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US3787691A - Source holder collimator for encapsulating radioactive material and collimating the emanations from the material - Google Patents

Source holder collimator for encapsulating radioactive material and collimating the emanations from the material Download PDF

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Publication number
US3787691A
US3787691A US00328154A US3787691DA US3787691A US 3787691 A US3787691 A US 3787691A US 00328154 A US00328154 A US 00328154A US 3787691D A US3787691D A US 3787691DA US 3787691 A US3787691 A US 3787691A
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Prior art keywords
sample
emissions
biological sample
lead
doughnut
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US00328154A
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English (en)
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G Laurer
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US Atomic Energy Commission (AEC)
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US Atomic Energy Commission (AEC)
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    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21K—TECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
    • G21K1/00—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating
    • G21K1/02—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating using diaphragms, collimators
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
    • G01N23/22—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material
    • G01N23/223—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material by irradiating the sample with X-rays or gamma-rays and by measuring X-ray fluorescence
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2223/00—Investigating materials by wave or particle radiation
    • G01N2223/07—Investigating materials by wave or particle radiation secondary emission
    • G01N2223/076—X-ray fluorescence

Definitions

  • 1 1e Jan the blood is molded into a doughnut-shaped sample PP 328,154 around an annular array of low energy radioactive material that is at the center of the doughnut-shaped 52 US. Cl. 250/272 250/273 Sample but encapsulated in a Qnimamr, the lane 51 Im. Cl.
  • Gtilr 23/22 shielding detect that is the Sample and [58] Field of 250/272 273 274 facing the same so that the detector receives secondary emissions from the sample while the collimator [56] Reerences Cited collimates the primary emissions from the radioactive material to direct these emissions toward the sample UNITED STATES PATENTS around 360 and away from the detector.- 3,011,060 ll/l96l Dorenb'osch 250/272 10 Claims, 3 Drawing Figures Blood "doughnut" Target PuO micro spheres IO ⁇ 3 34 5O Nickel source holder 22 minor axis 2 ⁇ v I i 38 34 l I n I n 5-
  • This invention overcomes the above-mentioned problems by providing, in one embodiment, an annular X-ray fluorescence system using a molded, doughnutshaped, sample configuration around a low energy radioactive source that is shielded from an X-ray detector in close proximity to the sample. With the proper selection of components, as described in more detail hereinafter, the desired detection is achieved.
  • this invention provides 360 irradiation of a molded, doughnut-shaped sample around an annular array of low energy radioactive material that is encapsulated and shielded from an X-ray detector by a collimator that collimates the primary emissions from the radioactive material away from the detector and toward the sample, the latter being in a plane that passes through the annular array and the molded, doughnut-shaped sample.
  • Thedetector provides the desired X-ray fluorescense analysis, I
  • One construction provides a radioactive source comprising an annular array of spheres of low energy encapsulated radioactive material for selectively exciting specific X-rays in the sample, and means having a semiconductor detector for detecting these X-rays for X-ray fluorescence analysis.
  • FIG. 1 is a partial top view of the collimator of one embodiment of this invention.
  • FIG. la is a detail taken from FIG. 1;
  • FIG. 2 is a partial cross-section of the apparatus of FIG. l through II II;
  • This invention provides a transportable device capable of detecting low levels of metal contaminants in biological samples with a minimum of sample preparation.
  • this invention detects normal levels of lead in blood, e.g., up to 0.02 mg%, and as such this invention provides a method and apparatus adapted for field use for screening blood samples for lead.
  • higher levels of lead than 0.02 mg% can be detected in blood or other samples in accordance with this invention for research purposes, or on an au tomatic basis, as will be understood in more detail from the following.
  • the system of this invention can and has also been used to detect trace elements in any sampleniolded into a doughnut, such as water, air pollution filters, etc.
  • the X-ray fluorescence method of analysis consists of the detection and measurement of the characteristic X-rays given off by the atoms of the elements in the sample on production of excited states, the excited states of the atoms referring to the creation of vacancies in the normally occupied electronic energy levels, e.g., the M, L, or K energy levels.
  • the subsequent readjustment of the electrons leads to the emission of specific X-rays with well-known energies that are characteristic of the elements, the energy required to produce the vacancies being known and the vacancies having been created by calibrated energy sources of irradiation, such as electrons, protons, alpha parti-v cles, or photons of sufficient energy to remove an electron from one of the electron shells of the atoms.
  • calibrated energy sources of irradiation such as electrons, protons, alpha parti-v cles, or photons of sufficient energy to remove an electron from one of the electron shells of the atoms. Since the electronic energy levels of -all the elements of the sample are discrete, and there is a finite difference in these levels between the elements thereof, accurate measurement of the energies emitted during the excitation of the sample has made it possible to identify many of the elements in a variety of samples.
  • the energy dispersion method has certain advantages over the wavelength dispersion method, the former being employed in accordance with this invention to achieve a portable detector system.
  • the energy dispersion method has a high efficiency by eliminating the use of diffraction crystals and collimators used heretofore in connection with the wavelength dispersion method and by bringing a detector whose output is a function of the energy deposited therein close to the sample being analyzed.
  • entire spectrum of the X-rays produced in the sample may be measured by electronic sorting of the detector pulses.
  • This invention utilizes this above-mentioned energy dispersive X-ray fluorescence method for detecting lead in blood, by employing a doughnut-shaped blood sample that is irradiated around 360 by collimated primary emissions passing through a collimator from an annular array of encapsulated radioactive source material at the center of the doughnut-shaped sample, the sample encircling the collimator for shielding the detector from the primary emissions from the source material.
  • one embodiment of this invention employs a specific arrangement having a detector, such as the semi-conductor detector that has recently been developed, the detector outputs being a function of the energy of the secondary X-ray emissions from the sample that are produced therein by the primary emissions from the source.
  • This invention utilizes, in one embodiment, a specific radioactive source in a compact arrangement for providing a portable device for detecting lead in a blood sample both quantitatively and qualitatively without prior separation of the lead from the blood.
  • the apparatus of this invention in a preferred embodiment, consists of a source holder separated from a detector 24 which receives and measures emitted secondary X-rays, as will be described later.
  • Holder 10 consists of a disc-shaped collimator 17 formed from a pair of trapezoidal shaped metal collimating means 34 and 34' assembled with slanted sides 38 and common bases 36 as shown, to form an annular collimating rectangular shaped channel 42 in its edge 39, and a smaller inner annular channel 40 concentric with channel 42.
  • Channel 40 is filled with source material 12 in an annular array 14, as described later.
  • Edge 39 supports the blood sample 22 along a minor axis 41, in a sample holder doughnut 52 to be irradiated.
  • One suitable material for doughnut 52 is
  • millipore absorbent pad made from white cellulose material that forms a blotter. In practice, it has been found, that no extraneous interfering fluorescence peaks are produced by the blotting material of the retaining blood container doughnut 52. The latter is supported by collimator 17 by a press fit on outer edge 39.
  • the sample 22 can be very close to the source of the radiation without interfering with the collimation effected by means 34 and 34.
  • Collimator 17 would be made from suitably material, such as nickel, which will provide proper shielding against the radiation from source material 12.
  • annular shaped beryllium exit window 50 Located within rectangular channel 42 is an annular shaped beryllium exit window 50 between the radioactive source material 12 located within channel 40 and sample holder doughnut 52, in order to retain the radioactive source material withinchannel 40 and also to transmit as a filter the desired primary radiation from the source material to the blood sample.
  • Detector 24 is located within a cryostat 51 cooled by liquid nitrogen in order to produce an output 26, and to retain the resolution capabilities of the detector ma terial to be described below and as is understood in the art.
  • Output 26 would be employed as is understood in the art and as described below to produce a spectral analysis from which the presence of lead can be detected and measured.
  • Collimator 17 is situated directly on cryostat 51 adjacent to or in contact with a beryllium window 49 permitting the X-rays emitted from the samle within container 52 to pass as shown by the arrows unimpeded in the direction ofdetector 24.
  • the annular source holding channel 40, annular beryllium window 50, and annular sample holding container 52 centered on axis of rotation 23, are all situated in a common plane that is parallel to window 49 in cryostat 51 so that detector 24 is effectively equidistant from all of the above elements of the arrangement.
  • a suitable radioactive source material 12 which forms an annular centered core means for use in channel 14, comprises an annular array of micro-spheres of about 250p. diam. made from PuO Pu decays by alpha particle emission with a half-life of 86 years so that replenishment of this material during the normal life time of the apparatus is not required.
  • the uranium- 234 daughter of this isotope emits L X-rays of 11.6 KeV, 13.5 KeV, 17.0 KeV and 20.2 KeV in approximately 13 percent of its disintegration. These X-rays are close to the L absorption edge of lead, resulting in a substantial increase in the absorption by lead of the X-rays.
  • the effect of the radiation from the luO source material is to cause the lead present in the samplc to emit secondary X-rays which can be detected and measured by detector 24.
  • a blood sample to be tested for lead is drawn by capillary action into a hematocrit tube and then droppered one drop at a time for the retention and molding thereof into an absorbent material pre-cut in the form of the described blood container doughnut 52.
  • the latter is then inserted on collimator 17, as shown in the drawing.
  • Radiation from source 12 is collimated
  • a standard lead solution can be added to a sample of lead-free whole blood from which an aliquot can be drawn and spun to separate the red blood cells containing percent of the blood lead burden. Spinning e.g. in a centrifuge, effectively concentrates the lead in the sample'by a factor of about two. After spinning by centrifuging, the portion con-' taining the red blood cells can be dropped onto the container formed by doughnut 52, the detector being calibrated by standard methods using a standard radioactive source and a single channel analyzer.
  • a semiconductor X-ray detector having high resolution and intrinsic efficiency was used.
  • One detector used was a lithium drifted, silicon [SI(Li)] detector.
  • This type of detector as described in US. Pat. Nos. 3,381,367 and 3,278,668 has a silicon intrinsic region and a lithium drifted region, as is well known in the art in connection with these and standard Ge detectors, which can alternately be used, the latter being described in Brookhaven Nat. Lab. Report-BNL 16610.
  • the 3 mm thick Si(Li) detector used had about 100 percent efficiency, and the L-shell X-rays of lead detected were all below this energy, lead X-rays having, e.g., energies of 14,762 ke V (L y 12.620 ke V(L 12.611 ke V (L 10.549 ke V(L ),or1 48 ke V(L).
  • the detector was housed in a vacuum tight container having an X-ray entrance window, comprising a 5 mil thick beryllium window 49, which was selected for 100 percent transmission of the secondary characteristic X-rays from the blood sample above kc V.
  • the Si( Li) detector was cooled to liquid nitrogen temperatures.
  • a calibration curve for the Si(Li) detector used was made with a C0 source with photon energies of 6.399 ke V, 7.057 ke V and 14.40 ke V. This provided an energy calibration wherein the midpoint of the 10.5 keV Pb L X-ray peak appeared in channel 270 of the analyzer.
  • a blank sample doughnut provided a first multichannel analyzer output, yielding a lead-free background count.
  • changing doughnuts containing lead produced the qualitative and quanitative channel output characteristic of the lead present in the doughnut.
  • the resolution was good enough to separate one, if not both, of the most abundant L X-rays from the lead in the blood sample, i.e. 10.5 ke V and 12.6 ke V, from the other X-rays from the blood sample.
  • the detector area was as large as possible to obtain maximum geometrical efficiency.
  • the L y X-ra'ys of the lead were avoided, and instead, the detector analyzed the remaining K (10.5 ke V) and L (12.6 ke V) X-rays of the lead, both of which were separated by about 900 ev from the possible interfering X-rays.
  • the minimum resolution was about 350 ev, f w h m (full width of peak at l maximum height).
  • a 200 mm Si(Li) detector width guaranteed resolutions of 300 ev,fw h m, at the 5.9 ke V Mn K energy was used.
  • the actual system used had a guaranteed resolution of 270 ev, f w h m (5.9 ke V), which was checked using 6.4 ke V Fe K X-ray s, at 280 ev,fw h m.
  • a system actually used was an ortec Model. No. 7016-16270, from Oak Ridge, Tenn.
  • the source was generally kept to milli curie strengths, which, how'ever,1imited the available primary output emissions therefrom to the order of 10 to 10 photons/sec.
  • isotopic source having the correct emissions for the required efficient excitation of the sample, equal size Pu microspheres'of Pu0 having diameters of 250p. were desirable although larger or smaller diameter sources could be used.
  • This sphere size has an activity per sphere as shown from the following Table II:
  • the sources was advantageously free of interferring radiations, and had a reasonable cost.
  • a plutonium-238 source decays by alpha particle emission with a half-life of 86 years, while the uranium-234 daughter emits L X-rays of 11.6 ke V, 13.5 ke V, 17.0 ke V and 20.2 ke V in approximately 13 percent of its disintigrations.
  • the uranium L X-rays are 2.5 times greater than those of "Cd.
  • Pu spheres in the form of PuO from 50;; to 400p. in diameter, the 250p. spheres desired have an activity per sphere calculated as indicated above.
  • the design of the annular source, holder and collimator of this invention optimized the source-sample-detector geometry by placing the sample close to the detector to maximize detection efficiency, while minimizing the number of directly transmitted X-rays from the source to the detector, minimizing the scatter and fluorescence from the structural materials around the source, and maximizing the fluorescence to scatter ratio from the sample.
  • the annular doughnut-shaped design of the source sample geometry, in accordance with this invention provided for the majority of excitation photons to scatter at the best angles for increasing the energy increment between the lead Xrays and the scatter interference, and reducing the number of scattered photons.
  • the blood sample was molded into a ringshaped doughnut for forming a doughnut-shaped target that was irradiated around 360.
  • the doughnuts were cut with an 8 mm outer diameter and a 4.2 mm inner diameter to allow the sample to slip easily over the 4 mm source.
  • Crosshairs which held the source in position, also kept the doughnut in position around a beryllium exit window 50 for the source in the collimating space formed in the collimator.
  • the doughnut was held on a 4.2 mm diameter shaft with a base fixture cut from a polytetra-fluoroethylene rod to which the blood did not adhere.
  • a filter-paper-like toroidal blotter 0.8 mm thick was shaped to form the doughnut, and after the addition of the blood sample thereto the doughnut was placed under a heat lamp to dry while still on the shaft. Adequate drying was accomplished in 3 to 4 minutes, after which the doughnut was ready for fluorescence analysis by placing the doughnut around an annular array of encapsulated radioactive pellets built as a hollow central core close to the sample around 360, while the sample, which was shieldedform the source by the collimator, was close to the detector around 360.
  • This configuration allowed irradiation of the sample throughout the 360 in the'plane of the source, while the source was brought to within a distance of about 1 mm from the surface of the sample, and the sample was brought to about 1 mm from the Be entrance window 49 of the detector cryostat 51.
  • the detector position within the cryostat was fixed by the manufacturer at a minimum distance of 5 mm from the window entrance of a vacuum tight container cryostat 51.
  • a 1 mm collimation space between the source and the sample prevented direct transmission of the source emissions from the source to the detector, and by placing the source inside the sample, external structural material was eliminated, thus limiting scattering interference to the sample itself, while a minimal amount of scattering and fluorescence from the edges of the source holder formed by the collimator was produced thereby.
  • the collimator was constructed of nickel so that its fluorescence X-rays did not interfere with the 10.5 ke V Pb region.
  • the scattering was predominantly thus taking advantage of the reduction in the number of photons scattered at that angle in the energy region of interest, and the increased energy separation between the 90 scatter and the Pb fluorescence energies.
  • the system sensitivity and detection limit for the measurement of lead in blood using the described 20 m Ci, Amersham-Searle source were determined by adding known amounts of a standardized lead solution 'to measured amounts of normal blood.
  • the standard lead solution used contained 1,000 ppm or 1 mg Pb/ml.
  • Nine blood solu tions were made up containing 0.5, 1.0, 2.0, 3.3, 4.3, 5.0, 6.2, 7.4, and 9.9 ppm of lead. e
  • Apparatus for encapsulating radioactive material and collimating the emanation therefrom for the detection by the principles of X-ray fluorescence analysis of a metal contaminant in a sample comprising:
  • Apparatus for encapsulating radioactive material and collimating the emissions therefrom for the detection by X-ray fluorescence of a metal contaminant in a biological sample comprising:
  • first means forming an annular array of radioactive material in a plane for producing primary emissions from said radioactive material
  • disc-shaped second means forming a holder with a groove around its outside edge for holding, enclosing and containing said annular array of radioactive material and for collimating said primary emissions therefrom outwardly in said groove in a direction away from the center of said annular array in the plane of said annular array;
  • doughnut-shaped third means forming an annular ring-shaped container for molding said biological sample into a corresponding shape, said container being centered on the axis of rotation of said annular array around the groove formed by the second means and around the centered, core, first means in the plane of the annular array thereof for receiving the collimated emissions from said radioactive material for interacting the same width said biological sample in said doughnut-shaped third means for producing characteristic secondary emissions from said metal element that contaminates said biological sample;
  • fourth means forminga detector adjacent said doughnut-shaped third means that is shielded from said radioactive material arid said emissions therefrom by said disc-shaped second means for detecting and analyzing said characteristic secondary emissions from said biological sample in said container by X-ray fluorescence analysis.
  • said fourth means has a semi-conductor selected from the group consisting of silicon, germanium, and lithium drifted semi-conductor detectors, and means for producing therefrom an output proportional to the energy of the characteristic secondary emissions received by said detectors from said biological sample as a nondestructive, portable, qualitative, and quantitative measure of the amount of said element that contaminates said biological sample without prior chemical separation from said sample.
  • X-rays for I 8 The apparatus of claim 2 in which said fourth means has a vacuum tight container that is cryogenically cooled, and a beryllium window for said fourth means, said latter means selecting and detecting the secondary emissions characteristic of a lead contaminate in a biological sample' of whole blood in said doughnut-sahped third means.
  • said first means is Pu for producing primary emissions in the energy range of the L absorption edge of lead and characteristic secondary emissions in the range of to 10 photons/second for the detection by said fourth means.

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US00328154A 1973-01-31 1973-01-31 Source holder collimator for encapsulating radioactive material and collimating the emanations from the material Expired - Lifetime US3787691A (en)

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JP (1) JPS49107588A (de)
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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3980882A (en) * 1973-05-16 1976-09-14 National Research Development Corporation Methods and apparatus for the chemical analysis of flowing materials
US5274688A (en) * 1992-04-07 1993-12-28 Lee Grodzins Lead-paint detector
US20090067572A1 (en) * 2007-09-06 2009-03-12 Lee Grodzins Measurement of Lead by X-Ray Fluorescence
US20100272232A1 (en) * 2009-04-23 2010-10-28 John Pesce Rapid Screening for Lead Concentration Compliance by X-Ray Fluorescence (XRF) Analysis
WO2016060883A1 (en) * 2014-10-13 2016-04-21 Honeywell International Inc. Apparatus and method for measuring alpha radiation from liquids

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS56500667A (de) 1979-06-07 1981-05-14
WO2024202197A1 (ja) * 2023-03-30 2024-10-03 株式会社島津製作所 Ｘ線分析装置、およびｘ線分析装置の制御方法

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3011060A (en) * 1958-01-31 1961-11-28 Philips Electronics Inc X-ray spectrograph

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3011060A (en) * 1958-01-31 1961-11-28 Philips Electronics Inc X-ray spectrograph

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3980882A (en) * 1973-05-16 1976-09-14 National Research Development Corporation Methods and apparatus for the chemical analysis of flowing materials
US5274688A (en) * 1992-04-07 1993-12-28 Lee Grodzins Lead-paint detector
US20090067572A1 (en) * 2007-09-06 2009-03-12 Lee Grodzins Measurement of Lead by X-Ray Fluorescence
US7702067B2 (en) 2007-09-06 2010-04-20 Thermo Niton Analyzers Llc Measurement of lead by X-ray fluorescence
US20100272232A1 (en) * 2009-04-23 2010-10-28 John Pesce Rapid Screening for Lead Concentration Compliance by X-Ray Fluorescence (XRF) Analysis
US8155268B2 (en) 2009-04-23 2012-04-10 Thermo Niton Analyzers Llc Rapid screening for lead concentration compliance by X-ray fluorescence (XRF) analysis
WO2016060883A1 (en) * 2014-10-13 2016-04-21 Honeywell International Inc. Apparatus and method for measuring alpha radiation from liquids

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FR2216579A1 (de) 1974-08-30
DE2404618A1 (de) 1974-08-01
GB1456098A (en) 1976-11-17
FR2216579B3 (de) 1976-11-26
CA984063A (en) 1976-02-17
JPS49107588A (de) 1974-10-12

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