X-ray or gamma ray systems or devices – Specific application – Computerized tomography
Reexamination Certificate
2003-05-15
2004-09-14
Bruce, David V (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Computerized tomography
C378S008000, C378S015000, C378S901000
Reexamination Certificate
active
06792066
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a method for controlling a tomogram acquisition device for acquiring tomograms of an examination subject, of the type wherein reference images of the subject are presented by means of a graphic user interface, and the positions of tomograms to be subsequently acquired are defined by slice position markings entered within the displayed reference images. The invention also is directed to a corresponding control device for a tomogram acquisition device as well as to a tomogram acquisition device having such a control device.
2. Description of the Prior Art
Tomograrn acquisition devices such as, for example, X-ray computed tomography systems and nuclear magnetic resonance tomography systems are primarily employed in the medical field. In most instances, the tomogram exposures serve the purpose of examining body parts or organs of a patient for a later diagnosis. They also are often employed in the context of surgical interventions. For example, German PS 198 46 687 discloses a method wherein a relatively exact three-dimensional presentation of the operation region is first recorded pre-operatively by means of a magnetic resonance apparatus. Moreover, ultrasound image data of the operation region are acquired with an ultrasound head both pre-operatively and at various points in time during the operation. Changes of the region being operated on are determined by comparing the ultrasound image data acquired at the various points in time, and the three-dimensional magnetic resonance dataset is updated on the basis of these changes and displayed. If a magnetic resonance imaging method that that produces an image of sufficient detail cannot be intra-operatively employed, this method makes it possible to generate “artificial magnetic resonance images” with the assistance of a relatively simple ultrasound acquisition method.
Further, a large variety of tomogram acquisition methods can be employed for the non-destructive examination of arbitrary, other subjects.
When using such tomogram acquisition methods, it is fundamentally desirable for optimally few exposures of the person or article under examination to be acquired so that an unambiguous, dependable examination result is achieved. This is especially important in the medical field since the examination time, what is usually uncomfortable for the patient, and possibly the radiation stress as well, can be reduced in this way. To this end, it is necessary that the positions of the tomograms to be acquired be selected such that the object of the examination within the article or person, for example a specific organ of a patient, is covered in a suitable way in the tomograms.
Particularly when examining a patient, however, the region of interest cannot always be exactly localized in advance from the outside since, first, the exact position of an organ in the body of the patient is dependent on the individual anatomy of the patient and, second, the region of the organ under examination wherein a pathological change that must be examined in greater detail is situated becomes clear only during the course of the examination.
In order to exactly position tomograms, the initially cited control method is currently generally employed. For example, standard tomograms of the test subject or of the body part to be examined, for example the head or the chest area, are first generated as reference images. The acquisition of the reference images usually ensues within the tomogram acquisition device itself. It is also possible, however, to employ tomograms generated with some other device insofar as there is a possibility of suitably positioning the patient under examination in the tomogram acquisition device on the basis of the exterior anatomy. With the assistance of suitable input means, for with a standard computer mouse, a graphics tablet, a keyboard or the like, the operator of the tomogram acquisition device can then set slice position markings within the reference images, for example in the form of section lines and/or projection presentations. In the medical field, a sagittal image, a coronary image and a transverse image are often generated as the reference images. In order to generate a simple plane within the three-dimensional examination subject, a slice position marking in the form of a section line in two of the images and a further slice position marking in the form of a projection presentation in the third image are usually required. Moreover, it is possible to set the size or the thickness of the slices. Usually, a number of slices to be acquired can be immediately marked within the reference images, for example a group of a number of parallel slices, in order to thus cover the region of the structure to be examined in the best way. This method of defining the positions of the tomograms to be acquired by means of a marking in reference images of the subject, which is rather comfortable for the user, is called “graphic slice positioning” (GSP). Further parameters required for the control of the tomogram acquisition device also can be defined for the individual tomograms to be acquired. In a magnetic resonance tomography apparatus, for example, these are the relaxation time TA and the echo time TE, etc., or for an X-ray computer tomography system, the dose to be set, etc. When the operator has set all parameters and optimally covered the measurement region with the planned slices, the measurement can be started by means of what is referred to as a “measurement queue”. The data of the slice position markings within the reference images are then converted into position data within the examination subject, and the tomogram acquisition device, or the scanner is driven such that the desired images are generated at the corresponding slice positions within the examination subject. The generated tomograms are then stored in an image databank. All measured images are directly available for further slice positioning, i.e. they can in turn be employed as reference images at the user interface in order to enter new slice position markings for further measurements.
Various methods of generating tomograms with the assistance of a graphic slice positioning are described, for example, in German OS 100 48 438 and 195 29 636.
German OS 100 48 438 discloses a method that generates a rotated presentation of the reference image dependent on a command input by a user and generates a spatial presentation of the slices on the picture screen corresponding to the rotation of the reference image. As a result, the spatial orientation of the slices that have been selected and are to be measured is visualized for the user with respect to the reference image of the measured body part of the patient. Particularly in instances of doubly inclined slice groups, the user can understand the actual situation in a simple way and judge whether the planned slices that are presented in the reference images in fact cover the region or the body part to be examined, without the user having to be exceptionally capable of imaging spatial relationships.
German OS 195 29 636 likewise discloses producing an overview exposure of the subject perpendicular to the desired slices and then graphically positioning the desired slices on the basis of the overview exposure. A 3D dataset that covers the prescribed slices is to be subsequently produced. The desired slices are then reconstructed from the 3D dataset and ultimately imaged.
A problem of all of the aforementioned methods occurs when the orientation of the subject changes perpendicularly to the desired image plane over time. In this case, the structures of interest are no longer completely imaged. The image plane therefore must be readjusted in conformity with the motion. A typical example of this is the examination of a heart valve of a patient. The position of the heart valve changes constantly due to respiration and the heart activity. A simultaneous derivation of motion information from the subject of interest for image readjustment is generall
Harder Martin
Oesingmann Niels
Bruce David V
Schiff & Hardin LLP
Siemens Aktiengesellschaft
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