Design And Evaluation Of An Olfactometer For FMRI-studies

Because of good temporal and spatial resolution and non-invasive detection,functional Magnetic Resolution Imaging (fMRI) is more and more extensively usedin human brain research. At present, most fMRI experiments are based on visual andauditory stimulation task, whereas much fewer fMRI experiments are based onolfactory stimulation task. One of the reasons is lack of special olfactory stimulationdevice which is also called as the olfactometer, so that it is hard to give subjectsaccurate olfactory stimulation automatically in MRI environment. The other reasonis that olfactory sense of human is very different from visual and auditory sense, sothat the experimental design of olfactory fMRI is not as same as that of traditionalfMRI. Thus its basic principles still need to be rebuilt. In this thesis, we mainlydevelop a computer-controlled olfactometer for fMRI studies and evaluate it in anolfactory fMRI experiment. The main achievements are as follows.After studying traditional fMRI experimental design methods and the feature ofhuman’s olfactory sense, we summarize experimental design concepts of olfactoryfMRI considering stimuli, human respiration, olfactory habituation, interferentialstimulation, synchronization with imaging and so on, and conclude basicexperimental design principles of olfactory fMRI.Based on the methodological research of olfactory fMRI, we analyze thefunctional and performance requirements of an olfactometer for fMRI experiment,then design and build a fMRI olfactometer prototype which consists of “the air transport system” and “the control system”. The olfactometer can give subjects threedifferent kinds of odor stimuli automatically during one experiment. And it is withfriendly user interface, good temporal accuracy and strong electromagneticcompatibility. Besides, it is easy to make the olfactory stimulation and MRI imagingsynchronous with the device. In all, the olfactometer basically meets therequirements of olfactory fMRI experiment.We test the olfactometer prototype on a Siemens3.0T MRI scanner using1healthy subject who was stimulated with a block design paradigm including fourodors, ethanol, acetic acid, isoamyl acetate and pyridine. At last, we get theactivation area mapping of the four stimuli and the time course of signal in two ROIsunder isoamyl acetate and pyridine stimulation. The fMRI experiment demonstratesthe good functioning of the our olfactometer and the feasibility of the stimulationparadigm with20s-stimulus-duration and25s-inter-stimulus-interval. In addition, itaffirms that although with same paradigm, the activation of human brain may bevaried for different stimuli.