A system for accurately determining the exposure density required for X-ray photography of a particular area of interest is provided. The light received from an X-ray image intensifier is applied to a beam splitting mirror which divides the light between a motion picture film camera and a television film camera. Between the beam splitter and the motion picture film camera, there is positioned another light beam splitter to direct some of the light at a mask having an opening which encloses only the image area of interest. Behind that opening there is positioned a photomultiplier intensity sensor for determining the exposure required and varying X-ray beam intensity accordingly

Berdahl, C. M.

English

NASA Technical Reports Server

United States Patent h191 
Berdahl 
[111 4,063,092 
[45] Dec. 13, 1977 
[54] SELECTIVE IMAGE AREA CONTROL OF 
[75] Inventor: C. Martin Berdahl, Sierra Madre, 
[73] Assignee: The United States of America as 
X-RAY FILM EXPOSURE DENSITY 
Calif. 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
[21] Appl. No.: 675,328 
[22] Filed: Apr. 9, 1976 
E511 Int. Cl .2  .............................................. G03B 41/16 
[52] U.S. Cl. .............................. 250/322; 250/416 TV 
I581 Field of Search ................ 250/322, 413, 416 TV, 
250/402, 355 
Pal References Cited 
U.S. PATENT DOCUMENTS 
3,126,480 3/1964 Bouwers .............................. 250/322 
3,439,114 4/1969 Taylor .................................. 250/322 
3,546,461 12/1970 Craig .................................... 250/322 
OTHER PUBLICATIONS 
Hewlett-Packard Journal, “An Automatic Exposure 
Control for Lab-Bench X-Ray Camera”, Brewster, 
V O ~ .  25, NO. 11, July 1974, pp. 20-24. 
Primary Examiner-Saxfield Chatmon, Jr. 
Assistant Examiner-B. C. Anderson 
Attorney, Agent, or Firm-Monte F. Mott; Wilfred 
Grifka, John R. Manning 
[571 ABSTRACX 
A system for accurately determining the exposure den- 
sity required for x-ray photography of a particular area 
of interest is provided. The light received from an x-ray 
image intensifier is applied to a beam splitting mirror 
which divides the light between a motion picture film 
camera and a televisiofi film camera. Between the beam 
splitter and the motion picture film camera, there is 
positioned another light beam splitter to direct some of 
the light at a mask having an opening which encloses 
only the image area of interest. Behind that opening 
there is positioned a photomultiplier intensity sensor for 
determining the exposure required and varying x-ray 
beam intensity accordingly. 
3 Claims, 1 Drawing Figure 
IO 
X-RAY MACHINE 
\ I  
IMAGE 
INTENSIFIER 
1 I 2 4  
L--. 
1 
16 
22 
https://ntrs.nasa.gov/search.jsp?R=19780007518 2020-03-20T13:02:36+00:00Z
U.S. Patent Dec. 13, 1977 4,063,092 
- IO 
a X-RAY MACHINE 
IMAGE 
INTENSIFIER 
:I4 
L 
20 
f 
I I24 
I L--- 
I 
J 
16 
22 
4,063,092 
1 
SELECITVE IMAGE AREA CONTROL OF X-RAY 
FILM EXPOSURE DENSITY 
ORIGIN OF THE INVENTION 
The invention described herein was made in the per- 
formance of work under a NASA contract and is sub- 
ject to the provisions of Section 305 of the National 
Aeronautics and Space Act of 1958, Public Law 85-568 
(72 Stat. 435; 42 USC 2457). 
BACKGROUND OF THE INVENTION 
This invention relates to an improved system for 
determining the x-ray exposure required for photogra- 
Medical diagnosis of internal human tissue is fre- 
quently performed by the use of motion picture x-ray 
techniques, particularly when the tissue of interest, such 
as, for example, the beating heart, is in motion. The 
technique involves use of an x-ray tube aimed at the 
patient, a fluorescent screen disposed on the opposite 
side of the patient, an image intensifier which views the 
fluorescent screen and increases the brightness of the 
image, and a motion picture film camera which records 
the moving image. A television system is often used to 
provide a display as the x-ray image is panned, so that 
the particular site of interest can be properly positioned 
while the motion picture film is being exposed. 
Proper exposure of the motion picture film requires 
accurate information with respect to light content of the 
image which is to be photographed. This is presently 
obtained by extracting and directing at a photomulti- 
plier exposure sensing system, a small sample of a por- 
tion of the light contained in a collimated beam formed 
from the visible image produced by the image intensi- 
fier. Since any part of the collimated beam is composed 
of light from all parts of the image, what is sensed is 
only an average sample which is representative of the 
total amount of light in the entire image. Since the 
image of the subject contains areas of both high and low 
x-ray absorptivity, it is difficult to determine accurately 
from a sample of the entire image the optimum exposure 
required for the particular body portion of interest 
which is only a part of that total image. Since, with the 
presently used system, the operator has no control over 
the location of the light sample taken, the result is often 
an unsatisfactory exposure. 
The patient must then be subjected again to x-radia- 
tion in order to obtain a better picture. Since it is desir- 
able to minimize exmsure of the Datient to x-radiation. 
phy. 
2 
a portion of the light to a television camera and a por- 
tion of the light to a film camera. The television camera 
is used to produce an image from which it can be deter- 
mined whether the part of the body of interest is being 
5 x-rayed or whether the person being x-rayed or the 
x-ray machine must be relocated to produce an image of 
the portion of the body of interest. In accordance with 
this invention, there is interposed between the film cam- 
era and the beam splitter, a second smaller beam splitter, 
10 which permits some light to pass therethrough to be 
imaged on the lens of the film camera, and which also 
directs a portion of the received light onto an imaging 
15 
20 
25 
30 
35 
40 
45 
50 
it is advantageous Ad  less pote&lly harmful to the 
patient to determine initially, the optimum exposure 
required for the particular body portion of interest. 
OBJECTS AND SUMMARY OF THE 
INVENTION 
It is an object of this invention to provide an arrange- 
ment fo enabling the optimum exposure required for 
photographing a particular area of interest to be ob- 
Another object of this invention is to provide a novel 
and improved arrangement for enabling optimum x-ray 
exposure required for a particular portion of a body of 
interest, using motion pictures. 
be achieved in a system in which the light output of an 
x-ray image intensifier is passed through a collimating 
lens and then onto a beam splitting mirror which passes 
55 
tained the first time x-ray radiation takes place. a 
The foregong and other objects of the invention may 65 
lens. The-imaging lens focuses the &age on a mask.-%; 
mask has an aperture whose diameter is selected to 
define the specific area of interest of the region of the 
body being x-rayed. The light passing through the 
image mask falls on a photomultiplier, which is used to 
sense the intensity of the light received whereby a de- 
termination of the correct exposure required for prop- 
erly photographing the desired portion of the body can 
be achieved. 
The novel features of the invention are set forth with 
particularity in the appended claims. The invention will 
best be understood from the following description when 
read in conjunction with the accompanying drawing. 
DESCRIPTION OF THE PREmRREJD 
EMBODIMENTS 
The drawing represents a schematic diagram which 
illustrates both the prior art system presently being 
used, as well as an embodiment of this invention. 
An x-ray machine 10 projects x-rays at a patient 12. 
X-rays passing through that patient impinge upon an 
image intensifier 14. The output of the image intensifier 
is collimated by a lens 16 disposed on the opposite side 
thereof. The collimated light falls upon a beam splitting 
mirror 18 which splits the light and directs one portion 
at a motion picture camera 20, and permits a second 
portion to pass therethrough to be directed at a televi- 
sion camera 22. 
In accordance with the prior art, a small mirror 24 is 
positioned in the collimated light beam, and intercepts 
and diverts a portion of the light for perception by the 
photomultiplier exposure sensing system 26. As previ- 
ously indicated, since any part of the collimated beam is 
composed of light from all parts of the image, what is 
sensed is only an average sample which is representa- 
tive of the total amount of light in the entire image. 
Since the image of the subject contains areas of high and 
low x-ray absorptivity, it is difficult to determine accu- 
rately from this sample, the optimum exposure required 
for a particular body portion of interest, which is only a 
part of that total image. Also, since the operator has no 
control over the location of the light sample taken, the 
result is often an unsatisfactory exposure. 
In accordance with this invention, the light reflected 
from the beam splitting mirror 18 is directed at another 
beam splitting mirror 24. The light passing there- 
through will still impinge upon the frlm camera 20 to be 
photographed. The light redirected by the mirror 24 is 
directed at an imaging lens 26, which in turn directs it at 
a mask 28, located at the image position. The mask will 
have a central aperture, (or an adjustable diaphragm) 
which will enclose the central portion of an area of 
interest. Accordingly, a photomultiplier 30, which is 
used for intensity sensing, and for controlliing the x-ray 
beam intensity, for example, is positioned to receive the 
light passing through the aperture of the mask. It there- 
4,063,092 
3 4 
fore senses only the light included in the image which 
exists in the predetermined area of interest. Accord- 
ingly, it will indicate more accurately, the quantity of 
this light and can thus provide an output signal which is 
applied to the x-ray machine 10 to establish the x-ray 5 
beam intensity provided by the x-ray machine 10. 
Thereby an accurate exposure of the film for the area of 
interest is achieved. The camera lens aperture may be 
left wide open so that the patient will have the 
of x-ray exposure for the Part of the body being photo- 
graphed. This occurs because the x-ray beam intensity is 
altered for exposure requirements, rather than altering 
the film camera controls. 
novel and useful arrangement for accurately determin- 
ing the exposure required for photographing an area of 
interest in a subject being x-rayed, the first time, and 
with a minimum of x-ray exposure for the patient. 
tured mask to pass therethrough and impinge upon 
said light intensity sensing means, and 
an imaging lens between said second beam splitter 
and said apertured mask for focusing the image 
defined by the light, directed by said second beam 
splitting means, on said apertured mask. 
2* A method Of improving the determination Of film 
exposure required for photographing a particular area 
of interest of an x-ray image in a system wherein x-rays 
10 passing through a subject are applied to an image inten- 
sifier for being converted into a light image, 
collimating said light image, 
directing said light image at a film camera and at a 
television camera, 
intercepting some of the light being directed to said 
motion picture camera and directing it at a light 
intensity sensing means, 
ofthe light directed at said light intensity 
sensing means except that coming from the area of 
I claim: 20 interest, whereupon said light sensing means pro- 
1. A system of the type wherein the x-rays passing vides an output signal representative of the light 
through a patient are applied to an image intensifier from the area of interest, and 
which generates a light image in response thereto, the controlling the intensity of x-rays passing through 
light image is collimated and then directed at a first said subject responsive to said output signal. 
beam splitting means which directs some of the light at 25 3. A system for determining film exposure density for 
a motion picture camera and passes the remainder ofthe a Specific image area from the light hage  produced, in 
light to a television camera. the imDrovement comDris- response to x-rays which have passed through a 
There has been described and shown a 15 
blocking 
h 3  
a 
a 
a 
by an image intensifier which is then collimated, com- 
prising means for directing some of said collimated light 
of the image being intensi- 30 at a motion picture camera and at a television camera, 
light intensity sensing means for controlling the inten- 
sity of said x-rays responsive to the light falling on 
said light sensing means and thereby said motion 
picture camera exposure, 
for directing a portion of the 
light directed at said motion picture camera, at said 
light intensity sensing means, 
masking means for permitting only the light from the 
image area of interest to be received by said light 
intensity sensing means, and 
lens means positioned between said beam splitting 
means and said masking means for focusing a light 
image on said masking means. 
mask having an aperture 
central area of 
tied by said image intensifier, 
light intensity sensing means responsive to light 
impinging thereon for controlling the x-ray inten- 
sity required for determining correct motion pic- 35 
ture camera exposure, said light intensity sensing 
means being positioned at one side of said aperture 
mask to receive an of light Passing there- 
through corresponding to the area of said aperture, 
second beam splitting means positioned between 40 
said first b e a ~ ~  splitting means and said motion 
picture camera for receiving light directed at said 
motion picture camera by said first beam splitting 
to encompass the 
beam splitting 
means and directing a portion thereof at said aper- * * * * *  
45 
50 
55 
65 


Selective image area control of X-ray film exposure density

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server