Search PubMed⌕ Search

Biomedical subjects

M Linzer

Publications and source records attributed to M Linzer.

At least 91 records · Page 5Linked to original sources
PubMed1983

Imaging the nonlinear ultrasonic parameter of a medium.

A technique for imaging the nonlinear ultrasonic parameter B/A has been developed. The nonlinear parameter describes the dependence of ultrasonic velocity on pressure and may well provide a new and powerful tool for characterizing both biological and nonbiological media. Our approach is based on observing the interaction of two ultrasonic waves with different frequencies and power levels. A low frequency pump wave, with power level suitable for medical diagnosis (1 mW/cm2), is used to sinusoidally modulate the sound pressure over the region of interest. A much lower intensity high-frequency probe beam is propagated perpendicularly to the pump beam. The phase of the probe wave is modified in proportion to the integral of the product of the nonlinear parameter B/A and the pressure of the pump wave, which varies sinusoidally along the probe beam. This phase change provides a Fourier component of the distribution of the nonlinear parameter B/A for the spatial frequency corresponding to the inverse of the pump wavelength. By changing the frequency of the pump waves, the spatial frequency is changed and a set of spatial Fourier coefficients of the distribution of the nonlinear parameter B/A is obtained. An inverse operation then gives the one-dimensional image along the probe beam. If the probe beam is scanned mechanically, the entire cross-sectional image is obtained. Several images of the nonlinear parameter of biological objects were generated with our system. To our knowledge, these represent the first images of the nonlinear parameter to be reported in the literature. The nonlinear parameter of water was also measured and agreed well with values obtained by other techniques.

Adipose Tissue↗
PubMedDate not supplied

Identifying patients with depression in the primary care setting: a more efficient method.

OBJECTIVE: To determine if there is a core subset of depressive symptoms that could be used to efficiently diagnose depression after administering the 2-item PRIME-MD a screening questionnaire for depression. METHODS: One thousand patients selected randomly and by convenience from 4 primary care clinics were assessed by PRIME-MD and completed a questionnaire measuring the following validation variables: functional status and well-being, disability days, somatic symptoms, depression severity, suicidal thoughts, health care utilization, and the physician-patient relationship. RESULTS: Four symptoms (sleep disturbance, anhedonia, low self-esteem, and decreased appetite) accounted for virtually all the depression symptom-related variance in functional status and well-being, with 8.3% of patients having 2 of these symptoms and 8.2% having 3 or 4 of these symptoms. There was excellent agreement between diagnosis based on core symptoms and major depression (K= 0.77; overall accuracy rate, 94%). There were significant differences (P<.001) among patients with negative depression screen, 0 to 1, 2, and 3 to 4 core symptoms with scores on each of the validation variables getting progressively worse in these 4 groups. A cutoff point of 2 core symptoms identified all but 3 patients with major depression and an additional 5% of the entire sample without major depression who were significantly (P<.05) worse than patients without depression on each of the validation variables. CONCLUSION: A strategy that includes the use of a 2-item depression screener followed by the evaluation of 4 core depressive symptoms is an efficient and effective way of identifying and classifying primary care patients with depression in need of clinical attention.

Alabama↗
PubMedDate not supplied

B-scan echo-amplitude measurement in patients with diffuse infiltrative liver disease.

B-scan echo-amplitude measurements of the liver were recorded in a prospective clinical trial involving 56 persons--28 normal volunteers and 28 patients with Gaucher disease. The nonspecular liver parenchymal echoes were found to be abnormally elevated in Gaucher patients despite relatively normal liver biochemical values and absence of symptomatic liver disease. Echo amplitude corresponded directly to the amount and histologic distribution of abnormal glycolipid accumulation within the liver. The highest abnormal values were recorded when there was clumping of the glycolipid cells, producing discontinuities within the range of ultrasound resolution. B-scan echo-amplitude measurements accurately represent the degree of histologic abnormality in Gaucher patients, suggesting that this technique should be useful for monitoring enzyme replacement therapy.

Adult↗