MSK imaging Flashcards
What is Computed Tomography?
Uses X-ray source & ionising radiation
Rotates around patient to acquire a volume of data which can be reconstructed as required
Attenuation in different structures in different ways similar to X-rays but uses ‘Hounsfield units’
Computer data processing / algorithms produces images in multiple planes / slice thicknesses
Computed Tomography-Benefits
Cross-sectional / multi-planar / 3d ability
such as coronal, sagittal and axial slices
Ability to remove overlying structures
Such as separating out superimposition
xcellent contrast resolution compared to plain film
Meaning that we can see more in terms of the soft tissues and organs
Very useful to assess trauma and bone tumours
Compared to X-rays higher sensitivity and specificity
Computed Tomography – Trauma
CT can be used to detect both the presence and extent of fractures (subtle/complex) e.g. spinal
Joints & Intra-articular abnormalities:
damage to articular cartilage
loose bodies / fracture fragments
associated soft tissue structures
Evaluation of spinal fractures in relation to spinal cord are almost 100% accurate
CT is particularly useful when looking at bone related tumors in particular……
Contrast resolution – ability to differentiate between tissue types
Extent of bone lesion- How far the lesion grows?
Look and identify presence of cortical interruption – tumour which breaks out of the bone is considered more aggressive
Helps to evaluate soft tissue structures and we can use contrast agents to help support this.
Evaluation of complex/ overlying structures
Can be used to guide intervention – biopsies and treatment e.g. thermal ablation (Heating it up to kill tumour
What are Benign tibial bone lesions?
The radiographic appearance;
ground glass appearance
higher density or attenuation
sclerotic bone lesions
white thickened appearance
The black area shows an osteoma a bone forming tumors which produces osteoid. CT allows use to see inside the bone (darker regions) which the tumor forms from and the outer areas are where the body reacts and lay down new bone.
Even though this tumor is benign, and not life-threatening patients will still find it very painful so will require certain pain killers such as aspirin and to treat this would require thermal ablation and needle biopsy.
Examples of tumours
Aggressive axial lesion of the spine
Osteochondroma
Aggressive axial lesion of the spine
Patient lies prone flat on stomach
One half the vertebrate is missing because this the tumor.
Thermal obliteration is taking place with the needle being inserted into the spine guided by CT
Osteochondroma
Benign lesion
Mushroom like appearance
Cartilage is present on the top hence the name osteochondroma ‘bone’ & ‘cartilage’ growth.
CT is better able to demonstrate the cartilage cap
In summary why CT?
Excellent contrast resolution-more detail
Multi-planar / 3d reconstruction e.g. pelvis
Considered the Gold standard when evaluating traumatic injuries / tumours
Why not CT?
Use of ionising radiation (relatively high dose to patient
Artefacts (movement, volume effect, metalwork)
Non-specific; unable to provide characterisation of tissues (tumour type
Metallic artefacts can cause starburst effects and distorts the image
Lack of soft tissue detail
Can’t ifferentiate between tissues.
Name 7 ways CT can be used and applied
Diagnosing: Diagnosing disease: A CT scan can help diagnose a number of conditions, including bone and muscle conditions, infections, blood clots, and tumors.
Staging: Staging cancer: A CT scan can help determine the stage of a cancer. Or even bowel cancer screening programs
Monitoring: Monitoring treatment: A CT scan can help monitor the effectiveness of treatments, such as cancer treatment.
Guilding: Guiding procedures: A CT scan can help guide procedures such as biopsies, surgery, and radiation therapy.
Detecting: Detecting recurrence: A CT scan can help detect if a tumor has returned.
Planning: Planning radiation therapy: A CT scan can help plan external-beam radiation therapy.
Screening: Screening for osteoporosis: A CT scan can help look for signs of bone loss in older adults..
Magnetic Resonance Imaging- description
Uses magnets and radiowaves to create a strong magnetic field when patients are placed inside it causes hydrogen particles in the body to align.
Different rf pulse sequences (eg SE, STIR, fat supression) which causes H particles to become excited, and these can be used to demonstrate different tissue types
Different signal intensities (brightness) according to tissue type e.g. areas in body with high levels of water give have a greater signal intensity.
T1 & T2 are MRI sequences that uses different times between magnetic pulses to create an image.
Differences in Intensity: MRI
T1-weighted
Uses short TE and TR times to create images where fat appears bright and water and fluids appear dark. T1-weighted images are used to show normal soft-tissue anatomy and fat.
T2-weighted
Uses longer TE and TR times to create images where fluid and abnormalities appear bright. T2-weighted images are used to show fluid, tumors, inflammation, and trauma.
T1 scan might be used to look for structural abnormalities in the brain, while a T2 scan might be used to look for fluid-related conditions.
Differences in T1 and T2 weighted tissues in MRI
T1
fat yellow bone marrow- high
cortical bone- low
fluid- intermediate
acute blood- intermediate
red bone marrow- low
tumours- intermediate/low
lipoma- high
t2
fat yellow bone marrow- intermediate
cortical bone- low
fluid - high
acute blood- high
red bone marrow- intermediate
tumours- High
lipoma- intermediate
The benefits of MRI?
Soft tissues
Image soft tissues: MRIs are particularly good at imaging soft tissues like muscles, ligaments, tendons, and the brain, spinal cord, and nerves.
Differentiating
Differentiate between tissues: MRIs can better differentiate between fat, water, muscle, and other soft tissues than CT scans.
Radiation
Avoid radiation: MRIs don’t use ionizing radiation like x-rays, making them a good choice when frequent imaging is needed.
Blood flow
Measure blood flow: MRIs can help measure blood flow.
Staging
Stage cancer: MRIs can help determine the size of a tumor and whether it has spread.
Treatment
Evaluate treatment: MRIs can help evaluate how well a treatment is working.
Why not MRI?
Time
The average scan takes between 30-60 minutes
Availability
Low availability requires booking and preparation
Cost
High cost.
Contraindication
metallic implants & claustrophobia
Information
No additional information in some conditions
Artefact
Movement artefacts
How can MRI help determine what the lesion is made up of.
Deciding if something is benign or malignant.
Using the T1 and T2 weighted images looking at fat, fluid and blood.
Helps to determine whether the tumor has a blood supply - bone infarct (interrupted blood supply).
Benign tumors don’t have a blood supply. Malignant tumors do.
What is ultrasound?
Uses sound waves sent from a transducer
These waves are partly reflected as an echo when they interact with structures in the body
Larger echoes display a brighter signal on the screen
Great for soft tissue structures
The echo are not strong enough pass through bone / gas
Traditionally used for deep soft tissue structures in the abdomen liver, kidney etc.
Ultrasound: pros and cons
Balance between frequency and resolution (detail)
Higher frequency results in higher resolution (detail)
However, higher frequency results in lower penetration (loss of engergy)
Better resolution vs. low penetration
Obs/abo uses lower frequencies but compromise with the detail/resolution
Ultrasound in MSK
Can produce high resolution images of soft tissue structures
Specifically for superficial structures
Highly detailed in real time
Ability to identify blood flow – doppler imaging
Why Ultrasound?
Resolution
-Highest resolution can be used to use to determine whether a child will develop genetic condition e.g. spinal bifida, cleft palate, heart abnormalities - Doppler used to assess for blood flow. E.g. tumour with a blood flow would suggest a malignancy
Soft tissue visualisation
Cheap
‘Safe’ does not use ionising radiation
High resolution images
Readily accessible
Guided intervention
Patient interaction
Symmetry y
Physiology as well as anatomy
Easy to repeat
Guidance of injections
Why Not Ultrasound?
Operator dependency
Cannot assess deep structures or deep to air / bone
Artefacts
Limited image storage
Dependent on patient body habitus
Bony / deep articular structures
Non-specific findings
Large areas / vague symptoms
Cannot assess deep structures or deep to air / bone
Pathology- Inflammation/ infection:
tendinous
abcess
tenosynovitis
cellulitis / oedema
synovitis
Pathology- Soft tissue masses:
benign
malignant
cysts / ganglions
nerve sheath
FB’s
