SEARCH · Search PubMed

Results for “Densitometry”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 181 records · Page 10Linked to original sources

PubMed1989

Changes in fat-free mass during weight loss measured by bioelectrical impedance and by densitometry.

A group of 13 apparently healthy, premenopausal obese women (134-196% ideal weight) volunteered in a weight reduction study for 8 wk on a 4200 kJ (1000 kcal) diet. Before and after the weight reduction period body composition was measured by densitometry and by the bioelectrical impedance method. Changes in fat mass and fat-free mass were calculated. Mean weight loss was 10.0 +/- 2.8 kg and loss of fat-free mass was measured to be 2.3 +/- 1.7 kg (23%) by densitometry and 0.6 +/- 1.9 kg (6%) by impedance measurements. The underestimation of the change in fat-free mass measured by the impedance method could be due to losses of water bound to glycogen after the weight-reduction period. For this reason the impedance method may be not applicable in studies in which changes in glycogen stores can be expected.

Adult↗

PubMed1992

Interaction of glycophorin with lipid bilayer studied by calorimetry, densitometry, static light scattering, and electron microscopy.

In the first part of the present work the interaction of glycophorin with dimyristoylphosphatidylcholine (DMPC) is studied by freeze fracture electron microscopy, densitometry, calorimetry, and 90 degree static light scattering. An exothermic lipid/protein interaction energy of WP = 190 kJ.mol-1 was found by application of the well known Van Laar relation for the displacement of the freezing point and the Gibbs-Duhem relationship. Secondly, the effects of Ca2+ on the lipid/protein interaction were studied. Following Ca2+ addition a remarkable decoupling of the interaction of the glycophorin head group with the bilayer surface was revealed by densitometry and gold-labeling electron microscopy. It is estimated that about 80% of lipid once disturbed by the adsorption of glycophorin head groups is decoupled after addition of Ca2+. Thirdly, the selective interaction of glycophorin with binary lipid mixtures was studied, including the mixtures of DMPC with dimyristoylphosphatidylserine (DMPS) and dilauroylphosphatidylcholine (DLPC), and the mixture of dipalmitoylphosphatidylcholine (DPPC) with DLPC.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed1997

Measurement of cardiac output by pulse dye densitometry using indocyanine green: a comparison with the thermodilution method.

BACKGROUND: A new method for determining cardiac output (CO, l/min) using dye dilution combined with pulse dye densitometry (PDD), based on the principle of pulse oximetry, has been developed. The aim of the study was to determine the accuracy and precision of PDD by comparing it with the thermodilution method. METHODS: A prospective study was performed in 22 patients having surgery who were monitored using a pulmonary arterial catheter. In addition to the catheter, a specially designed photodetector was placed on the nasal wing. Ten milliliters of ice-cold indocyanine green dissolved in a 5% glucose solution (0.5 mg/ml) was injected. The dye and thermal dilution curves were simultaneously measured to calculate CO. Three to six injections were performed before and after surgery. Paired data were assessed in absolute terms, and the percentage errors were calculated by the degree of agreement and compared at three levels of CO (low < or = 3.5 < medium < or = 6 < high) by analysis of variance. RESULTS: The mean and SDs of the differences between dye and thermodilution CO were 0.16 +/- 0.80 l/min or 4.5 +/- 19.6% for 191 paired data. Measurement after surgery failed in one patient. The percentage error with low CO (9.3 +/- 19.3%) was greater (P < 0.05) than those obtained with other CO. CONCLUSIONS: Pulse dye densitometry could measure CO repeatedly in patients having major surgery with the same degree of accuracy as the thermodilution method; however, a considerable degree of error was observed in some patients.

Adult↗

PubMed2000

Metastatic lung cancer detected by lumbar bone densitometry: a case report.

A lumbar bone densitometry examination was performed in a patient with severe low back pain but no pathologic findings on initial laboratory and radiologic investigations. The bone mineral density of the spine was in the low-normal range (90.5% age matched), with the L4 vertebra bone mineral density less than the others, whereas image analysis showed a defect in the right part of its body. Additional radiographs confirmed this finding, which was proved to be a metastatic lesion from a primary lung cancer. Although not intended for diagnosis, the results of image analysis of bone densitometry should be evaluated carefully.

Carcinoma, Non-Small-Cell Lung↗

PubMed1986

Less-invasive cardiac output monitoring by earpiece densitometry.

Cardiac output was measured by thermodilution and ear densitometry in surgical ICU patients who had pulmonary arterial catheters. Overall comparison based on 56 sets of triplicate measurements revealed a correlation coefficient (r) of 0.76 between the two techniques. Although ear densitometry was more accurate with injection via the antecubital vein (r = 0.88) vs. more distal injection (r = 0.67), these data suggest that this technique lacks the accuracy for clinical application.

Blood Flow Velocity↗

PubMed1993

Scanning laser densitometry in multiple evanescent white dot syndrome.

A 28-year-old man with multiple evanescent white dot syndrome (MEWDS) in the left eye was examined with a scanning laser densitometer. The first measurements were taken in the acute stage, and repeat examinations were performed during the process of recovery. Fundus pictures were obtained from a 20 degrees retinal field, in dark and light adapted stages. From these images visual pigment density maps were derived. In the acute stage of the disease, maps revealed small round areas of absent visual pigment, which did not always correspond with the visible white dots. The areas of absent visual pigment density were also larger than the white dots seen on funduscopic examination. Single spot densitometry at the fovea was also performed and showed no significant density difference of the foveal cones. Rod density difference measured at a locus 16 degrees in the temporal retina was much lower than normal with an increased time constant of rhodopsin regeneration. Ten weeks after the onset of the disease, no white dot lesions were visible on funduscopic examination. Rod density difference and regeneration time had become normal again, but with scanning laser densitometry the abnormal areas of no pigment were still faintly visible. It is concluded that these findings, completed with data of electroretinography, anomaloscopic testing, and perimetry, are in agreement with a metabolic disturbance at the level of the retinal pigment epithelium-photoreceptor complex.

Acute Disease↗

PubMed1988

Comparison of microcolumn chromatography and laser densitometry of isoelectric focusing strip for the quantitation of Hb A2 and Hb S.

Anion exchange microcolumn chromatography is the ICSH (1978) recommended procedure for the quantitation of Hb A2 and Hb S. The use of isoelectric focusing (IEF) followed by laser densitometry of the separated haemoglobin bands is evaluated as a quick and reliable method for quantitation for Hb A2 and Hb S. A paired comparison of 35 specimens, 25 normal and 10 with beta thalassaemia trait, were quantitated for Hb A2. The two groups were well separated by both procedures and Hb A2 levels were similar (r = +0.93, P less than 0.001). In addition, paired analyses of 30 specimens, 20 sickle cell trait and 10 with sickle cell trait combined with alpha thalassaemia, were quantitated for Hb S. The two groups were also well separated by both procedures and Hb S levels were similar (r = +0.94, P less than 0.001). In conclusion, IEF followed by laser densitometry appears to be a reliable, quick procedure for the screening of populations at risk from beta thalassaemia and populations at risk from sickle cell trait, with or without alpha thalassaemia interaction.

Chromatography, DEAE-Cellulose↗

PubMed1975

III. Evaluation of the forward triangle area in dye curves from infants and children studied by earpiece densitometry.

Onehundred and six dye curves recorded by earpiece densitometry in shunt-free children were analysed with respect to the spatial relationships between the forward triangle and the area under the total primary dye curve. It is suggested that the relationship between these two areas, the forward triangle factor, should be 0.32 for studies in children with the use of dichromatic earpiece densitometry.

Adolescent↗

PubMed1975

IV. Evaluation of dichromatic earpiece densitometry in children with left-to-right shunts.

Earpiece densitometry was performed in 60 infants and children with left-to-right cardiovascular shunts. The method was found to possess a high diagnostic sensitivity with respect to identification of the left-to-right shunt. Earpiece densitometry was in this respect clearly superior to conventional method using oxygen saturation figures. Quantitation of pulmonary blood flow by both densitiometric and oxygen content technique in a small number of patients indicates that the dye dilution technique gives values somewhat in excess of the Fick method. It is concluded that quantitation of the magnitude of the left-to-right shunt and pulmonary blood flow is disturbed by the fact that indicator material is recirculated before the ascending limb of the primary curve is fully inscribed.

Adolescent↗

PubMed1989

Bone mineralisation in preterm infants measured by dual energy radiographic densitometry.

Dual energy radiographic densitometry was used to follow postnatal changes in the bone mineral content of the radii of 15 infants of less than 30 weeks' gestation. The system permitted bone mineral content to be measured with minimal disturbance to the infants in their incubators. Mean bone mineral content at birth was 2.4 mg/mm shaft length, decreasing to 1.9 mg/mm at 6 weeks of age, before starting to rise. Mineralisation was poor compared with that of a fetus at an equivalent postconceptual age. Mean intakes of calcium and phosphate were considerably less than the intrauterine accumulation of these minerals and it is postulated that this was the main cause of the poor mineralisation. Radiographic densitometry is both accurate and precise and has advantages over photon absorptiometry in that it can be used to measure bone mineral in infants who are not only preterm, but also ill enough to require intensive care.

Aging↗

PubMed1996

Scanning laser densitometry in visual acuity loss of unknown origin.

AIM: To assess foveal cone photoreceptor function in patients with unexplained loss of central visual acuity. METHODS: Testing of foveal cone photoreceptor function was performed using scanning laser densitometry, colour matching (Rayleigh equation), and pattern electroretinography (ERG). Standard tests included full field ERG, electrooculography, visual evoked potentials, static perimetry, and fluorescein angiography. RESULTS: Decreased foveal cone photopigment density and abnormal pattern ERG were found in three patients. Results of colour matching were not unequivocal. CONCLUSION: Testing of foveal cone photoreceptor function using scanning laser densitometry may determine the location of pathological changes in certain patients with unexplained visual loss.

Adolescent↗

PubMed1989

Appropriate use of bone densitometry.

The authors discuss current capabilities of three common bone densitometry techniques--single photon absorptiometry, dual photon absorptiometry, and quantitative computed tomography--and potential capabilities of new innovations of each of these techniques. They believe that use of bone densitometry is valid in the following four clinical applications and recommend its usage to (a) assess patients with metabolic diseases known to affect the skeleton, (b) assess perimenopausal women for initiation of estrogen replacement therapy, (c) establish a diagnosis of osteoporosis or assess its severity in the context of general clinical care, and (d) monitor the efficacy of treatment interventions or the natural course of disease.

Bone Diseases, Metabolic↗

PubMed1992

The accuracy of the assessment of normal fetal intestinal echogenicity--electro-optical densitometry versus the ultrasonographer's eye.

Ten plates of normal fetal ultrasonography (at 16-20 weeks' gestation) showing fluid, liver, lung, bone and intestine were submitted to electro-optical transmission surface densitometry. A distinct echogenic gradient has been found and used as an 'internal standard' to evaluate intestinal echogenicity. Intestine had significantly different echogenic properties from bone, liver and fluid but similar to that of lung. Using this echogenicity scale for fetal bowel, observers were correct in 46%, overscored in 32.6% and underscored in 21.4%. These poor results may be due to the significant inconsistency in the interpretation of each plate compared to other plates (about 65%). Although the densitometry-derived grading scale seems valid at these gestational ages, interobserver variation is too large and precludes a simple ultrasonic diagnosis of the hyperechogenic fetal intestine. Densitometric evaluation may be indicated in suspected cases when fetal bowel seems to have increased echogenicity.

Amniotic Fluid↗

PubMed2002

From pixels to picograms: a beginners' guide to genome quantification by Feulgen image analysis densitometry.

The study of genome size variation is important from a number of practical and theoretical perspectives. For example, the long-standing "C-value enigma" relating to the more than 200,000-fold range in eukaryotic genome sizes is best studied from a broad comparative standpoint. Genome size data are also required in detailed analyses of genome structure and evolution. The choice of future genome sequencing projects will be dependent on knowledge regarding the sizes of genomes to be sequenced, and so on. To date, genome size data have been acquired primarily by Feulgen microdensitometry or flow cytometry. Each has several advantages but also important limitations. In this review, we provide a practical guide to the new technique of Feulgen image analysis densitometry. The review is designed for those interested in genome size measurements but not extensively experienced in histochemistry, densitometry, or microscopy. Therefore, relevant historical and technical background information is included. For easy reference, we provide recipes for required reagents, guidelines for cell staining, and a checklist of steps for successful image analysis. We hope that the accuracy, rapidity, and cost-effectiveness of Feulgen image analysis demonstrated here will stimulate further surveys of genome sizes in a variety of taxa.

Animals↗

PubMed1975

Atomic absorption spectrophotometry applied to photographic densitometry.

For this study of photographic densitometry, sections of cartilage stained with Alcian Blue, safranin O and high iron diamine were photographed at x40 with Nikon photomicrography equipment on Kodak Panatomic X film with appropriate filters to enhance contrast. Portions of the developed negative films were selected from intercellular matrix regions, and circles of film equivalent in diameter to a 30-mu circle of tissue were obtained with a hand-held paper punch. Silver was eluted from the circles of film with 35% nitric acid, and the quantity of silver deposited on the film was determined by atomic absorption spectrophotometry as a measure of stain intensity. The intensity determined by this analytic procedure compared favorably with results obtained previously from the same tissue with microspectrophotometry. This method of silver analysis has advantages over earlier studies which used silver elution to determine photographic densitometry in its technical ease, accuracy and sensitivity. Furthermore, this method compares well with microspectrophotometry in its results and has the advantages of relative inexpensiveness and availability of equipment.

Animals↗

PubMed2004

Official positions of the international society for clinical densitometry.

The International Society for Clinical Densitometry (ISCD) periodically holds Position Development Conferences for the purpose of establishing standards and guidelines for indications, acquisition, and interpretation of bone density tests. Topics are selected for consideration by the ISCD Scientific Advisory Committee, reviewed by scientific working groups, and presented to an international panel of experts. Topic categories addressed to date include indications for bone density testing, selection of reference databases for T-scores and Z-scores, clinical applications for central and peripheral bone densitometry, serial bone density testing, instrument precision assessment, phantom scanning and calibration testing, requirements for a bone density report, nomenclature, and diagnosis of osteoporosis in postmenopausal women, premenopausal women, men, and children. After an open session for public comment and discussion, the panel convenes for consideration of each topic and makes recommendations for positions to the ISCD Board of Directors. Recommendations that are accepted become the Official Positions of the ISCD. This Special Report summarizes the methodology of the ISCD Position Development Conferences and presents selected Official Positions of general interest.

Absorptiometry, Photon↗

PubMed2000

L/M cone ratios in human trichromats assessed by psychophysics, electroretinography, and retinal densitometry.

Estimates of the relative numbers of long-wavelength-sensitive (L) and middle-wavelength-sensitive (M) cones vary considerably among normal trichromats and depend significantly on the nature of the experimental method employed. Here we estimate L/M cone ratios in a population of normal observers, using three psychophysical tasks-detection thresholds for cone-isolating stimuli at different temporal frequencies, heterochromatic flicker photometry, and cone contrast ratios at minimal flicker perception--as well as flicker electroretinography and retinal densitometry. The psychophysical tasks involving high temporal frequencies, specifically designed to tap into the luminance channel, provide average L/M cone ratios that significantly differ from unity with large interindividual variation. In contrast, the psychophysical tasks involving low temporal frequencies, chosen to tap into the red-green chromatic channel, provide L/M cone ratios that are always close to unity. L/M cone ratios determined from electroretinographic recordings or from retinal densitometry correlate with those determined from the high-temporal-frequency tasks. These findings suggest that the sensitivity of the luminance channel is directly related to the relative densities of the L and the M cones and that the red-green chromatic channel introduces a gain adjustment to compensate for differences in L and M cone signal strength.

Color Perception↗

PubMed1977

Clinical evaluation of bone-densitometry in patients with final renal insufficiency operated for hyperparathyroidism.

Because of difficulties in evaluating bone mineral mass with conventional methods in patients with final renal insufficiency before and after parathyroidectomy, bone densitometry has been tried. During a three year period ten patients have been selected for surgery. The parathyroidectomy performed was total in nine patients and subtotal in one. Bone mineral mass was significantly lower preoperatively in the operated patients than in other patients on regular hemodialysis and also lower than in a normal material. In four of ten patients there was a transient decrease in bone mineral mass after parathyroidectomy. Thereafter there was a significant increase in five of ten patients and in the whole group of patients. Thus bone densitometry was found to be of value in following patients with renal insufficiency selected for parathyroidectomy.

Adult↗