Department of Radiology University of California San Diego. MR Angiography. Techniques & Applications. John R. Hesselink, M.D.

Transcription

1 Department of Radiology University of California San Diego MR Angiography Techniques & Applications John R. Hesselink, M.D.

2 Vascular Imaging Arterial flow void Flow enhancement Gadolinium enhancement

3 Vascular Flow Voids

4 History: 35-year-old male with intermittent diplopia due to a sixth nerve palsy

5 Vascular Encasement

6 The Absent Flow Void

7 90 RF 180 RF Signal MR Flow Void Arterial Flow TE Voxel Flow Voxel Signal No flow Flow = 1/3 voxel Flow = 2/3 voxel Flow = 1 voxel

8 Flow Enhancement

9 90 RF 180 RF Signal RF Flow Enhancement Venous Flow: Short TR-TE Spin-echo Short TR Voxel Flow Voxel Signal No flow Flow = 1/3 voxel / TR Flow = 2/3 voxel / TR Flow = 1 voxel / TR

10 Flow Enhancement Arterial Flow: Gradient echo RF RF TR

11 MR Angiography Pulse Sequences 2D time of flight 3D time of flight 2D phase contrast 3D phase contrast

12 2D Time of Flight TR msec, TE 4.0 msec Flip angle degrees 1.5 mm sections Moving SAT band MIP algorithm

13 Normal 2D-TOF MRA mra

14 Segmented MIP Q-205-6

15 History: 23 y/o female with neck pain & vertigo following a snowboard accident 457

16 {Page 2}

17 {Page 3} 4 months later Dx: Bilateral vertebral artery dissection

18 3D Time of Flight TR 9.0 msec, TE 2.0 msec Flip angle degrees 6-8 cm volume, phase encode in 2 directions mm sections Superior SAT band MIP algorithm

19 Normal 3D-TOF MRA {Video clip} {Video clip}

20 3D vs. 2D Time of Flight Higher signal-to-noise Shorter imaging times Less intravoxel dephasing Smoother vessel contours More saturation effects

21 3D TOF at 3T

22 History: 47 y/o man with von-hippel-lindau disease & new left arm weakness 486

23 {Page 2} Dx: Infarct & MCA stenosis

24 History: 40 y/o man with episodes of left sided weakness 506

25 {Page 2}

26 {Page 3} {Video clip} Dx: Cerebral arteritis

27 2D Phase Contrast TR 25 msec, TE 6-7 msec Flip angle degrees 2-4 cm slab VENC factor Single projection image

28 Phase Contrast MR Angiography Velocity Encoding Gradient 1st Excitation Time Gradient T 2nd Excitation Time

29 3D Phase Contrast TR 25 msec, TE 6-7 msec Flip angle degrees 6-8 cm volume mm section VENC factor MIP algorithm

30 PC vs. TOF Angiography Less saturation effects Not affected by thrombus Velocity / flow information Long imaging times Arterial VENC misses slow flow

31 Phase Contrast Flow Direction Q-197-8

32 TOF vs. PC 2D-TOF 3D-PC Q-170-2

33 PC: Pseudoocclusion 3D-PC TOF Q

34 Imaging Slow Flow Thin-section 2D TOF Longer TR Lower flip angle Lower VENC factor Gd enhancement

35 Intravoxel Dephasing & Signal Loss Q

36 Intravoxel Spin Dispersion Strategies To Minimize Smaller voxel size Shorter TE Flow compensation Gd-enhanced MRA

37 Gd-Enhanced MRA 3D gradient-echo sequence TR 4.5 msec, TE 1.5 msec High bandwidth & fractional echo Flip angle 25 degrees Matrix 173 x 256, FOV 187 x 250 Coronal volume 7 cm with 64 partitions 20 ml Gd 2ml/sec Acquisition time 21 sec

38 Timing Bolus Acquisition

39 Normal Gd-enhanced MRA {Click for video} mra

40 History: 83 y/o woman with slurred speech {Video clip} 503

41 {Page 2} Dx: Gd-MRA, multiple stenoses {Video clip}

42 History: 49 y/o man with neck pain following an MVA 523

43 {Page 2} {Video clip} Dx: Vertebral dissection

44 History: 51 y/o man with right-sided facial dysesthesias & ataxia 565

45 {Page 2} {Video clip} Dx: Lateral medullary syndrome & right vertebral occlusion

46 Vulnerable or High-Risk Atherosclerotic Plaque Imaging Criteria Thin fibrous cap Large lipid-necrotic core Fissured plaque Stenosis > 90 % Intraplaque hemorrhage Other factors: Inflammation, endothelial dysfunction, platelet aggregation

47 History: 48 y/o women with trauma to the neck Dx: Lipid core plaque 742

48 Venous / Sinus Occlusion Causes Hypercoagulable state Pregnancy Sepsis Dehydration Paranasal sinus infection Neoplastic invasion

49 2D TOF MR Venography TR 21 msec TE 4-6 msec Flip angle 60 o 1.5 mm sagittal or coronal sections Axial SAT band below skull base MIP algorithm {Video clip}

50 History: Newborn girl with seizures & decreased alertness

51 {Page 2}

52 Day 7 {Page 3} Dx: Hemorrhagic infarct with thrombosis of deep venous system, straight sinus & right transverse sinus 2 cm to right

53 History: 40 y/o woman with polycystic kidneys, renal failure, acute visual deficits & seizures 359

54 {Page 2} 2D PC Slabs Dx: Hypertensive encephalopathy

55 History: 32 y/o woman with headache, confusion & weakness 355

56 {Page 2}

57 Confusion & weakness {Page 3} Dx: Thrombosis of superior sagittal sinus, left transverse sinus & deep venous system

58 Meningioma

59 History: 60 y/o female with ataxia following trauma and concussion 387

60 {Page 2}

61 {Page 3} Dx: MCA aneurysm

62 History: 66 y/o male with dizziness and possible basilar insufficiency 542

63 {Video clip} {Page 2}

64 Dx: ACA aneurysm {Page 3}

65 History: A 62 y/o female with headaches for 3 weeks & a new 3 rd nerve palsy 3T 632

66 {Page 2} Dx: Acom & Pcom Aneurysms

67 History: 37 y/o woman with migraine headaches for many years 581

68 {Page 2} Dx: 2 mm AComm aneurysm

69 MR Angiography Aneurysms High risk patients 3D time-of-flight A screening procedure ONLY View source, collapse & MIP images 86-95% sensitivity for aneurysms 5 mm or larger

70 History: 80 y/o man with hypertension, slurred speech & unsteady gait {Video clip} 515

71 {Page 2}

72 {Page 3} Dx: Cavernous aneurysm

73 History: 63 y.o. man with episode of aphasia & right sided weakness. 16

74 Dx: Ethmoid mucocele Aphasia {Page 2}

75 History: 52 y/o woman with chronic seizures 604

76 Dx: AVM {Page 2}

77 History: 73 y.o. man with visual field deficits 1 2

78 3 5 4 Visual deficits {Page 2}

79 6 {Page 4} 7 8 Dx: AVM & basilar tip aneurysm

80 MR Angiography Problems & Pitfalls Turbulence / nonlaminar flow Slow flow / near complete occlusion Flow stasis & recirculation Thrombus Limited resolution Solution = Gd-enhanced MRA