Imaging in PT Flashcards
Academy of Orthopedics in 2016 stated that PTs:
- are capable of recognizing the need for imaging
- are capable of incorporating imaging results into initial and
subsequent clinical reasoning processes - can provide expert clinical examinations to determine wether imaging
is necessary - are capable of utilizing imaging in a safe and efficient manner to
reduce potential risks….lower costs…and minimize risks of
unnecessary early imaging in the course of a condition
Expanding use of imaging decision making in PT
- Facilitate interprofessional practice and communication * Expansion of direct access
- Screening
- Referral for conditions outside scope of PT practice * Patient education/ therapeutic alliance
- Treatment planning and progression
- Therapeutic PNE
Referral for imaging
Directly refer a patient for imaging without going through another provider
Recommend for imaging
Suggest or request imaging through another provider who then orders the imaging
Integration of imaging
Using imaging results to make well-reasoned decisions regarding individual patients
is referral for imaging dependent on direct access?
no
physical therapists should:
○ Understand the role of imaging
○ Idenfity when imaging is indicated
○ Idenfity what type of imaging is most appropriate
○ Obtaining necessary diagnostic imaging
○ Integrating imaging results into patient/client management
○ Effective communication strategies between providers and with patients/clients
Providers who sign the referral for imaging…
assume responsibility to manage the patients subsequent care
purpose of clinical decision tools for imaging
○ Identify when imaging is indicated
○ Specify the most appropriate type of imaging
available clinical decision tools for imaging
○ Clinical Decision Rules (e.g. Ottawa Ankle Rules, Canadian C-spine
rules etc.)
○ American College of Radiology (ACR) Appropriateness Criteria
benefits of clinical decision rules
○ Clear and simplified indications for imaging
■ Radiographs: knee, ankle, foot
■ CT: c-spine
○ Not medical specialty dependent
limitations of clinical decision rules
○ Acute trauma only; limited to assessment for fracture
○ All developed based on patients presenting to ED
○ Does your patient meet the “inclusion” criteria?
○ No indication about how to manage patients outside the research protocol
ACR Appropriateness Criteria - What
○ A set of of evidence-based imaging guidelines for specific clinical conditions
○ Expert consensus, reviewed annually
ACR Appropriateness Criteria - Purpose
○ Recommend type and sequence of imaging modalities
○ Optimize patient / client safety
ACR Appropriateness Criteria - Clinical Hypothesis Variants
○ Detailed variants based on clinical hypotheses
○ Primary focus is appropriate imaging modality
ACR Appropriateness Criteria - Author Narratives
○ Explains rationale
○ Captures clinical essence of imaging recommendations
○ Patient summaries
How is ACR Appropriateness Criteria helpful to us even though we can’t order imaging?
- Improve understanding of imaging terminology
- Facilitate integrating imaging report information into patient care
- identify conditions or situations outside the scope of PT practice
- Improve communication and recommendations to referral sources
Radiograph - Physical Position
- supine, upright, etc
Standard radiograph position
describes the body part closest to the image receptor
Radiograph - projections describe the path of the x-ray beam
- A-P, P-A, lateral, oblique etc.
- Lateral are defined by the side closest to the image receptor/plate
- Oblique views necessary to image specific structures
MRI
- Utilizes magnetic field physics
- Differences in magnetic field strengths
- Provides excellent tissue contrast and a means to evaluate brain, spinal cord, discs, ligaments, vertebral bodies, vascular structures, organs, tumors, muscle, and facet joints
- Significant contraindications exist (e.g., pacemaker, metal in the body, claustrophobia etc.)
MRI - TE
- TE (time to echo) is the time between application of
the RF pulse and the peak of the signa
MRI - TR
- TR (repetition time) is the time from application of
excitation pulse to the application of the next pulse
MRI - T1 and T2
- T1 and T2 are different processes related to the return of protons to alignment with the main magnetic field
- T1 weighted image: early part of the decay signal
- T2 weighted image: late stage of the decay signal
T1 Weighted images
- short TR and TE times
- signal is caught early when the difference in relaxation characteristics for fat and water is most noticeable and tissues that rapidly recover their longitudinal magnetization, such as fat, give rise to high signal
intensity (create a bright image) - short TE –> tissues that are slow to regain longitudinal
magnetization, such as tissues with high free-water content, render low signal intensity and appear dark on T1-weighted images
T1 provides images of …
good anatomic detail, displaying the tissues in a fairly balanced manner
T2 Weighted images have
long TR and TE times
How does T2 imaging work
- signal is measured late in the decay process so tissues that are most reluctant to give up energy are selectively imaged
- Free water is slow to give up its energy = high signal intensity on T2 sequences
- Fat, which gives up energy rapidly = low intensity on T2
T2 images
- T2 images are grainier and display less spatial resolution since they
are made at lower energy levels
What is T2 imaging valuable for
detecting inflammation
what does MRI excel in
display of soft tissue detail
what is MRI the best movability for
evaluation of disk herniation and other potential causes of nerve root impingement
MRI sensitivities
- very sensitive for detecting changes and variations in bone marrow
- can stage neoplasms in bone and soft tissues as well as evaluate the extent of tissue invasion
- more sensitive than bone scans for detecting bone metastases (although bone scan is more effective as a screening technique)
Computed Tomography
- Merges x-ray and computer technology to create cross sectional slices
major advantage of CT
demonstration of subtle bony
abnormalities
major disadvantage of CT
10-100 x increase in radiation exposure to the patient
CT is standard modality in…
ED for head trauma, CVA,
abdominal trauma
what is bone scan
A nuclear imaging technique that shows areas of increased bone
activity as the marker or tracer is taken up in the bone tissue as
increased mineral turnover
What is bone scan useful for
Useful for detecting subtle fracture, stress fracture, infections, various
types of arthritis, avascular necrosis, primary and secondary
metastatic tumors, and can be used in diagnosing CRPS
what is the most commonly used radionuclide in bone scan
Technetium-99
are bone scans sensitive
yes but not specific
not usually used alone
DEXA/DXA
- used to determine the density of bone to assess its strength.
- a standard method for diagnosing osteoporosis; used in combination
with risk factors it is also considered an accurate way to estimate fracture risk
see the supplemental table
Advantages of Xray
- familiarity
- readily available
- inexpensive
- quick
disadvantages of x ray
radiation exposure
availability may cause over use
CT advantages
- superior anatomic detail, improved fracture sensitivity
- transverse (axial) images
- computer storage
CT disadvantages
- radiation exposure
- expensive
- artifacts
- reactions to contrast
MRI advantages
- excellent anatomic detail, especially of soft tissue
- no radiation exposure
MRI disadvantages
- expensive
- lengthy study
- limited visualization of cortical bone
- no ferromagnetic objects
Nuclear studies advantages
- very sensitive
- identify extent of process
- low radiation exposure
nuclear studies disadvantages
- lack of specificity
- low resolution
- expensive
US advantages
- safe during pregnancy (no radiation)
- intermediate cost
- high sensitivity and specificity
US disadvantages
- poor screening tool; best when site of disease is known
- image deterioration; sound blocked by air
- operator dependent
Review Ottawa knee rules
review Ottawa ankle/foot rules
Pittsburg decision rule (knee pain following an injury)
Conventional radiographs when a patient has had “blunt trauma or a fall as a mechanism of injury” plus either or both of the following:
* Age < 12 years or > 50 years
* Inability to walk four weight-bearing steps in the ED
review Canadian c spine rules
what does NEXUS low risk criteria identify
patients following trauma who DO NOT need diagnostic imaging
NEXUS low risk criteria
Radiography is indicated following trauma unless a patient meets all five criteria:
1. No posterior midline cervical tenderness
2. No evidence of intoxication
3. Normal level of alertness and consciousness
4. No focal neurological deficit
5. No painful distracting injuries (for example, an injury in an area other than the cervical spine that may distract the patient from neck pain)
risk factors for cervical instability
- Rheumatoid arthritis
- Ankylosing spondylitis
- Os Odontoideum
- Klippel-Feil syndrome
- Down syndrome
- Morquios syndrome
- Ehler-Danlos syndrome
- Marfan syndrome
- Other hereditary connective tissue disorders
- Post-fusion
radiography cervical spine
- A-P allows visualization of C3-7 vertebra
- A-P odontoid (“open mouth”) for visualization of C1-2
- Oblique views to visualize IV foramen
should you do imaging for low back pain within the first six weeks?
no
unless there are red flags
imaging guidelines for acute LBP in primary care settings
- For adults younger than 50 years of age with no signs or symptoms of systemic disease, symptomatic therapy without imaging is appropriate.
- For patients 50 years and older or those whose findings suggest systemic disease, conventional radiography and simple laboratory tests can almost completely rule out underlying systemic disease. 3. Advanced imaging should be reserved for patients who are considering surgery or those in whom systemic disease is strongly suspected.
