X-ray or gamma ray systems or devices – Specific application – Computerized tomography
Reexamination Certificate
1999-01-22
2002-07-23
Church, Craig E. (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Computerized tomography
C378S019000, C378S020000
Reexamination Certificate
active
06424692
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a diagnostic system that provides images of patients (objects) to be interpreted, and particularly tot the diagnostic system that provides the relationship between a direction (scan direction) along which a scan position is moved and an display order of tomographic images is improved. The diagnostic system is realized, for example, by an X-ray CT scanner capable of simultaneously scanning a plurality of slices of an object with scanning positions moved repeatedly, with the result that scan data of a plurality of slices are acquired at each scan position, then a plurality of tomographic images are obtained for diagnosis.
In facilities such as hospitals, an X-ray CT scanner is used as one of medical imaging modalities. The scanner includes two types of scanners referred to as a “single slice CT” and a “multi-slice CT.”
The single slice CT scanner is an imaging modality that can provide a single tomographic image by performing a single scan (a one-time scan for acquiring data necessary for image reconstruction). This CT scanner is normally used as follows. At a desired slice position, scanning is performed one time for acquiring raw data (that is, projected X-ray data or original data) of the one slice, then, for example, the tabletop on which a patient lies is moved for the next scan by a length corresponding to its slice thickness measured at the rotational center of an imaging region. At this new scan position, raw data for the adjacent or contiguous slice are acquired again. Repeating this scan and tabletop travel (alternatively, moving of the X-ray tube and X-ray detector) in sequence provides data of a plurality of tomographic images in a desired region of interest at intervals. Reconstructed tomographic images are displayed on a monitor in the reconstructed order. This scan is called “multi-scan.”
On one hand, the multi-slice CT scanner is used for providing a plurality of images by the one-time scan. The number of images are usually agreed with that of detecting element rows in the slice direction of a two-dimensional X-ray detector used. For example, if the rows are five in the slice direction, raw data (projected data) of five slices can be acquired by the one-time scan.
The multi-scan can also be applied to multi-slice CT scanners. On having obtained raw data of a plurality of slices by performing the scan one time, the tabletop on which a patient lies is then moved in a scanning direction for the next scan by a length that corresponds to a total thickness of the slices (at the rotational center of an imaging region in the gantry). This can provide at a time raw data of a plurality of slices contiguous to the last plural slices.
The raw data of the plural slices are reconstructed with a given computation technique into a plurality of tomographic images, which are then displayed in the reconstructed order on a monitor. This repetition of scans and moving of the tabletop (or, moving of an X-ray tube and a detector) for a plurality of slices provides at intervals a plurality of tomographic images in a patient's region to be diagnosed.
In CT examination, there is a diagnostic method that allows a doctor or others to interpret displayed tomographic images on a monitor, concurrently with scanning. Additionally, in the conventional CT examination, a direction (hereinafter, referred to as a scan direction) along which the scan position advances in one of the slice directions is normally fixed to a one way, but reversible. For instance, selectively driving a drive unit installed in a patient couch in either of two predetermined ways leads to arbitrary selection of the scan direction in either of a head-to-feet direction or a feet-to-head direction.
In the case that single slice CT scanners adopts a diagnostic method that allows the concurrent execution of imaging (scanning) and interpretation, it is enough that images are reconstructed in the scanned order and reconstructed images are then displayed in sequence, because only one image (tomographic image) is obtained for each scan. That is, independently from the scan directions, the diagnostic method is realized under a constant processing flow along which scanning, reconstruction, and display are carried out consecutively.
However, when such diagnostic method is applied to multi-slice CT scanners, there poses a problem described below.
Conventionally, since the scan direction has been set to one way, raw data of a plurality of slices acquired at a time by the multi-scan are reconstructed in a fixed slice position order advancing in the one way. For example, in each of three multi-scans A to C shown in
FIG. 1A
or
1
D, the reconstructing orders are always set to “slices A
1
, A
2
, A
3
, and A
4
; slices B
1
, B
2
, B
3
, and B
4
; and slices C
1
, C
2
, C
3
, and C
4
.” Thus images are reconstructed and displayed in this order.
As understood from the figures, in the case of
FIG. 1A
, the order of reconstruction and display for slices accords with the scan direction “1” and becomes the order of “A
1
, A
2
, A
3
, A
4
, B
1
, B
2
, . . . .” Because the images appear in the order complying with the scan direction “1”, interpreting a plurality of images displayed in turn becomes are easier, providing interpreters three-dimensional, internal structure of a diagnostic region in an easily understandable manner.
In contrast, when the scan direction “2” is selected, the slices in the scan direction “2” proceed in the order of “C
4
, C
3
, C
2
, C
1
, B
4
, B
3
, . . . ,” while they are displayed in the order of “C
1
, C
2
, C
3
, C
4
, B
1
, B
2
, . . . .”
In other words, as to image display, slice images farthest from the front in the scan direction precedes those at the frontal side, providing observers (or interpreters) a feeling that the displayed images are spatially reversed. It is therefore difficult for observers to easily understand or grasp an internal structure of a diagnostic region three-dimensionally. This image observation imposes very troublesome, difficult work on observers. There is a fear that accuracy in interpretation may be lowered, in addition to increased interpretation work leading to lower efficiencies in interpretation
Furthermore, due to a fixed order to reconstruct and display images, the conventional image display technique is not useful, even if an operator wants to set the order in an arbitrary or highly flexible fashion.
SUMMARY OF THE INVENTION
The present invention has been made in consideration with the above problems. And one object of the present invention is to provide a diagnostic system (by way of example, which is realized by an X-ray CT scanner) capable of displaying images according to a specified or selected scan direction in performing the multi-scan, independently from in which way the scan direction is set, thus facilitating the three-dimensional understanding of an internal structure of a patient's region to be diagnosed.
Another object of the present example is to remarkably enhance flexibility in setting an order along which images are reconstructed and then displayed in the multi-scan.
Still another object of the present invention is to not only remarkably enhance flexibility in setting a scan order along which images are displayed in the multi-scan but also display images along the scan direction, regardless of any scan direction, thus facilitating the three-dimensional understanding of an internal structure of a patient's region to be diagnosed.
In the present invention, an order to reconstruct images (i.e., resulting in the order to reconstruct and display images: referred to as “reconstruction order”) and an order to display images (referred to as “display order”) are defined. Specifying either one of the reconstruction order or the display order permits images to be displayed on a display or monitor in a desired image-display order of slices scanned. That is, the reconstruction and display orders are parameters to control the image-display order.
In order to achieve the objects, as a first aspect of t
Church Craig E.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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