Osteocalcin as an indicator of bone metabolism during spaceflight.
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Animals↗
Biomedical subjects
C E Cann
Publications and source records attributed to C E Cann.
Osteoporosis: assessment by quantitative computed tomography.
The results presented in this article indicate that quantitative computed tomography provides a reliable means of evaluating and monitoring the many forms of osteoporosis and its various treatments. The greatest advantages of spinal QCT for noninvasive bone mineral measurement are its high precision, the high sensitivity of the vertebral spongiosa measurement site, and the potential for widespread application.
Adult↗
Assessment of metabolic bone diseases by quantitative computed tomography.
Advances in the radiologic sciences have permitted the development of numerous noninvasive techniques for measuring the mineral content of bone, with varying degrees of precision, accuracy, and sensitivity. The techniques of standard radiography, radiogrammetry, photodensitometry, Compton scattering, neutron activation analysis, single and dual photon absorptiometry, and quantitative computed tomography (QCT) are described and reviewed in depth. Results from previous cross-sectional and longitudinal QCT investigations are given. They then describe a current investigation in which they studied 269 subjects, including 173 normal women, 34 patients with hyperparathyroidism, 24 patients with steroid-induced osteoporosis, and 38 men with idiopathic osteoporosis. Spinal quantitative computed tomography, radiogrammetry, and single photon absorptiometry were performed, and a spinal fracture index was calculated on all patients. The authors found a disproportionate loss of spinal trabecular mineral compared to appendicular mineral in the men with idiopathic osteoporosis and the patients with steroid-induced osteoporosis. They observed roughly equivalent mineral loss in both the appendicular and axial regions in the hyperparathyroid patients. The appendicular cortical measurements correlated moderately well with each other but less well with spinal trabecular QCT. The spinal fracture index correlated well with QCT and less well with the appendicular measurements. Knowledge of appendicular cortical mineral status is important in its own right but is not a valid predictor of axial trabecular mineral status, which may be disproportionately decreased in certain diseases. Quantitative CT provides a reliable means of assessing the latter region of the skeleton, correlates well with the spinal fracture index (a semiquantitative measurement of end-organ failure), and offers the clinician a sensitive means of following the effects of therapy.
Aged↗
Radiation brain damage induced by interstitial 125I sources: a canine model evaluated by quantitative computed tomography.
The canine brain is a good model of the human brain for studying radiation damage after megavoltage x-irradiation for brain tumors. We have further developed this model to study radiation damage induced by high activity interstitial 125I sources. Removable 125I sources were implanted in normal canine brains, and doses of 1,000 to 10,000 rads were delivered to a reference point at a 10-mm radius from the source; dose rates were 35 to 40 rads/hour at the reference point. Serial quantitative analysis of tissue damage (tissue density and contrast enhancement) was done using computed tomographic scanning up to 6 months after implantation and was compared to histopathological findings after the animals were killed. At doses greater than 19,000 rads (i.e., inside the reference point), frank coagulation necrosis was observed. Pronounced vessel-related changes, manifest as areas of contrast enhancement, corresponded to tissues receiving a minimum of 6,000 rads and a maximum of 19,000 rads. These results indicate that this model can be used in serial noninvasive studies to quantify the development of damage induced by interstitial irradiation and to provide dose-response information in individual animals.
Animals↗
Decreased spinal mineral content in amenorrheic women.
Premenopausal amenorrheic women may be at risk for the development of osteoporosis. In hyperprolactinemia, cortical bone mass is decreased and the magnitude of the decrease correlates with the severity of the estrogen deficiency. However, bone loss in women with amenorrhea from other causes has not been assessed. We have studied women with hypothalamic and hyperprolactinemic amenorrhea and premature ovarian failure. Bone mass in the peripheral cortical bone was only slightly decreased from age-matched controls, but spinal trabecular bone was decreased 20% to 30%. Estradiol levels were 20 to 80 pg/mL in these women, not different from normal early follicular levels. The decrease in bone mass in the spine did not correlate with serum estradiol at these levels. The hypothalamic amenorrhea group was made up of athletes in whom the bone mass decrease was an unexpected finding.
Adolescent↗
Dual energy CT scanning for analysis of brain damage due to X-irradiation.
Therapeutic irradiation is commonly used in the treatment of malignant brain tumors and has the potential to cause severe injury to normal tissues adjacent to a lesion. Computed tomography (CT) can be used not only to visualize tissue damage but to monitor the development of a lesion using advanced quantitative CT techniques. We have used a postprocessing dual energy CT method to quantify changes in tissue composition following large single doses of X-rays to the normal canine brain. The results suggest that these techniques will provide more information about the character of a lesion than is obtainable from conventional imaging procedures.
Animals↗
Quantification of body fat distribution in the abdomen using computed tomography.
A computed tomographic method was used to assess the pattern of abdominal fat distribution in normal males and females at different abdominal levels. The method permitted site specific calculations of total body volume (TA), total fat volume (TF), subcutaneous fat volume (SF), and intraabdominal fat volume (IF) in each computed tomography scan. The ratio of TF/TA, SF/TF and IF/TF were calculated for the L1, L3, and L5 vertebral levels. Regression analysis of IF versus SF, SF versus TF, IF versus TF, TF versus TA, and TF versus body mass index and age were calculated. A significant linear correlation between the measured variables TA, SF, IF, and TF and between TF and body mass index was found for virtually all correlations attempted at all scanned levels. Females had a higher total fat volume and greater percentage of subcutaneous fat at all levels. Males accumulated more fat intraabdominally than subcutaneously at the L1 and L3 levels. The male-female differences were greatest at L1 and the ratio SF/IF statistically significant at the L1 and L5 levels. Our results demonstrate that computed tomography can noninvasively quantify abdominal fat distribution at various sites. There is an inherent difference in abdominal fat distribution between males and females that is not related to weight. The distribution of body fat in males and females varies markedly from level to level.
Adipose Tissue↗
A postprocessing dual energy technique for vertebral CT densitometry.
The influence of the fat content in the cancellous bone on CT densitometry was measured on the excised vertebrae from 42 elderly human subjects. Using single energy CT, the decrease of the measured mineral content was 12% for a fat content of 10% by volume at a mean mineral content of 100-110 mg/cm3. Using a dual calibration at 85 and 130 kVp with reference to K2HPO4 for mineral and to alcohol for fat, our experiment showed that the mineral content of the vertebra can be measured with an accuracy of 6% referred to the ash-weight.
Absorptiometry, Photon↗
Contrast medium accumulation and washout in canine brain tumors and irradiated normal brain: a CT study of kinetics.
Kinetics of an iodinated contrast medium were evaluated quantitatively as a function of time up to one hour after intravenous infusion in the brains of dogs with experimentally induced radiation damage and dogs with spontaneous brain tumor. Radiation damage was characterized by an increase in iodine accumulation soon after the infusion, while tumor concentration of iodine either showed no change or decreased with time. These results suggest that contrast kinetic studies may be useful in differentiating radiation damage to normal brain tissue from a malignant brain tumor.
Animals↗
Device for performing direct coronal CT scanning of the abdomen and pelvis.
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Humans↗
Computed tomography analysis of the canine brain: effects of hemibrain X irradiation.
Radiation damage induced by megavoltage X irradiation in normal brain tissue can manifest as one of several pathologic processes depending upon the time of brain examination after irradiation. Serial quantitative computed tomography (QCT) analyses were used to study the development of radiation damage in the normal canine brain. Tissue density, volume of low density areas, magnitude and volume of contrast uptake, and ventricular volume were measured following hemibrain irradiation and were correlated with histopathology. Low density areas correlated with edema, demyelination, axonal swelling, and necrosis and appeared 3-4 months after irradiation. Large regions of contrast enhancement (coagulation necrosis and associated vascular changes) appeared 5-6 months after irradiation. Results from this study demonstrated that the pathologic changes induced in the dog brain after single doses of X rays were similar to the changes observed in nonhuman primates and man after exposure to radiation.
Animals↗
Use of impedance plethysmography to continually monitor bone marrow blood flow.
Methods for measuring bone-blood flow are often time-consuming, tedious, single-point measurements which require sacrifice of the animal. An impedance plethysmographic technique is described which can be used to quantify temporal bone marrow blood flow changes. Results obtained with the impedance technique compare favorably with the data from simultaneously administered microspheres. Injection of sympathomimetic drugs produced measurable responses: isoproterenol caused a significant increase in bone marrow blood flow within 1 min and levarterenol decreased bone marrow blood flow. Data obtained with impedance plethysmography suggest that the technique is feasible for multiple measurements on the same animal and that the technique can be used to study acute or chronic changes in bone marrow blood flow following various experimental treatments.
Animals↗
X-ray computed tomography of brain tumors in cats.
X-ray computed tomography (CT) was used to depict intracranial space-occupying lesions in 5 cats. Computed tomographic findings were confirmed by surgical biopsy in 2 cases and at necropsy in 3 cases. The detailed anatomic information provided by CT scans facilitated surgical removal of a brain tumor in 2 cats, and allowed accurate tumor localization and dose optimization for radiation therapy in 1 cat. It was concluded that CT provides information required for accurate diagnosis and treatment of feline brain tumors.
Animals↗
How accurate are computed tomographic scans in assessment of changes in tumor size?
The computed tomographic scan plays an integral part in the diagnosis and management of tumors; however, its potential has not yet been fully exploited. With a computer-assisted volume determination method, the reproducibility of derived volume calculations was assessed, and radiologists' standard interpretations of interval change on serial scans were compared with the investigators' calculations of tumor volume change. Interobserver reproducibility of tumor volume calculations of the mean of two repeated volume determinations was satisfactory (mean of 3 percent, median of 1 percent). There were 29 comparisons (47 scans of 19 patients with liver tumors) of computed tumor changes with the radiologists' computed tomographic reports of consecutive scans. In only 41 percent (12 of 29) of the cases did the radiologists' interpretations and the computer-assisted volume determinations agree. It is concluded that objective computer-assisted volume determination provides a potentially more sensitive assessment of tumor change and that such precise, specific, reproducible determination of tumor volume should further clinical research and improve patient care.
Adult↗
Nuclear magnetic resonance imaging of experimentally induced liver disease.
Experimental animal models of hepatitis, fatty liver, and hepatic iron overload were evaluated using a 3.5-kGauss nuclear magnetic resonance (NMR) imaging system. Increases in image intensity measurements and in T2 relaxation times equalled the sensitivity of histologic findings for the detection of early stages of hepatitis. A significant shift in T1 relaxation times characterized the early stages of hepatic necrosis. Liver triglyceride content correlated significantly with increases in NMR intensity measurements (p less than 0.01); however, changes in liver water content had a much greater influence on intensity, T1, and T2. Thus, it may be possible to distinguish hepatitis from benign fatty liver. Liver iron content correlated with decreases in NMR intensity measurements (p less than 0.001), and iron levels as low as 1.2 mg/g were detected. NMR may more specifically identify hepatocellular iron overload than do other techniques that do not distinguish hepatocellular from reticuloendothelial iron.
Animals↗
Bone resorption and mineral excretion in rats during spaceflight.
Bone resorption was measured directly in flight and synchronous control rats during COSMOS 1129. Continuous tracer administration techniques were used, with replacement of dietary calcium with isotopically enriched 40Ca and measurement by neutron activation analysis of the 48Ca released by the skeleton. There is no large change in bone resorption in rats at the end of 20 days of spaceflight as has been found for bone formation. Based on the time course of changes, the measured 20-25% decrease in resorption is probably secondary to a decrease in total body calcium turnover. The excretion of sodium, potassium, and zinc all increase during flight, sodium and potassium to a level four to five times control values.
Animals↗
Brain nuclear magnetic resonance imaging enhanced by a paramagnetic nitroxide contrast agent: preliminary report.
Contrast-enhancing agents for demonstrating abnormalities of the blood-brain barrier may extend the diagnostic utility of proton nuclear magnetic resonance (NMR) imaging. "TES," a nitroxide stable free radical derivative, was tested as a central nervous system contrast enhancer in dogs with experimentally induced unilateral cerebritis or radiation cerebral damage. After intravenous injection of TES, the normal brain showed no change in NMR appearance, but areas of disease demonstrated a dramatic increase (up to 45%) in spin-echo intensity and a decrease in T1 relaxation times. The areas of disease defined by TES enhancement were either not evident on the nonenhanced NMR images or were better defined after contrast administration. In-depth tests of toxicity, stability, and metabolism of this promising NMR contrast agent are now in progress.
Animals↗