Imaging Flashcards
Key points to check before x ryas
Check if pregant, esp if pelvic or abdo
Remove metal incl udnerwired bras
Flurooscopy is a vide of continues radioopaque material
When is contrast used in CT
in highly vascularised areas to differentiate boundaries eg angiograms for clots
What is the best scan for aortic dissection?
CT angiogram chest and abdomen
When is CT abdo/pelvus with contrast used
Appendicitis, diverticulitis, bowel obstruction/perforation
What is high resolution chest CT and what is it used in?
More slices = extra detail - pulmonary fibrosis and ILD
What need to check before do contrast CT
Check kidney function and prev allergic reactions when considering iodine contrast
Need a large bore cannula
can u do a CT in pregnancy
No
When is contrast CT used vs non contrast for head
non contrast - bleed, stroke, trauma
Contrast - space occupying lesion eg tumour, infection
What is contrast induced nephropathy
Creatinine rises after a dose of contrast
May require oral/IVC fluids undergoing CT contrast OR contraindicated
How does T1 appear in MRI
Water is dark - used for anatomy and soft tissues
How does T2 appear in MRI
Water is bright - pathology eg inflammation or oedema
What contrast is used in MRIs
Gadolinium, also enhances vascular structures
MRI contraindications
Pacemakers, aneurysm clips, cardiac stents
Claustrophobia
First trimester of pregnancy
MRI safety questionnaries by them or doctor
Transdermal meds removed (some metal in them causes burns)
Common indications for MRI
MRI head - MS, space occupying lesion, stroke, inflammation
MRI spine - Cauda equina syndrome
Cardiac - structural, coronary heart disease
MSK - muscle/tendon damage
What scan do you use for gallstones
MRCP - as often radiolucent so not visible on x ray
Ultrasound considerations
Limited view if larger body habitus
Full bladder for pelvic scan
Fasting for 6 hours prior to abdo scan
Common uses of types of US
bdo/pelvic US - gallstones, prenancy, AAA
Transvaginal - ovarian and uterine masses, pregnancy
Bedside - FAST - after trauma - scan for free flud, guided bedside cannulation
Doppler for DVT
What is a doppler
An US to check blood flow and pulses
Investigation ofr acute cholecystitis
US of abdomen - impacted gallstones cause acute cholecysitits
When is mammograms used over US
Women over 40
No pregnanct or lactating
US often also indicated at the same time
Examples of nuclear imaging
PET scan - glucose for highly metabolic cancers
DMSA - kidney, DAT - dopamine + thyroid scanning
Sensitivity definition
Ability of a test to correctly identify those with the disease (true positive rate) and expressed as a %
Specificity definition
Ability of a test to identify people withoyt the disease eg the true negative rate
Positive PV definition
The porbability of the disease being present if the test is positice
Negative Preficitve value
Porbability that the disease is absent if the test is negative
What are predicitive values influenced by
The prevlence of the disease in the population
Likelihood ratio calculation
Sensitivity / (1-specificity)
