Write radiological methods of body composition analysis?

Radiological and isotope dilution methods of measuring body composition;

Radiological methods:

These methods rely on imaging technique to measure the body composition, diagnose and treat diseases. Imaging procedures used in these methods are X-ray radiography, ultrasound, computed tomography (CT) scan.

DEXA ( dual energy X-ray absorptiometry ) :

DEXA or DXA is also called bone density scanning or bone densitometry. It was originally developed for bone density measurements ( osteoporosis/osteopenia screening ). however, finds applications in body composition analysis to determine lean mass and percent fat DEXA determines relation proportion of FFM,

FM and bone mass by running full body scan to low energy X-ray beams are used in DEXA and their differential attenuation through the body allows the distinction between adipose and soft tissue, in addition to bone minerals content and bone mineral density.

The X-ray beam having variable energy level, are directed at the patient bones. After subtracting the absorption by soft tissue, the bone mineral density can be measured by the absorption of each beam by bone.

A typical whole body scan takes less than 5 min while the subject is exposed to 0.01- .04 mrem of radiation during one scan. This method is accurate, reliable and a gold standard measure of bone mineral content or bone density and is applicable for both adults and children. The test can be applied distinct areas or whole body.

There are certain limitation associated with this method as the calculated FM is variable with different tissue depths. It can cause problem during calibration and may lack standardization. It is slightly expensive method with limited utilization and has radiation exposure on a small scale.

Equipment require trained and educated staff to be operational. This methodology is not recommended for pregnant ladies. DEXA can yeilds which are compared with the reference value obtained through the scan of a healthy 30 years old of same score, the weaker the bones are and vice versa.

1)t-score of -1.0 or above is indicator of normal bone density

2)T-score between - 1.0 and -2.5 indicates low bone density, or osteopenia

3)T- score of 2.5or lower exhibits osteoporosis

DEXA scan also provide results using Z -score compares the bone mass with other person of same size, age and sex. It help to find of something unusual is leading to loss of bone mass. International society for clinical densitometry categorizes a Z- score of above- 2.0 as normal, while, a score of less than - 2.0 is considered lower than the normal range for the person 's age.

Computed Tomography(CT scan):

In 1970 Allan M. cormack and Godfrey N. Hounsfield were awarded Noble prize in physiology and medicine for the development of computed tomography or CT scan refer to ''a computerized x-ray imaging procedure in which a narrow beam of x-ray is aimed at a patient and quickly rotated around the body, producing singles that are processed by the machine's computer to generate cross-sectional images - or ''slices'' of the body.'

The x ray beam rotates around the subject with in the scanner in such a manner that multiple x ray projection pass through the subject creating detailed images of soft and hard tissue of body. CT scan generate three - dimensional (3-D) image of internal body structure providing accurate and high- quality data on the body composition, including muscle mass.

Does a CT scan show inside the bone?

Yes, a CT scan (also known as a CAT scan) can indeed provide images of the inside of the bones. It is a type of diagnostic imaging tool that uses a combination of X-ray equipment and sophisticated computers to produce detailed, cross-sectional images of the body, including bones, blood vessels, and soft tissues.

However, while a CT scan can give an image of the inside of the bone, it is not the most detailed or specific method for examining bone interior or for diagnosing certain conditions affecting the bone. For instance, it might not be as effective in identifying small fractures, infections, or early stages of bone diseases as compared to other imaging methods like an MRI or a bone scan.

CT scans are particularly useful when it comes to identifying and assessing the severity of fractures, tumors, infections in complex areas, and degenerative conditions like osteoarthritis.

It's important to remember that the choice of imaging technique can vary depending on the specific medical context and clinical judgement of the healthcare provider.

CT scan is precise and quick method as whole body can be scanned with in half hour and does not cause any pain. The method can measure original muscle mass and adipose tissue while differentiating between two type of learn mass i.e muscle and organ mass. Moreover, it can discriminate subcutaneous and intra- abdominal distribution of fat.

However, it is an expensive technique and may lack acceptability in some individual. Comparatively high dose of radiation is given in this method which makes it suitable for pregnant women and nursing children.

Isotope dilution method;

Isotope dilution was introduced by Von Hevesy and Hofer in 1943 and is a radiochemical method of analysis which measure the mass and amount of an element in a substances . The procedure involves adding to a substance a known quantity of radioisotope of the element to be measured and mixing it with the stable isotope of the element.

The three compartments of the body mass i.e extracellular solid (i.e bone, tendon, etc ) can be quantitated using established isotope dilution techniques.

Hydrometry or total body water (TBW)isotope dilution is the common method assess body composition at the molecular level. The method is premised on the notion that'' water is found exclusively with in the FFM, which is approximately 73.2% water in adults''

By measuring TBW through the isotope dilution, the amount of FFM can be calculated using appropriate hydration factor. Resultantly, body FM is difference between total body mass and FFM.

Isotope dilution is based on the principal of :

F1 N1=F2 N2

N2 =F1 N1 / F2

Where

F1is the deuterium enrichment or concentration of the dose

F2 is the deuterium enrichment or concentration of the distribution space (volume of human body in which the isotope is distribute, also called cool space or dilution space)

N1 is the size of the deuterium dose

N2 is size of the distribution space

N.B F1 N1 =F2 N2 is the isotope version of the principal of C1 V1=C2 V2 where c is the concentration and v is the volume. Once TBW has been quantified, FFM is simply TBW divided by the hydration factor:

FFM= TBW/ hydration factor

FM=weight-FFM

It is an accurate method with no radiation exposure. Energy expenditure can be simultaneously measured in this method using doubly labelled water. On the other hand, it is an expensive and difficult method as it requires sampling, storage and complete analysis.

The right amount of dose can be difficult tob decide. Since the assessment is carried out using mass spectroscopy, taking samples to central laboratory can be a difficult task.