X-ray or gamma ray systems or devices – Specific application – Computerized tomography
Reexamination Certificate
2002-10-21
2004-04-27
Bruce, David V. (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Computerized tomography
C378S019000, C378S901000
Reexamination Certificate
active
06728331
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to a method and apparatus for CT imaging and other radiation imaging systems and, more particularly, to utilizing an enhanced scout image for diagnostic purposes.
In at least some “computed tomography” (CT) imaging system configurations, an x-ray source projects a fan-shaped beam which is collimated to lie within an X-Y plane of a Cartesian coordinate system and generally referred to as an “imaging plane”. The x-ray beam passes through an object being imaged, such as a patient. The beam, after being attenuated by the object, impinges upon an array of radiation detectors. The intensity of the attenuated beam radiation received at a detector array is dependent upon the attenuation of the x-ray beam by the object. Each detector element of the array produces a separate electrical signal that is a measurement of the beam attenuation at the detector location. The attenuation measurements from all the detectors are acquired separately to produce a transmission profile.
In known third generation CT systems, the x-ray source and the detector array are rotated with a gantry within the imaging plane and around the object to be imaged, so the angle at which the x-ray beam intersects the object constantly changes. X-ray sources typically include x-ray tubes, which emit the x-ray beam at a focal spot. X-ray detectors typically include a collimator for collimating x-ray beams received at the detector, a scintillator adjacent the collimator, and photodetectors adjacent to the scintillator. A group of x-ray attenuation measurements, i.e., projection data, from the detector array at one gantry angle is referred to as a “view”. A “scan” of the object comprises a set of views made at different gantry angles, or view angles, during one revolution of the x-ray source and detector.
In an axial scan, the projection data is processed to construct an image that corresponds to a two dimensional slice taken through the object. One method for reconstructing an image from a set of projection data is referred to in the art as the filtered back projection technique. This process converts the attenuation measurements from a scan into integers called “CT numbers” or “Hounsfield units,” which are used to control the brightness of a corresponding pixel on a cathode ray tube display.
To reduce the total scan time required for multiple slices, a “helical” scan may be performed. To perform a “helical” scan, the patient is moved in the z-axis synchronously with the rotation of the gantry, while the data for the prescribed number of slices is acquired. Such a system generates a single helix from a fan beam helical scan. The helix mapped out by the fan beam yields projection data from which images in each prescribed slice may be reconstructed.
In at least one known imaging system, a single scout image is generated by fixing the position of the x-ray source and translating the object in a z-axis direction. A resulting scout image, often called a scanogram, is similar to a plain radiography image. Using the scout image, an operator may identify anatomical landmarks.
However, the scout image generated from a single projection angle does not provide depth information regarding the object anatomy.
A plurality of scout scans are performed to generate depth information scout images of an object. Specifically, in order to generate at least one depth information scout image, the imaging system performs each scout scan at a different projection angle, or scout angle, with respect to the scanned object, e.g., patient. For example, as the patient is translated along a z-axis at a constant speed, a plurality of scout, or projection, data is collected as the position of a gantry is adjusted along a plurality of projection angles, or scout angles. However, apart from acting as a localizer, scout or projection data is not currently used for any diagnostic purposes. It should be noted that the scout is acquired using a relatively low current or very low mA. The enhanced scout in comparison is acquired at a higher mA, which is still comparable or even less than that with regular x-ray films.
Typically trauma scenarios in an emergency room (ER) setting require acquisition of preliminary C spine and L spine radiographs of trauma victims in a general rad room that is invariably followed by a CT scan in a separate CT scanner room, for example. More specifically, the protocol requires a combined set of planar x-ray films and CT scans, most likely taken in two different locations. The patient in most cases has suffered severe injury and is often greatly inconvenienced to be moved around. In addition, there is great loss of productivity in time taken in waiting for x-ray film development and waiting for the individual x-ray and CT scan stations. Complications could also develop as a result of the increased lengths of time trauma victims wait to be seen and scanned at each station.
It is therefore seen to be desirable to reduce the time expended in medical imaging in ER trauma applications. It is also desirable to reduce the waiting time between different medical imaging modalities.
BRIEF DESCRIPTION OF THE INVENTION
In one aspect, an imaging system is configured to generate a plurality of clinically useful images in a short time frame. A computed tomography system includes a computer, a gantry having a detector array, an x-ray source for radiating an x-ray beam along an imaging plane toward a detector array including a plurality of detector cells. The computer is coupled to the x-ray source and the gantry. The system is configured to generate a scout image configured to prescribe a tomographic axial/helical image or target image, process the scout image to generate an enhanced scout image, and display the enhanced scout image and target image, wherein the enhanced scout image and the target image are clinically useful images for diagnostic purposes provided by the single imaging system.
In another aspect, a processor in the imaging system is programmed to acquire projection data in a computed tomography system of an object. The processor generates a scout image configured to prescribe a target image, processes the scout projection data to generate an enhanced scout image, and displays the enhanced scout image and target image, wherein the enhanced scout image and target image are clinically useful Images for diagnostic purposes provided by the single imaging system.
In yet another aspect, a computer-readable medium in the imaging system is provided which comprises a stored program configured to generate a scout image configured to prescribe a target image, process the scout projection data to generate an enhanced scout image, and display the enhanced scout image and the target image, wherein the enhanced scout image and the target image are clinically useful images for diagnostic purposes provided by the single imaging system.
REFERENCES:
patent: 6366638 (2002-04-01), Hsieh et al.
patent: 6393090 (2002-05-01), Hsieh et al.
patent: 1220153 (2002-07-01), None
Gopinath Priya
McDaniel Holly Ann
Bruce David V.
GE Medical Systems Global Technology Company LLC
Song Hoon
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