X-ray energy is used in a similar manner to radiography in CT scanning. In CT imaging, the x-ray tube rotates quickly around the patient, within the gantry. The detectors rotate in a synchronized manner, on the opposite side of the gantry, absorbing the x-rays that pass through the patient. Based on the absorbed or detected energy, the computer builds a 3D image of the patient, as a sum of many small volumes (voxels) of data. The whole patient may be thought of as a loaf of bread. Each CT image is a slice of bread that is viewed on the cut surface. The loaf may be sliced in any direction. This modality is ideal for examination of complex body parts (i.e., skull, pelvis, vertebrae) where superimposed, irregularly shaped structures make radiographs challenging to interpret. CT is ideal for examination of the thorax (chest) and abdomen (belly) for small masses that may not be apparent by routine radiographs or ultrasound exam. CT is helpful for evaluation of the skull and brain in cases of acute head trauma when skull fractures and recent bleeding are a concern. Assessment of the temporomandibular joints, temporal bullae, nasal passages, sinuses, pharynx, larynx, orbit and periorbital structures, maxilla and mandible are common applications of this modality. Identifying the extent of a soft tissue or bone mass for surgery or radiation therapy planning is also done by CT.