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Biomedical subjects

D A Rottenberg

Publications and source records attributed to D A Rottenberg.

At least 73 records · Page 4Linked to original sources
PubMed1982

Mass spectrometric measurement of end-tidal xenon concentration for clinical stable xenon/computerized tomography cerebral blood flow studies.

We have demonstrated the feasibility of using a compact dedicated mass spectrometer to monitor end-tidal xenon concentration in human subjects during stable xenon computerized tomography measurements of regional cerebral blood flow. End-tidal carbon dioxide concentration is monitored simultaneously and noninvasively without degrading the dynamic response to xenon. For clinical regional cerebral blood flow studies we employed a Nuclide 3-60-G Sectorr mass spectrometer with a 3 in radius, 60 degrees magnetic sector and a variable (0-5000 V) ion accelerating potential. The required high vacuum (10(-7) Torr) was achieved and maintained by means of a turbomolecular pump. A needlemetering valve was incorporated into an anesthesia mask connector, and exhaled gases were transported to the mass spectrometer via a 6 ft length of Teflon tubing (1/16 in i.d.). Molecular flow conditions between the sample and analysis chambers were provided by use of a gold foil leak (0.0005 in. hole). At an inlet pressure of 400 m Torr (achieved by means of the needle valve), the inlet system was characterized by a gas transport lag-time of 1.3 s and a rise-time constant of 85 ms. Xenon (doubly charged ion: m/z 68) and carbon dioxide (doubly charged ion: m/z 22) were monitored alternately at 75 ms intervals. Our experience with mass spectrometry has demonstrated the feasibility of using a compact dedicated instrument for accurately and non-invasively monitoring end-tidal xenon concentration in a clinical setting.

Brain↗
PubMed1982

The in vivo autoradiographic measurement of regional cerebral blood flow using stable xenon and computerized tomography: the effect of tissue heterogeneity and computerized tomography noise.

We have studied the effect of brain tissue (gray matter-white matter) heterogeneity and computerized tomography (CT) noise on the accuracy of xenon CT measurements of regional cerebral blood flow (rCBF) based upon "autoradiographic" and multiple-scan washin protocols. The results of our mathematical analysis indicate that both protocols are associated with a variety of measurement errors that lead to unacceptable and, to a large extent, unpredictable uncertainties in calculated values of rCBF. Brain tissue heterogeneity and high volumetric flow rates may--even in the absence of movement artifact and CT noise--lead to measurement errors in excess of 20%. Moreover, CT noise is additive in regard to these errors, and constitutes the most confounding variable of all.

Animals↗
PubMed1982

Repeated least squares analysis of simulated xenon computed tomographic measurements of regional cerebral blood flow.

Computer simulations were done as a feasibility study of xenon computed tomographic measurements of regional cerebral blood flow. Accuracy of initial least squares estimates of gray matter and white matter rate constants from a two-compartment model depended very little on the number and timing of scans, but did depend significantly on the enhancement-to-noise ratio as well as on the true values of the rate constants and gray/white ratio. Nonlinear least squares gives an optimal fit of the predicted wash-in--wash-out curve to the data rather than optimal estimates of the rate constants. A polynomial correction factor was obtained by regressing initial estimates on the true values used to generate the simulations. The correction factor substantially reduced error in the estimates and, in particular, eliminated large outliers.

Brain↗
PubMed1982

An inexpensive video patient repositioning system for use with transmission and emission computed tomographs.

We have designed and constructed a portable video system from commercially available components (total cost $5,000) to facilitate accurate patient repositioning for sequential computed tomographic (CT) and positron emission tomographic studies and for therapeutic radiation therapy. The repositioning accuracy of the video system, employed in conjunction with a Delta-Scan 2020 CT scanner, was compared qualitatively (skull phantom and patient subjects) and quantitatively (precision cone phantom) with that of a GE 8800 CT scanner equipped with ScoutView and crossed Gammex lasers (SVL system). Although the SVL and video systems both facilitated accurate repositioning, the video system proved slightly superior. With experience, Z-axis repositioning accuracy of better than 1 mm could be achieved.

Humans↗
PubMed1982

Synthesis of [2-11C]5,5-dimethyl-2,4-oxazolidinedione for studies with positron tomography.

We have developed a method for the synthesis of [2-11C]5,5-dimethyl-2,4-oxazolidinedione ([2-11C]DMO) for use with positron emission tomography to measure regional tissue pH in vivo in man. [2-11C]Dimethyl carbonate (DMC) was prepared from [C-11]phosgene and excess of sodium methoxide in methanol containing dimethyl carbonate as added carrier. The [2-11C]DMC solution was then reacted with 2-hydroxyisobutyramide at 150 degrees C for 10 min to yield, after HPLC separation, [2-11C]DMO with a radiochemical yield of 20-56%. Chemical yields were 78-92%, and specific activity ranged as high as 830 mCi/millimol.

Brain↗
PubMed1981

Lateral and third-ventricular CSF formation after metrizamide CT ventriculography.

We calculated the rates of lateral and third-ventricular (LTV) cerebrospinal fluid (CSF) formation in three patients undergoing metrizamide computed tomography (CT) ventriculography with reference to Ct estimates of ventricular volume and the time course of LTV metrizamide washout (elimination). Elimination rate constants for metrizamide were derived from measurements of LTV metrizamide concentration on serial postventriculography CT scans, and LTV volumes were estimated by partial volume analysis. CSF formation in the combined lateral ventricles averaged 0.14 ml per minute, and third-ventricular CSF formation averaged 0.014 ml per minute. Thus, the third ventricle accounted for approximately 10% of total LTV CSF production, which accords with relative weights of choroid plexus tissue in the lateral and third ventricles.

Adult↗
PubMed1981

Pituitary metastasis: incidence in cancer patients and clinical differentiation from pituitary adenoma.

Symptomatic pituitary metastases are uncommon and may be difficult to differentiate from pituitary adenomas. In order to ascertain the incidence of pituitary tumors in cancer patients and to characterize the clinical presentation of pituitary metastases, we reviewed the clinical experience with these tumors at Memorial Sloan-Kettering Cancer Center (MSKCC) during the period 1976-1979 and a recent series of 500 consecutive autopsies in which the pituitary fossa and gland were examined. In the clinical series, a histologic diagnosis was made in three of five patients. Radiologic evaluation, including polytomography and computed tomography, did not reliably distinguish metastasis from adenoma, but the clinical syndromes were distinctive. In the autopsy series, pituitary metastases were found in 3.6% of cases, pituitary adenomas in 1.8%.

Adenoma↗
PubMed1980

Progressive white matter destruction following irradiation of an extracranial neoplasm.

Although numerous "cures# have been reported following surgical extirpation of symptomatic foci of cerebral radiation nerosis, delayed progressive white matter destruction and neurological deterioration may occur in some patients who survive for prolonged periods after operation. The postoperative appearance on CT scans of hypodensity within heavily irradiated white matter structures at a distance from the initial radionecrotic focus or operative site suggests continuing radiation-induced tissue injury and a poor prognosis. Anticipated survival as well as administered radiation dose must be taken into account when "safe# radiation thresholds are calculated.

Carcinoma, Squamous Cell↗
PubMed1980

The pathogenesis of pseudotumor cerebri--a mathematical analysis.

Although the clinical and laboratory features of pseudotumor cerebri have been clearly delineated, the pathogenesis of idiopathic pseudotumor remains a mystery. A number of pathogenetic mechanisms have been proposed to account for some or all of the observed cases. We describe a model relating changes in CSF outflow resistance and/or dural sinus venous pressure to observed changes in (i) CSF pressure, (ii) cerebral blood volume and (iii) the volume and hydrodynamic flow resistance of the ventriculosubarachnoid space.

Cerebrovascular Circulation↗
PubMed1980

Hypothesis: the pathogenesis of pseudotumor cerebri.

In susceptible individuals, one of a variety of known or unknown precipitants affects the arachnoid villi so as to produce a large increase in CSF outflow resistance, Ra. This increase in Ra raises CSF pressure (CSFP), which rise provokes a redistribution of arteriovenous pressures across the cerebrovascular bed. The end result is a measurable increase in cerebral blood volume, compression of the ventricular system and compromise of the convexity subarachnoid space, which further increases CSF outflow resistance. Ultimately, a new steady state CSFP is attained.

Brain Edema↗
PubMed1979

A method of correcting for linear drift in computed tomography brain scans.

Linear drift of X-ray attenuation coefficients must be corrected if quantitative comparisons are to be made between computed tomography (CT) brain scans of the same individual performed at different times. Such a correction is accomplished by comparing the low (cerebrospinal fluid) end of the attenuation coefficient frequency histograms using a percentile--percentile plot. A "drift correction" permits serial quantitative assessments of the progression or regression of white matter hypodensity, such as occurs in drug induced leukoencephalopathy.

Adolescent↗
PubMed1978

Leukoencephalopathy following high-dose intravenous methotrexate chemotherapy: quantitative assessment of white matter attenuation using computed tomography.

A clinical or subclinical leukoencephalopathy occurs in some children after treatment of acute lymphatic leukemia with prophylactic cranial radiation therapy and parenteral or intrathecal methotrexate. We have observed a similar clinical leukoencephalopathy in patients with bone tumors treated with intravenous high-dose methotrexate and citrovorum factor without cranial irradiation. CT scans of such patients may indicate decreased white matter attenuation, but visual appraisal of this phenomenon is occasionally misleading. A computerized method for analyzing white matter hypodensity by determining the mean attenuation coefficient for one or several contiguous CT slices has therefore been developed. Serial comparisons of this mean attenuation coefficient appear to be more reliable than simple visual appraisal.

Adolescent↗
PubMed1978

Partial volume summation: a simple approach to ventricular volume determination from CT.

The accurate determination of ventricular volume from computed tomography (CT) is not a trivial problem. The direct approach of measuring the area within a visually determined boundary or contour level and multiplying by the nominal slice thickness may be subject to large errors because such boundaries are not, in general, well defined. When the ventricles are filled with a high-contrast material such as metrizamide, we may use the technique of 'partial volume summation,' a simple but accurate, clinically applicable method which may be performed on a standard DeltaScan-50 or similar system.

Cerebral Ventricles↗
PubMed1978

A statistical method for determining the proportions of gray matter, white matter, and CSF using computed tomography.

The brain may be considered as a collection of volume elements (voxels) containing unknown proportions of gray matter (GM), white matter (WM), and cerebrospinal fluid (CSF). If one assumes that (1) the attenuation coefficients for voxels with the same proportions of GM, WM, and CSF follow a Gaussian distribution whose mean is a weighted average of the mean attenuation coefficients of pure GM, WM, and CSF and (2) the voxel-to-voxel variation in proportion follows a Dirichlet probability distribution, then the overall proportions of GM, WM, and CSF can be calculated by optimizing the parameters of a compound Dirichlet-Gaussian distribution. This approach permits a quantitative analysis of the compartmental composition of the brain and may be useful in the evaluation of patients with cerebral edema, hydrocephalus, and leukoencephalopathy.

Brain↗
PubMed1978

Determination of ventricular volume following metrizamide CT ventriculography.

Volume averaging, relatively slight differences in the mean attenuation coefficients of CSF and white/grey matter, and the irregular contours of the human ventricular system have so far seriously limited the accuracy of CT estimation of ventricular volume. Taking advantage of the high attenuation of metrizamide-containing CSF, we have developed three methods for computing ventricular volume after metrizamide CT ventriculography; these methods depend upon computer analysis of X-ray absorption data obtained from contiguous CT brain slices. All three methods were validated by CT scanning a formalin-fixed cadaver brain containing an apoxy-resin cast of the ventricular system. Calculated ventricular volumes were compared with the actual measured volume of the ventricular cast.

Aged↗
PubMed1978

Metrizamide washout as a measure of CSF bulk flow.

Metrizamide was injected into the ventricular system of three adults and five children with indwelling ventricular catheters and subcutaneous CSF reservoirs. A first-order rate constant, k, for metrizamide washout from one lateral ventricle was determined with reference to ventricular metrizamide concentration on serial (up to six) postinjection CT scans. Lateral ventricular volume, Vv, was estimated after metrizamide injection by a planimetric method and by partial volume analysis, an interactive computerized technique. The rate of lateral ventricular CSF formation, If, was calculated as k X Vv and ranged from 0.0622 to 0.103 ml/min. Precise measurements of lateral ventricular CSF bulk flow depend upon adequate mixing of the injected contrast material with ventricular CSF and accurate measurements of lateral ventricular volume.

Adult↗