1. A 3-dimensional (3D) ultrasound system comprising: an extractor to scan an image of an object and to extract a region of interest (ROI) image from the image of the object, the ROI image including a measurement region of the object; a processor to detect an edge of a first side image, wherein the edge comprises a first edge and a second edge, and the first side image generated from the ROI image; and a controller to measure the thickness of the measurement region based on a distance between the first edge and the second edge, wherein the processor detects the first edge of which brightness intensity is changed from a large value to a small value in the first side image, and detects the second edge of which brightness intensity is changed from a small value to a large value in the first side image.