Contrast-enhanced T1-weighted Magnetic Resonance Imaging Research Articles

A novel intramedullary spinal cord tumor model: functional, radiological, and histopathological characterization

Survival rates for high-grade intramedullary spinal cord tumors (IMSCTs) are approximately 30%, and optimal therapy has yet to be determined. Development of a satisfactory intramedullary tumor model is necessary for testing new therapeutic paradigms that may prolong survival. The authors report the technique, functional progression, radiological appearance, and histopathological features of a novel intramedullary model in rabbits. Ten New Zealand white rabbits were randomized to receive an intramedullary injection of either 25 microl of VX2 carcinoma cells (500,000 cells; six rabbits) or 25 microl of medium (Dulbecco modified Eagle medium; four rabbits) into the midthoracic spinal cord. Postoperatively the rabbits were evaluated twice daily for neurological deficits. High-resolution magnetic resonance (MR) images were acquired preoperatively and weekly postoperatively until onset of paraparesis, at which point the animals were killed, and the midthoracic spines were processed for histopathological examination. The VX2-carcinoma cells grew in 100% of animals injected and resulted in a statistically significant mean onset of paraparesis of 16.8 +/- 1.7 days (p = 0.0035, log-rank test), compared with animals in the control group in which neurological deficits were absent by Day 45. Contrast-enhanced T1-weighted MR imaging best demonstrated space-occupying intramedullary lesions and histopathological findings confirmed the intramedullary location of the tumor. Animals in the control group exhibited no functional, radiographic, or pathological signs of tumor. Progression to paraparesis was consistent in all the VX2-injected animals, with predictable onset of paraparesis occurring approximately 17 days postinjection. Histopathological and radiological characteristics of the VX2 intramedullary tumor are comparable with those of aggressive primary human IMSCTs. Establishment of this novel animal tumor model will facilitate the testing of new therapeutic paradigms for the treatment of IMSCTs.

Reduction in levels of matrix metalloproteinases and increased expression of tissue inhibitor of metalloproteinase—2 in response to mild hypothermia therapy in experimental stroke

Mild hypothermia is a robust neuroprotectant, and the results of prospective clinical trials have indicated that it may improve neurological outcome in certain instances. One aspect of this protection has been associated with the prevention of blood-brain barrier (BBB) disruption. Matrix metalloproteinases (MMPs) have been implicated in BBB disruption because they can degrade the extracellular matrix. In this study the authors explored the relationship between hypothermia and MMPs and whether BBB preservation resulting from mild hypothermia therapy is due to alterations in MMP expression. Rats were subjected to middle cerebral artery occlusion for 2 hours; the animals were maintained in a state of normothermia or mild hypothermia (33 degrees C) immediately after the onset of ischemia. The animals' brains were collected 2, 6, and 24 hours after ischemia began. Contrast-enhanced T1-weighted magnetic resonance imaging was performed at 24 hours to assess the extent of BBB disruption. Consistent with prior reports, areas of BBB disruption detected on T1-weighted images were smaller in the brains of rats maintained in a state of hypothermia (normothermia group 8.6 +/- 3% of the brain; hypothermia group 0.2 +/-0.1% of the brain; p < 0.01). Expression of both MMP-2 and MMP-9 at the transcriptional and translational levels was reduced in hypothermic brains at 6 hours and 24 hours after ischemic injury. Matrix metalloproteinase-9 was primarily localized to cells of monocytic origin but was also observed in neurons and astrocytes. Matrix metalloproteinase-2 was found in some neurons and astrocytes but not in inflammatory cells. In addition, hypothermia increased the levels of the endogenous MMP inhibitor, tissue inhibitor of metalloproteinases-2. The authors conclude that mild hypothermia attenuates BBB disruption, decreases MMP expression, and suppresses MMP activity.

Magnetresonanztomographie nach Kryoablation langer Röhrenknochen im Tiermodell

To describe the MR findings following cryoablation of long bones. Cryoablation was performed in femoral and tibial bones of 24 sheep under general anesthesia. MRI of the treated and untreated contralateral bones was performed immediately thereafter and at 2, 4 and 6 months after the cryosurgical procedure. On the MRI performed immediately after cryotherapy, the lesions showed low signal intensities relative to the normal bone marrow on unenhanced T1- and T2-weighted images. At 2, 4 and 6 months after cryoablation, the lesions showed high signal intensities on STIR images, low signal intensities on T1-weighted and heterogeneous enhancement on contrast-enhanced T1-weighted MR images. The femoral lesions decreased in size from 31 +/- 3 mm immediately after the cryotherapy to 13 +/- 4 mm 6 month later and the tibial lesions from 29 +/- 7 mm to 19 +/- 4 mm. MRI shows bone marrow lesions immediately after cryotherapy and can easily monitor healing lesions. MR imaging is suitable for following cryotherapy.

Tuberculous Meningitis: Comparison of Contrast Enhanced T1-Weighted and Flair MR Imaging with Magnetization Transfer Contrast

Fluid-attenuated inversion recovery (FLAIR) imaging with contrast enhancement is highly sensitive for detecting subarachnoid space disease. We hypothesized that contrast-enhanced FLAIR imaging with magnetization transfer would offer superior sensitivity to contrast-enhanced T1-weighted MR imaging with magnetization transfer in detecting TB meningitis. Forty-four patients referred for suspected TB meningitis underwent MR imaging studies. The patients had either proven TB meningitis or negative TB meningitis. The MR imaging examinations included both contrast-enhanced FLAIR and T1-weighted MR images with magnetization transfers that were independently reviewed by two neuroradiologists. Each of the sequences was reviewed individually and separately and was assigned a score of positive or negative for TB meningitis. Of the 21 studies of patients with proven TB meningitis, nine were positive based on contrast-enhanced FLAIR images with magnetization transfer, and 13 were positive based on contrast-enhanced T1-weighted MR images with magnetization transfer. Of the 23 studies of patients without TB meningitis, 19 were negative based on contrast-enhanced FLAIR images, and 20 were negative based on contrast-enhanced T1-weighted MR images with magnetization transfer. The sensitivity and specificity for contrast-enhanced FLAIR images for detecting TB meningitis were 43% (nine of 21) and 82% (19 of 23), respectively. The sensitivity and specificity of contrast-enhanced T1-weighted MR images with magnetization transfer for detecting TB meningitis were 62% (13 of 21) and 87% (20 of 23), respectively. Contrast-enhanced FLAIR imaging with magnetization transfer is less sensitive than contrast-enhanced T1-weighted MR sequences with magnetization transfer in detecting TB meningitis.

Dural enhancement with primary calvarial lesions

The purpose of this study was to relate the pathological and imaging features of dural enhancement and meningeal sign ("dural tail") on contrast-enhanced T1-weighted magnetic resonance (MR) images from patients with primary calvarial lesions as well to assess the accuracy of MR imaging in predicting dural invasion. Thirty-two calvarial tumors studied with contrast-enhanced MR imaging and histopathological examination of the dural specimens were reviewed. Sixteen patients presented dural enhancement, eight with tumor invasion. Tumoral invasion of the dura was observed in one case without enhancement. Malignant lesions showed enhanced dura more commonly than benign lesions (P=0.02). Nodular and discontinuous dural enhancement was statistically associated with dural invasion (P=0.05). Dural tail did not show a specific pathological association. Meningeal enhancement is a nonspecific reaction to calvarial lesions unless nodular and discontinuous. False-negative and -positive cases of dural invasion imply some limitation of contrast-enhanced MR imaging in predicting dural invasion by calvarial neoplasms.

Longitudinal multivoxel MR spectroscopy study of pediatric diffuse pontine gliomas treated by radiotherapy

Longitudinal multivoxel MR spectroscopy study of pediatric diffuse pontine gliomas treated by radiotherapy

Radiofrequency thermal ablation: correlation of hyperacute MR lesion images with tissue response.

To investigate the hypothesis that the outer boundary of the hyperintense region observed in hyperacute (several minutes post-ablation) T2 and gadolinium contrast-enhanced (CE) T1-weighted magnetic resonance (MR) lesion images is an accurate predictor of eventual cell death from radiofrequency (RF) thermal ablation. A low-field, open MR imaging system was used to guide an ablation electrode into a thigh muscle of five rabbits and acquire in vivo T2 and CE T1-weighted MR volumes. Ablation occurred by applying RF current for two minutes with the electrode's temperature maintained at 90 degrees +/- 2 degrees C. After fixation, we sliced and photographed the tissue at 3 mm intervals, using a specially designed apparatus, to obtain a volume of tissue images. Digital images of hematoxylin and eosin (H&E) and Masson trichrome-stained histologic samples were obtained, and distinct regions of tissue damage were labeled using a video microscopy system. After the MR and histology images were aligned using a three-dimensional registration method, we compared tissue damage boundaries identified in histology with boundaries marked in MR images. The lesions have distinct zones of tissue damage histologically: a central zone of necrotic cells surrounded by an outer zone with cells that appeared non-viable and associated with marked interstitial edema. In 14 histology images from five lesions, the inner and outer boundaries of the outer zone were compared with the boundaries of a hyperintense rim that surrounds a central hypointense region in the T2 and CE T1-weighted MR images. For T2 and CE T1-weighted MR images, respectively, the mean absolute distance was 1.04 +/- 0.30 mm (mean +/- SD) and 1.00 +/- 0.34 mm for the inner boundaries, and 0.96 +/- 0.34 mm and 0.94 +/- 0.44 mm for the outer boundaries. The mean absolute distances for T2 and CE T1-weighted MR images were not sufficiently different to achieve statistical significance (P = 0.745, 0.818, for the inner and outer boundary, respectively). In hyperacute T2 and CE T1-weighted MR lesion images, observations strongly suggest that the outer boundary of the hyperintense rim corresponds to the region of eventual cell necrosis within a distance comparable to our ability to measure. This is good evidence that during RF ablation procedures, MR lesion images can be used to accurately localize the zone of irreversible tissue damage at the lesion margin.

Pathologic Quiz Case: Cerebellar Hemorrhage in an Octogenarian

An 80-year-old right-handed man with a history of hypertension and stable coronary artery disease presented with progressive lethargy, confusion, and unsteadiness. Four months previously, he had been admitted to the stroke service following the abrupt onset of severe headache, nausea, vomiting, and ataxia. An axial computed tomographic (CT) scan showed a 3 × 3-cm left cerebellar hemorrhage; magnetic resonance imaging was not performed. He was managed nonoperatively for hypertension-induced intracerebral hemorrhage, transferred to a rehabilitation hospital 1 week later, and discharged at 2 weeks with a normal neurological status.Three months later, the patient noted difficulty in coordinating his walking. Repeat noncontrast axial CT showed a resolving hematoma with minimal mass effect; there was no hydrocephalus. He was stable until 1 week prior to admission, at which point he became diffusely weaker, lethargic, and withdrawn. On the day before admission, he became abruptly more confused and was unable to walk. A nonenhanced CT scan revealed increased cerebellar edema. The patient was transferred to our hospital and steroids were administered, with clinical improvement. Neurological examination noted lethargy, lateral gaze nystagmus, and left hand dysdiadochokinesia. Magnetic resonance imaging, including axial T1-weighted, axial T1-weighted with gadolinium (Figure, A), and coronal, T1-weighted gadolinium-enhanced, demonstrated a solid, homogeneously enhancing 4.5 × 3.5-cm mass in the vermis and left cerebellar hemisphere with associated edema, mass effect, and resolving hemorrhage. Physical examination and detailed CT imaging of the chest, abdomen, and pelvis revealed no primary neoplasm.The patient underwent a suboccipital craniectomy. At surgery, a discrete, firm, pseudoencapsulated mass in the vermis and medial left cerebellum was encountered; there was no attachment to the pia or dura. Contrast and non–contrast-enhanced axial views 1 day postsurgery indicated that gross total resection was accomplished. The patient tolerated surgery and was discharged 4 days later. He was to receive radiation therapy to a total of 60 cGy.Hematoxylin-eosin, reticulin, and glial fibrillary acidic protein (GFAP)–immunostained sections of fixed tissue revealed a predominantly sarcomatous neoplasm populated by fascicles of spindle cells that often appeared to be associated with the adventitia of blood vessels (Figure, B). Mitotic activity in these fascicles was brisk. Reticulin stains and immunohistochemical analysis demonstrated extensive reticulin but no GFAP, HMB-45, desmin, or myoglobin immunoreactivity (Figure, C and D). Neither rhabdomyoblasts nor strap cells were found. Interspersed were islands of anaplastic GFAP-immunoreactive astrocytes with scattered mitoses. Multifocal necrosis was also present.What is your diagnosis?Gliosarcomas are uncommon malignant primary tumors of the brain that contain both glial and mesenchymal elements. They are most commonly encountered in the frontal, temporal, and parietal lobes in patients older than 60 years of age.1–6 Only rare cases of gliosarcomas have been reported in the cerebellum. These include 2 cases that occurred after radiation treatment of extracranial neoplasms78 and 2 primary gliosarcomas of the cerebellum in patients who were 62 and 71 years of age.910 One of these demonstrated multiple homogeneously enhancing masses on contrast-enhanced T1-weighted magnetic resonance images; each mass had extensive contact with the dura mater.9 Computed tomography of the other case demonstrated a single contrast-enhancing lesion that proved upon operation to have an attachment to the tentorium cerebelli. Typically, enhanced T1-weighted MR images of cerebral gliosarcomas demonstrate diffuse, inhomogeneous enhancement or irregular ringlike enhancement.4 Our case and that report by Nitta et al9 indicate that a pattern of more homogeneous enhancement may be encountered in primary gliosarcoma of the posterior fossa.Cerebral gliosarcomas show a predilection for a superficial location and dural invasion and thus may not be considered in the initial workup of parenchymal masses, as depicted here.4 Our case illustrates that gliosarcoma should be included in the differential diagnosis of deep lesions, such as other gliomas and metastatic lesions that present without dural involvement.The diagnosis of gliosarcoma rests on the exclusion of glioblastomas associated with reactive leptomeningeal or vascular changes and sarcomas with entrapped reactive astrocytes. Diagnosis requires identification of a malignant glial (usually astrocytic) component and at least one ×100 magnification field of a sarcoma histologically consistent with a malignant fibrous histiocytoma or fibrosarcoma. Although the source of the sarcomatous component has been debated, Boerman et al6 have now identified similar genetic alterations (ie, gains of chromosome 7, deletions of 9p, and losses of chromosome 10 in both the glial and sarcomatous components), indicating that this component arises from the same progenitor cell as the glial component.We conclude that sporadic primary gliosarcomas may involve the cerebellum in the very old with atypical radioimaging characteristics. Given the rarity of this tumor and the variability of its radiographic appearance, the diagnosis may be apparent only upon biopsy of the lesion.

Telangiectatic focal nodular hyperplasia: US, CT, and MR imaging findings with histopathologic correlation in 13 cases.

To review the ultrasonographic (US), computed tomographic (CT), and magnetic resonance (MR) imaging findings in 13 patients with telangiectatic focal nodular hyperplasia (FNH) and to compare imaging features with histopathologic results from resected specimens. US, helical multiphasic CT, and MR images in 13 patients with pathologically proven telangiectatic FNH were reviewed retrospectively. Two abdominal radiologists evaluated lesions for number, size, heterogeneity, surface characteristics, presence of a central scar, presence of a pseudocapsule, US appearance, attenuation at CT, signal intensity at MR imaging, and presence of associated lesions. Imaging and pathologic findings were compared. Sixty-one lesions (5-140 mm in diameter) were seen at imaging. Lesions were multiple in eight of 13 (62%) patients. Imaging characteristics were heterogeneity in 26 of 61 lesions (43%), well-defined margins in 43 of 61 (70%), lack of a central scar in 56 of 61 (92%), presence of a pseudocapsule in three of 61 (5%), hyperintensity on T1-weighted MR images in 17 of 32 (53%), strong hyperintensity on T2-weighted MR images in 24 of 54 (44%), and persistent enhancement on delayed contrast material-enhanced CT or T1-weighted MR images in 23 of 38 (61%). No specific US pattern was noted. Two patients had additional lesions: One had classic FNH, and the other had a cavernous hemangioma. Hyperintensity on T1-weighted MR images was due to sinusoidal dilatation. Hyperintensity on T2-weighted MR images correlated well with the presence of inflammation. Telangiectatic FNH differs from typical FNH at imaging: Atypical FNH features often observed with telangiectatic FNH are lack of a central scar, lesion heterogeneity, hyperintensity on T1-weighted MR images, strong hyperintensity on T2-weighted MR images, and persistent contrast enhancement on delayed contrast-enhanced CT or T1-weighted MR images.

Using relative cerebral blood flow and volume to evaluate the histopathologic grade of cerebral gliomas: preliminary results.

Relative cerebral blood flow has rarely been studied as part of the preoperative assessment of tumor grade, although relative cerebral blood volume is known to be useful for this assessment. The purpose of our study was to determine the usefulness of relative cerebral blood flow in assessing the histopathologic grade of cerebral gliomas. MR imaging was performed in 17 patients with proven cerebral gliomas (11 high-grade gliomas and six low-grade gliomas), using a first-pass gadopentetate dimeglumine-enhanced T2-weighted echoplanar perfusion sequence. The perfusion data were deconvoluted with an arterial input function, using singular value decomposition to obtain a color map of relative cerebral blood volume and flow; the relative cerebral blood volume and flow ratios were expressed relative to values measured in the contralateral white matter. The Wilcoxon's rank sum test was performed to test the difference between the mean of the relative cerebral blood volume (or flow) ratio in high-grade gliomas and that in low-grade gliomas. Receiver operating characteristic curve analysis was used to evaluate the association between the relative cerebral blood volume (or flow) ratio and the grade of the glioma, as well as to calculate the relative cerebral blood volume and flow ratio cutoff value permitting discrimination between high- and low-grade gliomas. The correlation between relative cerebral blood volume and flow ratios was evaluated using Spearman's rank correlation analysis. We also made a qualitative assessment regarding the match or mismatch of areas of maximal contrast enhancement with the areas of highest color perfusion maps. The mean of the relative cerebral blood volume ratio was 4.91 in the high-grade gliomas and 2.00 in the low-grade gliomas. The mean relative cerebral blood flow ratio was 4.82 in the high-grade gliomas and 1.83 in the low-grade gliomas. A significant difference in each relative cerebral blood volume and flow ratio was found between the high- and low-grade gliomas (Wilcoxon's rank sum test, p < 0.05). Both the relative cerebral blood volume and flow ratios strongly matched the grade of the glioma, but the difference between the two areas was not significant (receiver operating characteristic curve analysis, p > 0.05). The desired cutoff value was 2.93 in the relative cerebral blood volume ratio and 3.57 in the relative cerebral blood flow ratio. Additionally, there was a strong correlation between the relative cerebral blood volume and flow ratios (Spearman's rank correlation coefficient = 0.762; p < 0.05). There was frequent mismatch (33%) between the qualitative assessment of the contrast-enhanced T1-weighted MR images and the perfusion maps. First-pass gadopentetate dimeglumine-enhanced T2-weighted echoplanar perfusion MR imaging is useful for the preoperative assessment of tumor grade. A relative cerebral blood flow ratio, in addition to a relative cerebral blood volume ratio, can be a useful tool in the evaluation of the histopathologic grade of cerebral gliomas.

Detection of postoperative residual cholesteatoma with delayed contrast-enhanced MR imaging: initial findings.

Our objective was to assess the value of delayed contrast-enhanced T1-weighted spin-echo MR imaging in the detection of residual cholesteatoma in patients who have undergone canal wall-up tympanoplasty procedure. The MR imaging was obtained prior to revision surgery in 18 patients with opacity of the post-operative cavity at CT examination 12-18 months after canal wall-up tympanoplasty. In each patient the following was performed: precontrast T1- and T2-weighted images; and early and delayed contrast-enhanced axial and coronal T1-weighted imaging. Early and delayed MR imaging results were separately compared with surgical second-look findings. Sensitivity, specificity, and predictive values were evaluated for early and delayed post-contrast MR imaging, compared with second-look surgery findings. A residual cholesteatoma was correctly identified in 8 of 9 cases with delayed contrast-enhanced T1-weighted MR imaging. Mean sensitivity, specificity, positive predictive value, and interobserver agreement (evaluated by kappa statistics) were, respectively, 85.2, 92.6, 92.6%, and kappa=0.78 for the delayed contrast-enhanced MR imaging technique. The same parameters were, respectively, 96.3, 33.3, 60.6, and 0.30 for the early contrast-enhanced T1-weighted MR images. We conclude that delayed contrast-enhanced T1-weighted MR imaging is reliable for the detection of residual cholesteatomas of the middle ear in patients who have undergone canal wall-up tympanoplasty.

Sonographic and MR imaging findings of testicular epidermoid cysts.

The purpose of this study is to analyze the sonographic and MR imaging findings of testicular epidermoid cysts. Sonographic findings of a markedly heterogeneous intratesticular mass with or without alternating hypo- and hyperechoic layers surrounded by a hypoechoic or echogenic rim and the absence of flow on color Doppler sonography suggest the preoperative diagnosis of testicular epidermoid cysts. T2-weighted MR imaging findings of a high-signal-intensity mass with or without low-signal-intensity foci surrounded by a low-signal-intensity rim and the absence of enhancement on contrast-enhanced T1-weighted MR images can strengthen the preoperative diagnosis. These imaging findings can offer a basis for surgeons to attempt testis-sparing surgery instead of orchiectomy.

MR findings of renal cortical necrosis.

Evaluating the MR findings of renal cortical necrosis was the purpose of this study. Eight series of T1-/T2-weighted (n = 8) and contrast-enhanced T1-weighted (n = 4) MR images in six patients with renal cortical necrosis diagnosed by renal biopsy (n = 4) or on clinical grounds (n = 2) were reviewed. In those who had follow-up MRI (n = 2) or comparable CT (n = 3), interval changes of MR findings and comparison with CT images were done. Swollen kidney with dark signal intensity rim involving the inner cortex and column of Bertin was noted on T2-and T1-weighted images. It was more conspicuous on T2-weighted images. The lesion did not enhance and was differentiated from uninvolved renal parenchyma. In the follow-up MRI, thickened dark signal intensity was more prominent and proved to be calcification or fibrosis. MRI, especially T2-weighted and contrast-enhanced T1-weighted imaging, was helpful in evaluating renal cortical necrosis.

Characteristics of false positive lesions appeared in dynamic contrast-enhanced t1-weighted MR imaging of the breast

Characteristics of false positive lesions appeared in dynamic contrast-enhanced t1-weighted MR imaging of the breast

Unique linear and nodular MR enhancement pattern in schistosomiasis of the central nervous system: report of three patients.

The purpose of this paper is to describe the unique MR imaging appearance of schistosomiasis of the central nervous system (CNS). Contrast-enhanced T1-weighted MR images in all three patients with CNS schistosomiasis revealed a central linear enhancement surrounded by multiple enhancing punctate nodules, forming an "arborized" appearance. Pathologically, this enhancement pattern correlated with a host granulomatous response to Schistosoma species ova. Although the pattern is not present in all cases of CNS schistosomiasis, when it is observed, a diagnosis of CNS schistosomiasis should be considered.

Diagnosis of endolymphatic hydrops in vivo with magnetic resonance imaging.

High-resolution magnetic resonance imaging (MRI) at 1.5 T preferentially enhances the perilymph over endolymph after administration of contrast with gadodiamide, which allows for differentiation of the membranous labyrinth. Furthermore, this imaging allows for the detection of endolymphatic hydrops. Endolymphatic hydrops is believed to be associated with a number of ear diseases, including Ménière's disease. Although the pathologic changes of overaccumulation of endolymph in the inner ear are obvious on postmortem histologic examination of the temporal bone, they have yet to be observed in a living organism. Previous attempts to visualize this condition with high-resolution contrast-enhanced computed tomographic imaging and MRI have been unsuccessful. Healthy pigmented guinea pigs underwent a unilateral surgical ablation of the endolymphatic sac to create endolymphatic hydrops in the ear. High-resolution temporal bone imaging was performed by use of a 1.5-T MRI system. Two-dimensional images were acquired by a spin-echo technique with and without contrast enhancement by gadodiamide. T1-weighted gadodiamide contrast-enhanced MRI of the midmodiolar level of the cochlea demonstrated that the perilymph appeared to be preferentially enhanced relative to the endolymph, resulting in a clear distinction between the scalae of the inner ear. The contrast-enhanced T1-weighted MRI of the midmodiolar level of the hydropic cochlea demonstrated a significantly enlarged scala media in comparison with the normal cochlea in the same animal. The demonstration of endolymphatic hydrops has been possible for the first time in vivo by the use of a standard 1.5-T MRI system. This research has important clinical implications: Specifically, this technique may allow for the noninvasive diagnosis of Ménière's disease.

Prognostic impact of tumor perfusion in MR-imaging studies in Ewing tumors.

Intratumoral hypoxia is associated with poor prognosis in various solid tumors. Severe and long-lasting hypoxia results in necrosis. The presence of necrosis therefore might also be correlated with unfavorable outcome. This has been demonstrated for head and neck cancers, gliomas and adult soft tissue sarcomas. We have investigated whether or not the patterns of contrast enhancement and the presence of visible necrosis on pretreatment MR images has prognostic impact in Ewing tumors. From December 1993 though March 1997, 79 patients with Ewing tumors were prospectively analyzed for the presence and amount of necrosis in their tumors. The median age was 12 years (range 4-30 years). The median follow-up at the time of this analyses was 3 years. All patients were treated according to the multicentric EICESS-92 protocol with multi-agent chemotherapy (VACA or VAIA or EVAIA) and local therapy (radiotherapy with 50-60 Gy or surgery or surgery with pre- or postoperative irradiation with 45-50 Gy). For the measurement of necrosis, gadolinium contrast-enhanced T1-weighted MR images were used. Necrosis was defined as non-perfused areas in the tumor and the necrotic volume was expressed as percentage of total volume. Out of 79 tumors, 10 (13%) showed no necrosis, 30 (38%) had 1-25% necrosis, 21 (27%) had 26-50% necrosis and the remaining 18 (23%) more than 50% necrosis. There was a correlation between tumor size and necrosis (p = 0.001): the median tumor volume increased with amount of necrosis (47 cm3 in non-necrotic tumors, 59 cm3 vs 280 cm3 vs 284 cm3 for tumors with 1-25% vs 26-50% vs > 50% necrosis). Tumor site (central location vs proximal extremities vs distal extremities) had no impact on necrosis (p = 0.71). 23 out of 79 patients had metastases (M1) at the time of diagnosis. The frequency of metastatic spread increased with the amount of necrosis: 1/10 (10%) patients with non-necrotic tumors had metastases vs 7/30 (23%) vs 6/21 (28%) vs 9/18 (50%) for tumors with 1-25% vs 26-50% vs > 50% necrosis. "Unfavorable" metastatic spread (bone or multiple metastases) was only noted in patients with high amount of necrosis (> 25% necrosis) whereas even large tumors did not show unfavorable metastases if they contained no or only small amounts of necrosis. All patients with non-necrotic tumors survived event-free during the observation period. Patients with necrotic tumors had a 3-year event-free survival of 55% (p = 0.06 vs tumors without necrosis). The presence of non-perfused (presumably necrotic) areas on pretreatment contrast-enhanced MR-images is associated with an increased risk of metastases, especially an unfavorable pattern of metastatic spread at diagnosis. This observation may be explained by a more aggressive biological behavior of hypoxic tumor cells. The small group of patients with non-necrotic tumors (13%) had an excellent prognosis suggesting that the absence of necrosis might be helpful in identifying a very favorable prognostic subgroup in Ewing tumors.

Fast sequences with fat suppression in breath-hold mode: new standard in contrast-enhanced T1-weighted MR imaging of renal tumors?

Our purpose was to analyze detection, diagnostic characterization, and staging of renal solid lesions using different fast T1-weighted sequences with fat suppression in breath-hold mode compared with a gradient-echo sequence after contrast application. Twenty-five patients with focal renal lesions were examined with a T1-weighted ultrafast turbo spin-echo (UTSE) sequence with frequency selective fat suppression (SPIR), two different segmented echo-planar imaging (EPI) sequences - a spin-echo and a gradient-echo echo-planar sequence (SE-, FFE-EPI) combined with SPIR and a gradient-echo (fast field echo, FFE) sequence in a prospective study. The images of all sequences were visually evaluated and in addition to qualitative evaluation the contrast-to-noise ratio (CNR) for cyst and solid lesions was measured. Among the different T1-weighted sequences, the best detection and characterization of renal solid lesions were obtained with the UTSE SPIR and the SE-EPI sequence (sensitivity: 100 and 75%, respectively; specificity: 90 and 75%, respectively). The FFE and FFE-EPI sequences showed lower sensitivity (86%) and the same specificity (75%). The staging of renal tumors was best achieved with the UTSE SPIR and SE-EPI sequence (84 and 73%, respectively). The staging was correct in only 47% and 58 for the FFE and FFE-EPI sequences, respectively. The investigated sequences showed no significant differences in CNR. The combination of fat suppression and breath-hold mode improves detection, characterization, and staging of renal lesions. The UTSE SPIR and SE-EPI sequence in breath-hold mode showed specific image artifacts, but offered high sensitivity and specificity for detection and characterization of renal lesions compared with the FFE sequence. The results of this study suggest, for T1-weighted imaging of renal tumors, use of UTSE or SE-EPI sequences with fat suppression in breath-hold mode for renal imaging.

Contrast-enhanced T1-weighted black-blood fast spin-echo MR imaging of the brain: Technique for suppression of enhancing venous signal

Contrast-enhanced T1-weighted black-blood fast spin-echo MR imaging (BB-FSE) was performed to suppress enhancing venous signal and flow artifacts in the brain without sacrificing the T1-weighted imaging contrast. Twenty-five MR imaging sections (17 transverse and 8 coronal images) in 15 patients with various brain diseases were obtained by contrast-enhanced T1-weighted SE and BB-FSE images. In contrast-enhanced T1-weighted BB-FSE images, venous signal was significantly less and T1-weighted contrast of the brain was more evident. No differences in flow artifacts were found between the two imaging techniques. The interobserver agreements were good for the venous signal and flow artifacts using both techniques. Contrast-enhanced T1-weighted BB-FSE imaging reduced the venous signal in the brain with maintaining T1-weighted contrast. This novel MR technique can be used when the suppression of enhancing venous signal is expected to improve the depiction of enhancing lesions in the brain.

Evaluation by contrast-enhanced MR imaging of the lateral border zone in reperfused myocardial infarction in a cat model.

ObjectiveTo identify and evaluate the lateral border zone by comparing the size and distribution of the abnormal signal area demonstrated by MR imaging with the infarct area revealed by pathological examination in a reperfused myocardial infarction cat model.Materials and MethodsIn eight cats, the left anterior descending coronary artery was occluded for 90 minutes, and this was followed by 90 minutes of reperfusion. ECG-triggered breath-hold turbo spin-echo T2-weighted MR images were initially obtained along the short axis of the heart before the administration of contrast media. After the injection of Gadomer-17 and Gadophrin-2, contrast-enhanced T1-weighted MR images were obtained for three hours. The size of the abnormal signal area seen on each image was compared with that of the infarct area after TTC staining. To assess ultrastructural changes in the myocardium at the infarct area, lateral border zone and normal myocardium, electron microscopic examination was performed.ResultsThe high signal area seen on T2-weighted images and the enhanced area seen on Gadomer-17-enhanced T1WI were larger than the enhanced area on Gadophrin-2-enhanced T1WI and the infarct area revealed by TTC staining; the difference was expressed as a percentage of the size of the total left ventricle mass (T2= 39.2%; Gadomer-17 =37.25% vs Gadophrin-2 = 29.6%; TTC staining = 28.2%; p < 0.05). The ultrastructural changes seen at the lateral border zone were compatible with reversible myocardial damage.ConclusionIn a reperfused myocardial infarction cat model, the presence and size of the lateral border zone can be determined by means of Gadomer-17- and Gadophrin-2-enhanced MR imaging.