Kenji Torii

Methionine positron emission tomography for differentiation of recurrent brain tumor and radiation necrosis after stereotactic radiosurgery--in malignant glioma.

ObjectFollowing stereotactic radiosurgery (SRS), we examined how to differentiate radiation necrosis from recurrent malignant glioma using positron emission tomography (PET) with11C-methionine (Met).MethodsMet-PET scans were obtained from 11 adult cases of recurrent malignant glioma or radiation injury, suspected on the basis of magnetic resonance images (MRI). Patients had previously been treated with SRS after primary treatment. PET images were obtained as a static scan of 10 minutes performed 20 minutes after injection of Met. We defined two visual grades (e.g., positive or negative Met accumulation). On Met-PET scans, the portion of the tumor with the highest accumulation was selected as the region of interest (ROI), tumor-versus-normal ratio (TN) was defined as the ratio of average radioisotope counts per pixel in the tumor (T), divided by average counts per pixel in normal gray matter (N). The standardized uptake value (SUV) was calculated over the same tumor ROI. Met-PET scan accuracy was evaluated by correlating findings with subsequent histological analysis (8 cases) or, in cases without surgery or biopsy, by the subsequent clinical course and MR findings (3 cases).ResultsHistological examinations in 8 cases showed viable glioma cells with necrosis in 6 cases, and necrosis without viable tumor cells in 2 cases. Three other cases were considered to have radiation necrosis because they exhibited stable neurological symptoms with no sign of massive enlargement of the lesion on follow-up MR after 5 months. Mean TN was 1.31 in the radiation necrosis group (5 cases) and 1.87 in the tumor recurrence group (6 cases). Mean SUV was 1.81 in the necrosis group and 2.44 in the recurrence group. There were no statistically significant differences between the recurrence and necrosis groups in TN or SUV. Furthermore, we made a 2 x 2 factorial cross table (accumulation or no accumulation, recurrence or necrosis). From this result, the Met-PET sensitivity, specificity, and accuracy in detecting tumor recurrence were determined to be 100%, 60%, and 82% respectively. In a false positive-case, glial fibrillary acidic protein (GFAP) immunostaining showed a positive finding.ConclusionThere were no significant differences between recurrent malignant glioma and radiation necrosis following SRS in Met-PET. However, this study shows Met-PET has a sensitivity and accuracy for differentiating between recurrent glioma and necrosis, and presents important information for developing treatment strategies against post radiation reactions.

Correlation of amino-acid uptake using methionine PET and histological classifications in various gliomas

ObjectiveThe uptake of L-methyl-11C-methionine (MET) by gliomas is greater than that by intact tissue, making methionine very useful for evaluation of tumor extent. If the degree of malignancy of brain tumors can be evaluated by MET-PET, the usefulness of MET-PET as a means of diagnosing brain tumors will increase.MethodsWe performed this study on 67 glioma patients between 3 and 69 years of age (36 males and 31 females). Tumors included diffuse astrocytoma, anaplastic astrocytoma, glioblastoma, ependymoma, oligodendroglioma, medulloblastoma, dysembryoplastic neuroepithelial tumor, choroid plexus papilloma, central neurocytoma, optic glioma, gliomatosis cerebri, pleomorphic xanthoastrocytoma, and ganglioglioma. Tumor activity and degree of malignancy were evaluated using Ki-67LI (LI: labeling index) and Kaplan-Meier survival curves. The correlations between methionine uptake and tumor proliferation (tumor versus contralateral gray matter ratio (T/N) and Ki-67LI) were determined for the group of all subjects. The existence of significant correlations between T/N and KJ-67LI and between SUV and Ki-67LI was determined for astrocytic tumors. Receiver operating characteristics (ROC) analysis of T/N and standardized uptake value (SUV) was performed for the group of astrocytic tumors. We also determined the ROC cut-off levels to ensure high accuracy of the analysis.ResultsFor the 67 cases of glioma, the degree of accumulation was variable. Ki-67LI differed significantly between the high-grade group and low-grade group at T/N levels between 1.5 and 1.8 on analysis using tumor proliferative potential (p - 0.019–0.031). The prognosis differed significantly between the highgrade and low-grade groups when T/N was in the range of 1.6–1.8 (p = 0.028–0.032). The accuracy thus calculated was highest (85.7%) when T/N was 1.5 as determined by ROC analysis.ConclusionsWhen analysis was confined to cases of astrocytic tumor, a correlation was noted between methionine accumulation and Ki-67LI. For the astrocytic tumors, T/N ratio seemed to be more useful as a diagnostic indicator than SUV. The cut-off level of T/N ratio for distinction between high-grade and low-grade astrocytoma appears to lie between 1.5 and 1.6.

Distinguishing benign from malignant gallbladder wall thickening using FDG-PET.

ObjectiveBecause thickening of the gallbladder wall is observed not only in patients with gallbladder cancer but also in those with benign diseases such as chronic cholecystitis and gallbladder adenomyosis, it is difficult to distinguish between benign and malignant gallbladder wall thickening by conventional techniques of diagnostic imaging such as computed tomography (CT), magnetic resonance imaging (MRI), and abdominal ultrasonography (US). In the present study, we attempted to distinguish between benign and malignant gallbladder wall thickening by means of fluorine- 18-fluorodeoxyglucose (FDG)- Positron emission tomography (PET).MethodsFDG-PET was performed in 12 patients with gallbladder wall thickening detected by CT or US, to determine whether it was benign or malignant. Emission scans were taken, beginning 45 minutes after intravenous administration of FDG, and SUV was calculated as an indicator of glucose metabolism.ResultsOf the 12 patients, 4 showed positive uptake of FDG in the gallbladder wall. Of these 4 patients, 3 had gallbladder cancer. The remaining one, who had chronic cholecystitis, had false-positive findings. The other 8 patients had negative uptake of FDG in the gallbladder wall. Two of these 8 underwent surgical resection, which yielded a diagnosis of chronic cholecystitis. The other 6 patients exhibited no sign of gallbladder malignancy and have been followed without active treatment.ConclusionsFDG-PET appears able to distinguish between benign and malignant gallbladder wall thickening.

A case of hepatic inflammatory pseudotumor identified by FDG-PET

A 53-year-old man with a history of nausea and elevated liver functions presented to our clinic. A CT scan showed a small tumor in the right lobe of the liver. Fluorine-18-fluorodeoxyglucose (18F-FDG) positron emission tomography confirm abnormal metabolic activity with a high standardized uptake value of 7.3 in the lesion. These findings could indicate a malignancy such as well-differentiated hepatocellular carcinoma or cholangiocarcinoma, or a benign lesion such as hepatic abscess. He was diagnosed by histopathological examination as having an epithelioid granuloma with many inflammatory cells. This is the rare report of hepatic inflammatory pseudotumor featuring markedly increased18F-FDG uptake.

A case of diffuse hepatic angiosarcoma diagnosed by FDG-PET

A 76-year-old woman was admitted to our hospital with a 2-month history of increasing abdominal distension, leg edema, and dyspnea. The serum transaminase level was about twice the upper limit of normal. The CT showed no tumor. Fluorine-18 2-deoxy-2-fluoro-D-glucose (FDG)-positron emission tomography (PET) showed diffuse abnormal accumulation throughout the entire liver. She was diagnosed by histopathological examination as having hepatic angiosarcoma causing veno-occlusive disease (VOD). This is the first report of hepatic angiosarcoma with FDG-PET.

Natural course of changes in hepatic functional reserve in patients with chronic liver diseases evaluated by scintigraphy with GSA

Hepatic functional reserve can be evaluated in a noninvasive way by scintigraphy with 99mTc-DTPA-galactosyl human serum albumin (99mTc-GSA). We monitored hepatic functional reserve in patients with chronic hepatitis and cirrhosis using scintigraphy with 99mTc-GSA to determine the natural course of changes in their hepatic functional reserve. Computer acquisition of gamma-camera data was started before the injection of 185 MBq of 99mTc-GSA and was stopped 20 min later. Time-activity curves were generated from ROI for the heart and liver. A receptor index and index of blood clearance were calculated from radioactivity in the heart and liver. Scintigraphy with 99mTc-GSA was performed in 12 healthy subjects, 86 patients with chronic hepatitis, and 226 patients with cirrhosis. Seventy-two patients (23 with chronic hepatitis, 32 with cirrhosis in Child-Pugh stage A, 15 in stage B, and 2 in stage C) were examined at least twice with 12-72 months intervening. The receptor index was lower for more severe disorders, decreasing in the order of chronic hepatitis and cirrhosis in stages A, B, and C. The index of blood clearance was higher for more severe disorders, increasing in the order of chronic hepatitis and cirrhosis in stages A, B, and C. The mean annual change in the receptor index with chronic hepatitis was -0.0007, that with cirrhosis in stage A was -0.0023, and that with cirrhosis in stage B or C was -0.0117. The difference between the median annual change with cirrhosis in stage B or C and that with chronic hepatitis or cirrhosis in stage A was not significant (P=0.064 and 0.251, respectively). The mean annual change in the index of blood clearance with chronic hepatitis was 0.0018, that with cirrhosis in stage A was 0.0060, and that with cirrhosis in stage B or C was 0.0330. The difference between the median annual change in the index of blood clearance with cirrhosis in stage B or C and that with chronic hepatitis or cirrhosis in stage A was significant (P=0.004 and 0.007, respectively). Hepatic receptor imaging with 99mTc-GSA could be used to noninvasively evaluate the hepatic reserve of various liver diseases. Changes in hepatic functional reserve were not steady; it decreased gradually as disease advanced from chronic hepatitis to cirrhosis in Child-Pugh stage A, and decrease rapidly after development of stage B cirrhosis.

FDG uptake by tongue and muscles of mastication reflecting increased metabolic activity of muscles after chewing gum.

Glucose metabolic activity of the muscles increases during exercise. The authors report an example of intense F-18 fluorodeoxyglucose (FDG) uptake by the tongue and the muscles of mastication in a patient after 3 hours of chewing sugar-free gum before F-18 FDG administration.

Detection of local residual tumor after laryngeal cancer treatment using FDG-PET

Objective: Fluorine-18-fluorodeoxyglucose positron emission tomography (FDG-PET) is sometimes used as a means of follow-up after diagnosis and treatment of cancers of the head and neck region. The present study was undertaken to evaluate the ability of FDG-PET to detect local residual tumor after treatment of laryngeal cancer.Methods: Thirty-six patients with laryngeal cancer underwent FDG-PET before and after initial treatment. Of these patients, 20 received FDG-PET before treatment and 28 received it after treatment. The relationship between standardized uptake values (SUV) and the presence or absence of local residual tumor was investigated by setting the cut-off value of the SUV using the receiver operating characteristics (ROC) curve.Results: When the pre-treatment SUV threshold for laryngeal cancer was set at 7.20, the detection of local residual tumor after treatment using FDG-PET had a sensitivity of 77.78%, specificity of 81.82%, false positive rate of 18.18%, false negative rate of 22.22%, accuracy of 80% and a p value of 0.02. When the post-treatment SUV threshold for the larynx was set at 3.35, the test had a sensitivity of 93.75%, specificity of 91.67%, false positive rate of 8.33%, false negative rate of 6.25%, accuracy of 92.86% and a p value of 0.0001.Conclusions: FDG-PET was found to be useful for determining the presence of local residual tumor after treatment of laryngeal cancer.

A case of small cell carcinoma of the esophagus detected incidentally by FDG-PET

Small cell carcinoma (SmC) of the esophagus is rare, and is sometimes impossible to detect by macroscopic inspection using an endoscope or histological examination of biopsied specimens. A 73-year-old man received F-18 fluorodeoxyglucose positron emission tomography (FDG-PET) to evaluate the response to radiofrequency thermal ablation therapy for lung cancer. FDG-PET showed abnormal accumulation in the posterior mediastinum. Endoscopy disclosed ulcerous lesions with marginal elevation in the middle segment of the esophagus, but the biopsy specimen taken concurrently was not malignant histologically. FDG-PET, performed two months later, revealed abnormal accumulation in the suspect area, and the extent of accumulation was wider than previously. Histological examination of the specimen biopsied during the endoscopy led to a diagnosis of SmC. FDG-PET thus proved useful in the early detection of SmC.

Evaluation of ammonia metabolism in the skeletal muscles of patients with cirrhosis using N-13 ammonia PET

Objective: Skeletal muscle is said to compensate for the decreased ammonia metabolism in patients with cirrhosis. Branched-chain amino acids (BCAA) are being used as a treatment for hyperammonemia, and are believed to decrease blood ammonia by consumption of BCAA in skeletal muscles. We examined ammonia metabolism of the skeletal muscles in patients with liver cirrhosis after administration of BCAA using13N-ammonia positron emission tomography (PET).Methods: The subjects were patients with compensated or decompensated liver cirrhosis. PET studies were performed before and 2 hours after injection of BCAA. Serial dynamic PET scans (2 min × 10 frames) were started simultaneously with13N-ammonia injection. The standardized uptake value (SUV) of both thighs was calculated.Results: In the patient with compensated liver cirrhosis, there was little difference in the rate of increase in SUV before to after administration of BCAA. However, in the patient with decompensated liver cirrhosis, the rate of increase in SUV after administration was higher than that before administration of BCAA.Conclusion: Ammonia metabolism in the muscle of patients with liver cirrhosis could be examined noninvasively under physiological conditions using13N-ammonia PET. The muscles were found to metabolize ammonia partially, and the role of this contribution to metabolism of ammonia in patients with decompensated liver cirrhosis is particularly important.