Serial Magnetization Transfer Research Articles

Magnetization Transfer MRI of Breast Cancer in the Community Setting: Reproducibility and Preliminary Results in Neoadjuvant Therapy.

Repeatability and reproducibility of magnetization transfer magnetic resonance imaging of the breast, and the ability of this technique to assess the response of locally advanced breast cancer to neoadjuvant therapy (NAT), are determined. Reproducibility scans at 3 different 3 T scanners, including 2 scanners in community imaging centers, found a 16.3% difference (n = 3) in magnetization transfer ratio (MTR) in healthy breast fibroglandular tissue. Repeatability scans (n = 10) found a difference of ∼8.1% in the MTR measurement of fibroglandular tissue between the 2 measurements. Thus, MTR is repeatable and reproducible in the breast and can be integrated into community imaging clinics. Serial magnetization transfer magnetic resonance imaging performed at longitudinal time points during NAT indicated no significant change in average tumoral MTR during treatment. However, histogram analysis indicated an increase in the dispersion of MTR values of the tumor during NAT, as quantified by higher standard deviation (P = .005), higher full width at half maximum (P = .02), and lower kurtosis (P = .02). Patients' stratification into those with pathological complete response (pCR; n = 6) at the conclusion of NAT and those with residual disease (n = 9) showed wider distribution of tumor MTR values in patients who achieved pCR after 2–4 cycles of NAT, as quantified by higher standard deviation (P = .02), higher full width at half maximum (P = .03), and lower kurtosis (P = .03). Thus, MTR can be used as an imaging metric to assess response to breast NAT.

Perilesional gliosis around solitary cerebral parenchymal cysticerci and long-term seizure outcome: A prospective study using serial magnetization transfer imaging

Epilepsy following solitary cerebral cysticercosis (SCC) is possibly caused by perilesional gliosis, best visualized on magnetization transfer imaging (MTI).This study aims to describe development of gliosis around SCC by prospective serial MTI and to correlate this gliosis with long-term seizure outcome. We randomized 123 patients with SCC and new-onset seizures to treatment with albendazole plus antiepileptics (treatment), or antiepileptics only (control), and performed magnetic resonance imaging (MRI) scans at 0, 3, 6, 12, and 24 months. Prospective follow-up data regarding seizure outcome up to 5 years later were collected. MRI studies were analyzed for lesion characteristics and perilesional magnetization transfer (MT) hyperintensity. Clinical and radiologic data of 77 patients were analyzed. Demographic and seizure characteristics were similar in treatment and control groups. Clinical data were available up to 64 months after enrollment. At 12 months, 89.5% patients were seizure-free. MTI is more sensitive than routine imaging for detection of perilesional gliosis. Albendazole treatment did not affect imaging or clinical outcome, including development of gliosis. Independent of duration of follow-up, gliosis was associated with more seizures, and with seizure recurrence at 12 months; duration of seizures and antiepileptic therapy was longer. Gliosis was not dependent on seizure type or stage of degeneration at enrollment or persistence/calcification of the lesion. Perilesional gliosis around SCC helps prognosticate seizure outcome. Poorer outcome in patients with persistent lesions is likely to be related to mechanisms other than gliosis. The lack of effect of albendazole on seizure outcome may be due to its inability to decrease formation of gliosis.

Enhancing Central Nervous System Remyelination in Multiple Sclerosis

Recent studies on adult neural stem cells and the developmental biology of myelination have generated the expectation that neural precursors can repair the damaged central nervous system of multiple sclerosis patients where the endogenous remyelination process has failed. As a result, many laboratories are engaged in translational studies in which the goal is to design ways to promote remyelination and repair. Here we raise issues highlighted by prior experimental and human work that should be considered lest these studies become "lost in translation."

Serial magnetization transfer imaging in acute optic neuritis

MAGNETIZATION TRANSFER IMAGING (MT) ALLOWS the examination of tissues in more details than conventional MRI. In serial studies of multiple sclerosis lesions, reductions in magnetization transfer ratio (MTR) are thought to be due to demyelination and axonal loss, with later rises due to remyelination. In this study, the authors followed serial changes in MTR in acute optic neuritis in combination with clinical and electrophysiological measurements to determine if the MTR changes over time mirror the picture in multiple sclerosis lesions. They included 29 patients who had acute optic neuritis for a median of 13 days (range 7–24 days) since the onset of visual symptoms. A clinical examination and measurement of visual evoked potentials (VEP) was performed on each patient. Their optic nerves were imaged with a fat-saturated fast spin echo (FSE) sequence and a magnetization transfer sequence. Twenty-one had multiple subsequent examinations over the course of 1 year. In addition, 27 control subjects had their optic nerves imaged up to three times over 1 year. A blinded observer segmented the optic nerves from the MTR maps. Lesions were defined on the acute FSE images and, from the coordinates, the ratio of mean lesion MTR : healthy nerve MTR (lesion ratio) was calculated for each dataset. The time-averaged mean MTR in control optic nerves was 47.7 per cent units (pu). In diseased optic nerves, baseline mean MTR was 47.3 pu, with a mean lesion ratio of 0.98. The diseased optic nerve MTR and lesion ratio declined over time with a nadir at about 240 days at a mean MTR value of 44.2 pu and mean lesion ratio of 0.91. After 1 year the diseased optic nerve mean MTR was 45.1 pu (mean lesion ratio 0.93), although the difference was not significant compared with the nadir value. For each 0.01 increase in time-averaged lesion ratio logMAR visual acuity recovery improved by 0.03 (95% CI, 0.002, 0.08, P = 0.02). Time-averaged VEP central field latency was shorter by 6.1 ms (95% CI 1.5, 10.7, P = 0.012) per 1 pu rise in time-averaged diseased optic nerve MTR. The authors conclude that early fall in diseased optic nerve MTR is consistent with demyelination and Wallerian degeneration of transected axons. The late nadir compared with studies of multiple sclerosis lesions may have been due to slow clearance of myelin debris. Remyelination may have influenced subsequent MTR changes. The observations support using MTR to monitor symptomatic demyelinating lesions.—Valérie Biousse

Serial magnetization transfer imaging in acute optic neuritis.

In serial studies of multiple sclerosis lesions, reductions in magnetization transfer ratio (MTR) are thought to be due to demyelination and axonal loss, with later rises due to remyelination. This study followed serial changes in MTR in acute optic neuritis in combination with clinical and electrophysiological measurements to determine if the MTR changes over time mirror the picture in multiple sclerosis lesions, further validating MTR as a marker of tissue integrity. Twenty-nine patients were recruited who had acute optic neuritis for a median of 13 days (range 7-24 days) since the onset of visual symptoms. A clinical examination and measurement of visual evoked potentials (VEP) was performed on each patient. Their optic nerves were imaged with a fat-saturated fast spin echo (FSE) sequence and a magnetization transfer sequence. Twenty-one had multiple subsequent examinations over the course of 1 year. In addition, 27 control subjects had their optic nerves imaged up to three times over 1 year. A blinded observer segmented the optic nerves from the MTR maps. Lesions were defined on the acute FSE images and, from the coordinates, the ratio of mean lesion MTR : healthy nerve MTR (lesion ratio) was calculated for each dataset. The time-averaged mean MTR in control optic nerves was 47.7 per cent units (pu). In diseased optic nerves, baseline mean MTR was 47.3 pu, with a mean lesion ratio of 0.98. The diseased optic nerve MTR and lesion ratio declined over time with a nadir at about 240 days at a mean MTR value of 44.2 pu and mean lesion ratio of 0.91. Subsequently, diseased optic nerve MTR appeared to rise; after 1 year the diseased optic nerve mean MTR was 45.1 pu (mean lesion ratio 0.93), although the difference was not significant compared with the nadir value. For each 0.01 increase in time-averaged lesion ratio logMAR visual acuity recovery improved by 0.03 (95% CI, 0.002, 0.08, P = 0.02). Time-averaged VEP central field latency was shorter by 6.1 ms (95% CI 1.5, 10.7, P = 0.012) per 1 pu rise in time-averaged diseased optic nerve MTR. The early fall in diseased optic nerve MTR is consistent with demyelination and Wallerian degeneration of transected axons. The late nadir compared with studies of multiple sclerosis lesions may have been due to slow clearance of myelin debris. Remyelination may have influenced subsequent MTR changes. The observations support using MTR to monitor symptomatic demyelinating lesions.

Serial magnetization transfer imaging measures in patients with multiple sclerosis

Serial magnetization transfer imaging measures in patients with multiple sclerosis

Serial Magnetization Transfer Ratio Imaging Of MS

Serial Magnetization Transfer Ratio Imaging Of MS

Early structural changes in acute MS lesions assessed by serial magnetization transfer studies.

Whether acute MS lesions are primarily inflammatory or demyelinative is unresolved. Our study examined acute MS lesions longitudinally by quantitative magnetization transfer (MT), an MRI technique that identifies tissue integrity and destruction. Four MS patients were studied by serial MRI including MT, conventional T2-weighted images, and postgadolinium T1-weighted images for 9 to 12 months. In 15 new lesions, the MT ratio (MTR) was calculated retrospectively. In 13 lesions, a marked decrease in the MTR was present early during the first 2 months after the onset of the lesion and was followed by a variable increase. In two other lesions, the MTR progressively declined. These results suggest that major early structural changes compatible with demyelination and followed by remyelination and gliosis, or by continuous demyelination, occur in new MS lesions. The various MTR profiles provide in vivo confirmation of the current knowledge of the progression in MS lesions. Furthermore, MTR may be used to monitor in vivo drug efficacy in new MS lesions.

Serial magnetization transfer imaging to characterize the early evolution of new MS lesions.

To explore the temporal relation of demyelination and blood-brain barrier breakdown during new lesion formation. Conventional MRI appears sensitive for detecting changes due to MS, but may be limited by poor pathologic specificity. By indirectly assessing protons bound to rigid macromolecules, magnetization transfer (MT) imaging may provide information relating to tissue structure and, by inference, myelin integrity. Gadolinium contrast-enhanced MRI and MT imaging were performed at weekly intervals for 3 months in three patients with MS. For each enhancing lesion, the largest corresponding area of proton density hyperintensity seen during the study was outlined and magnetization transfer ratio (MTR) calculated at each time point from coregistered calculated MTR images. Lesions greater than 20 mm2, not affected by partial volume effects, and first enhancing after the baseline study were analyzed. Two-dimensional registration software allowed accurate evaluation of MTR in regions both before and after the initial appearance of MS lesions. Mean lesion MTR decreased significantly during the first week of enhancement (29.6 percent units [pu] immediately pre-enhancement versus 28.2 pu at first documented stage of enhancement). No significant MTR reduction was noted before this. The lack of observable change in MTR before the first detectable gadolinium enhancement within MS lesions suggests that blood-brain barrier disruption is closely related to, but not preceded by, demyelination.

Serial magnetization transfer and contrast-enhanced MR imaging in multiple sclerosis

Serial magnetization transfer and contrast-enhanced MR imaging in multiple sclerosis