Minimally invasive medical techniques are intended to reduce the amount of tissue that is damaged during medical procedures, thereby reducing patient recovery time, discomfort, and harmful side effects. Such minimally invasive techniques may be performed through natural orifices in a patient anatomy or through one or more surgical incisions. Clinicians may insert medical tools through these natural orifices or incisions to reach a target tissue location. Medical tools include instruments such as therapeutic instruments, diagnostic instruments, and surgical instruments. To reach the target tissue location, a minimally invasive medical tool may navigate natural or surgically created passageways in anatomical systems such as the lungs, the colon, the intestines, the kidneys, the heart, the circulatory system, or the like.
An image guided surgery process typically includes performing some type of pre-operative imaging of a target anatomy of a patient. For example, a Magnetic Resonance Imaging (MRI) image or a Computed Tomography (CT) image may be obtained. Through a manual and/or a computer software-based process, the images are partitioned into segments (e.g., pixels or voxels) that share certain characteristics or computed properties such as color, density, intensity, and texture. This segmentation process results in a two- or three-dimensional reconstruction that forms a model of the target anatomy based on the obtained image. To represent the model, the segmentation process may delineate sets of voxels representing the target anatomy and then apply a function, such as marching cube function, to obtain a 3D surface that encloses the voxels.
Segmentation may be particularly useful in modeling anatomic passageways. After the segmentation process, the obtained model may be used to navigate a medical instrument through the segmented passageways of the patient anatomy. In some cases, various branches within the patient's anatomy may not be properly segmented by the segmentation process. For example, some passageways that exist within the patient anatomy may be omitted from the model. Or, the segmentation process may indicate the existence of branches where there are, in fact, none. Thus, a surgeon or an operator of the medical instrument who is using the model for navigation to a particular anatomic location may be hampered by inaccuracies in the model. To avoid such issues, it is desirable to have an accurate model.