Seminar 3 - Imaging in patient with respiratory disease Flashcards
what are the pro’s for using thoracic radiography, why is it such a common tool to evaluate patients for thoracic disease?
- readily available
- time & cost efficient
- relatively easy to perform
- DOES NOT REQUIRE ANAESTHESIA
- disease increase or decrease opacity which is picked up easily on radiograph
why does lung disease such as pulmonary oedema, pneumonia or neoplasia result in an INCREASE in radiopacity of the pulmonary parenchyma?
alveoli filled with gas normally, gas = black opacity
w/ oedema, pneumonia, etc. alveoli disease fill w/ fluid or soft tissue = lighter opacity = increase opacity of parenchyma
what are the limitations with using radiography?
- veterinarian must acquire high quality radiograph
- need good understanding of normal radiographic anatomy
- need to understand paradigms to allow correct interpretation
- subtle lesions may not be seen on thoracic radiographs, or may be obscured by superimposition of other structures
describe how CT produces cross - sectional images
thin x-ray beam rotates around patient at high speed, producing cross-sectional images
is CT more or less sensitive than radiography?
more sensitive –> more superior than radiography at detecting extend of disease and relationship to surrounding organs
what are some indications for using CT?
- screening a patient for pulmonary metastases (on a radiograph need to be 5mm, on CT can detect at 1mm)
- when acquire normal thoracic radiograph but thoracic disease suspected
- a lesion is detected on radiograph but further classifications required ie/ severity, extent of lesion to assist with surgical planning, r/ship of lesion to surrounding organs, allow CT guided biopsy.
- eval of patients with pleural effusion
- eval of suspected thromboembolism
- eval of recurrent pneumothorax
- thoracic radiograph hard to interpret due to severe obesity, inflammation, abnormal shape/conformation
what are the two windows CT can be viewed as and what do they allow evaluation of
- soft tissue window - allows evaluation of mediastinal structures and the thoracic wall
- lung window - optimally show pulmonary parenchyma and small pulmonary vessels
for evaluation of the nasal cavity which method (CT or radiograph) is preferred and why?
CT preferred
radiograph complicated by superimposition of facial bones, maxillary teeth and mandible.
Radiograph insensitive at detecting early disease or foreign body
CT rapidly performed, eliminates all superimposition, very sensitive at detecting fluid accumulations, soft tissue masses and body erosions, superior at detecting foreign bodies, can distinguish inflamm rhinitis
what are the disadvantages of CT?
- general anaesthesia is required
- some patients may not be able to be safely anaesthetised
- availability of CT is limited to referral or large general practices
- correct operation of a CT machine requires skill
- CT requires higher ionising radiation = has safety implications for both veterinary staff and patients
you would like to image a patient with a mamamry tumour, to search for pulmonary metastases prior to surgical removal of the tumour. which imagine modality would you choose - thoracic radiograph or CT?
CT - can detect nodule of 1mm, needs to be 5mm before detection on radiograph
what is ultrasound used for in thoracic imaging?
useful to assess the surface of the lung
cranial and caudal mediastinum
which species is the ultrasound particularly useful in and why?
in the horse - because can’t fit through CT or radiograph
ultrasound is portable –> can take to stall of sick horse
can ultrasound penetrate air filled lung?
no - produces series of parallel lines of decreasing brightness known as reverberation artefact
artefact allows identification of normal aerated lung surface
why is ultrasound useful for patients with pleural effusion?
patients with pleural effusion can be evaluated for potential underlying causes such as neoplasm, areas of pneumonia
–> in radiography pleural effusion is the same radiographic opacity as diseased lung or mass lesions
is a dyspneic dog with dull chest sounds which modality would you choose to evaluate the thorax
ultrasound - dull chest sounds thinking pleural effusion
do energy ultrasound, find fluid = drain it can then radiograph to check for mass
