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Biomedical subjects

H F Li

Publications and source records attributed to H F Li.

15 recordsLinked to original sources
PubMed1995

Magnetic resonance imaging assessment of the severity of mitral regurgitation. Comparison with invasive techniques.

BACKGROUND: In the patient with mitral regurgitation who is being considered for valvular surgery, cardiac catheterization is usually performed to quantify the severity of regurgitation and to determine its influence on left ventricular volumes and systolic function. Magnetic resonance imaging (MRI) potentially provides a rapid, noninvasive method of acquiring these data. Thus, this study was done to determine whether MRI can reliably measure the magnitude of mitral regurgitation and evaluate the effect of regurgitation on left ventricular volumes and systolic function. METHODS AND RESULTS: Twenty-three subjects (14 women and 9 men 15 to 72 years of age) with (n = 17) or without (n = 6) mitral regurgitation underwent MRI scanning followed immediately by cardiac catheterization. The presence (or absence) of valvular regurgitation was determined, and left ventricular volumes and regurgitant fraction were quantified during each procedure. There was excellent correlation between invasive and MRI assessments of left ventricular end-diastolic (r = .95) and end-systolic (r = .95) volumes and regurgitant fraction (r = .96). All MRI examinations were completed in < 28 minutes. CONCLUSIONS: In the patient with mitral regurgitation, MRI compares favorably with cardiac catheterization for assessment of the magnitude of regurgitation and its influence on left ventricular volumes and systolic function.

Adolescent↗
PubMed1995

Quantitation of cardiac output with velocity-encoded, phase-difference magnetic resonance imaging.

Velocity-encoded, phase-difference magnetic resonance imaging (MRI) previously has been used to measure flow in the aorta, as well as in the pulmonary, carotid, and renal arteries, but these measurements have not been validated against currently accepted invasive techniques. To determine the accuracy of velocity-encoded, phase-difference MRI measurements of cardiac output, 23 subjects (11 men and 12 women, aged 15 to 72 years) underwent velocity-encoded, phase-difference MRI measurements of cardiac output in the proximal aorta, followed immediately by cardiac catheterization, with measurement of cardiac output by the Fick principle and by thermodilution. For MRI, Fick, and thermodilution measurements, stroke volume was calculated by dividing cardiac output by heart rate. The magnetic resonance images were acquired in 1 to 3 minutes. For all patients, the agreement between measurements of stroke volume was 3 +/- 9 ml for MRI and Fick, -3 +/- 11 ml for MRI and thermodilution, and 0 +/- 8 ml for MRI and the average of Fick and thermodilution. Compared with standard invasive measurements, velocity-encoded, phase-difference MRI can accurately and rapidly determine cardiac output.

Adolescent↗
PubMed1995

Assessment of left-to-right intracardiac shunting by velocity-encoded, phase-difference magnetic resonance imaging. A comparison with oximetric and indicator dilution techniques.

BACKGROUND: Velocity-encoded, phase-difference magnetic resonance imaging (MRI) has been shown to provide an accurate assessment of shunt magnitude in patients with large atrial septal defects, but its ability to determine shunt magnitude in patients with intracardiac left-to-right shunts of various locations and sizes has not been evaluated in a prospective and blinded manner. The objective of the present study was to determine whether velocity-encoded, phase-difference MRI can assess the magnitude of intracardiac left-to-right shunting in humans. METHODS AND RESULTS: Twenty-one subjects (15 women and 6 men; age range, 15 to 72 years) underwent velocity-encoded, phase-difference MRI measurements of flow in the proximal aorta and pulmonary artery, followed immediately by cardiac catheterization. The presence of left-to-right intracardiac shunting was assessed with hydrogen inhalation, after which shunt magnitude was measured by the oximetric and indocyanine green techniques. Of the 21 patients, 12 had left-to-right intracardiac shunting detected by hydrogen inhalation. There was a good correlation (r = .94) between the invasive and MRI assessments of shunt magnitude. In comparison to oximetry and indocyanine green, MRI correctly identified the 12 patients with a ratio of pulmonary to systemic flow (Qp/Qs) of < 1.5 (9 without intracardiac shunting and 3 with small shunts) and the 9 patients with a Qp/Qs of > or = 1.5 (6 with atrial septal defect, 1 with ventricular septal defect, 1 with patent ductus arteriosus, and 1 with both atrial septal defect and patent ductus arteriosus). CONCLUSIONS: Compared with measurements obtained during cardiac catheterization, velocity-encoded, phase-difference MRI measurements of flow in the proximal great vessels can reliably assess the magnitude of intracardiac left-to-right shunting.

Adult↗
PubMed1995

Measurement of absolute epicardial coronary artery flow and flow reserve with breath-hold cine phase-contrast magnetic resonance imaging.

BACKGROUND: Noninvasive measurement of absolute coronary arterial flow and coronary flow reserve would be of considerable use in the diagnosis and management of patients with coronary artery disease. Phase-contrast magnetic resonance imaging (MRI) has been used to measure flow in a variety of vessels. The goal of the present study was to determine if MRI measurements of coronary artery flow in a single breath-hold can be used to determine flow reserve and the severity of pericardial stenosis. METHODS AND RESULTS: In eight mongrel dogs, a closed chest model of partial left anterior descending coronary artery (LAD) occlusion was created. Coronary flows in the left circumflex artery (LCx) and LAD were measured at rest and during adenosine infusion using velocity-encoded, breath-hold MRI and perivascular ultrasound (US) flowmeters. MRI measurements of absolute coronary flow and coronary flow reserve were highly correlated with US (r = .96 and .94, respectively). Flow reserve measured in the constricted LAD was significantly lower than that in the unconstricted LCx by both US (P = .002) and MRI (P = .011). CONCLUSIONS: MRI measurements of coronary flow and flow reserve were in good agreement with US measurements. In addition, MRI measurements of coronary flow reserve successfully discriminated stenotic from normal vessels. These results indicate that MRI is a useful method for the noninvasive assessment of coronary flow and stenosis.

Adenosine↗
PubMed1995

[An investigation on acute flaccid paralysis (AFP) cases in some provinces with high risk of poliomyelitis of China].

In the mid Jun, 1994, a study team organized by MOPH investigated AFP cases in 10 provinces with high prevalence of poliomyelitis (polio). Twenty prefectures and ten counties were selected randomly from each of 10 provinces and relevant prefectures. The team identified 681 AFP cases under 15 years old from 45 hospitals at prefecture level and 13 hospitals at country level based on hospital records from cases occurred during 1991-1994. AFP, Polio, Non-polio AFP and GBS (Guillian-Barre Syndrome) cases aged from 0-14 years scattered around 101 counties (cities) among target population and their average incidences by year were 1.04, 0.48, 0.57 and 0.31 (per 10(5) respectively. Noticingly, the incidence of polio had reduced significantly since 1991, and its proportion among AFP was also reducing from first place yearly since 1991. In addition, over 95% of the polio cases were concentrated in the 4 year olds which indicated that the target population for surveillance and prevention should mainly be focusing on 0-4 year olds. As the incidence of non-polio AFP has been used as a current sensitive index of surveillance system, we noticed that the incidence rates had been significantly different from various regions. According to the analytic data, we recommend that "Rate of non-polio AFP in children 0-14 years of age greater than 1/10(5)" might be a better and more sensitive index for surveillance program in China.

Acute Disease↗
PubMed1995

[A study on the epidemiologic features of sporadic legionellosis in children].

317 hospitalized children and 86 healthy children were collected between April 4, 1991 and April 3, 1992 were detected for IgM antibodies to Legionella using ELISA with sonicated and EDTA antigens of 9 species (15 serogroups). The total positive rate was 13.25% (42/317) in hospitalized children and 2.33% (2/86) in healthy children. Legionellosis was diagnosed in 35 cases, of which 25 (11.68%) with respiratory illnesses, 5 (5/15) with kidney diseases or blood diseases and 1 (1.45%) with other disease. The proportion of legionellosis was 11.04% (35/317). Of the 15 antigens tested, significant antibodies levels were detected in 11. Tatlock micdadei constituted 47.62% (20/42). Lp(1-6)23.81% (10/42) and L. bozemane 14.29% (6/42). There was higher proportion of legionellosis in elder children and in summer time.

Antibodies, Bacterial↗
PubMed1995

[A study on the risk factors of Legionella infection in children].

In order to understand the risk factors of legionella infection in children a case-control study with two kinds of controls was conducted. The stepwise regression analysis included age, sex, season and immunosuppressive therapy in regression equation. The non-conditional logistic regression analysis showed that age, passive smoking and touching soil were associated with legionella infection. The statistics analysis also showed that there were dose-response relationship between age, passive smoking and immunosuppressive therapy and the frequency of legionella infection in children. It was suggested that age, season, immunosuppressive therapy, passive smoking and touching soil were risk factors for legionella infection.

Case-Control Studies↗
PubMed1994

[A benign neuroendocrine tumor of the lung: study on the origin of the so-called sclerosing hemangioma of the lung].

31 cases of the so-called sclerosing hemangiomas of the lung were studied by light microscope, immunohistochemical and electron microscopy. This tumor is benign and has 3 histologic patterns: papillary, hemangioma-like and solid type. Characteristic morphology being uniform round tumor cells, lying within the stroma in different patterns and regarded as the major component of sclerosing hemangioma, expressing neuroendocrine markers which include chromagranin A, neuron-specific enolase, ACTH, growth hormone, calcitonin and gastrin. Only a few tumor cells were positive for epithelial membrane antigen (EMA) and carcinoembryonic antigen (CEA), all the tumor cells were negative for keratin (Polyclonal, Z622) stain. However, in contrast to the round tumor cells, the cells lining papillary projections or cystic spaces, which presented as normal or hyperplastic alveolar cells, stained positive for keratin, EMA and CEA but negative for neuroendocrine markers. Both the surface cells and tumor cells were negative for Factor VIII-related antigen and alpha 1-AT. Therefore, pulmonary sclerosing hemangioma was regarded to be a benign tumor originating from the neuroendocrine cells of the lung and we suggest that it be renamed as benign neuroendocrine tumor of the lung (LBNET). This viewpoint has not been previously reported in the literature.

Adenoma↗
PubMed1988

Maximum length sequence applied to the measurement of brainstem auditory evoked responses.

An evoked response may be assumed to consist of synchronous electrical activities of groups of neurons in response to a stimulus. Unfortunately, this response is usually weak and often masked by the background EEG activity generated spontaneously by the brain. In order to extract the embedded evoked response we have employed the theory of maximum length sequence, assuming only a temporal linearity of the system from which measurements are taken. The technique has been applied successfully with the aid of a microcomputer. The system also supports the same measurement by a conventional averaging technique. The results of the two are compared, indicating the advantages of the maximum length technique: improved signal-to-noise ratio, repeatability and speed.

Animals↗
PubMed1984

A microcomputer-based binaural measurement system.

A microcomputer is used to control a dual-channel, sine-wave generator as the excitation to both the left and right ears in experimental subjects, and for on-line measurement of the neuronal spike counts. The effects of varying the walking pattern and phase angle between the two channels can be investigated. After normalisation of spike counts, the result can be displayed as a 3-D plot on a CRT or an x-y plotter. The system is useful for general steady state and transient binaural measurement.

Biomedical Engineering↗
PubMedDate not supplied

Microcomputer-based spike train analysis.

A system has been developed to analyse statistically the information contained within neuronal spike trains in the central nervous system. The system consists of a microprocessor development system, together with the peripheral components and transducers. Suitable software packages have been developed to analyse statistical parameters including the mean, variance, entropy, conditional entropy, serial correlation coefficients, Markov dependency and Markov order. By linking up the required routines, the system is capable of responding in real-time and plotting the desired results from the spike train obtained. Such system has been used to study the neuronal spike trains recorded from central vestibular neurons which could be affected by positional changes, anaesthetics and various drugs for the relief of motion sickness.

Animals↗