Cardiovascular Imaging in Renal Failure? Prof Graeme Houston Dundee This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 324487 Dundee July 2016

Cardiovascular Imaging

Cardiovascular Imaging 2016 Ultrasound – Percutaneous, IVUS Catheter Angiography Nuclear Medicine MRI Multislice CT PET

Cardiovascular MRI Cardiac MRI Vascular MRI Established as a routine clinical technique since 2003 Patients are scanned to answer specific clinical questions that cannot be obtained through other means Vascular MRI Established clinical technique routinely since 1998 Potential extensions to existing techniques to complement the service

Renal Failure and the Heart Fluid overload – left ventricular failure Renal cardiomyopathy - uraemic Increased coronary arterial disease Immunosuppression in renal transplantation Vascular access load Drug toxicity Underlying cause of renal failure

Capabilities of Cardiac MRI Morphology and function (white blood cine, black blood spin echo) Valve assessment Flow quantification Perfusion Viability (delayed enhancement)

Basic morphology Steady-state sequences give good anatomical images with bright-blood contrast. Cine imaging is possible with 20-30 images created that cover the whole cardiac cycle. Example images from a patient with LVH

Thrombus in right atrium Black blood imaging shows up thrombus well

Right Atrial tumour Cine scans demonstrate heart function with tumour present. Black blood post-contrast shows extent

Qualitative cardiac assessment White blood cine scans in 2 chamber, 4 chamber and short axis orientations in a patient with poor cardiac function

Quantitative LV assessment Acquire a stack of SA cine views from the base to the apex of the heart

Quantitative LV assessment By defining the endocardial and epicardial borders it is possible to calculate blood pool and left ventricular volume in each phase by considering the myocardium as a series of rings Distance between slices Apex Base

LV function Possible to build up a graph showing the filling and emptying of the LV ED phase ES phase In practice, only calculate the volumes at ED and ES as this allows the ejection fraction, stroke volume and the LV mass to be calculated LV blood pool volume / ml Time from R-wave trigger / ms

Quantitative cardiac reporting Reports of quantitative results (LVM and function) can be generated either as paper copies or electronic reports

Morphology with black blood Spin Echo Black blood scans give T1 weighing to images. Can also use fat suppression (black blood STIR) Black blood (double IR) Black blood STIR (triple IR)

Right ventricular assessment Use black blood and black blood STIR scans to look for fatty infiltration into the right ventricular wall Black Blood Black Blood STIR

Flow imaging Magnitude Phase Cine phase contrast imaging. Phase image is a measure of the velocity of the blood flow. mid-grey is stationary, black and white indicates flow either into or out of the slice, depending on how the scan has been set up

Quantitative flow analysis: Coarctation

Mitral and right AV valves Looking at valves Aortic valves Mitral and right AV valves

Bicuspid aortic valve

First pass perfusion imaging

Quantitative perfusion analysis Possible to measure uptake of contrast agent in the myocardium Draw contours around the myocardium, divide the myocardium into sectors and propagate through the time series

Quantitative perfusion analysis Calculate uptake parameters for each sector of the myocardium tfoot tpeak Slope peak Area under curve foot

Quantitative perfusion analysis Quantitative data can be summarised on bull’s-eye plots Peak Slope Area

Tissue enhancement Fibrosis/viability Phase-sensitive inversion-recovery short axis views approximately 10 minutes after contrast agent injection in a patient with suspected myocardial sarcoidosis

Myocardial Viability Acute MI Acute inferior MI – 4 days LV Morphology and Function

Delayed Gd Enhancement: Mid Inferior and Mid Inferiorospetal 50% wall thickness enhancement Role in prediction response revascularisation

Questions Cardiac MRI? Summary: Function Flow-ology Lumen-ology Wall-ology Perfusion-ology

Summary: Cardiac MRI Morphology and function (white blood cine, black blood spin echo) Valve assessment Flow quantification Perfusion Viability (delayed enhancement)

Vascular Imaging

Vascular MRI

Vascular MRI Lumen-ology Wall-ology Perfusion-ology Flow-ology Function

Cardiovascular MRI: Whole Body Atheroma Whole Body MRI Overview of atheroma High Resolution at disease site Focussed assessment of plaque morphology Large Vessel Compliance JG Houston

Whole body MRA – Atheroma Burden “Lesion” MRA - Index atheroma lesion

Carotid MRI “Wall-ology” 1.5 Tesla machine Dedicated phased-array carotid coil and standard neck coil Four sequences: Time of flight [TOF] T1-weighted [T1W] Proton density-weighted [PDW] T2-weighted [T2W] Series of illustrations of the sequences and resulting images, demonstrating what plaque looks like on each and how comparison of different sequences allows identification of different plaque components

Carotid MRI “Wall-ology” 1.5 Tesla machine Dedicated phased-array carotid coil and standard neck coil Four sequences: Time of flight [TOF] T1-weighted [T1W] Proton density-weighted [PDW] T2-weighted [T2W] Series of illustrations of the sequences and resulting images, demonstrating what plaque looks like on each and how comparison of different sequences allows identification of different plaque components

Plaque composition: necrotic core and cap rupture Focussing in on specific examples of particular “high risk” plaque characteristics: the cracked plaque cap with exposure of the thrombogenic necrotic core to flowing blood Time of flight T2-weighted

Carotid Plaque composition: Necrotic core and cap rupture Focussing in on specific examples of particular “high risk” plaque characteristics: the cracked plaque cap with exposure of the thrombogenic necrotic core to flowing blood MRI – Plaque Rupture Histology

New Insights Vascular Disease Anatomy MRI Flow pattern

New Insights Vascular Disease Computational Fluid Dynamics CFD predicted sites of carotid disease based on lack of spiral flow

Renal angiography Perfusion 20 40 60 80 100 7 14 21 45 120 180 240 Time(Sec) Signal intensity(a.u) Aorta Cortex Typical Contrast Uptake Curves

Renal MRA Research – How can renal perfusion MRI be used to select patients for renal intervention?

Optimal cortical medullary contrast (at TR 4.8ms) achieved at 25-35o 50 100 150 200 10 20 30 40 60 70 80 90 Cortex Medulla Noise Contrast Signal Intensity (a.u) Flip Angle (/o) MRI signal intensity v flip angle for porcine kidney tissue using a FLASH sequence Optimal cortical medullary contrast (at TR 4.8ms) achieved at 25-35o

Patient 1036 – moderate (31-50%) RAS on R, severe (70-100%) RAS on L Pre contrast Venous phase Subtraction Cortical volume Total volume Cortical volume Total volume 144cm3 226cm3 32cm3 77cm3 Patient 1036 – moderate (31-50%) RAS on R, severe (70-100%) RAS on L

Kidney Volumes and Lengths Moderate – Severe Stenosis: Mean kidney lengths were only reduced by 14%. Mean kidney volumes were reduced by 39%

Cortical Volumes and Function Mean GFR values dropped as the severity of combined RAS increased.

Cardiovascular MRI Summary Routine tool: Cardiac Morpholgy, function Valves Perfusion Viability Routine Vascular tool “Catheter Angiography Obselete” Vessel morphology Flow

Acknowledgements Tayside MR Imaging Radiographers Medical Physicists Wendy Milne Baljit Jagpal Medical Physicists Stephen Gandy Stephen Nicholas Shelley Waugh