Densitometry is a method to image the density of for example, the bones to measure the mineral content or lung tissue to quantify emphysema.
Densitometry is also used to control the optical density of x-ray films by shining light on the film and measuring the transmission with a densitometer.

See also Bone Densitometry and Osteo CT.

Bone densitometry measures the strength and density of bones. Changes in trabecular bone mineral density (BMD) is an early indicator of change in metabolic function. Bone densitometry measures the amount of calcium in regions of the bones. A bone densitometer is used to determine the risk of developing osteoporosis and can also be used to estimate a patient's risk of fracture.
Bone densitometry methods involve:
Dual energy x-rays (DEXA) or CT scans (Osteo CT or QCT) compare the numerical density of the bone (calculated from the image), with empirical data bases of bone density. DEXA is widely available and has an accuracy between those of QCT and ultrasound.

A computed tomography (CT) of the abdomen images the region from the thoracic diaphragm to the pelvic groin. The computed tomography technique uses x-rays to differentiate tissues by their different radiation absorption rates.
Oral contrast material can be given to opacify the bowel before scanning. An i.v. injection of a contrast agent (x-ray dye) improves the visualization of organs like liver, spleen, pancreas and kidneys and provides additional information about the blood supply.
Spiral- or helical CT, including improvements in detector technology support faster image acquisition with higher quality. Advanced CT systems can usually obtain a CT scan of the whole abdomen during a single breath hold. This speed increases the detection of small lesions (caused by differences in breathing on consecutive scans) and is beneficial especially in pediatric, elderly or critically-ill patients.
Changes in patient weight require variations in x-ray tube potential to maintain constant detector energy fluence. An increased x-ray tube potential improves the contrast to noise resolution (CNR).

An abdominal CT is typically used to help diagnose the cause of abdominal pain and diseases such as:
Other indications for CT scanning of the abdomen/pelvis include planning radiation treatments, guide biopsies and other minimally invasive procedures. Advanced techniques include for example 3D CT angiography, multiphasic contrast-enhanced imaging, virtual cystoscopy, virtual colonoscopy, CT urography and CT densitometry.

See also Contrast Enhanced Computed Tomography.

A myelography is a radiographic imaging procedure to visualize the spinal canal, the spinal cord, cerebrospinal fluid (CSF), intervertebral disks and nerve roots. A special contrast agent (dye) is injected through a needle into the subarachnoid space of the spinal canal. A myelogram provides a very detailed picture of the spinal cord and spinal column. A fluoroscopy displays the bones and the fluid-filled space of the spine also in motion. An additional computerized tomography (CT or CAT) scan helps to differentiate the spinal conditions better. The indications include disc herniation, spinal stenosis, tumor, and vertebral fracture.

See also Myeloscintigraphy, Fluoroscopic System, Hounsfield Unit, Bone Densitometry, Nonionic Contrast Agents.

An Osteo CT or quantitative computed tomography (QCT) is used to measure bone mineral density (BMD). The high contrast discrimination of computed tomography can be used to examine the central skeleton for osteoporosis. Common CT scanners require a standard of reference to properly perform quantitative tissue analysis.
Osteo CT is the most accurate bone densitometry study, but is not widely available and delivers more radiation to the patient than dual energy x-ray absorptiometry.