Quiz I Flashcards
What are the properties of Xray
Travel in straight lines at speed of light Diverge in space from source Cannot be detected by human senses Differential absorption Cannot be refracted by a lens Produce biological effects No "safe" dose
What is ALARA - 1994
As low as reasonably achievable
What is the minimal Equipment to produce radiographs
X-ray Source
Image recorder (film)
Subject
What is the path an X-ray takes to produce a radiograph?
Xray beam travels from source, through the subject onto the film
Process of Image Formation (5 Parts)
Xray tube - source of electrons
Xray beam - focused stream of photons directed at object
Object - beam is absorbed or passes through depending on density
Film - Photons that pass through object strike the film and react with silver coating to form an image
Image - record of photon interactions
How are X-ray photons produced?
Produced when electrons hit the target
How do Xray photons interact with the object and film?
Xray photons penetrate object and are absorbed or pass through and strike the film
What is the Xray beam? (shape and most important part)
Cone shaped from a point source and the central part is called the central ray and gives the truest image
What is Differential absorption
Denser object = less penetration
More beam striking the film = blacker
Less beam striking the film = whiter
What is the effect on tissue density on the image?
- Increased tissue density = whiter area on film
- (more tissue quantity)
- Decreased tissue density = darker area on film (less tissue quanitity)
Differential absorption from least to most (Black -> white)
- Air (lungs/trachea/outside the body)
- Fat (perirenal fat/ facial plane)
- Water (muscle/Organs)
- Bone (Bone/ Atherosclerotic plaquing)
- Metal (fillings/Markers/ Ortho devices)
What do Xray photons pass through?
- Non - dense objects (Air, soft tissue)
- Images appear blacker
- Radiolucent appearance
What absorbs Xray photons?
- Dense objects (metal, bone)
- Image appears whiter
- Radiopaque appearance
Define Radiolucent
- Readily allows x-rays to pass through the object
* Appears blacker on xray
Define Radiopaque
- Not permitting transmission of xrays through the object
* Appears whiter on x-ray
What is AP projection?
• Anterioposterior = ray travels front to back (film against back)
What is PA projection?
• Posterioanterior = ray travels back to front (film against front)
What is Lateral projection?
- Named for side the patient is against the film
* Left lateral = patient left side against film (rays travel in through the right to left)
What is Oblique projection?
- Patient is positioned oblique to film so the central ray passes through the patient at 45 degrees to their coronal and sagittal planes
- Named for the body part that is against the film
What are the 4 body positions to take xrays?
- Upright - AP, PA or lateral
- Recumbent - Supine, Prone or Lateral
- Oblique - right or left and anterior or posterior
- Decubitus - side lying view
Advantages of upright positions
- Allows for evaluation of postural information
* Upright lumbar/pelvis used to evaluate leg length inequalities
Advantages of recumbent positions
• Positioning is useful when the patient is in a lot of pain or when the patient is very large however no reliable evaluation of postural elements can be obtained
What is the typical minimum diagnostic series?
• Minimal of 2 views perpendicular to each other
What is the minimum diagnostic series of the cervical spine?
- 3 views
- AP Cervical
- AP Open Mouth
- Lateral Cervical
How to determine choice of positioning?
- Place structure that you wish to visualize closest to the film
- Start with standard (minimal diagnostic) series
What may influence choice of positioning?
- Particular structure wished to be visualized
- Patient’s clinical presentation
- Differential diagnoses under consideration
- Patient’s size
- Patient protection (ie: female pelvis due to ovaries easily damaged so PA view typically so ilium absorbs most of rays)
What are Mitchell Markers?
- Metal markers
- Taped to cassette prior to exposure
- Label anatomical side of patient
- Label side Closest to film
- Usually contain BBs that are gravity dependent due to their placement (recumbent = middle, gravity dependent for upright, site in a concave surface)
What does the Name Blocker contain
- Patient name, gender and age
- Doctor’s name
- Facility where films were taken
- Date of study
What is superimposition?
- Radiographic images of objects that lie in the same path of the xray beam
- Superimposition is not affected by the order (AP vs PA) that the beam strikes the objects
- Projection and superimposition are affected by the objects’ relationship to the central ray
What causes an image to be more magnified on an Xray?
- When the object is further from the film
* Moving the tube closer to the patient
What is Collimation?
- Shutters to block peripheral portions of beam
- Limits area exposed to beam; uses most central portion of beam
- Uses the smallest possible for good xray
- Decreases scatter radiation
- Decreases patient dose
What is compact bone?
- Cortex
- Outer shell of bone
- Encloses medullary bone
- Covered by periosteum
- Homogenous density on xray
What is spongy/cancellous bone?
• The network of trabeculae in the medullary portion of the bone
What is Periosteum
- Fibrous outer layer of bone
- Responsible for membranous bone formation, attachment of tendons and ligaments and contains vascular supplies to the bone
- Not present on surface of intra-articular bone
- Normal periosteum not distinguishable on radiographs
What are the 4 categories of bones
- Flat bones - ribs, sternum, scapula, cranium, iliac wing
- Short/square bones - carpals, tarsals, vertebrae
- Sesamoid bones - embedded in tendons
- Long/tubular bones - femur, humerus, etc.
What are the parts of a long bone?
- Epiphysis - articular end of the bone separated by the physis (growth plate)
- Metaphysis: the portion between the physis and the shaft, the site of growth and greatest metabolic activity
- Diaphysis - the shaft of bone where the medullary cavity is filled with red marrow
What is the method of evaluation of films?
- Alignment
- Bone
- Cartilage
- Soft Tissues
What is important with alignment evaluation?
- Spatial relationships of structures
- Look for offset of articular margins
- Evaluate structures for proper position
- Make pertinent specific measurements
What is important with bone evaluation?
- Shape
- Size
- Cortical integrity
- Internal matrix (trabeculation)
- Radiographic density
- Specific structures
What is important with cartilage evaluation?
- Evaluate joint spaces
- Joint shape
- Joint size
- Radiographic density
What is important with soft tissue evaluation?
- Shape
- Size
- Position
- Radiographic density
Steps in Evaluations
- Identify the study
- Identify the informational markers
- Note collimation, shielding and artifacts
- Note the technical quality of the film
- Evaluate anatomy using ABCS search pattern
What to note in the identify study step?
- Anatomy visualized
- Number of films
- Projections
- Use of contrast media
What to identify in the informational markers step?
- Name blocker (patient age, gender, date of study)
* Qualification of study (patient position and type of study)
What to identify in the collimation step?
• Collimation, shielding and artifacts
What to identify in the film quality step?
- Diagnostic quality?
- Proper positioning?
- Entire area visualized?
What are methods of evaluation?
- Compare one side to the other
* Compare one level to adjacent level
Where is the retopharyngeal space?
•Down to C2
Where is the Retrolaryngeal space?
•C3 to C5
Where is the retotracheal space
•C6 & Below
What is the rule of 2s and 6s
- At C2 < 6mm
* At C6 < 22mm
What is the atlantodental space?
• Space between posterior aspect of C1 anterior tubercle and the anterior aspect of the odontoid process
• Adults: < or = 3mm
Children: < or = 5mm
What is McGregor’s Line?
- Only visible on lateral cervical/skull
- Posterior hard palate to most inferior surface of the occipital bone
- Den’s should not project more than 8 mm above in males and 10 mm in females
What is the atlantodental interval
- Lateral cervical spine (neutral, extension and flexion)
- Midpoint of posterior margin of anterior tubercle of C1 to nearest point on anterior margin of odontoid process
- Normal is less than or = to 3mm in an adult
- Normal is less than or = to 5 mm in child
- Indicates rupture of transverse ligament
What is George’s Line?
- Also known as posterior body margin line
- Lateral Spine (neutral, flexion, extension)
- A line drawn along the posterior vertebral bodies across disc spaces
- Offset indicates antero or retrolisthesis
- Translation > or equal to 4 mm between two views may indicate instability
What is Spinolaminar junction line?
- AKA Posterior Cervical Line
- Lateral spine (neutral, flexion, extension)
- Most anterior point of the spinolaminar junction is identified at each level
- Offset indicates antero- or retrolisthesis
What is the minimum distances of C1 posterior surface of midvertebral body to spinolaminar junction?
•16mm
What is the minimum distances of C2 posterior surface of midvertebral body to spinolaminar junction?
•14mm
What is the minimum distances of C3 posterior surface of midvertebral body to spinolaminar junction?
•13 mm
What is the minimum distances of C4 - C7 posterior surface of midvertebral body to spinolaminar junction?
•12 mm
True or False: Lateral mass should overhang the lateral margin of C2 superior facet?
•False: >1mm
What is Jefferson’s fracture?
• Odontoid fracture where overhang of lateral mass of atlas overhangs the lateral margin of C2 superior facet by > or equal to 2 mm
What is the cervical gravity line?
- Lateral neutral cervical
- Vertical line drawn through the apex of the odontoid process and should pass through the C7 vertebral body
- Assesses where gravitational stresses are acting at the C/T junction
What is the angle of cervical curve?
- Lateral cervical
- Two lines are drawn, one through the parallel to the inferior endplate of the seventh cervical body, the other through the midpoints of the anterior and posterior tubercles of the atlas
- Construct perpendiculars that cross each other and measure the angle (35-45 degrees normally, avg 40)