Photon absorptiometry: Difference between revisions
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In [[medicine]], '''photon absorptiometry''' | {{TOC|right}} | ||
In [[medicine]], '''photon absorptiometry''' --[[User:Howard C. Berkowitz|Howard C. Berkowitz]] 01:05, 26 May 2010 (UTC)is a "noninvasive method for assessing body composition. It is based on the differential absorption of x-rays (or gamma rays) by different tissues such as bone, fat and other soft tissues. The source of ([[x-ray]] or [[gamma ray]]) photon beam is generated either from radioisotopes such as <sub>153</sub>[[gadolinium]], <sub>126</sub>[[iodine]] 125, or <sub>241</sub>[[americium]] which emit gamma rays in the appropriate range; or from an x-ray tube which produces x-rays in the desired range. It is primarily used for quantitating [[bone density|bone mineral content]], especially for the diagnosis of [[osteoporosis]], and also in measuring [[bone density|bone mineralization]]."<ref>{{MeSH}}</ref> | |||
{| class="wikitable" | |||
|- | |||
! Method | |||
! Source | |||
! Detection levels | |||
|- | |||
|Single-photon absorptiometry (SPA) | |||
| [[Isotope]] | |||
| Single | |||
|- | |||
|Dual-photon absorptiometry (DPA) | |||
| [[Isotope]] | |||
| Dual | |||
|- | |||
| Dual-Energy X-Ray Absorptiometry (DEXA) | |||
| [[X-ray]] | |||
| Dual | |||
|} | |||
==Measurement of bone density== | ==Measurement of bone density== | ||
{{main|Bone | {{main|Bone densitometry}} | ||
[[Bone density]] is generally scored by two measures, the T-score and the Z-score. Scores indicate the amount one's bone mineral density varies from the mean. Negative scores indicate lower bone density, and positive scores indicate higher. | [[Bone density]] is generally scored by two measures, the T-score and the Z-score. Scores indicate the amount one's bone mineral density varies from the mean. Negative scores indicate lower bone density, and positive scores indicate higher. | ||
Revision as of 19:05, 25 May 2010
In medicine, photon absorptiometry --Howard C. Berkowitz 01:05, 26 May 2010 (UTC)is a "noninvasive method for assessing body composition. It is based on the differential absorption of x-rays (or gamma rays) by different tissues such as bone, fat and other soft tissues. The source of (x-ray or gamma ray) photon beam is generated either from radioisotopes such as 153gadolinium, 126iodine 125, or 241americium which emit gamma rays in the appropriate range; or from an x-ray tube which produces x-rays in the desired range. It is primarily used for quantitating bone mineral content, especially for the diagnosis of osteoporosis, and also in measuring bone mineralization."[1]
| Method | Source | Detection levels |
|---|---|---|
| Single-photon absorptiometry (SPA) | Isotope | Single |
| Dual-photon absorptiometry (DPA) | Isotope | Dual |
| Dual-Energy X-Ray Absorptiometry (DEXA) | X-ray | Dual |
Measurement of bone density
Bone density is generally scored by two measures, the T-score and the Z-score. Scores indicate the amount one's bone mineral density varies from the mean. Negative scores indicate lower bone density, and positive scores indicate higher.
T-score
The T-score is a comparison of a patient's bone density to that of a healthy thirty-year-old. The criteria of the World Health Organization are[2]:
- Osteoporosis is defined as -2.5 or lower, meaning a bone density that is two and a half standard deviations below the mean of a thirty year old woman.
- Osteopenia is defined as less than -1.0 and greater than -2.5
- Normal is a T-score of -1.0 or higher
Z-score
The Z-score is a comparison of a patient's bone density to the average bone density of their, sex, and race. This value is used in premenopausal women, men under aged 50, and in children.[3]
References
- ↑ Anonymous (2024), Photon absorptiometry (English). Medical Subject Headings. U.S. National Library of Medicine.
- ↑ WHO Scientific Group on the Prevention and Management of Osteoporosis (2000 : Geneva, Switzerland) (2003). Prevention and management of osteoporosis : report of a WHO scientific group (pdf). Retrieved on 2007-05-31.
- ↑ Raisz LG (July 2005). "Clinical practice. Screening for osteoporosis". N. Engl. J. Med. 353 (2): 164–71. DOI:10.1056/NEJMcp042092. PMID 16014886. Research Blogging.