Recommendations of the Polish Medical Society of Radiology and the Polish Society of Neurology for a protocol concerning routinely used magnetic resonance imaging in patients with multiple sclerosis

Recommendations for MRI in MS patients on MRI scanners with field strength at least 1.5T

General comments

Patients with multiple sclerosis (MS) are recommended to undergo magnetic resonance imaging (MRI) with an intra­venous administration of a paramagnetic contrast medium (gadolinium) solely as a part of initial diagnostics.
A follow-up gadolinium-enhanced MRI with the use of macrocyclic contrast agents is recommended only in cases of a clinical progression of the disease, or if the need arises for another differential diagnosis of MS, or in another clinically justified situation. The retention characteristics of each gadolinium-based contrast agent (GBCA) should be considered in all patients; linear GBCAs have been shown to result in greater retention, and retention for longer, than macrocyclic GBCAs. This is why the use of linear contrast agents based on gadolinium (GBCA) is not recommended in following up the treatment of MS in clinically and radiologically stable patients, due to the potential occurrence of long-term side effects associated with the accumulation of contrast agent within the central nervous system (CNS).
Patients with clinically isolated syndrome (CIS) or suspected MS should undergo:
Head MRI before and after an intravenous administration of a contrast agent (Table 1).
It is recommended that an additional scan of the cervical and thoracic sections of the spinal cord (in accordance with the referral/indication of the neurologist) is performed after an intravenous administration of a contrast agent, especially when head MRI does not meet the dia­gnostic criteria or when clinical symptoms suggest the lesions are located in the spinal cord (Table 2). Ideally, MRI studies of the head and the cervical/thoracic spine should be performed within a single MRI imaging session. MRI of the spinal cord is particularly important in the diagnosis of primary progressive MS according to the current disease diagnosis criteria (Table 3).
In patients with multifocal damage to the nervous system involving symptomatology associated with both brain and spinal cord impairment, in order to shorten the diagnostic time, (and according to the referring neurologist’s recommendations) it is possible to perform simultaneously an MRI of the head and of a selected section of the spinal cord using a combined protocol (Table 4).
Recommendations for disease progression follow-up based on MRI:
Head MRI to show new/enlarging demyelinating lesions (Table 1) at least every 12 months during the initial years of treatment, but possibly less frequently later in patients with complete clinical stability. Cervical and/or thoracic spinal cord scan is recommended, according to the neurologist’s referral/indication.
For patients under the age of 18, the MRI protocol for brain and spinal cord examination remains unchanged; examination is the same as in the adult population.

Brain MRI protocol for MS patients

In order to use the same scanning planes during the follow-up examinations, it is recommended to achieve slices in the true midline plane.
For this purpose, once three localisation slices have been performed, five slices with a thickness of 3 mm should be planned as accurately as possible in the sagittal plane on T2-weighted images.
The planned slices should be set parallel to the longitudinal cerebral fissure using the localisation slices, in the transverse and frontal planes. The third of these five slices should pass through the median fissure as accurately as possible.
Cross-sectional slices should be set on the thereby obtained midline slice in parallel to the lower limits of the rostrum (anterior commissure – AC) and splenium of the corpus callosum (posterior commissure – PC), according to the AC-PC reference line (Figure 1).
Note: During the follow-up examinations, when the scanning plan is set in the reference to the corpus callosum, it is vital to compare the angulation of the planned slices with the angulation of the slices in the previous study.
Some scanners do not have the possibility of remembering a single slice; in such case the slice should be carefully defined as shown in Figure 1.
Note:
1. The direction of scanning in axial scans must be upwards, whereas in sagittal scans it must be from right to left (also when scanning spinal cord).
2. Gaps between slices should be as small as possible (we propose 0.3 mm, i.e. 10% slice thickness or no gap).
3. 3DT1 – we recommend performing this sequence first, to avoid motion artifacts in the course of the examination. This sequence allows for precise volumetric evaluation of the brain.
4. Both FLAIR sequences should be performed after the administration of a contrast medium, to delay the onset of T1+C acquisition (within the range of 5-10 minutes) in order to achieve better contrast enhancement. A contrast medium does not lessen the quality of FLAIR images. At the same time, the patient’s time spent in the scanner is used optimally. The possible enhancement of cortical demyelinating lesions or leptomeninges does not affect study interpretation, because enhancement is in any case assessed on the basis of T1-weighted sequences.
5. If scanning with 3DT2 and 3DFLAIR sequences, if possible they should be done in the sagittal plane and should be used with subsequent cross-reconstruction with 3 mm slices in the plane set up to the lower edge of the corpus callosum. When scanning in this way, clinicians should consider conducting the 3DT2 sequence scan after a contrast medium injection, so as to ensure an appropriate delay in T1 acquisition.
6. If software which automatically determines the angulation/range of the layers can be used, as in the previous examination, such a function is recommended.
A radiological report should include standard termino­logy used in brain assessment.
Description of focal lesions:
1. Location (supratentorial region: cortical, juxtacortical, central white matter, periventricular, infratentorial, corpus callosum, brainstem, spinal cord).
2. Size – the range of the longest dimension provided i.e. from–to. In the case of multiple lesions, report the size of the largest lesion only (in mm). According to the current definition, demyelinating lesions are defined as lesions of ≥ 3 mm in diameter.
3. The number of demyelinating lesions – specify according to the following scheme: 1, 2, 3-8, ≥ 9.
4. The nature of the lesion, i.e. specify whether the appearance is typical for MS demyelination, or whether differential diagnosis is required, e.g. ischaemic lesion.
5. Whether the lesions are disseminated in space (DIS) and meet the 2017 McDonald criteria (Table 3 and Table 5).
6. Comparison with the previous head and spinal cord MRI (if available). In patients with suspected MS, comparison with the previous MRI to assess disease activity and eligibility for treatment. In on-treatment patients, comparison with the previous examination and baseline examination performed prior to treatment initiation.
7. Activity assessment, i.e. the number of contrast-enhancing foci in the current examination and the number of new/ enlarging lesions compared to the baseline and the previous examination. Please specify according to the scheme: 1, 2, 3–8, ≥ 9.
8. Assessment of brain atrophy. We recommend avoiding expressions such as “brain atrophy” or “cerebral atrophy” in the report. If possible, provide current whole brain volume, grey matter volume, white matter volume, corpus callosum volume, and the volume of the right and left thalami.
There is a growing need for volumetry assessment in MS patient imaging, because it potentially can change treatment decisions. Many important factors influence volumetric calculations, including acquisition parameters, intrascanner variability, pseudoatrophy, and patient hydration or movement. Having appropriate 3DT1 sequences in the protocol makes it possible to use software available on the market that can measure patient atrophy over time. Volumetric applications differ in the range of output results, and cost is another very important factor. This is why volumetric analysis of the brain should be performed using certified software, and preferably by a central institution in order to standardise results.

Conflict of interest

The authors report no conflict of interest.

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