Intercrystal Scatter Rejection for Pixelated PET Detectors

Ritzer, Christian; Hallen, P.; Schug, David; Schulz, Volkmar

doi:10.1109/tns.2017.2664921

Cited by 31 publications

(28 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Simulation studies indicate that our recovery performance is mainly limited by inter-crystal detector scatter, which is not included in the resolution recovery of our image reconstruction. Collimator measurements of our detector stack have shown that the crystal identification in our light-sharing detectors performs well for non-scattered events (Ritzer et al 2017). Additionally, the recovery performance improves when using higher energy thresholds at the price of degrading uniformity.…”

Section: Discussionmentioning

confidence: 96%

PET performance evaluation of the small-animal Hyperion II ^D PET/MRI insert based on the NEMA NU-4 standard

Hallen

Schug

Weissler

et al. 2018

Biomed. Phys. Eng. Express

Self Cite

View full text Add to dashboard Cite

The Hyperion IID PET insert is the first scanner using fully digital silicon photomultipliers for simultaneous PET/MR imaging of small animals up to rabbit size. In this work, we evaluate the PET performance based on the National Eletrical Manufacturers Association (NEMA) NU 4-2008 standard, whose standardized measurement protocols allow comparison of different small-animal PET scanners. The Hyperion IID small-animal PET/MR insert comprises three rings of 20 detector stacks with pixelated scintillator arrays with a crystal pitch of 1 mm, read out with digital silicon photomultipliers. The scanner has a large ring diameter of 209.6 mm and an axial field of view of 96.7 mm. We evaluated the spatial resolution, energy resolution, time resolution and sensitivity by scanning a 22Na point source. The count rates and scatter fractions were measured for a wide range of 18F activity inside a mouse-sized scatter phantom. We evaluated the image quality using the mouse-sized image quality phantom specified in the NEMA NU4 standard, filled with 18F. Additionally, we verified the in-vivo imaging capabilities by performing a simultaneous PET/MRI scan of a mouse injected with 18F-FDG. We processed all measurement data with an energy window of 250 keV to 625 keV and a coincidence time window of 2 ns. The filtered-backprojection reconstruction of the point source has a full width at half maximum (FWHM) of 1.7 mm near the isocenter and degrades to 2.5 mm at a radial distance of 50 mm. The scanner’s average energy resolution is 12.7% (ΔE/E FWHM) and the coincidence resolution time is 609 ps. The peak absolute sensitivity is 4.0% and the true and noise-equivalent count rates reach their peak at an activity of 46 MBq with 483 kcps and 407 kcps, respectively, with a scatter fraction of 13%. The iterative reconstruction of the image quality phantom has a uniformity of 3.7%, and recovery coefficients from 0.29, 0.91 and 0.94 for rod diameters of 1 mm, 3 mm and 5 mm, respectively. After application of scatter and attenuation corrections, the air- and water-filled cold regions have spill-over ratios of 6.3% and 5.4%, respectively. The Hyperion IID PET/MR insert provides state-of-the-art PET performance while enabling simultaneous PET/MRI acquisition of small animals up to rabbit size.

show abstract

Section: Discussionmentioning

confidence: 96%

PET performance evaluation of the small-animal Hyperion II ^D PET/MRI insert based on the NEMA NU-4 standard

Hallen

Schug

Weissler

et al. 2018

Biomed. Phys. Eng. Express

Self Cite

View full text Add to dashboard Cite

show abstract

“…To the best of our knowledge, there is no preclinical PET scanner with a better CTR than the reported 194 ps (FWHM) at low activity [16]- [27]. The majority of the 511-keV gamma rays are scattered in the LYSO crystals [28], [29]. Therefore, some of these scattered rays escape the original crystal of interaction and interact again in neighboring crystals.…”

Section: B Pet Resultsmentioning

confidence: 99%

Initial Characterization of the SAFIR Prototype PET-MR Scanner

Ritzer

Becker

Buck

et al. 2020

IEEE Trans. Radiat. Plasma Med. Sci.

Self Cite

View full text Add to dashboard Cite

The SAFIR collaboration is currently developing a high-rate positron emission tomography (PET) insert to study fast kinetic processes in small animals. Our insert is designed for simultaneous image acquisition with a preclinical 7 T magnetic resonance (MR) imaging device. In contrast to existing preclinical PET scanners and inserts, our hardware is optimized for high-rate measurements with source activities up to 500 MBq. As a first step, the SAFIR Prototype insert was constructed. This already incorporates the final components, but has a reduced axial field-of-view (35.6 mm). We use lutetiumyttrium oxyorthosilicate crystals (2.12 mm × 2.12 mm × 13 mm) one-to-one coupled to silicon photomultipliers. All analog signals are digitized within the insert. We use 49 MR-compatible dcdc converters in the insert to provide the power to all readout electronics. After shimming, no degradation of the homogeneity of the static B 0 field in the MR scanner was observed. During full operation, we saw a minor reduction in the signal-to-noise ratio of the MR data of 4.9%. With a low activity point source ( 22 Na 0.65 MBq) we obtained a coincidence energy resolution of 13.8% full width at half maximum (FWHM) and a coincidence timing resolution of 194 ps (FWHM). First PET/MR rat brain and high-rate mouse cardiac images (84.9 MBq) are shown in this article.

show abstract

“…Currently, collimated gamma beams are mainly employed for the calibration of monolithic scintillation detectors. As recently shown, collimated gamma beams give additional insights for pixelated arrays as well [40]. A pinhole collimator was used to study general characteristics of Compton scatter for a single highly segmented crystal to identify and exclude such gamma interactions on system level.…”

Section: Discussionmentioning

confidence: 99%

“…The gamma photons' beam profile for slit widths of 0.4 mm and 1 mm was measured by step-wise moving the edge of the detector under study into the beam as presented in [11] and [40]. The profile b(y) is given by a discrete derivative of the count rate m(y) at the measurement points y i as…”

Section: B Experimental Beam Characterizationmentioning

confidence: 99%

Characterization and Simulation of an Adaptable Fan-Beam Collimator for Fast Calibration of Radiation Detectors for PET

Hetzel

Mueller

Grahe

et al. 2020

IEEE Trans. Radiat. Plasma Med. Sci.

Self Cite

View full text Add to dashboard Cite

Monolithic scintillators for positron emission tomography systems perform best when calibrated individually. We present a fan-beam collimator with which a crystal can be calibrated within less than 1 h when suitable positioning algorithms are applied. The collimator is manufactured from lead, features an easily adaptable slit to tune the beam width and can be operated together with a coincidence detector to select a clean sample of 511-keV annihilation photons. We evaluated the performance of the collimator with a Geant4 simulation for slit widths of 0.25 mm, 0.4 mm, and 1 mm and validated the shape of the beam profile experimentally by step-wisely moving a detector into the beam. This shows a clear narrow and box-shaped beam profile even if the collimator is operated without the coincidence setup. In the latter configuration, the fraction of gammas in the beam region on a 50×50 mm 2 large detector is between 48% and 79% which is improved significantly to more than 94% by using only coincidence events. Analyzing the energy distribution shows that the fraction of 511-keV photons is increased from less than 50% to more than 96% by selecting coincidences.

show abstract

Intercrystal Scatter Rejection for Pixelated PET Detectors

Cited by 31 publications

References 20 publications

PET performance evaluation of the small-animal Hyperion II ^D PET/MRI insert based on the NEMA NU-4 standard

PET performance evaluation of the small-animal Hyperion II ^D PET/MRI insert based on the NEMA NU-4 standard

Initial Characterization of the SAFIR Prototype PET-MR Scanner

Characterization and Simulation of an Adaptable Fan-Beam Collimator for Fast Calibration of Radiation Detectors for PET

Contact Info

Product

Resources

About

Intercrystal Scatter Rejection for Pixelated PET Detectors

Cited by 31 publications

References 20 publications

PET performance evaluation of the small-animal Hyperion II D PET/MRI insert based on the NEMA NU-4 standard

PET performance evaluation of the small-animal Hyperion II D PET/MRI insert based on the NEMA NU-4 standard

Initial Characterization of the SAFIR Prototype PET-MR Scanner

Characterization and Simulation of an Adaptable Fan-Beam Collimator for Fast Calibration of Radiation Detectors for PET

Contact Info

Product

Resources

About

PET performance evaluation of the small-animal Hyperion II ^D PET/MRI insert based on the NEMA NU-4 standard

PET performance evaluation of the small-animal Hyperion II ^D PET/MRI insert based on the NEMA NU-4 standard