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Advanced Imaging 2
Dr. Warshel's Advanced Imaging Final
| Question | Answer |
|---|---|
| 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 |
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