X-ray or gamma ray systems or devices – Specific application – Mammography
Patent
1988-07-13
1990-05-29
Cohen, Lee S.
X-ray or gamma ray systems or devices
Specific application
Mammography
128653R, A61B 604
Patent
active
049301438
DESCRIPTION:
BRIEF SUMMARY
Mammography is a radiographic method for early detection of breast cancer. It is not always possible to decide whether the detected lesions are benign or malignant. One way to decide this is punction with a thin cannula in order to extract cells for microscopic diagnosis. In order to succeed it is necessary to hit the lesions with the cannula. The suspicious lesions are often so small that they can not be palpated (felt with the fingers) and therefore some technique for mammographic localization is necessary.
Mammographic apparatus at present available comprises special versions for the said purpose with stereotactic localization facilities. These imply an extensive modification of the apparatus and raise the price with about 250,000 Swedish crowns. The stereotactic principle (tomography) traditionally used in radiology is based on the object being stationary and the X-ray tube (radiation source) and film cassette (image medium) moving synchronously. Two exposures are made and with the aid of simple geometry it is possible to calculate the position within the object. Such equipment is technically complicated and therefor expensive, especially since it is usually combined with relatively sophisticated computerization.
The present invention suggests a principle that is the reverse of the above and not previously used in radiological technique, i.e. to allow the X-ray tube and the image to remain stationary and to move the object. As a consequence, the X-ray unit need not be modified. The geometry in this case is also simple, being based on similar triangles. There is, however, requested an apparatus having a movable holder adapted to hold the object--the female breast--during the movement between the two positions of exposure. The invention can be adapted to all existing mammography units without having to modify these.
The invention is described in the following specification, and the accompanying drawings show:
FIGS. 1a and b, the principle for a conventional standard mammography unit without stereographic means.
FIGS. 2a to c, a conventional X-ray unit with stereographic means.
FIGS. 3 to 7 show various details of the present invention.
FIG. 4, an object holder on the stand.
FIG. 5, a compression plate on the object holder.
FIGS. 6a and b and FIG. 7, a needle director on the compression plate.
FIG. 8, a perspective view of devices for X-ray tube and light source.
FIGS. 9 and 10, different functions of the invention.
FIGS. 9a and b, lateral movement of object holder.
FIGS. 10a and b, vertical movement of compression plate.
FIGS. 11 to 13, handling of unit according to the present invention.
FIGS. 11a to d, the principle for exposure.
FIGS. 12a and b, exposure in the two outer positions.
FIGS. 13a and b, the exposures put together.
FIGS. 14 to 18, the mathematical basis for calculation of the depth of punction.
FIG. 19, illustration of direction of punction.
CONVENTIONAL MAMMOGRAPHY
The principle for a conventional mammography unit without stereographic means is shown in FIGS. 1a and b. The X-ray tube 10 is mounted on a stand 11 which is immovable in relation to the film cassette holder 12. The outer limits of the radiation field from the X-ray tube are schematically shown by the continuous lines 13. The primary diaphragm 14 of the X-ray tube and the radiation window 15 decide the size of the radiation field.
FIG. 1b shows the object 16, a female breast, with the suspicious lesion 17. The object is fixed by a compression plate 18 on top of the film cassette, also fixed. The X-ray beam passing through the lesion is shown by a broken line 19.
TOMOGRAPHY
FIGS. 2a to c show a conventional X-ray unit with stereographic means for tomography. The X-ray tube is mounted on a stand which is movable around an axis 21. The movement limits of the X-ray tube are delineated by line 22. The stand is mechanically fixed to the film cassette holder 23, which will move accordingly in a direction opposite to the X-ray tube. FIGS. 2b and c show exposures in the two extreme positions. As mentioned the unit is technically ad
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Lundgren Bengt
Wallner Anders
Cohen Lee S.
Schaetzle Kennedy J.
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