• Started on: 2005-01-01
• Field area: Medical Physics
• Cientific coordenator: João Lima
• funding:
• url:

Following the design phase performed in 2006 a prototype head with active dimensions 30x30cm, 50 glass layers and an electrical length of 2m was built. The readout was designed for simultaneous time and position measurements with resolution below 2mm and DOI accuracy of 5 mm.

A 16-channel data acquisition module that will allow the measurement of the event coordinates in the RPC volume is under development. The module is based on a high-speed Xilinx FPGA and is suitable for on-line data reduction. Due to the expected data-reduction capability, a commodity host interface like the USB 2.0 can be used and is being developed. The use of the resources available on the FPGA is also foreseen to generata a time stamp to be added to the data.

Simulations were performed using the GEANT4 simulation toolkit to access the gain in sensitivity of a PET scanner based on crystal detectors with increasing Axial Field Of View (AFOV). Similar simulations were performed for a PET scanner based on RPCs with Time Of Flight (TOF) information, and the results compared with the sensitivity of present commercial PET scanners. In both cases the sensitivity was assessed following the NEMA NU-2 1994 standard.

Based on previous work, detectors were parameterized in order to increase the speed of simulations. Simulations were validated against published experimental data.

Reading and reconstruction of the simulated data is now possible using two-dimensional algorithms. Estimates of data sizes for RPC-PET have been obtained and data compression schemes have been implemented in the list-mode to sinogram routines. The large data sizes require time-optimized processing and exact rebinning techniques plus two-dimensional iterative image reconstruction is considered the most practical approach to achieve a good compromise between image quality and processing speed. In this regard, we are implementing the exact rebinning technique FORE-J. The feasibility of correcting for scatter in RPC-PET is also being investigated using simulated data. In what concerns multimodality, an RPC-PET/CT seems feasible and desirable relative to the alternative of having activity sources for transmission measurements.

Publications

Conclusions will be drawn regarding the feasibility and interest of a full-body FOV scanner. In case of a positive conclusion, a patent registration will be considered and financement will be procured for the implementation of a much more realistic engineering prototype.

Final tests of the prototype. Conclusions.

The 16-channel data acquisition module, suitable for on-line data reduction, and its commodity host interface will be finalised and implemented in the data taking of the protopype.

A full, physically realistic simulation of a 2 m long RPC PET scanner is in preparation. This will provide accurate data on detector scatter, NEC and will provide reference data for image reconstruction.

Implementing of the FOREJ rebinning algorithm and its evaluation will take place.

Evaluation of a possible alternative (list-mode reconstruction) in terms of image quality and calculation time will also be considered.

Using simulated data, scatter and normalization corrections will be studied and implemented

Finally, estimates of reconstructed images in close to clinical conditions will be produced.