Method and device for sensing ultrasound images

Details Method and device for sensing ultrasound images Method and device for sensing ultrasound images

2000-01-27

2001-10-30

Pihulic, Daniel T. (Department: 3662)

Communications, electrical: acoustic wave systems and devices

Acoustic image conversion

Reexamination Certificate

active

06310828

ABSTRACT:

The invention relates to a method and a device for sensing ultrasound images, more particularly for sensing and representing three-dimensional ultrasound images in real time according to the preamble of claim
1
.
Methods and devices for sensing ultrasound images of an object of this type are known, wherein an ultrasound transmitter emits ultrasound waves towards an object while an ultrasound receiver receives the ultrasound waves reflected by the object. In order to sense the object, the ultrasound transmitter or, respectively, the ultrasound receiver is moved along the object while individual image subdomains of the object are sensed. Normally, these image subdomains correspond to a line-wise scanning process sensing the object in a line-wise manner along a sensing direction in which the ultrasound transmitter or, respectively, the ultrasound receiver is moved. In the known ultrasound devices, the images generated in the ultrasound device may be taken to a post-processing device or, respectively, to a data processing system digitally or via a video output. Therein, the images may be stored or directly post-processed.
The object to be examined is sensed in a line-wise manner by the scanning process, i.e. individual parallel “layers” of the object are impinged upon with ultrasound waves and the corresponding reflected ultrasound waves are received in the ultrasound device. The received ultrasound waves are processed in a data processing system so that there results a grey value image on the display device, the individual grey values corresponding to ultrasound waves being reflected correspondingly stronger or weaker. These grey values provide information on the individual layers of the object, i.e. about the locations where the object comprises cavities or higher densified material regions, for instance.
The individual layers of the object, i.e. the individual line pictures of the ultrasound scanning process are “piled on top of each other” in the data processing system so that a three-dimensional representation of the object may be obtained on the display device. The differing spacings of different regions of a layer, i.e. the position of cavities or more densified material regions of the object, relative to the ultrasound device, are obtained via the evaluation of the grey value of each layer.
Between the ultrasound device and the object to be sensed, there is a sound medium promoting the propagation of ultrasound waves. This sound medium presents itself by a uniform grey value in the corresponding grey value image. More particularly, the outer contours of an object may be determined by detecting the first grey value changes on the boundary between the sound medium and the object to be examined in the grey value image and measuring their relative spacings to the ultrasound device.
The ultrasound methods use a predefined grey value step (threshold) or one to be calculated in order to find contours in the image. The contour information is then stored in an image and results in a three-dimensional image impression after evaluation of the distances between the ultrasound device or, respectively, the ultrasound head and the outer contours of the object to be examined.
These known ultrasound methods are for instance suitable for the examination of a foetus within the abdominal cavity of the mother or for the detection of renal calculi within the human body. In order to sense the object to be examined, which is situated within the human body, the ultrasound device is connected with the skin surface of the human body by means of a sound medium like for instance oil or water and moved along a desired sensing direction while ultrasound images are sensed in uniform time intervals. The whole scanning process extends over a specific region of the human body, individual layers of the object to be examined within the body being sensed successively during the scanning process. The individual ultrasound images are then put together in a subsequent data processing system so that there results a complete two-dimensional or three-dimensional image of the object as the individual images are “piled up”.
It is especially important in this method that the spacings between the individual “layers”, i.e. between the individual image subdomains of the object to be examined are almost constant in order to avoid any length distortion of the whole image along the sensing direction, i.e. along the scanning direction. In order to obtain a uniform sensing velocity, i.e. a uniform velocity of the ultrasound device along the sensing direction during the scanning process, the methods of the conventional type either use motor-controlled mechanisms for moving the ultrasound device or, respectively, magnetic position detectors in order to detect the respectively precise position of the ultrasound device with respect to the corresponding picture of the image subdomain, i.e. of the corresponding “layer” of the object to be examined. By detecting the precise position of the ultrasound device during the sensing of such a “layer”, the individual image subdomains, i.e. the individual “layers” of the object to be examined may later be put together realistically in the data processing system. This makes it possible to avoid image distortions along the sensing direction in conventional systems.
If the extents of individual subdomains of the object are known, like for instance the orbital cavity of a foetus, the respectively corresponding image subdomains may be allocated directly among themselves, even without any evaluation subdomain. If a continuous sensing velocity is chosen, e.ge. an espeically uniform scanning through the examining doctor, all sensed image subdomains may even be allocated among themselves without any evaluation subdomain.
U.S. Pat. No. 5,582,173 discloses another method, which subdivides the individual image subdomains into image elements after the sensing of the individual image subdomains, wherein the image elements discriminate among themselves by different grey-value-information (speckles), in order to correlate the image elements or the different grey-value-information of adjacent image subdomains, respectively, among themselves by correlation-functions, to assess the distances between the individual image subdomains among themselves or the extent of the object.
These conventional systems are disadvantageous in that the corresponding ultrasound devices must be produced in a very expensively and cost-intensive manner, that the imaging method is very cumbersome to handle and that the operator like for instance the doctor must reckon with long imaging and post-processing times during the examination of a foetus in the womb. Also, the object had to stand still relatively to the movement mechanism of the ultrasound device in order to avoid the above-mentioned image distortions. Accordingly, it had been necessary for medical applications, for instance, to fix the patient in an ultrasound device in order to be able to carry out a controlled and uniform scanning process. Also, the conventionally used mathematical calculation methods for assessing and determining the distances of the image subdomains among themselves or the extent of the object require expensive and costly data processing equipment and a time consuming data processing.
It is the object underlying the invention to improve a method of the above-mentioned type to the effect that motor-controlled mechanisms or position recognitions of the ultrasound head may be renounced and thereby to provide a simple, economical ultrasound method or, respectively, ultrasound device which is easy to handle.
Moreover, it is the object underlying the invention to specify a method for sensing ultrasound images wherein the ultrasound head may be guided and operated manually, without additional devices for the guiding or the position recognition of the ultrasound head being necessary.
The invention meets the object as specified by the features specified in the characterising portion of claim
1
. Advantageous embodiments of the invention are characterised in the

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