X-ray or gamma ray systems or devices – Specific application – Mammography
Reexamination Certificate
1995-02-10
2001-10-02
Church, Craig E. (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Mammography
Reexamination Certificate
active
06298114
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to medical X-ray systems, and more particularly, to an improved X-ray mammography apparatus for detecting breast cancer or other breast diseases.
BACKGROUND ART
Mammography machines are used for X-ray examination of the female human breast (the milk-producing organ) to detect cancer or other growths. A typical machine is described in detail in U.S. Pat. No. 5,164,976, the disclosure of which is hereby incorporated by reference.
FIG. 1
depicts a conventional mammography machine shown in the above United States Patent. The mammography machine includes an operator control unit and X-ray generator portion indicated at
20
. The portion
20
incorporates the control electronics for the machine as well as the power supply for an X-ray source. The machine portion indicated at
22
is sometimes referred as a C-arm assembly and includes a film table
24
, an overlaying compression paddle
26
and an X-ray source
28
. The C-arm assembly may be rotatable about a horizontal axis
30
for obtaining different angular images. A radiation shield
32
isolates the operator control area adjacent portion
30
from the patient area adjacent film table
24
. The C-arm
22
is vertically adjustable, in the position shown in
FIG. 1
, to accommodate date patients of different heights. The table
24
accepts standard X-ray film cassettes for image recording.
In conducting a mammography examination, a patient's breast is placed upon film table
24
and is compressed by compression paddle
26
. The compression is required in order to have a substantially uniform density or thickness of the breast typically necessary to provide rather uniform X-ray image density characteristics. The reason is that the conventional X-ray films have relatively small dynamic ranges, and therefore the X-ray beam intensity must be within a certain small variation when reaching the film table
24
. Otherwise, higher intensity area will be overexposed or lower intensity area will be underexposed depending on the exposure time.
The foregoing mammography machine includes many drawbacks. One of the most obvious ones is demonstrated in
FIG. 2
, wherein two cancer areas
80
and
82
are shown in a patient's breast
38
. If the breast
38
is compressed by the compression paddle
26
, the cancer area
82
moves toward the center of the field of view while the cancer area
80
moves out of the field of view. This means that there is a significant possibility that we cannot detect a cancer being located near the chest wall. Another disadvantage is that the compression procedures are often painful for patients having smaller breasts due to higher compression force.
DISCLOSURE OF THE INVENTION
A primary object of the invention is to provide a mammography machine that gives significantly higher cancer detectability near the chest wall.
Another object of the invention is to provide a mammography machine that gives less pain to a patient.
The above and other objects of the invention are satisfied, at least in part, by providing means for elongating the patient's breast by applying to the breast a tensile force.
In accordance with a preferred embodiment of the invention, means for elongating the breast using gravity is provided. Preferably, the patient is lain prone on a bed having a hole or cut area for elongating the breast. An X-ray source and an X-ray image detector are located under the bed, thereby allowing an X-ray beam going horizontally through the elongated breast.
According to one aspect of the invention, means for elongating the breast under force of suction such as by applying negative pressure is provided. Preferably, this configuration can be added to the system using gravity. In other words, the patient is lain prone on a bed having a hole for elongating the breast. An X-ray source and an X-ray image detector are located under the bed, thereby allowing an X-ray beam running horizontally through the breast. Furthermore, at least a part of the breast is covered by one end portion of a tube, wherein the internal pressure is controlled to be negative compared to the atmospheric pressure by operating a vacuum pump that is connected to the tube. The tube is made of an X-ray transparent material such as plastic.
According to another aspect of the invention, only the body portion above the chest is placed horizontally for elongating the breast using gravity. The elongation can be achieved by the gravity and the negative pressure at the same time.
According to still another aspect of the invention, a water reservoir is placed under the breast in order to provide almost the same X-ray attenuation with respect to the incoming X-ray beams even when avoiding the use of the compression paddle. Because the X-ray attenuation rate of the water is very close to that of human tissues, this configuration can reduce the dynamic range of the X-ray beam intensity on the X-ray film surface.
Alternatively, a semiconductor type X-ray image detector can be used for increasing the detector dynamic range, so that we can avoid using the compression paddle. A higher contrast X-ray film may also be used for increasing the detector dynamic range.
According to another aspect of the invention, means for elongating the breast using negative pressure can be provided without being prone. In this case, the patient can be vertically or uprightly positioned. Thus, we can use any conventional mammography apparatus by adding a tube and a vacuum pump. The tube is made of an X-ray transparent material such as plastic. One end of the tube covers at least a part of the breast while the other end being connected to the vacuum pump for applying the negative pressure to the breast.
Still other objects and advantages of the present invention will become readily apparent to those skilled in this art from the following detailed description, wherein only the preferred embodiment of the invention is shown and described, simply by way of illustration of the best mode contemplated of carrying out the invention. As will be realized, the invention is capable of modifications in various obvious respects, all without departing from the invention. Consequently, the drawing and description are to be regarded as illustrative in nature, and not as restrictive.
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P.E. Sijens et al., “NMR Spectroscopy of human breast tumors before and after radiotherapy, using a 1.5 T MRI system,” MR research note, Selected Abstracts submitted to the 6th SMRM 1987, Phillips Medical Systems, Documentation No. 4535 983 00655 (Aug., 1987).
Church Craig E.
McDermott & Will & Emery
Mitsubishi Denki & Kabushiki Kaisha
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