ARCH AND CAROTID PROTOCOL

(GE 1.5 Tesla Neurovascular magnet at 8.4 Software using MRI devices neurovascular coil)

Overview

This carotid MRA protocol has been devised by Dr. Richard Watts and the team of Physicists and Radiologists at Cornell. It is based on a cleverly designed 3D Gd MRA pulse sequence which starts initially without any phase encoding in the slice direction. This enables acquisition of a Projection of the 3D volume at a temporal rate of two times per second. In this mode, the operator watches for the arrival of the Gadolinium bolus. When the operator sees the bolus arriving in the carotid arteries, the phase encoding is activated to begin the 3D Gd MRA scan beginning with acquisition of the center of K-space.

Sometimes it is difficult to see the contrast arriving in the carotid arteries. To make the contrast easier to detect, the 2D Projection image can be shifted down into the chest. This way the operator can watch Gadolinium entering via the subclavian vein, passing through the right heart, then through the lungs, back to the left heart and finally with Gadolinium reaches the aortic arch, the 3C scan is activated. This ensures perfect bolus timing for every case.

In order to position the 3D volume optimally, we first acquire a 20 time-of-flight scan of the carotid arteries. This is done in two acquisitions. One high resolution 2D TOF from the circle of Willis down to the base of the neck. This provides an additional sequence for evaluating the carotid bulb where disease is most prevelant. A second 2D time-of-flight scan is performed to identify the location of the aortic arch for positioning the 3D volume correctly.

Patient Preparation	Locator	2D TOF	Gd-MRA
Plane	Sagittal	Axial	Coronal
Mode	2D	2D	3D
Pulse Seq.	Spin Echo	Vasc TOF SPGR	SPGR
Imaging Options	Fast	FC, Seq, VBW, EDR, Fast	Fast, MPh
Password Name		2d to fx	psd/rw/efgre3d_rt
*SCAN TIMING*
# of Echoes	1, ETL=4	1	1
TE	Min Full	Minimum	Minimum
TR	325	33	-
Flip Angle	-	60	30
Bandwidth	-	15.63	31.25
*ADDITIONAL PARAMETERS (see attached instructions)*
SAT	Inferior	Superior	None
*ACQUISITION TIMING*
Freq	256	256	256
Phase	160	128	192
NEX	1.00	1.00	1.00
Phase FOV	1.00	0.75	0.70
Locs Before Pause	0	-	-
Freq DIR	S/I	A/P	S/I
Auto Center Freq	Peak	Water	Water
Auto Shim	On	On	On
Contrast	-	-	20ml
*SCANNING RANGE*
FOV	36(24-40)	20(16-32)	28(20-36)
Slice Thickness	6	1.5	2(1.4-2.6)
Spacing	Intleave	0	0
Start - End	L57-R57	Graphic	Graphic
Locs per slab	10	<134	32(24-40)
*Scan Time*	1:52	0:04 per slice	0:26

Common Indications:

Stroke

Suspected stroke

Transient ischemic attack (TIA)

Confirm carotid ultrasound finding

Pre-op for carotid endarterectomy

Scheduling Guidelines:

MRA of the neck with Gadolinium

MRA of Head (optional)

MRA of Chest (optional)

First Ask

Have you had carotid MRA before?
Have you had carotid ultrasound or doppler ultrasound?
Have you had carotid artery surgery?
Have you had a carotid endarterectomy?

Patient Preparation:

Start intravenous line (20 or 22 gauge iv) in the right arm to avoid filling the left brachiocephalic vein with highly concentrated gadolinium.
Valium (diazepam: 5-10mg po) or Xanax (1-2 mg po) if patient is claustrophobic. Instruct the patient not to take the Valium until arriving at the MRI center in case we are running behind schedule. Also the patient will need to be accompanied by a friend or relative to take them home and absoutely they cannot drive for 10 hours.

Coil: A neurovascular coil which extends down low enough on the chest to include the aortic arch is essential for simultaneously imaging the carotid origins and the bifurcations with a single injection of contrast. If a neurovascular, head/neck coil is not available then it maybe acceptable to use a torso array coil with elements placed anterior and posterior to the upper chest and neck. For our MRI devices, use neurovascular coil, "NVARRAY".

Patient Positioning: Supine, head first,

Landmark: If imaging neck only, Landmark just below the angle of mandible. If imaging brain and neck landmark above the angle of the mandible and use larger FOV.

Series 1: Spin Eco Locator

This Black Blood, T1 weighted, spin echo localizer shows the location of Aortic Arch for positioning the 3D Gd MRA and it also shows the neck for prescribing the 2D time of flight series. Use Interleave, so that half of the slices are available half-way through the scan for use in prescribing the next series.

Series 2: Axial 2D TOF

Scan from sella turcica down to bottom of neck (just above the sternum)

ADDITIONAl PARAMETERS

Vascular Screen
- Projection Image: 19
- Collapse: On

Series 3: Coronal 3D Gd-MRA

ADDITIONAL PARAMETERS
- Multi Phase Screen
  - Phases per location: 2
  - Delay After Acquisition: Minimum
User Control Variables
- CV1 0.00
- CV2 5.00
- CV3 3.00
- CV4 3.00
- CV5 3.00
- CV6 0.00
- CV7 1.00
- CV8 1.00
- CV9 1.00
- CV10 0.00
- CV11 1.00
- CV13 1.00
- CV17 400.00
- CV18 5.00
- CV19 10.00
- CV20 1000.00

Positioning of Coronal 3D volume

Anterior to the carotid arteries as seen on 2D TOF
Posterior to the verterbrals and the left subclavian artery origin
Superior to foramen magnum
Inferior to top of aortic arch.

Activate Realtime visualization on SUM Computer

Open command window
Type "kill.sdc" to turn off Browser
Type "cd/rw" to enter Dr. Watts program directly
Once 3D Gd: MRA sequence is pre-scanned and prepped, type "fl"
Enter Realtime parameters:
- Angle- 45
- Frequency Shift- 60
- Slice Thickness- 10
Start 3D Gd MRA Scan
Verify 2D Projection images are appearing and show the expected location of Aortic Arch
Inject Gadolinium (20 ml) as 10 second bolus followed immediately with 30 ml saline flush using Smart Set i.v. tubing
Watch for Gadolinium in right subclavian vein, right heart, pulmonary arteries, left heart and aortic arch
Press "Go" button when contrast appears in aortic arch to activate 3D MRA scan.

Billing Instrucions:

MRA Head or Neck: 770541
MRI Neck:770540 N
Computer Reconstructions: 76375

ICD9 Codes:

Carotid Atherosclerosis: 433.1
Basilare artery atherosclerosis: 433.1
Cerebral artery atherosclerosis
Carotid aneurysm in neck: 442.81
Intracranial internal carotid aneurysm: 437.3
Subclavian artery aneurysm: 442.82
Cerebral artery aneurysm: 437.3
Ruptured: 430
Congenital: 747.81
Takayusu’s Disease:446.7
Giant Cell arteritis:446.1
Kawasaki Disease: 446.1
Arteritis, unspecified: 447.6
Aortic arch: 446.7
Cerebral:437.4

Sample Normal Dictation:

The Patients carotid arteries and neck were imaged on Sagittal T1,Axial 2D TOF and coronal 3D dynamic Gd:MRA. MRA data was post-processed on a computer work station to obtain reformations and sub-volume MIP’s optimized for each carotid artery and the aortic arch.
The great vessel origins are all widely potent. Both right and left carotid arteries have normal caliber and contour with no significant stenosis, atherosclerotic disease or dissection. The vertebrae is larger suggesting (right/left) dominance.

Impression:
Normal Carotid MRA

Examples: