Biomedical subjects

Daniel Strul

Publications and source records attributed to Daniel Strul.

2 recordsLinked to original sources

PubMed2003

Monte Carlo simulations of a scintillation camera using GATE: validation and application modelling.

Geant4 application for tomographic emission (GATE) is a recently developed simulation platform based on Geant4, specifically designed for PET and SPECT studies. In this paper we present validation results of GATE based on the comparison of simulations against experimental data, acquired with a standard SPECT camera. The most important components of the scintillation camera were modelled. The photoelectric effect. Compton and Rayleigh scatter are included in the gamma transport process. Special attention was paid to the processes involved in the collimator: scatter, penetration and lead fluorescence. A LEHR and a MEGP collimator were modelled as closely as possible to their shape and dimensions. In the validation study, we compared the simulated and measured energy spectra of different isotopes: 99mTc, 22Na, 57Co and 67Ga. The sensitivity was evaluated by using sources at varying distances from the detector surface. Scatter component analysis was performed in different energy windows at different distances from the detector and for different attenuation geometries. Spatial resolution was evaluated using a 99mTc source at various distances. Overall results showed very good agreement between the acquisitions and the simulations. The clinical usefulness of GATE depends on its ability to use voxelized datasets. Therefore, a clinical extension was written so that digital patient data can be read in by the simulator as a source distribution or as an attenuating geometry. Following this validation we modelled two additional camera designs: the Beacon transmission device for attenuation correction and the Solstice scanner prototype with a rotating collimator. For the first setup a scatter analysis was performed and for the latter design. the simulated sensitivity results were compared against theoretical predictions. Both case studies demonstrated the flexibility and accuracy of GATE and exemplified its potential benefits in protocol optimization and in system design.

Algorithms↗

PubMed2002

Simultaneous PET and NMR.

There is currently great interest in combining data from different imaging modalities, either by image registration methods that are performed after the data has been acquired or using new devices that can acquire data from two modalities simultaneously, or near simultaneously. In this paper a small prototype NMR-compatible PET scanner capable of acquiring PET images simultaneously with either NMR images or NMR spectra is described. In an associated paper [1], Pamela Garlick describes some investigations of cardiac metabolism that have been made using this system. One of the main challenges in constructing an NMR-compatible PET scanner is that photomultiplier tubes, which are an essential element of nearly all current PET systems, will not function in a high magnetic field. In collaboration with Simon Cherry and the Crump Institute of Biomedical Imaging at UCLA Medical School, a small (5.4 cm diameter) NMR-compatible PET scanner that will operate within the bore of an NMR magnet has been developed. Long optical fibres are used to transport light from the scintillation crystals that form the detector head to photomultiplier tubes situated in a low magnetic field region several metres from the magnet. This system has been used to perform simultaneous PET and NMR spectroscopy measurements with a 9.4T spectroscopy system, and has also been used to obtain simultaneous PET and MR images in several MRI scanners including a 4.7T small bore animal imaging system. Current efforts in the development of this technology are directed at experimental studies on small animals, both because this is less demanding technically and because it is in this area that applications are likely to appear first. However, there is no reason in principle why human PET-MR would not be feasible. Below, work with the prototype system and the next stage in its development are described, and some of the future possibilities and challenges are discussed.

Animals↗