Experimental comparison of high-density scintillators for EMCCD-based gamma ray imaging

Abstract

Detection of x-rays and gamma rays with high spatial resolution can be achieved with scintillators that are optically coupled to electron-multiplying charge-coupled devices (EMCCDs). These can be operated at typical frame rates of 50 Hz with low noise. In such a set-up, scintillation light within each frame is integrated after which the frame is analyzed for the presence of scintillation events. This method allows for the use of scintillator materials with relatively long decay times of a few milliseconds, not previously considered for use in photon-counting gamma cameras, opening up an unexplored range of dense scintillators. In this paper, we test CdWO₄ and transparent polycrystalline ceramics of Lu₂O₃:Eu and (Gd,Lu)₂O₃:Eu as alternatives to currently used CsI:Tl in order to improve the performance of EMCCD-based gamma cameras. The tested scintillators were selected for their significantly larger cross-sections at 140 keV ((99m)Tc) compared to CsI:Tl combined with moderate to good light yield. A performance comparison based on gamma camera spatial and energy resolution was done with all tested scintillators having equal (66%) interaction probability at 140 keV. CdWO₄, Lu₂O₃:Eu and (Gd,Lu)₂O₃:Eu all result in a significantly improved spatial resolution over CsI:Tl, albeit at the cost of reduced energy resolution. Lu₂O₃:Eu transparent ceramic gives the best spatial resolution: 65 µm full-width-at-half-maximum (FWHM) compared to 147 µm FWHM for CsI:Tl. In conclusion, these 'slow' dense scintillators open up new possibilities for improving the spatial resolution of EMCCD-based scintillation cameras.

Spectroscopic properties of transparent Y_3Al_5O_12: Eu ceramics

“…Among some primary characteristics such as density, light yield, decay time and radiation discrimination, decay time of the scintillator has always been considered an important parameter that needs to be minimized. In most circumstances where high count-rate is required, slow scintillation will cause light pulse pile-up and background build-up in the photomultiplier tube (PMT) signal, deteriorating the energy and spatial resolution of the camera [6]. However, scintillators with long decay times of a few milliseconds can now be used with new devices other than conventional PMT-based gamma cameras, such as electronmultiplying charge-coupled devices (EMCCDs) [6].…”

Physicochemical, microbiological, rheological, and sensory properties of yoghurts with new polysaccharide extracts from Lactarius volemus Fr. using three probiotics

“…The water‐holding capacity of the yoghurt was examined by centrifugation (Heemskerk et al ) with slight modification. Yoghurt samples (~3.0 g) were measured and put into a centrifuge cup.…”

Cramer–Rao lower bound optimization of an EM-CCD-based scintillation gamma camera

“…As the QE for the back-illuminated EM-CCD is already as high as 90%, little improvement in the number of detected photons is possible by a further increase of the QE. However, an increase in the number of detected photons can also be achieved by using improved scintillation light collection efficiency (Heemskerk et al 2009) or choosing a different scintillator material to increase the scintillator light output (Heemskerk et al 2012). A resulting increase in detected photons of 50% is predicted to improve the spatial resolution by 26% and energy resolution by 33%.…”

“…Parameters considered here are EM gain, DOI, the number of detected scintillation photons and noise originating in the image area, such as dark current noise and clock-induced charge (cic) noise. Investigating the effect of the number of detected photons and noise on the performance is relevant because of the ongoing search for scintillators (Heemskerk et al 2012) and recently Diagram showing three different processes that determine the light distribution as detected by the EM-CCD; the distribution of the centroid of the energy deposition in the scintillator (gray, dotted), the light distribution in the scintillator including transmission through the optical coupling for a single optical point source (red, solid) and the minimum light spread in the optical components between scintillator and EM-CCD (green, dashed). It was assumed that a convolution of these three distributions accurately represents the mean light distribution on the EM-CCD.…”

“…Parameters considered here are EM gain, DOI, the number of detected scintillation photons and noise originating in the image area, such as dark current noise and clock-induced charge (cic) noise. Investigating the effect of the number of detected photons and noise on the performance is relevant because of the ongoing search for scintillators (Heemskerk et al 2012) and recently developed new EM-CCD electronics that can reduce the noise by more than a factor of 10 (Daigle et al 2009(Daigle et al , 2012. Trends predicted for EM gain and DOI are validated by experiments.…”