MRI as a tool for pre and post-operative assessm ent of - - PowerPoint PPT Presentation

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MRI as a tool for pre and post-operative assessm ent of - - PowerPoint PPT Presentation

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MRI as a tool for pre and post-operative assessm ent of arterio-venous fistulas Conor MacDonald PhD Student Molecular and Clinical Medicine, University of Dundee Supervisors: Dr. R Ross, Prof. JG Houston This project has received funding

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This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 324487

MRI as a tool for pre and post-operative assessm ent of arterio-venous fistulas

Conor MacDonald PhD Student Molecular and Clinical Medicine, University of Dundee Supervisors: Dr. R Ross, Prof. JG Houston

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This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 324487

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The arteriovenous fistula ( AVF)

  • HD requires high blood flow

for good clearance (600ml/ min)

  • CVC not suitable for long-term

use due to stenosis/ infection

  • AVF - Surgical connection

between artery and vein

  • Vein dilates & flow increases

Credit: Blausen medical

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This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 324487

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Problem s

  • High failure rates: meta-reviews find 60%

patency rates between 1-2 years [ Rooijens 2004, Weale 2008]

  • Multiple factors identified as predictors of lower

failure rates

  • NIH main factor behind flow limiting stenosis

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This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 324487

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Pre-operative im aging

  • Patients commonly undergo pre-
  • p US
  • Vessel sizes, and health assessed
  • Central vessel problems can be

missed

  • "Pre-access vessel mapping alone

is clearly not enough to plan a dialysis vascular access." - Pre- Access Creation Evaluation—Is Vein Mapping Enough?, Vachharajani 2015

Credit: Rose Ross (ReDVA)

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This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 324487

Post-operative surveillance

  • Monitoring/ surveillance physical

& US exams

  • If monitoring or surveillance

indicate a problem -> DSA

  • Diagnostic imaging of

dysfunctioning AVFs

  • DSA can identify stenosis, and

treatment performed in same session

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Credit: Marco Salsano

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This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 324487

MR im aging of Vascular Access

  • MRI research has showed

good stenosis detection in VA patients

  • NSF association with GBCAs

may have lead to negative trend in research

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This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 324487

Study intro

  • Evaluation of MEDIC sequence for upper-

limb extremity angiography

  • MRI imaging of healthy and patient

volunteers

  • Comparison with US results
  • Post-operartive imaging of patient

volunteers

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This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 324487

Materials and m ethods - participants

  • 16 Volunteers – 10 healthy

(NHV1-10), 6 ESRD (AVP1-6 awaiting AVF

  • 2 imaging locations – upper or

lower arm

  • AVP1,3,6 brachio-cephalic AVF
  • AVP2,5,7 radio-cephalic AVF

Characteristic Num ber ( N= 1 6 ) Age 44± 16 W hite race 16 Diabetes 4 Arterial fibrillation 2 Upper arm im aging 5 Low er arm im aging 11

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This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 324487

Materials and Methods – I m aging tim es

  • 10 healthy volunteers – 1

US and 1 MRI scan

  • 6 Patient volunteers:
  • Pre & post-op US
  • 4 patients pre & post-
  • p MRI
  • 2 patients pre-op MRI

Pre-op imaging AVF Creation post-op imaging

AVP1 AVP2 AVP3 AVP5 AVP6 AVP7

4 days 10 days 8 days 38 days 20 days 26 days 17 days 24 days 8 days 9 days

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This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 324487

Methods - Ultrasound im aging

  • Siemens s2000
  • Volunteers imaged in seated

position

  • Arterial, venous diameters and

peak-systolic velocity measured

  • PSV from US used to guide

subsequent MRI

Doppler-US image of arterial segment of AV fistula on patient-vol

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This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 324487

Methods - MRI im aging

PC-MRI – flow

  • TR/ TE: 61.7/ 5.88ms
  • Flip angle: 8
  • FOV 150* 200mm
  • VENC: 70-250cm/ s

MEDI C – m orphology

  • TR/ TE: 29/ 16ms
  • Flip angle: 30
  • Thickness: 6mm
  • 3T Siemens Trio-PrismaFIT
  • Imaging in lying position with arm relaxed
  • 10cm region covering upper or lower arm
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This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 324487

Methods – MRI I m age analysis

Morphology Assessm ent

  • Osirix light
  • Vessels assumed to be oval
  • 2 diameter measurements on minor

and major axis

  • Area plotted as a distance of

anastomosis

  • Biological landmarks used to

manually register image locations Velocity Assessm ent

  • Segment
  • ROI drawn round vessel of interest
  • Semi-auto propagation of ROI
  • Automatically exports flow info to

excel

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This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 324487

Results – I m aging outcom e of volunteers

  • All 16 volunteers scanned as planned
  • Initial observation revealed PC-MRI unsuccessful in

AVP5 and HV2

  • MEDIC poor quality in HV4
  • US data not recorded for HV6

MEDIC MRI images of AV fistula in patient-vol

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This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 324487

Results - Surgical outcom e of patients

  • AVP1 original fistula site abandoned

due to calcification – secondary site successful

  • AVF7 developed infection – affected

MRI image quality

  • Stenosis developed in 4 patients

(AVF1,2,3,6) between 6-12 weeks after surgery

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This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 324487

Results - Statistical com parisons

US MRI p-value Whole- Group (n= 16) Cephalic vein diameter Cephalic vein diameter 0.78 Radial artery diameter Radial artery diameter 0.68 Radial artery PSV Radial artery PSV 0.88 HV-AVP cephalic vein diameter

  • 0.07

radial artery diam eter

  • 0 .0 2

radial artery PSV

  • 0.12

brachial artery PSV

  • 0.12
  • cephalic vein

diam eter 0 .0 1 2

  • radial artery

diam eter 0 .0 0 0 2

  • radial artery

PSV 0 .0 0 1 6

  • Whole group results compared

between MRI and US

  • Differences between groups

compared for each modality

  • No differences between MRI and

US for whole group

  • Differences seen in

measurements on MRI between healthy and patient groups

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This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 324487

Results – Radial artery PSV on MRI

  • Radial artery PSV in ESRD group

P< 0.05

  • Mean
  • Low patient sample size for radial

PSV measures

10 20 30 40 50 60 70 80 HV1 HV3 HV4 HV5 HV7 HV8 HV9 HV10 AVP2 AVP7 Peak PSV (cm/ s) Identifier

Radial artery PSV on MRI

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This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 324487

Results – Radial artery diam eter

  • n MRI
  • Lower radial artery diameter in

patients

  • Difference seen on MRI (P< 0.05)
  • Also seen on US (P= 0.02)

0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 HV1 HV3 HV5 HV7 HV8 HV9 HV10 AVP2 AVP5 AVP7

Radial artery diameter (mm) Volunteer identifier

Radial diameter artery on MRI

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This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 324487

Results – Cephalic vein diam eter

  • n MRI
  • Lower diameter in patient

volunteers (red)

  • P= 0.012
  • Mean healthy
  • Mean patients

1 2 3 4 5 6 7 8 HV1 HV2 HV3 HV4 HV5 HV6 HV7 HV8 HV9 HV10 AVP1 AVP2 AVP3 AVP5 AVP6 AVP7

Diameter (mm) Volunteer identifier

Cephalic vein diameter on MRI

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This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 324487

Results - Pre and Post-Surgery - m orphology

  • Large increases in vessel size seen on

both modalities

  • MRI shows non-uniformity in these

changes

  • Significant spots of lower dilation in AVP3

– pictured (red)

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This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 324487

Results - Pre and Post-Surgery - flow

  • Large increases in arterial PSV shown
  • n both modalities
  • Large increase in venous velocity
  • Changes in waveform seen on both

modalities

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This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 324487

Conclusions & Discussion

  • MRI able to provide detailed 3D spatial

information – area areas of low dilation important?

  • MRI may be more sensitive to velocity and

geometric differences between groups

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This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 324487

Lim itations

  • Small numbers – exacerbated by different

scanning locations

  • MRI wasn’t used in AVF planning
  • MRI known to underestimate vessel sizes
  • potential mismatch between measurement

areas

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This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 324487

Future w ork

  • Subsequent analysis of MRI and US

data – six month post-operative

  • CFD simulations of blood flow using

patient specific models

  • Comparison of MEDIC with ToF

sequences

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This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 324487

Acknow ledgem ents

  • Vascular laboratory, Ninewells
  • Medical Physics, Ninewells
  • Clinical Medicine, UoD
  • Sinapse
  • IPEM