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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↗
PubMed1995

Intraoperative data acquisition for the study of cerebral dysfunction following cardiopulmonary bypass.

As a first step in our study to document postoperative cerebral dysfunction, and to determine whether global cerebral blood flow can be implicated in the etiology of this postoperative change, we have assembled a flexible data acquisition system to acquire and record data from four independent sources, three in digital form and one analog. Each of the monitors that we use has a different requirement: One has eight channels of analog output; the other three have RS-232 digital outputs, each with a data stream with different characteristics. The central element of our data collection is a personal computer running the data acquisition and analysis program, LabVIEW for Windows (National Instruments, Austin, TX). All data are processed through separate LabVIEW global variables; the data strings are concatenated and stored on the hard disk in a spreadsheet format for further analysis. We illustrate an intraoperative recording made during cardiopulmonary bypass (CPB) by showing a graph of the mean arterial pressure (MAP), mixed venous oxyhemoglobin saturation recorded from the jugular bulb (JVO2Sat), and temperature measured from the nasopharynx. A decrease in the MAP after unclamping the aorta is accompanied by a decrease in JVO2Sat.

Blood Pressure↗
PubMed2002

A prospective study to determine whether cover gowns in addition to gloves decrease nosocomial transmission of vancomycin-resistant enterococci in an intensive care unit.

BACKGROUND: Vancomycin-resistant enterococci (VRE) remain a significant nosocomial pathogen. Current guidelines of the Hospital Infection Control Practices Advisory Committee (HICPAC) of the Centers for Disease Control and Prevention (CDC) recommend the use of gowns and gloves for some interactions with VRE-infected or -colonized patients to prevent nosocomial transmission of VRE. OBJECTIVE: To assess the effect of disposable cover gowns on preventing nosocomial transmission of VRE. DESIGN AND SETTING: Prospective study in a 16-bed medical intensive care unit of a university teaching hospital. PATIENTS: All patients who were at risk to acquire VRE, were admitted to the intensive care unit from August 1998 to January 1999, and had at least two perirectal cultures were included in the analysis of VRE acquisition. INTERVENTION: VRE isolation precautions were changed from gowns and gloves to gloves alone. MAIN OUTCOME risk factors for VRE acquisition. RESULTS: The VRE acquisition rate was 1.80 cases per 100 days at risk in the gown and gloves period compared with 3.78 in the gloves only period (P = .04). In a proportional hazards model adjusted for length of stay, gloves only precautions with a hazard ratio of 2.5 (P = .02; 95% confidence interval, 1.2 to 5.3) were the only independent risk factor for VRE acquisition. CONCLUSION: Our data lend support to current HICPAC recommendations for the use of cover gowns to decrease nosocomial transmission of VRE.

Baltimore↗
PubMed1991

A 37-channel DC SQUID magnetometer system.

A 37-channel DC SQUID magnetometer system has been built for biomagnetic studies. The SQUID loop of each magnetometer serves as the active sensing element, thereby eliminating the need for flux coupling circuits. The magnetometers are located approximately 3 cm above the outer dewar bottom. The SQUIDs are directly coupled to highly simplified read-out electronics using only five wires per channel; no helium temperature impedance matching circuits are required. Each channel can be independently inserted into or removed from the dewar. Using a novel electronic noise reduction technique the system white and 1 Hz flux density noise values are typically 5 and 10 fT Hz-1/2, respectively, including the noise contribution of the in-house fabricated dewar and the magnetically shielded room. The two parts of the data-processing system allow independent handling of the acquisition and analysing task. Two example measurements demonstrate the advantage of the electronic noise reduction method.

Equipment Design↗
PubMed2002

Spinal surgery procedure discretization.

In the last decades, scientists developed analytic models of spinal surgery to assess surgical choices and instrumentation parameters. They noted the difficulty to represent the boundary conditions on their deterministic models and recognize the lack of knowledge in surgical procedures. This paper presents a formalization technique applied to spinal surgery to improve the formulation of biomechanical models. This technique consisted into two steps: knowledge extraction and knowledge representation. The protocol was established with an expert surgeon using Colorado2 instrumentation. Surgeon's knowledge acquisition has permitted to define eleven detailed independent data cards for the different steps of surgery like hook or screw insertion, rod installation, etc... The behaviour of the concerned elements on its neighbouring entity were specified using three matrices. The link between surgery and modelling becomes easier and permits to better define the boundary conditions on each entity during the simulation.

Artificial Intelligence↗
PubMed2006

Systematic review: impact of health information technology on quality, efficiency, and costs of medical care.

BACKGROUND: Experts consider health information technology key to improving efficiency and quality of health care. PURPOSE: To systematically review evidence on the effect of health information technology on quality, efficiency, and costs of health care. DATA SOURCES: The authors systematically searched the English-language literature indexed in MEDLINE (1995 to January 2004), the Cochrane Central Register of Controlled Trials, the Cochrane Database of Abstracts of Reviews of Effects, and the Periodical Abstracts Database. We also added studies identified by experts up to April 2005. STUDY SELECTION: Descriptive and comparative studies and systematic reviews of health information technology. DATA EXTRACTION: Two reviewers independently extracted information on system capabilities, design, effects on quality, system acquisition, implementation context, and costs. DATA SYNTHESIS: 257 studies met the inclusion criteria. Most studies addressed decision support systems or electronic health records. Approximately 25% of the studies were from 4 academic institutions that implemented internally developed systems; only 9 studies evaluated multifunctional, commercially developed systems. Three major benefits on quality were demonstrated: increased adherence to guideline-based care, enhanced surveillance and monitoring, and decreased medication errors. The primary domain of improvement was preventive health. The major efficiency benefit shown was decreased utilization of care. Data on another efficiency measure, time utilization, were mixed. Empirical cost data were limited. LIMITATIONS: Available quantitative research was limited and was done by a small number of institutions. Systems were heterogeneous and sometimes incompletely described. Available financial and contextual data were limited. CONCLUSIONS: Four benchmark institutions have demonstrated the efficacy of health information technologies in improving quality and efficiency. Whether and how other institutions can achieve similar benefits, and at what costs, are unclear.

Biomedical Technology↗
PubMed1998

Evaluation of the ECAT EXACT HR+ 3-D PET scanner in H2(15)O brain activation studies: dose fractionation strategies for rCBF and signal enhancing protocols.

We evaluated the performance of the ECAT EXACT HR+ 3-D whole-body positron emission tomography (PET) scanner when employed to measure brain function using H2(15)O bolus activation protocols that are completed in single same-day data acquisition sessions. Using vibrotactile and auditory stimuli as independent activation tasks, we studied the scanner performance under different imaging conditions in five healthy volunteers. Cerebral blood flow images were acquired from each volunteer using H2(15)O bolus injections of activity varying from 5-20 mCi. One-session dose-fractionation strategies were analyzed for rCBF, standard activity-concentration, switched, and cold-bolus/switched protocols. Performance characteristics. The scanner dead time grew linearly with injected dose from 10% to 25%. Random events varied from 30% to 50% of the detected events. Random and scattered events were corrected adequately at all doses. Estimated noise-effective-count curves plateau at about 10 mCi. One-session 12-injection bolus PET activation protocols. Using an acquisition protocol that accounts for the scanner performance and the practical aspects of imaging volunteers and neurological patients in a single same-day session, we assessed the correlation between the significance of activation foci and the dose/injection used. The one-session protocol employs 12 bolus injections/subject. We present evidence suggesting that when an rCBF protocol is used, image noise is reduced significantly when the activity injected increases from 5 to 10 mCi. Increasing the dose from 10 to 15 or 20 mCi yielded further but smaller reductions. Our observations also suggest that image noise will be strongly reduced if a 20-mCi dose/injection is used when data are collected using protocols that employ long acquisition times such as a switched or a cold-bolus/switched protocol.

Adult↗
PubMed2004

Clinical, histopathologic, and molecular markers of prognosis: toward a new disease risk stratification system for medulloblastoma.

PURPOSE: To assess the feasibility of performing central molecular analyses of fresh medulloblastomas obtained from multiple institutions and using these data to identify prognostic markers for contemporaneously treated patients. MATERIALS AND METHODS: Ninety-seven samples of medulloblastoma were collected. Tumor content in samples was judged by frozen section review. Tumor ERBB2 protein and MYCC, MYCN, and TRKC mRNA levels were measured blind to clinical details using Western blotting and real-time polymerase chain reaction, respectively. Histopathologic and clinical review of each case was also performed. All data were subjected to independent statistical analysis. RESULTS: Sample acquisition and analysis times ranged from 3 to 6 days. Eighty-six samples contained sufficient tumor for analysis, including 38 classic, 30 nodular desmoplastic, and 18 large-cell anaplastic (LCA) medulloblastomas. Protein and mRNA were extracted from 81 and 49 tumors, respectively. ERBB2 was detected in 40% (n=32 of 81) of tumors, most frequently in LCA disease (P=.005), and was independently associated with a poor prognosis (P=.031). A combination of clinical characteristics and ERBB2 expression provided a highly accurate means of discriminating disease risk. One hundred percent (n=26) of children with clinical average-risk, ERBB2-negative disease were alive at 5 years, with a median follow-up of 5.6 years, compared with only 54% for children with average-risk, ERBB2-positive tumors (n=13; P=.0001). TRKC, MYCC, and MYCN expression and histopathologic subtype were not associated with prognosis in this study. CONCLUSION: Central and rapid molecular analysis of frozen medulloblastomas collected from multiple institutions is feasible. ERBB2 expression and clinical risk factors together constitute a highly accurate disease risk stratification tool.

Adolescent↗
PubMed2006

Application of magnetic resonance virtual endoscopy as a presurgical procedure before sialoendoscopy.

OBJECTIVES: The objectives of this study were to investigate the feasibility of clinical application of magnetic resonance (MR) virtual endoscopy as a presurgical procedure before sialoendoscopy and to evaluate its value in the diagnosis of obstructive salivary gland diseases and preoperative visualization of endoluminal views. STUDY DESIGN: This study presents our initial experience to use MR virtual endoscopy for the presurgical visualization of salivary duct lumen and ductal pathologies in comparison to the sialoendoscopy findings in a feasibility study. METHODS: Six consecutive patients with suspected obstructive salivary gland diseases underwent MR sialography with a three-dimensional fast imaging using steady-state acquisition. The three-dimensional MR data were transferred to an independent workstation and were postprocessed with navigator software to generate three-dimensional reconstruction and virtual endoscopic images. The fly-through mode was used to imitate the sialoendoscopic exploratory procedure. Then the patients underwent sialoendoscopy and the endoscopic findings were compared with the preoperative virtual endoscopic images. RESULTS: The MR data acquisition and postprocessing protocol were feasible. The virtual endoscopy created clear endoluminal views of salivary duct and the ductal pathologies. The diagnoses were all confirmed by surgical sialoendoscopy. The virtual endoscopic images showed close resemblance to the sialoendoscopic findings. CONCLUSIONS: MR virtual endoscopy is an effective and noninvasive diagnostic method for evaluating the endoluminal anatomy and pathologies of the salivary duct. The clinical application of MR virtual endoscopy as a presurgical procedure before sialoendoscopy is a valuable and promising approach, which can provide surgeons useful morphologic and pathologic information.

Adult↗
PubMed1996

Three-dimensional image reconstruction for electrical impedance tomography.

Very little work has been conducted on three-dimensional aspects of electrical impedance tomography (EIT), partly due to the increased computational complexity over the two-dimensional aspects of EIT. Nevertheless, extending EIT to three-dimensional data acquisition and image reconstruction may afford significant advantages such as an increase in the size of the independent data set and improved spatial resolution. However, considerable challenges are associated with the software aspects of three-dimensional EIT systems due to the requirement for accurate three-dimensional forward problem modelling and the derivation of three-dimensional image reconstruction algorithms. This paper outlines the work performed to date to derive a three-dimensional image reconstruction algorithm for EIT based on the inversion of the sensitivity matrix approach for a finite right circular cylinder. A comparison in terms of the singular-value spectra and the singular vectors between the sensitivity matrices for a three-dimensional cylinder and a two-dimensional disc has been performed. This comparison shows that the three-dimensional image reconstruction algorithm recruits more central information at lower condition numbers than the two-dimensional image reconstruction algorithm.

Algorithms↗
PubMed1999

Complete clinical outcomes audit. Resource requirements and validation of the instrument.

BACKGROUND: Clinically relevant surgical outcomes are usually monitored by surgeons only for new and/or high-volume procedures. Prospective outcomes audit studies are rarely done on 100% of procedures performed by a single surgeon, a surgical practice, or an institution. Therefore, we set out to determine the resource utilization and accuracy of a well-validated system at its introduction into a North American university surgical practice. METHODS: The Otago Surgical Audit, which has been validated in a wide spectrum of surgical practices in Australasia, was applied to a university practice in general and laparoscopic surgery. Data were recorded by the surgeon on the day of operation, at discharge, and during any subsequent readmission. Resource utilization was determined by timing the important steps in data acquisition and computer entry. Data accuracy was assessed by an independent chart review of 22% of all records. Case capture was audited by reviewing operating room case logs. RESULTS: Over 1 year, from October 1, 1996 to September 30, 1997, 338 procedures were performed. Data recording and coding by the surgeon required 2 min per form, or a total of 676 min (11.3 h) annually. Data entry required 2.11 min per form, or a total of 713 min (11.9 h) for the year. Eight percent of cases were returned to the surgeon for additional information. In the medical record audit, no additional mortality or readmissions were discovered, and one minor complication was recorded in the hospital record but not the outcomes audit. One complication and three operations recorded in the audit database were omitted from operating room records. Two minor procedures on the operating room log were omitted from the audit database. Operating time reported by the surgeon averaged 19 min less than recorded in the operative log. Data accuracy and coding accuracy improved significantly between the 1st month (month 4) and the 2nd month audited (month 12), (p <.01). CONCLUSIONS: It is possible to perform a 100% clinical outcome audit with the use of minimal resources. When the surgeon is involved with data acquisition and coding, the accuracy and completeness of the log may outstrip the medical record, but a learning curve of 4-6 months may be required to achieve this goal.

Humans↗
PubMed1992

Within-subject behavioral analysis of recent memory in aging mice.

Two experiments addressed the utility of a T-maze, delayed reversal paradigm for assessment of recent memory impairment in aging C57BL/6NNia mice. This paradigm involved acquisition of a learning set for identification of the correct arm choice in a daily multiple-trial discriminated avoidance session. During each session, the correct arm was always opposite that entered on an initial "information trial" and maximal performance thus required a reversal (or "lose-shift") strategy. Once the learning set had been acquired, retention performance was examined following delays of varying length which were introduced following the information trial during each session. In the first experiment, acquisition and retention components of delayed reversal were considered in a cross-sectional study involving separate groups of mice aged 7, 10, 15, or 27 months. Analysis of acquisition components suggested that relative to young mice, the old mice were slower to acquire both the first reversal and the learning set. Analysis of the retention phase suggested that memory decay gradients for goal arm discrimination became more pronounced with increasing age, whereas decay gradients for the avoidance response were similar among the age groups. Correlational analysis of data for the old mice suggested independence of age-related deficits in the acquisition and recent memory components of the delayed reversal paradigm. In the second experiment, survivors from the previous 7- and 10-month-old groups were retested when 27 months of age. The cross-sectional and longitudinal data led to the same conclusions with regard to the effect of age on recent memory function. Overall, these results suggest that the delayed reversal paradigm will be a valuable tool in the analysis and evaluation of interventions potentially affecting age-related cognitive impairment.

Journal Article↗
PubMed1987

A device for spike train sampling with built-in memory.

The described interface to a digital computer measures interspike interval durations with a resolution of 10 microseconds. A built-in first-in first-out (FIFO) memory relieves the host computer from frequent I/O intensive tasks. The internal FIFO buffer can store up to 512 data words (wordlength is 16 bit) and works on the dual-port principle. This way the acquisition of a neuronal spike train is completely independent of the computer's simultaneously ongoing data access. A simple handshake protocol between the interface and the computer prevents any overhead communication. The buffer architecture of the instrument releases the host computer from high speed I/O handling schemes like real-time, clock-controlled, polling or interrupt procedures, that would request assembly language support. The body of two software, driver routines in the BASIC and the PASCAL language is presented. A complete and detailed schematic diagram of the circuitry is included.

Computer Literacy↗
PubMed2000

Application of topographical methods to clinical esophageal manometry.

OBJECTIVE: Topographical manometric methods have improved the understanding of esophageal peristalsis in research applications but require a large number of recording sensors. Commonly used methods limited to four sensors were compared to topographical methods to determine whether the latter also had significant clinical utility. METHODS: Two hundred twelve patients referred for esophageal manometry were studied with a data acquisition system having 21 intraluminal recording sites, and the findings were analyzed independently using both limited (pull-through plus four recording sites) and topographical approaches (all sites). Discrepant results were clarified using supportive clinical data. RESULTS: The two methods were in diagnostic agreement in 187 cases (88.2%). Topographical methods correctly identified all 26 patients with achalasia within the group with aperistalsis (n = 36). The limited methods could not confidently identify six achalasia patients and were significantly less effective in segregating aperistaltic disorders (p < 0.05 across methods). Topographical methods alone detected evidence of incomplete lower esophageal sphincter relaxation in 12 additional patients, eight of whom had clinical data supporting the findings. Topographical methods identified the upper margin of the lower sphincter in all but three subjects (1.4%); limited methods could not identify this location in these and five additional subjects (3.8%) and differed from the topographical measurement by > or = 2 cm in 11.9% of cases. CONCLUSIONS: Topographical methods are more accurate than commonly used methods in diagnosing the type of severe motor dysfunction and provide additional information important in the clinical practice of esophageal manometry.

Adolescent↗
PubMed2002

Platform-independent image reconstruction for spiral magnetic resonance imaging.

The distinct feature of data acquisition for magnetic resonance imaging (MRI) is that the data are sampled in frequency domain instead of spatial domain. Therefore, the acquired data must be inverse Fourier transformed to generate images. To apply fast Fourier transform (FFT), the data are usually acquired on rectilinear grids. However, acquiring data on rectilinear grids is not very efficient in MRI. A spiral trajectory, which starts at the origin of the frequency domain and spins out to higher spatial frequency is more efficient and faster than the conventional method. Since the spiral trajectories do not sample on rectilinear grids, raw data must be re-interpolated onto rectilinear grids prior to inverse FFT. This re-gridding process is done using a reconstruction program. When the platforms to run the program grow, the efforts required to maintain the program become prohibitive. This problem can be solved through the platform-independent Java programming language. In this paper, we report on our attempt to implement the spiral MRI reconstruction program in Java. We show that the performance is not significantly affected and that it is practical to use a platform-independent reconstruction software.

Fourier Analysis↗
PubMed2003

Clinical and angiographic outcome of patients with mild coronary lesions treated with balloon angioplasty or coronary stenting. Implications for mechanical plaque sealing.

AIMS: To investigate the clinical and angiographic outcome of patients with mild coronary lesions treated with balloon angioplasty or coronary stenting (coronary plaque sealing, i.e. dilatation of angiographically non-significant lesions) compared to moderate and severe stenoses. METHODS AND RESULTS: Patients with chronic stable angina and a single de novo lesion in a native coronary vessel scheduled to undergo percutaneous coronary intervention (PCI) were selected from 14 different studies. Off-line analysis of angiographic outcomes was assessed in all patients using identical and standardised methods of data acquisition, analysis and definitions. Clinical endpoints were adjudicated by independent clinical events committees. All quantitative coronary angiographic (QCA) analyses were performed in the same core laboratory. Stenosis severity prior to PCI was categorised into three groups: <50% diameter stenosis (DS), 50-99%DS and >99%DS pre. A total of 3812 patients were included in this study; 1484 patients (39%) were successfully treated with balloon angioplasty (BA) only and stented angioplasty was performed in 2328 patients (61%).One-year mortality and rate of non-fatal myocardial infarction (MI) (Kaplan-Meier) did not differ between BA and stented angioplasty for any of the stenosis severity categories. Following BA, the combined event rate (death and non-fatal MI) was 4.8, 4.6 and 0% in the <50, 50-99 and >99%DS categories, respectively. Following stented angioplasty, the combined event rate was 3.1, 4.4 and 4.8% in the same categories. The need for repeat revascularisation corrected for stenosis severity in the Cox proportional-hazards regression model was reduced by 20% after stented angioplasty (hazard ratio (HR) 0.80, 95%CI 0.69-0.93). CONCLUSION: The concept of plaque sealing is appealing from the theoretical point of view. However, with current technology, plaque sealing cannot prevent death and future non-fatal MIs in the long-term because 1-year event rates after PCI of non-significant stenoses remain unacceptably elevated when compared with the estimated 1-year probability of a non-fatal MI in lesions with a <50%DS. Moreover, major adverse cardiac events at 1-year after PCI are not directly related to the degree of pre-procedural stenosis severity.

Angina Pectoris↗
PubMed2006

Flux balance analysis in the era of metabolomics.

Flux balance analysis (FBA) has emerged as an effective means to analyse biological networks in a quantitative manner. Much progress has been made on the extension of FBA to incorporate a priori biological knowledge, provide more practical descriptions of observed cell behaviours, and predict the outcome of network perturbations. Metabolomics is independently advancing as a set of high-throughput data acquisition tools providing dynamic profiles of metabolites in an unbiased manner. These data sets are neither yet sufficiently comprehensive nor accurate enough for generating large-scale kinetic models. Thus, there is a pressing need to develop quantitative techniques that can make use of the emerging data and embrace the associated uncertainties. This article reviews recent advances in FBA to meet this need and discusses the utility of FBA as a complement to metabolomics and the expected synergy as a result of combining these two techniques.

Animals↗
PubMed1990

[Brain perfusion SPECT imaging before and during the acetazolamide test using 99mTc-HMPAO].

A new method using brain perfusion 99mTc-HMPAO SPECT imaging was developed for evaluating cerebral perfusion reserve by the acetazolamide test with a short period. The first SPECT study was carried out for 13.5 min to obtain SPECT images at the resting state after 3 min postinjection of 555 MBq (15 mCi) of 99mTc-HMPAO. At the same time as the start of the first SPECT study, 1 g of acetazolamide was intravenously injected. Immediately after the stop of the 1st SPECT study, 925 MBq (25 mCi) of 99mTc-HMPAO from the same vial as in the first study was additionally injected. Three minutes later the second SPECT study was carried out for 10 min. After reconstruction the tomographic images in the first study were subtracted from the images in the second study to obtain those during the acetazolamide test after correction of the time differences in data acquisition between the two studies. This subtraction technique gives independent brain perfusion SPECT images before and during the acetazolamide test. Besides, the regional flow changes during the test were quantitatively analyzed. In conclusion this method seems to be practically useful for evaluating regional brain perfusion before and during drug treatments as a consecutive study with a short period of approximately 30 min.

Acetazolamide↗