Radiation Dose

Doses in mammography should be maintained as low as possible without reducing the high image quality needed for early detection of the breast cancer. The breast is composed of tissues with very close composition and densities. It increases the difficulty to detect small changes in the normal anatomical structures which may be associated with breast cancer. To achieve the standards of definition and contrast for mammography, the quality and intensity of the X-ray beam, the breast positioning and compression, the film-screen system, and the film processing have to be in optimal operational conditions. This study sought to evaluate average glandular dose (AGD) and image quality on a standard phantom in 134 mammography units in the state of Minas Gerais, Brazil, between December 2004 and May 2006. AGDs were obtained by means of entrance kerma measured with TL LiF100 dosimeters on phantom surface. Phantom images were obtained with automatic exposure technique, fixed 28 kV and molybdenum anode-filter combination. The phantom used contained structures simulating tumoral masses, microcalcifications, fibers and low contrast areas. High-resolution metallic meshes to assess image definition and a stepwedge to measure image contrast index were also inserted in the phantom. The visualization of simulated structures, the mean optical density and the contrast index allowed to classify the phantom image quality in a seven-point scale. The results showed that 54.5% of the facilities did not achieve the minimum performance level for image quality. It is mainly due to insufficient film processing observed in 61.2% of the units. AGD varied from 0.41 to 2.73 mGy with a mean value of 1.3270.44 mGy. In all optimal quality phantom images, AGDs were in this range. Additionally, in 7.3% of the mammography units, the AGD constraint of 2 mGy was exceeded. One may conclude that dose level to patient and image quality are not in conformity to regulations in most of the facilities. This indicates that ongoing actions are needed to optimize image quality and radiation dose for early detection of the breast cancer.

In almost every single application of ionising radiation, the accurate determination of absorbed radiation energy is of great importance. Radiation sensitive gels were first proposed for non-destructive and non-invasive measurements of the spatial distribution of radiation absorbed dose in 1984 [1]. Two different systems were developed but neither of these systems is widely used in practice due to some technical drawbacks. To overcome the problems associated with previous systems a gelatin gel of different composition has been devised and characterised for radiation dosimetry. This system is based on the changes in the optical properties of a transparent gel medium when it is exposed to ionising radiation. The detection material was carefully investigated and the role of each constituent of this system has been studied in order to determine the optimum composition. Gel with this formula has a linear dose response in the range 0.1-30 Gy, this range can be altered to suit other applications by changing the concentration of the active chemicals. The gel sensitivity, defined as the change in optical density per unit radiation dose, was found to be 70×10 -3 cm -1 Gy -1 and the system stability was studied for both pre- and post-irradiation effects. This new formulation allows a convenient, rapid and economic readout method using an optical tomography system operating at visible wavelengths.

Partial desiccation treatment was applied to improve plant regeneration response in irradiated in vitro cultures. Embryogenic callus cultures of sugarcane cv. Co-671 were exposed to different doses of gamma radiation (0-80 Gy) and radiation effect was evaluated in terms of post-irradiation callus recovery, growth and regeneration of plants. Proliferative capacity of cultures was inversely correlated with radiation dose as the percentage surviving cultures or white proliferating clumps (WPC) decreased as the radiation dose increased up to 80 Gy. LD50 was found to be around 20-30 Gy and at higher doses, poor regeneration frequency was observed after 4-6 weeks of post-irradiation culture. To stimulate regeneration response, irradiated cultures were subjected to partial desiccation for 6 h and the treatment resulted in enhanced plant regeneration response. The study suggests that partial desiccation treatment can be useful in stimulating regeneration response of irradiated in vitro cultures.

Gamma irradiation is widely used for sterilization; however, its effect on elimination of amplifiable DNA, an issue of relevance to molecular diagnostic approaches, has not been well studied. The effect of gamma irradiation on the viability of Staphylococcus epidermidis and Escherichia coli (using quantitative cultures) and on their DNA (using quantitative 16S rRNA gene PCR) was evaluated. Viability was abrogated at 2.8 and 3.6 kGy for S. epidermidis and E. coli, respectively. The radiation dose required to reduce viable bacteria by one log10 (D10 value) was 0.31 and 0.35 kGy for S. epidermidis and E. coli, respectively. D10 values for amplifiable DNA extracted from bacteria were 2.58 and 3.09 kGy for S. epidermidis and E. coli, respectively, whereas D10 values for amplifiable DNA were significantly higher for DNA extracted from irradiated viable bacterial cells (22.9 and 52.6 kGy for S. epidermidis and E. coli, respectively; P<0.001). This study showed that gamma irradiation of ...

Background and purpose: Some types of radiation therapy have been associated with an increased risk of cardiac mortality and morbidity in patients with early-stage breast cancer. A relationship has been observed between cardiac radiation dose-volume and the level of excess risk of cardiac mortality. However, relatively few data are available on the morbidity from myocardial infarction associated with adjuvant radiotherapy.

Due to the relatively high activity concentrations of 210 Po and 210 Pb that are found in tobacco and its products, cigarette smoking highly increases the internal intake of both radionuclides and their concentrations in the lung tissues. That might contribute significantly to an increase in the internal radiation dose and in the number of instances of lung cancer observed among smokers. Samples of most frequently smoked fine and popular brands of cigarettes were collected from those available on the Egyptian market. 210 Po activity concentrations were measured by alpha spectrometry, using surface barrier detectors, following the radiochemical separation of polonium. Samples of fresh tobacco, wrapping paper, fresh filters, ash and postsmoking filters were spiked with 208 Po for chemical recovery calculation. The samples were dissolved using mineral acids (HNO 3 , HCl and HF). Polonium was spontaneously plated-out on stainless steel disks from diluted HCl solution. The 210 Po activity concentration in smoke was estimated on the basis of its activity in fresh tobacco and wrapping paper, fresh filter, ash and post-smoking filters. The percentages of 210 Po activity concentrations that were recovered from the cigarette tobacco to ash, post-smoking filters, and smokes were assessed. The results of this work indicate that the average (range) activity concentration of 210 Po in cigarette tobacco was 16.6 (9.7-22.5) mBq/cigarette. The average percentages of 210 Po content in fresh tobacco plus wrapping paper that were recovered by post-smoking filters, ash and smoke were 4.6, 20.7 and 74.7, respectively. Cigarette smokers, who are smoking one pack (20 cigarettes) per day, are inhaling on average 123 mBq/d of 210 Po and 210 Pb each. The annual effective doses were calculated on the basis of 210 Po and 210 Pb intake with the cigarette smoke. The mean values of the annual effective dose for smokers (one pack per day) were estimated to be 193 and 251 µSv from 210 Po and 210 Pb, respectively.

This is the 14th report in a series of periodic general reports on mortality in the Life Span Study (LSS) cohort of atomic bomb survivors followed by the Radiation Effects Research Foundation to investigate the late health effects of the radiation from the atomic bombs. During the period 1950-2003, 58% of the 86,611 LSS cohort members with DS02 dose estimates have died. The 6 years of additional follow-up since the previous report provide substantially more information at longer periods after radiation exposure (17% more cancer deaths), especially among those under age 10 at exposure (58% more deaths). Poisson regression methods were used to investigate the magnitude of the radiation-associated risks, the shape of the dose response, and effect modification by gender, age at exposure, and attained age. The risk of all causes of death was positively associated with radiation dose. Importantly, for solid cancers the additive radiation risk (i.e., excess cancer cases per 10 4 person-years per Gy) continues to increase throughout life with a linear dose-response relationship. The sex-averaged excess relative risk per Gy was 0.42 [95% confidence interval (CI): 0.32, 0.53] for all solid cancer at age 70 years after exposure at age 30 based on a linear model. The risk increased by about 29% per decade decrease in age at exposure (95% CI: 17%, 41%). The estimated lowest dose range with a significant ERR for all solid cancer was 0 to 0.20 Gy, and a formal dose-threshold analysis indicated no threshold; i.e., zero dose was the best estimate of the threshold. The risk of cancer mortality increased significantly for most major sites, including stomach, lung, liver, colon, breast, gallbladder, esophagus, bladder and ovary, whereas rectum, pancreas, uterus, prostate and kidney parenchyma did not have significantly increased risks. An increased risk of non-neoplastic diseases including the circulatory, respiratory and digestive systems was observed, but whether these are causal relationships requires further investigation. There was no evidence of a radiation effect for infectious or external causes of death.

The long-term biokinetics and dosimetry of carbon-14 were studied in nine adults and eight children undergoing carbon-14 urea breath test for Helicobacter pylori (HP) infection. The elimination of 14 C via exhaled air and urine was measured with the liquid scintillation counting technique and with accelerator mass spectrometry. After the subjects had been given 110 kBq 14 C-urea (children: 55 kBq) orally, samples of exhaled air were taken up to 180 days after administration and samples of urine were collected up to 40 days. Sixteen of the subjects were found to be HP-negative. In these subjects a total of 91.1%±3.9% (mean of adults and children ± standard error of the mean) of the administered 14 C activity was recovered. The majority of the administered activity, 88.3%±6.2% in adults and 87.7%±5.0% in children, was excreted via the urine within 72 h after administration. A smaller fraction was exhaled. In adults 4.6%±0.6% of the activity was exhaled within 20 days and in children 2.6%±0.3%. Uncertainties in the biokinetic results are mainly due to assumptions concerning endogenous CO 2 production and urinary excretion rate and are estimated to be less than 30%. The absorbed dose to various organs and the effective dose were calculated using the ICRP model for urea and CO 2 . The urinary bladder received the highest absorbed dose: in adults, 0.15±0.01 mGy/MBq and in children of various ages (7-14 years), 0.14-0.36 mGy/MBq. The findings indicate that an investigation with 14 C-urea gives an effective dose to adults of 2.1±0.1 µSv (for 110 kBq) and to children of 0.9-2.5 µSv (for 55 kBq). From a radiation protection point of view, there is thus no reason for restrictions on even repeated screening investigations with 14 C-urea in whole families, including children.

Since 1971, a series of annual Environmental Surveillance. .. reports have served as the official public record of Los Alamos National Laboratory's (LANL) environmental performance. In northern New Mexico, where past LANL emissions are a public health concern, there is public skepticism over the accuracy of information contained in these reports. To test the hypothesis that LANL Environmental Surveillance. .. reports systematically understate past emissions, we compared the data on releases in LANL's own internal Occurrence Reports Collection (ORC) to the data reported to the public in the Environmental Surveillance. .. reports. A data set of 89 environmental occurrences recorded in the ORC in the time period from 1971 through 1980 was assembled. We did not find a systematic pattern of quantitative underreporting of source terms. However, 17 of the 89 (19%) environmental occurrences recorded in the ORC were not reported to the public in the Environmental Surveillance. .. reports. The observed discrepancies are discussed in terms of their relevance to public health concerns. Methodological caveats dictate restraint in applying these findings beyond the scope of the relative comparison performed here. Possible social origins for the rejected hypothesis are discussed. Areas for further consideration by the Centers for Disease Control's dose reconstruction study of LANL are identified.

A nonfluoroscopic temporomandibular joint arthrographic technique is contrasted with a more widely employed fluoroscopically guided technique. The nonfluoroscopic technique uses a posterior approach to joint injection, as contrasted with the lateral injection approach of the fluoroscopically guided technique. The advantages of the nonfluoroscopic technique are less radiation dose to the patient, less expensive and less sophisticated imaging equipment, and less potential for neurovascular trauma. The fluoroscopic technique offers greater control of the procedure, less patient and operator time, and the capability for a dynamic videofluoroscopic study. Both techniques appear to be safe and efficacious. Differences in anatomy, imaging modalities, patient radiation exposure, and potential complications are also discussed as part of this comparison.

In radionuclide therapy, absorbed dose is calculated by convolution of a three-dimensional activity matrix with a three-dimensional dose point kernel. A technique employing the fast Hartley Transform (FHT) has been developed to perform this calculation. An important part of that development was the indexing scheme for 3D data. The results of this new FHT convolution technique were compared to direct convolution. A cube was convolved with itself by these two techniques. The results differed by less than 2 percent. In an effort to show the practical applicability of 3D convolution, a three-dimensional activity matrix from a I-131-labeled 16.88 monoclonal antibody patient was convolved with beta and photon dose point kernels using direct convolution. Isodose contours were then generated from the calculated absorbed dose matrix and overlaid on a CT image of the patient

We have studied the distribution of natural radioactivity in the soil of Interlagos, in São Paulo city and Billings Reservoir, in São Bernardo do Campo, São Paulo, Brazil. The main contribution of the effective radiation dose is due to the elements of the 238 Th decay series, with smaller contributions from 40 K and the elements of the series of 238 U. The results indicate the dose in all of the studied areas is around the average international dose due to external exposure to gamma rays (0.48 mSv/yr) proceeding from natural terrestrial elements.

This review focuses on the present status of kidney protection during peptide receptor radionuclide therapy (PRRT) using radiolabelled somatostatin analogues. This treatment modality for somatostatin receptor-positive tumours is limited by renal reabsorption and retention of radiolabelled peptides resulting in dose-limiting high kidney radiation doses. Radiation nephropathy has been described in several patients. Studies on the mechanism and localization demonstrate that renal uptake of radiolabelled somatostatin analogues largely depends on the megalin/ cubulin system in the proximal tubule cells. Thus methods are needed that interfere with this reabsorption pathway to achieve kidney protection. Such methods include coadministration of basic amino acids, the bovine gelatin-containing solution Gelofusine or albumin fragments. Amino acids are already commonly used in the clinical setting during PRRT. Other compounds that interfere with renal reabsorption capacity (maleic acid and colchicine) are not suitable for clinical use because of potential toxicity. The safe limit for the renal radiation dose during PRRT is not exactly known. Dosimetry studies applying the principle of the biological equivalent dose (correcting for the effect of dose fractionation) suggest that a dose of about 37 Gy is the threshold for development of kidney toxicity. This threshold is lower when risk factors for development of renal damage exist: age over 60 years, hypertension, diabetes mellitus and previous chemotherapy. A still experimental pathway for kidney protection is mitigation of radiation effects, possibly achievable by cotreatment with amifostine (Ethylol), a radiation protector, or with blockers of the reninangiotensin-aldosterone system. Future perspectives on improving kidney protection during PRRT include combinations of agents to reduce renal retention of radiolabelled peptides, eventually together with mitigating medicines. Moreover, new somatostatin analogues with lower renal retention may be developed. Furthermore, knowledge on kidney protection from radiolabelled somatostatin analogues may be expanded to other peptides.

The LabVIEW system suitability for a device research laboratory is evaluated in this paper. The system is applied successfully to the study of MOSFET device degradation under low radiation doses with the highly repetitive measurement using the well known charge pumping technique. Radiationinduced threshold voltage shift (ΔV TH ), Radiation-induced flatband voltage shift (ΔV FB ), radiation-induced oxide-trap (ΔN OT ), and radiation-induced interface-trap (ΔN IT ) are extracted. The irradiated MOSFET transistors are characterized with the developed software.

Purpose/Objective(s): To determine the efficacy of utilizing an external surrogate to monitor intra-fraction tumour position during stereotactic radiation delivery in early stage non-small cell lung cancer patients. Materials/Methods: A study was initiated to evaluate the value of optical tracking to monitor the stability of patients under treatment for stereotactic radiation therapy of the lung. Hardware components include the NDI Polaris stereoscopic IR emitting camera (RMS = 0.35 mm), a light-weight, pyramidal plastic frame (7 cm  7 cm  5 cm) supporting three passive IR reflective spheres, and an in-room PC housing custom software modules. Within an REB approved protocol, 10 patients diagnosed with stage I/II lung cancer received SBRT between November 2006 and February 2007. Intra-fraction patient position was monitored simultaneously using cone-beam CT (CBCT) and the optical system at four time points: initial setup (IS), after adjustment (AA), mid-delivery (MD), and post-delivery (PD). Optical measurements were based on surface anatomy using the optical reflector frame placed on the surface of the skin below the xiphoid process. CBCT imaging was performed using 360-degree acquisitions and involved manual alignment to soft-tissue targets from the reference planning CT. A total of 78 CBCT image and corresponding optical tracking data sets were acquired. A retrospective review of this data compared the CBCT determined tumour position (CBCT vs Reference CT) with observed displacements in the location of the optical frame.

In positron emission tomographic (PET) scanning, transmission measurements for attenuation correction are commonly performed by using external germanium-68 rod sources. Recently, combined PET and computed tomographic (CT) scanners have been developed in which the CT data can be used for both anatomicalmetabolic image formation and attenuation correction of the PET data. The purpose of this study was to evaluate the difference between germanium-and CT-based transmission scanning in terms of their radiation doses by using the same measurement technique and to compare the doses that patients receive during brain, cardiac and whole-body scans. Measurement of absorbed doses to organs was conducted by using a Rando Alderson phantom with thermoluminescent dosimeters. Effective doses were calculated according to the guidelines in the International Commission on Radiation Protection Publication Number 60. Compared with radionuclide doses used in routine 2-[fluorine-18]-fluoro-2-deoxy-D-glucose PET imaging, doses absorbed during germanium-based transmission scans were almost negligible. On the other hand, absorbed doses from CT-based transmission scans were significantly higher, particularly with a whole-body scanning protocol. Effective doses were 8.81 mSv in the high-speed mode and 18.97 mSv in the high-quality mode for whole-body CT-based transmission scans. These measurements revealed that the doses received by a patient during CT-based transmission scanning are more than those received in a typical PET examination. Therefore, the radiation doses represent a limitation to the generalised use of CT-based transmission measurements with current PET/CT scanner systems.

Radiostereometric analysis (RSA) has become one of the recommended techniques for pre-market evaluation of new joint implant designs. In this study we evaluated the effect of repositioning of X-ray tubes and phantom model on the precision of the RSA method. In precision measurements, we utilized mean error of rigid body fitting (ME) values as an internal control for examinations. ME value characterizes relative motion among the markers within each rigid body and is conventionally used to detect loosening of a bone marker. Three experiments, each consisting of 10 double examinations, were performed. In the first experiment, the X-ray tubes and the phantom model were not repositioned between one double examination. In experiments two and three, the X-ray tubes were repositioned between one double examination. In addition, the position of the phantom model was changed in experiment three. Results showed that significant differences could be found in 2 of 12 comparisons when evaluating the translation and rotation of the prosthetic components. Repositioning procedures increased ME values mimicking deformation of rigid body segments. Thus, ME value seemed to be a more sensitive parameter than migration values in this study design. These results confirmed the importance of standardized radiographic technique and accurate patient positioning for RSA measurements. Standardization and calibration procedures should be performed with phantom models in order to avoid unnecessary radiation dose of the patients. The present model gives the means to establish and to follow the intra-laboratory precision of the RSA method. The model is easily applicable in any research unit and allows the comparison of the precision values in different laboratories of multicenter trials. r

Pulsed optically stimulated luminescence measured from quartz under certain combinations of annealing and measurement temperature can be resolved into multiple lifetime components. We have studied the influence on these lifetime components of annealing temperature up to 900 C, beta irradiation dose as high as 1700 Gy, and temperature of stimulation up to 200 C. Although the time-resolved spectra from which the lifetimes are determined may be measured without heating between irradiation and measurement, a necessary protocol in steady-state optical stimulation applications, studies reported in this paper have been augmented with investigations on the effect of temperature and duration of preheating on the principal and secondary lifetimes. Luminescence spectra for measurements up to 200 Gy consist of a single lifetime but two components occur thereafter, both are independent of radiation dose. The principal lifetime of w35 ms is not affected by temperature of anneal whereas the secondary lifetime increases from 9 to 18 ms when the annealing temperature is changed from 600 to 900 C. The dependence of both the principal and secondary luminescence lifetimes on measurement temperature can be explained by thermal quenching of the associated luminescence. However, the influence of irradiation, preheating, and annealing on the lifetimes can be explained with reference to an energy band scheme in which the primary mechanism in the processes leading up to luminescence emission is the change in concentration of holes at various luminescence centres caused by annealing.

Improvements in software and hardware have enabled the integration of dual imaging modalities into hybrid systems, which allow combined acquisition of the different data sets. Integration of positron emission tomography (PET) and computed tomography (CT) scanners into PET/CT systems has shown improvement in the management of patients with cancer over stand-alone acquired CT and PET images. Hybrid cardiac imaging either with single photon emission computed tomography (SPECT) or PET combined with CT depicts cardiac and vascular anatomical abnormalities and their physiologic consequences in a single setting and appears to offer superior information compared with either stand-alone or side-by-side interpretation of the data sets in patients with known or suspected coronary artery disease (CAD). Hybrid systems are also advantageous for the patient because of the single short dual data acquisition. However, hybrid cardiac imaging has also generated controversy with regard to which patients should undergo such integrated examination for clinical effectiveness and minimization of costs and radiation dose, and if software-based fusion of images obtained separately would be a useful alternative.

Both sides of tobacco leaves accumulate 210 Po through their sticky hairs (trichomes) by means of diffusive deposition. It is known that tobacco leaves may contain high amounts of 210 Po concentrations. However, there is less information about radionuclides in tobacco plants. In the study, the 210 Po concentrations were determined monthly in different morphological parts of tobacco plants (leaf, stem, root) and soil samples and soil-to-plant transfer factor for 210 Po was determined and the activity concentrations of 210 Po radionuclide in 16 different popular brands of cigarettes were investigated in order to estimate the annual effective doses of 210 Po to smokers. Besides the study investigated (focused on) the correlation between the amount of rainfall and 210 Po concentration of tobacco leaf. The results of the present study indicated that the activity concentration of 210 Po in cigarettes distributed in Turkey ranged from 16.1 ± 1.0 to 37.6 ± 2.6 mBq per cigarette and the mean value of their activity concentrations was 22.4 ± 1.5 mBq per cigarette. The mean value of annual effective doses of 210 Po to smokers (20 cigarettes smoked by an individual per day) obtained from these activity concentrations was estimated to be 188.5 ± 12.4 μSv y −1 .

It is difficult to estimate the fetal or ovarian radiation dosage for female patients undergoing Gamma Knife radiosurgery. Our goals are to determine the fetal and ovarian radiation dose at various distances from a cranial isocenter, to provide a reference for practitioners to estimate the fetal dose with respect to gestational age, and to identify the components of pelvic extracranial radiation.

The study objectives were: to investigate current cervical spine radiographic imaging practices in conscious adult patients with suspected neck injury; reasons behind variation and consideration of dose estimates were explored. Comparison with a previous survey 19 has been made.

Coronary angioplasties can be performed with either single-plane or biplane imaging techniques. The aim of this study was to determine whether biplane imaging, in comparison to single-plane imaging, reduces radiation dose and contrast load and shortens procedural time during (i) primary and elective coronary angioplasty procedures, (ii) angioplasty to the main vascular territories and (iii) procedures performed by operators with various levels of experience. This prospective observational study included a total of 504 primary and elective single-vessel coronary angioplasty procedures utilising either biplane or single-plane imaging. Radiographic and clinical parameters were collected from clinical reports and examination protocols. Radiation dose was measured by a dose-area-product (DAP) meter intrinsic to the angiography system. Our results showed that biplane imaging delivered a significantly greater radiation dose (181.4¡121.0 Gycm 2 ) than single-plane imaging (133.6¡92.8 Gycm 2 , p,0.0001). The difference was independent of case type (primary or elective) (p50.862), vascular territory (p50.519) and operator experience (p50.903). No significant difference was found in contrast load between biplane (166.8¡62.9 ml) and single-plane imaging (176.8¡66.0 ml) (p50.302). This non-significant difference was independent of case type (p50.551), vascular territory (p50.308) and operator experience (p50.304). Procedures performed with biplane imaging were significantly longer (55.3¡27.8 min) than those with single-plane (48.9¡24.2 min, p50.010) and, similarly, were not dependent on case type (p50.226), vascular territory (p50.642) or operator experience (p50.094). Biplane imaging resulted in a greater radiation dose and a longer procedural time and delivered a non-significant reduction in contrast load than single-plane imaging. These findings did not support the commonly perceived advantages of using biplane imaging in single-vessel coronary interventional procedures.

A range of digital image acquisition devices exists in diagnostic radiology. This study compares contrast performance of two such systems: an amorphous Silicon/caesium iodide (a-Si:CsI) based flat panel (DR) digital chest radiography system and a computed radiography (CR) system. Images of a contrast detail resolution phantom were acquired at a range of radiation doses. Three observers assessed all hardcopy images using a four-alternative forced choice observer perception technique. Contrast detail performance was calculated and low contrast performance quantified.

Electron-beam initiated crosslinking of a poly(vinyl chloride)/epoxidized natural rubber blend (PVC/ENR), which contained trimethylolpropane triacrylate (TMPTA), was carried out over a range of irradiation doses (20 -200 kGy) and concentrations of TMPTA (1-5 phr). The gelation dose was determined by a method proposed by Charlesby. It was evident from the gelation dose, resilience, hysteresis, glasstransition temperature (T g ), IR spectroscopy, and scanning electron microscopy studies that the miscible PVC/ENR blend underwent crosslinking by electron-beam irradiation. The acceleration of crosslinking by the TMPTA was further confirmed in this study. Agreement of the results with a theory relating the T g with the distance between crosslinks provided further evidence of irradiation-induced crosslinking. The possible mechanism of crosslinking induced by the irradiation between PVC and ENR is also proposed.

The accident at the Chernobyl nuclear power plant was the worst industrial accident of the last century that involved radiation. The unprecedented release of multiple different radioisotopes led to radioactive contamination of large areas surrounding the accident site. The exposure of the residents of these areas was varied and therefore the consequences for health and radioecology could not be reliably estimated quickly. Even though some studies have now been ongoing for 25 years and have provided a better understanding of the situation, these are yet neither complete nor comprehensive enough to determine the long-term risk. A true assessment can only be provided after following the observed population for their natural lifespan. Here we review the technical aspects of the accident and provide relevant information on radioactive releases that resulted in exposure of this large population to radiation. A number of different groups of people were exposed to radiation: workers involved in the initial clean-up response, and members of the general population who were either evacuated from the settlements in the Chernobyl nuclear power plant vicinity shortly after the accident, or continued to live in the affected territories of Belarus, Russia and Ukraine. Through domestic efforts and extensive international co-operation, essential information on radiation dose and health status for this population has been collected. This has permitted the identification of high-risk groups and the use of more specialised means of collecting information, diagnosis, treatment and follow-up. Because radiation-associated thyroid cancer is one of the major health consequences of the Chernobyl accident, a particular emphasis is placed on this malignancy. The initial epidemiological studies are reviewed, as are the most significant studies and/or aid programmes in the three affected countries.

The bactericidal radiation dosages at specific wavelengths in the ultraviolet (UV)-visible spectrum are not well documented. Such information is important for the development of new monochromatic bactericidal devices to be operated at different wavelengths. In this study, radiation dosages required to cause mortality of an Escherichia coli strain, ATCC 25922, at various wavelengths between 250 and 532 nm in the UV and visible spectrum were determined. Radiation at 265 nm in the UV region was most efficient in killing the E. coli cells and 100% mortality was achieved at a dose of 1.17 log mJ/cm 2 . In the visible spectrum, the radiation dosages required for a one-log reduction of the E. coli cell density at 458 and 488 nm were 5.5 and 6.9 log mJ/cm 2 , respectively. However, at 515 and 532 nm, significant killing was not observed at radiation dosage up to 7 log mJ/cm 2 . Based on the cell survival data at various radiation dosages between 250 and 488 nm, a predictive equation for the survival of E. coli cells is derived, namely log(S/S 0 ) ¼ À(1.089 Â 10 7 e À0.0633l )D. The symbols, S 0 , S, l, and D, represent initial cell density, cell density after irradiation, wavelength of the radiation and radiation dosage, respectively. The proportion of the surviving E. coli cells decreases exponentially with the increase in radiation dosage at a given wavelength. In addition, the radiation dose required for killing a certain fraction of the E. coli cells increases exponentially as the wavelength of radiation increases.

A small field irradiation technique to deliver high doses of single fraction photon radiation to small, precisely located volumes (0.5 to 8 cm3) within the brain has been developed. Our method uses a modified Brown-Roberts-Wells (BRS), CT-guided, stereotactic system and a 6 MV linear accelerator equipped with a special collimator (diameters of 12.5 mm to 30.0 mm projected to isocenter) located 23 cm from isocenter. Target localization via planar angiography has been added. Treatment consists of a series of arcing beams using both gantry and couch rotations. During treatment, the patient's head is immobilized independently of the radiotherapy couch and is precisely positioned without reference to room lasers or light field. A precise verification of alignment precedes each treatment. Extensive performance tests have shown that a target, localized by CT, can be irradiated with a positional accuracy of 2.4 mm in any direction with 95% confidence. If angiography is used for localization, the results are better. The dose 1.0 cm outside the target volume is less than 20% of the prescribed dose for a medium sized collimator.

Digital radiography systems based on flat-panel detectors have been introduced into clinical practice in the past few years. The high detective quantum efficiency of these detectors allows the radiation dose to be reduced while maintaining image quality, an issue particularly significant for pediatric radiography. Another important aspect for dose optimization and monitoring is the integration of the detector into a computer-controlled x-ray examination system. This enables full control and complete reporting of all dose-relevant exposure parameters, including the determination of the exposure indicator and the patient dose (kerma-area product). In this paper the implementation of these principles in the Philips Digital Diagnost DR system is described and their relevance for pediatric applications is discussed.

Purpose: To retrospectively report the outcome of head and neck cancer patients following re-irradiation. Patients and Methods: A total of 51 patients with recurrent or second primary head and neck cancer received re-irradiation at Leuven University Hospital. Survival and locoregional control were calculated. Doses to organs at risk were retrieved from dosevolume histograms. Radiation-related toxicities were reported. Results: The 2-year actuarial overall survival rate was 30%. On univariate analysis, surgery before re-irradiation and high radiation dose were associated with superior survival. Grade 3 acute and grade 3 or more late toxicity occurred in respectively 29.4% and 35.3% of the patients. Conclusion: Re-irradiation in head and neck cancer patients is feasible with acceptable late toxicity, although the survival remains poor.

Diagnostic X-ray examinations play an important role in the health care of the population. These examinations may involve significant irradiation of the patient and probably represent the largest manufactured source of radiation exposure for the population. This study was performed in Dar Elalag hospital and Elkawati Hospital. This study performed to assess the Mean Glandular Dose (MGD) received in mammography examination using Robson's parametric method and Dance's additional factors. The parameters were recorded in this study were patient's age, breast thickness, tube target filter and the exposure factors (mAs and kVp). The results of MGD values calculated showed that patient exposure was were significantly lower than the standard dose determined by IAEA. The mean MGD values calculated were 1.59 + 0.17 (p<0.01) and 1.63 + 0.22 (p<0.01) for Craniocaudal and Oblique projections, respectively.

Purpose Using 123 I for diagnostic purposes avoids the risk of stunning for subsequent radioiodine treatment and affords an excellent image quality. In this study we assessed the role of 123 I in comparison with 131 I post-treatment imaging in patients with thyroid cancer. Methods We compared a total of 292 123 I scans with their corresponding post-treatment 131 I images. Patients received a therapeutic dose of 131 I following diagnostic scanning with 50-111 MBq of 123 I. All patients were in a hypothyroid state (>30 μIU/l) before radioiodine administration for either diagnostic or therapeutic purposes. Results In 228 out of 263 patients with a positive diagnostic scan, 123 I whole-body scan findings were concordant with those of corresponding post-treatment 131 I images (concordance rate 87%). However, there were 44 additional foci of abnormal uptake on post-treatment 131 I scans in 22 discordant cases with no impact on therapeutic management of the patients. In 13 patients, there was at least one new site on post-treatment images that had been missed on pretreatment 123 I images. Twenty-nine patients with a negative diagnostic scan were treated with 131 I owing to a high serum thyroglobulin level (range 11.3-480 ng/ml). Radioiodine uptake sites were seen in eight post-treatment scans. In 21 pairs of whole-body scans, both the pre-and the post-treatment scan were negative (concordance rate 72.4%). Conclusion 123 I scanning is comparable to high-dose 131 I post-treatment imaging in thyroid carcinoma patients, and 123 I offers excellent image quality as a diagnostic agent. It avoids disadvantages such as stunning before treatment and delivery of a high radiation dose to patients.

Objective: To estimate the absorbed organ dose and effective dose for a wide range of cone beam computed tomography scanners, using different exposure protocols and geometries. Materials and methods: Two Alderson Radiation Therapy anthropomorphic phantoms were loaded with LiF detectors (TLD-100 and TLD-100H) which were evenly distributed throughout the head and neck, covering all radiosensitive organs. Measurements were performed on 14 CBCT devices: 3D Accuitomo 170, Galileos Comfort, i-CAT Next Generation, Iluma Elite, Kodak 9000 3D, Kodak 9500, NewTom VG, NewTom VGi, Pax-Uni3D, Picasso Trio, ProMax 3D, Scanora 3D, SkyView, Veraviewepocs 3D. Effective dose was calculated using the ICRP 103 (2007) tissue weighting factors. Results: Effective dose ranged between 19 and 368 Sv. The largest contributions to the effective dose were from the remainder tissues (37%), salivary glands (24%), and thyroid gland (21%). For all organs, there was a wide range of measured values apparent, due to differences in exposure factors, diameter and height of the primary beam, and positioning of the beam relative to the radiosensitive organs. Conclusions: The effective dose for different CBCT devices showed a 20-fold range. The results show that a distinction is needed between small-, medium-, and large-field CBCT scanners and protocols, as they are applied to different indication groups, the dose received being strongly related to field size. Furthermore, the dose should always be considered relative to technical and diagnostic image quality, seeing that image quality requirements also differ for patient groups. The results from the current study indicate that the optimisation of dose should be performed by an appropriate selection of exposure parameters and field size, depending on the diagnostic requirements.

Objectives: To evaluate the adequacy of patient data and clinical information transmitted to the radiological departments by the referring clinicians in view of the justification demands concerning the radiological examinations, as those are described in the Radiation Protection Regulations of the European Union Nations. Materials and methods: Request forms for 1708 patients referred to radiology department and 410 referred to the CT department were evaluated concerning the proper completion of the form fields. Furthermore, for CT examinations a more detailed evaluation was carried out, to assess the rationalistic use of CT within the diagnostic algorithm. Results: Not properly completed request forms to both departments were observed, however, the omissions were more prominent for the referrals to the radiology department, where the age and the probable clinical diagnosis was not given in 81.5 and 46% of the forms, respectively. Furthermore, the emergency indication was less cautiously used compared to the CT requests. For the CT department 33.3% of requests were justified and the final diagnosis was included in the referring doctor's probable clinical diagnosis. U/S was the examination of choice in 51% of the cases where an examination should have been performed before CT and in 70.6% of the cases where an alternative examination was proposed. Conclusions:

The purpose of the study was to evaluate image quality (IQ) associated with vascular radiology and vascular surgery procedures in Belgium and to determine reference values for future image quality assessment. IQ was evaluated with the CD-DISC contrast-detail phantom. This circular PMMA phantom contains 225 holes with different diameter and depth, to quantify resolution and contrast. Images of the phantom were acquired for both fluoroscopy and subtraction images on 21 systems. Three observers evaluated the images by determining the threshold contrast visible for every diameter. This results in contrast-detail curves and image quality figures. We observed a large difference in IQ between the centres. No straightforward correlation could be found with radiation dose or other exposure settings.