Exclusion Of Artifacts Research Articles

Potentiostat design keys for analytical applications

In this article the principles of potentiostat designs are discussed. Novel technical solutions for the design of electrochemical devices with a focus on portable applications are considered. Known solutions for analytical potentiostats are discussed, and the functionality of existing devices is analysed. Key points of the discussion include a brief introduction to specific terminology for potentiostat characterization, analysis of schematics, operation principles and requirements for basic units including control amplifier, voltage follower and transimpedance amplifier. Moreover, the substantial functions of potentiostat unit operation and corresponding limitations were described. The reasons for the inevitably high cost of versatile devices, as well as design recommendations for potentiostats, are also discussed. The proposed explanation will be helpful for potentiostats’ comprehensive design and application in analytical practice, for recognition and exclusion of artefacts from experimental data.

Artifact identification in X-ray diffraction data using machine learning methods.

In situ synchrotron high-energy X-ray powder diffraction (XRD) is highly utilized by researchers to analyze the crystallographic structures of materials in functional devices (e.g. battery materials) or in complex sample environments (e.g. diamond anvil cells or syntheses reactors). An atomic structure of a material can be identified by its diffraction pattern along with a detailed analysis of the Rietveld refinement which yields rich information on the structure and the material, such as crystallite size, microstrain and defects. For in situ experiments, a series of XRD images is usually collected on the same sample under different conditions (e.g. adiabatic conditions) yielding different states of matter, or is simply collected continuously as a function of time to track the change of a sample during a chemical or physical process. In situ experiments are usually performed with area detectors and collect images composed of diffraction patterns. For an ideal powder, the diffraction pattern should be a series of concentric Debye-Scherrer rings with evenly distributed intensities in each ring. For a realistic sample, one may observe different characteristics other than the typical ring pattern, such as textures or preferred orientations and single-crystal diffraction spots. Textures or preferred orientations usually have several parts of a ring that are more intense than the rest, whereas single-crystal diffraction spots are localized intense spots owing to diffraction of large crystals, typically >10 µm. In this work, an investigation of machine learning methods is presented for fast and reliable identification and separation of the single-crystal diffraction spots in XRD images. The exclusion of artifacts during an XRD image integration process allows a precise analysis of the powder diffraction rings of interest. When it is trained with small subsets of highly diverse datasets, the gradient boosting method can consistently produce high-accuracy results. The method dramatically decreases the amount of time spent identifying and separating single-crystal diffraction spots in comparison with the conventional method.

P109 The association between sleep microarchitecture and cognitive function in middle-aged and older men: A community-based study

Abstract Introduction Sleep microarchitecture metrics determined by quantitative power spectral analysis (PSA) of the electroencephalogram (EEG) have been proposed as potential biomarkers of cognitive function. However, there remain no data from community-based samples. This study examined cross-sectional associations between sleep microarchitecture metrics determined by PSA and cognitive function outcomes in community-dwelling men. Methods Men, Androgen, Inflammation, Lifestyle, Environment, and Stress (MAILES) study participants (n=477) underwent home-based polysomnography between 2010–2011. All-night EEG recordings were processed using PSA following exclusion of artefacts. MAILES participants also completed the inspection time task, Fuld object memory evaluation, and trail-making test A (TMT-A) and B (TMT-B). Multivariable linear regression models were used to determine the associations of sleep microarchitecture (relative spectral power) with cognitive function in the complete and age-stratified samples. Results Power spectral densities in theta-alpha ranges during NREM and REM sleep were associated with worse TMT-A performance, whereas higher delta density was associated with better TMT-A performance in the complete sample and men ≥65 years (all p<0.05). Similar associations were observed with TMT-B performance in men ≥65 years. Furthermore, in men <65 years, higher sigma density during NREM sleep was associated with faster inspection time (B= -3.14, 95% CI [-6.00, -0.27], p=0.032), whereas in men ≥65 years, higher theta density during NREM sleep was associated with faster inspection time (B = -3.33, 95% CI [-6.65, -0.02], p=0.049). Discussion PSA markers of sleep microarchitecture are independently associated with cognitive function. Longitudinal studies are needed to determine whether sleep microarchitecture metrics predict future cognitive dysfunction and decline.

CERMEP-IDB-MRXFDG: a database of 37 normal adult human brain [18F]FDG PET, T1 and FLAIR MRI, and CT images available for research

We present a database of cerebral PET FDG and anatomical MRI for 37 normal adult human subjects (CERMEP-IDB-MRXFDG). Thirty-nine participants underwent static [18F]FDG PET/CT and MRI, resulting in [18F]FDG PET, T1 MPRAGE MRI, FLAIR MRI, and CT images. Two participants were excluded after visual quality control. We describe the acquisition parameters, the image processing pipeline and provide participants’ individual demographics (mean age 38 ± 11.5 years, range 23–65, 20 women). Volumetric analysis of the 37 T1 MRIs showed results in line with the literature. A leave-one-out assessment of the 37 FDG images using Statistical Parametric Mapping (SPM) yielded a low number of false positives after exclusion of artefacts. The database is stored in three different formats, following the BIDS common specification: (1) DICOM (data not processed), (2) NIFTI (multimodal images coregistered to PET subject space), (3) NIFTI normalized (images normalized to MNI space). Bona fide researchers can request access to the database via a short form.

Detection of muscle artifact epochs using entropy based M-DDTW technique in EEG signals

The exclusion of artifacts plays an indispensable role in the processing of Electroencephalographic (EEG) recordings. This work highlights one such inescapable artifactual event known as muscle artifacts (MA) and its detection methodology. These are high-frequency signals that are recurrently present in EEG and generally recorded via Electromyogram. The paper presents an entropy based Manhattan derivative dynamic time warping (M-DDTW) technique for MA epoch detection. Manhattan (City block) and Canberra distance have been proposed as the distance to be optimized by using them with dynamic time warping (DTW) and derivative dynamic time warping (DDTW) technique. The study reduces the computational time and improves the performance by utilizing entropy for reference generation and identifies the optimal threshold value for each technique. The results for the optimal threshold have been validated on the real EEG dataset. It was observed that the proposed entropy based M-DDTW technique exhibits the highest performance of 90 % and an accuracy of 95 % at an optimal threshold surpassing state of the art techniques. The testing of qualitative performance and time consumption has been done using traditional mode decomposition methods. The proposed Entropy based M-DDTW technique along with EEMD showed a noteworthy performance compared to other techniques. Overall the combination of entropy with time warping based local distance variation appears to be an adequate solution for muscle artifact detection.

Automatic Computer Analysis of Digital Images of Triple-Antibody-Stained Prostate Biopsies

Background: Worldwide, prostatic adenocarcinoma is the most common tumour type among men. Aim: The aim of the present investigation was to develop a computer program to identify normal prostate biopsies and distinguish them from biopsies showing premalignant alterations (LGPIN, HGPIN) and adenocarcinoma. Method: Prostate biopsies (n = 2094) taken from 191 consecutive men during 2016 were stained with triple immunehistochemisty (antibodies to AMACRA, p63 and CK 5). Digital images of the biopsies were obtained with a scanning microscope and used to develop an automatic computer program (CelldaTM), intended to identify the morphological alterations. Visual microscopic finding was used as a reference. Result: Of the 191 men, 121 (63.4%) were diagnosed as having prostate adenocarcinoma and 70 (36.6%) as having no malignancy on the basis of the visual microscopy. In comparison, computer analysis identified 134 (70.2%) men with malignant disease and 57 (29.8%) with non-malignant disease after exclusion of artifacts, which constituted 10.4% of areas (indicated as malignant disease). Discrepant results were recorded in 15 (7.9%) men, and in 14 of these cases, HGPIN and areas suggestive of early invasion were common. Thus, it was uncertain whether these cases should be regarded as malignant or not. The agreement between the visual examination and the computer analysis was 92.1% (kappa value 0.823, sensitivity 99.2 and specificity was 0.80). Conclusion: It seems that computer analysis could serve as an adjunct to simplify and shorten the diagnostic procedure, first of all by ensuring that normal prostate biopsies are sorted out from those sent for visual microscopic evaluation.

Impact of Pathogenic Germ Line Variants in Adults with Acquired Bone Marrow Failure Syndromes Vs. Myeloid Neoplasia

Background. While childhood leukemia and bone marrow failure disorders always raise suspicions of a familial trait, recognition of germ line (GL) contribution to the pathogenesis of adult presentation of these disorders may be difficult because of the absent and unreliable family history, long disease anticipation and incomplete penetrance due to various factors, including competing mortality and interaction with environmental factors. The search for such GL alterations may involve unbiased whole exome sequencing or genome wide analysis studies approaches or, as we conducted here, rely on identification of GL variants in a rationally selected panel of genes previously involved in leukemia and bone marrow failure (BMF). Methods. We hypothesize that, in analogy to pediatric disease, pathogenic GL alterations may exist also in a subset of adult patients with BMF and myeloid neoplasia (MN). Such lesions may contribute to the clinical features and the preferential occurrence of somatic hits leading to disease manifestation. We analyzed genomic data of 350 patients with BMF syndromes (AA, PNH, AA/PNH) and a cohort of 2,827 patients with MN (MDS, MDS/MPN, and AML) disorders. Our analysis included variant calling, stringent exclusion of artifacts and selection of GL variants (GLVs). These were then subjected to a bioanalytic pipeline and classified as tier-1, tier-2 and variants of uncertain significance according to their potential pathogenic importance. Tier-1 was defined as structurally predicted pathogenic mutations with known disease association, frameshift/nonsense mutations and highly recurrent missense mutations with low frequency in the general population. Tier-2 was defined as missense mutations with a high general population frequency (≥.01 but <1%). GL confirmation was performed in 33% of all cases. When we compared BMF vs. MN we found 42 vs. 202 Tier-1 GLVs and 309 vs. 962 Tier-2, respectively. Results. In the BMF cohort, 10% had tier-1 and 44% had tier-2 GLVs. Remarkably, 27 patients (pts) (7%) had concomitant tier-1 and tier-2 mutations in different genes, among those, 5 were biallelic (SBDS, FANCM, BARD1, TERT, PALB2) and the rest were compound heterozygous. When we focused on tier-1 lesions, FA GLVs were most prevalent in this cohort comprising 18/350, including FANCA (n=3), BRCA1 (n=2) BRCA2 (n=2) and 11 other FA gene (affected once). In addition, we found also 60 tier-2 FA gene mutations. Surprisingly, telomerase-associated GLVs fulfilling tier-1 criteria were found only in 7 patients [CTC1 (n=4), TERT, TINF2, and WRAP53 (1 each)] and tier-2 in 18 patients. The rest of the tier-1 GLVs were [NF1 (n=4), SBDS (n=3) SAMD9L (n=2), BARD1, BCOR, BLM, CBLC, CHEK2, MLH1, MRE11A, XRCC3 (1pt each). Further analysis of the BMF cohort assessing disease outcomes revealed that among 40 pts, who progressed to MDS, 25% had tier-1 and 27% had only tier-2 GLVs. Reverse analysis showed that 27% of carriers of tier-1 GLVs progressed to MDS/AML as compared to only 10% of negative cases (P<.01), but no difference was found in terms of the frequency of tier-2 variants. Exclusion of patients with PNH clone did not enrich for the carrier status of GL tier-1/2 variants. No specific variants were associated with the PNH clone or the highly expanded PNH clone (manifest PNH). Adult MN was used as a comparative cohort: 7% of cases had tier-1 GLVs, while tier-2 were present in 25% of cases while 3% had concomitant tier-1/-2 GLVs. Patients with tier-1 GLVs were on average younger (median 65 years vs. 69 in those without any GLVs, P=0.008). Tier-1 variant distribution per gene family was as follows; 57/202 in FA, 45/202 in MN-predisposing genes (e.g. RUNX1, DDX41, CEBPA, SAMD9, SAMD9L), 27/202 DNA damage repair genes (e.g. ATM, RAD50, MSH2) and 26/202 GLVs in various other cancer predisposing genes (e.g. APC or CUX1). Biallelic GL hits were found in e.g. CHEK2, FANCI, FANCL. We further analyzed the impact of GLVs on the somatic genotype of evolving leukemias. For instance, biallelic GL/somatic variants were common for some genes (e.g. DDX41, SAMD9, SAMD9L, CEBPA, TP53) while other correlated with functionally seeming unrelated mutations. In summary. Our analysis indicates that a significant fraction of adult patients with BMF are carriers of predisposition variants with broad clinical and social implications. Disclosures Patel: Alexion: Other: educational speaker. Carraway:Jazz: Consultancy, Speakers Bureau; Stemline: Consultancy, Speakers Bureau; Takeda: Other: Independent Advisory Committe (IRC); ASTEX: Other: Independent Advisory Committe (IRC); Abbvie: Other: Independent Advisory Committe (IRC); BMS: Consultancy, Other: Research support, Speakers Bureau; Novartis: Consultancy, Speakers Bureau. Maciejewski:Novartis, Roche: Consultancy, Honoraria; Alexion, BMS: Speakers Bureau.

Effect of artifact area on cone beam computed tomography scans when integrated with intraoral scans

The aim of this study was to examine whether integration accuracy increases upon removing artifacts from the registration area when integrating maxillofacial cone beam computed tomography (CBCT) scans and intraoral scans. Three methods were implemented according to the region of interest (ROI): R0, all teeth included as the registration area (artifacts included); R1, anterior teeth included as the registration area (artifacts in premolars and molars not included); and R2, anterior teeth and second molars included as the registration area (artifacts in premolars and first molars not included). Discrepancies between the 2 images were evaluated by using color-mapping methods. The average surface distance was calculated by measuring the shell/shell deviations for overall discrepancies and 3-dimensional distances between the surface points on the 2 images for registration discrepancies. The R1 method showed more discrepancies between the CBCT and intraoral scans compared with the other 2 methods. The R2 method showed smaller overall discrepancy values compared with the R1 method. Most CBCT artifacts were located in the posterior area. Registration discrepancies were greatest in the x-dimension. The results suggest that intraoral and CBCT scans might be integrated by using a registration method that involves exclusion of artifacts and inclusion of the second molar on both sides.

Evaluation of Spike Sorting Algorithms: Application to Human Subthalamic Nucleus Recordings and Simulations

An important prerequisite for the analysis of spike synchrony in extracellular recordings is the extraction of single-unit activity from the multi-unit signal. To identify single units, potential spikes are separated with respect to their potential neuronal origins (‘spike sorting’). However, different sorting algorithms yield inconsistent unit assignments, which seriously influences subsequent spike train analyses. We aim to identify the best sorting algorithm for subthalamic nucleus recordings of patients with Parkinson's disease (experimental data ED). Therefore, we apply various prevalent algorithms offered by the ‘Plexon Offline Sorter’ and evaluate the sorting results. Since this evaluation leaves us unsure about the best algorithm, we apply all methods again to artificial data (AD) with known ground truth. AD consists of pairs of single units with different shape similarity embedded in the background noise of the ED. The sorting evaluation depicts a significant influence of the respective methods on the single unit assignments. We find a high variability in the sortings obtained by different algorithms that increases with single units shape similarity. We also find significant differences in the resulting firing characteristics. We conclude that Valley-Seeking algorithms produce the most accurate result if the exclusion of artifacts as unsorted events is important. If the latter is less important (‘clean’ data) the K-Means algorithm is a better option. Our results strongly argue for the need of standardized validation procedures based on ground truth data. The recipe suggested here is simple enough to become a standard procedure.

Quantitative electroencephalography measures in rapid eye movement and nonrapid eye movement sleep are associated with apnea-hypopnea index and nocturnal hypoxemia in men.

Quantitative electroencephalography (EEG) measures of sleep may identify vulnerability to obstructive sleep apnea (OSA) sequelae, however, small clinical studies of sleep microarchitecture in OSA show inconsistent alterations. We examined relationships between quantitative EEG measures during rapid eye movement (REM) and non-REM (NREM) sleep and OSA severity among a large population-based sample of men while accounting for insomnia. All-night EEG (F4-M1) recordings from full in-home polysomnography (Embletta X100) in 664 men with no prior OSA diagnosis (age ≥ 40) were processed following exclusion of artifacts. Power spectral analysis included non-REM and REM sleep computed absolute EEG power for delta, theta, alpha, sigma, and beta frequency ranges, total power (0.5-32 Hz) and EEG slowing ratio. Apnea-hypopnea index (AHI) ≥10/h was present in 51.2% (severe OSA [AHI ≥ 30/h] 11.6%). In mixed effects regressions, AHI was positively associated with EEG slowing ratio and EEG power across all frequency bands in REM sleep (all p < 0.05); and with beta power during NREM sleep (p = 0.06). Similar associations were observed with oxygen desaturation index (3%). Percentage total sleep time with oxygen saturation <90% was only significantly associated with increased delta, theta, and alpha EEG power in REM sleep. No associations with subjective sleepiness were observed. In a large sample of community-dwelling men, OSA was significantly associated with increased EEG power and EEG slowing predominantly in REM sleep, independent of insomnia. Further study is required to assess if REM EEG slowing related to nocturnal hypoxemia is more sensitive than standard PSG indices or sleepiness in predicting cognitive decline.

Quantification of Underivatized Amino Acids on Dry Blood Spot, Plasma, and Urine by HPLC-ESI-MS/MS.

Enzyme deficiencies in amino acid metabolism may increase the levels of a single or several compounds in physiological fluids becoming diagnostically significant biomarkers for one or a group of metabolic disorders. Therefore, it is important to monitor a wide range of free amino acids simultaneously and to quantify them. This is time consuming if we use the classical methods and, especially now that many laboratories have introduced Newborn Screening Programs for the semiquantitative analysis, the detection and quantification of some amino acids need to be performed in a short time to reduce the rate of false positives.We have modified the stable isotope dilution HPLC-ESI-MS/MS method previously described by Qu (Qu et al., 2002) for a more rapid, robust, sensitive, and specific detection and quantification of underivatized amino acids. The modified method reduces the time of analysis to 10min with very good reproducibility of retention times and a better separation of the metabolites and their isomers.The omission of the derivatization step, enabledto achieve some important advantages: fast and simple sample preparation, exclusion of artifacts, and interferences. The use of this technique is highly sensitive and specific and allowed to monitor 40 underivatized amino acids including the key isomers and quantification of some of them, in order to cover many diagnostically important intermediates of metabolic pathways.We propose this HPLC-ESI-MS/MS method for underivatized amino acids as a support for the newborn screening as secondary test using the same dried blood spots for a more accurate and specific examination in case of suspected metabolic diseases. In this way we avoid plasma collection from the patient as it normally occurs, reducing anxiety for the parents and further costs for analysis.The same method was validated and applied also to plasma and urine samples with good reproducibility, accuracy, and precision. The fast run time, the feasibility of high sample throughput, and the small amount of sample required make this method very suitable for routine analysis in the clinical setting.

A Concept for a Novel Test for Chemical Parity

Deviations from chemical parity (PV) were evaluated with the search for very small enantiomeric excesses in a racemate prepared from non chiral materials and were detected by means of the circular dichroism (CD). Thus, intensely light-absorbing perylenebiscarboximides were attached to axially chiral biphenyls for the amplification of CD effects by exciton interactions of the adjacent chromophores. A rapidly racemising system was applied for the exclusion of artifacts and compared with an analogous with locked chirally. A very slight enantiomeric excess was detected for the (M) enantiomer. Application of the method for other systems was suggested and relations to natural products discussed.

Flow cytometric sorting coupled with exon capture sequencing identifies somatic mutations in archival lymphoma tissues

The enormous number of archived formalin-fixed paraffin-embedded (FFPE) tissues available are a valuable resource of material for research. However, the use of such tissues poses many challenges, among which is the difficulty of isolating different cell populations within the tissue. In this study, we used tissue from two types of non-Hodgkin lymphoma as a model to demonstrate a method we have established and optimized to separate FFPE samples into distinct tumor and nonmalignant populations. Using FFPE reactive tonsil sections, various approaches for antigen retrieval and labeling, and the effectiveness of flow cytometric sorting were tested. We found that, among the 11 cell surface or intracellular antigen markers investigated, CD3ɛ, CD79A, LAT, PD-1, and PAX5 could be successfully labeled after antigen retrieval in Tris-EDTA buffer (pH 8.0) at 65 °C for 60 min, and 1.8–2.7 μg DNA per million cells could be extracted after sorting with DNA quality similar to that of tissue without staining or sorting. To test whether we could perform next-generation sequencing using a custom capture platform on sorted cells, we used three lymphoma cases with FFPE tissues which had been stored for 1 to 4 years. We demonstrated that the DNA from sorted cells was adequate for exon capture sequencing. By comparing the sequencing results between neoplastic and normal populations, somatic mutations could be clearly identified in the tumor population with variant frequencies as low as 11.7%.The corresponding normal fraction clearly helps in the analysis of somatic mutations and the exclusion of artifacts. This study provides an approach using flow cytometric sorting to separate different cellular populations in paraffin-embedded tissues and to unambiguously distinguish somatic mutations from germline variants or artifacts. This approach is also useful in enriching the tumor component in samples with heterogeneous components and low tumor content.

Reliability of EEG Measures of Interaction: A Paradigm Shift Is Needed to Fight the Reproducibility Crisis

Measures of interaction (connectivity) of the EEG are at the forefront of current neuroscientific research. Unfortunately, test-retest reliability can be very low, depending on the measure and its estimation, the EEG-frequency of interest, the length of the signal, and the population under investigation. In addition, artifacts can hamper the continuity of the EEG signal, and in some clinical situations it is impractical to exclude artifacts. We aimed to examine factors that moderate test-retest reliability of measures of interaction. The study involved 40 patients with a range of neurological diseases and memory impairments (age median: 60; range 21–76; 40% female; 22 mild cognitive impairment, 5 subjective cognitive complaints, 13 temporal lobe epilepsy), and 20 healthy controls (age median: 61.5; range 23–74; 70% female). We calculated 14 measures of interaction based on the multivariate autoregressive model from two EEG-recordings separated by 2 weeks. We characterized test-retest reliability by correlating the measures between the two EEG-recordings for variations of data length, data discontinuity, artifact exclusion, model order, and frequency over all combinations of channels and all frequencies, individually for each subject, yielding a correlation coefficient for each participant. Excluding artifacts had strong effects on reliability of some measures, such as classical, real valued coherence (~0.1 before, ~0.9 after artifact exclusion). Full frequency directed transfer function was highly reliable and robust against artifacts. Variation of data length decreased reliability in relation to poor adjustment of model order and signal length. Variation of discontinuity had no effect, but reliabilities were different between model orders, frequency ranges, and patient groups depending on the measure. Pathology did not interact with variation of signal length or discontinuity. Our results emphasize the importance of documenting reliability, which may vary considerably between measures of interaction. We recommend careful selection of measures of interaction in accordance with the properties of the data. When only short data segments are available and when the signal length varies strongly across subjects after exclusion of artifacts, reliability becomes an issue. Finally, measures which show high reliability irrespective of the presence of artifacts could be extremely useful in clinical situations when exclusion of artifacts is impractical.

Reproducibility of MRI Dixon-Based Attenuation Correction in Combined PET/MR with Applications for Lean Body Mass Estimation.

The aim of this study was to assess the reproducibility of standard, Dixon-based attenuation correction (MR-AC) in PET/MR imaging. A further aim was to estimate a patient-specific lean body mass (LBM) from these MR-AC data. Ten subjects were positioned in a fully integrated PET/MR system, and 3 consecutive multibed acquisitions of the standard MR-AC image data were acquired. For each subject and MR-AC map, the following compartmental volumes were calculated: total body, soft tissue (ST), fat, lung, and intermediate tissue (IT). Intrasubject differences in the total body and subcompartmental volumes (ST, fat, lung, and IT) were assessed by means of coefficients of variation (CVs) calculated across the 3 consecutive measurements and, again, across these measurements but excluding those affected by major artifacts. All subjects underwent a body composition measurement using air displacement plethysmography (ADP) that was used to calculate a reference LBMADP A second LBM estimate was derived from available MR-AC data using a formula incorporating the respective tissue volumes and densities as well as the subject-specific body weights. A third LBM estimate was obtained from a sex-specific formula (LBMFormula). Pearson correlation was calculated for LBMADP, LBMMR-AC, and LBMFormula Further, linear regression analysis was performed on LBMMR-AC and LBMADP. The mean CV for all 30 scans was 2.1 ± 1.9% (TB). When missing tissue artifacts were excluded, the CV was reduced to 0.3 ± 0.2%. The mean CVs for the subcompartments before and after exclusion of artifacts were 0.9 ± 1.1% and 0.7 ± 0.7% for the ST, 2.9 ± 4.1% and 1.3 ± 1.0% for fat, and 3.6 ± 3.9% and 1.3 ± 0.7% for the IT, respectively. Correlation was highest for LBMMR-AC and LBMADP (r = 0.99). Linear regression of data excluding artifacts resulted in a scaling factor of 1.06 for LBMMR-AC CONCLUSION: LBMMR-AC is shown to correlate well with standard LBM measurements and thus offers routine LBM-based SUV quantification in PET/MR. However, MR-AC images must be controlled for systematic artifacts, including missing tissue and tissue swaps. Efforts to minimize these artifacts could help improve the reproducibility of MR-AC.

Cross Calibration of Bone Mineral Density Values Among Three Dual Energy X-Ray Absorptiometry Systems

Cross Calibration of Bone Mineral Density Values Among Three Dual Energy X-Ray Absorptiometry Systems

STEM mode in the SEM: A practical tool for nanotoxicology

The addition of a transmitted electron detector to a scanning electron microscope (SEM) allows the recording of bright and dark field scanning transmission electron microscope (STEM) images and the corresponding in-lens secondary electron images from the same region of a thin sample. These combined imaging techniques have been applied here to the analysis of ultrathin sections of cells exposed in vitro to nanomaterials for toxicology investigation. Electron microscopy in general permits the exact nature of the interaction of nanomaterials and cells to be elucidated, and in addition the use of STEM mode in the SEM enables the easy identification and exclusion of artefacts produced by ultramicrotome sectioning. The imaging and analysis obtained by using the STEM mode in the SEM configuration from three different nanomaterial systems of importance (iron oxide nanoparticles, single-walled carbon nanotubes and cadmium selenide quantum dots) indicate that it is a simple, practical and cost-effective tool for nanotoxicological research.

Frontiers in Cardiovascular Magnetic Resonance

Cardiovascular magnetic resonance (MR) is emerging as a multipurpose imaging modality for the assessment of cardiovascular disease in general and ischemic heart disease in particular. Currently, the pace of innovation is rapid, and the modality is changing from one that is used primarily as a research tool to one that is increasingly used in routine clinical practice. The process of innovation includes not only improvements in scanner hardware, such as coil and gradient technology, and the development of new contrast agents but also the development of novel pulse sequences. The concept of the pulse sequence, in which programming changes at the scanner can lead to fundamental changes in activating tissue, is unique to MR and gives this modality the potential to assess a vast number of biological parameters. Cardiovascular MR promises to play an important clinical and investigational role in both vascular and cardiac systems. Current and potential future applications of cardiovascular MR will be discussed with a particular focus on ischemic heart disease. Multidetector-row computed tomography, another promising and complementary noninvasive imaging technology, will be discussed briefly in relation to cardiovascular MR for the assessment of atherothrombotic disease. ### Nomenclature and Evolving Imaging Assessment Atherothrombosis is a systemic or multiterritory arterial disease that primarily affects the large- and medium systemic arteries, including the aorta and the carotid, coronary, and peripheral arteries. Although the epicardial coronary arteries appear to be the most susceptible to atherothrombosis,1,2 intramyocardial arteries are relatively resistant. The concept of multiterritory atherothrombosis has been addressed in 2 large studies of symptomatic patients that showed that at entry into the studies, 3% to 8% had symptomatic atherothrombotic disease in all 3 main arterial districts and 23% to 32% had disease in 2 districts.3,4 From a structural point of view, the 4 main components of the atherothrombotic plaques are as follows: (1) fibrocellular, …

The Correlation of the Bispectral Index with Propofol Effect Site Concentrations is not Altered by Epochs Indicated as Artefact-Loaded by Narcotrend

Artefact detection is an essential feature of automatic EEG monitoring systems used in anaesthesia. Clinical experience indicates that Narcotrend monitoring (MonitorTechnik, Bad Bramstedt, Germany, version 4.0) excludes more EEG epochs because of artefacts than bispectral index monitoring (BIS, Aspect Medical Systems, Newton, MA, version XP). Whether this increased exclusion of epochs is justified has not been investigated yet. Eighteen adult patients undergoing radical prostatectomy were investigated. Induction of anaesthesia was performed with a fentanyl bolus and a propofol infusion. Additionally, following intubation patients received 15 ml bupivacaine 0.5% epidurally. After a waiting period of 45 min depth of anaesthesia was varied two times by increasing and decreasing propofol concentrations. Narcotrend index, BIS values and calculated propofol effect site concentrations were automatically recorded at intervals of 5 s. We tested the hypothesis whether exclusion of artefacts detected by the Narcotrend monitor would possibly improve the prediction probability of the BIS monitor, justifying the necessity of artefact suppression. Simulated propofol effect site concentrations ranged from 2 microg/ml to 6 microg/ml. The Narcotrend monitor excluded a significantly higher percentage of epochs because of artefact detection (12.6 + 1.0%) than the BIS monitor (0.4 +/- 0.1%). The performance of BIS as an indicator of predicted propofol effect site concentrations did not differ when including (P(K) = 0.86 +/- 0.05) or excluding (P(K) = 0.85 +/- 0.04) the data pairs where Narcotrend monitor but not BIS monitor indicated an artefact. Artefacts were evenly distributed over the investigated range ofpropofol effect site concentrations. Exclusion of data pairs that were detected as artefacts by Narcotrend but not by BIS did not change the performance of bispectral index as an indicator of propofol effect site concentration.

Circadian profile of QT interval and QT interval variability in 172 healthy volunteers.

The limited prognostic value of QT dispersion has been demonstrated in recent studies. However, longitudinal data on physiological variations of QT interval and the influence of aging and sex are few. This analysis included 172 healthy subjects (89 women, 83 men; mean age 38.7 +/- 15 years). Beat-to-beat QT interval duration (QT, QTapex [QTa], Tend [Te]), variability (QTSD, QTaSD), and the mean R-R interval were determined from 24-hour ambulatory electrocardiograms after exclusion of artifacts and premature beats. All volunteers were fully active, awoke at approximately 7:00 AM, and had 6-8 hours of sleep. QT and R-R intervals revealed a characteristic day-night-pattern. Diurnal profiles of QT interval variability exhibited a significant increase in the morning hours (6-9 AM; P < 0.01) and a consecutive decline to baseline levels. In female subjects the R-R and Tend intervals were significantly lower at day- and nighttime. Aging was associated with an increase of QT interval mainly at daytime and a significant shift of the T wave apex towards the end of the T wave. The circadian profile of ventricular repolarization is strongly related to the mean R-R interval, however, there are significant alterations mainly at daytime with normal aging. Furthermore, the diurnal course of the QT interval variability strongly suggests that it is related to cardiac sympathetic activity and to the reported diurnal pattern of malignant ventricular arrhythmias.