Prognostic value of an increase in fluorine-18 deoxyglucose uptake in patients with myocardial infarction: comparison with stress thallium imaging.

OBJECTIVES: This study was undertaken to evaluate the prognostic value of an increase in fluorine (F)-18 deoxyglucose uptake compared with clinical, angiographic and stress thallium findings in patients with myocardial infarction. BACKGROUND: Positron emission tomography (PET) imaging using F-18 deoxyglucose has been applied to assess tissue viability in patients with coronary artery disease. We hypothesized that patients with a myocardial segment with augmented F-18 deoxyglucose uptake are at high risk for a future cardiac event. METHODS: One hundred fifty-eight consecutive patients with myocardial infarction referred for F-18 deoxyglucose PET and stress thallium scans were studied. Follow-up was obtained in 84 patients at a mean interval of 23 months to investigate prognostic implications of radionuclide studies. RESULTS: Seventeen patients had a cardiac event during the follow-up interval. Univariate analysis showed that an increase in F-18 deoxyglucose uptake was the best predictor of a future cardiac event (p = 0.0006), followed by the number of stenosed vessels (p = 0.008). In the multivariate analysis, when an increase in F-18 deoxyglucose uptake was entered into the model, only angiographic variables had an independent prognostic value, whereas no other radionuclide variables showed significant prognostic value. Among patients who did not show redistribution, a future cardiac event was observed more often in patients with than in those without an increase in F-18 deoxyglucose uptake (p < 0.05). CONCLUSIONS: Thus, an increase in F-18 deoxyglucose uptake seemed to be the best predictor of a future cardiac event among all clinical, angiographic and radionuclide variables in this study of stable patients with myocardial infarction. Even when a stress thallium-201 scan does not show redistribution, those patients who have an increase in F-18 deoxyglucose uptake in a PET study may be at risk for a future cardiac event, and these patients may need aggressive treatment to prevent a future cardiac event.

Comparison of myocardial blood flow during dobutamine-atropine infusion with that after dipyridamole administration in normal men.

OBJECTIVES: The present study was designed to compare the absolute myocardial blood flow (MBF) after intravenous dipyridamole infusion with that during dobutamine-atropine administration in normal healthy male volunteers. BACKGROUND: Both safety and usefulness of dobutamine-atropine stress in myocardial perfusion imaging have been reported. However, no information exists on whether the magnitude ofhyperemia achieved with dipyridamole and dobutamine-atropine is comparable. METHODS: Myocardial blood flow was measured with positron emission tomography and 15O-labeled water in 20 healthy young men (23 +/- 3 years) 1) at baseline, 2) after dipyridamole infusion (0.56 mg/kg over 4 min), and 3) during dobutamine (40 microg/kg/min) and atropine (0.25 to 1.0 mg) infusion. RESULTS: The MBF was significantly increased during dipyridamole infusion and during dobutamine-atropine stress compared with at rest (4.33 +/- 1.23 and 5.89 +/- 1.58 vs. 0.67 +/- 0.16 ml/min/g, respectively, p < 0.0001). Moreover, dobutamine-atropine infusion produced greater MBF compared with dipyridamole (p = 0.0011), while coronary vascular resistance did not differ significantly after dipyridamole administration and during dobutamine-atropine infusion (17.6 +/- 7.9 vs. 18.6 +/- 5.6 mm Hg/[ml/min/g], respectively). CONCLUSIONS: Near maximal coronary vasodilatation caused by dipyridamole is attainable using dobutamine and atropine in young healthy volunteers. Dobutamine in conjunction with atropine is no less effective than dipyridamole in producing myocardial hyperemia.

Cholinergic projection from the basal forebrain and cerebral glucose metabolism in rats: a dynamic PET study.

To investigate the influence of cholinergic projections from the basal forebrain on cerebral cortex metabolism, we evaluated the cerebral metabolic rate of glucose (CMRGlu) after selective inhibition of cholinergic neurons in the rat basal forebrain using the pyruvate dehydrogenase complex inhibitor 3-bromopyruvic acid (BPA), and compared the results with those obtained after lesioning the basal forebrain with ibotenic acid, as well as with those from a sham-operated control group. CMRGlu was measured using positron emission tomography (PET) with [18F]-2-fluoro-2-deoxy-D-glucose (FDG). Three days after surgery, CMRGlu and k3 (phosphorylation of FDG) were reduced similarly in the frontal cortex on the BPA-injected side and in the ibotenic acid-treated group, whereas K1 (transport rate of FDG from the plasma to brain) showed no marked changes. At 3 weeks postoperatively, the CMRGlu and k3 of the frontal cortex in both groups recovered to levels similar to those of the sham-operated group. The main difference between the BPA and ibotenic acid groups was that CMRGlu showed mild reduction on the side contralateral to the operation in the former, while such reduction was confined to the ipsilateral hemisphere in the latter. The present results indicate that the cholinergic system in the basal forebrain regulates cerebral cortex glucose metabolism through direct excitation of cortical neurons.

Radioiodinated 2'-iododiazepam: a potential imaging agent for SPECT investigations of benzodiazepine receptors.

2'-Iododiazepam (2'-IDZ) is the diazepam analogue iodinated at the 2'-position of C-5 phenyl ring which was synthesized and evaluated as a potential radiopharmaceutical for investigating brain benzodiazepine receptors by SPECT. The 125I-2'-iododiazepam was synthesized by halogen exchange reaction and purified by HPLC. In vitro competitive binding studies with 3H-diazepam, using rat cortical synaptosomal membranes, showed that the affinity of 2'-IDZ for benzodiazepam receptors was higher than that in diazepam and flumazenil (RO15-1788). Biodistribution studies in mice showed that the brain uptake of 2'-iododiazepam was rapid and profound, and in the brain higher accumulation was found in the cortex than in other regions. Furthermore, the cortical uptake was displaced by benzodiazepinergic compounds. In vivo uptake was assessed by autoradiographic studies. Thus, 2'-iododiazepam bound to benzodiazepine receptors in vivo and therefore holds great potential for in vivo benzodiazepine receptor studies.

Evaluation of experimental liver tumors using fluorine-18-2-fluoro-2-deoxy-D-glucose PET.

Japanese white rabbits transplanted with VX2 liver tumors are considered to be a suitable experimental model for the evaluation of therapeutic modalities. However, there has been no adequate method of assessing the changes of tumor metabolism during treatment. In the present study, 15 rabbits with VX2 liver tumors were examined by PET using 18F-2-fluoro-2-deoxy-D-glucose (18F-FDG). After an intravenous injection of 18F-FDG, serial arterial blood sampling was performed. One hour after tracer injection, small pieces of normal liver tissue and tumor tissue were excised to determine radioactivity. Dynamic PET images were obtained in 11 of the tumor-bearing rabbits, and tumor enzyme activities were determined in six rabbits. Fluorine-18-FDG uptake by the VX2 liver tumors was 3.5 +/- 0.9 times higher than that by the normal liver tissue; so good contrast between tumor and normal liver tissue was achieved on PET scans. The enzyme activity study showed that VX2 tumors had increased levels of hexokinase and pyruvate kinase activity, suggesting an increase of glycolysis. We conclude that transplanted VX2 liver tumors could be appropriately evaluated by 18F-FDG PET.

Nonlinearity correction of brain perfusion SPECT based on permeability-surface area product model.

UNLABELLED: It is well known that many cerebral perfusion tracers underestimate cerebral blood flow in high flow range. A model has been proposed to correct nonlinear relationship of flow and uptake of the tracers that accounts for the permeability-surface area product (PS model). METHODS: We examined 43 patients in this study. To test the feasibility of this method for 123I-IMP, 99(m)Tc-HMPAO and 99(m)Tc-ECD, radioactivity ratios of cerebral regions to cerebellum (C/Cr) on SPECT images were compared with those of rCBF (F/Fr) measured by PET using the 15O CO2 steady-state method. Coefficient for correction in the PS model was estimated by the least squares method, and SPECT data were corrected using these coefficients. RESULTS: Estimated PS value by this method was highest in IMP (116 ml/min/100 g) followed by ECD (66 ml/min/100 g) and HMPAO (46 ml/min/100 g). The corrected SPECT data demonstrated an excellent linear relationship, which was close to unity, with rCBF. CONCLUSION: These results indicate that the PS model can be used for nonlinearity correction of brain perfusion SPECT.

FDG-PET evaluation of therapeutic effects on VX2 liver tumor.

UNLABELLED: Transplanted VX2 liver tumor in the rabbit is an experimental liver tumor model in which 18F-2-fluoro-2-deoxy-D-glucose (FDG) accumulates to a 3.5-fold level that surrounds normal liver tissue. In this study, changes in FDG uptake were assessed in this liver tumor model after transcatheter arterial embolization (TAE) and radiotherapy. METHODS: Fifteen rabbits bearing VX2 liver tumors were treated with TAE with gelatin sponges 1 day before the FDG study, and 18 rabbits received local irradiation with electron beams at a dose of 12-36 Gy 1-10 days before the FDG study. In the FDG study, serial arterial blood sampling was performed to determine arterial input (AI), and 1 hr after tracer injection, normal liver tissue and tumor tissue were excised to measure radioactivity. The tumor FDG level per AI and the tumor-to-normal liver ratio were assessed. Dynamic PET images were obtained in 20 of the 46 rabbits. RESULTS: Tumor FDG uptake was significantly decreased 1 day after TAE (from 3.54 to 0.83 in the tumor-to-normal liver ratio) and 5 days after 30 Gy of irradiation (from 3.54 to 1.28). The decrease in tumor FDG uptake was dose-dependent, especially in the relatively low dose range (12-24 Gy). The untreated tumors could be clearly distinguished from the surrounding normal liver tissue, while the embolized tumors or the irradiated tumors were not clearly delineated. Histological analysis showed that the decrease in tumor FDG after treatment agreed well with the decrease in number of viable tumor cells. CONCLUSION: The VX2 liver tumor is an appropriate experimental tumor model for evaluating the change in FDG uptake in various therapeutic modalities. Moreover, the therapeutic effects can be assessed 1 day after TAE and 5 days after irradiation. Further clinical trials for the early evaluation of therapeutic effects on liver tumors using FDG-PET are warranted.

Glucose transporter protein-independent tumor cell accumulation of fluorine-18-AFDG, a lipophilic fluorine-18-FDG analog.

UNLABELLED: Fluorine-18-fluorodeoxyglucose (FDG) is used clinically for tumor diagnosis, but its mechanism of accumulation in tumor cells is complicated because two factors, glucose transporter protein (GLUT) and hexokinase, govern [18F]FDG uptake directly. We selected a lipophilic [18F]FDG analog, 1,3,4,6-tetra-acetyl-2-[18F]-2-deoxy-D-glucose ([18F]AFDG), to regulate the effects of hexokinase and evaluated its characteristics in an in vitro cell culture system. METHODS: Fluorine-18-AFDG was synthesized by the method used to produce [18F]FDG, as an intermediate of [18F]FDG. Fluorine-18-AFDG uptake study was performed with LS180 tumor cells, and its metabolites were also investigated by thin-layer chromatography. To evaluate the relationship between [18F]AFDG and GLUT, we also examined [18F]AFDG uptake in the presence of cytochalasin B or with increased medium glucose concentration. The effects of lowered temperature (4 degrees C) on [18F]AFDG uptake were also investigated. RESULTS: Fluorine-18-AFDG (lipophilicity: octanol/water = 3.5) uptake was 3.3-fold higher than that of [18F]FDG. Metabolic analysis showed that [18F]AFDG was extremely stable in the incubation medium but was quickly hydrolyzed and metabolized to 2-fluoro-[18F]-2-deoxy-D-glucose-6-phosphate ([18F]FDG-6P) in tumor cells. Fluorine-18-FDG-6P accounted for approximately 45% of the total radioactivity after a 60-min incubation of [18F]AFDG. Incubation with 50 microM cytochalasin B did not affect [18F]AFDG uptake. In medium with double the control glucose level, [18F]FDG uptake was decreased by about 50%, but [18F]AFDG uptake was not affected. Fluorine-18-AFDG uptake and [18F]FDG-6P production did not show saturation and increased linearly with addition of a 10-fold higher concentration of [18F]AFDG. Lowered incubation temperature caused decreased [18F]AFDG uptake due to reduced [18F]FDG-6P production. CONCLUSION: Fluorine-18-AFDG rapidly penetrated the cell membrane as a result of its high lipophilicity and was metabolized to [18F]FDG-6P within cells. Fluorine-18-AFDG was thus characterized as "GLUT-independent [18F]FDG."

Metabolic activity in the areas of new fill-in after thallium-201 reinjection: comparison with positron emission tomography using fluorine-18-deoxyglucose.

Reinjection of thallium-201 after recording the 3-hr delayed scan often demonstrates improvement in areas of persistent abnormalities. To determine the metabolic activity of these areas, the changes seen on stress/redistribution/reinjection thallium SPECT were compared with PET using fluorine-18-fluorodeoxyglucose (FDG) in 18 patients with coronary artery disease. Of 48 segments showing no redistribution on the delayed scan, the reinjection scan identified new fill-in in 20 segments (42%), all of which demonstrated FDG uptake. In contrast, only 7 of the 28 segments (25%) showing no fill-in after reinjection were PET viable (p less than 0.01). Eleven patients had coronary bypass graft surgery after the radionuclide study. The majority of the segments showing redistribution (87%) and new fill-in after reinjection (65%) improved in wall motion, whereas only eight segments (25%) without new fill-in improved after surgery. Of those without new fill-in, two segments showing PET ischemia improved in wall motion, whereas the remaining six segments showing PET scar did not improve after surgery. Thus, the segments showing new fill-in after reinjection are PET viable myocardium. However, reinjection thallium imaging still underestimates the extent of tissue viability compared to PET imaging.

Regional wall thickening of left ventricle evaluated by gated positron emission tomography in relation to myocardial perfusion and glucose metabolism.

Regional wall thickening was assessed by electrocardiographically gated positron emission tomography (ECG-gated PET) in 26 patients with coronary artery disease. The standardized percent count increase from end-diastole to end-systole (S-percent Cl) was calculated as an index of wall thickening. The S-percent Cl was 77.8% +/- 28.9% in the segments with normal perfusion at rest, 51.9% +/- 29.5% in those with mild hypoperfusion, and 32.8% +/- 30.9% in those with severe hypoperfusion (p less than 0.001, each). Among the segments with resting hypoperfusion, the S-percent Cl was 38.9% +/- 31.5% in those without stress-induced ischemia and 48.7% +/- 30.9% in those with ischemia (p less than 0.05). Furthermore, among resting severe hypoperfusion, the S-percent Cl was 23.0% +/- 23.9% in the segments without fluorine-18-fluorodeoxyglucose (FDG) uptake and 37.8 +/- 32.9% in those with FDG uptake (p less than 0.05). These results suggest that stress-induced ischemia and FDG accumulation correlated with wall thickening. Thus, quantitative analysis of regional wall thickening seems to be useful for combined analysis of regional function, perfusion and metabolism in coronary patients.

Simple quantification of regional myocardial uptake of fluorine-18-deoxyglucose in the fasting condition.

Quantitative measurement of myocardial uptake of fluorine-18-deoxyglucose (FDG) is required for assessing tissue viability in the fasting state due to suppressed FDG uptake in the normal myocardium. A simple FDG uptake index (% dose per 100 ml tissue) has been introduced to compare with the fractional FDG uptake in 21 patients who underwent serial arterial blood sampling (14 under fasting and 7 under post-prandial conditions) and to measure the normal range in each myocardial segment in the study of 10 normal subjects (all in the fasting condition). Since the integral of plasma FDG values correlated with the body-weight corrected injected FDG dose (r = 0.82), an excellent correlation was observed between the FDG uptake index and the fractional FDG uptake (r = 0.98) in the fasting condition. In addition, the FDG uptake index correlated well with the regional metabolic rate of glucose calculated with the Patlak graphic analysis (r = 0.99). But this correlation was different in the postprandial condition and in the fasting condition in diabetic patients. In the study of normal subjects, the FDG uptake index was slightly higher in the lateral and inferior segments, as compared to the septal and anterior segments (p less than 0.05, each). We conclude that the FDG uptake index is considered as a simple and reliable parameter for quantitative assessment of myocardial FDG uptake in the nondiabetic patients in the fasting condition. Since its uptake was heterogeneous, FDG uptake should be carefully evaluated for assessing myocardial viability by comparing normal values in each segment.

Effects of hyperglycemia on FDG uptake in human brain and glioma.

UNLABELLED: This study evaluates the effects of hyperglycemia on fluorodeoxyglucose (FDG) uptake in the human brain and in brain tumors. METHODS: We performed glucose loading during FDG PET studies in nine patients with brain tumors (eight gliomas and one brain metastasis) and one with resected glioma. Two FDG PET scans were obtained in all cases within 1 wk in a control state and with glucose loading by intravenous infusion of 10% glucose solution. Serial arterial blood sampling was performed in all cases to obtain fractional uptake of FDG normalized by the plasma integral uptake of radioactivity (FU). RESULTS: In all nine patients with brain tumors, the tumor was depicted more clearly with glucose loading than in the control state. Glucose loading decreased FU in the cerebral cortex (54.2% +/- 13.8%) nearly in inverse proportion to the plasma glucose level, while the tumors showed a decrease (42.5% +/- 15.6%), resulting in an increased tumor-to-cortex ratio by 26.0% +/- 5.7%. Fractional uptake in the cerebellum, white matter and the edematous area also decreased by glucose loading (53.9% +/- 13.2%, 49.6% +/- 10.3% and 34.9% +/- 9.6%, respectively). CONCLUSION: These results demonstrate the different effects of hyperglycemia on normal brain tissue and on tumor, suggesting that glucose loading may be a valuable adjunct to FDG PET to enhance detection of recurrent or residual brain tumors.

Clinical application and quantitative evaluation of generator-produced copper-62-PTSM as a brain perfusion tracer for PET.

UNLABELLED: Copper-62-pyruvaldehyde bis(N4-methylthiosemicarbazone) copper II (62Cu-PTSM) has been proposed as a generator-produced positron-emitting tracer for perfusion imaging. To evaluate the characteristics of 62Cu-PTSM as a cerebral perfusion tracer, brain PET images of 62Cu-PTSM were compared with cerebral blood flow (CBF). METHODS: Following an intravenous injection of 62Cu-PTSM, a serial dynamic PET scan was performed for 10 min with arterial sampling in 10 subjects. CBF was measured by 15O-labeled water before the 62Cu-PTSM study. RESULTS: Dynamic PET scan with octanol-extracted arterial input function indicated the presence of significant back-diffusion of 62Cu-PTSM from the brain within 3 min after injection, followed by stable activity from 3 to 10 min. Comparison with 15O-water PET demonstrated less contrast between high- and low-flow regions in 62Cu-PTSM image and a nonlinear relationship of flow and 62Cu-PTSM uptake, which suggests the underestimation of CBF in high-flow regions due to the existence of back-diffusion. CONCLUSION: Although 62Cu-PTSM can be used widely for evaluation of brain perfusion with PET, kinetic analysis and correction may be needed to quantify regional CBF.

Value of fluorine-18-FDG-PET to monitor hepatocellular carcinoma after interventional therapy.

METHODS: Thirty-two tumors in 30 patients with hepatocellular carcinoma (HCC) were studied preoperatively using PET with 18F-labeled 2-fluoro-2-deoxy-D-glucose (FDG) to evaluate the metabolic activity of the lesions after interventional therapy. All patients had received transcatheter arterial chemoembolization therapy using iodized oil (Lipiodol, Laboratoire Guerbet, Alnaysous-Bois, France) before the PET study. The tumors were 2 to 18 cm in diameter. FDG uptake at 48 to 60 min after tracer injection was used to determine the standardized uptake value (SUV). The SUVs of the tumor and nontumor regions of the liver were calculated to obtain the tumor-to-nontumor ratio (SUV ratio). The PET results were compared with the findings of CT and histologic examination. RESULTS: The tumors were divided into three types, consisting of those with increased FDG uptake (SUV ratio of 1.07-2.66, Type A, n = 19), similar FDG uptake to the surrounding nontumor region (SUV ratio of 0.77-1.04, Type B, n = 7) and decreased or absent FDG uptake (SUV ratio of 0.13-0.58, Type C, n = 6). In histologic examination, viable HCC tissue remained in all Type A and B tumors, whereas more than 90% necrosis was found in the Type C tumors, indicating that interventional therapy had been effective. These PET findings reflected tumor viability more accurately than the extent of intratumor Lipiodol retention on CT images. CONCLUSION: FDG-PET appears to be a valuable method for the assessment of tumor viability after interventional therapy for HCC.

Impairment of BMIPP uptake precedes abnormalities in oxygen and glucose metabolism in hypertrophic cardiomyopathy.

UNLABELLED: Impairment of fatty acid uptake is shown to precede myocardial perfusion abnormality using 123I-labeled 15-(p-iodophenyl)-3-(R,S)-methylpentadecanoic acid (BMIPP) in an experimental model of hypertrophic cardiomyopathy (HCM) and in human studies. We have recently demonstrated that abnormalities of both glucose and oxidative metabolism precede the reduction of blood flow in HCM. The main purposes of this study were to assess the frequency of abnormal findings in FDG uptake, BMIPP uptake and oxygen metabolism and to clarify the relationship among these metabolic parameters by using PET and SPECT. METHODS: Twenty-eight subjects with HCM underwent FDG- and acetate-PET and thallium- and BMIPP-SPECT studies at rest, respectively. After correcting for partial volume effect, real percentages of FDG and BMIPP uptake were calculated. In addition, the clearance rate constant (K mono) of acetate was measured and normalized (%) to estimate the oxygen metabolism. RESULTS: There were various metabolic abnormalities observed in patients with HCM. BMIPP uptake was often impaired without significant reduction of K mono values or FDG uptake. Thus, abnormality of BMIPP uptake was more frequently observed than that for FDG uptake or K mono values (p < 0.0001, respectively). FDG uptake was relatively maintained even in the segments with reduced K mono values and reduced BMIPP uptake. CONCLUSION: HCM shows a variety of metabolic patterns; however, the results of our study suggest that reduction of BMIPP uptake appears to be the most sensitive indicator of metabolic abnormalities followed by reduction of oxidative metabolism in patients with HCM.

SPECT images of technetium-99m-ethyl cysteinate dimer in cerebrovascular diseases: comparison with other cerebral perfusion tracers and PET.

UNLABELLED: To assess the clinical role of 99mTc-ethyl cysteinate dimer (ECD) as a cerebral perfusion tracer, 10 patients with unilateral cerebral infarction were studied. METHODS: ECD SPECT images were compared with IMP and/or HMPAO SPECT in nine patients, seven in chronic phases and two in subacute phases. Five of these patients and one additional patient with chronic infarction received PET imaging in order to compare ECD distribution with quantitative regional cerebral blood flow (rCBF) and oxygen metabolism (rCMRO2) images. RESULTS: In patients with chronic cerebral infarction, regression analysis showed excellent correlation between ECD and IMP in the uptake ratio of lesions-to-nonaffected cortices (r = 0.91). In two cases of subacute infarction, decreased uptake of ECD was observed in the area of "luxury perfusion," which showed elevated or preserved rCBF with diminished rCMRO2. On visual analysis, ECD image contrast was less prominent compared to that of IMP, but contrast was better than that of HMPAO. CONCLUSIONS: ECD uptake showed a curvilinear relationship against rCBF, suggesting flow-limited uptake in a high flow range. ECD is a clinically useful cerebral perfusion tracer with distinct characteristics when compared with other available agents.

Iodinated free fatty acid and 201T1 uptake in chronically hypoperfused myocardium: histologic correlation study.

UNLABELLED: 123I-15-(p-iodophenyl)-3-(R,S)-methylpentadecanoic acid (BMIPP) is a tracer for the evaluation of ischemic heart disease. The purpose of this study was to assess the relationship between 1231-BMIPP uptake and myocardial fibrosis. METHODS: Fifteen patients who underwent cardiac surgery were examined by imaging with 201TI and 123I-BMIPP, and histologic specimens were taken during surgery. The relative uptake of 201TI (%TI) and that of 123I-BMIPP (%BMIPP) were calculated. The percentage of fibrosis (%fibrosis) was analyzed with the specimen. RESULTS: %TI correlated strongly with %fibrosis (r = -0.94; P < 0.001). %BMIPP also correlated significantly with %fibrosis (r = -0.88; P < 0.001), but the change in %BMIPP looked biphasic. In the category of only mild fibrosis, %BMIPP showed a steep decrease. 123I-BMIPP-201TI mismatch was found only for fibrosis <20%. CONCLUSION: 123I-BMIPP gave specific information about metabolic changes that occurred in ischemic myocardium without severe fibrotic changes.

In vivo assessment of glucose metabolism in hepatocellular carcinoma with FDG-PET.

UNLABELLED: The present study was designed to assess glucose metabolism in hepatocellular carcinoma (HCC) with PET and [18F]fluorodeoxyglucose (FDG) and to compare the results with the measured in vitro enzymatic activity of glucose metabolism and the histologic grading of HCC. METHODS: Dynamic FDG-PET scans were obtained in 17 preoperative patients with HCC. From the serial tissue and arterial radioactivities obtained by dynamic PET, FDG kinetic rate constants (K1 to k4) were obtained. The standardized uptake value (SUV) was also determined from the images acquired 48 to 60 min after FDG administration. These PET results were compared with hexokinase and glucose-6-phosphatase (G6Pase) activities and histologic grading of HCC in surgically resected tumor materials. According to histologic grading, the tumors were divided into low-grade and high-grade HCCs. RESULTS: The k3 and SUV of high-grade HCCs were significantly higher than those of low-grade HCCs (p < 0.005, each). In addition, high correlations were observed between the hexokinase activities and these two parameters (r = 0.715 0.768, respectively). In some HCCs, relatively high G6Pase activities and k4 values modified tumor FDG uptake. CONCLUSION: FDG PET is a valuable method for assessing glucose metabolism and histologic grading of HCC.

Decreased uptake of iodinated branched fatty acid analog indicates metabolic alterations in ischemic myocardium.

UNLABELLED: We previously reported that uptake of 123I-labeled 15-iodophenyl 3-methyl pentadecanoic acid (BMIPP) was lower than that of thallium in ischemic myocardium. Such discordant findings between BMIPP and thallium were compared with those of PET using 18F-deoxyglucose (FDG) and 11C-acetate to assess metabolic alterations in such segment. METHODS: Sixteen patients with coronary artery disease underwent both BMIPP SPECT and PET. Relative FDG uptake (% FDG uptake) and the clearance rate constant (% Kmono) of 11C-acetate from the myocardium were calculated as markers of glucose and oxidative metabolism, respectively. RESULTS: Relative FDG uptake of the myocardial segments with reduced BMIPP uptake and normal thallium uptake (discordant segments) was similar (85.3 +/- 10.3) to that of the normal segments (86.5 +/- 11.7) but higher than that of segments with reduced uptake of both BMIPP and thallium (67.5 +/- 19.9). Similarly, the discordant segments showed a higher % Kmono value (77.8 +/- 13.1 versus 70.0 +/- 19.1) and FDG-to-perfusion ratio (1.15 +/- 0.08 versus 1.01 +/- 0.22) than in the concordantly reduced segments. CONCLUSION: BMIPP uptake appears to provide metabolic information independent of thallium uptake. Combined imaging of BMIPP and thallium may potentially identify ischemic but viable myocardium.

Myocardial oxidative metabolism in hyperthyroid patients assessed by PET with carbon-11-acetate.

UNLABELLED: Hyperthyroid patients often complain of cardiovascular symptoms because of increased metabolism. This study was designed to quantitatively evaluate myocardial oxidative metabolism in these patients. METHODS: Dynamic PET with 11C-acetate was performed in 19 patients who had not undergone treatment for hyperthyroidism. Eight were restudied 2 wk after oral administration of propranolol. The clearance rate constant of 11C-acetate (Kmono) was calculated with monoexponential fitting of tracer washout from the myocardium as a marker of myocardial oxidative metabolism. The results were compared with those in nine normal subjects both at rest and during dobutamine infusion. RESULTS: Kmono in our patients (0.109 +/- 0.028 min-1) was significantly increased compared to normal subjects (0.066 +/- 0.016 min-1) (p < 0.05). After propranolol treatment, Kmono decreased (0.082 +/- 0.014 min-1) but remained significantly higher in eight patients than normal subject levels (p < 0.05), while the rate pressure product decreased significantly (7500 +/- 1700) toward the normal range (7900 +/- 1500). CONCLUSION: These results suggest the possibility of excessive myocardial oxygen consumption in hyperthyroid patients. The clearance rate of 11C-acetate is a new and valuable index to assess myocardial oxidative metabolism not closely related to the pressure rate product or thyroid hormones in these patients.