Flashcards in EXAM PREP Deck (54):
What is digital post processing? (smoothing)
Brightness values of pixels brought together.
What is digital post processing? (Edge enhancement)
Brightness can be increased along edges
What is the digital post processing? (Annotation)
Text on image
What is the digital post processing? (Subtraction)
Removal of background anatomy
What is digital post processing? (windowing)
adjust the image
What is digital post processing? (image reversal)
Bright and light pixels reversed
What is the digital post processing? (Magnification)
All parts of the image magnification
What limits digital post processing?
-You have to have a good quality (exposure index)
Film radiography artefacts?
-Finger prints/finger nails
-Clear Film (machine malfunction)
-Black film- exposed to light
-Clear film- Bubbles in chemicals
What is exposure index (EI)?
A value used to accurately determine whether you are giving the correct exposure value which is recommended for the examination.
What is noise?
Something that reduces the clarity of the image
What is window width?
Controls the contrast on the image (within a range)
What is the window level?
Controls the brightness on an image?
What is distortion?
Defined as: the misrepresentation of object size or shape as projected onto radiographic recording media.
Factors that affect distortion are:
-Source Image Distance (SID)
-Object Image Distance (OID)
-Central Ray Alignment.
Signal to noise ratio?
The number of x‐ray photons that strike the detector (mAs) can be considered the “signal” : to the amount of x-rays that don't reach the detector
How does air/gas appear on a x-ray?
e.g lung, bowel and stomach
How does fat appear on an x-ray?
e.g subcutaneous tissue, retroperitoneal fat, blood vessels
How does bone appear on an x-ray?
How does contrast/metal appear on an image?
What is Bone processing assessment?
B- bones, congruency of joints
O- Opacities (white) Overlapping
L- Lucencies ( Black- fracture)
S- Soft tissue
What is the checking process after an examination?
M- Marker locations correct
A- Anatomy correct in field
C- Collimation (changing shape of beam)
E- Exposure index
A- Additional requirements? (good image?)
P- Pathology (BOLTS)
Who do we need to check before MRI?
-accompanying friends or family
-patient support personal
The processing of flipping protons from the transverse to the longitudinal axis (along the z axis).
The time it takes to flip protons from the transverse to longitudinal
-Flips on the x-y plane
-While it does this the protons de-phase, until completely out of phase
-At the same time giving off energy
(Fat de-phases fast, fluid slower)
What is the difference between the RF coil and gradient coil?
Gradient coil--> Sends the RF pulse in causing excitation of protons
RF coil--> Receives RF signal from patient
What does the faraday cage do?
MRI shielded in copper to stop RF going into the room and destroying the image quality (e.g Zipper)
What is the CT number range for lung?
-830 to -200
What is the CT number range for fat?
-30 to -250
What is the CT number range for heart?
10 to 60
What is the CT number range for brain?
20 to 40
What is the CT number range for blood?
20 to 80
What is the CT number range for liver?
20 to 80
What is the CT number range for muscle?
35 to 50
What is the CT number range for spleen?
40 to 60
What is the CT number range for bone?
150 to 500
What is the CT number range for bone (dense)?
350 to 1000
What is the CT number range for Metal?
Artefacts of CT?
What is pre vs post collimation?
-Determines slice thickness
-Determines the amount of scatter reaching the detector
What is CR?
Uses a cassete. image is put in a plate and then it is displayed on an image display device.
Allows more effecint workflow does not use chemicals (like film).
Can do post processing
Allows a wider exposure range (than film)
Does not use cassetes or imaging plates. Image is generated at the detector and goes straight to the monitor.
The same detector can be used for the next patient.
With cassetes you had to choose the correct size and shape but with the detector its one size fits all.
Able to the post processing
Good storage - can be put on PACS.
Pateints need fewer repeats compared to film - because you can manipulate data unlike film.
What is PACS?
Picture archiving computer system
Where are the paramamary lymph nodes?
along the lateral aspects of breast tissue
Describe three advantages?
Image storage (increased space)
image transmission (easily transferring images for patients)
Image manipulation- SEA SWIM
List the four principles of a scout?
-Should not be used for diagnostic purposes (low quality)
-Sets the Limits for the CT SCAN
-The couch moves at a low speed
-Allows you to check if it can be used for planning (patient straight, gas, pathology)
Benefit of multiple detectors?
What are some common radiography artefacts?
-Image impositioning (double exposure, two pts on one image)
-Grid Cut off (field size)
What is bright in T1?
-Venous (slow flow)
What is black (dark) in T1?
-fast flow (arteries)
What is t1 mid-signal? (grey)
- White matter is white
-Grey matter is grey
What is bright on a T2 image?
-venous (slow flow)
What is dark on a T2 image?
-Venous (fast flow)