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Peripheral MRA(MRA Legs) : Protocol and Planning

Indications for MRA(magnetic resonance angiography) legs

Please check our new video tutorial for protocols and planning

Contraindications

Patient preparation for peripheral MRA

Positioning for peripheral MRA

Recommended Peripheral MRA Protocols and Planning

localiser MRA lower leg

A three plane T1 localiser must be taken initially to localise and plan the sequences. These are fast single shot T1 scans with aqusition time under 25s, which are excellent for localising.   Peripheral MRA Protocol should be setup with an auto move of the table after the lower leg localiser acquisition. Usually, in MRA leg protocols an auto move of 380-420 mm set by default, that means after the lower leg localiser table will automatically move  towards the feet for the upper leg scans. 

localizer MRA upper leg

A three plane T1 localizer must be taken in the upper leg to localize and plan the sequences. 

Phase contrast(PC) vessel localiser upper leg

A Sagittal Phase contrast vessel localiser must be taken in the upper leg for further localisation and planning of the coronal 3D flash sequence. Phase contrast localisers are fast scans with acquisition time less than 1minute, which are excellent for localising vascular structures. Protocol should be setup with an auto move of the table after the upper leg localiser acquisition. Usually, in MRA leg protocols an auto move of 380-420 mm set by default, which means after the lower leg localiser table will automatically move towards the feet for the abdominal scans.  

localiser MRA abdomen

A three plane T1 localiser must be taken in the abdomen to localise and plan the sequences. 

Phase contrast (PC) vessel localiser abdomen

A Sagittal Phase contrast vessel localiser must be taken in the abdomen for further localisation and planning of the coronal 3D flash sequence. Phase contrast localisers are fast scans with acquisition time less than 1minute, which are excellent for localising vascular structures.

T1 flash 3D coronal 0 .9mm -1.1mm pre-contrast abdomen

Plan the coronal slices on the sagittal Phase contrast vessel localiser; angle the position block parallel to the aorta. Check the positioning block in the other two planes. An appropriate angle must be used in the axial plane (parallel to the long axia of both kidneys). Slices must be sufficient to cover the aorta and iliac arteries. The FOV must be big enough to cover the vessels  from the heart to femoral arteries. Enough 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 department we instruct the 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 (scan time should be less than 20 seconds to get the best results). Protocol should be setup with an auto move of the table after the abdominal 3D flash acquisition.

Parameters

TR

2-3

TE

1-2

FLIP

20

NEX

1

SLICE

1 MM

MATRIX

384×384

FOV

450-470

PHASE

R>L

OVERSAMPLE

50%

IPAT

OFF

Parallel acquisition technique(IPAT)

Parallel imaging is a newly developed technique used to reduce scan time without affecting the scan resolution. Using parallel acquisition MRI techniques, it is possible to reconstruct full-FOV images from under sampled k-space data by using the uncorrelated information from RF array coil elements. The main disadvantage of parallel acquisition techniques is the signal-to-noise ratio (SNR) is degraded because of the reduced data samples and the spatially correlated nature of multiple RF receivers.

T1 flash 3D coronal .9mm -1.1mm pre-contrast upper leg

Plan the coronal slices on the sagittal Phase contrast vessel localiser; angle the position block parallel to the femoral artery. Check the positioning block in the other two planes. An appropriate angle must be given in the axial plane (parallel to the right and left femur). Slices must be sufficient to cover the femoral arteries .FOV must be big enough to cover the vessels  from iliac arteries down to popliteal arteries . Phase oversampling and slice oversample, must be used to avoid wrap around artefacts. It’s important to overlap the abdominal and femoral blocks by 1 to 2 centimetres to avoid any misregistration. It is highly advisable to use Parallel acquisition technique to reduce the scan time (scan time should be less than 15 seconds to get best results). Protocol should be setup with an auto move of the table after the upper leg 3D flash acquisition.

 

Parameters

TR

2-3

TE

1-2

FLIP

20

NEX

1

SLICE

1 MM

MATRIX

384×384

FOV

450-470

PHASE

R>L

OVERSAMPLE

30%

IPAT

OFF

T1 flash 3D coronal 1mm -1.3mm pre-contrast lower leg

Plan the coronal slices on the sagittal localiser; angle the position block parallel to the tibia. Check the positioning block in the other two planes. An appropriate angle must be given in the axial plane (parallel to the right and left tibia). Slices must be sufficient to cover the  whole lower leg .FOV must be big enough to cover the vessels  from  knee joint down to ankle joint  . Phase oversampling and slice oversample, must be used to avoid wrap around artefacts. It’s important to overlap the  upper leg and lower leg  blocks by 1 to 2 centimetres to avoid any misregistration. It is highly advisable to use Parallel acquisition technique to reduce the scan time (scan time should be less than 15 seconds to get best results).

Parameters

TR

2-3

TE

1-2

FLIP

20

NEX

1

SLICE

1 MM

MATRIX

384×384

FOV

450-470

PHASE

R>L

OVERSAMPLE

30%

IPAT

OFF

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 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 aorta. Therefore the post contrast T1 acquisition should start within 15s 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 watch the contrast bolus arriving in the heart and then 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.

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 3D coronal 0 .9mm -1.1mm post-contrast abdomen

Plan the coronal slices on the sagittal Phase contrast vessel localiser; angle the position block parallel to the aorta. Check the positioning block in the other two planes. An appropriate angle must be given in the axial plane (parallel to the right and left kidneys). Slices must be sufficient to cover the aorta and iliac arteries .FOV must be big enough to cover the vessels  from heart down to femoral arteries . Phase oversampling and slice oversample, must be used to avoid wrap around artefacts. Instruct the patient to hold their breath during image acquisition. (In our department we instruct the patients to breath 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 (scan time should be less than 20 seconds to get best results). Protocol should be setup with an auto move of the table after the abdominal 3D flash acquisition.

Parameters

TR

2-3

TE

1-2

FLIP

20

NEX

1

SLICE

1 MM

MATRIX

384×384

FOV

450-470

PHASE

R>L

OVERSAMPLE

50%

IPAT

OFF

Parameters  of Pre and post contrast T1 scans should be exactly same except from the Sequence preparation time(preparation time should be nil in the post-contrast scans )

T1 flash 3D coronal .9mm -1.1mm post-contrast upper leg

Plan the coronal slices on the sagittal Phase contrast vessel localiser; angle the position block parallel to the femoral artery. Check the positioning block in the other two planes. An appropriate angle must be given in the axial plane (parallel to the right and left femur). Slices must be sufficient to cover the femoral arteries .FOV must be big enough to cover the vessels  from iliac arteries down to popliteal arteries . Phase oversampling and slice oversample, must be used to avoid wrap around artefacts. It’s important to overlap the abdominal and femoral blocks by 1 to 2 centimetres to avoid any misregistration. It is highly advisable to use Parallel acquisition technique to reduce the scan time (scan time should be less than 15 seconds to get best results). Protocol should be setup with an auto move of the table after the upper leg 3D flash acquisition.

Parameters

TR

2-3

TE

1-2

FLIP

20

NEX

1

SLICE

1 MM

MATRIX

384×384

FOV

450-470

PHASE

R>L

OVERSAMPLE

30%

IPAT

OFF

T1 flash 3D coronal 1mm -1.3mm post contrast lower leg

Plan the coronal slices on the sagittal localiser; angle the position block parallel to the tibia. Check the positioning block in the other two planes. An appropriate angle must be given in the axial plane (parallel to the right and left tibia). Slices must be sufficient to cover the  whole lower leg .FOV must be big enough to cover the vessels  from  knee joint down to ankle joint  . Phase oversampling and slice oversample, must be used to avoid wrap around artefacts. It’s important to overlap the  upper leg and lower leg  blocks by 1 to 2 centimetres to avoid any misregistration. It is highly advisable to use Parallel acquisition technique to reduce the scan time (scan time should be less than 15 seconds to get best results).

Parameters

TR

2-3

TE

1-2

FLIP

20

NEX

1

SLICE

1 MM

MATRIX

384×384

FOV

450-470

PHASE

R>L

OVERSAMPLE

30%

IPAT

OFF