Thirty-five patients scheduled to undergo a neck dissection for squamous cell carcinoma of the head and neck were evaluated preoperatively by magnetic resonance (MR) imaging. Axial and occasionally ...sagittal and coronal images were obtained. To define the most reliable technique to detect cervical lymph node metastasis, we compared several MR pulse sequences with and without Gd-DTPA administration to histopathologic findings in the neck dissection specimens. T1-weighted spin echo combined with T2-weighted gradient recalled echo (GE) sequences were found to be more useful than any other combination of pulse sequences in localizing lymph nodes. On T2-weighted GE images, lymph nodes were depicted with intermediate to high signal intensity in contrast to low signal muscular and fatty tissue. Gadolinium DTPA enhanced T1-weighted GE images reliably depict central lymph node necrosis, the most specific criterion for lymph node metastasis.
Purpose:
In Multiple Sclerosis (MS) increasing attention is given to cortical demyelination. At 1.5T, cortical lesions are best visualized with Fluid Attenuated Inversion Recovery (FLAIR) and Double ...Inversion Recovery (DIR) sequences. At higher field, the gain in SNR can be used to increase spatial resolution, which may enhance the sensitivity of these sequences. In this study FLAIR and DIR are compared with 2D PD/T2, and 3D-T1 weighted imaging at 3 and 7 Tesla.
Materials and Methods:
15 MS patients and 5 healthy volunteers were examined at 3T (GE HDxt) and 7T (Philips, Achieva), at time intervals <2 weeks. 3D sequences were used for T1, FLAIR and DIR, and conventional 2D Pd/T2 weighted imaging. Total acquisition time was about 50min. on both scanners. No adverse reactions or complaints of subjects were observed. Images were evaluated for quality and artefacts. Lesions were scored and classified per location: peri-ventricular (PV), deep white matter (DWM), juxta-cortical (JC), mixed grey/white matter (type I) and grey matter lesions (type II). Other lesion types were infrequently found but were not used for this comparison.
Results:
Images at 7T with high spatial resolution showed high contrast between cerebral structures. In controls only two atypical lesions were found, which were visible on all sequences and at both field strengths. Provisional analysis showed higher numbers of lesions for all 7T sequences. Especially around the cortex, lesion detection was substantially improved as compared with 3T. At 7T FLAIR, the outer cortical layers appear hyper-intense 4, which cannot be seen at 3T. DIR images at 7T show a similar phenomenon, which can influence classification of lesions around the motor cortex. Furthermore, DIR images at 7T have poorly attenuated peri-vascular spaces (PVS) in white matter which can be mistaken for lesions. However, the differentiation between inflammatory white matter lesions and pure PVS can be made by following them over several slices.
Conclusion:
Overall, higher lesion numbers were observed at 7T than at 3T, thanks to high resolution as well as higher signal and contrast to noise factors. Additionally, 7T revealed different contrasts as compared with 1.5 and 3.0T. These changes ask for a reassessment of image interpretation in MS patients at higher field. This is the first demonstration in patients of clinically feasible, high contrast and high resolution, non contrast enhanced 3D FLAIR and DIR at 7T. The higher sensitivity at 7T is particularly seen for cortical lesions, which are smaller than WM lesions.
We used high-resolution MRI to study the post-mortem appearance of spinal cord multiple sclerosis in relation to histopathology and low-resolution images. Fifty-nine 3 cm long formalin-fixed spinal ...cord specimens from 19 multiple sclerosis patients and three controls were studied. Clinical characteristics of each patient were reviewed. High-field MRI consisted of proton-density weighted spin-echo imaging with an in-plane resolution of 80 μm. Specimens were also imaged at 1.0 T, with 1 mm pixel resolution. After MRI, the specimens were cut at 5 mm intervals and stained for myelin (Luxol fast blue/cresyl violet) and axons (Bodian method). Two observers scored the MRIs for abnormalities and divided them into (i) well-delineated areas of high signal intensity (SI) and (ii) poorly defined areas of mildly increased SI. Abnormalities were scored semiquantitatively, white matter and grey matter separately. In 81 sections the total area of abnormalities per section was measured on both histopathology sections and on matched high-field MRIs. Abnormalities ranged from just a few abnormal areas to complete involvement of the spinal cord specimen. Patients with an aggressive disease course had more abnormalities than patients with a mild or intermediate disease course. Areas of mildly increased SI were seen in all specimens, and were often found around focal high-SI lesions. However, in six patients, areas of mildly increased SI were the predominant finding on the MRIs, correlating with a primary progressive disease course. Histopathologically, high-SI areas correlated with complete demyelination, while mildly increased SI corresponded with partial demyelination. All areas scored as abnormal by the neuropathologist were also found on the MRIs, and sizes measured using both methods correlated well (r = 0.85, P < 0.01). On conventional MRIs, abnormalities could be recognized fairly well. However, better differentiation could be made between high-SI and mildly increased SI abnormalities on the 4.7 T images. In conclusion, high-resolution MRI revealed a great range of abnormalities in spinal cord multiple sclerosis, which related to disease course during life. Furthermore, we found very good correlation between the extent of abnormalities shown by histopathology and the SI changes on proton-density MRIs, mainly relating to demyelination revealed histopathologically.
As society demands for an ever more reliable and sustainable energy supply, distribution system operators (DSOs) are driven to minimize the impact of faults in their grids and reduce network losses. ...This paper describes a method for optimal placement of distribution automation (DA) in closed-ring medium voltage (MV) distribution grids, resulting in a more efficient distribution of electrical energy, while ensuring reliable grid operation.
MR imaging of the normal larynx Castelijns, J A; Doornbos, J; Verbeeten, Jr, B ...
Journal of computer assisted tomography,
1985 Sep-Oct, Letnik:
9, Številka:
5
Journal Article
Recenzirano
Magnetic resonance imaging of the larynx was performed on 15 volunteers. Searching for optimal images in the sagittal, frontal, and transverse planes, we compared images made with a special surface ...coil and the standard head coil, images with different slice thicknesses, images with different repetition times (TR) and images with different matrices. The field of view and the scan times were kept as small as possible. Using a surface coil, we obtained high resolution images in all three planes. These images provide clinically relevant information, not shown by current radiological techniques: hyoepiglottic ligament, thyrohyoid ligament, thyroepiglottic ligament and cricothyroid ligament, the borders between the preepiglottic space and both paraglottic spaces (PGS), the borders between both PGS and thyroid cartilage, and the vocalis and thyroarytenoid muscles. Short TR is preferred because, with shorter scan time, more measurements could be made. Images with a 128 X 128 matrix size had a much better signal-to-noise ratio than images with a 256 X 256 matrix size. Magnetic resonance has great potential in imaging normal and pathological anatomy of the larynx.
The synthesis and characterization of a new series of polypropylenimine dendrimers is reported. Using a repetition of the sequence of a Michael addition to a primary amine, followed by a ...heterogeneously catalyzed hydrogenation, ultra-pure polypropylenimine macromolecules with molecular weights up to 6912 are synthesized. The reaction sequence allows the preparation of these dendrimers at very large scales, whilst the availability of a simple purification in the sequence affords ultra-pure samples. The polypropylenimine dendrimers are fully characterized; apart from the first 0.5 generation they are all oils, possess a Tg in the range from −90 to −40 °C, are unexpectedly stable, and their intrinsic viscosity drops after generation 4.
A swelling in the neck is often caused by one or more enlarged lymph nodes, usually due to a harmless disorder. Particularly in adults, a swelling in the neck may represent a metastasis of a ...malignancy in the head and neck region, for instance a squamous cell carcinoma arising from the oral mucosa. Palpation of the neck can provide valuable information, although its reliability is restricted, even when executed by an experienced clinician. Therefore, additional examination is required,for instance by fine needle aspiration cytology, ultrasound examination with or without guided fine needle aspiration, computer tomography and magnetic resonance imaging. In case a malignant tumour has been diagnosed in the upper aerodigestive tract, a sentinel node procedure may be performed. The question arises whether general practicing dentists should examine routinely every patient's neck, or only the necks of patients older than 40 years of age.
Imaging of laryngeal cancer CASTELIJNS, J. A; HERMANS, R; VAN DEN BREKEL, M. W. M ...
Seminars in ultrasound, CT, and MRI,
1998, Letnik:
19, Številka:
6
Journal Article
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