ABSTRACT
Distribution of cerebral blood flow was measured with an array of 200 ultra-pure germanium radiation detectors and 133-Xe by inhalation. The array "sees" the head as a composite of different subvolumes and enables measurement of the concentration history of tracer every 1-10 sec in each subvolume simultaneously. Subvolume mean flows, (fm), and partition coefficients, lambda m, are derived by compartmental analysis of tissue concentration washout curves. Errors from "cross talk," scalp radiation, "look through," and assumed partition coefficients are eliminated. Average fm adjusted for 40 mm Hg PACO2 in 14 cortical subvolumes (7 right, 7 left) of four normal 21-24 year old controls ranged from 50 to 60 ml/100 cc tissue/min, and lambda m ranged from 0.97 to 1.14. Average fm and lambda m in white matter was 24 ml/100 cc/min and 1.42 - 1.14 respectively. During CO2 inhalation, right and left hemispheric fm increased 6.4% and 5.7%/mm Hg respectively, whereas white matter fm increased 2.2% and 3.4% mm Hg respectively. There was no systematic difference between front and back or dominant vs non-dominant sides. Three 73-84 year old controls had reduced fm and CO2 reactivity in all subvolumes, lambda m was in the same range as in younger controls. Two patients with intracranial cerebrovascular disease showed excellent localization of ischemic subvolumes. One patient with asymptomatic unilateral 98% stenosis of the internal carotid artery had a similar distribution of blood flow in both hemispheres.
Subject(s)
Cerebrovascular Circulation , Cerebrovascular Disorders/physiopathology , Germanium , Xenon Radioisotopes , Adult , Aged , Carbon Dioxide , Cerebrovascular Disorders/diagnostic imaging , Female , Humans , Male , Partial Pressure , Tomography, Emission-Computed/instrumentation , Tomography, Emission-Computed/methodsABSTRACT
A new stationary 200-element ultrapure germanium (HPGe) array has been tested for accuracy and sensitivity in quantitating the distributed concentration of single-gamma-emitting radionuclides in phantoms approximating the size of the human brain. The phantoms consisted of 42 blocks of 39.1 cm3 average volume. Fourteen different permutations were studied. The concentrations in the blocks varied from 0i to 4.64 muCi/cm3. This first-generation instrument makes it possible to reconstruct the distributed concentration with a mean relative error of 8.3% at 200,000 counts per sample (1,000 counts/detector), and has sensitivities of 6,200 and 12,000 cps, respectively, for 1 muCi/cm3 of Xe-133 and Tc-99. The reconstruction algorithm is based on the conjugate gradient method of solving the set of linear equations that account for geometric, attenuation, and scatter factors. The results have implications for measuring the distribution of the partition coefficients, blood flow, blood volume, and concentration of tracers emitting single gamma photons in 42 anatomic subvolumes (30 cm3 average) of the entire brain simultaneously.
Subject(s)
Germanium , Models, Structural , Radionuclide Imaging/instrumentation , Cadmium , Cobalt Radioisotopes , Evaluation Studies as Topic , Models, Theoretical , Radioisotopes , Reference Values , Technetium , Xenon RadioisotopesABSTRACT
A formal 44-month clinical evaluation was conducted to determine the suitability of selected electronic equipment for use in high-level quadriplegia. A total of 52 traumatic high-level quadriplegic patients (C-2 to C-5,6) participated in the testing of 13 commercial electronic assistive devices including 8 environmental control units, 1 self-contained telephone, and 4 typewriter systems. Most devices were pneumatically ("breath") controlled. Devices were tested in an occupational therapy laboratory, bedside, and homes. Testing yielded data on device reliability, suitability, and acceptance by patients.