What determines radiographic opacity?
What material appears BLACK on a radiograph?
What is this characteristic called?
AIR appears black b/c there's no object to "cast a shadow"
Black areas are where the Xrays shine through = "lucent"
What is the term for a material that appears WHITE on a radiograph?
"Radioopaque" - this is when objects "cast a shadow"
Arrange in order from most lucent to most radioopaque:
titanium screw, adipose, bone, lung, soft tissue, muscle
(most lucent) lung - adipose - muscle - soft tissue - bone - titanium screw (most radioopaque)
Can you determine an object's shape from a single radiograph?
If not, what's the minimum you need?
You need two to determine shape (more can be a waste and cause unnecessary radiation exposure)
Name and describe the orientation of the three imaging planes.
- Sagittal = cuts the body longitudinally
- Coronal = cuts the body front-to-back
- Transverse = cuts the body parallel to the floor view
Order the steps of generating a radiographic image:
A. Electrons hit a tungsten target & are reflected off
B. Electrons are "boiled off" of the filament
C. Remaining electrons hit a film/sensor
D. Object of interest blocks electrons
E. A tungsten filament is heated
E, B, A, D, C
1. A tungsten filament is heated
2. Electrons are "boiled off" of the filament
3. Electrons hit a tungsten target & are reflected off
4. Object of interest blocks electrons
5. Remaining electrons hit a film/sensor
Describe the basic concept of contrast radiography
Technique using a "contrast" (aka dye) to bring out the details in a radiographic image by giving contrast to a structure in question.
What does the term "echogenicity" refer to?
This term describes how a tissue/object/etc appears when examined via Ultrasound
- Hyperechoic = bright
- Hypoechoic = dim
- Echogenic = any tissue
- Anechoic = fluid, air
What is the specific term for image "density" in a CT scan?
What does a HIGH attenuation look like on CT scan?
High = white
Low = black
List four advantages of CT scanning
2. Low cost
3. Readily available
4. Great resolution (~1500x greater than XRay)
List four disadvantages of CT scanning
1. Patient's pathology may change from the time the scan was taken
2. Volume averaging
3. Radiation risk from multiple scans
4. Equipment is expensive to procure
List four advantages of MRI scanning
1. No radiation
3. Low cost
4. Generally available
List four disadvantages of MRI scanning
1. Changing Pathology
2. Potential for claustrophobia
3. Metal in/on patient
4. Magnetic Field and Radio Frequency cause interference and create inaccurate images
How are bright structures described in relation to MRI scans? Dark structures?
Bright = hyperintense
Dark = hypointense
Of the T1 and T2 MRI modalities, which makes fat appear white, and which makes water appear white?
T1 = fat
T2 = water (think T2 = H2O)
What is Arterial Spin Labeling (ASL)?
MR Angiography that can be done without the use of a contrast
List two advantages to vascular contrast studies (aka angiography)
1. Examines all vessels to find defects
2. Great contrast provided downstream of contrast injection
List two disadvantages to performing angiography
1. Can be invasive
2. Exposes patient and staff to increased background radiation (via radioactive tracers)
Which is a better term to use around patients and their families, and why?
"Contrast" or "dye"
- sounds professional, yet simple
- avoids reminding the Pt about death/dying