Bolus Chase Peripheral MRA

Start IV: 20 or 22 guage is adequate when using SmartSet (for more information, please contact: 734-623-6400). Load 30 cc of saline flush in 30 cc syringe and use 10 cc to prime flush Smart Set and test iv. Save remaining 20 cc saline to use later for flushing Gadolinium through tubing.

Sedation:A valium (5-10 mg po) or Xanax (1-2 mg po) are recommended for patients who are claustrophobic or anxious about the MRA examination. This will also reduce motion artifact and reduce cardiac output to maximize Gadolinium-MRA image quality.

Coil: initially use head coil for ankle to knee, then body coil for bolus chase MRA

Patient Positioning: Feet First, Supine. Cover legs with blanket if patient is cold. This will help avoid peripheral vaso-constriction.

• Position with cushion under knees to that foot will point more horizontally. This way the blood flow will be nearly perpendicular to the axial imaging plane to maximize in-flow. The toes should be sticking out slightly beyond the end of the coil. Tape feet together to remind the patient to hold still.
• Landmark on mid-coil
• Place vitamin E capsules 12 cm superior to landmark
• ADDITIONAL PARAMETERS
• Vascular Options: Projection Images: Collapse/19
• Always look at the first images to make sure the inferior sat pulse is working

• Remove cushion from under knees
• Reposition patient so mid-coil is 12 cm above vitamin E capsules
• Re-landmark on mid-coil
• ADDITIONAL PARAMETERS
• Vascular Options: Projection Images: Collapse/19
• If this second station does not reach above the tibia, then perform a third station with the head coil if the patient’s legs are thin enough for both knees to fit within the head coil.

Preparations:

• Position the patient on the table so that the feet line up with the end of the table
• Place cushions under the ankles and knees so that the calf and thigh are perfectly horizontal and in line with the aorta.
• Use a ruler to determine if three 40 cm stations or three 36 cm stations will be preferable to cover from the ankle to well above the iliac crest. If the patient is hypertensive, make sure to cover superior enough to image the renal arteries. For example in the patient below, 36cm stations are good for imaging from diaphragm to ankle. Use 40cm stations in this patient if you want to image the chest also, including the entire thoracic aorta.

• Tape the feet together and also place velcro wraps over the legs to help the patient cooperate with holding perfectly still during the exam.
• Landmark on mid-calf and advance to scan: verify that the table position corresponds to hole "C" on the positioning pole. (See schematic diagram of positioning pole in appendix)
• Then "Landmark" high on the chest at the level of the sternum-manubrium junction.
• "Advance to Scan" but disconnect table from drive chain and reposition to hole A on positioning pole to line up with the abdomen and pelvis

Note: That different pole lengths are required for different types of GE Magnets.

Prescribing 3D volume

• First perform the Sagittal locator (series 3) of the pelvis with the table positioned at hole A
• Then perform Axial 2D time-of-flight slices (series4) at 3 inch (7-8cm) intervals starting at hole A and ending at hole C on the positioning pole. You must pull the table manually and "start scan" for each slice.
• Prescribe the fast 3D spoiled gradient echo pulse sequence in the coronal plane with sufficient slice thickness and slices to cover the arteries on the axial 2D TOF locator in the A-P direction. Also check the position of the aorta and iliac arteries on the sagittal locator to be sure they are encompassed within the imaging volume
• 3D enhancements:
• Enable smart prep: 0
• Max monitor: 40
• Image Acq Delay: 8
• Special: 0
• 512 Zip: 0
• Slice Zip: 2
• Burst Scan Time: 30

• Position at hole C (calf) and press "start scan"
• After first scan finishes, move to hole B (thigh) and press "start scan"
• Finally move to hole A (abdomen-pelvis) and press "start scan"
• Check images to be sure they appropriately cover the anatomy and make sure the level of transition from one station to the next are in suitable locations so complex branching anatomy (eg the tifurcation) will be easy to evaluate.

Dynamic Gadolinium Enhanced Images

• Gd Dose: at least 0.3 mMol/kg or 60ml
• Gd: Infusion Rate: total dose/(scan time x 2) ~ 60ml/(2x30sec) ~ 1 ml/sec
• Delay time =
• 20 - scan time/2 for the average patient
• 30 - scan time/2 for patients with slow flow (>70, CHF, AAA…)
• use 10 seconds if you are uncertain: That means start injecting and 10 seconds later start scanning during breath holding
• For more precise measurement of infusion rate and scan delay, measure the time for a gadolinium test bolus to reach the aorta with a sagittal 2D SPGR sequence. Prescribe one thick slice centered on the aorta and repeat at 1-2 second intervals for 60 seconds after initiating test bolus injection. Also consider Doppler ultrasound contrast agent to determine the circulation time from the iv site to the infrarenal abdominal aorta, the common femoral artery and the popliteal artery. Ideally measure the circulation time to both legs but at a minimum, measure the most symptomatic leg. Then calculate infusion rate and scan delay with the following formulas assuming partial Fourier imaging (0.5NEX) with center of k-space acquired at the end of the acquisition:
• Infusion Rate = 1cc/sec
• Scan Delay = Time to aorta peak bolus – Scan Time/2
• Gd Bolus Duration2.5 x Scan Time + Table Move Time – Popliteal Peak Time + Aorta Peak Time – US bolus duration

If there is a full acquisition of k-space with sequential mapping such that the center of k-space acquired in the middle of the scan then use the following formula for Scan Delay:

• Before pressing "prep to scan" be sure that the phorder is set to 0 (sequential mapping of k-space)
• This is a four person procedure: One to talk to the patient and move the table. The second person moves the pole between stations. A third injects the gadolinium precisely at 1 cc/sec. A third fourth operates the scanner from the console where control variables can be modified and there is also a "prep to scan" button.

The First Station: Abdomen-Pelvis

• The table should be aligned with notch A for the pelvis at the end of the 3 pre-contrast acquisitions. Check to be sure that phorder = 0, arm the pump if using an automatic injection, and press "prep to scan".
• Start hyperventilating the patient ("deep breath in"…."deep breath out"…)
• Start the contrast infusion at the correct rate

• After scan delay (calculated above or empirically use 10-15 seconds or longer in patients who are older, have CHF or aortic aneurysm), start the scan during breath holding



• After first station finishes
• Person outside room rapidly presses "modify CV" à "phorder = 1" à "download" à "prep to scan" and then verifies that the start button lights up in the scanner room
• Two people inside room move table to second location "B" and "start" the second station scan
• All the while the contrast infusion continues at 1 ml/sec and switches automatically to saline flush out 1 ml/sec the moment the 60 mil gadolinium syringe is empty

• After second station finishes
• Person outside room touches "prep to scan" and verifies start button lights up in the scanner room
• Two people inside room move table to final location, "C" and "start" the third station scan
• Transfer images to computer workstation
• Subtract mask images from dynamic enhanced images

MRA Pelvis 772198

MRA lower extremity 773725

Atherosclerosis 440.2

Gangrene 440.24

Ulceration 440.23

Bypass graft 440.3

Aneurysm, iliac 442.2

Aneurysm, extremity 442.3

Embolism/thrombosus 444.22

Iliac thrombosus 444.81

A-V fistula 447.0

Stenosis 447.1

Venous Thrombosus 451.2