摘要:

AbstractMRI revealed activation foci in human somatosensory cortex during protocols involving stimulation of the fingertips with a textured surface. A 2D T2*‐weighted gradient echo sequence was used to acquire images. The imaging protocol included acquiring images while subjects performed specific tactile stimulation paradigms (activation scans) or rested. Three different paradigms were used to produce functional activation using a textured surface to rub the fingertips of one hand. First, motor sensory activation was produced by rubbing the textured surface held in one hand against the fingertips of the opposite hand only during the activation scans. Second, the hand holding the textured surface moved throughout the experiment but touched the fingertips of the opposite hand only during the activation scans. Third, subjects remained still in the magnet throughout the entire study while an investigator rubbed the textured surface against the subjects' fingertips during the activation scans. Images were postprocessed using a cross‐correlation scheme. The results revealed multiple foci of motor sensory activation near the central sulcus, postcentral sulcus, and prefrontal cor

ISSN:1053-1807    

DOI:10.1002/jmri.1880060402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractT1s and magnetization transfer (MT) parameters of 36 intracranial tumors were determined in vivo at 0.1 T to assess their use in tissue characterization. The mobile water relaxation times (T1w) did not differ between tumor groups, whereas the T1s, the apparent MT relaxation times (T1a), and the parameters MT contrast (MTC) differed significantly between several tumor types. The MT rates (Rwm) demonstrated the most significant differences;Rwmvalues could reliably separate high grade and low grade gliomas. T1ws of the tumors were commonly in the same range as that of normal gray matter, whereas other parameters differed from those of normal brain. The results indicate that MT rates are superior to other parameters in the characterization of intracranial tumors and may be also useful clinically in the grading of gliomas.

ISSN:1053-1807    

DOI:10.1002/jmri.1880060403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractWe have evaluated macroscopic white matter abnormalities (visible lesions) together with microscopic abnormalities in the normal appearing white matter (NAWM) of patients with multiple sclerosis (MS) to determine their relative contributions to the development of disability. The total visible lesion volume (TLV) was computed as a measure macroscopic changes, whereas both texture analysis and T2 were used as possible indicators of diffuse disease in the NAWM. Dual echo T2‐weighted SE images were obtained from 41 patients with definite MS: 10 primary progressive (PP), 11 secondary progressive (SP), 10 benign (BE), 10 early relapsing remitting (ERR), as well as from 10 healthy controls. Calculation of T2 and texture parameters were performed in a region of frontal NAWM of patients and controls. The TLV of each patient was measured using a semiautomated lesion detection program.No significant differences were found between the controls and the patients for all texture parameters examined. However, NAWM T2 was longer in the patients than in the controls (P= .02). Mean TLV was highest for SP and lowest for BE and ERR patients. A significant correlation was found between TLV and EDSS (P<.01) but not between NAWM T2 or texture and expanded disability status score (EDSS).Our study suggest that: (a) diffuse changes are present in NAWM, (b) texture analysis is unable to detect any subtle structure in the NAWM abnormalities, possibly because of the limited image resolution; (c) in the development of disability in MS, macroscopic lesions are more important than microscopic abnormalities in the NAW

ISSN:1053-1807    

DOI:10.1002/jmri.1880060404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractThis prospective study evaluates the ability of MRI using T1‐weighted fat‐suppressed spin‐echo (T1FS) and dynamic gadolinium chelate (Gd) enhanced spoiled‐gradient echo (SGE) to detect the presence of pancreatic tumor in patients in whom spiral CT findings are inconclusive.Sixteen consecutive patients who underwent spiral CT and had findings that were considered inconclusive for pancreatic tumor underwent MR within 2 weeks of CT. Spiral CT and MR images were interpreted in a prospective fashion by separate individual investigators blinded to the results of the other imaging modality. CT was performed on a spiral CT scanner. MRI was performed on a 1.5‐T MR machine. Imaging sequences included T1FS pre‐Gd and post‐Gd and SGE pre‐Gd and immediately post‐Gd. Data were analyzed using receiver operating characteristic (ROC) analysis. Confirmation was obtained by pancreatic biopsy (n= 4), surgical resection (n= 1), and clinical imaging (n= 4) or clinical follow‐up (n= 7).MRI was superior to spiral CT (P= .027) in this selected patient group at detecting or excluding pancreatic tumor by ROC analysis, with areas under the curve of .982 and .764, respectively, which was significant (P= .041). The greatest advantage of MRI was in patients in whom spiral CT demonstrated enlargement of the pancreatic head without clear definition of tumor, which was significant (P= .033). In 10 patients with this CT appearance, MRI demonstrated a high confidence for presence of tumor in four and a high confidence of absence in six. Association of imaging findings with patient diagnosis was significant for MRI (P= .001) but not significant for CT (P= .148).The results of our study suggest that MRI may add significant diagnostic information in patients in whom spiral CT is inconclusive for the presence of pancreatic tumor. The greatest advantage of MRI was in the evaluation of patients in whom spiral CT findings revealed an indeterminate enlar

ISSN:1053-1807    

DOI:10.1002/jmri.1880060405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractForty‐one patients with 61 proved focal liver lesions underwent MRI of the liver at 1.0 T, with the aim of evaluating the usefulness of turbo spin‐echo (TSE) sequences in characterizing focal liver lesions, by comparing them with conventional spin‐echo (CSE) sequences. Two different TSE protocols were employed, with constant echo time and varying repetition time: TSE‐S (3000 msec) and TSE‐L (5100 msec). All images were evaluated quantitatively (signal‐to‐noise ratio ‘SNR’) and qualitatively: because benign lesions were all liquid (12 cysts and 10 hemangiomas), they were well characterized morphologically on the basis of signal intensity.Mean SNR was significantly different between metastases and benign lesions (P<.0001) with all T2 sequences. Among the single T2 sequences tested, logistic regression analysis showed TSE‐L to have the best predictive ability of the nature of focal lesions, with a G value of 42.02, compared to 29.87 of TSE‐S and 25.55 of CSE second echo (SE II). The combination of TSE‐L with TSE‐S did not modify these results, whereas the combination of TSE‐L with CSE only resulted in slight improvement (G= 46.95). Comparison of the receiver operating characteristic (ROC) curves showed only SE II (area under the ROC curve of .8312) to be significantly inferior to the best single sequence, or TSE‐L (area under the ROC curve of .9176;P= .027). All sequences were equivalent in qualitative evaluation, with good reproducibility, sensitivity ranging from .94 to 1.0, and specificity ranging from .86 to .93.This study confirms the value of TSE sequences in characterization of focal liver lesions. Time of acquisition is strongly reduced with these sequences, whereas results are fairly similar to those obtained with CSE. TSE sequences could therefore replace CSE for the

ISSN:1053-1807    

DOI:10.1002/jmri.1880060406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractTo compare liver lesion detection rates, tissue signal and noise data, and qualitative parameters for breathhold (BH) and non‐breath‐hold (NBH) hybrid rapid acquisition with relaxation enhancement (RARE) and conventional spin‐echo (CSE) T2‐weighted (CSE‐T2) MR sequences, 20 patients were imaged using all three sequences. Lesion detection rates were 73.5% for the CSE‐T2 sequence and 81.1% and 88.6% for the BH‐RARE and NBH‐RARE sequences, respectively (P= .027). Mean lesion‐to‐liver signal‐difference‐to‐noise ratio for the NBH‐RARE sequence was 14.0 ± 11.5, significantly greater than 9.8 ± 7.8 obtained for the BH‐RARE sequence (P= .050) and 9.0 ± 6.2 obtained for the CSE‐T2 sequence (P= .015). The NBH‐RARE sequence demonstrated fewer artifacts and greater overall image quality compared to the CSE‐T2 sequence. The NBH‐RARE sequence is a useful alternative to the CSE‐T2 sequence providing a higher mean lesion‐to‐liver signal‐difference‐to‐noise ratio and le

ISSN:1053-1807    

DOI:10.1002/jmri.1880060407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractThe accuracy of water T2 maps generated from a fast spin‐echo (FSE) sequence was compared with data obtained by conventional single and multi‐echo spin‐echo pulse sequences using a commercial gel phantom. Spatially localized stimulated echo acquisition mode (STEAM) proton spectroscopy was also used to confirm the reported water T2 values of the gels contained in the phantom. The FSE sequence was shown to be superior in accuracy to both the single and multi‐echo spin echo sequences and comparable to STEAM, producing results that were within 10% of known values. The effectiveness of the FSE sequence was further demonstrated by generating T2 maps of the normal and diseased prostate in clinically acceptable imaging times, resulting in comparable T2 values to those obtained using STEAM. Accurate quantitative T2 maps can be produced with the FSE s

ISSN:1053-1807    

DOI:10.1002/jmri.1880060408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractIn 24 patients presenting with 55 renal lesions (mean size, 20.8 mm), single‐breath‐hold (SBH) fast spin‐echo (FSE) techniques allowing T1 and T2 images to be produced within 20 and 23 sec, respectively, were compared with routine non‐breath‐hold (NBH) spin‐echo (SE) T1 and NBH‐FSE T2 sequences. Contrast‐to‐noise ratios (CNRs) measured from SBH‐FSE T1 images were an average of 97% higher than their NBH counterparts (P= .0001) and allowed an improved lesion conspicuity in 80% of the cases (P= .0001). For T2 imaging, SBH‐FSE and NBH‐FSE sequences were not statistically different with respect to lesion conspicuity (P= .55) and CNR values (P= .19). This was observed despite a 35% average decrease in CNR of SBH‐FSE compared to NBH‐FSE images. By reducing respiratory motion artifacts while preserving SE‐like image contrast, SBH‐FSE techniques have the potential to replace routine NBH sequences for an op

ISSN:1053-1807    

DOI:10.1002/jmri.1880060409

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractStunned myocardium has been detected in patients treated successfully with thrombolytic agents. The hypothesis of this study was that fast gradient echo (GRE) imaging could be used to characterize the regional functional and perfusion abnormalities that are indicative of myocardial stunning. This study was designed to monitor and correlate the extent of wall thickness and perfusion abnormalities as determined by fast (segmented k space) cine and contrast enhanced GRE imaging, respectively. Dogs were subjected to left circumflex (LCX) coronary artery occlusion (15 min) followed by 30‐minute reperfusion (n= 8). Perivascular flow probes were used to continuously measure flow in left anterior descending (LAD) and LCX coronary arteries. Short‐axis inversion recovery prepared fast GRE and cine images were acquired at baseline, at occlusion, and at 1, 10, and 30 minutes of reflow. Regional signal intensity and percent systolic wall thickening were determined at 26 equally spaced circumferential positions to compare the extent of functional and perfusion abnormalities. During occlusion and reperfusion, the ischemic region was demonstrated on contrast‐enhanced images as a hypointense and hyperintense region, respectively. During occlusion, the extent of the perfusion defect (32% ± 2% of the circumference of the equatorial slice) correlated closely (r= .74) with the extent of contractile dysfunction (35% ± 2%). After reperfusion, there was transient recovery in the percent wall thickening (26% ± 4% vs 36% ± 4% normal), coinciding with the reactive hyperemic response, but this was followed by a significant decline in wall thickening at 10 minutes (19% ± 4%) and 30 minutes (12% ± 2%). Fast MR imaging may be useful to monitor postischemic myocardial abnormalities after thrombolytic therapy and the response to pharmacologic in

ISSN:1053-1807    

DOI:10.1002/jmri.1880060410

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractThe purpose of this paper was to evaluate the use of dynamic gadopentetate dimeglumine‐enhanced, breath‐hold spoiled gradient‐recalled (SPGR) MR imaging with cardiac compensation (CMON) compared to spin‐echo MR imaging in patients with thoracic malignancy. We retrospectively reviewed MR images from 29 patients with thoracic tumors. MR imaging included axial electrocardiogram (ECG)‐gated T1‐weighted, fast spin echo (FSE) T2‐weighted, and contrast‐enhanced breath‐hold fast multiplanar SPGR imaging with CMON, which selects the phase‐encoding gradient based on the phase within the cardiac cycle. Images were reviewed for lung masses, mediastinal or hilar tumor, disease of the pleura, chest wall, and bones, and vascular compression or occlusion. Contrast‐enhanced fast multiplanar SPGR imaging with CMON produces images of the chest that are free of respiratory artifact and have diminished vascular pulsation artifact. ECG‐gated T1‐weighted images were preferred for depicting mediastinal and hilar tumor. The gadopentetate dimeglumine‐enhanced fast multiplanar SPGR images were useful for depicting chest wall tumor, vascular compression or thrombosis, osseous metastases, and in distinguishing a central tumor mass from peripheral lung consolidation. Pleural tumor was depicted best on the FSE T2‐weighted images and the contrast‐enhanced SPGR images. As an adjunct to spin echo T1‐weighted and T2‐weighted imaging, contrast‐enhanced fast multiplanar SPGR imaging with CMON is useful in

ISSN:1053-1807    

DOI:10.1002/jmri.1880060411

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY