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Microcalcification, a type of vascular calcification, increases the instability of plaque and easily leads to acute clinical events. Positron emission tomography (PET) is a new examination technology with significant advantages in identifying vascular calcification, especially microcalcification. The use of the 18F-NaF is undoubtedly the benchmark, and other PET tracers related to vascular calcification are also currently in development. Despite all this, a large number of studies are still needed to further clarify the specific mechanisms and characteristics. This review aimed at providing a summary of the application and progress of different PET tracers and also the future development direction. [ABSTRACT FROM AUTHOR]

Objectives: Attenuation correction (AC) is crucial for ensuring the quantitative accuracy of positron emission tomography (PET) imaging. However, obtaining accurate μ-maps from brain-dedicated PET scanners without AC acquisition mechanism is challenging. Therefore, to overcome these problems, we developed a deep learning-based PET AC (deep AC) framework to synthesize transmission computed tomography (TCT) images from non-AC (NAC) PET images using a convolutional neural network (CNN) with a huge dataset of various radiotracers for brain PET imaging.Methods: The proposed framework is comprised of three steps: (1) NAC PET image generation, (2) synthetic TCT generation using CNN, and (3) PET image reconstruction. We trained the CNN by combining the mixed image dataset of six radiotracers to avoid overfitting, including [18F]FDG, [18F]BCPP-EF, [11C]Racropride, [11C]PIB, [11C]DPA-713, and [11C]PBB3. We used 1261 brain NAC PET and TCT images (1091 for training and 70 for testing). We did not include [11C]Methionine subjects in the training dataset, but included them in the testing dataset.Results: The image quality of the synthetic TCT images obtained using the CNN trained on the mixed dataset of six radiotracers was superior to those obtained using the CNN trained on the split dataset generated from each radiotracer. In the [18F]FDG study, the mean relative PET biases of the emission-segmented AC (ESAC) and deep AC were 8.46 ± 5.24 and - 5.69 ± 4.97, respectively. The deep AC PET and TCT AC PET images exhibited excellent correlation for all seven radiotracers (R2 = 0.912-0.982).Conclusion: These results indicate that our proposed deep AC framework can be leveraged to provide quantitatively superior PET images when using the CNN trained on the mixed dataset of PET tracers than when using the CNN trained on the split dataset which means specific for each tracer. [ABSTRACT FROM AUTHOR]

Objective: Many studies have demonstrated the superiority of white matter (WM) reference regions (RR) in amyloid PET studies in comparison to cerebellar RR. However, the principle behind its improved measurement stability is yet to be elucidated. Our study aimed to determine the origin of WM stability; stability over cerebral blood flow and input function fluctuation or the greater statistical noise in the cerebellum due to its smaller size and its location in the axial periphery of the PET scanner bore.Methods: We conducted simulations of [[Formula: see text]F] florbetapir using in-house program varying [Formula: see text] and input function, and adding statistical noise.Results: Our simulations revealed that WM RR were more susceptible to CBF variation and input function fluctuation than cerebellar RR. WM RR did not gave superior measurement stability unless cerebellar statistical noise exceeded 4.55 times that in WM, a figure often surpassed in traditional amyloid PET studies. The greater statistical noise in cerebellum is likely the etiology for improved measurement stability of WM RR.Conclusion: A longitudinal [[Formula: see text]F] florbetapir PET study should be conducted with a long bore PET. It can also be hypothesized that a second scan with the cerebellum in the axial center of a 3D PET, using a cerebellar RR to calculate changes in tracer concentration may improve the measurement stability of longitudinal [[Formula: see text]F] florbetapir studies. [ABSTRACT FROM AUTHOR]

Objective: This study aimed to compare the qualities of whole-body positron emission tomography (PET) images acquired by the step-and-shoot (SS) and continuous bed motion (CBM) techniques with approximately the same acquisition duration, through phantom and clinical studies.Methods: A body phantom with 10-37 mm spheres was filled with 18F-fluorodeoxyglucose (FDG) solution at a sphere-to-background radioactivity ratio of 4:1 and acquired by both techniques. Reconstructed images were evaluated by visual assessment, percentages of contrast (%Q H) and background variability (%N) in accordance with the Japanese guideline for oncology FDG-PET/computed tomography (CT). To evaluate the variability of the standardized uptake value (SUV), the coefficient of variation (CV) for both maximum SUV and peak SUV was examined. Both the SUV values were additionally compared with those of standard images acquired for 30 min, and their accuracy was evaluated by the %difference (%Diff). In the clinical study, whole-body 18F-FDG PET/CT images of 60 patients acquired by both techniques were compared for liver signal-to-noise ratio (SNRliver), CV at end planes, and both SUV values.Results: In the phantom study, the visual assessment and %Q H values of the two techniques did not differ from each other. However, the %N values of the CBM technique were significantly higher than those of the SS technique. Additionally, the CV and %Diff for both SUV values in the CBM images tended to be slightly higher than those in SS images. In the clinical study, the SNRliver values of CBM images were significantly lower than those of SS images, although the CV at the end planes in CBM images was significantly lower than those in SS images. In the Bland-Altman analysis for both SUV values, the mean differences were close to 0, and most lesions exhibited SUVs within the limits of agreement.Conclusions: The CBM technique exhibited slightly lesser uniformity in the center plane than the SS technique. Additionally, in the phantom study, the CV and %Diff of SUV values in CBM images tended to be slightly higher than those of SS images. However, since these differences were subtle, they might be negligible in clinical settings. [ABSTRACT FROM AUTHOR]

Background: The neuroinflammatory glial response contributes to the degenerative process in Parkinson's disease (PD). However, the pattern of microglial progression remains unclear. Methods: We evaluated microglial activation in early stage PD patients by quantifying changes in neuroinflammation using PET with [(11)C]DPA713, a selective PET tracer for microglial activation. Eleven PD patients (Hoehn and Yahr stages 1-2) without dementia underwent the [(11)C]DPA713 PET scan two times with 1 year apart. The binding potential (BPND) was estimated with the simplified reference tissue model. Voxelwise and regions of interest analyses were used to compare the regional BPND among groups. Results: Significant increase in [(11)C]DPA713 BPND was found extrastriatally in the occipital, temporal and parietal cortex in PD patients, and the degree of BPND became much higher over the brain regions predominantly in the temporal and occipital cortex 1 year later. Conclusion: The current results indicated that an extrastriatal spreading of microglial activation reflects one of PD pathophysiology occurring at an early stage. [ABSTRACT FROM AUTHOR]

Objective: Molecular imaging with positron emission tomography (PET) provides a powerful means of identifying and characterizing cancerous processes, as well as providing a quantitative framework within which response to therapy can be ascertained. Unfortunately, the most commonly used PET radiotracer, ¹⁸F-fluorodeoxyglucose (FDG), has not demonstrated a definitive role in determining response to therapy in metastatic renal cell carcinoma (RCC). As a result, new radiotracers able to reliably image RCC could be of tremendous value for this purpose.Methods: Five patients with known metastatic RCC were imaged with the low-molecular weight radiotracer ¹⁸F-DCFPyL, an inhibitor of the prostate-specific membrane antigen at 60 min post injection. ¹⁸F-DCFPyL PET/CT and conventional images (either contrast-enhanced computed tomography or magnetic resonance imaging) were centrally reviewed for suspected sites of disease.Results: In all five patients imaged, sites of putative metastatic disease were readily identifiable by abnormal ¹⁸F-DCFPyL uptake, with overall more lesions detected than on conventional imaging. These PET-detected sites included lymph nodes, pancreatic parenchymal lesions, lung parenchymal lesions, a brain parenchymal lesion, and other soft tissue sites. ¹⁸F-DCFPyL uptake ranged from subtle to intense with maximum standardized uptake values (SUVmax) for the identified lesions of 1.6-19.3. Based upon this small patient series, limited pathology and imaging follow-up of these patients suggests a higher sensitivity for ¹⁸F-DCFPyL compared to conventional imaging in the detection of metastatic RCC (94.7 versus 78.9%).Conclusions: PSMA expression in the tumor neovasculature of RCC has been previously established and is believed to provide the basis for the imaging findings presented here. PSMA-based PET/CT with radiotracers such as ¹⁸F-DCFPyL may allow more accurate staging of patients with RCC and conceivably the ability to predict and follow therapy in patients treated with agents targeting the neovasculature. [ABSTRACT FROM AUTHOR]

Purpose: To characterize the heterogeneity of metastatic neuroendocrine tumor (NET) lesions, we compared the [F]-fluorodeoxyglucose (FDG) uptake and the In-pentetreotide (SRS) uptake for somatostatin receptor scintigraphy using the CT-based fusion imaging techniques of PET/CT and SPECT/CT. Methods: Fifteen consecutive patients with NET lesions were examined using both FDG-PET/CT and SRS SPECT/CT prospectively. A total of 45 metastatic NET lesions were evaluated for FDG uptake according to the standardized uptake value (SUV) and for SRS uptake according to the tumor-to-muscle count ratio (T/M ratio); these values were then compared according to the grade of NET (G), also compared to the tumor volume. Results: Both the SRS uptake and FDG uptake showed no significant correlation to the tumor volume, and suggested no significant artifacts in these data. The T/M ratio for the SRS uptake ranged from 192.7 to 1.9 and exhibited very wide range of distribution. The SUV for the FDG uptake ranged from 13.8 to 0.77 and exhibited narrow range of distribution. The uptake of the two tracers in individual lesions showed an inverse correlation. The G1 + 2 lesions had a higher SRS uptake than the G3 lesions, but the difference was not significant because of the large variation (40.65 ± 48.03, n = 39 vs. 8.66 ± 13.13, n = 6). However, the G1 + 2 lesions had a significantly lower FDG uptake than the G3 lesions (3.52 ± 1.84, n = 39 vs. 10.82 ± 4.50, n = 6). The tracer uptakes varied largely not only in an inter-subject manner, but also in an intra-subject manner. Conclusion: An inverse correlation between SRS uptake and FDG uptake in the metastatic NET lesions observed in this study may be consistent with the opposing ideas of differentiation and proliferation in oncology. The large variations in SRS and FDG uptake by metastatic NET lesions suggest the biological heterogeneity of advanced NET. These results support the idea that combination therapy targeting both receptor-positive cells and proliferating cells may be beneficial from a functional imaging perspective. [ABSTRACT FROM AUTHOR]

Aim: The aim of the study was (1) to evaluate the reconstruction strategies with dynamic [ $$_{ }^{11}\mathrm C$$ ]-raclopride human positron emission tomography (PET) studies acquired from ECAT high-resolution research tomograph (HRRT) scanner and (2) to justify for the selected gap-filling method for analytical reconstruction with simulated phantom data. Methods: A new transradial bicubic interpolation method has been implemented to enable faster analytical 3D-reprojection (3DRP) reconstructions for the ECAT HRRT PET scanner data. The transradial bicubic interpolation method was compared to the other gap-filling methods visually and quantitatively using the numerical Shepp-Logan phantom. The performance of the analytical 3DRP reconstruction method with this new gap-filling method was evaluated in comparison with the iterative statistical methods: ordinary Poisson ordered subsets expectation maximization (OPOSEM) and resolution modeled OPOSEM methods. The image reconstruction strategies were evaluated using human data at different count statistics and consequently at different noise levels. In the assessments, 14 [ $$_{ }^{11}\mathrm C$$ ]-raclopride dynamic PET studies (test-retest studies of 7 healthy subjects) acquired from the HRRT PET scanner were used. Besides the visual comparisons of the methods, we performed regional quantitative evaluations over the cerebellum, caudate and putamen structures. We compared the regional time-activity curves (TACs), areas under the TACs and binding potential (BP $$_{\text {ND}}$$ ) values. Results and conclusions: The results showed that the new gap-filling method preserves the linearity of the 3DRP method. Results with the 3DRP after gap-filling method exhibited hardly any dependency on the count statistics (noise levels) in the sinograms while we observed changes in the quantitative results with the EM-based methods for different noise contamination in the data. With this study, we showed that 3DRP with transradial bicubic gap-filling method is feasible for the reconstruction of high-resolution PET data with missing sinogram bins. The calculated intraclass correlation coefficient (ICC) values were similar for all tested methods and validated the test-retest study. The gap-filling and 3DRP method can be used for quantitative PET studies in which high temporal information is crucial and can serve as a reference method for comparison studies of the other reconstruction methods. [ABSTRACT FROM AUTHOR]

Objective: Dopamine transporter (DAT) density is considered as a marker of pre-synaptic function. Numerous neuroimaging studies have consistently demonstrated an age-related decrease in DAT density in normal human brain. However, the precise degree of the regional decline is not yet clear. The purpose of this study was to evaluate the effect of the normal aging process on DAT densities in human-specific brain regions including the substantia nigra and thalamus using positron emission tomography (PET) with [F]FE-PE2I, a new PET radioligand with high affinity and selectivity for DAT. Methods: Thirty-six healthy volunteers ranging in age from 22 to 80 years were scanned with PET employing [F]FE-PE2I for measuring DAT densities. Region of interest (ROI)-based analysis was used, and ROIs were manually defined for the caudate, putamen, substantia nigra, thalamus, and cerebellar cortex. DAT binding was quantified using a simplified reference tissue model, and the cerebellum was used as reference region. Estimations of binding potential in the caudate, putamen, substantia nigra, and thalamus were individually regressed according to age using simple regression analysis. Estimates of DAT loss per decade were obtained using the values from the regression slopes. Results: There were 7.6, 7.7, and 3.4 % per-decade declines in DAT in the caudate, putamen, and substantia nigra, respectively. By contrast, there was no age-related decline of DAT in the thalamus. Conclusions: [F]FE-PE2I allowed reliable quantification of DAT, not only in the caudate and putamen but also in the substantia nigra. From the results, we demonstrated the age-related decline in the caudate and putamen as reported in previous studies, and additionally for those in the substantia nigra for the first time. [ABSTRACT FROM AUTHOR]

Objective: Application of the electrocardiographically (ECG) gated positron emission tomography (PET) technique with C-hydroxyephedrine (HED) would allow the simultaneous assessment of cardiac sympathetic and contractile functions. However, there are uncertainties regarding the diagnostic accuracy of left ventricular (LV) volume measurements using ECG-gated HED-PET. The purpose of this study was to clarify the minimal requirement of count statistics to measure LV volumes with ECG-gated HED-PET and to investigate the reliability of the measurements. Methods: Five healthy volunteers and 11 patients with heart failure underwent a 40-min list-mode PET scan after an injection of HED (197 ± 35 MBq). The list-mode data were histogrammed into multiple sets of acquisition periods at 0.5, 1.0, 2.0, 4.0, 6.0, 8.0, 12.0 Mcount/bin and reconstructed into corresponding gated images using an iterative algorithm. The LV end-diastolic volume (LVEDV), the LV end-systolic volume (LVESV), and the LV ejection fraction (LVEF) were calculated in each acquisition period. These values were compared with those obtained by cardiac magnetic resonance imaging (MRI). Possible effects of HED retention on the accuracy of the volume measurements were investigated. Results: Collecting less than 4.0 Mcount/bin resulted in noisy cardiac images. The lower counts resulted in underestimation in the volume measurements. Reasonably accurate volume measurements required equal to or greater than 6.0 Mcount/bin. This corresponded to 7.0 ± 1.9 min (range, 4.0-10.3 min) for the acquisition period. Volumetric results using the 6.0 Mcount/bin data highly correlated with cardiac MRI (LVEDV: r = 0.85, p < 0.0001; LVESV: r = 0.89, p < 0.0001; LVEF: r = 0.77, p < 0.01). The HED retention did not affect the volumetric results compared to the MRI volumetry. Conclusions: The volumetric accuracy with ECG-gated HED-PET was affected by the count statistics rather than the HED retention. LV volume measurements were feasible with 10-min acquisition period for most of the patients. This technique allows the simultaneous assessment of cardiac sympathetic and contractile functions without the need for an additional injection or scanning time, thus reducing overall costs for diagnostic imaging. [ABSTRACT FROM AUTHOR]

Objective: 3-[F]Fluoro-α-methyl- l-tyrosine ( l-[F]FAMT) is a useful amino acid tracer for positron emission tomography (PET) imaging of malignant tumors. Because d-amino acids are not well distributed in non-target organs and are rapidly excreted in urine, the d-isomer of [F]FAMT could allow clear PET imaging of tumors early after administration. In this study, we prepared 3-[F]fluoro-α-methyl- d-tyrosine ( d-[F]FAMT) and evaluated its usefulness. Methods: d-[F]FAMT was synthesized according to the method for preparation of l-[F]FAMT. The in vitro and in vivo stability of [F]FAMT were evaluated by high-performance liquid chromatography. Cellular uptake of [F]FAMT was evaluated using LS180 colon adenocarcinoma cells. Biodistribution studies were performed in LS180 tumor-bearing mice, and the tumors were imaged using a small-animal PET scanner. Results: The radiolabeling yield of d-[F]FAMT was approximately 10 %, similar to that of l-[F]FAMT. Over 95 % of d-[F]FAMT remained intact in mice until 60 min after administration. d-[F]FAMT was gradually taken up by the LS180 cells. Tumor uptake of d-[F]FAMT was competitively inhibited by pretreatment with α-methyl- l-tyrosine, a selective substrate for the system l-amino acid transporter 1 (LAT1), suggesting the involvement of LAT1 in tumor uptake of d-[F]FAMT. In biodistribution studies, d-[F]FAMT showed rapid clearance from the blood, marked accumulation and retention in the tumor, and lower accumulation in non-target organs, especially kidney and pancreas, compared to l-[F]FAMT. The amount of d-[F]FAMT in the tumor was also reduced, and tumor-to-blood ratio and tumor-to-muscle ratio of d-[F]FAMT were similar to those of l-[F]FAMT at every time point. PET imaging with d-[F]FAMT did not provide a clear image of the tumor early after administration. However, d-[F]FAMT provided higher tumor-to-background contrast than l-[F]FAMT. Conclusions: d-[F]FAMT showed rapid blood clearance, low accumulation in non-target organs, and tumor-selective imaging compared with l-[F]FAMT. Thus, d-[F]FAMT could potentially serve as a novel PET tracer for imaging malignant tumors. [ABSTRACT FROM AUTHOR]

Objective: 6-[F]Fluoro- l-DOPA (FDOPA) is a radiopharmaceutical valuable for assessing the presynaptic dopaminergic function when used with positron emission tomography (PET). More specifically, the striatal-to-occipital ratio (SOR) of FDOPA uptake images has been extensively used as a quantitative parameter in these PET studies. Our aim was to develop an easy, automated method capable of performing objective analysis of SOR in FDOPA PET images of Parkinson's disease (PD) patients. Methods: Brain images from FDOPA PET studies of 21 patients with PD and 6 healthy subjects were included in our automated striatal analyses. Images of each individual were spatially normalized into an FDOPA template. Subsequently, the image slice with the highest level of basal ganglia activity was chosen among the series of normalized images. Also, the immediate preceding and following slices of the chosen image were then selected. Finally, the summation of these three images was used to quantify and calculate the SOR values. The results obtained by automated analysis were compared with manual analysis by a trained and experienced image processing technologist. Results: The SOR values obtained from the automated analysis had a good agreement and high correlation with manual analysis. The differences in caudate, putamen, and striatum were −0.023, −0.029, and −0.025, respectively; correlation coefficients 0.961, 0.957, and 0.972, respectively. Conclusions: We have successfully developed a method for automated striatal uptake analysis of FDOPA PET images. There was no significant difference between the SOR values obtained from this method and using manual analysis. Yet it is an unbiased time-saving and cost-effective program and easy to implement on a personal computer. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the usefulness of [F]fluoromisonidazole ([F]FMISO)-positron emission tomography (PET) prior to the treatment of head and neck squamous cell carcinoma. Methods: Seventeen patients with untreated HNSCC underwent pretreatment [F]FMISO PET. Six of them underwent definitive surgery and the remaining 11 definitive (chemo-)radiotherapy. We evaluated 30 lesions from the 17 patients. SUVmax and tumor-to-muscle ratios (TMR) were measured as hypoxia indicators. Tumors equal to or above the median value were defined as tumor with high uptake of [F]FMISO and those below as tumor with low uptake of [F]FMISO in both indicators. Local control rates with radiotherapy, event-free survival and disease-specific survival (DSS) rates with radiotherapy or operation were compared. Result: [F]FMISO-PET imaging of 30 lesions resulted in a SUVmax median value of 2.3 and a TMR median value of 1.3. Local control rates with radiotherapy (20-month median follow-up duration) were significantly lower in the tumor group with high uptake of [F]FMISO compared to the tumor group with low uptake of [F]FMISO using either SUVmax or TMR as the hypoxic indicator ( P = 0.02 and 0.04, respectively). DSS rate with radiotherapy or operation (21-month median follow-up duration) was significantly lower in the patient group with high uptake of [F]FMISO compared to the patient group with low uptake of [F]FMISO defined by SUVmax ( P = 0.04), but was not by TMR ( P = 0.57). Conclusions: Radiotherapy outcome and survival prognosis (radiotherapy or operation) in HNSCC may be predicted by carrying out [F]FMISO PET before treatment. [ABSTRACT FROM AUTHOR]

Objective: [C]Flumazenil ([C]FMZ) positron emission tomography (PET) can be used as a measure of neuronal loss. The purpose of this study was to validate reference tissue kinetic modelling of [C]FMZ PET within a group of patients with head injury. Methods: Following earlier studies, the pons was used as the reference region. PET scans were performed on 16 controls and 11 patients at least 6 months following injury, each of whom also had arterial blood sampling to provide whole blood and metabolite-corrected plasma input functions. Regional non-displaceable binding potentials (BP) were calculated from five reference tissue models and compared to BP from arterial input models. For the patients, the regions included a peri-lesional region of interest (ROI). Results: Total distribution volume of the pons was not significantly different between control and patient groups ( P = 0.24). BP from all the reference tissue approaches correlated well with BP from the plasma input models for both controls ( r = 0.98-1.00; P < 0.001) and patients ( r = 0.99-1.00; P < 0.001). For the peri-lesional regions ( n = 11 ROI values), the correlation was also high ( r = 0.91). Conclusions: These results indicate that reference tissue modelling with the pons as the reference region is valid for [C]FMZ PET in head-injured patients at 6 months following injury within both normal appearing and peri-lesional brain regions. [ABSTRACT FROM AUTHOR]

Objective: Telmisartan, a nonpeptide angiotensin II AT1 receptor antagonist, is an antihypertensive drug. Positron emission tomography (PET) imaging with [C]Telmisartan is expected to provide information about the whole body pharmacokinetics of telmisartan as well as the transport function of hepatic OATP1B3. We developed a first automatic preparation system of [C]Telmisartan to applicable clinical research using a new C and F multipurpose synthesizer. Methods: Two milligrams of precursor ( 1) in 5 μl of 1 M KOH in 0.5 ml of dimethyl sulfoxide was reacted with [C]CHI for 5 min at 120°C. The resultant solution was hydrolyzed with 1 M NaOH at 100°C for 3 min. The neutralization was carried out with acetic acid, followed by purification with high-performance liquid chromatography. The desired radioactive fraction was collected and solvent was replaced by 10 ml saline containing 0.3 ml of EtOH and 0.5 ml of PEG400, and then passed through a sterile 0.22 μm filter (Millex-GV, Millipore) to a pyrogen-free vial as the final product. Results: The yield of [C]Telmisartan for clinical research use was 16.8 ± 2.9% EOB as decay corrected ( n = 8, mean ± SD) in 32-36 min. The radiochemical purity of [C]Telmisartan was >97%, and specific activity was higher than 86.3 MBq/nmol. Conclusions: We succeeded in the first synthesis of [C]Telmisartan for clinical research use by appropriate quality tests. [ABSTRACT FROM AUTHOR]

Positron emission tomography (PET) scanners require periodic monitoring in order to maintain scanner performance. The aim of the present study was to examine the deterioration of PET scanner performance caused by aging. We retrospectively examined PET scanner performance alterations in terms of sensitivity, spatial resolution, false coincidences due to scatter and random coincidences based on 13 years of follow-up data, including data when the PET scanner underwent an overhaul at the 10th year after installation. Sensitivity and scatter fraction were calculated by using cross calibration factor (CCF) measurement data, which are collected routinely. Efficacy of the examining the sensitivity and scatter was confirmed by NEMA measurements. Trans-axial resolution was measured as full width at half-maximum (FWHM) and full width at tenth-maximum (FWTM) at 0–20 cm offset from the field of view (FOV) center at the time of installation, 8 years after installation, and immediately after the overhaul. Random coincidence rate fraction was measured in a wide range of count rates before and after the overhaul. The results indicated that the total reduction of sensitivity during the first 10 years was 41% of the initial value in terms of NEMA measurement, and that the annual reduction of sensitivity progressed at a rate of 4.7% per year in terms of CCF measurement data. The changes in sensitivity can be calculated using CCF measurement data. Regarding the spatial resolution, mean FWHM and FWTM values were increased by 1.7 and 3.6%, respectively, in 8 years after installation. The relative scatter fraction was significantly increased compared with that before the overhaul. The random fraction decreased by 10–15% after the overhaul within a certain range of random count rates (1–120 kcps). In the case of our scanner, the parameter that displayed the largest change was the sensitivity, and this change was thought to be caused by the reduction of photomultiplier tube (PMT) gain, although the changes in PMT gain can cause various types of performance deterioration, as investigated in this study. We observed that the sensitivity of our PET scanner generally deteriorated due to aging. Sensitivity monitoring using CCF measurements can be an easy and useful method for monitoring and maintaining the performance of PET scanners against aging. Since the data were obtained from a single scanner, the authors would encourage the initiation of a follow-up study involving various scanners. [ABSTRACT FROM AUTHOR]

To assess the utility of 11C-choline PET/CT in the restaging of prostate cancer (PC) patients who showed a single finding on bone scintigraphy (BS) that was classified as equivocal or suspected for metastatic lesion. A total of 25 PC patients with biochemical failure (mean PSA value 11.1 ng/mL; median value 6.3 ng/mL; range 0.2–37.7 ng/mL) after primary treatment were included in this retrospective study. All of them showed a single lesion on BS reported as suspected for metastatic lesion or as equivocal finding. Patients underwent 11C-choline PET/CT within 1–4 months from BS. Validation was established by follow-up for at least 6 months. On the basis of biopsy confirmation and/or 6-month follow-up, 22 of 25 patients were classified as positive for the presence of metastatic bone lesions: 13 with a single lesion and 9 with multiple lesions. 11C-choline PET/CT was positive in 19/25 patients and, on a lesion basis, it showed 50 positive findings. BS results were confirmed in 8/25 (32%) patients. 11C-choline PET/CT detected multiple sites of relapse in 11/25 (44%) patients: in 2/11, a single bone lesion associated with other extraosseous sites of relapse; in 6/11, multiple bone lesions; in 3/11, multiple bone lesions and other extraosseous localizations. Finally, 6/25 patients were negative on 11C-choline PET/CT. In 3/6 patients, an osteoblastic lesion was seen on CT attenuation correction images (PET false negative; BS true positive), while in 3/6 patients only findings suggestive of the presence of degenerative disease were found (PET true negative; BS false positive). On a patient basis, 11C-choline PET/CT showed a diagnostic sensitivity of 86% (19/22) and a specificity of 100% (19/19). In our study, 11C-choline PET/CT detected unknown lesions in 11/25 patients. Patients with a single equivocal finding on BS could have important additional information from 11C-choline PET/CT study, especially in the detection of additional metastases, to choose an appropriate treatment. [ABSTRACT FROM AUTHOR]

Elevated levels of serum carcinoembryonic antigen (CEA) in patients with colorectal cancer (CRC) during follow-up suggest recurrence, which can be visualized by 18F-FDG PET/CT. Since the magnitude of CEA elevation reflects cancer volume, the ability of PET/CT to detect recurrence in patients with only mildly elevated CEA might be limited. However, the accuracy of PET/CT in detecting recurrence associated with elevated CEA has not been fully assessed. We retrospectively evaluated the diagnostic performance of 18F-FDG PET/CT postoperatively relative to CEA levels among patients with CRC. We visually assessed 75 PET/CT evaluations of 57 postoperative patients with CEA >5.0 ng/ml. Tumor volumes were also determined using image analysis software. The final diagnosis was confirmed based on histopathological findings, or at least on 6 months of clinical follow-up. Two lung cancers were excluded and we finally analyzed data from 73 of the 75 PET/CT evaluations. Recurrences were diagnosed in 54 (prevalence 74%). The sensitivity and specificity of PET/CT to detect recurrence was 50/54 (93%) and 14/19 (74%), respectively. The positive and negative predictive values were 91 and 78%, respectively, and the positive and negative likelihood ratios were 3.52 and 0.10, respectively. Values for the sensitivity of PET/CT were 88 and 95%, and those for specificity were 78 and 70%, at serum CEA concentrations of 5–10 and >10 ng/ml, respectively. Serum CEA ( r = 0.500, p < 0.001) significantly correlated with cancer volumes. The present findings showed that 18F-FDG PET/CT could accurately detect recurrent CRC irrespective of the elevated CEA concentration. [ABSTRACT FROM AUTHOR]

XR9576 (tariquidar) is an anthranilic acid derivative and potent P-glycoprotein (P-gp) inhibitor. XR9576 has undergone phase I and II studies as combined chemotherapy against cancer. XR9576 has been developed as a useful therapeutic agent but not as a PET probe. We therefore developed [11C]XR9576 as a PET probe and assessed whether PET studies using [11C]XR9576 are a promising approach to assess P-gp function primarily. We synthesized [11C]XR9576 by methylation of 7- O-desmethyl XR9576 with [11C]methyl iodide. In in vivo tissue distribution, the effects of co-injection with XR9576 on the uptake of [11C]XR9576 in mice were investigated. PET studies using [11C]XR9576 were performed in P-gp and/or Bcrp knockout mice as well as in wild-type mice. Metabolites of [11C]XR9576 were measured in the brain and plasma of mice. [11C]XR9576 was successfully synthesized with suitable radioactivity for injection as well as appropriate radiochemical purity and stability. In in vivo tissue distribution, the brain uptake of [11C]XR9576 significantly increased about tenfold of control on co-injection with >10 mg/kg of XR9576. In PET studies, the AUCbrain [0–60 min] in P-gp and P-gp/Bcrp knockout mice was 2- and 11-fold higher than that in wild-type mice. [11C]XR9576 showed a high metabolic stability (>90% unchanged form) in the brain and plasma of mice 30 min after injection. These results suggest that a tracer amount of [11C]XR9576 behave as the P-gp and Bcrp substrate, and the increased brain uptake or AUCbrain of [11C]XR9576 correlates with P-gp and Bcrp functions. PET studies using [11C]XR9576 may be a promising approach for evaluating deficiency of the function of drug efflux transporters targeting intracranial diseases and tumors. [ABSTRACT FROM AUTHOR]

Dopamine transporter (DAT) is a reuptake carrier of dopamine at presynapse that regulates dopaminergic neural transmission. [11C]PE2I is a cocaine analog developed as a potent positron emission tomography (PET) ligand for DAT with high selectivity. The aim of this study was to evaluate the applicability of quantification methods using reference tissue models for [11C]PE2I. Dynamic PET scans were performed in 6 young healthy male volunteers after an intravenous bolus injection of [11C]PE2I. Metabolite-corrected arterial plasma-input functions were obtained. Compartment model analysis and plasma-input Logan analysis were performed to determine the kinetic parameters and distribution volume ( VT). The distribution volume ratio ( DVR) was calculated as the ratio of VT in the cerebral region to that in the cerebellum. DVRs were also determined by the original multilinear reference tissue model method (MRTMo) and the simplified reference tissue model method (SRTM), comparing the results with those obtained from graphical analysis using arterial input function. To estimate errors in DVR calculated using the reference tissue model, a simulation study that focused on cerebellar kinetics and scan duration was performed. The highest [11C]PE2I binding was observed in the striatum, followed by the midbrain and thalamus. The 2-tissue model was preferable to the 1-tissue model for describing the [11C]PE2I kinetics in the cerebellum. Both the measured and 90-min simulated data showed that reference tissue models caused an underestimation of DVR in the striatum. The simulation showed that 90-min scan duration was insufficient when cerebellar kinetics was described as a 1-tissue model. Nevertheless, DVR values determined by MRTMo and SRTM were in good agreement with those by the graphical approach in other lower binding regions. Due to the [11C]PE2I kinetics in the cerebellum and limited scan duration for 11C, MRTMo and SRTM underestimated the striatal DVR. Despite this limitation, the present study demonstrated the applicability of reference tissue models. Since DAT in the midbrain and thalamus is of interest in the pathophysiology of neuropsychiatric disease, this noninvasive quantitative analysis will be useful for clinical investigations. [ABSTRACT FROM AUTHOR]

The guidelines for microdosing in clinical trials were published in Japan in 2008 following the guidelines of the European Medicines Agency and the Food and Drug Administration. They recommend utilizing accelerator mass spectrometry (AMS) and positron emission tomography as candidates for monitoring drug metabolites in preclinical studies. We correlate the two methods by measuring appropriately labeled tissue samples from various mouse organs using both AMS and gamma counter. First, we measured the 14C background levels in mouse organs using the AMS system. We then clarified the relationship between AMS and gamma counter by simultaneously administering 14C-2-fluoro-2-deoxyglucose (14C-FDG) and 18F-2-fluoro-2-deoxyglucose (18F-FDG). Tissue distribution was examined after 30 min, 1 h, 2 h and 4 h using the AMS system for 14C-FDG and gamma counter for 18F-FDG. Background 14C levels were subtracted from the data obtained with radiotracer administration. The background 14C concentration differed with tissue type measured. Background 14C concentration in mouse liver was higher than in other organs, and was approximately 1.5-fold that in blood. The correlation coefficient ( r) of the measurements between AMS (14C-FDG) and gamma counter (18F-FDG) was high in both normal (0.99 in blood, 0.91 in brain, 0.61 in liver and 0.78 in kidney) and tumor-bearing mice (0.95 in blood and 0.99 in tumor). The clearance profile of 18F-FDG was nearly identical to that of 14C-FDG measured with AMS. Accelerator mass spectrometry analysis has an excellent correlation with biodistribution measurements using gamma counter. Our results suggest that the combination of AMS and PET can act as a complementary approach to accelerate drug development. [ABSTRACT FROM AUTHOR]

Our aim was to evaluate changes in glucose metabolism of skeletal muscles and viscera induced by different workloads using 18F-2-fluoro-2-deoxyglucose ([18F]FDG) and three-dimensional positron emission tomography (3-D PET). Five male volunteers performed ergometer bicycle exercise for 40 min at 40% and 70% of the maximal O2 consumption ( $$ \dot V $$ O2max). [18F]FDG was injected 10 min later following the exercise task. Wholebody 3-D PET was performed. Five other male volunteers were studied as a control to compare with the exercise group. The PET image data were analyzed using manually defined regions of interest to quantify the regional metabolic rate of glucose (rMRGlc). Group comparisons were made using analysis of variance, and significant differences ( P < 0.05) were determined using Scheffe’s test (post hoc analysis). Quantitative analysis demonstrated that rMRGlc increased ( P < 0.05) in the skeletal muscles of the thigh at mild or moderate workloads when compared with the resting controls. For visceral organs such as the liver and brain, metabolic reduction was significant ( P < 0.05) at mild and/or moderate exercise workload. The present study demonstrated linear increases or decreases in glucose uptake by skeletal muscles and viscera with mild and moderate exercise workloads, suggesting the presence of homeostatic energy metabolism. This result supports the finding that [18F]FDG-PET can be used as an index of organ energy metabolism for moderate exercise workloads (70% $$ \dot V $$ O2max). The results of this investigation may contribute to sports medicine and rehabilitation science. [ABSTRACT FROM AUTHOR]

To determine an appropriate threshold value for delineation of the target in positron emission tomography (PET) and to investigate whether PET can delineate an internal target volume (ITV), a series of phantom studies were performed. An ellipse phantom (background) was filled with 1028 Bq/ml of [18F] fluoro-2-deoxyglucose (18FDG), and six spheres of 10 mm, 13 mm, 17 mm, 22 mm, 28 mm, and 37 mm in diameter inside it were filled with 18FDG activity to achieve source-to-background (S/B) ratios of 10, 15, and 20. In static phantom experiments, an appropriate threshold value was determined so that the size of PET delineation fits to an actual sphere. In moving phantom experiments with total translations of 10 mm, 20 mm, and 30 mm and a period of oscillation of 4 s, the maximum size of PET delineation with the appropriate threshold value was measured in both the axial and sagittal planes. In the static phantom experiments, the measured maximum 18FDG activities of spheres of less than 22 mm were lower than 80% of the injected 18FDG activity, and those for the larger spheres ranged from 90% to 110%. Appropriate threshold values determined for the spheres of 22 mm or more ranged from 30% to 40% of the maximum 18FDG activity, independent of the S/B ratio. Therefore, we adopted an appropriate threshold value as 35% of the measured maximum 18FDG activity. In moving phantom experiments, the maximum 18FDG activity of spheres decreased significantly, dependent on the movement distance. Although the sizes of PET delineation with 35% threshold value tended to be slightly smaller (<3 mm) than the actual spheres in the axial plane, the longest sizes in the sagittal plane were larger than the actual spheres. When a threshold value of 35% of the measured maximum 18FDG activity was adopted, the sizes of PET delineation were almost the same for static and moving phantom spheres of 22 mm or more in the axial plane. In addition, PET images have the potential to provide an individualized ITV. [ABSTRACT FROM AUTHOR]

Recurrent respiratory papillomatosis (RRP) is an indolent and primary disease of the larynx and the trachea and rarely extends to smaller airways. F-18 fluoro-2-deoxy- d-glucose positron emission tomography and computed tomography (FDG-PET/CT) evaluation in this condition has not been reported earlier. We report FDG-PET/CT findings in a case of RRP that included a large papillomatous lung mass resembling cancer. [ABSTRACT FROM AUTHOR]

We report on a case with an inflammatory pseudotumor of the spleen, which showed a moderate accumulation of F-18 fluorodeoxyglucose (FDG) in the tumor. F-18 FDG accumulated mainly in the peripheral portion of this tumor that showed abundant hypercellular inflammatory cells histopathologically. Splenic inflammatory pseudotumors should be recognized as F-18 FDG-avid benign tumors of the spleen. [ABSTRACT FROM AUTHOR]

To assess whether FDG PET could localize the recurrent or metastatic lesions in papillary thyroid cancer patients with negative radioiodine scan. Whole body PET was performed after injecting 370-555 MBq of18F-FDG in 108 patients, who were suspected of having recurrence or metastasis and whose131I whole body scans were negative. Recurrence or metastasis occurred in 63 patients by pathology or clinical assessment, whereas 45 patients remained in remission. FDG PET revealed recurrence or metastases in 59 patients (sensitivity 93.7%), whereas thyroglobulin (Tg) levels were elevated in 41 (sensitivity 65.1%). In 35 of 45 patients in remission, FDG PET was negative (specificity 77.8%). When patients positive for antithyroglobulin antibody were excluded, the sensitivity and specificity of serum Tg became 84.8% and 46.9%, respectively. Compared to Tg measurement, FDG PET detected more metastatic lesions in cervical lymph nodes. Of 40 patients with a negative radioiodine scan showing diffuse hepatic uptake, metastases occurred in 23 patients and remission in 17. FDG PET showed 100% sensitivity and 76.5% specificity in the detection of recurrence in these 40 patients. FDG PET is useful for localizing recurrent or metastatic lesions in131I scan-negative thyroid cancer patients. In particular, it is superior to serum Tg measurement for identifying metastases to cervical lymph nodes. We recommend its use in cases of negative radioiodine scan with diffuse hepatic uptake. [ABSTRACT FROM AUTHOR]

We report two cases of young women with a solid pseudo-papillary tumor of the pancreas which having cystic and hemorrhagic components with marked calcification on computed tomography and magnetic resonance imaging. F-18 fluorodeoxyglucose positron emission tomography revealed abnormally increased accumulation of F- 18 fluorodeoxyglucose in the pancreas tail tumors, especially in the non-calcified solid portion of the tumors. These patients underwent elective resection of the masses and distal pancreatectomy and were diagnosed with solid pseudo-papillary tumors by histopathological analysis. There was no evidence of distant metastasis on follow-up after surgery and they showed no histopathological findings suggesting malignancy. These cases suggest that solid pseudo-papillary tumor may show high uptake of F-18 fluorodeoxyglucose. [ABSTRACT FROM AUTHOR]

We recently experienced a case with asymmetrical cortical abnormality on MRI with focal status epilepticus following severe hypoglycemia. The cerebral blood flow and metabolisms for oxygen and glucose were determined using positron emission tomography (PET) during focal status epilepticus following severe hypoglycemia and at the follow-up period. Prolonged seizure activity produced profound glucose hypermetabolism and mild hyperemia in the region of the presumed cortical focus of epilepsy and in structures anatomically remote from the focus, corresponding to the areas of abnormal signal intensity on the MRI. The patient remained comatose and exhibited a diffuse hypoperfusion/hypometabolism and symmetrical brain atrophy on the follow-up PET and MRI, respectively. Cytotoxic brain edema due to profound glucose metabolism without compensatory increase of the blood flow during status epilepticus may account for the brain abnormality observed on the early MRI. Simultaneous examination of the cerebral blood flow and metabolism using PET can provide useful information about the pathology in patients with status epilepticus. [ABSTRACT FROM AUTHOR]

Background: Incorporating mediastinoscopy (MS) into the PET-based strategy for non-small cell lung carcinoma (NSCLC) patients might be cost-effective because MS can allow unnecessary thoracotomies to be avoided. The objective of our study was to assess the cost-effectiveness of incorporating MS into a PET strategy for NSCLC patients.Methods: To determine life expectancy (LE), quality adjusted life years (QALY), and the incremental cost-effectiveness ratio (ICER), a decision-tree sensitivity analysis was designed for histopathologically confirmed NSCLC patients with M0 disease, based on the three competing strategies of chest CT only vs. PET + CT vs. PET + CT + MS. A simulation of 1000 NSCLC patients was created using baselines of other relevant variables in regard to sensitivity, specificity, mortality, LE, utilities and cost from published data. One-way sensitivity analyses were performed to determine the influences of mediastinal metastasis prevalence on LE, QALY and ICER.Results: The LE and QALY per patient in the CT only strategy, PET + CT strategy and PET + CT + MS strategy were 4.79 and 4.35, 5.33 and 4.93 and 5.68 and 5.33 years, respectively, with a 20% prevalence of mediastinal metastasis. The ICERs were 906.6 yen x 10(3) (7555 US dollars)/QALY/patient at a 20% mediastinal metastasis prevalence, and 2194 yen x 10(3) (18,282 US dollars)/QALY/patient at a 50% prevalence, but exceeded 5280 yen x 10(3) (44,000 US dollars)/QALY/ patient at 80%.Conclusions: Our study quantitatively showed the CT + PET + MS strategy in place of the PET + CT strategy in managing NSCLC patients to be cost-effective. MS should be incorporated into the PET + CT strategy for NSCLC patients except in those highly suspected of having mediastinal disease on chest CT or PET. [ABSTRACT FROM AUTHOR]

Objectives: To investigate regional differences in cerebral glucose metabolism and blood flow of dementia with Lewy bodies (DLB), we studied 7 subjects with DLB and 20 normal controls using F-18 fluorodeoxyglucose (FDG) and positron emission tomography (PET) and then examined the same 7 subjects and 20 other normal controls with I-123 iodoamphetamine (IMP) and single photon emission computed tomography (SPECT).Methods: The anatomically standardized images were produced with NEUROSTAT and the regional relative metabolic and perfusional values were calculated.Results: The mean reduction ratios of FDG uptake in the DLB group relative to the mean normal controls in the parietal lobe and occipital lobe were 0.72 and 0.83, respectively, while the corresponding mean reduction ratios of IMP uptake were 0.81 and 0.88, respectively. In the DLB group, parietal FDG uptake was significantly lower than parietal IMP uptake (p < 0.05), occipital FDG uptake was significantly lower than occipital IMP uptake (p < 0.05), and parietal IMP uptake was significantly lower than occipital IMP uptake (p < 0.01), but there was no difference between parietal and occipital FDG uptake.Conclusions: Our findings suggest that parietal metabolism and perfusion are severely affected in DLB patients, though the occipital metabolic and perfusional reduction is thought to be a feature of DLB. FDG-PET is thought to be superior to IMP-SPECT in detecting functional changes in the DLB brain. [ABSTRACT FROM AUTHOR]

To validate functional analysis of gated SPECT in detecting myocardial viability, seventeen patients (male 15, female 2, mean age 58) with angiographically proven chronic ischemic heart disease (RCA 6, LAD 10, LCX 1) and eight normal volunteers (all male) were studied. All patients underwent18F FDG PET and99mTc tetrofosmin (TF) gated SPECT within a week. After being displayed in a polar map, myocardial perfusion was regionally determined by the mean count in 9 segments at end diastole (ED) and end systole (ES) in gated SPECT. Systolic function was determined by the count increase ratio from ED to ES (WTI: ES — ED/ED). Glucose metabolism was assessed by18F FDG PET in the segments correspondent to those defined for SPECT. TF %uptake of < 60% was defined as hypoperfusion, and FDG %uptake of < 50% was defined as reduced glucose metabolism. Results: The myocardial segments were classified into 3 categories: “normal” perfusion (n = 85), “mismatch” (reduced perfusion with reserved FDG uptake, n = 25) and “matched” reduced perfusion and metabolic reduction (n = 26). Mean WTI in “mismatch” segment was 0.38 ± 0.21, and was significantly greater than that in “matched reduced” segments, 0.15 ± 0.20 (p < 0.001). It was also greater than that in “normal” segments, 0.27 ± 0.16. Regression analysis showed that association between WTI and FDG %uptake was significant (r = 0.57, p < 0.0005) for the ischemic segments (“mismatch” + “matched”, n = 51), but the association was weak for the entire segments although it was statistically significant (r = 0.26, p = 0.02, n = 136). Conclusion: For the segments determined as infarct by perfusion image, systolic functional analysis by gated SPECT is helpful in differentiation of a viable myocardial region or artifact from a scar. Nevertheless, further clinical and technical assessment is required for ECG gating to eliminate overestimation of viability and to warrant clinical use. [ABSTRACT FROM AUTHOR]

3D positron emission tomography (PET) refers to an acquisition geometry and recon-struction procedure that allows all coincidence events within the solid angle of the tomograph to be recorded and subsequently reconstructed. The reconstruction algorithm must consider the angle of each coincidence event relative to the central axis of the scanner. The aim of the technique is to maximise the sensitivity of the system by utilising all events that it is possible to record from the object. Conventional cylindrical 2D PET systems typically detect ∼0.4%-0.5% of decaying nuclei within the field of view; with a 3D system this can increase to over 3%. Reconstruction in 3D using filtered-backprojection techniques has been developed and provides results that show little degradation of physical characteristics compared with 2D systems, apart from an increased scatter event rate. 3D techniques may be used to (i) improve data quality using currently acceptable doses of radioactivity and scanning times; (ii) extend the scanning period for short-lived tracers, especiallyC-labeled ligands; or, conversely (iii) decrease injected doses of radiotracer or reduce scanning times to achieve similar results as those using current methods in 2D. [ABSTRACT FROM AUTHOR]

We report a case of maxillary sinus (MS) aspergillosis studied by positron emission tomography (PET) with F-18 fluorodeoxyglucose (FDG) and by 67Ga-citrate (Ga) single photon emission computed tomography (SPECT). The FDG uptake existed in the lesion and along the inflammatory edematous mucous membrane of the MS. Ga uptake occurred not only in the lesion and in the mucous membrane but also in the MS. Relative quantification, the standardized uptake value (SUV) of the lesion showed relatively high FDG uptake (3.7). But in other reports, many malignant head and neck tumors had a SUV below 3.7. It was thought to be difficult to differentiate between aspergillosis and malignant head and neck tumors by FDG-PET. [ABSTRACT FROM AUTHOR]

A data base and management system connected to an image analysis system has been developed and utilized for clinical positron emission tomography (PET). This data base system, 1) is based on "GBASE", a general purpose data base, which runs on a UNIX work station, 2) works on a network file system and is connected to PET cameras and other data acquisition devices as well as to an image analysis system "Dr.View", 3) centrally manages the data stored in a data storage unit, 4) is easily modifiable and expandable, and 5) has a human friendly interface which requires minimum operation for registration, retrieval and management. We have been using this system to handle clinical PET data for seven years and have optimized the data base schema. As a result, this system has become a truly practical tool for the daily operation and is well-received by technologists, nuclear physicians and attending physicians. [ABSTRACT FROM AUTHOR]

In the cancer screening with FDG PET for 1,872 medical health club members, high FDG accumulation in the parotid gland was found in four males (age, 57-70 years). Warthin's tumor was confirmed by surgical pathology. The exact mechanism of high FDG accumulation in Warthin's tumor is not yet known. This tumor may be found incidentally during FDG PET studies. When high FDG accumulation is found in the parotid gland, integrated consideration of the results of the physical examination, medical history and 99mTc-pertechnetate scintigraphy makes it possible to differentiate Warthin's tumor from other lesions. [ABSTRACT FROM AUTHOR]

To provide a simple means of quantifying myocardial glucose metabolism, we tried to estimate the K complex (KC) from the myocardium to background ratio (MB ratio), which was obtained with a single static FDG scan and single venous sampling. In 48 fasting subjects and 74 subjects under oral glucose loading or insulin clamp, the reference KC was obtained from Patlak analysis by using an input function. We compared the reference KC with the MB ratio at 35 min 45 sec, 45 min 45 sec, and 55 min 45 sec, and with the FDG uptake index (FUI) reported by Tamaki. The correlation between KC and each index was very close during fasting (r = 0.97, 0.98, 0.98 and 0.97, respectively n = 48), and clinically acceptable during oral glucose loading and insulin clamp (r = 0.92, 0.91, 0.90 and 0.93, respectively n = 74). The average differences between the reference KC and KC estimated from the simple method were 13%, 10%, 8%, and 13%, respectively, during fasting, and 15%, 14%, 14%, and 16%, respectively, during oral glucose loading and insulin clamp. Both the MB ratio and FDG uptake index can be used for the simple estimation of myocardial glucose metabolism not only during fasting but also during oral glucose loading and insulin clamp, although the MB ratios at 45 min and at 55 min were slightly better than MB that at 35 min and the FDG uptake index during fasting. [ABSTRACT FROM AUTHOR]

Unlabelled: The authors' goal was to show the importance of starting scanning at a uniform time after F-18 fluorodeoxyglucose injection in positron emission tomography (PET) brain study.Method: Fifteen healthy normal subjects underwent FDG-PET to obtain glucose metabolic images starting 60 min and 70 min after FDG injection, respectively. The two sets of images were compared in a voxel-by-voxel analysis.Results: In the bilateral posterior cingulate gyrus, parietal and frontal association cortices, the FDG uptakes were larger on the 70 min scan images than on the 60 min scan images; the 60 min scans resembled Alzheimer's metabolic reduction area. Similarly the FDG uptakes were larger in the pons and vermis on the 60 min scan image than on the 70 min scan image.Conclusions: Regional FDG uptake is different depending on the time scanning starts after FDG injection, even with a 10 minute difference in start time and different scanning time may lead to misdiagnosis. It is important to standardize the start time of FDG PET after FDG injection in brain PET. [ABSTRACT FROM AUTHOR]

Objective: The authors' goal was to determine whether FDG uptakes in various regions of the brain are different for early and late scanning time in positron emission tomography (PET).Method: F-18 fluorodeoxyglucose (FDG) PET was performed on 15 healthy normal subjects to obtain early and late acquisition glucose metabolic images (30 and 60 min after FDG injection), respectively. The two sets of images were compared in a voxel-by-voxel analysis.Results: In the bilateral posterior cingulate gyrus, parietal and frontal association cortices, and subcallosal cortices, the FDG uptakes were larger on the late scan image than on the early scan image, and the FDG uptakes were larger in the cerebellar hemisphere, vermis and frontal basis on the early scan image than on the late scan image.Conclusions: These results suggest that there are different regional FDG uptakes depending on the scanning time after FDG injection and we must be careful in replacing conventional FDG PET scanning with early scanning in FDG PET study. [ABSTRACT FROM AUTHOR]

We report two cases of chronic tonsillitis studied by FDG-PET. Symmetrical high FDG uptake by the tonsils was observed in both cases. On histopathologic examination of the resected tonsils, follicular hyperplasia was observed with proliferation of lymphocytes in the germinal centers. Increased glucose metabolism in active inflammation involving lymphocyte proliferation was thought to be a cause of high FDG uptake by tonsils in chronic tonsillitis. [ABSTRACT FROM AUTHOR]

We report a functional neuroimaging study of a patient clinically diagnosed with Korsakoff syndrome. Positron emission tomography (PET) with the15O inhalation method showed decreased regional cerebral blood flow (rCBF) and decreased regional cerebral metabolic ratio for oxygen (rCMRO2) in the bilateral fronto-temporal areas and in the left thalamus. These results suggest that dysfunction of the frontal-thalamic neural network plays a role in the disturbance of Korsakoff syndrome. [ABSTRACT FROM AUTHOR]