A comprehensive Monte Carlo simulation of the neutron response of multi-element microdosimetric detectors based on THick Gas Electron Multiplier.

We present comprehensive Monte Carlo simulations for the neutron response of the multi-element microdosimetric detector based on THick Gas Electron Multiplier (THGEM). Simulations were carried out using the MCNP6.2 code to calculate the deposited energy spectrum in the gaseous sensitive volumes for three different configurations, 7 × 3, 19 × 5, 37 × 7 that occupy a cylindrical volume of 5-cm diameter by 5-cm length. The energy response was computed from 10 keV to 2 MeV. The response variation was investigated between sensitive volumes as well as between layers. The simulated energy response showed a good agreement against the evaluated fluence-to-kerma conversion coefficients in the energy region 10-100 keV, whereas discrepancies were observed in the region above 250 keV. The angular response simulations showed a variation of less than 10%.

Eye lens dosimetry in Canadian CANDU nuclear power plants based on operational dosimetric quantities Hp(10) and Hp(0.07).

In this article, we present a methodology for performing eye lens dosimetry in CANDU nuclear power plants using an existing and highly accurate Harshaw 4-element TLD-700 dosemeter. This dosemeter, which has been specially designed for Ontario Power Generation (OPG) and Bruce Power (BP), measures the deep and shallow personal dose equivalent quantities Hp(10) and Hp(0.07), respectively. Using these measured personal dose equivalent quantities and applying a beta-ray strength scaling factor to the Hp(0.07) measurement in particular, we have developed an algorithm that can be used to calculate the dose to the lens of the eye in mixed beta-gamma fields. This scaling factor has been developed and is primarily based on results obtained from extensive collaborative study, performed by Ontario Power Generation (OPG), Bruce Power (BP) and McMaster University, through Candu Owners Group (COG) support (Bohra et al., 2021; Laranjeiro et al., 2020). Furthermore, scaling factor F, also includes effects of protective glass eyewear and results from Whole body dosimetry intercomparison exercises. The algorithm to calculate eye lens dose at CANDU power plants has been developed, based on this scaling factor and operational dosimetric quantities Hp(10) and Hp(0.07).

Sympathetic predominance before tourniquet deflation is associated with a reduction in arterial blood pressure after tourniquet deflation during total knee arthroplasty.

High dependency of arterial blood pressure (ABP) on enhanced sympathetic activity, which maintains vascular tone, leads to hypotension after hemodynamic insults that blunt the sympathetic activity. Therefore, we hypothesized that sympathovagal balance before tourniquet deflation (TD) determines the extent of a reduction in ABP after TD during total knee arthroplasty (TKA). Fifty-four hypertensive female patients undergoing TKA under spinal anesthesia were analyzed. The sympathovagal balance [low-to-high frequency ratio of heart rate variability (LF/HF)] before TD was defined as (LF/HF during 5 min before TD-preanesthetic LF/HF)/preanesthetic LF/HF (%). An increase in its value represents a shift in sympathovagal balance toward sympathetic predominance. The percent change in the mean ABP (MAP) after TD was defined as (minimum MAP during 10 min after TD-averaged MAP during 5 min before TD)/averaged MAP during 5 min before TD (%). Simple linear regression was performed to assess the correlation between the sympathovagal balance before TD and change in MAP after TD. The correlation was also assessed by multiple linear regression controlling for age, duration of tourniquet inflation, and spinal anesthesia-induced hypotension. Thirty-two minutes (on average) after tourniquet inflation, the MAP was decreased by 12.1 (-3.0 to 47.9) % [mean (range)] upon TD (P<0.001). The sympathovagal balance before TD was negatively proportional to the change in MAP after TD in both simple and multiple linear regression models (R2=0.323 and 0.340, P<0.001). A shift in sympathovagal balance toward sympathetic predominance before TD is associated with a decrease in ABP after TD.

Quantification of pure beta spectra in mixed beta gamma fields as part of eye lens dosimetry at CANDU power plants.

To address the issue of eye lens dosimetry in nuclear industry, we initiated the project to quantify the beta and gamma-ray source term in CANDU power plants and to convert this source term into dosimetric quantities of interest, such as eye lens dose and personal dose equivalents Hp(10), Hp(0.07). This way, the eye lens dose can be compared with dosimetric operational quantities to evaluate whether independent dosimetry is required for eye lens protection, or present dosimetry is adequate.

Increased risk of chronic otitis media in chronic rhinosinusitis patients: a longitudinal follow-up study using a national health screening cohort.

BACKGROUND: Chronic rhinosinusitis (CRS) and chronic otitis media (COM) share pathophysiological mechanisms such as bacterial infection, biofilm, and persistence of the obstruction state of ventilation routes. However, only a few studies have investigated the relationship between these two diseases nationwide and in the general population. The purpose of this study was to determine whether the incidence of COM in patients with CRS differed from that of a matched control from the national health screening cohort. METHODS: Data from the Korean Health Insurance Review and Assessment Service-National Patient Samples were collected from 2002 to 2015. Participants who were treated ≥ ≥ ≥2 times and underwent head and neck computed tomography evaluation were selected. A 1:4 matched CRS group (n=8,057) and a control group (n=32,228) were selected. The control group included participants who were never treated with the ICD-10 code J32 from 2002 to 2015. The CRS group included CRS patients with/without nasal polyps. RESULTS: The incidence of COM was significantly higher in the CRS group than in the control group. In a subgroup analysis, the incidence of COM in all age groups and in men and women was significantly higher in the CRS group than in the control group. More, CRS increased the risk of COM. CONCLUSIONS: A significant association was observed between CRS and COM. This indicates that CRS patients have a high risk of developing COM.

CHARACTERIZATION OF A LANTHANUM BROMIDE DETECTOR FOR EYE LENS DOSIMETRY AT THE CANDU NUCLEAR POWER PLANTS BASED ON DIRECT MEASUREMENTS OF THE GAMMA-RAY SPECTRA.

Gamma-ray spectra were measured using a LaBr$_{3}$(Ce) spectrometer during the outage periods, aiming at quantifying the gamma source term of radiation workers' exposure, at the CANDU nuclear power reactors, for the purposes of eye lens dosimetry. The spectra were measured inside the boiler rooms, of the Bruce Power and Ontario Power Generation (OPG) CANDU nuclear power plants, where workers are exposed to relatively high dose rates radiation fields during the maintenance work. Prior to measurements at the CANDU reactors, the pulse shaping parameters of the gamma spectrometer were optimised for high rates gamma fields, up to an input rates of 120 kcps, in order to accomplish a high output rate with a reasonable energy resolution. In parallel, the response of the LaBr$_{3}$(Ce) detector was characterized by experiments and Monte Carlo simulations. The gamma spectra measured at the CANDU reactors were reported in terms of the gamma-ray fluence rate spectrum. In all measured data, $^{60}$Co and $^{95}$Nb were main contributors of the gamma fields. The measured spectra have been used to calculate the dosimetric quantities of interest: personal dose equivalents H$_{p}$(10) and H$_{p}$(0.07) and eye lens absorbed dose.

Optimization of a Neutron Long Counter Design by Monte Carlo Simulation.

In a search to optimize neutron long counter design for overall efficiency and flat energy response, Monte Carlo simulations were carried out for a variety of detector design parameters using the Monte Carlo N-Particle Extended code. Based on the standard long counter design by McTaggart, moderator diameter, moderator back length, and longitudinal hole diameter were sequentially varied, and the sensitivity of each parameter to the long counter response was systematically analyzed. For each design, simulations were done in the neutron energy range of 1 keV to 10 MeV. From the simulation results, it turned out that out of the three moderator parameters, the moderator diameter is most sensitive for optimizing the long counter response. As the last design parameter, the effect of the central slow-neutron counter was investigated, which showed a significant difference in the response. The investigation of each design parameter gave clear insight on its effect on the long counter response and enabled one to determine the optimum condition.

Shift in Sympathovagal Balance Toward Parasympathetic Predominance Is Associated With Attenuation of Portal Hyperperfusion in Cirrhotic Recipients Undergoing Living Donor Liver Transplant.

BACKGROUND: The autonomic innervation to a liver graft remains lost up to 1 year after liver transplant. Therefore, we investigated the effects of recipients' autonomic nervous activity on the extent of portal hyperperfusion of a partial liver graft in the absence of the autonomic innervation. METHODS: A total of 31 cirrhotic recipients undergoing right lobe living donor liver transplant were analyzed. Following a 10-minute absence of surgical stimulation after hepatic artery and bile duct reconstruction, the electrocardiogram and blood pressure waveforms were recorded for 5 minutes. Low-frequency (LF) and high-frequency (HF) powers and their ratio (LF/HF) were calculated using fast Fourier transform from the electrocardiogram waveform. A decrease in LF/HF represents a shift in sympathovagal balance toward parasympathetic predominance. Then, portal venous (PVF) and hepatic arterial (HAF) blood flows were measured in mL/min per 100 g of liver weight using spectral Doppler ultrasonography. A decrease in their ratio (PVF/HAF) represents attenuation of portal hyperperfusion. RESULTS: The medians of the PVF and HAF were 349 and 27 mL/min/100 g liver weight with interquartile ranges of 272 to 617 mL/min/100 g liver weight and 22 to 41 mL/min/100 g liver weight, respectively, yielding a median of the PVF/HAF of 13.7 (interquartile range, 8.5-21.3). The median of LF/HF was 0.67 (interquartile range, 0.16-1.45). With a reduction in LF/HF, PVF/HAF decreased according to an S-curve regression model between them (PVF/HAF=e2.743+-0.031LF/HF,adjustedR2=0.129,P=0.027). CONCLUSION: A shift in sympathovagal balance toward parasympathetic predominance is associated with attenuation of portal hyperperfusion in a partial liver graft.

Long-term Follow-up of Complicated Crown Fracture With Fragment Reattachment: Two Case Reports.

Two cases of complicated crown fracture of the maxillary incisors were restored using the fragment reattachment technique. Root canal treatment was performed, and the fractured fragment was bonded to the tooth structure using a dentin adhesive system and a flowable composite resin, followed by the insertion of a fiber post using dual-cured resin cement. Reattached fragments have shown reliable prognosis without inflammatory signs around bonded junctions after long-term follow-up.

NEUDOSE: A CubeSat Mission for Dosimetry of Charged Particles and Neutrons in Low-Earth Orbit.

During space missions, astronauts are exposed to a stream of energetic and highly ionizing radiation particles that can suppress immune system function, increase cancer risks and even induce acute radiation syndrome if the exposure is large enough. As human exploration goals shift from missions in low-Earth orbit (LEO) to long-duration interplanetary missions, radiation protection remains one of the key technological issues that must be resolved. In this work, we introduce the NEUtron DOSimetry & Exploration (NEUDOSE) CubeSat mission, which will provide new measurements of dose and space radiation quality factors to improve the accuracy of cancer risk projections for current and future space missions. The primary objective of the NEUDOSE CubeSat is to map the in situ lineal energy spectra produced by charged particles and neutrons in LEO where most of the preparatory activities for future interplanetary missions are currently taking place. To perform these measurements, the NEUDOSE CubeSat is equipped with the Charged & Neutral Particle Tissue Equivalent Proportional Counter (CNP-TEPC), an advanced radiation monitoring instrument that uses active coincidence techniques to separate the interactions of charged particles and neutrons in real time. The NEUDOSE CubeSat, currently under development at McMaster University, provides a modern approach to test the CNP-TEPC instrument directly in the unique environment of outer space while simultaneously collecting new georeferenced lineal energy spectra of the radiation environment in LEO.

In vivo neutron activation study of the short-term kinetic behaviour of sodium and chlorine in the human hand.

The time-dependent behaviour of sodium and chlorine was studied as a spinoff from a study of aluminum in the hand of subjects suffering from Alzheimer's disease and a control group, involving 15 Alzheimer's and 16 control subjects with an age range of 63-89 years. This was achieved using the in vivo neutron activation analysis system developed at McMaster University for the non-invasive measurement of aluminum, where a subject's hand is placed in a beam of accelerator-based thermalized neutrons, which activates elements by neutron capture. Following irradiation, the subject's hand is placed in a detection system comprising 9 NaI(Tl) detectors arranged in a 4π geometry to measure activated elements. The redistribution half-lives of the activation products 24Na and 38Cl from the hand were determined after correction for the physical half-life, by means of sequential analysis of the residual activity in the hand. The kinetic behaviours of sodium and chlorine were best characterized by an exponential function corresponding to the rapidly exchangeable pool. The mean redistribution half-lives from the hand for sodium and chlorine in the control subjects were 40.5 ± 17.4 min and 24.2 ± 8.5 min, respectively. For Alzheimer's disease subjects the mean redistribution half-lives were 58.2 ± 36.1 min for sodium and 33.6 ± 16.7 min for chlorine. There was no significant difference in chlorine and sodium redistribution half-lives between the Alzheimer's disease and control group subjects. These results are promising, given that the irradiation and counting protocol were optimized for the aluminum study, rendering them suboptimal for analyzing other elements and their rate of change with time. Further improvements include optimizing the irradiation protocol, longer counting times, and measuring the activity in the un-irradiated hand in various time intervals following irradiation.

Optimization of data analysis for the in vivo neutron activation analysis of aluminum in bone.

An existing system at McMaster University has been used for the in vivo measurement of aluminum in human bone. Precise and detailed analysis approaches are necessary to determine the aluminum concentration because of the low levels of aluminum found in the bone and the challenges associated with its detection. Phantoms resembling the composition of the human hand with varying concentrations of aluminum were made for testing the system prior to the application to human studies. A spectral decomposition model and a photopeak fitting model involving the inverse-variance weighted mean and a time-dependent analysis were explored to analyze the results and determine the model with the best performance and lowest minimum detection limit. The results showed that the spectral decomposition and the photopeak fitting model with the inverse-variance weighted mean both provided better results compared to the other methods tested. The spectral decomposition method resulted in a marginally lower detection limit (5µg Al/g Ca) compared to the inverse-variance weighted mean (5.2µg Al/g Ca), rendering both equally applicable to human measurements.

Surgical management of damaged inferior alveolar nerve caused by endodontic overfilling of calcium hydroxide paste.

AIM: To evaluate the neurosensory outcome of management of damaged inferior alveolar nerves caused by endodontic overfilling and to assess the efficacy of delayed surgical intervention. METHODOLOGY: Nine patients who underwent surgical removal of extruded endodontic material were included. All patients were evaluated for neurosensory function using a set of standardized tests. The outcome of surgical intervention was evaluated through patient interview and quantitative statistical analysis. RESULTS: Surgical procedures included foreign body removal, microsurgical external/internal decompression, excision of neuroma followed by nerve repair, and excision of damaged nerve segment with interpositional nerve graft. Seven of the nine patients had significant improvement according to the follow-up neurosensory assessment. Four patients reported significant improvement, three patients reported mild improvement and two patients reported no appreciable improvement in the Visual Analog Scale (VAS). Two patients who reported no appreciable improvement in VAS also did not achieve FSR. In these patients, calcium hydroxide was spread widely along the IAN and a surgical approach was obtained via sagittal spit osteotomy. The mean time to reach FSR was 222.7 (±41.8) days with a range of 106-397 days. In the early repair group who received surgery within 60 days, three out of five patients achieved FSR in a mean time of 198.0 (±76.2) days. The mean time to FSR in all four subjects who received surgical attention over 60 days after injury was 241.3 (±139.8) days with a range of 106-397 days. As all four cases in the late repair group with limited amount of nerve injury achieved FSR, only 3 of 5 early repair cases with wide-spread injury achieved a similar outcome. CONCLUSION: The results of this case series confirmed the notion that surgical management of the inferior alveolar nerve is effective in the treatment of nerve injuries caused by endodontic extrusion of calcium hydroxide paste. Delayed surgical repair of the inferior alveolar nerve can be indicated and helpful for the neurosensory recovery of damaged IAN, however, the surgical management was less effective in case of widespread nerve injuries.

COMPREHENSIVE RADIATION DOSE MEASUREMENTS AND MONTE CARLO SIMULATION FOR THE 7Li(p,n) ACCELERATOR NEUTRON FIELD.

In order to investigate the radiation dose dependence on the incident proton energy, neutron and gamma-ray doses were measured using a tissue-equivalent proportional counter in the proton energy range of 1.95-2.50 MeV for the McMaster 7Li(p,n) neutron facility. Microdosimetric spectra were collected, and absorbed doses were determined at various positions inside the irradiation cavity, along the lateral axis and outside the shield to find out the spatial distributions of neutron and gamma-ray doses for each proton energy. In parallel with the absorbed dose measurements, MCNP Monte Carlo simulations were carried out and neutron fluence spectra were computed at various positions, which enabled determination of the neutron weighting factors. It was found that neutrons make a substantially dominant contribution to the total equivalent dose for most proton energies and positions. The effective dose for a human subject increased from 0.058 to 1.306 µSv µA-1 min-1 with the increase of proton energy from 1.95 to 2.5 MeV. It is expected that the reported data will be useful for 7Li(p,n) accelerator neutron users.

Polymorphisms in the promoter regions of the CXCL1 and CXCL2 genes contribute to increased risk of alopecia areata in the Korean population.

Alopecia areata (AA) is a common disease, which causes hair loss in humans. AA has a genetically complex inheritance. This study investigated the possible correlations between single nucleotide polymorphisms (SNPs) in the promoter regions of the chemokine (C-X-C motif) ligand 1 (melanoma growth stimulating activity, alpha) (CXCL1) and chemokine (C-X-C motif) ligand 2 (CXCL2) genes and the development of AA in the Korean population. Two hundred and thirty-five AA patients and 240 control subjects were recruited. The specific SNPs occurring in the promoter regions of the CXCL1 and CXCL2 genes (rs3117604, -429C/T and rs3806792, -264T/C, respectively) were genotyped. All data obtained was evaluated using the SNPStats, SPSS 18.0, and the Haploview v.4.2 software platforms. The Odd's ratios (OR), 95% confidence intervals (CI), and P values were calculated using multiple logistic regression models. Analyses of the genetic sequences obtained revealed a significant correlation between the two SNPs and the development of AA (rs3117604, P = 0.0009 in co-dominant model 1, P = 0.01 in co-dominant model 2, P = 0.004 in the dominant model, P = 0.005 in the log-additive model, P = 0.012 in allele distribution; rs3806792, P = 0.036 in co-dominant model 2, P = 0.0046 in the log-additive model). The TT and CC haplotypes were also observed to show a significant association with increased risk of AA (TT haplotype, P = 0.0018; CC haplotype, P = 0.0349). Our data suggests that the CXCL1 and CXCL2 genes may be associated with AA susceptibility.

Feasibility of measuring selenium in humans using in vivo neutron activation analysis.

Selenium (Se) is an element that, in trace quantities, plays an important role in the normal function of a number of biological processes in humans. Many studies have demonstrated that selenium deficiency in the body may contribute to an increased risk for certain neoplastic, cardiovascular, osseous, and nervous system diseases including retardation of bone formation. However, at higher concentrations Se is cytotoxic. For these reasons it is desirable to have a means of monitoring selenium concentration in humans.This paper presents the outcome of a feasibility study carried out for measuring selenium in humans using in vivo neutron activation analysis (IVNAA). In this technique a small dose of neutrons is delivered to the organ of interest, the neutrons are readily captured by the target nuclei, and the γ-rays given off are detected outside of the body. For the present study, human hand (bone) tissue equivalent phantoms were prepared with varying amounts of Se. These were irradiated by a low energy fast neutron beam produced by the (7)Li(p,n)(7)Be reaction employing the high beam current Tandetron accelerator. The counting data saved using a 4π NaI(TI) detection system were analyzed. The selenium was detected via the neutron capture reaction, (76)Se(n,γ)(77 m)Se, whereas calcium was detected through the (48)Ca(n,γ)(49)Ca reaction for the purpose of normalization of the Se signals to the calcium signals. From the calibration lines drawn between Se/Ca concentrations and Se/Ca counts ratio, the minimum detection limits (MDLs) were computed for two sets of phantoms irradiated under different irradiation parameters.In this study the optimized MDL value was determined to be 81 ng g(-1) (Se/phantom mass) for an equivalent dose of 188 mSv to the phantom. This MDL was found at least 10 times lower than the reported data on Se concentration measured in bone tissues. It was concluded that the NAA technique would be a feasible means of performing in vivo measurements of selenium in humans. Currently the data on in vivo measurement of selenium in humans are limited; the results of the present study would greatly contribute to the present data.

A neutron activation technique for manganese measurements in humans.

Manganese (Mn) is an essential element for humans, animals, and plants and is required for growth, development, and maintenance of health. Studies show that Mn metabolism is similar to that of iron, therefore, increased Mn levels in humans could interfere with the absorption of dietary iron leading to anemia. Also, excess exposure to Mn dust, leads to nervous system disorders similar to Parkinson's disease. Higher exposure to Mn is essentially related to industrial pollution. Thus, there is a benefit in developing a clean non-invasive technique for monitoring such increased levels of Mn in order to understand the risk of disease and development of appropriate treatments. To this end, the feasibility of Mn measurements with their minimum detection limits (MDL) has been reported earlier from the McMaster group. This work presents improvement to Mn assessment using an upgraded system and optimized times of irradiation and counting for induced gamma activity of Mn. The technique utilizes the high proton current Tandetron accelerator producing neutrons via the (7)Li(p,n)(7)Be reaction at McMaster University and an array of nine NaI (Tl) detectors in a 4 π geometry for delayed counting of gamma rays. The neutron irradiation of a set of phantoms was performed with protocols having different proton energy, current and time of irradiation. The improved MDLs estimated using the upgraded set up and constrained timings are reported as 0.67 µgMn/gCa for 2.3 MeV protons and 0.71 µgMn/gCa for 2.0 MeV protons. These are a factor of about 2.3 times better than previous measurements done at McMaster University using the in vivo set-up. Also, because of lower dose-equivalent and a relatively close MDL, the combination of: 2.0 MeV; 300 µA; 3 min protocol is recommended as compared to 2.3 MeV; 400 µA; 45 s protocol for further measurements of Mn in vivo.

The feasibility of in vivo quantification of bone-fluorine in humans by delayed neutron activation analysis: a pilot study.

Fluorine (F) plays an important role in dental health and bone formation. Many studies have shown that excess fluoride (F(-)) can result in dental or skeletal fluorosis, while other studies have indicated that a proper dosage of fluoride may have a protective effect on bone fracture incidence. Fluorine is stored almost completely in the skeleton making bone an ideal site for measurement to assess long-term exposure. This paper outlines a feasibility study of a technique to measure bone-fluorine non-invasively in the human hand using in vivo neutron activation analysis (IVNAA) via the (19)F(n,γ)(20)F reaction. Irradiations were performed using the Tandetron accelerator at McMaster University. Eight NaI(Tl) detectors arranged in a 4π geometry were employed for delayed counting of the emitted 1.63 MeV gamma ray. The short 11 s half-life of (20)F presents a difficult and unique practical challenge in terms of patient irradiation and subsequent detection. We have employed two simultaneous timing methods to determine the fluorine sensitivity by eliminating the interference of the 1.64 MeV gamma ray from the (37)Cl(n,γ)(38)Cl reaction. The timing method consisted of three counting periods: an initial 30 s (sum of three 10 s periods) count period for F, followed by a 120 s decay period, and a subsequent 300 s count period to obtain information pertaining to Ca and Cl. The phantom minimum detectable limit (M(DL)) determined by this method was 0.96 mg F/g Ca. The M(DL) was improved by dividing the initial timing period into three equal segments (10 s each) and combining the results using inverse variance weighting. This resulted in a phantom M(DL) of 0.66 mg F/g Ca. These detection limits are comparable to ex vivo results for various bones in the adult skeleton reported in the literature. Dosimetry was performed for these irradiation conditions. The equivalent dose for each phantom measurement was determined to be 30 mSv. The effective dose was however low, 35 µSv, which is comparable to other clinical diagnostic tools. The M(DL), relatively low radiation dose and non-invasiveness indicate the suitability of this method for routine in vivo analysis of bone-fluorine content. This prompted us to perform a trial study in human subjects. A preliminary human study on 34 participants was completed, with 33 of the 34 measurements proving to be successful. The in vivo M(DL) based on the improved timing method was determined to be 0.69 mg F/g Ca for the 33 successful human measurements. In our opinion, this technique has been demonstrated to be a suitable method for in vivo assessment of fluorine bone-burden.

The feasibility of in vivo detection of gadolinium by prompt gamma neutron activation analysis following gadolinium-based contrast-enhanced MRI.

The feasibility of using the McMaster University in vivo prompt gamma neutron activation analysis system for the detection of gadolinium has been investigated. Phantoms have been developed for the kidney, liver, and the leg muscle. The initial detection limits are determined to be 7.2 ± 0.3 ppm for the kidney, 3.0 ± 0.1 ppm for the liver, and 2.33 ± 0.08 ppm for the lower leg muscle. A few system optimizations have been tested and show significant detection limit reduction from these initial values. The technique is promising and shows feasibility for in vivo studies of gadolinium retention.

In vivo assessment of magnesium status in human body using accelerator-based neutron activation measurement of hands: a pilot study.

Magnesium (Mg) is an element essential for many enzymatic reactions in the human body. Various human and animal studies suggest that changes in Mg status are linked to diseases such as cardiac arrhythmia, coronary heart disease, hypertension, premenstrual syndrome, and diabetes mellitus. Thus, knowledge of Mg levels in the human body is needed. A direct measurement of human blood serum, which contains only 0.3% of the total body Mg, is generally used to infer information about the status of Mg in the body. However, in many clinical situations, Mg stored in large levels, for example in bones, muscles, and soft tissues, needs to be monitored either to evaluate the efficacy of a treatment or to study the progression of diseases associated with the deficiency of total body Mg. This work presents a feasibility study of a noninvasive, in vivo neutron activation analysis (IVNAA) technique using the 26Mg (n, gamma) 27Mg reaction to measure Mg levels in human hands. The technique employs the McMaster University high beam current Tandetron accelerator hand irradiation facility and an array of eight NaI (T1) detectors arranged in a 4 pi geometry for delayed counting of the 0.844 and 1.014 MeV gamma rays emitted when 27Mg decays in the irradiated hand. Mg determination in humans using IVNAA of hands has been demonstrated to be feasible, with effective doses as low as one-quarter of those delivered in chest x rays. The overall experimental uncertainty in the measurements is estimated to be approximately 5% (1 sigma). The results are found to be in the range of the in vitro measurements reported for other cortical bones collected from different sites of the human skeleton, which confirms that this technique mainly provides a measure of the amount of Mg in hand bones. The average concentration of Mg determined in human hands is 10.96 +/- 1.25 (+/- 1 SD) mg Mg/g Ca. The coefficient of variation (11%) observed in this study is comparable with or lower than several studies using in vitro measurements reported in the literature and therefore allows for a quantitative intersubject comparison, even if to a limited extent. The features of the developed technique such as its simplicity, rapidity, accuracy, robustness, noninvasive nature, and very effective use of radiation doses, present the technique as a viable diagnostic tool available for trial in a clinical environment.