Slat collimator design issues for dual-head coincidence imaging systems

Joung, Jinhun; Miyoka, R.S.; Kohlmyer, S.G.; Harrison, Robert L.; Vannoy, Steven D.; Lewellen, T.K.

doi:10.1109/tns.2002.998741

Cited by 7 publications

(4 citation statements)

References 9 publications

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“…Much of the previous work on collimation in PET concerned the design of axial slats for coincidence imaging with dual-head gamma cameras (e.g. 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: 99%

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: 99%

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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“…After the invention of position sensitive photo-detectors and of high Z and density scintillating crystals with high light yield, such as LSO, many academic research groups [2][3][4] have also attempted to use continuous scintillating crystals in PET detectors. However, due to several difficulties, mainly border effects in small animal PET cameras, most of the groups end-up abandoning this idea.…”

Section: Introductionmentioning

confidence: 99%

Design and Calibration of a Small Animal Pet Scanner Based on Continuous LYSO Crystals and PSPMTs

Benlloch

Carrilero²,

Catret

et al. 2006

2006 IEEE Nuclear Science Symposium Conference Record

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We report on the design of a small animal PET scanner based on continuous LYSO crystals and Position Sensitive Photomultiplier Tubes (PSPMTs), together with the first results from the calibration. The scanner consists of eight compact modules forming an octagon and leaving a port of 110 mm aperture. Each module is made out of a continuous LYSO crystal and a PSPMT, and contains its associated electronics together with its power supply. For each module, five signals are read, summarizing all the information coming out from its 64 anode pads. Therefore, for the whole scanner only 40 signals are digitized. A calibration procedure has been implemented, measuring a spatial resolution of approximately 1.5 mm at the center of the Field of View and an energy resolution of 18%. The sensitivity of the system at the center of the Field of View, using only 4 modules, is observed to be of about 1%.

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“…Several recent abstracts have studied the effects of changing pitch (centre-to-centre spacing) while holding septal thickness and height constant, finding a moderate improvement in collimator performance near the optimal operating point (Glick et al 2001, Turkington and Sampson 2000. In a paper by Joung et al (2002), Monte Carlo simulations were used to examine several values of septal height (54, 64 and 74 mm), septal thickness (1, 3 and 5 mm) and pitch (13, 16 and 26 mm). Deadtime for a specific hybrid PET gamma camera was modelled, and the noise equivalent count rates (NECR) for several clinically relevant activity levels were used as figures-of-merit.…”

Section: Introductionmentioning

confidence: 99%

Survey of parallel slat collimator designs for hybrid PET imaging

Rust

Kadrmas

2003

Phys. Med. Biol.

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Hybrid PET gamma cameras with coincidence detection electronics are commonly equipped with parallel slat collimators in order to reduce detection of singles and scattered photons, and create a pseudo-2D imaging geometry. The objective of this work was to survey a broad range of parallel slat collimator designs using a series of Monte Carlo simulated PET acquisitions. Collimator properties including septal height, septal thickness and pitch were independently examined over a wide range of values. Simulations were performed for hybrid PET imaging of a long cylindrical phantom uniformly filled with water and radioactivity. The performance for each collimator design was evaluated in terms of the trues-to-singles ratio, scatter fraction, and noise equivalent count rate for a wide range of camera trigger rates. Results indicate that increasing septal height offers the biggest performance gain. Septal thickness should be at least 0.5 mm, and should be optimized in conjunction with pitch to obtain the best performance. This survey provides the groundwork necessary for optimizing slat collimators, and provides a starting point for investigating new slat collimator designs.

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Slat collimator design issues for dual-head coincidence imaging systems

Cited by 7 publications

References 9 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

Design and Calibration of a Small Animal Pet Scanner Based on Continuous LYSO Crystals and PSPMTs

Survey of parallel slat collimator designs for hybrid PET imaging

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