Abstract: Apparatus and methods are described including, while an endoluminal data-acquisition device is being moved through a lumen of a subject, acquiring a plurality of endoluminal data points of the lumen using the endoluminal data-acquisition device. It is determined that, at least one location, no endoluminal data point was acquired. An output is generated using at least a portion of the plurality of endoluminal data points of the lumen acquired using the endoluminal data-acquisition device, the output including an indication that no endoluminal data point was acquired at the location. Other applications are also described.