Contrast-enhanced multi-shot echo-planar FLAIR in the depiction of metastatic tumors of the brain: comparison with contrast-enhanced spin-echo T1-weighted imaging.

BACKGROUND: The usefulness of fast fluid-attenuated inversion-recovery (FLAIR) sequences after administration of contrast medium (f-FLAIR (+)) has been shown in depicting brain tumors including metastases and meningeal carcinomatosis. Contrast-enhanced multi-shot echo-planar FLAIR (Ms-EPI-FLAIR (+)), comprising combined sequences of f-FLAIR (+) and Ms-EPI, may provide the advantages of f-FLAIR (+) along with rapid acquisition. PURPOSE: To compare Ms-EPI-FLAIR (+) with post-contrast spin-echo T1-weighted imaging (SE-T1WI (+)) in the depiction of brain metastases. MATERIAL AND METHODS: In 14 patients with metastatic tumors of the brain, spin-echo precontrast T1-weighted imaging (SE-T1WI (-)), fast spin-echo T2-weighted imaging (FSE-T2WI), fast-FLAIR, SE-T1WI (+), and Ms-EPI-FLAIR (+) were acquired. For qualitative evaluation of SE-T1WI (+) and Ms-EPI-FLAIR (+), receiver operating characteristic (ROC) analysis was performed in two different readers. For quantitative analysis, the intensity ratios (intensity of tumor divided by intensity of peritumoral region) in SE-T1WI (+) and Ms-EPI-FLAIR (+) were compared. RESULTS: Although pre-contrast f-FLAIR detected 84 of 106 tumors, Ms-EPI-FLAIR (+) detected 98 of 106 tumors. In the ROC analysis for observers A and B, Az values in SE-T1WI (+) did not differ from values in Ms-EPI-FLAIR (+). Quantitatively, the intensity ratio in Ms-EPI-FLAIR (+) also did not differ from that in SE-T1WI (+). CONCLUSION: Detectability of brain metastases with Ms-EPI-FLAIR (+) is almost similar to that with SE-T1WI (+). Ms-EPI-FLAIR (+) could be an alternative to SE-T1WI (+) in the depiction of brain metastases.

Differentiation between Treatment-Induced Necrosis and Recurrent Tumors in Patients with Metastatic Brain Tumors: Comparison among 11C-Methionine-PET, FDG-PET, MR Permeability Imaging, and MRI-ADC-Preliminary Results.

BACKGROUND AND PURPOSE: In patients with metastatic brain tumors after gamma knife radiosurgery, the superiority of PET using 11C-methionine for differentiating radiation necrosis and recurrent tumors has been accepted. To evaluate the feasibility of MR permeability imaging, it was compared with PET using 11C-methionine, FDG-PET, and DWI for differentiating radiation necrosis from recurrent tumors. MATERIALS AND METHODS: The study analyzed 18 lesions from 15 patients with metastatic brain tumors who underwent gamma knife radiosurgery. Ten lesions were identified as recurrent tumors by an operation. In MR permeability imaging, the transfer constant between intra- and extravascular extracellular spaces (/minute), extravascular extracellular space, the transfer constant from the extravascular extracellular space to plasma (/minute), the initial area under the signal intensity-time curve, contrast-enhancement ratio, bolus arrival time (seconds), maximum slope of increase (millimole/second), and fractional plasma volume were calculated. ADC was also acquired. On both PET using 11C-methionine and FDG-PET, the ratio of the maximum standard uptake value of the lesion divided by the maximum standard uptake value of the symmetric site in the contralateral cerebral hemisphere was measured (11C-methionine ratio and FDG ratio, respectively). The receiver operating characteristic curve was used for analysis. RESULTS: The area under the receiver operating characteristic curve for differentiating radiation necrosis from recurrent tumors was the best for the 11C-methionine ratio (0.90) followed by the contrast-enhancement ratio (0.81), maximum slope of increase (millimole/second) (0.80), the initial area under the signal intensity-time curve (0.78), fractional plasma volume (0.76), bolus arrival time (seconds) (0.76), the transfer constant between intra- and extravascular extracellular spaces (/minute) (0.74), extravascular extracellular space (0.68), minimum ADC (0.60), the transfer constant from the extravascular extracellular space to plasma (/minute) (0.55), and the FDG-ratio (0.53). A significant difference in the 11C-methionine ratio (P < .01), contrast-enhancement ratio (P < .01), maximum slope of increase (millimole/second) (P < .05), and the initial area under the signal intensity-time curve (P < .05) was evident between radiation necrosis and recurrent tumor. CONCLUSIONS: The present study suggests that PET using 11C-methionine may be superior to MR permeability imaging, ADC, and FDG-PET for differentiating radiation necrosis from recurrent tumors after gamma knife radiosurgery for metastatic brain tumors.

Linearization correction of 99mTc-labeled hexamethyl-propylene amine oxime (HM-PAO) image in terms of regional CBF distribution: comparison to C15O2 inhalation steady-state method measured by positron emission tomography.

The radioisotope distribution following intravenous injection of 99mTc-labeled hexamethylpropyleneamine oxime (HM-PAO) in the brain was measured by single photon emission computed tomography (SPECT) and corrected for the nonlinearity caused by differences in net extraction. The "linearization" correction was based on a three compartment model, and it required a region of reference to normalize the SPECT image in terms of regional cerebral blood flow distribution. Two different regions of reference, the cerebellum and the whole brain, were tested. The uncorrected and corrected HM-PAO images were compared with cerebral blood flow (CBF) image measured by the C15O2 inhalation steady state method and positron emission tomography (PET). The relationship between uncorrected HM-PAO and PET-CBF showed a correlation coefficient of 0.85 but tended to saturate at high CBF values, whereas it was improved to 0.93 after the "linearization" correction. The whole-brain normalization worked just as well as normalization using the cerebellum. This study constitutes a validation of the "linearization" correction and it suggests that after linearization the HM-PAO image may be scaled to absolute CBF by employing a global hemispheric CBF value as measured by the nontomographic 133Xe clearance method.

Evaluation of regional differences of tracer appearance time in cerebral tissues using [15O] water and dynamic positron emission tomography.

The tracer appearance time relative to the radial artery-sampling site has been evaluated in six brain locations in five human subjects using dynamic positron emission tomography (PET) following the bolus injection of H2(15)O. There was a maximum difference of +/- 2 s from the average in each location. To globally adjust the timing difference between the measured arterial curve and the PET scan, a correction method was developed based on a nonlinear least-squares fitting procedure. This new technique determined the global time delay with an accuracy of +/- 0.5 s. On the other hand, the linear backward extrapolation method resulted in a systematic error of 4 s.

Therapeutic results of intra-arterial chemotherapy in patients with malignant glioma.

Thirty-three adult patients with anaplastic astrocytoma or glioblastoma multiforme, verified between 1990 and 1997, received postoperative intra-arterial ACNU chemotherapy and irradiation. Since our previous strategies to malignant gliomas had included intra-venous ACNU, the purpose of the present study is to evaluate the advantage of intra-arterial ACNU over its intra-venous counterpart as the historical control (37 patients). The median survival was 74.7 weeks for the former and 81.7 weeks for the latter. Although both groups were equivalent in survival, toxicity was less frequent in the intra-arterial group. Histopathological diagnosis, patient age and the Karnofsky's performance status related well with the survival.

High uptake of 123I-metaiodobenzylguanidine related to olfactory neuroblastoma revealed by single-photon emission CT.

We studied a case of olfactory neuroblastoma by noting 123I-metaiodobenzylguanidine (MIBG) uptake revealed by single-photon emission CT (SPECT). MR imaging revealed an enhancing tumor extending from the left nasal cavity to the bilateral anterior frontal cranial fossae. SPECT revealed high 123I-MIBG uptake in the enhancing tumor. SPECT-revealed 123I-MIBG uptake appears to be clinically useful for distinguishing olfactory neuroblastomas from other tumors, especially suprasellar meningiomas.

Dural arteriovenous fistula of the cavernous sinus with venous congestion of the brain stem: report of two cases.

We present two cases of dural arteriovenous fistula of the cavernous sinus with venous congestion of the brain stem. Both cases were detected by MR imaging and showed significant improvement on MR images after transvenous embolization.

Central neurocytoma with clinically malignant behavior.

We describe two cases of central neurocytoma that did not show histopathologic features of anaplasia but did show tumor dissemination after surgery and radiation therapy. CT and MR imaging before surgery depicted extraventricular extension of the tumors. The importance of radiologic findings is stressed.

Superselective angio-CT of brain tumors.

PURPOSE: To determine the efficacy of superselective angio-CT in the diagnosis of astrocytoma. METHODS: Nineteen patients with astrocytoma had superselective angio-CT before chemotherapeutic agents were administered via superselective intraarterial infusion. CT was performed after contrast material was delivered through a microcatheter, which had been advanced into the feeding arteries of the tumor. Superselective angio-CT scans were compared with digital subtraction angiograms, conventional contrast-enhanced CT scans, and contrast-enhanced T1-weighted MR images. RESULTS: Superselective angio-CT scans depicted contrast enhancement of the tumor in all of the patients and the medullary veins of the tumors in 32% of the patients. Digital subtraction angiograms showed tumor stains in 68% of the patients and the medullary veins in only 5%. Conventional CT scans and MR images showed contrast enhancement of the tumor in 89% of the patients. Superselective angio-CT scans confirmed the proper position of the catheter tip for the infusion of a chemotherapeutic agent. CONCLUSIONS: Superselective angio-CT can be used to depict contrast enhancement of tumors and the vascular structures that are characteristic of astrocytomas.

Extradural neuromas at the petrous apex: report of two cases.

OBJECTIVE AND IMPORTANCE: Two rare cases of middle cranial fossa neuroma located in the epidural space at the petrous apex are reported. CLINICAL PRESENTATION: Two women, aged 58 and 49 years, were admitted to our hospital with diagnoses of cavernous sinus tumor. Analysis of preoperative computed tomography scans showed bone erosion of the petrous apex, and magnetic resonance imaging demonstrated the presence of an extradural mass located along the course of the petrous internal carotid artery in both patients. INTERVENTION: The tumor was completely removed in one patient and partially removed in the other by use of the epidural middle cranial fossa transpetrosal approach. In both patients, histological examination of tumor specimens revealed neuroma. CONCLUSION: Because surgical exploration revealed that these epidural tumors adhered tightly to the internal carotid artery, and because they had no relationship to the trigeminal nerve, facial nerve, or proximal greater superficial petrosal nerve, in our opinion, these tumors originated from the distal portion of the greater superficial petrosal nerve or the deep petrosal nerve. These neuromas were mainly found in a site under the cavernous sinus at the petrous apex, a location not previously reported.

Multiple medullary venous malformations decreasing cerebral blood flow: case report.

A rare case of multiple medullary venous malformations in the right cerebral hemisphere is reported. The literature review yielded only one case of multiple medullary venous malformations. Computed tomography scan showed multiple calcified lesions with linear contrast enhancement representing abnormal dilated vessels and mild atrophic change of the right cerebral hemisphere. Single-photon emission computed tomography using N-isopropyl-p-(123I) iodoamphetamine demonstrated decreased cerebral blood flow in the right cerebral hemisphere.

A case of medullary venous malformations with an arterial component coexisting with arteriovenous malformations.

We present a rare case of medullary venous malformations with an arterial component coexisting with two small arteriovenous malformations in the same area. The onset was abrupt with subcortical hematoma due to the rupture of one arteriovenous malformation in the frontal area. Single photon emission computed tomography using 99mTc-hexamethylpropyleneamine oxime showed a high-uptake area around the hematoma suggesting increased blood flow. Two types of vascular malformation coexisting in the same area support a theory of congenital malformation originating in intrauterine life.

Evaluation of critically perfused area in acute ischemic stroke for therapeutic reperfusion: a clinical PET study.

To evaluate critically perfused areas in the acute ischemic brain, 9 patients were studied by positron emission tomography (PET) within 7-32 hours after the onset. The cerebral blood flow (CBF) and oxygen metabolic rate (CMRO2) were evaluated and compared with sequential change in CT findings. In all the regions developing subsequent necrosis on CT, CBF dropped below 17 ml/100 g/min. But in some of these lesions, CMRO2 remained above the minimum value for regions in which infarction did not develop, and the tissue density on CT obviously remained normal for several hours after PET scan. The mean CBF in these lesions (14.0 ml/100 g/min, range: 9.9-17.3 ml/100 g/min) was significantly higher than that in ischemic areas with low density on CT before or just after PET study (approximately 10 ml/100 g/min, range: 7.7-14.1 ml/100 g/min). These findings suggest that a part of the tissue with CBF between 10-17 ml/100 g/min is still viable at least 7 hours after the onset of ischemia, but becomes non-viable in a longer period of ischemia. These lesions should respond to effective treatment, including therapeutic reperfusion.

Perineural extension of nasopharyngeal carcinoma into the posterior cranial fossa detected by magnetic resonance imaging.

We report a case with perineural extension of carcinoma arising from the nasopharynx. Magnetic resonance (MR) imaging with gadolinium-DTPA enhancement detected subtle but evident findings of perineural tumor extension through the jugulare foramen into the posterior cranial fossa.

Caudal regression syndrome: MR appearance.

This article reports a case of caudal regression syndrome with hypoplasia of the sacrum, accompanied by an imperforate anus with ano-vestibular fistula. Magnetic resonance images showed a characteristic wedge-shaped cord terminus and the separation of anterior and posterior spinal roots at the level of the cauda equina.

Comparison of MR imaging and CT in discriminating tumor infiltration of bone and bone marrow in the skull base.

We compared MR imaging with CT in revealing tumor infiltration of bone and bone marrow in the skull base of 54 patients. MR imaging had no advantages over when tumor involved the anterior compartment. However, precontrast T1-weighted MR images were more efficient than CT in 37.5% of tumors involving the middle compartment and in 54.5% of tumors involving the posterior compartment, respectively. Precontrast T1-weighted images were more accurate than other pulse sequences in revealing bone and bone marrow that were replaced by tumors.

Three-dimensional computed tomography in the head and neck diseases with bony abnormalities.

The purpose of this study was to define the role of three-dimensional (3D) computed tomography (CT) in the head and neck diseases with bony abnormalities. Thirty-two patients were examined with a low dose radiation technique. Three-dimensional CT clearly delineated bony lesions in 27 of 32 patients. Three-dimensional CT could not demonstrate subtle bony erosions infiltrated by tumor, a temporal bone fracture, and a blow-out fracture, although two-dimensional (2D) images obtained before the 3D reconstructions clearly depicted those lesions. These two kinds of CT technique were thought to be complimentary.

Increased blood flow in human brain tumor after administration of angiotensin II: demonstration by PET.

To evaluate the changes of regional cerebral blood flow (CBF) in artificial hypertensive state, we investigated vascular responses to changes of arterial carbon dioxide tension (PCO2) and blood pressure by means of positron emission tomography (PET). The subjects were eight brain tumors which were histologically proven. We calculated CBF changes in hypercapnic and hypocapnic state, and then using those results, CBF changes in hypertensive state were corrected. Every patient represented a selective increase of tumor blood flow in hypertensive state induced by angiotensin II, demonstrating a loss of autoregulation in tumor. Our results suggested the possibility of enhancement of chemotherapy for brain tumors.

Preliminary results with technetium-99m MIBI SPECT imaging in patients with brain tumors: correlation with histological and neuroradiological diagnoses and therapeutic response.

SPECT using Tc-99m MIBI was performed in patients with brain tumors in order to determine Tc-99m MIBI uptake in brain tumors and to evaluate the efficacy of MIBI imaging in the assessment of treatment response. A MIBI uptake index was calculated on SPECT imaging. All tumors with a MIBI-index higher than 7.5 were malignant. In the tumors evaluated before and after radiochemotherapy, the MIBI-index immediately following therapy correlated with treatment response 2 months after therapy. Thus, semiquantitative assessment using Tc-99m MIBI SPECT imaging may be useful in the evaluation of treatment response.

Germ cell tumors of the central nervous system originating from non-pineal regions: CT and MR features.

CT and MR findings were retrospectively reviewed in 12 patients with germ cell tumors originating from the non-pineal regions. Cystic or necrotic components were seen in 6 patients. Of 4 germinomas, 2 showed mixed density on the CT. The MR signal intensity of the tumor was non-specific. Of 8 germinomas, 4 were inhomogeneously enhanced on postcontrast CT and T1-weighted MR images. CT and MR features of germinomas originating from non-pineal regions frequently differ from those of germinomas originating from the pineal region. The mass of the tumor often appeared cystic and inhomogeneously enhanced following contrast infusion.