Ortho Introduction to Radiology

Question 1

X-Ray Properties

Answer 1

high energy electromagnetic waves that pass through a body part onto a film
Most of the radiation is passed through the body, but some is absorbed producing the image

Question 2

3 factors of radio-opacity

Answer 2

1. atomic number: higher is more radiopaque
2. physical density: air (black), fluid and soft tissue (grey), bone (white)
3. Thickness: thicker structures result in more attenuation, more radiopaque
   Overlapping structures will be additive and appear more radiopaque than if they were separate

Question 3

General Opacities

Answer 3

1. Mineral opacity
2. Soft tissue/fluid opacity
3. Fat opacity
4. Gas Opacity
5. Metal Opacity

Question 4

X-Ray Components

Answer 4

Electrode pair, glass vacuum tube in a lead case
Cathode generates electrons that strike the tungsten anode
Electron collides with tungsten atom knocks an e- out of a lower orbit
When a higher orbital electron falls to fill the gap, energy is released as a photon (x-ray)
95% of energy is deposited as heat, only 5% generates x-rays

Question 5

Digital radiography

Answer 5

Photostimulable plate absorbs x-rays and emits light (flourescence) that is detected by an image reader

Question 6

Flat Panel Detectors

Answer 6

most common
Amorphous silicon: x-ray converted to light, which is converted digital output signal (indirect image)
Amorphous selenium: x-ray photons converted directly into charge on a sensor (direct image)

Question 7

High Density Line Scan Solid State Detectors

Answer 7

Phosphor detectors records X-ray energy during exposure

Question 8

Radiation Protection

Answer 8

1. Reduce time of exposure
2. Increased distance from radiation source
3. Radiation shielding (lead shields)

Question 9

Scanograms

Answer 9

Measure leg lengths precisely

Used in children if correction is necessary to equalize growth of legs

Question 10

Comparison X-Rays

Answer 10

When comparing left to right

Done to verify a fracture in a pediatric patient (compare epiphysis)

Question 11

Stress X-Rays

Answer 11

Usually done to assess ligamentous stability

Question 12

Arthrogram

Answer 12

Contrast is injected into a joint capsule and a radiograph is taken
If the contrast extraverts then the capsule has a tear in it

Question 13

Myelogram

Answer 13

Image the subdural space

Useful in diagnosing spinal stenosis

Question 14

How many views are needed when doing conventional x-ray exams?

Answer 14

Radiographs provide a 2D image

3D must be reconstructed mentally (from orthogonal projections, need at least 2 views)

Question 15

Orthogonal projections

Answer 15

two radiographic projections made at right angles

Question 16

X-Ray Naming

Answer 16

Direction primary beam enters and leaves the tissues being examined (AP)
Position of the patient (prone, supine, seated, standing) during exposure, left/right markers identified

Question 17

Radiographic planes

Answer 17

1. Median or midsagittal plane
2. Coronal plane
3. Axial or transverse cross-sectional plane

Question 18

Computed Tomography

Answer 18

Fanned x-ray beam rotated around a patient is measured by a series of detectors
Measurement of transmission at different angles allows computation of an image
Image densities are the same as conventional X-rays
Density and contrast varied by varying amount of radiation and time of exposure
Good for viewing fractures

Question 19

Ultrasonography

Answer 19

Displays an image based on acoustic properties of the tissue
Sound waves are sent into a patient and returning echo is converted into an image
Resolution depends on wavelength and frequency of waves

Question 20

Types of Ultrasound

Answer 20

1. Low frequency-longer wavelength, less resolution, greater depth of penetration
2. High frequency-smaller wavelength, greater image detail, superior for images of tendons, ligaments and bone

Question 21

High Frequency US

Answer 21

Better for tendons, ligaments and bone
Smaller wavelength
Greater image detail

Question 22

MRI

Answer 22

Tissue in magnetic field causes magnetic moment spin of hydrogen nuclei to line up
Deflecting the nuclei from this orientation using RF signals causes protons to emit RF signals that are used to generate images
Good for soft tissue contrast
Good for bone marrow, cartilage, soft tissues, ligaments, muscle and fat

Question 23

T1

Answer 23

Measures energy released as proton exposed to RF signal realigns to magnetic orientation
Fat and muscle appear different on T1 (visualize fluid better)

Question 24

T2

Answer 24

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 “larmor frequency”
2nd RF blast is used
Normal muscle and striated muscle appear different on T2

Question 25

Radio-isotope absorption

Answer 25

Tissues with increased circulation will receive more isotope

Question 26

Strontium 85

Answer 26

1961 | 1st isotope used for bone scanning

Question 27

Strontium 87

Answer 27

Shorter half life, poor soft tissue clearance

Question 28

Technetium tc99

Answer 28

``` 1971 Short half life Excreted into urine 4 hours post injection Administered as phosphate complex Binds with Ca2+ in bone ```

Question 29

Indium 111

Answer 29

leukocyte scan | Used to tag WBCs and assess uptake into areas of infection (useful in osteomyelitis)

Question 30

Gallium 67

Answer 30

impregnates into Ca2+ hydroxyapatite crystals Uptake in neutrophils and bacteria Track progression of treatment of infection

Question 31

Factors that affect uptake of isotopes

Answer 31

1. Bone turnover rate 2. Blood flow to trauma 3. Trauma 4. Time isotope is in the system

Question 32

PET

Answer 32

1. metabolic imaging (good for diagnosing tumors) 2. Tracer is used to measure the rate of glucose absorption by tissue 3. Accumulation rate reflects glucose utilization in tissue 4. Based on increased glycolytic rate in pathologic tissues

Question 33

Advantages of PET

Answer 33

high sensitivity for bone pathology, allow imaging metabolic activity, white cell scintgraphy used to dx osteomyelitis, scintigraphy used to dx metastsis, stress fx, occult fx, etc

Question 34

Disadvantages of PET

Answer 34

Lack of detail and special resolution Limited early sensitivity to detect acute fx in patient with slow bone metabolism, low sensitivity with lytic diseases (multiple myeloma) Low specificity for bone pathology

Question 35

DEXA Scan

Answer 35

Dual energy X ray absorption Measures absorption of 2 beams of radiation into hip and spine Results are compared to standard T-scores calculated and used to identify if patient has osteopenia or osteoporosis Measures bone mineral density

Question 36

Dexa scan values

Answer 36

Osteopenia-T-score at or below -2.5 Severe osteoporosis-T-score at or below -2.5 and history of one or more fractures Normal T-score -1 and above

Question 37

BMD differences

Answer 37

20-40 for healthy caucasian women One standard deviation on either side represents 68% of population 85% of women 20-40 have normal BMD

Question 38

CT Advantages

Answer 38

Better cross sectional capability

Question 39

Bone Scan Advantages

Answer 39

Early detection of fracture Stress fracture, can be positive as early as 48 hours post injury Detection of infection and degree of involvement

Question 40

MRI

Answer 40

Bone contusion Articular cartilages Relationships of neurovascular structures to other anatomy

Question 41

Ultrasound advantages

Answer 41

Fluid filled tissue and vascular supply