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At least 415 records · Page 23Linked to original sources
PubMed1995

Acute subarachnoid hemorrhage: MR imaging with fluid-attenuated inversion recovery pulse sequences.

PURPOSE: To evaluate the usefulness of fluid-attenuated inversion recovery (FLAIR) magnetic resonance (MR) imaging sequences in the detection of acute subarachnoid hemorrhage (SAH). MATERIALS AND METHODS: MR imaging with FLAIR sequences was performed with a 0.5-T superconducting unit in 20 patients (aged 30-72 years) with acute SAH due to a ruptured aneurysm and in 27 control subjects (aged 32-72 years). FLAIR images were obtained 2 hours to 2 days after ictus. Findings were evaluated and compared with computed tomographic (CT) findings. RESULTS: In all patients, acute SAH was clearly demonstrated as an area with signal intensity that was high relative to that of the normal cerebrospinal fluid and surrounding brain parenchyma at FLAIR imaging. This sequence was especially useful in demonstration of acute SAH in the posterior fossa, which was difficult to show at CT because of beam-hardening artifacts. In a double-blind comparison, no FLAIR images acquired in control subjects were confused with those acquired in control subjects were confused with those acquired in patients. CONCLUSION: FLAIR sequences reliably provide diagnostic images in patients with acute SAH.

Acute Disease↗
PubMed1998

Focal hepatic lesion detection: comparison of four T2-weighted MR imaging pulse sequences.

PURPOSE: To evaluate T2-weighted magnetic resonance (MR) imaging with conventional spin-echo, breath-hold fast spin-echo, respiratory-triggered fast spin-echo, and breath-hold multishot spin-echo echo-planar sequences for detection of focal hepatic lesions. MATERIALS AND METHODS: T2-weighted MR images obtained with the four sequences in 56 patients with 107 solid and 124 nonsolid lesions were retrospectively analyzed. Image review was conducted on a liver segment-by-segment basis; a total of 408 liver segments were reviewed separately and independently for solid and nonsolid lesions by three radiologists. Diagnostic accuracy was evaluated with receiver operating characteristic analysis. RESULTS: Lesion-to-liver contrast-to-noise ratio was highest with multishot echo-planar images of both solid and nonsolid lesions. Diagnostic accuracy for solid lesions was statistically significantly better with conventional spin-echo images than with any other type of image (P < .0001). Diagnostic accuracy for nonsolid lesions was statistically significantly better with respiratory-triggered fast spin-echo images than with any other type of image (P < .0001). Image quality was best with breath-hold fast spin-echo images. CONCLUSION: Conventional spin-echo MR imaging should not be replaced with breath-hold fast spin-echo or multishot spin-echo echo-planar imaging, despite the shorter acquisition times that are possible with the latter two sequences.

Female↗
PubMed1999

Focal hepatic lesion detection: comparison of four fat-suppressed T2-weighted MR imaging pulse sequences.

PURPOSE: To evaluate fat-suppressed T2-weighted magnetic resonance (MR) imaging with conventional spin-echo (SE), breath-hold fast SE, respiratory-triggered fast SE, and breath-hold multishot SE echo-planar sequences for the detection of focal hepatic lesions. MATERIALS AND METHODS: Fat-suppressed T2-weighted MR images obtained with the four sequences in 55 patients with 81 solid and 129 nonsolid lesions were retrospectively analyzed. Image review was conducted on a segment-by-segment basis; a total of 440 liver segments were reviewed separately for solid and nonsolid lesions by three independent radiologists. Diagnostic accuracy was evaluated with receiver operating characteristic analysis. RESULTS: The mean lesion-to-liver contrast-to-noise ratio was highest on the multishot SE echo-planar images of both solid and nonsolid lesions. Fat-suppressed respiratory-triggered fast SE images had significantly better (P < .05) or comparative detectability of both solid and nonsolid lesions compared with the other types of images. Image quality was best on the respiratory-triggered fast SE images. CONCLUSION: Fat-suppressed respiratory-triggered fast SE imaging should replace fat-suppressed conventional SE imaging as a standard T2-weighted imaging examination in the detection of focal hepatic lesions.

Adipose Tissue↗
PubMed2004

MRI in the evaluation of hepatocellular nodules: role of pulse sequences and contrast agents.

Magnetic resonance (MR) imaging is more useful than computed tomography (CT) in the evaluation of hepatocellular nodules based on the excellent soft-tissue image contrast of MR imaging. In addition, recent MR units have allowed various fast MR imaging techniques (i.e., parallel imaging or echo-planar imaging) to dramatically improve image quality and image contrast. A variety of liver-specific MR contrast agents are also currently available or have been evaluated in clinical trials to improve the contrast between the liver parenchyma and hepatocellular nodules.

Aged↗
PubMed1994

Technical note: use of a double inversion recovery pulse sequence to image selectively grey or white brain matter.

The design of a double inversion recovery (DIR) sequence, to image selectively grey or white brain matter, is described. Suitable choice of inversion times allows either cerebrospinal fluid (CSF) and white matter to be suppressed, to image the cortex alone, or CSF and grey matter to be suppressed, to image the white matter. The DIR sequence was found to give clear delineation of the cerebral cortex.

Adult↗
PubMed1998

Use of fluid-attenuated inversion recovery (FLAIR) pulse sequences in perinatal hypoxic-ischaemic encephalopathy.

The purpose of this study was to evaluate the usefulness of fluid-attenuated inversion recovery (FLAIR) techniques in patients with perinatal hypoxic-ischaemic encephalopathy. 13 patients with a history of perinatal hypoxic-ischaemic encephalopathy (age range 1 month to 3.6 years) underwent T1 and T2 weighted spin echo and FLAIR imaging with a 1.5 T superconducting unit. FLAIR images were qualitatively evaluated in comparison with T1 and T2 weighted images by three experienced radiologists. Quantitative analysis (contrast and contrast-to-noise ratio) was also performed. FLAIR images were preferred to T1 and T2 weighted images in the demonstration of periventricular leukomalacia (PVL), cystic PVL and subcortical lesions near the brain surface. On T1 and T2 weighted images, almost all lesions were demonstrated as hypointense or hyperintense areas, respectively. However, FLAIR images could differentiate cystic lesions by their signal intensities. FLAIR images were not diagnostic in two cases with PVL. In conclusion FLAIR sequences provide useful information in patients with perinatal hypoxic-ischaemic encephalopathy.

Child, Preschool↗
PubMed1999

MRI of arachnoid granulations within the dural sinuses using a FLAIR pulse sequence.

The purpose of the study was to assess the signal intensities of arachnoid granulations within the dural sinuses using the FLAIR sequence for differentiation of space-occupying lesions in and adjacent to the dural sinuses. We retrospectively reviewed MR images of the brain of 1118 consecutive subjects, ranging in age from 0 to 93 years (mean 57.2 years). Nodules within the dural sinuses with signal intensities similar to that of cerebrospinal fluid (CSF) on both T1 and T2 weighted images were defined as arachnoid granulations. The location, signal intensity on T1 weighted spin echo (SE), T2 weighted fast SE and FLAIR images, the impression on the inner table of the skull, and the size of the lesion were assessed. 112 subjects (10.0%), age range 4-89 years old (mean 58.9 years), were found to have 134 arachnoid granulations. The commonest location was the transverse sinus, with 115 granulations (85.8%). The prevalence of the granulations showed a peak in the sixth decade of age. All granulations were isointense relative to CSF on T2 weighted images and almost all lesions were isointense relative to CSF on T1 weighted images. On FLAIR images, 90.3% of the granulations were isointense relative to CSF and the other 9.7% granulations were slightly hyperintense compared with the CSF. 21 (15.7%) subjects showed impressions on the inner table; one case involved the outer table. In conclusion, arachnoid granulations were isointense or slightly hyperintense relative to CSF on FLAIR. FLAIR images are helpful in differentiating arachnoid granulations from other dural sinus lesions or skull lesions which have an intensity similar to that of CSF on T1 weighted and T2 weighted images.

Adolescent↗
PubMed1997

Use of fluid-attenuated inversion recovery (FLAIR) pulse sequences for differential diagnosis of hepatic hemangiomas and hepatic cysts.

Fluid-attenuated inversion recovery (FLAIR) imaging of hepatic hemangiomas (10 patients, 16 lesions) and hepatic cysts (8 patients, 10 lesions) was performed. All hemangiomas were hypointense on T1-weighted images and hyperintense on T2-weighted images. With Gd-DTPA (0.1 mmol/kg), all hemangiomas were enhanced but not all cysts. It was necessary to perform contrast enhanced imaging to differentiate hepatic hemangiomas from hepatic cysts. However, on FLAIR imaging, hepatic hemangiomas were strongly hyperintense and 9 of the 10 hepatic cysts were isointense. One of the hepatic cysts was slightly hyperintense. FLAIR images were useful in differential diagnosis of hepatic hemangiomas and hepatic cysts without using Gd-DTPA.

Cysts↗
PubMed1990

Diagnosis of femoropopliteal venous thrombosis with MR imaging: a comparison of four MR pulse sequences.

In a prospective study, MR images were evaluated in seven patients with femoropopliteal venous thrombosis with symptoms of less than 5 days duration. T1-weighted (600/25 [TR/TE]), intermediate (2000/30), and T2-weighted (2000/100) spin-echo series and a gradient-recalled acquisition in the steady state (GRASS) series were compared. Using venography as the standard for diagnosis, we found GRASS to be the most sensitive of the MR techniques, showing thrombi in all patients. It provided good contrast between the low-intensity thrombus and high-intensity flowing blood and also between thrombus and intermediate- or high-intensity perivascular tissues. The T1-weighted series was the least sensitive technique. All thrombi showed heterogeneity in the transaxial image with differences in signal between the peripheral and central regions. A higher intensity signal in the center than in the periphery at some level of the thrombus was found in six of seven T2-weighted or GRASS images. Heterogeneity in the signal intensity was more frequent in distal portions of thrombi, whereas the most proximal extent was homogeneous in appearance in six of seven cases. The heterogeneous appearance may be related to the greater age of the distal thrombus, because deep venous thrombi are known to begin in the calf and extend proximally over time. We conclude, on the basis of our experience with a small number of patients, that the GRASS MR technique is more sensitive for detecting acute deep venous thrombosis than T1-weighted, intermediate, and T2-weighted MR images.

Adult↗
PubMed1992

MR imaging of the lungs: value of short TE spin-echo pulse sequences.

OBJECTIVE: An experimental short echo delay (TE = 7 msec) T1-weighted spin-echo sequence was compared with a conventional (TE = 20 msec) T1-weighted spin-echo sequence in the assessment of normal and abnormal lung parenchyma. Comparison was also made with high-resolution CT of abnormal lung parenchyma. SUBJECTS AND METHOD: At 1.5 T, an experimental short echo delay T1-weighted multislice spin-echo sequence (TR = RR interval, TE = 7 msec) was compared with an optimal conventional T1-weighted spin-echo sequence (TR = RR interval, TE = 20 msec, spatial presaturation). Ten healthy volunteers were examined with both sequences. The mean signal intensity and signal-to-noise ratios were calculated in lung parenchyma for both sequences. Two radiologists compared the visualization of normal lung parenchymal structures with the two techniques. In 24 patients with diffuse lung disease, results with both MR sequences and with high-resolution CT were compared. RESULTS: The signal intensity was significantly greater (p < .001) with the TE of 7 msec than with the TE of 20 msec, resulting in a 3.5-fold improvement in the signal-to-noise ratio. The 7-msec TE improved visualization of lung parenchymal structures, including peripheral vessels, interlobular septa or veins, and centrilobular arteries. In the patients with diffuse lung disease, pulmonary parenchymal abnormalities were better visualized on the images with TEs of 7 msec than on images with TEs of 20 msec. When compared with high-resolution CT, the sequence with a TE of 7 msec provided comparable assessment of air-space opacification and dense consolidation, but it was inferior to high-resolution CT in the anatomic assessment of lung parenchyma. CONCLUSION: This experimental spin-echo sequence with a TE of 7 msec significantly improves the signal-to-noise ratio, allowing improved visualization of normal and abnormal pulmonary parenchyma when compared with conventional spin-echo images with a TE of 20 msec. Although anatomic detail remains inferior to that seen with high-resolution CT, the improved image quality with a TE of 7 msec suggests that assessment and follow-up of parenchymal lung disease might be possible with MR, thereby avoiding ionizing radiation.

Adult↗
PubMed1994

MR imaging of high-grade cerebral gliomas: value of diffusion-weighted echoplanar pulse sequences.

OBJECTIVE: The purpose of this study was to evaluate the usefulness of diffusion-weighted echoplanar MR imaging in the examination of high-grade brain gliomas compared with that of conventional spin-echo (SE) or fast spin-echo (FSE) MR imaging. We hypothesize that diffusion-weighted MR imaging may enable us to differentiate various tumor components on the basis of differences in the diffusion of water. SUBJECTS AND METHODS: Conventional SE and FSE MR images were obtained in 10 patients with high-grade brain glioma. Diffusion-weighted echoplanar MR images were obtained with a head gradient coil capable of providing diffusion-weighted imaging along the cephalocaudal axis. Using SE and FSE MR images as a baseline, we evaluated the diffusion-weighted MR images for usefulness in distinguishing tumor components on the basis of differences in diffusion. RESULTS: Areas of tumor that showed significant enhancement on T1-weighted SE MR images obtained after injection of contrast material were markedly hyperintense on diffusion-weighted images and had a lower apparent diffusion coefficient (ADC) than the ADCs for nonenhancing tumor and peritumoral edema. Cystic or necrotic portions of tumor showed the most signal suppression on diffusion-weighted images and were associated with the highest ADCs. On T2-weighted FSE MR images, areas of hyperintensity observed in white matter oriented parallel to the direction of the diffusion gradient could be differentiated into two patterns on the basis of findings on diffusion-weighted images: areas that showed marked signal suppression with a higher ADC, most likely representing areas of predominantly peritumoral edema, and areas that showed a lesser degree of signal suppression with similar but slightly lower ADCs than those of edema, most likely representing areas of predominantly nonenhancing tumor. CONCLUSION: Diffusion-weighted echoplanar MR imaging is a useful technique for examining high-grade cerebral gliomas. It enabled us to differentiate various components of the tumor (e.g., enhancing, nonenhancing, cystic, or necrotic) and to distinguish areas of predominantly nonenhancing tumor from areas of predominantly peritumoral edema when the abnormality was located in the white matter aligned in the direction of the diffusion-weighted gradient. Diffusion-weighted echoplanar MR imaging appears to be a powerful tool in the characterization of brain neoplasms.

Adolescent↗
PubMed1994

MR imaging of the spine: recent advances in pulse sequences and special techniques.

A number of new techniques have been developed to enhance MR imaging of the spine. Fat-suppression techniques used in conjunction with gadolinium-based contrast material improve visualization of enhancing inflammatory and neoplastic diseases. Fast spin-echo (FSE) sequences can be used to decrease imaging times, to increase resolution, or to improve signal-to-noise ratios on T2-weighted images. In general, FSE images provide a better myelographic effect with reduced magnetic susceptibility compared with gradient-recalled echo (GRE) techniques. With volume GRE sequences, thin contiguous sections can be obtained, and images can be reformatted into multiple planes from a single data set. High-contrast imaging can be accomplished by using three-dimensional (3D) turbo-fast low-angle shot (FLASH) or magnetization prepared rapid acquisition gradient-echo (MP RAGE) techniques with gadolinium contrast enhancement. Finally, CSF flow dynamics within the subarachnoid space and within cystic lesions can be elucidated with phase-contrast techniques. Judicious selection of these methods and other innovative MR techniques is necessary to maximize the potential of MR in diagnosis of spinal disease.

Contrast Media↗
PubMed1994

MR diagnosis of meniscal tears of the knee: value of fast spin-echo vs conventional spin-echo pulse sequences.

OBJECTIVE: Contrast can be similar on fast spin-echo and conventional spin-echo MR images, but data acquisition is faster with fast spin-echo sequences. This study was designed to evaluate the performance of fast spin-echo sequences in the detection of meniscal tears in the knee, with the established conventional spin-echo technique used as a reference standard. SUBJECTS AND METHODS: We imaged 66 consecutive patients (129 menisci) who were referred for MR examination with suspected meniscal tears. We used our routine two-dimensional, multisection, long repetition time/double-echo spin-echo sequence and one of two fast spin-echo sequences. The fast spin-echo parameters were chosen to minimize the loss of high-resolution detail while otherwise maintaining the sequence as close as possible to the spin-echo sequence. We then did a retrospective evaluation of the fast spin-echo images, using the spin-echo images as the gold standard. RESULTS: Fast spin-echo images showed only 30 (65%) of the 46 meniscal tears seen on the conventional spin-echo images. In addition, four of the 30 tears seen with both sequences were diagnosed with greater confidence on the conventional spin-echo images. In the cases in which both sequences allowed a diagnosis of definite meniscal tear, the abnormalities tended to be more conspicuous on the spin-echo images. CONCLUSION: Our results suggest that the fast spin-echo sequence should not be used for the diagnosis of meniscal tears.

Adult↗
PubMed1995

MR imaging of diseases of the brain: comparison of GRASE and conventional spin-echo T2-weighted pulse sequences.

OBJECTIVE: The purpose of this study was to compare a combined gradient and spin-echo (GRASE) technique, which is a rapid T2-weighted imaging sequence, with conventional spin-echo (SE) sequences for imaging brain lesions. The GRASE sequences would allow increased patient throughput with potential cost savings and be useful in uncooperative patients without requiring echoplanar imaging techniques and specialized hardware. SUBJECTS AND METHODS: Conventional SE and GRASE T2-weighted images of 49 consecutive patients (20-86 years old) were reviewed independently by three neurora-diologists for the presence and characterization of lesions (most of which were nonspecific foci of hyperintensity within the white matter), gray-white matter differentiation, conspicuity of lesions, and periventricular signal abnormality. The MR studies were performed on a 1.0-T Siemens Magnetom Impact scanner, with the SE images obtained using a TR/TE of 2400/40 and the GRASE images obtained using a TR/effective TE of 4400/110. RESULTS: The number of lesions detected that were 5 mm or larger in maximal diameter did not significantly differ among techniques. For lesions smaller than 5 mm, conventional SE T2-weighted images showed more lesions (p < .01). The SE images were better than the GRASE images for assessing gray-white matter differentiation, conspicuity of lesions, and periventricular signal abnormality. The two hypointense lesions were better assessed on the conventional SE images. CONCLUSION: Although GRASE imaging may be potentially useful for rapid imaging of the brain, our experience shows it has a markedly diminished sensitivity for detecting lesions smaller than 5 mm in diameter. Currently, GRASE imaging should not replace the routine clinical use of conventional SE sequences.

Adult↗