Lecture 15 - Medical Imaging

Question 1

Types of imaging that use X-Rays

Answer 1

X-ray
Fluoroscopy
CT

Question 2

Basic principle on how X-Rays work

Answer 2

Electrons accelerated towards detector and patient
Some X-rays pass through patient hitting detector (BLACK)
Some X-rays attenuated by patient (absorbed scattered) GOES WHITE

Question 3

What colour will dense structures appear on X-Ray images and why

Answer 3

White
X-rays attenuated and don’t reach detector

Question 4

What colour will non dense structures appear on X-rays and why?

Answer 4

BLACK
X-rays pass through patient and reach detector

Question 5

Densities visible on X-ray from Darkest (least dense) to Lightest/Whitest (Most DENSE)

Answer 5

AIR
FAT
WATER
SOFT TISSUE/MUSCLE
BONE
METAL

Question 6

Clinical uses of X-Ray

Answer 6

Chest - Infection, pulmonary oedema, pleural effusion,pneumothorax

Abdomen/pelvis - Perforation, colitis, obstruction

MSK - Fracture, dislocation, effusion, soft tissue injury

Question 7

Adv of X-ray

Answer 7

Quick
Portable
Cheap
Simple

Question 8

Disadvantage of X-ray

Answer 8

Ionising radiation
Poor soft tissue imaging
1 plane
Cant see all pathology

Question 9

What is Fluroscopy

Answer 9

Continuos pulsed X-Rays creating real time moving images

Question 10

Clinical use of FLuroscopy

Answer 10

Diagnostic and Interventional
Angiography (Vascular) - stenting, embolisation
GI - (BArium swallowed and observed)

Question 11

Fluroscopy adv

Answer 11

Real time study can assess function and carry out intervention
Quick

Question 12

Fluroscopy disadvantage

Answer 12

High ionising radiation dose (continual pulsing X-rays)
Clinician doing intervention exposed to radiation
Then all X-Ray disadvantages

Question 13

What is Computed Tomography (CT)/How does it work?

Answer 13

X-ray tube and detectors move around patients creating cross sectional images

Question 14

What PLane are CT Scans read in?

Answer 14

Transverse plane

Question 15

CT uses

Answer 15

MANY
Diagnosis
Monitor conditions
Interventional

Question 16

ADV CT

Answer 16

Quick
Can scan most body parts
Good spatial resolution

Question 17

Disadvantage CT

Answer 17

Radiation from ionising x-rays
Doesn’t portray (delineate) soft tissues well
affected by movement of patients (artefacts)
Patient holds breath (might be unable)

Question 18

Positron Emission Tomography (PET)

Answer 18

Involves release of Gamma rays (Ionising radiation)

Question 19

What does a patient need to be given in Positron Emission Tomography (PET) ?

Answer 19

A radiopharmaceutical

Question 20

2 Components of a radiopharmaceutical

Answer 20

Pharmaceutical - Takes compound to target tissue

Radionuclide - Decays and releases Gamma radiation. (E.g Flurine 18)

Question 21

CLinical use of PET

Answer 21

Oncology -Detection, staging, response to treatment

Neurological - Early diagnosis of Alzheimer’s

Cardiac - Identify poorly perfumed myocardium

Infectio/INflammation - Vasculitits, unknown origin pyrexia

Question 22

PET ADV

Answer 22

Good contrast + spatial arrangement
Anatomy and function analysis

Question 23

PET DISADVANTAGE

Answer 23

Radiation dose to patient (GAMMA)
Radiation to others
Radioactive waste produced
Expensive
Actual uptake of radiopharmaceutical

Question 24

MRI (magnetic Resonance Imaging) How it works

Answer 24

Strong magnetic field aligns H atoms
Strong radio frequency pulse applied which knocks the H atoms
This creates a detectable magnetic field which induces an electrical current in the coils in the MRI machine producing an image

Question 25

Hyper intense meaning for MRI

Answer 25

Bright

Question 26

Hypointense meaning MRI

Answer 26

Dark

Question 27

Clinical uses of MRI

Answer 27

MANY Neurological Imaging (CNS) Cardiac Paediatric/pregnancy (No ionising radiation)

Question 28

MRI ADV

Answer 28

NO RADIATION Good contrast resolution

Question 29

MRI DISADVANTAGE

Answer 29

Expensive Time COnsuming Features stopping patients having MRI (Contraindications) Claustrophobia, metal items , pacemakers, cochlear implants

Question 30

Ultrasound (How it works)

Answer 30

High freq sound waves emitted Sound waves travel through tissues and reflected back from boundaries with different densities Echoes detected and converted into electrical signal then image

Question 31

Hyperechoic meaning

Answer 31

More reflection of ultrasound waves so white on image

Question 32

Hypoechoic meaning

Answer 32

Less reflection of ultrasound waves = Dark image

Question 33

What is Acoustic Shadowing?

Answer 33

Sound waves get completely reflected back so structures behind it hard to see

Question 34

Ultrasound clinical uses

Answer 34

MANY Obstetrics - Pregnancy dating, Fetal anomaly, placental location Solid organs Breast MSK - Muscles, tendons, ligaments joints Interventions

Question 35

Ultrasound ADV

Answer 35

No radiation Cheap Portable Dynamic (Can see movement)

Question 36

Ultrasound Disadvantage

Answer 36

NO BONE OR GAS PENETRATION Difficult with obese/frail/unwell patients (can’t move)