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Objective: FDG PET/CT plays a significant role in the diagnosis of inflammatory heart diseases and cardiac tumors. We attempted to determine the optimal FDG uptake threshold for volume-based analyses and to evaluate the relationship between the myocardial physiological uptake volume in FDG PET and several clinical factors., Methods: A total of 190 patients were retrospectively analyzed. The cardiac metabolic volume (CMV) was defined as a volume within the boundary determined by a threshold (SUVmean of blood pool × 1.5)., Results: The SUVmean of the blood pool measured in the descending aorta (DA) (r = 0.86, intraclass correlation coefficient [ICC] = 0.93, P < 0.0001) and that in the left ventricle (LV) cavity (r = 0.87, ICC = 0.90, P < 0.0001) showed high inter-operator reproducibility. However, the SUVmean in the LV cavity showed a significant correlation with the CMV (P = 0.0002, r = 0.26). The CMV in the patients who fasted < 18 hours were significantly higher (49.7  ±  73.2 vs. 18.0  ±  53.8 mL, P = 0.0013) compared to the patients with > 18-hour fasting. The multivariate analysis demonstrated that only the fasting period > 18 hours was independently associated with CMV = 0., Conclusion: Our findings revealed that the DA is suitable to decide the threshold for the volume-based analysis. The fasting time was significantly associated with the cardiac FDG uptake.

Purpose: Myocardial glucose utilization (MGU) is altered in various heart diseases. The aim of this study was to quantitatively assess regional myocardial glucose utilization in patients with left ventricular (LV) dysfunction by dynamic( 18)F-fluorodeoxyglucose positron emission tomography (FDG PET)., Methods: A total of 18 subjects were studied, including ten with LV dysfunction (seven with idiopathic dilated cardiomyopathy and three with aortic regurgitation; NYHA II in 8 and III in 2) and eight healthy normal volunteers. Patients with diabetes mellitus were excluded. A dynamic PET study was performed for 40 min following the injection of 370 MBq of FDG after 50-g glucose loading. On the basis of a three-compartment model, MGU, K1, k2, and k3 were computed on a pixel by pixel basis to generate LV myocardial parametric maps. FDG standardized uptake value (SUV) was also calculated using static images obtained 40 min after FDG injection. These metabolic values were compared with myocardial flow distribution (%Flow), LVEF, LV volumes, and LV wall thickening (WT) determined by gated myocardial single-photon emission computed tomography using QGS software in eight myocardial segments., Results: MGU correlated positively with LV volumes and negatively with LVEF. K(1) was significantly higher in the segments of the patients than in those of the normal volunteers (0.082+/-0.055 vs 0.041+/-0.017 ml min(-1) g(-1), p<0.05), although there was no difference in MGU between the groups. On the other hand, SUV, k2, and k3 did not differ significantly between the groups. Among the patients, the K1 values were significantly higher in the areas with impaired WT (%WT<17%) (0.109+/-0.063 vs 0.069+/-0.062 ml min(-1) g(-1), p<0.05) and in the areas with flow reduction (%Flow<71%) (0.112+/-0.076 vs 0.071+/-0.046 ml min(-1) g(-1), p<0.05)., Conclusion: These results indicate that glucose utilization was preserved in the patients with LV dysfunction, mainly due to an increase in glucose transport, particularly in the regions with severely impaired LV function. Thus, the quantitative assessment of myocardial glucose utilization by FDG dynamic PET may provide useful information for assessing the regional myocardial metabolic status in patients with LV dysfunction.

Single photon emission computed tomography (SPECT) using ultra-high energy collimators permits wide clinical application of (18)F-fluorodeoxyglucose (FDG) imaging without the use of expensive positron emission tomography (PET) cameras. This study was designed to evaluate the value of FDG SPECT using ultra-high energy collimators in assessing myocardial viability compared with FDG PET on a regional basis. We prospectively studied 33 patients with ischaemic heart disease. The patients were injected with 555 MBq of FDG under a hyperinsulinaemic glucose clamp, and FDG PET was performed 40 min later. FDG SPECT using ultra-high energy collimators was performed immediately after FDG PET. The images of the left ventricular myocardium were divided into nine segments and the regional defect score was assessed visually using a four-point scale (0=normal to 3=defect). Regional FDG uptake (%uptake) was quantitatively analysed using polar maps. In 297 segments of all the 33 patients, agreement between the defect scores based on FDG SPECT images and those based on FDG PET images was 70%, and agreement within one rank was 96% (kappa value=0.52). The %uptake based on FDG SPECT images significantly correlated with that based on FDG PET images (r=0.77, P<0.01). However, the defect scores in the inferior wall based on FDG SPECT images were higher (1.41+/-1.14) than those based on FDG PET images (1.06+/-1.12, P<0.01). When the viable region is defined as %uptake > or =50% in FDG PET studies, the optimal cut-off level of %uptake based on FDG SPECT images was 60% in the anterior wall, apex, septum and lateral wall (accuracies, 97%, 93%, 96% and 99%, respectively), and 45% in the inferior wall (accuracy, 99%). It is concluded that FDG SPECT using ultra-high energy collimators can be used for the assessment of myocardial viability as accurately as FDG PET. However, a slight difference was observed in the defect scores mainly due to attenuation in the inferior wall. Therefore, a slightly different cut-off level for assessing myocardial viability should be applied to the inferior wall when using FDG SPECT.

In extrahepatic bile duct cancer, preoperative evaluation is important because only surgical excision of all detectable tumours is associated with improvement in 5-year survival. However, morphological imaging techniques, including computed tomography (CT), are still insufficient for accurate staging. The purpose of this study was to assess the additional value, in relation to CT, of 2-[(18)F]fluoro-2-deoxy- D-glucose positron emission tomography ((18)F-FDG PET) for the evaluation of extrahepatic bile duct cancer. Thirty patients with extrahepatic bile duct cancer underwent both (18)F-FDG PET and CT for initial staging. The results of the two modalities for evaluation of primary tumours and regional lymph nodes were compared with the final diagnoses based on pathological or clinical findings. The primary tumours were interpreted as malignant on the basis of CT in 24 (80%) of the patients, while (18)F-FDG PET revealed increased (18)F-FDG uptake in 18 (60%) of them. On the other hand, (18)F-FDG PET showed focal accumulation of (18)F-FDG in the bile duct in three of the six patients with equivocal findings on CT. The sensitivity, specificity and accuracy of CT for regional lymph node metastases were 54%, 59% and 57%, while those of (18)F-FDG PET were 38%, 100% and 73%, respectively. The specificity of (18)F-FDG PET for regional lymph node metastases was significantly higher than that of CT ( P<0.01). Of 14 patients with N1 or N2 disease diagnosed by CT, only seven (50%) had a final diagnosis of regional lymph node metastasis. In these 14 patients, (18)F-FDG PET accurately evaluated the N component of the disease in 12 patients (86%). In conclusion, in the initial staging of patients with extrahepatic bile duct cancer, (18)F-FDG PET offers additional value in relation to CT in evaluating both the primary tumour and regional lymph nodes.

The detection of viable myocardium is important for the prediction of functional recovery after revascularisation. However, a fixed perfusion defect often includes viable myocardium, and perfusion imaging then underestimates myocardial viability. We previously reported that low-dose dobutamine stress gated single-photon emission tomography (SPET) provides similar findings to dobutamine stress echocardiography in the assessment of myocardial viability. The present study investigated whether low-dose dobutamine stress gated SPET is of additional value as compared with stress-rest technetium-99m tetrofosmin SPET for the detection of myocardial viability. Standard stress-rest perfusion SPET, low-dose dobutamine stress gated SPET and fluorine-18 fluorodeoxyglucose positron emission tomography (FDG PET) were studied in 23 patients (mean age 67+/-7.6 years) with previous myocardial infarction. Twenty-one of them were successfully studied with each technique. FDG PET viability (FDG uptake >/=50%) was employed as the gold standard. One-day stress-rest (99m)Tc-tetrofosmin myocardial SPET was performed. After the resting study, gated SPET was acquired following infusion of 7.5 microg kg(-1) min(-1) of dobutamine. Left ventricular wall motion in 16 segments was assessed by cine mode display using a four-point scale. Myocardial viability was considered present when there was improvement by one point. Of a total of 336 segments analysed, 53 had persistent defects on stress-rest perfusion SPET. FDG viability was seen in 16 of 17 dobutamine-responsive segments, but in only 11 of 36 dobutamine non-responsive segments ( P<0.01). Thus, in the segments with persistent defects, viability findings on low-dose dobutamine stress gated SPET were concordant with those on FDG PET in 77% of segments (kappa value =0.55). For the detection of FDG-viable myocardium, the combination of stress-rest perfusion SPET and low-dose dobutamine stress gated SPET achieved a better sensitivity than stress-rest perfusion SPET alone (35/46, 76% vs 19/46, 41.3%, P<0.001), with a similar specificity (25/29, 86% vs 26/29, 90%, P=NS). We conclude that in the identification of viable myocardium, low-dose dobutamine stress gated SPET may provide additional information missed on a routine stress-rest perfusion scan. Dobutamine stress gated SPET may provide new insights into myocardial viability on the basis of ischaemia and contractile reserve.

Unlabelled: There are several reports about the usefulness of (18)F-FDG PET in thyroid cancer. However, few studies have compared FDG PET with (131)I and (201)Tl scintigraphy. The aim of this study was to evaluate the clinical significance of whole-body FDG PET in differentiated thyroid cancer and to compare the results with those obtained from (131)I and (201)Tl scintigraphy., Methods: Whole-body FDG PET was performed on 32 patients (10 men, 22 women; age range, 30-77 y; mean age, 54 y) with differentiated thyroid cancer (5 cases of follicular cancer and 27 of papillary cancer) after total thyroidectomy. An overall clinical evaluation was performed, including cytology, thyroglobulin level, sonography, MRI, and CT, to allow a comparison with functional imaging results for each patient. Metastatic regions were divided into five areas: neck, lung, mediastinum, bone, and other. Multiple lesions in one area were defined as one lesion. The tumor-to-background ratio (TBR) was measured for the lesions that were positive for both (201)Tl uptake and FDG PET uptake., Results: The number of lesions totaled 47. Forty-one (87%) were detected by all scintigraphic methods. FDG uptake was concordant with (131)I uptake in only 18 lesions (38%). FDG uptake was concordant with (201)Tl uptake in 44 lesions (94%). Only one lesion was negative for FDG uptake and positive for (201)Tl uptake, and two lesions were positive for FDG uptake and negative for (201)Tl uptake. A significant correlation was seen between the TBR of (201)Tl and that of FDG (r = 0.69; P<0.05)., Conclusion: These data indicate that for detecting metastatic lesions, FDG PET and (131)I scintigraphy may provide complementary information, whereas FDG PET may provide results similar to those of (201)Tl scintigraphy. Thus, the combination of (131)I scintigraphy and FDG PET (or (201)Tl scintigraphy) is the method of choice for detecting metastatic thyroid cancer after total thyroidectomy.

It is important to know FDG accumulation in the normal distributions for interpreting whole-body PET imaging for tumor detection. Twenty-eight normal subjects were studied with whole-body PET imaging and were examined the intensity of FDG uptake in major organs and the factors which caused it's variety. Emission images were acquired and images were reconstructed without attenuation correction. The intensity of FDG uptake was classified into 4 grades visually. No accumulation was found in the thyroid, the esophagus and the spleen. The oral cavity, the liver, the stomach, and the colon were visualized in all subjects. The laryngeal muscle, the cervical muscle, and the heart accumulated FDG with various grade from 1 to 4 grades. No association was found between the intensity of uptake in the organs and volunteer's age. The fasting time was shorter in volunteers whose heart showed "high" grade than those showed less accumulation (p < 0.05). Serum concentration of free fatty acid was significantly lower in them, too (p < 0.05). Various FDG uptake was observed in many organs, especially the laryngeal muscle, the cervical muscle, and the heart. In our study, there was no facter which caused FDG uptake in organs except for the fasting time and the value of free fatty acid in the heart. Such analysis of whole-body FDG distributions in the normal subjects is valuable for tumor detection with FDG-PET.

We synthesized 18F-FDG by using an automated synthetic apparatus "FDG MicroLab" (GE Medical Systems) which produces 18F-FDG by a solid phase 18F-fluorination. Its quality and reproducibility were evaluated in order to assess feasibility of the apparatus for routine clinical production of 18F-FDG. For 5 consecutive 18F-FDG synthesis, target irradiation was carried out at 15 microA for 60 min. 18F-FDG was obtained in 50 min after EOB with an end-of-synthesis yield of 9.34 +/- 1.06 GBq. Radiochemical yield and radiochemical purity were 47 +/- 3% (decay corrected) and 98.0 +/- 0.5%, respectively. Other several quality control parameters tested conformed with "Standards of Compounds Labeled with Positron Nuclides" (RADIOISOTOPES, 44, 1995). Thus, the automated synthetic apparatus "FDG MicroLab" has proven to stably produce 18F-FDG with high yield and high purity. The apparatus is feasible for routine clinical production of 18F-FDG.