Midterm Exam Material Flashcards
Ordering MR
“I have a clinical suspicion of ________”
MR
H ions are excited by energy in the form of radio frequency using a surface coil. A strong magnet makes them spin in alignment. The changing moment causes an electric current in the surface coil.
Field Strength
Low vs high: how long does it take for the H ions to stop gyrating
Magnetic strengths measured in Tesla
0.3-0.5 Low field strength: Sufficient for spine
0.5-1.0 Intermediate field strength
1.5-3.0 High field strength: Required for extremities
<4.0 creates too much heat and human eyes cannot see any difference
MR contraindications
Brain aneurysm clips Intra-ocular foreign bodies Subcutaneous metal Pacemakers and some heart valves Neurotransmitting spinal implants Cochlear implants High iron tatoos
Water’s view
X-ray to check orbit for metal
Echo time (TE)
Time from excitation to detection of signal
Repetition time (TR)
Time between excitation pulses (longer TR result in T2 images)
Fast spin echo (FSE)
Multiple echoes between repetition time (making it faster with good resolution)
Larmor Frequency
Frequency of precession of a proton
Radio Frequency (RF)
The energy that excites the protons
High/ bright signal
White
Intermediate signal
Light gray
Low signal
Dark gray
Signal void
Black
Hypo intense
Darker
Hyper intense
Brighter
Iso intense
Same
T1
Fat is bright: good anatomical detail
T2
Water is bright: physiologic information especially edema
Fat suppressed (T1)
STIR or FS PD FSE: Eliminate fat then image should be dark and anything that shows as bright is ABNORMAL WATER (Ex inflamed bone marrow or new vasculature of neoplasm)
Proton Density (PD) not very common
Fat is light gray
Water is medium gray
Good for cartilage evaluation
STIR
Short T1 Inversion Recovery
FS PD FSE
Fat Suppressed Proton Density Fast Spin Echo
STIR information
Fat is black (suppressed)
Water is bright
Takes longer than FS PD FSE
Good for bone marrow edema, synovial fluid, tendons, ligaments and cartilage evaluation
Gadolinium Contrast used in spinal MRI when?
- Looking for a tumor or px with history of tumor
- Infection (contrast enhances sepsis)
- ddx scar tissue from other tissue in px with previous surgery
Chronic back pain associated with?
Atrophied multifidi
MCC leg pain in the world
Lateral recess stenosis
Nerve entrapment in lateral recess via
Enlarged facet joint
Evaluating IVF in C-spine
Plain film and/or CT: NOT MRI
Evaluating dens
CT is preferred if pathology is suspected. (Normal for dens to have less signal since very little fatty marrow)
Disc bulge (P)
Physiologic: 1-3mm due to compressive forces throughout the day
Disc bulge (D)
Degenerative: not a herniation, can contribute to stenosis, due to lack of water binding from decreased GAGs, can’t be undone
Degenerative disc bulge/ desiccation
Decreased disc signal on MRI
Normally innervated part of disc
Outer 1/3 of disc
Annular tears
Typically on periphery of disc
Contributes to DDD
Increased signal on T2 (Torn fibers fill with fluid)
Associated with disc herniation in lumbar spine ONLY
High intensity zone (HIZ)
Presence of HIZ means tear is recent
Significance of annular tears
Increased capillaries and decreased nerve conduction velocity (Pain and neurologic findings)
Disc displacement
Extends past boundary of endplate
Applies to bulges and herniations
Herniation
Local aka focal 0-25%
Bulge
Broad based 26-50%
Circumferential >51%
Percent of population with asymptomatic disc herniation
30%
Protrusion
Base is wider than posterior extension
Can be herniation or non-contained herniation (sometimes asymptomatic)
Extrusion
Base is narrower than posterior extension. Always associated with symptoms
Sequestration
Disc material has lost continuity with parent disc and may migrate
Relief from herniation
Herniation needs to shrink 20% (?) before symptoms go away
Signs of disc herniation (need 3 of 5)
- Leg pain
- Confined to dermatome
- Neural stretch tests recreate/exacerbate leg pain
- Neurologic findings (2 of 4: weakness, reflex, pinwheel, atrophy)
- MR/CT correlating to dermatome
Leg pain causes
Disc herniation, lateral recess stenosis, degenerative spondylolisthesis
Spondylosis deformans
Normal aging
IVOC
Pathologic process
IVOC characteristics
Loss of disc height, vacuum phenomenon, disc calcification, decreased T2 signal, posterior spur (osteocartilagenous ridge)
Spondylosis deformans endplate changes
Aka modic changes
Modic Type 1
Decreased T1 (fat)
Increased T2 (water) INFLAMMATION
Sign of acute degeneration
Associated with PAINFUL discs
Modic Type 2
Increased T1 (fat) Isointense T2 (water) Change in nutrition of disc causes endplate changes not yet visible on X-ray
Modic Type 3
Decreased T1 (fat) Decreased T2 (water) Sclerosis visible on X-ray No active marrow End stage endplate change
Subchondral sclerosis
Associated with poorer outcomes
Modic Type 1 summary
Reversible inflammation of cartilaginous endplate (painful)
Modic Type 3 consequences
Changes at one level predispose adjacent areas for degeneration
Lateral recess stenosis
Canal is supposed to look like isosceles triangle, only TPs should be lateral
Clinical result of bilateral lateral recess stenosis caused by facet osteoarthrosis…
Back pain and non-dermatome leg pain
Clinical result of central stenosis
Sclerotogenous pain
Signs of degenerative spondylolisthesis
Intermittent scleratogenous leg pain (not past knee)
Often reduced by leaning forward or sitting down
No neurologic findings
Very common (female, fat, 40, L4)
Recent compression fracture on MR
Fracture causes bleeding and bone marrow edema which dissipates in 6 weeks (up to 1 year)
Pathologic compression fracture ddx
Mets (+ bone scan)
MM (+ lab work)
OP (- both)
Benign characteristics
Normal marrow Focal involvement No pedicle involvement Posteriorly angulated fragment? No soft tissue mass Fluid sign
Malignant characteristics
Abnormal fatty marrow Multifocal involvement (why bone scan is needed) Pedicle involvement Posterior convexity? Soft tissue mass No fluid sign
Homogenous alteration in signal indicates…
Destruction of endplates
Arnold-Chiari malformation
Type 1: 1-4mm usually asymptomatic
Type 2: >5mm MC symptoms are HA and dizziness, may cause syrinx formation
Associated with upper cervical anomalies
Syrynx/ syringomyelia
CSF filled cavity within the parenchyma of the spinal cord
Caused by arnold-chiari, cord tumor, cord trauma, idiopathic, left sided thoracic scoliosis
Syrinx treatment
Drainage or laminectomy
MRI and tumors
Fat suppressed MRI very sensitive. Provides extent of soft tissue extension when present (*calcium is a signal void)
Hemangioma
An A/V malformation Decreased T1 (fat) Increased T2 (water) In 100% of population on MRI Not clinically significant
MRI for spinal mets
Very sensitive, limited to FOV, marrow replacement alters signal, assess extent of cortical involvement and soft tissue extension if present
Paget’s
Thickening of osteoid, enlargement and softening
Brain bleeds
First 24-48 hours blood is isointense with brain tissue (CT is needed)
>48 hours blood is hyperintense (signal is increased as hemoglobin degrades)
Subdural hematoma
Small vessel bleeds: worsening headaches, altered mental status
Diffusion tensor imaging (DFI)
Assesses how water moves, helpful in acute brain bleeds, helpful in brain injuries assessing neural flow
Evaluating for stroke (immediately?)
Diffusion MRI
Evaluating for brain tumors
MRI (sensitive and shows surrounding edema)
Evaluating MS
MRI: sensitive and shows plaque as increased signal (especially on T1)
