Application Of Analysis Techniques Research Articles

The future of ultrasonics in diagnostic medicine

Ultrasonics has been the poor relation of twentieth century physics and it is only recently that thought has been given to investigating the scientific basis of ultrasonic diagnostic methods. The physics of acoustic wave interactions with human tissues is complex but suggests the existence of a rich supply of diagnostically useful information. Static imaging technology may now be approaching a resolution limit imposed by variability of refractive index in overlying tissues, but advances are to be expected in the direction of quantification of the imaging process. Supplementary information on fine structure of tissues is also to be expected from the application of analytical techniques, of which frequency dependence of backscattering and diffraction pseudo-crystallography are two examples in which there is current research interest. Recent rapid advances in dynamic or ‘real time’ imaging reflect the potential of ultrasound for providing hitherto unobtainable information on patterns of tissue movement both in health and disease. Major advances in application will come, in many areas of medicine, simply as good equipment, experience and expertise become more generally available but particular impact from scientific advances may occur in the diagnosis and management of both cardiovascular disease and cancer, with effective early detection of breast cancer being one of a number of distant but compelling prospects.

Laboratory aids to diagnosis and therapy.

Clinical Chemistry is a branch of analytical chemistry devoted to the application of analytical techniques to biological systems on the molecular level as aids to diagnosis, prognosis, and treatment. Its operations may be divided into three parts: (a) isolation of the substance sought from interfering materials, (b) reaction of the substance with a suitable reagent, and (c) meas­ urement of a product of the reaction. In a few instances when no appreciable interferences are encountered (enzymatic determination of urea, determina­ tion of bilirubin) or when the substance can be measured directly (photo­ metric determination of hemoglobin, falling drop technique for serum pro­ tein) either one of the first two steps may not be required. Frequently, the most time-consuming operation in an analytical method consists in the isolation of the compound to be analyzed. This is particularly evident in the procedure commonly employed in the hydrolysis and extrac­ tion of urinary keto-steroids and estrogens, in wet ashing and extraction of biological materials for heavy metal analysis, and in extraction, enzymatic dephosphorylation, chromatographic adsorption, and elution, required for the determination of thiamine. The inconvenience of such procedures, rather than disinterest in the results, hampers the more frequent analysis of the substances in question. As an outstanding illustration, sodium and potassium determinations have but recently become a routine procedure after the de­ velopment of the flame photometer as a practical laboratory instrument. Preliminary isolation is necessary only when interfering substances are expected to be present. Although values obtained with Volhard's chloride method will also include bromide and iodide, only traces of these ions occur normally in biological fluids and may, thus, be ignored. Again, since no in­ terferences are encountered in the diazotization reaction for serum bilirubin, this procedure is performed directly without prior preparation of the sample. The necessary degree of preliminary isolation of the ingredient to be meas­ ured depends upon the specificity of the reagent employed in the second step of the analysis. Thus, since urease acts specifically on urea, this com­ pound may be determined in blood directly. However, because ammonia is the product of urease activity which is usually measured, urea in ammonia­ containing fluids must be determined after preliminary removal of ammonia or by correction for its quantity as found by separate analysis.