MRA and MRV of Subclavian Artery and Vein
Indications for MRA (magnetic resonance angiography) and MRV (venography) of subclavians
- Thoracic outlet syndrome
- Subclavian vein thrombosis
- Subclavian steal syndrome
- Pre-pacemaker placement
- Pre-op for dialysis fistula
- Subclavian artery dissection
- Subclavian stenosis
- Arm swelling
Contraindications
- Any electrically, magnetically or mechanically activated implant (e.g. cardiac pacemaker, insulin pump biostimulator, neurostimulator, cochlear implant, and hearing aids)
- Intracranial aneurysm clips (unless made of titanium)
- Pregnancy (risk vs benefit ratio to be assessed)
- Ferromagnetic surgical clips or staples
- Metallic foreign body in the eye
- Metal shrapnel or bullet
Patient preparation for MRA and MRV of Subclavian Artery and Vein
- A satisfactory written consent form must be taken from the patient before entering the scanner room
- Ask the patient to remove all metal objects including keys, coins, wallet, cards with magnetic strips, jewellery, hearing aid and hairpins
- Ask the patient to undress and change into a hospital gown
- Instruct the patient to hold their breath for the breath hold scans (its better to coach the patient two to three times before starting the scan)
- An intravenous line must be placed with extension tubing extending out of the magnetic bore intravenous line must be placed in the unaffected side e.g if the problem exists in RT subclavian the canula should be in LT side
- Contrast injection risk and benefits must be explained to the patient before the scan
- Gadolinium should only be given to the patient if GFR is > 30
- Claustrophobic patients may be accompanied into the scanner room e.g. by staff member or relative with proper safety screening
- Offer headphones for communicating with the patient and ear protection
- Explain the procedure to the patient and answer questions
- Note down the weight of the patient
Positioning for arm down MRA and MRV of subclavians
- Position the patient in supine position with head pointing towards the magnet (head first supine)
- Position the patient over the spine, head and neck coil and place the neck and body\large flex coil over the neck and upper chest (nose tip down to xiphoid process)
- Give cushions under the legs for extra comfort
- Centre the laser beam localiser over sternoclavicular joint
Recommended MRA and MRV of Subclavian Protocols and Planning
localiser arm down MRA and MRV of subclavians
A three-plane TrueFISP localizer must be taken initially to localize and plan the sequences. These are fast single-shot localizers with under 25s acquisition time, which are excellent for localizing vascular structures. Take at least 5-8 slices in all planes to get the best results.
T1 flash 3D coronal .9mm -1.1mm pre-contrast
Plan the coronal slices on the sagittal plane; angle the positioning block parallel to the carotid arteries and veins (alternatively, make it parallel to the cervical spine). Check the positioning block in the other two planes. Provide an appropriate angle in the axial plane (parallel to the right and left shoulder joint). The slices must be sufficient to cover the subclavians from the anterior chest wall to the spinous process of the vertebrae. The Field of View (FOV) must be large enough to cover both shoulder joints. Phase oversampling and slice oversample must be used to avoid wrap-around artifacts. Instruct the patient to hold their breath during image acquisition (in our institution, we instruct patients to breathe in and out twice before the “breath in and hold” instruction). It is highly advisable to use Parallel Acquisition Technique to reduce the scan time (the scan time should be less than 16 seconds to get the best results).
Parameters
TR 2-3 | TE 1-2 | FLIP 20 | NEX 1 | SLICE 1 MM | MATRIX 384×384 | FOV 400-450 | PHASE R>L | OVERSAMPLE 50% | IPAT OFF |
Parallel acquisition technique (IPAT)
Parallel imaging is an advanced MRI technique that accelerates image acquisition by simultaneously utilizing multiple receiver coils to acquire data. In conventional MRI, the image is acquired sequentially from each coil, which can be time-consuming. In parallel imaging, the data from multiple coils is collected simultaneously, significantly reducing the scan time.
This method relies on spatial information obtained from the different receiver coils and utilizes algorithms to reconstruct the final image. By combining information from multiple coils, parallel imaging enhances the signal-to-noise ratio and improves the quality of the final image.
Parallel imaging offers several advantages, such as reducing motion artifacts, enabling high-resolution imaging, and minimizing the need for patient breath-holding. Moreover, it allows for faster scanning, reducing the overall examination time, which is particularly beneficial for patients who may find longer scans uncomfortable or challenging.
Contrast administration and timing of scans
Guess timing technique:- This is one of the simplest methods. It works by estimating the time of contrast travel from the site of injection to the vascular structure of the abdomen. This technique is highly dependent upon the site of contrast injection, age of the patient, cardiac output, and vascular anatomy. Generally, the contrast takes about 15-20 seconds to travel from the antecubital vein to the arch of the aorta. Therefore, the post-contrast T1 acquisition should start within 15 seconds of contrast administration.
Care bolus technique:– “Care bolus” is the most commonly used bolus detection technique. This technique uses a coronal fast gradient refocused sequence. Real-time images are obtained every second through the vascular structure of interest (normally placed over the heart). The operator can then observe the contrast bolus arriving in the heart and subsequently switch to the centric 3D sequence.
Planning care bolus
Plan the coronal care bolus slice on the sagittal plane; angle the slice parallel to the ascending aorta. Check the positioning block in the other two planes. Provide an appropriate angle in the axial plane (parallel to the right and left shoulder joint). Use a saturation band on both sides of the care bolus slice to avoid artifacts from breathing and heartbeats.
Care bolus scans must start one second prior to the contrast administration. The operator can then watch the scans live and wait for the contrast bolus to arrive in the heart. When the contrast reaches the heart, the care bolus must be stopped immediately, and the patient instructed to hold their breath before starting the centric 3D dynamic sequence.
T1 flash dynamic 3D coronal .9mm - 1.1mm post-contrast 2 measurements
Plan the coronal slices on the sagittal plane; angle the positioning block parallel to the carotid arteries and veins (alternatively, make it parallel to the cervical spine). Check the positioning block in the other two planes. Provide an appropriate angle in the axial plane (parallel to the right and left shoulder joint). The slices must be sufficient to cover the subclavians from the anterior chest wall to the spinous process of the vertebrae. The Field of View (FOV) must be large enough to cover both shoulder joints. Phase oversampling and slice oversample must be used to avoid wrap-around artifacts. Instruct the patient to hold their breath during image acquisition (in our institution, we instruct patients to breathe in and out twice before the “breath in and hold” instruction). It is highly advisable to use Parallel Acquisition Technique to reduce the scan time (the scan time should be less than 16 seconds to get the best results).
Parameters
TR 2-3 | TE 1-2 | FLIP 20 | NEX 1 | SLICE 1 MM | MATRIX 384×384 | FOV 400-450 | PHASE R>L | OVERSAMPLE 50% | IPAT OFF |
Positioning for arm up MRA and MRV of subclavians
- Position the patient in supine position with arm up
- Position the patient over the head and neck coil and place the body coil over the neck and upper chest (nose tip down to nipple)
- Give cushions under the arms for extra comfort
- Body coil must be placed over small cushions to prevent any obstruction in the patient's airway
- Centre the laser beam localiser over the sternoclavicular joint
Suggested sequence parameters and planning
localiser arm up MRA and MRV of subclavians
A three-plane TrueFISP localizer must be taken initially to localize and plan the sequences.
T1 flash 3D coronal .9mm -1.1mm pre-contrast
Plan the coronal slices on the sagittal plane; angle the positioning block parallel to the carotid arteries and veins (alternatively, make it parallel to the cervical spine). Check the positioning block in the other two planes. Provide an appropriate angle in the axial plane (parallel to the right and left shoulder joint). The slices must be sufficient to cover the subclavians from the anterior chest wall to the spinous process of the vertebrae. The Field of View (FOV) must be large enough to cover both shoulder joints. Phase oversampling and slice oversample must be used to avoid wrap-around artifacts. Instruct the patient to hold their breath during image acquisition
Parameters
TR 2-3 | TE 1-2 | FLIP 20 | NEX 1 | SLICE 1 MM | MATRIX 384×320 | FOV 400-450 | PHASE R>L | OVERSAMPLE 50% | IPAT OFF |
Planning care bolus
Plan the coronal care bolus slice on the sagittal plane; angle the slice parallel to the ascending aorta. Check the positioning block in the other two planes. Provide an appropriate angle in the axial plane (parallel to the right and left shoulder joint). Use a saturation band on both sides of the care bolus slice to avoid artifacts from breathing and heartbeats.
The care bolus scans should commence one second before the administration of the contrast. During the scan, the operator can monitor it in real-time to detect when the contrast bolus reaches the heart. As soon as the contrast arrives in the heart, the care bolus must be promptly halted, and the patient should be advised to hold their breath before initiating the centric 3D dynamic sequence. It might be challenging to visualize the contrast during this stage, as it is the second dose of gadolinium, and the first dose could still be present in the heart.
T1 flash dynamic 3D coronal .9mm - 1.1mm post-contrast 2 measurements
Plan the coronal slices on the sagittal plane; angle the positioning block parallel to the carotid arteries and veins (alternatively, make it parallel to the cervical spine). Check the positioning block in the other two planes. Provide an appropriate angle in the axial plane (parallel to the right and left shoulder joint). The slices must be sufficient to cover the subclavians from the anterior chest wall to the spinous process of the vertebrae. The Field of View (FOV) must be large enough to cover both shoulder joints. Phase oversampling and slice oversample must be used to avoid wrap-around artifacts. Instruct the patient to hold their breath during image acquisition
Parameters
TR 2-3 | TE 1-2 | FLIP 20 | NEX 1 | SLICE 1 MM | MATRIX 384×320 | FOV 400-450 | PHASE R>L | OVERSAMPLE 50% | IPAT OFF |
CLICK THE SEQUENCES BELOW TO CHECK THE SCANS
MRA subclavian arteries arm down
MRA subclavian arteries arm up
