MRI Liver ( Free Breathing Compressed Sensing GRASP-VIBE)
Indications for liver MRI
- Evaluation of diffuse liver disease such as haemochromatosis, haemosiderosis, fatty infiltration
- Detection of focal hepatic lesions metastasis, focal nodular hyperplasia, hepatic adenoma
- Lesion characterization, e.g. cyst, focal fat, haemangioma, hepatocellular carcinoma
- Clarification of findings from other imaging studies or laboratory abnormalities
- Evaluation of tumour response to treatment, e.g. post-chemotherapy or surgery
- Evaluation of known or suspected congenital abnormalities
- Liver iron content determination
- Potential liver donor evaluation
- Evaluation of vascular patency
- Evaluation of cirrhotic liver
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 MRI Liver
- 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 breathe gently for the respiratory gated scans.
- An intravenous line must be placed with extension tubing extending out of the magnetic bore
- 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 MRI Liver
- Position the patient in supine position with head pointing towards the magnet (head first supine)
- Position the patient over the spine coil and place the body coil over the upper abdomen (nipple down to iliac crest)
- Securely tighten the body coil using straps to prevent respiratory artefacts
- Give a pillow under the head and cushions under the legs for extra comfort
- Centre the laser beam localizer over xiphoid process of sternum
Recommended Dynamic MRI Liver Protocols 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.
T2 tse BLADE(PROPELLER) coronal 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.
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.
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.
BLADE(PROPELLER)
BLADE is an innovative MRI technique designed to minimize the impact of motion during MRI examinations. With BLADE acquisition, the k-space data is gathered in concentric rectangular strips that rotate around the k-space. Each strip acquisition samples the central portion of the k-space. The phase, translation, and rotation corrections are performed using an averaged strip.
Parameters
TR 2000-3000 | TE 90-110 | FLIP 140 | NEX 1 | SLICE 4MM | MATRIX 320×320 | FOV 350 | PHASE R>L | OVERSAMPLE 100% | TRIGGER YES |
T2 tse BLADE(PROPELLER) axial respiratory gated
Plan the axial slices on the coronal free-breathing localizer 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 can either be right to left or anterior-posterior, as radial k-space sampling will eliminate potential motion artifacts. Use phase oversampling to prevent radial k-space-related artifacts.
Parameters
TR 3000-4000 | TE 90 | FLIP 140 | NEX 1 | SLICE 3MM | MATRIX 320×320 | FOV 350 | PHASE A>P | OVERSAMPLE 100% | TRIGGER YES |
T2 TSE fat-suppressed BLADE / T2 STIR respiratory gated
Plan the axial slices on the coronal free-breathing localizer 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 can either be right to left or anterior-posterior, as radial k-space sampling will eliminate potential motion artifacts. Use phase oversampling to prevent radial k-space-related artifacts.
Parameters
TR 5000-6000 | TE 90 | FLIP 140 | NEX 1 | SLICE 3MM | MATRIX 320×320 | FOV 350 | PHASE A>P | FAT SAT SPAIR | TRIGGER YES |
T1 In-phase 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. Use phase oversampling to prevent wrap-around artifacts.
Parameters
TR 2000 | TE 1.44 | FLIP 15 | NXA 1 | SLICE 3 MM | MATRIX 256×224 | FOV 320 | PHASE A>P | OVERSAMPLE 20% | TI 700 |
T1 out-of-phase 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. Use phase oversampling to prevent wrap-around artifacts.
Parameters
TR 2000 | TE 2.31 | FLIP 15 | NXA 1 | SLICE 3 MM | MATRIX 256×224 | FOV 320 | PHASE A>P | OVERSAMPLE 20% | TI 900 |
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 5 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 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. Use phase oversampling to prevent wrap-around artifacts.
Parameters
| TR 4-5 | TE 2 | FLIP 12 | NEX 1 | SLICE 3MM | MATRIX 256X256 | FOV 350 | PHASE A>P | DYNAMIC 4 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.
VIBE DIXON BH performed on an uncooperative patient.
scan acquisition time 18sec.
CS-FB GRASP VIBE performed on an uncooperative patient.
DYNAMIC 4 trace scan time 5min.
DWI epi 3 scan trace axial 3mm free breathing
Plan the axial slices on the coronal free-breathing localizer 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 by aligning it horizontally across the liver. Ensure that the slices adequately cover the entire liver, from the diaphragm down to the C loop of the duodenum. Consider adding saturation bands at the top and bottom of the block to minimize artifacts caused by fat signal, arterial pulsation, and breathing.
Parameters
TR 6000-7000 | TE 90 | IPAT ON | NEX 3 5 8 | SLICE 3 MM | MATRIX 192X192 | FOV 300-400 | PHASE R>L | GAP 10% | B VALUE 0 |
T1 Compressed Sensing GRASP-VIBE axial delayed 20 minutes
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. Use phase oversampling to prevent wrap-around artifacts.
Parameters
TR 4-5 | TE 2-3 | FLIP 12 | NEX 1 | SLICE 3MM | MATRIX 320X320 | FOV 350 | PHASE A>P | DYNAMIC OFF | IPAT ON |
Delayed phase is necessary for the characterization of lesions. Many liver lesions exhibit progressive filling patterns. Haemangioma typically demonstrates progressive fill-in, with lesion density similar to that of the blood pool. Most hypovascular metastatic lesions exhibit a peripheral enhancement pattern with no central enhancement. Cholangiocarcinomas display a progressive enhancement pattern, with maximum enhancement in the delayed phase due to the slow enhancement of the fibrous center.
