Bone Mineral Densitometry (BMD)
DEXA collimation - ✔️✔️Pencil beam:
-no longer being manufactured, but still commonly seen
- include a collimated x-ray beam and a single detector that move in sync
-scanning occurs at a point
Fan beam (array scanning):
-scan line by line
-wide angle fan beam orientated towards long axis of body
-narrow angle beam parallel to long axis of the body
-significantly shorter scan time, decreased image resolution and higher radiation doses
Accuracy is almost equal
Central DXA - ✔️✔️Considered most current and accepted modality.
Provides excellent repoducibility
Widely used in epidemiological studies as well as pharmaceutical trials. (have
successfullly related DXA measurement of bmd to fracture risk)
Volume of calium hydroxypatite is 2.5 or more SD *below* the young gender match with
peak bone mass (T-score)
osteoperotic patients - ✔️✔️Have a 2x increased fracture risk.
Address demineralization process with medications such as Premarin and Fosamax
Normal T-score - ✔️✔️equal or greater than -1
Ultrasound and CT - ✔️✔️Other modalities used to visually quantify BMD
Lumbar spine, hip, and forearm - ✔️✔️Most common body areas used to measure bmd
Central skeleton - ✔️✔️Includes:
vertebral column
ribs and sternum
pelvis
proximal femur
Peripheral Skeleton - ✔️✔️Includes:
upper extremities
lower extremities (not including proximal femur)
, What BMD is - ✔️✔️exam that measures the amount of bone mineral calcium
hydroxyapatite per unit volume of bone
How osteoporosis is described - ✔️✔️Reduced volume of bone minerals.
Central BMD devices - ✔️✔️Designed to mea
sure bone density of spine and hip (capable of measuring forearm and body id
necessary)
Common modalities: dual-energy absorptiometry (DXA) and quantitative computed
tomography (QCT)
Peripheral Devices - ✔️✔️Designed to measure bone density in wrist, heel, finger, and
other extremities
Use all possible modalities:
Peripheral DXA(pDXA) - measures BMD forearm, heel or finger
Peripheral QCT(pQCT) - provides CT volumetric measurement of forearm
Quantitative ultrasound(QUS) -
measures the speed of sound through bone
DEXA operations - ✔️✔️Same systems as x-rays: tube, collimator, and x-ray detector
Same radiographice factorsapply
Single DXA - ✔️✔️Allows measurement of the amount of tranmitted beam through a
body part.
Not possible to separate density of bone vs. ST
Dual energy DXA - ✔️✔️Measures proportion of radiation transmitted through patient.
Takes into account energy of x-ray photons, density + thickness of part being scanned.
The 2 diff. photon energies allow recording of attenuation profiles at different photon
energies
How bone mineral density is measured with 2 different energies - ✔️✔️Bone
mass/Bone mineral content is measured in grams.
Divided by given area of bone measured in cm2.
Projected area of bone recognized by indicating pixels in area of interest and use of
edge detection algorithm
Bone mineral density - ✔️✔️Division of bone mineral content be projected area.
Reported in g/cm2
K-Edge Filtering - ✔️✔️Use of generator that produces constant potential(as with
general rad)
DEXA collimation - ✔️✔️Pencil beam:
-no longer being manufactured, but still commonly seen
- include a collimated x-ray beam and a single detector that move in sync
-scanning occurs at a point
Fan beam (array scanning):
-scan line by line
-wide angle fan beam orientated towards long axis of body
-narrow angle beam parallel to long axis of the body
-significantly shorter scan time, decreased image resolution and higher radiation doses
Accuracy is almost equal
Central DXA - ✔️✔️Considered most current and accepted modality.
Provides excellent repoducibility
Widely used in epidemiological studies as well as pharmaceutical trials. (have
successfullly related DXA measurement of bmd to fracture risk)
Volume of calium hydroxypatite is 2.5 or more SD *below* the young gender match with
peak bone mass (T-score)
osteoperotic patients - ✔️✔️Have a 2x increased fracture risk.
Address demineralization process with medications such as Premarin and Fosamax
Normal T-score - ✔️✔️equal or greater than -1
Ultrasound and CT - ✔️✔️Other modalities used to visually quantify BMD
Lumbar spine, hip, and forearm - ✔️✔️Most common body areas used to measure bmd
Central skeleton - ✔️✔️Includes:
vertebral column
ribs and sternum
pelvis
proximal femur
Peripheral Skeleton - ✔️✔️Includes:
upper extremities
lower extremities (not including proximal femur)
, What BMD is - ✔️✔️exam that measures the amount of bone mineral calcium
hydroxyapatite per unit volume of bone
How osteoporosis is described - ✔️✔️Reduced volume of bone minerals.
Central BMD devices - ✔️✔️Designed to mea
sure bone density of spine and hip (capable of measuring forearm and body id
necessary)
Common modalities: dual-energy absorptiometry (DXA) and quantitative computed
tomography (QCT)
Peripheral Devices - ✔️✔️Designed to measure bone density in wrist, heel, finger, and
other extremities
Use all possible modalities:
Peripheral DXA(pDXA) - measures BMD forearm, heel or finger
Peripheral QCT(pQCT) - provides CT volumetric measurement of forearm
Quantitative ultrasound(QUS) -
measures the speed of sound through bone
DEXA operations - ✔️✔️Same systems as x-rays: tube, collimator, and x-ray detector
Same radiographice factorsapply
Single DXA - ✔️✔️Allows measurement of the amount of tranmitted beam through a
body part.
Not possible to separate density of bone vs. ST
Dual energy DXA - ✔️✔️Measures proportion of radiation transmitted through patient.
Takes into account energy of x-ray photons, density + thickness of part being scanned.
The 2 diff. photon energies allow recording of attenuation profiles at different photon
energies
How bone mineral density is measured with 2 different energies - ✔️✔️Bone
mass/Bone mineral content is measured in grams.
Divided by given area of bone measured in cm2.
Projected area of bone recognized by indicating pixels in area of interest and use of
edge detection algorithm
Bone mineral density - ✔️✔️Division of bone mineral content be projected area.
Reported in g/cm2
K-Edge Filtering - ✔️✔️Use of generator that produces constant potential(as with
general rad)
