Can a multiphasic contrast-enhanced three-dimensional fast spoiled gradient-recalled echo sequence be sufficient for liver MR imaging?

OBJECTIVE: The purpose of this study was to determine the accuracy of a multiphasic gadolinium-enhanced three-dimensional (3D) fast spoiled gradient-recalled echo sequence alone in the detection and characterization of focal liver lesions compared with a comprehensive liver evaluation using multiphasic gadolinium-enhanced 3D fast spoiled gradient-recalled echo, T1-weighted, and fat-suppressed fast spin-echo T2-weighted sequences. MATERIALS AND METHODS:A retrospective review of abdominal MR imaging examinations in 61 patients was performed. All MR examinations included unenhanced spin-echo T1-weighted, unenhanced fat-suppressed fast spin-echo T2-weighted, and multiphasic gadolinium-enhanced 3D fast spoiled gradient-recalled echo sequences obtained during successive breath-holds. The liver was evaluated for focal lesions first with the 3D spoiled gradient-recalled echo sequences and then, during a separate sitting, with the T1- and T2-weighted sequences. The usefulness of each sequence in the detection and characterization of lesions was recorded. The gold standard for lesion detection and characterization was all three imaging sequences reviewed together. RESULTS:A total of 114 focal liver lesions were identified, 54 of which were simple cysts. The 3D spoiled gradient-recalled echo sequence alone detected 92 (81%) of the 114 lesions, and the T1- and T2-weighted sequences detected 95 (83%) of the 114 lesions. Of the 60 lesions that were not simple cysts, the 3D spoiled gradient-recalled echo sequence alone detected 58 (97%), and T1- and T2-weighted sequences detected 51 (85%). In 24% of the patients with lesions, the T1- and T2-weighted sequences were found to be helpful for the characterization of lesions. CONCLUSION:A multiphasic contrast-enhanced 3D fast spoiled gradient-recalled echo sequence alone detects most of the clinically relevant focal liver lesions. Additional liver examination using both unenhanced T1- and T2-weighted sequences is helpful for lesion characterization but increases the detection rate only minimally.     

Low-cost high-resolution fast spin-echo MR of acoustic schwannoma: an alternative to enhanced conventional spin-echo MR?

PURPOSETo determine whether unenhanced high-resolution T2-weighted fast spin-echo MR imaging provides an acceptable and less expensive alternative to contrast-enhanced conventional T1-weighted spin-echo MR techniques in the diagnosis of acoustic schwannoma.METHODSWe reviewed in a blinded fashion the records of 25 patients with pathologically documented acoustic schwannoma and of 25 control subjects, all of whom had undergone both enhanced conventional spin-echo MR imaging and unenhanced fast spin-echo MR imaging of the cerebellopontine angle/internal auditory canal region. The patients were imaged with the use of a quadrature head receiver coil for the conventional spin-echo sequences and dual 3-inch phased-array receiver coils for the fast spin-echo sequences.RESULTSThe size of the acoustic schwannomas ranged from 2 to 40 mm in maximum dimension. The mean maximum diameter was 12 mm, and 12 neoplasms were less than 10 mm in diameter. Acoustic schwannoma was correctly diagnosed on 98% of the fast spin-echo images and on 100% of the enhanced conventional spin-echo images. Statistical analysis of the data using the kappa coefficient demonstrated agreement beyond chance between these two imaging techniques for the diagnosis of acoustic schwannoma.CONCLUSIONSThere is no statistically significant difference in the sensitivity and specificity of unenhanced high-resolution fast spin-echo imaging and enhance T1-weighted conventional spin-echo imaging in the detection of acoustic schwannoma. We believe that the unenhanced high-resolution fast spin-echo technique provides a cost-effective method for the diagnosis of acoustic schwannoma.     

MR imaging of pelvic masses in women: contrast-enhanced vs unenhanced images.

OBJECTIVE. We compared the value of contrast-enhanced MR images with that of T2-weighted MR images in the diagnosis and staging of pelvic masses in women. MATERIALS AND METHODS. The findings on preoperative MR studies of 97 patients with a total of 124 surgically proved lesions were retrospectively analyzed. Unenhanced T1- and T2-weighted spin-echo images were compared with contrast-enhanced T1-weighted images. The final diagnosis included benign (36 patients), borderline (six patients), and malignant (15 patients) ovarian masses, fallopian tube masses (15 patients), endometrial tumors (seven patients), cervical carcinomas (32 patients), subserous leiomyomas (11 patients), and two masses of extragenital origin. RESULTS. In the depiction of pelvic lesions, the sensitivity of contrast-enhanced MR imaging (96%) was equal to that of unenhanced T2-weighted imaging (97%). Contrast-enhanced images were useful in the definition of intratumoral architecture and tumor borders of 72 adnexal masses, resulting in better determination of malignancy (accuracy, 95%) than on T2-weighted images (85%). Size of viable tumor, differentiation of tumor from retained fluid, and depth of myometrial invasion of six endometrial carcinomas were most reliably shown on contrast-enhanced images. In the evaluation of cervical carcinoma, overall staging accuracy of contrast-enhanced imaging (80%) was slightly inferior to that of T2-weighted imaging (83%). However, contrast-enhanced images improved assessment of parametrial and organ invasion in seven cases in which findings on T2-weighted MR images were equivocal. Administration of contrast material was not helpful in the evaluation of subserous leiomyomas or masses of extragenital origin. CONCLUSIONS. The findings suggest that when results of unenhanced T1- and T2-weighted MR imaging of pelvic masses are equivocal, contrast-enhanced MR images should be used as supportive and complementary pulse sequences to (1) improve definition of intratumoral architecture and prediction of malignancy in adnexal tumors, (2) stage endometrial carcinoma, and (3) determine tumor extension in cervical carcinoma.     

MR imaging of leptomeningeal metastases: comparison of three sequences

BACKGROUND AND PURPOSE: Recent work has shown that fluid-attenuated inversion recovery (FLAIR) imaging with contrast enhancement is highly sensitive for detecting subarachnoid space disease. We hypothesized that contrast-enhanced FLAIR imaging has superior sensitivity to contrast-enhanced T1-weighted MR imaging in detecting leptomeningeal metastases. METHODS: Sixty-eight patients referred for suspected leptomeningeal metastases underwent 74 MR imaging studies. The patients had either temporally related cytologic proof of leptomeningeal metastases or negative results of clinical follow-up confirming absence of leptomeningeal metastases. The MR imaging examinations included unenhanced and contrast-enhanced FLAIR images and contrast-enhanced T1-weighted MR images that were independently reviewed by two neuroradiologists blinded to the results of cytology. Each of the three sequences was reviewed individually and separately and was assigned a score of positive or negative for leptomeningeal metastases. Discrepancies were settled by consensus. RESULTS: Of the 17 studies of patients with cytology-proven leptomeningeal metastases, two were positive based on unenhanced FLAIR images, seven were positive based on contrast-enhanced FLAIR images, and 10 were positive based on contrast-enhanced T1-weighted MR images. Of the 57 studies of patients without leptomeningeal metastases, 53 were negative based on unenhanced FLAIR images, 50 were negative based on contrast-enhanced FLAIR images, and 53 were negative based on contrast-enhanced T1-weighted MR images. The sensitivity and specificity of unenhanced FLAIR images for detecting leptomeningeal metastases were 12% (two of 17) and 93% (53 of 57), respectively. The sensitivity and specificity for contrast-enhanced FLAIR images for detecting leptomeningeal metastases were 41% (seven of 17) and 88% (50 of 57), respectively. The sensitivity and specificity of contrast-enhanced T1-weighted MR images for detecting leptomeningeal metastases were 59% (10 of 17) and 93% (53 of 57), respectively. CONCLUSION: Contrast-enhanced fast FLAIR sequences are less sensitive than standard contrast-enhanced T1-weighted MR sequences in detecting intracranial neoplastic leptomeningeal disease.     

Magnetic resonance imaging in suspected rectal cancer: determining tumor localization, stage, and sphincter-saving resectability at 3-Tesla-sustained high resolution

Purpose: To assess image quality and overall accuracy of 3-Tesla (3T)-sustained high-resolution magnetic resonance (MR) imaging for diagnostic preoperative workup in suspected rectal carcinoma.

Material and Methods: Twenty-three patients with suspected rectal cancer underwent unenhanced and contrast-enhanced fat-suppressed pelvic high-resolution MR imaging using a four-channel phased-array pelvic coil at 3T. Image quality, tumor stage, distance from the anorectal margin, and sphincter-saving resectability were prospectively assessed by two blinded readers. The results were correlated with clinical, surgical, and histopathologic findings.

Results: In all 23 patients, MR images were of diagnostic quality, and malignancy was correctly identified in 21 patients. The accuracy for determining sphincter-saving resectability was 100% (19/19). T stage and N stage were correctly diagnosed in 95% and 91%, respectively. MRI allowed correct identification of tumor extension and its relation to surgically relevant pelvic structures including the anorectal margin and mesorectal fascia. Transverse T2-weighted fast spin-echo images compared superiorly to all other sequences for the diagnosis of mesorectal infiltration and lymph node involvement. Moreover, transverse fat-suppressed contrast-enhanced T1-weighted images were valuable for identifying tumor infiltration, while sagittal sections were useful for the detection of longitudinal tumor extension.

Conclusion: MR imaging with phased-array receiver coils at 3T facilitated both visualization of different pathologic conditions of the rectum and accurate determination of tumor stage in rectal carcinomas. Thus, this noninvasive diagnostic approach appeared highly suitable for the assessment of patients with suspected rectal carcinoma.     

Intravertebral cleft sign on fat-suppressed contrast-enhanced MR: correlation with cement distribution pattern on percutaneous vertebroplasty

RATIONALE AND OBJECTIVES: Filling intravertebral clefts during percutaneous vertebroplasty (PVP) is considered to be important for optimal pain control. It is often difficult to detect clefts on non-contrast MR and some fractures show a solid pattern distribution of injected cement without a cleft sign on non-contrast MR. In this study, we evaluated usefulness of fat-suppressed contrast-enhanced MR to predict a solid pattern distribution of injected cement on PVP. MATERIALS AND METHODS: Twenty-six patients with 35 vertebral compression fractures due to osteoporosis were studied. We performed sagittal T1-weighted, T2-weighted and fat-suppressed contrast-enhanced T1-weighted images prior to PVP. First we evaluated the presence of fluid-filled or gas-containing clefts on non-contrast MR. Next we evaluated contrast-enhanced MR of the same vertebrae for the presence of cleft-shaped unenhanced areas within the diffuse enhancement area. We correlated MR findings with cement distribution patterns of injected cement. RESULTS: Based on MR findings, 35 osteoporotic fractures were divided into 3 types. Type 1 (11 fractures, 31%): There were no clefts on non-contrast MR and no unenhanced areas on contrast-enhanced MR; Type 2 (13, 37%): There were no clefts on non-contrast MR but there were unenhanced areas on contrast-enhanced MR; Type 3 (13, 37%): There were clefts on non-contrast MR and unenhanced areas on contrast-enhanced MR. Of 35 osteoporotic fractures, thirteen vertebral fractures (37%) were noted to contain clefts on non-contrast MR, while 24 vertebral fractures (69%) contained unenhanced areas on contrast-enhanced MR. Cement distributed as a solid pattern within clefts or unenhanced areas in all fractures with them. CONCLUSION: Fat-suppressed contrast-enhanced MR is useful to predict a solid pattern distribution of injected cement prior to PVP.     

MR imaging of hepatic metastases caused by neuroendocrine tumors: comparing four techniques

OBJECTIVE: The aim of our prospective study was to assess the MR imaging characteristics of hepatic metastases of neuroendocrine tumors and to determine the optimal MR sequence for their detection. SUBJECTS AND METHODS: Thirty-seven consecutive patients with liver metastases from neuroendocrine tumors underwent 1.5-T MR imaging of the liver comprising T2-weighted fast spin-echo with respiratory monitoring, breath-hold T2-weighted single-shot fast spin-echo, and T1-weighted gradient-recalled echo sequences before and after the injection of gadoterate dimeglumine. Images were reviewed independently by three observers for the number, location, and pattern of signal and enhancement of metastases. RESULTS: A total of 359 metastases were detected, 279 on T2-weighed fast spin-echo, 231 on T2-weighed single-shot fast spin-echo, 272 on unenhanced T1-weighted, 322 on hepatic arterial phase, and 228 on portal venous phase images. Hepatic arterial phase images revealed the greatest number of metastases in 70% of patients, including 35 metastases seen only on this sequence, and was significantly superior to the unenhanced T1-weighted and portal venous phase sequences (p < 0.01). The lesion-to-liver contrast was significantly greatest with T2-weighed fast spin-echo sequences. The enhancement patterns of metastases were predominantly hypervascular, hypovascular, peripheral with progressive fill-in, and delayed in, respectively, 27, four, four, and two patients. Most metastases with peripheral enhancement and progressive fill-in were heterogeneous on T2-weighted images and were without globular peripheral enhancement. CONCLUSION: Hepatic metastases of neuroendocrine tumors had a typical hypervascular pattern in 73% of patients. Hepatic arterial phase and fast spin-echo T2-weighed sequences are the most sensitive.     

MR signal intensity characteristics in Legg-Calvé-Perthes disease. Value of fat-suppressed (STIR) images and contrast-enhanced T1-weighted images

PURPOSE: To evaluate the MR signal intensity characteristics in Legg-Calvé-Perthes disease on fat-suppressed (STIR) images and contrast-enhanced T1-weighted spin-echo images, and to develop criteria for the administration of contrast material. MATERIAL AND METHODS: Twenty children with Legg-Calvé-Perthes disease underwent conventional radiography and MR imaging of the hip utilizing fat-suppressed (STIR) sequences and T1-weighted spin-echo sequences before and after i.v. contrast administration. The signal intensity characteristics of the femoral head and the proximal femoral metaphysis were assessed retrospectively by two pediatric radiologists. RESULTS: Evaluation of the MR images revealed six different signal patterns within the femoral head: 1) isointense signal on all images; 2) complete signal void on all images; 3) hyperintense signal on STIR images with; or 4) without contrast enhancement on T1-weighted spin-echo images; 5) isointense signal on STIR images with; or 6) without contrast enhancement on T1-weighted images. Within the metaphysis three different signal patterns were differentiated. CONCLUSION: Combination of fat-suppressed (STIR) sequences and T1-weighted pre- and post-contrast sequences allows an accurate evaluation of Legg-Calvé-Perthes disease. In patients without signal alterations or complete signal loss on fat-suppressed and T1-weighted spin-echo images, administration of i.v. contrast is not necessary. In case of bone marrow edema on fat-supressed images, contrast-enhanced T1-weighted images are required to identify viable osseous fragments.     

Renal lesions: controlled comparison between CT and 1.5-T MR imaging with nonenhanced and gadolinium-enhanced fat-suppressed spin-echo and breath-hold FLASH techniques.

Nonenhanced and gadolinium-enhanced fat-suppressed spin-echo and breath-hold fast low-angle shot (FLASH) magnetic resonance (MR) imaging techniques were compared with iodine contrast material-enhanced computed tomography (CT) for the detection and characterization of renal masses. MR studies included T1-weighted fat-suppressed spin-echo (T1FS) and FLASH images followed by rapid injection of gadopentetate dimeglumine and a repeated FLASH image obtained at 1 second, a T1FS image at 30 seconds, and a FLASH image at 10 minutes. Of 38 patients, 17 had renal cysts, 18 had solid tumors, two had cortical scarring, and one had a hypertrophied column of Bertin. With contrast-enhanced T1FS, contrast-enhanced FLASH, and CT images, 114, 110, and 109 lesions, respectively, were detected. With MR imaging and CT, cysts smaller than 5 mm in diameter and solid tumors as small as 1 cm in diameter were detected. With combined contrast-enhanced FLASH and T1FS images, 112 lesions were correctly characterized as cystic or solid; with nonenhanced T1FS images, 110; with nonenhanced FLASH images, 107; and with nonenhanced CT, 103.     

Venous angiomas: plain and contrast-enhanced MRI and MR angiography

We studied 17 patients with venous angiomas, 4 of whom had associated cavernous angiomas. All underwent MRI with spin-echo T1- and T2-weighted images and T1-weighted images after Gd-DTPA; MR angiography (MRA) was also performed with 3D and 2D time-of-flight technique; 5 patients underwent conventional angiography. Contrast-enhanced MRI demonstrated all the lesions, showing the peripheral medullary veins, the collector and the type of drainage. Both 3D and 2D MRA provided diagnostic information identical to that obtained after infusion of Gd-DTPA. Contrast-enhanced were T1-weighted images and MRA superior in all the cases to images without gadolinium. The possible association with cavernous angiomas (24% in our study) indicates T2-weighted imaging.     

Comparing MR imaging and CT in the staging of gastric carcinoma

OBJECTIVE: The purpose of this study was to assess the usefulness of breath-hold two-dimensional (2D) fast low-angle shot (FLASH) and T2-weighted turbo spin-echo fast MR imaging compared with helical CT in the staging of gastric carcinoma. SUBJECTS AND METHODS: Thirty patients with gastric carcinoma underwent preoperative MR imaging and helical CT. MR imaging at 1.5 T was performed immediately after the intramuscular injection of scopolamine and the oral administration of water or effervescent granules. Breath-hold 2D FLASH T1-weighted images in all three planes, turbo spin-echo T2-weighted axial images, and gadolinium-enhanced fat-suppressed 2D FLASH axial images were included. Helical CT was performed 60 sec after initiation of i.v. contrast medium injection (2.5-3 ml/sec). Two groups of two radiologists each independently analyzed the MR and helical CT findings, and these results were compared with the pathologic findings. RESULTS: For T staging, MR imaging accuracy was higher than that of helical CT (73.3% and 66.7%, respectively); however, the accuracies of the two methods were not significantly different from each other (McNemar test, p > 0.05). Overstaging was noted in 6.7% of cases with MR imaging and 10% with helical CT. Understaging was noted in 20% of cases with MR imaging and 23.3% with helical CT. For N staging, the accuracies of MR imaging and helical CT were 55% and 58.6%, respectively, with no statistical significance (overstaging, 10% and 6.9%; understaging, 34.5% and 34.5%, respectively). CONCLUSION: MR imaging was comparable to helical CT in the T and N staging of gastric cancer.     

MR imaging in the evaluation of benign uterine masses: value of gadopentetate dimeglumine-enhanced T1-weighted images.

Forty-six patients with surgically proved disease (115 leiomyomas, 19 cases of adenomyosis, and 14 endometrial polyps) were studied to determine if gadopentetate dimeglumine-enhanced T1-weighted MR images improve the detection and characterization of benign tumors of the uterus. Lesion detection and characterization were assessed separately for each sequence (unenhanced T1-weighted, proton-density-weighted, and T2-weighted and contrast-enhanced T1-weighted images) and for combinations of sequences (unenhanced T1- and T2-weighted images, unenhanced and contrast-enhanced T1-weighted images, and unenhanced T1- and T2-weighted and contrast-enhanced T1-weighted images). In the evaluation of leiomyomas, analysis of all three sequences provided the best detection (92%) and characterization (92%), but the improvement, except when compared with unenhanced T1-weighted images alone, was not statistically significant. The use of contrast medium did not contribute to either tumor detection or characterization. In the evaluation of adenomyosis, T2-weighted images provided significantly better lesion detection and characterization than did either unenhanced or contrast-enhanced T1-weighted images. In the evaluation of endometrial polyps, however, contrast-enhanced T1-weighted images provided significantly better lesion detection and characterization than did unenhanced images. With contrast-enhanced images, the detection rate was 79%, compared with 36% for T2-weighted images and 7% for T1-weighted images. Lesion characterization was the best (73%) when all imaging sequences were analyzed. Our study shows that with conventional spin-echo sequences, the use of contrast-enhanced T1-weighted images does not improve the detection or characterization of uterine leiomyomas or adenomyosis but significantly improves the detection of endometrial polyps.     

A comparison of MR sequences for lesions of the parotid gland.

PURPOSETo compare six MR sequences (plain and gadolinium-enhanced fat suppressed T1-weighted spin echo, T2-weighted standard spin echo, fat-suppressed and non-fat-suppressed T2-weighted fast spin echo, and inversion-recovery T2-weighted fast spin echo) in their ability to detect, delineate, and characterize lesions of the parotid gland.METHODSFifty-eight parotid gland lesions imaged on 47 examinations were retrospectively evaluated by three blinded observers. Several outcome-related variables were compared by the above six sequences: imaging time, image quality, anatomic sharpness of parotid space, subjective lesion conspicuity, detected abnormality volume, number of individual lesions or discrete lobulations, conspicuity of invasion into adjacent boundaries and structures, and overall diagnostic value.RESULTSDifferences in the above outcome variables between sequences did not correlate with MR scanner software upgrade level, coil type, or lesion-dependent characteristics. Fat-suppressed fast spin-echo T2-weighted and inversion-recovery fast spin-echo T2-weighted sequences resulted in significantly higher scores for lesion conspicuity, detected abnormality volume, and overall diagnostic value. T1-weighted images resulted in the next highest scores, whereas gadolinium-enhanced T1-weighted and standard spin-echo T2-weighted sequences performed poorly for most parotid lesions.CONCLUSIONMR imaging of the parotid gland should include fat-suppressed, long-repetition-time, fast spin-echo T2-weighted, and T1-weighted sequences. Gadolinium-enhanced images need not be obtained routinely.     

FLAIR MR imaging for diagnosing intracranial meningeal carcinomatosis

OBJECTIVE: The purpose of this study was to compare unenhanced and contrast-enhanced fluid-attenuated inversion recovery (FLAIR) imaging with other sequences to visualize meningeal carcinomatosis. MATERIALS AND METHODS: Unenhanced FLAIR images were compared with spin echo T2-weighted and contrast-enhanced FLAIR images in five patients with documented meningeal carcinomatosis and four patients with suspected meningeal carcinomatosis. Comparisons were also made between contrast-enhanced T1-weighted and FLAIR images. RESULTS: In six patients, the unenhanced FLAIR images showed areas of abnormal hyperintensity within the sulci that were not noted on the spin-echo T2-weighted images. In all patients, the contrast-enhanced FLAIR images also showed meningeal enhancement, periventricular enhancement, or both. The contrast-enhanced T1-weighted and FLAIR images were equivalent in their depiction of abnormal enhancement in five of the nine patients; contrast-enhanced FLAIR images were superior in three patients. CONCLUSION: Unenhanced FLAIR images are of more value than spin-echo T2-weighted images for the diagnosis of intracranial meningeal carcinomatosis. Contrast-enhanced FLAIR images can sometimes surpass contrast-enhanced T1-weighted images in their quality.     

MR cholangiopancreatography: value of axial and coronal fast Spin-Echo fat-suppressed T2-weighted sequences

OBJECTIVE: To compare axial and coronal fast Spin-Echo fat-suppressed T2-weighted sequences with three-dimensional (3D) maximum intensity projection (MIP) images in patients with suspected pancreaticobiliary obstruction. MATERIAL AND METHODS: MR cholangiopancreatography (MRCP) was performed in 108 consecutive patients with a non-breath-hold, fat-suppressed, 2D, heavily T2-weighted fast spin-echo sequence in coronal plane. Axial T1- and T2-weighted images were previously obtained. In addition, 3D reconstructions of the coronal images were analysed separately by using a MIP algorithm. Both two-dimensional (2D) (axial and coronal) and 3D MIP images were separately evaluated by two readers in conference and their results were compared with that of endoscopic retrograde cholangiopancreatography, percutaneous trans-hepatic cholangiography, surgery and/or imaging follow-up. Statistical analysis of 2D and 3D MRCP images in diagnosing the level and probable cause of pancreaticobiliary obstruction were separately calculated. RESULTS: 106/108 of MRCP examinations were judged diagnostic by the two reviewers for adequacy of visualisation of the biliary and pancreatic ducts. Sensitivity, specificity, positive predictive value, negative predictive value and global diagnostic accuracy of 2D (axial and coronal) and 3D MRCP images in diagnosing the pancreaticobiliary obstruction were 94 and 57%,, 95 and 93%, 97 and 92%, 91 and 60%, 94 and 72% respectively. CONCLUSION: Our results do indicate a higher global accuracy for axial and coronal fast Spin-Echo fat-suppressed T2-weighted sequences versus 3D MIP images in diagnosis of the level and probable cause of pancreaticobiliary obstruction and stress the limitations of 3D images in depiction of small intraductal pathology such as calculi and biliary neoplastic.     

Fat-suppressed MR of the orbit and cavernous sinus: comparison of fast spin-echo and conventional spin-echo.

PURPOSETo compare T2-weighted fat-suppressed fast spin-echo imaging with fat-suppressed conventional spin-echo imaging in the detection of normal intraorbital and pericavernous anatomy and orbital disease, and to determine the efficacy of fat saturation with T2-weighted fast spin-echo imaging of the cavernous sinus.METHODSContrast-to-noise ratios of normal intraorbital anatomy were calculated and compared in 10 consecutive patients using fat-suppressed fast spin-echo and conventional spin-echo T2-weighted images. Contrast-to-noise ratios of common intraorbital lesions were calculated and compared using fat-suppressed fast spin-echo and fat-suppressed conventional spin-echo. Qualitative evaluation was performed and compared for normal intraorbital anatomy using both fat-suppressed fast spin-echo and fat-suppressed conventional spin-echo in 16 patients. Qualitative evaluation for the detection of normal anatomic structures of the pericavernous region was performed and compared using fast spin-echo with and without fat suppression and fat-suppressed conventional spin-echo T2-weighted images in 16 patients. Fat saturation was performed using standard commercially available chemical saturation technique.RESULTSReduced imaging time allowed more acquisitions for fat-suppressed fast spin-echo images, which significantly improved visibility of intraorbital and pericavernous anatomy over fat-suppressed conventional spin-echo. Anatomic visibility was also improved because of reduced motion, phase encoding, and susceptibility artifacts. There was no significant difference between contrast-to-noise ratios for fat-suppressed fast spin-echo and fat-suppressed conventional spin-echo imaging of the lateral and medial rectus muscles. Contrast-to-noise ratios of fat suppressed fast spin-echo of orbital disease was significantly greater than contrast-to-noise ratios of fat-suppressed conventional spin-echo. Detection of several normal anatomic structures of the pericavernous region was significantly improved with non-fat-suppressed fast spin-echo over fat-suppressed fast spin-echo because of significantly reduced magnetic susceptibility artifact.CONCLUSIONSFat-suppressed fast spin-echo is superior to fat-suppressed conventional spin-echo for T2-weighted orbital imaging. Non-fat-suppressed fast spin-echo is the preferred pulse sequence for T2-weighted imaging of the cavernous sinus because of the minimal susceptibility artifact.     

Retrograde cortical and deep venous drainage in patients with intracranial dural arteriovenous fistulas: comparison of MR imaging and angiographic findings

BACKGROUND AND PURPOSE: We assessed MR imaging, specifically contrast-enhanced three-dimensional (3D) magnetization-prepared rapid gradient-echo (MP-RAGE), in evaluating retrograde venous drainage in patients with intracranial dural arteriovenous fistulas (dAVFs) that may result in catastrophic venous infarction or hemorrhage. METHODS: Twenty-one patients with angiographically proved dAVFs underwent nonenhanced spin-echo (SE) and fast SE imaging, 3D fast imaging with steady-state precession, and enhanced SE and 3D MP-RAGE imaging. Retrograde venous drainage was categorized as cerebral cortical, deep cerebral, posterior fossa medullary, ophthalmic, or spinal venous. We assessed retrograde venous drainage and graded its severity. MR imaging and angiographic severities were correlated. Sensitivity, specificity, and accuracy were calculated to evaluate the diagnostic utility of each technique compared with conventional angiography. We retrospectively correlated angiograms and MR images. RESULTS: Enhanced 3D MP-RAGE and T1-weighted SE images had higher diagnostic accuracy higher than nonenhanced images, especially when retrograde drainage involved cerebral cortical, posterior fossa, and spinal veins. Correlation of severity for enhanced MP-RAGE images and enhanced T1-weighted images with angiograms was good to excellent and better than that with nonenhanced images. All sequences had low diagnostic accuracy when drainage was via deep cerebral veins. On retrospective review, 3D MP-RAGE images showed two thrombotic inferior petrosal sinuses. CONCLUSION: Enhanced MR images were superior to nonenhanced images in assessing retrograde venous drainage in intracranial dAVFs. Enhanced 3D MP-RAGE is superior to enhanced T1-weighted SE imaging for determining the route and severity of venous reflux because of its increased spatial resolution and ability to contiguously delineate the venous system.     

Intracranial leptomeningeal metastases: comparison of depiction at FLAIR and contrast-enhanced MR imaging

PURPOSE: To compare contrast material-enhanced T1-weighted and fluid-attenuated inversion-recovery (FLAIR) magnetic resonance (MR) images in depicting leptomeningeal metastases. MATERIALS AND METHODS: Malignant lesions detected at cytologic examination of cerebrospinal fluid in 70 patients were reviewed. There were 58 studies in which both FLAIR and contrast-enhanced T1-weighted spin-echo MR images were available. A senior neuroradiologist reviewed the images from each sequence individually and separately for signs of leptomeningeal metastases and assigned a diagnostic rating of positive, indeterminate, or negative. RESULTS: Leptomeningeal metastases were depicted in 38 cases on contrast-enhanced T1-weighted spin-echo images and in 20 cases on FLAIR images. In three cases, leptomeningeal metastases were detected by using only FLAIR images. In 20 cases, leptomeningeal metastases were detected by using only contrast-enhanced T1-weighted spin-echo images. FLAIR imaging has a sensitivity of 34% for cytologically proved leptomeningeal metastases. Gadolinium-enhanced MR imaging has a sensitivity of 66%. CONCLUSION: Used alone, contrast-enhanced T1-weighted images are better than FLAIR images for detecting leptomeningeal metastases. This is particularly true for cases in which leptomeningeal metastases manifest primarily or solely as cranial nerve involvement.     

Central nodal necrosis and extracapsular neoplastic spread in cervical lymph nodes: MR imaging versus CT.

Computed tomographic (CT) scans and magnetic resonance (MR) images obtained in 24 patients with cervical lymphadenopathy were retrospectively and blindly evaluated by two readers for the presence of central nodal necrosis (CNN) and extracapsular nodal spread (ENS). The CT studies were all enhanced, and the MR images were obtained with short repetition time (TR)/echo time (TE), long TR/double echo, and enhanced short TR/TE fat-suppressed sequences. Each MR imaging sequence was interpreted separately and then collectively. Sixty lymph nodes were identified with CT. Sensitivity for CNN was 16%-67% with the unenhanced MR pulse sequences, 50% with enhanced sequences, and 83%-100% with CT. The most accurate reading of MR images for CNN was with the unenhanced T1-weighted and T2-weighted images (86%-87%); the accuracy of CT was 91%-96%. The accuracy of MR imaging for detecting ENS was maximal with T1-weighted images (78%-90%). Gadolinium-enhanced, fat-suppressed images did not improve accuracy in evaluating CNN or ENS. CT is currently more accurate than unenhanced or enhanced MR imaging in detecting CNN or ENS.     

Diffusion-weighted MR imaging sequence in the detection of postoperative recurrent cholesteatoma

PURPOSE: To prospectively evaluate a fast spin-echo (SE) diffusion-weighted sequence for magnetic resonance (MR) imaging of recurrent cholesteatoma in patients who have undergone middle ear surgery. MATERIALS AND METHODS: The study was approved by the institutional review board, and informed consent was obtained from all patients. Twenty-four patients (10 female and 14 male patients; mean age, 44 years) who had undergone resection of cholesteatoma were referred for MR imaging. MR imaging was performed with a 1.5-T unit by using unenhanced diffusion-weighted fast SE imaging at b factors of 0 and 800 sec/mm(2), unenhanced T2-weighted fast SE imaging, unenhanced T1-weighted SE imaging, and delayed contrast material-enhanced T1-weighted imaging. Two radiologists evaluated the diffusion-weighted fast SE images for the presence of a high-signal-intensity cholesteatoma. Results from MR imaging were compared with reports from second- or third-look surgery. Interobserver agreement was assessed with the kappa statistic. RESULTS: A recurrent cholesteatoma was correctly identified in 13 of 14 patients with diffusion-weighted fast SE images obtained with a b factor of 800 sec/mm(2), for a positive predictive value of 93%. In patients without recurrent cholesteatoma, all diffusion-weighted fast SE MR images obtained with a b factor of 800 sec/mm(2) were correctly interpreted as showing no high signal intensity. Thus, the negative predictive value was 100%. Sensitivity and specificity were 100% (13 of 13 patients) and 91% (10 of 11 patients), respectively. Interobserver agreement was excellent (kappa = 0.92). The smallest recurrent cholesteatoma was 5 mm in diameter, and this was correctly detected with the diffusion-weighted fast SE sequence. CONCLUSION: Diffusion-weighted fast SE imaging enables the depiction of recurrent cholesteatoma in patients who have undergone middle ear surgery.