Unenhanced MRI without contrast can accurately detect new brain lesions in patients with multiple sclerosis (MS), researchers from Germany report.
"In our MS clinic, the Departments of Neurology and Neuroradiology in 2017 decided to omit contrast agent in routine follow-up scans of MS patients," Dr. Benedikt Wiestler from Technische Universitaet Muenchen told Reuters Health by email. "Seeing that the use of 3D sequences in combination with subtraction maps yields such a high diagnostic accuracy, missing only 4 in 1,992 new lesions and not missing a single patient with disease activity in over 500 follow-up scans, strongly reassured us in doing so."
MRI scan. Source: Getty
Studies from more than two decades ago suggested that administration of contrast material was necessary to maximize sensitivity for detecting new MS lesions, Dr. Wiestler and colleagues note in Radiology, online March 12. But those studies were based on two-dimensional images obtained at magnetic field strengths of 1.5 T and lower, they add.
The team examined data on 359 patients who underwent 866 MRI examinations, between one month and more than two years apart, using modern three-dimensional sequences performed at a field strength of 3.0 T.
Unenhanced MRI together with the use of longitudinal subtraction maps identified 1,992 new or enlarged lesions on 264 of the 507 follow-up images (median, three per patient).
Contrast-enhanced MRI identified 207 enhancing lesions in 69 of the follow-up images. All but four were also detected as new or enlarged lesions on unenhanced MRI; these four undetected lesions were retrospectively confirmed as true new lesions that were missed by both readers on unenhanced MR images.
Overall, disease progression was not missed in any patient when only the unenhanced images were assessed.
"There is already an active debate about whether contrast agent is truly necessary in routine follow-up imaging of MS patients," Dr. Wiestler said. "I expect our and others' findings to encourage physicians to review the routine use of contrast agent."
"When using 3D sequences in conjunction with longitudinal subtraction maps, omitting contrast agent does not decrease sensitivity for detecting new lesions/disease activity," he concluded.
Dr. Massimo Filippi from Vita-Salute San Raffaele University and San Raffaele Scientific Institute, in Milan, Italy, who has studied the use of MRI to evaluate MS, told Reuters Health by email, "Considering the recent safety concerns regarding the serial administration of gadolinium-based contrast agents, this study suggests that, by acquiring MRI sequences of good quality and by applying subtraction imaging, we could avoid gadolinium administration, thus reducing possible safety issues and also limiting the costs of MRI exams."
"Gadolinium administration remains relevant in several situations," said Dr. Filippi, who was not involved in the new work. "For instance, in the diagnostic work-up of patients with suspected MS, post-contrast sequence can be relevant in the differential diagnosis and to confirm dissemination in time already after the acquisition of a single MRI. Moreover, since gadolinium-enhancement is a short-lived feature, its presence suggests that a lesion is recent, with possible implications for patients' management. Finally it could be relevant to exclude possible treatment-related side effects (e.g., progressive multifocal leukoencephalopathy)."
"Before the application of this approach in the clinical setting, validation is necessary also at lower field strengths (e.g., 1.5 T) and with 2D sequences," he said.
Dr. Filippi added, "To apply subtraction imaging, baseline and follow-up acquisitions should be acquired with the same scanner and the same sequence. This could be quite challenging in the clinical setting, where patients often do not undergo MRI acquisitions in the same center."