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Advanced Imaging 2

Dr. Warshel's Advanced Imaging Final

QuestionAnswer
What is a voxel? Volume element; 3 dimensional section of tissue a pixel represents the 2 dimensional gray shade of a voxel
In what advanced imaging do we use the term signal? Attenuation? Signal is MRI; Attenuation is CT; generally high is bright/white and low is dark
What is Lamour frequency? H+ 90 degrees off axis when hit w/ radiofrequency pulse all rotating at same time, speed and direction, this creates a signal via electromagnetic induction
Discuss timing of TR and TE threshold values. TR >1000ms is long and <1000ms is short; TE >60ms is long and <60ms is short; Long TR and TE allows water (and fat) to relax = T2; Short TR and TE allows fat only to relax = T1
What MRI sequence is good for disc herniations? T2! Detects fluid, edema
What MRI sequence is good for fibrocartilage? Proton Density; long TR, short TE; does not evaluate edema well
What MRI sequence is good for cartilage? Gradient Echo; has a flip angle other than 90; Good for cervical axial series, wrist and ankle
What tissue pathology is best imaged w/ STIR? Very sensitive for fluid, edema, and marrow pathology; has a TI
When would fatsat be utilized? On T1 distinguish fat from hemorrhage; On T2 increases visualization of marrow pathology
What are indications for IV contrast on MRI? Malignancy/tumor mass, infection, post-surgical back
What are indications for arthrography contrast on MRI? Increases sensitivity for for cartilage defects
What is the protocol for MRI IV contrast scan? Standard MRI series is performed precon; an additional T1 postcon is then done
What is the protocol for MRI arthrogram contrast scan? Intra-articular injection w/ standard MRI of the region that is followed by a T1 fatsat postcon
What renal clearance measure is needed before MRI contrast? Creatinine cannot be over 2.0 b/c renal insufficiency can cause nephrogenic systemic fibrosis; over 40 y/o check renal clearance first
What is a flow void? A black area on MRI b/c blood is moving
What is signal void? black area on MRI b/c air doesn’t have much free hydrogen
What Hounsfield unit must we know? 0 is water (distilled)
What does IV CT contrast highlight? Vascular tissue; chest studies highlight the mediastinum, lung vasculature, not used when evaluating lung nodules or interstitial lung disease; Abdomen studies almost all abdomen CT
What are IV CT contrast contraindications? Renal insufficiency, renal failure, pregnancy, allergy to iodine or shellfish, thyroid diseases/cancers, previous contrast reactions
Discuss window and level in CT. Window width (“window”) effects contrast; window level (“level”) effects brightness
What is a scout image? Localizer; perpendicular image that tells you where you are looking; never read TR/TE on localizer to determine if T1 or T2
What is often seen w/ congenital block vertebra? Wasp waist deformity, hypoplastic disc, half have anterior and posterior fusion; get flex/ext views w/ fusion >3.5mm mvmt unstable in C/S, 4.5mm in L/S
What is frequently associated w/ occipitalization? C2-3 fusion, chiari malformation, skull base abnormality
What is a chiari malformation? Herniation of the cerebellum more than 5mm beyond the margin of the foramen magnum; associated w/ syrinx formation and syringomyelia
What is a syrinx/syringomyelia? Fluid in the central aqueduct; can cause pain, loss of pain sensation, loss of heat/cold sensation; effect the upper extremity most commonly
What is a tethered cord? Conus medullaris should terminate above L2 inferior endplate; can be associated w/ intraspinal lipomas or thickened filum terminale
What limbus bone location is not good? Posterior, disc material comes back w/ limbus bone – acquired spinal stenosis; can -> cauda equina
What part of the disc is innervated? Only the outer annulus
Discuss annular tears. Peripheral tears result in growth of osteophytes; peripheral tears are more common anterior and lateral; posterior disc tends to have radial tears
What are the shapes of the IVDs at the various levels of the spine? Cervical – oval; Thoracic – oval -> kidney bean; Lumbar – T12-L1 – L3-4 kidney bean, L4-5 flat across back, L5-S1 oval
What is an imaging finding for DDD? Decreased T2 nuclear signal; also have loss of disc height, diffuse disc bulging, osteophyte formation
What are modic changes? Changes in marrow in response to degenerative changes
How does Modic type 1 appear? Low on T1, High on T2; replacement w/ firbrovascular tissue; edematous, acute, thorugh to be associated w/ Sx
How does Modic type 2 appear? High T1, can be hyperintense, hypointense or isointense on T2; fatty replacement of red marrow; considered chronic, not associated w/ Sx’s
How does Modic type 3 appear? Low on T1, Low on T2; replacement of marrow space w/ bony sclerosis; signal approaches that of cortical bone; only type visible on x-ray; hemispheric spondylosclerosis
What are the 3 types of annular tears? Transverse, concentric, radial; tear does not necessarily represent a traumatic etiology; AKA annular fissures, annular tears, HIZ
Where are transverse annular tears seen? Seen as bright spots on annulus, right next to endplate
How are concentric annular tears visualized? Separation b/w layers that are vertical on sagittal and horizontal on axial
How do radial annular tears look? Longitudinal fissuring through multiple layers of annulus, allow for nuclear migration, considered to be associated w/ Sx of discogenic pain; Horizontal on sagittal, perpendicular to fibers on axial
Who standardized the nomenclature for disc herniations? ASNR since terminology wasn’t always precise
What are the 2 classifications of morphology w/ disc herniations? Contained and uncontained; contained includes bulge and protrusion and uncontained includes extrusion and sequestered fragment
What are the 4 classifications of location w/ disc herniations? Central, paracentral, foraminal, extraforaminal
When are the terms focal and broad based applied? Only applies to protrusions and extrusions
What does focal disc herniation mean? Involves less than 25% of disc circumference
What does broad based disc herniation mean? Involves more than 25% and less than 50% of disc circumference
What are the 4 general classes of disc herniation morphology? Bulge, protrusion, extrusion, sequestered fragment; classification requires viewing both axial and sagittal images
Describe a disc bulge. Associated w/ degeneration, disc loses height, expands outward, disc extends beyond body margin by at least 2mm and involves at least 50% of the circumference; can be symmetric or asymmetric
Describe disc protrusion. Focal asymmetric extension of disc beyond the vertebral body margin that does NOT extend beyond the endplates; can be broad based or focal based; base wider than disc is deep
Describe disc extrusion. Disc material not contained by the outer annular fibers; maintains continuity w/ the parent disc; Base is narrower than disc is deep; compare sagittal and axial, worse Dx wins
Describe sequestered fragment. Uncontained disc material, not connected to the parent disc, can migrate in the spinal canal and affect multiple nerve roots giving migrating radic/pain pattern
What locations of disc herniation are MC and what anatomical area does most NR compression occur? Central and paracentral MC; lateral recess is where most NR compression happens
What nerve root is affected in central and paracentral herniations in the cervical spine? Exiting nerve root and sometimes transiting nerve root
What nerve root is affected in a forminal disc herniation in the cervical spine? Exiting nerve root but unusual area for herniation b/c of uncovertebral joints
What nerve root is affected in a extraforminal disc herniation in the cervical spine? Exiting nerve root or nerve roots from above
What nerve root is affected in central and paracentral herniations in the lumbar spine? Transiting nerve roots, next level down; central can involve lower roots
What nerve root is affected in foraminal and extraforaminal herniations in the lumbar spine? Exiting nerve root; extraforaminal can affect roots from above but not common
How does infectious spondylitis appear on MRI? Low on T1, Intermediate to high on T2 and High on STIR; there will be obliteration of disc w/ marrow changes in adjacent vertebrae; TB can skip levels, bacterial will not skip levels
How does neoplastic disc pathology appear on MRI? High on T2, Low on T1, Multifocal marrow involvement; can be mets and plasmacytoma, chordoma crosses disc
What type of modic change is seen on CT and x-ray? Type 3, only type visible on these
What contributes to canal stenosis in the cervical spine? Posterior osteophytes and buckling of the ligamentum flavum from approximation of the vertebra
What are the MC facet joints to have DJD? C5-C7 and L5-S1; can contribute to stenosis
What appearance is seen in lumbar spine w/ facet DJD? Portabella mushroom appearance
What are the optimal sequences for facet joint evaluation in the cervical spine? Sagittal T1 and T2
What are the optimal sequences for facet joint evaluation in the lumbar spine? Axial T1 and T2
What are the optimal sequences for evaluating the uncinate joints? Best evaluated on coronal but not a standard sequence so best seen on axial gradient echo or use T2
How is spinal stenosis classified? Location: central canal vs lateral recess vs IVF; Etiology: congenital vs acquired; Type of encroachment: hard (osteophyte) vs soft (disc/lig flavum)
Where is the lateral recess? Medial border of the pedicles, extends to refer to the lateral aspect of the thecal sac, frequent location for NR impingement, best evaluated in the axial plane
What types of stenosis occur together and how do they result? Central canal and lateral recess stenosis typically involved together; combination results in a trefoil canal
What contributes to a trefoil canal? disc herniation or disc-osteophyte complex, facet joint hypertrophy from DJD, ligamentum flavum hypertrophy/buckling, uncinate ostephytes projecting posteriorly
Central canal is narrowed by what? Disc material (central HNP for central; paracentral HNP for lateral recess, disc-osteophyte complex), facet DJD, epidural fibrosis, synovial cyst
How does facet DJD contribute to canal narrowing? Associated w/ ligamentum flavum hypertrophy
How does epidural fibrosis contribute to canal narrowing? Post surgical scarring
How do synovial cysts contribute to canal narrowing? Lumbar facet DJD; facet injections
How do we evaluate cervical IVF stenosis? On T2/GE axials; mostly from uncinates and facets; quantify narrowing, measurements are not useful
How do we evaluate lumbar IVF stenosis? On T1 sagittal, allows for evaluation of perineural fat; narrowing is also called keyholing
What causes keyholing? From foraminal HNP, facet DJD, ligamentum flavum, synovial cysts
What can cause congenital stenosis? Short pedicles or over-developed lamina; achondroplasia
What can cause acquired stenosis? Degenerative, spondylolisthesis, OPLL, epidural lipomatosis, fracture fragments, masses
What is soft acquired stenosis d/t? Soft is secondary to disc or ligamentum flavum and seen best w/ MRI
What is hard acquired stenosis d/t? From disc-osteophyte complex, facet or uncinate osteophytes and best seen w/ CT but can be seen w/ MRI
What are the 5 types of spondylolisthesis? dysplastic, isthmic (spondylolytic), degenerative, traumatic, pathologic; isthmic and degenerative MC
How do we visualize pars defect activity? SPECT scan; MRI shows marrow edema, linked w/ activity of pars Fx; CT shows defects, cannot gauge activity
What is the MC location for isthmic spondylolisthesis? L5
What is the MC location for degenerative spondylolisthesis? L4
What is seen w/ myelomalacia? Cord signal change on MRI
DDX DISH and OPLL. DISH MC I TL spine, OPLL is MC in cervical spine, might not see signs of DISH in same region as OPLL
What is epidural lipomatosis? Deposition of excess adipose tissue in the epidural space; seen in corticosteroid patients, endogenous hyperadrenocorticism, obesity; results in spinal stenosis; best seen on T1 sagittal
What are the sequela of central stenosis in the lumbar spine? Cauda equina syndrome, no imaging findings beyond stenosis, clinical correlation is required
What are sequela of central stenosis in the cervical and thoracic spine? Myelomalacia (STIR best to see), edema of the cord w/ softening, evaluate on T2 sagittal for hyperintense region, contraindication for manipulation
Where do compression fractures MC’ly occur? T11-L2
What are the 3 hallmark signs of compression fracture? Sharp step defect, white line of condensation, paraspinal edema (AP view, thoracic only above T12)
How does MRI tell if new or old compression fracture? If acute will be high on T2 and low on T1
What imaging procedures are needed for burst fracture? Both MRI and CT; CT to evaluate bony fragments w/ higher resolution; MRI to evaluate the neural structures
How does hemangioma appear on MRI? Typically high T1, high T2
When imaging the post-surgical back, what are we evaluating? Recurrent disc herniation vs scar tissue; scar tissue enhances, a recurrent disc will not
How is post-surgical back imaging done? Must have IV contrast; precontrast sequence performed then IV injection of Gad performed; Compare precon and post con T1 sequences to evaluate for enhancement
What does MR angiography do? Evaluates blood vessels w/o negative consequences of conventional angiography but not equal to conventional; used for chronic blood vessel problems
What are MR angiography indicated for? AVM, aneurysm w/o acute rupture, occlusive disease, tumor evaluation
When is MR arthrogram used? Extremities; increase sensitivity of the exam for cartilaginous defects – glenoid, acetabular labrum, knee meniscus, wrist TFCC
What are the 2 types of bone scan? Planar for mets, stress Fx, polyostotic bone lesions, AVN; 3 phase for soft tissue infxn vs osteomyelitis determinations
What are indications for bone scan? Infxn, malignancy; stress injury; AVN; monostotic vs polyostotic bone disease; acute pars stress fx; RSDS/CRPS; prosthetic joint loosening
When is SPECT scan used? Concern for active pars Fx’s (ta da sports) or re-injury of old pars defects; determine new vs old compression Fx’s
When is PET scan used? To evaluate tissues metabolic activity; primarily for neurologist and oncologists
When is conventional myelography indicated? Only in patients w/ a contraindication to MRI
What are the 3 positive findings on myelography? Intramedullary – something in neural structure; Intradural extramedullary; Extradural – outside neural structure but inside thecal sac gives cat under the rug appearance
When is MRI myelogram used? As a presurgical aid, little value over standard MRI in conservative MSK field
What are indications for discography? Persistent pain exists and noninvasive procedures like CT or MRI are uninformative; surgical fusion is being considered; differentiating post-surgical scar from recurrent disc herniation
Where should DEXA scan be done on Grandma? Hips and lumbar spine; hyperparathyroidism can use DEXA scan for distal forearm
What score is helpful with DEXA scan? T score: compares patient to 18-25 y/o gender and race match – helps determine bone density
What is the WHO criteria of T score for >+1.0? Increased bone density, can be a result of DJD, fluorosis, hyper vit D…
What is the WHO criteria of a T score for +1.0 to -1.0? Normal bone density
What is the WHO criteria of a T score for -1.0 to -2.5? Osteopenia
What is the WHO criteria of a T score for <-2.5? Osteoporosis
What is the WHO criteria of a T score for <-2.5 w/ Hx of fragility Fx? Severe osteoporosis; fragility Fx = TLJ compression Fx, Colle’s Fx
What does the T score predict? Fracture risk; as go down the number value double risk of fracture
What are MSK US applications? Spine, Spinal rehab; Extremities, much broader application than in the spine; Abdominal tissues; Vascular imaging
What areas of the extremities are seen w/ US? Superficial tendons and ligaments: rotator cuff tears, evaluation of inflammatory arthritis and response to treatment
When is fluoroscopy used? For looking at mid-range instabilities, rather than the terminal range seen in flexion/extension x-rays; used for looking at ligamentous instabilities like facet capsule tears, intercarpal ligaments
What are the semantics w/ AVN? In epiphyses we call it AVN; in metaphyses called medullary infarct
What are the 4 phases of AVN? Avascular, Revascularization, Repair/remodeling, Deformity
What is seen on imaging modalities in the avascular phase of AVN? X-ray: indistinguishable from normal bone; MRI: edematous changes; Bone scan: photopenia – no uptake
What is seen on imaging modalities in the revascularization phase of AVN? X-ray: mottled bone density, osteopenia and snowcapping; MRI: low signal rim at the revascularizing border called double line sign; Bone scan: double density sign where high uptake surrounds photopenic zone
What is seen on imaging modalities in the repair/remodeling phase of AVN? X-ray: crescent sign; MRI: persistence of double line sign and crescent sign; Bone scan: homogenously hot
What sequences can show the magic angle phenomenon? Low TE sequences: T1, PD; compare w/ high TE sequences that have no magic angle and pathology will still be high signal
How can tenosynovitis appear on MRI? Tendon can look normal or have fusiform enlargement b/c synovial sheath is filled w/ more fluid than normal
How does tendon degeneration appear on MRI? Fusiform enlargement, intrasubstance signal, indistinguishable from intrasubstance tearing
What are the tear patterns of tendons and ligaments? Based on height (longitudinal) and width (tangential); partial vs full thickness (height) and incomplete vs complete (width)
What are the 4 SLAP tear types? Type 1: MC, fraying of the free margin; Type 2: labrum and biceps anchor torn from glenoid; Type 3: bucket handle labral tear, intact biceps anchor; Type 4: bucket handle labral tear, splitting the biceps tendon
In a VISI and DISI what ligament is torn? VISI: tear of lunotriquetral ligament; DISI: tear of scapholunate ligament
What are the 4 types of Meniscus tears? Horizontal/oblique (MC), Bucket-handle (double PCL sign), Radial, Parrot beak
Created by: Kelly Brown Kelly Brown on 2012-04-08



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