Equivalent Dose Values Research Articles

Temporal Lobe Toxicity Analysis After Proton Radiation Therapy for Skull Base Tumors

Temporal lobe (TL) parenchyma toxicity constitutes one of the most frequent late adverse event in high-dose proton therapy (PT) for tumors of the skull base. We analyzed clinical events with dosimetric parameters in our patients treated for skull base tumors with spot-scanning PT. Between 1998 and 2005, a total of 62 patients received PT to a median dose of 71.7 Gy (relative biologic effectiveness [RBE]) (range, 63-74 Gy). The dose-volume histogram of each TL and the entire brain parenchyma (BP) were analyzed according to maximum, mean, and minimum dose as well as doses to 0.5, 1, 2, and 3 cc of brain volume (D(0.5), D(1), D(2), D(3)) and correlated with clinical events. Generalized equivalent uniform dose (gEUD) values were calculated. At a mean follow-up of 38 months (range, 14-92 months), 2 patients had developed symptomatic Grade 3 and 5 patients asymptomatic Grade 1 TL toxicity. Mean doses to a 2-cc volume of BP increased from 71 ± 5 Gy (RBE) for no toxicity to 74 ± 5 Gy (RBE) for Grade 1 and to 76 ± 2 Gy (RBE) for Grade 3 toxicity. TL events occurred in 6 of 7 patients (86%) at or above dose levels of ≥ 64 Gy (RBE) D(3), ≥ 68 Gy (RBE) D(2), ≥ 72 Gy (RBE) D(1), and ≥ 73 Gy (RBE) D(0.5), respectively (p = NS). No statistically significant dose/volume threshold was detected between patients experiencing no toxicity vs. Grade 1 or Grade 3. A strong trend for Grade 1 and 3 events was observed, when the gEUD was 60 Gy. A statistically significant normal tissue threshold dose for BP has not been successfully defined. However, our data suggest that tolerance of TL and BP to fractionated radiotherapy appears to be correlated with tissue volume included in high-dose regions. Additional follow-up time and patient accrual is likely needed to achieve clinical significance for these dose-volume parameters investigated. Our findings support the importance of establishing an organ-at-risk maximally permissible dose for BP.

Application of single-grain OSL to date quartz xenocrysts within a basalt flow, San Francisco volcanic field, northern Arizona, USA

Previous age estimates for SP Crater in the San Francisco volcanic field in northern Arizona, USA, suggested it erupted 70 ka; however its non-weathered geomorphic character places it as one of the youngest volcanic vents in the region. Samples of quartz xenocrysts were extracted from the SP Crater basalt flows and dated using single-grain dating. Analysis of the luminescence signals indicate they were dominated by medium- to slow-decaying OSL components, which can produce age underestimates if not removed. In order to reduce their contribution, the fast component was deconvolved from the initial OSL signal, a high-temperature bleach (blue-green LED exposure at 280 °C) was added at the end of each measurement cycle and elevated cutheat temperatures were used. Fading tests and crushing experiments indicate no dependence on recovered equivalent dose values. Resultant single-grain quartz xenocryst OSL ages are consistent with the geomorphic character of SP Crater and suggest it erupted 5.5–6 ka. Revision of the age of SP Crater has implications for the eruption recurrence interval in the region and assessment of volcanic hazards in nearby communities.

Area dosimetry in the Praid-salt mine

The aim of the paper is to present a special application of the Romanian thermoluminescent dosemeters system, based on the use of the LiF:Mg,Cu,P, commercial GR-200A detectors, for the measurement of the ultra-low-level ambient dose equivalent rate values, situated within the interval of 1-100 nSv h(-1). The paper briefly describes the system and presents in detail the experimental procedure, including the corrections to be applied to the experimental values. The final characterisation of a Romanian salt mine, proposed to be used as an underground accelerator laboratory, is given. The comparison with the previous measurement results in the Slanic Prahova former salt mine and with the results obtained using the gamma-ray spectrometry method validates the results reported in this paper. The conclusion is that the system provides reliable results in the measurement of the ultra-low-level radiation background.

Testing the application of post IR-IRSL dating to fine grain waterlain sediments

The polymineral fine grain fraction of a set of ten known age samples were used to test the suitability of elevated temperature post-IR infrared stimulated luminescence (pIRIR) to date waterlain sediments in Switzerland. Equivalent Dose (De) values were obtained using elevated temperatures of 225 °C (pIRIR225) and 290 °C (pIRIR290) and IRSL50/225 (preceding measurement of pIRIR225), and these displayed a systematic increase with increasing stimulation temperature, which brought those derived from the pIRIR protocols into saturation for the older half of the samples (>100 ka). Significant residuals were recorded for the pIRIR signals, and these were found to further increase following attenuation of the bleaching source confirming that these signals are harder to bleach than the IRSL measured at 50 °C. Fading tests recorded g-values of between 1 and 4%, and displayed no obvious decrease with increasing stimulation temperature. For the younger half of the samples, fading corrected ages for all protocols resulted in overestimation compared to robust independent dating for all samples, and draw into question the relationship of fading measured in a laboratory generated signal to that which is naturally generated. Uncorrected IRSL50/225 ages for all samples were in good agreement with independent dating, but still displayed a general overestimation using pIRIR signals. These overestimations may largely be due to the significant residual doses resulting from the harder to bleach nature of the elevated temperature signal, and present a considerable problem when dating waterlain sediments. A considerable challenge when using the pIRIR signal is to be able to separate the effects of both residual doses and fading and confirm that one is not masking the other. Despite this, the pIRIR protocols were successful at one site, although they offered no benefit compared to dating with more conventional luminescence signals. A comparison of De values derived from a standard IRSL signal to that from IRSL50/225, suggest that the latter overestimates by ∼10% due to a decrease in sensitivity of the sample prior to measurement of the test dose.

Comparisons of several transport models in their predictions in typical space radiation environments

We have used several transport codes to calculate dose and dose equivalent values as well as the particle spectra behind a slab or inside a spherical shell shielding in typical space radiation environments. Two deterministic codes, HZETRN and UPROP, and two Monte Carlo codes, FLUKA and Geant4, are included. A soft solar particle event, a hard solar particle event, and a solar minimum galactic cosmic rays environment are considered; and the shielding material is either aluminum or polyethylene. We find that the dose values and particle spectra from HZETRN are in general rather consistent with Geant4 except for neutrons. The dose equivalent values from HZETRN and Geant4 are not far from each other, but the HZETRN values behind shielding are often lower than the Geant4 values. Results from FLUKA and Geant4 are mostly consistent for considered cases. However, results from the legacy code UPROP are often quite different from the other transport codes, partly due to its non-consideration of neutrons. Comparisons for the spherical shell geometry exhibit the same qualitative features as for the slab geometry. In addition, results from both deterministic and Monte Carlo transport codes show that the dose equivalent inside the spherical shell decreases from the center to the inner surface and this decrease is large for solar particle events; consistent with an earlier study based on deterministic radiation transport results. This study demonstrates both the consistency and inconsistency among these transport models in their typical space radiation predictions; further studies will be required to pinpoint the exact physics modules in these models that cause the differences and thus may be improved.

Re-design of 241Am–Be neutron source irradiator facility at NNRI using MCNP-5 code

Evaluation of the flux in various irradiation channels and the absorbed dose rate of radiation by operators 3 cm from the surface of the concrete surrounding the vessel of the 241Am–Be irradiator facility at NNRI, after it had been theoretically modified using MCNP-5 transport code is presented in this work. The 241Am–Be neutron facility at NNRI consist of a single centrally placed neutron source and flanked by two irradiation channels. The theoretical models however had the number of neutron sources increased gradually to five with a fixed number of five irradiation channels of various radii. These were to help assess the viability to increase the irradiator performance and operational capacity. The results indicated an increase in flux in the irradiation channels as well as absorbed dose rates and their dose equivalents as the number of neutron sources increased. The dose equivalent values were all well within the limits set by ICRP and Radiation Protection Board (RPB – Ghana).

Shot sequencing based on biological equivalent dose considerations for multiple isocenter Gamma Knife radiosurgery

Rapid delivery of multiple shots or isocenters is one of the hallmarks of Gamma Knife radiosurgery. In this study, we investigated whether the temporal order of shots delivered with Gamma Knife Perfexion would significantly influence the biological equivalent dose for complex multi-isocenter treatments. Twenty single-target cases were selected for analysis. For each case, 3D dose matrices of individual shots were extracted and single-fraction equivalent uniform dose (sEUD) values were determined for all possible shot delivery sequences, corresponding to different patterns of temporal dose delivery within the target. We found significant variations in the sEUD values among these sequences exceeding 15% for certain cases. However, the sequences for the actual treatment delivery were found to agree (<3%) and to correlate (R2 = 0.98) excellently with the sequences yielding the maximum sEUD values for all studied cases. This result is applicable for both fast and slow growing tumors with α/β values of 2 to 20 according to the linear-quadratic model. In conclusion, despite large potential variations in different shot sequences for multi-isocenter Gamma Knife treatments, current clinical delivery sequences exhibited consistent biological target dosing that approached that maximally achievable for all studied cases.

Single-grain OSL dating at La Grotte des Contrebandiers (‘Smugglers’ Cave’), Morocco: improved age constraints for the Middle Paleolithic levels

Optically stimulated luminescence (OSL) measurements of individual quartz grains are reported for Middle Paleolithic (MP) or Middle Stone Age (MSA) deposits in La Grotte des Contrebandiers, Morocco. Single-grain measurements enable rejection of grains that may lead to under- or over-estimation of age due to malign luminescence properties or remobilisation of grains after burial. We identified the former using a range of experimental procedures and objective rejection criteria. Three post-depositional factors influenced the distribution pattern of equivalent dose ( D e) values for the remaining single grains: the disintegration of roof spall liberating unbleached, older grains into otherwise well-bleached sediments; the intrusion of a small number of younger grains from the overlying Upper Paleolithic deposits; and small-scale differences in the beta dose received by individual grains. Roof spall contamination was a significant problem, so we characterised the OSL signals and obtained D e values for the calcareous sandstone in which the cave is formed, which allowed bedrock-derived grains in the MP/MSA deposits to be identified and rejected prior to age determination. We collected 31 samples from the MP/MSA deposits, and were able to calculate ages for 30 of them. These ages suggest that MP/MSA occupation of Contrebandiers was restricted to the interval between about 120 and 90 ka ago (Marine Isotope Stages 5d to 5b). Weighted mean OSL ages were obtained for samples associated with archaeologically sterile deposits at the base of the excavations (126 ± 9 ka), followed by two phases of the Moroccan Mousterian (122 ± 5 and 115 ± 3 ka), interspersed with archaeologically sterile deposits (112 ± 4 ka). The base and top of the Aterian were dated to 107 ± 4 and 96 ± 4 ka, respectively. Based on the grand weighted mean ages of 116 ± 3 and 103 ± 3 ka for the Moroccan Mousterian and Aterian at Contrebandiers, we suggest that these two industries may be separated by an occupation hiatus of up to 13 ± 3 ka at this site. Our single-grain OSL chronology confirms previous age estimates obtained for Contrebandiers and other sites in the vicinity, but are generally more precise and stratigraphically more coherent, due to the inherent advantages of measuring individual quartz grains and rejecting contaminant and other unsuitable grains before age determination.

TL measurement of ambient dose at a Nuclear Medicine Department

Abstract An investigation of ambient dose at the Nuclear Medicine Department, Instituto Nacional de Cancerologia, Mexico, was performed using two types of thermoluminescent dosemeters: TLD-100 and TLD-900. In addition, ambient dose was measured at the outside corridor of the hospitalization room for 137 Cs brachytherapy patients. Radionuclides used at the Nuclear Medicine Department are 131 I, 18 F, 67 Ga, 99m Tc, 111 In, 201 Tl. Main gamma emission energies from these elements are in the range from 93 to 511 keV. High dose values were obtained at the waste storage room, the outside corridor of 131 I patients, the PET/CT room and the outside corridor of 137 Cs brachytherapy patients. The maximum ambient dose equivalent rate equal to about 19 μSv/h was obtained for the 137 Cs brachytherapy corridor. Sites with minimum doses are the gamma camera rooms, having ambient dose equivalent rates equal to about 0.05 μSv/h. At most sites where both types of dosemeters were placed ambient dose equivalent values obtained with TLD-900 were 25–45% higher than TLD-100 values. This result was attributed to scattered radiation producing low energy photons which results in over response of TLD-900 and thus, TLD-100 values are considered to be more reliable. Knowledge of ambient dose values is relevant to the occupational exposure personnel who may limit the time spent at high dose areas. Recommendations were given to the Department authorities to implement actions in order to reduce doses at high dose sites in order to comply with the ALARA principle.

Evaluation of risk of secondary cancer occurrence after proton radiotherapy of ocular tumours

Abstract Reduction of undesired exposure to scattered neutron and gamma radiation associated with proton therapy should reduce the risk of occurrence of secondary cancers, especially in paediatric patients. By replacing the patient with a RANDO ® antropomorphic phantom, we determined the undesired radiation doses during the entire course of treatment at the ocular proton radiotherapy facility at IFJ PAN in Krakow and estimated the associated risk of secondary cancers. The highest exposure from the scattered radiation, per therapeutic proton absorbed dose, was found in the brain close to the target volume. Using TASTRAK PADC track detectors we estimated the fast neutron dose equivalent in the brain at 15.2 μSv/Gy, a value consistent with 17.06 μSv/Gy obtained from MCNPX 2.5.0 Monte Carlo calculations. The ambient dose equivalent, H ∗ (10), determined with WENDI II and FHT 192 detectors at the position of the patient (50 cm below the isocentre), was 2.41 μSv/Gy from neutrons and 0.43 μSv/Gy from γ -rays, respectively. Based on estimated values of organ dose equivalents, we evaluate the whole-body risk of fatal secondary cancers per course of treatment at below 0.001%.

A Comprehensive Analysis of Cardiac Dose in Balloon-Based High-Dose-Rate Brachytherapy for Left-Sided Breast Cancer

To investigate radiation dose to the heart in 60 patients with left-sided breast cancer who were treated with balloon-based high-dose-rate brachytherapy using MammoSite or Contura applicators. We studied 60 consecutive women with breast cancer who were treated with 34 Gy in 10 twice-daily fractions using MammoSite (n= 37) or Contura (n= 23) applicators. The whole heart and the left and right ventricles were retrospectively delineated, and dose-volume histograms were analyzed. Multiple dosimetrics were reported, such as mean dose (D(mean)); relative volume receiving 1.7, 5, 10, and 20 Gy (V1.7, V5, V10, and V20, respectively); dose to 1 cc (D(1cc)); and maximum point dose (D(max)). Biologic metrics, biologically effective dose and generalized equivalent uniform dose were computed. The impact of lumpectomy cavity location on cardiac dose was investigated. The average ± standard deviation of D(mean) was 2.45 ± 0.94 Gy (range, 0.56-4.68) and 3.29 ± 1.28 Gy (range, 0.77-6.35) for the heart and the ventricles, respectively. The average whole heart V5 and V10 values were 10.2% and 1.3%, respectively, and the heart D(max) was >20 Gy in 7 of 60 (11.7%) patients and >25 Gy in 3 of 60 (5%) patients. No cardiac tissue received ≥30 Gy. The V1.7, V5, V10, V20, and D(mean) values were all higher for the ventricles than for the whole heart. For balloons located in the upper inner quadrant of the breast, the average whole heart D(mean) was highest. The D(mean), biologically effective dose, and generalized equivalent uniform dose values for heart and ventricles decreased with increasing minimal distance from the surface of the balloon. On the basis of these comprehensive cardiac dosimetric data, we recommend that cardiac dose beroutinely reported and kept as low as possible in balloon-based high-dose-rate brachytherapy treatment planning for patients with left-sided breast cancer so the correlation with future cardiac toxicity data can be investigated.

Closely-spaced recuperated OSL dating of the last interglacial paleosol in the southeastern margin of the Chinese Loess Plateau

The objective of this study is to construct a numerically dated chronology of the last interglacial paleosol (S 1) in Chinese loess using luminescence dating. The recuperated optically stimulated luminescence (ReOSL) dating approach was applied to 18 closely-spaced (20 cm intervals) samples, with 15 of these collected from the S 1 unit at the Weinan site, which is located at the southeastern margin of the Chinese Loess Plateau (CLP). By using the multiple-aliquot regenerative-dose (MAR) approach, 18 fine-grained quartz ReOSL equivalent dose ( D E ) values, spanning about 249–466 Gy, were obtained. The validity of ReOSL MAR protocol was checked by dose recovery measurements and recycling ratio tests. By comparison of the dose-response curves of all the samples, we found that it is feasible to construct a standardized growth curve (SGC) for the ReOSL signal at the Weinan site. Considering the effects of pedogenesis of the S 1 unit during formation, the dose rate during the last interglacial was corrected, which should be beneficial for constructing a more reliable chronology. Finally, a detailed chronology of the S 1 unit was established. The results show that S 1 was deposited between approximately 76–127 ka, which confirms the early suggestion that the S 1 unit in Chinese loess corresponds to the whole marine oxygen-isotope stage (MIS) 5. The detailed ReOSL chronology of S 1 indicates the consistency of the substrata of S 1 with MIS 5a-e, but cannot determine whether they are exactly coeval. According to the present ReOSL age results, it is suggested that dust deposition is continuous at timescales larger than 14.1 ± 11.8 ky during the last interglacial and there is no hiatus longer than 4.4 ± 13.0 ky at the L 2/S 1 transition. Further work, e.g. minimizing the errors on ages and reducing the luminescence sampling intervals, is needed to understand the more detailed dust deposition conditions during the last interglacial in Chinese loess.

Simulations of thermally transferred OSL signals in quartz: Accuracy and precision of the protocols for equivalent dose evaluation

Thermally-transferred optically stimulated luminescence (TT-OSL) signals in sedimentary quartz have been the subject of several recent studies, due to the potential shown by these signals to increase the range of luminescence dating by an order of magnitude. Based on these signals, a single aliquot protocol termed the ReSAR protocol has been developed and tested experimentally. This paper presents extensive numerical simulations of this ReSAR protocol. The purpose of the simulations is to investigate several aspects of the ReSAR protocol which are believed to cause difficulties during application of the protocol. Furthermore, several modified versions of the ReSAR protocol are simulated, and their relative accuracy and precision are compared. The simulations are carried out using a recently published kinetic model for quartz, consisting of 11 energy levels. One hundred random variants of the natural samples were generated by keeping the transition probabilities between energy levels fixed, while allowing simultaneous random variations of the concentrations of the 11 energy levels. The relative intrinsic accuracy and precision of the protocols are simulated by calculating the equivalent dose (ED) within the model, for a given natural burial dose of the sample. The complete sequence of steps undertaken in several versions of the dating protocols is simulated. The relative intrinsic precision of these techniques is estimated by fitting Gaussian probability functions to the resulting simulated distribution of ED values. New simulations are presented for commonly used OSL sensitivity tests, consisting of successive cycles of sample irradiation with the same dose, followed by measurements of the sensitivity corrected L/T signals. We investigate several experimental factors which may be affecting both the intrinsic precision and intrinsic accuracy of the ReSAR protocol. The results of the simulation show that the four different published versions of the ReSAR protocol can reproduce accurately the natural doses in the range 0–400 Gy with approximately the same intrinsic precision and accuracy of ∼1–5%. However, these protocols underestimate doses above 400 Gy; possible sources of this underestimation are investigated. Two possible explanations are suggested for the modeled underestimations, possible thermal instability of the TT-OSL traps, and the presence of thermally unstable medium OSL components in the model.

On the intrinsic accuracy and precision of luminescence dating techniques for fired ceramics

Luminescence dating techniques have been used extensively for archaeological and geological samples. Such techniques are based on thermally or optically stimulated signals. This paper presents simulations of several luminescence techniques for equivalent dose (ED) estimation for ceramic materials containing quartz. The simulations are carried out using a recently published comprehensive kinetic model for quartz, consisting of 11 electron and hole traps and centers. The complete sequence of the experimental protocols for several thermoluminescence (TL) and optically stimulated luminescence (OSL) techniques are simulated using the same set of kinetic parameters. The specific simulated protocols are: additive dose TL protocol, predose technique (both additive and multiple activation versions), phototransfer protocol, single aliquot regenerative optically stimulated luminescence (SAR-OSL) protocol, and SAR thermoluminescence protocol (SAR-TL). One hundred random variants of the natural samples were generated by keeping the transition probabilities between energy levels fixed, while allowing simultaneous random variations of the concentrations of the 11 energy levels. The relative intrinsic accuracy and precision of the protocols are simulated by calculating the equivalent dose (ED) within the model, for a given natural burial dose of the sample. The intrinsic accuracy of these techniques is estimated by simulating natural irradiation of the samples with a known burial dose, followed by simulation of the luminescence method used to recover the estimated dose ED. The percent difference between the burial dose and the ED value represents the simulated accuracy of the luminescence technique. The relative intrinsic precision of these techniques is estimated by fitting Gaussian probability functions to the ED values obtained with the 100 model variants. It is found that the various techniques can reproduce natural paleodoses in the range 10 mGy–10 Gy with a typical intrinsic accuracy of +1 to 10%. Techniques based on single aliquot protocols were found in general to be more precise than techniques requiring the use of multiple aliquots. In addition, techniques based on interpolation of experimental data were found to be consistently both more precise and accurate than those based on extrapolation of experimental data.

Hp(0.07) photon irradiations at Seibersdorf for the EURADOS extremity dosemeter intercomparison 2009

In August 2009, almost 1000 passive extremity dosemeters were irradiated at the Dosimetry Laboratory Seibersdorf as part of the EURADOS intercomparison IC2009. Forty-four European individual monitoring services participated, with a total of 59 dosimetry systems (46 finger ring, 4 finger tip and 9 wrist/ankle dosemeter systems). Additionally, finger-ring dosemeters from the Dosimetry Service Seibersdorf were irradiated in a non-competitive manner. Dosemeter irradiations on rod and pillar phantoms in four photon-radiation fields complying with the ISO standard 4037 were performed with personal dose equivalent values (H(p)(0.07)) ranging from 4 to 480 mSv. Traceability was established by using an air-kerma-calibrated monitor ionisation chamber together with the X-ray facility as well as a calibrated (137)Cs gamma radiation field with a collimated beam geometry. The ISO-tabulated conversion coefficients from air kerma free-in-air to H(p)(0.07) were applied, resulting in the main contribution to the expanded measurement uncertainties.

Comparison of the transport codes HZETRN, HETC and FLUKA for galactic cosmic rays

The HZETRN deterministic radiation code is one of several tools developed to analyze the effects of harmful galactic cosmic rays (GCR) and solar particle events on mission planning and shielding for astronauts and instrumentation. This paper is a comparison study involving the two Monte Carlo transport codes, HETC–HEDS and FLUKA and the deterministic transport code, HZETRN. Each code is used to transport an ion from the 1977 solar minimum GCR spectrum impinging upon a 20 g/cm 2 aluminum slab followed by a 30 g/cm 2 water slab. This research is part of a systematic effort of verification and validation to quantify the accuracy of HZETRN and determine areas where it can be improved. Comparisons of dose and dose equivalent values at various depths in the water slab are presented in this report. This is followed by a comparison of the proton and forward, backward and total neutron flux at various depths in the water slab. Comparisons of the secondary light ion 2H, 3H, 3He and 4He fluxes are also examined.

Cognitive Bizarreness in the Dream and Waking Mentation of Nonpsychotic Patients With Parkinson's Disease

Cognitive Bizarreness in the Dream and Waking Mentation of Nonpsychotic Patients With Parkinson's Disease

Infrared stimulated luminescence dating of an Eemian (MIS 5e) site in Denmark using K-feldspar

Buylaert, J.-P., Huot, S., Murray, A.S. & Van den haute, P.: Infrared stimulated luminescence dating of an Eemian (MIS 5e) site in Denmark using K-feldspar. Boreas, 10.1111/j.1502-3885.2010.00156.x. ISSN 0300-9483. Infrared stimulated luminescence (IRSL) dating of K-feldspars may be an alternative to quartz optically stimulated luminescence (OSL) dating when the quartz OSL signal is too close to saturation or when the quartz luminescence characteristics are unsuitable. In this paper, Eemian (MIS 5e) coastal marine sands exposed in a cliff section on the coast of southern Jutland (Denmark) are used to test the accuracy and precision of IRSL dating using K-feldspars. This material has been used previously to test quartz OSL dating (Murray & Funder 2003): a small systematic underestimation of <10% compared to the expected age of ∼130 ka was reported. In our study, a single-aliquot regenerative-dose (SAR) IRSL protocol is used to determine values of equivalent dose (De) and the corresponding fading rates (g values). A significant age underestimation (of up to ∼35%) is observed; this is attributed to anomalous fading. Using a single site-average fading rate of 3.66 ± 0.09%/decade to correct the IRSL ages for all samples provides good agreement between the average fading-corrected K-feldspar age (119 ± 6 ka) and the independent age control (132–125 ka). This is despite the reservations of Huntley & Lamothe (2001) that their fading correction method is not expected to work on samples older than ∼20–50 ka. This fading-corrected feldspar result is not significantly different from the overall revised quartz age (114 ± 7 ka) also presented here. We conclude that fading-corrected IRSL ages measured using K-feldspar may be both precise and accurate over a greater age range than might be otherwise expected.

Whole-body biodistribution and brain PET imaging with [18F]AV-45, a novel amyloid imaging agent — a pilot study

The compound (E)-4-(2-(6-(2-(2-(2-(18)F-fluoroethoxy)ethoxy)ethoxy) pyridin-3-yl)vinyl)-N-methylbenzenamine ([(18)F]AV-45) is a novel radiopharmaceutical capable of selectively binding to beta-amyloid (A beta) plaques. This pilot study reports the safety, biodistribution, and radiation dosimetry of [(18)F]AV-45 in human subjects. In vitro autoradiography and fluorescent staining of postmortem brain tissue from patients with Alzheimer's disease (AD) and cognitively healthy subjects were performed to assess the specificity of the tracer. Biodistribution was assessed in three healthy elderly subjects (mean age: 60.0+/-5.2 years) who underwent 3-h whole-body positron emission tomography (PET)/computed tomographic (CT) scans after a bolus injection of 381.9+/-13.9 MBq of [(18)F]AV-45. Another six subjects (three AD patients and three healthy controls, mean age: 67.7+/-13.6 years) underwent brain PET studies. Source organs were delineated on PET/CT. All subjects underwent magnetic resonance imaging (MRI) for obtaining structural information. In vitro autoradiography revealed exquisitely high specific binding of [(18)F]AV-45 to postmortem AD brain sections, but not to the control sections. There were no serious adverse events throughout the study period. The peak uptake of the tracer in the brain was 5.12+/-0.41% of the injected dose. The highest absorbed organ dose was to the gallbladder wall (184.7+/-78.6 microGy/MBq, 4.8 h voiding interval). The effective dose equivalent and effective dose values for [(18)F]AV-45 were 33.8+/-3.4 microSv/MBq and 19.3+/-1.3 microSv/MBq, respectively. [(18)F]AV-45 binds specifically to A beta in vitro, and is a safe PET tracer for studying A beta distribution in human brain. The dosimetry is suitable for clinical and research application.

Environmental impact and natural hazards on Kharga Oasis monumental sites, Western Desert of Egypt

Kharga Oasis monumental sites are important to the cultural heritage in the South Western Desert of Egypt. These sites are scattered on the floor of the oasis representing ancient civilizations. The studied sites include the Hibis, EI-Nadura, EI-Ghueita and El-Zayyan temples as well as El-Bagawat Cemetery. The present study found that natural hazards have remarkable impacts on these sites. The impact of weathering processes, encroachment of sand dunes, stability of foundation beds and shallow groundwater seepage were documented. The present study found that humidity, temperature, sunlight and water content conditions seem to be favorable for biodegradation as evidenced by the presence of algae, bat blood and bird excretions. The radioactivity levels at the investigated sites are also measured via gamma-ray spectrometry. Sand dunes in the area pose a serious natural threat to the monumental sites. Active sand dunes are rapidly encroaching upon the components of these monuments, partially covering some monuments such as El-Ghueita Temple. These dunes load wind storms with fine sand particles. This causes wind erosion through sand blasting of these sites. Some monuments, such as EI-Nadura, EI-Ghueita and El-Zayyan temples were constructed on a suitable hard sandstone ground, whereas others, such as the Hibis Temple, were constructed on unsuitable soft shale ground in relatively topographically low area. The impact of the unstable foundation and shallow groundwater levels have caused severe structural damage as evidenced by tilted columns, cracked walls and salt-crystal growth in the porous building stones. These destructive elements threaten some other temples in Kharga Oasis and will eventually cause total physical collapse. Although rain is rare in this area, it can form a real threat to mud brick monuments such as El-Bagawat Cemetery. The natural radioactivity sources resulted in an annual effective dose equivalent values averaging 0.20, 0.13, 0.09 and 0.07 mSv/year for the monumental sites at Hibis, El-Nadura, El-Ghueita and El-Zayyan, respectively.