X-ray or gamma ray systems or devices – Specific application – Absorption
Reexamination Certificate
2001-09-14
2002-11-05
Bruce, David V. (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Absorption
C378S051000, C382S132000
Reexamination Certificate
active
06477228
ABSTRACT:
SUMMARY OF THE INVENTION
1. Field of the Invention
The invention relates to a method for operating an X-ray diagnosis device for producing X-ray images using an X-ray appliance, for processing the X-ray images using a computation unit and for displaying the X-ray images using a reproduction apparatus.
2. Background of the Related Art
In X-ray departments for general radiography and for mammography, the capability to display the recorded image or images immediately is a major advantage in the course of X-ray examination (workflow). With the sheet-film or memory-film-based cassette systems that are normally used, several minutes typically pass before the image can be viewed. In one case, the film must be developed, and in the other case the memory film must be read in a reader. Until this has been done, it is impossible to decide whether the record has survived the recording technique, and the patient can leave the examination area. Additional time is therefore consumed in the event of incorrect exposures, and this interferes with and/or slows down the workflow.
It is advantageous to minimize the time between making the record and the first opportunity for assessing it because this speeds up the decision as to whether the records are technically good or whether they may need to be repeated. Fast verification is thus a considerable aid to a better workflow.
FIG. 1
shows an X-ray diagnosis device which is known from German patent document DE 195 27 148 C1 having an X-ray tube
2
which is supplied with high voltage and heating voltage from a high-voltage generator
1
and which produces a conical X-ray beam
3
, which passes through a patient
4
and produces beam images on an X-ray detector
5
which is sensitive to X-ray radiation
3
. The output signal from the X-ray detector
5
, the image data
6
, is supplied to an imaging system
7
. The imaging system
7
may have converters, image stores and processing circuits, and is connected to a monitor
8
for reproduction of the detected X-ray images. Control elements
9
are connected via a system controller and system communication
10
to the other components of the X-ray diagnosis device.
FIG. 2
shows a perspective cross section of the X-ray detector
5
. The core components of the X-ray detector
5
comprise a solid-state pixel matrix, line drivers and amplifiers. The solid-state pixel matrix is composed, for example, of a layer with a scintillator
11
, for example composed of cesium iodide (CsI), which, when illuminated by the X-ray radiation
3
, feeds visible photons to a pixel matrix
12
composed of amorphous silicon, and these produce a visible X-ray image. Each of the pixels or picture points in the pixel matrix
12
comprises, as is shown on an enlarged scale in
FIG. 2
, a photodiode
13
and a switch
14
, which is connected to row lines
15
and column lines
16
. The pixel matrix
12
is applied to a glass substrate
20
.
All of the pixels in a row are in each case addressed and read simultaneously by the line drivers
17
. In the simplest case, an image is read progressively, line by line. The signals are supplied to a processing circuit
18
, in which the signals are processed in parallel in a large number of amplifiers, are joined together by multiplexers, and are converted in an analog/digital converter (A/D converter) to a digital output signal for further digital processing.
The image information is converted in an X-ray converter, for example cesium iodide (CsI) by way of these solid-state detectors for X-ray imaging, which were developed some years ago and are based on active read matrices composed, for example, of amorphous silicon (a-Si). This image information is stored as an electrical charge in the photodiodes of the matrix, and is then read out and converted from analog to digital via an active switching element having dedicated electronics. These detectors, or else other digital detectors or detectors based on CCDs, are used to send an image directly to the imaging station, the imaging system
7
and the monitor
8
, and it is thus in principle possible to produce an immediate image, which provides the recording technician or medical practitioner with the required feedback that the record is correct within a very short time (a few seconds).
However, in practice, the detector initially provides only a raw image, which cannot be viewed as such. A range of preprocessing steps, such as offset, gain and defect correction and postprocessing steps such as dynamic range matching, grey-scale mapping, grey-scale inversion, filtering of widely different types and windowing must be carried out in the imaging system
7
before the image is in the desired form and can be assessed. Since the image matrices for general digital radiography and mammography comprise several thousand pixels in both directions (for example 3000×3000 or more), large amounts of data need to be processed. If one does not wish to use special expensive hardware, times of 30 seconds or more are required with present-day standard PC-based technology—depending on the processing complexity. These long times are not acceptable. Since, in general, the complexity of the algorithms increases linearly with the improvement in computer performance, this problem will likely not be resolved.
European patent document EP 0 567 174 B1 discloses a method and an apparatus for reproducing X-ray images, in which the original data (raw images) are supplied to a digital processor, and as a security copy to a workstation, after logarithm formation and quantization, from a read apparatus for storing fluorescent materials. The image processor reduces the amplitude by clipping so that the images can be recorded on a film.
The images provided for recording are reproduced on a preview monitor. If the detected image is intended to be recorded just on one image, then this image is also reproduced completely, without reduction. If, on the other hand, a number of images are intended to be recorded like a mosaic on a film, then the number of pixels and hence the resolution of the images are correspondingly reduced. These mosaic images are reproduced on the preview monitor and, provided the viewer accepts the records, can be stored as a hard copy on the film in this reduced form.
SUMMARY OF THE INVENTION
The invention is based on the object of providing a method for operating an imaging system by using a large-area image detector of the type mentioned above that permits an assessment immediately after image production as to whether the record has been correctly exposed and includes the object completely.
According to the invention, the object is achieved by the following steps: converting the X-ray images into images with low resolution; processing the images with low resolution with images and/or parameters matched to the reduced resolution; immediately reproducing the images with low resolution; subsequently processing the X-ray images with parameters for full resolution, and reproducing the X-ray images with full resolution.
This method means that the individual preprocessing and postprocessing steps are considerably speeded up, with a low level of processing performance and a minimal amount of time involved, with the amount of data being reduced using suitable undersampling, so that images can be reproduced with low resolution on the monitor
8
in a very short time (for example, within a few seconds of the production of the X-ray images from the raw images); this makes it possible to see whether the record has all the features required for diagnosis, i.e., whether the record has been correctly exposed and contains the object completely.
According to the invention, preprocessing of the X-ray images with parameters for full resolution can be carried out at the first step. The X-ray images can be undersampled in order to convert the X-ray images, according to the invention, to images with low resolution. The parameters entered for preprocessing and image processing may advantageously be the images required for this purpose, parameters such as the sampling depth, t
Bruce David V.
Hobden Pamela R.
Schiff & Hardin & Waite
Siemens Aktiengesellschaft
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