Brain MR post-gadolinium contrast in multiple sclerosis: the role of magnetization transfer and image subtraction in detecting more enhancing lesions

Abstract

Our purpose was to evaluate the role of magnetization transfer and image subtraction in detecting more enhancing lesions in brain MR imaging of patients with multiple sclerosis (MS). Thirty-one MS patients underwent MR imaging of the brain with T1-weighted spin echo sequences without and with magnetization transfer (MT) using a 1.5 T imager. Both sequences were acquired before and after intravenous injection of a paramagnetic contrast agent. Subtraction images in T1-weighted sequences were obtained by subtracting the pre-contrast images from the post-contrast ones. A significant difference was found between the numbers of enhanced areas in post-gadolinium T1-weighted images without and with MT (p=0.020). The post-gadolinium T1-weighted images with MT allowed the detection of an increased (13) number of enhancing lesions compared with post-gadolinium T1-weighted images without MT. A significant difference was also found between the numbers of enhanced areas in post-gadolinium T1-weighted images without MT and subtraction images without MT (p=0.020). The subtraction images without MT allowed the detection of an increased (10) number of enhancing lesions compared with post-gadolinium T1-weighted images without MT. Magnetization transfer contrast and subtraction techniques appear to be the simplest and least time-consuming applications to improve the conspicuity and detection of contrast-enhancing lesions in patients with MS.

Cerebral lesions of multiple sclerosis: is gadolinium always irreplaceable in assessing lesion activity?

“…He et al (21) noted that lesion activity should not be equated with enhancement; more activity is taking place that is not necessarily defined by enhancement alone. Another explanation might be linked to the fact that poorly enhanced lesions could have escaped detection, as shown in previous reports using the magnetization transfer and image subtraction techniques (22)(23)(24).…”

Active MS plaques: efficiency of contrast-enhanced magnetization transfer subtraction technique

“…Patients may experience relapses either during the relapsing-remitting or secondary progressive or primary progressive MS. Relapses represent new or ongoing disease activity within the central nervous system (2). Complementary to clinical assessment, magnetic resonance imaging (MRI) sensitively demonstrates the spatial and temporal dissemination of demyelinating plaques in the brain and spinal cord (3)(4)(5). It has been a useful tool for the diagnosis and assessment of treatment in MS patients (4)(5)(6)(7).…”

“…after contrast material injection), triple dosing (0.3 mmol/kg), examination with 3 mm slices without gap, or magnetization transfer (MT) technique may improve the conspicuity of acute plaques (8)(9)(10)(11). Late phase imaging and triple dosing increase the cost and may cause false positive results in regions with small vessels and flow artifacts (3)(4)(5)9). Magnetization transfer (MT) technique which has increased sensitivity in the detection of MS plaques has roles in identifying the earliest stage of MS lesion genesis, edema and demyelination (12,13).…”

“…T1W imaging with MT technique is not only superior in detection of the plaques but it also causes relative hyperintensity of plaques that actually do not enhance with gadolinium chelates (pseudoenhancement) (3)(4)(5)15). If postcontrast T1W images with MT are taken into consideration alone, false positive results may occur.…”

“…If postcontrast T1W images with MT are taken into consideration alone, false positive results may occur. To overcome this problem, subtraction technique may be used (3,15). MT pulse decreases signal-to-noise ratio (SNR) of the white matter causing an increase in the contrast-to-noise ratio (CNR) of the acute plaque.…”