A major teaching hospital of Harvard Medical School Angiography: What are our goals? Non-Contrast MRA: How and When Neil M. Rofsky, M.D. Professor of Radiology, Harvard Medical School Director of MRI & Associate Chief at Large Beth Israel Deaconess Medical Center Boston, MA, USA Accuracy Excellent correlation with reference std Allows for correct management decisions Clinician acceptance Familiar presentation Artifact free! Reproducibility Across vendors Across software platforms Across users Simplicity The goals have been achieved with Gd-enhanced MRA 1996! Why Non-Contrast MRA? NSF concerns Allergy concerns Failed IV access Physiologic adjuncts (multiple repeats) Velocity & Flow Determinations Response to vasodilators Non-Contrast MRA Inflow Techniques Differences in excitation hx Velocity Techniques Phase Contrast Triggered FSE Intrinsic Bright Blood T1 and T2 of blood
Non-Contrast MRA Inflow Techniques Flow-related enhancement 0 Flow Time of Flight TOF Inflow Inversion Recovery IFIR Arterial Spin Labeling ASL Mz Time 2 1 Saturation Signal loss Static tissue Slice Flow-related enhancement 0 Flow Flow-related enhancement 0 Flow 1 1 2 2 Mz Mz Static tissue Static tissue Thin Slice Thin Slice Time Saturation Signal loss Time Saturation Signal loss Plan Scans TOF Feet: TOF; Occult Vessels Rt foot Lt foot 2mm sections 3mm sections
TOF Intra-op angio DSA In-plane saturation Longer TE s (flow comp) metal artifacts Slice misregistration artifact Long acquisition time (less with parallel imaging) DSA occult vessel Non-Contrast MRA What s Changed???? Faster Sequences New Sequences d bkgd suppression d d motion compensation Pt #1 88 yo woman with poorly controlled HTN and worsening renal failure (egfr 30); presenting with SOB Positive stress test and cardiac cath. Other: cholesterol, family Hx heart dz Prior Doppler US (prior to cath) No renal artery stenosis Limitations of 2D time-of of- flight Noncontrast MRA Pt #1 IFIR (In Flow Inversion Recovery) Non-contrast MRA technique Respiratory-triggering triggering Magnetic alteration of the blood properties to produce MRA images w/o contrast media Conventional Angio: Normal right Moderate RAS left
Principles of IFIR Resp Gate IFIR Volunteer Scan Result on 1.5T TI 1200ms Based on 3D Fiesta Selective IR suppress the venous and bkgd Special ChemSat suppress Fat signal Artery signal depends on the in flow effect Selective IR prep (Ax plane) SPIR SSFP Respiratory Gating motion artifacts Orange Volume: acq volume Green volume: IR Prep volume IFIR Volunteer Scan Result on 3.0T IFIR (In Flow Inversion Recovery) QuickTime and a Video decompressor are needed to see this picture. 3 min, 11 sec acquisition IFIR (Non Contrast MRA) DSA Pt #2 71 yo woman Poorly controlled HTN on 3 medications (215/91) egfr= 62 ml/min/1.73 m2 MRA Kidney ordered Pt #2 MRA (3/24/09) IFIR Gd-MRA Conventional Angio: 70% stenosis right 90% stenosis left
Pt #3 44 yo female with severe bronchitis/asthma, currently active Dyspneic at time of exam Left renal mass with extensive hilar lymphadenopathy I just need to see the arteries, veins and nodes, before I operate. Pt #3 Non-contrast MRA/MRV Pt #4 TOF Renal Veins IFIR Renal Arteries Triggered 3D Echo train Trigger delays Signal Intensity sys vein artery diastole 2D GRE Phase contrast data Systole (fastest arterial flow) Zero ms Dyastole 200 400 600 800 Time (ms)
Principle of FSE Non-contrast MRA Principle of FSE Non-contrast MRA - V A V A - - V A V A V A Diastole Systole Diastole Systole Subtraction Peripheral MR angiography in a patient with claudication Non-contrast Fresh Blood Imaging Time-resolved 3D MRDSA Volume rendered Image ECG-Triggered FSE Gd- MRA Miyazaki, M. et al. Radiology 2008;248:20-43 Courtesy of Dr. Nakamura Kyoritsu Tobata Hosp. Arterial Spin Labeling: Schematic 45-year-old woman with limited scleroderma Spatially Selective Inversion Arterial Inflow Inverted Spins T1 Tissue 34-year-old female volunteer w/hx of cold sensitivity left thumb Venous Outflow Lim, et al. Radiology 2009;252:874-881
Miyazaki, M. et al. Radiology 2008;248:20-43 Nonenhanced renal MR angiogram in a 27-year-old male volunteer by using ASL with balanced SSFP (5.0/2.5; 120{degrees} flip angle; inversion time, 1100 msec; parallel imaging factor, two) Non-contrast MRA (Arterial Spin Label based) TI=800 ms c/o Mitsue Miyazaki, PhD TI=1700 ms Results: Dynamic Inflow Visualization MIP views of 8-slice image for each time point (2 min per time point) Labeling in the common carotid artery Labeling duration before imaging: between 200 ms and 3000 ms Vessel Selectivity - ICA Labeling MIP views of 8-slice image (2 min scan time) Excellent contra-lateral suppression Symmetric Filling Healthy volunteer ~1 sec to fill ACA/MCA branches above CoW and basilar artery below CoW ~2 sec to fill the extracranial arteries Right Left 8 9 Vessel Selectivity - Rt ECA and vertebral MIP views of 8-slice image (2 min scan time) ECA and cerebellar branches separated Sufficient selectivity to identify collateral flow Real Time Duplex MR Physiologic Adjuncts 10 Phase contrast based technique
Conclusions Non-Contrast MRA is back! Broader offerings for non-invasive angio Different techniques for different apps Physiologic adjuncts Improved dx Improved outcomes