Brain imaging in MS, 3 steps to optimize your MRI protocol

Feb 5, 2020

The ultimate goal of medical imaging is to acquire more meaningful data in less time. Finding a good tradeoff between information and speed is important for both clinical purposes and patient experience. Fortunately, advancements in hardware, acquisition and post-processing software allow you to optimize this equation with the help of artificial intelligence.

Medical imaging innovation in multiple sclerosis (MS) is of particular importance due to the high prevalence of MS and the standard usage of MRI in the diagnosis and monitoring. In this blog, we discuss the 3 key elements of MRI protocols for the monitoring of MS; MRI sequences, scanning frequency, and communication.

Sequences

The modern brain MRI protocol for MS includes two standard sequences:

1. T1 Weighted - 3D Fast Gradient Echo (GRE)

2. FLAIR (T2 Weighted) - preferably 3D FLAIR, 2D is acceptable (with a slice thickness below 3 mm)

   
   

   

   
   

Top: Left-T1 sequence, Right-icobrain segmentation gray . matter (blue) and T1 hypointensities (red) Bottom: Left - T2 FLAIR sequence, Right - icobrain segmentation of FLAIR white matter hyperintensities

The 3D T1 GRE sequence not only provides more brain tissue coverage and the ability to perform high quality multiplanar reformats, but it is also superior in identifying T1 hypointensities or ‘black holes' on brain MRI images.

The T2 weighted Fluid Attenuated Inversion Recovery (FLAIR) sequence is essential in an MS MRI brain protocol because it makes the detection of T2 lesions easier.

For this reason, these MRI image biomarkers can be incredibly insightful to clinicians in correlating symptomology and making disease-modifying therapy decisions sooner.

By implementing these two sequences you not only far exceed the protocol guidelines in demyelinating imaging by the American College of Radiology (ACR)1 , but you will be adhering to the much more stringent guidelines of the Consortium of Multiple Sclerosis Centers (CMSC)2 and Magnetic Resonance Imaging in MS (MAGNIMS)3

Advantages and differences between MRI protocol guidelines

	ACR	CMSC	MAGNIMS
Core sequences	- Axial, sagittal, or coronal FSE T1 - Sagittal and axial T2 FLAIR - Axial T2 - Axial or coronal T1 post-contrast	2D/3D Sagittal and axial FLAIR - 2D/3D Axial T2 - Axial 2D DWI * - 3D IR-prep GE T1	- Axial proton- density and/ or T2 FLAIR/T2 - 2D/3D T1 post-contrast
Slice thickness	Max. 5.0 mm	Max. 3.0 mm	Max. 3.0 mm
Slice gap	Max. 2.0 mm or less	No gap	-
Pixel resolution	1.2 mm or less	1mm or less	1mm or less

FSE - Fast Spin Echo, IR-prep GE - Inversion-recovery prepared Gradient Echo * not recommended by ACR1, but a very important sequence in determining pathology and acute dissemination

The CMSC2 guidelines are more advantageous in imaging neurologic MS and can be achieved by just adjusting a few specific basic parameters:

Slice Thickness and Space Gap

• - Thinner slices and little to no gap = More brain tissue coverage = More clinical data Isotropic voxels with pixels of 1mm or less

• - Isotropic voxels = Higher quality reformats = Improved quantitative segmentation

• - Eliminates the need for cross-plane sequences = saved time

Changing these parameters may require adjusting other parameters to regain signal to noise ratios. However, with modern-day software and hardware in MRI equipment, these trade-offs are easy to regain and, in the end, you have optimized sequences that surpass “expectations”. The acquisition of 3D data also permits volumetric post-processing to quantify brain atrophy, which has become an integral part of the imaging reporting and disease monitoring in MS.

Optional Sequences

To truly have a comprehensive diagnostic MRI brain evaluation there are other sequences needed for the radiologist to make an insightful decision.

These additional sequences are:

	Optional sequences	Added value
ACR	- Sagittal and Axial DIR FLAIR	Increased cortical, juxtacortical, grey matter, and mixed white matter hyperintensity detection. Easier visualization (See examples below).
CMSC	- SWI - 2D/3D Axial T1 (pre-contrast) - Axial Proton Density (PD)	SWI - ability to see vasculature feed to lesion (MS lesions are hypervascular, typically only visible microscopically) allows easier characterization of hyperintensities. PD - intermediate echo time (TE) can increase visualization of lesions versus a long TE (See example below).
MAGNIMS	- 2D/3D T1 (pre-contrast) - 2D/3D DIR - Axial DWI	DWI - one of the most important sequences in an MRI brain protocol; essential for characterization of numerous pathologies; in MS can help identify acute/active lesion

SWI - Susceptibility Weighted, DIR - Double Inversion Recovery, DWI - Diffusion Weighted

Top: Left - Traditional Sagittal T2 FLAIR, Right - Sagittal Dual IR Bottom: Left- PD Weighted (Intermediate TE), Right - T2 Weighted (Long TE)

Gadolinium usage

The use of Gadolinium-based contrast agents in the monitoring of MS patients has been a widely debated topic. Guidelines unanimously recommend the use of contrast only when investigating unexpected clinical deterioration or when reassessing the diagnosis of MS. The CMSC2 and MAGNIMS3 guidelines state that the use of contrast can be helpful in the detection of new lesions in patients with a large lesion burden. However, image post-processing tools can detect and label new- and enlarging lesions between scans beyond the average 3-week period of enhancement. One of the biggest concerns with MS and gadolinium administration is the periodical MRI evaluations and the increased chances of gadolinium retention with increased exposure due to frequency of MRI scans with contrast.

Left - T2 FLAIR time point 1, Middle - icobrain segmentation time point 2 indicating new (red), enlarging (orange), and pre- existing (green), Right - T2 FLAIR time point 2

The lesson we’ve learned from analyzing thousands of clinical scans is that, above all, the consistency of these factors is necessary to allow for a reliable comparison of MRI data over time. Sequence parameters, scanner type, and scanner software can have a significant impact on the visualization of brain tissue and lesions, making it difficult to reliably relate changes to parameter variability or disease progression. Consistent scanning of patients on the same scanner over time is advisable, for both visual reading and post-processing.

MRI Scanning Frequency

Regular MRI follow-up is necessary to keep track of potential subclinical progression. Generally speaking, an MRI evaluation every 6 months to 2 years is recommended, depending on the patient’s clinical course and disease status. The availability of a usable baseline scan is important and serves as a reference for the correct interpretation of your patients’ disease progression. Scanning is, therefore, advised:

• - To (re)establish baseline MRI

• - As routine follow up to detect activity and/or PML

• - Before starting or switching treatment

• - 6 months after starting or switching treatment

• - In case of sudden clinical worsening

• - To re-evaluate the diagnosis

• - After pregnancy

  
  

Healthcare Team Communication - MRI Requests and Reports

Clear communication between the neurologist and radiologist is crucial for efficient patient follow-up. Both the request for an MRI exam by the referring neurologist and the radiological report drafted by the radiologist are imperative. MRI requests should provide the necessary information to acquire the correct sequences.

There are no standardized guidelines on how to properly structure MRI requests but the following elements are essential:

• - Clinical purpose (diagnosis or monitoring)

• - Clinical history (onset, symptoms, and relapses)

• - Current MS disease-modifying treatment

• - Recent corticosteroid administration

• - Timing and location previous scan

  
  

Guidelines on the radiological reporting for MS monitoring recommend to include a comparison of the new lesions and atrophy with the previous study and to identify the findings as (a)typical for or not MS. Standardized and structured radiological reporting has been proven beneficial for thoroughness, consistency, speed, and physician satisfaction.4,5,6 You can download an MS reporting template here:

Download here your MS monitoring reporting template.

The purpose of this blog post is to help you optimize MRI sequences and develop consistency and standardization in your protocol, reporting, and communication. Nowadays, with advancements in medical imaging and artificial intelligence, we can and should provide better patient care where possible.

Visit the icobrain ms page to learn more about brain quantification for the monitoring of applications like multiple sclerosis.

Any questions about the optimization of your MS protocol? Shoot our support team a message at support@icometrix.com.

References:

1. American College of Radiology. 2019. MR Accreditation Program Testing Instructions. Retrieved from the ACR.

2. Consortium of MS centers (CMSC) MRI protocol and clinical guidelines for the diagnosis and follow-up of MS. 2018 revised guidelines.

3. Rovira, À., Wattjes, M., Tintoré, M. et al. MAGNIMS consensus guidelines on the use of MRI in multiple sclerosis—clinical implementation in the diagnostic process. Nat Rev Neurol 11, 471–482 (2015). https://doi.org/ 10.1038/nrneurol.2015.106

4. Dickerson et al J Am Coll Radiol. 2017 Mar;14(3):371-379.e1. https://doi.org/10.1016/j.jacr.2016.09.037.  Epub 2016 Dec 5.

5. Alessandrino et al American Journal of Roentgenology. 2018;210: 24-29. 10.2214/AJR.17.18451

6. Diana et al. icobrain's pre-populated reporting template for multiple sclerosis follow-up. Neurorad 2019 poster