Medical Informatics Europe 2002 G Surjdn et al. (eds) IOS Press 2002 13 A General Algorithm for Magnetic Resonance Imaging Simulation: a Versatile Tool to Collect Information about Imaging Artefacts and New Acquisition Techniques Giuseppe PLACIDI, Marcello ALECCI, and Antonello SOTGIU INFM, c/o C e n t r o I n t e r d i p a r t i m e n t a l e d i R i s o n a n z a Magnetica a n d D i p a r t i m e n t o S.T.B., Universitd dell'Aquila, Via Vetoio 10, 67010 Coppito, L'Aquila, ITALY Abstract. An innovative algorithm for Magnetic Resonance Imaging (MRI) capable of demonstrating the source of various artefacts and driving the hardware and software acquisition process is presented. The algorithm is based on the application of the Bloch equations to the magnetization vector of each point of the simulated object, as requested by the instructions of the MRI pulse sequence. The collected raw data are then used to reconstruct the image of the object. The general structure of the algorithm makes it possible to simulate a great range of imaging situations in order to explain the nature of unwanted artefacts and to study new acquisition techniques. The way the algorithm structures the sequence has also allowed the easy implementation of MRI data acquisition on a commercial general-purpose DSP-based data acquisition board, thus facilitating the comparison between simulated and experimental results. 1. Introduction In an MRI experiment several parameters are involved in the data acquisition process. In fact, a static homogeneous magnetic field, linear time-varying magnetic field gradients (one for each spatial coordinate), radio-frequency (RF) pulses and data sampling are the necessary ingredients for an acquisition sequence. An MRI sequence is strongly dependent upon the values of these parameters, the waveforms they assume, and the temporal sequence of their application. Moreover, it also depends on the sample to be imaged due to its intrinsic parameters: the relaxation times Ti and T2, the chemical shift, and the noise that the sample produces. Ultimately, the sequence is also dependent on the hardware acquisition device which drives and synchronizes the various tasks involving the sequence (switching time and shape of RF and gradient pulses, start of data acquisition) and the optimal timing between them. Due to MRI's highly parametrical nature, which makes it a very important diagnostic tool, it is the subject of continuous studies to discover innovative coding sequences which would make it possible to correct artefacts, to reduce application costs, to reduce acquisition times and to explore new applications [1]. For these purposes, several different simulation techniques have been developed [2-4]. Nevertheless, the previously proposed algorithms have been devoted to simulating particular effects, sequences, or aspects of an MRI experiment In this work, we present a general simulation algorithm for M R I which can be applied to the study of both existing and new acquisition sequences and to the artefacts they produce. The algorithm was implemented using Matlab® and simulated results are reported. Moreover, the general structure of the