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At least 19 recordsLinked to original sources
PubMed1975

[New bases and theories from improving angio-cine-densitometry. II Improvements in the signal-to-noise ratio by the quotient method in cine densitometry].

In radio-cine-densitometry, random variations can be smoothed and reduced in two ways: temporal (frame to frame) and spatial (each frame). Both methods may, however, alter the signal measurements. The advantage of quotient cine-densitometry depends on the elimination of interference or random variations without changing the signal. Elimination of the variations occurs during signal recording. Amongst others the following are eliminated: variations in mains voltage, uneven development, absorption by other tissues and organs. A more suitable signal-to-noise ratio can be obtained. If an artery or a vein are opacified simultaneously it is possible, by means of quotient cine densitometry, to distinguish the arterial and venous phase and to analyse these separately from the overlying tissues.

Absorptiometry, Photon↗
PubMedDate not supplied

Rod densitometry in night blindness: a review and two puzzling cases. Rod densitometry in night blindness.

Since the non-invasive technque of retinal densitometry became available in 1955, rhodopsin kinetics could be studied in vivo. It was obvious that with this new tool investigators focussed attention on the aetiology of night blindness in various diseases. A brief review about the clinical developments in the past two decades is given. Also three case-reports are presented, which suggest that in some cases of congenital stationary night blindness (CSNB) the night blindness might arise from the absence of rhodopsin. This is contrary to the standing opinion and present problems regarding the integrity of the retina.

Adolescent↗
PubMed1975

[A new basis and theories for improving angio-cine-densitometry. V. The effect of the injection method of the contrast on measurements during angio-cine-densitometry (author's transl)].

The theoretical basis for measuring speed of flow in vessels of conscious patients obtained by estimating dilution of injected contrast is described. Previously, measurements at two separate points had to be carried out in order to obtain a flow profile, but with the present method, a single measurement point is adequate. If contrast is distributed evenly in the circulation during its flow to the periphery, the measurement can be carried out at some distance from the point of injection. The ability to select ones point of measurement makes it possible to avoid areas covered by overlying shadows and eliminates the difficulties inherent in measurements in curved vessels.

Absorptiometry, Photon↗
PubMed1992

Results of bone densitometry affect women's decisions about taking measures to prevent fractures.

OBJECTIVE: To describe how the results of bone densitometry affect women's decisions about measures to prevent fractures and to determine whether labeling women as having below-normal bone density has adverse effects. DESIGN: Mail survey of a random sample of women. SETTING: Four community hospitals in the San Francisco Bay area. PATIENTS: A total of 261 women (response rate, 81.3%) who had undergone bone densitometry. MEASUREMENTS: Bone densitometry and self-report of changes in attitude and behaviors. RESULTS: Fifty-three percent of the women reported that their first bone density measurements were below normal, and 44% said that they were diagnosed as having osteoporosis on the basis of their test results. Women who reported that their bone density measurements were below normal were much more likely than women with normal results to begin some type of measure to prevent fractures (94% compared with 56%; P less than 0.01), to start hormone therapy (38% compared with 8%; P less than 0.01), and to take precautions to avoid falling (50% compared with 9%; P less than 0.01). Women reporting low bone density, however, also became more fearful of falling (38% compared with 2%; P less than 0.01) and limited their activities to avoid falling (24% compared with 2%; P less than 0.01). CONCLUSIONS: The results of bone densitometry substantially influence women's decisions about beginning estrogen replacement therapy and other preventive measures for osteoporotic fractures. The potential effects of labeling a woman as having below-normal bone density need to be considered before densitometry is widely used for unselective screening of women.

Absorptiometry, Photon↗
PubMed1990

Comparison of flow cytometry with static densitometry in papillary thyroid carcinoma.

The prognostic accuracy of flow cytometric and static densitometric DNA analysis was compared in 31 patients who had undergone surgery for papillary thyroid carcinoma between 1959 and 1978 (median follow-up 18 years). There were five deaths from papillary thyroid carcinoma. Three of six patients with DNA aneuploid tumours on flow cytometry died (P greater than 0.05, Fisher's exact test) compared with four of eight patients whose tumours were found to be aneuploid by static densitometry (P less than 0.02). When quantitative analysis was applied to the static densitometry data, all five patients who died from papillary carcinoma were distinguished, with no false positives (P less than 0.002). The prognostic accuracy of flow cytometric DNA analysis is less than that of static densitometry in which morphological selection of malignant cells permits quantitative measurements. DNA analysis may add refinement to existing scoring systems in predicting the risk of death from papillary thyroid carcinoma. Such information could provide the basis for controlled prospective evaluation of bilateral resection as opposed to lobectomy in defined high risk patients. At present there is insufficient evidence upon which aneuploidy should be used as a determinant of the extent of operation for papillary thyroid carcinoma.

Adult↗
PubMed1992

Assessment of neutrophil chemotaxis by laser and video densitometry.

A laser densitometer and a video densitometer were used to evaluate neutrophil chemotaxis slides which were also assessed by the standard microscopic technique. A linear relationship was observed between cell number per high power field (HPF) and peak height by laser densitometry (r2 = 0.66) or peak area by video densitometry (r2 = 0.81). For wells containing more than 20 cells/HPF the least variability was observed with video densitometry. Quantitative results from neutrophil chemotaxis assays performed in 48-well microchambers can be obtained rapidly and conveniently by the use of commercially available video densitometers.

Chemotaxis, Leukocyte↗
PubMed1991

Assay and purity control of metacycline by thin-layer chromatography combined with UV and fluorescence densitometry--a comparison with liquid chromatography.

A thin-layer chromatographic (TLC) method involving UV and fluorescence densitometry is described for the assay and purity control of metacycline. With a mobile phase dichloromethane-methanol-water (58:35:7, v/v/v) and a silica gel thin-layer, previously sprayed with 10% sodium edetate solution adjusted to pH 9.0, all the potential impurities of metacycline were well separated from the main component and from each other. Results obtained with UV densitometry (TLC-UV) and fluorescence densitometry (TLC-F) were compared with those obtained by a liquid chromatography (LC) method using a poly(styrene-divinylbenzene) stationary phase. The correlation coefficients (r) for TLC-UV and LC or TLC-F and LC were better than 0.9999. For TLC-UV the relative standard deviation (RSD) for the assay of the main component was less than 2%, for TLC-F less than 3.0% and for LC less than 1.0%.

Anti-Bacterial Agents↗
PubMed1990

Body composition of adult cystic fibrosis patients and control subjects as determined by densitometry, bioelectrical impedance, total-body electrical conductivity, skinfold measurements, and deuterium oxide dilution.

This study contrasts body compositions (by six methods) of eight cystic fibrosis (CF) subjects with those of eight control subjects matched for age, height, and sex. CF subjects weighed 84% as much as control subjects. Densitometry and two bioelectrical impedance-analysis methods suggested that reduced CF weights were due to less lean tissue (10.7, 9.5, and 10.4 kg). Total-body electrical conductivity (TOBEC) and skinfold-thickness measurements indicated that CF subjects were leaner than control subjects and had less fat (5.4 and 3.6 kg) and less lean (5.2 and 7 kg) tissue. D2O dilution showed a pattern similar to TOBEC (8.3 kg less lean, 2.7 kg less fat tissue). Densitometry estimates of fat (mass and percent) were not correlated (r less than 0.74, p greater than 0.05) with any other method for CF subjects but were correlated with all other methods for control subjects. CF subjects contained less fat and lean tissue than did control subjects. Densitometry by underwater weighing is unsuitable for assessing body composition of CF patients.

Adipose Tissue↗
PubMed1979

Reliable estimation of hemoglobin A2 concentration by electrophoresis with densitometry.

Elevated hemoglobin A2 (Hb A2) levels can be identified conveniently by densitometry after electrophoresis on cellulose acetate strips. Because a recent report questioned the accuracy of this technic, the method was re-evaluated by paired comparison with microcolumn chromatography. Analysis of 100 patient specimens showed high correlation (r = +0.84), but an average Hb A2 concentration 0.7% higher by densitometry than by chromatography (P less than 0.001). With upper limits set at 4.5%, and 3.8%, respectively, results were divided into "normal" and "high" for each method. Concordant results were obtained in 97 of the 100 cases (82 normal, 15 high). Another densitometer of improved design was used for paired analysis of 50 additional specimens, 25 normal and 25 with beta-thalassemia trait. The two groups were well separated by both procedures, and Hb A2 levels were similar (r = +0.92, P greater than 0.6). This study demonstrates that it is possible, with carefully controlled technics and properly calibrated instruments, to use electrophoresis with densitometry as a reliable means of identifying abnormal Hb A2 levels.

Child↗
PubMed1989

Duchenne muscular dystrophy: detection of deletion carriers by spectrophotometric densitometry.

DNA isolated from a family segregating a deletion in the Duchenne muscular dystrophy gene and control families was digested with restriction enzymes, Southern transferred, and probed with a radioactive dystrophin cDNA probe. The resulting autoradiographs were analyzed with a densitometric spectrophotometer to detect carriers of the deletion. The carrier status of females in the deletion pedigree was independently determined by genomic probes and confirmed by densitometry. In many Duchenne families, deletions will only be observed using cDNA probes which show few restriction fragment length polymorphisms (RFLPs). Such deletions would normally have to be detected using dosage gels. The spectrophotometric densitometry technique used by us does not require dosage gels, and avoids problems arising from non-informative meioses and cross-overs. It should be possible to screen every family with an exon deletion by spectrophotometric densitometry provided the presently available cDNA is suitably reduced to produce fewer bands on autoradiographs.

Autoradiography↗
PubMed1991

Edge detection versus densitometry for assessing coronary stenting quantitatively.

The optimal method used to analyze quantitatively the immediate angiographic results of coronary stenting in the coronary arteries has not been studied. Accordingly, minimal luminal cross-sectional area was determined by 2 methods, edge detection and densitometry, in 19 patients who underwent percutaneous transluminal coronary angioplasty (PTCA) and then coronary stent implantation for symptomatic coronary stenoses. The correlation coefficient, 0.73 before angioplasty, decreased to 0.59 after coronary angioplasty and then increased to 0.83 after stent implantation. The mean differences between edge detection and densitometric determinations of minimal luminal cross-sectional area were 0.31 +/- 0.51 mm2 before PTCA, -0.38 +/- 1.22 mm2 after angioplasty and 0.35 +/- 0.79 mm2 after coronary stenting. It is concluded that, although the correlation and variability in the measurement of minimal luminal cross-sectional area between edge detection and densitometry deteriorate after PTCA, they are improved after stenting, probably because of smoothing of the vessel contours by the stent and remodeling of the stented segment into a more circular configuration. Therefore, in the stented coronary artery, edge detection and densitometry are equally acceptable methods of analysis.

Absorptiometry, Photon↗
PubMed1990

Color matching and foveal densitometry in patients and carriers of an X-linked progressive cone dystrophy.

We describe a family with an as yet undescribed form of X-linked progressive cone dystrophy in a five-generation pedigree, from which we report here the results of 17 male patients and 31 obligate and 13 possible female carriers. The affected males showed the characteristic picture of cone dystrophy. Foveal cone photopigment density was impaired (judged from anomaloscope settings and foveal densitometry), even at an early stage of the disease. The carriers showed no fundus abnormalities, except occasional changes due to myopia. The anomaloscope demonstrated mild pseudoprotanomaly in 27 of 31 obligate carriers and in six of 13 possible carriers. Foveal densitometry findings performed in 11 carriers always agreed with the anomaloscope findings. We conclude that the findings of pseudoprotanomaly and abnormal density differences in females of this family were the only ocular abnormalities and thus are indicative of the carrier state.

Adult↗
PubMed1990

Quantitative densitometry from the point of view of information theory.

The process of quantitative densitometry is analyzed with methods developed in information theory. It is shown that the steps involved in densitometry, e.g. gel staining, mechanical, optical and electronic processing, as well as all the steps of data processing, can be viewed as communication channels. The factors affecting both the relevant and irrelevant part of the total information passed through these channels are discussed in the consistent frame provided by information theory. This view leads to a unifying context for analyzing the performance of quantitative densitometers.

Densitometry↗
PubMed1990

Electrophoretic separation of nucleic acids: evaluation by video and photographic densitometry.

The separation of DNA by gel electrophoresis provides a rapid method for determining size distributions of DNA in solution. Densitometric scanning of photographs of gels has been the standard method of analysis of agarose gels. However, analysis of photographs is complicated by the non-linear response of photographic film. Charged-coupled device video cameras have become popular for quantitative densitometry and we have used a charge-coupled device camera to image agarose gels to quantitate DNA damage. We compare video and photographic densitometry for quantitation of ultraviolet radiation (UV)-induced DNA damage and find that the two methods give equivalent results.

DNA↗
PubMed1988

Transmission densitometry of stained nitrocellulose paper.

We report a simple solution to the problem of quantitative densitometry of stained nitrocellulose paper. By immersing the paper in a household lubricating oil of matching refractive index, the light-scattering properties of the paper are largely eliminated, allowing precise transmission densitometry in any flat bed densitometer. The method was evaluated on immunochemically stained Western blots of the proteinases cathepsins B and L. An approximately linear relationship was found between the integrated absorbance of the stained zone and the logarithm of the amount of protease applied to the polyacrylamide gel over the range of 150 to 350 ng of cathepsin B and 50 to 250 ng of cathepsin L.

Blotting, Western↗
PubMed1992

Foveal densitometry in adult-onset diffuse drusen.

We compared the results of foveal densitometry with results of other retinal function tests in five asymptomatic subjects with adult-onset diffuse drusen. All results of routine retinal function tests, including visual acuity, Rayleigh equation color matches, multiple static perimetry, electroretinography, and electro-oculography, were normal. All five subjects had decreased foveal cone photopigment density with densitometry, indicating an early dysfunction at the level of the foveal cone photoreceptors. Several functional defects may be responsible for the densitometric results in adult-onset diffuse drusen, including retinal pigment epithelium dysfunction, foveal cone photoreceptor misalignment, and a reduction of the in situ foveal cone photopigment.

Adult↗
PubMed1978

A rapid, sensitive method for accurate analysis of individual bile acids in biological fluids by high performance thin-layer chromatography and densitometry.

1. A rapid new micromethod for quantitative analysis of individual bile acids in duodenal juice by high performance thin-layer chromatography (HPTLC) and densitometry is described and evaluated by comparison with standard TLC and spectrophotometry. 2. Advantages of HPTLC over TLC include more rapid separation, better resolution and more sensitive detection (5 - 10 fold), without the need for prior extraction. Densitometry provides simple, direct and rapid quantitation. 3. The method is accurate and reliable over a range of bile acid concentrations. In the 0.5 mM range, recovery was greater than 89%, and coefficients of variation for within-day analysis were 2 - 12% and for between-day analysis were 6 - 18% for the individual bile acids. Twenty analyses can be performed by one worker in a single day. 4. We conclude that the method offers several advantages over most currently described techniques, is suitable for routine use and is deserving of wider application.

Bile Acids and Salts↗