Robley D. Evans

Radioactive Iodine as an Indicator in the Study of Thyroid Physiology.

The known facts of thyroid physiology indicate that iodine is selectively taken up by the thyroid gland, and that in some measure that glands function is regulated by its iodine content. Artificial radioactivity may be induced in a variety of elements by means of neutron bombardment. It seemed that the possibility of using “tagged” (radioactive) iodine as a physiologic indicator was one which demanded investigation. Ethyl iodide (600-1000 cc) was irradiated in a paraffin-surrounded bottle by immersing in it a neutron source consisting of 110 mg of radium mixed with beryllium in a sealed tube. The radioactive iodine thus obtained was concentrated by a method which has been described elsewhere. 1 This method gave a precipitate of radioactive silver iodide, which was dissolved in a solution of 0.5-1.0 g of sodium thiosulphate, and then diluted to 10-15 cc for intravenous injection. In a series of 48 rabbits, no toxic effects from the acute administration of such quantities were experienced. Aliquot portions of the solution of radioactive iodine used for injection were withheld for measurement of radioactivity. A Geiger-Müller counter connected to a suitable vacuum tube amplifier and register to record the individual disintegrations of the radioactive atoms was used for detection of the radioactive iodine in various tissues. This apparatus is standardized and has been fully described elsewhere. 2 3 4 Since no gamma rays could be observed from radioactive iodine,1 determinations had to be made from the beta radiations. The half-period of radioactive iodine is 26 minutes, so that accurate measurements could not be extended beyond about 40 minutes after injection, with the activities available to date.

Radioactivity of rocks

Although numerous previous measurements of the radioactivity of terrestrial materials have been made, most of these researches are of qualitative value only in their applications to geology, geophysics, and cosmology because of inadequate recognition of the analytical care necessary in order to obtain reliable results. In the present study of the radioactivity of terrestrial materials, a systematic program of standardization, calibration, and interchecking has been followed throughout. As part of an international intercalibration among the various workers in this field and a general program of helium age research, several hundred radioactivity measurements have been made. These results represent the most reliable collection of radioactivity determinations which have yet been made within the range of concentrations involved. By combining these newer measurements with the limited number of well-authenticated earlier analyses available, average values have been obtained as follows: 1.37 ± 0.17 × 10 −12 g Ra/g for 43 acidic igneous rocks, 0.51 ± 0.05 × 10 −12 g Ra/g for 7 intermediate igneous rocks, 0.38 ± 0.03 × 10 −12 g Ra/g for 54 basic igneous rocks, and 0.57 ± 0.08 × 10 −12 g Ra/g for 28 sedimentary rocks; 3.0 ± 0.3 × 10 −6 g U/g, 13 ± 2.0 × 10 −6 g Th/g, and a Th/U ratio of 5.0 for 26 acidic igneous rocks; 1.4 ± 0.2 × 10 −6 g U/g, 4.4 ± 1.2 × 10 −6 g Th/g, and a Th/U ratio of 2.6 for 6 intermediate igneous rocks; 0.96 ± 0.11 × 10 −6 g U/g, 3.9 ± 0.6 × 10 −6 g Th/g, and a Th /U ratio of 4.0 for 34 basic igneous rocks. These values are substantially lower than those obtained by Jeffreys in a compilation of most of the measurements reported prior to 1936. The present averages show a more marked decrease of radioactivity with increasing basicity, the Th/U ratios are considerably greater than those compiled by Jeffreys and are in better agreement with those to be expected from geochemical considerations. Two ultrabasic rocks were found to have radio-activities comparable to the low values for iron meteorites. Specific inaccuracies in earlier investigations have been, discovered. Estimates are made of the rate of production of heat by radioactive decay based on the above average values for the different rock types.

Statistical Analysis of the Counting Rate Meter

The counting rate meter, or vacuum tube speedometer, is an integrating and averaging instrument with an electrical, exponentially decaying memory. It is designed to replace message‐register equipment in all particle counting apparatus, and is ideally suited to continuous photographic recording. The average current to the output meter is proportional to the counting rate for constant sources or for decaying sources whose mean life is significantly greater than the time constant RC of the output tank circuit. This RC is analogous to a radioactive mean life and may be regarded as the mean memory time. While the output current depends only on the output resistance R, and not on the output capacitance C (except for very rapidly decaying sources), the statistical fluctuations in the output current depend upon RC, and are equivalent to the fluctuation expected in a time interval of 2RC. Expressions are derived for the condenser charge Q, or output current Q/RC, for constant and decaying sources of radiation, as ...

Apparatus for the Determination of Minute Quantities of Radium, Radon and Thoron in Solids, Liquids and Gases

The radium content of ordinary materials is determined by removing and measuring the radon which is in equilibrium with the radium. I. Generalization of the direct fusion furnace method now permits the rapid and complete deemanation of any solid by direct boiling at 2000°C. II. Improved boiling apparatus for the removal of radon from liquids avoids loss of traces of radon by absorption. III. Gaseous samples, at atmospheric pressure, may be examined directly for radon. IV. Double ionization chambers, coupled to a high sensitivity string electrometer, permit observations on very feeble sources. Statistical fluctuations in the emission of contamination alpha‐rays from the ionization chamber walls impose a natural observational limit of 7.2×10−14(n)−½ curies of radon, when the ionization currents are observed for n hours. V. Photographic recording of the ionization current, with hourly automatic recalibration of the electrometer at three arbitrary potentials, makes possible long runs and higher precision, par...

THE MEASUREMENT OF POST-TRANSFUSION SURVIVAL OF PRESERVED STORED HUMAN ERYTHROCYTES BY MEANS OF TWO ISOTOPES OF RADIO-ACTIVE IRON

The evaluation of the efficacy of whole blood transfusion in augmenting total red cell volume has always been of interest to physicians called upon to care for patients with hemorrhage, burns, blood dyscrasias, or traumatic shock. The establishment of blood banks, resulting in an increasing use of stored blood, has focused more attention on the problem. Military requirements have created a demand for the preservation of whole blood over far longer periods than are required for civilian purposes. The urgent need for better preservative solutions and for the selection of the best conditions for overseas air transport of whole blood for the Armed Forces made it imperative that an accurate method of measuring the post-transfusion survival of stored human erythrocytes be available. The morphological and chemical changes that take place in red cells during storage have been studied by several laboratory methods. The rate. of spontaneous hemolysis, changes in cell dimension, changes in the permeability of the cell membrane, changes in osmotic resistance to hypotonic solutions of NaCl, rate of diffusion of potassium, and disturbances in carbohydrate metabolism have all been proposed as in vitro tests for the evaluation of the ability of stored red cells to survive after transfusion. Each of these tests assays only changes in one functional characteristic of the. erythrocyte and it is for this reason that the opinion has been expressed that in vitro tests fail as a guide to the

THE EFFECT OF VARYING TEMPERATURES ON THE POST-TRANSFUSION SURVIVAL OF WHOLE BLOOD DURING DEPOT STORAGE AND AFTER TRANSPORTATION BY LAND AND AIR

The successful establishment of a military whole blood transfusion service is dependent upon reducing damage to the cells from mechanical agitation incident to land, sea, and air transportation to a minimum. Robertson (1) successfully transported whole blood in Rous-Turner solution by ambulance for short distances in World War I. Blood from civilian donor centers was shipped to front lines during the Spanish Civil War (2). Maycock has reported on the use of blood transported in refrigerated trucks during the Battle of Flanders (3). During the invasion of Europe blood banks were in operation in many theatres, blood being obtained from military personnel, a necessarily limited source of supply. The establishment of the American Red Cross Blood Donor Service, taking blood for processing of plasma, afforded a potentially adequate supply source, provided blood could withstand shipment across the Atlantic and far out into the Pacific oceans. The distances involved were so great that air transport was the only feasible means of transportation that would get blood to medical personnel before it had seriously deteriorated. It was obvious that only the best known whole blood preservatives would suffice, and 2 solutions, Alsevers (4) and acid-citrate-dextrose (5), were under consideration by the Armed Forces at the time this study was undertaken. The comparative value of these 2 solutions for depot storage under constant refrigeration has been reported (6), ACD being superior to Alsevers. The survival of these cells in these preservatives after long-range ship-

A Direct‐Reading Counting Rate Meter for Random Pulses

Randomly distributed pulses, of any voltage shape, and of varying magnitude, actuate an amplifier whose output meter indicates only the average rate of arrival of the pulses. Counting rates of 30 per minute up to several thousand per minute are read directly from a rugged meter. The apparatus is a.c. operated, is portable, and is particularly adapted to the study of feeble gamma‐radiation. The apparatus consists essentially of a preamplifier, a uniform pulse generator based on a relaxation oscillator or on an inverter circuit, an output amplifier stage, and a capacity‐resistance electrical tank circuit for performing the averaging process.

LITHIUM-DRIFTED GERMANIUM DETECTORS: APPLICATIONS TO NEUTRON-ACTIVATION ANALYSIS

Lithium-drifted germanium detectors for high-resolution gamma-ray spectroscopy reduce the need for wet chemistry in neutron-activation analysis. Problems in fields as diverse as geochemistry and the history of 15th-century printing have proved susceptible to this analytic technique.

Treatment of Hyperthyroidism with Radioactive Iodine

Roentgen discovered the rays that bear his name in 1895. Madame Curie separated radium from pitchblende in 1898. Henri Becquerel in 1901 carried a small vial of radium in his pocket, and the reaction produced on the skin of his belly led him to see Dr. Ernest Besnier. Therein was produced the idea of treating diseased tissues by means of radioactive materials. In 1905, Dr. Robert Abbe (1) reported the first case of hyperthyroidism successfully treated by implanting radium directly into the substance of the thyroid gland. Treatment by means of x-rays directed externally over the thyroid has also been used effectively. The next great advance in the radiation treatment of the hyperplastic thyroid began in 1936 through the stimulation of medical men by Dr. Karl T. Compton of the Massachusetts Institute of Technology. Thereafter, followed a series of co-operative researches undertaken by the Massachusetts Institute of Technology and the Massachusetts General Hospital. Prof. Robley D. Evans, Dr. Saul Hertz (2),...Roentgen discovered the rays that bear his name in 1895. Madame Curie separated radium from pitchblende in 1898. Henri Becquerel in 1901 carried a small vial of radium in his pocket, and the reaction produced on the skin of his belly led him to see Dr. Ernest Besnier. Therein was produced the idea of treating diseased tissues by means of radioactive materials. In 1905, Dr. Robert Abbe (1) reported the first case of hyperthyroidism successfully treated by implanting radium directly into the substance of the thyroid gland. Treatment by means of x-rays directed externally over the thyroid has also been used effectively. The next great advance in the radiation treatment of the hyperplastic thyroid began in 1936 through the stimulation of medical men by Dr. Karl T. Compton of the Massachusetts Institute of Technology. Thereafter, followed a series of co-operative researches undertaken by the Massachusetts Institute of Technology and the Massachusetts General Hospital. Prof. Robley D. Evans, Dr. Saul Hertz (2),...

Design and Operation of an Improved Counting Rate Meter

The counting rate meter is an electronic amplifier and computing circuit whose output is a d.c. current or voltage proportional to the number of pulses fed into the circuit. The input pulses may be either uniformly spaced or distributed randomly in time, as in the most common use of the instrument as an amplifier and recorder for use with Geiger‐Muller counters. The electronic design and operation is discussed for each of the circuit components: amplifiers, pulse equalizer, integrating circuit, degenerative vacuum‐tube voltmeter, and the stabilized high voltage and low voltage supplies. The statistical interpretation of the counting rate meter output readings due to the randomly distributed pulses from radioactive sources requires a special statistical theory because an integrating and averaging circuit produces an exponential interdependence of successive observations on all preceding observations. Practical methods, with curves, are developed for determining the mean counting rate and the probable error...