Acceleration techniques in magnetic resonance imaging: Elevating radiology

Leadership Matters Article 4 Minute Read GE Healthcare Global

Recent initiatives in healthcare have pushed professionals to provide a more personalized approach for each patient. As a result, radiology departments have begun attempting to provide more personalized scans. Radiology departments in general may be experiencing a face lift of sorts. This is due to the departments feeling the need to increase scan speed and image quality. In some cases, radiologists may also be interested in reducing their scan times. Different acceleration techniques can be used during magnetic resonance (MR) scans to better approach these goals.

What are some acceleration techniques?

Acceleration techniques, seek to enhance magnetic resonance imaging (MRI) through the use of shorter scan times. Techniques such as compressed sensing (CS), parallel imaging (PI) and fast spin echo (FSE) may aid radiologists and enhance the patient experience.

Compressed sensing (also know as compressive sensing) is an imaging method used in MRI to accelerate an MR scan.1 With this method, the data is undersampled in the k-space and then goes through iterative reconstruction. This basically means that the scan time can be decreased, because the scanner collects less data for each pixel of the scan. A review of the literature on CS has shown that there is little difference in the image quality between conventional and CS MRI.1 Similarly, Dr. Paul Malcolm of Norfolk and Norwich University Hospital found CS to be particularly useful for patients who couldn’t complete the breath-hold sequence in MRCP protocol.2 Using CS, the same quality of images could be acquired in two-thirds the time or less.2

Parallel imaging is another method that can be used to accelerate a scan. PI takes advantage of the pre-determined space from the coil to the region of interest.3 It then takes the data from multiple different receiver coils, like conventional MRI, and creates the images. The main difference is that the information from each coil is used individually instead of being combined. PI may be faster than traditional imaging due to the fact that it does not have to acquire as much spatial information, much like CS. The strength of the signal on one coil over another allows for some of the spatial encoding to occur. PI may be used to improve acquisition time, spatial resolution and image quality.4

Fast spin echo, also referred to as turbo spin echo, is the faster version of the traditional scanning method, spin echo.4 Instead of only acquiring a single echo at a time during each pulse in the sequence, multiple echos are acquired quickly. The scan time reduction is directly related to the number of echos acquired. This technique may be beneficial for reducing the effect of magnetic field inhomogeneity. Unfortunately, FSE suffers from a reduced signal to noise ratio, because the echo amplitude diminishes over time.5

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How does acceleration affect a radiology department’s equation?

As patients attempt to lay completely still on the MR table, they may find it difficult to hold their position for a long period of time. This is especially true in pediatric patients and those in extreme pain. These patients would probably love to see a world where they arrive for their scan, get in on time, finish the scan in the predicted time, and go about the rest of their days. Honestly, they probably would be exceedingly happy if they were able to finish their scan is less than the predicted time.

Acceleration techniques can help with this predicament. Techniques such as CS, PI and FSE all aim to help decrease the amount of time spent on the table. Additionally, they may enable the radiologist to complete more scans on areas of concern, helping to enable radiologists’ patient-specific approaches. Each patient is different, and, therefore, each patient may require additional imaging in a different area of the region of interest. For example, in abdominal imaging, one patient’s physician may find more detailed images of the stomach helpful. Another patient’s doctor may want to see the liver in more detail. The extra time could be used to acquire extra scans of that area.

Radiologists may also find acceleration techniques to be useful for their practice in another way: increasing throughput. As MR scans utilize the acceleration techniques mentioned above, the department may find that they can scan more patients per day. This is due to the decreased scan time and may be especially useful in emergency situations. Once the department begins to see the scan time drop, they might even be able to add more appointment slots, helping patients get in sooner than they may have been previously able. This allows the patient and their doctor to get the results sooner as well.

Acceleration techniques such as compressed sensing, parallel imaging and fast spin echo can enable radiology departments to complete their scanning quicker without losing image quality. Additionally, the radiologist may find it necessary to spend more time imaging one area over another to provide more detailed, higher-quality images. In some cases, the radiology department may want to consider adding appointment slots because of the decrease in time. Elevating radiology may be just a step away, through the use of acceleration techniques.

For more information about Dr. Paul Malcolm’s study, see “Using HyperSense to reduce scan times and elevate diagnostic success.”

References

1. Oren N. Jaspan, Roman Fleysher and Michael L. Lipton. “Compressed sensing MRI: a review of the clinical literature.” Br J Radiol. December 2015; 88(1056): 20150487. Web. 27 March 2019. doi: 10.1259/bjr.20150487.

2. Mary Beth Massat. “Using HyperSense to reduce scan times and elevate diagnostic success.” SIGNA Pulse. Spring 2018. Web. 27 March 2019. <http://www.gesignapulse.com/signapulse/spring_2018/MobilePagedArticle.action?articleId=1396187#articleId1396187>.

3. “Parallel Imaging?: What is parallel imaging? How does this differ from ‘regular’ imaging?” MRIQuestions.com. Web. 27 March 2019. <http://mriquestions.com/what-is-pi.html>.

4. Anagha Deshmane, et al. “Parallel MR Imaging.” J Magn Reson Imaging. July 2012; 36(1): 55-72. Web. 27 March 2019. doi: 10.1002/jmri.23639.

5. Andrew Murphy, et al. “Fast spin echo.” Radiopaedia. 2018. Web. 27 March 2019. <https://radiopaedia.org/articles/fast-spin-echo/revisions?lang=us>.