Intracranial black-blood MR angiography with high-resolution 3D fast spin echo

Three-dimensional fast spin-echo (3DFSE) techniques are promising for black-blood imaging of cerebral vessels. In this study, flow-related signal dephasing was demonstrated as the primary mechanism for blood signal attenuation. Parameter optimization of TR (1500 to 3000 ms), receiver bandwidth (25 to 31.25 kHz), effective TE (25.7 to 30.1 ms), and ETL (7 to 8) was accomplished by making measurements of vessel-to-tissue contrast-to-noise ratios on vessels. A comparison of high-resolution 3DFSE and 3DTOF magnetic resonance angiography demonstrated that 3DFSE can generate images with equivalent or better small vessel detail than conventional techniques. 3DFSE black-blood techniques may provide improved sensitivity of small arteries and veins with slow or in-plane flow and immunity to flow-related distortions. Future studies with optimized parameters will determine the clinical efficacy of this technique.     

Lumbar spine magnetic resonance imaging: comparison between fast spin echo proton density and spin echo T1 axial scans

Spin echo (SE) T1 axial scans are routinely obtained in magnetic resonance imaging of the lumbar spine in many centres. This study directly compared matched SE T1 and fast SE (FSE) proton density (PD) axial scans. Both SE T1 and FSE PD axial scans of the lumbar spine were obtained in 116 consecutive patients. The imaging parameters (field-of-view, slice thickness, interslice gap, number of excitations and matrix size) and scan levels were identical for each pair of sequences. At two selected levels, L4/5 and L5/S1, various structures were independently graded by two observers. In 232 lumbar levels analysed, the bone marrow, epidural fat, disc, extradural nerve root and facet joint were equally well seen on both sequences by both observers (combined mean grades of 2.93-2.99). The thecal sac was marginally better depicted on FSE PD than on SE T1 images, with mean grades of 2.96 and 2.88, respectively. The psoas muscle was adequately visualized for diagnostic purposes on both sequences (mean grades of 2.30-2.32). The cauda equina were better seen on FSE PD (mean grade 1.92) than on SE T1 (mean grade 1.00) images. In conclusion, FSE PD scans are comparable to and may potentially replace SE T1 axial MR scans of the lumbar spine.     

Inner ear volumetric measurements using high-resolution 3D T2-weighted fast spin-echo MR imaging: initial experience in healthy subjects

BACKGROUND AND PURPOSE: Adult size is achieved in the inner ear labyrinth by approximately 25 weeks' gestation, and minimal variability in age, sex, side, and race is found after birth. In this study, we opted to determine the reproducibility of inner ear volumetric measurements generated from high-resolution heavily T2-weighted 3D fast spin-echo MR images. METHODS: The temporal bones of 23 volunteers were imaged using a heavily T2-weighted 3D fast spin-echo MR imaging technique. The images were assessed by a neuroradiologist for the presence of inner ear configurational anomalies and, most important, for complete coverage of the inner ear labyrinth. Subsequently, the volume of the fluid in the inner ear was determined by two observers using a semiautomated segmentation algorithm. The mean, SD, range, and coefficient of variation of fluid volume in the inner ear were calculated. Age-, sex-, and side-related differences in the inner ear volumetric measurements were evaluated using analysis of variance. Interrater consistency in the inner ear volumetric measurements was evaluated by comparing the calculated coefficients of reliability. RESULTS: Volumetric measurements were available from 46 inner ears in 23 volunteers. The mean volume was 227.8 mm3 (SD, 24.4 mm3), and the coefficient of variation was 10.7%. No age-, sex-, or side-related differences in the inner ear volumetric measurements were found (F ratios were 4.33, 5.04, and 0.26, respectively). Interrater consistency, as assessed by the coefficient of reliability, was 5.3%. CONCLUSION: Reproducible volumetric measurements of the inner ear labyrinth can be obtained by applying a semiautomated segmentation algorithm to a heavily T2-weighted 3D fast spin-echo MR imaging data set. These volumetric measurements may help identify patients with congenital sensorineural hearing loss and normal inner ear configuration.     

Hepatic cavernous hemangioma: appearance on T2-weighted fast spin-echo MR imaging with and without fat suppression

OBJECTIVE: The goals of our study were to define the morphologic appearance of cavernous hemangioma of the liver on T2-weighted fast spin-echo MR imaging and to determine if the use of fat suppression may quantitatively and qualitatively modify the MR imaging appearance of cavernous hemangioma. SUBJECTS AND METHODS: Twenty-six patients with cavernous hemangiomas of the liver were prospectively studied with T2-weighted MR imaging with a fast spin-echo technique with and without fat suppression. Thirteen patients had known hemangiomas for more than 2 years, with no change in size or morphology during this period. The remaining 13 patients had diagnoses based on dynamic CT and sonography and an absence of change in the morphology and size of their lesions during follow-up of more than 6 months (range, 6-12 months) after the MR imaging studies. Values for signal intensity and contrast-to-noise (C/N) ratios in cavernous hemangiomas that were obtained with and without fat suppression were compared. Images were qualitatively analyzed separately at identical level and window settings by two interpreters for morphologic features of cavernous hemangiomas. RESULTS: No significant difference was found between signal intensity values obtained using the fat-suppressed fast spin-echo MR imaging technique (5.62 +/- 1.14 [SD]) and those obtained without fat suppression (5.51 +/- 1.23). Values for C/N ratios obtained with the fat-suppressed fast spin-echo MR imaging technique (20.13 +/- 7.63) were significantly superior to those obtained without fat suppression (16.59 +/- 5.31) (p < .001). On T2-weighted fast spin-echo MR imaging without fat suppression, 100% of cavernous hemangiomas were hyperintense relative to the spleen, 90% had well-defined and sharp margins, 55% were isointense to CSF, and 76% were homogeneous. Without fat suppression, 34% of cavernous hemangiomas showed the combination of isointensity to CSF, well-defined margins, and homogeneity. On T2-weighted fast spin-echo MR imaging with fat suppression, all cavernous hemangiomas showed this same combination of features. CONCLUSION: Seventy-six percent of hepatic cavernous hemangiomas were homogeneous on T2-weighted fast spin-echo MR imaging, and 55% were isointense to CSF. However, only 34% of hepatic cavernous hemangiomas showed typical features. Although fat suppression significantly increased the C/N ratio of cavernous hemangiomas of the liver, fat suppression did not affect their morphologic appearance on T2-weighted fast spin-echo MR imaging.     

Preoperative staging of endometrial carcinoma: diagnostic effect of T2-weighted fast spin-echo MR imaging

PURPOSE: To evaluate the usefulness of T2-weighted fast spin-echo magnetic resonance (MR) imaging with a 512 x 256 matrix for assessment of the preoperative stage of endometrial carcinoma. MATERIALS AND METHODS: Twenty-eight women with histopathologically proved endometrial carcinoma underwent preoperative T2-weighted fast spin-echo, dynamic T1-weighted fast spin-echo, and postcontrast T1-weighted spin-echo MR imaging with a phased-array surface coil. The uterine long-axis planes in each sequence were reviewed at separate sessions by three radiologists blinded to the histopathologic data. RESULTS: For the diagnosis of myometrial invasion, no statistically significant differences were found among T2-weighted imaging, dynamic imaging, and postcontrast T1-weighted imaging. For the diagnosis of deep myometrial invasion, T2-weighted and dynamic images showed higher specificity than postcontrast T1-weighted images (T2-weighted, 89%; dynamic, 88%; and postcontrast T1-weighted, 80%). For cervical invasion, T2-weighted and dynamic images showed larger areas under receiver operating characteristic curves than did postcontrast T1-weighted images (T2-weighted, 0.78; dynamic, 0.71; and postcontrast T1-weighted, 0.67). CONCLUSION: T2-weighted imaging is useful for identifying the stage of endometrial carcinoma.     

Hyperparathyroidism--comparison of flash imaging with spin echo MR imaging

MR images of the neck were prospectively studied in 19 patients with hyperparathyroidism. Fast low angle shot (FLASH) sequence was performed in addition to T1- and T2-weighted spin echo (SE) sequences. FLASH images were obtained with 320/12/20 degrees (TR/TE/flip angle) using presaturation technique. TE of 12 ms was chosen to eliminate high signal of fat tissue. In the evaluation of detectability, a combination of T1-weighted SE and FLASH images (T1WI + FLASH) was compared with a combination of T1- and T2-weighted SE images (T1WI + T2WI). MR imaging correctly depicted 20 of 30 abnormal glands on both T1WI + FLASH and T1WI + T2WI. FLASH imaging effectively eliminated high signal of fat tissue. Nineteen abnormal glands demonstrated higher signal than surrounding tissues on FLASH images, whereas 12 glands were high-intense on T2-weighted SE images. We conclude that FLASH imaging provides improved tissue contrast and anatomic delineation and, thus, may replace T2-weighted SE imaging in the neck.     

Fast spin echo vs conventional spin echo in cervical spine imaging

The major attraction of fast-spin-echo (FSE) imaging is reduced acquisition time; however, careful review of the literature reveals many weaknesses: phase-encoded blurring, truncation artefact, bright fat signal, reduced magnetic susceptibility and increased motion artefact. Our aim was a prospective, blinded comparison of FSE and conventional spin echo (CSE) in the cervical spine. Both sequences were performed in 43 patients (19 males and 24 females; mean age 45 years, range 15-66 years). Twenty-eight patients were studied at 1.5 T and 15 at 0.5 T. Typical sequence parameters were: at 1.5 T, TR/TE 2000/90 CSE and 3000/120 FSE, and at 0.5 T, 2200/80 CSE and 2800/120 FSE. Time saved on the FSE was used to increase the matrix and the number of acquisitions. Two neuroradiologists evaluated the images for pathology, artefacts, disc signal intensity, thecal sac compression and image quality. Ten patients had cord lesions; 2 (20 %) were missed on CSE. In 4 of 10 patients with moderate/severe thecal sac compression, the degree of stenosis was apparently exaggerated on CSE. The mean degree of confidence for the CSE sequences was 1.8 and for the FSE 1.1, where 1 is optimal. For cervical spine imaging, FSE should be preferred to CSE.     

T2-weighted spin-echo MR imaging of the liver: breath-hold fast spin-echo versus non-breath-hold fast spin-echo images with and without fat suppression

OBJECTIVE: The goal of our study was to compare a T2-weighted breath-hold fast spin-echo (BHSE) technique with T2-weighted non-breath-hold fast spin-echo techniques for imaging the liver. SUBJECTS AND METHODS: Thirty-three patients with hepatic lesions had T2-weighted BHSE images obtained in 22 sec and conventional T2-weighted non-breath-hold fast spin-echo images obtained in 3 min 12 sec with and without fat suppression. Images were analyzed quantitatively by measuring the lesion-liver contrast, spleen-liver contrast, and signal-to-noise ratios of lesions and qualitatively by evaluating the sharpness of hepatic contours, visibility of intrahepatic vessels and other segmental landmarks, and presence of artifacts. RESULTS: Quantitatively, lesion-liver contrast, spleen-liver contrast, and signal-to-noise ratios obtained with the BHSE technique were inferior to those obtained with fast spin-echo techniques with and without fat suppression (11.2 +/- 7.1 versus 15.4 +/- 10.6 and 14.5 +/- 9.8, p < .001; 5.3 +/- 3.7 versus 8.7 +/- 3.5 and 7.0 +/- 3.8, p < .001; 16.2 +/- 8.2 versus 20.1 +/- 10.9 and 19.7 +/- 9.5, p < .01, respectively; Student's t test). Qualitatively, image artifacts and intrahepatic vessel depiction on BHSE images were similar to those obtained with the fast spin-echo techniques. The BHSE technique was superior to fat-suppressed fast spin-echo technique for showing hepatic contours (p < .01; Wilcoxon signed-rank test). CONCLUSION: The BHSE technique is quantitatively inferior to non-breath-hold fast spin-echo techniques. However, further studies with a surgical standard of reference are needed to compare the three techniques in terms of sensitivity.     

Breath-hold fast spin-echo MR imaging of the liver: a technique for high-quality T2-weighted images

The added technical complexity associated with the transfixion screws for interlocking nailing has introduced new complications. We present a case of a femoral arteriovenous fistula caused by the distal interlocking screw after intramedullary nailing of a comminuted diaphyseal femoral fracture.     

FASE (fast advanced spin echo)

RF-refocused single or multi-shot EPI provides high-contrast 2D or 3D T2-weighted images in a very short scan time. Applications include MR cholangiopancreatography, MR myelography, imaging detailed structures of the internal auditory canal and in situations in which very fast T2 imaging is required. FASE offers both 2D and 3D techniques. 2D FASE technique permits high-resolution images of 384 matrix or more to be obtained at 2 to 3 seconds per image. It is easy to perform and suitable for screening. 3D FASE permits acquisition of isotropic voxels, allowing high-resolution viewing from any desired direction by post-processing (MIP and/or MPR). This technique is best suited to detailed examinations in which multiple projection angles will be reconstructed or high-resolution diagnosis of source images.     

Hepatic T2-weighted MRI: a prospective comparison of sequences, including breath-hold, half-Fourier turbo spin echo (HASTE)

The purpose of this study was to quantitatively compare the hepatic contrast characteristics of conventional spin-echo (CSE) and fast spin-echo (FSE) sequences with breath-hold T2-weighted images acquired with half-Fourier turbo spin echo (HASTE). Forty-five patients were examined with a phased-array surface coil. Nineteen patients had focal hepatic lesions, including eight malignant tumors, 10 cavernous hemangiomas, and one hepatic adenoma. Twenty-six patients had no focal hepatic lesions. T2-weighted images with comparable TE were acquired with CSE, FSE, and HASTE pulse sequences. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) for liver, spleen, and lesions were measured. FSE demonstrated significantly better quantitative performance than CSE for liver-spleen CNR (P .0084). No statistically significant difference was demonstrated between FSE and CSE for liver or spleen SNR. FSE demonstrated clear scan time and resolution advantages over CSE. HASTE performed significantly poorer than CSE and FSE for liver-spleen CNR (P < .0001), liver SNR (P = .0002 for CSE and P < .0001 for FSE), and spleen SNR (P < .0001). Optimized FSE images with a short echo train length performed comparably to CSE images of equivalent TE. Liver-lesion CNR was suppressed on HASTE images, suggesting that long echo train length FSE sequences could diminish solid lesion detection compared to CSE and short echo train length FSE.     

Single shot fast spin echo (SSFSE)

Single Shot Scan methods, which acquire all the necessary data for reconstruction with one excitation, are very useful methods to minimize motion artifacts. Single Shot Scan can be categorized in 2 groups, one is EPI method using gradient by Echo data acquisition, and another is SSFSE method using RF. SSFSE method is Single Shot FSE method using 0.5 NEX. SSFSE produces images with less motion artifacts and heavy PD and T2 images with high contrast. New RF reduces Echo Space and minimizes image quality degradation caused by Single Shot. SSFSE is useful for long T2 like MRCP. Long TE mode can be used with very long ETE even with 0.5 NEX. New applications development for Single Shot using RF is awaited in the future.     

MR sialography: initial experience using a T2-weighted fast SE sequence

OBJECTIVE: To determine whether reactive oxygen species in peritoneal fluid might be a factor in infertility. DESIGN: Prospective study. SETTING: Andrology laboratory and gynecology clinic at a tertiary care facility. PATIENT(S): Women with endometriosis (n = 15) or idiopathic infertility (n = 11) who underwent laparoscopy for infertility. Patients undergoing tubal ligation served as controls (n = 13). INTERVENTION(S): Aspiration of peritoneal fluid. MAIN OUTCOME MEASURE(S): Reactive oxygen species levels, presence of polymorphonuclear granulocytes, and leukocyte distribution in peritoneal fluid. RESULT(S): Reactive oxygen species were present in the peritoneal fluid of patients with endometriosis, idiopathic infertility, and tubal ligation. Levels of reactive oxygen species did not show a statistically significant difference between patients with endometriosis and the control group in either unprocessed or processed (cell-free) peritoneal fluid, but did differ significantly between patients with idiopathic infertility and controls in processed peritoneal fluid. Polymorphonuclear granulocytes (> 1 x 10(6)/mL) were not present in the peritoneal fluid of any patient. Macrophage concentrations of peritoneal fluid did not differ significantly between controls and patients with endometriosis or idiopathic infertility. CONCLUSION(S): Reactive oxygen species in the peritoneal fluid may not affect fertility directly in women with endometriosis; however, they may have a role in patients with idiopathic infertility.     

MRI of the uterus, uterine cervix, and vagina: diagnostic performance of dynamic contrast-enhanced fast multiplanar gradient-echo imaging in comparison with fast spin-echo T2-weighted pulse imaging

The aim of this study was to compare the diagnostic performance of contrast-enhanced fast multiplanar gradient-echo (GRE) and T2-weighted fast spin-echo (FSE) image sets in the assessment of uterus, cervix, and vagina. Fast (up to 20 contiguous sections in 23 s) multiplanar GRE and FSE images of 45 patients referred for imaging of the female pelvis were evaluated retrospectively with regard to overall image quality and the ability to detect normal anatomic structures, as well as lesion conspicuity. Results were compared with histologic findings (n = 29) or clinical follow-up. Furthermore, a quantitative assessment of contrast-to-noise ratios among normal uterine and cervical structures as well as uterine lesions was performed for both sequences. On GRE images, uterine and cervical differentiation was best seen on the image sets acquired 15 and 60 s following contrast enhancement and results were significantly better compared with delayed images (p < 0.05). Delineation of the junctional zone was significantly (p < 0.05) better on FSE compared with GRE images; no significant difference was seen for the other anatomic structures. Overall image quality of GRE and FSE images was similar. Sensitivity for lesion detection based on both GRE and FSE images was 96% with a sensitivity of 93% for GRE, and 81% for FSE images alone, respectively. Using the extended McNemar chi 2 test, the difference in diagnostic performance between FSE and GRE revealed no significant difference, whereas the combination of both techniques performed better than FSE imaging alone (p < 0.05). The presented data suggest that dynamic contrast-enhanced GRE imaging should be part of an MR examination of the female pelvis. Combined GRE and FSE imaging provide an excellent sensitivity in the assessment of uterine and vaginal pathologies.     

Hepatic lesions: discrimination of nonsolid, benign lesions from solid, malignant lesions with heavily T2-weighted fast spin-echo MR imaging

PURPOSE: To determine whether the combined use of heavily and moderately T2-weighted fast spin-echo magnetic resonance (MR) images improves differentiation of non-solid, benign hepatic lesions from solid malignancies. MATERIALS AND METHODS: Three radiologists reviewed moderately (n = 133) and heavily (n = 133) T2-weighted and multiphasic dynamic contrast material-enhanced (n = 93) MR images in 133 patients with proved focal hepatic lesions (95 benign, 38 malignant). The radiologists used a five-point scale to rate their confidence in determination of malignancy. RESULTS: All three reviewers were statistically significantly better able to differentiate small (diameter less than 3 cm; n = 84) benignancies from small malignancies with the combination of moderately and heavily T2-weighted images (area under the receiver operating characteristic curve, 0.99 for each reader) than with moderately T2-weighted images alone (area, 0.88-0.90; P < .05). Confident diagnoses were rendered in 69 (82%) patients, with 100% accuracy for the combined use of moderately and heavily T2-weighted images. For larger lesions (diameter 3 cm or larger; n = 49), accurate differentiation was possible with moderately T2-weighted images alone. Additional use of multiphasic images did not improve the sensitivity, specificity, or accuracy of image interpretation. CONCLUSION: The combined use of moderately and heavily T2-weighted fast spin-echo MR images improves differentiation of small benign hepatic lesions from small malignant lesions.     

Hemorrhagic and nonhemorrhagic stroke: diagnosis with diffusion-weighted and T2-weighted echo-planar MR imaging

PURPOSE: To determine if diffusion- and T2-weighted echo-planar magnetic resonance (MR) imaging can be used to detect acute hemorrhagic stroke and to differentiate hemorrhagic from nonhemorrhagic stroke. MATERIALS AND METHODS: A total of 118 examinations (diffusion- and T2-weighted MR imaging) in 19 patients with 27 nonhemorrhagic strokes and in six patients with seven hemorrhagic strokes were performed. The ratios of apparent diffusion coefficient and of signal intensity on T2-weighted MR images in lesions to those in contralateral control areas were calculated. RESULTS: Decreased ADC was shown in lesions of acute (0-3 days) hemorrhagic stroke, as well as in lesions of acute nonhemorrhagic stroke. Hypointense areas were seen on T2-weighted MR images in patients with acute hemorrhagic stroke, in contrast to normal to increased signal intensity in those with acute nonhemorrhagic stroke. Apparent diffusion coefficient tended to remain decreased in hemorrhagic stroke lesions even 100 days after onset, in contrast to the increased coefficient in nonhemorrhagic stroke lesions at the late chronic stage (31 days or older). CONCLUSION: Diffusion- and T2-weighted echo-planar MR imaging can be used to detect and distinguish between acute hemorrhagic and nonhemorrhagic stroke.     

Bithalamic hyperintensity on T2-weighted MR: vascular causes and evaluation with MR angiography

PURPOSE: To determine whether MR angiography can be used to differentiate between the two vascular causes of bithalamic hyperintensity on T2-weighted MR images: "top of the basilar" artery occlusion and deep cerebral vein thrombosis. METHODS: A retrospective review identified six patients with bithalamic T2 hyperintensity of vascular causes. MR angiography was performed in four patients, MR angiography and conventional angiography in one patient, and conventional angiography in one patient. Data pertaining to clinical presentation and hospital course were collected. MR angiographic techniques were multislab overlapping three-dimensional time-of-flight, 2-D time-of-flight, and 2-D phase-contrast. RESULTS: Three cases of top of the basilar artery occlusion and three cases of deep cerebral vein thrombosis were recognized. In all cases, T2 hyperintensity in a vascular distribution suggested cerebral occlusive disease. Infarction involving the thalami and basal ganglia was present in two cases of deep cerebral vein thrombosis. Infarction of the thalami, mesodiencephalic region, and cerebellar hemispheres was present in two cases of basilar artery occlusion. Bithalamic infarction alone was seen in one case of deep cerebral vein thrombosis and one case of basilar artery occlusion. In the five cases in which MR angiography was used, this technique accurately distinguished the vessels involved (arterial or venous). CONCLUSION: MR angiography is a useful adjunct to MR imaging in the evaluation of bithalamic T2 hyperintensity. It does help distinguish between the two vascular causes: top of basilar artery occlusion and deep cerebral vein thrombosis.