Lecture Notes: Radiation Dose, DXA, Osteoporosis Treatments & Bone Biology

A comprehensive set of vocabulary-style flashcards covering radiation dose concepts, DXA technology, osteoporosis pharmacology, bone biology, and key skeletal anatomy details from the notes.

Absorbed Dose (Gray, Gy)

The amount of energy absorbed per unit mass of the irradiated material.

Equivalent Dose (Sievert, Sv)

Quantifies the biological effect of radiation exposure, accounting for the type and energy of the radiation.

Effective Dose (Sievert, Sv)

Measure of the overall risk of the radiation exposure, considering radiation type and tissue sensitivity.

Roentgen Equivalent Man (REM)

Unit used to quantify the equivalent dose, reflecting varying biological effectiveness of different ionizing radiations.

Annual dose limit for radiation workers

50 mSv per year (5 rem).

Annual dose limit for the public

1 mSv (0.1 rem)

Collimation

A tunnel that shapes and focuses the X-ray beam onto the area of interest.

Scintillation Detectors

Detectors in DXA systems that emit light when X-rays interact; light is converted to an electrical signal.

Solid-State Detectors

Detectors using semiconductor materials to directly convert X-ray energy to electrical signals.

Pregnant women dosimeters (belly and collar)

Two dosimeters placed on the belly and around the collar to monitor fetal and maternal exposure.

Cosmic Radiation

Natural background radiation from space (sun and galactic sources).

Terrestrial Radiation (radon, thoron)

Natural background radiation from radioactive materials in the Earth's crust.

Internal radiation (radionuclides)

Radiation from radioactive atoms naturally present inside the body.

Bremsstrahlung (braking radiation)

Decelerating electrons emit X-rays with a broad spectrum of energies.

Characteristic radiation

X-rays produced when inner-shell electrons are ejected, yielding energies specific to the target material.

Voltage (kVp)

Higher kVp yields higher energy X-rays with deeper penetration.

Current (mA)

Higher mA increases X-ray intensity and patient dose.

Time (s)

Longer exposure increases the number of photons and dose.

Antiresorptives

Drugs that slow bone resorption by suppressing osteoclast activity.

Calcitonin

A drug that helps regulate calcium and bone metabolism by inhibiting osteoclasts.

Bisphosphonates

Drugs (e.g., alendronate, ibandronate, risedronate, zoledronic acid) that slow bone resorption.

RANKL Inhibitors

Drugs like denosumab that inhibit RANKL, reducing osteoclast formation and activity.

Anabolic agents

Drugs (teriparatide, abaloparatide, romosozumab) that stimulate bone formation.

Estrogen/estrogen-progestin (raloxifene)

Selective estrogen receptor modulator that acts as an estrogen agonist/antagonist.

Tissue-specific estrogen complex (estrogen/bazedoxifene)

Combination therapy that provides estrogen effects with tissue-selective actions.

Oral Bisphosphonates: Alendronate (Fosamax)

Weekly oral bisphosphonate used for osteoporosis and Paget’s disease.

Risedronate (Actonel)

Bisphosphonate taken weekly or monthly for osteoporosis.

Ibandronate (Boniva)

Monthly bisphosphonate for postmenopausal osteoporosis and Paget’s disease.

Zoledronic Acid (Reclast)

Intravenous bisphosphonate given annually for high fracture risk osteoporosis.

Denosumab (Prolia)

RANKL inhibitor that reduces osteoclast formation; side effect includes osteonecrosis of the jaw (ONJ).

Teriparatide (Forteo)

natural hormone that stimulates the growth and activity of bone-forming cells, osteoblasts, to increase bone mineral density leading to a reduction in fracture risk.

administered via daily subcutaneous injections, or under the skin, daily for up to 2 years

Abaloparatide (Tymlos)

PTH1 receptor–activating peptide; increases bone density; daily subcutaneous injections up to 18 months.

Romosozumab (Evenity)

Monoclonal antibody targeting sclerostin; stimulates bone formation and increases bone density.

Recommended calcium intake for adults 19-50.

Adults 19-50 years calcium: 1000 mg/day

Recommended calcium intake for men 51-70.

Adult men 51-70 calcium: 1000 mg/day

Higher calcium intake recommended for women 51-70.

Adult women 51-70 calcium: 1200 mg/day

Higher calcium intake recommended for older adults.

Adults 71+ calcium: 1200 mg/day

Higher calcium intake recommended for pregnant/breastfeeding teens.

Pregnant/breastfeeding teens calcium: 1300 mg/day

Calcium intake for pregnant or breastfeeding adults.

Pregnant/breastfeeding adults calcium: 1000 mg/day

FRAX factors

Assesses fracture risk using age, sex, weight, height, prior fractures, family history, and certain medical conditions (e.g., rheumatoid arthritis).

Hip fracture risk threshold (FRAX)

FRAX hip score >3% indicates high risk within 10 years.

Any osteoporotic fracture risk threshold (FRAX)

FRAX overall fracture risk >20% indicates high risk within 10 years.

Trabecular Bone Score (TBS)

Measurement evaluating trabecular bone microarchitecture (size, shape, connectivity).

Intramembranous ossification

Bone formation from mesenchyme: centers form, osteoblasts become osteocytes, trabecular bone and periosteum form, then cortical bone and red marrow via vascularization.

Endochondral ossification

Bone formation from a cartilage model where chondrocytes hypertrophy, matrix is mineralized, blood vessels invade, and osteogenic cells form bone.

Primary ossification center

Forms in the diaphysis within the periosteum, creating the periosteal collar.

Secondary ossification centers

Develop in the epiphyses after birth.

T-score

Compares a patient’s BMD to a young healthy adult of the same sex; thresholds define normal(≥ -1), osteopenia(between -1 and -2.5), osteoporosis( ≤ -2.5).

Z-score

Compares BMD to the average for people of the same age, sex, and size; normal:(≥-2.0), Below normal:( between -2.0 and -3.0),Very low (≤ -3.0).

BMC (Bone Mineral Content)

Total amount of mineral in the analyzed bone area (grams).

BMD (Bone Mineral Density)

Concentration of mineral per unit area (grams/cm2); measures bone strength.

DXA measurement unit

Glycers? No — grams per square centimeter (g/cm2).

BMC equation

BMC = BMD × Area.

BMD equation

BMD = BMC / Area.

Area (DXA measurement)

Measured area in square centimeters (cm2).

Key features of anatomic position

Standing upright; arms at sides; palms forward; feet parallel.

Axial skeleton

Contains 80 bones: skull, spine, ribs.

Appendicular skeleton

Contains 126 bones: shoulder girdle, pelvic girdle, limbs.