Week 6 - Intro To Image Interpretation Flashcards
Diagnostic imaging can be essential tool to:
- facilitate diagnosis
- for research
- grade severity of disease/injury
An accurate diagnosis will always be dependent on;
Thorough history
Clinical examination
Understanding relevant anatomy and likely pathological conditions
Examples of when to image
Confirm diagnosis and extent of injury and potential complications
Uncertain diagnosis which can affect management
Treatment is unsuccessful and diagnosis is questioned
Objective assessment of pathology progression/regression
Surgical work up
Plain radiographs are used to confirm, assist or exclude diagnosis
Imaging rights for Pods under MBS
Pods In aus may refer patients via Medicare for plain radiographs of the foot, knee, leg and femur as well as US examination of soft tissue conditions of the foot
Can order CT, MRI and other imaging techniques but is expensive as not covered by Medicare
Ethical considerations
The benefit to be contained from images must outweigh the risk of tissue damage from the technique - radiation: plain radiography, CT, fluoroscopy and NM
Only order imagines if the outcome of the plain radiography has the potential to alter treatment
There is a cost to any imaging technique
-financially
- radiation exposure
- ALARA
Health stewardship
Any practitioner who has the ability to refer directly for imaging must have a sufficient level of knowledge to be able to request appropriate investigations and understand the fundings of reports as we,L as the ability to act appropriately on the findings
What imaging modality do I choose
Conventional radiography (CR) remains the most commonly performed imaging investigation for assessment of the MSK system. Generally indicated in all fractures and dislocations and are sufficient for diagnosis in the majority of cases
CR can only identify general bone conditions, bone tumours and other focal bone lesions when comboned with clinical history and physical examination
A major limitation of CR is insensitivity go early bone changes in conditions such as osteomyelitis inflammatory arthritides and stress fractures
Appropriateness criteria for imaging - ACR
Developed by American college of radiology have specifically been developed to assist clinicians in selecting the best type of imaging study for the identification of a suspected pathology or which imaging type may be indicated across a diverse range of clinical scenarios
The appropriateness criteria are based on the supporting evidence base and expert consensus and they provide specific recommendations on which projections should be requested and the typical radiological features associated with specific pathologies
Many appropriateness criteria have been incorporated into commercially available electronic health record, referral and payment systems in an attempt to reduce unnecessary imaging referrals
To obtain the best result from images
Provide enough clinical and supporting information to assist imaging examination
- identify the specific anatomy involved in the pathology
- offer some guiding differential diagnosis for the radiographer so you are on the same page
- provide some clinical notes so appropriate imaging sequence can be obtained
MRI
Beneficial for soft tissue analysis
MRI sequences
An MRI pulse sequence is a programmed set of changing magnetic gradients
Different pulse sequences allow the radiologist to image the same tissue in various ways and combinations of sequences reveal important diagnostic info about the tissue in question
MRI sequences - T1 and T2
T1 weighted - fat bright, fluid dark, bones bright
T2 weighted image - fat intermediate-bright, fluid bright, bone intermediate
MRI intensity
White areas = high signal intensity
Black areas = low signal intensity
MRI Reports will describe the appearance of the intensity of the signal by relative terms that is, how bright the signal appears relative to a comparative sits and it may be described as: hyperintense (brighter), hypointense (darker) or isointense (same brightness)
MRI T1
T1 weighted = most anatomical of images and particularly useful for demonstrating trabecular detail and oasesous pathology including osteomyelitis
How will MRI reports describe the appearance of the intensity of the signal by relative terms
how bright the signal appears relative to a comparative sits and it may be described as: hyperintense (brighter), hypointense (darker) or isointense (same brightness)
T1 weighted scan
Anatomical
Fat gives the highest signal (white)
Joint effusion (fluid), tumours, inflammation and infection give lower signals (dark)
Gives good contrast between grey and white matter
T2 weight scan
Pathological - fat saturation
- water the higher signal
- good for inflammation
- dark structures show calcification and fibrous tissue
Viewing
Ligament - view along its length
Tendons - view cross section
Bont pathology - T1 anatomical images
Fluid/inflammation- T2 fat saturation images
Cartilage- sagittal and frontal planes
MRI contraindications and complications
No radiation but is expensive
Contraindicated for patients with MRI ferromagnetic materials Within the patient could potentially be moved/cause damage
MRI considerations
Contrast can be used to enhance specific tissues making them easier to appreciate
The most commonly used contrast agents in MRI are gadolinium based - These agents have the effect of causing the T1 signal to be increased especially in areas of active inflammation
Contrast media reactions can vary considerably from normal transient phenomena through to severe anaphylactoid reacqtiins and the later development of contrast-induced nephropathy
CT
Relies on X-ray transmitted through the body - X-ray tubes and detectors rotate around the patient
More sensitive as there are a series of slices taken through the body which are manipulated
Reflect radio densities of the tissues - relatively free from superimposing the shades of Greg more accurately reflect the radio density of the tissues
Can detect very small changes in X-ray absorption
Advantages of CT
Has the ability to choose the range of radiodensities displayed making it possible to better distinguish between tissue types of similar densities
Fat can be separated
IV contrast can be used in Ct for better visualisation or specific structures including blood vessels
US features
Tendon - mixed
Bursa - hyperechoic (low echoes) - not very dense and the speed of sound in fluid is much slower than that in bone
Bone - hyperechoic (high echoes) - very dense structure and speed of sound in bone is very fast! Therefore it is highly reflective and will appear white on the screen
US Structures and features (artery, vein and muscle)
Artery - hypoechoic, pulsatile, non-compressible - Doppler
Vein - hypoechoic, non-pulsatile, compressible - Doppler continuous flow
Muscle - hypoechoic with multiple hyperechoic lines
US structure and feature (tendon, nerves, ligament, bone)
Tendon - hyperechoic with bright ,ines longitudinally or bright dots in transverse section
Nerves - variable hypo or hyperechoic with fascicles pattern
Ligament - hyleeechoic hands with well defined borders
Bone - hyperechoic
Sonoanatomt of bone and cartilage
Bone and joint capsule - reflects entire US beam, bright white outline, acoustic shadowing below
Cartilage- hyaline - articular surfaces
Sonoanatomt of tendons
Hypoechoic fibrillar pattern along the long axis
Hypoechoic stripped pattern in the transverse axis
Sonoanatomy of nerves and ligaments
Nerves - linear, fibrillar structure
Ligaments - fibrillar structure similar to tendons but extends between 2 bones
Doppler imaging
Power and colour
Allows display of pulsatile information and vascular supply
Clinical examination vs US
Us has been shown to be superior to clinical examination techniques for assessment of active joint inflammation
Us detected remission occurs later than clinical remission and may explain progressive joint changes
Clinical examination can be over sensitive and lacks pathological specificity
Clinical examination vs US
Us has been shown to be superior to clinical examination techniques for assessment of active joint inflammation
Us detected remission occurs later than clinical remission and may explain progressive joint changes
Clinical examination can be over sensitive and lacks pathological specificity
Scope of US in podiatry
High resolution beneficial in diagnosis of foot and ankle pathologies and for treatment monitoring across a range of pathologies
US referrals
When referring a patient for an US, be as specific as possible; identify the tissue of assessed and exact location
