Computer tomograph having means for displaying shadowgraphs

• US 5,315,628 A
• Filed: 06/09/1993
• Issued: 05/24/1994
• Est. Priority Date: 06/24/1992
• Status: Expired due to Term

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Guendel, Lutz
• Primary Examiner(s): Porta, David P.
• Application Number:
  US08/073,515
• Time in Patent Office: 349 Days
• Field of Search: 378/4, 378/20, 378/8, 378/14, 378/62, 378/205, 378/207, 378/146
• US Class Current: 378/20
• CPC Class Codes: A61B 6/032 Transmission computed tomography [CT]
• CPC Class Codes: A61B 6/0487 Motor-assisted positioning
• CPC Class Codes: A61B 6/4435 the source unit and the detector unit being coupled by a rigid structure
• CPC Class Codes: A61B 6/5223 generating planar views from image data, e.g. extracting a coronal view from a 3D image
• CPC Class Codes: H05G 1/60 Circuit arrangements for obtaining a series of X-ray photographs or for X-ray cinematography

Abstract

A medical imaging apparatus includes a measurement unit with an x-ray source and a radiation detector rotatable around an examination subject to conduct a scan of the examination subject and thereby to obtain a data set, which is supplied to a computer. Within the computer, a shadowgraph of the examination subject is calculated in real time as the examination subject is displaced during the scan relative to the measurement unit. The data used to construct the shadowgraph are obtained at a selected projection angle, which is reached a number of times by the measurement unit during the scan. The shadowgraph is displayed in real time as well, to an extent correlated with the amount of relative displacement between the examination subject and the measurement unit. The shadowgraph can be calculated using a convolution equation, wherein the data are twice convolved, once in the longitudinal direction, i.e., the direction of displacement between the examination subject and the measurement unit, and once in a direction corresponding to the direction along which the radiation detector extends. A standard computer tomogram can also be calculated from the same data set from which the data for calculating the shadowgraph are selected.

Claims

1. A medical imaging apparatus comprising:

measurement means for conducting a scan of an examination subject, said measurement means including an x-ray source and a radiation detector rotatable around said examination subject for irradiating said examination subject with an x-ray beam from said x-ray source at at least one projection angle, said radiation detector generating electrical output signals corresponding to radiation incident thereon at each projection angle;

means for effecting relative longitudinal displacement between said measurement means and said examination subject;

means for calculating a shadowgraph of said examination subject in real time as said relative longitudinal displacement takes place, from output signals with said measurement means disposed at a selected projection angle a plurality of times during said scan; and

means for displaying said shadowgraph, as said shadowgraph is calculated, to an extent correlated with the amount of relative longitudinal displacement between said examination subject and said measurement means.

2. A medical imaging apparatus as claimed in claim 1 wherein said measurement means includes an x-ray source and a radiation detector rotatable around said examination subject for irradiating said examination subject with an x-ray beam from said x-ray source at a plurality of projection angles, and further comprising means for calculating and displaying a tomographic image of said examination subject from said output signals.

3. A medical imaging apparatus comprising:

measurement means for conducting a scan of an examination subject, including an x-ray source and a radiation detector rotatable around an examination subject for irradiating said examination subject with an x-ray beam from said x-ray source at at least one projection angle, said radiation detector extending in a direction designated β and

generating electrical output signals corresponding to radiation incident thereon at each projection angle;

means for effecting relative displacement in a longitudinal direction between said measurement means and said examination subject;

means for calculating a shadowgraph of said examination subject in real time as said relative displacement takes place by convolution of said output signals, with said measurement means disposed at a selected projection angle a plurality of times during said scan, according to the equation;

##EQU2## wherein l denotes the index in the β

-direction, k denotes the index in the longitudinal direction, χ

denotes the numerical index for the convolution, u_l (k) denotes the output signals convolved in the β

-direction, b_l (k) denotes the output signals additionally convolved in the longitudinal direction, h denotes the convolution core and n denotes the degree of the convolution core; and

means for displaying said shadowgraph, as said shadowgraph is calculated, to an extent correlated with the amount of relative displacement between said examination subject and said measurement means.

4. A medical imaging apparatus as claimed in claim 3 wherein said measurement means includes an x-ray source and a radiation detector rotatable around said examination subject for irradiating said examination subject with an x-ray beam from said x-ray source at a plurality of projection angles, and further comprising means for calculating and displaying a tomographic image of said examination subject from said output signals.