Time-resolved MR angiography for evaluation of the central ... · internal jugular Nonfilled left internal jugular Large collateral Small collateral • Little or no collateralization

Time-resolved MR angiography for evaluation of the central veins of the

chest

Charles Kim, M.D.Duke University Medical Center

Dept. of Vascular & Interventional Radiology

Indications for evaluation of the central veins of the chest

• SVC syndrome– Neoplastic compression or invasion– Stenoses / occlusions from prior

catheters– Deep venous thrombosis

• Venous access planning• Venous access planning– ESRD pts: hemodialysis catheters,

upper extremity AV fistulas / grafts– Chronic intravenous meds: sickle cell,

oncology pts, autoimmune dz• Venous anomalies

– Left SVC– Duplicated SVC– Anomalous pulmonary venous return

Central venous segments

• SVC• L & R brachiocephalic veins• L & R brachiocephalic veins• L & R internal jugular veins• L & R subclavian veins

Collateral pathways for central venous occlusion

• Azygous v (posterior)• Hemiazygous v (posterior)• Internal mammary v / inf

epigastric v (anterior)epigastric v (anterior)• Lateral thoracic v• Local mediastinal veins • Vertebral venous plexus • Superficial thoraco- abdominal v

(via any of these collateral veins)

Imaging the central veins of the chest

• Conventional angiography• Ultrasound• Ultrasound• MR

Conventional venography

• Considered the “gold standard”• Dynamically acquired images• Imaged one side at a time• Utilizes iodinated contrast (20-

50mL per side)Video of nice

• Requires angio suiteVideo of nice central venogram

Conventional venography: Limitations

• Requires bilateral IV’s **• Internal jugular veins typically

not opacified• Nonopacified inflow artifact • Hemodilution centrally

??????

Internal jugular v

Dorsal scapular v

• Hemodilution centrally • Breathing artifact• Iodinated contrast: allergies /

contrast-induced nephropathy

Ultrasound• Excellent eval of the internal jugular veins • Acceptable eval of the subclavian veins (noncompressible)• Poor eval of brachiocephalic v and SVC (noncompressible)• Excellent for DVT• Limited by obesity

Color Doppler of internal jugular v (and carotid a)

Noncompressed and compressed internal jugular v

Subclavian v (suboptimally visualized)

MR venography of the central veins of the chest

• High-spatial resolution MRA coronal datasetdataset

• Time-resolved MRA coronal MIP dataset

MR venography of the central veins: advantages

• Equally sensitive and specific for detection of stenoses and occlusions compared to conventional venography1-4

• No ionizing radiation• No ionizing radiation• Entire bilateral central venous system imaged with

only one IV• CVC’s can be utilized **

1. Nael et al. Magn Reson Imaging Clin N Am 2005;13:359-380.2. Thornton et al. AJR Am J Roentgenol 1999;173:999-1003.3. Tanju et al. Diagn Interv Radiol 2006; 12:74-79.4. Shinde et al. Radiology 1999; 213:555-560.

MR venography of the central veins: disadvantages

• Contraindicated with MR-unsafe metallic implants or MR-incompatible implants near structures of interest

• Limited patency assessment for many metallic • Limited patency assessment for many metallic stents

• Potential for nephrogenic systemic fibrosis in patients with renal impairment *

NSF• Nephrogenic Systemic Fibrosis• Involves skin and internal organs• Histopath similar to scleroderma• Culprit: gadolinium• Patients with CRI / CRF : 2.4% risk1• Patients with CRI / CRF : 2.4% risk• Develops days, to weeks, to yrs after Gd• Progressive skin hardening, flexion contractures• No treatment

1. Deo et al Clin J Am Soc Nephrol. Mar 2007;2(2):264-7

High-spatial-resolution MRV acquisition

• Precontrast breath hold coronal images • 30mL gadolinium followed by 20mL saline• 1st pass coronal images acquired 15-20sec after

contrast• 2nd pass after additional 15-20 sec• 3rd pass after additional 15-20 sec

High-spatial-resolution MRV acquisition

Gd

Arterial phase

15-20 sec 15-20 sec

Venous phase

15-20 sec

precon 1st pass 3rd pass2nd pass

High-spatial-resolution MRV interpretation

• Images viewed as four separate set of contiguous coronal images, 1mm slice thickness

• 100-150 contiguous coronal images

Time-resolved MRV techniques

• TRICKS (Time-Resolved Imaging of Contrast KineticS) : GE• TREAT (Time-Resolved Echo-Shared Angiographic Technique) :

Siemens• TWIST (Time-resolved angiography With Interleaved Stochastic • TWIST (Time-resolved angiography With Interleaved Stochastic

Trajectories : Siemens• 4D TRAK (Time-Resolved Angiography using Keyhole) : Philips

• TWIST-SUB-MIP-COR (20)

Time-resolved MRA physics

A In initial image acquisition, most of K-space is obtained (Circle A). This information is used as an information filler with each subsequent frame.with each subsequent frame.

K-space


A

Rapid images are then obtained by repeatedly covering the center of K-space (Circle B) and using the previously obtained K-space (Circle A) as information filler.

B


AOne increases temporal resolution (acquisition speed) by decreasing the size of Circle B.

B


AConversely, one increases data accuracy (spatial resolution) by increasing the size of circle B.

B

Time-resolved MRV acquisition

• Precontrast coronal images obtained for subtraction mask• 5-10mL of gadolinium injected intravenously with saline chaser

bolus of 20mL• Imaging initiated 5 seconds after injection• Coronal images obtained at rapid 2-5 second time intervals at • Coronal images obtained at rapid 2-5 second time intervals at

2mm slice thickness; corresponding mask image is subtracted from each enhanced image

• Continuous imaging for 1-3 minutes• Images obtained coronally, processed into one MIP image per time

point.

Time-resolved MRV acquisition

Arterial phase

Gd

Inflow phase venous phase

3-5 sec

2-5 min2-5 min

Subtraction mask image

(MIP)

Interpretation of time-resolved MRA

Inflow Veins between injection site to heart

PHASE of contrast

Structures visualized

Arterial

Venous

Maximal arterial opacification*

Maximal venous opacification

Interpreting time-resolved MRV

Early inflow phase


Late inflow phase


Early arterial phase


Mid arterial phase


Late arterial phase


Late arterial phase


Early venous phase


Mid venous phase


Late venous phase

Choice of injection site for time-resolved MRA

• For peripheral IV’s, the ipsilateral subclavian, brachiocephalic, and SVC are opacified twice

Therefore, ideal to inject a peripheral IV ipsilateral to side of concern (contrary to prior guidelines)

• Central venous injection is adequate if poor peripheral IV candidate

Evaluating venous stenosis on time-resolved MRV

• Luminal narrowing• Collateral vessel flow if

hemodynamically significant

• If acute, there may be no • If acute, there may be no collaterals

Evaluating occlusions on time-resolved MRV

• Nonfilling of a vessel• Prominent collaterals if

chronic

Nonfilled rt internal jugular

Nonfilled left internal jugular

Large collateral Small collateral

• Little or no collateralization if acute or subacute

Nonfilled left brachiocephalic

Dx:

1. Chronic occlusion right internal jugular vein

2. Acute / subacute occlusion of the left internal jugular and brachiocephalic veins

Evaluating vascular anomalies on time-resolved MRV

• Left SVC• Duplicated SVC• Anomalous pulmonary

Left upper lobe pulmonary v drains into left brachiocephalic v

Small local collaterals

venous return• Route and degree of

preferential flow

Dx:

1. Subacute right brachiocephalic vein occlusion

2. Partial anomalous pulmonary venous return

Wraparound artifact from right arm

Occluded rt brachiocephalic vein

Evaluating vascular tumors on time-resolved MRV

• Can visualize vascular masses, and their effect on the central veins

• can help presurgical planning

narrowing of the left brachiocephalic vein

• can help presurgical planning• enhancement dynamics of

may be assessed with time-resolution

Occlusion of the left subclavian vein

Dx:

1. Left apex NSCLC invading chest wall, compressing left subclavian and brachiocephalic v

Evaluating metallic stent patency with time-resolved MRV

• Metallic stent artifact often precludes visualization of intraluminal contrast

• Temporal appearance of contrast pre and post stent can allow inference of occlusion or inference of occlusion or nonocclusion, with ipsilateral injection, considering presence or absence of local collaterals

• Signal void on high-res images precludes any info

Dx: Patent left BC / SVC stentFirst and second image of the inflow phase

Suboptimal subclavian vein visualization with time-resolved MRV• Often poor opacification of

subclavian vein contralateral to peripheral IV

• Poor bilateral subclavian opacification with CVC injectioninjection

• Relatively slow upper extremity venous return ? ?

Suboptimal brachiocephalic vein evaluation with time-resolved MRV

• Sometimes poor left brachicephalic v opacification

• MIP overlap with aorta / arteries• Transient compression

between aorta and sternum between aorta and sternum during breath hold

• If no clinical side of interest, inject a left arm IV.

Inflow phase image

??

Suboptimal DVT visualization with time-resolved MRV

Difficult to visualize DVT due to low spatial resolution

Voxel size

Time-resolved 3mm3

High-resolution 1mm3

Nonopacified rt subclavian may be occluded or artifactual

Filling defect c/w DVT

Field of view artifact with time-resolved MRV

• AP field of view minimized for time-resolution• If a collateral vessel is very anterior or posterior, it may be

partially or completely outside of the field of viewResults in artificial stenosis or occlusion

Continuous azygous Apparently occluded enlarged

??

Continuous azygous vein

Apparently occluded enlarged collateral azygous vein

Problem solving with time-resolved MRV

1st time resolved image 2nd time resolved imageHigh-res images

??

SVC stenosis or occlusion? Motion artifact and volume averaging with rt pulm v

Image 1: Nonopacified central SVC, right heart, and IVC. Markedly enlarged azygous vein.

Image 2: The central SVC is still nonopacified, but the IVC and rt heart are opacified via the azygous collateral.

Dx: Complete SVC occlusion

Further explanation: SVC stenosis vs occlusion

Rt brachiocephalic

Rt subclavian Rt cephalic v

Image #1 of TREAT dataset (raw)

Azygous vein (markedly enlarged)

Rt brachiocephalic

Occluded SVC

Image #1 of TREAT dataset (annotated)

Further explanation: SVC stenosis vs occlusion

IVC

Rt heart

Pulm artery

Image #2 of TREAT dataset (raw) Image #2 of TREAT dataset (annotated)

High-spatial-resolution versus time-resolved MRV: Which sequence is more helpful?sequence is more helpful?

High resolution versus Time-resolved datasets: sensitivity for detecting stenoses

and / or occlusions

0.8

1

0.96 0.98 0.98

0.900.81

0.88

sensitivity

0

0.2

0.4

0.6

0.8

Time-resolved High res Both

Stenosis or occlusion

Occlusion only

No statistically significant differences between TR and HRKim et al. Radiology 2008 247(2):558-66

High resolution versus Time-resolved datasets: specificity for detecting stenoses

and / or occlusions

p<0.05p<0.001

specificity

0.74

0.96

0.87

0.99

0.911

Occlusion only

Stenosis or occlusion

0.74

0.63

0.87 0.91

0

0.2

0.4

0.6

0.8

1

Time-resolved High res Both

Kim et al. Radiology 2008 247(2):558-66

High resolution is superior

High resolution versus Time-resolved datasets: Radiologist confidence levels

Time-resolved:High res: Both:

2.63.43.5Both: 3.5

p < 0.001 between all resultsScale: 1-5, 5=most confident


High resolution is superior

High resolution versus Time-resolved datasets: Average study interpretation time

3.4

3.33.3

3.4

3.5p<0.001

minutes

3.0

3.3

2.8

2.9

3

3.1

3.2

Time-resolved High res BOTH


Time-resolved is faster

Summary: High-spatial resolution vs time-resolved MRV

• Extremely high sensitivity and specificity Superior assessment of morphology and length of stenosis / occlusion

• Extremely high sensitivity but low specificity

• Improved visualization of

High-res advantages Time-resolved advantages

stenosis / occlusion• More consistent opacification of

all segments• Superior detection of DVT• Superior interpretation confidence

• Improved visualization of collaterals

• Superior evaluation of stent patency

• Faster to interpret• Problem solving

Conclusion? Use both!

Combination MRV: High resolution + Time-resolved

• Improved specificity for detecting occlusions• Increases reader confidence• Does not increase the total time for study

interpretationinterpretation• Minimally increased disk space utilization

(average 19 images for time-resolved images)• Acquisition time of time-resolved images is ~5

minutes• Additional gadolinium required: 5-10mL

Summary: MRV

• MRV is the only modality to demonstrate the entire central venous system of the chest

• Contraindicated for patients with MR-• Contraindicated for patients with MR-incompatible implants or renal insufficiency / failure

• Demonstrates stenoses /occlusion, DVT, anomalous anatomy

Summary: Time-resolved MRV

• Improved visualization of collaterals and stent patency• Equally sensitive compared to high-res MRA and

conventional angiography• Suboptimal specificity• Suboptimal specificity• Combination with high-res MRA results in maximum

specificity for occlusions, without adding study interpretation time

• Ideal to inject a peripheral IV ipsilateral to side of interest, or, left arm if no side of interest

Thank You

Documents

Time-resolved MR angiography for evaluation of the central ... · internal jugular Nonfilled left internal jugular Large collateral Small collateral • Little or no collateralization