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PubMed1991

Ultrafast imaging using gradient echoes.

Ultrafast magnetic resonance (MR) imaging techniques can reduce scan times to less than 1 s. The rapid acquisition minimizes motion artifacts that have plagued MR studies of the heart and abdomen, and facilitates dynamic studies to observe physiological function. We first discuss fast gradient-echo methods, including various spoiled and steady-state gradient-echo techniques. Ultrafast methods are then considered, with the focus on turbo-fast low-angle shot (FLASH) (also known as snapshot or subsecond FLASH) imaging. Although turbo-FLASH is a subset of gradient echo methods, there are several distinguishing features. For instance, with T1- or T2-weighted turbo-FLASH, the magnetization never reaches a steady state, so that the phase encode order becomes an important imaging parameter. Furthermore, image contrast is obtained by adjusting the magnetization preparation module, which is independent of the data acquisition module that follows. The signal behavior and strategies for contrast optimization are discussed. Potential clinical applications, including perfusion imaging, cardiac cine, breath-hold abdominal imaging, angiography, diffusion imaging, and three-dimensional studies, are explored.

Fourier Analysis↗

PubMed2006

Perioperative complications of laparoscopic and robotic assisted laparoscopic radical prostatectomy.

PURPOSE: While it remains controversial whether LRP or da Vinci RAP offers any advantages over radical retropubic prostatectomy, LRP and RAP are being used more frequently. We reviewed our experience with these minimally invasive techniques. MATERIALS AND METHODS: We reviewed intraoperative and early postoperative complications of 358 LRPs performed from October 2000 to January 2003 with those of 322 RAPs performed from June 2003 to June 2004. The transperitoneal approach with bilateral pelvic lymph node dissection was performed using each technique. Data acquisition was done independently of the 3 surgeons. RESULTS: The LRP and RAP groups had similar clinical characteristics in terms of patient race, body mass index, prostate specific antigen, risk group, and pathological tumor grade and stage. Median operative time and estimated blood loss for LRP and RAP were 4.1 and 3.1 hours, and 200 and 250 ml, respectively. No blood transfusions were given intraoperatively, although 8 patients with LRP (2.2%) and 5 with RAP (1.6%) were transfused postoperatively. Of the LRP and RAP patients 21 (5.9%) and 3 (0.3%), respectively, experienced intraoperative complications. Postoperatively 48 patients with LRP (13.4%) and 24 with RAP (6.8%) experienced urine leakage, while 19 with LRP (5.3%) and 9 with RAP (2.8%) had ileus. There were no deaths, myocardial infarctions, pulmonary emboli or cerebrovascular accidents. CONCLUSIONS: In our series surgeon experience derived from LRP may contribute to the lower complication rate and operative time of RAP. Dissemination of surgical technique and management of complications may lead to improved perioperative LRP and RAP morbidity. However, the morbidity of these 2 approaches compares favorably with that of radical retropubic prostatectomy.

Adult↗

PubMed1982

Data acquisition and control system for multiparameter cell sorting based on DEC LSI-11 microprocessor.

A computer system has been developed to add data acquisition, display, storage, and processing capability to a multiparamenter flow cytometer/sorter. The system can handle one or two parameters in histogram mode. Alternatively one, two or more parameters are stored event-by-event on an external storage device in list-mode with a resolution of 12 bit. The processor can also control cell sorting. Usual multichannel analyzer features are implemented in software, using standard interface boards without special electronics. Data are accepted via Direct Memory Access (DMA), which depends only on hardware. Data acquisition deadtime is nearly independent of software routines such as graphics display and interactive work. Since more than 8000 events/sec are achieved for eight paramenter handling, the computer system has capacity for rapid data acquisition. Although there is no need for such high data acquisition rates in present flow cytometry, it gives the advantage of short single event acquisition and longer process control handling.

Cell Separation↗

PubMed2003

System to monitor task chair seating.

OBJECTIVE: To record chair data such as seat occupancy, back recline angle, lumbar engagement, and armrest location using an independent, unbiased real time data acquisition system. DESIGN: The system should be inconspicuous. The users should be able to work effectively in their environment oblivious to concurrent data collection. BACKGROUND: While human acquisition and measurement instruments provide an acceptable approach for collecting data on changing chair positions, they may bias data. Current data collection methods such as video playback can also be successful in collecting chair data, but are often time-consuming and expensive to set up. METHODS: Four key areas were concentrated upon for monitoring: seat, lumbar, back recline, and armrest position. A position switch was mounted to each locale and linked to a microprocessor to track the changing positions of the chair in real time. RESULTS: The chair provides time stamped data on the changes that take place to the chair. The data can be downloaded at the convenience of the user and researcher. CONCLUSIONS: The chair is complete and ready for data acquisition. It permits easy data collection on chair positions without hindering the user's movement. RELEVANCE: This tool provides an automated, independent method for collecting data on chair positions. Information can be collected and studies conducted on seated durations, chair back motion while seated, chair lumbar usage, and common armrest location while in a visual display terminal workstation.

Data Collection↗

PubMed2006

Isolation and minimization of head motion-induced signal variations in fMRI data using independent component analysis.

Task-related head movement during acquisition of fMRI data represents a serious confound for both motion correction and estimates of task-related activation. Cost functions implemented in most conventional motion-correction algorithms compare two volumes for similarity but fail to account for signal variability that is not due to motion (e.g., brain activation). We therefore recently proposed the theoretical basis for a novel method for fMRI motion correction, termed motion-corrected independent component analysis (MCICA), that allows for brain activation present in an fMRI time-series to be implicitly modeled and mitigates motion-induced signal changes without having to directly estimate the motion parameters (Liao et al., IEEE Transactions on Medical Imaging 2005;25:29-44). To explore the effects of non-movement-related signal changes on registration error, we performed several previously proposed test simulations (Freire et al., IEEE Transactions on Medical Imaging 2002;21:470-484) to evaluate the performance of MCICA and compare it with the conventional square-of-difference-based measures such as LS-SPM and LS-AIR. We demonstrate that for both simulated data and real fMRI images, the proposed MCICA method performs favorably. Specifically, in simulations MCICA was more robust to the addition of simulated activation, and did not lead to the detection of false activations after correction for simulated task-correlated motion. With actual data from a motor fMRI experiment, the time course of the derived continually task-related ICA component became more correlated with the underlying behavioral task after preprocessing with MCICA compared to other methods, and the associated activation map was more clustered in the primary motor and supplementary motor cortices without spurious activation at the brain edge. We conclude that assessing the statistical properties of a motion-corrupted volume in relation to other volumes in the series, as is done with MCICA, is an accurate means of differentiating between motion-induced signal changes and other sources of variability in fMRI data.

Algorithms↗

PubMed1997

Power spectral analysis of EEG in a multiple-bedroom, multiple-polygraph sleep laboratory.

OBJECTIVES: We describe the methods for power spectral analysis (PSA) of sleep electroencephalogram (EEG) data at a large clinical and research sleep laboratory. The multiple-bedroom, multiple-polygraph design of the sleep laboratory poses unique challenges for the quantitative analysis of the data. This paper focuses on the steps taken to ensure that our PSA results are not biased by the particular bedroom or polygraph from which the data were acquired. METHODS: After describing the data acquisition system hardware, we present our signal amplitude calibration procedure and our methods for performing PSA. We validate the amplitude calibration procedure in several experiments using PSA to establish tolerances for data acquisition from multiple bedrooms and polygraphs. RESULTS: Since it is not possible to acquire identical digitized versions of an EEG signal using different sets of equipment, the best that can be achieved is data acquisition that is polygraph-independent within a known tolerance. We are able to demonstrate a tolerance in signal amplitude of +/- 0.25% when digitizing data from different bedrooms. When different data acquisition hardware is used, the power tolerance is approximately +/- 3% for frequencies from 1 to 35 Hz. The power tolerance is between +/- 3 and +/- 7% for frequencies below 1 Hz and frequencies between 35 and 50 Hz. Additional data demonstrate that variability due to the hardware system is small relative to the inherent variability of the sleep EEG. CONCLUSION: The PSA results obtained in one location can be replicated elsewhere (subject to known tolerances) only if the data acquisition system and PSA method are adequately specified.

Calibration↗

PubMed2005

Three-dimensional fusion digital subtraction angiography: new reconstruction algorithm for simultaneous three-dimensional rendering of osseous and vascular information obtained during rotational angiography.

This report describes three-dimensional (3D) fusion digital subtraction angiography (FDSA), a new algorithm for rotational angiography that combines reconstructions of the blood vessels and the osseous frame in a single 3D representation. 3D-FDSA is based on separate reconstructions of the mask and contrast sequences of the rotational acquisition. The two independent 3D data sets (3D-bone and 3D-digital subtraction angiography [DSA]) are fused in a single 3D representation. The algorithm uses a modification of the Feldkamp method that compensates for signal intensity inhomogeneity inherent to the reconstruction of nonsubtracted rotational acquisitions. By separately reconstructing the osseous and vascular information obtained from the rotational angiogram, 3D-FDSA provides optimal angiographic resolution and precise topographic analysis even when the studied vascular tree is in the immediate vicinity of bone.

Algorithms↗

PubMed1990

Human psychoneuroimmunology today.

Studies in human psychoneuroimmunology began around 1919, but a systematic approach wasn't used until the work of Solomon in the 1960s. Recently, the new specialty has achieved relative independence due to considerable data acquisition. Stress research has revealed relationships between neuroendocrine and immune changes. In parallel, increasing evidence of immunological alterations in psychiatric diseases has expanded the field; presently, immunological correlates of psychosomatic diseases and personality are sought. On the other hand, while immunological disease has been psychologically assessed for many years, a clear-cut link between psyche and immunological changes has yet to be shown. This fact, along with the therapeutic implications of advancing knowledge, will influence strongly the future trends of psychoneuroimmunology. Concepts emerging from the study of this field will be of heuristic value to both psychiatry and immunology and will help define new and expanded limits for both disciplines.

Acquired Immunodeficiency Syndrome↗

PubMed1990

Design of an optimal ventilator.

When a patient is incapable of adequate ventilation by natural processes, mechanical assistance must be provided. Ventilation assures sufficient Oxygen delivery to the organs and tissues of the body and excessive amounts of Carbon Dioxide are not permitted to accumulate. Ventilators are employed continuously or intermittently to improve the ventilation of the lungs. The present work involves design of a ventilator that virtually eliminates any work done by the patients in their breathing process. Presently available ventilators approach this level of performance but they have a few reported shortcomings. These limitations include insufficiency of inspiratory airflow and rigidity of operating cycles. The new ventilator is built around an optimal controller and its performance is based on computational capability of microprocessors. Real time measurements of volume, flow rates and pressure are managed and processed by these devices for optimal determination of controlled parameters of the ensuing respiratory cycle. These measured parameters are used for estimating the lung characteristics such as lung compliance and airway resistance. An independent microprocessor system incorporating data acquisition and processing features with scope for a number of additional capabilities such as graphic output, database and communications functions can prove very useful in health care institutions.

Biomechanical Phenomena↗

PubMed1993

Imaging time reduction through multiple receiver coil data acquisition and image reconstruction.

A technique is described for the simultaneous acquisition of MRI data using two independent receiver coils surrounding the same region of tissue, which enables the collection of data necessary for image reconstruction in a reduced number of phase-encoded acquisitions. This results in a 50% reduction in minimum scan time and may be useful in time-critical procedures. The algorithm and imaging procedures are described, and example images are shown that illustrate the reconstruction. Signal to noise is decreased by the square root of the time savings, making this technique applicable to cases in which the need to decrease minimum scan time outweighs the signal to noise penalty.

Algorithms↗

PubMed2006

Contrast-enhanced coronary artery visualization by dual-source computed tomography--initial experience.

UNLABELLED: Multi-detector computed tomography (CT) scanners, by virtue of their high temporal and spatial resolution, permit imaging of the coronary arteries. However, motion artifacts, especially in patients with higher heart rates, can impair image quality. We thus evaluated the performance of a new dual-source CT (DSCT) with a heart rate independent temporal resolution of 83 ms for the visualization of the coronary arteries in 14 consecutive patients. METHODS: Fourteen patients (mean age 61 years, mean heart rate 71 min(-1)) were studied by DSCT. The system combines two arrays of an X-ray tube plus detector (64 slices) mounted on a single gantry at an angle of 90 degrees With a rotation speed of 330 ms, a temporal resolution of 83 ms (one-quarter rotation) can be achieved independent of heart rate. For data acquisition, intraveous contrast agent was injected at a rate of 5 ml/s. Images were reconstructed with 0.75 slice thickness and 0.5 mm increment. The data sets were evaluated concerning visibility of the coronary arteries and occurrence of motion artifact. RESULTS: Visualization of the coronary arteries was successful in all patients. Most frequently, image reconstruction at 70% of the cardiac cycle provided for optimal image quality (50% of patients). Of a total of 226 coronary artery segments, 222 (98%) were visualized free of motion artifact. In summary, DSCT constitutes a promising new concept for cardiac CT. High and heart rate independent temporal resolution permits imaging of the coronary arteries without motion artifacts in a substantially increased number of patients as compared to earlier scanner generations. Larger and appropriately designed studies will need to determine the method's accuracy for detection of coronary artery stenoses.

Artifacts↗

PubMed2003

Remote-sensing reflectance of turbid sediment-dominated waters. Reduction of sediment type variations and changing illumination conditions effects by use of reflectance ratios.

Variations of sediment type (grain size and refractive index) and changing illumination conditions affect the reflectance signal of coastal waters and limit the accuracy of sediment-concentration estimations from remote-sensing measurements. These effects are analyzed from numerous in situ remote-sensing measurements carried out in the Gironde and Loire Estuaries and then reduced and partly eliminated when reflectance ratios between the near infrared and the visible are considered. These ratios showed high correlation with the sediment concentration. On the basis of the obtained relationships, performing correspondence functions were established that allow an accurate estimation of suspended sediments in the estuaries from Système Probatoire d'Observation de la Terre, Landsat, and Sea-Viewing Wide Field-of-View Sensor data, independently of the date of acquisition.

Journal Article↗

PubMed1994

Quantitative pO2 imaging in vivo with perfluorocarbon F-19 NMR: tracking oxygen from the airway through the blood to organ tissues.

The physiological redistribution of perfluorocarbon (PFC) compounds to liver, spleen, bone marrow, and lung after intravenous (i.v.) or intraperitoneal (IP) administration of PFC emulsions affords the unique opportunity for non-invasive monitoring of oxygenation status of these organs and tissues utilizing fluorine (F-19) nuclear magnetic resonance (NMR) imaging techniques. PFCs also may be introduced directly into the pulmonary airways by procedures such as liquid ventilation, intratracheal instillation, or aerosol inhalation. Considerations of importance when establishing methodology for accurate quantitation of oxygen partial pressure (pO2) in vivo using F-19 NMR include: 1.) error analysis of the calibration curves which relate pO2 to the measured PFC F-19 relaxation rate, 2.) optimization of the NMR pulse sequence for efficient oxygen sensitive data acquisition and, 3.) fluorine signal independence from emulsion aqueous phase bioconstituents. The porcine model was investigated at 0.14T following i.v. or IP administration of the PFC emulsion containing perfluorotributylamine (FC-43) to demonstrate the capability for tracking oxygen with F-19 NMR from the lung through the blood to selected organ tissues. Quantitative pO2 projection images and isobaric contour graphs were derived for the liver, spleen, and lungs as a function of inspired oxygen. Blood pO2 levels in aorta, pulmonary artery, and hepatic vein were monitored simultaneously with NMR imaging for correlative analysis.

Animals↗

PubMed1990

The anion exchanger and Na+K(+)-ATPase interact with distinct sites on ankyrin in in vitro assays.

This report demonstrates that the high affinity binding of ankyrin to two well characterized ankyrin-binding proteins, the erythrocyte anion exchanger and kidney Na+K(+)-ATPase, requires interaction of these proteins with unique sites on the ankyrin molecule. Binding of 125I-labeled erythrocyte ankyrin and ankyrin proteolytic domains was measured to the anion exchanger and Na+K(+)-ATPase incorporated into phosphatidylcholine liposomes. 125I-Labeled ankyrin associated with both anion exchanger and Na+K(+)-ATPase liposomes with a high affinity (KD ranging from 10 to 25 nM), and a capacity approaching 1 mol of ankyrin/2 mol of ATPase and 1 mol of ankyrin/8 mol of anion exchanger. The 43 kDa cytoplasmic domain of the erythrocyte anion exchanger inhibited binding of ankyrin to both the anion exchanger and Na+K(+)-ATPase liposomes with a 50% reduction at approximately 90 nM for both proteins. Further binding experiments using proteolytic domains derived from ankyrin demonstrated the following differences between the anion exchanger and Na+K(+)-ATPase in interactions with ankyrin: 1) 125I-Labeled Na+K(+)-ATPase associated with both the 89-kDa domain as well as the spectrin binding domain of ankyrin, while the anion exchanger only associated with the 89-kDa domain. 2) The 125I-labeled 89-kDa domain of ankyrin associated with Na+K(+)-ATPase liposomes with at least a 20-fold lower affinity compared with intact ankyrin while this domain associated with the anion exchanger with a 2-3-fold increase in affinity compared with intact ankyrin. 3) The 125I-labeled spectrin-binding domain of ankyrin associated with the Na+K(+)-ATPase liposomes to at least an 8-fold greater extent than to anion exchanger liposomes. The data are consistent with an independent acquisition of high affinity ankyrin binding activity for the anion exchanger and Na+K(+)-ATPase proteins through a convergent evolutionary process.

Animals↗

PubMed2006

Measurement of the viscosity-density product using multiple reflections of ultrasonic shear horizontal waves.

We have developed an on-line computer-controlled sensor, based on ultrasound reflection measurements, to determine the product of the viscosity and density of a liquid or slurry for Newtonian fluids and the shear impedance of the liquid for non-Newtonian fluids. A 14 MHz shear wave transducer is bonded to one side of a 45-90 degrees fused silica wedge and the base is in contract with the liquid. Twenty-eight echoes were observed due to the multiple reflections of an ultrasonic shear horizontal (SH) wave within the wedge. The fast Fourier transform of each echo was obtained for a liquid and for water, which serves as the calibration fluid, and the reflection coefficient at the solid-liquid interface was obtained. Data were obtained for 11 sugar water solutions ranging in concentration from 10% to 66% by weight. The viscosity values are shown to be in good agreement with those obtained independently using a laboratory viscometer. The data acquisition time is 14s and this can be reduced by judicious selection of the echoes for determining the reflection coefficient. The measurement of the density results in a determination of the viscosity for Newtonian fluids or the shear wave velocity for non-Newtonian fluids. The sensor can be deployed for process control in a pipeline, with the base of the wedge as part of the pipeline wall, or immersed in a tank.

Journal Article↗

PubMed2003

Contemporary evaluation of operative parameters and complications related to open radical retropubic prostatectomy.

OBJECTIVES: To determine the impact of recent advances in surgical technique, management, and early detection on outcome after open radical retropubic prostatectomy. METHODS: Between October 2000 and August 2002, 500 men with clinically localized prostate cancer underwent radical retropubic prostatectomy by a single surgeon (H.L.). One of the unique aspects of this prospective outcomes analysis was that both data acquisition and entry were conducted totally independent of the primary surgeon. RESULTS: The mean operative and prostatectomy time was 142.9 and 65.2 minutes, respectively. A single ureteral injury was the only intraoperative complication. The overall incidence of pulmonary embolus and/or deep vein thrombosis was 0.4%. The overall risk of allogeneic transfusion was 4.6%. The mean length of hospital stay was 2.11 +/- 0.04 days. Of the catheters, 83.6% were removed by postoperative day 8. The positive surgical margin rate was 8%. CONCLUSIONS: In the hands of experienced surgeons, outcomes after open radical prostatectomy are excellent. Laparoscopic and robotic prostatectomy must be compared with concurrent experiences with open radical prostatectomy.

Adenocarcinoma↗

PubMed1987

Two-parameter data acquisition system for rapid slit-scan analysis of mammalian chromosomes.

A data acquisition system is described for recording two independent signals simultaneously from a laser-based flow cytometer for rapid slit-scan chromosome analysis. High-aperture microscope optics allow recording of fluorescence distributions along the longest axis of metaphase chromosomes with a spatial resolution better than 1 micron. Fluorescence and small angle forward light scatter as well as dual-wavelength fluorescence signals from Indian muntjac chromosomes stained with propidium iodide (PI) or acridine orange (AO) have been recorded simultaneously. While maintaining the multi-user operation of the computer, photomultiplier signals are digitized at a rate of 400 signals per second, stored temporarily in high-speed cache memories, and transferred subsequently to a minicomputer for further storage. Extensive software packages for data acquisition, analysis, and display of the results are described. Data acquisition is generally done in list mode, allowing complete reconstruction of individual signals (profiles) at any time. The distribution of stained constituents along the chromosomes can be displayed. Furthermore, histograms of various parameters of the input signals may be generated.

Acridine Orange↗

PubMed2006

Method for multimodal analysis of independent source differences in schizophrenia: combining gray matter structural and auditory oddball functional data.

The acquisition of both structural MRI (sMRI) and functional MRI (fMRI) data for a given study is a very common practice. However, these data are typically examined in separate analyses, rather than in a combined model. We propose a novel methodology to perform independent component analysis across image modalities, specifically, gray matter images and fMRI activation images as well as a joint histogram visualization technique. Joint independent component analysis (jICA) is used to decompose a matrix with a given row consisting of an fMRI activation image resulting from auditory oddball target stimuli and an sMRI gray matter segmentation image, collected from the same individual. We analyzed data collected on a group of schizophrenia patients and healthy controls using the jICA approach. Spatially independent joint-components are estimated and resulting components were further analyzed only if they showed a significant difference between patients and controls. The main finding was that group differences in bilateral parietal and frontal as well as posterior temporal regions in gray matter were associated with bilateral temporal regions activated by the auditory oddball target stimuli. A finding of less patient gray matter and less hemodynamic activity for target detection in these bilateral anterior temporal lobe regions was consistent with previous work. An unexpected corollary to this finding was that, in the regions showing the largest group differences, gray matter concentrations were larger in patients vs. controls, suggesting that more gray matter may be related to less functional connectivity in the auditory oddball fMRI task.

Acoustic Stimulation↗