mrimaster

MRA AND MRV OF ABDOMEN

Indications for MRA and MRV abdomen

Magnetic Resonance Angiography(MRA) of abdomen

Magnetic resonance venography (MRV) of abdomen

Contraindications

Patient preparation

Positioning

Register the patient in the scanner as head first supine.

Suggested protocols, parameters and planning

localiser

A three-plane TrueFISP localizer needs to be acquired initially for localization and sequence planning purposes. These fast single-shot localizers have an acquisition time of under 25 seconds, making them highly effective for localizing vascular structures. It’s recommended to obtain a minimum of 5-8 slices in all planes to achieve optimal results.

T1 vibe 3d DIXON axial pre contrast 4 mm

Plan the axial slices on the coronal plane. Angle the positioning block parallel to the line along the right and left iliac crests. Check the positioning block in the other two planes. Ensure an appropriate angle is used in the sagittal plane (perpendicular to the lumbar spine). The slices should sufficiently cover the entire abdomen from the diaphragm down to the symphysis pubis. The field of view (FOV) should be large enough to encompass the entire abdomen (usually 350mm-400mm).

Parameters

TR

6-7

TE

2.39   4.77

FLIP

10

NXA

1

SLICE

4 MM

MATRIX

320×320

FOV

320-350

PHASE

A>P

OVERSAMPLE

20%

BH

YES

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

Plan the coronal slices on the axial plane, angling the positioning block parallel to the midline along the right and left kidneys. Verify the positioning block in the other two planes. An appropriate angle must be applied in the sagittal plane, parallel to the Inferior vena cava, ensuring slices cover the entire Inferior vena cava. Utilize phase oversampling and, for 3D blocks, slice oversample, to prevent wrap-around artifacts. The field of view (FOV) must adequately encompass the entire IVC. Instruct the patient to hold their breath during image acquisition (In our department, we instruct patients to breathe in and out twice before the “breath in and hold” instruction). Using the Parallel acquisition technique is highly recommended to reduce scan time (scan time should be under 15 seconds for optimal results).

Parameters

TR

4-5

TE

2-3

FLIP

10

NEX

1

SLICE

1 MM

MATRIX

320×320

FOV

400-450

PHASE

R>L

OVERSAMPLE

100%

IPAT

ON

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 18-25 seconds to travel from the antecubital vein to the abdominal aorta. Therefore, the post-contrast T1 acquisition should start within 20 seconds of contrast administration.

Care bolus technique:- Care bolus is the most commonly used bolus detection technique. This technique utilizes a coronal fast gradient refocused sequence to obtain real-time images of the vascular structure of interest, typically positioned over the heart, at a frequency of one image per second. The operator can observe the arrival of the contrast bolus in the heart and subsequently switch to the centric 3D sequence.

Planning care bolus

Plan the coronal care bolus slice on the sagittal plane. Position the block over the mid-heart and angle the slice parallel to the ascending aorta. Verify the position in the other two planes. Establish the appropriate angle in the axial plane, aligning it horizontally across the heart.

Care bolus scans should commence one second before contrast administration. The operator can then observe the scans in real-time and monitor the arrival of the contrast bolus in the heart. Once the contrast reaches the heart, the care bolus should be promptly halted, and the patient should be instructed to hold their breath before initiating the centric 3D dynamic sequence.

T1 flash dynamic 3D coronal .9mm - 1.1mm post-contrast 3 measurements

Plan the coronal slices on the axial plane, angling the positioning block parallel to the midline along the right and left kidneys. Verify the positioning block in the other two planes. An appropriate angle must be applied in the sagittal plane, parallel to the Inferior vena cava, ensuring slices cover the entire Inferior vena cava. Utilize phase oversampling and, for 3D blocks, slice oversample, to prevent wrap-around artifacts. The field of view (FOV) must adequately encompass the entire IVC. Instruct the patient to hold their breath during image acquisition (In our department, we instruct patients to breathe in and out twice before the “breath in and hold” instruction). Using the Parallel acquisition technique is highly recommended to reduce scan time (scan time should be under 15 seconds for optimal results).

A dynamic flash 3D sequence comprises three flash 1mm 3D scans, with a 15-second delay between the first and second scans and a 20-second delay between the second and third scans. The initial scan captures the arterial phase, followed by the venous phase in the second scan, and finally, the delayed venous phase in the third scan. Precise timing is crucial for each scan, particularly during the arterial and venous phases. Providing accurate breathing instructions is vital during the first and second scans, as well as between the second and third scans. Instruct the patient to breathe normally after the arterial phase scan and then to hold their breath when approximately 4 seconds remain for the venous scan. Repeat this procedure between the second and third scans.

Parameters

TR

4-5

TE

2-3

FLIP

10

NXA

1

SLICE

1 mm

MATRIX

320X320

FOV

400-450

PHASE

R>L

DYNAMIC

3 SCANS

IPAT

ON

 
In order for subtraction of the images to be possible, it is crucial that the measurements of pre and post contrast T1 scans are identical. Any differences in slice thickness, FOV, or planning would hinder the ability to perform image subtraction.

T1 vibe 3d fat sat axial post contrast 4mm

Plan the axial slices on the coronal plane. Angle the positioning block parallel to the line along the right and left iliac crests. Check the positioning block in the other two planes. Ensure an appropriate angle is used in the sagittal plane (perpendicular to the lumbar spine). The slices should sufficiently cover the entire abdomen from the diaphragm down to the symphysis pubis. The field of view (FOV) should be large enough to encompass the entire abdomen (usually 350mm-400mm).

Parameters

TR

6-7

TE

2.39   4.77

FLIP

10

NXA

1

SLICE

4 MM

MATRIX

320×320

FOV

320-350

PHASE

A>P

OVERSAMPLE

20%

BH

YES