US3714486A - Field emission x-ray tube - Google Patents

Field emission x-ray tube Download PDF

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US3714486A
US3714486A US3714486DA US3714486A US 3714486 A US3714486 A US 3714486A US 3714486D A US3714486D A US 3714486DA US 3714486 A US3714486 A US 3714486A
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cathode
anode
tube
ray
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Crary J Mc
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Crary J Mc
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    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J35/00X-ray tubes
    • H01J35/02Details
    • H01J35/14Arrangements for concentrating, focusing, or directing the cathode ray
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J35/00X-ray tubes
    • H01J35/02Details

Abstract

A miniature X-ray tube with D.C. power supply and a cold cathode field emission electron beam for continuous or steady state X-ray output. A tube a few centimeters in length with a needle cathode along the axis of the tube and with an exit window at the end behind the cathode for optimum X-ray output.

Description

United States Patent 1 [111 3,714,486 McCrary 1 Jan. 30, 1973 54 FIELD EMISSION X-RAY TUBE 3,466,485 9/l969 Arthur et 211...... .......313 351 Inventor: James H y 3032 Phoenix 3,52-l,O73 7/1970 Brock et a]. ..3l3/336 Street, Las g Clark y. FOREIGN PATENTS OR APPLICATIONS ev 987.478 3/1965 Great Britain 313/55 [22] Filed: Oct. 7,1970

Primary ExaminerRoy Lake [21'] 78,778 Assistant ExaminerDarwin R. Hostetter Attorney-Harris, Kiech, Russell 8L Kern [52] U.S.Cl ..3l3/55,3l3/336 [51] Int. Cl. ..H0lj 35/00 [57] ABSTRACT [58] Field of Search ..3l3/55, 59, 336 A minimum tube with DC power pp y and a d cold cathode field emission electron beam for continu- [56] References ous or steady state X-ray output. A tube a few cen- UNITED STATES PATENTS timeters in length with a needle cathode along the z xis of the tube and with an exit window at the end behind 3,309,523 et al. the cathode for ptimum X-ray output 3,046,439 7/l962 Houston I. ....3l3/336 3,303,372 2/1967 Gager ..3l3/336 '6 Claims, 3 Drawing Figures O I l Z Z /7 v5 PATENTEDJM 30 I915 H.1/ POWER SUPPLY OT Z 2,

mums/701?. JAMES H. MC Cmqm BY H/S ATTORNEYS. HARP/5, f1 III-SCH, Aussau. & K 510/ 1 FIELD EMISSION X-RAY TUBE This invention relates to X-ray tubes and in particular to steady state field emission tubes which provide continuous output with low power requirements and high efficiency and which can be provided in very small sizes.

The X-ray tube in common use utilizes a heated cathode to provide an electron beam directed toward an anode to generate the X-rays. Typically the cathode comprises a filament in the form of a coil of tungsten wire and is energized from a low voltage AC source which produces resistive heating and an electron beam by thermionic emission. A substantial amount of electrical power is required to' heat the cathode and the resultant tube and associated power supply are large and cumbersome and expensive, usually weighing hundreds of pounds and costing thousands of dollars.

An electron beam may be produced between a cathode and an anode by field emission, that is, by emission of electrons from an unheated, pointed metal cathode due toan intense electric field in the vicinity of the cathode. Some field emission X-ray machines are presently known for producing intense, fast pulses of X-rays. Such machines utilize large banks'of capacitors which are charged-to high voltage from a DC source, with the capacitors then being discharged across the electrodes of the tube to provide a single burst of X- rays. These pulse type field emission machines with their capacitors are also large, cumbersome, and expensive, typically weighing many hundreds of pounds and costing tens of thousands of dollars and substantially filling a room.

The X-ray tube of the present invention utilizes a high voltage power supply connected across the electrodes to provide a field emission electron beam and a continuous X-ray output. This instrument provides a number of significant advantages over the presently known equipment. The efficiency is very high as most of the electrical power delivered to the tube is converted into X-rays, since a cold cathode is utilized. Also, operation with a cold cathode results in no deposit of cathode material on the anode. The simplicity of tube design and efficient power utilization permit miniaturization of the system, with the tube being a few centimeters long and with the tube and power supply 50 cubic inches, weighing about 2 pounds and selling for less than a thousand dollars. The instrument is quite smalland is readily operated from batteries, thereby making it readily portable.

The instrument has relatively high radiation output in terms of'electrical power consumption, has a very small anode focal spot, and permits fabricating the anode from various metals to provide different characteristic X-ray outputs.

Other objects, advantages and results will more fully appear in the course of the following description. The drawing merely shows and the description merely describes a preferred embodiment of the present invention which is given by way of illustration or example.

In the drawing:

FIG. 1 is a longitudinal sectional view of an X-ray tube incorporating the preferred embodiment of the invention;

FIG. 2 is a sectional view taken along the line 2-2 of FIG. 1; and

FIG. 3 is a sectional view taken along the line 3-3 of FIG. 1.

In the preferred embodiment, a housing is formed of a glass tube 11 with an anode end ring or anode holder 12 and a cathode end ring or cathode holder 13. An anode 15 preferably is formed as part of the ring 12 and projects into the tube 11. A plurality of openings 17 in the anode communicate with the interior of a hollow stem 16 and provide a passageway for evacuation of the interior of the tube. A needle-shaped cathode 20 is supported at the center of the end ring 13. The end of the tube is closed by a window 22 formed of a material which passes X-rays, typically beryllium.

A DC power supply 25 is connected to the anode and cathode, as by conductors 26, 27. The power supply provides a high voltage for producing a high intensity electric field in the vicinity of the cathode. The voltage desirably should be variable, permitting variation of the X-ray intensity. While a well regulated DC power supply is preferred, an AC supply can be used. The output intensity would be less since X-rays are produced requiring a very small volume, typically in the order of only when the anode is at a high positive voltage with respect to the cathode. Operation at 60H, would provide the desired continuous X-ray output.

The cathode end ring 13 typically may be of brass and the cathode 20 typically may be a conventional nickel-plated steel sewing needle pressed into an opening in the center of the holder 13. The anode 15 may be made of any metal, although metals which are easily machined and plated are preferred. Copper and aluminum are presently being used. The stem 16 may be pressed into the end ring 12, the parts may be soldered or welded together, or the parts may be made as a single piece, if desired. The tube 11, end rings 12, 13 and window 22 may be assembled using a vacuum compatible epoxy. The glass tube 11 provides electrical insulation between the anode and cathode.

The assembled housing may be evacuated following conventional techniques and typically is evacuated to a pressure of about 10 Torr and the stem 16 is sealed at 28. Conventional gettering material may be used if desired. The cathode end ring 13 provides a support for the window 22 and the openings 29, 30 in the cjatho de end ring define the X-ray beam from the tube.

The X-ray tube may be made quite small and one unit assembled as illustrated in the drawing is 5.5 centimeters long over the end rings with an outside diameter of 2.54 centimeters. The end of the anode -15 preferably is hemispherical and in this embodiment has a radius of 0.64 centimeters. The tip of the cathode needle has a radius approximately-0.03 millimeters. The window 22 is formed of beryllium in the order of 0.025 to 0.05 mm thick. Electrode spacing is determined by the desired operating voltage and beam current, with the X-ray intensity being a function of the applied voltage. The electrode spacing is in the order of a few millimeters and preferably in the range of 0.2 to 2 mm. The applied voltage preferably is in the range of about 10 kv to 3 0 kv.

In an instrument manufactured as shown in the drawing, with a copper anode, and a space of 1.5 mm

between the electrodes, an applied voltage of 25 kv DC produces a beam current of about 20 microamperes, indicating anode-cathode impedance to be in excess of one million ohms. Moving the electrodes closer together would provide the same current with a lower voltage. With 25 kv dc applied, the X-ray intensity measured 30 cm from the window 22 -is 100 mR/h. increasing the voltage to 30 kv dc increases the X-ray intensity to 1,000 mR/h. The power consumption is less than l watt, with little heating, thereby eliminating the requirement for anode cooling. Analysis of cathode shadows observed in radiographs utilizing the tube indicate that the effective diameter of the radiation source is 0.1 mm or less. The shape of the X-ray spectrum as measured with a Si(Li) spectrometer shows the typical bremsstrahlung spectrum cutting off at 25 keV with intense Cu K and'K lines at 8.0 keV and 8.9 keV respectively.

The electron beam trajectories between cathode and anode are parallel with the axis of the tube 11 and the housing construction permits locating the outlet window 22 behind the cathode and perpendicular to the trajectories/This results in a more efficient utilization of X-rays than in the conventional design where the exit window is located at the side of the housing parallel to the trajectories. Exiting X-rays traverse less anode material in the present design.

The X-ray tube illustrated and described above is extremely small, light and simple in design. It has low power consumption and high efficiency and does not have any heat dissipation problems, since it is a cold cathode device. The power supply requirements are low resulting in an inexpensive, reliable, small and portable unit.

In operation, a high voltage is'connected across the anode and cathode, producing a field emission electron beam from the tip of the cathode to the anode. lmpingement of electrons on the anode produce X-rays which exit through the window 22 providing the desired output of the tube.

I Although an exemplary embodiment of the invention has been disclosed and discussed, it will be understood that other applications of the invention are possible and that the embodiment disclosed may be subjected to various changes, modifications and substitutions without necessarily departing from the spirit of the invention.

lclaim:

1. ln a tube for continuously producing X-rays by field emission, the combination of:

a housing;

an anode mounted in said housing;

an unheated cathode mounted in said housing and spaced and electrically insulated from said anode; an X-ray transmitting window in said housing; and

a high voltage DC electric power supply connected across said anode and cathode for producing by field emission, a continuous stream of electrons from said cathode to said anode producing a continuous X-ray output through said window, with the electrical impedance across said anode and cathode in excess of I 1 900,000 ohms.

2. An X-ray tube as defined in claim 1 in which said housing includes an insulating tube, an anode support ring at one end of said tube and a cathode support ring at the other end of said tube,

with said anode having a generally hemispherical end and carried in said anode support ring along the axis of said tube and I with said cathode being needle shaped and carried in said cathode support ring along the axis of said insulating tube with the needle tip pointing to and spaced from the anode end.

3. An X-ray tube as defined in claim 1 in which the anode-cathode spacing is in the order of 0.2 to 2 mm. and with an anode-cathode potential in the order of 10-30 kv.

4. An Xray tube as defined in claim 1 in which said housing is generally tubular in configuration and in the order of a few centimeters in length, and in which the anode-cathode spacing is in the order of a millimeter.

5. An X-ray tube as defined in claim 4 with said anode carried at one end and said cathode carried at i the other end of said tubular housing with the electron

Claims (6)

1. In a tube for continuously producing X-rays by field emission, the combination of: a housing; an anode mounted in said housing; an unheated cathode mounted in said housing and spaced and electrically insulated from said anode; an X-ray transmitting window in said housing; and a high voltage DC electric power supply connected across said anode and cathode for producing by field emission, a continuous stream of electrons from said cathode to said anode producing a continuous X-ray output through said window, with the electrical impedance across said anode and cathode in excess of 1,000,000 ohms.
1. In a tube for continuously producing X-rays by field emission, the combination of: a housing; an anode mounted in said housing; an unheated cathode mounted in said housing and spaced and electrically insulated from said anode; an X-ray transmitting window in said housing; and a high voltage DC electric power supply connected across said anode and cathode for producing by field emission, a continuous stream of electrons from said cathode to said anode producing a continuous X-ray output through said window, with the electrical impedance across said anode and cathode in excess of 1,000,000 ohms.
2. An X-ray tube as defined in claim 1 in which said housing includes an insulating tube, an anode support ring at one end of said tube and a cathode support ring at the other end of said tube, with said anode having a generally hemispherical end and carried in said anode support ring along the axis of said tube, and with said cathode being needle shaped and carried in said cathode support ring along the axis of said insulating tube with the needle tip pointing to and spaced from the anode end.
3. An X-ray tube as defined in claim 1 in which the anode-cathode spacing is in the order of 0.2 to 2 mm. and with an anode-cathode potential in the order of 10-30 kv.
4. An X-ray tube as defined in claim 1 in which said housing is generally tubular in configuration and in the order of a few centimeters in length, and in which the anode-cathode spacing is in the order of a millimeter.
5. An X-ray tube as defined in claim 4 with said anode carried at one end and said cathode carried at the other end of said tubular housing with the electron beam from cathode to anode parallel with the longitudinal axis of said housing, and with said window disposed at said other end of said housing generally perpendicular to said axis.
US3714486A 1970-10-07 1970-10-07 Field emission x-ray tube Expired - Lifetime US3714486A (en)

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Cited By (34)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5090043A (en) * 1990-11-21 1992-02-18 Parker Micro-Tubes, Inc. X-ray micro-tube and method of use in radiation oncology
US5153900A (en) * 1990-09-05 1992-10-06 Photoelectron Corporation Miniaturized low power x-ray source
US5369679A (en) * 1990-09-05 1994-11-29 Photoelectron Corporation Low power x-ray source with implantable probe for treatment of brain tumors
US5422926A (en) * 1990-09-05 1995-06-06 Photoelectron Corporation X-ray source with shaped radiation pattern
US5452720A (en) * 1990-09-05 1995-09-26 Photoelectron Corporation Method for treating brain tumors
US5854822A (en) * 1997-07-25 1998-12-29 Xrt Corp. Miniature x-ray device having cold cathode
US6069938A (en) * 1998-03-06 2000-05-30 Chornenky; Victor Ivan Method and x-ray device using pulse high voltage source
WO2000042631A1 (en) * 1999-01-18 2000-07-20 The Wahoo Trust High energy x-ray tube
US6095966A (en) * 1997-02-21 2000-08-01 Xrt Corp. X-ray device having a dilation structure for delivering localized radiation to an interior of a body
US6108402A (en) * 1998-01-16 2000-08-22 Medtronic Ave, Inc. Diamond vacuum housing for miniature x-ray device
US6148061A (en) * 1997-04-28 2000-11-14 Newton Scientific, Inc. Miniature x-ray unit
US6195411B1 (en) 1999-05-13 2001-02-27 Photoelectron Corporation Miniature x-ray source with flexible probe
US6289079B1 (en) 1999-03-23 2001-09-11 Medtronic Ave, Inc. X-ray device and deposition process for manufacture
US6353658B1 (en) 1999-09-08 2002-03-05 The Regents Of The University Of California Miniature x-ray source
US6377846B1 (en) 1997-02-21 2002-04-23 Medtronic Ave, Inc. Device for delivering localized x-ray radiation and method of manufacture
US6400069B1 (en) 1998-07-22 2002-06-04 Robert Espinosa E-M wave generation using cold electron emission
US6464136B2 (en) 1999-12-28 2002-10-15 Christopher S. Walsh Record and verification method, apparatus and system
US6477233B1 (en) * 1999-06-04 2002-11-05 Radi Medical Technologies Ab Miniature x-ray source
US6497358B1 (en) 1999-09-13 2002-12-24 Christopher S. Walsh Record and verification method and system for radiation therapy
US20030179854A1 (en) * 2002-03-20 2003-09-25 Ali Jaafar X-ray apparatus with field emission current stabilization and method of providing x-ray radiation therapy
US6799075B1 (en) 1995-08-24 2004-09-28 Medtronic Ave, Inc. X-ray catheter
US20050031069A1 (en) * 2003-08-07 2005-02-10 General Electric Company System and method for detecting an object by dynamically adjusting computational load
US20050226360A1 (en) * 2004-04-06 2005-10-13 General Electric Company System and method for detecting objects with differential operators
US20050249416A1 (en) * 2004-05-07 2005-11-10 General Electric Company Contraband detection system and method using variance data
US20060008055A1 (en) * 2004-07-09 2006-01-12 Sundaram Senthil K insulation methods and arrangements for an X-ray generator
US7492855B2 (en) 2003-08-07 2009-02-17 General Electric Company System and method for detecting an object
US7609807B2 (en) 2004-02-17 2009-10-27 General Electric Company CT-Guided system and method for analyzing regions of interest for contraband detection
US7624027B1 (en) 2002-10-29 2009-11-24 Practice Velocity, LLC Method and system for automated medical records processing
US20120152722A1 (en) * 2010-07-01 2012-06-21 Advanced Fusion Systems Llc Method of Inducing Chemical Reactions
US8606594B2 (en) 2002-10-29 2013-12-10 Practice Velocity, LLC Method and system for automated medical records processing
US8897419B1 (en) 2011-02-14 2014-11-25 Science Research Laboratory, Inc. Systems and methods for accelerating charged particle beams
US8915833B1 (en) 2011-02-15 2014-12-23 Velayudhan Sahadevan Image guided intraoperative simultaneous several ports microbeam radiation therapy with microfocus X-ray tubes
US9636525B1 (en) 2011-02-15 2017-05-02 Velayudhan Sahadevan Method of image guided intraoperative simultaneous several ports microbeam radiation therapy with microfocus X-ray tubes
US9842188B2 (en) 2002-10-29 2017-12-12 Practice Velocity, LLC Method and system for automated medical records processing with cloud computing

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GB987478A (en) * 1962-09-24 1965-03-31 Field Emission Corp Vacuum arc x-ray tube system and method
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GB987478A (en) * 1962-09-24 1965-03-31 Field Emission Corp Vacuum arc x-ray tube system and method
US3309523A (en) * 1963-06-24 1967-03-14 Field Emission Corp X-ray tube having field emission cathode and evaporative anode in combination with electrical pulser means
US3303372A (en) * 1964-08-20 1967-02-07 Dunlee Corp X-ray generator with a knife edged cold cathode emitter
US3521073A (en) * 1965-11-26 1970-07-21 Gen Dynamics Corp Light emitting semiconductor diode using the field emission effect
US3466485A (en) * 1967-09-21 1969-09-09 Bell Telephone Labor Inc Cold cathode emitter having a mosaic of closely spaced needles

Cited By (46)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5442678A (en) * 1990-09-05 1995-08-15 Photoelectron Corporation X-ray source with improved beam steering
US5153900A (en) * 1990-09-05 1992-10-06 Photoelectron Corporation Miniaturized low power x-ray source
US5528652A (en) * 1990-09-05 1996-06-18 Photoelectron Corporation Method for treating brain tumors
US5369679A (en) * 1990-09-05 1994-11-29 Photoelectron Corporation Low power x-ray source with implantable probe for treatment of brain tumors
US5422926A (en) * 1990-09-05 1995-06-06 Photoelectron Corporation X-ray source with shaped radiation pattern
US5452720A (en) * 1990-09-05 1995-09-26 Photoelectron Corporation Method for treating brain tumors
US5090043A (en) * 1990-11-21 1992-02-18 Parker Micro-Tubes, Inc. X-ray micro-tube and method of use in radiation oncology
WO1992009998A1 (en) * 1990-11-21 1992-06-11 Parker Micro-Tubes Incorporated X-ray micro-tube and method of use in radiation oncology
USRE34421E (en) * 1990-11-21 1993-10-26 Parker William J X-ray micro-tube and method of use in radiation oncology
US5428658A (en) * 1994-01-21 1995-06-27 Photoelectron Corporation X-ray source with flexible probe
US6799075B1 (en) 1995-08-24 2004-09-28 Medtronic Ave, Inc. X-ray catheter
US6377846B1 (en) 1997-02-21 2002-04-23 Medtronic Ave, Inc. Device for delivering localized x-ray radiation and method of manufacture
US6095966A (en) * 1997-02-21 2000-08-01 Xrt Corp. X-ray device having a dilation structure for delivering localized radiation to an interior of a body
US6148061A (en) * 1997-04-28 2000-11-14 Newton Scientific, Inc. Miniature x-ray unit
US5854822A (en) * 1997-07-25 1998-12-29 Xrt Corp. Miniature x-ray device having cold cathode
US6108402A (en) * 1998-01-16 2000-08-22 Medtronic Ave, Inc. Diamond vacuum housing for miniature x-ray device
US6069938A (en) * 1998-03-06 2000-05-30 Chornenky; Victor Ivan Method and x-ray device using pulse high voltage source
US6400069B1 (en) 1998-07-22 2002-06-04 Robert Espinosa E-M wave generation using cold electron emission
WO2000042631A1 (en) * 1999-01-18 2000-07-20 The Wahoo Trust High energy x-ray tube
US6289079B1 (en) 1999-03-23 2001-09-11 Medtronic Ave, Inc. X-ray device and deposition process for manufacture
US6320932B2 (en) 1999-05-13 2001-11-20 Photoelectron Corporation Miniature radiation source with flexible probe and laser driven thermionic emitter
US6195411B1 (en) 1999-05-13 2001-02-27 Photoelectron Corporation Miniature x-ray source with flexible probe
US6477233B1 (en) * 1999-06-04 2002-11-05 Radi Medical Technologies Ab Miniature x-ray source
US6353658B1 (en) 1999-09-08 2002-03-05 The Regents Of The University Of California Miniature x-ray source
US6497358B1 (en) 1999-09-13 2002-12-24 Christopher S. Walsh Record and verification method and system for radiation therapy
US6464136B2 (en) 1999-12-28 2002-10-15 Christopher S. Walsh Record and verification method, apparatus and system
US20030179854A1 (en) * 2002-03-20 2003-09-25 Ali Jaafar X-ray apparatus with field emission current stabilization and method of providing x-ray radiation therapy
US6985557B2 (en) 2002-03-20 2006-01-10 Minnesota Medical Physics Llc X-ray apparatus with field emission current stabilization and method of providing x-ray radiation therapy
US8606594B2 (en) 2002-10-29 2013-12-10 Practice Velocity, LLC Method and system for automated medical records processing
US7624027B1 (en) 2002-10-29 2009-11-24 Practice Velocity, LLC Method and system for automated medical records processing
US9842188B2 (en) 2002-10-29 2017-12-12 Practice Velocity, LLC Method and system for automated medical records processing with cloud computing
US20050031069A1 (en) * 2003-08-07 2005-02-10 General Electric Company System and method for detecting an object by dynamically adjusting computational load
US7889835B2 (en) 2003-08-07 2011-02-15 Morpho Detection, Inc. System and method for detecting an object by dynamically adjusting computational load
US7492855B2 (en) 2003-08-07 2009-02-17 General Electric Company System and method for detecting an object
US7609807B2 (en) 2004-02-17 2009-10-27 General Electric Company CT-Guided system and method for analyzing regions of interest for contraband detection
US20050226360A1 (en) * 2004-04-06 2005-10-13 General Electric Company System and method for detecting objects with differential operators
US7031430B2 (en) 2004-04-06 2006-04-18 General Electric Company System and method for detecting objects with differential operators
US7356174B2 (en) 2004-05-07 2008-04-08 General Electric Company Contraband detection system and method using variance data
US20050249416A1 (en) * 2004-05-07 2005-11-10 General Electric Company Contraband detection system and method using variance data
US20060008055A1 (en) * 2004-07-09 2006-01-12 Sundaram Senthil K insulation methods and arrangements for an X-ray generator
US7430278B2 (en) * 2004-07-09 2008-09-30 General Electric Company Insulation methods and arrangements for an X-ray generator
US20120152722A1 (en) * 2010-07-01 2012-06-21 Advanced Fusion Systems Llc Method of Inducing Chemical Reactions
US9406478B2 (en) * 2010-07-01 2016-08-02 Advanced Fusion Systems Llc Method and apparatus for inducing chemical reactions by X-ray irradiation
US8897419B1 (en) 2011-02-14 2014-11-25 Science Research Laboratory, Inc. Systems and methods for accelerating charged particle beams
US8915833B1 (en) 2011-02-15 2014-12-23 Velayudhan Sahadevan Image guided intraoperative simultaneous several ports microbeam radiation therapy with microfocus X-ray tubes
US9636525B1 (en) 2011-02-15 2017-05-02 Velayudhan Sahadevan Method of image guided intraoperative simultaneous several ports microbeam radiation therapy with microfocus X-ray tubes

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