PERIPHERALCTA

RichardL.Hallett,MDChief,CardiovascularImagingNorthwestRadiologyNetworkIndianapolis,INAdjunctAssistantProfessor–ImagingCardiovascularImagingSectionStanfordUniversityStanford,CA

RC312B 29November2016 0830–1000

Outline§  GoalsofLECTA§  CTAAcquisitionTechniques

ú  ScanAcquisitionú  ContrastMediuminjection

ú  Reconstruction

§  ClinicalEfficacyinPAD

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GoalsofCTAimaginginPAD

Indications (n) (2001-05)

DSA

DiagnosisandStagingofPAD

=symptoms+ABI

poorcorrelationofsymptomsandABIwith

number,locationandseverityoflesions

Example:calfclaudicationcanbecausedby

isolateddiseaseorcombinationofiliacand/or

femoropopliteallesions

Indications (n) (2001-05)

DSA

RoleofCTAImagingisNOTdiagnosis/

staging

CTAroleistomaplesionstothe

patient‘ssymptoms

fortreatmentplanning

GoalofReportingLECTA§  Answertheclinicalquestions

ú  NEEDtogethistory

ú  IntermittentClaudicationvsCriticalLimbIschemia?

§  Organizebyleg:ú  Aorto-iliac(inflow)

ú  Femoropopliteal

ú  BelowKneerunoff

ú  Pedalvessels(2crossankle)

IndicationsforCTAinPAD•  IntermittentClaudication

•  CriticalLimbIschemia

•  AcuteIschemia(urgent)

•  MonitoringofTherapy(complications)

Whichlesionsmatter?TreatmentSegment Aka,utility

Aorto-iliac “Inflow”,“Supra-inguinal”

CommonFemorala. Bypasstargetandsource

ProfundaFemorisa. Importantcollateralsw/SFAocclusionImportants/pamputation

Femoro-popliteal(SFA-Pop)

“Infra-inguinalrunoff”Notelevelofreconstitutionabove(P1)or

below(P3)knee

Trifurcationvessels “Infra-poplitealrunoff”OnlyrelevantinCLIpts(notIC)

Pedalaa. “2vesselscrossingankle”(DP,PT)OnlyinCLI/bypasstargets

CTAScanAcquisition

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•  ScanAcquisition•  ContrastMediumInjection

Optional Scanning Range 2 above the knees à toes Always pre-programmed, but only initiated by RT if no contrast in pedal vessels

Scanning Range 1 celiac artery (~T12) à toes (105 – 130 cm)

Recons: Thin, overlapped FOV = greater trochanters

PeripheralCTAScanAcquisition/Recon

DetectorConfiguration(mm)

TI/360°(mm)

TableSpeed(mm/s) ScanTime(s)

16-ChannelMDCT

16×.75 18 36 30-40

16×.63 18 35 30-40

16×1.5 33 66 15-20

16×1.25 35 70 15-20

~35 mm/s slow slow

fast fast

Anatomic coverage: 105 – 130cm

64-ChannelMDCT

64×.63 55 92 11-14

64×.60 29 78 13-17 fast very

~85 mm/s

~65 mm/s

FLASH Modes

128x2x0.60 128 458 <3

192x2x0.60 184 737 <2 BLAZING

Speedconsiderationsfor>64sliceCTA

§  OutrunningBolus

§  Delayedfillingofdistalarteries

Free-FlapPlanningCTA

preprogrammed, optional 2nd acquisition

Arteriomegaly

1st acquisition

Table speed (mm/s)

0

0.2

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0 30 60 90 120 150 180

vAO->POP (mm/s)

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Table speed (mm/s)

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Aorto-popliteal transit speed (mm/s)

Table speed (mm/s)

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vAO->POP (mm/s)Cu

mulat

ive

Prop

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0

0.2

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Peripheralarterialboluspropagation

< .01

~.33

> .50

Fleischmann D and Rubin GD. Radiology 2005, 1076-1082

ContrastAdministrationforperipheralCTA

Fleischmann D. How to design injection protocols for multiple detector-row CT angiography (MDCTA). Eur Radiol. 2005 Dec 1;15 Suppl 5:E60–5.

ContrastconsiderationsforperipheralCTA

§  Aorto-poplitealtransittime:4-24sec(10sec)

ú  Contrastspeed:29-177mm/s

§  Biphasicinjectionsyieldmoreconsistent

enhancementprofile

Fleischmann et al. JVIR 2006, 17(1) 3-26.

0

100

200

300

400

0 8 16 24 32 40 48 56 64 72 80

0

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4

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8

1 9 17 25 33

INPUT intravenous injection rate (mL/s)

OUTPUT arterial enhancement (ΔHU)

Phase I (surge phase)

Phase II (continuing phase)

Biphasic Injection for Peripheral CTA

0

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400

0 8 16 24 32 40 48 56 64 72 80

0

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0 8 16 24 32 40 48 56 64 72 80

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0 8 16 24 32 40 48 56 64 72 80

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Biphasic Injection

Fleischmann D. Eur. J. Radiol. 2003 Mar 1;45 Suppl 1:S88–93.

PatientFactors

§ Arterialenhancementisinverselyrelatedto:§ Cardiacoutput(CO)

§ Centralbloodvolume(CBV)

§ CO(andCBV)correlatewithbodyweight

§  atleastinpts.with~normalcardiacfunction

§ Weight-baseddosinghelpsconsistency

1) Hittmair & Fleischmann, JCAT 2001

usually unknown

IntegratedContrast/ScanProtocolSimple,weightbasedinjectionvolumesandflowrates,combinedwithafixedscantimeorscantime/diagnosticdelaysum.

automatedbolustriggering

Usephysiology(notscannerspeed)BENEFITS:

DecreasepatienttopatientvariabilityinscanqualityOptimizeimagingtimingImageallofthecontrastgiven!

(Potentially)savecontrast

STANFORDIntegratedScanning-InjectionProtocol:(Siemens)

§ Scantime: 40sforALLpatients(pitchvariable)§  Inj.duration:35sforALLpatients§ Delay: bolustriggering

weight Biphasic Injection <55kg 20 mL (4.0mL/s) + 96 mL (3.2mL/s) <65kg 23 mL (4.5mL/s) + 108 mL (3.6mL/s)

75kg 25 mL (5.0mL/s) + 120 mL (4.0mL/s) >85kg 28 mL (5.5mL/s) + 132 mL (4.4mL/s) >95kg 30 mL (6.0mL/s) + 144 mL (4.8mL/s)

ST.VINCENTIntegratedScanning-InjectionProtocol:(GEHD-750,VCT)

§ Scantime: Variable(can’tspecifytime)

§  Add�diagnosticdelay�tomake40sec§  Inj.duration:35sforALLpatients§ Delay: bolustriggering

weight Biphasic Injection <55 kg 20 mL (4.0mL/s) + 96 mL (3.2mL/s)

55-95 kg 25 mL (5.0mL/s) + 120 mL (4.0mL/s) >95 kg 30 mL (6.0mL/s) + 144 mL (4.8mL/s)

SpecialScenarios§  RenalDysfunction§  ContrastMediumSavings

AdaptationsforRenalDysfunction:LESSISMORE

§  DecreaseCMdose

§  DecreasekVimaging

§  Decreasescanrange

Background:§  ThereisclinicalevidencethatratioofCMto

eGFRcanpredictCINoccurrence

§  Bestdiscriminator:CMdose(mL)>3.7xeGFR

ú  Correspondsto1xeGFRingramsofiodine(assuming

370mgI/mLcontrast)

§  ThereisalsoevidencethatCINriskisnotincreasedforvolumeslessthan2.0mLxeGFR

(PCIdata)Gurm HS, et al. J Am Coll Cardiol 2011; 58:907-14

eGFR-basedCMcalculation§  DetermineeGFR:http://touchcalc.com/e_gfr

§  IfeGFR<60ml/min/m2(e.g.CKD):

MAXvolume(mL)=eGFRx2

(thisisfor75kgbodyweight)

Then,adjustforBW:

MAXvolume=eGFRx2x(BW/75)

** Low concentration CM (300 mgI-/mL)

Cou

rtesy

: D. F

leis

chm

ann,

MD

LowkVpImaging

§  K-edgeofiodine:33.2KeV§  Attenuationofiodineincreasesby25%from120to100

kVp,andagainfrom100to80kVp

§  Each“step”downinkVpcorrespondsto~25%lessCM

needed

140kVp 120kVp 100kVp 80kVp 70kVp

IodineAttenuation(comparedto120kVp)

-25% - +25% +50% +70%

Chapter 3: Contrast Medium Injection Technique. In: Schoepf and Meinel, eds. Multidetector-Row CT of the Thorax (2016)

LowkVpimaging-modifications

§  Keepinjectionduration,scan-time,andscandelaysconstant

§  Foreach“step”downinkVp,increasemAs30-50%

§  NoiseControloptions:ú  Slowpitchdown

ú  Slowgantryrotationtime

ú  Keepnoiseindexthesame

ú  MatchCTDIvolbetweenprotocols

OtherissuesinlowkVpimaging

§  Ca++blooming/metalbeamhardeningworsens

§  Largerfocalspotrequirementdecreasesspatialresolution(focalspotbloom)

ú  Improvedwnewerscannertechnology

CTAReconstruction

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Tips:CTAReconstructionandInterpretation

§  UsesmallerFOV(trochantertotrochanter)

§  UseIterativeReconstruction§  Reconthin,overlappingimagesandreviewin3D

ú  VR/MIPoverviewthenMPR,CPR

ú  3-5mmAxialsinA/P

§  Reconlargermatrix–1024x1024

** Fleischmann D, Hallett RL, Rubin GR. JVIR 2006, 17: 3-26.

CTAPost-processingTips§  BigchallengeinlowerextremityCTA:

differencebetweenquickreadvs.painful(literally)scrollingthroughimages

§  axial(transverse)imagesinadequate,exceptinacuteischemia(i.e.thromboembolic)

§  Volumetricreviewofvolumetricdatasets!

CTAPost-processingTips§  needlongitudinalcrosssections(MPR/CPR)

§  Maplesionswitha‘map’:

ú  multipathcurvedplanarreformations(MPCPR)

ú  CPRsmadeon3DSolution

§  trytodelegate(3D-Lab,trainedtechnologist)ifroutinelyperformingrunoffCTAs

TheAchilles�HeelofExtremityCTA......

PredictorsofVascularCalcification

Aboveknee:1SeverePAD(FontaineIII-IV),Diabetes

BelowKnee:1RenalFailure(esp.dialysis),

Diabetes

Also:2Age,cardiacdisease

Ifheavy,significantdecreaseinSENS/SPECincalf1

1 Meyer BC Eur Radiol (2010) 20:497-505 2 Ouwendijk R. Radiology (2006) 241, 603-608

Time-ResolvedCTA-Runoff•  Technique

timingbolusatpoplitealartery

50mLat5mL/sec+50mLsalinechaser

12low-doseCTAacquisitionsover30sec

Rapid�shuttle�ofdetectorarray

•  Then:standardCTArunoffprotocol

•  Significantlygreaterenhancement,lessvenousoverlap

•  Significantlyhigherdiagnosticconfidence

•  Directlyvisualizeasymmetric/delayed/diminishedflow

Sommer Eur. Radiol (2010) 20: 2876-2881

EfficacyofLECTAinPAD

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Detection of >50% Stenosis or Occlusion By Anatomical Region

Vessels Sens(95%CI) Spec(95%CI)

Aortoiliac 96(91-99) 98(95-99

Femoropopliteal 97(95-99) 94(85-99)

Trifurcation 95(85-99) 91(79-97)

CTA:DiagnosticPerformancevs.DSACTChannels Sens(95%CI) Spec(95%CI)

2-4 92(88-96) 98(95-99

16-64 97(95-98) 98(96-99)

Performance

Met R et al. JAMA 2009;301:415-424

DiagnosticPerformance:64-sliceCTA

§  SymptomaticPAD:242pts,7420segments

§  CTAandDSAperformed

§  For>70%stenosis:

ú  SENS/SPEC96%PPV98%NPV99%

ú  NosigdifferencevsDSAfindings

ú  ResultssimilarinCa++vs.Non-Ca++lesions

Napoli A. Radiology. 2011 Dec 1;261(3):976–86.

ClinicalUtilityofLECTAinPAD

§  IntermittentClaudication(IC)

§  CriticalLimbIschemia(CLI)

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CTADirectedManagementofIntermittentClaudication

§  FontaineIIbpatients,TxdecisionsbyTASCIIcriteria

§  57/58correctTxdecision-makingbyCTA

ú  OneCFAstenosismissed

ú  29endovasc/surgTxú  29conservativemgmt

Schernthaner R, et al. AJR 2007; 189:1215-1222

CTADirectedManagementofIntermittentClaudication

CTADirectedManagementofCLI

§  41pts,1435segments§  64-CTA§  FontaineIIb,III,IV§  2.2%segmentsnon-diagnostic

ú  notincludedincalculationú  91%infrapopsegmentsevaluable

§  For>50%stenosis:ú  Sens99% Spec98% Acc:98%

Fotiadis N, et al. Clinical Radiology 2011; 66: 945-52

CTADirectedManagementofCLI

§  28pts,FontaineIV§  64-detectorCTA§  14/28àendovascularand/orsurg.Tx

§  correctdecision-makingforinterventions,amputation,andmedicalTxbasedonDSA

andTxresponse

Schernthaner R, et al. AJR 2009; 192: 1416-1424

CTADirectedManagementofCLI

ManagementofbothICandCLIbyCTA

§  TreatedusingTASCIIguidelinesú  49conservativeTXú  87Endovascularú  38surgeryú  17hybrid

§  TxrecommendationsfromCTAsameasDSA

inallbutONE

Napoli A. Radiology. 2011 Dec 1;261(3):976–86.

Examples:AtheroscleroticDisease-TherapyPlanning

CTAforpost-treatmentfollowup

Willmann JK, et al. Radiology 2003; 229: 465-474.

Post-TXAssessmentbyCTA

CTAforstentassessment§  Moststentsassessable(76%)

byCTAú  Gold/platinummarkers

ú  Motion

ú  Streckerstent(Tantalum):Increasedluminaldensity2

§  Ifevaluable,sens/spec~95%forsignificantin-stentrestenosis(vs.DSA)

1 Li X, et al. Eur J Radiol 2010; 98-103 2 Strotzer, Invest. Radiol. 2001:36(11)

CTAforassessmentofcomplications

AcuteRlegpain

Value-AddedInfofromCTA:GSVmapping1-2§  Pre-OpCTA:AdequateforevaluationofGSVsize1-2

ú  SENS/SPEC>90%(betterinthigh)

ú  Chargesavingsof~50Katauthorssitealone2

ú  IfGSV<2mm,thendoDopplerUS 1DeFreitas DJ, et al. J Vasc Surg 2013; 57(1): 5-55.

2Johnston WF, et al. J Vasc Surg 2012: 56(5) 1331-37.

Conclusions§  Goals: Maplesionstosymptomstodirecttherapy

Answertheclinicalquestions§  Implement:

IntegratedCM/scanprotocoltoimproveconsistency   Injectlong,scanslow

  Weight-basedCMdosing

§  3DVolumetricReviewofDatasetsneeded

§  Specialthanksto…..

DominikFleischmann,MD

ThanksforyourAttention!

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