Collimation of a /sup 137/Cs point source for transmission scanning in PET

et al. 2008

IEEE Trans. Nucl. Sci.

3D Continuous Emission and Spiral Transmission (CEST) scanning provides a high-throughput whole-body PET study by using two dedicated detectors for 3D emission and singles transmission, together with continuous bed movement. To supress the amount of transmission scatter components (TSC) in singles transmission data, the transmission detector was designed to have a short axial extent with a highly collimated 137 Cs point source, and to remove the amount of emission contamination (EC) in post-injection scanning, real-time EC correction was implemented. However, transmission images can be still affected by residual EC and TSC, depending on patient size and injected dose. This produces slight variations in attenuation coefficients, depending on the patient's axial and radial positions.In this study, we developed a new soft-tissue segmentation (STS) method based on histogram scaling at each axial position of the spiral transmission. Peaks, corresponding to soft-tissue in a histogram of attenuation coefficients, were found at each axial position and the transmission image was scaled using the ratio of softtissue histogram peaks to the theoretical water attenuation coefficient. In scaled transmission images, pixel values near soft-tissue peaks were replaced with their theoretical water attenuation coefficients. Quantitative evaluation of the transmission images obtained was performed under various acquisition conditions, both with and without the proposed STS method. Final imaging performance evaluations included quantification of emission images reconstructed using both STS attenuation correction and hybrid scatter correction. Results showed that the proposed STS method for spiral transmission scanning provided quantitative images that contained activity, independent of object size.

Section: T He Continuous Emission and Spiral Transmission (Cest)mentioning

confidence: 99%

Implementation of Histogram Based Soft-Tissue Segmentation for Single Spiral Transmission Scanning in Whole Body PET

et al. 2008

IEEE Trans. Nucl. Sci.

“…The source rotation speed is 3 seconds per rotation, and, since the point source is highly collimated axially, the emission scanner's background coincidence rate from the transmission source is considered to be negligible. Axial collimation also decreases the scatter fraction of the transmission data and provides more accurate attenuation values [7].…”

Section: A Scanner Configurationmentioning

confidence: 99%

Retrospective Respiratory Motion Compensation Under Deep Breathing in Spiral Transmission Scanning of 3D PET

2006 IEEE Nuclear Science Symposium Conference Record

et al. 2006

3D Continuous Emission and Spiral Transmission (CEST) scanning can minimize respiratory motion artifacts inherent in normal free breathing, due to the averaging of emission and transmission images over multiple breathing cycles during the stay time of axial detector rings. However, under deep breathing, which is synchronized approximately with the rotation speed of the transmission source, mushroom-shaped artifacts are produced occasionally where the diaphragm and lung intersect. In this work, we have developed a retrospective respiratory motion-compensation method applied to transmission data which was acquired using six detector rings under deep breathing. Our scheme uses a hybrid compensation method that is based on the filtering and summation of different time-stamp images (FDT) and the filtering of sharp edges (FSE) in the axial plane. FDT calculates the deviations from the average image produced using six time-frame images. FDT first identifies pixels in six time frames whose deviations are over the predetermined threshold, then replaces those pixel values with the minimumdeviation pixel value. Since the bed moves continuously through these detector rings, the six time-frame images can be obtained by reconstructing the six transmission sinograms acquired by each detector ring. After FDT compensation is applied, FSE detects residual sharp edges in the axial direction and applies median filtering, using widths calculated based on edge sharpness. We evaluated this method using patient data that displayed artifacts at the intersection of the diaphragm and lung. These results show that this proposed method provides a practical means to significantly reduce artifacts without using a respiratory gating device.

“…Since the point source is highly collimated axially, the background coincidence rate of the emission scanner from the transmission source is considered to be negligible. Axial collimation also decreases the scatter fraction of the transmission data and gives more accurate attenuation value [4]. As shown in a photograph of SET-3000G/X scanner in Figure 2, the gantry size is relatively small even though it contains the two scanners and all electronics including signal processing and coincidence circuits.…”

Section: Introductionmentioning

confidence: 99%

3D continuous emission and spiral transmission scanning for high-throughput whole-body PET

IEEE Symposium Conference Record Nuclear Science 2004.

et al.

In order to achieve high-throughput whole-body PET studies, we have developed 3D Continuous Emission and Spiral Transmission (CEST) scanning for a newly developed PET scanner: SET-3000G/X. In this method, the patient couch moves continuously through the emission and dedicated transmission scanners separated axially by a lead shield. Transmission single data are acquired with a rotating 137 Cs point source as spiral fan-beam data with emission singles contamination correction. These data are sequentially rebinned and reconstructed to estimate 3D attenuation table for 511 keV photons. Emission 3D coincidence data are acquired in histogram mode with on-the-fly attenuation correction and Fourier rebinning at each axial sampling. Attenuation corrected 3D emission images can then be obtained in a single continuous bed movement. The CEST acquisition has the potential of reducing whole body acquisition times significantly while improving the data processing efficiency.