1、ORIGINALRESEARCHDetection and Classification of Cranial DuralArteriovenous Fistulas Using 4D-CT Angiography:Initial ExperienceP.W.A. WillemsP.A. BrouwerJ.J. BarfettK.G. terBruggeT. KringsBACKGROUND AND PURPOSE: The criterion standard to diagnose and classify cranial DAVFs is DSA.Since this is invasi
2、ve, relatively expensive and time-consuming, a noninvasive alternative is of interest.We aimed to evaluate the capabilities and pitfalls of 4D-CTA in a consecutive series of patients whopresented with a newly diagnosed cranial DAVF, as demonstrated by conventional DSA.MATERIALS AND METHODS: Eleven p
3、atients were included in this study after biplane DSA demon-strated a cranial DAVF. They subsequently underwent 4D-CTA imaging by using a 320-detector CTscanner. DSA and 4D-CTA studies were independently read by 2 blinded observers, by using astandardized scoring sheet. 4D-CTA results were analyzed
4、with DSA as the criterion standard.RESULTS: In 10 cases, there was full agreement between DSA and 4D-CTA regarding the Bordenclassification. However, in the remaining patient, a slow-filling DAVF with a low shunt volume wasmissed by both readers on 4D-CTA. In all 10 detected cases, H113501 of the ma
5、jor contributing arteriescould be identified with 4D-CTA. Although, by using DSA, the 2 observers identified additional arterialfeeders in 7 and 8 cases, respectively, these discrepancies did not influence clinical decision making.CONCLUSIONS: Although novel 4D-CTA imaging may not rule out a small s
6、low-flow DAVF, it appearsto be a valuable new adjunct in the noninvasive diagnostic work-up, treatment planning, and follow-upof patients with cranial DAVFs.ABBREVIATIONS: CTA H11005 CT angiography; DAVF H11005 dural arteriovenous fistula; 4D-CTA H11005 4D(time-resolved) CTA; DSA H11005 digital subt
7、raction angiography; ECA H11005 external carotid artery; ICA H11005internal carotid artery; IVH11005 intravenous; MRA H11005 MR angiography; trMRA H11005 time-resolved MRA;VA H11005 vertebral arteryDAVFscaneitherbeasymptomaticorpresentwithavarietyof symptoms, including hemorrhage, focal neurologicde
8、ficits, chronic headache, bruit, dementia, seizures, or signsofintracranialhypertension.1TheaggressivenessofaDAVFisrelatedtoitsvenousdrainagepattern1-4(ie,whetheritsdrain-age is solely antegrade through a venous sinus or includes ret-rograde flow into cortical veins). Therefore, correct diagnosisand
9、 classification1,5of a DAVF greatly influences the appro-priate treatment strategy.The criterion standard to demonstrate and classify the in-appropriate filling of a pial vein or dural sinus fromH113501 duralartery,thehallmarkofaDAVF,isconventionalcatheter-basedangiography (DSA). Because DSA is rela
10、tively expensive andtime-consuming and carries a rather high incidence of silentembolic events6and a small risk of transient or permanentneurologic deterioration,7-9a noninvasive alternative angio-graphicmethodisofinterest.Moreover,patientswithaDAVFmay undergo multiple angiographic evaluations with
11、time. Inrecent years, MRA and CTA have shown sufficient spatial res-olution to answer many clinical neurovascular questions.10-12However, these vessel-cast techniques lack the temporal reso-lution necessary to visualize arteriovenous shunts or venousdrainage patterns.More recently, time-resolved tec
12、hniques have emerged forboth MRA13,14and CTA.15Aside from generating cross-sec-tional images, these datasets enable visualization of blood-flow dynamics in cranial vessels with the first pass of an IVcontrast bolus. Hence, it is conceivable that they may replaceDSA in cases in which time-resolved im
13、aging is required. Weaimedtoevaluatethecapabilitiesandpitfallsof4D-CTAinaninitialseriesofpatientswhopresentedwithanewlydiagnosedDAVF, as demonstrated by DSA.Materials and MethodsPatient Selection and Data CollectionApproval for this study was obtained from our institutional researchethics board in N
14、ovember 2008, and patients were admitted to thestudybetweenNovember2008andMay2009.PatientswereincludedifDSAdemonstratedapreviouslyuntreatedDAVF.Exclusioncriteriawerepatientageyoungerthan18years,currenttreatmentfordiabetesmellitus, known allergy for iodinated contrast agents, renal failure(indicated
15、by a baseline serum creatinine level of H11022133 H9262mol/L),inability to undergo 4D-CTA inH110211 month from their DSA, and lackof informed consent.After obtaining informed consent, we performed 4D-CTA imag-ing. Subsequently, all DSA and 4D-CTA studies were anonymizedandindependentlyevaluatedby1ra
16、diologistand1neurosurgeon,byusing a standardized scoring sheet (Table 1). The 4D-CTA resultswere scored first, and the DSA results were scored at least 24 hourslater.Furthermore,wedocumentedthemodeofpresentationandtheReceived March 30, 2010; accepted after revision June 16.From the Department of Rad
17、iology (P.W.A.W., P.A.B., K.G.t.), Leiden University MedicalCenter, Leiden, the Netherlands; and Department of Medical Imaging (J.J.B., K.G.t., T.K.),Toronto Western Hospital, Toronto, Ontario, Canada.Please address correspondence to P.W.A. Willems, MD, PhD, Department of Radiology,Leiden University
18、 Medical Center, Postal Zone C2-S, PO Box 9600, 2300 RC Leiden, theNetherlands; e-mail: p.w.a.willemslumc.nlDOI 10.3174/ajnr.A2248BRAINORIGINALRESEARCHAJNR Am J Neuroradiol 32:4953 H20841 Jan 2011 H20841 www.ajnr.org 49delay between the 2 studies as well as whether treatment was subse-quentlyperform
19、edand,ifso,whetherinvolvementofthevesselsusedfor treatment had been recognized in the 4D-CTA evaluation.DSA ExaminationDiagnostic intra-arterial DSA was performed with standard biplanefluoroscopy equipment (Infinix, Toshiba Medical Systems, Tochigi,Japan; or LCL-P, GE Healthcare, Buckinghamshire, Un
20、ited King-dom).BecausepatientswereonlyincludedinthestudyafterDSAhaddemonstratedaDAVF,theangiographicprotocolwasnotinfluencedby the study. It generally consisted of bilateral injections of the ICA,ECA, or VA, supplemented with selective injections of the occipital,ascending pharyngeal, or internal ma
21、xillary arteries, when indicated.4D-CTA ExaminationAll 4D-CTA examinations were performed by using an Aquilion 1multidetectorCTscanner(ToshibaMedicalSystems),equippedwith320H110030.5 mm detector rows covering 16 cm of volume per rotation.Imaging was performed in the same manner as previously de-scri
22、bed.15,16In short, a test-bolus acquisition at the level of the skullbasewasperformedtooptimizethetimingofthedynamicacquisitionsequence. Subsequently, IV infusion of 60 mL of nonionic contrastmediumand20mLofsalinewasperformed,followedbythedynamicacquisition sequence with a gantry rotation speed of 1
23、 Hz. The dy-namicacquisitionsequenceconsistedof1maskvolume(80kVp,300mAs) and 22 dynamic volumes (80 kVp, 120 mAs). After subtractingthe mask volume from the dynamic volumes, a total of 7040 (22 H11003320) images were stored in DICOM files. The standard scanner soft-ware was capable of using these fi
24、les to generate time-resolved (arte-rial-to-venous)volumerenderingsormaximumintensityprojectionsby using any part of the cranial volume at any viewing angle. Thisstudyrequiredatleastanteroposteriorandlateralmaximumintensityprojectionsfromtheentirecranialvolume,reconstructedat1-secondintervals. Addit
25、ional images could be used at the discretion of thereader.ResultsBetween November 2008 and May 2009, 11 patients with anewly diagnosed DAVF were included, 8 men and 3 women.Their mean age was 52H110069.7 years. The mean delay betweenthe2imagingmodalitieswas4H110064.0days,withamaximumof14days.Thefreq
26、uenciesofpresentingsymptomsaccordingtoBorden type5, as demonstrated by DSA, are shown in Table 2.All DAVFs were detected by both readers on DSA. Ten ofthe 11 DAVFs were detected using 4D-CTA. The single casethat remained undetected by 4D-CTA (Fig 1) was a slow-flowshunt with a low shunt volume and c
27、ortical venous drainage,which had presented with an intracranial hemorrhage. It wasclassified as a Borden grade III and Cognard1grade III lesion.With regard to the 10 DAVFs that were detected in the4D-CTA data, there was full agreement according to the Bor-den classification (see Fig 2 for an exampl
28、e). Both readers dis-agreedontheCognardclassificationof1lesion,recordingitasIIaH11001b on DSA and as IIb only on 4D-CTA data, recognizingthe pial reflux but missing the retrograde sinusoidal flow (Fig3).Regarding feeding arteries, H113501 of the major contributingarteries could be identified with 4D
29、-CTA in all 10 detectedcases. However, by using DSA, the 2 observers identified ad-ditional arterial feeders in 7 and 8 cases, respectively. Whenfeeders were classified according to their territory (ECA, ICA,or VA), both readers showed discrepancies between DSA and4D-CTA in 4 of 10 cases. In those c
30、ases, 4D-CTA results re-flected the ECA supply to the DAVF correctly but failed toidentify additional smaller feeders from the ICA and/or VA.When comparing separate branches from these territories,listed in Table 1 under “Arterial feeders, small,” 1 readershowed disagreement in 3 more cases and the
31、other in 4 morecases. In such cases, only the largest feeders from a given ter-ritory were recognized in the 4D-CTA data (Fig 2).With regard to the type of fistula (focal or diffuse) and theexistence of venous obstruction or an isolated sinus, eachreader individually showed full concordance between
32、DSAand 4D-CTA. However, there was some disagreement be-tween the 2 observers regarding these characteristics: In 4cases, the readers disagreed as to whether the fistula was of afocal or diffuse nature; and in 2 cases, there was disagreementregarding the existence of venous outflow obstruction.Table
33、1: Items scored by each reader for both DSA and 4D-CTAimagesItem OptionsDAVF detected Yes/noClassification of Borden et al5I Drains through dural sinusII Retrograde flow from sinus into corticalveinsIII Direct flow into cortical veinsClassification of Cognard et al1I Antegrade sinusoidal flowII Refl
34、ux: a) sinusoidal, b) arachnoid or bothIII Direct flow into cortical veinsIV Same as III, but with venous ectasiasV Flow into perimedullary veinsArterial feeders, largeECAICAVAAny combination of the aboveArterial feeders, smallECA: Occipital artery, auricular artery,superficial temporal artery, midd
35、lemeningeal artery, ascending pharyngealartery, internal maxillary arteryICA: Posterior group, inferolateral trunk,meningohypophyseal trunk, ophthalmicsystemVA: Muscular/occipital branches, posteriormeningeal artery, posterior inferiorcerebellar arteryAny combination of the aboveFistula type Single
36、hole (focal)/multihole (diffuse)Venous outflow obstruction Yes/noIsolated/trapped sinus Yes/noTable 2: The frequencies of presenting symptoms according to thetype of venous drainage, using the classification of Borden et al,5as demonstrated with DSABordenTypePresenting SymptomsIncidental Tinnitus He
37、morrhageI030II 0 2 1III 1 1 350 Willems H20841 AJNR 32 H20841 Jan 2011 H20841 www.ajnr.orgConservative management was chosen in 2 patients with abenign lesion who had presented with tinnitus. Endovasculartreatment was attempted in the other 9 patients. A trans-venous approach was chosen in 3 of thes
38、e and a transarterialapproach, in the remaining 6. In 4 of the 6 patients treatedtransarterially,4D-CTAhadcorrectlyidentifiedallfeedingar-teries used to gain access to the shunt to deposit embolicmaterial.The radiation dose involved in 4D-CTA imaging will vary,dependingontheprotocolused.Withourcurre
39、ntacquisitionprotocol, the total radiation dose received during 4D-CTAimaging amounted to 5.2 mSv. The radiation dose receivedduring a DSA study is even more variable because it is depen-dent on many variables, such as the fluoroscopy time neededto navigate into vessels, the number of vessels studie
40、d, fluoro-scopic parameters, type of fluoroscopic equipment, and soforth. In 4 typical DSA studies, the radiation dose was calcu-lated to vary between 7.89 and 9.12 mSv. These calculationswerebasedonMonteCarlosimulationsbyusingthedose-areaproduct values and beam geometry information. Ninety-fiveperc
41、entofthisdosewasestimatedtohavebeendeliveredtothecranium, with minor exposure of the thorax, abdomen, andpelvis.DiscussionThis study looked at the initial results of 4D-CTA in cranialDAVFs, compared with DSA, in an attempt to recognize thepotential capabilities and pitfalls of 4D-CTA in such lesions
42、.In agreement with previous findings,3all hemorrhages oc-curredinpatientswithaDAVFofBordentypeII(1patient)orIII (1 patient). However, 1 DAVF incidentally found was ofBorden type III and 3 of 5 patients with tinnitus as their onlypresenting symptom harbored a type II or III DAVF. Thus,mild or absent
43、symptoms do not exclude the possibility of apotentiallyaggressiveDAVF.Thesefindingsunderlinethene-cessity of an imaging tool capable not only of detecting theDAVFbutalsoofdescribingitscorticalvenousrefluxpattern,when present, because this is considered to be the major de-termining factor of the subs
44、equent treatment strategy. Thepotentialaddedadvantageof4D-CTA,asidefromthefactthatit is noninvasive and requires simple logistics, would be theavailability of cross-sectional images. These could be helpfulFig 1. Imaging of a 65-year-old man who presented with an intracranial hemorrhage and whose DAV
45、F was missed by 4D-CTA. A, Nonenhanced cranial CT scan on admission demonstratesthe presenting hemorrhage. B, DSA, lateral view after left ECA injection, demonstrates abnormal retrograde filling of a pial vein (arrow), indicative of a DAVF. C, Lateral view of 4D-CTA,maximum intensity projection of t
46、he early venous phase, shows the same pial vein (arrow). Because visualization of the pial veins is expected on global opacification, only early fillingwould indicate a DAVF. However, due to the slow flow through the fistula, early venous filling could not be identified. Hence, this 4D-CTA study was
47、 read as having normal findings.Fig 2. Imaging of a 60-year-old woman who presented with a right-sided pulse-synchronous tinnitus. A, DSA, lateral view after right ECA injection, demonstrates a DAVF (Borden I andCognard I) at the level of the left sigmoid sinus (large arrow). The lesion is fed throu
48、gh a small arterial network (small arrow), which is mainly supplied by a branch from the occipitalartery (large arrowhead) and to a lesser degree by a branch from the middle meningeal artery (small arrowhead). B, Lateral view of 4D-CTA, maximum intensity projection of late arterialphase, shows the e
49、arly venous drainage into the right sigmoid sinus (large arrow). Compared with the DSA, the 4D-CTA is in agreement with regard to the site and classification of thelesion, as well as to its dominant feeder from the occipital artery (large arrowhead). However, although the smaller feeder from the middle meningeal artery can be seen (small arrowhead),neither reader had recorded it as such The small arrow indicates the arterial network feeding the fistula.AJNR Am J Neuroradiol 32:4953 H20841 Jan 2011 H20841 www.ajnr.org 51for observing structural changes such as hydrocephalus or ahematoma or f