mrimaster

MRI Kidneys (Respiratory Gated)

Indications for MRI kidney's

Contraindications

Patient preparation

Positioning

MRI kidneys positioning image

Suggested protocols, parameters and planning

localiser

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.

mri kidney scan localiser image

T2 HASTE coronal 4mm sfov respiratory gated

Plan the coronal slices on the axial plane and angle the positioning block parallel to the right and left kidneys. Check the positioning block in the other two planes. Provide an appropriate angle in the sagittal plane (parallel to the long axis of the kidney). Ensure that the slices are sufficient to cover both kidneys from anterior to posterior. Phase oversampling must be used to avoid wrap-around artifacts. Additionally, consider adding saturation bands at the top and bottom of the block to minimize artifacts caused by fat signal, arterial pulsation, and breathing. Instruct the patient to breathe gently throughout the sequence, as very shallow or erratic breathing can diminish the effectiveness of the navigator.

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.

MRI kidneys (respiratory gated) protocol and planning of coronal scan

Parameters

TR

2000-2500

TE

90-110

FLIP

130

NEX

1

SLICE

4MM

MATRIX

256×256

FOV

300-320

PHASE

R>L

OVERSAMPLE

50%

TRIGGER

Yes

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 in kidney imaging

T2 BLADE\HASTE 4mm respiratory gated

Plan the axial slices on the coronal free-breathing localizer and angle the positioning block parallel to the right and left renal pelvis. Check the positioning block in the other two planes. An appropriate angle must be given in the sagittal plane (perpendicular to the long axis of the kidney). Ensure that the slices are sufficient to cover both kidneys, starting from two slices above the upper pole of the kidneys and extending down to two slices below the lower pole of the kidney. Use phase oversampling to avoid wrap-around artifacts. Consider adding saturation bands at the top and bottom of the block to minimize artifacts caused by fat signal, arterial pulsation, and breathing. Instruct the patient to breathe gently throughout the sequence.

MRI kidneys (respiratory gated) protocol and planning of axial scan

Parameters HASTE

TR

2000-2500

TE

90-110

FLIP

130

NEX

1

SLICE

4MM

MATRIX

256×256

FOV

300-320

PHASE

R>L

OVERSAMPLE

50%

TRIGGER

Yes

T2 BLADE\HASTE fat saturated 4mm respiratory gated

Plan the axial slices on the coronal free-breathing localizer and angle the positioning block parallel to the right and left renal pelvis. Check the positioning block in the other two planes. An appropriate angle must be given in the sagittal plane (perpendicular to the long axis of the kidney). Ensure that the slices are sufficient to cover both kidneys, starting from two slices above the upper pole of the kidneys and extending down to two slices below the lower pole of the kidney. Use phase oversampling to avoid wrap-around artifacts. Consider adding saturation bands at the top and bottom of the block to minimize artifacts caused by fat signal, arterial pulsation, and breathing. Instruct the patient to breathe gently throughout the sequence.

MRI kidneys (respiratory gated) protocol and planning of axial scan

Parameters HASTE FS

TR

2000-2500

TE

90-110

FAT SAT

SPAIR

NEX

1

SLICE

4MM

MATRIX

256×224

FOV

300-320

PHASE

R>L

OVERSAMPLE

50%

TRIGGER

Yes

T1 In-phase 4mm respiratory gated 4mm

Plan the axial slices on the coronal free-breathing localizer and angle the positioning block parallel to the right and left renal pelvis. Check the positioning block in the other two planes. An appropriate angle must be given in the sagittal plane (perpendicular to the long axis of the kidney). Ensure that the slices are sufficient to cover both kidneys, starting from two slices above the upper pole of the kidneys and extending down to two slices below the lower pole of the kidney. Use phase oversampling to avoid wrap-around artifacts. Consider adding saturation bands at the top and bottom of the block to minimize artifacts caused by fat signal, arterial pulsation, and breathing. Instruct the patient to breathe gently throughout the sequence.

MRI kidneys (respiratory gated) protocol and planning of axial scan

Parameters

TR

2000

TE

1.44

FLIP

15

NXA

1

SLICE

4 MM

MATRIX

256×224

FOV

300-320

PHASE

A>P

OVERSAMPLE

20%

TI

700

T1 out-of-phase respiratory gated 4mm

Plan the axial slices on the coronal free-breathing localizer and angle the positioning block parallel to the right and left renal pelvis. Check the positioning block in the other two planes. An appropriate angle must be given in the sagittal plane (perpendicular to the long axis of the kidney). Ensure that the slices are sufficient to cover both kidneys, starting from two slices above the upper pole of the kidneys and extending down to two slices below the lower pole of the kidney. Use phase oversampling to avoid wrap-around artifacts. Consider adding saturation bands at the top and bottom of the block to minimize artifacts caused by fat signal, arterial pulsation, and breathing. Instruct the patient to breathe gently throughout the sequence.

MRI kidneys (respiratory gated) protocol and planning of axial scan

Parameters

TR

2000

TE

2.31

FLIP

15

NXA

1

SLICE

4 MM

MATRIX

256×224

FOV

300-320

PHASE

A>P

OVERSAMPLE

20%

TI

900

DWI epi 3 scan trace axial 4mm free breathing

Plan the axial slices on the coronal free-breathing localizer and angle the positioning block parallel to the right and left renal pelvis. Check the positioning block in the other two planes. An appropriate angle must be given in the sagittal plane (perpendicular to the long axis of the kidney). Ensure that the slices are sufficient to cover both kidneys, starting from two slices above the upper pole of the kidneys and extending down to two slices below the lower pole of the kidney. Use phase oversampling to avoid wrap-around artifacts. Consider adding saturation bands at the top and bottom of the block to minimize artifacts caused by fat signal, arterial pulsation, and breathing. Instruct the patient to breathe gently throughout the sequence.

MRI kidneys (respiratory gated) protocol and planning of axial scan

Parameters

TR

6000-7000

TE

90

IPAT

ON

NEX

 3     5     8

SLICE

4 MM

MATRIX

192X192

FOV

300-330

PHASE

R>L

GAP

10%

B VALUE

0
500
1000

T1 Compressed Sensing GRASP-VIBE axial Dynamic free breathing

Compressed Sensing GRASP-VIBE is an innovative MRI technique that combines Compressed Sensing (CS) and GRASP-VIBE (Golden-angle Radial Sparse Parallel MRI with View-sharing) to transform abdominal imaging. The dynamic liver sequence of Compressed Sensing GRASP-VIBE comprises multiple scans with high temporal resolution and incorporates motion correction. The entire sequence lasts approximately 4 minutes and includes one pre-contrast acquisition followed by several post-contrast acquisitions.

During the scan, the scanner provides a 20-second countdown for the administration of contrast injection. Within this timeframe, the scanner performs the pre-contrast scans. As a user, you simply need to initiate the sequence, monitor the countdown, and administer the contrast agent once the countdown concludes. This streamlined process minimizes user involvement, allowing for efficient and hassle-free implementation of the technique.

Plan the axial slices on the coronal free-breathing localizer and angle the positioning block parallel to the right and left renal pelvis. Check the positioning block in the other two planes. An appropriate angle must be given in the sagittal plane (perpendicular to the long axis of the kidney). Ensure that the slices are sufficient to cover both kidneys, starting from two slices above the upper pole of the kidneys and extending down to two slices below the lower pole of the kidney. Use phase oversampling to avoid wrap-around artifacts. Consider adding saturation bands at the top and bottom of the block to minimize artifacts caused by fat signal, arterial pulsation, and breathing. Instruct the patient to breathe gently throughout the sequence.

mri kidney scan axial planning and protocol image

Parameters

TR 4-5

TE

2

FLIP

12

NEX

1

SLICE

3MM

MATRIX

256X256

FOV

320

PHASE

A>P

DYNAMIC 2 measurements

IPAT

ON

Compressed Sensing GRASP-VIBE

Compressed Sensing GRASP-VIBE combines the principles of Compressed Sensing and GRASP-VIBE to revolutionize abdominal MRI. This technique allows for high-resolution dynamic abdominal imaging under free-breathing conditions, expanding the patient population eligible for the procedure. Patients who have limited breath-hold capability or difficulty following breathing commands can now undergo this exam with ease.

With its intelligent reconstruction and processing framework, Compressed Sensing GRASP-VIBE automatically identifies different phases of liver dynamics and outputs only the clinically relevant information. This streamlines the workflow and brings the advantages of this technique to daily clinical routines.

The acquisition is performed in one continuous run using a golden-angle stack-of-stars radial scheme, providing robustness against motion and the flexibility to choose temporal resolution. Reconstruction utilizes a Compressed Sensing GPU accelerated iterative algorithm with through-time regularization, resulting in improved image quality. This combination enables free-breathing abdominal exams with both diagnostic image quality and high temporal resolution to capture dynamic contrast enhancement phases.

Additional features include auto bolus detection, configuration of exam phases, auto-labeling of relevant phases, self-gating for further motion reduction, and inline reconstruction using GPU acceleration for quick image access. Compressed Sensing GRASP-VIBE offers protocols for both abdomen and prostate imaging, making it a versatile technique.

Optional Scans

T2 HASTE axial 4 mm 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 respiratory-gated images and angle the positioning block parallel to the right and left renal pelvis. Check the positioning block in the other two planes. An appropriate angle must be given in the sagittal plane (perpendicular to the long axis of the kidney). Ensure that the slices are sufficient to cover both kidneys, starting from two slices above the upper pole of the kidneys and extending down to two slices below the lower pole of the kidney. Use phase oversampling to avoid wrap-around artifacts. Consider adding saturation bands at the top and bottom of the block to minimize artifacts caused by fat signal, arterial pulsation, and breathing. Instruct the patient to breathe gently throughout the sequence.

mri kidneys planning of axial images

Parameters

TR 2000-3000

TE

130

FLIP

150

NEX

1

SLICE

4MM

MATRIX

288X256

FOV

300-320

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