imaging abdominal viscera Flashcards
imaging modalities for the abdomen
Xray/fluroscopy
US
CT
MRI
what are the two types of imaging views
plain (superimposed front to back) and cross sectional (slices)
planes - axial cronal and sagittal
what are the differences in resolutions
spatial and contrast resolution
what are the images of MRI
Many types of image sequences, weighted T1 - fluid is black and T2- white
what is contrast
used to increase contrast resolution (eg highlight specific areas/organs)
given via IV or enteral (oral/PR) before scan
either more or less dense than surrounding tissues (XR/CT) or paramagnetic (MRI)
pros of xray
cheap quick easy for pt high spatial resolution low radiation dose
cons of xray
poor contrast resolution
planar imaging
pros of CT
quick
widely available
cross sectional images
high contrast resolution
cons of CT
radiation dose
IV contrast risks
pros of US
cheap quick no radiation cross sectional images US guided interventions
cons of US
saved images are only a snapshot of exam (operation dependant)
pros of MRI
contrast resolution
specific applications
no radiation
cons of MRI
limited availability
patient experience (time, space)
expense
magent/contrast risks
how does the structure of an organ affect imaging
solid (eg kidney) vs hollow (eg bladder) viscera
modalities look at different ones better, eg US can’t go through air in hollow viscera
how does positioning affect imaging
intra vs retroperitoneal (inside peritoneal layer, single layer or double surrounding)
determines how pathology spreads through abdomen
how does circulation affect imaging
systemic vs portal circulation
what are the solid abdominal viscera
liver spleen pancreas
what is the liver structure (basic)
RHV, LHV and MHV entering top to drain
CBD, HA and PV entering bottom, triad goes to 8 segments (divided by portal vein horizontally and hepatic veins vertically)
biliary system
how is the liver imaged via US
hepatic and portal veins IVC fluid movement via doppler flow can see GB (useful for gallstones, shadowing white structure) metastasis (dark blobs)
How is the liver imaged by CT
Hepatic veins (R, M, L) IVC, portal vein from celiac artery (axial) downwards can see stomach via air and other organs can do contrast eg to see vessels gallstones, dilated bile ducts and metastasis
how else can the liver be imaged
intervention radiologists (real time imaging to diagnose and sort issues eg blocked vessels)
ERCP (endoscope with camera, also using xray to guide)
PTC (see bile system)
DSA (see arteries via catheter)
MRI (detail of biliary system)
what is basic structure of the spleen
LUQ at tail of pancreas
splenic vein
how is the spleen viewed
coronal above kidney
axial stomach and liver anterior
imaging pathologies of spleen
spleen can be shattered by trauma and replaced by haematoma
lymphoma
lesions
CT
basic structure of the pancreas
head of pancreas in curve of duodenum to boy and fungus
lobules
pancreatic duct to join CBD into duodenum
how is the pancreas seen on US
courses round splenic vein
how is the pancreas seen on CT
crisp outline with sup mes vein and artery
how is pathology seen
loss of outline, enlarged, irregular and areas of lower density - acute inflammation (pancreatitis)
hollow viscera of the abdomen
stomach, SB, LB
Xray good first line rest then MRI and CT (avoids endoscopy)
imaging the bowel by xray
normal calibre (LB 5cm and SB 3cm) looking for free air, normal distribution of bowel gas
how is the stomach seen on xray
LUQ, fundus under left hemidiaphragm, obliquely orientated
contains fluid and air
wall is regal folds
size variable
how is the SB seen on xray
central abdomen fluid and air contents encircling valvular conniventes- wider in ileum spaced out when distended <3cm diameter
how is the LB seen on xray
peripheral, LB frames SB faeces (liquid and hard) haustral folds spaced out when distended <6cm, <9cm caecum
how can a chest xray be used
perforation (free gas in highest point, diaphragm)
how is the bowel screened
fluoroscopy
single contrast barium follows through
works with gas for double contrast (barium enema, hard for frail and elderly)
bowel imaging via CT scan
CT colonography
look for polyps or 3D fly through to prompt colonoscopy
bowel imaging via MRI
Seen detail in bowel
IBD in SB and rectal tumour staging in LB
