3 - Introduction to Imaging

Question 1

What should I know?

Answer 1

1. How x rays are made
2. The 2 main densities on x ray exams
3. Which radiology exams use x rays
4. Understand some of the other techniques used for investigations i.e. us, ct, nm, mri, pet

Question 2

What did the discovery of x rays follow

Answer 2

Electricity, magnetism and importantly the ability to produce a vacuum within a glass tube

Question 3

What 4 things does an x ray tube consist of?

Answer 3

1. An electron source (the cathode)
2. A strong accelerating force
3. A vacuum within a glass (no air)
4. Tungsten focal spot that creates x rays upon impact (the anode)

Question 4

What are the 2 types of radiation created when tungston is bombarded with electrons?

Answer 4

1. Braking Radiation (the e- whirls around the nuclei and is bent)
2. Characterestic Radiation (e- hits another e- to an outer level)
   The energy given off by these forms x rays

Question 5

Wavelength of xrays?

Answer 5

0.01nm - 0.1nm

Only gamma rays are shorter

Question 6

When first discovered how did they enhance xrays

Answer 6

They put a photosensitive source under the body part and subsequently saw the shadows of bones

Question 7

What kind of radiation is xrays

Answer 7

electromagnetic

Question 8

What initially happened when people used xrays without control

Answer 8

Radio-necrosis

Was 5 years until it what recognised as dangerous

Question 9

Grid?

Answer 9

Ensures that only the direct rays make it through to the film and the ones at weird angles that would blur the film are bounced out

Question 10

What are the 4 x ray density levels (important)

Answer 10

1. Calcium (bone) - white
2. Water (tissue) - grey
3. Fat - darker grey
4. Air (lung/fundus) - black

Question 11

What is the 5th density

Answer 11

Metal. Shows as white i.e. medical tools

Question 12

How are x rays made

Answer 12

• play a high electrical potential across and evacuated tube and pass a current through it
• the resulting x rays penetrate tissue and densities to varying degrees and creates shadows

Question 13

Why is viewing soft tissue structures less successful in xray

Answer 13

The difference in density and penetration and so shadowing of middle level tissues (fat, tissues, blood) is small

Question 14

How may an x ray contrast be improved

Answer 14

Using less voltage like in a mammograph

Question 15

Difference between radiographer and radiologist

Answer 15

grapher - takes x ray (medical imaging technologist)

ologist - interprets the x rays

Question 16

X ray diagnosis (pros and cons)

Answer 16

• good spatial resolution
• limited contrast resolution
• depicts differences in density via ranges of greys
• can age and stage kids wrists

Question 17

How many views do you do

Answer 17

at least 2 of every bone

Question 18

Why does the heart look radio opaque?

Answer 18

Bones behind it

Question 19

What does pneumonia look like on an x ray

Answer 19

Opaque (shouldn’t as should be filled with air and be black). Takes out whole lobe while a mass is more well defined (also get weight loss with a tumour)

Question 20

Completely white lungs?

Answer 20

Drowned and filled with water

Question 21

What does a pneumothorax look like

Answer 21

Air in pleural space so looks like lung has collapsed. If it is filled with fluid it is called a hydropneumothorax

Question 22

What is a pleural effusion?

Answer 22

Excess fluid build up around the lung. Looks like a great big white opacity at the bottom of the lung

Question 23

4 ways to increase contrast in x ray

Answer 23

1. Barium sulphate
2. Iodine
3. Gadolinium (MRI)
4. Air

Question 24

Barium Sulphate

Answer 24

Given by mouth, injected into gut, up rear (enemas) GI studies, no one is allergic to barium some people are allergic to iodine. Can see ulcers

Question 25

Iodine

Answer 25

Injected into BVs (angiography). 1/40 000 people die from iodine. Excreted by kidney so good to view. Plain x rays and ct to enhance vessels and kidney

Question 26

Gadolinium

Answer 26

MRI. Injected. Used as iodine isn't good in a magnet

Question 27

Air

Answer 27

Brain (encephalograms) - used to make air go into brain. Not used anymore as high mortality

Question 28

Haematuria?

Answer 28

RBCs in urine

Question 29

Presentation of kidney stones?

Answer 29

- groins pain and haematuria - inject iodine - US in young CT in old

Question 30

Why use an angiogram?

Answer 30

With iodine. See if vessels still patent

Question 31

Nuclear medicine

Answer 31

- radioactive substances are ingested or injected - gamma rays detected using a gamma camera - bone scans (goes to osteoblasts), thyroid scans, lung scans - head (stroke), bone, lung, thyroid, renal

Question 32

Ultrasound

Answer 32

- short pulses of sound waves - piezo-electric crystal - images by the transmission or reflection of waves - inexpensive, safe, portable - but can't penetrate bone and air containing structures

Question 33

How much does a US machine cost

Answer 33

more than $1 million probes $10 000

Question 34

US

Answer 34

- produces 2d or 3d images - the location is determined by the time taken to receive the reflected signal - appearance is determined by differences in tissue impedence (Z) Z = pc

Question 35

In US what colour are vessels and the GB

Answer 35

Fluid is black as no sound waves reflected

Question 36

What is US used for

Answer 36

``` abdominal pain LFT bumps/mass swelling renal dysfunction vascular imaging cancer screening pregnancy children pelvic pain ovarian pathology scrotum ```

Question 37

CT (computed tomography)

Answer 37

- xrays in transverse plain - cross sectional imaging - LESS spatial resolution than x ray but much better contrast resolution - added contrast with iodine - 300 xrays - blood is white - bowel obstruction - go to first for trauma

Question 38

When would you do a head ct

Answer 38

headache, dizziness, hemiplegia (paralysis on one side of body), trauma - may be a haemorrhage (sudden severe headache and vomiting )

Question 39

When would you do abd ct

Answer 39

- when us not helpful - trauma - cancer - bowel obstruction - vascular imaging

Question 40

Magnetic Resonance Imaging (MRI)

Answer 40

- uses magnetism in any plane - hydrogen nuclei within the body align with the mag field - added radiofrequency pulses change this alignment and energy is released when the protons realign to the mag field - no radiation - good brain pics - renal cancer - BOTH good spatial and contrast resolution - can get 3D images in any plane - expensive and takes a long time to set up and image - availability - contradictions (pacemakers, claustraphobia) - gadolinium used to increase contrast

Question 41

PET imaging

Answer 41

- die with radioactive tracers - injected into veins - cancer soaks up and shows bright node at metastases - short 1/2 life -