BY Dr. Mohamed Samieh Lecturer in Radiology Department Bone Densitometry BY Dr. Mohamed Samieh Lecturer in Radiology Department

Slide Title Course Learning Objectives This course is designed to introduce to the students the different modalities used in bone densitometry, different bone densitometry techniques. Teaching and Learning Methods Lectures:(Tools: board, data show) Interactive learning ( Discussions ) Self-study ( Research ) Other methods: (Problem Based Learning)

Bone densitometry Bone densitometry definition It is also called dual-energy x-ray absorptiometry or DEXA, it an X ray imaging technique primarily used to derive the mass of one material in the presence of another through knowledge of their unique X ray attenuation at different energies.

It uses a very small dose of ionizing radiation to produce pictures of the inside of the body (usually the lower spine and hips) to measure bone mineral density and for body composition assessment.

Dedicated commercial DXA systems first became available in the late 1980s DXA’s primary commercial application has been to measure BMD to assess fracture risk and to diagnose osteoporosis; the X ray energies used are optimized for bone density assessment. The whole body can also be scanned to measure whole body bone mass and soft tissue body composition. In image areas that contain only soft tissue, lipid and lean tissue can be assessed, from which percent lipid mass can be calculated, while areas that contain bone use an estimated per cent lipid from the surrounding tissue.

Standards of biological composition The body is represented as five compartments: water, protein, mineral, glycogen and lipid Composition of the body according to DXA DXA defines the composition of the body as three materials having specific x ray attenuation properties: Bone mineral Lipid (triglycerides, phospholipid membranes, etc.) Lipid free soft tissue

The term fat is commonly used to refer to adipose tissue The term fat is commonly used to refer to adipose tissue. However, adipose tissue contains lipid free mass, such as water and proteins as well. Fat is best described chemically as the lipids in our body that are soluble in organic solvents and not in water, the largest category of body fat being triglycerides found in adipocytes.

The non-lipid soft tissue mass (STM) is the sum of Body water Protein Glycerol Soft tissue mineral mass. For each pixel in a DXA image, these three mass components are quantified. However, the distribution of the lipid, bone mineral and non-lipid soft tissue within the volume projected onto the image pixel