Diagnostic imaging Flashcards
what are the advantages of using radiography to image the abdomen?
gives a good overview and is better for assessing size/shape of structures
what are the advantages of using ultrasound to image the abdomen?
excellent assessment of internal architecture and luminal spaces (unless gas filled)
what technique should be used to radiograph the abdomen?
low kV - high mAs technique
why should a low kV - high mAs technique be used to image the abdomen?
avoid scatter radiation and improve contrast resolution
why is the contrast poor when radiographing the abdomen?
mostly soft tissue with some fat contrast
what is the issue with using high mAs to image the abdomen?
there is a longer exposure which increases the chances of motion artefacts
what phase of respiration should an abdominal radiograph be taken in?
expiratory phase (end of expiration)
what view is the best for imagine the abdomen?
ventrodorsal
why is ventrodorsal view used to image the abdomen?
spreads out the organs so reduces superimposition
what are the two views used to image the abdomen?
ventrodorsal and right lateral
what are the two types of positive contrast media?
iodine containing
barium
what are the two types of iodine containing positive contrast media?
ionic/non-ionic
high/low osmolarity
what are the two negative contrast medias?
air
carbon dioxide
when is the only time barium is used as a contrast media?
GI studies
why is barium only used as a contrast media for the GI tract?
if it gets into body cavities it causes severe granulomatous inflammation and possibly death
what can iodine containing positive contrast media be used for?
GI tract
urinary tract
IV
myelography
what is the safest type of iodine containing positive contrast media?
non-ionic and low osmolar iodinated media (draw the least amount of fluid towards them)
what is the side effect seen if iodinated contrast media gets into body cavities?
anaphylaxis
what is the only time air is used as a contrast?
bladder (pneumocystogram)
what steps should be taken to ensure you achieve the best abdominal ultrasound possible?
perform after radiography
sedate in a dark quiet room
clip widely
use plenty of gel
what are some blind spots or places that we struggle to imagine in the abdomen?
organs within the pelvic canal
vascular malformation
ectopic ureters
what are the radiological signs (rontgen signs)?
number
size
shape (margination)
opacity (gas, fat, soft tissue, bone/mineral, metal)
location
what is the mass effect?
look at what organs have been displaced to determine where and what size the mass is
what is dystrophic tissue damage always secondary to?
tissue damage
what is metastatic mineralisation always secondary to?
hypercalcaemia
how does the location of dystrophic and metastatic mineralisation compare?
dystrophic is generally very focal whereas metastasis is often widespread
why is the fat in the omentum so important to radiography?
key to abdominal contrast and serosal detail
what is the peritoneum?
space around organs lined by a serous membrane and containing a tiny amount of fluid
what are the six differential diagnoses for loss of serosal detail in the abdomen?
lack of fat (emaciation)
brown fat in young animals (higher water content so appears as soft tissue)
peritoneal fluid
peritonitis
carcinomatosis/sarcomatosis
visceral crowding (due to very large mass)
what are the three main differentials for pneumoperitoneum?
post surgery (up to 4 weeks)
rupture GIT
penetrating trauma
how will a pneumoperitoneum look a radiograph?
increased contrast between gas/soft tissue
organs serosal surfaces are highlighted (eg. intestinal walls)
gas bubbles that are confined to GI tract
what are the features of a normal liver on a radiograph?
most cranial organ of abdomen
acute ventrocaudal angle pokes just past costal arch
should be parallel to gastric axis
what are the general features seen on radiograph of animals with hepatomegaly?
rounded margins
mass effect
gastric acid displaced caudally
ventrocaudal angle extends further past costal arch
how is the gastric axis displaced in micro-hepatica?
cranial
what are the differential diagnoses for microhepatica?
vascular (portosystemic shunt, primary portal vein hypoplasia…)
inflammatory (chronic hepatitis with cirrhosis…)
how is the normal spleen seen on a lateral radiograph?
tail - flat triangle caudal to ventral liver (mobile)
head - flat triangle on left that superimposes the right kidney (fixed)
what is the retroperitoneum?
dorsal to peritoneal cavity and most most organs
contains kidneys, adrenal glands, large vessels, lymph nodes…
should adrenal glands be visible on radiographs?
no (can see them on cats when they are mineralised - harmless)
are abdominal lymph nodes visible on a radiograph?
no (unless abnormal)
can the normal pancreas be seen on a plain radiograph?
no (ultrasound more useful)
what mass effect with an enlarged pancreas have?
lateral displacement of duodenum
caudal displacement of transverse colon
what structure is the oesophagus found in?
mediastinum
when can the oesophagus be visualised on a plain radiograph?
if it contains gas or a contrast media
what is marked dilation of the oesophagus known as?
megaoesophagus
what radiographic sign indicates there is gas in the oesophagus?
trachea-oesophageal stripe (summation of tracheal and oesophageal wall soft tissue)
what sites of the oesophagus are predisposed to foreign bodies?
thoracic inlet, heart base and cranial to diaphragm
if barium contrast studies indicated for foreign bodies in the oesophagus?
no - could be perforations or could aspirate
what can gas distribution/redistribution be used for?
to provide contrast and highlight structures within the abdomen (can reposition patient)
where does gas rise to in the stomach of a right lateral radiograph?
fundus (on the left)
where does gas rise to in the stomach of a left lateral radiograph?
pylorus (pyloric antrum)
where does gas rise to in the stomach of a ventrodorsal radiograph?
body of the stomach
where does gas rise to in the stomach of a dorsoventral radiograph?
fundus
what are the compartments of a stomach?
cardia, fundus, body, pyloric antrum
what are the five layers of the stomach seen on uiltrasound?
(outside)
serosa
muscularis
submucosa
mucosa
lumen
(inside)
what layers of the stomach are seen as hypoechoic? (dark)
muscularis and mucosa
what are the two causes of gastric dilation?
gas dilation - aerophagia, GDV…
fluid/gas dilation - outflow obstruction…
what can cause bizarre gas pattens in the stomach?
gas trapped in foreign bodies (eg. socks…)
what axis does the stomach rotate around in GDV cases?
longitudinal axis
where is the fundus displaced in GDV cases?
caudoventrally and right
where is the pyloric antrum displaced in GDV cases?
craniodorsally and left
how much gas is it normal to have in the small intestinal tract?
dogs - some homogenous gas filling is normal
cats - little to none
why may the small intestines look thickened on a radiograph? (wall thickness illusion)
wall can’t be reliably assessed because fluid and soft tissue are indistinguishable on radiographs
how does the mucosal layer of the wall in the stomach compare to the small intestines?
thickest layer in the small intestine
how does the submucosa of the small intestine appear on transverse ultrasound images?
flower/wheel like appearance
what are the two main causes of small intestinal dilation?
mechanical obstruction (foreign body, tumour…)
functional ileus (inflammation, toxic, stress…)
what is dilation with gas and fluid of the small intestine associated with?
obstruction
what is the small intestine diameter compared to to determine dilation?
height of L5 (take with pinch of salt)
what is the obstructive pattern seen in the small intestine?
creates two populations of intestine - dilation proximal to obstruction and normal diameter distal to obstruction
how does intussusception of small intestine appear on ultrasound?
onion appearance
what are some possible artefacts/limitations of radiographing the musculoskeletal system?
geometric distortion - not collimated well or not truly parallel to the cassette
poor soft tissue contrast
when may serial radiographs be indicated for the musculoskeletal system?
monitor disease progression
assess dynamic component of disease
if diagnosis is uncertain
what are the radiographic (rontgen) signs?
number
size
shape (including margins)
location
opacity
what are the three main things to consider when assessing radiographs of the musculoskeletal system?
soft tissues (swelling/loss)
bones (shape, defects, growth plates…)
joints (swelling, effusion, suchondral bone…)
what are the two main causes of reduced size of soft tissue in the musculoskeletal system?
atrophy (focal) - neurogenic, fibrosis, lameness
weight loss (general)
what are some possible causes of focal increase in soft tissue of the musculoskeletal system?
trauma, abscess, granuloma, neoplasia
what are some possible causes of diffuse increase of soft tissue of the musculoskeletal system?
oedema, cellulitis, diffuse neoplasia
what are the anatomical regions of long bone?
epiphysis
metaphysis
diaphysis
what are the layers of long bone?
(outside)
periosteum
cortex
endosperm
(inside)
how long does mineral loss have to be going on to identify reduction in opacity of bones on a radiograph?
minimum 7 days
what are the ways lysis of bone can be described?
geographical (unified focal area)
moth-eaten (many coalescing holes)
permeative (many tiny holes)
how aggressive are the different types of radiographic bone loss?
(least)
geographical
moth-eaten
permeative
(most)
what are the ways of describing the periosteal reaction (bone surface) seen on radiographs? (in order of aggression)
(least - inactive)
smooth
rough
brush border
palisading
spicular
sunburst
amorphous
(most - aggressive)
how can the transition zone of a bone lesion on radiograph help determine how aggressive it is?
long transition - aggressive
short - less aggressive (well circumscribed)
what does monostotic?
single bone involved
how can the distribution of skeletal lesions be described on a radiograph?
monostotic
polystotic
focal
generalised
symmetrical
asymmetrical
what is polystotic?
multiple bone involved
what is it important to critically assess regarding the joints on a radiograph?
soft tissue swelling
joint space width
sunchondral bone opacity
osteophyte/enthesophytes
periarticular mineralisation
what are enthesophytes?
new bone formation around tendons/ligament attachments
what are osteophytes?
new bone formation around the joint capsule
what joint can joint effusion be determined from radiograph?
stifle - infrapatellar fat pad gets squashed
can cartilage be seen on radiographs?
no - needs contrast
what are some possible defects seen of the subchondral bone?
osteochondrosis
septic arthritis
erosive arthrits
neoplasia
trauma
what are some signs of osteoarthritis on radiographs?
soft tissue swelling
periarticular osteophytes (predilection sites)
subchondral sclerosis
narrowed joint space
what are the predilection sites for osteosarcoma?
proximal humerus
distal radius/ulna
distal femur
proximal tibia
what are the predilection sites for osteosarcoma?
proximal humerus
distal radius/ulna
distal femur
proximal tibia
what are the predilection sites for osteosarcoma?
proximal humerus
distal radius/ulna
distal femur
proximal tibia
what are the predilection sites for osteosarcoma?
proximal humerus
distal radius/ulna
distal femur
proximal tibia
what modes of imaging can be used for the urogenital tract?
plain radiograph
contrast radiograph
ultrasound
can the uterus and ovaries be visualised on plain radiograph?
no - unless markedly enlarged
why is it difficult to ultrasound the uterus and ovaries?
located between the bladder (ventrally) and descending colon (dorsally)
what are the signs of a pyometra on radiography?
dilated soft tissue opacity loops between the bladder and colon
intestines displaced cranially and dorsally (mass effect)
what are the signs of pyometra on ultrasound?
fluid filled uterine horns/body
thin/thick/cystic walls
where is the prostate located?
caudal to bladder and partly within the pelvic canal
what shape is the prostate?
symmetrical and ovoid/round
what opacity is the prostate?
soft tissue
what does the size of the prostate depend on?
age and neutering status
how big should the prostate of an entire male be in comparison to the pelvic inlet?
no more than 70%
what can cause prostatomegaly?
benign prostatic hyperplasia
prostatic neoplasia
prostatitis
what opacity is seen with prostatitis on radiograph?
soft tissue with some mineralisation
what causes of prostatomegaly are only seen in entire males?
bengin prostatic hyperplasia
prostatitis
what signs of prostatic neoplasia will be seen on radiography?
mineralisation
irregular shape (only one lobe effected)
metastasis (lumbar vertebrae)
what is the most likely diagnosis of mineralisation of the prostate in neutered dogs?
prostatic neoplasia
where do prostatic neoplasias metastasise to?
medial iliac lymph nodes
lumbar vertebrae (periostea reaction)
lungs
what are the categories of contrast radiographic studies for the urogenital tract?
positive/negative cystography
iodinated retrograde urethrography
iodinated intravenous urography
what positive contrast media can be used for cystography?
iodinated contrast
what negative contrast media can be used for cystography?
usually air
what is the process of cystography?
catheterise and empty bladder
instil contrast medium until distended
what contrast is best for looking at mucosal detail on cystography?
double contrast
how is a double contrast cystogram carried out?
catheterise and empty bladder
instil positive contrast and massage to coat mucosa
instil negative contrast (air)
how do calculi appear in a double contrast cystogram?
central defects in the contrast pool
how do blood clots appear in double contrast cystography?
can adhere to the wall and be irregular, can be scattered around bladder
how is a retrograde urethrogram carried out?
catheterise and empty bladder then slightly inflate with air to create some back pressure (allow urethral dilation)
place catheter at tip of urethra and clamp
inject iodine based contrast
why do retrograde urethrograms need to be done under GA?
clamping penis/vulva is very painful
what is needed for an IV urogram to be diagnostic?
adequate renal function/hydration
GA
lot of time (>2 hours)
multiple radiographs
what are the indications for cystography?
radiolucent calculi
bladder mass
bladder rupture
chronic cystitis
what are the indications for retrograde urethrogram?
stranguria (uroliths, stenosis, neoplasia…)
ectopic ureter
bladder rupture/integrity
what are the indications for an intravenous urogram?
suspected Coptic ureter
ureteroliths
ureteral stenosis
renomegaly
what mode of imaging is needed to visualise cystitis?
double contrast cystography
ultrasound
what bladder calculi can be visualised on plain radiography?
struvite, oxalate, calcium phosphate
what bladder calculi can’t be visualised on plain radiography?
cystine and urate
why can’t masses in the bladder be diagnosed on plain radiography?
soft tissue and fluid have the same opacity
what mode of imaging is used to diagnose a bladder rupture?
positive contrast cystogram
what is the only mode of imaging that can be used for assessment of the urethra?
retrograde urethrogram
which kidney is more cranial?
right (left is left behind)
what do you compare the kidneys to to determine if they are the correct size?
L2
what mass effect will an enlarged kidney cause?
ventrally displace colon
what diseases could be suspected if there is irregular (focal) renomegaly?
unilateral - neoplasia, cysts. abscess
bilateral - neoplasia, FIP,
what diseases could be suspected if there is a smooth (generalised) renomegaly?
unilateral - neoplasia, hydronephrosis
bilateral - AKI, FIP, pyelonephritis, lymphoma
what is pyelectasia?
mild/moderate dilation of the renal pelvis secondary to diuresis or inflammation
what is hydronephrosis?
moderate to seere pelvic dilation often due to secondary obstruction
what are the three main causes of microrenale (small kidneys)?
CKD
atrophy
dysplasia (congenital)
what breed is predisposed to polycystic kidney disease?
Persians
what is needed to visualise the ureters in diagnostic imaging?
intravenous urography
what shape to the ureters form when they enter the trigonal region?
a J shape
what are some indications for neurological imaging?
confirm diagnosis with expected changes
rule out differentials
what are the indications for an aural radiograph?
chronic otitis
peripheral vestibular syndrome
facial nerve paralysis
Horners syndrome
(all caused by middle ear disease)
what imaging modality is the best for imaging middle ear disease?
CT
what is an open mouth rostrocaudal radiograph useful for?
highlight tympanic bulla
what are some considerations for taking spinal radiographs?
straight positioning (sand bags…)
exposure in expiratory pause (no motion artefacts)
take multiple sections (avoid geometric distortion)
why is a ventrodorsal view of the spine used instead of dorsoventral?
spine is closer to the cassette in ventrodorsal so there is less distortion
why are multiple sections needed to radiograph the entire spine?
to avoid geometric distortion by not having parallel rays to the area of interest
what are horses heads when discussing radiographs of the spine?
intervertebral foramina
what dog breed is predisposed to having mineralised intervertebral discs?
dachshund
what causes atlanto-axial subluxation?
congenital malformation of dens or excessive ligament laxity
(less common through trauma)
what is the major cause of luxation/subluxation of vertebra?
trauma
what is the most important radiographic view if laxation of the spine is suggested?
lateral - if confirmed don’t take orthogonal and could damage further
what is discospondylitits?
infection of an intervertebral disc that extended to cause osteomyelitis of adjacent endplates
what radiographic changes are seen with discospondylitis?
no changes in disc apparent
irregular shaped endplates with new bone formation appear after 3 weeks
what are the possible locations of soft tissue lesions within the vertebral canal?
extradural
intradural
intramedullary
what mode of imaging is used to asses for soft tissue injury to the vertebral canal?
myelography
how is myelography carried out?
injecting iodinated positive contrast into subarachnoid space followed by orthogonal radiography
what are the indications for CT as neurological imaging?
suspected bone trauma/anatomy abnormality
otitis media
intracranial tumours
peripheral nerve tumours
what lesions of the neurological system is MRI not good at imaging?
anything to do with bone
what can degenerative intervertebral disc disease predispose to?
disc herniation
infections (discospondylitis)
what is spondylosis deformans?
briding/spur formation of new bone arising from the ventral aspect of endplates
not clinically significant
what breeds are predisposed to vertebral anomalies?
brachycephalic (usually not clinical significant but can predispose to neurological disease)
