Transcript 5/19/08 IPedrosa

MR Venography
Ivan Pedrosa, M.D.
Beth Israel Deaconess Medical Center
Harvard Medical School
Boston, MA
Why MR Imaging?
• Conventional venography
– Multiple injections
– I.V. access in affected edematous extremity
– Radiation / iodinated contrast
• US
– Limited in central veins
– Limited FOV and anatomic landmarks
Why MR Imaging?
• CT
– Radiation
– Iodinated contrast
– Pitfalls due to poor opacification /
mixing artifacts
• Nephrogenic Systemic
Fibrosis (NSF)
– Increased indications for non-contrast
MRV
MRV
• Techniques
– Dark Blood Imaging
– Bright Blood Imaging
– Gd-enhanced MRV
• Clinical Applications
– Chest
– Abdomen
– Pelvis
MRV
techniques
Non-contrast MRV
Dark blood Sequences
Bright blood Sequences
Double IR Spin echo
Double IR SSFSE
Dynamic SSFSE
TOF
GRE (Cine)
FIESTA (Cine)
Phase Contrast
Gd-enhanced MRV
3D FS T1-W GRE
(VIBE, LAVA, THRIVE)
Spin Echo (“dark blood”)
180º
90º
180º
90º
HAlf-Fourier Single shot Turbo Spin Echo
(HASTE or SSFSE)
K space
180º
90º
• One second to collect the
whole image
• Dark blood
• Protons exit slice
• Slow flow - ↑↑ SI
• Thrombus - ↓↑ SI
SSFSE/HASTE
Dynamic HASTE
• Intravascular
signal void
• Valsalva
–  intrathoracic P
–  Venous return
• T2 of blood is long
VALSALVA
Dynamic HASTE
• Valsalva
–  intrathoracic P
–  Venous return
• T2 of blood is long
VALSALVA
DB HASTE (“dark blood”)
180º
180º
180º
90º
TI
180º
Double IR T1 FSE
IR-T1W
Cardiac-gated
1 slice (~16 sec) breath-hold
2 slices with ASSET
IR-HASTE
~20 slices ( sec) breath-hold
Bright blood Sequences
•
•
•
•
TOF
GRE (Cine)
FIESTA (Cine)
Phase Contrast
Time-of-Flight (TOF)
Time-of-Flight (TOF)
Time-of-Flight (TOF)
Time-of-Flight (TOF)
Time-of-Flight (TOF)
Time-of-Flight (TOF)
Time-of-Flight (TOF)
Time-of-Flight (TOF)
TOF
TOF optimization for slow flow
TOF: in-plane saturation
Sagittal
Axial
acquisition
Gad-MRV
Sagittal
TOF optimization for slow flow
• Slice perpendicular
to vessel of interest
• Decrease slice
thickness
• Cardiac gating?
ECG
Tracing
Blood flow
(Pulse
Oximeter)
Systole (arterial)
True FISP / FIESTA / Balanced FFE
• True Fast Imaging with Steady-state
Precession
• Gradients are fully balanced in order to
recycle the transverse magnetization in long
T2 species
• Contrast
– T2 / T1 ratio
– Blood vessels are bright (T2 of blood is )
True FISP
Pros
• Fast
– Road map
• No breathing artifacts
• Thrombus
– Filling defect  SI
• Cine True FISP
– FIESTA
Cons
• Artifacts
– Pulsatile flow
– Off-resonace
• Acute / subacute
thrombus
True FISP
True FISP
True FISP
Gd-enhanced MRV
True FISP
L
True FISP
Gd-enhanced MRV
Pedrosa I. AJR 2005
Phase Contrast (PC)
• 2 equal and opposite Venc gradients between the
excitation and echo.
• With stationary protons, phase shifts induced by the first
gradient are reversed and canceled by the second
gradient.
• In moving protons, the second gradient does not quite
cancel out phase shifts induced by the first gradient
• These phase shifts are detected and proportional to the
amount of motion in the direction of the encoding
gradients
Phase Contrast (PC)
High velocity flow
towards the head
(Ascending aorta)
Moderate velocity
flow towards the head
(Pulmonary artery)
• Venc gradient applied in the
slice (superior-inferior) direction
• In the phase (velocity) image
– Gray represents stationary
background tissues
– White represents blood flowing
caudally (towards feet)
– Black represents blood flowing
cranially (towards head)
– The intensity of white or black
represents the magnitude of
velocity in the respective
directions
Moderate velocity
flow towards the feet
(SVC)
Phase
Image
High velocity flow
towards the feet
(Descending aorta)
Magnitude
Image
Phase Contrast (PC)
• If Venc is chosen to be too low,
aliasing (“wrap-around artifact”)
occurs when velocities exceed that
value causing velocities to mimic a
“lower” value
Venc set to
140 cm/sec,
appropriate
for this
volunteer
• If Venc is chosen to be too high,
sensitivity to slow flow and
accuracy of quantitative analysis of
velocity/flow are diminished
Venc set to
70 cm/sec,
too low for
this volunteer.
Aliasing or
“wrap-around”
results in the
high-velocity
flow areas of
the aorta.
• Venc for venous imaging?
– 40-60 cm/sec
Phase Images
Phase Contrast (PC)
Venc = 40 cm/sec
Phase Contrast (PC)
QuickTime™ and a
YUV420 codec decompressor
are needed to see this picture.
3D PC
Gadolinium-enhanced MRV
• Indirect MRV
• Direct MRV
Indirect Venography
• I.V. access in any peripheral vein
– Antecubital vein (Right UE)
• Gadolinium
– Single dose (~20 cc) @ 2 cc/seg
– Single dose (~20 cc) @ 0.8 cc/seg
– 20 cc saline @ 0.8 cc/seg
• 3D GRE T1
• Subtractions
– Venogram-like MIP reconstructions
Double dose Gd
Single injection/dual rate
Timing arterial phase
QuickTime™ and a
decompressor
are needed to see this picture.
Indirect Venography
VENOUS
PHASE
=
ARTERIAL
PHASE
SUBTRACTION
Indirect Venography
SUBSTRACTION
MIP
Direct Venography
• I.V. access in affected extremity or
bilateral
• Gadolinium
– 5 cc Gd in 100 cc saline (1:20)
• Tourniquet in lower extremities
• 3D GRE T1
Li W et al. J Magn Reson Imaging 1998; 8(3): 630-3
Direct Venography
Thrombus Characterization
– Bland thrombus
No enhancement
– Variable SI
–
– Tumor thrombus
–Enhancement on Gd-MRV
» Subtractions!
» Absence of enhancement does NOT exclude
tumor thrombus
– SI on T2-weighted images
Tumor thrombus: Intravenous leiomyomatosis
U
Staging
• Acute thrombus
– Enlargement of vein by intraluminal thrombus
–  SI on T2-weighted images
• Vessel wall
• Thrombus
– Perivascular soft tissue edema
–  SI on T1-weighted images (subacute)
• Chronic thrombus
– Vein attenuated or not visible
– Venous collaterals
– ↓ SI on all sequences
Acute thrombosis of the portal vein
T2W
T1W post-contrast
Paget von Schrotter syndrome or “effort” thrombosis
Chronic Thrombosis
Venous thrombosis
Is the thrombosis acute or chronic?
Do I need to anticoagulate this patient?
Acute/subacute thrombosis
brachiocephalic vein: chronic occlusion
Central catheter malfunction
Fibrin sheath
Clinical
Indications
SVC syndrome
Venous Access
• Central catheters
–
–
–
–
Hemodyalisis
Chemotherapy
Parenteral nutrition
Thrombosis in first 3 months (10%)
• MRV chest
– 15 pts with occlusion or stenosis central veins
– Venous access possible in 14 pts
Shinde TS et al. Radiology 1999;213:555-560
IVC in Renal Cell Carcinoma
QuickTime™ and a
YUV420 codec decompressor
are needed to see this picture.
51 yo male with PE
Papillary carcinoma
Pulmonary Embolism
Isolated Iliac Vein DVT
Conclusion
• Central veins of the chest, abdomen and
pelvis
– Limited evaluation with US
• Whole-body venous roadmap
– Vascular access
• Pregnancy