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.

PET findings of intramedullary tumors of the spinal cord using [18F] FDG and [11C] methionine.

BACKGROUND AND PURPOSE: Only a few reports on intramedullary tumors of the spinal cord using PET have been published. We report findings of PET by using [(18)F] fluorodeoxyglucose and [(11)C] methionine and discuss the usefulness of the findings in patients with intramedullary tumors of the spinal cord. MATERIALS AND METHODS: PET/CT was performed in 9 patients with intramedullary tumors of the spinal cord: Six had ependymomas, 1 had an anaplastic astrocytoma, 1 had a hemangioblastoma, and 1 had a cavernous angioma. The maximum standardized uptake value of the tumor was measured and compared with pathologic findings. RESULTS: The SUVmax of FDG and MET in a case of anaplastic astrocytoma was high. The SUVmax of FDG and MET was relatively high in 4 of 6 cases of ependymoma (excluding myxopapillary ependymomas). A case of hemangioblastoma showed decreased uptake of both FDG and MET (SUVmax = 2.0 and 1.4, respectively). Three cases with hemorrhage (1 case of ependymoma, 1 case of cellular ependymoma, and 1 case of cavernous angioma) showed a relatively increased uptake of FDG. CONCLUSIONS: Both FDG and MET accumulated to a large degree in an anaplastic astrocytoma and accumulated in ependymomas (excluding a myxopapillary ependymoma). FDG can accumulate in tumors with hemorrhage. More investigation of a larger number of patients is required to evaluate the diagnostic value of PET with FDG and MET for imaging intramedullary tumors of the spinal cord.

[Experimental study of differentiation between tumor and inflammation using MR imaging: correlation between VX2 tumors and croton oil induced inflammation in the rabbit's femoral muscle].

We evaluated the various Magnetic Resonance (MR) sequences for differentiation between tumors and inflammation. Experimental models of rabbit's tumors (VX2) and inflammation induced by croton oil in the femoral muscle were used for this evaluation. Both types of lesions presented a high intensity area on T2-weighted and heavy T2-weighted images. An inflammatory lesion was revealed with iso-/low intensity area and tumors were defined as high signal lesions on Sinc saturation fat suppression T1-weighted, standard T1-weighted and fat suppression T1-weighted images by the 3 Point dixon method. T1, T2 values of tumor and inflammatory lesions were also measured. The T1 value of the tumors was 1186 +/- 58 msec (n = 5) and that of the inflammatory lesion was 1097 +/- 40 msec (n = 3). The T2 value of the tumors was 71 +/- 13 msec (n = 5) and that of the inflammatory lesions was 70 +/- 5.5 msec (n = 3). There were no significant differences between both the T1 and T2 values. Calculated relative proton density was 0.69 +/- 0.14 (n = 4) in the tumors, and 0.42 +/- 0.12 (n = 3) in the inflammatory lesions. A statistical difference (p < 0.05) was found in both value. These results suggest that a T2-weighted image is not useful for differentiation between tumors and inflammation, and a T1-weighted image might be useful for such differentiation. This phenomenon is related to the difference of the proton density.

[Significance of CT findings and catecholamine determination in peripheral blood of asymptomatic pheochromocytoma and paraganglioma].

The purpose of this study was to assess the CT findings and significance of hormone determination in the peripheral blood of asymptomatic patients with pheochromocytoma and paraganglioma. CT findings in 29 patients with surgically proven pheochromocytoma(n = 19) and paraganglioma(n = 10) were reviewed. Nine patients(31%) were symptomatic and 20 (69%) were asymptomatic. Tumor size ranged from 39 mm to 114 mm(mean: 60 mm) in symptomatic patients and 11 mm to 100 mm(mean: 50 mm) in asymptomatic ones. Of the 9 symptomatic patients and 18 asymptomatic patients, a homogeneous solid pattern was seen in 4 and 4, mixed pattern in 2 and 6, and massive necrotic pattern in 3 and 8 patients, respectively, on CT scans. The CT attenuation values in symptomatic cases ranged from 30 HU to 50 HU(mean: 41 HU) on precontrast CT scans and 60 HU to 111 HU(mean: 77 HU) on postcontrast CT scans, while those in asymptomatic cases ranged from 15 HU to 48 HU(mean: 33 HU) on precontrast CT scans and 66 HU to 133 HU(mean: 95 HU) on postcontrast CT scans. There were no statistically significant differences in tumor size, homogeneity, or CT attenuation values between symptomatic and asymptomatic patients. All symptomatic patients and 17(89%) of 19 asymptomatic cases showed elevated levels of catecholamine (epinephrine) or norepinephrine in the peripheral blood. Our study showed that the CT findings in asymptomatic patients were similar to those in symptomatic patients, and 89% of asymptomatic patients showed elevation of catecholamine in the peripheral blood. Determination of catecholamine level in the peripheral blood is recommended for preoperative diagnosis in patients suspected of having asymptomatic pheochromocytoma or paraganglioma on CT scans.

[MR imaging of cerebral palsy].

We evaluated 35 patients with cerebral palsy on the basis of MR imaging findings in the brain. The types of palsy were spastic quadriplegia (n = 11), spastic diplegia (n = 9), spastic hemiplegia (n = 2), double hemiplegia (n = 1), athetosis (n = 10) and mixed (n = 2). Of all patients, 28 (80%) generated abnormal findings. In spastic quadriplegia, although eight cases revealed severe brain damage, two cases showed no abnormal findings in the brain. One of the three had cervical cord compression caused by atlanto-axial subluxation. In spastic diplegia, the findings were divided according to whether the patient was born at term or preterm. If the patient had been born prematurely, the findings showed periventricular leukomalacia and abnormally high intensity in the posterior limbs of the internal capsule on T2-weighted images. MR imaging in spastic hemiplegia revealed cerebral infarction. In the athetoid type, half of all cases showed either no abnormal findings or slight widening of the lateral ventricle. Three cases showed abnormal signals of the basal ganglia. The reason why athetoid-type palsy did not show severe abnormality is unknown. We believe that MR imaging is a useful diagnostic modality to detect damage in the brain in cerebral palsy and plays an important role in the differentiation of cerebral palsy from the spastic palsy disease.