Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Patent
1997-07-29
1998-10-06
Lateef, Marvin M.
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
A61B 800
Patent
active
058170200
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. TECHNICAL FIELD
This invention relates to an ultrasonic reflection type of apparatus and method for diagnosing osteoporosis by emitting ultrasonic pulses toward predetermined cortical bone in a subject so as to measure the echo levels from the surface of the cortical bone.
2. BACKGROUND ART
With the advent of an ageing society in recent years, the bone disease referred to as osteoporosis has become a problem. This is a disease in which the loss of bone calcium results in brittleness and susceptibility to fractures with minimal trauma, and can cause the elderly to become bedridden. The physical diagnosis of osteoporosis is managed by the precise measurement of bone density using a diagnostic apparatus featuring the use of X-rays such as DXA, but problems involved in physical diagnosis with X-rays are that the equipment is large and expensive, and its use is limited in many ways in the interests of protecting against harm caused by radiation exposure.
Diagnostic apparatuses featuring the use of transmitted ultrasonic waves or reflected ultrasonic waves have begun to enjoy more popularity as simple devices which do not suffer from such drawbacks.
The diagnostic apparatuses noted in Japanese Laid-Open Patent Application 2-104337 and U.S. patent application Ser. No. 193,295 are known as ultrasonic transmitting types of diagnostic devices. In these diagnostic apparatuses, the acoustic velocity in bone is measured by setting up two ultrasonic transducers facing each other on either side of a part of a subject's body, so that ultrasonic pulses are emitted from one ultrasonic transducer at the osseous tissue, and the ultrasonic pulses passing through the osseous tissue are received by the other ultrasonic transducer. The extent of osteoporosis is diagnosed on the assumption that a slower acoustic velocity in osseous tissue indicates lower bone density due to loss of bone calcium.
The theoretical basis linking bone density and acoustic velocity is uncertain, however. Strictly speaking, the acoustic velocity in osseous tissue is not proportional to bone density, but is given by the square the elastic modulus of bone and bone density play mutually cancelling roles in acoustic velocity, where increases in the bone density (denominator) are met by increases in the elastic modulus of bone (numerator), the acoustic velocity in osseous tissue is not capable of sensitive response to increases in bone density. As such, there is not that high a correlation between the acoustic velocity in osseous tissue and bone density. Reliability is accordingly a problem in conventional ultrasonic transmission types of diagnostic apparatuses in which bone density is estimated on the basis of the acoustic velocity in osseous tissue.
Ultrasonic reflection types of diagnostic apparatuses have meanwhile been proposed by the applicant in Japanese Patent Applications 6-310445, 7-140730, 7-140731, 7-140732, 7-140733, and 7-140734, and International Laid-Open Patent Application WO 96/18342. In these diagnostic apparatuses, a single ultrasonic transducer capable of both transmission and reception is used to emit ultrasonic pulses toward cortical bone in a subject, echoes reflected on the surface of the cortical bone are received, and the acoustic impedance of the subject's cortical bone is calculated on the basis of the resulting echo data. The progress of osteoporosis is then diagnosed based on the level of the acoustic impedance thus calculated. modulus.times.density! of bone, and since, as described above, the elastic modulus of bone increases (or decreases) as bone density increases (or decreases), the elastic modulus of bone and bone density play a synergistic role in acoustic impedance. Thus, the latter ultrasonic reflection type of apparatus in which acoustic impedance is used as an index can be considered more reliable because it is capable of more sensitive response to the extent of the progress of osteoporosis than is the former ultrasonic transmission type of apparatus in which acoustic velocity is used as an index.
Altho
REFERENCES:
patent: 4930511 (1990-06-01), Rossman et al.
Ishii Tetsuya
Kubota Yasuyuki
Kuriwaki Masashi
Lateef Marvin M.
Patel Maulin
Sekisui Kagaku Kogyo Kabushiki Kaisya
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