Since its introduction in the 1970s,<unk>  has become an important tool in medical imaging to supplement X-rays and medical ultrasonography. It has more recently been used for preventive medicine or screening for disease, for example,<unk>  colonography for people with a high risk of colon cancer, or full-motion heart<unk> s for people with a high risk of heart disease. Several institutions offer full-body<unk> s for the general population although this practice goes against the advice and official position of many professional organizations in the field primarily due to the radiation dose applied. The use of<unk> s has increased dramatically over the last two decades in many countries. An estimated 72 million<unk> s were performed in the United States in 2007 and more than 80 million in 2015. Head Computed tomography of human brain, from base of the skull to top. Taken with intravenous contrast medium.<unk> ning of the head is typically used to detect infarction (stroke), tumors, calcifications, haemorrhage, and bone trauma. Of the above, hypodense (dark) structures can indicate edema and infarction, hyperdense (bright) structures indicate calcifications and haemorrhage and bone trauma can be seen as disjunction in bone windows. Tumors can be detected by the swelling and anatomical distortion they cause, or by surrounding edema.<unk> ning of the head is also used in<unk> -guided stereotactic surgery and radiosurgery for treatment of intracranial tumors, arteriovenous malformations, and other surgically treatable conditions using a device known as the N-localizer. Neck Contrast<unk>  is generally the initial study of choice for neck masses in adults.<unk>  of the thyroid plays an important role in the evaluation of thyroid cancer.<unk>  often incidentally finds thyroid abnormalities, and so is often the preferred investigation modality for thyroid abnormalities. Lungs A<unk>  can be used for detecting both acute and chronic changes in the lung parenchyma, the tissue of the lungs. It is particularly relevant here because normal two-dimensional X-rays do not show such defects. A variety of techniques are used, depending on the suspected abnormality. For evaluation of chronic interstitial processes such as emphysema, and fibrosis, thin sections with high spatial frequency reconstructions are used; often<unk> s are performed both on inspiration and expiration. This special technique is called high resolution<unk>  that produces a sampling of the lung, and not continuous images. HRCT images of a normal thorax in axial, coronal and sagittal planes, respectively.120x120px Bronchial wall thickness (T) and diameter of the bronchus (D) Bronchial wall thickening can be seen on lung<unk> s and generally (but not always) implies inflammation of the bronchi. An incidentally found nodule in the absence of symptoms (sometimes referred to as an incidentaloma) may raise concerns that it might represent a tumor, either benign or malignant. Perhaps persuaded by fear, patients and doctors sometimes agree to an intensive schedule of<unk> s, sometimes up to every three months and beyond the recommended guidelines, in an attempt to do surveillance on the nodules. However, established guidelines advise that patients without a prior history of cancer and whose solid nodules have not grown over a two-year period are unlikely to have any malignant cancer. For this reason, and because no research provides supporting evidence that intensive surveillance gives better outcomes, and because of risks associated with having<unk> s, patients should not receive<unk>  screening in excess of those recommended by established guidelines. Angiography embolus (dark horizontal line) occluding the pulmonary arteries (bright white triangle) Computed tomography angiography <unk> A) is a type of contrast<unk>  to visualize the arteries and veins throughout the body. This ranges from arteries serving the brain to those bringing blood to the lungs, kidneys, arms and legs. An example of this type of exam is<unk>  pulmonary angiogram <unk> PA) used to diagnose pulmonary embolism (PE). It employs computed tomography and an iodine-based contrast agent to obtain an image of the pulmonary arteries. Cardiac A<unk>  of the heart is performed to gain knowledge about cardiac or coronary anatomy. Traditionally, cardiac<unk> s are used to detect, diagnose, or follow up coronary artery disease. More recently<unk>  has played a key role in the fast-evolving field of transcatheter structural heart interventions, more specifically in the transcatheter repair and replacement of heart valves. The main forms of cardiac<unk> ning are: *Coronary<unk>  angiography (CCTA): the use of<unk>  to assess the coronary arteries of the heart. The subject receives an intravenous injection of radiocontrast, and then the heart is<unk> ned using a high-speed<unk> ner, allowing radiologists to assess the extent of occlusion in the coronary arteries, usually to diagnose coronary artery disease. *Coronary<unk>  calcium<unk> : also used for the assessment of severity of coronary artery disease. Specifically, it looks for calcium deposits in the coronary arteries that can narrow arteries and increase the risk of a heart attack. A typical coronary<unk>  calcium<unk>  is done without the use of radiocontrast, but it can possibly be done from contrast-enhanced images as well. To better visualize the anatomy, post-processing of the images is common. Most common are multiplanar reconstructions (MPR) and volume rendering. For more complex anatomies and procedures, such as heart valve interventions, a true 3D reconstruction or a 3D print is created based on these<unk>  images to gain a deeper understanding. Abdomen and pelvis<unk>  of a normal abdomen and pelvis, in sagittal plane, coronal and axial planes, respectively.160x160px<unk>  is an accurate technique for diagnosis of abdominal diseases like Crohn's disease, GIT bleeding, and diagnosis and staging of cancer, as well as follow-up after cancer treatment to assess response. It is commonly used to investigate acute abdominal pain. Non-enhanced computed tomography is today the gold standard for diagnosing urinary stones. The size, volume and density of stones can be estimated to help clinicians guide further treatment; size is especially important in predicting spontaneous passage of a stone. Axial skeleton and extremities For the axial skeleton and extremities,<unk>  is often used to image complex fractures, especially ones around joints, because of its ability to reconstruct the area of interest in multiple planes. Fractures, ligamentous injuries, and dislocations can easily be recognized with a 0.2 mm resolution. With modern dual-energy<unk> ners, new areas of use have been established, such as aiding in the diagnosis of gout. Biomechanical use<unk>  is used in biomechanics to quickly reveal the geometry, anatomy, density and elastic moduli of biological tissues.
CT scan
Fluoroscopy
Contrast CT
SAP scan
Imaging
Radiography
Exploratory surgery
Autoradiograph