Adaptive vessel tracking: automated computation of vessel trajectories for improved efficiency in 2D coronary MR angiography

A new method was investigated for improving the efficiency of ECG-gated coronary magnetic resonance angiography (CMRA) by accurate, automated tracking of the vessel motion over the cardiac cycle. Vessel tracking was implemented on a spiral gradient-echo pulse sequence with sub-millimeter in-plane spatial resolution as well as high image signal to noise ratio. Breath hold 2D CMRA was performed in 18 healthy adult subjects (mean age 46 +/- 14 years). Imaging efficiency, defined as the percentage of the slices where more than 30 mm of the vessel is visualized, was computed in multi-slice spiral scans with and without vessel tracking. There was a significant improvement in the efficiency of the vessel tracking sequence compared to the multi-slice sequence (56% vs. 32%, P < 0.001). The imaging efficiency increased further when the true motion of the coronary arteries (determined using a cross correlation algorithm) was used for vessel tracking as opposed to a linear model for motion (71% vs. 57%, P < 0.05). The motion of the coronary arteries was generally found to be linear during the systolic phase and nonlinear during the diastolic phase. The use of subject-tailored, automated tracking of vessel positions resulted in improved efficiency of coronary artery illustration on breath held 2D CMRA.

Chronic toxicity/oncogenicity study of styrene in CD-1 mice by inhalation exposure for 104 weeks

Groups of 70 male and 70 female Charles River CD-1 mice were exposed whole body to styrene vapor at 0, 20, 40, 80 or 160 ppm 6 h per day 5 days per week for 98 weeks (females) or 104 weeks (males). The mice were observed daily; body weights, food and water consumption were measured periodically, a battery of hematological and clinical pathology examinations were conducted at weeks 13, 26, 52, 78 and 98 (females)/104 (males). Ten mice of each gender per group were pre-selected for necropsy after 52 and 78 weeks of exposure and the survivors of the remaining 50 of each gender per group were necropsied after 98 or 104 weeks. An extensive set of organs from the control and high-exposure mice were examined histopathologically, whereas target organs, gross lesions and all masses were examined in all other groups. Styrene had no effect on survival in males. Two high-dose females died (acute liver toxicity) during the first 2 weeks; the remaining exposed females had a slightly higher survival than control mice. Levels of styrene and styrene oxide (SO) in the blood at the end of a 6 h exposure during week 74 were proportional to exposure concentration, except that at 20 ppm the SO level was below the limit of detection. There were no changes of toxicological significance in hematology, clinical chemistry, urinalysis or organ weights. Mice exposed to 80 or 160 ppm gained slightly less weight than the controls. Styrene-related non-neoplastic histopathological changes were found only in the nasal passages and lungs. In the nasal passages of males and females at all exposure concentrations, the changes included respiratory metaplasia of the olfactory epithelium with changes in the underlying Bowman's gland; the severity increased with styrene concentration and duration of exposure. Loss of olfactory nerve fibers was seen in mice exposed to 40, 80 or 160 ppm. In the lungs, there was decreased eosinophilia of Clara cells in the terminal bronchioles and bronchiolar epithelial hyperplasia extending into alveolar ducts. Increased tumor incidence occurred only in the lung. The incidence of bronchioloalveolar adenomas was significantly increased in males exposed to 40, 80 or 160 ppm and in females exposed to 20, 40 and 160 ppm. The increase was seen only after 24 months. In females exposed to 160 ppm, the incidence of bronchiolo-alveolar carcinomas after 24 months was significantly greater than in the controls. No difference in lung tumors between control and styrene-exposed mice was seen in the intensity or degree of immunostaining, the location of tumors relative to bronchioles or histological type (papillary, solid or mixed). It appears that styrene induces an increase in the number of lung tumors seen spontaneously in CD-1 mice.

Coronary artery magnetic resonance imaging: a patient-tailored approach

Coronary artery magnetic resonance imaging strategies have tended to focus on the use of a single method performed during either breath-holding or free-breathing for all patients. However, significant variations exist among patients in terms of breath-holding ability and respiratory regularity that make the use of a single technique alone not universally successful. Therefore, it is prudent to make available a number of magnetic resonance imaging methods such that an appropriate respiratory motion reduction strategy can be tailored to suit the patient's respiratory pattern and characteristics. A tailored approach that can draw on different image acquisition techniques for coronary artery imaging is presented. A decision tree is proposed to triage patients into imaging regimes with the greatest probability of success, according to the patient's ability to breath-hold or exhibit steady respiration. Methods include volume free-breathing acquisitions using navigator echoes for respiratory monitoring in the 8- to 10-min scan time range, two-dimensional spiral navigators (2- to 3-min scan time), breath-held multislice and vessel-tracking spirals (16- to 20-second scan time), and real-time imaging approaches incorporating adaptive signal averaging. The development of multiple acquisition strategies substantially improves the opportunities to generate high-quality, diagnostic images of the coronary arteries.

Coronary angiography by real-time MRI with adaptive averaging

Cardiac and respiratory motion present significant challenges for MR coronary angiography, which have not been completely resolved to date by either breath-holding or respiratory navigation. Adaptive averaging during real-time MRI may provide a useful alternative to these techniques. In this method, cross-correlation is used to automatically identify those real-time imaging frames in which the vessel is present, and to determine the location of the vessel within each frame. This information is then used for selective averaging of frames to increase the signal-to-noise ratio and to improve visualization of the vessel. The correlation theorem was employed to raise the speed of this algorithm by up to two orders of magnitude. Segmenting data collection and reconstruction into subimages allows the extension of this technique to higher spatial resolution. Adaptive averaging provides a robust method for coronary MRI which requires no breath-holding, navigation, or ECG gating.

Systemic lupus erythematosus (SLE) and hair treatment: a large community based case-control study

OBJECTIVE

To investigate the association of hair treatment, including permanent and non-permanent dyes, bleach, highlights and lowlights on the development of systemic lupus erythematosus (SLE).

METHODS

150 SLE patients and 300 controls from Nottingham, UK were interviewed in a case-control study. Controls were matched to cases for gender and year of birth. All patients met at least four of the American Rheumatology Association criteria for SLE. Controls were randomly selected from the Nottingham Family Health Services Authority register. Information was collected via an interview-administered questionnaire concerning demographic variables and hair treatment.

RESULTS

For hair treatment no significant associations were observed between ever using permanent colouring, non-permanent colouring, bleach or lowlights, and disease. Nevertheless a significant association (OR 0.55, 95% CI 0.31-0.95) was observed between 'ever having' used highlights and disease with cases having used highlights less frequently than their healthy counterparts. No significant differences were observed in duration of usage of hair bleach, permanent colouring, non-permanent colouring, highlights and lowlights between cases and controls.

CONCLUSIONS

Hair treatment or duration of hair treatment usage is not significant in the aetiology of SLE. Although patients with SLE were less likely in this study to have highlights than controls, for all other hair treatments no differences were observed.

Pregnancy outcome and family size in systemic lupus erythematosus: a case-control study

OBJECTIVE

To establish pregnancy outcomes and family size in a geographically defined population of systemic lupus erythematosus (SLE) patients.

METHODS

One hundred and thirty-eight SLE patients (all women satisfying at least four American Rheumatism Association criteria) and 276 age-matched female controls, from the Nottingham area, were interviewed by a single investigator. Demographic details and maternity histories were obtained, and the data collected were analysed statistically to calculate odds ratios (ORs) for risk of fetal loss (through miscarriage, stillbirth and abortion). Family size was also determined in White and non-White cases and controls.

RESULTS

Women with SLE are at greater risk of spontaneous fetal loss than their healthy counterparts (OR = 2.21, 95% CI 1.46-3.35, P < 0.01) and they are more likely than controls to have a surgical abortion (OR 2.44, 95%, CI 1.22-4.87, P = 0.01). The excess risk of both of these outcomes exists both before and after diagnosis of SLE. The median number of children in White and non-White families of cases and controls is the same, i.e. two. White women with SLE, however, appear less likely than controls to have more than two children, whereas non-White lupus women tend to retain their propensity to have larger families, i.e. more than two children.

CONCLUSIONS

We confirm that lupus women who have, or later develop, SLE are at greater risk of pregnancy loss by spontaneous or surgical means. We have also shown that race, and the inherent differences in social and cultural influences, appears to be an important determinant of ultimate family size; White women with SLE have fewer children than controls, whilst non-White lupus women tend to have larger families.

Inhalation toxicity and genotoxicity of hydrochlorofluorocarbon (HCFC)-225ca and HCFC-225cb

The acute, subchronic and genetic toxicity of the hydrochlorofluorocarbons HCFC-225ca and HCFC-225cb were evaluated to assist in establishing proper handling guides. In acute inhalation studies, rats were exposed for 4 h to various concentrations of each isomer. Based on the mortality incidence, the LC50 value for HCFC-225cb for males and females (combined) was 36800 ppm. For HCFC-225ca, the LC50 for males and females (combined) was 37300 ppm. Narcotic-like effects, e.g. prostration, incoordination and reduced motor activity, were observed during exposure to either isomer, but these signs were not evident 15 min after termination of exposure. Histopathological examination of the liver revealed an increase in mitotic figures with vacuolation of hepatocytes and fluid-filled, congested hepatic sinusoids. In cardiac sensitization studies, HCFC-225cb induced a cardiac sensitization response at 20000 ppm, with one fatal response, whereas a blend of the two isomers (45% HCFC-225ca/55% HCFC-225cb) produced a cardiac sensitization response at 15000 ppm. In 4-week subchronic inhalation studies, male and female rats were whole-body exposed to HCFC-225cb at concentrations of 0, 1000, 5000 or 15000 ppm for 6 h a day, 5 days per week. Similarly, male and female rats were whole-body exposed to HCFC-225ca concentrations of 0, 50, 500 or 5000 ppm for 6 h a day, 5 days per week. During exposure, narcotic-like and irritant effects were observed. A dose-related decrease in cholesterol and triglycerides was observed in the treated rats, with males being affected more than females. Increases in liver weight were observed in most male and female rats exposed to either isomer. The increase in liver weight was consistent in male rats with microscopic evidence of hepatocyte hypertrophy. Although liver weight was increased in female rats, no hepatocyte enlargement was observed in treated female rats. Increases in cytochrome P-450 and beta-oxidation activities were also observed in male and female rats exposed to either isomer. Neither of the HCFC-225 isomers was mutagenic in the Ames reverse mutation assay, or clastogenic in the chromosomal aberration assay with Chinese hamster lung cells. Also, neither isomer induced unscheduled DNA synthesis in liver cells. However, both isomers were clastogenic in the chromosomal aberration assay with human lymphocytes in the absence of S-9. No increases in aberrant cells were observed in activated cells exposed to either isomer.

Chronic toxicity/oncogenicity study of styrene in CD rats by inhalation exposure for 104 weeks

Groups of 70 male and 70 female Charles River CD (Sprague-Dawley-derived) rats were exposed whole body to styrene vapor at 0, 50, 200, 500, or 1000 ppm 6 h/day 5 days/week for 104 weeks. The rats were observed daily, body weights and food and water consumption were measured periodically, and a battery of hematologic and clinical pathology examinations was conducted at weeks 13, 26, 52, 78, and 104. Nine or 10 rats per sex per group were necropsied after 52 weeks of exposure and the remaining survivors were necropsied after 104 weeks. Control and high-exposure rats received a complete histopathologic examination, while target organs, gross lesions, and all masses were examined in the lower exposure groups. Styrene had no effect on survival in males, but females exposed to 500 or 1000 ppm had a dose-related increase in survival. Levels of styrene in the blood at the end of a 6-h exposure during week 95 were proportional to exposure concentration. Levels of styrene oxide in the blood of rats exposed to 200 ppm or greater styrene were proportional to styrene exposure concentration. There were no changes of toxicologic significance in hematology, clinical chemistry, urinalysis, or organ weights. Males exposed to 500 or 1000 ppm gained less weight than the controls during the first year and maintained the difference during the second year. Females exposed to 200, 500, or 1000 ppm gained less weight during the first year; those exposed to 500 or 1000 ppm continued to gain less during months 13-18. Styrene-related non-neoplastic histopathologic changes were confined to the olfactory epithelium of the nasal mucosa. There was no evidence that styrene exposure caused treatment-related increases of any tumor type in males or females or in the number of tumor-bearing rats in the exposed groups compared to controls. In females, there were treatment-related decreases in pituitary adenomas and mammary adenocarcinomas. Based on an overall evaluation of eight oncogenicity studies, there is clear evidence that styrene does not induce cancer in rats.

Smoking history, alcohol consumption, and systemic lupus erythematosus: a case-control study

OBJECTIVE

To investigate the effect of smoking on the development of systemic lupus erythematosus (SLE), and the association between alcohol consumption and the disease.

METHODS

450 subjects (150 SLE patients and 300 controls) from Nottingham, UK were interviewed in a case-control study. Controls were matched to cases for age and sex. All patients met at least four of the American Rheumatology Association criteria for SLE. Controls were randomly selected from the Nottingham Family Health Services Authority register. Information was collected by interview administered questionnaire concerning demographic variables, smoking histories, and drinking habits.

RESULTS

Analysis of the data by conditional logistic regression revealed current smokers to have a significantly increased risk of development of SLE compared with never smokers (odds ratio (OR) 1.95, 95% confidence intervals (CI) 1.14, 3.31), although ex-smokers were not at increased risk. There was also suggestion of a marked, highly significant negative association between SLE and alcohol consumption, the magnitude of which increased with units consumed.

CONCLUSIONS

This study suggests that current smokers are at increased risk of developing SLE compared with non-smokers and ex-smokers. In contrast, alcohol consumption seems to be negatively associated with the disease.

Accuracy of arterial pulse-wave velocity measurement using MR

The performance of a one-dimensional MR technique for the estimation of pulse-wave velocity in the aorta was evaluated. An expression for the error in this estimate was formulated and verified both by simulation and by experiment. On the basis of this formulation, guidelines for increasing the efficiency of the acquisition were established. The technique was further validated by comparison with pulse-wave velocity measurements made with a pressure catheter. All data were acquired from a latex tube driven by a pulsatile flow system. MR measurements of pulse-wave velocity in the tube were found to be very reproducible in the presence of white noise. Measurements by other techniques were in good agreement, falling within 2 SD of the mean. Because of its sensitivity and spatial resolution, this technique shows promise for making spatially resolved estimates of vessel distensibility. This would allow assessment of diseases, such as atherosclerosis, that cause local changes in the material properties of the vasculature.

Interactive coronary MRI

The acquisition of complete three-dimensional (3D), segmented gradient-echo data sets to visualize the coronary arteries can be both time consuming and sensitive to motion, even with use of multiple breath-holding or respiratory gating. An alternate hybrid approach is demonstrated here, in which real-time interactive imaging is first used to locate an optimal oblique coronary scan plane. Then, a limited number of contiguous slices are acquired around that plane within a breath-hold with use of two-dimensional (2D) segmented gradient-echo imaging. Dual inversion nulling is used to suppress fat and myocardium. Finally, if needed, a limited reformat of the data is performed to produce images from relatively long sections of the coronaries. This approach yields relatively rapid visualization of portions of the coronary tree. Several different methods are compared for interactively moving the scan plane.

Real-time interactive MRI on a conventional scanner

A real-time interactive MRI system capable of localizing coronary arteries and imaging arrhythmic hearts in real-time is described. Non-2DFT acquisition strategies such as spiral-interleaf, spiral-ring, and circular echo-planar imaging provide short scan times on a conventional scanner. Real-time gridding reconstruction at 8-20 images/s is achieved by distributing the reconstruction on general-purpose UNIX workstations. An X-windows application provides interactive control. A six-interleaf spiral sequence is used for cardiac imaging and can acquire six images/s. A sliding window reconstruction achieves display rates of 16-20 images/s. This allows cardiac images to be acquired in real-time, with minimal motion and flow artifacts, and without breath holding or cardiac gating. Abdominal images are acquired at over 2.5 images/s with spiral-ring or circular echo-planar sequences. Reconstruction rates are 8-10 images/s. Rapid localization in the abdomen is demonstrated with the spiral-ring acquisition, whereas peristaltic motion in the small bowel is well visualized using the circular echo-planar sequence.

Twenty-eight-day repeated-dose inhalation exposure of rats to diethylene glycol monoethyl ether

This study was carried out to provide information on the effects of inhalation of diethylene glycol monoethyl ether, a substance used in industry which may be accidentally inhaled by man. Sprague-Dawley CD rats were exposed by inhalation to a test atmosphere containing diethylene glycol monoethyl ether in a nose-only exposure system for 6 hr a day, 5 days a week for 28 days. Mean exposure levels were 0. 09, 0.27, and 1.1 mg/liter. At the two lowest exposure levels the test substance was present entirely as vapor, but at the highest exposure level the test atmosphere was approximately equally divided by mass into respirable droplets (aerosol) and vapor. A comprehensive battery of toxicological evaluations including food consumption, body weight, clinical signs, hematology, and biochemistry revealed no evidence of a systemic effect of exposure. Histopathological examination showed changes indicative of mild nonspecific irritation in the upper respiratory tract of rats exposed at the two highest exposure levels. These changes consisted of foci of necrosis in the ventral cartilage of the larynx of rats exposed at 0.27 or 1.1 mg/liter and an increase in eosinophilic inclusions in the olfactory epithelium of the nasal mucosa of rats exposed at 1.1 mg/liter. The no observed adverse effect level for systemic effects was 1.1 mg/liter and the no observed adverse effect level for signs indicative of mild nonspecific irritation of the upper respiratory tract was 0.09 mg/liter.

Subchronic inhalation studies of styrene in CD rats and CD-1 mice

Groups of 10 male and 10 female Charles River (CRL) CD (Sprague-Dawley-derived) rats were exposed to styrene vapor at 0, 200, 500, 1000, or 1500 ppm 6 hr per day 5 days per week for 13 weeks. Styrene had no effect on survival, hematology, or clinical chemistry. Males at 1500 ppm weighed 10% less after 13 weeks and males and females at 1000 and 1500 ppm consumed more water than controls. Histopathologic changes were confined to the olfactory epithelium of the nasal mucosa. Groups of 20 male and 20 female CRL CD-1 and B6C3F1 mice were exposed to styrene vapor at 0, 15, 60, 250, or 500 ppm 6 hr per day 5 days per week for 2 weeks. Mortality was observed in both CD-1 and B6C3F1 mice exposed to 250 or 500 ppm; more female mice, but not males, died from exposure to 250 ppm than from 500 ppm. Groups of 10 male and 10 female CRL CD-1 mice were exposed to styrene vapors at 0, 50, 100, 150, or 200 ppm 6 hr per day 5 days per week for 13 weeks. Two females exposed to 200 ppm died during the first week. Liver toxicity was evident in the decedents and in some female survivors at 200 ppm. Changes were observed in the lungs of mice exposed to 100, 150, or 200 ppm and in the nasal passages of all treatment groups, those exposed to 50 ppm being less affected. Satellite groups of 15 male rats and 30 male mice were exposed as described above for 2, 5, or 13 weeks for measurement of cell proliferation (BrdU labeling). No increase in cell proliferation was found in liver of rats or mice or in cells of the bronchiolar or alveolar region of the lung of rats. No increase in labeling index of type II pneumocytes was seen in mouse lungs, while at 150 and 200 ppm, an increased labeling index of Clara cells was seen after 2 weeks and in occasional mice after 5 weeks. Large variations in the labeling index among animals emphasize the need for large group sizes. For nasal tract effects, a NOAEL was not found in CD-1 mice, but in CD rats, the NOAEL was 200 ppm. For other effects, the NOAEL was 500 ppm in rats and 50 ppm in mice.

Pencil excitation with interleaved fourier velocity encoding: NMR measurement of aortic distensibility

A technique is presented for rapidly and noninvasively determining aortic distensibility, by NMR measurement of pulse-wave velocity in the aorta. A cylinder of magnetization is excited along the aorta, with Fourier-velocity encoding and readout gradients applied along the cylinder axis. Cardiac gating and data interleaving improve the effective time resolution to as high as 3 ms. Wave velocities are determined from the position of the foot of the flow wave in the velocity profiles. Evidence of helical flow distal to the aortic arch can be seen in normal subjects, while disturbed flow patterns are visible in patients with aneurysms and dissections.

Simultaneous magnetic resonance phase and magnitude temperature maps in muscle

Noninvasive magnetic resonance temperature maps that are used to monitor thermal ablation of tissue are described. In magnetic resonance images, thermally induced proton nuclear magnetic resonance frequency shifts, and changes in the longitudinal relaxation time produce both phase and magnitude changes in the MR signal. Temperature maps with improved sensitivity are derived from the complex-difference nuclear magnetic resonance signal. Bovine muscle specimens were heated with focused ultrasound to model thermal surgery and create a known thermal distribution to test the method. Resulting MR images acquired in 2 s produce temperature maps with 1 min resolution and 2 degrees C temperature sensitivity. The temperature sensitivity was increased by extending the acquisition to 5 s, by decreasing the receiver bandwidth, and increasing the echo time.

Evaluation of the genotoxicity potential and chronic inhalation toxicity of 1,1-dichloro-1-fluoroethane (HCFC-141b)

A battery of in vitro and in vivo tests were conducted on HCFC-141b as a vapour. Bacterial gene mutation assays with Escherichia coli and Salmonella typhimurium were negative in all tester strains. In vitro chromosomal aberration assays were positive on CHO cells but negative on human lymphocytes. Moreover, HCFC-141b was negative in vivo in a mouse micronucleus inhalation assay. On the basis of these data and previously reported genotoxicity testing, HCFC-141b is considered non-genotoxic. Groups of 80 male and 80 female Sprague-Dawley rats were exposed, by inhalation (6 hr/day, 5 days/wk) to vapours of HCFC-141b for 104 wk at target concentrations of 0 (control), 1500, 5000 and 20,000 ppm (increased from 15,000 ppm after 17 wk of exposure). No exposure-related effects of toxicological significance were noted with respect to survival, clinical signs, ophthalmoscopy, haematology, clinical chemistry, urinalysis or organ weight analysis. Reduced food intake and body weight gain were noted in both sexes of the 15,000 ppm group during the first 16 wk; thereafter, body weight gains in all groups were similar although the intergroup differences in body weight remained evident. Reduced food intake persisted in both sexes through wk 52 and in females during the second year of exposure. Treatment-related effects on macroscopic pathology were confined to increased incidences of testicular masses and altered appearance. Microscopic pathology examinations confirmed the testes as the target organ with findings of increased incidences of benign interstitial cell tumours and hyperplasia at 5000 and 20,000 ppm. The no-observable-adverse-effect level (NOAEL) was 1500 ppm. The testicular changes at high exposure levels were considered to be due to a change of the senile hormonal imbalance in geriatric rats and of little significance for the assessment of human health effects.

Superconducting open-configuration MR imaging system for image-guided therapy

PURPOSE

To develop a superconducting magnetic resonance (MR) imager that provides direct access to the patient and permits interactive MR-guided interventional procedures.

MATERIALS AND METHODS

A 0.5-T superconducting magnet that allows a region of vertical access to the patient was designed and constructed. This magnet was integrated with newly designed shielded gradient coils, flexible surface coils, and nonmagnetic displays and with position-monitoring probes and device-tracking instrumentation.

RESULTS

The magnet homogeneity was 12.3 ppm, and the gradient field was linear to within 1% over an imaging region 30 cm in diameter. The signal-to-noise ratio was 10% higher than in a comparable 0.5-T superconducting imager. Images were obtained in several anatomic regions with use of routine pulse sequences. Interactive image plane selection and near real-time imaging, with use of fast gradient-recalled echo sequences, were demonstrated at a rate of one image every 1.5 seconds.

CONCLUSION

MR-guided interventional procedures can be performed with full patient access with use of an open-configuration, superconducting MR magnet with near real-time imaging and interactive image plane control.

Practice effects with the NIMH AIDS abbreviated neuropsychological battery

The degree of practice effects with the Brief NIMH Neuropsychological Battery for HIV Infection and AIDS is reported using a 7-10 day test-retest interval. The patient groups were asymptomatic and symptomatic of HIV while the control group was made up of "at risk" volunteers. Statistically significant practice effects were obtained on the California Verbal Learning Test, the Paced Auditory Serial Addition Task and the Visual Search Test among the infected individuals. The controls subjects demonstrated statistically significant practice effects on all of the neuropsychological tests. The implications of these findings in prospective studies are discussed.

Measurement of body surface area in children with liver disease by a novel three-dimensional body scanning device

Body surface area (BSA) is used in paediatrics to assess fluid requirement, drug doses, cardiac output and glomerular filtration rate. The aim of this study was to examine, in children with liver disease, the relationship between BSA determined by a traditional nomogram and BSA measured by a novel three-dimensional technique--Loughborough Anthropometric Shadow Scanner (LASS). Subjects were 16 children, mean age 8.1 (range 3.6-14.9) years, with a variety of liver diseases. Twenty-eight controls had a mean age of 7.1 (3.1-10.5) years. All had LASS scans performed as well as 21 anthropometric measurements taken by a single observer. There was a significant relationship between BSA (LASS) and BSA nomogram for liver-diseased children (r = 0.99) and controls (r = 0.96). The BSA nomogram values were significantly greater (P < 0.05) than BSA (LASS) for liver-diseased subjects by 10.1% (-0.35 to +20.6; 95% confidence interval), and for controls by 9.6% (4.1-23.2). Best prediction of BSA (LASS) for liver-disease subjects used height, body weight and gluteal furrow circumference [r2 = 0.997; standard estimated error (SEE) = 0.015 m2] and for controls used body weight alone (r2 = 0.907; SEE = 0.048 m2). BSA nomogram has no additional error in children with liver disease, but may overestimate BSA by 10% compared with a novel three-dimensional body surface scanning technique.

Brain and cerebrospinal fluid motion: real-time quantification with M-mode MR imaging

PURPOSE

To assess motion of brain parenchyma and cerebrospinal fluid (CSF) with magnetic resonance (MR) phase imaging in real time.

MATERIALS AND METHODS

Repetitive excitation of a cylinder with two-dimensional selective excitation followed by one-dimensional imaging along the cylinder axis yielded profiles analogous to those of M-mode echography. Bipolar gradients provided velocity sensitivity in an arbitrary spatial direction.

RESULTS

Brain and CSF of healthy volunteers exhibited periodic motion in the frequency range of normal heart rate. Both brain hemispheres showed periodic squeezing of the ventricles, with peak velocities up to 1 mm/sec followed by a slower recoil. Superimposed on the regular displacement of the brain stem was a slow, respiratory-related periodic shift of the neutral position. During the Valsalva maneuver, the brain stem showed initial caudal and subsequent cranial displacement of 2-3 mm. Coughing produced a short swing of CSF in the cephalic direction.

CONCLUSION

Real-time MR phase imaging allows observation of non-periodic events in brain and CSF motion.

MR temperature mapping of focused ultrasound surgery

Deep lying soft tissue tumors may be treated by a nonincisional surgical procedure executed inside an MR imaging system using a thermal effect delivered by a focused ultrasound transducer. A prototype system is constructed to assess MRI thermal monitoring and the localization of the heat zone in muscle. The temperature distribution of the focal spot is imaged with MRI while mechanically moving the transducer with an hydraulic 3-axis positioner. Acoustic power is applied with a spherical shell transducer using 1- to 10-s duration pulses at frequencies of 1.5 MHz to selectively coagulate tissue at 60-70 degrees C. The procedure is monitored with a series of fast second gradient echo, T1-weighted, temperature sensitive MR sequences. Acquisitions are optimized for high temperature sensitive images that yield the thermal diffusivity, heat flow time constant and the focal spot size in muscle. MR temperature maps of muscle provide localization and dosimetry both in the focal region and near field.

One-dimensional NMR thermal mapping of focused ultrasound surgery

OBJECTIVE

The aim of this study was to evaluate a technique for real-time monitoring of tissue temperature and tracking of the heat source during minimally invasive thermal interventions such as focused ultrasound surgery.

MATERIALS AND METHODS

A temperature-sensitive NMR line scan pulse sequence was directed interactively from a workstation during the application of focused ultrasound to samples of excised bovine skeletal muscle. The NMR signal along a sensitive line was monitored during and after heating by means of a scrolling display on the workstation.

RESULTS

The temperature sensitivity was found to be approximately 2 degrees C with a time resolution of 300 ms along a line intersecting the ultrasonic focal point. Experimental temperature rises determined from the NMR signal showed close agreement with theoretical temperature behavior derived from the heat equation. Temperature quantitation capabilities were lost upon onset of thermal denaturation and coagulation.

CONCLUSION

This technique could serve as a noninvasive guide in tracking the heat source and in monitoring thermal dose during focused ultrasound surgery and other minimally invasive thermal interventions.

A one-dimensional velocity technique for NMR measurement of aortic distensibility

A technique is presented for rapidly and noninvasively determining aortic distensibility, by NMR measurement of wave velocity in the aorta. A two-dimensional NMR selective-excitation pulse is used to repeatedly excite a cylinder of magnetization in the aorta, with magnetization read out along the cylinder axis each time. A toggled bipolar flow-encoding pulse is applied prior to readout, to produce a non-dimensional phase-contrast flow image. Cardiac gating and data interleaving are employed to improve the effective time resolution to 2 ms. Wave velocities are determined from the slope of the leading edge of flow measured on the resulting M-mode velocity image. The technique is sensitive over a range of distensibilities from 10(-6) to 10(-3) m s2/kg. The average value in the descending thoracic aorta in seven normal subjects was found to be 4.8 x 10(-5) m s2/kg, with a significant inverse correlation with age.

Real-time acquisition, display, and interactive graphic control of NMR cardiac profiles and images

A highly interactive MRI scanner interface has been developed that allows, for the first time, real-time graphic control of one-dimensional (1D) and two-dimensional (2D) cardiac MRI exams. The system comprises a Mercury array processor (AP) in a Sun SPARCserver with two connections to the MRI scanner, a data link that passes the NMR data directly to the AP as they are collected, and a control link that passes commands from the Sun to the scanner to redirect the imaging pulse sequence in real time. In the 1D techniques, a cylinder or "pencil" of magnetization is repeatedly excited using gradient-echo or spin-echo line-scan sequences, with the magnetization read out each time along the length of the cylinder, and a scrolling display generated on the Sun monitor. Rubber-band lines drawn on the scout image redirect the pencil or imaging slice to different locations, with the changes immediately visible in the display. M-mode imaging, 1D flow imaging, and 2D fast cardiac imaging have been demonstrated on normal volunteers using this system. This platform represents an operator-"friendly" way of directing real-time imaging of the heart.

An in vivo study of phosphorus and glucose metabolism in Alzheimer's disease using magnetic resonance spectroscopy and PET

OBJECTIVES

To study phosphorus and glucose metabolism in whole-brain slices of otherwise healthy patients with dementia of the Alzheimer type (DAT) and healthy controls.

DESIGN

We used proton nuclear magnetic resonance imaging phosphorus spectroscopy and positron emission tomography to study in vivo brain phosphorus and glucose metabolism.

PATIENTS

Whole-brain slice phosphorus metabolism was studied in nine drug free patients with mild to moderately severe dementia of the Alzheimer type (DAT) and in eight age- and sex-matched healthy controls. Mean ages (+/- SD) of the patients and controls were 60 +/- 10 years and 64 +/- 16 years, respectively. Positron emission tomography was used to study cerebral glucose metabolism in seven of the patients with DAT and seven of the healthy controls.

RESULTS

Patients with DAT had significant brain glucose hypometabolism compared with controls, but there was no significant group difference in any phosphorus metabolite concentration or ratio in the same volume of brain tissue. Also, within patients with DAT there was no correlation between any phosphorus metabolite concentration or ratio and either severity of dementia or glucose metabolism.

CONCLUSIONS

We suggest glucose metabolism is reduced early in DAT (reflecting decreased basal synaptic functioning) and is unrelated to a rate limitation in glucose delivery, abnormal glucose metabolism, or abnormal coupling between oxidation and phosphorylation. Normal or near-normal levels of phosphorus metabolites are maintained in mild, moderate, and severe DAT. Therefore, altered high-energy phosphate levels are not a consequence of reduced glucose metabolism in DAT, and do not play a major role in the pathophysiology of the disorder, at least in whole-brain sections.

An NMR phased array for human cardiac 31P spectroscopy

A four-coil phased-array 31P NMR receiver was designed and tested for human cardiac applications, to determine whether the combination of relatively high signal-to-noise ratio (SNR) and large field of view produced in 1H imaging is also realized for in vivo 31P spectroscopy. Spectra were acquired in parallel from an array of four overlapping 6.5-cm surface coils using one- and two-dimensional phase-encoding pulse sequences and were optimally combined to yield composite spectroscopic images. The phased array was found to generate useful 31P spectra from a 2.5-fold wider lateral region around the anterior myocardium than a single receiver of the same size as the array elements, with no increase in imaging time. In addition, the sensitive depth was increased by up to 2 cm over that of a single coil. Spectra could be acquired in roughly 15 min from a region extending to the middle of the heart, with voxel sizes of 2 x 2 x 4 cm3. For the average heart voxel, the SNR of the combined spectrum was higher than that of the best spectrum from any one coil in the array by 30%, with some voxels showing an increase as high as 60%.

Alzheimer dementia: quantification of energy metabolism and mobile phosphoesters with P-31 NMR spectroscopy

To determine whether high-energy phosphate metabolism and mobile phosphoester indexes of membrane metabolism are altered in Alzheimer disease and to help resolve some inconsistencies in the literature, brain phosphate metabolite concentrations and ratios were measured in 11 patients with mild to severe dementia of the probable Alzheimer type and 14 healthy subjects. Fully relaxed, spatially localized, phosphorus-31 nuclear magnetic resonance (NMR) spectroscopy and proton (hydrogen-1) MR imaging were performed. No significant differences were found in the concentrations and relative ratios of phosphocreatine, nucleoside triphosphate, inorganic phosphate, phosphomonoester, and phosphodiesters in whole axial sections through the lateral cerebral ventricles of the brain that could not be accounted for by atrophy. There was no correlation between P-31 NMR indexes and the severity of dementia as assessed with neuropsychologic testing. High-energy phosphate and membrane metabolism, as detected in vivo with P-31 NMR spectroscopy in whole-brain sections, do not appear to play a major role in the disease process, except as a direct consequence of atrophy quantified with H-1 MR imaging.

Proton Overhauser enhancements in human cardiac phosphorus NMR spectroscopy at 1.5 T

Narrowband irradiation of water protons with a surface coil yields significant nuclear Overhauser enhancement (nOe) of phosphocreatine (PCr) and some adenosine triphosphate (ATP) moieties in localized and unlocalized phosphorus (31P) NMR spectra from chest and heart muscle. In seven normal subjects at 1.5 T the nOe values were 0.6 +/- 0.3, 0.6 +/- 0.3, 0 +/- 0.3, and 0.3 +/- 0.2 for myocardial PCr, gamma-ATP, alpha-ATP, and beta-ATP, respectively, not significantly different from those in chest muscle. Distortion of the measured PCr/ATP ratios due to differences in the nOe may require accurate correction to realize the full benefit of the effect in studies involving quantitative intergroup comparisons.

Quantitative measurement of blood flow using cylindrically localized Fourier velocity encoding

A procedure for the quantitative measurement of blood velocity was developed and evaluated in the portal vein, aorta, and vena cava of healthy volunteers. This procedure utilizes Fourier velocity encoding and can be performed with or without cardiac gating. The accuracy of velocity measurements is determined by the accuracy of the gradient subsystem. Flow measurements derived from the velocity measurement are further limited in their accuracy by the luminal cross-section measurement. Spatial localization is accomplished with an excitation pulse having a cylindrical rather than slab geometry. Data are acquired in the presence of a readout gradient to provide resolution along the cylindrical axis.

Myocardial high-energy phosphate metabolism and allograft rejection in patients with heart transplants

To determine whether myocardial high-energy phosphate metabolism is altered in cardiac allograft patients undergoing rejection, 14 patients with heart transplants were examined with image-guided, one-dimensional, phase-encoded surface-coil phosphorus-31 nuclear magnetic resonance (NMR) spectroscopy on 19 occasions 39-2,021 days after transplantation. On average, patients underwent mild rejection (detected with endomyocardial biopsy) and had a reduced ratio of anterior myocardial phosphocreatine (PCr) to adenosine triphosphate (ATP) (1.57 +/- 0.50 [standard deviation] vs 1.93 +/- 0.2; P less than .01) compared with that of 17 healthy control subjects. Ratios of PCr to inorganic phosphate also appeared lower whenever detectable. However, P-31 NMR spectroscopy did not permit reliable identification of patients who required augmented therapy for rejection detected with biopsy either on the day of the P-31 NMR spectroscopic study or at the next scheduled biopsy 10-140 days thereafter (sensitivity, 50%, and specificity, 73% with use of cardiac-averaged PCr/ATP values for each heart; sensitivity, 88%, and specificity, 55% with use of the lowest myocardial PCr/ATP ratios measured in each heart).

Altered myocardial high-energy phosphate metabolites in patients with dilated cardiomyopathy

Myocardial high-energy phosphate metabolism in patients with dilated cardiomyopathy (DCM) of ischemic or idiopathic etiology was assessed at rest by one-dimensional phase-encoded 31P-nuclear magnetic resonance (NMR) spectroscopy studies performed in conjunction with 1H imaging in 20 patients with DCM and in 12 normal volunteers. The measured values of anterior myocardial phosphocreatine/beta-adenosine triphosphate (PCr/beta-ATP), corrected for partial saturation and contamination of the spectra by blood metabolites, averaged 1.80 +/- 0.06 (mean +/- SE) in normal volunteers and 1.46 +/- 0.07 in the patients overall, a highly significant (p less than 0.001) decrease. In patients with DCM accompanied by coronary artery disease (n = 9), the PCr/beta-ATP ratio averaged 1.53 +/- 0.07, while in those with DCM alone it was 1.41 +/- 0.12 (n = 11), a value that was not significantly different. There was no significant correlation (r = 0.34) between myocardial PCr/ATP ratio and left ventricular ejection fraction in patients. These studies demonstrate that myocardial PCr/ATP ratios are reduced at rest in human ischemic and idiopathic dilated cardiomyopathy.

Rapid NMR cardiography with a half-echo M-mode method

A real-time NMR cardiac profiling pulse sequence has been developed that incorporates two-dimensional (2D) selective excitation and a half-echo readout. The time resolution has been improved by a factor of two relative to the previous flow-compensated, full-echo version. The technique produces a 2D plot of "beam"-axis position versus time, analogous to M-mode echocardiography. In human subjects, details of valve leaflet motion, intracardiac flow, wall motion, and wall thickening may be observed along optimal lines of sight selected interactively. The pulse sequence uses a low-tip-angle 2D selective-excitation pulse derived from a spiral k-space trajectory to excite a narrow cylinder of magnetization, followed by a half-echo readout gradient oriented along the axis of the cylinder. One-dimensional Fourier transformation of the acquired signal results in a magnetization profile along the length of the cylinder, or beam. The pulse sequence is effectively flow compensated without any additional gradient lobes, because the rapid oscillation in the gradient wave forms of the 2D excitation pulse produces relatively small net gradient moments, and the shortened readout gradient has minimal first-order moment relative to center echo. The signal from moving blood can alternatively be velocity encoded by the addition of bipolar gradients along any of the three axes, producing Doppler-like traces of intracardiac blood flow.

31P spectroscopic localization using pinwheel NMR excitation pulses

Spectroscopic imaging with a one-dimensional phase-encoding gradient and surface-coil reception relies on the restricted range of sensitivity of the surface coil to provide localization in the dimensions transverse to the coil axis and consequently suffers from relatively poor localization in these dimensions. A two-dimensional (2D) cylindrically selective excitation pulse with a large spectral bandwidth is presented here to remedy this problem. The gradient waveforms are derived from multiple spirals in k space which form an overall pinwheel pattern, resulting in a pulse which is much shorter than the equivalent single-spiral trajectory. Nonuniform traversal of the spirals further reduces the pulse width under conditions of gradient slew-rate limitations, yielding overall gains in bandwidth of up to about 30 compared with the equivalent single-spiral trajectory traversed at constant angular rate. The accompanying rf waveform is obtained by weighted 2D Fourier transformation of the desired sensitivity profile. A new weighting factor is introduced into the rf waveform to compensate for nonuniform sampling of k space by the pinwheel near the origin. This factor is independent of the weighting used to account for the rate of traversal of the trajectory and is applicable to 2D pulse design in general. Pulse sequences employing pinwheel excitation in conjunction with either phase-encoding or slice-selective inversion are used to produce multiple-voxel and single-voxel localization in a human heart and a phantom. Pinwheel pulses may be used to advantage on moieties with long spin-lattice relaxation times and short transverse relaxation times and are therefore ideal for applications in phosphorus (31P) NMR.

Fast MR cardiac profiling with two-dimensional selective pulses

A rapid-profiling NMR pulse sequence has been designed to provide an interactive, real-time cardiac probe analogous to M-mode ultrasound. The pulse sequence employs a two-dimensional (2D) selective NMR pulse to excite a narrow (nominally 1-cm-diameter) cylinder of magnetization intersecting the heart. This procedure is followed by a readout gradient applied along the length of the cylinder, or "beam," to yield an M-mode type profile with a one-dimensional Fourier transform reconstruction. k-space techniques were used to design 2D pulses which excite cylinders characterized by either Gaussian or square radial excitation profiles. Images of phantoms acquired at 1.5 T confirm the predictions of the k-space analysis. The cylinder can be displaced interactively by modulating the rf excitation and the beam axis can be reoriented to any oblique direction by changing the relative mixing of the gradient waveforms. Flow compensation using bipolar gradient waveforms inverts the contrast of flowing blood and suppresses flow artifacts. A gated cardiac image is acquired as a reference to locate the excitation axis. A series of cardiac experiments was performed on several healthy volunteers. As the beam is moved and rotated to probe the myocardium, the profile plots resemble an M-mode echocardiogram. Unlike in M-mode echocardiography, however, the axis of interrogation is not limited to specific windows, and there is distinct flexibility of contrast. However, the temporal resolution is currently less than that achieved by ultrasound. NMR M-mode profiling provides a direct, fast method of measuring heart motion to assess cardiac function as part of an MR cardiac exam.

Regional myocardial metabolism of high-energy phosphates during isometric exercise in patients with coronary artery disease

BACKGROUND

The maintenance of cellular levels of high-energy phosphates is required for myocardial function and preservation. In animals, severe myocardial ischemia is characterized by the rapid loss of phosphocreatine and a decrease in the ratio of phosphocreatine to ATP.

METHODS

To determine whether ischemic metabolic changes are detectable in humans, we recorded spatially localized phosphorus-31 nuclear-magnetic-resonance (31P NMR) spectra from the anterior myocardium before, during, and after isometric hand-grip exercise.

RESULTS

The mean (+/- SD) ratio of phosphocreatine to ATP in the left ventricular wall when subjects were at rest was 1.72 +/- 0.15 in normal subjects (n = 11) and 1.59 +/- 0.31 in patients with nonischemic heart disease (n = 9), and the ratio did not change during hand-grip exercise in either group. However, in patients with coronary heart disease and ischemia due to severe stenosis (greater than or equal to 70 percent) of the left anterior descending or left main coronary arteries (n = 16), the ratio decreased from 1.45 +/- 0.31 at rest to 0.91 +/- 0.24 during exercise (P less than 0.001) and recovered to 1.27 +/- 0.38 two minutes after exercise. Only three patients with coronary heart disease had clinical symptoms of ischemia during exercise. Repeat exercise testing in five patients after revascularization yielded values of 1.60 +/- 0.20 at rest and 1.62 +/- 0.18 during exercise (P not significant), as compared with 1.51 +/- 0.19 at rest and 1.02 +/- 0.26 during exercise before revascularization (P less than 0.02).

CONCLUSIONS

The decrease in the ratio of phosphocreatine to ATP during hand-grip exercise in patients with myocardial ischemia reflects a transient imbalance between oxygen supply and demand in myocardium with compromised blood flow. Exercise testing with 31P NMR is a useful method of assessing the effect of ischemia on myocardial metabolism of high-energy phosphates and of monitoring the response to treatment.

AIDS dementia complex: brain high-energy phosphate metabolite deficits

To test whether compromised high-energy phosphate metabolism is implicated in the neurologic impairment of acquired immunodeficiency syndrome dementia complex (ADC), brain phosphate metabolite concentrations and ratios were measured noninvasively in 12 patients with mild to moderate ADC and 29 healthy volunteers by use of localized phosphorus-31 nuclear magnetic resonance (NMR) spectroscopy and proton (hydrogen-1) magnetic resonance (MR) imaging. In patients, brain phosphocreatine (PCr) and nucleoside triphosphate (NTP) concentrations in sections through the centrum semiovale that were seen with NMR spectroscopy were reduced significantly from normal values of 4.92 mmol/kg wet weight +/- .13 (standard error of the mean) and 2.79 mmol/kg +/- .11, respectively, to 3.33 mmol/kg +/- .26 and 1.99 mmol/kg +/- .13 (P less than .0001). The ratios of metabolites detectable with P-31 NMR spectroscopy did not differ significantly from those of control subjects. The magnitude of the PCr and NTP deficits in ADC was not explicable by focal abnormalities or cerebral atrophy quantified in images of the same regions. These results are consistent with the hypothesis of a generalized virus-associated toxic process affecting brain cell function in ADC. Noninvasive measurement of metabolite concentrations with NMR spectroscopy provides new functional information that may help quantify disease progression and response to therapy.

Phosphate metabolite imaging and concentration measurements in human heart by nuclear magnetic resonance

Cardiac-gated phosphorus (31P) nuclear magnetic resonance (NMR) spectroscopic imaging with surface coils resolves in three dimensions the spatial distribution of high energy phosphate metabolites in the human heart noninvasively. 31P spectra derive from 6- to 14-cm3 volumes of myocardium in the anterior left ventricle, septum, and apex, at depths of up to about 8 cm from the chest, as identified by proton (1H) NMR anatomical images acquired without moving the subject. Spectroscopic images are acquired in 9 to 21 min at 1.5 T. Metabolite concentrations are quantified with reference to a standard located outside the chest, yielding normal in vivo concentrations of phosphocreatine and adenosine triphosphate of about 11.0 +/- 2.7 (SD) and 6.9 +/- 1.6 mumol/g of wet heart tissue, respectively. High energy phosphate contents did not vary significantly with location in the normal myocardium, but 2,3-diphosphoglycerate signals from blood varied with subject and location.

Continual NMR cardiography without gating: M-mode MR imaging

A magnetic resonance (MR) pulse sequence was designed and implemented to examine the heart continually without gating, at rates in excess of 256 images in 7 seconds. The results are analogous to those of M-mode ultrasound, allowing interactive exploration of cardiac dynamics and flow in real time with full three-dimensional freedom of view. The technique is based on designed two-dimensional excitation pulses in which the magnetic field gradient is not constant, as in section-selection pulses, but varies in time to define a trajectory that results in a specified (eg, cylindric) region of excitation. The technique was implemented on a 1.5-T clinical imager with no special hardware and was tested on phantoms and volunteers. In human subjects, details of valve motion, intracardiac flow, and wall motion could be observed from moment to moment along optimal lines of sight selected interactively, with or without flow compensation and without gating. The momentary physiologic changes in chamber volumes and blood pool replenishment that occur during rhythm disturbances, the Valsalva maneuver, and simple breathing and breath-holding were readily demonstrated.

Proton-decoupled, Overhauser-enhanced, spatially localized carbon-13 spectroscopy in humans

Spatially localized, natural abundance, carbon (13C) NMR spectroscopy has been combined with proton (1H) decoupling and nuclear Overhauser enhancement to improve 13C sensitivity up to five-fold in the human leg, liver, and heart. Broadhand-decoupled 13C spectra were acquired in 1 s to 17 min with a conventional 1.5-T imaging/spectroscopy system, an auxiliary 1H decoupler, an air-cooled dual-coil coplanar surface probe, and both depth-resolved surface coil spectroscopy (DRESS) and one-dimensional phase-encoding gradient NMR pulse sequences. The surface coil probe comprised circular and figure-eight-shaped coils to eliminate problems with mutual coupling of coils at high decoupling power levels applied during 13C reception. Peak decoupler RF power deposition in tissue was computed numerically from electromagnetic theory assuming a semi-infinite plane of uniform biological conductor. Peak values at the surface were calculated at 4 to 6 W/kg in any gram of tissue for each watt of decoupler power input excluding all coil and cable losses, warning of potential local RF heating problems in these and related experiments. The average power deposition was about 9 mW/kg per watt input, which should present no systemic hazard. At 3 W input, human 13C spectra were decoupled to a depth of about 5 cm while some Overhauser enhancement was sustained up to about 3 cm depth, without ill effect. The observation of glycogen in localized natural abundance 13C spectra of heart and muscle suggests that metabolites in the citric acid cycle should be observable noninvasively using 13C-labeled substrates.

Comparative inhalation toxicity of technical chlordane in rats and monkeys

Technical chlordane (1,2,4,5,6,7,8,8-octachloro-3a,4,7,7-tetrahydro-4,7-methanoinda ne) is used extensively for control of certain wood-boring insects. The present study was conducted to evaluate the inhalation toxicity of technical chlordane in rats and monkeys. Range-finding (28-d) and subchronic (90-d) inhalation studies with Wistar rats, and subchronic (90-d) inhalation studies with cynomolgus monkeys were conducted. In the range-finding study in rats, the threshold of toxicity for technical chlordane was approximately 5.8 micrograms/l. Among the observations made during the course of the 90-d study, in which technical chlordane was administered by inhalation to rats and monkeys at concentrations close to 0.1, 1.0, and 10 micrograms/l, the most significant were associated with alterations in the liver and were confined to rats only. However, in the rat, the effects on the liver were largely reversible during 90 d following cessation of administration of technical chlordane. The no-effect level of chlordane inhalation in rats appears to be between 0.1 and 1.0 microgram/l, while in monkeys the no-effect level is in excess of 10 micrograms/l. This study demonstrated that the monkey, a species closely related to humans, can tolerate relatively high chlordane concentrations without any adverse effects.

Rapid, reliable in vivo assays of human phosphate metabolites by nuclear magnetic resonance

This accurate, reliable, and fast method of assaying absolute concentrations of phosphate metabolites noninvasively in living tissue, including that of humans, combines 31P nuclear magnetic resonance (NMR) spectroscopy and 1H NMR imaging. The images are used to measure the areas of metabolite-bearing tissue in selected sections through the subject, and 31P spectra are acquired from the same section, together with a concentration reference located on the periphery. Metabolite concentrations are calculated from the ratios of areas and integrated signal intensities. Apparatus and protocol are designed to eliminate corrections due to magnetic field nonuniformities and NMR relaxation times. Mean (and SD) concentrations of adenosine triphosphate (ATP), phosphocreatine, and inorganic phosphate (Pi) measured in the brains of 15 normal adult human volunteers with a 1.5-T NMR system were 3.03 (0.49), 5.18 (0.89), and 1.5 (0.7) mmol per liter of wet tissue, respectively. Acquisition times of only a few minutes should facilitate metabolic studies of patients with disorders in limbs and brain, particularly those affecting entire organs.

Rapid, reliable in vivo assays of human phosphate metabolites by nuclear magnetic resonance

This accurate, reliable, and fast method of assaying absolute concentrations of phosphate metabolites noninvasively in living tissue, including that of humans, combines 31P nuclear magnetic resonance (NMR) spectroscopy and 1H NMR imaging. The images are used to measure the areas of metabolite-bearing tissue in selected sections through the subject, and 31P spectra are acquired from the same section, together with a concentration reference located on the periphery. Metabolite concentrations are calculated from the ratios of areas and integrated signal intensities. Apparatus and protocol are designed to eliminate corrections due to magnetic field nonuniformities and NMR relaxation times. Mean (and SD) concentrations of adenosine triphosphate (ATP), phosphocreatine, and inorganic phosphate (Pi) measured in the brains of 15 normal adult human volunteers with a 1.5-T NMR system were 3.03 (0.49), 5.18 (0.89), and 1.5 (0.7) mmol per liter of wet tissue, respectively. Acquisition times of only a few minutes should facilitate metabolic studies of patients with disorders in limbs and brain, particularly those affecting entire organs.