Thallium-activated Sodium Iodide Crystal Research Articles

Effects of ? rays on the inherent resolution of a thallium-activated sodium iodide crystal

Effects of ? rays on the inherent resolution of a thallium-activated sodium iodide crystal

Charged particle counters in the pre-modern period

The history of nuclear particle and radiation counting techniques divides itself naturally into three epochs that may be labeled ; Early, Pre-Modern, and Modem. Figs . 1 and 2 are facsimile reproductions of figures from two of the seminal papers of the Early period. With this division the Modern era dates from the advent of photomultiglier-scintillation counters using anthracenet°) and thallium activated sodium iodide crystals'') followed in 1958-63 by practical solid-state ionization counters using crystals of silicon or germanium. And with this division we then designate the PreModern era as the period starting in the 1930's during which the several types of gas-ionization counters of the Early period were perfected Ind coupled to vacuum tube circuits and recording apparatus . As a young graduate student starting research in 1940 1 found the gas counter field in a developed state and one which has changed but little since. Neher's famous chapter on Geiger and Geiger-Mueller counters had appeared in Strong's Procedures in experimental physics, published in 1938. Fig. 3 is a reproduction of one of the artistic drawings from this chapter . Various recipes for making reliable GM counters were well known, although there was controversy on the reasons for

Estimation of body fat in rats by whole-body counting.

A method for determining body fat in vivo in rats by whole-body counting of 40K is described. The technique utilizes a Nuclear Chicago Corporation TOBOR system with 5-in thallium-activated sodium iodide crystals. To test the method a regression equation was developed using the 40K counts and body weight of young adult rats weighing 333-788 g; the results were compared with those obtained from the gravimetric determination of fat in the carcass. The correlation coefficient between the two methods was 0.945.

Optimal Detection Sensitivities in Activation with Fast Neutrons from an 241Am-242Cm—Be Source

The detection sensitivities of 60 chemical elements in activation with the fast neutrons from an 241Am-242Cm—Be source have been measured. The source consisted of six slugs with a total output of 4.8X109 unmoderated neutrons/sec, and a flux of 1.4×108 fast neutrons/sec-cm2. In general, the sensitivity (counts in a selected photopeak per gram of target element) for each element was obtained with irradiation for two to three half-lives of the short product nuclide, and counting for the same length of time. Neither irradiation nor counting was longer than 1 h. The detector was a cylindrical thallium-activated sodium iodide crystal 10 cm long and 10 cm in diam. The measured sensitivities are compared with reported sensitivities in activation with thermal neutrons.

The relationships between light output and energy resolution in thallium activated sodium iodide crystals

The electron response and energy resolution of twelve crystals of thallium activated sodium iodide have been measured. The effect of the electron response and energy resolution of straining crystals, either thermally or by subjection to hydrostatic pressure was also investigated. An empirical relationship is established between the shape of the electron response curve and the magnitude of the gamma energy dependent contribution to resolution. The possible origins of this relationship are discussed.

Uptake and biliary excretion of Cu64 in rabbits in relation to blood ceruloplasmin.

It has been postulated that one of the important biological functions of the alpha-2 globulin, ceruloplasmin, is the regulation of the biliary excretion of inorganic copper(1). However, there is little experimental evidence to support this theory(2,3). With the availability of an experimental technique for modifying the blood ceruloplasmin levels(4), it became feasible to reexamine the problem as to possible correlations between serum ceruloplasmin, liver uptake, and biliary excretion of Cu64 in the rabbit. Three groups containing 9 to 12 male albino rabbits (12-13 weeks old) were employed. One group was maintained for 10–15 days on a commercial dry ration containing molybdate-sulfate, a diet known to reduce ceruloplasmin levels in the rabbit and greatly elevate total blood copper(4,5). A second group, which served as controls, was maintained on the commercial ration without added salts. A third group was maintained on a ration mixed with inorganic copper, 0.005% copper as Cu2SO4 for 4 weeks in order to elevate serum ceruloplasmin levels (5,6). Ceruloplasmin was measured as p-phenylenediamine oxidase activity in each rabbit serum 24 hours before administration of the isotope(7). Animals were given an intravenous injection of 75 microcuries of high activity Cu64 acetate (6 μg copper) via the marginal ear vein and sacrificed 2, 25, and 50 hours later. Levels of Cu64 activity were measured in 0.1–0.5 ml of bile immediately withdrawn from the gall bladder. Suitable samples of liver and cross sections of cortex and medulla of the kidney were hydrolyzed with sulfuric, perchloric and nitric acids(8). Each sample was returned to a standard volume and Cu64 activity determined. The values obtained were corrected for radioactive decay and expressed as percent of the dose administered (Table I). Radioactive copper was determined in a well-type, thallium-activated sodium iodide crystal scintillation counter. In those rabbits maintained on a high molybdate-sulfate diet there resulted a marked diminution of serum ceruloplasmin levels, uptake of Cu64 by liver, and excretion of copper at 2, 25, and 50 hours (Table I). Cu64 uptake by liver in this group was reduced to 35.7% of the control level 2 hours after injection. Along with a 20% reduction in serum ceruloplasmin, the biliary excretion of Cu64 was virtually zero. This sharp suppression in liver uptake and biliary copper excretion in 2, 25, and 50 hours occurred despite an elevation in the non-ceruloplasmin copper pool(4,5). On the other hand, a significant increase in the concentration of Cu64 in the kidney was noted in this group as compared to the other 2 groups.

The use of a lithium-drifted germanium diode to determine carbon in steels by measurement of prompt γ-radiation

A lithium-drifted germanium p-i-n diode was used as detector to measure the prompt radiation emitted by the reaction 12C (d,p) 13C during the irradiation of steels with low-energy deuterons. Typical spectra obtained using a diode and a thalliumactivated sodium iodide crystal are compared, and results given for a number of standard steel samples.

Studies of metastatic bone lesions with stontium 85.

In 1949 and 1950, Dudley and his associates (1, 2) showed that radiogallium 72 concentrated in areas of osteogenic activity, but Brucer et al. (3) subsequently demonstrated the impracticability of use of the isotope therapeutically because of toxicity of the non-radioactive carrier. Later, Desgrez et al. (4) investigated further the distribution of radioactive gallium in the skeleton and particularly in bone tumors. More recently Bauer and his co-workers (5, 6) found a high uptake of Sr85 by external counting over skeletal lesions such as fractures, metastatic carcinoma, eosinophilic granuloma, chondroma, osteomyelitis, and Paget's disease. In 1961, Fleming and his group first demonstrated the use of Sr85 for the photoscanning of bone lesions (7). Strontium 85 is admirably suited for photoscanning since, in its decay by electron capture to stable rubidium 85, a single gamma photon of 0.51 Mev is emitted. The material is administered intravenously, 50 µc to adults and 20 µc to patients under twenty years of age. The estimated total body dose to a standard man is 0.325 rads and the bone dose is 2.28 rads (7). Strontium 85 is obtained2 as the nitrate in 0.91N nitric acid solution, with specific activity of 2,720 mc per gram or greater. Purity is of the order of 98 per cent, with less than 1 per cent strontium 89. The material is not neutralized but merely diluted appropriately and administered intravenously. Approximately twenty-four to forty-eight hours later, the patient is scanned with the Picker magnascanner equipped with a 3 × 2-inch thallium-activated sodium iodide crystal and a 19-hole focusing collimator. Case Reports Case I: M. F., a 64-year-old white male, complained of pain in the right femur of one month duration. X-ray studies revealed an osteolytic lesion of the middle third of the shaft of the femur (Fig. 1). A photoscan with radioactive strontium was performed and the lesion was visualized as it appeared on the film. Subsequently, a biopsy was reported as showing metastatic carcinoma, probably from the lungs. Case II: R. A. N., a 45-year-old Negro female, was admitted to the hospital Oct. 1, 1962, complaining of pain and swelling of the left knee of four months duration. During this time, several x-ray examinations failed to reveal any abnormality. In spite of medical treatment, the pain persisted and gradually increased in severity so that at the time of admission it was constant. In May 1961 a right hemicolectomy had been performed for carcinoma. In view of this history and the persistent pain, a scan with radioactive strontium was performed, revealing a localized area of uptake in the region of the head of the tibia. Accordingly, an open bone biopsy was carried out and the pathologist reported the presence of adenocarcinoma consistent with metastasis from the colon.

Brain tumor localization utilizing mercury 203.

The localization of brain tumors by scintillation scanning has been studied for many years, but has ailed to gain widespread use as a diagnostic tool. In 1960, Bender and Blau (1,4) reported that mercury 203 was localized in some brain tumors and that it was readily eliminated as the compound Neohydrin (mercurated allylurea). In this study we have used Hg203 chlormerodrin (Neohydrin) with a physical half-life of forty-seven days and a single gamma-energy emission of 280 kev (Fig. 1). The material was supplied with an activity of 0.09 millicuries per milligram at a concentration of 5.3 milligrams per milliliter. The low gamma photopeak minimizes the scattering problem and the low energy of the beta particles (210 kev) from mercury 203 reduces the radiation dosage to the patient. Technic: In all patients studied brain tumors were suspected clinically. In all instances, the patients had diagnostic studies such as cerebral arteriograms, ventriculograms and/or skull roentgenograms. Twenty-four hours prior to the administration of the radioisotope, 1 c.c. of stable Neohydrin was administered intramuscularly to block renal concentration of the material. A dosage of 10 microcuries of Hg203 Neohydrin per kilogram of body weight was administered intravenously, the maximum dose being limited to 700 microcuries. Scintillation scanning was performed with a Picker Magnascanner utilizing a 3 × 2-inch thallium-activated sodium iodide crystal with a 19-hold focusing collimator shielded with 2.5 cm of lead. A 50 kev spectrometric window centered on the 280 kev photopeak of Hg203 was used. Scanning was performed in both the anteroposterior and lateral projections at two and a half, five, twenty-four, and forty-eight hours. Twenty-four- and forty-eight hour urinary excretion determinations of Hg203 were made, and blood level radioactivity was also measured. There was no evidence of toxicity or untoward effects from the radioisotope and no significant difficulty was experienced in the scanning. Seventeen patients have been studied, 1 on two occasions, with this technic (Table I). Five areas of brain tumor (primary or metastatic carcinoma) were identified and proved. In 1 patient, the brain scan showed no areas of localization, but an ependymoma was found at operation (Case VII). This is probably related to the fact that ependymomas are midline in location, are in an area difficult to scan accurately, and are relatively avascular. In Case VI, the arteriogram showed a left cerebral vascular tumor but the scan was negative. No adequate explanation can be offered for this. There were no false positives. In 9 patients the absence of tumor was confirmed by the Hg203 brain scan. The urinary excretion of Hg203-labeled Neohydrin was determined at twenty-four and forty-eight hours. At the end of twenty-four hours, an average of 20 per cent of the administered dose had been excreted in the urine.

Diagnosis of renal vascular disease and renal tumors by photoscanning.

INTRAVENOUS DOSES of I¹³¹-labelled sodium<i>o</i>-iodohippurate (Hippuran) or Hg²⁰³-labelled chlormerodrin (Neohydrin) are concentrated sufficiently by the kidneys to permit their anatomical visualization with the aid of a photoscanner. We have reported a preliminary evaluation of the use of the photoscanner in the diagnosis of renal disease. After an experience of more than 100 renal photoscans, we wish to document some of the more important clinical uses of this technique. Materials and Methods Scanning Equipment.—Scintiscans were performed using a 19-hole collimator, a 3" x 2" thallium activated sodium iodide crystal, a pulse height analyzer, and a pulsed light photorecording system. Technique—In the early part of the study scintiscans were performed with both I¹³¹sodium o-iodohippurate and Hg²⁰³chlormerodrin. Since February, 1961, all scintiscans have been performed with Hg²⁰³chlormerodrin. I¹³¹sodium o-iodohippurate scintiscans were performed during a slow intravenous infusion (2-4 μC. per minute) of 200 /μC. of I¹³¹sodium o-iodohippurate.

The Hanford whole-body counter program.

The Hanford whole-body counter is a low-background gamma-ray spectrometer operated by the Hanford Laboratories. The shielded counting chamber approximates a 3-meter cube with shielding walls consisting of 10-inch thick steel plates. The gamma-ray detector is a large thallium-activated sodium-iodide crystal, 9 3/8 inches in diameter and 4 1/2 inches thick, viewed by four selected photomultiplier tubes of three-inch diameter. The assembly provides 8.3 per cent resolution of the 0.66 Mev gamma rays of cesium 137. The signals from the detector are transmitted to a multichannel pulse height analyzer provided with accessory electronic systems for data presentation and processing. The data accumulated in the pulse height analyzer memory are available as a visual presentation on an oscilloscope, a digital print-out of the counts per channel, a penned plot on Cartesian co-ordinates, and a punched paper tape prepared for electronic data processing. The radionuclides principally found in individuals examined in the ...

Photoscanning of bone lesions utilizing strontium 85.

The metabolism of strontium 85 in man has been extensively studied by Bauer and colleagues (1, 2). Significant localization in bone of strontium 85 occurs in fractures, metastatic cancer, eosinophilic granuloma, chondromas, osteomyelitis, and Paget's disease. Quite recently, Gynning et al. (3) reported the usefulness of skeletal strontium-85 localization for detection of carcinoma metastatic from the breast. We should like to call attention here to the feasibility of photoscanning selected skeletal areas which harbor localized strontium 85. Technic Strontium 85 was obtained from Oak Ridge National Laboratory. The isotope was in an acid solution of approximately one normal and had a specific activity greater than 500 millicuries per gram. Purity was of the order of 98 per cent, with less than 1 per cent strontium 89. The stock solution was prepared by first neutralizing with 3 per cent sodium hydroxide and diluting the strontium 85 in physiologic saline to 20 microcuries per milliliter. This solution was then passed through a Millipore bacterial filter3 to insure sterility. Twenty microcuries were given intravenously to selected patients under twenty years of age, and 50 to 60 microcuries were utilized in indicated adult cases. At least twenty-four hours were allowed for localization of the isotope. Areas to be scanned were selected either on the basis of x-ray changes or by probe counting over suspected bone areas. Scanning was performed with a Picker magnascanner equipped with a 3 × 2-in. thallium-activated sodium iodide crystal and a 19-hole, coarse-focus collimator (4). With an 80-kev window about strontium 85, single 0.51 Mev gamma, count rates over positive areas of the skeleton averaged 500 counts per minute above surrounding bone tissue. Satisfactory scans were made at a scanning speed of 16 to 20 cm. per minute with a count per minute range differential setting (4) of 10 per cent and a film density of 100. Appropriate markers were placed on the photoscan and, with lead overlays of these identifying marked areas, a roentgenogram was made for superimposition (Figs. 1 and 2). Comment Strontium 85 has a half-life of sixty-five days. It decays by electron capture to metastable Rb85, which emits a single gamma photon of 0.51 Mev and becomes stable Rb85. There are no beta or alpha emissions and hence the bone radiation dose is small. Of the administered dose, approximately 55 per cent is excreted by the fifth day (2). The remaining strontium 85 becomes permanently fixed in the skeleton. Correcting for 50 per cent excretion in the first five days, one may estimate the total whole-body dose to a standard man at 0.326 rads, with a bone dose of approximately 2.28 rads (5). The rather energetic 0.51 Mev gamma of strontium 85 presented no unusual collimation problems, as the shielding on the probe of the equipment utilized was adequate. Preliminary work indicates that photoscanning of bone lesions is practical, desirable, and informative.

Low-Energy Standards for Gamma-Ray Spectrometry

A simple type of low-energy calibration standard for gamma -ray spectrometry has been developed for the range 5 to 75 kev. Standards are made by placing a target of a single element over a pure beta emitter, such as promethium- 147 or strontium-90. Characteristic x rays of the target element are generated, usually the K alpha radiation, although L x rays are predominant for very thin targets. For energy calibrations greater than 17 to 20 kev it is best to use thin metallic foil targets or pressed oxide disks. Standards for energies less than 17 kev are best prepared by mixing a solution of the beta emitter with a few milligrams of a salt of the target element, and evaporating to dryness on a micro cover glass. By this technique, the lowest energy K alpha x ray clearly observed was that of vanadium at 4.96 kev, using a 1 1/2 x 1/2 inch thallium-activated sodium iodide crystal equipped with a 0.005-inch beryllium window. The use of these standards affords a simple and convenient technique for checking nonlinear response in the low-energy region for scintillation detector systems, measuring the noise level of multiplier phototubes, and identifying radioactive elements which emit convertedmore » gamma rays.« less

Directional scintillation counters of improved sensitivity.

Directional counters and the methods of increasing their efficiency are briefly reviewed. A simple Perspex conical crystal holder is described. This acts as a reflector, provides an airtight mounting for hygroscopic crystals, and allows a narrow aperture detector to utilise the full photocathode surface. Calcium tungstate and thallium-activated sodium iodide crystals are compared when used with such a holder. The detection efficiency of the apparatus as a whole was increased in both cases.

The Long-Lived Phosphorescent Components of Thallium-Activated Sodium Iodide

Using a cobalt-60 source as a means of primary irradiation, the long-lived phosphorescent decay of thallium-activated sodium iodide crystal has been studied at several crystal temperatures. The results have been interpreted assuming that the different trap levels act independently of each other and that each trap decays according to the monomolecular process. Values for the experimental trap depths and vibrational frequency factors are given.

Energy Resolution of ?-Radiation up to 18 MeV by Sodium Iodide Scintillation Counters

The pulse-height distributions to be expected from scintillation counters using thallium-activated sodium iodide crystals have been investigated for ?-radiation of energies 6, 12, and 18 MeV. with two sizes of cylindrical crystal (2�5 cm. long by 2�5 cm. diameter and 7�5 cm. long by 4 cm. diameter). A Monte Carlo calculation of the partial shower process by which photons are absorbed in the crystals has given the probability distributions of ionization energy from homogeneous incident photons. The spreading of the distributions by statistical effects in the photomultiplier has been measured using light flashes of constant integrated intensity from a rotating mirror. The curves predicted by combining these two factors are compared with experimental pulse-height distributions for ?-radiation from proton bombardment of fluorine, boron, and lithium.

I131-labeled serum albumin: its use in the study of cardiac output and peripheral vascular flow.

During the past several years a method for measuring plasma volumes has been under investigation in our laboratory (1, 2). This method involved the use of a tagged serum protein (I131-tagged albumin) and gave promising results which appeared useful. It became obvious that the slow rate of disappearance of tagged albumin from the blood would make this a satisfactory substance for the study of vascular flow measurements. Before this could be achieved, however, it was necessary to develop a number of instruments which would make it possible to detect small amounts of radioactivity by their gamma emission and to record the events rapidly enough so that critical alterations in dilution and mixing of the radioactive albumin could be recorded. The essence of the method which will be described concerns itself with measuring and recording the manner and rate in which iodinated plasma is mixed and diffused through the blood. The character of the curve which is obtained on isolated arteries has proved suitable for quantitation. The curves recorded for peripheral flow over the extremities do not as yet permit quantitation but, as will be demonstrated later, there are definite qualitative changes which may signify alterations in peripheral flow. Description of Recording Equipment As intimated above, the inherent problems in measurement of any vascular flow are twofold. The first requisite is a detector sufficiently sensitive to measure and detect low levels of radioactivity by gamma emission. Since the standard method of detection, a Geiger counter, has poor sensitivity to the comparatively low-energy gamma rays of I131, a scintillation counter was deemed necessary (3) and an anthracene crystal counter was adapted for this purpose. This gave an increase of sensitivity of approximately fiftyfold and made it possible for the iodinated protein to be used in tracer amounts. At the present time, thallium-activated sodium iodide crystals are being utilized and show an even greater improvement. The second device required for adequate representation of vascular flow data was a recording apparatus that would report the concentration of the tagged atoms in the vascular system as a function of time. Since in many proposed studies of various flow channels the change in concentration during very short intervals (i.e., seconds) would be of interest, it was considered that the method of withdrawing blood every one to three seconds would be both unwieldy and restrictive in respect to the total volume of blood required. Because of this, an in vivo system of measuring seemed desirable. Recording by an ordinary counting rate meter is possible except that the counting rate at any time is influenced by the previous count on this instrument.

Scintillation Counters for Radioactive Sample Measurement

A gamma-ray counter for liquid or solid samples is described. It uses an RCA 5819 phototube at room temperature with a thallium activated sodium iodide crystal in the shape of an annular ring. The gamma-ray counting efficiencies of this counter for 2-milliliter samples of Fe59, Co60, and I131 are about equal to the beta-particle counting efficiency of a mica-window G-M counter when counting thin samples. When the counter is heavily shielded, the background is about 160 counts per minute. The phototube operating voltage is not critical since over a wide range of operating voltage the counting efficiency and background count change only slightly. A directional gamma-ray counter is also described.

The Detection of Gamma-Rays with Thallium-Activated Sodium Iodide Crystals

Thallium-activated sodium iodide crystals may be used as efficient detectors of gamma-rays and other ionizing radiations. The crystals are used in combination with a photo-multiplier after the manner of Kallmann. Curves are given which show the duration of the light emission process, the distribution of light pulse sizes, the energy discrimination possibilities, and the dependence of number of counting events on photo-multiplier voltage and amplifier gain. Comparison curves are shown for NaI(Tl) and anthracene. A description is given of the method of preparation of polycrystalline samples and single crystal specimens of the sodium iodidethallium phosphor. A few remarks are made concerning the combination of alkali halide phosphor crystals with photographic plates.