Abstract
Ultrasound is a common medical imaging modality. The ultrasound examination is performed by placing an ultrasound probe on the skin of the patient, as close as possible to the part of the body that is of clinical interest. In order to image the inner organs, it is important to position the ultrasound probe so that there are no obstacles between the probe and the organ or tissue of interest, e.g. no ribs, lungs or bowel gas. Ribs and gas filled spaces produce shadows which may give poor images of the part of the body that is studied. In addition, the image quality of ultrasound images is affected by e.g. a grainy pattern called speckle, caused by interference of tissue structures that are too small to be imaged individually, and by ultrasound attenuation which reduces the ability to detect organs deep inside the body. Ultrasound imaging is routinely used for diagnosis of e.g. the heart and vascular system, the foetus and the inner organs of the abdomen. In order to learn how to obtain ultrasound images of the organs of interest without obstruction by shadows and to correctly interpret the images despite e.g. speckle and attenuation, training is necessary. Training is often performed in a setting where the trainee is instructed and guided by an experienced ultrasound operator how to image and diagnose a patient or healthy volunteer. Among the disadvantages of this way of instruction are that it can be unpleasant for the patient, that it can be difficult to find the right patient cases at the time of training, and that the experienced ultrasound users and ultrasound equipment are busy training students instead of working in the clinic. In order to overcome some of these disadvantages, the ultrasound simulator has been proposed as a part of ultrasound training. Advantages of simulator training are that it allows for training on many patient cases, encourages learning by trial and error, can include many normal and pathological patient cases, poses no threats to the comfort of the patient, and frees time for the professional practitioner and the actual ultrasound equipment. One important part of the ultrasound simulator is the simulated ultrasound-like image. The aim of the PhD project was to simulate ultrasound-like images that could be used in a simulator for detection of free fluid by ultrasound, using the procedure Focused Assessment with Sonography in Trauma (FAST). The methods that were developed, produced ultrasound-like images at a realistical frame-rate. A method for comparing these images concurrently to actual ultrasound images was developed, and the image realism was promising with respect to integration into a complete FAST simulator.