ITERATIVE RECONSTRUCTION OF MULTIPLE-PEAK ISOTOPE IMAGES

Abstract

In an imaging method, estimated data is iteratively projected and backprojected. The iterative projecting and backprojecting includes projecting or backprojecting the estimated data along parallel paths each employing energy-dependent parameters appropriate for a different energy. During each iteration, the estimated data is adjusted based on comparison of the estimated data with measured data.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may take form in various components and arrangements of components, and in various process operations and arrangements of process operations. The drawings are only for the purpose of illustrating preferred embodiments and are not to be construed as limiting the invention.

FIG. 1 shows an imaging system including a gamma camera for acquiring measured data and a diagrammatically represented reconstruction processor for performing iterative image reconstruction of the measured data taking into account multiple emission energy peaks.

FIG. 2 diagrammatically shows another reconstruction processor for performing iterative image reconstruction of measured data acquired from a subject having been administered two or more radiopharmaceuticals.

Claims

1. An imaging method comprising: iteratively projecting and backprojecting estimated data, the iterative projecting and backprojecting including projecting or backprojecting the estimated data along parallel paths each employing one or more energy-dependent parameters appropriate for a different energy; andduring each iteration, adjusting the estimated data based on comparison of the estimated data with measured data.

2. The imaging method as set forth in claim 1, wherein each iteration of the iterative projecting and backprojecting includes: forward projecting an estimated image along the parallel paths each employing one or more energy-dependent parameters appropriate for a different energy and combining results of the parallel paths based on an energy ratio to generate estimated projection data;backprojecting a comparison of the estimated projection data with the measured data to generate an image correction; andadjusting the estimated image using the generated image correction.

3. The imaging method as set forth in claim 2, wherein the one or more energy-dependent parameters of each parallel path include at least one of (i) an energy-dependent scattering parameter, (ii) an energy-dependent attenuation parameter, (iii) an energy-dependent detector efficiency parameters, (iv) a collimator response parameter, (v) a lead x-ray correction parameter due to collimator material, and (vi) a scattering correction parameter for correcting for scattering within the detector.

4. The imaging method as set forth in claim 2, further including: making a parameter correction to the estimated projection data after the combining of the results of the parallel paths.

5. The imaging method as set forth in claim 2, wherein the parallel paths include first and second parallel paths corresponding to first and second different peak energies emitted by a radiopharmaceutical.

6. The imaging method as set forth in claim 2, further including: administering a radiopharmaceutical to a subject, the radiopharmaceutical including a radioisotope emitting at two or more different photon energies corresponding to the parallel paths of the iterative projecting and backprojecting; andmeasuring radiopharmaceutical emissions from the subject after administering the radiopharmaceutical to generate the measured data used for the adjusting.

7. The imaging method as set forth in claim 1, wherein the energy-dependent parameters of the parallel paths include at least one of an energy-dependent scattering parameter, an energy-dependent attenuation parameter, and an energy-dependent detector efficiency parameters.

8. The imaging method as set forth in claim 1, wherein the iterative projecting and backprojecting includes projecting the estimated data along parallel paths each employing energy-dependent parameters appropriate for a different energy.

9. The imaging method as set forth in claim 8, wherein the iterative projecting and backprojecting further includes combining results of the parallel paths based on an energy ratio.

10. The imaging method as set forth in claim 1, wherein the adjusting includes adjusting an estimated image based on an image correction generated by the comparison of the estimated data with measured projection data.

11. The imaging method as set forth in claim 1, further including: administering two or more radiopharmaceuticals to a subject, each administered radiopharmaceutical emitting at one or more photon energies, the parallel paths of the iterative projecting and backprojecting corresponding to the different photon energies of the two or more radiopharmaceuticals; andmeasuring radiopharmaceutical emissions from the subject after administering the radiopharmaceutical to generate the measured data used for the adjusting.

12. The imaging method as set forth in claim 11, wherein the administered two or more radiopharmaceuticals have generally different spatial distributions in the subject, and the iterative projecting and backprojecting further includes: iteratively projecting and backprojecting a different set of estimated data for each radiopharmaceutical, the iterative projecting and backprojecting including projecting or backprojecting the different sets of estimated data along the parallel paths.

13. The imaging method as set forth in claim 1, further including: administering a radiopharmaceutical to a subject, the radiopharmaceutical emitting at two or more different photon energies corresponding to the parallel paths of the iterative projecting and backprojecting; andmeasuring radiopharmaceutical emissions from the subject after administering the radiopharmaceutical to generate the measured data used for the adjusting.

14. The imaging method as set forth in claim 13, wherein the measuring includes: acquiring single photon emission computed tomography (SPECT) data from the subject after administering the radiopharmaceutical.

15. A computer medium or processor programmed to perform the method of claim 1.

16. An imaging system comprising: a radiation detector for acquiring measured data from a subject after having administered to the subject a radiopharmaceutical emitting at two or more different photon energies; anda reconstruction processor for performing an image reconstruction process including: iteratively projecting and backprojecting estimated data, the iterative projecting and backprojecting including projecting or backprojecting the estimated data along parallel paths each employing one or more energy-dependent parameters appropriate for a different energy, andduring each iteration, adjusting the estimated data based on comparison of the estimated data with the measured data acquired by the radiation detector.

17. The imaging system as set forth in claim 16, wherein the radiation detector includes: a gamma camera for acquiring tomographic projection data.

18. A reconstruction processor programmed to iteratively reconstruct an image from measured data, each iteration including (i) projecting or backprojecting estimated data along parallel paths each employing one or more energy-dependent parameters appropriate for a different energy and (ii) adjusting the estimated data based on comparison of the projected or backprojected estimated data with measured data.

19. The reconstruction processor as set forth in claim 18, wherein the projecting or backprojecting comprises projecting an estimated image along the parallel paths to produce projected data, and the adjusting includes: adjusting the estimated image based on comparison of the projected data with measured projection data.

20. The reconstruction processor as set forth in claim 19, wherein the measured projection data is unsorted measured projection data that is not sorted by energy, and the iterative reconstruction further includes: combining the projected data from the parallel paths and comparing the combined projected data with the unsorted measured projection data.

21. A digital storage medium encoding instructions which when executed by a processor perform reconstruction processing operations including (i) projecting or backprojecting estimated data along parallel paths each employing one or more energy-dependent parameters appropriate for a different energy and (ii) adjusting the estimated data based on comparison of the projected or backprojected estimated data with measured data.

22. An imaging method comprising: receiving projection data from an isotope which emits a first percentage of its emitted radiation at a first energy peak and a second percentage of its emitted radiation at a second energy peak;forward projecting an image estimate;operating on the forward projected image estimate in accordance with the first energy percentage and at least one of a first energy-dependent scattering correction, a first energy-dependent attenuation correction, and a first energy-dependent detector efficiency coefficient to generate a first energy corrected projected image estimate;operating on the forward projected image estimate in accordance with the second energy percentage and at least one of a second energy-dependent scattering correction, a second energy-dependent attenuation correction, and a second energy-dependent detector efficiency coefficient to generate a second energy corrected projected image estimate;comparing the received projection data with a combination of the first and second energy corrected projected image estimates to generate an estimated image correction; andcorrecting the estimated image with the estimated image correction.

23. An imaging apparatus including means for performing each of the steps of claim 22.