L21 - Imaging Flashcards
Clinical practice guidelines (CPGs)
Clinical Practice Guidelines (CPGs)
- Assist clinicians in making evidence-based decisions for optimal use of MSK imaging
- Recommend imaging only when it’s likely to affect patient management
- Consider patient history, physical exam & initial conservative treatment before imaging
- Use appropriate imaging modalities for suspected pathology
- Avoid unnecessary imaging
American college of radiology appropriateness criteria
American college of Radiology / Appropriateness Criteria (ACR-AC)
- Offers evidence-based, expert consensus-driven recommendations to guide clinicians on most appropriate imaging modalities for specific conditions
- Assign appropriateness ratings to various imaging techniques
- Provides recommendations tailored to specific indications
- Encourage the least invasive & most cost-effective imaging options first, escalating advanced imaging only as needed
- Minimize unnecessary radiation exposure é ensure imaging aligns with patient needs &
healthcare efficiency
Difference between CPGs vs ACR-AC
CPGs vs ACR-AC
- CPGs: Broader clinical decision-making tools used to determine whether imaging necessary as part of overall patient care.
- ACR-AC: Focused, radiology-specific criteria helping select best imaging modality for given
clinical scenario once imaging is warranted
Key principles of diagnostic imaging
KEY PRINCIPLES OF DIAGNOSTIC IMAGING
- Do not harm
- Use diagnostic imaging when findings will inform management decisions
- Form clinical diagnosis or know what you aim to rule in or out
- Look at images after examination & considered ddx
- Image findings must be placed in context of entire examination & clinical suspicion
- Look at images, don’t rely on reports
- Always get at least 2 views
Ordering medical imaging prescribing
ORDERING MEDICAL IMAGING PRESCRIBING
Consider following:
• What is the objective of ordering an Xray?
• What am I expecting to see?
• Risk to benefit
• Influence on patient injury/recovery trajectory
• Will it influence my management plan for this patient?
- X-rays exit tube via small aperture iris that is used to regulate size of beam
- X ray beam is then directed at X ray receptor (traditionally film – now digital)
- Object to be imaged placed between beam & receptor in standardized position
- Shadow of radio opaque tissues is then seen as negative image
Production of X-ray images attenuation
- Degree to which X-rays absorbed or deflected by tissues
- Bones have high atomic weight & effectively “block” X-rays from passing through
- Less X-rays passing through lighter the image (remember it is “negative”)
Shades of gray
Table
Skeletal radiology terminology:
- osteoblastic
- osteoclastic
Osteoblastic
- Radiopaque
- Opacity
- Sclerosis
- Hypertrophic bone
- Increased radiodensity
- Blastic lesion
o Reparative
o Reactive bone
Osteoclastic
- Radiolucent
- Lucency
- Rarefaction
- Osteopenia
- Decreased radiodensity
- Demineralization
- Lytic lesion
o Bone destroying
A-B-C’S meaning
Alignment
Bone
Cartilage spaces
Soft tissues
Description alignment
1) Alignment
- Bone size: assess for normal size of bony anatomy (Acromegaly, Giantism, Paget’s disease)
- Number of bones: count bones to assess for extra or missing parts
- Congenital abnormalities: cervical ribs, transitional vertebrae
- Developmental deformities: scoliosis, genu valgum
- Bony shape & contours:
o Shape & contour of bone should be assessed for developmental as well as pathologic
alterations
o Trace cortical outline, should be smooth & continuous
- Bone / joint position: assess for bone & joint position
Bone description:
- general bone density
- focal bone density
- trabecular alteration
- sclerosis
2) Bone
- General bone density
o View from regional standpoint (step back & admire scene)
o Health mineralized bone distinctive differences in shades of gray between denser
cortical bone & less dense cancellous bone
o Bone may de-mineralize as much as 30 to 50% before it will be noticeable on radiograph
o Clear contrast between bone & surrounding soft tissue
o Clear contrast within bone itself
▪ Between denser cortical shell & less dense cancellous bone
▪ Healthy cortical bone shows up with greater density as clear white margin along bone shafts
- Focal bone density
o Look for focal changes in bone density
o Wolff’s law (phenomenon of remodeling, bone deposited in sites subjected to stress)
o Bone cells will align in such way as most efficiently withstand stress - Trabecular alteration
o Changes in trabecular appearance often early indication of mineralization changes of bone
o Fluffy, often seen in Paget’s disease & hyperparathyroidism
o Smudged, indistinct trabeculae characteristic of osteomalacia
o Coarsening, often seen in chronic renal failure & osteoporosis
o Lacy, secondary to Cooley’s anemia - Sclerosis
o Evidence of bony repair (reaction to increased stress bone callus
o Indication of degenerative osteoarthritis
o Excessive sclerosis, healing site of fractures
o Reactive sclerosis, body acting to surround diseased area
Cartilage spaces:
- joint space
- subchondral bone
- epiphyseal plates
Joint space
- Width
o Well-preserved joint space implies normal cartilage or disc thickness
o Decreased joint space implies loss of cartilage or disc thickness as result of degenerative
process
- Symmetry
Subchondral bone
- Contour
- Density
Epiphyseal plates
Views of spine: lumbar
- lateral
- AP
- flexion / extension
- oblique
Table
Views of spine: cervical
- lateral
- AP
- flexion / extension
- oblique
- swimmers view
- peg view
Table
Other types of MSK imaging
- Fluoroscopy
- Bone Scan
- Computed Tomography (CT)
- Magnetic Resonance Imaging (MRI)
- Diagnostic Ultrasound
Fluoroscopy description
Fluoroscopy
- Real time Xray
- Xray source is connected to receptor screen to move simultaneously (C-arm)
- Patient positioned within C-arm
- Used in fracture fixation, surgery, facet joint injections etc.
Bone scan description
Bone scan
- Patient injected with marker to reflect increased blood flow
- Marker absorbed by bony structures of increased metabolic activity (infection, recent trauma or neoplasm).
- Useful for – occult fractures, osteomyelitis, prosthesis failure post joint replacement
CT spect & PET/CT
CT SPECT & PET/CT
- Radioactive isotope injection
- Taken up in areas of high bony uptake/turnover (high metabolic activity),
often considered to be bony pain generators
- More often used for Spine
Computed tomography
Computed tomography
- Highly sensitive modality
- But low specificity
- Used for: localizing bone tumors, skeletal metastasis, early diagnosis of stress
fractures
Ultrasound imaging:
- utility
- benefits
- limitations
- clinical utility
Ultrasound imaging
Utility
- Assessment of musculotendinous structures
- Detailed examination of internal structure of muscle/tendon
Benefits
- Assess many planes/angles
- Activate musculature during exam
- Stress elements during the exam (traction, compression, strain)
- Visualize inflammation
Limitations
- Limited field of view
- Operator dependent
- Doesn’t visualize bone
- Not ideal for patients with high adipose tissue
Clinical utility
- Shoulder: Dx of RC tears
- Elbow: lateral/medial elbow soft tissue
- Ankle: archillis, retrocalcaneal structures
- Muscle: tears, hematoma, tendon rupture
- Other: abscesses
MRI
- acronym
- definition
- different types of views & description of each
Magnetic Resonance Imaging (MRI)
- Sensitive to bone marrow changes (bony tumors/necrosis)
- Soft tissue details (ligaments/tendon)
- Non-invasive
- 3D
- DDx for disc herniations/nerve root compression
Table
MRI: difference T1 & T2
Table
MRI: herniation description
Image
Words matter
WORDS MATTER
- Imaging reports often are full of words such as:
o Degenerative
o Arthrosis
o Severe joint space narrowing
o Scuffing/fraying
o Severe osteoarthritis
- Simplifying & giving context to these findings to patients is important
- Avoid using nocebic language
Importance of clinical exam
IMPORTANCE OF CLINICAL EXAM
- Generate provisional diagnosisG
- Differential diagnoses
- Start with common conditions, considering:
o Main complaint
o Age/sex
o Past medical/MSK history
- Using tests with high diagnostic utility where available
- Determine importance of imaging in patient’s management plan
Is a diagnosis needed?
Dependent on clinical setting and types of encountered conditions
Questions to clinically reason:
- Would a specific Dx impact my treatment plan?
- Are there signs making this presentation “unusual”?
- Are there red flag signs?
- Is the patient improving in an expected manner?
- Patient-related factors**
Key messages
KEY MESSAGES
- Imaging findings is not a diagnosis
- Be vigilant: understand prevalence of sinister pathology and natural hx of specific pathology.
- Continue medical/pathology-specific screening throughout period of care
- Monitor treatment responses
- Critically ask yourself what your intention of ordering imaging is:
1) What are you trying to rule in or out?
2) How will this change management?
3) Benefit vs harm?
