WordNet

join together into a mass or collect or form a mass; "Crowds were massing outside the palace"
the property of a body that causes it to have weight in a gravitational field
a body of matter without definite shape; "a huge ice mass"
an ill-structured collection of similar things (objects or people)
remove the bones from; "bone the turkey before roasting it" (同)debone
the porous calcified substance from which bones are made (同)osseous_tissue
consisting of or made up of bone; "a bony substance"; "the bony framework of the body"
a shade of white the color of bleached bones (同)ivory, pearl, off-white
rigid connective tissue that makes up the skeleton of vertebrates (同)os
having bones as specified; "his lanky long-boned body"
having had the bones removed; "a boneless rib roast"; "a boned (or deboned) fish" (同)deboned
(Roman Catholic Church and Protestant Churches) the celebration of the Eucharist
a musical setting for a Mass; "they played a Mass composed by Beethoven"
a sequence of prayers constituting the Christian Eucharistic rite; "the priest said Mass"
a percussion instrument consisting of a pair of hollow pieces of wood or bone (usually held between the thumb and fingers) that are made to click together (as by Spanish dancers) in rhythm with the dance (同)castanets, clappers, finger cymbals

PrepTutorEJDIC

〈C〉(一定の形をもたない物に用いて)…の)『固まり』,集まり《+『of』+『名』》 / 〈C〉『多数』,多量(の…)《+『of』+『名』》 / 〈C〉《the ~》『大部分』(の…),(…の)主要部《+『of』+『名』》 / 〈U〉(物体の)大きさ,かさ / 《the masses》『一般大衆』,庶民 / 〈U〉質量(物体の基本的性質を表す量) / 〈人・物〉‘を'集める,一団にする / 〈人・物が〉一かたまりになる,一団となる / 大衆の,一般に付及した / 大規模な
〈C〉骨 / 〈U〉骨を作っている物質,骨質 / 《複数形で》骨格;死骸(がい) / 〈魚など〉‘の'骨を取る
(魚など)骨を取り除いた / (衣服が)(コルセットなどで)骨で張りをつけた[ような]

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/05/07 22:37:02」(JST)

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A scanner used to measure bone density with dual energy X-ray absorptiometry.

Bone density (or bone mineral density) is a medical term normally referring to the amount of mineral matter per square centimeter of bones.^[1] Bone density (or BMD) is used in clinical medicine as an indirect indicator of osteoporosis and fracture risk.

This medical bone density is not the true physical "density" of the bone, which would be computed as mass per volume. It is measured by a procedure called densitometry, often performed in the radiology or nuclear medicine departments of hospitals or clinics. The measurement is painless and non-invasive and involves low radiation exposure. Measurements are most commonly made over the lumbar spine and over the upper part of the hip.^[2] The forearm may be scanned if the hip and lumbar spine are not accessible. Average density is around 1500 kg m⁻³

There is a statistical association between poor bone density and higher probability of fracture. Fractures of the legs and pelvis due to falls are a significant public health problem, especially in elderly women, leading to much medical cost, inability to live independently, and even risk of death. Bone density measurements are used to screen women for osteoporosis risk and to identify those who might benefit from measures to improve bone strength.

Testing [edit]

Bone density tests are not necessary for people without risk factors for weak bones.^[3]^[4] Unnecessary testing is more likely to result in superfluous treatment rather than discovery of a true problem.^[4]

Indications for testing [edit]

The following are risk factors for low bone density and primary considerations for the need for a bone density test.

females age 65^[4]
males age 70^[4]
people over age 50 with any of the following:
- previous bone fracture from trauma^[4]
- rheumatoid arthritis^[4]
- low body weight^[4]
- a parent with a hip fracture^[4]
Individuals with vertebral abnormalities.^[5]
Individuals receiving, or planning to receive, long-term glucocorticoid (steroid) therapy.^[5]
Individuals with primary hyperparathyroidism.^[5]
Individuals being monitored to assess the response or efficacy of an approved osteoporosis drug therapy.^[5]
Individuals with a history of eating disorders^[5]

Other considerations which related to risk of low bone density and the need for a test include smoking habits, drinking habits, the long-term use of corticosteroid drugs, and a vitamin D deficiency.^[4]

Overtesting and treatment [edit]

For those people who do have bone density tests, two conditions which may be detected are osteoporosis and osteopenia.^[4] The usual response to either of these indications is consultation with a physician.^[4]

Terms [edit]

Results are often reported in 3 terms:

Measured areal density in g cm⁻³
z-score, the number of standard deviations above or below the mean for the patient's age, sex and ethnicity
t-score, the number of standard deviations above or below the mean for a healthy 30 year old adult of the same sex and ethnicity as the patient

Limitations [edit]

Use of BMD has several limitations.

Measurement can be affected by the size of the patient, the thickness of tissue overlying the bone, and other factors extraneous to the bones.
Bone density is a proxy measurement for bone strength, which is the resistance to fracture and the truly significant characteristic. Although the two are usually related, there are some circumstances in which bone density is a poorer indicator of bone strength.
Reference standards for some populations (e.g., children) are unavailable for many of the methods used.
Crushed vertebrae can result in falsely high bone density so must be excluded from analysis.

Types of tests [edit]

While there are many different types of BMD tests, all are non-invasive. Most tests differ in which bones are measured to determine the BMD result.

These tests include:

Dual-energy X-ray absorptiometry (DXA or DEXA)
Quantitative computed tomography (QCT)
Qualitative ultrasound (QUS)
Single photon absorptiometry (SPA)
Dual photon absorptiometry (DPA)
Digital X-ray radiogrammetry (DXR)
Single energy X-ray absorptiometry (SEXA)

DEXA is currently the most widely used, but ultrasound has been described as a more cost-effective approach to measure bone density.^[6]

The test works by measuring a specific bone or bones, usually the spine, hip, and wrist. The density of these bones is then compared with an average index based on age, sex, and size. The resulting comparison is used to determine risk for fractures and the stage of osteoporosis in an individual.

Average bone mineral density = BMC / W [g/cm²]

BMC = bone mineral content = g/cm
W = width at the scanned line

Interpretation [edit]

Results are 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 [edit]

The T-score is the relevant measure when screening for osteoporosis. It is the bone mineral density at the site when compared to the young normal reference mean. It is a comparison of a patient's BMD to that of a healthy thirty-year-old of the same sex and ethnicity. This value is used in post-menopausal women and men over age 50 because it better predicts risk of future fracture.^[7] The criteria of the World Health Organization are:^[8]

Normal is a T-score of -1.0 or higher
Osteopenia is defined as between -1.0 and -2.5
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 man/woman.

Hip fractures per 1000 patient-years^[9]
WHO category	Age 50-64	Age > 64	Overall
Normal	5.3	9.4	6.6
Osteopenia	11.4	19.6	15.7
Osteoporosis	22.4	46.6	40.6

Z-score [edit]

The Z-score is the comparison to the age-matched normal and is usually used in cases of severe osteoporosis. This is the number of standard deviations a patient's BMD differs from the average BMD of their age, sex, and ethnicity. This value is used in premenopausal women, men under the age of 50, and in children.^[7] It is most useful when the score is less than 2 standard deviations below this normal. In this setting, it is helpful to scrutinize for coexisting illnesses that may contribute to osteoporosis such as glucocorticoid therapy, hyperparathyroidism, or alcoholism.

Diet [edit]

There may be associations between some forms of BMD and diet.^[10]

References [edit]

^ Bone Density at the US National Library of Medicine Medical Subject Headings (MeSH)
^ Cole RE (June 2008). "Improving clinical decisions for women at risk of osteoporosis: dual-femur bone mineral density testing". J Am Osteopath Assoc 108 (6): 289–95. PMID 18587077.
^ American Academy of Family Physicians, "Five Things Physicians and Patients Should Question", presented by ABIM Foundation, Choosing Wisely: an initiative of the ABIM Foundation (American Academy of Family Physicians), retrieved August 14, 2012
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k Consumer Reports; American Academy of Family Physicians (May 2012), "Bone-density tests: When you need them — and when you don't", Choosing Wisely: an initiative of the ABIM Foundation (Consumer Reports), retrieved August 14, 2012
^ ^a ^b ^c ^d ^e "NOF - Bone Mass Measurement". Archived from the original on 2008-03-07. Retrieved 2008-03-20.
^ "Bone densitometry". Retrieved 2008-09-02.
^ ^a ^b Richmond, Bradford (2007-11-13). "Osteoporosis and bone mineral density.". American College of Radiology. Retrieved 2008-05-11.
^ 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 2007-05-31.
^ Cranney A, Jamal SA, Tsang JF, Josse RG, Leslie WD (2007). "Low bone mineral density and fracture burden in postmenopausal women". Canadian Medical Association Journal 177 (6): 575–80. doi:10.1503/cmaj.070234. PMC 1963365. PMID 17846439.
^ Diet can influence BMD in postmenopausal women http://www.searchmedica.com/resource.html?rurl=http%3A%2F%2Fwww.modernmedicine.com%2Fmodernmedicine%2FModern%2BMedicine%2BNow%2FDiet-can-influence-BMD-in-postmenopausal-women%2FArticleNewsFeed%2FArticle%2Fdetail%2F745343&q=herb&cq=herb&c=ps&ss=defLink&p=Convera&fr=true&ds=20&srid=4

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