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PubMedDate not supplied

An improved method using densitometry for evaluating severity of laser photocoagulation induced CNV.

Laser photocoagulation induced choroidal neovascularization currently is the most effective model available for the study of this disease in terms of efficacy of new drugs and therapies. Previously, evaluating the extent of choroidal neovascularization using this model was time-consuming and required the use of experienced personnel. We describe a new method for simple and rapid evaluation of laser induced choroidal neovascularization using densitometry. Fluorescein angiograms of a laser photocoagulated rat eye were scanned into a computer. Densitometry software subsequently was used to calculate the severity of the laser lesions. The densitometry method proved effective for calculating the extent of laser induced choroidal neovascularization. In addition, this method was more rapid than visual evaluations and less likely to produce errors.

Animals↗
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↗
PubMed1973

The optical density of erythrolabe determined by retinal densitometry using the self-screening method.

1. Retinal densitometry has been used to determine the optical density of erythrolabe in foveal cones.2. A self-screening method was used, as in Rushton's (1963b) measurements on chlorolabe.3. Psychophysical experiments have demonstrated that self-screening in cones depends on the direction of the light in the same manner as the Stiles-Crawford efficiency. Stiles-Crawford measurements were therefore made on each subject and a method was devised to allow for the corresponding reduction in self-screening in densitometry.4. Complications arising from coloured bleaching products, the presence of a second visual pigment and the fluorescence of visual pigments are considered.5. The mean value for optical density at 560 nm was found to be 0.40 +/- 0.07 S.E. of mean for the five subjects (two deuteranopes, two deuteranomalous subjects and one normal subject).6. This result is in good agreement with Rushton's (1963b) value of 0.35 for chlorolabe using retinal densitometry.7. The densitometry results are also in reasonable accord with recent psychophysical and microspectrophotometry measurements. This provides evidence that densitometry measures all the cone pigment in an unbiased manner and not just a superficial sample.

Color Vision Defects↗
PubMed1985

Studies of bone morphology, bone densitometry and laboratory data in patients on maintenance hemodialysis treatment.

Bone morphological parameters of renal osteodystrophy such as abundance of osteoid surface, osteoid seam width index, calcification fronts, osteoclast activity and trabecular bone volume were studied in 71 patients on maintenance hemodialysis and compared with bone densitometry, laboratory and clinical data. Increased osteoclast activity (hyperparathyroidism) was by far the most common bone morphological finding. Patients with chronic pyelonephritis or polycystic kidney disease had more than double the amount of osteoid than patients with chronic glomerulonephritis. The trabecular bone volume seemed to be increased in most patients in contrast to the cortical bone volume which was decreased, judged from bone densitometry and previously from X-ray. Despite that patients with polycystic kidney disease were older, their trabecular volume was larger than in patients with glomerulonephritis. The bone mineral content evaluated by bone densitometry was low in most patients, and more associated with bone morphological signs of osteomalacia than with secondary hyperparathyroidism. Serum phosphate (S-PO4) and serum parathyroid hormone (S-PTH) seemed to discriminate better between osteomalacia and secondary hyperparathyroidism than serum alkaline phosphatase (S-Alk. phosph.), which was elevated in both groups. Patients who had been bilaterally nephrectomized were no more abnormal than other patients, and they had lower S-Alk. phosph. The abundance of osteoclasts was found to be a predictor of future development of clinical secondary hyperparathyroidism.

Adolescent↗
PubMed1995

The validation of auricular densitometry for indocyanine green clearance measurement of hepatic blood flow during and after cardiopulmonary bypass in children.

The clinical measurement of hepatic perfusion is complicated by a dual blood supply and the invasive nature of the majority of techniques available. The aim of this study was to validate indocyanine green clearance and noninvasive auricular densitometry as a measure of hepatic perfusion in the context of paediatric cardiac surgery. The effects of different dye concentrations on densitometer recording were assessed in vitro and found to have a linear relationship. Similarly, variations in haematocrit, within the range 21-47%, also had little effect on accuracy. Comparison of densitometry and direct blood sampling with plasma spectrophotometry in six postoperative, normothermic children showed no significant difference between the noninvasive and invasive techniques (r = 0.968; p > 0.05, t-test). Comparison in 10 hypothermic children during cardiopulmonary bypass also showed no significant difference between the two methods, provided that no further cooling or rewarming took place (r = 0.83; p > 0.05, Wilcoxon test). Noninvasive auricular densitometry can, therefore, provide a reliable assessment of hepatic perfusion in children undergoing cardiac surgery.

Cardiopulmonary Bypass↗
PubMed2002

Position statements of the International Society for Clinical Densitometry: methodology.

Given the need for authoritative positions in areas of controversy in the field of bone densitometry, the International Society for Clinical Densitometry (ISCD) convened a Position Development Conference in Denver, CO, USA, in July 2001. Four general areas were selected on the basis of clinical importance and likelihood of reaching agreement. These areas were discussed at length prior to the conference by the Scientific Advisory Committee of the ISCD and presented to a panel of experts at the conference. The four areas included discussions of (1). the regions of interest of central dual X-ray densitometry (DXA), (2). the criteria by which a densitometric diagnosis of osteoporosis can be made in men and non-Caucasian women, (3). the role of serial BMD measurements in patient management, and (4). the standards by which bone mass measurements at peripheral sites should be used in the diagnosis of osteoporosis. Details of the methodology used at the conference are discussed. The following papers explain the results of the discussions and describe the official ISCD positions.

Bone Density↗
PubMed2004

Noninvasive evaluation of cardiac output during postural change and exercise in humans: comparison between the modelflow and pulse dye-densitometry.

To investigate whether the Model-flow method, by simulating the aortic input impedance model from a noninvasive monitoring of arterial blood pressure, reflected a reliable measure of cardiac output (CO) during postural change and whole-body exercise occurring in daily life, we compared the Modelflow-estimated CO with a simultaneous reference determined by the pulse dye-densitometry. Nine healthy volunteers performed postural change from supine to upright and dynamic stepping exercise. The Modelflow-estimated CO decreased to 4.8 +/- 0.5 l/min, from 5.8 +/- 0.6 l/min, during the postural change and increased to 12.8 +/- 1.3 l/min during a stepping exercise, returning to 5.1 +/- 0.4 l/min at 5 min after exercise. When comparing the pooled data of CO during resting and following exercise between the Modelflow and pulse dye-densitometry, we found that the average CO did not differ between the two estimates and that there was a significant correlation between them; the slope of the linear regression line corresponded to approximately 1.0. Although such linear relationship was also observed in an individual subject, the slope of the regression line varied from 0.737 to 1.588 among the subjects. The calibration of the Modelflow-estimated CO with the dye-densitometry value at supine or upright improved a correlation between the two estimates. Thus it is likely that the noninvasive Modelflow simulation from arterial blood pressure can provide a reliable estimation of group-average cardiac output during postural change and stepping exercise occurring in daily life. It will be recommended for a more accurate estimation of cardiac output in a given subject to calibrate the Modelflow data with an independent measure.

Adult↗
PubMed1986

Evaluation of a chest phantom for CT nodule densitometry.

The characteristics of a chest phantom used for CT nodule densitometry were determined by use of a GE CT 9800 scanner (General Electric, Milwaukee, WI). The supplied reference rods were scanned in different positions within the lung fields of the phantom and with varied chest wall thicknesses. The liver/spleen inserts were added. The CT attenuation values of different-size rods and their mineral content were also tested. The size of the standard rod is the major determinant of its CT number, which varied from 1 to 83 H. The standard rods contained no measurable calcium or other mineral. Position-dependent variability in CT numbers was relatively small with the GE CT 9800 scanner. The simulated chest wall additions and liver/spleen inserts produced only small increases in CT density. We conclude that the GE CT 9800 scanner, as an example of one of the newer CT scanners, shows improved operating characteristics for pulmonary nodule densitometry. Nodule densitometry should be further evaluated with simplified phantoms.

Densitometry↗
PubMed2001

Separate assessment of forearm cortical and trabecular bone density from standard densitometry data.

BACKGROUND: Cortical and trabecular bone are different bone components. Their mineral density cannot be measured directly by areal bone densitometry. AIM: To introduce a method for assessment of pure radial cortical and trabecular bone density based on standard densitometry data. METHOD: The study included 418 healthy females (aged 20-83 years, body mass index between 19 and 30) free of previous fractures and conditions or drugs affecting bone metabolism; as well as a group of 64 age-matched females with early menopause. Forearm bone density was measured by single X-ray absorptiometry and calculated separately for cortical and trabecular bone. Age-adjusted bone density curves were built. RESULTS: Peak bone density was found to occur between 30 and 34 years of age and was 0.561 g/cm2 for cortical and 0.281 g/cm2 for trabecular bone. In comparison, lowest values were registered between 70 and 74 years of age; cortical bone density reduced by 26% and trabecular density by 44%. Both bone density profiles through life reflected the earlier peri- and postmenopausal (mainly trabecular) and later senile (cortical bone also involved) changes in bone mass. A step-wise pattern of trabecular bone reduction was registered with acceleration around 45, 55 and 65 years. The effects of early menopause on trabecular and cortical bone were tested in the prematurely menopausal women. CONCLUSIONS: The ability of our model to discriminate between natural and premature menopause was moderate. Although hypothetical (based on calculations from integral densitometry data rather than on direct measurements), our method could differentiate between cortical and trabecular osteopenia and may prove helpful in assessing the type of osteoporosis, in making therapy choices and monitoring response to therapy based on forearm bone density.

Adult↗
PubMed2000

[Optimal dose of indocyanine-green injected from the peripheral vein in cardiac output measurement by pulse dye-densitometry].

Cardiac output is measured by pulse dye-densitometry using indocyanine-green (ICG). This cardiac output is estimated by correlating with the cardiac output measured by pulmonary artery catheter using thermodilution method. Twenty-four patients scheduled for elective cardiovascular surgeries under general anesthesia were studied. The pulse dye-densitometry monitoring system used was DDG-2001 (Nihon Kohden, Japan). In group A (13 patients: 19 times), ICG was administered from the peripheral vein as bolus doses of 5, 10 or 20 mg (5 mg.ml-1 water solution). In group B (11 patients: 12 times), ICG was administered from the peripheral vein as bolus doses of 20, 10 or 5 mg (5 mg.ml-1 water solution). The correlation (Pearson's correlation coefficient) and precision (the method proposed by Bland and Altman) compared with cardiac output measured by pulmonary artery catheter were examined. Better correlation and precision were recognized after 20 mg ICG injection than 5 or 10 mg ICG injection. In conclusion, the measurement of cardiac output by pulse dye-densitometry with peripheral vein ICG injection was useful using a bolus dose of ICG 20 mg.

Aged↗
PubMed2000

[Bone densitometry: interpretation of a single measurement].

The use of bone densitometry in clinical practice is wide, since it is very useful to confirm osteoporosis, predict a fracture or monitor the treatment. In some cases the result of a single, sometimes by chance densitometry can provide a false conclusion and therapeutic decision when interpreted without sufficient knowledge of an individual clinical picture and methodological conditions. A number of densitometric analyses were carried out in healthy male showing a considerable dispersion in the results. Especially methods used in screening studies (SPA, SXA, QUS) provided results lower in contrast to results obtained by standard methods (DEXA, QCT). It suggests to be very careful when interpreted the result of a single densitometry without personal contact with patient and his history, or without sufficient knowledge of densitometric methods.

Adult↗
PubMed2003

Preclinical thalassemic cardiopathy: a study by acoustic densitometry.

BACKGROUND: The cardiac function in thalassemia major has never been studied at ultrasonic backscatter techniques. We assessed the utility of acoustic densitometry in thalassemic patients without clinical or echocardiographic signs of heart failure. METHODS: Three groups of subjects with comparable age, sex and body surface area were analyzed: 25 with beta-thalassemia major (group A), 14 with thalassemia intermedia (group B) and 10 healthy subjects (group C). All patients were asymptomatic and without conventional echocardiographic signs of systo-diastolic dysfunction. The left ventricular mass and volumes were echocardiographically evaluated. The ultrasonic myocardial integrated backscatter signal (IBS) was recorded and analyzed by means of acoustic densitometry in the parasternal long-axis view at the septum and posterior wall, both at the basal and intermediate levels. Both the average image intensity and the systo-diastolic variations of the IBS (cyclic variation index-CVIibs and peak-to-peak intensity-PPI), respectively related to the structure and contractility of the myocardium, were calculated. The serum ferritin and liver iron concentrations were also measured, as markers of tissue iron storage. RESULTS: The CVIibs was significantly lower in groups A and B than in group C at basal (22.7 +/- 8.4 vs 22.1 +/- 7.8 vs 31.8 +/- 10.2%; p = 0.001) and intermediate septum (24.4 +/- 7.6 vs 25.3 +/- 8.1 vs 30 +/- 9.8%; p = 0.03) and at basal (25.9 +/- 7.6 vs 24.5 +/- 6.1 vs 31.1 +/- 10.6%; p = 0.02) and intermediate posterior wall (25.1 +/- 5.1 vs 24.3 +/- 6.2 vs 30.2 +/- 6.6%; p = 0.02). The PPI was also significantly lower in groups A and B than in group C. Both CVIibs and PPI were comparable in groups A and B. The average image intensity and left ventricular mass and volumes were not significantly different in the three groups. No correlation was found between the densitometric findings and markers of tissue iron storage. CONCLUSIONS: In asymptomatic patients with thalassemia major with normal conventional indexes of systo-diastolic cardiac function, acoustic densitometry may show a reduced cyclic variation of the IBS as a possible marker of initial myocardial contractile deficiency. On the contrary, neither structural alterations nor the extent of myocardial iron stores are detectable by this technique in this type of patients.

Acoustics↗
PubMed1994

Limitation of detection and evaluation of coronary arterial stenosis by densitometry.

In coronary cineangiography, both X-ray absorption and light scatter in the image intensifier tend to degrade image quality, and so affect the accuracy of densitometric measurement of vessel diameter. To investigate this problem, we compared the accuracy and precision of the densitometric method and the edge detection method in the automated detection of stenosis in both vessel phantom and clinical studies. In the phantom study, the X-ray penetration was varied by altering the thickness of the model, and the change in the measured diameter obtained by each of the two methods was evaluated simultaneously. A difference of 5 mm in the thickness of the model was found to alter significantly (P < 0.01) measurement of the diameter obtained using the densitometric method, but not that obtained by the edge detection method. In the clinical part of the study, the accuracy of each method in the automated detection of coronary stenosis was evaluated. With respect to the detection of stenosis, the level of disagreement between the assessment of the 3 observers and what was detected by densitometry (22.8%) was 2.9 times higher than the disagreement between the observers' assessment and what was detected using the edge detection method (7.9%). When the background density of the coronary cineangiogram along the axis of the vessel was uneven, many vessel segments which had been evaluated as normal when edge-detection was used were evaluated as stenosed when densitometry was used. This study, then, demonstrates that the Lambert-Beer law does not apply in cases where the thickness of the subject varies in different locations along the axis of the same vessel. We therefore conclude that densitometry is not a reliable means of assessing coronary stenosis in such cases, due to veiling-glare and scatter, and recommend that it not be routinely used in the automated detection of coronary arterial stenosis.

Absorptiometry, Photon↗
PubMed1982

[Correlation between compression characteristics and CAT densitometry values of vertebral bodies (author's transl)].

The compression characteristics of 25 fresh cadaveric vertebrae of different height had been analysed in static compression tests and related to CAT densitometry values. A relationship between fracture load and CAT densitometry values of the vertebral body (spongiosa and corticalis) had been found, which can be described as a logarithmical function (r2 = 0.91). Separated CAT measurements of spongiosa also showed a logarithmical function (r2 = 0.89). Consequently, the thin corticalis of vertebral waist is of subordinate importance in correlation to fracture load. An analogously explored average CAT densitometry value showed no definite dependence on corticalis capacity. The graphic description of analysed spongiosa areas in absorption profile (CAT histogram) almost resulted in a Gauss distribution.

Adult↗
PubMedDate not supplied

The prevalence of coeliac disease among female subjects having bone densitometry.

BACKGROUND: Osteoporosis frequently complicates coeliac disease but most studies focus on symptomatic patients at the time of diagnosis. Screening tests have revealed that many individuals with coeliac disease have mild, atypical, or absent symptoms. AIM: To evaluate the relationship between coeliac disease and osteopenia or osteoporosis in female subjects attending for bone densitometry. METHODS: We studied 371 female subjects attending for bone densitometry, without secondary causes of osteoporosis and included those with normal and with reduced bone mineral density. Mineral density was measured by dual energy X-ray absorptiometry. Screening for coeliac disease was by measurement of anti-endomysial antibody by indirect immunofluorescence. RESULTS: Two of 115 (1.7%) female subjects with normal bone density and five of 256 (1.9%) female subjects with sub-normal bone density were positive for endomysial antibody. Five subjects who underwent small bowel biopsy had histological changes suggestive of coeliac disease. CONCLUSIONS: In females referred for bone densitometry, endomysial antibody positivity was not more prevalent among those with reduced bone mineral density. Examining only patients with clinically detected coeliac disease may overestimate the frequency of complications. This study does not support population screening for coeliac disease in an area with a high frequency of the condition.

Absorptiometry, Photon↗
PubMed2003

A prospective study of discordance in diagnosis of osteoporosis using spine and proximal femur bone densitometry.

The T-score definition of osteoporosis, originally intended for epidemiologic research in this condition, is frequently used in making treatment decisions for individual patients. Discordance in classification depending on the site and type of measurement has been reported in retrospective and cross-sectional studies, but the impact of such discordance on clinical practice is unknown. This is potentially important in view of a recent proposal to confine osteoporosis diagnosis to densitometry at the hip. Having excluded those with degenerative changes in the lumbar spine, we compared the T-score classification of a prospective cohort of patients referred for their first dual-energy X-ray absorptiometry (DXA) scan, analyzing data for men and women in 10-year age groups. Total hip and neck of femur DXA identified significantly fewer osteoporotic patients than spine DXA, and this reduced sensitivity could not be improved by adjusting the T-score threshold without an unacceptable increase in non-osteoporotic cases. The majority of patients undetected by proximal femur DXA were at significantly increased risk of vertebral fracture. DXA at the lumbar spine had only moderate sensitivity and specificity for osteoporosis redefined by total hip densitometry, indicating differential rates of bone loss at the proximal femur and spine. We conclude that, as the most usual indication for bone densitometry is to aid the determination of an individual's fracture risk, both proximal femur and lumbar spine should continue to be assessed.

Absorptiometry, Photon↗