mrimaster

MRCP respiratory gated

Indications for magnetic resonance cholangiopancreatography

Contraindications

Patient preparation

Positioning

MRI MRCP positioning photo

Suggested protocols, parameters and planning

localiser free breathing

To localize and plan the sequences, it is essential to acquire a three-plane T2 HASTE localizer initially. These fast single-shot localizers have an acquisition time of under 25 seconds and are highly effective in accurately localizing abdominal structures.

Planning and protocol of Magnetic resonance cholangiopancreatography (MRCP) localiser

T2 HASTE coronal 6mm respiratory gated

Plan the coronal slices on the axial localizer and position the block horizontally across the liver as depicted. Verify the position in the other two planes. Establish an appropriate angle in the sagittal plane, aligning it vertically across the liver. Ensure that the slices adequately cover the entire liver, extending from the anterior abdominal wall to the erector spinae muscles. The phase direction should be from right to left to minimize ghosting artifacts from the lungs and heart. Employ phase oversampling to prevent wrap-around artifacts. Instruct the patient to breathe gently throughout the scan. 

In modern scanners, respiratory gating is achieved using phase scout navigators placed inside the liver tissues. In older generation scanners, the liver dome respiratory trigger method can be utilized. However, in our department, we prefer using phase scout navigators. For respiratory gated scans utilizing phase scout navigators, it is essential to accurately position the respiratory navigator box within the liver. Ensure that no part of the navigation box extends beyond the liver boundaries. Planning should be conducted using a free breathing localizer, as the diaphragm’s downward movement during inhalation can result in improper slice planning and positioning of the respiratory navigator box.

Magnetic resonance cholangiopancreatography (MRCP) MRI protocol and planning of coronal respiratory gated scans

Parameters

TR

2000-2500

TE

90-110

FLIP

130

NEX

1

SLICE

6MM

MATRIX

256×256

FOV

350

PHASE

R>L

OVERSAMPLE

50%

TRIGGER

NO

Phase scout respiratory gating

Phase scout respiratory gating is a technique used to synchronize image acquisition with the patient’s respiratory motion. It involves acquiring a low-resolution, single-shot MR image during free breathing, referred to as a phase scout or navigator scan. This scout image is typically acquired in the liver region, as it exhibits prominent respiratory motion.

The acquired phase scout image is used to track the patient’s respiratory motion by monitoring changes in the position of anatomical structures, such as the diaphragm or liver dome, between successive acquisitions. The position information is then used to trigger the start of image acquisition at specific phases of the respiratory cycle, typically during end-expiration when motion artifacts are minimal.

By employing phase scout respiratory gating, scanner can acquire images at specific respiratory phases, resulting in reduced motion artifacts and improved image quality. This technique is particularly beneficial when imaging anatomical regions affected by respiratory motion, such as the liver, allowing for clearer and more accurate diagnostic images.

Phase scout respiratory gating MRI

T2 HASTE axial fat saturated 6mm respiratory gated

Plan the axial slices on the coronal breath hold images and position the block horizontally across the liver as shown. Verify the positioning in the other two planes. Establish an appropriate angle in the sagittal plane, aligning it horizontally across the liver. The slices must be sufficient to cover the entire liver from the diaphragm down to the C loop of the duodenum. The phase direction should be from right to left to minimize ghosting artifacts from the anterior abdominal wall. Use phase oversampling to prevent wrap-around artifacts. Adding saturation bands on the top and bottom of the axial block will help reduce arterial pulsation and breathing artifacts. Instruct the patient to breathe gently throughout the scan. 

For respiratory gated scans utilizing phase scout navigators, it is essential to accurately position the respiratory navigator box within the liver. Ensure that no part of the navigation box extends beyond the liver boundaries. Planning should be conducted using a free breathing localizer, as the diaphragm’s downward movement during inhalation can result in improper slice planning and positioning of the respiratory navigator box.

Magnetic resonance cholangiopancreatography (MRCP) MRI protocol and planning of axial respiratory gated scans

Parameters

TR

3000-4000

TE

110

FLIP

150

NEX

1

SLICE

6 MM

MATRIX

320X320

FOV

400-450

PHASE

A>P

OVERSAMPLE

50%

IPAT

Off

T2 HASTE axial 6mm respiratory gated

Plan the axial slices on the coronal breath hold images and position the block horizontally across the liver as shown. Verify the positioning in the other two planes. Establish an appropriate angle in the sagittal plane, aligning it horizontally across the liver. The phase direction should be from right to left to minimize ghosting artifacts from the anterior abdominal wall. Use phase oversampling to prevent wrap-around artifacts. Adding saturation bands on the top and bottom of the axial block will help reduce arterial pulsation and breathing artifacts. Instruct the patient to breathe gently throughout the scan.

Magnetic resonance cholangiopancreatography (MRCP) MRI protocol and planning of axial respiratory gated scans

Parameters

TR

3000-4000

TE

110

FLIP

150

NEX

1

SLICE

6 MM

MATRIX

320X320

FOV

400-450

PHASE

A>P

OVERSAMPLE

50%

IPAT

Off

T2 SPACE 3D(or T2 TSE) coronal respiratory gated 1MM

Plan the coronal 3D sequence on the axial HASTE scan. Position the block across the common bile duct and pancreatic duct. Verify the positioning in the other two planes. Establish an appropriate angle in the sagittal plane, aligning it horizontally across the bile duct. Ensure that the slices adequately cover the entire common bile duct, pancreatic duct, and gall bladder. Use phase oversampling to prevent wrap-around artifacts. 

In our department, we utilise liver dome navigators for coronal 3D space sequences. It is crucial to accurately position the respiratory navigator box for liver dome respiratory gated scans. Place the box in the middle of the right dome of the diaphragm, ensuring that half of the box is positioned over the right lobe of the liver (segment 8) and the other half over the lungs. Planning should be carried out in a non-breath hold localizer, as the liver is pushed down by the diaphragm during inhalation, which can result in improper slice planning and positioning of the respiratory navigator box.

Instruct the patient to breathe gently throughout the sequence, as very shallow or erratic breathing can diminish the effectiveness of the navigator.

Parameters

TR

2500-3000

TE

500-700

FLIP

12

NEX

1

SLICE

1MM

MATRIX

320X320

FOV

350

PHASE

R>L

OVERSAMPLE

50%

IPAT

ON

OPTIONAL SCANS

T2 HASTE axial 6mm respiratory gated using table respiratory sensor

Respiratory gating in modern scanners can now be accomplished using built-in table respiratory sensors. This feature proves particularly beneficial when patients have irregular breathing patterns or are at risk of falling asleep during the scan. The advantage of table sensors is that they do not necessitate any specific planning. The only requirement is to ensure that the patient’s chest is accurately positioned over the table sensors to enable accurate monitoring of breathing. Additionally, it is important to select the appropriate gating option, such as the table sensor gating, in the protocol settings.

Plan the axial slices on the coronal breath hold images and position the block horizontally across the liver as shown. Verify the positioning in the other two planes. Establish an appropriate angle in the sagittal plane, aligning it horizontally across the liver. The phase direction should be from right to left to minimize ghosting artifacts from the anterior abdominal wall. Use phase oversampling to prevent wrap-around artifacts. Please advise the patient to maintain a gentle and steady breathing pattern throughout the entire scan.

MRCP planning and protocol of axial slices

Parameters

TR

4000-5000

TE

500

FLIP

150

NEX

1

SLICE

40MM

MATRIX

320X320

FOV

300-400

PHASE

R>L

OVERSAMPLE

50%

IPAT

ON

Table sensors

Advanced MRI scanners are equipped with built-in table sensors that detect the respiratory waveform and trigger data acquisition during the expiration phase of the respiratory cycle. Proper patient positioning over the sensor is critical for accurate respiratory gating. This method eliminates the need for external respiratory gating equipment, such as sensors and belts.

Advanced MRI scanners are equipped with built-in table sensors