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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_6022_Библиотеки_им_академика_М_И_Перельмана
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FSEimages.
Theuseofphased-arraycoilsisextremelyvaluableinobtainingbetterS/N
and obviating the needto move the coilor the patient when covering a large
portionofthespine(asinscreeningforepiduralcordcompression).
InadditiontoT1-weightedimages,IR(orpreferably,FSEIR)sequencesalso
demonstratevertebralmarrowmetastasesbynullingtheneighboringmarrowfat
(30,31).IRimages,likeT2-weightedimages,clearlydemonstrateintramedullary
edemaortumorsasbrightsignal.Coronalimagingmaybeuseful,forexample,
inimagingcervicothoracicneurofibromas.
FIGURE6.61Spinal-duralAVfistulaina42-year-oldmanpresenting
withparaplegia.(A)Sagittal T2-weightedMR imageshows swelling
and edema (white arrows) within the mid-lowerthoracicspinal cord
and multiple serpiginous flow-voids of an abnormal draining vein
immediately dorsal to the spinal cord. (B) Spinal angiogram with
injection at the T7 level shows an abnormal fistulous connection
(blackarrowhead)betweentheradicularartery(whitearrow)andthe
abnormal tortuous, dilated draining vein coursing superiorly. The
patient’s symptoms resolved within 2 minutes of endovascular
embolizationwithglue.
AV,arteriovenous.
GRET2* imagesaregenerally notusefulin theimagingof spinaltumors.
ThedifferentiationbetweensofttissueortumorandCSFispoorerthanontrueT2orFSE-T2images.GREimagesareonlyusefulfordetectingsmallamounts
ofhemosiderinorcalcium,whichcouldbemissedonFSEimagesandmaybe
missedonSET2-weightedimages.
Spine tumors are generally classified according to anatomic location as
extradural,intradural,extramedullary,orintramedullary.
ExtraduralTumors
Theseaccountforaboutathirdofallspineneoplasmsandgenerallyinvolvethe
vertebrae(95).Themajorityare metastasestobone.Metastasesto theepidural
spacearelesscommon,andevenlesscommonaretumors(benignormalignant)
arisingfromtheosseousornotochordalstructuresofthespine.Asmallfraction
ofneurofibromasandmeningiomasarecompletelyextradural.(SeeChapter36.)
Primarybonelesionsmayhaveamorecharacteristicappearanceonplainxrays than on MRI because the cortical pattern and calcification are not well
appreciatedonMR.However,MRIdetectschangesinmarrow,ratherthaninthe
bony matrix, and so is the most sensitive detector of vertebral body tumors
(101).
ExtraduralMalignancy
Metastasestobonearebyfarthemostcommonmalignanttumorsinvolvingthe
spineandencounteredineverydaypractice.Oftenthesiteofdiseasecannotbe
accuratelylocalized clinically. Hence, itis importanttobe able toquickly and
efficiently screen the entire spine in these patients. It is impractical and
unnecessarytoobtainsagittalandaxialT1-andT2-weightedimages,aswellas
pre-and postgadoliniumimagesthrough alllevelsof the spine.These patients
oftensufferexcruciatingpainandareunabletoliemotionlessforevenmoderate
lengthsoftime.
Instead, the screening examination should first consist of a single T1weightedsequenceusingalargeFOV(48–50cm)withalargematrix(512×512
or512× 384)inthesagittalplane.Thiswillcovernearlytheentire spineina
singleacquisitionofabout6minutesorless(Figure6.62).AnFSE–T2-weighted
(FSE-T2) sagittal screening sequence can give a myelogram-effect scan in
another few minutes, pointing out the regions of CSF effacement by tumor.
Then,4-mm axial images (eitherT1-or FSE-T2) maybeobtainedonly at the
levels of cord compression to better delineate the degree of compression.
Gadoliniumisgenerallynotneededtodiagnoseandevaluatecordcompression
frombonyvertebralmetastases.Hence,acompleteexaminationcanbeobtained
inabout20minutes,whichcanbetoleratedbyalmostallpatients.
Goodanalgesia,suchas morphine, is important to aidpatientcomfortand
preventimagedegradationbymotion.Anxiolyticssuchasdiazepam(Valium)or
midazolam are less valuable; these patients move around in the scanner more
frompainthanfromclaustrophobiaoranxiety.
FIGURE6.62Metastatic bladderrhabdomyosarcomaina6-year-old
girl.(A) SagittalT1-weighted largefield-of-view imageofthe entire
spineobtainedinonly5minutesshowstheregionsofvertebraltumor
involvement (large arrows) and cord compression (arrowhead). (B)
Axial T1-image shows the large amount of vertebral and paraspinal
tumor,whichanteriorlydisplacestheaortaandvenacavaandextends
medially through the neural foramina into the spinal canal and
compressesthecord(blackarrow)frombothsides.
Source:FromLeeRR.Spinaltumors.In:LeeRR,ed.SpinalImaging(Spine:StateoftheArt
Reviews,Vol.9).Philadelphia,PA:Hanley&Belfus;1995;261–286.
Phased-array coils give superb S/N and enable complete spinal coverage
withoutmovingthepatientorthecoil.However,lackingaphased-arraycoil,the
bodycoilshould beused toscreentheentirespineusingthe singlelargeFOV
T1-weighted sagittal sequence. Use of a conventional “license-plate” coil to
initiallyseparatelyscreenthecervicalspine,thethoracicspine,andthelumbar
spineusingbothT1-andT2-weightedsequencesintheaxialandsagittalplanes
followedby postgadoliniumsagittaland axial imagesofthe cervical,thoracic,
and lumbar regions will take hours, result in extreme patient discomfort, and
generatereamsofunnecessaryandmotion-degradedimages.
As mentioned, T1-weighted SE images are sensitive to detecting these
lesions,buttheirMRIappearanceisnotspecific.TheyaredarkonT1,brighton
T2, and enhance variably with contrast. Type I (fibrovascular) Modic
degenerative changes and infection have similar signal characteristics. An
important distinguishing characteristics between infection and tumor is that
tumorgenerallysparesthediscspace,whereasinfection(exceptingtuberculosis)
characteristicallyinvolvesit.AninfecteddiscappearsasaverywhiteT2-bright
signal and often shows erosion of the adjacent end-plates. Conversely,Modic
degenerative changes are associated with degenerated (i.e., T2-dark) discs,
whereastumorshouldnotaffectthediscsignal.
Althoughsome authorshavetried tofind radiographicsignsdistinguishing
pathologicfromosteoporoticfractures,suchascompletereplacementofmarrow
byT1-darksignalorposterior-convexvertebralbodyborderindicatingtumor,it
isoftennotpossibletomakethedistinctionwithcertainty(102,103).
MultipleMyeloma
Plasma cell neoplasms commonly involve the spine, usually in the thoracic
region and generally in patients beyond middle age (104). The classic
radiographicappearanceofsmall“punchedout”lyticlesionsmayalsobeseen
asmultiplesmallT1-darkfociinthevertebralbodymarrowonMRI.MRIisan
efficientwaytoscreentheentirespineformyeloma,andespeciallytoevaluate
forcordcompression(Figure6.63).
FIGURE 6.63 Multiple myeloma in a 61-year-old woman. Left.
SagittalT1-weighted image shows diffuse abnormal low intensity in
all the marrow because of multiple myeloma infiltration. Right.
SagittalFSET2-weightedimagegivesamyelogrameffectandshows
good conspicuity between the posteriorly bulging tumor-laden
vertebraeandtheCSFandneuralstructures.
Source:FromLeeRR.Spinaltumors.In:LeeRR,ed.SpinalImaging(Spine:StateoftheArt
Reviews,Vol.9).Philadelphia,PA:Hanley&Belfus;1995;261–286.
LeukemiaandLymphoma
The spinal marrow is often involved by these tumors of hematopoietic and
lymphoid cells. Both may show variable radiographic appearance on MRI,
including diffuse or patchy infiltration of marrow, sometimes causing cord
impingement by compression fracture or by focal tumor deposits in bone.
Extraduraltumormayalsopresentasseparateepiduralfoci(105)(Figure6.64).
Hemangioma
These lesions, which are actually vascular malformations and not tumors, are
very common incidental findings on MRI. They are found in 10% to 15% of
patientsatautopsy (104), increasing in incidence with age. Inour experience,
small bone hemangiomas are seen in almost every older patient. The most
common location is the thoracic spine, followed by the lumbar spine (105).
MottledT1-brightsignal causedby interspersedadiposetissueanda T2-bright
signalof fluidand cellsare characteristic(Figure6.65).Thehemangiomas are
usually round and small when found incidentally but may occupy the entire
vertebral body, expanding it and causing neurologic symptoms. The bony
striationsand spicules classically seen on plain films and CT may be seen on
MRI.
OtherPrimaryBoneTumors
GiantCellTumor
Hemangiomasarethemostcommonbenignspinalbonetumor;giantcelltumors
are the second most common (106). Their appearance on MRI is somewhat
nonspecific,asistheirappearanceonplainfilms(Figure6.66).
AneurysmalBoneCyst
These are expansile benign masses containing multiple blood-filled cysts well
seenonMRI.Signalintensityissomewhatvariabledependingonthestateofthe
bloodcontents.Only20%ofaneurysmalbonecystsinvolvethespine(105).
Otherbonetumorsincludeeosinophilicgranuloma(histiocytosisX),osteoid
osteoma,osteoblastoma,andthechondraltumorssuchasosteochondromasand
chondrosarcomas.
Intradural-ExtramedullaryTumors
NerveSheathTumors
These comprise schwannomas (Figure 6.67) and neurofibromas (Figure 6.68)
andoccurmostoftenin thethoracicspine.Mostareintradural-extramedullary,
although about 10% are both intradural and extradural; occasionally they are
completelyextradural(95).Schwannomasareusuallysolitaryunlessthepatient
has neurofibromatosis-2 (NF-2); these, along with meningiomas,are theusual
intradural-extramedullaryspinal neoplasm of NF-2 (Figure 6.69). (The typical
intramedullarytumorofNF-2istheependymoma;107)Mostcasesareseenin
youngto middle-aged adults(males slightly youngerthanfemales); malesand
femalesareequally affected, unlike the case with meningiomas,whichhavea
strongfemalepredominance(95).Inalargeseriesofintraspinaltumorscitedin
Slooffet al. (108), schwannomas (29%) had a slightlyhigher prevalence than
meningiomasorgliomas.
FIGURE6.64B-celllymphomaina23-year-oldman.(A)SagittalT1
MR-image shows patchy increased and decreased signal within the
vertebral marrow, indicating tumor involvement. A large posterior
epiduraltumormasscompressesthecordfrombehind.(B)AxialT1image at this level shows vertebral marrow involvement, a large
paravertebral tumor mass, and the posterior epidural mass (arrow)
compressingthecord.
Source:FromLeeRR.Spinaltumors.In:LeeRR,ed.SpinalImaging(Spine:StateoftheArt
Reviews,Vol.9).Philadelphia,PA:Hanley&Belfus;1995;261–286.
Schwannomas and neurofibromas have a similar radiographic appearance.
They are fairly isointense on T1 and bright on T2, and they enhance with
contrast. Sometimes schwannomas have a cystic component (Figure 6.67),
unlike neurofibromas (109). On postgadolinium and T2-weighted images,
neurofibromasmayhaveacentral,nonenhancing,T2-darkfocus(110)(Figures
6.68and6.70).
FIGURE6.65 Smallhemangioma (arrows) ina 38-year-oldwoman.
Left.T1-weightedsagittalimage.Right.T2-weightedsagittalimage.
Source:FromLeeRR.Spinaltumors.In:LeeRR,ed.SpinalImaging(Spine:StateoftheArt
Reviews,Vol.9).Philadelphia,PA:Hanley&Belfus;1995;261–286.
FIGURE6.66Giantcelltumor,withvertebralcollapseandposterior
retropulsion into the spinal canal in a 28-year-old man, shown on a
sagittalT1-weightedMRimage.
Source:FromLeeRR.Spinaltumors.In:LeeRR,ed.SpinalImaging(Spine:StateoftheArt
Reviews,Vol.9).Philadelphia,PA:Hanley&Belfus;1995;261–286.
FIGURE 6.67 Schwannoma in a 52-year-old man. Consecutive
sagittalpostgadolinium T1 images show an oval, well-circumscribed
intradural-extramedullaryenhancingmassthatcontainsdarkercysticappearing components and markedly compresses the mid-thoracic
spinalcord.
Source:FromLeeRR.Spinaltumors.In:LeeRR,ed.SpinalImaging(Spine:StateoftheArt
Reviews,Vol.9).Philadelphia,PA:Hanley&Belfus;1995;261–286.
FIGURE6.68MultiplecervicalneurofibromasinNF-1ina15-yearold boy. Consecutive postgadolinium coronal T1 MR images show
multiplebilateralenhancingneurofibromas atnearlyeverylevel.The
cordismarkedlycompressedbythebilateraltumors.Notethetypical
nonenhancingcentralcoreintheseneurofibromas.
Source:FromLeeRR.Spinaltumors.In:LeeRR,ed.SpinalImaging(Spine:StateoftheArt
Reviews,Vol.9).Philadelphia,PA:Hanley&Belfus;1995;261–286.
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