Orthopedics 03-04 - Radiology - Msk

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Strontium 85

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1st isotope used for bone scanning

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Strontium 87

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Shorter half-life but poor soft tissue clearance

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Technetieum(tc99)

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Used to detect fractures : Short half-life -> excreted in urine 4hrs after injection (administered as phosphate complex-binds w/calcium in bone)

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Indium 111

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Used to detect infection: Leukocyte scan - used to tag WBC and asses uptake in infected areas

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Gallium 67

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Impregnatns into calcium hydroxyapatite crystals uptake in neutrophils and bacteria -> good for bone infections (checks progress in treatment of bone infection)

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PET scan

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Metabolic image -> soft tissue neoplasmas or osseous metastasis

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2-deoxy-2-fluoro-d-glucose (FDG)

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Tracer for PET scan

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t-score between -1 and 2.5

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Osteopenia - bone marrow density is lower then normal but not osteoperosis yet!

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t-score -2.5 or below

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Osteoporosis - ↓ bone marrow density by a lot

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t-score at -2.5 or below and history of one or more fractures

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Severe osteoperosis

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t-score -1 and above

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normal

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Scan that has cross sectional capability

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CT scan

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Scan w/early detection of fracture or infection and the degree of involvement

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Bone scan (utilizes isotopes)

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Scan for bone contusion, articular cartilages, relationships of neurovascular structures to other anatomy

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MRI

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Scan for fluid filled tissue and vascular supply

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Ultrasound

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Scan that is used to detect soft tissue neoplasms or osseous metastasis or ↑ glucose metabolism?

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PET scan

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T-scores

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Used in women for ostoperosis or in men on corticosteroids

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What scan is use to check a patients bone density?

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DEXA scan

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x-ray machine

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Electrode pair (cathode + anode) -> glass vacuum tube -> heated element (cathode) + tungsten plate or disc (anode) -> adjustible KV to energize cathode

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Flat panel detectors

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Amporphous silicon - converts x-ray radiation into light and light is converted to a digital output signal (indirect image), amorphous selenium - x-ray photons are converted directly into charge on sensor (direct image)

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High density line scan solid state detectors

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Phosphor detector records x-ray energy during exposure

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What is the ways to protect against radiation?

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1. Reduced time of exposure, 2. ↑ distance from radiation source, 3. provide radiation shielding

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Scanogram

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Used to determine leg length descrepency

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Comparison x-rays

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Usually done to verify a fracture in a pediatric patient

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Stress x-ray

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Used to assess ligamentous stability

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3rd ° sprain

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Entire tear of ligament

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Tomography

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Generates an image that is only in focus in one plane, multiple cuts. Aka laminograms

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Discograms

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Look for extravasation of dye into spinal cord or try to mimic the place where pain is

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How is the x-ray named?

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According to the direction the primary beam enters and leaves the tissue and the body part being examined (AP pelvis, lateral wrist)

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Cat scan

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Most important for boney density- fracture is it compressed, Much more clear on CT scan than an MRI

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MRI

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Shows fluid contents of bone, bone bruises, soft tissue contusions

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MRI -T1

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Measures energy released as proton exposed to RF signal realigns to magnetic orientation

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MRI - T2

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Measures energy transmitted by the wobbling effect of protons that have been exposed to RF signal (they are out of phase and release energy as they become in phase "lamor frequency")

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MRI striated muscle/normal muscle

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T2

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MRI of fat and muscle

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T1

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Low frequency ultrasound

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Longer wavelength - less resolution -> greater depth of penetration

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High frequency ultrasound

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Smaller wavelength - greater image detail -> superior for orthopedics images of tendons and ligaments

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What is the size limitation of CT scan?

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Pt >350lbs dosent fit

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Scan used to measure leg length differences

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scanogram

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More radioopaque

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More dense it is

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More radioluscent

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Least dense

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Define: mineral opacity

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Bone is composed primarily of calcium and phosphorus

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Define: soft tissue/fluid opacity

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Both soft tissue and fluids have the same radiopacity, this is the radiopacity of normal soft tissue and fluid -filled organs

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Define: fat opacity

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Fat is more lucent then bone or soft tissue, but is more opaque then gas; fat produces radiographic contrast for differentiation and visualization of many organs and structures, in that fat surrounding an organ or structure will allow it to be delineated

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Gas opacity

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Gas is the most radiolucent material visible on a film

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Metal opacity

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This is the most opaque shadow seen on radiographs, and may be seen as, orthopaedic implants, metallic foreign bodies