Biomedical subjects

Armen Sarvazyan

Publications and source records attributed to Armen Sarvazyan.

5 recordsLinked to original sources

PubMed2006

Ultrasound velocity in human muscle in vivo: perspective for edema studies.

The present study examines the association of the changes in ultrasound velocity measured at 1 MHz using 1.5 micros duration tone burst in the human soleus muscle in vivo with several pathologies including patients with chronic renal failure (CRF) and disorders of the cardiovascular system. Total 127 subjects were investigated, with approximately equal number of male and female subjects uniformly distributed by age, from 15 to 70 years old. Since molecular composition of the tissue is thought to have greater effect on the bulk ultrasound velocity, potential contribution of both water and fat, two main variable components of a muscle, were taken into account. Observed negative correlation of ultrasound velocity with the body mass index was considered a result of an elevated fat content. Based on the obtained data, presence of leg edemas results in a measurably lower ultrasound velocity in the soleus muscle. Unless patients had visibly detected leg edema, no difference between healthy individuals, patients with chronic heart failure, or CRF was found. Despite relatively high individual variations in velocity, ranging from 1530 to 1615 m/s, a statistically significant gender correlated difference between average values of the velocity was observed. No dependence of velocity on subject age was detected. An indirect confirmation of the muscle fluid homeostasis was revealed in patients with CRF undergoing hemodialysis procedure. After hemodialysis, a significantly smaller increase (0.3% in average) of ultrasound velocity in the soleus muscle was observed than otherwise could be expected if a uniform relative loss of total body fluids was assumed (1-1.3%). In general, the study findings set a premise for using ultrasound velocity as a potential quantitative parameter for edema assessment.

Adolescent↗

PubMed2006

Protein self-organization patterns in dried serum reveal changes in B-cell disorders.

BACKGROUND: Detection of serum monoclonal proteins is a common laboratory analysis used in the evaluation of patients with B-cell disorders. Since many individuals with elevated immunoglobulin have no symptoms, it is important to have simple methods for initial screening of patients with suspected B-cell disorders. METHODS: Samples of serum from healthy donors and from patients with elevated immunoglobulin levels were tested using a technology named Droplet MicroChromatography (DMC). DMC was developed at Artann Laboratories (West Trenton, New Jersey, USA) for the rapid assessment of changes in the composition of serum. DMC is based on the dynamics of the sediment pattern formation during drying of a fluid microdroplet. RESULTS: Results of this pilot study confirm the hypothesis that the pattern formation created by drying droplets of serum would differ between normal samples and those containing monoclonal proteins. Reproducible differences in the patterns formed by the two types of specimens are shown. Strong correlation between abnormally elevated levels of immunoglobulins in the serum of myeloma patients and the patterns formed by drying droplets of serum indicates that the DMC technique may be suitable for semi-quantitative analysis of serum samples. We also demonstrate that computer identification of the drying droplet structure and dynamics is a tractable issue. CONCLUSIONS: DMC has significant diagnostic potential and can serve as a basis for development of a simple, rapid, and inexpensive method for initial screening of patients suspected of having multiple myeloma and other pathologies of lymphoid origin that are associated with the overproduction of monoclonal immunoglobulins. The DMC test requires only approximately 1 microL of serum and could therefore be performed in any facility where it is safe to work with serum.

B-Lymphocytes↗

PubMed2006

Model-based imaging.

The concept of model-based imaging provides a possibility of integration of both structural and functional information obtained by imaging and nonimaging sources of diagnostically relevant information. Merging information of different origin and nature in a simulated computer patient-specific three-dimensional (3-D) model is important for multimodal imaging approaches to medical diagnostics. The work of F. L. Lizzi on life-like imaging done nearly 20 years ago was the first successful attempt of patient-specific 3-D computer modeling using conventional ultrasonography data. He demonstrated the applications of such 3-D models, which incorporated acoustic, optical and thermal properties of imaged tissue, in physiologic studies, in planning and monitoring ultrasonic hyperthermia and ablation. However, numerous obstacles hinder the wide use of the model-based imaging concept. Using the example of model-based imaging of prostate, the advantages and limitation on the applicability of the concept are discussed. Attempts of implementing the model-based imaging concept in the mechanical imaging technology--imaging with the use of measurements of stress pattern on the surface of tissue--are described. It is shown that composing a patient-specific 3-D model requires well-defined and carefully validated algorithms for translating features of the object assessed by an imaging modality into the quantitative anatomic and histopathologic parameters.

Algorithms↗

PubMed2005

Use of multiple acoustic wave modes for assessment of long bones: model study.

Multiple acoustic wave mode method has been proposed as a new modality in axial bone QUS. The new method is based on measurement of ultrasound velocity at different ratio of wavelength to the bone thickness, and taking into account both bulk and guided waves. It allows assessment of changes in both the material properties related to porosity and mineralization as well as the cortical thickness influenced by resorption from inner layers, which are equally important in diagnostics of osteoporosis and other bone osteopenia. Developed method was validated in model studies using a dual-frequency (100 and 500 kHz) ultrasound device. Three types of bone phantoms for long bones were developed and tested: (1) tubular specimens from polymer materials to model combined changes of material stiffness and cortical wall thickness; (2) layered specimens to model porosity in compact bone progressing from endosteum towards periosteum; (3) animal bone specimens with both cortical and trabecular components. Observed changes of the ultrasound velocity of guided waves at 100 kHz followed gradual changes in the thickness of the intact cortical layer. On the other hand, the bulk velocity at 500 kHz remained nearly constant at the different cortical layer thickness but was affected by the material stiffness. Similar trends were observed in phantoms and in fragments of animal bones.

Acoustics↗

PubMed2005

Ultrasonic assessment of tissue hydration status.

Tissue water content is an important diagnostic parameter that can be used for estimation of water loss in muscles such as common dehydration during high endurance exercises. It could be also applied for evaluation of the increased fluids content in the tissue caused by the variety of pathological conditions or edemas. Ultrasonic method for tissue water content monitoring is based on the premise that the speed of a bulk or compression sound wave is determined mainly by the molecular content of the tissue. Most soft tissues, including muscles that consist of about 70-80% water, exhibit shift of the ultrasound velocity associated with the change in their water content. In the present paper, we tested the feasibility of assessing changes in tissue water content by measurements of ultrasound velocity in ex vivo animal muscle tissues. An increase in the ultrasound velocity correlated with the volumetric water loss in the tissue was observed when other tissue components (proteins, fat) remained constant. Possibility to assess muscle dehydration with 1% accuracy was confirmed in model dehydration experiments, where ultrasound velocity slope of about 3 m/s per 1% of water loss was revealed at measurement error less than 2 m/s. Hence, the ultrasonic approach can provide basis for a convenient, lightweight system in sports medicine for monitoring total body hydration during long-term endurance exercise in hot conditions, as well as for edemas monitoring and other medical applications.

Animals↗