week 1- terminology

Question 1

what are the key components of SFOV

Answer 1

• Information that will be reconstructed and available to see
• Anatomy should be positioned in the isocentre
• Anatomy outside SFOV cannot be displayed

Question 2

what anatomy requires a small SFOV

Answer 2

head
spine
orthopaedic

Question 3

what anatomy requires a large sfov

Answer 3

chest, abdo, pelvis

Question 4

what factors influence slice thickness

Answer 4

beam collimation and detector array configuration

Question 5

what is automatic tube current modulation

Answer 5

• Automatically adjusts mA during scan in accordance with tissue density

Question 6

what is longitudinal tube current modulation

Answer 6

• Allows for variable mA in accordance to the body part you are scanning (calculates average mA)
• Uses information from one or two view localisers

Question 7

why is patient centring important?

Answer 7

• Patient positioned above or below isocentre can affect calculation of attenuation and impact implementation of AEC
• Patient mispositioning to the left or right of isocentre will result in one side of the body receiving more radiation dose than the other

Question 8

what are the differences between a pitch >1 and a pitch <1 and which is better

Answer 8

> 1
- Decreased dose, faster scan time, lower quality MPR/3D reformats, bigger the gap, lower the quality
<1
- Increased dose, slow scan time, improves MPR/ 3D reformats, more overlap better the quality, therefore this is superior

Question 9

what are the two types of image reconstruction

Answer 9

filtered back projection

Iterative reconstruction

Question 10

what are HU

Answer 10

Every pixel is assigned a HU based on location and attenuation; each slice has a scan matrix (commonly 512-1024)

Question 11

what is volume imaging?

Answer 11

Reconstruct images into slices (axial, coronal, sagittal)
Each slice has a thickness and scan matrix (usually 512 or 1024)
Stack slices together to create a volume of data/ image information
Thinner slice thickness = greater resolution; increased noise, overlap in acquisition, improves quality of MPR’s

Question 12

what are reconstruction filters/ algorithms used for?

Answer 12

• Used to enhance features of certain structures; sharpen or smooth edges of reconstructed image
• Smooth filters decrease noise (soft tissue)
• Edge enhancement filter sharpens edges (bone and lung)

Question 13

define thickness and interval

Answer 13

• Thickness = how we acquire the data (thickness of image)
• Interval = the gap between each of the slices that occur (how far apart the images are)
• Used when scanning axially or reformatting images for viewing

Question 14

what is window width and window levels?

Answer 14

different WW and WL highlight areas of anatomy to better differentiate structures within the image

Question 15

what is metal artefact reduction

Answer 15

-Beam hardening artefacts caused by metallic implants, reduce effect by applying MAR, IR algorithm

Question 16

what is the post-processing technique, multiplanar reformations

Answer 16

• We take all the axial information we have acquired and are now reconstructing it into coronal and sagittal planes
• Used to demonstrate anatomy and pathology from different planes to that of scan
• Viewed as an average of HU
• Maximum Intensity Projection (MIP), commonly used in CTA; uses the highest HU and creates an average based on that

Question 17

what are 6 examples of post-processing techniques

Answer 17

MPRs
averages density MPR
oblique MPR
curved MPR
2D MPR MIPS
MinIP

Question 18

what are 5 types of 3D image processing

Answer 18

SSD
volume rendering
3D MIP
vessel tracking
virtual reality navigation

Question 19

define hypodense pathology

Answer 19

less dense

if an abnormality is less dense than the reference structure

Question 20

define isodense pathology

Answer 20

the same density

if an abnormality is the same density as the reference structure

Question 21

define hyperdense pathology

Answer 21

more dense

if an abnormality is bright (white) on CT

Question 22

define abdominal aortic aneurysm (AAA) pathology

Answer 22

a ballooning out of a segment of artery caused by disease or weakness in the vessel wall that occurs in the portion of the aorta that runs through the abdomen

Question 23

define ascites pathology

Answer 23

a condition in which fluid accumulates in the abdomen and causes swelling

Question 24

define bronchiectasis pathology

Answer 24

a dilation of the bronchi, often caused by infection

Question 25

describe embolic stroke pathology

Answer 25

this type of stroke occurs when a blood clot that has formed elsewhere in the body breaks away and travels to a blood vessel in the brain, blocking the flow of oxygen-carrying blood

Question 26

describe myeloma pathology

Answer 26

a tumour of the bone marrow. Multiple myeloma is an uncommon cancer of the white blood cells in the bone marrow that is associated with anemia, haemorrhage, recurrent infections and weakness

Question 27

define pericardial effusion pathology

Answer 27

excessive fluid within the sac surrounding the heart, usually due to inflammation

Question 28

define subarachnoid stroke pathology

Answer 28

blood collection between middle (arachnoid) and inner (pia matter) linings of the brain. It can be a result of trauma, or a bursting (ruptured) aneurysm

Question 29

define metastasis pathology

Answer 29

the development of secondary malignant growths at a distance from the primary site of cancer