Many patients, especially those who are inpatient or from the emergency department, struggle to hold their breath for the length of time required for a magnetic resonance imaging (MRI) exam. Breath-holds for liver imaging can be 15 seconds long, and a patient's inability to comply can impact image quality. Patients who have extensive liver disease or are experiencing side effects of cancer treatments may also struggle to hold their breath. In some cases, the study may be difficult or impossible to read. However, magnetic resonance (MR) may provide detailed images of the liver using a non-invasive method without exposing patients to the ionizing radiation that computerized tomography (CT) and positron emission tomography (PET) scans involve.
Advanced MR techniques for liver imaging
Multiple advanced techniques can provide additional information during liver imaging with MRI. Diffusion-weighted imaging (DWI) and fast spin echo (FSE) techniques can both be used to expand on the images produced with conventional MRI.1,2,3 Some advanced imaging techniques may also aid radiologists in determining the different tissue structures in the region of interest and the malignancy of certain lesions in the liver.3
DWI is a technique used during magnetic resonance imaging (MRI) that uses the Brownian motion (random motion of water molecules) to create detailed images of the tissue structures and organs within the body. This method is frequently used in liver imaging, because it can improve detection of primary and secondary lesions.1 These secondary lesion are metastatic in nature, meaning that the cancer cells have spread from the origin to other areas of the body. DWI may aid quantitative and qualitative magnetic resonance imaging without the use of contrast.2
In some cases, DWI may be particularly helpful in detecting malignant liver lesions.3 This may allow physicians and radiologists to determine whether a lesion is worrisome or not. If this is possible, it may help a physician decide if a biopsy is necessary.
FSE is a variation on the spin echo acquisition technique. During a basic spin echo sequence, one echo is measured during each repetition time (TR), which is the time between consecutive points from one pulse or echo to the next in a repetitive sequence.4 FSE takes this principle and measures multiple echos during each repetition time. As a result, the scan may be sped up. FSE is typically used in place of the standard spin echo technique. It is able to be paired with other techniques and software programs, enhancing the scan further.
Motion-correction and acceleration
Claire Moisson and Stephanie Sellie from the Médipôle de Savoie in Challes-les-Eaux, France have seen an improvement in liver imaging in their radiology department since the introduction of motion-correction software.1 This software allows them to image their patients using magnetic resonance imaging (MRI) without the need for breath-holding. This software can be used with a variety of different advanced magnetic resonance imaging techniques, which may lead to improved image quality.
When combined with the motion-corrected, free-breathing software, DWI scans may provide high b-values, leading to additional information necessary for evaluation of lesions.1 In many cases, this can be done while still maintaining an adequate signal-to-noise ratio. The motion-correcting software allowed one man to be scanned, even though he could not hold his breath for longer than seven seconds, by enabling free-breathing.1 Because of this, the radiologist was able to obtain high-resolution images.
MRI can provide high-quality images of and data about a patient and their body. In some cases, pairing standard MR and advanced acquisition techniques, such as DWI and FSE, provides even better resolution images of different tissue structures. With the introduction of motion-correction software, as at the Médipôle de Savoie, radiology departments may find they have an easier time scanning their challenging patients, by allowing their patients to breathe freely.
- Free-breathing liver imaging using DISCO with Auto Navigator. SIGNA Pulse. Last accessed July 1, 2019.
- Diffusion-weighted MR Imaging of the Liver. Radiology. https://pubs.rsna.org/doi/10.1148/radiol.09090021. Last accessed July 2, 2019.
- Diffusion-weighted imaging of the liver: Current applications. World Journal of Radiology. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5120245/. Last accessed July 2, 2019.
- Fast spin echo. Radiopaedia. https://radiopaedia.org/articles/fast-spin-echo?lang=us. Last accessed July 2, 2019.