A Low Intensity X ray Imaging device with the acronym LIXISCOPE is described. The Lixiscope has a small format and is powered only by a 2.7V battery. The high inherent gain of the Lixiscope permits the use of radioactive sources in lieu of X-ray machines in some fluoroscopic applications. In this mode of operation the complete X ray imaging system is truly portable and pocket-sized

Seltzer, S. M.

Yin, L. I.

English

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NASA
Technical Memorandum 78084
(NASA -TM-78064) THE LIXISCOPE: A	 N78-28934
POCKET-SIZE X-RAY IMAGING SYSTEM (NASA)
15 p HC A02/MF A01	 CSCL 20F
Unclas
G3/74 24684
THE LIXISCOPE: A POCKET-SIZE
X-RAY IMAGING SYSTEM
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PUBLICLY RELEASED JULY il, 1 978	 1
1
JANUARY 1978
National Aeronautics and
Space Administration
Goddard Spai -lbc
Greenbelt, Mar^t^
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BIBLIOGRAPHIC DATA SHEET
.1
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1. Report No. 2. Government Accession No. 3. Recipient's Catalog No.
TM 78064
4. Title and Subtitle 5. Report Date
THE LIXISCOPE: A POCKET-SIZE X-RAY IMAGING
Jan.	 10.	 1978
6. Performing Organization Code
SYSTEM
7. Author(s) 8. Performing Organization Report No.
Lo I Yin and Stephen M. Seltzer (NBS)
9. Performing Organization Name and Address 10. Work Unit No.
GSFC
11. Contract or Grant No.Laboratory for Astronomy 6 Solar Physics
Code 684
Greenbelt, Md .	 20771 13. Type of Report and Period Covered
Preprint
12. Sponsoring Agency Name and Address
Same as 9
14. Sponsoring Agency Code
15. Supplementary Notes
To be published in Physics in Medicine and Biology
16. Abstract
A Low Intensity X-ray Imaging device with the acronym LIXISCOPE is
described.	 The Lixiscope has a small format and is powered only by a
2.7V battery.	 The high inherent gain of the Lixiscope permits the use of
radioactive sources in lieu of x-ray machines in some fluoroscopic
applications.
	
In this mode of operation th- complete x-ray imag.ng system
is truly portable and pocket-sized.
17. Key Words (Selected by Author(s)) 18. Distribution Statement
Lixiscope; X-ray Imaging
19. Security C!assif. (of this report) 120. Security Classif. (of this page) 21. No. of Pages 22. Price`
No No 12
GSFC 25 .44 (10/77)
C
I -----vim
Lo I Yin, Ph. D.
Laboratory for Astronomy and Solar Physics, Code 684
Goddard Space Flight Center, Greenbelt, Md., 20771, USA
and
Stephen M. Seltzer, M. S.
Center for Radiation Research
National Bureau of Standards
Washington, D.C., 20234, USA
Instrumentation Note
Short Title; Lixiscope
- , 4 io - ^"
CONTENTS
Page
1. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . 	 1
2. THE LIXISCOPE . . . . . . . . . . . . . . . . . . . . . . . .	 1
3. PRELIMINARY RESULTS . . . . . . . . . . . . . . . . . . . . 4
4. DISCUSSION . . . . . . . . . . . . . . . . . . . . . . . . . .
	
6
5. ACKNOWLEDGEMENTS . . . . . . . . . . . . . . . . . . . . 7
REFERENCES. . . . . . . . . . . . . . . . . . . . . . . . . . .
	 8
ILLUSTRATIONS
Figure	 Page
1	 Schematic showing the major components of the Lixiscope
	 9
2	 Prototype Lixiscope with an I 125 radioactive point source
and dental phantom . . . . . . . . . . . . . . . . . . . . . 10
31.	 Image of Jental phantom from Kodak Ultraspeed DF-57 dental
film with x-ray tube operating at 60 kVp and 10 mA . . . . . . 11
3B	 Image of dental phantom from Lixiscope with x-ray tube
operating at 60 kVp and 0.5 mA . . . . . . . . . . . . . . . 11
3C	 Image of dental phantom from Lixiscope using 20 mCi I125
point source at 3 cm . . . . . . . . . . . . . . . . . . . . 11
iii
1	 7" =i
1ORIGINAL PAGE IS
1. Introduction	
OF POUR QUALM
This note describes a low intensity x-ray imaging device with
the acronym Lixiscope. This device was originally conceived for
use in x-ray astronomy where single-photon imaging is required;
however, the extension of its capabilities to medical and den-
tal radiography soon became evident. The high sensitivity and
large gain of the Lixiscope makes it possible to reduce the
patient dose by — 10 3 in certain diagnostic procedures as coin-
pared to conventional practice. Such extensive dose reduction
not only allows safe fluoroscopic examinations, but also enables
	
}	 the use of radioactive sources in lieu of x-ray machines.
	
`	 Furthermore, because the Lixiscope produces a visible-light out-	 `	 I
put image, it zan be easily recorded on fast instant-processing
i
	 films or used in conjunction with any other image recordin g a.-.d
processing devices. As will be shown, the small format of the
Lixiscope in conjunction with a minute radioactive source provides
	
1 I	 a truly portable, nearly pocket-size fluoroscopic system. 	 j
2. The Lixiscope
The prototype Lixiscope is extremely simple in concept (Fib•.
1). Each x-ray photon is converted into a large number of visibie -
light photons by means of a phosphor screen, in this case, 1 nix.
The phosphor screen, shielded by an opaque material, is in con-
n• tact with the input fiber-optics face plate of a second generation
night-vision (visible-light) image intensifier. (The image inten-
sifier was generously loaned to us by the Night Vision Laboratory,
Fort Belvoir, Va., and the Lanex screen was given to as by the
1
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Eastman Kodak Research Laboratory, Rochester, N.Y.). in this
manner, both the high conversion efficiency of the Lanex screen
and the high visible-light gain (,w 4x104 ) of the rugged night-
vision intensifier are fully utilized without either loss of
l
	 x-ray quantum efficiency through a window or introducing con- 	
r
taminants and fragility into the intensifier.
The night-vision intensifier used here consists of an input
fiber-op-t ics face plae with <5 }+m diameter fibers.  On the
back face (vacuum side) of the input fiber-optics plate is a
5-25 photocathode. The initial x-ray image is thus converted
first into a visible-light image by the Lanex screen and then to
an electron image by the photocathode with little loss of resolu-
tion. Furthermore, in these conversions each absor;icd x-ray
produces a large number of photoelectrons. Thus the probability
of information loss is neglible after the initial absorption.
The photoelectrons are multiplied by a microchannel plate
(MCP) electron multiplier operated in the unsaturated mode with
an average gain of roughly 10 3 . The microchannels are 12 pm in
diameter, have a length-to diameter ratio of 40, and a center-to-
center distance of 14.5'0m. The output electrons of the MCP are
accelerated by o- 5 kV across a 1.3 mm gap to impinge on an alumi-
nized P-39 phosphor screen deposited on the output fiber-optics
face plate. The aluminized phosphor prevents visible light
feedback to the photocathode.
Both the input and output fiber-optics face plate also
serve as vacuum seals ('r 10-9 torr). Ti.. output plate brings
the final intensified image to a plane flush with the viewing
2
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OF POOR PAGE IbQ AI,ITY
surface of the intensifier thus making it easy to couple with
any fora: of image recording device. The intensifier provides a
1 : 1 intensified image with an inherent resolution of about
30 1p/mm.
The night-vision
 intensifier shown in Fig. 2 has also an
electrostatic inversion lens between the photocathode and the
input of the MCP. The purpose of the lens is to produce an
upright image when the intensifier is used with night viewing
optics. It is not necessary in the present application. The
elimination of the inversion lens will result in a wafer tube
device that is much more compact with a thickness of only-w-1.5 cm,
and an improved inherent resoltuion.
The entire intensifier is powered by a single 2.7 V battery
and has a light gain of 4x104 . Electronic circuitry which
supplies voltages to the various stages of the intensifier as
well as protects the phosphor screen and photocathode from
accidental overexposure is encased in silicon rubber around the
external cylindrical wall of the intensifier.
Previously (Gould et al. 1976, 1977), the MCP itself has
been used directly to convert x-rays into photoelectrons. Un-
fortunately, in this energy region, the quantum efficiency of
such direct conversion is low (— 10%); and, in addition, the
incident x-ray beam must be attenuated further (perhaps around
30%) by an entrance window to the vacuum tube. Because such a
large information loss ( >90%) cannot be retrieved at later stages,
increased patient dose becomes necessary to maintain image quality.,-
`	 !	 1 11
Another design (Woodhead and Eschard 1971) intorduces the x-ray
phosphor inside the vacuum tube. In this case a fragile window
is still necessary. In contrast, the Lixiscope has no x-ray
window and combines the high efficiency of the x
-ray phosphor
screen with the high gain and ruggedness of the night-vision
intensifier.
The radioactive source shown in Fig. 2 is a 20 mCi 1125
source manufactured by Amersham/Searle Corp. in their standard
point-source configuration. Henrikson ( 1967) has shown that of
suitable radioisotopes the energy of I 125 x-rays (27 keV) are
most suitable for dental applications.
3. Preliminary Results
The results shown in Fig. 3 were obtained to demonstrate
the feasibility of the Lixiscope concept without any attempt at
the present time to optimize either the experimental conditions
or the components of the Lixiscope itself. Dental radiographs
were taken because in this area immediate application of the
Lixiscope seems most promising. All three photographs in Fig. 3
were obtained from the same dental phantom (see Fig. 2).
Photographs 3A and 3B were taken at the Bureau of Radio-
logical Health, Rockville, MD using a calibrated x-ray generator
operated at 60 kVp. The dental phantom was placed 200 cm from
the x -ray source, and dosimeter readings were made at the phantom
position. Fig. 3A shows a 12 sec exposure on Kodak Ultraspeed
DF-57 dental film with the x-ray tube operating at 10MA. The
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recommended exposure range. Next, the phantom was examined by
the Lixiscope with the x-ray tube operating at 60 kVp and 0.65 MA.
Using an available Polaroid oscilloscope camera which has an
image reduction ratio of 0.7 and an object-to-lens distance of
19 cm, a good duality photograph of the Lixiscope image was
obtained at f/4.5 and 0.1 sec on ASA 3000 (Type 107) film. The
measured radiation exposure in this case was 0.1 mR, giving a
reduction factor of > 10 3 . Unfortunately, the positive image and
its reduced size makes comparison with the dental negative diffi-
cult. Therefore we recorded the Lixiscope image on 35 mm Tri-X
(ASA 400) film as shown in Fig. 3B.
Fig. 3C shows the Tri-X film recording of the Lixiscope
image  using the 20 mCi 1 125 source in the configuration of Fig. 2 at
a source-to-teeth distance of 3 cm. A comparable Polaroid photo-
graph using 1 125 source was obtained at 0.2 sec with a measured
radiation exposure of about 0.3 mR. However, because of the
nearly monoenerget is (27 keV) spectrum of the 1 1` 5 source, tho
image in Fig. 3C shows better contrast than that of Fiq. 3B.
From Figs. 3B and 3C it is obvious that the resolution of
the Lixiscope is interior to that of the dental tilm. Vie
measured resolution of this prototype Lixiscope using either
the x-ray machine or the 1125 source is about 4 1 p;/"mm.	 5 tnGe
the inherent resolution of the night-vision intensitier is
about 30 1p/nun the resolution of this prototype Lixiscope is
essentially limited by the Laney phosphor screen.
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The measured output luminance of the Lixiscope using the
20 mci I125 source at 4.4 cm from the Lanex screen is 1.75 M.
The background without the radioactive source is 3.6x10-4 M.
4. Discussion
These preliminary results demonstrate the feasibility of a
low-dose, compact, rugged and fully portable x-ray image intensi-
fier system which is suitable for both laboratory and field use.
The entire system is fabricated solely from available components.
It is important to note that in this prototype system, no effort
has been made to optimize the performance ckaracteristics such
as signal-to-noise, gain, spectral sensitivity and efficiency,
MTF, contrast and spatial resolution. These problems are present-
ly being investigated in our laboratory.
The potential applications of the Lixiscope in radiography
and fluoroscopy are most promising in areas where small format
and portability are desirable. Restricting our attention to
the dental example, for instance, the Lixiscope in combination
with an intraoral, collimated radioactive source equipped with
an on/off shutter will not only eliminate all unnecessary ex-
posures to other sensitive organs which are unintentionally
irradiated by conventional extraoral x-ray machines, but also
provides a low-dose rate means of in-situ instantaneous observa-
tion of surgical progress in root canal and other operations
where high resolution is not required. Furthermore, and perhaps
more importantly, the Lixiscope in combination with radioactive
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sources will make fluoroscopy and radiography available in
regions where electricity is not generally accessible.
5. Acknowledgements
This work would not have been possible without the generous
advice and assistance of many individuals from various organi-
zations. We gratefully acknowledge R. Webber, National Institute
of Dental Research, National "Institute of Health, Bethesda, Md.,
for his guidance and enlightening discussions in addition to
critical liaisons; J. Rennie and M. Farr, Night Vision Laboratory,
Fort Belvoir, Va., for their indispensable advice and loan of
night-vision intensifier tubes; R. Wagner and E. Denny, Bureau
of Radiological Health, Rockville, Md., for making the definitive
measurements with their calibrated x-ray generator; B. Roth, Kodak
Research Laboratory, Rochester, N.Y., for providing us with
various kinds of x-ray phosphors; and J. Troi!bka, Goddard Space
Flight Center, Greenbelt, Md., for his constant encourgement and
advice.
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References:
Gould, R., Bjarngard, B., and Judy, P., 1976 Diy__,.
	 ....o
4th International Conference on Medical Physics, Physics in
Canada 32, p.8.
Gould, R.G., Judy, P.F., Klopping, J.C., and Bjarngard, B.E.,
1977, Nuc. Instr. Methods, 144, 493, (1977)
Henrikson, C.O., 1967, Acta Radiologica, Suppl. 269, 1.
Woodhead, A.W., and Eschard, G., 1971, Acta Electronica 14, 181.
4
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FIBER
OPTICS
FIBER
OPTICS
HIGH VACUUM
l
	 VISIBLE-LIGHT	 1
F
	 INTENSIFIER
TUBE
VACUUM
SCINTILLATOR	 PHOTO-	 PHOSPHOR
CATHODE SCREEN
Figure 1. Schematic showing the major components of the l.ixi:;copc•.
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ORIGINAL PAGV* 1S
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ORIGINAL PAGE IS
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Figure ?. Prototype Lixiscope with an I 125 radioactive point
source and dental phantom.
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ORIGINAL PAGE M
OF POOR QUALM
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Figure 3. (A) Image L: dental phantom from Kodak Ultraspeed DF-57 dental
film with x-ray tube operating at 60 kVp and 10 MA. (B) Image of dental phan-
tom from Lixiscope with x-ray tube operating at 60 kVp and 0. 5 mA. (C) Imago
of dental phantom from Lixiscope using 20 mCi I 125 point source at 3 cm.
11
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