PURPOSE: We developed and evaluated clinically T1-weighted three-dimensional gradient-echo magnetization transfer (MT) sequences for contrast-enhanced MR imaging of the brain.METHODS: A short-repetition-time, radio frequency-spoiled, 3-D sequence was developed with a 10-millisecond MT pulse at high MT power and narrow MT pulse-frequency offset, and the enhancing lesion-to-normal white matter background (L/B) and the contrast-to-noise (C/N) ratios on these images were compared with those on T1-weighted spin-echo images and on non-MT 3-D gradient-echo images in a prospective study of 45 patients with 62 enhancing lesions. In the 24 patients who had intracranial metastatic disease, the number of lesions was counted and compared on the three types of images.RESULTS: The MT ratio of normal callosal white matter was 55% on the MT 3-D gradient-echo sequences, The L/B and C/N on the MT 3-D gradient-echo images were more than double those on the 3-D gradient-echo images, and were significantly greater than those on the T1-weighted spin-echo images, In patients with metastatic disease, the MT 3-D gradient-echo images showed significantly more lesions than did the T1-weighted spin-echo or 3-D gradient-echo images.CONCLUSION: MT 3-D gradient-echo MR imaging improves the contrast between enhancing lesion and background white matter over that obtained with conventional T1-weighted 3-D gradient-echo and spin-echo imaging. MT 3-D gradient-echo imaging provides practical sampling, image coverage, and spatial resolution attributes that may be advantageous over MT T1-weighted spin-echo techniques.

We describe a patient with AIDS who presented with an acute encephalitis caused by infection with varicella-zoster virus. The hemorrhagic, necrotizing encephalitis had an unusual MR appearance, with innumerable discrete, small, targetlike lesions in the right cerebral hemisphere, which were coalescent in the posterior temporal, parietal, and occipital regions. Of the several known disease patterns of varicella-zoster viral infection in the CNS, this histopathologic pattern of multifocal leukoencephalitis is rare. It is important to recognize, as effective antiviral drug treatments are available.

PURPOSE:To develop a simple tissue phantom to study the effects of various imaging parameters and gadolinium concentrations on magnetization transfer (MT) and lesion-to-background ratios.METHODS:A commercial egg product was doped with gadolinium in concentrations of 0.0 to 1.0 mmol/L and cooked. The T1 and T2 values were determined for the phantom materials and for the white and gray matter of a healthy volunteer subject. The gadolinium-doped egg phantom and human brain were studied using a short-repetition-time three-dimensional gradient-echo MT sequence with various effective MT powers, frequency offsets, and section-select flip angles. The normalized signal intensities, MT ratios (MTRs), and simulated lesion-to-background normal white matter contrast ratios were determined for a variety of experimental conditions.RESULTS:The MTR and lesion-to-background contrast ratios for all materials were greatest at the highest effective MT power (270 Hz, root-mean-square of amplitude) and the narrowest MT pulse frequency offset (1000 Hz). There was an inverse relationship between gadolinium concentration and MTR, and a positive relationship between the gadolinium concentration and lesion-to-background contrast. MTR was greatest at low flip angles, where there was little T1 weighting. The simulated lesion-to-background contrast showed a complex, gadolinium concentration-dependent relationship with section excitation flip angle.CONCLUSIONS:The tissue phantom has relaxation properties and MT behavior close to that expected for enhancing brain lesions, allowing a rigorous analysis of simulated lesion-to-background contrast for high MT power, short-repetition-time, three-dimensional gradient-echo sequences.

PURPOSE: To evaluate white matter disorders with magnetization transfer (MT) techniques.MATERIALS AND METHODS: In 46 healthy volunteers and 46 clinical patients, MT Z spectra were obtained with various continuous-wave-equivalent MT powers (B1(cw)) and frequency offsets.RESULTS: With B1(cw) of 270 Hz and 4,000-Hz frequency offset, the MT ratio of normal callosal white matter was 59.2% +/- 1.5 (standard deviation), with less than 5% contribution from direct saturation and spin locking. A small statistically significant (P < .01) regional variation in normal white matter was seen. Plaques in MS patients had a broad (or wide) range of MT ratios; normal appearing white matter had a slightly reduced MT ratio. Vasogenic edema had a minimal effect on MT ratio, and radiation necrosis showed prominent reductions in MT ratio.CONCLUSION: High MT power techniques can expand the dynamic range of MT ratios, maintain a relatively pure MT effect, and be used effectively in MT imaging to evaluate white matter disorders.

Two cases of trilateral retinoblastoma (a syndrome of midline, undifferentiated, intracranial tumor in a child with hereditary, bilateral ocular retinoblastoma) are described, one with a unique location of the intracranial tumor, and the other with an unusual temporal course of disease.

PURPOSE To prove that the contrast of enhancing brain lesions on post-gadolinium T1-weighted spin-echo (SE) images can be statistically significantly improved with magnetization-transfer (MT) indirect saturation. MATERIALS AND METHODS The contrast-to-noise ratios (C/Ns) of 201 enhancing brain lesions in 110 patients were compared on conventional and MT T1-weighted SE images obtained at 1.5 T after injection of 0.05-0.10 mmol/kg gadopentetate dimeglumine or gadodiamide. RESULTS The MT T1-weighted SE images showed a 37% reduction in signal intensity of background white matter and thereby provided a 108% improvement in the C/N of enhancing brain lesions over the conventional T1-weighted SE images (P < .001). CONCLUSION The C/Ns obtained with single-dose gadolinium and the MT T1-weighted SE technique were twice those obtained with the conventional technique and are at least equivalent to reported values obtained with triple-dose gadolinium and conventional T1-weighted SE images.

Previous theoretical reports described the dependence of interpretation of the observed phase of the NMR signal on the time origin(s) of moment calculations and position's Taylor series expansion. This work provides experimental confirmation of predictions derived from that theory. For accelerative motion, experimental phase-encoded velocity measurements give instantaneous values at a time corresponding to the origin used for waveform moment calculations. For laminar flow, experimental intensity profiles agree well with theoretical simulations; new findings extend amplitude and spatial distributions of oblique flow profiles beyond previous descriptions. Experiments using sequences with controlled position of the time origins for phase and read axes show that displacement and motion artifacts are reduced when they're coincident (pulsed flow, nongated acquisitions), and virtually eliminated when combined with gating. Potentially significant clinical consequences of coincident and noncoincident time origins are demonstrated in human head MIP MRA images. These results have fundamental implications in waveform design.

The authors present two cases of 5-month-old children with early infantile Krabbe disease studied by CT and MR. Both infants had characteristic CT scans for the disease consisting of symmetric hyperdensity involving the cerebellum, thalami, caudate, corona radiata, and brain stem. One of the infants had a deceptively normal initial MR examination, with dramatic progression of the white-matter disease over the following 4 months.

PURPOSE: To evaluate whether magnetization transfer (MT) can improve image contrast on gradient-recalled echo (GRE) magnetic resonance (MR) images of the cervical spine.MATERIALS AND METHODS: Sagittal and axial two-dimensional conventional GRE and MT GRE images were obtained in 103 patients with degenerative disk disease or intrinsic cord lesions. The contrast-to-noise ratios (C/Ns) for the cervical spinal cord and cerebrospinal fluid (CSF) were compared for images obtained at various MT power level and section-select flip angle combinations. Axial three-dimensional GRE images were also obtained with application of MT and C/N evaluated in 10 additional patients.RESULTS: Tailored two-dimensional MT GRE Images, obtained with a moderate MT power level and a section-select flip angle similar to the Ernst angle for CSF, provided an average of 2.2-2.4-fold improvement in spinal cord-CSF C/N than conventional GRE images (P < .001).CONCLUSION: The MT GRE images demonstrated superior delineation of disk herniations, foraminal stenosis, and intrinsic cord lesions over conventional GRE and T2-weighted spin-echo images in clinical cervical spine examinations.