[Accuracy Verification for Slice Sensitivity Profile Measurement Method by Averaging the Multiple Tilted Wires in Computed Tomography Image].

PURPOSE: Several studies present the unsuitability of the tilted-wire method for slice sensitivity profile (SSP) in helical scan. We compared the accuracy for SSP by the tilted-wire averaging method using multiple wire profiles and by the conventional micro-coin method. METHODS: A micro-coin phantom positioned at the center or the off-center was scanned using a 64-detector row CT scanner in different positions where an X-ray tube starts scanning. In the same way, tilted-wire averaging phantoms, approximately 70 mm in diameter, in the shape of a donut, 8 wires tilted from the circumference toward the center, were scanned. Images were reconstructed with a slice thickness of 0.5 mm. RESULTS: The relative errors of full width at half maximum (FWHM) by the tilted-wire averaging method were -0.015 mm to -0.004 mm (-1.98% to -0.56%) at the center compared to those by the micro-coin method, and it is almost the same value regardless of the number of wires. Relative errors were 0.001 mm to 0.029 mm (0.11% to 3.74%) at the upper 8 cm from the center, and 0.014 mm to 0.078 mm (1.86% to 10.25%) at the upper 16 cm, and the value of relative errors increased as it got farther from the center and as the number of wires went fewer. CONCLUSION: This study indicated that accurate measurement of SSP may be achieved by using 4 (arranged every 90 degrees) or more averaging wires.

Sensitivity profile of blood culture isolates in a clinical analysis laboratory, Fortaleza, CE / Perfil de sensibilidade de isolados de hemocultura em um laboratório de análises clínicas, Fortaleza, CE / Perfil de sensibilidad de hemocultivos aislados en un laboratorio de análisis clínicos, Fortaleza, CE

Background and objectives: bacteremia is defined from the presence of bacteria in the bloodstream. Its clinical importance is associated with the high morbidity and mortality rate in the world. In severe cases, it can culminate in sepsis, with a constant increase in cases in Brazil. Therefore, this study aims to assess the main bacterial isolates in blood cultures and a possible change in their sensitivity profiles in a clinical analysis laboratory in Fortaleza, Ceará. Methods: an epidemiological, descriptive, retrospective study was carried out, with a quantitative approach of positive blood cultures, seeking to assess the main isolated microorganisms and their sensitivity profiles. The data used were obtained from the laboratory system through the EpiCenter→ software, from January 2019 to December 2020. Statistical analysis was performed using the Graphpad 7.0 software. Results: 840 microorganisms were identified from blood cultures, and the main ones were E. coli, K. pneumoniae, P. aeruginosa, S. epidermidis, S. aureus and S. haemolyticus. Some isolates show a change in the sensitivity profile, such as K. pneumoniae and P. aeruginosa, showing an increase in sensitivity to carbapenems and cephalosporins, while S. epidermidis showed a decrease in sensitivity to minocycline in the comparison between years 2019 and 2020.Conclusion: clinical isolates from blood cultures showed a change in the sensitivity profile between 2019 and 2020, taking into account that, for K. pneumoniae, P. aeruginosa, this change resulted in an increase in sensitivity, with an increase in resistance in S. epidermidis isolates.(AU)

Justificativa e objetivos: bacteremia é definida a partir da presença de bactérias na corrente sanguínea. Sua importância clínica está associada à alta taxa de morbidade e mortalidade no mundo. Nos casos graves, pode culminar em sepse, com constante aumento dos casos no Brasil. Portanto, o presente estudo tem como objetivo avaliar os principais isolados bacterianos em hemoculturas e uma possível alteração nos seus perfis de sensibilidade em um laboratório de análises clínicas de Fortaleza, Ceará. Métodos: foi realizado um estudo epidemiológico, descritivo, retrospectivo, com abordagem quantitativa de hemoculturas positivas, buscando avaliar os principais microrganismos isolados e seus perfis de sensibilidades. Os dados utilizados foram obtidos a partir do sistema laboratorial através do software EpiCenter→, referente ao período de janeiro de 2019 a dezembro de 2020. A análise estatística foi realizada pelo software Graphpad 7.0. Resultados: foram identificados 840 microrganismos a partir das hemoculturas, sendo os principais E. coli, K. pneumoniae, P. aeruginosa, S. epidermidis, S. aureus e S. haemolyticus. Alguns isolados apresentam uma alteração no perfil de sensibilidade, como K. pneumoniae e P. aeruginosa, apresentando um aumento na sensibilidade frente aos carbapenêmicos e as cefalosporinas, enquanto o S. epidermidis apresentou uma diminuição na sensibilidade frente à minociclina na comparação entre os anos de 2019 e 2020. Conclusão: os isolados clínicos de hemocultura apresentaram uma alteração no perfil de sensibilidade entre 2019 e 2020, levando em consideração que, para K. pneumoniae e P. aeruginosa, essa alteração resultou no aumento na sensibilidade, com aumento na resistência nos isolados de S. epidermidis.(AU)

Justificación y objetivos: la bacteriemia se define por la presencia de bacterias en el torrente sanguíneo. Su importancia clínica está asociada con la alta tasa de morbimortalidad en el mundo. En casos severos, puede culminar en sepsis, con un aumento constante de casos en Brasil. Por tanto, este estudio tiene como objetivo evaluar los principales aislados bacterianos en hemocultivos y un posible cambio en sus perfiles de sensibilidad en un laboratorio de análisis clínicos en Fortaleza, Ceará. Métodos: se realizó un estudio epidemiológico, descriptivo, retrospectivo, con abordaje cuantitativo de hemocultivos positivos, buscando evaluar los principales microorganismos aislados y sus perfiles de sensibilidad. Los datos utilizados se obtuvieron del sistema de laboratorio a través del software EpiCenter→, para el período de enero de 2019 a diciembre de 2020. El análisis estadístico se realizó mediante el software Graphpad 7.0. Resultados: se identificaron 840 microorganismos a partir de hemocultivos, siendo los principales E. coli, K. pneumoniae, P. aeruginosa, S. epidermidis, S. aureus y S. haemolyticus. Algunos aislados muestran un cambio en el perfil de sensibilidad, como K.pneumoniae y P. aeruginosa, mostrando un aumento en la sensibilidad a los carbapenémicos y cefalosporinas, mientras que S. epidermidis mostró una disminución en la sensibilidad a la minociclina, en la comparación entre los años de 2019 y 2020. Conclusiones: los aislados clínicos de hemocultivos mostraron un cambio en el perfil de sensibilidad entre 2019 y 2020, teniendo en cuenta que para K. pneumoniae, P. aeruginosa, este cambio resultó en un aumento de la sensibilidad, con un aumento de la resistencia en los aislados de S. epidermidis

Method for determining slice sensitivity profile of iterative reconstruction CT images using low-contrast sphere phantom.

A novel method for measuring the slice sensitivity profile (SSP) of computed tomography (CT) images reconstructed using an iterative reconstruction (IR) algorithm is proposed herein. A phantom that included a low-contrast spherical object was scanned and consecutive cross-sectional images were reconstructed. The mean CT values in a region including the sphere were measured for all images and plotted as a function of slice position along the longitudinal [Formula: see text] direction to yield a mean CT value profile [Formula: see text]. Next, we numerically generated an object function corresponding to the sphere and obtained the mean CT value profile [Formula: see text]. Subsequently, the SSP was modeled as a product of the Gaussian and cosine functions. We convolved [Formula: see text] with the modeled SSP to obtain [Formula: see text]. The difference between [Formula: see text] and [Formula: see text] was evaluated using the root mean square error (RMSE), which was minimized via optimization of the SSP model parameters. To validate the methodology, we first used filtered back projection (FBP) images to compare the SSPs determined using the proposed and standard coin methods. Subsequently, the proposed method was applied to measure the SSPs of four types of IR algorithms in two scanners. The SSPs of the FBP images determined using the proposed and coin methods showed good agreement. Additionally, in the SSP measurements using the proposed method, [Formula: see text] agreed well with [Formula: see text] for every IR algorithm. The RMSEs for all measurements were less than 0.7 HU, indicating the accuracy of the SSPs. Thus, the proposed method is effective for obtaining valid SSPs.

Automated procedure for slice thickness verification of computed tomography images: Variations of slice thickness, position from iso-center, and reconstruction filter.

PURPOSE: The purpose of this study is to automate the slice thickness verification on the AAPM CT performance phantom and validate it for variations of slice thickness, position from iso-center, and reconstruction filter. METHODS: An automatic procedure for slice thickness verification on AAPM CT performance phantom was developed using MATLAB R2015b. The stair object image within the phantom was segmented, and the middle stair object was located. Its angle was determined using the Hough transformation, and the image was rotated accordingly. The profile through this object was obtained, and its full-width of half maximum (FWHM) was automatically measured. The FWHM indicated the slice thickness of the image. The automated procedure was applied with variations in three independent parameters, i.e., the slice thickness, the distance from the phantom to the iso-center, and the reconstruction filter. The automated results were compared to manual measurements made using electronic calipers. RESULTS: The differences of the automated results from the nominal slice thicknesses were within 1.0 mm. The automated results are comparable to those from manual approach (i.e., the difference of both is within 12%). The automatic procedure accurately obtained slice thickness even when the phantom was moved from the iso-center position by up to 4 cm above and 4 cm below the iso-center. The automated results were similar (to within 0.1 mm) for various reconstruction filters. CONCLUSIONS: We successfully developed an automated procedure of slice thickness verification and confirmed that the automated procedure provided accurate results. It provided an easy and effective method of determining slice thickness.

Technical Note: A simple method for measuring the slice sensitivity profile of iteratively reconstructed CT images using a non-slanted edge plane.

PURPOSE: A method for measuring the slice sensitivity profile (SSP) of computed tomography (CT) images reconstructed with iterative reconstruction (IR) algorithms was reported by the AAPM Task Group 233 (TG233). In this method, the phantom plane edge is slightly slanted with respect to the scan plane to obtain a composite oversampled edge-spread function (ESF). However, it is expected that a fine-sampled ESF can be obtained directly from images reconstructed with a small slice increment without slanting the edge plane. This study aimed to investigate the validity of using a non-slanted edge plane. METHODS: In the proposed non-slanted edge method, the phantom was positioned so that the plane edge was perpendicular to the longitudinal z-axis, and images were reconstructed with a 1-mm slice thickness and 0.1-mm increment. The mean CT value was obtained in each slice and plotted as a function of slice position along the z-axis, thereby generating the ESF. The SSP was calculated from the ESF by differentiation. In the TG 233-recommended slanted edge method, the SSP was obtained by following the procedure described in the TG233 report. To validate the methodology, we first used filtered back projection (FBP) images to compare SSPs obtained using the non-slanted edge method, slanted edge method, and a standard method using a high-contrast thin object (coin). Next, for two types of IR algorithms, we compared the SSPs obtained using the non-slanted and slanted edge methods. RESULTS: For the FBP images, the SSP measured using the non-slanted edge method agreed well with SSPs measured using the coin and slanted edge methods. For the IR images, the SSPs measured using the non-slanted and slanted edge methods showed good agreement. CONCLUSIONS: The non-slanted edge method was demonstrated to be valid. The simplicity and practicality of the method allows routine and accurate determination of the SSP.

Frecuencia de Streptococcus pneumoniae aislados de enfermedad invasiva en Paraguay, serotipos y perfil de sensibilidad (2010-2018) / Frequency of Streptococcus pneumoniae isolated from invasive disease in Paraguay, serotypes and sensitivity profile (2010-2018)

Streptococcus pneumoniae sigue siendo una de las causas más importantes de morbilidad y mortalidad en niños y adultos alrededor del mundo. El objetivo del estudio fue describir la frecuencia de aislamiento de S. pneumoniae en enfermedad invasiva, distribución de serotipos y sensibilidad antimicrobiana en Paraguay (2010-2018). Se estudiaron 793 cepas de S. pneumoniae aisladas de pacientes de todas las edades con enfermedad invasiva en Paraguay, provenientes de los diferentes centros centinelas y colaboradores en el marco de la vigilancia de meningitis y neumonías, durante el periodo 2010-2018. La frecuencia general según diagnóstico resultó 74.9% de neumonías (n=594), 18.4% de meningitis (n=146) y 6.7% de sepsis (n=53). El serotipo 14 fue más frecuente con 174 aislamientos (22.0%), seguido del serotipo 19A con 84 aislamientos (10.6%), el serotipo 3 con 66 aislamientos (8.3%) y el 6A con 37 aislamientos (4.7%). En meningitis se registró una frecuencia general de resistencia a penicilina del 32,2% y de ceftriaxona del 1,4%. En los casos de no meningitis la resistencia a penicilina fue del 0,8% y ceftriaxona del 0,3%. Los resultados de serotipos y sensibilidad antimicrobiana proporcionarán información necesaria para la implementación de estrategias de prevención y tratamiento de la enfermedad neumocócica en nuestro país, por lo que es necesaria una vigilancia continua para evaluar la carga de enfermedad, los serotipos circulantes y el aumento de la resistencia a los antibióticos

Streptococcus pneumoniae remains one of the most important causes of morbidity and mortality in children and adults worldwide. The objective of the study was to describe the frequency of isolation of S. pneumoniae in invasive disease, serotype distribution and antimicrobial susceptibility in Paraguay (2010-2018). We studied 793 strains of S. pneumoniae isolated from patients of all ages with invasive disease in Paraguay, from different sentinel centers and collaborators in the framework of meningitis and pneumonia surveillance during the period 2010-2018. The general frequency according to diagnosis was 74.9% of pneumonia (n = 594), 18.4% of meningitis (n = 146) and 6.7% of sepsis (n = 53). Serotype 14 was more frequent with 174 isolates (22.0%), followed by serotype 19A with 84 isolates (10.6%), serotype 3 with 66 isolates (8.3%) and 6A with 37 isolates (4.70%). In meningitis, there was a general frequency of penicillin resistance of 32.2% and ceftriaxone of 1.4%. In cases of non-meningitis, penicillin resistance was 0.8% and ceftriaxone 0.3%. The results of serotypes and antimicrobial sensitivity will provide necessary information for the implementation of prevention strategies and treatment of pneumococcal disease in our country, therefore it is necessary to continue monitoring in order to assess the burden of the disease, circulating serotypes and increased antibiotic resistance

Impact of baseline calibration on semiquantitative assessment of myocardial perfusion reserve by adenosine stress MRI.

In this study, we sought to investigate the impact of baseline calibration, which is used in quantitative cardiac MRI perfusion analysis to correct for surface coil inhomogeneity and noise, on myocardial perfusion reserve index (MPRI) and its contribution to previously reported paradoxical low MPRI < 1.0 in patients with unobstructed coronary arteries. Semiquantitative perfusion analysis was performed in 20 patients with unobstructed coronary arteries undergoing stress/rest perfusion CMR and in ten patients undergoing paired rest perfusion CMR. The following baseline calibration settings were compared: (1) baseline division, (2) baseline subtraction and (3) no baseline calibration. In uncalibrated analysis, we observed ~ 20% segmental dispersion of signal intensity (SI)-over-time curves. Both baseline subtraction and baseline division reduced relative dispersion of t0-SI (p < 0.001), but only baseline division corrected for dispersion of peak-SI and maximum upslope also (p < 0.001). In the assessment of perfusion indices, however, baseline division resulted in paradoxical low MPRI (1.01 ± 0.23 vs. 1.63 ± 0.38, p < 0.001) and rest perfusion index (RPI 0.54 ± 0.07 vs. 0.94 ± 0.12, p < 0.001), respectively. This was due to a reversed ratio of blood-pool and myocardial baseline-SI before the second perfusion study caused by circulating contrast agent from the first injection. In conclusion, baseline division reliably corrects for inhomogeneity of the surface coil sensitivity profile facilitating comparisons of regional myocardial perfusion during hyperemia or at rest. However, in the assessment of MPRI, baseline division can lead to paradoxical low results (even MPRI < 1.0 in patients with unobstructed coronary arteries) potentially mimicking severely impaired perfusion reserve. Thus, in the assessment of MPRI we propose to waive baseline calibration.

Risk of triclosan based on avoidance by the shrimp Palaemon varians in a heterogeneous contamination scenario: How sensitive is this approach?

As the exposure of organisms to contaminants can provoke harmful effects, some organisms try to avoid a continuous exposure by using different strategies. The aim of the current study was to assess the ability of the shrimp Palaemon varians to detect a triclosan gradient and escape to less contaminated areas. Two multi-compartmented exposure systems (the linear system and the HeMHAS-Heterogeneous Multi-Habitat Assay System) were used and then results were compared. Finally, it was aimed how sensitive the avoidance response is by comparing it with other endpoints through a sensitivity profile by biological groups and the species sensitive distribution. The distribution of the shrimps along the triclosan gradient was dependent on the concentrations, not exceeding 3% for 54 µg/L in the linear system and 7% for 81 µg/L in the HeMHAS; 25% of organisms preferred the compartment with the lowest concentrations in both systems. Half of the population seems to avoid concentrations around 40-50 µg/L. The triclosan concentration that might start (threshold) to trigger an important avoidance (around 20%) was estimated to be of 18 µg/L. The profile of sensitivity to triclosan showed that avoidance by shrimps was less sensitive than microalgae growth and avoidance by guppy; however, it might occur even at concentrations considered safe for more than 95% of the species. In summary, (i) the HeMHAS proved to be a suitable system to simulate heterogeneous contamination scenarios, (ii) triclosan triggered the avoidance response in P. varians, and (iii) the avoidance was very sensitive compared to other ecotoxicological responses.

Perfil de sensibilidad de Escherichia coli aislados de infecciones del tracto urinario de pacientes del Hospital Regional de Villarrica en el periodo de julio 2013 a agosto 2015 / Sensitivity profile of Escherichia coli isolated from urinary tract infections of patients of the Regional Hospital of Villarrica from July 2013 to August 2015

Introducción: El uso inapropiado de los antimicrobianos está conduciendo a la disminución de la sensibilidad antimicrobiana de microorganismos que producen enfermedades infecciosas. El uso clínico de los antimicrobianos ha sido paralelo al surgimiento de bacterias resistentes a su acción. Materiales y Métodos: Se realizó un estudio observacional, descriptivo, retrospectivo de corte transversal, con muestreo no probabilístico de casos consecutivos. La selección de antibióticos incluyó solo aquellos que tienen actividad frente a bacilos gram negativos y para la interpretación de los diámetros de los halos de inhibición se tomaron en cuenta los estándares de la Clinical and Laboratory Standards Institute (CLSI versión 2015). Resultados: La ampicilina presentó una resistencia del 100%, en cambio la ciprofloxacina presentó una sensibilidad del 73%, la amikacina del 100% y la gentamicina del 82%. La familia de los carbapenemicos presentó una sensibilidad del 100%. Dentro del grupo de los nitrofuranos se constató una sensibilidad del 96%. El trimetoprim/ sulfametoxazol, presentó una sensibilidad del 57%. Se determinó la presencia de Beta Lactamasa de Espectro Extendido (BLEE) en 13% de las cepas de Escherichia coli estudiadas. Conclusiones: La gentamicina, la nitrofurantoína y los carbapenemes presentaron una elevada sensibilidad, por lo que en presencia de cepas con BLEE serían opciones factibles acompañados siempre de la evaluación del perfil renal y clasificando la ITU como complicada o no.

Introduction: The inappropriate use of antimicrobials is leading to a decrease in the antimicrobial sensitivity of microorganisms that cause infectious diseases. The clinical use of antimicrobials has been parallel to the emergence of bacteria resistant to its action. Materials and methods: The sensitivity profile of Escherichia coli isolated from patients with urinary tract infections (UTI) concurrent to the Regional Hospital of Villarrica in the period from 2013 to 2015 was determined. Results: Ampicillin showed a resistance of 100%, ciprofloxacin showed a sensitivity of 73%. Amikacin showed a sensitivity of 100% and gentamicin 82%. The family of carbapenem showed a sensitivity of 100%. Within the group of nitrofurans a sensitivity of 96% was found. Trimethoprim / sulfamethoxazole had a sensitivity of 57%. The presence of Extended Spectrum Beta Lactamase (ESBL) was determined in 13% of the strains of Escherichia coli studied. Conclusions: Gentamicin, nitrofurantoin and carbapenem have a high sensitivity, so in the presence of strains with ESBL they would be feasible options always accompanied by the evaluation of the renal profile and classifying the UTI as complicated or not.

Cue identification in phenology: A case study of the predictive performance of current statistical tools.

Changes in the timing of life-history events (phenology) are a widespread consequence of climate change. Predicting population resilience requires knowledge of how phenology is likely to change over time, which can be gained by identifying the specific environmental cues that drive phenological events. Cue identification is often achieved with statistical testing of candidate cues. As the number of methods used to generate predictions increases, assessing the predictive accuracy of different approaches has become necessary. This study aims to (a) provide an empirical illustration of the predictive ability of five commonly applied statistical methods for cue identification (absolute and relative sliding time window analyses, penalized signal regression, climate sensitivity profiles and a growing degree-day model) and (b) discuss approaches for implementing cue identification methods in different systems. Using a dataset of mean clutch initiation timing in wild great tits (Parus major), we explored how the days of the year identified as most important, and the aggregate statistic identified as a cue, differed between statistical methods and with respect to the time span of data used. Each method's predictive capacity was tested using cross-validation and assessed for robustness to varying sample size. We show that the identified critical time window of cue sensitivity was consistent across four of the five methods. The accuracy and precision of predictions differed by method with penalized signal regression resulting in the most accurate and most precise predictions in our case. Accuracy was maximal for near-future predictions and showed a relationship with time. The difference between predictions and observations systematically shifted across the study from preceding observations to lagging. This temporal trend in prediction error suggests that the current statistical tools either fail to capture a key component of the cue-phenology relationship, or the relationship itself is changing through time in our system. These two influences need to be teased apart if we are to generate realistic predictions of phenological change. We recommend future phenological studies to challenge the idea of a static cue-phenology relationship and should cross-validate results across multiple time periods.

Sensitivity enhancement of methacrylic acid gel dosimeters by incorporating iodine for computed tomography scans.

PURPOSE: Polymer gel dosimeters provide three-dimensional absorbed dose information and have gradually become a popular tool for quality assurance in radiotherapy. This study aims to incorporate iodine into the MAGAT-based gel as radiation sensitizer and investigate whether it can be used to measure the radiation dose and slice thickness for CT scans. METHODS: The nMAGAT(I) gel was doped with 0.03, 0.05, and 0.07-M iodine. The absorbed dose was delivered using a CT scanner (Alexion 16, Toshiba Medical Systems, Japan) with tube voltages of 80, 100, 120, and 135 kVp. The irradiated nMAGAT(I) gel was read using a cone beam optical CT scanner to produce dose-response curves. The nMAGAT(I) gel was used to obtain the slice sensitivity profile (SSP) and the CT dose index (CTDI) for quality assurance of CT scans. RESULTS: The 0.07-M iodine-doped nMAGAT(I) gel exhibited maximum sensitivity with the dose enhancement ratio of 2.12. The gel was chemically stable 24 h after its preparation, and the polymerization process was completed 24-48 h after the irradiation. For CT quality assurance, the full width at half maximum measured by the nMAGAT(I) gel matched the nominal slice thickness of CT. The CTDI at center, CTDI at peripheral, and weighted CTDI obtained by the nMAGAT(I) gel differed from those obtained by the ionization chamber by -4.2%, 3.1%, and 0.7%, respectively. CONCLUSIONS: The nMAGAT(I) gel can be used to assess radiation doses and slice thickness in CT scans, thus rendering it a potential quality assurance tool for CT and other radiological diagnostic applications.

A method to measure slice sensitivity profiles of CT images under low-contrast and high-noise conditions.

Noise reduction features of iterative reconstruction (IR) methods in computed tomography might accompany the sacrifice of the longitudinal resolution, or slice sensitivity profile (SSP), at low contrast-to-noise ratio (CNR) conditions. To assess the benefit of IR methods correctly, the difference of SSP between IR methods and filtered-backprojection (FBP) must be taken into account. Therefore, SSP measurement under low-CNR conditions is necessary. Although edge methods are predominantly used, their performance under low-CNR conditions appears to be not fully established. We developed a method that is compatible with extremely low-CNR conditions. Thin plastic disk-shaped sheets embedded in acrylic resin were used as low-contrast test objects. The lowest peak contrast used was approximately 17 [HU]. We assessed the performance of our method by using FBP images. We identified a source of measurement instability aside from noise: the measured thin-slice SSP is dependent on the orbital phase of helical scan, presumably because of cone-beam artifacts. This impediment to high accuracy is manageable using phase-controlled scans. We confirmed that table position repeatability is much better than the value of the specifications, and therefore the ensemble-averaged images of multiple scans can be used for SSP measurement. Accurate measurement of SSP under extremely low-CNR conditions is possible, even when the test object is visually indiscernible from the noisy background. Low-contrast SSP behavior is elucidated for IR methods (AIDR-3D, FIRST, and AiSR-V) by using this measurement method.

Head motion measurement and correction using FID navigators.

PURPOSE: To develop a novel framework for rapid, intrinsic head motion measurement in MRI using FID navigators (FIDnavs) from a multichannel head coil array. METHODS: FIDnavs encode substantial rigid-body motion information; however, current implementations require patient-specific training with external tracking data to extract quantitative positional changes. In this work, a forward model of FIDnav signals was calibrated using simulated movement of a reference image within a model of the spatial coil sensitivities. A FIDnav module was inserted into a nonselective 3D FLASH sequence, and rigid-body motion parameters were retrospectively estimated every readout time using nonlinear optimization to solve the inverse problem posed by the measured FIDnavs. This approach was tested in simulated data and in 7 volunteers, scanned at 3T with a 32-channel head coil array, performing a series of directed motion paradigms. RESULTS: FIDnav motion estimates achieved mean absolute errors of 0.34 ± 0.49 mm and 0.52 ± 0.61° across all subjects and scans, relative to ground-truth motion measurements provided by an electromagnetic tracking system. Retrospective correction with FIDnav motion estimates resulted in substantial improvements in quantitative image quality metrics across all scans with intentional head motion. CONCLUSIONS: Quantitative rigid-body motion information can be effectively estimated using the proposed FIDnav-based approach, which represents a practical method for retrospective motion compensation in less cooperative patient populations.

Variations in slice sensitivity profile for various height settings in tomosynthesis imaging: Phantom study.

Understanding the properties of slice sensitivity profile (SSP), or slice thickness, is crucial for an accurate and highly reproducible diagnosis using tomosynthesis imaging. The objectives of the present study are therefore to quantitatively evaluate how the SSP with the use of a small metal bead is affected by different settings of the height from the table and the height of the center of rotation (COR) in tomosynthesis imaging except for the digital breast tomosynthesis, and visually verify the effects on tomosynthesis images. The reconstruction filters used were three types of filtered back-projection and iterative reconstructions. The SSP was measured from the full width at half maximum (FWHM-SSP) of the profile curve of the bead in the perpendicular direction (z direction) relative to the table. Two types of anthropomorphic phantoms simulating the human body, with bones and soft tissues, were used to study the effects of different settings for the COR height. In all reconstruction filters, the FWHM-SSP changed as the height of the bead varied when the bead and COR were set to the same height from the table. If the bead and the COR were set to different heights, the FWHM-SSP increased (decreased) when the height of the bead was set to be greater (less) than the height of the COR. These changes were also confirmed on the anthropomorphic phantom images of the bones and soft tissues.

Characteristics of temporal resolution in 16- and 64-row computed tomography scanners.

This study aimed to analyze the temporal sensitivity profile (TSP) shapes and temporal resolutions of computed tomography (CT) and investigate the effect of a combination of a given rotation time and helical pitch on the TSP and image quality. The study was performed on 16- and 64-row CT scanners, and the TSP and temporal resolution were measured using the impulse method. A shorter gantry rotation time and larger helical pitch improved the temporal resolution of both CT scanners. Although the measured TSP shapes were dependent on the helical pitch, the maximum helical pitch did not improve the temporal resolution of either CT scanner. Different combinations of gantry rotation time and helical pitch yielded different TSP shapes such as the triangle, trapezoid, and rectangle, despite the use of equivalent scan speeds. We suggest that the different combinations of rotation time and helical pitch can greatly affect the TSP shapes.

Role of reactive oxygen species in the anticancer activity of botanicals: Comparing sensitivity profiles.

Numerous botanicals have been shown to exhibit in vitro and in vivo anticancer activity, some of which is the result of the induction of reactive oxygen species (ROS) in cancer cells with a high ROS content. The present study compared sensitivities to a series of botanicals among cancer cell lines, using an XTT viability test, in order to create a specific cancer-herb profile. Of the 27 botanicals screened, 10 exhibited a cytotoxic effect, 7 of which were ROS-mediated. The sensitivity profiles of the ROS-inducing botanicals in 10 cancer cell lines were similar, unlike 3 cytotoxic ROS-independent botanicals that displayed divergent botanical-specific profiles. The correlation between sensitivity profiles of ROS-inducing botanicals suggests a common mechanism of action, in contrast to the varied mechanism of ROS-independent botanicals. This implies that the investigation of the anticancer activity of botanicals should start with the examination of ROS-mediated activity. Further investigation of ROS sensitivity among various tumor types is required in order to guide research into developing evidence-based guidelines in the use of botanicals for cancer treatment.

Reserve drug indent form and its impact on antimicrobial consumption and sensitivity pattern in the medical intensive care unit of a tertiary care hospital.

OBJECTIVES: A world without effective antibiotics is a terrifying but a real prospect. Overuse or misuse especially of newer and higher antimicrobials (AM) is of particular concern, as this contributes to development of resistance among microorganisms. To check this trend, the Reserve Drug Indent Form (RDIF) was introduced in our hospital and its impact on AM consumption, cost of therapy and the sensitivity pattern was studied in the medical intensive care unit (MICU). MATERIALS AND METHODS: A retrospective descriptive study in the medical ICU of a tertiary care hospital from July 2012 to August 2013. From March 2013, RDIF was made mandatory to be filled up prior to prescribing reserve antimicrobials. AM consumption (expressed as DDD/100 bed days) and sensitivity pattern (expressed in percentage) six months prior to and six months after implementation of the form were analysed. RESULTS: The total Reserve AM consumption was 125.79 per 100 bed days during the study period. Average occupancy index was 0.50 and length of ICU stay was 6 days. The total consumption reduced from 85.55/100 to 40.24/100 bed days after the introduction of the RDIF. However, Imipenem usage increased from 11.35/100 to 23.94/100 bed days, which can be attributed to sensitivity profile to Imipenem (82.1%) compared to Meropenem (65.7%). Cost of therapy reduced from Rs 6,27,951 to 4,20,469. CONCLUSION: Reserve AM consumption showed a declining trend after introduction of the RDIF. Hence, the RDIF served as an important tool to combat inappropriate use, reducing the cost burden and also helped to improve the sensitivity to reserve drugs.

Assessment of temporal resolution of multi-detector row computed tomography in helical acquisition mode using the impulse method.

The purpose of this study was to propose a method for assessing the temporal resolution (TR) of multi-detector row computed tomography (CT) (MDCT) in the helical acquisition mode using temporal impulse signals generated by a metal ball passing through the acquisition plane. An 11-mm diameter metal ball was shot along the central axis at approximately 5 m/s during a helical acquisition, and the temporal sensitivity profile (TSP) was measured from the streak image intensities in the reconstructed helical CT images. To assess the validity, we compared the measured and theoretical TSPs for the 4-channel modes of two MDCT systems. A 64-channel MDCT system was used to compare TSPs and image quality of a motion phantom for the pitch factors P of 0.6, 0.8, 1.0 and 1.2 with a rotation time R of 0.5 s, and for two R/P combinations of 0.5/1.2 and 0.33/0.8. Moreover, the temporal transfer functions (TFs) were calculated from the obtained TSPs. The measured and theoretical TSPs showed perfect agreement. The TSP narrowed with an increase in the pitch factor. The image sharpness of the 0.33/0.8 combination was inferior to that of the 0.5/1.2 combination, despite their almost identical full width at tenth maximum values. The temporal TFs quantitatively confirmed these differences. The TSP results demonstrated that the TR in the helical acquisition mode significantly depended on the pitch factor as well as the rotation time, and the pitch factor and reconstruction algorithm affected the TSP shape.

Analytic quantification of bias and variance of coil sensitivity profile estimators for improved image reconstruction in MRI.

Magnetic resonance (MR) imaging provides a unique in-vivo capability of visualizing tissue in the human brain non-invasively, which has tremendously improved patient care over the past decades. However, there are still prominent artifacts, such as intensity inhomogeneities due to the use of an array of receiving coils (RC) to measure the MR signal or noise amplification due to accelerated imaging strategies. It is critical to mitigate these artifacts for both visual inspection and quantitative analysis. The cornerstone to address this issue pertains to the knowledge of coil sensitivity profiles (CSP) of the RCs, which describe how the measured complex signal decays with the distance to the RC. Existing methods for CSP estimation share a number of limitations: (i) they primarily focus on CSP magnitude, while it is known that the solution to the MR image reconstruction problem involves complex CSPs and (ii) they only provide point estimates of the CSPs, which makes the task of optimizing the parameters and acquisition protocol for their estimation difficult. In this paper, we propose a novel statistical framework for estimating complex-valued CSPs. We define a CSP estimator that uses spatial smoothing and additional body coil data for phase normalization. The main contribution is to provide detailed information on the statistical distribution of the CSP estimator, which yields automatic determination of the optimal degree of smoothing for ensuring minimal bias and provides guidelines to the optimal acquisition strategy.

Improved SENSE imaging using accurate coil sensitivity maps generated by a global magnitude-phase fitting method.

PURPOSE: To develop a novel coil sensitivity processing technique that is able to reduce or eliminate aliasing artifacts and noise amplification in image-domain parallel imaging (i.e., SENSE). METHODS: Initial coil sensitivity maps were derived from the center k-space lines by a common self-calibration method. Then continuous trigonometric functions were used to fit both magnitude and phase maps of the self-calibrated coil sensitivity profile globally. Further, the global fitted coil sensitivity maps were adopted for SENSE reconstruction. Numerical simulations, as well as experiments on phantoms and human subjects were performed to evaluate and compare the effectiveness of this global magnitude-phase fitting approach with traditional local fitting methods. RESULTS: Both simulation and experimental results demonstrated that the proposed novel global fitting method was able to obtain accurate coil sensitivity profiles without Gibbs oscillations. The resultant SENSE images were improved substantially in terms of aliasing imaging artifacts. CONCLUSION: A global magnitude-phase fitting method for better estimation of accurate coil sensitivity maps was developed, and it was successfully used in producing high-quality parallel images. Magn Reson Med 74:217-224, 2015. © 2014 Wiley Periodicals, Inc.