Experimental allergic encephalomyelitis and multiple sclerosis: lesion characterization with magnetization transfer imaging.

Dousset, V.; Grossman, Robert I.; Ramer, Karen; Schnall, Mitchell D.; Young, Lindon H.; González‐Scarano, Francisco; Lavi, Ehud; Cohen, Jeffrey A.

doi:10.1148/radiology.182.2.1732968

Cited by 580 publications

(426 citation statements)

References 0 publications

Supporting

Mentioning

403

Contrasting

Unclassified

Order By: Relevance

“…A decrease in MTR has been predominantly associated with the loss of myelin in tissue (8). MTR imaging visualizes the interaction between protons of free tissue water with those associated with macromolecular structures like cell membranes predominantly present in myelin.…”

Section: Discussionmentioning

confidence: 99%

“…The latter techniques have been shown to be sensitive in detecting pathogenic processes that contribute to lesion formation in MS, i.e. inflammation and edema, demyelination, axonal destruction and gliosis (8)(9)(10). We compared the presentation of end stage lesions on in vivo MRI with quantitative ex vivo MRI and with histo-pathological characterization, including quantitation of axonal injury (11) and the presence and activity of macrophages (12), which have been recognized as important pathophysiological features of lesion development.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Quantitative MRI‐pathology correlations of brain white matter lesions developing in a non‐human primate model of multiple sclerosis

et al. 2006

View full text Add to dashboard Cite

Experimental autoimmune encephalomyelitis (EAE) induced with recombinant human myelin/oligodendrocyte glycoprotein in the common marmoset is a useful preclinical model of multiple sclerosis in which white matter lesions can be well visualized with MRI. In this study we characterized lesion progression with quantitative in vivo MRI (4.7 T ; T 1 relaxation time AE Gd-DTPA; T 2 relaxation time; magnetization transfer ratio, MTR, imaging) and correlated end stage MRI presentation with quantitative ex vivo MRI (formaldehyde fixed brains; T 1 and T 2 relaxation times; MTR) and histology. The histopathological characterization included axonal density measurements and the numeric quantification of infiltrated macrophages expressing markers for early active [luxol fast blue (LFB) or migration inhibition factor-related protein-14 positive] or late active/inactive [periodic acid Schiff (PAS) positive] demyelinating lesion. MRI experiments were done every two weeks until the monkeys were sacrificed with severe EAE-related motor deficits. Compared with the normal appearing white matter, lesions showed an initial increase in T 1 relaxation times, leakage of Gd-DTPA and decrease in MTR values. The progressive enlargement of lesions was associated with stabilized T 1 values, while T 2 initially increased and stabilized thereafter and MTR remained decreased. Gd-DTPA leakage was highly variable throughout the experiment. MRI characteristics of the cortex and (normal appearing) white matter did not change during the experiment. We observed that in vivo MTR values correlated positively with the number of early active (LFBþ) and negatively with late active (PASþ) macrophages. Ex vivo MTR and relaxation times correlated positively with the number of PAS-positive macrophages. None of the investigated MRI parameters correlated with axonal density.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Quantitative MRI‐pathology correlations of brain white matter lesions developing in a non‐human primate model of multiple sclerosis

et al. 2006

View full text Add to dashboard Cite

show abstract

“…Conventional T1-weighted spin-echo, fluid-attenuated inversion recovery (FLAIR)-weighted, and dual (proton density and T2-weighted) imaging was performed on all patients. Images were interpreted by an experienced neuroradiologist In addition to conventional MRI, all patients underwent MTI, which was performed using a 3-dimensional (3-D) gradient-echo pulse sequence with a 106-msec TR, a 6-msec TE, and a flip angle of 12° (10). These scan parameters were chosen to minimize T1 and T2 weighting, resulting in a proton-density contrast in the absence of MT saturation pulses.…”

Section: Methodsmentioning

confidence: 99%

Association of global brain damage and clinical functioning in neuropsychiatric systemic lupus erythematosus

Bosma¹,

Middelkoop²,

Rood³

et al. 2002

Arthritis & Rheumatism

View full text Add to dashboard Cite

Objective. To investigate the relationship between quantitative estimates of global brain damage based on magnetization transfer imaging (MTI) and cerebral functioning, as measured by neurologic, psychiatric, and cognitive assessments, as well as disease duration in patients with a history of neuropsychiatric systemic lupus erythematosus (NPSLE).Methods. In patients with systemic lupus erythematosus (SLE), neurologic, psychiatric, and psychological symptoms often occur. The frequency of nervous system involvement has been reported to range from 11% to 60% (1). Infection, drug side effects, hypertension, or metabolic derangements, as well as an intrinsic brain manifestation of SLE (i.e., neuropsychiatric SLE [NPSLE]), can cause such symptoms. The uncertain pathogenesis and the wide variety of manifestations of NPSLE complicate the development of a uniform diagnostic decision-making protocol and a uniform method of monitoring a patient with this type of SLE. Findings of routine brain imaging studies are often unremarkable in patients with NPSLE, or the studies reveal abnormalities, such as cerebral atrophy and white matter hyperintensities (on magnetic resonance imaging [MRI]), that can also be found in SLE patients without neuropsychiatric symptoms. Furthermore, no correlation has thus far been demonstrated between quantitative measures of such nonspecific abnormalities and measures of brain function (2-5).Recently, magnetization transfer ratio (MTR) histogram analysis, a quantitative MRI technique based on magnetization transfer imaging (MTI), was applied in patients with primary NPSLE but without abnormalities on MRI that could account for the clinical picture. With this technique, cerebral abnormalities were identified in these patients (6,7). Such abnormalities were found in SLE patients who had had episodes of neuropsychiatric symptoms in the past (chronic NPSLE) as well as in patients who were experiencing an active phase of neuropsychiatric symptoms (active NPSLE) (6,7). The

show abstract

“…6) and thus validate the proposed concept for compensation of finite RF pulse effects using balanced time-averaged magnetization trajectories. Frequently, MT effects are assessed from so-called MTR maps (27) derived from the normalized signal difference between scans performed with and without presaturation of restricted pool protons. With non-RF spoiled SSFP, however, MT effects can efficiently be modulated using the on-resonance RF pulse train itself (22): the average saturation rate hWi (see Eq.…”

Section: Figmentioning

confidence: 99%

Superbalanced steady state free precession

Bieri

2011

Magnetic Resonance in Med

View full text Add to dashboard Cite

Steady state free precession (SSFP) signal theory is commonly derived in the limit of quasi-instantaneous radiofrequency (RF) excitation. SSFP imaging protocols, however, are frequently set up with minimal pulse repetition times and RF pulses can thus constitute a considerable amount to the actual pulse repetition time. As a result, finite RF pulse effects can lead to 10-20% signal deviation from common SSFP theory in the transient and in the steady state which may impair the accuracy of SSFP-based quantitative imaging techniques. In this article, a new and generic approach for intrinsic compensation of finite RF pulse effects is introduced. Compensation is based on balancing relaxation effects during finite RF excitation, similar to flow or motion compensation of gradient moments. RF pulse balancing, in addition to the refocusing of gradient moments with balanced SSFP, results in a superbalanced SSFP sequence free of finite RF pulse effects in the transient and in the steady state; irrespective of the RF pulse duration, flip angles, relaxation times, or off-resonances. In multipulse experiments, the time evolution of spins is commonly analyzed in the limit of quasi-instantaneously acting radiofrequency (RF) pulses. This concept separates the Bloch equations (1) into repetitive units of RF excitation and interpulse delays (2) and thereby allows the derivation of closed form solutions to steady state free precession (SSFP) sequences in the steady state (3-7) and the transient phase (8-11). In practice, however, RF pulses have a finite duration (T RF ) and may cause systematic deviations from the solutions derived in the limit of quasi-instantaneous RF pulses (12,13). An introductory example of this behavior is presented in Fig. 1 for balanced SSFP (bSSFP). The range of finite RF pulse effects is illustrated for the steady state amplitude (Fig. 1a) and for the decay factor of the transient (Fig. 1b) as a function of the flip angle (a) for the two extremes of quasi-instantaneous (T RF ! 0) and quasi-continuous (T RF ! pulse repetition time [TR]) excitation. Generally, finite RF pulse effects increase with increasing flip angle and relaxation time ratio (L :¼ T 1 /T 2 ) and show a smooth transition with the fractional RF pulse duration (l :¼ T RF /TR) (12). However, neither bSSFP contrast nor its spin-echo nature is affected by finite RF pulse effects (13).Following the common doctrine, SSFP imaging protocols have minimal TR and short excitation periods. Short RF pulses, however, lead to pronounced magnetization transfer (MT) effects in tissues (14) which may impair the accuracy of common SSFP-based quantitative MR imaging techniques, such as fast relaxation time mapping with inversion recovery SSFP (15,16) or variable nutation SSFP (17). Thus, long RF pulses were proposed to be used with these techniques to suppress MT effects (18,19), but it also became evident that signal modulations from finite RF pulses can no longer be neglected (18,20,21). In principle, signal models of quantitative SSFP imaging techniques c...

show abstract

Experimental allergic encephalomyelitis and multiple sclerosis: lesion characterization with magnetization transfer imaging.

Cited by 580 publications

References 0 publications

Quantitative MRI‐pathology correlations of brain white matter lesions developing in a non‐human primate model of multiple sclerosis

Quantitative MRI‐pathology correlations of brain white matter lesions developing in a non‐human primate model of multiple sclerosis

Association of global brain damage and clinical functioning in neuropsychiatric systemic lupus erythematosus

Superbalanced steady state free precession

Contact Info

Product

Resources

About