METHOD AND SYSTEM FOR ACHIEVING AN OPTIMAL RADIATION DOSE THROUGH COMPUTED TOMOGRAPHY SCANNER
Publication Date: 2009-Nov-20
The IP.com Prior Art Database
AbstractA method and system for achieving an optimal radiation dose through computed tomography scanner is disclosed. The present disclosure proposes an articulated collimator, gated source and a sequence controller to control flux rate reaching the detector of the computed tomography scanner. The articulated collimator and the gated source generate a sequence of partial illumination of a patient with control of the flux reaching the detector. The equalization of the flux at the detector further reduces radiation dose to the patient and maintains a flux rate consistent with photon counting detection.
FAULT TOLERANT SOLID-STATE PHOTOMULTIPLIER BASED PET DETECTOR
A fault-tolerant detector design that successfully mitigates the risk of Solid State Photo Multiplier (SSPM) failure in a Positron Emission Tomography (PET) detector is disclosed. The fault-tolerant detector design in one example of the present invention couples each scintillator to multiple SSPM devices. If an SSPM fails, energy and timing information is available from a pixel that is coupled to the failed SSPM.
SSPM, Solid State Photo Multiplier, Positron Emission Tomography, PET, scintillator, Scintillation crystals, PET detector, photosensor, photomultiplier tubes, PMT, pixel, photodiodes
Positron Emission Tomography (PET) is a type of nuclear medicine imaging used to examine physiologic processes within the body. Generally, for a PET scan, a radiotracer, introduced into the body, accumulates in an area of the body being examined and emits gamma rays. These gamma rays are detected by PET detectors. The PET detectors consist of scintillation crystals coupled with photomultiplier tubes (PMTs). A potential replacement for PMTs in many
applications is a Solid State Photo Multiplier (SSPM). The SSPM is a photo sensor consisting of an array of photodiodes that are connected in parallel.
A high detection efficiency, low noise, high gain, and low timing jitter of SSPMs make them attractive for PET detector applications. However, since SSPMs have only recently been developed, their long term reliability is an unknown risk. Further, typically detector designs rely on one-to-one coupling of PMT and scintillator crystals. In such a design, if an SSPM replacing the PMT fails, then all information from the corresponding pixel is lost.
The proposed technique in one example describes a fault-tolerant detector design that successfully mitigates the risk of SSPM failure. The fault-tolerant detector design couples each scintillator to multiple SSPM devices. A PET detector employing a detector design in one embodiment primarily includes 3 elements: 1) A fault-tolerant detector design; 2) A method to identify when an SSPM has failed, and then disable or ignore the failed SSPM; 3) A method to use partially redundant information from neighboring SSPMs to estimate energy and timing of events in pixels that are read-out by a failed SSPM. The third step includes estimating or measuring a new energy and timing calibration for affected pixels.
The fault-tolerant detector of the proposed techniques is applicable to many detector configurations depicted in Figures 1-3 as well as dual-end read- out configurations. Figure 1 shows a case where a single scintillator pixel is connected to multiple SSPMs (e.g.: four SSPMs). If one, two, or three SSPMs fail, energy and timing signal can still be derived from t...