TY  - JOUR
AU  - Muñoz, E.
AU  - Barrientos, L.
AU  - Bernabeu, J.
AU  - Borja-Lloret, M.
AU  - Llosa, G.
AU  - Ros, A.
AU  - Roser, J.
AU  - Oliver, J. F.
PY  - 2020
DA  - 2020//
TI  - A spectral reconstruction algorithm for two-plane Compton cameras
T2  - Phys. Med. Biol.
JO  - Physics in Medicine and Biology
SP  - 025011
EP  - 17pp
VL  - 65
IS  - 2
PB  - Iop Publishing Ltd
KW  - Compton imaging
KW  - Compton camera
KW  - hadron therapy
KW  - image reconstruction
AB  - One factor limiting the current applicability extent of hadron therapy is the lack of a reliable method for real time treatment monitoring. The use of Compton imaging systems as monitors requires the correct reconstruction of the distribution of prompt gamma productions during patient irradiation. In order to extract the maximum information from all the measurable events, we implemented a spectral reconstruction method that assigns to all events a probability of being either partial or total energy depositions. The method, implemented in a list-mode maximum likelihood expectation maximization algorithm, generates a four dimensional image in the joint spatial-spectral domain, in which the voxels containing the emission positions and energies are obtained. The analytical model used for the system response function is also employed to derive an analytical expression for the sensitivity, which is calculated via Monte Carlo integration. The performance of the method is evaluated through reconstruction of various experimental and simulated sources with different spatial and energy distributions. The results show that the proposed method can recover the spectral and spatial information simultaneously, but only under the assumption of ideal measurements. The analysis of the Monte Carlo simulations has led to the identification of two important degradation sources: the mispositioning of the gamma interaction point and the missing energy recorded in the interaction. Both factors are related to the high energy transferred to the recoil electrons, which can travel far from the interaction point and even escape the detector. These effects prevent the direct application of the current method in more realistic scenarios. Nevertheless, experimental point-like sources have been accurately reconstructed and the spatial distributions and spectral emission of complex simulated phantoms can be identified.
SN  - 0031-9155
UR  - https://doi.org/10.1088/1361-6560/ab58ad
DO  - 10.1088/1361-6560/ab58ad
LA  - English
N1  - WOS:000520111400001
ID  - Munoz_etal2020
ER  -