Real-time tomographic system with flat panel detectors

• US 6,222,902 B1
• Filed: 11/25/1998
• Issued: 04/24/2001
• Est. Priority Date: 11/25/1998
• Status: Expired due to Fees

• Current Assignee: Picker International, Inc. (Koninklijke Philips N.V.)
• Original Assignee: Picker International, Inc. (Koninklijke Philips N.V.)
• Inventors: Lin, Zhongmin, Crish, Timothy J., Plut, Leonard F.
• Primary Examiner(s): Church, Craig E.
• Application Number:
  US09/200,651
• Time in Patent Office: 881 Days
• Field of Search: 378/22, 378/21
• US Class Current: 378/22
• CPC Class Codes: A61B 6/032 Transmission computed tomography [CT]

Abstract

An object (14) is positioned on an object support (16). A radiation source (10) projects a beam of radiation through a region of interest (12) of the object. A plurality of focal planes (F₁, F₂, . . . , F_n) mark the center of selected slice images through the region of interest. A gantry (20) rotates the radiation source (10) around a circular trajectory (22) as an encoder (26) monitors a radius (r) of the trajectory and an angular position (φ) of the radiation source (10) around the trajectory (22). A look-up table (40) is addressed with the selected focal plane(s) (F₁, F₂, . . . , F_n) and (r, φ) to generate a correction or shift value (S₁, . . . , S_n.) for each selected focal plane (F₁, F₂, . . . , F_n). A flat panel detector (18) is read out a plurality of times to generate a plurality of electronic data views as the radiation source rotates. Each view is corrected with a corresponding correction or shift value and integrated in a summation circuit (50) with preceding views to generate an image representation of the slice(s) through the selected focal plane(s) (F₁, F₂, . . . , F_n) or a 3D volume. The slice image or 3D volume image representation is converted into a human-readable display (56) substantially in real-time, e.g., each time a preselected number of views has been summed.

Claims

1. An apparatus for real-time diagnostic imaging comprising:

a support for stationarily supporting a region of interest of an object to be examined;

a radiation source for projecting a beam of penetrating radiation through the region of interest;

a movable gantry for moving the radiation source with respect to the support;

a planar radiation detector which spans the region of interest for detecting the beam of penetrating radiation and converting the detected radiation into electronic data, the radiation detector being held stationary and repeatedly sampled as the radiation source moves to generate a plurality of electronic views; and

,

an image processing circuit for processing the plurality of electronic views to generate an electronic image representation of a selected slice or selected volume through the region of interest, which image representation is continuously updated as the radiation source moves.

2. The apparatus as set forth in claim 1 further including:

an encoder for monitoring a position of the radiation source;

a second encoder for monitoring a radiation source to image distance;

an electronic circuit for converting the position of the radiation source monitored by the encoder into a view correction value;

a circuit for operating on each of the plurality of electronic views in accordance with the view correction value to generate a corrected view for each of the plurality of electronic views;

a view combining device which combines each corrected view with a plurality of the corrected views previously generated to generate the continuously updated image representation.

3. The apparatus as set forth in claim 2 further including:

a first slice image memory and a second slice image memory;

a toggle circuit for connecting the view combining device with a first one of the first and second slice image memories until a preselected number of views have been combined into the image representation, and then zeroing a second one of the first and second slice image memories and connecting the view combining device with the second one of first and second slice image memories until the preselected number of views have been combined into the image representation; and

,

a video processor which is connected by the toggle circuit with the one of the first and second slice image memories in which the preselected number of views have been combined for converting the image representation stored therein into appropriate format for display on a monitor.

4. The apparatus for real-time imaging as set forth in claim 3, wherein the encoder monitors the angular position of the radiation source along its annular trajectory, further including:

a frame rate controller which monitors the encoder and changes the position of the toggle circuit after a preselected angular displacement of the radiation source along its annular trajectory; and

,

a control circuit which selectably controls a rotational drive motor which rotates the radiation source along its annular trajectory such that said preselected angular displacement corresponds to a frame rate of the video processor.

5. An apparatus for real-time diagnostic imaging comprising:

a support for supporting a region of interest of an object to be examined;

a radiation source for protecting a beam of penetrating radiation through the region of interest;

a moveable gantry which rotates the radiation source in an annular trajectory;

a radiation detector for detecting the beam of penetrating radiation and converting the detected radiation into electronic data, the radiation detector being repeatedly sampled as the radiation source moves to generate a plurality of electronic views;

an image processing circuit for processing the plurality of electronic views to generate an electronic image representation of a selected slice or selected volume through the region of interest, which image representation is continuously updated as the radiation source moves;

a slice thickness selection input device through which an operator selects a slice thickness of structure in the region of interest which contributes to a slice image;

a circuit for converting the slice thickness into a corresponding radius of the annular trajectory; and

,

a radius adjusting circuit which controls the gantry to adjust the radius of the annular trajectory.

6. An apparatus for real-time imaging of a plurality of parallel slices comprising:

a support for stationarily supporting a region of interest of an object to be examined;

a radiation source for prolecting a beam of penetrating radiation through the region of interest;

a flat panel radiation detector disposed in a fixed relationship to and spanning the region of interest for detecting the beam of penetrating radiation and converting the detected radiation into a plurality of electronic views;

a movable gantry for moving the radiation source relative to the support and the flat panel detector;

an encoder for monitoring a position of the radiation source;

an electronic circuit for converting the position of the radiation source monitored by the encoder into a view correction value;

a circuit for correcting each of the plurality of electronic views in accordance with (i) the view correction value and (ii) a different shift for each slice through the region of interest to be imaged;

a plurality of view combining circuits each combining the plurality of corrected views corresponding to one of the slices to update concurrently a plurality of slice image representations in real-time; and

,

a volume image memory for storing the plurality of slice image representations.

7. The apparatus for real-time imaging as set forth in claim 6, wherein the encoder monitors the angular position of the radiation source along its annular trajectory, further including:

a plurality of pairs of slice image memory, wherein each pair includes a first slice image memory and a second slice image memory;

a plurality of toggle circuits, each toggle circuit connecting (i) one of the plurality of view combining circuits to a corresponding slice image memory pair and (ii) the corresponding slice image memory pair to the volume image memory, wherein each toggle circuit alternately switches (i) the summed image from the corresponding view combining circuit between the first or second slice image memory of the slice image memory pair and (ii) the slice image from the opposing first or second slice image memory of the slice image memory pair to the volume image memory;

a frame rate controller which monitors the encoder and changes the position of each of the plurality of toggle circuits after a preselected angular displacement of the radiation source along its annular trajectory; and

,

a frame rate selection circuit which selectably controls a rotational drive motor which rotates the radiation source along its annular trajectory such that said preselected angular displacement is timed to coordinate with a frame rate of a video processor which converts image representations from the volume image memory into appropriate format for display on a monitor.

8. An apparatus for real-time diagnostic imagine comprising:

a support for stationarily supporting a region of interest of an object to be examined;

a radiation source for prolecting a beam of penetrating radiation through the region of interest;

a movable gantry for moving the radiation source relative to the support;

a flat panel radiation detector which spans the region of interest for detecting the beam of penetrating radiation and converting the detected radiation into electronic data, the radiation detector being held stationary and repeatedly sampled as the radiation source moves to generate a plurality of electronic views;

an encoder for monitoring a position of the radiation source;

an electronic circuit for converting the position of the radiation source monitored by the encoder into a view correction value;

a focal plane selection input device through which an operator inputs a designation of a focal plane corresponding to the selected slice, the focal plane selection input device being connected with the electronic circuit for converting monitored position into the view correction value such that the electronic circuit generates appropriate view correction values for the plurality of views for the selected slice;

a circuit for shifting each view correction value such that the electronic circuit shifts each of the plurality of electronic views in accordance with a focal plane of the selected slice, a radius of the trajectory, and an angular position along the trajectory of the radiation source; and

,

a summation circuit which combines each corrected view with a plurality of the corrected views previously generated to update the image representation with each sampled view.

9. A method of diagnostic imaging comprising:

projecting a beam of radiation through a region of interest of an object with a radiation source;

moving the radiation source relative to the region of interest;

at a stationary monitoring plane which spans the region of interest, converting the beam of radiation which has passed through the region of interest into an electronic view, the beam of radiation being converted into the electronic view a plurality of times during the relative movement the radiation source with respect to the region of interest;

selecting a focal plane through the region of interest to be imaged;

monitoring the relative movement of the radiation source and determining a view correction factor for each view in accordance with a relative position of the radiation source and the selected focal plane through the region of interest to be imaged;

correcting each view in accordance with a corresponding view correction factor;

combining the plurality of corrected views to generate an electronic slice image representation depicting radiation opacity of structures in the slice defined by the selected focal plane;

continuously combining each subsequent corrected view with the slice image representation to update the stored slice image; and

,

converting the slice image representation to video display format to view the selected focal plane as a continuously updated diagnostic image in real-time.

10. The method as set forth in claim 9 wherein:

the radiation source moves along an annular trajectory which lies in a trajectory plane, which trajectory plane is parallel to the selected focal plane which is parallel to a plane at which radiation is detected and converted into the electronic view.

11. The method as set forth in claim 9, wherein the radiation source moving step includes rotating the radiation source and further including:

coordinating a rate of rotation of the radiation source with a frame rate of the video display format.

12. The method as set forth in claim 9 wherein the relative movement includes rotation of the radiation source around a circular trajectory and further including:

selecting a thickness of the region of interest to be depicted in the slice image representation;

converting the selected thickness into a corresponding selected radius value; and

,

adjusting a radius of the circular trajectory of the radiation source to a radius corresponding to the selected radius value.

13. The method as set forth in claim 9 wherein:

correcting each generated view includes translating each view; and

,

combining each generated view includes summing the translated generated views.

14. A method of diagnostic imaging comprising:

a) moving a radiation source relative to a region of interest of an object;

b) prolecting a beam of radiation through the region of interest with the radiation source;

c) monitoring the relative position of the radiation source;

d) detecting the radiated beam after it passes through the region of interest at a stationary planar detector which spans the region of interest and generating an electronic view, the detector being sampled a plurality of times during the relative movement of the radiation source with respect to the region of interest to generate a plurality of views;

e) selecting a focal plane through the region of interest to be imaged;

f) determining a view correction factor for each view in accordance with (i) the relative position of the radiation source when the view is sampled and (ii) the selected focal plane through the region of interest to be imaged;

g) correcting each view in accordance with a corresponding view correction factor;

h) combining corrected views with a previously generated slice image representation to generate an updated slice image representation in a first image memory;

i) displaying the updated slice image representation from the first slice image memory on a monitor as subsequently generated corrected views are combined with the updated slice image representation in a second slice image memory to generate a further updated slice image representation;

j) displaying the further slice image representation from the second slice image memory as the further updated slice image representation in the first slice image memory is updated with subsequently generated views; and

,

k) alternating steps (i) and (j) in accordance with a display rate of the monitor such that the display on the monitor is continuously updated.

15. The method as set forth in claim 14, wherein the step of moving the radiation source includes rotating the radiation source along an annular trajectory and further including:

monitoring angular rotation of the radiation source along the annular trajectory; and

,

controlling the alternating step (k) to alternate between steps (i) and (j) after a preselected monitored rotation of the radiation source along the annular trajectory.

16. A system for real-time monitoring of a user selected region of interest of an object, the system including:

a radiation source for sending radiation through the user selected region of interest in the object;

a control system for controlling a thickness of a slice through the user selected region of interest during monitoring;

a stationary detector for receiving the radiation passing through the region of interest and generating image data values;

an image processing system which receives the image data values and converts the image data values into display values in real-time to display an image; and

,

a display device which receives the display values and displays the image for the user while the image processing system concurrently updates the display values with more recently generated image data values.

17. The system as set forth in claim 16, wherein the control system further includes:

a user input device;

a correlation device;

a controller; and

,

a control device wherein the user inputs a slice thickness value into the user input device which sends the thickness value to the correlation device to determine a corresponding radius value for an annular trajectory of the radiation source, the radius value is then sent to the controller to position the radiation source at the desired radius and to the control device such that the control device controls an angle at which the radiation from the radiation source passes through the region of interest in the object, wherein the angle defines the thickness of the user selected slice being monitored.

18. The system as set forth in claim 17, wherein:

the radiation source is an x-ray source and the detector is a flat panel detector;

the x-ray source is driven around a circular or oval path;

the control device adjusts a radius of the circular or oval light path to allow the flat panel detector to receive the radiation passing through the user selected region of interest of the object, where the thickness of the user selected slice is a thickness within the region of interest of the object which extends horizontally with respect to a focal plane in the object which defines the thickness axis of symmetry; and

,

the focal plane is parallel with the flat panel detector.

19. The system as set forth in claim 17, wherein:

the thickness of the user selected slice is a plane in the object which is parallel to the detector; and

,

the control device is controlled by the user during the real-time monitoring of the object to display different thicknesses in real-time correlating to the thickness value input by the user to allow continual adjusting of the thickness during the monitoring.

20. A method of diagnostic imaging comprising:

moving a radiation source relative to a region of interest of an object;

prolecting a beam of radiation through the region of interest with the radiation source;

monitoring the relative position of the radiation source;

detecting the radiated beam after it passes through the region of interest at a stationary flat panel detector which spans the region of interest;

storing the detected image as an electronic view, a plurality of detected images being stored as a corresponding plurality of views during the relative movement of the radiation source with respect to the region of interest;

selecting a plurality of focal planes;

for each focal plane, deriving a corresponding correction factor for each view in accordance with (i) the relative position of the radiation source when the view was detected and (ii) the focal plane;

correcting each view in accordance with the correction factor corresponding to each selected focal plane;

continuously and separately summing the plurality of corrected views for each selected focal plane to generate slice image representations corresponding to each slice;

storing the plurality of slice image representations in a Plurality of pairs of slice image memories, each slice image representation having a corresponding slice image memory pair, each slice image representation being alternately updated with a newly generated view in a first slice image memory as the slice image representation in a second slice image memory of the corresponding slice image memory pair is converted into a frame for display on a monitor; and

,

alternately switching the first slice image memory and second slice image memory of each slice image pair to display the updated slice image representation and update the image representation again with a yet more recently generated view.