Survey of parallel slat collimator designs for hybrid PET imaging

Rust, Thomas; Kadrmas, Dan

doi:10.1088/0031-9155/48/6/402

Cited by 9 publications

(6 citation statements)

References 12 publications

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“…Joung et al (2002) and Rust and Kadrmas (2003)). The noise equivalent count (NEC) rate on these hybrid systems suffers due to the relatively low photo-electric cross section of the sodium iodide (NaI(Tl)) scintillation crystal at 511 keV.…”

Section: Introductionmentioning

confidence: 98%

Measured count-rate performance of the Discovery STE PET/CT scanner in 2D, 3D and partial collimation acquisition modes

MacDonald¹,

Schmitz²,

Alessio³

et al. 2008

Phys. Med. Biol.

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We measured count rates and scatter fraction on the Discovery STE PET/CT scanner in conventional 2D and 3D acquisition modes, and in a partial collimation mode between 2D and 3D. As part of the evaluation of using partial collimation, we estimated global count rates using a scanner model that combined computer simulations with an empirical live-time function. Our measurements followed the NEMA NU2 count rate and scatter-fraction protocol to obtain true, scattered and random coincidence events, from which noise equivalent count (NEC) rates were calculated. The effect of patient size was considered by using 27 cm and 35 cm diameter phantoms, in addition to the standard 20 cm diameter cylindrical count-rate phantom. Using the scanner model, we evaluated two partial collimation cases: removing half of the septa (2.5D) and removing two-thirds of the septa (2.7D). Based on predictions of the model, a 2.7D collimator was constructed. Count rates and scatter fractions were then measured in 2D, 2.7D and 3D. The scanner model predicted relative NEC variation with activity, as confirmed by measurements. The measured 2.7D NEC was equal or greater than 3D NEC for all activity levels in the 27 cm and 35 cm phantoms. In the 20 cm phantom, 3D NEC was somewhat higher (~15%) than 2.7D NEC at 100 MBq. For all higher activity concentrations, 2.7D NEC was greater and peaked 26% above the 3D peak NEC. The peak NEC in 2.7D mode occurred at ~425 MBq, and was 26-50% greater than the peak 3D NEC, depending on object size. NEC in 2D was considerably lower, except at relatively high activity concentrations. Partial collimation shows promise for improved noise equivalent count rates in clinical imaging without altering other detector parameters.

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Section: Introductionmentioning

confidence: 98%

Measured count-rate performance of the Discovery STE PET/CT scanner in 2D, 3D and partial collimation acquisition modes

MacDonald¹,

Schmitz²,

Alessio³

et al. 2008

Phys. Med. Biol.

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show abstract

“…For PET image acquisitions, less attention has been paid to the design of the slicedefining septa. Most of the previous work on partial collimation systems concerns hybrid PET systems e.g., [12] and [13], where axial slats were investigated as a means of reducing random coincidences. For full ring PET scanners, Aykac et al [14] evaluated different septa designs in conjunction with a modification of their prototype high-resolution PET scanner, using the NEC metric as a figure of merit.…”

Section: Introductionmentioning

confidence: 99%

Optimization of Noise Equivalent Count Rate Performance for a Partially Collimated PET Scanner by Varying the Number of Septa

Schmitz

Harrison

Stearns³

et al. 2007

IEEE Trans. Med. Imaging

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We present a simulation study of the global count-rate performance of a positron emission tomography (PET) scanner with different levels of partial collimation to maximize the noise equivalent count rate for whole-body PET imaging. We achieve partial collimation by removing different numbers of septal rings from the standard 2-D septa set for the GE Advance PET scanner. System behavior is studied with a photon tracking simulation package, which we modify to enable the production of random coincidences. The simulations are validated with measured data taken in 2-D and fully 3-D acquisition mode on a GE Advance system using the National Electrical Manufacturers Association NU-2 count-rate phantom with two sets of annular sleeves to expand the diameter to 27 and 35 cm. For all diameters and in 2-D and fully 3-D mode, there is good agreement between measurements and simulations. All studies use the three phantom diameters to evaluate the effect of patient thickness for each amount of collimation. Optimized system parameters, such as maximum ring difference for single slice rebinning, are determined for the five partially collimated systems considered. The resulting global count rates for true, scattered, and random coincidences, the noise equivalent count (NEC) rates, and the scatter fractions for different levels of collimation are compared along with the results from the conventional 2-D and fully 3-D modes. Improved statistical data quality relative to both 2-D and fully 3-D data is found with the partially collimated systems, particularly when one-half or twothirds of the septal rings are removed. An increase in NEC rates of as much as 50% is found for clinically relevant activities between 5-10 mCi (184-370 MBq). Scatter fractions for the partially collimated systems are intermediate between the 2-D and fully 3-D numbers. Many factors that affect image quality have not been considered in this paper. However, the significant increase in

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“…Here we study the effect of different septa designs on the system performance using Monte Carlo simulations. Septa designs have been studied for conventional PET scanners [2], [3], [4], [5], [6], [7], as well as the coincidence gamma cameras [8], [9], [10]. In this work we focus on the specific application and special geometry of the prostate camera.…”

Section: Introductionmentioning

confidence: 99%

Septa design for a prostate specific PET camera

Huber

Huesman

et al. 2005

IEEE Trans. Nucl. Sci.

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Abstract-The recent development of new prostate tracers has motivated us to build a low cost PET camera optimized to image the prostate. Coincidence imaging of positron emitters is achieved using a pair of external curved detector banks. The bottom bank is fixed below the patient bed, and the top bank moves upward for patient access and downward for maximum sensitivity. In this paper, we study the design of septa for the prostate camera using Monte Carlo simulations. The system performance is measured by the detectability of a prostate lesion. We have studied 17 septa configurations. The results show that the design of septa has a large impact on the lesion detection at a given activity concentration. Significant differences are also observed between the lesion detectability and the conventional noise equivalent count (NEC) performance, indicating that the NEC is not appropriate for the detection task.

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Survey of parallel slat collimator designs for hybrid PET imaging

Cited by 9 publications

References 12 publications

Measured count-rate performance of the Discovery STE PET/CT scanner in 2D, 3D and partial collimation acquisition modes

Measured count-rate performance of the Discovery STE PET/CT scanner in 2D, 3D and partial collimation acquisition modes

Optimization of Noise Equivalent Count Rate Performance for a Partially Collimated PET Scanner by Varying the Number of Septa

Septa design for a prostate specific PET camera

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