Topics in Magnetic Resonance Angiography Research

and Some Potential New Directions

Dennis L. Parker et al.

Goal – Increase Vessel Signal

• Acquisition Techniques• RF coils, Pulse sequences, Field strength

• Post Processing• Vessel enhancement, noise reduction techniques

• Vessel Segmentation

• Aneurysm Screening

• New contrast agents

Outline

• Acquisition Techniques• RF coils, Pulse sequences, Field strength

• Post Processing• Vessel enhancement, noise reduction techniques

• Vessel Segmentation

• Aneurysm Screening

• New contrast agents

MRA - TOF : Time-Of-Flight

Slab THK

blood flow

vessel

Partially Saturated Spins

v

Saturated Static Tissue

d=v TR

TR

v3

v2v1

v1 >v2 >v3

tn = THK / vn (n=1,2,3)

t3t2t1

Blood Flow Signal

TR

Static Tissue Signal

FreshInflow

TR : Repetition time

Acquisition Techniques

• RF Coils• Reduce electric coupling, reduce noise figure

• Pulse Sequences• Variable echo time• Double echo 3D TOF

– Segment blood from tissue– Post processing noise reduction

• 3D PR for ultrashort echo time (TE)• Novel Black-Blood sequences for carotid artery

MRI Projects:3D TOF Complete FC +

Variable Echo Time (VTE) • Eun Kee Jeong

Non-VTE with Complete FC VTE with Complete FC

Efficient Double Inversion FSE

• DL Parker, EK Jeong, SE Kim, Eugene Kholmovski

MRI Projects: Carotid Imaging• Triple Double FSE:

Interleaved Double Inversion Double Echo

Non-interleaved acquisition.Interleaved acquisition.

FreeSlices

MRI Research: Carotid Imaging• Triple Double FSE: Interleaved Double Inversion

Double Echo

zslice

zni

zinterl eaved

Artery Segment

Slice N+1Slice 1

• Eugene: Triple Contrast: Interleaved Double Inversion Double Echo with interleaved T1

Outline

• Acquisition Techniques• RF coils, Pulse sequences, Field strength

• Post Processing• Vessel enhancement, noise reduction techniques

• Vessel Segmentation

• Aneurysm Screening

• New contrast agents

Post ProcessingBrian Chapman

• Noise Reduction

• Vessel Enhancement Filtering

Original vs. Filtered vs. Noise

Post ProcessingEugene Kholmovski

• Noise Reduction

• Image Redundancy

Double Echo FSE Motion Artifact Reduction

• Eugene Kholmovski

Original PD Original T2

Spectral energy (non-image support)

Corrected PD Corrected T2

Standard Image POCS SENSE

Reduction = 2, Ncoils = 4

Eugene Kholmovski

Standard SENSE POCS SENSE

Reduction = 4, Ncoils = 4

Eugene Kholmovski

Outline

• Acquisition Techniques• RF coils, Pulse sequences, Field strength

• Post Processing• Vessel enhancement, noise reduction techniques

• Vessel Segmentation

• Aneurysm Screening

• New contrast agents

Z-Buffer Segmentation (ZBS) Algorithm

Conventional MIP Depth (Z-)Buffer Image

Future Segmentation• Incorporate Additional Information

• Directionality• Signal intensity continuity

• Segment the segmentation• Centerline recognition• Label vessel segments• Shape descriptors (tortuosity)

– Use sparse vessel locations to speedup 3D PC and 2D PC techniques.

Outline

• Acquisition Techniques• RF coils, Pulse sequences, Field strength

• Post Processing• Vessel enhancement, noise reduction techniques

• Vessel Segmentation

• Aneurysm Screening

• New contrast agents

High Resolution MRA Applications to Aneurysm Screening

3 Aneurysms, without (left) and with (right) Gadolinium Contrast. Parker, Tsuruda, et al., University of Utah

Kindred 7450

2 2

2

S38

105

S61

110

FAM

117

FAM

10 9

MR

1

S34

5

S41

6

S45

7

S42

15

S0

16

FAM

S47

26

MR 39

S48

21

S38

104 103

FAM

115 116

11 8

S71

13

S71

12 18

S69

17

S77

96 97 98 96

4 3

94 95

Aneurysm Screening Pedigrees

MRA Aneurysm Screening Results

• Screening of high risk families– 143 high-risk intracranial aneurysm pedigrees

found– 3400 total members– 340 relatives screened with MRA (29 aneurysms

detected)– Evidence for a gene detected

Dennis L. Parker, University of Utah

Outline

• Acquisition Techniques• RF coils, Pulse sequences, Field strength

• Post Processing• Vessel enhancement, noise reduction techniques

• Vessel Segmentation

• Aneurysm Screening

• New contrast agents

General Focus• Goal to increase visibility of vascular disease

• Aneurysms, embolic disease, atherosclerosis

• Improve efficiency in MRA• Increase signal, post processing for noise reduction.

• Use MRA for longitudinal studies of disease• Aneurysm Screening, carotid disease

• New contrast agents• Blood pool, targeted agents

MzT1 (slow ~ 1s)

Signal Regrowth

MxMy

T2 (fast ~ 100ms)

Blood T2 should appear Longer than tissue T2