HIGH CONTRAST IMAGING AND FAST IMAGING RECONSTRUCTION

• US 20110194747A1
• Filed: 10/06/2009
• Published: 08/11/2011
• Est. Priority Date: 10/10/2008
• Status: Active Grant

• Current Assignee: Koninklijke Philips N.V.
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Wieczorek, Herfried Karl
• Granted Patent: US 8,781,198 B2
• Time in Patent Office: Days
• US Class Current: 382/131
• CPC Class Codes: G06T 11/006 Inverse problem, transformation from projection-space into object-space, e.g. transform methods, back-projection, algebraic methods
• CPC Class Codes: G06T 2207/10104 Positron emission tomography [PET]
• CPC Class Codes: G06T 2207/10108 Single photon emission computed tomography [SPECT]
• CPC Class Codes: G06T 2207/20056 Discrete and fast Fourier transform, [DFT, FFT]
• CPC Class Codes: G06T 2211/416 Exact reconstruction
• CPC Class Codes: G06T 2211/424 Iterative
• CPC Class Codes: G06T 5/10 using non-spatial domain filtering
• CPC Class Codes: G06T 5/94 based on local image properties, e.g. for local contrast enhancement

Abstract

When reconstructing low-collimation nuclear scan data (18) (e.g., SPECT) into a nuclear image volume (19), a spatial frequency-dependent (SFD) filter function is applied in Fourier space to the reconstructed image (19) to improve image resolution given a predefined number of reconstruction iterations and/or to reduce the number of reconstruction iterations required to achieve a predetermined level of image resolution. Size of an object to be imaged is determined, and the SFD filter function is determined or generated based on signal power spectrum (and/or modulated transfer function) data, object size, and desired image quality (or number of reconstruction iterations). The SFD filter function amplifies higher-energy components (e.g., corresponding to a lesion or tumor, or the like) of the spatial frequency spectrum to improve viability in a low collimated nuclear image (19) using fewer reconstruction iterations.

Claims

1. A nuclear image optimization system, including:

a nuclear scanner that acquires nuclear scan data of a volume of interest (VOI), and having one or more collimators that provide a low level of collimation during nuclear scan data acquisition;

an object size detector that determines a size of the VOI;

a filter function library having a lookup table that identifies one or more object size-dependent filter functions for each of a plurality of object sizes; and

a processor that performs an iterative reconstruction algorithm, executes the object size-dependent filter function after executing a predetermined number of reconstruction algorithm iterations, and outputs an enhanced nuclear image volume representation.

2. The system according to claim 1, wherein the object size-dependent filter function is a spatial frequency-dependent (SFD) filter function and is applied to the image volume after the predetermined number of reconstruction algorithm iterations.

3. The system according to claim 2, wherein the processor generates the SFD filter function based on at least one of signal power spectrum data and modulation transfer function (MTF) data acquired from nuclear scan data of the VOI or from scan data acquired on appropriate test phantoms.

4. The system according to claim 1, wherein the object size detector determines object size using at least one of a proximity sensor, a camera sensor, a laser gauge, a computed tomography (CT) imaging device, the acquired nuclear scan data, or angular dependence of the object size in respective transaxial slices of the acquired nuclear scan data.

5. A method of increasing image reconstruction speed for a predetermined number of reconstruction iterations, including:

acquiring scan data of an object;

determining a size of the object;

identifying an object size-dependent filter function for application to a reconstructed image of the object based on the object size and the predetermined number of reconstruction iterations;

performing the predetermined number of reconstruction iterations to reconstruct an image of the object;

applying the object size-dependent filter function to the reconstructed image after a selected number of reconstruction iterations to enhance resolution; and

storing the enhanced reconstructed image to memory.

6. The method according to claim 5, wherein the object size-dependent filter function is a spatial frequency-dependent (SFD) filter function and is applied in Fourier space.

7. The method according to claim 6, wherein the scan data is nuclear scan data acquired using a low collimation technique.

8. The method according to claim 7, further including:

generating one or more SFD filter functions based on object size and on the predetermined number of reconstruction iterations.

9. The method according to claim 8, further including:

analyzing at least one of signal power spectrum (SPS) data and modulation transfer function (MTF) data when generating the one or more SFD filter functions; and

determining at least one corner frequency for each SFD filter function from the analyzed spectrum data.

10. The method according to claim 8, further including:

storing the one or more SFD filter functions to a filter function library for subsequent lookup when identifying an SFD filter function for a determined object size and number of reconstruction iterations.

11. A computer-readable medium having stored thereon software for controlling one or more computers to perform the method according to claim 5.

12. A processor programmed to control one or more computers configured to perform the method of claim 5.

13. A single photon emission computed tomography (SPECT) scanner including a processor programmed to perform the method of claim 5.

14. A method of decreasing a number of reconstruction iterations executed to achieve a desired level of image resolution, including:

acquiring low-collimation nuclear scan data of an object;

determining a size of the object;

identifying an object size-dependent filter function for application to a reconstructed image of the object based on the object size and the desired image resolution;

performing a number of reconstruction iterations to reconstruct a nuclear image of the object;

applying the object size-dependent filter function during reconstruction to enhance resolution; and

storing the enhanced reconstructed image to memory.

15. The method according to claim 14, wherein the object size-dependent filter function is a spatial frequency-dependent (SFD) filter function and is applied in Fourier space.

16. The method according to claim 15, further including:

generating one or more SFD filter functions based on object size and on the predetermined number of reconstruction iterations and evaluation of at least one of signal power spectrum (SPS) data and modulation transfer function (MTF) data for the object; and

determining at least one corner frequency for each SFD filter function from the analyzed spectrum data.

17. The method according to claim 16, further including:

storing the one or more SFD filter functions to a filter function library for subsequent lookup when identifying an SFD filter function for a determined object size and number of reconstruction iterations.

18. The method according to claim 14, wherein object size is determined as a function of pixel count for the object.

19. A computer-readable medium having stored thereon software for controlling one or more computers to perform the method according to claim 14.

20. A processor programmed to control one or more computers configured to perform the method of claim 14.

21. A single photon emission computed tomography (SPECT) scanner including a processor programmed to perform the method of claim 14.