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trans-Vinylene unsaturations generated in ultrahigh-molecular-weight polyethylene (UHMWPE) after radiation treatment scales linearly with the absorbed dose level, and can serve as an internal dosimeter for determining the radiation dose level for sterilizing or crosslinking UHMWPE. We measured the trans-vinylene concentration using infrared spectroscopy and generated calibration curves for ultrahigh-molecular-weight polyethylene (ram-extruded GUR 1050) after cold e-beam, cold gamma, and warm e-beam irradiations. The trans-vinylene content increased linearly with the absorbed dose level in all cases except with cold gamma irradiation at dose levels higher than approximately 70 kGy. At that dose level the trans-vinylene content of the warm irradiated samples was higher than those of the cold irradiated samples. Following postirradiation melting, the trans-vinylene content of the gamma irradiated samples increased. Such trans-vinylene quantification can be an internal dosimeter for crosslinked UHMWPE when radiation is used for improving its wear resistance or sterilizing the device made thereof. It can also be utilized to assess the spatial uniformity of the absorbed radiation dose level.

A method is described for the distinction between the normal, “dynamic” radiation exposure of a personal radiation dosimetry badge during normal wear of the badge, and an abnormal, or “static” exposure of the badge in a fixed position relative to a radiation source. An example of a static exposure would be the intentional (unauthorized), or accidental, exposure of the badge to a radiation source when the badge is not being worn by a person. Other abnormal exposure conditions of interest include when the badge is accidentally partially shielded by (say) coins or other heavy material during incorrect wear of the badge (e.g. in a pocket) such that the usual reading of the badge may reveal a lower-than-expected absorbed dose reading. This paper describes the use of Pulsed Optically Stimulated Luminescence (POSL) as a dosimetric readout mode and the application of this technique to “imaging” of the dose distribution across the face of a large area Al2O3:C dosimeter. The technique relies upon the use of a radiation filter with a periodic array of holes, or other weakly absorbing regions, such that the Al2O3:C is exposed in a pattern which follows the pattern of the filtration. Subsequent illumination of the Al2O3:C using a defocused laser beam reveals a pattern of luminescence emission corresponding to the pattern of the absorbed dose. During static exposure, the absorbed radiation pattern is sharp and clear, whereas during dynamic exposure the absorbed radiation pattern is diffuse. Image processing of the collected POSL emission pattern using a Discrete Fourier Transform produces a spatial frequency spectrum of the collected image from which a factor is calculated which indicates the probability of static versus dynamic exposure. Furthermore, the POSL image obtained (vis-a-vis the absorbed radiation dose pattern) can also reveal accidental shielding. The image collection procedure, the image processing algorithms, and two different methods to determine the probability factor are described. Application of the technique to several exposure conditions is illustrated.

The outer layer of Teflon® fluorinated ethylene propylene (FEP) multi-layer insulation (MLI) on the Hubble Space Telescope (HST) was observed to be significantly cracked at the time of the Second HST Servicing Mission (SM2), 6.8 years after HST was launched into low Earth orbit (LEO). Comparatively minor embrittlement and cracking were also observed in the FEP materials retrieved from solar-facing surfaces on the HST at the time of the First Servicing Mission (3.6 years exposure). After SM2, a failure review board was convened to address the problem of degradation of MLI on the HST. In order for this board to determine possible degradation mechanisms, it was necessary to consider all environmental constituents to which the FEP MLI surfaces were exposed. Based on measurements and various models, the environmental exposure conditions for the FEP surfaces on the HST were estimated, including: the number and temperature ranges of thermal cycles; equivalent sun hours; fluence and absorbed radiation dose of x-rays, trapped protons and electrons and plasma electrons and protons; and atomic oxygen (AO) fluence. This paper presents the environmental exposure conditions for FEP on the HST, briefly describing the possible roles of the environmental factors in the observed FEP embrittlement and providing references to the published works which describe in detail testing and analysis related to FEP degradation on the HST.

Dosimetric labels produced on a commercial scale are usually prepared carefully and in a reproducible way, as concerns the composition of active matrix. It supplies reactive intermediates, products of radiolysis which cause changes in optical absorption of dyes added to the composite. The thickness and texture of labels is also controlled, at least within one batch. Therefore the conditions are fulfilled for the application of quantitative methods of evaluation, which are better than visual inspection or comparison with a standard scale of colours. The most appropriate method is spectrophotometry. Due to the poor transparency of labels, caused by opacity of nonactive support (paper or polymer not taking part in the modification of colour) the best mode of measurement is diffuse reflected light spectrophotometry, also called Diffuse Reflectance Spectroscopy (DRS). Application of DRS to commercial labels has shown that they are developed on the basis of a mixture of dyes. Recording of full absorption spectra is therefore advised followed by measuring of peak heights rather than measuring of absorption at one selected wavelength.

Purpose: The lack of any consistent correlation between radioimmunotherapy (RIT) dose and observed hematologic toxicity has made it difficult to validate RIT radiation dose estimates to marrow. Stable chromosomal translocations (SCT) which result after radiation exposure may be a biologic parameter that more closely correlates with RIT radiation dose. Increases in the frequency of SCT are observed after radiation exposure and are highly correlated with absorbed radiation dose. SCT are cumulative after multiple radiation doses and conserved through an extended number of cell divisions. The purpose of this study was to evaluate whether increases in SCT frequency were detectable in peripheral lymphocytes after RIT and whether the magnitude of these increases correlated with estimated radiation dose to marrow and whole body. Methods and Materials: Patients entered in a Phase I dose escalation therapy trial each received 1–3 intravenous cycles of the radiolabeled anti–carcinoembryonic antigen (CEA) monoclonal antibody, 90Y-chimeric T84.66. Five mCi of 111In-chimeric T84.66 was co-administered for imaging and biodistribution purposes. Blood samples were collected immediately prior to the start of therapy and 5–6 weeks after each therapy cycle. Peripheral lymphocytes were harvested after 72 hours of phytohemagglutinin stimulation and metaphase spreads prepared. Spreads were then stained by fluorescence in situ hybridization (FISH) using commercially available chromosome paint probes to chromosomes 3 and 4. Approximately 1000 spreads were evaluated for each chromosome sample. Red marrow radiation doses were estimated using the AAPM algorithm and blood clearance curves. Results: Eighteen patients were studied, each receiving at least one cycle of therapy ranging from 5–22 mCi/m2. Three patients received 2 cycles and two patients received 3 cycles of therapy. Cumulative estimated marrow doses ranged from 9.2 to 310 cGy. Increases in SCT frequencies were observed after each cycle for both chromosomes 3 and 4 in 16 of 18 patients and in at least one chromosome for the remaining 2 patients. Cumulative increases in SCT frequencies ranged from 0.001 to 0.046 with no major differences observed between chromosomes 3 and 4. A linear correlation between cumulative marrow dose and increases in SCT frequencies was observed for chromosome 3 (R2 = 0.63) and chromosome 4 (R2 = 0.80). A linear correlation was also observed between increases in SCT frequency and whole body radiation dose or administered activity (R2 = 0.67–0.89). There was less correlation between observed decrease in wbc or platelet counts and marrow dose, whole body dose, or administered activity (R2 = 0.28–0.43). Conclusions: Increases in SCT frequency were detectable in peripheral lymphocytes after low dose-rate RIT irradiation. A linear correlation was observed between increases in SCT and marrow dose, whole body dose, and administered activity. This correlation provides one of the strongest radiation dose–response and activity–response relationships observed with RIT. The detection of SCT may therefore have application as an in situ integrating biodosimeter after RIT. This biologic parameter should prove useful in comparing effects on marrow for different therapeutic radionuclides and in comparing effects of RIT and external beam radiation doses on a cGy per cGy basis. As a result, this should allow for a more direct comparison between different methods of irradiation and in further refinement of radioimmunotherapy dose estimates and dosimetry methodology.

Radiation therapy (radiotherapy) is a valuable technique used in medicine for cancer treatment. It is a fact that many of the incidents and accidents involve only partial body irradiation and the extremities are the most frequently injured parts of the body. As it is still not general practice to use infrared (IR) thermographic imaging for the more precise diagnosis of local injuries, the availability of these techniques is very rarely mentioned in the publications. In this paper attention is drawn to what was introduced more than a decade ago, namely the use of IR thermographic procedures in diagnosing local radiation injuries. Further justification for introducing these techniques is that, in the relevant cases, the assessment of absorbed radiation dose through the widely known biological indicators or biological dosimetry assays is not always possible.

Irradiated alanine when heated in differential scanning calorimetry cell (DSC) gives thermal profiles which have varying decomposition temperatures correlated to absorbed radiation dose between 0 to 250 Gy with high precision. Higher absorbed doses give characteristic decomposition peaks in DSC thermal profile. DSC studies indicate that changes in the thermal profiles are mainly due to exothermic decomposition of peroxides. Based on the information, it may be possible to develop a low cost and simple thermal device for estimating low absorbed doses in industrial radiation processing applications.

A method for the determination of absorbed radiation dose is described based on pulsed optically stimulated luminescence (POSL). The method relies upon the stimulation of an irradiated sample with a train of light pulses from a suitable light source (e.g. a laser using a wavelength which is within the range of wavelengths corresponding to the radiation-induced optical absorption in the irradiated sample. The subsequent emitted light, due to the detrapping of trapped charges and their subsequent recombination with charge of the opposite sign, is synchronously detected in the period between each stimulation pulse. The total luminescence is summed over the desired number of stimulation pulse and this forms the measured POSL signal. By monitoring the emitted light only in the period between stimulation pulses one can reduce the optical filtering required to discriminate between the stimulation light and the emission light: in this way a high measurement efficiency, and, therefore, a high radiation sensitivity (luminescence intensity per unit absorbed dose) is achieved. Key parameters in the method are the intrinsic luminescence lifetime for the material being used as the luminescent detector, the width of the optical stimulation pulse. and the period between pulses. For optimum operation the measurement parameters should be such that both the pulse width and the time between pulses are much less than the luminescence lifetime. By appropriate choice of the power of the optical stimulation, the frequency of the stimulation pulses, and the total stimulation period, one can also re-measure the absorbed dose several times. In this way, a re-read capability is available with the procedure. The method is illustrated using light from a 2nd-harmonic Nd:YAG laser, with irradiated, anion-deficient aluminium oxide as the luminescent detector material.

The dependence of o- and m-tyrosine levels in protein rich products upon the absorbed radiation dose offers the possibility for identification of radiation processed foodstuffs. A simple and fast method was applied for determining irradiation of industrial processed food. Free amino acids of irradiated and unirradiated liquid egg samples (liquid egg, liquid egg yolk) and homogenized turkey sausage samples were extracted with trichloroacetic acid. After centrifugation and filtration aliquots of the crude extract were applied for HPLC analysis using a RP-C18 column and trichloroacetic acid as ion-pairing agent in combination with an electrochemical dual cell detector. o- and m-Tyrosine were identified by relative retention times and their peak height ratios at different potentials in comparison to those of a standard mixture and quantified by calibration curves. The commercial products investigated were unirradiated.

Polyacrylamide gels (PAGs) are used for magnetic resonance imaging radiation dosimetry. Fourier transform (FT) Raman spectroscopy studies were undertaken to investigate cross-linking changes during the copolymerization of polyacrylamide gels in the spectral range of 200-3500 cm(-1). Vibrational bands of 1285 cm(-1) and 1256 cm(-1) were assigned to acrylamide and bis-acrylamide single CH2 deltaCH2 binding modes. Bands were found to decrease in amplitude with increasing absorbed radiation dose as a result of copolymerization. Principal component regression was performed on FT-Raman spectra of PAG samples irradiated to 50 Gy. Two components were found to be sufficient to account for 98.7% of the variance in the data. Cross validation was used to establish the absorbed radiation dose of an unknown PAG sample from the FT-Raman spectra. The calculated correlation coefficient between measured and predictive samples was 0.997 with a standard error of estimate of 0.976 and a standard error of prediction of 1.140. Results demonstrate the potential of FT-Raman spectroscopy for ionizing radiation dosimetry using polyacrylamide gels.

Inhaling metal tritide particles is a potential occupational hazard. The radiation dose to tissue from tritide particles depends on their solubility and retention in the body. In each tritide particle, a portion of the beta particles from decay of tritium is absorbed by the metal matrix and therefore cannot contribute to absorbed radiation dose to tissue. A theoretical model for estimating the self-absorption of tritium betas in spherical metal tritide particles is presented. Numerical calculations are made with this method for titanium, zirconium, and erbium particles from 0.5 to 50 microm in diameter. The tritium spectrum is divided into energy groups to facilitate estimation of the energy that escapes the particle for dose calculations. Our results show considerable absorption of beta particles and their energy, even for respirable particles smaller than 5 microm. Limited experimental data of self-absorption for titanium and zirconium tritides supported the theoretical calculation. It is concluded that the self-absorption factors should be required for counting tritide particle samples as well as for estimating absorbed radiation dose to tissue.

Purpose: Previously we have demonstrated that radioimmunoconjugates can be injected into glioma resection cavities to deliver a boost of radiation to the cavity edge with little toxicity to the normal brain. In the mathematical models we have previously published to assist in the development of this strategy we assumed that antibody remains associated with the cavity edge and no diffusion occurs. However, moderate diffusion might be beneficial while, if this were excessive, it would decrease the therapeutic index markedly. Methods and Materials: Selected individuals with relapsed malignant glioma underwent further surgical debulking; 90 Y MoAb radioimmunotherapy; and open biopsy to determine the extent to which the conjugate diffuses from the cavity edge. Samples from these patients were taken in radial tracts and the corrected activity in each sample was plotted against distance from the cavity wall to determine appropriate diffusion constants. Results: Our data indicates that diffusion of radioimmunoconjugate from the edge of a glioma resection cavity appears to be an exponential process. The mean R o for each patients data set ranged from 0.48–0.63 (overall mean 0.6) cm. A dosimetric model was developed that translates these measurements into estimates of radiation dose. Applying the clinical data to this model indicates that, in each patient, the peak dose is delivered 0.16–0.18 cm below the cavity margin, and the mean dose at 2 cm deep is 5.3% (4.4–5.8%) of the peak. Conclusion: The model described can be used to translate diffusion constants measured by any method into estimates of absorbed radiation dose. Assuming similar diffusion kinetics, it can also be used to predict the dose deposited if alternative radionuclides are linked to MoAb, although the effect of dose rate should also be considered. In the future, it may be possible to manipulate diffusion by using either different antibodies or antibody fragments for intracavity radioimmunotherapy. Before this can be done, however, further data are needed and a noninvasive approach to measuring diffusion would clearly be optimal.

We have observed that the 230°C TL glow peak in porcelain possesses the same pre-dose properties as the 110°C TL glow peak in quartz. The pre-dose effect is the increase in TL radiation sensitivity observed after irradiation and subsequent heating of quartz and the increase is proportional to the total absorbed radiation dose prior to heating. It is a useful technique in dating and authentication of art objects as well as in retrospective dosimetry after radiation accidents. The disadvantage of the 110°C pre-dose peak is that it rapidly becomes non-linear and can only be used for doses less than 1 Gy. Porcelain contains quartz and exhibits both the 110°C TL glow peak and a peak at 230°C. Both peaks are observed to have approximately the same amplitude when using narrow band blue filters. The thermal activation properties, radiation dose response and dosimetric applicability of 230°C pre-dose TL glow peak of porcelain were investigated, and we found that it has the same TL properties as the 110°C peak but has advantages for dose evaluation due to its longer half-life and linearity up to a dose of 3 Gy.

The effect of lead impurities on the radiation resistance of potassium chloride is studied experimentally. It is shown that the efficiency of accumulation of F centers depends on the lead content, the absorbed radiation dose, and the prehistory of the sample. The important factors governing the stabilization of radiation-induced defects are the aggregation and dissolution of the impurities, the electron-acceptor properties of lead, and the ability of lead ions to stabilize interstitial atoms of the haloid.

The influence of x-ray irradiation to absorbed radiation doses D = (0.5−12) × 108 rad on the properties of ferroelectric ceramic Pb(TixZr1−x )O3 solid solutions with compositions close to the morphotropic phase boundary was studied. The effects of x-ray radiation on the electrical conductivity of ferroelectric ceramics are shown to differ with x ranging from 0.42 to 0.60. Using empirical equations and numerical techniques, quantitative relations are established between the composition, absorbed radiation dose, and electrical conductivity for Pb(TixZr1−x )O3.

A number of fused silica samples were evaluated for their resistance to densification by deep UV radiation at 193 nm wavelength. Density changes for all the samples equal the product of a material dependent constant and the absorbed two-photon dose to a sublinear power of about 2/3. This dose dependence is consistent with earlier compaction studies using UV, electron, and gamma radiation. We also studied the isothermal-annealing behavior of UV-induced compaction in fused silica and found a correlation between thermal recovery of compaction and the compaction rates for different fused silica samples. Preheat-treatment at 950 °C for 1 h increased the UV-induced compaction rate of two types of fused silica samples, but did not affect that of the other two types of samples. Based on these experimental observations and the well-accepted network structure model of glasses, we propose a model to explain the sublinear power dependence on absorbed radiation dose for the ionization-induced compaction.

Purpose: The radionuclide 186 Re has favorable physical characteristics for use in radioimmunotherapy, including tbe emission of β-particles of a high-energy and a low-abundance of γ-emission. The γ-emission, in particular, is ideal for tumor imaging and poses less hazards to the patient and the medical personnel when compared with the γ-emission of the widely used radionuclide 131 I. In the present study, we determined whether 186 Re-labeled monoclonal antibody 323/A3 may be better suited for the treatment of ovarian cancer than 131 I-323/A3. Methods and Materials: We compared the biodistribution and the efficacy of 186 Re- and 131 I-labeled 323/A3 in nude mice bearing s.c. the human ovarian cancer xenografts FMa, OVCAR-3 and Ov.Pe. 186 Re was conjugated to 323/A3 with the use of the S-benzoylmercaptoacetyltriglycine (S-benzoyl-MAG3) chelate. Results: A molar ratio of Re-MAG3:323/A3 of 3:1 did not affect the integrity and the pharmacokinetic behaviour of the MAb. The tumor uptake and the retention of 186 Re- and 131 I-labeled 323/A3 were comparable, but the cumulative absorbed radiation dose in the tumor delivered by 186 Re-323/A3 was 1.3-fold higher than that of 131 I-323/A3. When mice were treated with equivalent radionuclide doses, the tumor growth inhibition induced by 186 Re-323/A3 was similar or slightly better wben compared with the efficacy of 131 I-323/A3. When mice were treated with radionuclide doses that were adjusted to obtain equal cumulative absorbed radiation doses in the tumor for both conjugates, 131 I-323/A3 was slightly more effective in the inhibition of the growth of FMa and OVCAR-3 xenografts. Conclusions: The favorable physical characteristics of 186 Re as well as its efficacy when conjugated to a MAb indicate 186 Re as an attractive radionuclide in radioimmunotherapy of ovarian cancer patients.

PURPOSE A phase I trial that evaluated for extrahematopoietic toxicity was conducted with iodine-131 (131I) labeled monoclonal antibody (MAb) CC49. Correlative studies included pharmacokinetic and biodistribution analyses, estimates of absorbed radiation dose, and measurement of human antimonoclonal antibodies (HAMA). PATIENTS AND METHODS After collection and cryopreservation of hematopoietic stem cells, 15 patients with gastrointestinal cancers were administered a tracer dose of 131I-MAb CC49. Within 5 to 6 days, 14 patients (two to three per activity level) underwent a single treatment with 131I-MAb CC49 (50, 100, 150, 200, 250, and 300 mCi/m2). Biodistribution was determined using planar and single photon emission computer tomographic (SPECT) imaging. Pharmacokinetic studies were performed by measuring radioactivity in serial blood samples. In some patients, biopsies of metastases and related normal tissues were obtained for radioactivity measurements. Radiation dosimetry estimates were calculated using available biodistribution, pharmacokinetic, and tissue biopsy data. Toxicity was evaluated using the National Cancer Institute (NCI) Common Toxicity Criteria. RESULTS No dose-limiting extrahematopoietic toxicity was identified. Twelve patients experienced grade IV myelosuppression and met criteria for infusion of hematopoietic stem cells. Radioimmunolocalization was excellent. The T1/2 for 131I-MAb CC49 after diagnostic and therapeutic administration was 39.7 +/- 10.4 and 46.1 +/- 10.6 hours, respectively. The percent injected dose per killigram of tumor ranged from 0.2 to 2.1. Absorbed radiation dose in metastatic tumor sites ranged from 630 to 3300 cGy. CONCLUSION Although extrahematopoietic dose-limiting toxicity was neither observed or predicted, suboptimal absorbed dose estimates suggested that further escalation of 131I-MAb CC49 would not be useful. Future studies should focus on the use of radionuclides with high energy beta emissions, such as yttrium 90, and on strategies to optimize access of antibody to target antigens.

Computed Tomography scan is a method applied to examine the anatomy of a human body. A CT scan is also used as an alternative way to detect cancer. However due to the utilization of X-Rays, organs being examined are considered to be at risk of radiation effect. The purpose of this research is to measure absorbed radiation dose to meet the requirements of radiation protection on patients. A solid humanoid phantom was used to simulate the patient body. For the dose measurement, a lithium fluoride thermoluminescent dosemeters (TLD-100) were mounted within the head and neck area of the phantom. This research is also aimed to make the commonly used scanning protocol within a hospital to its full potential. This is done by comparing the radiation dose between different scanning protocols to find the smallest radiation exposure. It can be concluded that, the thicker the slice, the lower the exposed radiation dose will be.

Cone-beam computed tomography (CBCT) has become increasingly popular in dental and maxillofacial imaging due to its accurate 3D information, minimal radiation dose, and low machine cost. In this paper, we have proposed the newly developed CBCT scanner, called DentiiScan. Our gantry system consisting of a cone-beam X-ray source and an amorphous silicon flat panel detector is rotated around a patient's head. With the large area detector, only a single rotation is needed to reconstruct the field-of-view area from chin to eyes and our reconstructed algorithm based on GPU calculation is about 30 times faster than the CPU-based algorithm. The radiation dose was measured and compared to other dental and medical CT machines. The absorbed radiation dose from our proposed CBCT machine is significantly low. In addition, geometric accuracy was analyzed when the test object was scanned at the normal position as well as the inclined position. The results from three observers repeated for five times confirm that the machine can produce reconstructed images with high accuracy.

Naturally occurring radionuclides of uranium, thorium, radium, lead and polonium were determined in bushes and trees and in the smoke from summer forest fires. Activity concentrations of radionuclides in smoke particles were much enriched when compared to original vegetation. Polonium-210 ((210)Po) in smoke was measured in concentrations much higher than all other radionuclides, reaching 7,255 ± 285 Bq kg(-1), mostly associated with the smaller size smoke particles (1.0 μm). Depending on smoke particle concentration, (210)Po in surface air near forest fires displayed volume concentrations up to 70 m Bq m(-3), while in smoke-free air (210)Po concentration was about 30 μ Bq m(-3). The estimated absorbed radiation dose to an adult member of the public or a firefighter exposed for 24h to inhalation of smoke near forest fires could exceed 5 μSv per day, i.e, more than 2000 times above the radiation dose from background radioactivity in surface air, and also higher than the radiation dose from (210)Po inhalation in a chronic cigarette smoker. It is concluded that prolonged exposure to smoke allows for enhanced inhalation of radionuclides associated with smoke particles. Due to high radiotoxicity of alpha emitting radionuclides, and in particular of (210)Po, the protection of respiratory tract of fire fighters is strongly recommended.

Intraperitoneal (IP) injection is frequently reported to be as effective as intravenous (IV) injection. Because it allows administering a larger volume with more radioactivity, we have investigated this route and the possibility of using it to circumvent the volume constraint we earlier experienced with pretargeting radiotherapy. Using (99m)Tc as the label, the pharmacokinetics (PK) of the cMORF effector (a DNA analogue) was evaluated after IP or IV injection in normal mice by necropsy and SPECT/CT imaging. In another experiment, nude mice bearing tumors were used and they received MORF-CC49 pretargeting antibody IV 2 days earlier than labeled cMORF IV or IP. Tumor accumulations of cMORF were measured at 6 hours after its injections. The absorbed radiation doses for (188)Re or (90)Y pretargeting were estimated using the (99m)Tc data and a self-absorbed model. Although the absorbed radiation doses to other organs were comparable, the dose to intestines after IP injection was 30-fold higher than IV injection due to the slow entry into the circulation. It had reached such a level as high as the dose to the kidneys that cleared the radioactivity and usually were at the highest level. Nevertheless, the slow entry did not reduce the tumor accumulation. In conclusion, using IP in place of IV led to an unacceptably high absorbed radiation dose to the intestines although the tumor accumulation was not compromised. This effect may be applicable to other radiotherapeutic agents as well.

In order to address mass casualty situations in the event of radiation exposure from nuclear attacks or accidents, there is an urgent and unmet need for point-of-care (POC) diagnostic devices for rapid assessment of absorbed radiation dose. Patients receiving whole body irradiation (WBI), which is often included as part of the preparative regimen prior to hematopoietic stem cell transplantation (HSCT), can be used as subjects for evaluation of radiation biodosimeters that may be of use in a nuclear event as well as in radiation therapy. The level of WBI exposure in patients is frequently associated with treatment-related complications to multiple tissues and involves individual variations in radiosensitivity. Thus, early and predictive indicators of individual outcomes of radiation exposure would allow pre-emptive clinical management before the onset of tissue injury. To address these critical needs, we are developing an ocular dosimeter (OCDOS) that noninvasively assesses radiation-induced damage by measuring light scattered by proteins present in the aqueous humor (AH) the eye. Therefore, we initiated a clinical study to assess the potential of OCDOS in patients before and during a fractionated course of WBI conditioning therapy prior to HSCT. Early results in three patients show a clear difference in light scattering properties of the AH from measurements taken before and after irradiation that persists for several days into treatment. This preliminary study provides proof of principle that this non-invasive and POC device can assess dose-related changes in proteins in patients receiving WBI and is suitable for high throughput, triage assessment of individuals exposed in a mass casualty scenario of a nuclear event.

Rhenium-188 (Re-188) is a high energy -emitting radioisotope obtained from the tungsten-188/rhenium-188 (W-188/Re-188) generator, which has shown utility for a variety of therapeutic applications in nuclear medicine, oncology, and interventional radiology/cardiology. Re-188 decay is accompanied by a 155 keV predominant energy -emission, which could be detected by -cameras, for imaging, biodistribution, or absorbed radiation dose studies. Its attractive physical properties and its potential low cost associated with a long-lived parent make it an interesting option for clinical use. The setup and daily use of W-188/Re-188 generator in hospital nuclear medicine departments are discussed in detail. The clinical efficacy, for several therapeutic applications, of a variety of Re-188-labeled agents is demonstrated. The high energy of the -emission of Re-188 is particularly well suited for effective penetration in solid tumours. Its total radiation dose delivered to tissues is comparable to other radionuclides used in therapy. Furthermore, radiation safety and shielding requirements are an important subject of matter. In the case of bone metastases treatment, therapeutic ratios are presented in order to describe the efficacy of Re-188 usage.

Laser methods, such as laser-induced fluorescence diagnostics, photodynamic therapy (PDT), and hyperthermia, are finding increasing use in medicine. Irradiation can be performed both with and without contact on the tissue surface. In the case of contact irradiation, especially when laser radiation is introduced into biological tissue through an optical fiber, it is important to know the processes taking place at the irradiation fiber end. These processes affect diffusely reflected radiation which returns to the fiber. By analyzing backscattered radiation, we can evaluate the quality of the radiation procedure and the state of the fiber end. The objectives of this study were to develop a method and device for measuring backscattered radiation power and using this method, to determine the time and temperature ranges realized in PDT and hyperthermia.Light propagation is discussed in bent optical fibers. A technique is proposed for measuring laser radiation intensity in the optical fiber bend. Based on this technique, a system was developed for monitoring the laser radiation dose absorbed in biological tissues. We studied samples of bovine liver, muscle and brain tissues. Experiments were performed using a 675 nm, 100–2200 mW continuous wave semi-conductor laser. Laser radiation was delivered through a silica/polymer optical fiber. Data concerning the temperature and transmitted radiation intensity was acquired.Modeling of the light propagation in a bent optical fiber showed that the sensitivity of the method depends on the position of the photodetectors, but is independent of the loop number of the optical fiber. The results of experiments are presented using different types of biological tissues. We obtained the experimental dependencies of backward and transmitted radiation intensities and the temperature of the tissue surface in the irradiated region on the irradiation time measured with a flat-end fiber. The characteristic ranges of tissue heating caused by irradiation were determined for use in clinical practice.The optical parameters of biological tissues change with increasing temperature. This affects the intensity of transmitting radiation and diffuse radiation entering the fiber. The change in the backscattered radiation intensity greatly depend on the temperature of the irradiated area. The control of the irradiation of biological objects provides an efficient delivery of laser radiation to biological tissues and increases hyperthermia and PDT treatment effect.

Polymer gel dosimeters are fabricated from radiation sensitive chemicals which, upon irradiation, polymerize as a function of the absorbed radiation dose. In this research stiffness of MAGIC gel dosimeter improved by addition of agarose and was named MGICA. MAGICA gel dosimeter irradiated by moderated fission neutrons in Tehran Research Reactor (TRR) thermal column, and the response of gel was investigated as variation of spin-spin relaxation rate in MR image of gel phantoms. The linearity of the response (R2) versus absorbed dose (D), sensitivity, dose resolution and minimum detectable dose (MDD) were investigated. For calibration of gel response versus dose, foil activation analysis was performed. A cadmium covered gold foil was placed at the end of column (nearest to core) to ensure avoidance of non thermal neutrons in the thermal column. Sensitivity and MDD of MAGICA gel dosimeter for thermal neutron were 0.17 ± 0.01 Gy− 1s− 1 and 1.2 Gy respectively. From this study it concluded that MAGICA gel dosimeter is a capable instrument for ther-mal neutron dosimetry.

As small animal studies using radiation exposure increase, it becomes more important to estimate accurate dose for the animals in order to explain and control the potential radiation toxicity or treatment efficacy. The purpose of this study was to determine the radiation dose in a realistic mouse brain tissue for dosimetric estimates using geant4 application for tomographic emission simulations (GATE), and to extend its techniques to various small animal CT applications. The realistic mouse phantom (MOBY phantom) is based on high resolution 3D magnetic resonance microscopy data, and the geometry was developed using a segmented C57BL/6 mouse that weighed 33 g. Recently, 37 segmented tissues have been added to voxel-based MOBY brain developed by Johns Hopkins University. A small animal CT system (micro-CT) with Gd2O2S scintillator was performed using 50 kVp, 0.15 mAs (0.5 second), 360° of rotation, and 400 projections. For validating simulation studies with respect to physical measurements for micro-CT, the measured and simulated airkerma values were compared, and the measured and simulated values measured in the validation CT ion chamber study were 3.32 and 3.69 μC/kg air, respectively. The total absorbed dose over all measurements to the brain (37 tissues) is 60.2 mGy. Among tissues of brain, the absorbed dose of cerebral_cortex (20.55 mGy) was highest while the one of pineal_gland (0.02 mGy) was lowest. This result can be used in control of brain tissue doses and preclinical targeted radiotherapy experiments as dosimetric database. In addition, in order to calculate accurate absorbed dose of brain tissues, accurate modeling is needed for X-ray spectrum, detector alignment, and uncertainty in elemental composition of simulated materials.

Approximately 2 weeks after accidental overexposure to X-ray radiation, a worker developed acute radiodermatitis on fingers of both hands. Exposure simulation indicated that total ionizing radiation absorbed by his fingers amounted to about 20 Gy. After 2 years, acute radiodermatitis evolved to chronicity of lesions with presence of atrophic skin, teleangiectasia, alopecia, and dyskeratosis on three right-hand fingers. Cytogenetic dosimetry of peripheral blood lymphocytes, performed 2 months after acute radiation, showed an increase of micronuclei (7% vs. 1 +/- 0.4% according to laboratory reference data). The increase was ascribed to the high dose of ionizing radiation absorbed by circulating lymphocytes in the vessels of overexposed tissues. The cytogenetic examination was repeated 27 months after acute irradiation; it was found that the percentage of micronuclei had been restored to within reference levels. The possibility of using cytogenetic dosimetry, following acute partial exposure to X-rays, not just as an indicator of previous exposure, but also as an indicator of the absorbed radiation dose is examined. Lastly, the possible stochastic effects that may set in on the skin of the affected fingers and the need for periodically monitoring the evolution of chronic skin lesions, are discussed.

Current systems used to measure bone mineral content (BMC) in the neonate have the major drawback that the child must be well enough to be moved to the scanner. Consequently, low birth weight pre-term neonates, a group at particular risk of mineral compromise, cannot be measured. This paper describes a portable neonatal bone mineral device capable of measuring bone mineral in the incubator. It uses a radiation sensitive, charge coupled device (CCD) to acquire a bone mineral image enabling bone mineral to be measured at various sites. It measures bone mineral density (BMD) with a precision of 5.5 mg cm-2 in vivo, reduced to 7.5 mg cm-2 when repositioning between scans is taken into account. The procedure takes under 5 min with an image acquisition time of 30 s and an absorbed radiation dose to skin of 6 microSv. Calibration has been undertaken with aluminium foils of differing thickness to confirm the linearity of the system throughout the intended measurement range. A regression line fitted to the data demonstrated linearity and correlation between BMD and aluminium thickness with r = 0.99 (p0.0001). Preliminary measurements on pre-term neonates show values of BMD ranging from 43 to 115 mg cm-2 in babies aged 23-41 weeks post-conception. These figures are within the linear range of the system.

A modification of an X-ray fluorescence (XRF) technique that could be applied to the noninvasive measurement of transdermal absorption in human subjects with a low absorbed radiation dose was investigated. Secondary X-rays that were produced in a samarium foil by an isotopic 241Am source were used to induce iodine Kα X-rays in an iodine-containing compound. The disappearance of this compound was measured following topical administration to a human volunteer. The use of the secondary X-ray fluorescence technique resulted in an 11-fold reduction in the absorbed radiation dose to the skin compared to conventional XRF bringing the technique within acceptable dosimetry limits for human studies.

A study was undertaken to determine the effect of low-dose gamma irradiation on aseptically admixed total parenteral nutrition (TPN) solutions to which large inocula of three test bacterial species, recognised as common contaminants of these products, were added. Attainable SALs of TPN solutions containing test bacteria were subsequently calculated. Results showed that a minimum absorbed radiation dose as low as 1.5 kGy improved the SAL of aseptically prepared TPN solutions from a SAL of 10 −3 to a value of less than 10 −8 for the microorganisms investigated. No measurable changes in amino acid, electrolyte, glucose and lipid components of the solutions were detected up to a dose of 8.3 kGy. Practical experience applying this radiation treatment of TPNs rendered excellent results leading to the routine application of the process in South Africa.

Introduction and objective Digital mammography is being introduced worldwide for breast cancer diagnosis and screening. While the technique is known to offer a good image quality–dose balance, its introduction in specific regions should be investigated. Present study focuses on the absorbed radiation dose, and more in particular on estimations of average glandular dose (AGD).The present work concerns a dosimetric study in digital mammography in Morocco. Materials and methods A dosimetric study was conducted in a Moroccan university hospital with system full-field digital mammography, Siemens Mammomat Inspiration. The average glandular dose of about hundred patients was calculated taking into account the entrance dose (tube output), half value layer and thickness of the compressed breast. Dose values were calculated with PMMA phantoms. Results The results showed that almost values were located below the achievable dose limit curve of the European Guidelines. For average thickness of 55 mm, the AGD is about 1.24 mGy for the Clinical–Caudal (CC) view and 1.32 mGy for the Mediolateral–Oblique (MLO) view with the same SD = 0.3. The results show also that the mean patients AGD is about 30% lower than that given by the PMMA. Conclusion The results show an increase in the average glandular dose as a function of breast thickness. Average and maximal doses are in line with values obtained in European studies. This study will now be performed in more Moroccan hospitals and the data obtained could be used to work at breast cancer screening in our country.

We have investigated in detail radiation and thermal stabilities and transformations of adenosine mono- and triphosphates in liquid and frozen solid aqueous solutions within a wide range of absorbed radiation dose (up to 75 kGy) and temperature (up to 160 degrees C). Dephosphorylation is the main pathway of high temperature hydrolysis of adenine nucleotides. Basic thermodynamic and kinetic parameters of this process have been determined. Radiolysis of investigated compounds at room temperature results in scission of N-glycosidic bond with a radiation yield about of 1 mol/100 eV. Solution freezing significantly enhances radiation stability of nucleotides as well as other biomolecules. This circumstance is essential in the discussion of panspermia concepts.

pMOS radiation sensitive field effect transistors (RADFET's) have applications as integrating dosimeters in spacecraft, laboratories and medicine to measure the amount of radiation dose absorbed. The suitability of these dosimeters to a certain application depends on the sensitivity of the RADFET being used. To date, this sensitivity is limited to the sensitivity of the gate oxide to radiation. The aim of this paper is to introduce a new design approach which will allow greater sensitivities to be achieved than is currently possible. An additional attractive feature of this design approach is that the sensitivity of the dosimeter may be changed depending on the total dose which is to be measured; essentially a dosimeter with auto-scaling may be achieved. This study introduces this auto-scaling concept along with presenting the optimum RADFET device requirements which are necessary for this new design approach. >

Three-dimensional X-ray imaging of living specimens is challenging due to the limited resolution of conventional absorption contrast X-ray imaging and potential irradiation damage of biological specimens. In this letter, we present microtomography of a living specimen combining phase-contrast imaging and a Fourier-based iterative algorithm termed equally sloped tomography. Non-destructive 3D imaging of an anesthetized living yellow mealworm Tenebrio molitor was demonstrated with a relatively low dose using synchrotron generated X-rays. Based on the high-quality 3D images, branching tracheoles and different tissues of the insect in a natural state were identified and analyzed, demonstrating a significant advantage of the technique over conventional X-ray radiography or histotomy. Additionally, the insect survived without problem after a 1.92-s X-ray exposure and subsequent absorbed radiation dose of ∼1.2 Gy. No notable physiological effects were observed after reviving the insect from anesthesia. The impro...

Multiple-source structure is promising in the development of computed tomography, for it could effectively eliminate motion artifacts in the cardiac scanning and other time-critical implementations with high temporal resolution. However, concerns about the dose performance shade this technique, as few reports on the evaluation of dose performance of multiple-source CT have been proposed for judgment. Our experiments focus on the dose performance of one specific multiple-source CT geometry, the triple-source CT scanner, whose theories and implementations have already been well-established and testified by our previous work. We have modeled the triple-source CT geometry with the help of EGSnrc Monte Carlo radiation transport code system, and simulated the CT examinations of a digital chest phantom with our modified version of the software, using x-ray spectrum according to the data of physical tube. Single-source CT geometry is also estimated and tested for evaluation and comparison. Absorbed dose of each organ is calculated according to its real physics characteristics. Results show that the absorbed radiation dose of organs with the triple-source CT is almost equal to that with the single-source CT system. As the advantage of temporal resolution, the triple-source CT would be a better choice in the x-ray cardiac examination.

Aim: The spleen receives a high mean absorbed radiation dose during peptide receptor radionuclide therapy (PRRNT). The aim of this study is to correlate the radiation dose to spleen with the effect on blood cell count after PRRNT. Methods: Fifty-three neuroendocrine tumor (NET) patients were treated with 3.8–8.5 GBq 177Lu-DOTATATE or 177Lu-DOTATOC. Dosimetry was performed according to MIRD scheme. Eleven NET patients who had undergone splenectomy before PRRNT and who received 4.7–7.6 GBq 177Lu-DOTATATE or 177Lu-DOTATOC were selected as controls. RBC, WBC (total and differential), and platelet counts before and after each cycle of PRRNT were documented. Results: The median dose to the spleen in the study group was 6.34 Gy (2.32–20.06 Gy). There was no significant difference in the posttherapy changes in the blood cell counts (RBC, WBC, or platelets) between the study group and the control group. Mild hematological toxicity was found in 7 of the 53 (13.2%) patients in the study group and in 1 out of the 11 patients (9.1%) in the control group. However, there was no correlation between the incidence or grade of hematological toxicity and the dose to the spleen. Conclusion: This study demonstrates for the first time that hematological toxicity after PRRNT is not related to the radiation dose to the spleen.

Gel dosimetry measures the absorbed radiation dose with high spatial resolution in 3D. However, recently published data show that the response of metacrylic-based polymer gels depends on the segmented delivery pattern, which could potentially be a considerable disadvantage for measurements of modern dynamic radiotherapy techniques. The aim of this study is to design a dynamic compartment model for the response of a gel dosimeter, exposed to an arbitrary irradiation pattern (segmented delivery and intensity modulation), in order to evaluate the associated effects on absorbed dose measurements. The model is based on the separation of the protons affecting the magnetic resonance signal (i.e. the R2 value) into six compartments, described by a set of differential equations. The model is used to calculate R2 values for a number of different segmented delivery patterns between 0-4 Gy over 1-33 fractions. Very good agreement is found between calculated and measured R2 values, with an average difference of 0.3 ± 1.1% (1 SD). The model is also used to predict the behaviour of a gel dosimeter exposed to irradiation according to typical IMRT, VMAT and respiratory gating scenarios. The calculated R2 values are approximately independent of the segmented delivery, given that the same total dose is delivered during the same total time. It is concluded that this study helps to improve the theoretical understanding of the dependence of metacrylic-based polymer gel response to segmented radiation delivery.

The use of positron emitter–labeled compounds for somatostatin receptor imaging (SRI) has become attractive because of the prospect of improved spatial resolution, accelerated imaging procedures, and the ability to quantify tissue radioactivity concentrations. This paper provides results from first-in-humans use of 64Cu-DOTATATE, an avidly binding somatostatin receptor ligand linked to a radioisotope with intermediate half-life and favorable positron energy (half-life, 12.7 h; maximum positron energy, 0.653 MeV). Methods: In a prospective setup, 14 patients with a history of neuroendocrine tumors underwent both PET/CT with 64Cu-DOTATATE and SPECT/CT with our current routine imaging agent 111In-diethylenetriaminepentaacetic acid–octreotide. After intravenous injection of 193–232 MBq of 64Cu-DOTATATE, whole-body PET scans were acquired at 1 h (n = 14), 3 h (n = 12), and 24 h (n = 5) after administration. Tissue radioactivity concentrations for normal organs and lesions were quantified, and standardized uptake values were calculated for the early (1 h) and delayed (3 h) scans. Using the data for 5 patients, we assessed the radiation dose with OLINDA/EXM software. Furthermore, the clinical performance of 64Cu-DOTATATE with respect to lesion detection was compared with conventional SRI. Results: SRI with 64Cu-DOTATATE produced images of excellent quality and high spatial resolution. Images were characterized by high and stable tumor-to-background ratios over an imaging time window of at least 3 h. Compared with conventional scintigraphy, 64Cu-DOTATATE PET identified additional lesions in 6 of 14 patients (43%). In 5 patients, lesions were localized in organs and organ systems not previously known as metastatic sites, including the early-stage detection of a secondary neuroendocrine tumor in a patient with a known mutation in the multiple endocrine neoplasia type I gene. All major additional findings seen only on PET could be confirmed on the basis of a clinical follow-up interval of 18 mo. Calculated radiation dose estimates yielded an effective dose of 6.3 mSv for an injected activity of 200 MBq of 64Cu-DOTATATE, with the liver being the organ with the highest absorbed radiation dose (0.16 mGy/MBq). Conclusion: This first-in-humans study supports the clinical use of 64Cu-DOTATATE for SRI with excellent imaging quality, reduced radiation burden, and increased lesion detection rate when compared with 111In-diethylenetriaminepentaacetic acid–octreotide.

Bone marrow is usually dose-limiting for radioimmunotherapy. In this study, we directly estimated red marrow activity concentration and the self-dose component of absorbed radiation dose to red marrow based on PET/CT of 2 different 124I-labeled antibodies (cG250 and huA33) and compared the results with plasma activity concentration and plasma-based dose estimates. Methods: Two groups of patients injected with 124I-labeled monoclonal antibodies (11 patients with renal cancer receiving 124I-cG250 and 5 patients with colorectal cancer receiving 124I- huA33) were imaged by PET or PET/CT on 2 or 3 occasions after infusion. Regions of interest were drawn over several lumbar vertebrae, and red marrow activity concentration was quantified. Plasma activity concentration was also quantified using multiple patient blood samples. The red marrow–to–plasma activity concentration ratio (RMPR) was calculated at the times of imaging. The self-dose component of the absorbed radiation dose to the red marrow was estimated from the images, from the plasma measurements, and using a combination of both sets of measurements. Results: RMPR was observed to increase with time for both groups of patients. Mean (±SD) time-dependent RMPR (RMPR(t)) for the cG250 group increased from 0.13 ± 0.06 immediately after infusion to 0.23 ± 0.09 at approximately 6 d after infusion. For the huA33 group, mean RMPR(t) was 0.10 ± 0.04 immediately after infusion, 0.13 ± 0.05 approximately 2 d after infusion, and 0.20 ± 0.09 approximately 7 d after infusion. Plasma-based estimates of red marrow self-dose tended to be greater than image-based values by, on average, 11% and 47% for cG250 and huA33, respectively, but by as much as −73% to 62% for individual patients. The hybrid method combining RMPR(t) and plasma activity concentration provided a closer match to the image-based dose estimates (average discrepancies, −2% and 18% for cG250 and huA33, respectively). Conclusion: These results suggest that the assumption of time-independent proportionality between red marrow and plasma activity concentration may be too simplistic. Individualized imaged-based dosimetry is probably required for the optimal therapeutic delivery of radiolabeled antibodies, which does not compromise red marrow and may allow, for some patients, a substantial increase in administered activity and thus tumor dose.

One‐hundred‐and‐twenty‐eight–section dual X‐ray source computed tomography (CT) systems have been introduced into clinical practice and have been shown to increase temporal resolution. Higher temporal resolution allows low‐dose spiral mode at a high pitch factor during CT coronary angiography. We evaluated radiation dose and physical image qualities in CT coronary angiography by applying high‐pitch spiral, step‐and‐shoot, and low‐pitch spiral modes to determine the optimal acquisition mode for clinical situations. An anthropomorphic phantom, small dosimeters, a calibration phantom, and a microdisc phantom were used to evaluate the radiation doses absorbed by thoracic organs, noise power spectrums, in‐plane and z‐axis modulation transfer functions, slice sensitivity profiles, and number of artifacts for the three acquisition modes. The high‐pitch spiral mode had the advantage of a small absorbed radiation dose, but provided low image quality. The low‐pitch spiral mode resulted in a high absorbed radiation dose of approximately 200 mGy for the heart. Although the absorbed radiation dose was lower in the step‐and‐shoot mode than in the low‐pitch spiral mode, the noise power spectrum was inferior. The quality of the in‐plane modulation transfer function differed, depending on spatial frequency. Therefore, the step‐and‐shoot mode should be applied initially because of its low absorbed radiation dose and superior image quality. PACS numbers: 87.57.‐s; 87.57.C‐; 87.57.cf; 87.57.cm; 87.57.cp; 87.57.Q‐; 87.57.qp; 87.57.uq

Over recent years there has been significant progress in the development of optical storage phosphors and materials for ionizing radiation, resulting in important applications in the fields of dosimetry and computed radiography. The aim of this Chapter is to provide some background information as well as an overview of a range of modern storage phosphors and materials and their applications in dosimetry and computed radiography. Dosimetry is the measurement of absorbed dose of ionizing radiation by matter or tissue and is measured in the SI unit of gray (Gy) or sievert (Sv), respectively, where 1 Gy and 1 Sv are equal to 1 joule per kilogram. It is noted here that the non-SI units of rad (absorbed radiation dose; for matter) and rem (Roentgen equivalent in man; for tissue) are still heavily used; their conversions are given by 1 Gy=100 rad and 1 Sv=100 rem. A dosimeter allows us directly or indirectly to measure exposure, kerma, absorbed or equivalent dose and associated rates of ionizing radiation. A dosimetry system consists of the actual dosimeter and an associated reader. A dosimeter is characterized by its accuracy and precision, linearity, energy response, dose and dose rate dependence, spatial resolution and directional dependence. It is well documented that even low doses of ionizing radiation can induce cancer. Thus personal radiation monitoring, i.e. dosimetry applied to people, has become highly important in recent years as the number of potential radiation sources is ever increasing. Radiation monitoring will also become more important in medical diagnostics and in radiation therapy as regulations become stricter. Nuclear accidents, such as the recent events in Fukushima, Japan, have highlighted the need for inexpensive and effective radiation monitoring systems that can be deployed to a large population. We note here that, of course, the exposure to natural background radiation is, to a great extent, unavoidable. For example, the average annual radiation dose per capita from natural and medical sources is 2.0 mSv/year and 2.8 mSv/year in Australia and the United Kingdom, respectively. The amount of radiation exposure is a function of geography and building standards. For example, in European homes there is a relatively high level of radon as the internal walls are based on clay bricks. This is reflected in the fact that the average equivalent dose by radiation from radon progeny is 0.2 mSv/year and 1.4 mSv/year in Australia and the United Kindom, respectively. Ionizing radiation has a wide range of applications such as in the sterilization of medical hardware and food, in medical diagnostics and radiotherapy and in technical and scientific imaging (Andersen et al., 2009; Dyk, 1999; Eichholz, 2003; Mijnheer, 2008; Podgorsak, 2005

Human exposure to ionizing radiation is a natural part of life on earth. These exposures occur every day from radiation associated with naturally occurring radionuclides in soil, air, and food, and also from cosmic rays. In addition, many people are exposed to dental and medical diagnostic procedures and therapy involving: x rays, gamma rays, charged particles, radionuclides, or other ionizing radiation sources. Others may be exposed in their workplace such as in laboratories, hospitals, underground mines, or nuclear power plants. Excessive exposures may lead to the development of cancer by promotion of ongoing carcinogenic biological processes or by independent cancer induction. Ionization converts a neutral atom to a charged atom. The γ rays and x rays are ionizing electromagnetic radiation with energies above ultraviolet in the electromagnetic spectrum. The difference between x rays and γ rays is a matter of nomenclature. The γ rays are emitted from the nucleus of a radioactive atom while x rays originate in the orbital electrons of a energized atom. The α2+ particle has been identified as a positively charged helium nucleus with 2 protons and two neutrons emitted from the nucleus of certain radionuclides. The βradiation was identified as negatively charged electrons emitted from the nucleus of certain radionuclides. There are other types of ionizing radiation including most prominently uncharged neutrons emitted from the nucleus of atoms that ionize atoms via nuclear interactions, and positrons and that are positive beta particles, β+. The measure of absorbed radiation dose in matter or tissue is the gray (Gy) equal to one joule of energy per kilogram of matter or tissue. To account for different types of ionizing radiation, such as gamma, alpha, and beta radiations, the dose from ionizing radiation is corrected for the theoretical relative biological effectiveness of the different radiations in causing cellular damage using a radiation weighting factor, wR (Sv/Gy), and this is reported as the equivalent dose in sieverts (Sv). Hence, the measure of biological dose is the sievert (Sv), equal to the absorbed dose in Gy times the radiation weighting factor. The γ rays, x rays, and β radiation typically have a radiation weighting factor of 1, while α radiation has a radiation weighting factor of 20 and neutrons may have a radiation weighting factor from 5 to 20 depending on energy. The quantity of radioactivity is measured in becquerel (Bq), equal to one radioactive atomic event or nuclear disintegration per second. Radiation induced cancer is a complex and not completely understood process involving multiple events including but not limited to cellular DNA damage, up and down regulation of genes, intercellular communication, tissue and organ responses, clonal expansion of

The interest in studying γ-radiation effects on hexamethylenetetramine (HMTA) is due to its importance in nuclear fuel technology. The current study indicates that γ-radiation induces electrical conductivity (RIC) and pH changes in HMTA aqueous solutions. The effects of HMTA concentration, absorbed radiation dose, absorbed dose rate and storage time on RIC and pH changes were studied. HMTA aqueous solutions could be considered as a promising γ-radiation dosimeter, in both technical and medical fields.

The purpose of this study was to compare the thickness of the compressed breast between mediolateral oblique and craniocaudal mammograms and to relate these differences in thickness to image quality and radiation dose. These differences may partially explain why some subtle tumors are better visualized on the craniocaudal view.The study population consisted of 250 paired mediolateral oblique and craniocaudal mammograms obtained on one mammographic unit by seven certified mammography technologists during a 2-month period. Only women with breast implants, prior lumpectomy and radiotherapy, or chest wall deformity were excluded. The digital readout of compressed breast thickness and applied compression force was recorded. Mammographic positioning was assessed using standard criteria. Absorbed radiation dose at different thicknesses was measured with a BR-12 breast phantom. Image quality differences for geometric unsharpness and contrast were calculated for the observed breast thickness differences between mediolateral oblique and craniocaudal mammograms.The mean thickness of the compressed breast on the craniocaudal view was less than the mean thickness on the mediolateral oblique view (4.4 versus 4.8 cm, p.0001) despite the greater force used to compress the breast for mediolateral oblique than for craniocaudal views (93 versus 86 newtons, p.0001). The breast thickness on the mediolateral oblique view exceeded that on the craniocaudal view in 98 (84%) of 117 pairs that differed in thickness by 5 mm or more and 46 (94%) of 49 pairs that differed by 10 mm or more (p.0001). Geometric unsharpness increased by 8% and 19% when a 4.4-cm-thick breast was compared to a 4.8- and 5.4-cm-thick breast, respectively. A 5% and 12% loss of contrast was noted when a 4.4-cm-thick breast was compared to a 4.8- and 5.4-cm-thick breast. Mean glandular radiation dose at 4.4, 4.8, and 5.4 cm was 1.40, 1.70, and 2.33 mGy, respectively.The compressed breast is 8% thicker on mediolateral oblique than on craniocaudal mammograms, a small but statistically significant difference. This difference results in a small loss of spatial and contrast resolution on the mediolateral oblique views and an increase in radiation dose. These image quality differences may partially explain why some subtle carcinomas are better visualized on the craniocaudal view.

This article presents a survey of recent progress in the development and application of analytical methods for calculating macroscopic and microscopic radiation dose distributions for Boron Neutron Capture Therapy (BNCT). Such calculations are an essential component of in vivo BNCT research and will ultimately also be required for human BNCT treatment planning. Calculations of macroscopic absorbed dose distributions for BNCT are more complex than for photon therapy. There are several different dose components, each of which has its own characteristic spatial distribution, linear energy transfer, and relative biological effectiveness (RBE). Three-dimensional (3-D) energy-dependent radiation transport models with a detailed treatment of particle scattering are required. Geometric descriptions for such models are typically constructed directly from medical image data and both the Monte Carlo stochastic simulation method and the discrete-ordinates deterministic approach have been successfully used to perform the necessary radiation transport calculations. Microdosimetric effects can profoundly influence the therapeutic benefit that may be attainable in BNCT. These effects must be carefully taken into account in the interpretation of experimental data, especially when correlating observed in vivo radiobiological response with absorbed radiation dose. Calculations of microdosimetric parameters for BNCT are typically performed using the Monte Carlo method to generate single-event energy deposition frequency distributions for critical targets in various cell types of interest. This information is useful in the development of apparent RBE factors, or “compound factors” for the various dose components in BNCT.

Stimulation spectra of several TLD materials in the short-wave spectral region are measured using the optically stimulated afterglow (OSA) method for determination of absorbed dose. Optical stimulation spectra are studied in the region of wavelengths lower than those of emission spectra. The effective optical stimulation hands have been found for examined materials in the regions of wavelengths which overlap with fluorescence excitation bands. Application of short-wave OSA bands for determination of absorbed dose is analysed.

Radiation dosimetry is a basic requirement when using radioactive substances for targeted therapies (targeted radionuclide therapy, TRT). The objective of dosimetry is, in simple terms, taking a closer look at the effects of ionizing radiation. In order to do this it is most common to start with dedicated assessments of the distribution of the radioactive substance in the patient over time. In the case of 131I-MIBG the radionuclide can easily be measured using counting techniques and quantitative imaging. From a series of measurements an individual function is obtained that can be converted into a quantity describing the amount of nuclear disintegrations in a defined region. From this quantity the absorbed radiation dose can be derived. It is obvious that the absorbed radiation dose representing the degree of energy deposited by nuclear transformations in a defined region should correlate with the therapeutic efficacy in a tumor, in an organ or in the whole body. But knowledge concerning the absorbed doses and the relationship between dose and therapeutic outcome needs more detailed clarification than is accessible at present. This contribution provides a survey on the different techniques and related findings concerning MIBG therapies. The authors first of all want to lay focus on the basic knowledge required for understanding the interaction of radiation with matter and, consequently, the impact of radiopharmaceuticals on biological material. Experiences with targeted therapies using 131I-MIBG have been conveyed by many studies since the 1980s. Although dosimetry is still only sporadically reported there are some assumptions concerning dose-effect relationships for 131I-MIBG that are vindicated by many authors.

The radiation chemistry of CMPO has been investigated using a combination of irradiation and analytical techniques. The {alpha}-, and {gamma}-irradiation of CMPO resulted in identical degradation rates (G-value, in {mu}mol Gy{sup -1}) for both radiation types, despite the difference in their linear energy transfer (LET). Similarly, variations in {gamma}-ray dose rates did not affect the degradation rate of CMPO. The solvent extraction behavior was different for the two radiation types, however. Gamma-irradiation resulted in steadily increasing distribution ratios for both forward and stripping extractions, with respect to increasing absorbed radiation dose. This was true for samples irradiated as a neat organic solution, or irradiated in contact with the acidic aqueous phase. In contrast, {alpha}-irradiated samples showed a rapid drop in distribution ratios for forward and stripping extractions, followed by essentially constant distribution ratios at higher absorbed doses. These differences in extraction behavior are reconciled by mass spectrometric examination of CMPO decomposition products under the different irradiation sources. Irradiation by {gamma}-rays resulted in the rupture of phosphoryl-methylene bonds with the production of phosphinic acid products. These species are expected to be complexing agents for americium that would result in higher distribution ratios. Irradiation by {alpha}-sources appeared to favor rupture of carbamoyl-methylenemore » bonds with the production of less deleterious acetamide products.« less