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.     

Focal hepatic lesions: detection and characterization with combination gadolinium- and superparamagnetic iron oxide-enhanced MR imaging

PURPOSE: To compare gadolinium- and superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance (MR) imaging for detection and characterization of focal hepatic lesions when different contrast agent administration sequences are used. MATERIALS AND METHODS: Unenhanced, dynamic gadolinium-enhanced, and SPIO-enhanced hepatic MR images were obtained in 134 patients. SPIO-enhanced MR imaging was performed immediately after gadolinium-enhanced dynamic MR imaging in 50 patients, 1 day after gadolinium-enhanced dynamic MR imaging in 40 patients, and before gadolinium-enhanced dynamic MR imaging in 44 patients. Two radiologists independently reviewed the gadolinium image set (unenhanced and gadolinium-enhanced dynamic MR images) and the SPIO image set (unenhanced and SPIO-enhanced MR images) in random order. Lesion detection sensitivity and lesion characterization accuracy were compared by analyzing the area under the receiver operating characteristic curve (Az). RESULTS: Overall lesion detection accuracy for pooled data was significantly higher with the SPIO set (Az = 0.903) than with the gadolinium set (Az = 0.857) (P <.05). When hypovascular lesions were excluded, the detection rate was similar with the two sets. When hepatocellular carcinomas were excluded, the detection rate was significantly higher with the SPIO set (P <.01). Readers were more accurate in differentiating benign from malignant lesions with the gadolinium set (Az = 0.915) than with the SPIO set (Az = 0.847) (P <.01). Detection accuracy tended to be better with the images obtained after the second contrast agent was used. CONCLUSION: Hypovascular lesion detection was better with SPIO-enhanced MR images than with gadolinium-enhanced MR images. Detection and characterization of hypervascular lesions were improved with gadolinium-enhanced MR images.     

Renal MR angiography at 1.0 T: three-dimensional (3D) phase-contrast techniques versus gadolinium-enhanced 3D fast low-angle shot breath-hold imaging.

OBJECTIVE: The purpose of this study was to evaluate the diagnostic usefulness of three different MR angiographic techniques at 1.0 T. SUBJECTS AND METHODS: In 22 patients with renal artery stenosis confirmed at intraarterial catheter angiography, we also performed unenhanced and gadolinium-enhanced three-dimensional phase-contrast MR angiography and gadolinium-enhanced single breath-hold three-dimensional fast low-angle shot MR angiography. We determined circulation time to optimize signal acquisition in gadolinium-enhanced breath-hold MR angiography after bolus injection of contrast material. RESULTS: Sensitivity, defined as the detection of a hemodynamically significant stenosis (>50% luminal narrowing), was 85% for enhanced phase-contrast MR angiography, 91% for gadolinium-enhanced MR angiography, and 95% for unenhanced phase-contrast MR angiography. The combination of unenhanced phase-contrast MR angiography and gadolinium-enhanced MR angiography yielded 100% sensitivity for hilar artery stenoses. There were 13 false-positive findings with unenhanced phase-contrast MR angiography, 10 with enhanced phase-contrast MR angiography, and four with gadolinium-enhanced MR angiography (specificity: 38%, 52%, and 79%, respectively). Accessory renal arteries were not seen on unenhanced or enhanced phase-contrast MR angiography (0/8 patients) but were detected with gadolinium-enhanced MR angiography in five of the eight patients. Interobserver agreement (kappa = .62) was best with gadolinium-enhanced MR angiography. The quality of the images was unsatisfactory for adequate evaluation of segmental renal arteries with all three MR angiographic techniques. CONCLUSION: A combination of unenhanced phase-contrast MR angiography and gadolinium-enhanced MR angiography at 1.0 T proved useful as a screening protocol for renal artery stenosis.     

Persistence of gadolinium in CSF: a diagnostic pitfall in patients with end-stage renal disease

Two dialysis-dependent patients with end-stage renal disease underwent brain and spine MR imaging a few days after having undergone gadolinium-enhanced imaging studies. Increased signal intensity in the subarachnoid space on T1-weighted and fluid-attenuated inversion recovery images was noted. Excretion of gadolinium into the CSF was proven in one case by mass spectrometry. Dialysis-dependent patients with end-stage renal disease and neurologic abnormalities often undergo contrast-enhanced MR imaging. Recognition that these patients may show increased signal intensity in the subarachnoid space because of gadolinium excretion into CSF may prevent diagnostic errors.     

Hepatocellular carcinoma: detection with gadolinium- and ferumoxides-enhanced MR imaging of the liver.

PURPOSE: To test the hypothesis that the accuracy of gadolinium- and ferumoxides-enhanced magnetic resonance (MR) imaging is different in small (< or =1.5-cm) and large (>1.5-cm) hepatocellular carcinomas (HCCs). MATERIALS AND METHODS: Forty-three consecutive patients with chronic liver disease were enrolled in this study. The imaging protocol included unenhanced breath-hold T1-weighted fast field-echo sequences, unenhanced respiratory-triggered T2-weighted turbo spin-echo (SE) sequences, dynamic gadolinium-enhanced T1-weighted three-dimensional turbo field-echo sequences, and ferumoxides-enhanced T2-weighted turbo SE sequences. Images of each sequence and two sets of sequences (ferumoxides set and gadolinium set) were reviewed by four observers. The ferumoxides set included unenhanced T1- and T2-weighted images and ferumoxides-enhanced T2-weighted turbo SE MR images. The gadolinium set included unenhanced T1- and T2-weighted images and dynamic gadolinium-enhanced three-dimensional turbo field-echo MR images. In receiver operating characteristic (ROC) curve analysis, the sensitivity and accuracy of the sequences were compared in regard to the detection of all, small, and large HCCs. RESULTS: Imaging performance was different with gadolinium- and ferumoxides-enhanced images in the detection of small and large HCCs. For detection of small HCCs, the sensitivity and accuracy with unenhanced and gadolinium-enhanced imaging (gadolinium set) were significantly (P =.017) superior to those with unenhanced and ferumoxides-enhanced imaging (ferumoxides set). The area under the composite ROC curves, or A(z), for the gadolinium set and the ferumoxides set was 0.97 and 0.81, respectively. For large HCC, the ferumoxides set was superior compared with the gadolinium set, but this difference was not statistically significant. Analysis of all HCCs demonstrated no significant differences for gadolinium- and ferumoxides-enhanced imaging. CONCLUSION: For the detection of early HCC, gadolinium-enhanced MR imaging is preferred to ferumoxides-enhanced MR imaging because the former demonstrated significantly greater accuracy in the detection of small HCCs.     

Contrast enhancement in spinal MR imaging

We evaluated 44 patients with suspected spinal tumors or previous laminectomies with gadolinium-DTPA MR imaging in order to characterize the enhancement in normal, postoperative, and neoplastic intraspinal tissue. Using the signal intensity of CSF as an internal control, we calculated the percentage increase in signal intensity from pre- to postgadolinium studies. Tumors (astrocytoma, ependymoma, schwannoma) enhanced 70-350%; epidural scar, normal epidural venous plexus, and dorsal root ganglion enhanced up to 200%. Contrast enhancement does not per se distinguish neoplastic from normal tissue. Enhancement with gadolinium-DTPA appeared to increase the conspicuousness of intramedullary tumors but not intraosseous metastases. We believe that gadolinium-enhanced MR imaging is a valuable adjunct to routine MR imaging in the evaluation of intraspinal neoplastic processes and may be useful in delineating normal and postoperative structures in the spinal canal.     

The role of gadolinium-DTPA in the evaluation of extracranial head and neck mass lesions

Based on our experience with 28 patients, there is good evidence that gadolinium-enhanced MR will be useful in evaluation of skull base involvement, sinus involvement, or intracranial extension by neoplasms that involve the neck above the hard palate. This region has historically been a difficult area to image with any modality, because of the detailed anatomy and numerous important structures that traverse it. Gadolinium-enhanced MR should provide a valuable tool in the evaluation and management of these patients. The evidence that gadolinium is useful in staging of primary and nodal squamous cell carcinoma of the extracranial head and neck is less apparent. Areas where gadolinium may be helpful include size and extent of primary tumor and internal architecture of nodes that do not meet size criteria for malignant adenopathy. This is an area in which more experience is necessary, employing careful correlation with enhanced CT, unenhanced MR, and surgical specimens. Posttreatment follow-up of head and neck squamous cell lesions is a potential use for gadolinium, but this too is yet to be adequately studied. We have found that gadolinium enhancement provides no additional information important to the management of benign head and neck lesions over enhanced CT or unenhanced MR.     

Multicenter study of gadodiamide injection as a contrast agent in MR imaging of the brain and spine

To evaluate the safety and efficacy of gadodiamide injection, a nonionic gadolinium chelate complex, in magnetic resonance (MR) imaging of the head and spine, a phase II-III trial was conducted in 439 patients with known or suspected lesions in the central nervous system. All patients received gadodiamide injection in a dosage of 0.1 mmol/kg and were monitored; MR images were evaluated for contrast material enhancement. No serious adverse events or clinically important trends in vital signs, laboratory values, or neurologic status were observed. Gadodiamide injection enhanced or facilitated the visualization of lesions in 266 or 353 patients (75.4%) in whom lesions were shown on unenhanced images, enhanced images, or both; in these 266 patients, the diagnosis was changed in 76 patients (28.6%) and facilitated in 190 patients (71.4%). It is concluded that gadodiamide injection is safe and effective for MR imaging of the head and spine in patients with suspected abnormalities of the central nervous system.     

Ovarian lesions: detection and characterization with gadolinium-enhanced MR imaging at 1.5 T

Magnetic resonance (MR) imaging for detection and characterization of ovarian masses was assessed in 33 patients with a total of 60 lesions. Lesions were characterized prospectively as benign or malignant by using T2-weighted MR images and unenhanced and gadolinium-enhanced T1-weighted MR images. MR imaging findings were compared with results of surgical laparotomy performed for staging of lesions. When malignancy was suspected, staging with MR imaging was performed. MR imaging demonstrated 57 of 60 (95%) surgically proved ovarian masses (34 of 36 were benign, 23 of 24 were malignant). Five significant primary criteria and four ancillary criteria for malignancy were established. For all MR pulse sequences combined, characterization of either type of lesion was correct in 84% of cases (48 of 57) when the five primary criteria were used and 95% (54 of 57) were correct when the four ancillary criteria were added. With gadolinium-enhanced images, correct characterization of malignant lesions increased from 56% to 78% with use of the five primary criteria and from 83% to 100% with use of both sets of criteria. Malignancies were correctly staged with MR imaging in 12 of 16 patients. Staging accuracy was 63% with unenhanced images and 75% with the addition of enhanced images.     

High-dose gadolinium-enhanced MRI for diagnosis of meningeal metastases

We compared high-dose (0.3 mmol/kg) and standard-dose (0.1 mmol/kg) gadolinium-enhanced MRI for diagnosis of meningeal metastases in 12 patients with suspected meningeal metastases. They were imaged with both standard-dose and high-dose gadolinium. All patients with abnormal meningeal enhancement underwent at least one lumbar puncture for cerebrospinal fluid (CSF) cytology, while patients with normal meningeal enhancement were followed clinically. All patients with negative CSF cytology also were followed clinically. A single observer reviewed all the images, with specific attention to the enhancement pattern of the meninges. Abnormal leptomeningeal enhancement was present in three cases, and abnormal pachymeningeal enhancement in three other patients. All of these patients had abnormal CSF analyses. In two of the three cases of abnormal leptomeningeal enhancement the disease was more evident on high-dose than on standard-dose imaging; in one case the abnormal enhancement was visible only on high-dose imaging. In one of the three cases with abnormal pachymeningeal enhancement, the disease was evident prospectively only with high-dose imaging. Received: 5 June 1997 Accepted: 12 June 1997     

Preoperative detection of malignant hepatic tumors: comparison of combined methods of MR imaging with combined methods of CT

OBJECTIVE: We compared radiologists' performance on combined unenhanced, gadolinium-enhanced, and ferumoxides-enhanced MR imaging with their performance on helical CT during arterial portography (CTAP) and biphasic CT during hepatic arteriography (CTHA) for the preoperative detection of malignant hepatic tumors. SUBJECTS AND METHODS: MR images and CT scans obtained in 33 patients were retrospectively analyzed. Images of the liver were reviewed on a segment-by-segment basis; a total of 261 segments with 39 hepatocellular carcinomas and 21 metastases were independently reviewed by three radiologists who were invited from outside institutions. Unenhanced and gadolinium-enhanced MR images were reviewed first, then ferumoxides-enhanced MR images were added for combined review. CTAP images and biphasic CTHA images were reviewed together. RESULTS: Sensitivity for the detection of hepatic tumors was analogous for combined unenhanced, gadolinium-enhanced, and ferumoxides-enhanced MR images (86%) and for combined CTAP images and biphasic CTHA images (87%). Specificity was higher with MR images (95%, p < 0.01) than with CT images (91%). Radiologists' performances were improved (Az = 0.962, p = 0.0502) by combining ferumoxides-enhanced MR images with unenhanced and gadolinium-enhanced MR images (Az = 0.950), and were analogous for combined unenhanced, gadolinium-enhanced, and ferumoxides-enhanced MR images and for combined CTAP images and biphasic CTHA images (Az = 0.959). CONCLUSION: Radiologists' performances on combined unenhanced, gadolinium-enhanced, and ferumoxides-enhanced MR imaging compared with their performances on combined helical CTAP and biphasic CTHA are analogous for the preoperative detection of malignant hepatic tumors. Such a dedicated combination of MR imaging may obviate the need for more invasive angiographically assisted helical CT for the preoperative detection of malignant hepatic tumors.     

"Ivy sign" in childhood moyamoya disease: depiction on FLAIR and contrast-enhanced T1-weighted MR images

PURPOSE: To compare contrast material-enhanced T1-weighted and fluid-attenuated inversion recovery (FLAIR) magnetic resonance (MR) images with or without gadolinium in depicting the leptomeningeal ivy sign in children with moyamoya disease. MATERIALS AND METHODS: Twenty-nine sets of FLAIR and postcontrast T1-weighted MR images were available in 19 consecutive children with primary moyamoya disease confirmed with conventional and MR angiography. Contrast-enhanced FLAIR MR images also were available in 15 sets. Two pediatric radiologists reviewed FLAIR and postcontrast T1-weighted images in separate sessions for the leptomeningeal ivy sign and assigned a rating of "present," "absent," or "equivocal" by consensus. Unenhanced and contrast-enhanced FLAIR MR images were compared side by side to determine which better depicted leptomeningeal high signal intensities. RESULTS: Postcontrast T1-weighted MR images revealed the leptomeningeal ivy sign in 40 hemispheres (frequency of visualization, 71% [40 of 56 hemispheres]), whereas unenhanced FLAIR MR images depicted it in 26 hemispheres (frequency of visualization, 46% [26 of 56 hemispheres]). An equivocal rating was given in 21 hemispheres versus in 11 on FLAIR and postcontrast T1-weighted images, respectively. FLAIR and postcontrast T1-weighted images agreed in 40 hemispheres. There was no case with a positive rating on FLAIR images when postcontrast T1-weighted images were negative. Unenhanced FLAIR MR imaging was superior to contrast-enhanced FLAIR imaging in seven hemispheres, whereas enhanced FLAIR was better in four of 28 hemispheres. In the remaining 17, findings with each sequence were similar. CONCLUSION: Contrast-enhanced T1-weighted images are better than FLAIR images for depicting the leptomeningeal ivy sign in moyamoya disease.     

Metastatic disease of the brain: extra-axial metastases (skull, dura, leptomeningeal) and tumour spread

Extra-axial intracranial metastases may arise through several situations. Hematogenous spread to the meninges is the most frequent cause. Direct extension from contiguous extra-cranial neoplasms, secondary invasion of the meninges by calvarium and skull base metastases, and migration along perineural or perivascular structures are less common. Leptomeningeal invasion gives rise to tumour cell dissemination by the cerebrospinal fluid (CSF), eventually leading to neoplastic coating of brain surfaces. Contrast-enhanced magnetic resonance (MR) imaging is complementary to CSF examinations and can be invaluable, detecting up to 50% of false-negative lumbar punctures. MR findings range from diffuse linear leptomeningeal enhancement to multiple enhancing extra-axial nodules, obstructive communicating and non-communicating hydrocephalus. Both calvarial and epidural metastases infrequently transgress the dura, which acts as a barrier against tumour spread. Radionuclide bone studies are still a valuable screening test to detect bone metastases. With computed tomography (CT) and MR, bone metastases extending intracranially and primary dural metastases show the characteristic biconvex shape, usually associated with brain displacement away from the inner table. Although CT is better in detecting skull base erosion, MR is more sensitive and provides more detailed information about dural involvement. Perineural and perivascular spread from head and neck neoplasms require thin-section contrast-enhanced MR.     

MR imaging in retinoblastoma

We studied the appearance of retinoblastoma on unenhanced and gadolinium-enhanced images and the accuracy of tumour staging with MR imaging. The MR images were obtained in 18 children with retinoblastoma and compared with histopathological findings after enucleation. The MR imaging included T1-weighted and dual-echo T2-weighted images before, and T1-weighted images after, gadopentetate dimeglumine injection. The contrast between tumour and ipsilateral vitreous strongly increased (57%) after gadolinium on T1-weighted images (p=0.004). Tumour was strongly hypointense as compared with ipsilateral vitreous in all patients using heavily T2-weighted (TE=120 ms) images (p=0.001). The estimated T2 of tumour (mean 96+14 ms) did not correlate with histological grading or degree of calcification. Unenhanced T1-weighted MR images rightfully excluded extrascleral growth in 16 of 16 cases, but its presence was confirmed after enucleation in only one of 2 abnormal MR scans. Invasion of the optic nerve behind the cribriform plate was confirmed in 2 of 3 abnormal gadolinium-enhanced MR scans, but also in 1 of the 15 cases in which MR images were normal. The T2-weighted images were useful in assessing retinal detachment. We conclude that heavily T2-weighted images, unenhanced T1-weighted images and gadolinium-enhanced T1-weighted MR images are complementary in characterizing and staging retinoblastoma.     

Contrast-enhanced flair imaging in the evaluation of infectious leptomeningeal diseases

PURPOSE: The purpose of our study was to compare contrast-enhanced fluid-attenuated inversion recovery (FLAIR) images with contrast-enhanced T1 weighted images for infectious leptomeningitis. MATERIALS AND METHODS: We studied twenty-four patients with a clinical suspicion of infectious meningitis with unenhanced FLAIR, contrast-enhanced T1 weighted and contrast-enhanced FLAIR MR sequences. Twelve patients had cytologic and biochemical diagnosis of meningitis on cerebrospinal fluid (CSF) examination obtained 48 h before or after the MR study. Sequences were considered positive if abnormal signal was seen in the subarachnoid space (cistern or sulci) or along pial surface. RESULTS: Twenty-seven examinations in 24 patients were performed. Of the 12 patients (thirteen studies) in whom cytology was positive, unenhanced FLAIR images were positive in six cases (sensitivity 46%), contrast-enhanced FLAIR images were positive in 11 (sensitivity 85%), and contrast-enhanced T1 weighted MR images were positive in 11 patients (sensitivity 85%). Of the 12 patients (14 studies) in whom cerebrospinal fluid study was negative, unenhanced FLAIR images were negative in 13, contrast-enhanced FLAIR images were negative in 11, and contrast-enhanced T1 weighted MR images were negative in eight. Thus, the specificity of unenhanced FLAIR, contrast-enhanced FLAIR and contrast-enhanced T1 weighted images was 93, 79 and 57%, respectively. CONCLUSION: Our results suggest that post-contrast FLAIR images have similar sensitivity but a higher specificity compared to contrast-enhanced T1 weighted images for detection of leptomeningeal enhancement. It can be a useful adjunct to post-contrast T1 weighted images in evaluation of infectious leptomeningitis.     

Meningeal Gd-DTPA enhancement in patients with malignancies

Nineteen patients with malignant diseases and pathologically enhancing meninges were studied by pre- and postcontrast (Gd-diethylene-triamine pentaacetic acid) magnetic resonance (MR) scans. Two patterns of enhancement were recognized: the dural (14 patients) and the leptomeningeal (mainly pial) (5 patients). Positive cytology was found in only 3 of the 14 patients with dural enhancement (21%), whereas in the remaining 11 patients we noted either nonspecific CSF findings such as elevated protein, high white blood cell count, and low glucose or entirely normal CSF. Four patients (80%) in the group with leptomeningeal enhancement showed positive cytology and one had normal CSF analysis. We conclude that meningeal enhancement as seen on MR imaging is a nonspecific finding and correlates well with positive cytology only when the more rare form of leptomeningeal enhancement is encountered.     

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.     

Comparison of spin echo T1-weighted and FLASH 90 degrees gadolinium-enhanced magnetic resonance imaging in the detection of cerebral metastases

A direct comparison of post-gadolinium FLASH 90 degrees magnetic resonance (MR) images against conventional post-gadolinium T1-weighted spin echo MR images obtained in patients with suspected cerebral metastatic disease shows the FLASH sequence to be inferior. False negative FLASH 90 degrees gadolinium-enhanced MR scans are thought to be a result of either magnetic susceptibility artefact or inferior contrast resolution. False positive FLASH 90 degrees gadolinium-enhanced MR images are a result of either difficulty in interpreting the high signal seen in small vessels or, again, magnetic susceptibility effects. In addition, our study shows small abnormalities suggestive of cerebral metastases on the FLASH 90 degrees gadolinium-enhanced sequences which were not seen on the spin echo T1-weighted gadolinium-enhanced sequences. We believe that spin echo T1-weighted gadolinium-enhanced MR sequences demonstrated 131 out of 139 (94.2%) and FLASH 90 degrees gadolinium-enhanced MR sequences detected 122 out of 139 (87.8%) possible metastases. From this, we conclude that spin echo T1-weighted gadolinium-enhanced MR sequences is a better test than FLASH 90 degrees gadolinium-enhanced MR in the diagnosis of brain metastases and that either sequence alone is limited as a screening test.     

Increased signal in the subarachnoid space on fluid-attenuated inversion recovery imaging associated with the clearance dynamics of gadolinium chelate: a potential diagnostic pitfall

BACKGROUND AND PURPOSE: Hyperintense CSF in the subarachnoid space (SAS) on fluid-attenuated inversion recovery (FLAIR) imaging has been reported in numerous pathologic conditions, including subarachnoid hemorrhage, meningitis, meningeal carcinomatosis, superior sagittal thrombosis, adjacent tumors, status epilepticus, and stroke. It has also been reported in otherwise healthy patients undergoing anesthesia with supplemental oxygen. We present a series of 11 patients with hyperintense CSF signal intensity in the SAS on FLAIR imaging after previous administration of gadolinium chelate. MATERIALS AND METHODS: Head MR images of patients who had a prior gadolinium-enhanced body, spine, or brain MR imaging and who had increased signal intensity in the SAS on FLAIR images were prospectively and retrospectively reviewed. Correlation was made with the clinical and laboratory findings. RESULTS: Eight of the 11 patients had negative findings on lumbar punctures. Seven patients had either chronic renal insufficiency or acute renal failure, but the remaining 4 had normal renal function. Nine patients had no other significant intracranial abnormalities, and 2 patients had acute infarcts remote from the CSF hyperintensity. One patient had follow-up studies at 24 and 48 hours, documenting resolution of the CSF hyperintensities. CONCLUSION: Given the sharp rise in volume of contrast-enhanced MR imaging studies, it is inevitable that some patients will have undergone a contrast-enhanced MR imaging 24-48 hours before an MR imaging of the brain. The neuroradiologist should be aware that previous administration of gadolinium chelate can cause increased signal intensity in the SAS on FLAIR imaging in patients with or without a history of renal insufficiency and without abnormalities known to disrupt the blood-brain barrier.     

Usefulness of dynamic contrast-enhanced MRI in the evaluation of the viability of acute scaphoid fracture

Objective

To evaluate the usefulness of dynamic gadolinium-enhanced magnetic resonance imaging (MRI) for assessing the viability of the proximal pole of the scaphoid in patients with acute scaphoid fractures.

Methods

Eighteen consecutive patients with acute scaphoid fracture who underwent dynamic gadolinium-enhanced MRI 7 days or less before surgery were prospectively included between August 2011 and December 2012. All patients underwent MR imaging with unenhanced images, enhanced images, and dynamic enhanced images. A radiologist first classified the MRI results as necrotic or viable based on T1- and T2-weighted images only, followed by a second blinded interpretation, this time including analysis of pre- and post-gadolinium administration images and a third blinded interpretation based on the time–intensity curve of the dynamic enhanced study. The standard of reference was the histologic assessment of a cylindrical specimen of the proximal pole obtained during surgery in all patients. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated for unenhanced, enhanced, and dynamic gadolinium-enhanced MRI studies.

Results

The sensitivity, specificity, PPV, and NPV were 67, 67, 50, and 80 % for unenhanced images, 83, 100, 100, and 92 for enhanced images, and 83, 92, 83, and 92 for dynamic contrast-enhanced images.

Conclusions

Our data are consistent with previously reported data supporting contrast-enhanced MRI for assessment of viability, and showing that dynamic imaging with time–intensity curve analysis does not provide additional predictive value over standard delayed enhanced imaging for acute scaphoid fracture.