpin, and a universal dose calibration curve. In contrast, IRSN used a more sensitive Q-band stationary spectrometer (EMXplus) with a new approach for the dose assessment (dose saturation method), derived by additional dose irradiation to known doses. The protocol used by NDC is significantly faster than that used by IRSN, nondestructive, and could be done in field conditions, but it is probably less accurate and requires more sample for the measurements. The IRSN protocol, on the other hand, potentially is more accurate and requires very small amount of sample but requires more time and labor. In both EPR laboratories, the intense radiation-induced signal was measured in the accidentally irradiated fingernails and the resulting dose assessments were different. The dose on the fingernails from the right thumb was estimated as 14 ± 3 Gy at NDC and as 19 ± 6 Gy at IRSN. Both EPR dose assessments are given in terms of tissue kerma. This paper discusses the experience gained by using EPR for dose assessment in fingernails with a stationary spectrometer versus a portable one, the reasons for the observed discrepancies in dose, and potential advantages and disadvantages of each approach for EPR measurements in fingernails.

Characterisation of radiation field for irradiation of biological samples at nuclear reactor--comparison of twin detector and recombination methods

Central Laboratory for Radiological Protection is involved in achieving scientific project on biological dosimetry. The project includes irradiation of blood samples in radiation fields of nuclear reactor. A simple facility for irradiation of biological samples has been prepared at horizontal channel of the nuclear reactor MARIA in NCBJ in Poland. The radiation field, composed mainly of gamma radiation and thermal neutrons, has been characterised in terms of tissue kerma using twin-detector technique and recombination chambers.

Alteration of the Serum N-glycome of Mice Locally Exposed to High Doses of Ionizing Radiation

Exposure of the skin to ionizing radiation leads to characteristic reactions that will often turn into a pathophysiological process called the cutaneous radiation syndrome. The study of this disorder is crucial to finding diagnostic and prognostic bioindicators of local radiation exposure or radiation effects. It is known that irradiation alters the serum proteome content and potentially post-translationally modifies serum proteins. In this study, we investigated whether localized irradiation of the skin alters the serum glycome. Two-dimensional differential in-gel electrophoresis of serum proteins from a man and from mice exposed to ionizing radiation showed that potential post-translational modification changes occurred following irradiation. Using a large-scale quantitative mass-spectrometry-based glycomic approach, we performed a global analysis of glycan structures of serum proteins from non-irradiated and locally irradiated mice exposed to high doses of γ-rays (20, 40, and 80 Gy). Non-supervised descriptive statistical analyses (principal component analysis) using quantitative glycan structure data allowed us to discriminate between uninjured/slightly injured animals and animals that developed severe lesions. Decisional statistics showed that several glycan families were down-regulated whereas others increased, and that particular structures were statistically significantly changed in the serum of locally irradiated mice. The observed increases in multiantennary N-glycans and in outer branch fucosylation and sialylation were associated with the up-regulation of genes involved in glycosylation in the liver, which is the main producer of serum proteins, and with an increase in the key proinflammatory serum cytokines IL-1β, IL-6, and TNFα, which can regulate the expression of glycosylation genes. Our results suggest for the first time a role of serum protein glycosylation in response to irradiation. These protein-associated glycan structure changes might signal radiation exposure or effects.

Measurement of Neutron Dose under Criticality Accident Conditions at TRACY Using TLDs

Applicability of a neutron dose equivalent monitor with thermoluminescence dosimeter (TLD monitor) as an area dosimeter for criticality accidents was studied through measurements at Transient Experiment Critical Facility (TRACY). The TLD monitor is composed of two TLD badges and a cubical polyethylene case, and has a response similar to the values of the conversion coefficients for the ambient dose equivalent in the energy range from 0.1 to 10MeV. TRACY was operated with and without a water reflector when irradiating the TLD monitors. The neutron doses measured with the TLD monitors were converted into tissue kerma using dose conversion factors calculated with MCNP5. Factors to correct for the difference between responses of the TLD monitor to the spontaneous fission spectrum of a 252Cf calibration source and to spectra of TRACY were also calculated with MCNP5 and applied to the tissue kerma. The values of tissue kerma were proportional to the integrated power of TRACY. The measured tissue kerma ranged from 0.034 to 16 Gy, which covers the range from 0.1 to 10Gy specified as important in criticality accident dosimetry by the IAEA. The presented method of measurement also satisfies the time limit on dose determination.

Measurement of Neutron Dose under Criticality Accident Conditions at TRACY Using TLDs

Applicability of a neutron dose equivalent monitor with thermoluminescence dosimeter (TLD monitor) as an area dosimeter for criticality accidents was studied through measurements at Transient Experiment Critical Facility (TRACY). The TLD monitor is composed of two TLD badges and a cubical polyethylene case, and has a response similar to the values of the conversion coefficients for the ambient dose equivalent in the energy range from 0.1 to 10MeV. TRACY was operated with and without a water reflector when irradiating the TLD monitors. The neutron doses measured with the TLD monitors were converted into tissue kerma using dose conversion factors calculated with MCNP5. Factors to correct for the difference between responses of the TLD monitor to the spontaneous fission spectrum of a 252Cf calibration source and to spectra of TRACY were also calculated with MCNP5 and applied to the tissue kerma. The values of tissue kerma were proportional to the integrated power of TRACY. The measured tissue kerma ranged from 0.034 to 16 Gy, which covers the range from 0.1 to 10Gy specified as important in criticality accident dosimetry by the IAEA. The presented method of measurement also satisfies the time limit on dose determination.

Calculated Fluence Spectra at Neutron Therapy Facilities

The Monte Carlo transport codes LAHET and MCNP were used to calculate energy fluence spectra at three neutron therapy facilities. The results compare very favourably with measured data. Kerma spectra and the ratio of ICRU muscle tissue kerma to A-150 kerma, along with the carbon to oxygen kerma ratio, were determined. Absorbed dose rate calculations are in reasonable agreement with measured values. Use of these codes to study modifications to existing therapy beams is briefly discussed.

Incidence of Salivary Gland Tumors among Atomic Bomb Survivors, 1950-1987. Evaluation of Radiation-Related Risk

A wide-ranging search for benign and malignant tumors of the major and minor salivary glands among members of the Life Span Study sample of the Radiation Effects Research Foundation identified 41 malignant and 94 benign incident tumors, including 14 malignant and 12 benign tumors of the minor salivary gland, plus 10 major gland tumors of unknown behavior. Dose-response analyses found statistically significant increases in risk with increasing A-bomb dose for both cancer and benign tumors. Estimated relative risks at 1 Sv weighted tissue kerma (RR1Sv, with 90% confidence interval in parentheses) were 4.5 (2.5-8.5) for cancer and 1.7 (1.1-2.7) for benign tumors. When analyzed by histological subtype within these two broad groups, it appeared that most of the dose response for malignant tumors was provided by an exceptionally strong dose response for mucoepidermoid carcinoma [11 exposed cases with dose estimates, RR1Sv = 9.3 (3.5-30.6)], and most or all of that for benign tumors corresponded to Warthin's tumor [12 cases, RR1Sv = 4.1 (1.6-11.3)]. There was a marginal dose response for malignant tumors other than mucoepidermoid carcinoma [RR1Sv = 2.4 (0.99-5.7)] but no significant trend for benign tumors other than Warthin's tumor [RR1Sv = 1.3 (0.9-2.2)]. Re-examination of the original data from published studies of other irradiated populations may shed new light on the remarkable type specificity of the salivary tumor dose response observed in the present study.

Thermoluminescence dosimetry of the Hiroshima atomic-bomb gamma rays between 1.59 km and 1.63 km from the hypocenter.

Gamma-ray kermas from the Hiroshima atomic bomb were measured by a thermoluminescence (TL) method using tile specimens collected from five locations on the rooftop of a building (Postal Saving Bureau), 1,591-1,635 m from the hypocenter. Four tile specimens each from five locations were sampled and quartz grains were extracted from them. TL of these grains were analyzed by the high temperature TL method and gamma-ray kermas were obtained. The results in tissue kerma, on average, are 21% higher (standard errors are 4.3-7.3%) than the DS86 estimation. The present data and the reported TL results indicate that the measured gamma-ray kermas begin to exceed the DS86 values at about 1.3 km and the discrepancy between them increases with ground distance. This discrepancy is attributed to errors in the DS86 neutron source spectrum and is supported by previous neutron activation measurements.

Sensitivity/Uncertainty Analysis for Free-in-Air Tissue Kerma Due to Initial Radiation at Hiroshima and Nagasaki

Uncertainty estimates and cross correlations by range/survivor have been calculated for the Hiroshima and Nagasaki free-in-air (FIA) tissue kerma obtained from two-dimensional air/ground transport calculations. The uncertainties due to modeling parameter and basic nuclear transport data uncertainties were calculated for 700-, 1000-, and 1500-m ground ranges. Only the FIA tissue kerma due to initial radiation was treated in the analysis; the uncertainties associated with terrain and building shielding and phantom attenuation were not considered in this study. Uncertainties of --20% were obtained for the prompt neutron and secondary gamma kerma and 30% for the prompt gamma kerma at both cities. The uncertainties on the total prompt kerma at Hiroshima and Nagasaki are --18 and 15%, respectively. The estimated uncertainties vary only slightly by ground range and are fairly highly correlated. The total prompt kerma uncertainties are dominated by the secondary gamma uncertainties, which in turn are dominated by the modeling parameter uncertainties, particularly those associated with the weapon yield and radiation sources.

Dosimetric evaluation of 252Cf beam for use in radiobiology studies at Hiroshima University

A fission neutron converter at the Kyoto University Research Reactor (KUR) which provides a relatively high kerma rate has been used to evaluate the effects of fission neutrons on radiobiological materials. To assess such effects at a relatively low kerma rate, a 252Cf source was installed in a linear accelerator facility at Hiroshima University, in March 1984. In these experiments, reliable tissue kerma in free air data must be used as a base for determining RBE. Before the radiobiological studies were begun, tissue kerma in free air were determined under obvious irradiation conditions. The 252Cf source emits two types of radiation; one third gamma ray and two thirds neutron tissue kermas. From among the dosimetry methods usually used to study such mixed radiation fields, the authors selected the method of paired chambers. Reliable tissue kerma in free air data are provided by characterising the 252Cf irradiating system and by comparing the dosimetry methods. Measurements of absorption by materials were also made by conventional methods.

Spectral energy measurements in a fast neutron therapy field

Various basic physical parameters are needed to convert a specific dosimeter reading in air to tissue kerma or to absorbed dose in a phantom. In a neutron radiation field, spectral information is required for the evaluation of these parameters. Using NE213 liquid scintiillator as a proton recoil spectrometer, neutron spectra were measured in the collimated d(16)+ Be beam of the Pretoria fast neutron therapy facility. The neutron events wer eidentified by means of pulse shape discrimination and a well established computer code employed to unfold the acquired pulse height data. The analysed neutron spectrum was used to compute the neutron kerma ratio ( K t/ K m) N and the ratio of the average energies W N/ W c required to create an ion pair in an A-150/TE gas ionization chamber. The determined values concur with published data from other centres with similar neutron beams. The mean neutron energy E n of the therapy beam was also calculated from the spectral distribution.

Comparison of measurements on tissue kerma and photon radiation dose made with emergency dosemeters

The purpose of this paper is to compare the tissue equivalence and tissue kerma for dosimetric tissue-equivalent detectors with allowance for the neutron spectra. Results are given for the calculated dose sensitivities for the DINA and GNEIS dosemeters for a portion of the neutron spectra recommended by IAEA for comparative tests. The measurements were made with five nuclear systems - BR-10, RF-GS, BR-1-21, BR-1-21, and IBR-30 - as well as with accelerators. Doses from photon radiation were also measured using thermoluminescent and photoluminescent dosemeters sensitive to neutrons.

Solid state nuclear track detectors in high energy particle dosimetry

Abstract Responses of some polymer SSNTD to high energy charged particles were systematically studied, experiments were performed in beams of synchrophasotron of the Joint Institute of Nuclear Research at Dubna, USSSR. SSNTD like CR39, Kodak CN85, LR115 and Melinex 0 were studied. Depending of the type of detector and that of particle, responses established are between lE-07 and lE-04 tracks per normally incident particle, following general sensitivity of a detector. It permits to use them to measure tissue kerma in the range between 0.1 mGy to some 10 of Gy. Results of some dosimetric applications are also presented.

A New Dosimetry for A-Bomb Survivors

Considerable progress has been achieved in the development of revised dose estimates for the Japanese A-bomb survivors. New calculations have been made of the initial radiation escaping from the bombs and, for Hiroshima, validated by experiments with a replica weapon. Air-over-ground transport of the initial radiations and decay radiation from debris in the fireball has been calculated and results are being compared with measurements at weapon tests and with samples irradiated at the time of the bombings. A new system based on adjoint Monte Carlo calculations is being used to calculate the differential fluence, in energy and angle, at locations within Japanese houses and then the organ doses of each survivor. Preliminary estimates of the tissue kerma in the open and inside the houses of proximally exposed survivors are compared with estimates made with the older T65 dosimetry.

A New Dosimetry for A-Bomb Survivors

Considerable progress has been achieved in the development of revised dose estimates for the Japanese A-bomb survivors. New calculations have been made of the initial radiation escaping from the bombs and, for Hiroshima, validated by experiments with a replica weapon. Air-over-ground transport of the initial radiations and decay radiation from debris in the fireball has been calculated and results are being compared with measurements at weapon tests and with samples irradiated at the time of the bombings. A new system based on adjoint Monte Carlo calculations is being used to calculate the differential fluence, in energy and angle, at locations within Japanese houses and then the organ doses of each survivor. Preliminary estimates of the tissue kerma in the open and inside the houses of proximally exposed survivors are compared with estimates made with the older T65 dosimetry.

Comparison of Measured and Calculated Radiation Transport in Air-Over-Ground Geometry to 1.6 km from a Fission Source

Neutron and gamma-ray tissue kerma and scalar spectrum measurements have been made at the Army Pulse Radiation Division (APRD), Aberdeen Proving Ground, to 1.6 km in air-over-ground geometry from a fission source and are compared to state-of-the-art transport calculations. Measurements have been made by the APRD staff as well as German, Canadian, and French scientists. A variety of integral detectors and differential spectrometers were used. Agreement among the various groups ranges from good to excellent. Calculations have been made in support of shielding programs and in connection with the Hiroshima-Nagasaki dose reevaluation effort. The DOT transport calculations have been performed at the Lawrence Livermore and Oak Ridge National Laboratories, the Defence Research Establishment, Ottawa, and at Science Applications, Inc. Monte Carlo calculations have been performed at Los Alamos National Laboratory. The calculations are generally consistent. Average calculated-to-measured kerma ratios range from 0.83 to 1.27. Calculated-to-measured neutron flux ratios vary from about 0.6 near 1 keV and about 0.8 near 5 MeV to about 1.7 near 0.8 MeV. These spectral differences tend to cancel when determining tissue kerma, raising the possibility that some of the agreement in kerma may be fortuitous. Sources of possible discrepancies are discussed.