New position arithmetic for scintillation camera based on floating weight system

Abstract

Over the last thirty years we have been seeing impressive advances in photodetection technology and in scintillation crystal production and manufacturing. Researchers proposed an impressive variety of small FoV scintillation cameras or detector modules for SPET and PET. The original position arithmetic based on linear weight is still widely used although this logic generates a conflict between position linearity and spatial resolution. In this paper, we propose a method of position arithmetic based on floating weights, simply utilizing non linear amplification of anode charge. The method has been tested on a continuous LaBr3:Ce scintillation crystal 51x51 mm(2) area and 4.0 mm thickness coupled to a Hamamatsu H8500 multi-anodes PMT. The charge collected on each anode was independently digitized, so to be free to apply to the charge distribution any different non linear transformation. In this way the charge around the peak is much more weighed then the remaining. As a result, we obtain a floating weighting matrix according to event interaction location. Comparing the data with the analogous ones from linear weights, it resulted a general improvement of more than 30% of position calibration slope and of spatial resolution values. Position linearity response and spatial resolution values resulted in good agreement with simulated ones. The best spatial resolution value was about 1.0 mm and position linearity resulted in close agreement with that of scintillation array

LaBr3:Ce small FOV gamma camera with excellent energy resolution for multi-isotope imaging

“…The reflective treatment of surfaces gives rise to FOV compression and spatial resolution degradation at the edges, due to the presence of light distribution tails which are reflected inwards (for a crystal with absorbent treatment of surfaces, the light distribution tails are cut off at the edges). In order to reduce these effects and obtain good imaging performances, images were reconstructed with a customized algorithm (named Raise To Power -RTP) [12]. This algorithm is a re-elaborated version of the standard centroid (Anger) method.…”

Imaging performance dependence on crystal absorption properties: the CRY018 and CRY019 comparison

“…A crystal with a full reflective surfaces treatment suffers from strong position non linearity and field of view (FoV) compression generated by the light reflection at the boundary edges that widen the light distribution. To correct these strong non linearities a modified Anger Logic is needed [12][13][14][15]. The Raise to the Power (RTP-α) algorithm has been used to reconstruct position.…”

Comparison of the imaging performances for recently developed monolithic scintillators: CRY018 and CRY019 for dual isotope gamma ray imaging applications

“…This algorithm is based on the standard centroid method [12] but differs from it because the charge collected by each anode is raised to power and a threshold is applied, after an electronic offset subtraction. In this way, the algorithm works on the light distribution shape reducing the charge spread and improving the iSR and the position linearity [11]. The position linearity and the dual isotope imaging performances have been evaluated scanning the crystals surface with double 2.5 m collimated sources ( 133 Ba-57 Co for CRY018 and 57 Co-137 Cs for CRY019) in correspondence of each anode center.…”

“…As a consequence, a wrong position estimation could arise reducing the position linearity range. Taking into account the problems encountered, a new reconstruction algorithm Raise To Power (RTP) is utilized [11]. This algorithm is based on the standard centroid method [12] but differs from it because the charge collected by each anode is raised to power and a threshold is applied, after an electronic offset subtraction.…”