Superior Li+ Kinetics by "Low-Activity-Solvent" Engineering for Stable Lithium Metal Batteries.

The structure of solvated Li+ has a significant influence on the electrolyte/electrode interphase (EEI) components and desolvation energy barrier, which are two key factors in determining the Li+ diffusion kinetics in lithium metal batteries. Herein, the "solvent activity" concept is proposed to quantitatively describe the correlation between the electrolyte elements and the structure of solvated Li+. Through fitting the correlation of the electrode potential and solvent concentration, we suggest a "low-activity-solvent" electrolyte (LASE) system for deriving a stable inorganic-rich EEI. Nano LiF particles, as a model, were used to capture free solvent molecules for the formation of a LASE system. This advanced LASE not only exhibits outstanding antidendrite growth behavior but also delivers an impressive performance in Li/LiNi0.8Co0.1Mn0.1O2 cells (a capacity of 169 mAh g-1 after 250 cycles at 0.5 C).

One-tenth-activity total-body positron emission tomography versus full-activity imaging in patients with a complex of hepatic malignant tumors: a retrospective study.

Background: The value of ultra-low-activity 2-[18F]-fluoro-2-deoxy-D-glucose (18F-FDG) positron emission tomography (PET) imaging in patients with hepatic malignancies remains unclear. Methods: A cross-sectional study was conducted from April 2019 to May 2021 in Zhongshan Hospital, Fudan University. A total of 49 patients with hepatic malignancies, including hepatocellular carcinoma (HCC) (n=13) or intrahepatic cholangiocarcinoma (ICC) (n=36), underwent 60-min dynamic PET imaging, with 15 undergoing full-activity 18F-FDG and 34 undergoing ultra-low-activity 18F-FDG. The kinetic metrics (K1-k3, and Ki) of tumors were calculated and compared between the activity groups. Another 54 patients (27 each group) with hepatic malignancies, including HCC (n=9), ICC (n=34), and metastases (n=11), underwent static imaging. Image qualities were compared between the groups in terms of 5-point Likert scores (with a score ≥3 fulfilling the clinical requirement), the mean standardized uptake value (SUVmean), the standard deviation of standardized uptake value (SUVSD), and the signal-to-noise ratio (SNR) of the liver; the SUVmean of blood pool and muscle; and the tumor-to-liver ratio (TLR), tumor-to-blood ratio (TBR), and tumor-to-muscle ratio (TMR) of lesions. Intergroup comparisons were performed using Chi-squared test for categorical variables and the Student's t-test or the Mann-Whitney test for continuous variables depending on the normality of variables. Results: There was a nonsignificant difference in the kinetic metrics (K1-k3 and Ki) of tumors between the activity groups. In static imaging, 1-min full-activity (F1) and 8-min ultra-low-activity (L8) images obtained image-quality scores >3 and were thus selected for intergroup comparisons. Nonsignificant differences in SUVmean of liver, blood pool, and muscle were identified between F1 and L8 images (P=0.641, P=0.542, and P=0.073, respectively) although the liver SNR was slightly higher in F1 (13.10 vs. 11.31; P=0.003). Lesion detectability was 98.5% and 100% for F1 and L8 images, respectively, but there were no significant differences in TLR, TBR, or TMR between the groups. Conclusions: The results of this single-center study indicate that the performance of ultra-low-activity PET imaging is comparable to that of full-activity imaging in patients with hepatic malignancies.

Does expert opinion match the definition of lupus low disease activity state? Prospective analysis of 500 patients from a Spanish multicentre cohort.

OBJECTIVES: To apply the lupus low disease activity state (LLDAS) definition within a large cohort of patients and to assess the agreement between the LLDAS and the physician's subjective evaluation of lupus activity. METHODS: We conducted a cross-sectional analysis of a prospective multicentre study of SLE patients. We applied the LLDAS and assessed whether there was agreement with the clinical status according to the physician's opinion. RESULTS: A total of 508 patients [92% women; mean age 50.4 years (s.d. 3.7)] were recruited and 304 (62.7%) patients were in the LLDAS. According to physician assessment, 430 (86.1%) patients were classified as remission or low activity. Overall agreement between both evaluations was 71.4% (95% CI: 70.1, 70.5) with a Cohen's κ of 0.3 [interquartile range (IQR) 0.22-0.37]. Most cases (96.1%) in the LLDAS were classified as remission or low activity by the expert. Of the patients who did not fulfil the LLDAS, 126 (70.4%) were classified as having remission/low disease activity. The main reasons for these discrepancies were the presence of new manifestations compared with the previous visit and a SLEDAI 2K score >4, mainly based on serological activity. CONCLUSIONS: Almost two-thirds of SLE patients were in the LLDAS. There was a fair correlation between the LLDAS and the physician's evaluation. This agreement improves for patients fulfilling the LLDAS criteria. The discordance between both at defining lupus low activity, the demonstrated association of the LLDAS with better outcomes and the fact that the LLDAS is more stringent than the physician's opinion imply that we should use the LLDAS as a treat-to-target goal.

Acute quadriplegia and epileptic seizures in a 47-year-old man.

We present a case of a cerebral and spinal infarction caused by paradoxical embolism following traveller's thrombosis in a patient with a low activity of protein S.

Removal of CrO42-, a Nonradioactive Surrogate of 99TcO4-, Using LDH-Mo3S13 Nanosheets.

Removal of chromate (CrO42-) and pertechnetate (TcO4-) from the Hanford Low Activity Waste (LAW) is beneficial as it impacts the cost, life cycle, operational complexity of the Waste Treatment and Immobilization Plant (WTP), and integrity of vitrified glass for nuclear waste disposal. Here, we report the application of [MoIV3S13]2- intercalated layer double hydroxides (LDH-Mo3S13) for the removal of CrO42- as a surrogate for TcO4-, from ppm to ppb levels from water and a simulated LAW off-gas condensate of Hanford's WTP. LDH-Mo3S13 removes CrO42- from the LAW condensate stream, having a pH of 7.5, from ppm (∼9.086 × 104 ppb of Cr6+) to below 1 ppb levels with distribution constant (Kd) values of up to ∼107 mL/g. Analysis of postadsorbed solids indicates that CrO42- removal mainly proceeds by reduction of Cr6+ to Cr3+. This study sets the first example of a metal sulfide intercalated LDH for the removal of CrO42-, as relevant to TcO4-, from the simulated off-gas condensate streams of Hanford's LAW melter which contains highly concentrated competitive anions, namely F-, Cl-, CO32-, NO3-, BO33-, NO2-, SO42-, and B4O72-. LDH-Mo3S13's remarkable removal efficiency makes it a promising sorbent to remediate CrO42-/TcO4- from surface water and an off-gas condensate of nuclear waste.

Exploration of the total-body PET/CT reconstruction protocol with ultra-low 18F-FDG activity over a wide range of patient body mass indices.

PURPOSE: The purpose of this study was to investigate the image quality and diagnostic performance of different reconstructions over a wide range of patient body mass indices (BMIs) obtained by total-body PET/CT with ultra-low 18F-FDG activity (0.37 MBq/kg). METHODS: A total of 63 patients who underwent total-body PET/CT with ultra-low activity (0.37 MBq/kg) 18F-FDG were enrolled. Patients were grouped by their BMIs. Images were reconstructed with the following two algorithms: the ordered subset expectation maximization (OSEM) algorithm (2, 3 iterations), both with time of flight (TOF) and point spread function (PSF) corrections (hereinafter referred as OSEM2, OSEM3) and HYPER Iterative algorithm (ß-values of 0.3, 0.4, 0.5, 0.6) embedded TOF and PSF technologies (hereinafter referred as HYPER0.3, HYPER0.4, HYPER0.5 and HYPER0.6, respectively). Subjective image quality was assessed by two experienced nuclear medicine physicians according to the Likert quintile, including overall image quality, image noise and lesion conspicuity. The standard deviation (SD) and signal-to-noise ratio (SNR) of the liver, and maximum standard uptake value (SUVmax), peak standard uptake value (SUVpeak), tumour background ratio (T/N) and the largest diameter of lesions were quantitatively analysed by a third reader who did not participate in the subjective image assessment. RESULTS: Increased noise was associated with increased BMI in all reconstruction groups. Significant differences occurred in the liver SNR among BMI categories of OSEM reconstructions (P < 0.001) but no difference was seen in the HYPER Iterative reconstructions between any of the BMI categories (P > 0.05). With the increase in BMI, overall image quality and image noise scores decreased significantly in all reconstructions, but there was no statistically significant difference of lesion conspicuity. The overall image quality score of the obese group was not qualified (score = 2.7) in OSEM3, while the others were qualified. The lesion conspicuity scores were significantly higher in HYPER Iterative reconstructions and lower in OSEM2 than in OSEM3 (all P < 0.05). The values of SUVmax, SUVpeak and T/N in HYPER0.3, HYPER0.4 and HYPER0.5 were higher than those in OSEM3. In different reconstructions, there was a correlation between lesion size (median, 1.55 cm; range, 0.7-11.0 cm) and SUVpeak variation rate compared to OSEM3 (r = 0.388, - 0.515, - 0.495, - 0.464, and - 0.423, respectively, and all P < 0.001). CONCLUSION: Considering the image quality and lesion analysis in 18F-FDG total-body PET/CT with ultra-low activity injection, OSEM reconstructions with 3 iterations meet the clinical requirements in patients with BMI < 30. In patients with BMI ≥ 30, it is recommended that the HYPER Iterative algorithm (ß-value of 0.3-0.5) be used to ensure consistent visual image quality and quantitative assessment.

Feasibility of Acquisitions Using Total-Body PET/CT with an Ultra-Low 18F-FDG Activity.

The present study aimed to evaluate the feasibility of ultra-low 18F-FDG activity in total-body PET/CT oncologic studies. Methods: Thirty patients with cancer were enrolled prospectively and underwent a total-body PET/CT scan 60 min after injection of an ultra-low 18F-FDG activity (0.37 MBq/kg). Of the 30 enrolled patients, 11 were diagnosed with colorectal cancer (CRC). PET raw data were acquired within 15 min and reconstructed using data from the first 1, 2, 4, 8, and 10 min and the entire 15 min (G1, G2, G4, G8, G10, and G15, respectively). Image quality was qualitatively assessed twice by 2 readers using a 5-point Likert scale. The Cohen κ-test was used to investigate the intra- and interreader agreement. The SUVmax of lesions; the SUVmax, SUVmean, and SD of the livers; the tumor-to-background ratio; and the signal-to-noise ratio were measured and compared. The acquisition time for a clinically acceptable image quality using an ultra-low-activity injection was determined. In a matched-pair study, 11 patients with CRC who received a full 18F-FDG activity (3.7 MBq/kg) with an acquisition time of 2 min were selected retrospectively by matching sex, height, weight, body mass index, glucose level, uptake time, and pathologic types with the 11 CRC subjects in the prospective study. Qualitative and quantitative analyses were performed and compared between the 11 patients with CRC in the ultra-low-activity group and their matched full-activity controls. Results: Qualitative analysis of image quality showed good intra- and interreader agreements (all κ > 0.7). All the images acquired for 8 min or longer scored over 3 (indicating clinical acceptability). There was no significant difference in tumor-to-background ratio and liver signal-to-noise ratio among all the images acquired for 8 min or longer. In the matched study, no significant difference was found in the image quality score and quantitative parameters between the ultra-low-activity group with an 8-min acquisition and the full-activity group with a 2-min acquisition. Conclusion: An ultra-low 18F-FDG activity with an 8-min acquisition in a total-body PET/CT study can achieve acceptable image quality equivalent to that in the full-activity group after a 2-min acquisition.

Radioactivity and Space Range of Ultra-Low-Activity for in vivo Off-line PET Verification of Proton and Carbon Ion Beam-A Phantom Study.

Purpose: The radioactivity induced by proton and heavy ion beam belongs to the ultra-low-activity (ULA). Therefore, the radioactivity and space range of commercial off-line positron emission tomography (PET) acquisition based on ULA should be evaluated accurately to guarantee the reliability of clinical verification. The purpose of this study is to quantify the radioactivity and space range of off-line PET acquisition by simulating the ULA triggered by proton and heavy ion beam. Methods: PET equipment validation phantom and low activity 18F-FDG were used to simulate the ULA with radioactivity of 11.1-1480 Bq/mL. The radioactivity of ULA was evaluated by comparing the radioactivity in the images with the values calculated from the decay function with a radioactivity error tolerance of 5%. The space range of ULA was evaluated by comparing the width of the R50 analyzed activity distribution curve with the actual width of the container with a space range error tolerance of 4 mm. Results: When radioactivity of ULA was >148 Bq/mL, the radioactivity error was <5%. When radioactivity of ULA was >30 Bq/mL, the space range error was below 4 mm. Conclusions: Off-line PET can be used to quantify the radioactivity of proton and heavy ion beam when the ULA exceeds 148 Bq/mL, both in radioactivity and in space range.

Ultra-low-activity total-body dynamic PET imaging allows equal performance to full-activity PET imaging for investigating kinetic metrics of 18F-FDG in healthy volunteers.

PURPOSE: To investigate the feasibility of ultra-low-activity total-body positron emission tomography (PET) dynamic imaging for quantifying kinetic metrics of 2-[18F]-fluoro-2-deoxy-D-glucose (18F-FDG) in normal organs and to verify its clinical relevance with full-activity imaging. METHODS: Dynamic total-body PET imaging was performed in 20 healthy volunteers, with eight using full activity (3.7 MBq/kg) of 18F-FDG and 12 using 10× activity reduction (0.37 MBq/kg). Image contrast, in terms of liver-to-muscle ratio (LMR), liver-to-blood ratio (LBR), and blood-to-muscle ratio (BMR) of radioactivity concentrations were assessed. A two-tissue compartment model was fitted to the time-to-activity curves in organs based on regions of interest (ROIs) delineation using PMOD, and constant rates (k1, k2, and k3) were generated. Kinetic constants, corresponding coefficients of variance (CoVs), image contrast, radiation dose, prompt counts, and data size were compared between full- and low-activity groups. RESULTS: All constant rates, corresponding CoVs, and image contrast in different organs were comparable with none significant differences between full- and ultra-low-activity groups. PET images in the ultra-low-activity group generated significantly lower effective radiation dose (median, 0.419 vs. 4.886 mSv, P < 0.001), reduced prompt counts (median, 2.79 vs. 55.68 billion, P < 0.001), and smaller data size (median, 71.11 vs. 723.18 GB, P < 0.001). CONCLUSION: Total-body dynamic PET imaging using 10× reduction of injected activity could achieve relevant kinetic metrics of 18F-FDG and comparable image contrast with full-activity imaging. Activity reduction results in significant decrease of radiation dose and data size, rendering it more acceptable and easier for data reconstruction, transmission, and storage for clinical practice.

Whole-Genome Sequencing of Inbred Mouse Strains Selected for High and Low Open-Field Activity.

We conducted whole-genome sequencing of four inbred mouse strains initially selected for high (H1, H2) or low (L1, L2) open-field activity (OFA), and then examined strain distribution patterns for all DNA variants that differed between their BALB/cJ and C57BL/6J parental strains. Next, we assessed genome-wide sharing (3,678,826 variants) both between and within the High and Low Activity strains. Results suggested that about 10% of these DNA variants may be associated with OFA, and clearly demonstrated its polygenic nature. Finally, we conducted bioinformatic analyses of functional genomics data from mouse, rat, and human to refine previously identified quantitative trait loci (QTL) for anxiety-related measures. This combination of sequence analysis and genomic-data integration facilitated refinement of previously intractable QTL findings, and identified possible genes for functional follow-up studies.

Higher-Order Cumulants Drive Neuronal Activity Patterns, Inducing UP-DOWN States in Neural Populations.

A major challenge in neuroscience is to understand the role of the higher-order correlations structure of neuronal populations. The dichotomized Gaussian model (DG) generates spike trains by means of thresholding a multivariate Gaussian random variable. The DG inputs are Gaussian distributed, and thus have no interactions beyond the second order in their inputs; however, they can induce higher-order correlations in the outputs. We propose a combination of analytical and numerical techniques to estimate higher-order, above the second, cumulants of the firing probability distributions. Our findings show that a large amount of pairwise interactions in the inputs can induce the system into two possible regimes, one with low activity ("DOWN state") and another one with high activity ("UP state"), and the appearance of these states is due to a combination between the third- and fourth-order cumulant. This could be part of a mechanism that would help the neural code to upgrade specific information about the stimuli, motivating us to examine the behavior of the critical fluctuations through the Binder cumulant close to the critical point. We show, using the Binder cumulant, that higher-order correlations in the outputs generate a critical neural system that portrays a second-order phase transition.

A Kinetic Study of the Pozzolanic Reaction of Fly Ash, CaO, and Na2O in the Preparation of Fly Ash Belite Cement.

Fly ash belite cement is a kind of low-carbon cement prepared by a two-step process involving hydrothermal synthesis and low-temperature calcination. Pozzolanic reaction pastes, as the precursors of fly ash belite cement prepared by hydrothermal synthesis, are affected mainly by reaction temperature, time, ratios of the mass of fly ash/lime (FA/CA), and the dosage of Na2O. The absorbance rate of CaO with reaction time was tested for all samples, and the reaction kinetic model and parameters of the granule-hydrothermal synthesis method were discussed. A kinetic model for the hydrothermal synthesis in the presence of Na2O was proposed based on the Kondo's modified Jander equation and Arrhenius equation. The activation energy (Ea) of the process was determined to be 67.76 kJ/mol. In addition, with an increasing dosage of Na2O, the pre-exponential factor A of the Arrhenius equation increased. However, the hydrothermal reaction degree was accurately predicted using the kinetic model characterized by the absorption rate of CaO. The results indicated that Na2O, as an alkali activator, facilitated the diffusion of Ca2+ firstly, then partly dissolved the amorphous phase in the mixtures and, finally, accelerated the formation of poorly crystallized hydrates.

Clinical outcomes of low and intermediate risk differentiated thyroid cancer patients treated with 30mCi for ablation or without radioactive iodine therapy

ABSTRACT Objective To retrospectively evaluate the outcomes of patients with low and intermediate risk thyroid carcinoma treated with total thyroidectomy (TT) and who did not undergo radioiodine remnant ablation (RRA) and to compare them to patients receiving low dose of iodine (30 mCi). Subjects and methods A total of 189 differentiated thyroid cancer (DTC) patients treated with TT followed by 30mCi for RRA or not, followed in two referral centers in Brazil were analyzed. Results From the 189 patients, 68.8% was ATA low-risk, 30.6% intermediate and 0.6% high risk. Eighty-seven patients underwent RRA and 102 did not. The RRA groups tended to be younger and had a higher frequency of extra-thyroidal extension (ETE). RRA did not have and impact on response to initial therapy neither in low (p = 0.24) nor in intermediate risk patients (p = 0.66). It also had no impact on final outcome and most patients had no evidence of disease (NED) at final follow-up. Recurrence/persistence of disease was found in 1.2% of RRA group and 2% in patients treated only with TT (p = 0.59). Conclusions Our study shows that in low and intermediate-risk patients, RRA with 30 mCi seems to have no major advantage over patients who did not undergo RRA regarding response to initial therapy in each risk group and also in long term outcomes.

Assessing good operating conditions for intraoperative imaging of melanoma sentinel nodes by a portable gamma camera.

OBJECTIVE: To provide guidance for reliable identification of low-activity sentinel nodes in the setting of melanoma surgery using a commercial hand-held gamma camera. METHODS: The average uptake of (99m)Tc nanocolloid by sentinel nodes was evaluated in 95 excised nodes using a Sentinella 102(®) (Oncovision, Valencia, Spain) portable gamma camera. The device sensitivity was assessed for different source depths and collimator distances, imaging an 8-mm sphere filled with a known-activity solution of (99m)Tc. Five nuclear medicine physicians were asked to identify the source at different activity levels and positions within the field of view. For each image the number of signal counts inside a circular region of interest (ROI) was measured, while the variability of ROI counts among operators was assessed. The number of counts providing a minimal, near-constant inter-operator variability was determined as a criterion for a consistent identification of the source. Either the minimum activity or the acquisition time needed to collect the appropriate statistics were then calculated. RESULTS: The median SN uptake (0.5%) turned out to be compatible with values reported in the literature. The sensitivity of the compact gamma camera ranged from ∼25 cpm/kBq to ∼1 cpm/kBq. A total of 50 counts in the ROI circumscribing the lymph node-simulating sphere appeared to be a robust criterion for identification of the source. CONCLUSIONS: Ten megabecquerels of injected activity at the time of surgery and one minute of acquisition allows reliable identification of sentinel nodes for collimator-to-source distances up to 10 cm.

The interactive effect of MAOA-LPR genotype and childhood physical neglect on aggressive behaviors in Italian male prisoners.

Aggressive disorders are moderately heritable; therefore, identification of genetic influences is important. The X-linked MAOA gene, encoding the MAOA enzyme, has a functional 30 bp repeat polymorphism in the promoter region (MAOA-LPR) that has been shown to influence aggression. Childhood trauma is a known risk factor for numerous psychopathologies in adulthood including aggressive behaviors. We investigated the interactive effect of MAOA-LPR genotype and a history of childhood trauma in predicting aggressive behaviors in a prisoner population. A total of 692 male prisoners were genotyped for MAOA-LPR with genotypes grouped into high and low transcriptional activity. Participant evaluations included measures of aggression (Brown-Goodwin Lifetime History of Aggression, BGHA), hostility (Buss-Durkee Hostility Inventory), impulsivity (Barratt Impulsiveness Scale), violence directed toward self and others, and childhood trauma [Childhood Trauma Questionnaire (CTQ)]. MAOA-LPR interacted with CTQ physical neglect (PN), the most common (47%) form of childhood trauma in this sample, to predict BGHA aggression (P = 0.002). Within the group not exposed to PN, carriers of the MAOA-LPR high-activity variant were more aggressive: (tR = 2.47, P < 0.014). We observed a crossover effect in that the increase in aggression scores with PN was greater in low-activity individuals (tR = 5.55, P < 0.0001) than in high-activity individuals (tR = 4.18, P < 0.0001). These findings suggest that childhood trauma and the functional MAOA-LPR polymorphism may interact to specifically increase risk for over aggressive behavior but not impulsivity or hostility. The MAOA-LPR low-activity variant may be protective against the development of aggressive behavior under low stress conditions, at least in this prisoner population.

PON1 status evaluation in patients with chronic arterial occlusion of lower limbs due to atherosclerosis obliterans.

INTRODUCTION: Human paraoxonase (PON1) is a calcium-dependent enzyme physically associated with HDL, and it is believed to contribute to the atheroprotective effect of HDL. The aim of the study was to evaluate PON1 status in patients with atherosclerosis obliterans as an effect of ischemia regarding its activity and phenotype distribution. MATERIAL AND METHODS: The study group consisted of patients with chronic arterial occlusion of the lower limbs due to atherosclerosis obliterans (AO). The patients were divided into two groups according to the degree of ischemia: moderate (MI), and critical (CI). The ratio of the hydrolysis of salt-stimulated PON1 activity to the hydrolysis of phenylacetate was used to assign individuals to one of three possible phenotypes (low activity - A, medium activity - AB, high activity - B). It was observed that PON1 arylesterase activity was affected by ischemia of the lower limbs depending on its degree. RESULTS: The odds ratio and the relative risk analysis showed that the patients with moderate ischemia are much more often characterized by phenotype A than by phenotype B. The low activity phenotype A occurs over twice as often in patients with chronic ischemia of the lower limbs as in individuals from the control group (OR = 2.125; 1.96 to 3.776, p = 0.0143). CONCLUSIONS: This study presents the low activity phenotype A in relation to the risk of ischemia of the lower limbs due to atherosclerosis and shows the potentially important role of PON1 in conclusion of the process leading to intensification of ischemia degree.

Performance and limitations of positron emission tomography (PET) scanners for imaging very low activity sources.

Emerging applications for positron emission tomography (PET) may require the ability to image very low activity source distributions in the body. The performance of clinical PET scanners in the regime where activity in the field of view is <1 MBq has not previously been explored. In this study, we compared the counting rate performance of two clinical PET/CT scanners, the Siemens Biograph Reveal 16 scanner which is based on lutetium oxyorthosilicate (LSO) detectors and the GE Discovery-ST scanner which is based on bismuth germanate (BGO) detectors using a modified National Electrical Manufacturers Association (NEMA) NU 2-2007 protocol. Across the activity range studied (2-100 kBq/mL in a 5.5 mL line source in the NEMA scatter phantom), the BGO-based scanner significantly outperformed the LSO-based scanner. This was largely due to the effect of background counts emanating from naturally occurring but radioactive (176)Lu within the LSO detector material, which dominates the observed counting rate at the lowest activities. Increasing the lower energy threshold from 350 keV to 425 keV in an attempt to reduce this background did not significantly improve the measured NECR performance. The measured singles rate due to (176)Lu emissions within the scanner energy window was also found to be dependent on temperature, and to be affected by the operation of the CT component, making approaches to correct or compensate for the background more challenging. We conclude that for PET studies in a very low activity range, BGO-based scanners are likely to have better performance because of the lack of significant background.

Optimization of a measurement facility for radioactive waste free release by Monte Carlo simulation.

A novel free release measurement facility (FRMF) was developed within the joint research project "Metrology for Radioactive Waste Management" of the European Metrology Research Programme. Before and during FRMF design and construction, Monte Carlo calculations with MCNPX and PENELOPE codes were used to optimize the thickness of the shielding, the dimensions of the container, and the shape of detector collimators. Validation of the numerical models of the FRMF detectors and the results of the optimization are discussed in the paper.