Adenosine A2A Receptor Occupancy by Caffeine After Coffee Intake in Parkinson's Disease.

BACKGROUND: Coffee intake can decrease the risk for Parkinson's disease (PD). Its beneficial effects are allegedly mediated by caffeine through adenosine A2A receptor (A2A R) antagonist action. OBJECTIVE: We aimed to calculate occupancy rates of striatal A2A Rs by caffeine after coffee intake in PD. METHODS: Five patients with PD underwent 11 C-preladenant positron emission tomography scanning at baseline and after intake of coffee containing 129.5 mg (n = 3) or 259 mg (n = 2) of caffeine. Concurrently, serum caffeine levels were measured. RESULTS: The mean serum caffeine level (µg/mL) was 0.374 at baseline and increased to 4.48 and 8.92 by 129.5 and 259 mg of caffeine, respectively. The mean occupancy rates of striatal A2A Rs by 129.5 and 259 mg of caffeine were 54.2% and 65.1%, respectively. CONCLUSIONS: A sufficient A2A R occupancy can be obtained by drinking a cup of coffee, which is equivalent to approximately 100 mg of caffeine. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Determination of a reliable assessment for occupational eye lens dose in nuclear medicine.

The most recent statement published by the International Commission on Radiological Protection describes a reduction in the maximum allowable occupational eye lens dose from 150 to 20 mSv/year (averaged over 5-year periods). Exposing the eye lens to radiation is a concern for nuclear medicine staff who handle radionuclide tracers with various levels of photon energy. This study aimed to define the optimal dosimeter and means of measuring the amount of exposure to which the eye lens is exposed during a routine nuclear medicine practice. A RANDO human phantom attached to Glass Badge and Luminess Badge for body or neck, DOSIRIS and VISION for eyes, and nanoDot for body, neck, and eyes was exposed to 99m Tc, 123 I, and 18 F radionuclides. Sealed syringe sources of each radionuclide were positioned 30 cm from the abdomen of the phantom. Estimated exposure based on measurement conditions (i.e., air kerma rate constants, conversion coefficient, distance, activity, and exposure time) was compared measured dose equivalent of each dosimeter. Differences in body, neck, and eye lens dosimeters were statistically analyzed. The 10-mm dose equivalent significantly differed between the Glass Badge and Luminess Badge for the neck, but these were almost equivalent at the body. The 0.07-mm dose equivalent for the nanoDot dosimeters was greatly overestimated compared to the estimated exposure of 99m Tc and 123 I radionuclides. Measured dose equivalents of exposure significantly differed between the body and eye lens dosimeters with respect to 18 F. Although accurately measuring radiation exposure to the eye lenses of nuclear medicine staff is conventionally monitored using dosimeters worn on the chest or abdomen, eye lens dosimeters that provide a 3-mm dose equivalent near the eye would be a more reliable means of assessing radiation doses in the mixed radiation environment of nuclear medicine.

[Cross-validation of Quantitative Analytical Software Using 18F-florbetapir PET Imaging].

BACKGROUND: 18F-florbetapir is an amyloid ß (Aß) -targeted 18F-labeled positron emission tomography (PET) tracer for the clinical diagnosis of Alzheimer's disease. The standardized uptake value ratio (SUVR) serves as a tool with which to differentially diagnose. The present study aimed to cross-validate and compare SUVR derived from Amygo neuro and MIMneuro software. METHODS: We injected 40 individuals with 18F-florbetapir and then acquired PET images from 50 to 60 minutes later. All images were separately normalized to the standard 18F-florbetapir PET template using Amygo neuro and MIMneuro. Volumes of interest (VOIs) were automatically placed on six target regions each in Amygo neuro and MIMneuro. The composite SUVR (cSUVR) and regional SUVR (rSUVR) were calculated from mean values measured in VOI. A cSUVR of>1.10 was defined as representing Aß positivity. Correlation coefficients were calculated in the two types of software. RESULTS: A cSUVR>1.10 was determined by Amygo neuro and MIMneuro in 15 of the 40 individuals. The rSUVR in the posterior cingulate, parietal lobe, precuneus, and temporal lobe significantly differed between Amygo neuro and MIMneuro, whereas the cSUVR did not. The SUVR calculated by the two types of software closely correlated to each other (R=0.89-0.96, P<0.05). CONCLUSIONS: The cSUVR was not different between Amygo neuro and MIMneuro. We suggest that Amygo neuro is comparable to MIMneuro in quantitative analysis using SUVR for 18F-florbetapir imaging, thus facilitating the use of standardized quantitative approaches to amyloid PET imaging.

Neural substrate of a cognitive intervention program using Go game: a positron emission tomography study.

BACKGROUND: Influence of cognitive intervention programs on brain activity has not been enough explored. AIMS: The aims of the present study were to clarify changes in brain activity from a cognitive intervention program utilizing the board game "Go" and to examine the relationship between brain activity and the acquisition of Go skills. METHODS: Eighteen community-dwelling older adults were randomly assigned either to an intervention group (IG), in which members attended 12 Go lessons either in groups or individually using tablet computers, or a control group (CG), in which members attended health education lectures unrelated to Go. Fluorine-18 fluorodeoxyglucose (18F-FDG) positron emission tomography (PET), cognitive assessments, and Go tests were performed before and after the intervention. RESULTS: The results showed different patterns of regional FDG uptake in both groups: regional cerebral glucose metabolism was significantly increased in the left middle temporal gyrus (MTG) and bilateral putamen (p < 0.01; cluster level) in the IG, and in the left superior frontal gyrus in the CG, (p < 0.01; cluster level). Furthermore, Go test scores were significantly improved in the IG (p < 0.05), and a significant association was observed between changes in Go test scores and glucose metabolism in the left MTG (p < 0.05). CONCLUSIONS AND DISCUSSION: This study indicates that a cognitive intervention program using Go may enhance brain activity. Further studies with larger populations and longer observation periods are needed to clarify the neural mechanisms underlying our Go intervention program.

Dynamic Exercise Elicits Dissociated Changes Between Tissue Oxygenation and Cerebral Blood Flow in the Prefrontal Cortex: A Study Using NIRS and PET.

Neuronal activity causes changes in both cerebral metabolic rate of oxygen (CMRO2) and cerebral blood flow (CBF). Since the relationship between tissue oxygenation and regional CBF (rCBF) during exercise has not been elucidated, we compared the data obtained using near-infrared spectroscopy (NIRS) and rCBF examined using positron emission tomography (PET). Participants in this study comprised 26 healthy young men. Changes in concentration of oxygenated hemoglobin (ΔO2Hb) and deoxygenated hemoglobin (ΔHHb) in the prefrontal cortex (PFC) were measured using NIRS continuously during a 15-min bout of the constant-load low-intensity cycling exercise (n = 14). Under the same protocol as the NIRS study, rCBF was measured using H215O and PET by the autoradiographic method at baseline (Rest) and at 3 min (Ex1) and 13 min (Ex2) after starting exercise (n = 12). As systematic factors influenced by exercise, heart rate, end-tidal pressure of carbon dioxide (PETCO2) and blood pressure (BP) were monitored. For each region investigated by NIRS, rCBF was analyzed quantitatively using PET-MRI co-registered standardized images. Despite inter-individual differences, changing patterns of ΔO2Hb and ΔHHb in the PFC were similar between channels. Significant main effects for time point were identified in ΔO2Hb, ΔHHb and changes in rCBF. While rCBF increased from rest, ΔO2Hb was not changed at Ex1. Conversely, rCBF was unchanged from rest but ΔO2Hb was significantly increased at Ex2. Fluctuations of PETCO2 and BP evoked by exercise were not in accordance with changes in ΔO2Hb, ΔHHb and rCBF, while BP may affect the forehead skin blood flow. Given that NIRS data are a mixture of skin and brain effects, our results suggest that CMRO2 may differ between the phases in a bout of dynamic exercise. The present study indicates the utility of NIRS to examine the relationship between CMRO2 and rCBF during exercise.

Response of Cerebral Blood Flow and Blood Pressure to Dynamic Exercise: A Study Using PET.

Dynamic exercise elicits fluctuations in blood pressure (BP) and cerebral blood flow (CBF). This study investigated responses in BP and CBF during cycling exercise and post-exercise hypotension (PEH) using positron emission tomography (PET). CBF was measured using oxygen-15-labeled water (H215O) and PET in 11 human subjects at rest (Rest), at the onset of exercise (Ex1), later in the exercise (Ex2), and during PEH. Global CBF significantly increased by 13% at Ex1 compared with Rest, but was unchanged at Ex2 and during PEH. Compared with at Rest, regional CBF (rCBF) increased at Ex1 (20~42%) in the cerebellar vermis, sensorimotor cortex for the bilateral legs (M1Leg and S1Leg), insular cortex and brain stem, but increased at Ex2 (28~31%) only in the vermis and M1Leg and S1Leg. During PEH, rCBF decreased compared with Rest (8~13%) in the cerebellum, temporal gyrus, piriform lobe, thalamus and pons. The areas showing correlations between rCBF and mean BP during exercise and PEH were consistent with the central autonomic network, including the brain stem, cerebellum, and hypothalamus (R2=0.25-0.64). The present study suggests that higher brain regions are coordinated through reflex centers in the brain stem in order to regulate the cardiovascular response to exercise.

Unique Angiographic Appearances of Moyamoya Disease Detected with 3-Dimensional Rotational Digital Subtraction Angiography Imaging Showing the Hemodynamic Status.

BACKGROUND: The aim of this study was to identify the unique morphological arterial features in patients with moyamoya disease on 3-dimensional rotational digital subtraction angiography. MATERIALS AND METHODS: One hundred seven hemispheres of 58 consecutive patients with moyamoya disease that were analyzed with fused 3-dimensional images of internal carotid angiograms and vertebral angiograms that were marked with different colors were reviewed. Angiographic findings in the posterior watershed area were classified, and the utility of the classification was analyzed by comparing it with clinical presentations and quantitative hemodynamic parameters obtained with positron emission tomography. RESULTS: Two unique angiographic appearances were identified. A vacant vessel appearance (no arterial inflow despite absence of cortical infarction) was observed mostly in transient ischemic attack hemispheres. In hemispheres with a vacant vessel appearance, cerebral blood flow was decreased, cerebral blood volume was increased, and mean transit time was prolonged significantly (P = .00017, P = .0061, and P = .00026, respectively). A cocktail vessel appearance (mixture of carotid and vertebral arterial flow) was most commonly observed in asymptomatic cases, as well as in ischemic hemispheres. Cerebral blood volume increased and mean transit time was prolonged significantly (P = .036 and P = .014, respectively) in hemispheres with a cocktail vessel appearance. The trend of progression in hemodynamic severity in the order of normal appearance, cocktail vessel appearance, and vacant vessel appearance in the watershed area was statistically significant. CONCLUSION: Fused 3-dimensional digital subtraction angiography demonstrated unique angiographic features in the watershed area, and this represented the degree of cerebral hemodynamic impairment in moyamoya disease.

Validation of Cross-calibration Schemes for Quantitative Bone SPECT/CT Using Different Sources under Various Geometric Conditions.

PURPOSE: Several cross-calibration schemes have been proposed to produce quantitative values in bone SPECT imaging. Differences in the radionuclide sources and geometric conditions can decrease the accuracy of cross-calibration factor (CCF). The present study aimed to validate the effects of calibration schemes using different sources under various geometric conditions. METHODS: Temporal variations as well as variations in acquisition counts and the shapes of 57Co standard and 99mTc point sources and a 99mTc disk source were determined. The effects of the geometric conditions of the source-to-camera distance (SCD) and lateral distance on the CCF were investigated by moving the camera or source away from the origin. The system planar sensitivity of NEMA incorporated into a Symbia Intevo SPECT/CT device (Siemens®) was defined as reference values. RESULTS: The temporal variation in CCF using the 57Co source was relatively stable within the range of 0.7% to 2.3%, whereas the 99mTc source ranged from 2.7% to 7.3%. In terms of source shape, the 57Co standard point source was the most stable. Both SCD and lateral distance decreased as a function of distance from the origin. Errors in the geometric condition were higher for the 57Co standard point source than the 99mTc disk source. CONCLUSIONS: Different calibration schemes influenced the reliability of quantitative values. The 57Co standard point source was stable over a long period, and this helped to maintain the quality of quantitative SPECT/CT imaging data. The CCF accuracy of the 99mTc source decreased depending on the preparative method. The method of calibration for quantitative SPECT should be immediately standardized to eliminate uncertainty.

[A Comparison of Planar Sensitivity and Spatial Resolution among Different Collimators and Energy Windows on 223Ra Imaging].

OBJECTIVE: The present study aimed to reveal the influence of combination of different collimators and energy windows on the planar sensitivity and the spatial resolution during experimental 223Ra imaging, and to determine optimal imaging parameters. METHODS: A vial type source containing 223Ra solution (4.55 MBq / 5.6 ml) was placed in the air at 100 mm away from the collimator surface. Planar images were acquired with LEHR, LMEGP, ELEGP and MEGP collimators on two dual-head gamma cameras (Symbia intevo (Siemens) and Infinia 3 (GE)). We compared three energy window combinations: 1) single window at 82 keV, 2) double window at 82+154 keV, 3) triple window at 82+154+270 keV. The energy spectrum, the sensitivity and the spatial resolution, such as full-width at half-maximum (FWHM) and full-width at tenth-maximum (FWTM), of each collimator were assessed. RESULTS: Five energy spectra (at around 82, 154, 270, 351 and 405 keV) were essentially observed among four collimators. The sensitivity was high for LEHR collimator, then ELEGP and LMEGP collimator was 3-4 fold, which is greater than MEGP collimator. The 82 keV energy window of four collimators has best spatial resolution. Moreover, the spatial resolution of the 82 keV energy window with LMEGP and ELEGP collimator was almost equal to that of the triple window with MEGP collimator. CONCLUSIONS: Optimal imaging parameters were single energy window using LMEGP or ELEGP, and then triple energy window using MEGP collimator.

Calculation Accuracy of Gross Tumor Volume at the Diaphragm Boundary Evaluated Using Respiratory-gated PET/CT.

OBJECTIVE: The present study aimed to clarify gross tumor volume (GTV) contouring accuracy at the diaphragm boundary using respiratory-gated PET/CT. METHODS: The lung/diaphragm boundary was simulated using a phantom containing 18F solution (10.6 kBq/mL). Tumors were simulated using spheres (diameter, 11-38 mm) containing 18F and located at the positions of the lungs and liver. The tumor background ratios (TBR) were 2, 4, and 8. The phantom was moved from the superior to inferior direction with a 20-mm motion displacement at 3.6 s intervals. The recovery coefficient (RC), volume RC (VRC), and standardized uptake value (SUV) threshold were calculated using stationary, non-gated (3D), and gated (4D) PET/CT. RESULTS: In lung cancer simulation, RC and VRC in 3D PET images were, respectively, underestimated and overestimated in smaller tumors, whereas both improved in 4D PET images regardless of tumor size and TBR. The optimal SUV threshold was about 30% in 4D PET images. In liver cancer simulation, RC and VRC were, respectively, underestimated and overestimated in smaller tumors, and when the TBR was lower, but both improved in 4D PET images when tumors were >17 mm and the TBR was >4. The optimal SUV threshold tended to depend on the TBR. CONCLUSIONS: The contouring accuracy of GTV was improved by considering TBR and using an optimal SUV threshold acquired from 4D PET images.

Alteration of the regional cerebral glucose metabolism in healthy subjects by glucose loading.

High plasma glucose (PG) levels can reduce fluorine-18-labeled fluorodeoxyglucose ((18) F-FDG) uptake, especially in the Alzheimer's disease (AD)-related regions. This fact is supported by studies showing that the resting-state activity in diabetes can be altered in the default mode network (DMN)-related regions, which considerably overlap with the AD-related regions. In order to expand the current knowledge, we aimed to investigate the relationship between increasing PG levels and the regional cerebral metabolic rates for glucose (CMRglc ) as a direct index of brain activity. We performed dynamic (18) F-FDG positron emission tomography with arterial blood sampling once each in the fasting and glucose-loading conditions on 12 young, healthy volunteers without cognitive impairment or insulin resistance. The absolute CMRglc values were calculated for the volume-of-interest (VOI) analysis, and normalized CMRglc maps were generated for the voxelwise analysis. The normalized measurement is known to have smaller intersubject variability than the absolute measurement, and may, thus, lead to greater statistical power. In VOI analysis, no regional difference in the CMRglc was found between the two conditions. In exploratory voxelwise analysis, however, significant clusters were identified in the precuneus, posterior cingulate, lateral parietotemporal, and medial prefrontal regions where the CMRglc decreased upon glucose loading (P < 0.05, corrected). These regions include the representative components of both the DMN and AD pathology. Taken together with the previous knowledge on the relationships between the DMN, AD, and diabetes, it may be inferred that glucose loading induces hypometabolism in the AD-related and DMN-related regions. Hum Brain Mapp 37:2823-2832, 2016. © 2016 Wiley Periodicals, Inc.

Evaluation of a New Motion-correction Algorithm Using On-rigid Registration in Respiratory-gated PET/CT Images of Liver Tumors.

OBJECTIVE: The present study aimed to determine the qualitative and quantitative accuracy of the Q.Freeze algorithm in PET/CT images of liver tumors. METHODS: A body phantom and hot spheres representing liver tumors contained 5.3 and 21.2 kBq/mL of a solution containing 18F radioactivity, respectively. The phantoms were moved in the superior-inferior direction at a motion displacement of 20 mm. Conventional respiratory-gated (RG) and Q.Freeze images were sorted into 6, 10, and 13 phase-groups. The SUVave was calculated from the background of the body phantom, and the SUVmax was determined from the hot spheres of the liver tumors. Three patients with four liver tumors were also clinically assessed by whole-body and RG PET. The RG and Q.Freeze images derived from the clinical study were also sorted into 6, 10 and 13 phase-groups. Liver signal-to-noise ratio (SNR) and SUVmax were determined from the RG and Q.Freeze clinical images. RESULTS: The SUVave of Q.Freeze images was the same as those derived from the body phantom using RG. The liver SNR improved with Q.Freeze, and the SUVsmax was not overestimated when Q.Freeze was applied in both the phantom and clinical studies. Q.Freeze did not degrade the liver SNR and SUVmax even though the phase number was larger. CONCLUSIONS: Q.Freeze delivered qualitative and quantitative motion correction than conventional RG imaging even in 10-phase groups.

[Comparison of (18)F-fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography image quality between commercial and in-house supply of FDG radiopharmaceuticals].

OBJECTIVE: PET images are affected by scanner model, reconstruction conditions, injected dose, scan duration, patient health status and FDG radiopharmaceutical supply systems. The present study compares images of 40 patients using commercial and in-house FDG systems with one PET scanner (Aquiduo). METHODS: The PET images were evaluated using the physical indexes of NECpatient, NECdensity and SNRliver proposed by the Japanese guidelines for oncological FDG-PET/CT, and by visual assessment. RESULTS: There were no significant differences in the physical indexes between PET images generated using commercial and in-house FDG. The physical indexes were also acceptable according to the recommended Japanese guidelines. NECdensity was higher when a higher dose/body weight of commercial FDG was injected (correlation coefficient: r=0.576, p<0.001) and lower when BMI was lower and in-house FDG was injected (r=-0.786, p<0.0001). These results suggest that scan duration should be increased if the injected dose of commercial FDG/body weight is <5.5 MBq/kg, and if individuals with BMI >21.4 kg/m(2) are injected with in-house FDG. CONCLUSIONS: Scan duration should be varied depending on FDG supply systems to ensure more accurate image quality and quantitative values during evaluations of response to therapy and prognostic prediction.

[Technical features and roles of cobalt-57 flood sources for daily quality control of gamma cameras].

Quality control (QC) detects changes in the performance of gamma cameras that could adversely affect interpretations of clinical studies. We used plate and sheet (57)Co flood sources to measure extrinsic uniformity during daily QC. Each source, when placed on the top of a collimated detector, allowed the acquisition of uniform images from both detectors, thus reducing the amount of time needed to perform daily QC. No serious problems with the gamma camera system were revealed by visual checks, and changes in detector sensitivity were rapidly determined by observing daily variations in the measured values of extrinsic uniformity. Furthermore, (57)Co flood sources confer advantages in that they shorten the time required for preparation of flood sources and reduce the consequent exposure of medical staff to radiation.

[Improvement of quantitative accuracy using phase-based respiratory-gated PET/CT in phantom and clinical studies].

OBJECTIVE: The present study aimed at determining the quantitative accuracy of phase-based respiratory-gated PET/CT imaging using phantom and clinical studies. METHODS: The effects of target size, target-to-background ratio (TBR), and respiratory motion on PET images were estimated using a NEMA body phantom comprising six spheres (diameter 10-37mm) in a solution of F-18 of three different TBRs (4, 6, 8). The phantom was moved in a superior-inferior direction at motion displacements of 0, 10, 20 and 30 mm. Stationary images of the phantom as well as non-gated (3D) and gated (4D) images of the phantom while moving were reconstructed and the recovery coefficient (RC) of individual spheres was calculated from each image. We then determined the RC improvement rate to evaluate improvements conferred by 4D-PET/CT. We retrospectively analyzed data from 14 patients with lung cancer who were examined by 3D- and 4D-PET/CT. Each lesion on the 3D-PET/CT and each of the five phases of the 4D-PET/CT were analyzed. RESULTS: Larger motion displacement and TBR resulted in increased RC degradation for small spheres. The RC improvement rate showed that 4D acquisition improved the RC of spheres with larger motion displacement exceeding 13 mm in diameter. 4D-PET/CT alone can reduce the effects of motion blurring, but partial volume effects may still be the dominant source of quantitative inaccuracy for small lesions. The trends of phantom and clinical studies for evaluating the improvement rate were similar. CONCLUSIONS: 4D-PET/CT significantly improved the quantitative accuracy of PET images particularly when larger motion displacement exceeded 17mm in diameter such as in lung cancer.

[Radiation Dose Considerations for Breast Sonographers Following 99mTc-HMDP Bone Scan Administration].

PURPOSE: Patients who were administered radiopharmaceuticals can be a source of radiation exposure to sonographers. This study aimed to identify factors associated with radiation exposure to breast sonographers from patients administered radiopharmaceuticals for bone scanning. METHODS: The exposure dose of six sonographers was measured during breast sonography in 59 patients administered 99mTc-HMDP. We predicted the following factors to be related to exposure dose: time interval between administration and sonography, sonography examination time, estimated radioactivity at sonography, sonographer's years of experience, and patients' clinical data (age, renal function and surgical procedure). Spearman's rank correlation coefficient was used to examine the relationship between radiation dose and the aforementioned factors. RESULTS: The mean±standard deviation of the exposure dose for the sonographers was 9.3±3.8 µSv. The time interval between administering the radiopharmaceutical agent and sonography, the sonography examination time and estimated radioactivity at sonography were found to be factors related to the exposure of the sonographer. The exposure dose increased as a function of the shorter time interval, longer examination time and higher estimated radioactivity at sonography. CONCLUSION: The time interval between drug administration and sonography, sonography examination time and estimated radioactivity at sonography contributed to the increased dose to breast sonographers. Although we considered that the exposure dose of sonographers would not possibly exceed the dose limit in the present study, we suggested that radiological technologists need to educate the physicians requesting sonography, and the sonographers about the radiation exposure in nuclear medicine.

Optimization of penalization function in Bayesian penalized likelihood reconstruction algorithm for [18F]flutemetamol amyloid PET images.

Point-spread-function (PSF) correction is not recommended for amyloid PET images due to Gibbs artifacts. Q.Clear™, a Bayesian Penalized Likelihood (BPL) reconstruction method without incorporating PSF correction reduces these artifacts but degrades image contrast by our previous findings. The present study aimed to recover lost contrast by optimizing reconstruction parameters in time-of-flight (TOF) BPL reconstruction of amyloid PET images without PSF correction. We selected candidate conditions based on a phantom study and then determined which were optimal in a clinical study. Phantom images were reconstructed under conditions of 1‒9 iterations, ß 300-1000 and γ factors from 2 to 10 in TOF-BPL without PSF correction. We evaluated the %contrast and the coefficients of variation (CV, %). Standardized uptake value ratios (SUVr) and Centiloid scales (CL) were calculated from PET images acquired from 71 participants after an [18F]flutemetamol injection. Both %contrast and CV were independent of iterations, whereas a trade-off was found between γ factors and ß. We selected a γ factors of 5 without PSF correction (iterations, 1; ß, 500) and of 10 without PSF correction (iterations, 1; ß, 800) as candidates for clinical investigation. The SUVr and CL remained stable across various conditions, and CL scales effectively discriminated amyloid PET using measured values. The optimal reconstruction parameters of TOF-BPL for [18F]flutemetamol PET images were γ factor 10, iterations 1 and ß 800, without PSF correction.

Phantom test procedures for a new neuro-oncological amino acid PET tracer: [18F]fluciclovine.

OBJECTIVE: Amino acid positron emission tomography (PET) examinations using anti-1-amino-3-[18F]-fluorocyclobutane-1-carboxylic acid ([18F]FACBC) were allowed for routine clinical use in July 2024. However, phantom test procedures for [18F]FACBC reconstruction parameters have not yet been established. The present study aimed to establish new phantom test procedures for [18F]FACBC brain PET imaging to determine optimal reconstruction parameters. METHODS: Background (BG) activity as well as hot sphere and target-to-background ratios (TBRs) of [18F]FACBC were estimated based on brain activity and tumor-to-normal tissue ratios (TNR) in a Japanese clinical trial of [18F]FACBC. Phantom experiments proceeded under [18F]FACBC or L-[methyl-11C]-methionine ([11C]MET) conditions. The number of iterations and the Gaussian filter parameters were determined from the reconstruction parameters %contrastmean and coefficients of variation (CVs) in ordered subset expectation maximization (OSEM) and time-of-flight (TOF) with or without point-spread-function (PSF) correction. RESULTS: The amounts of activity in the hot spheres and BG were 1.1 and 5.5 kBq/mL, respectively, and the TBR was 5.0 at the start of acquisition. The %contrastmean of all hot spheres was higher with [18F]FACBC than [11C]MET, and %contrastmean converged between 4 and 6 iterations in hot spheres with diameters < 10 mm. We used four iterations for OSEM + TOF and five for OSEM + TOF + PSF correction for [18F]FACBC and [11C]MET images. The CV was higher for [18F]FACBC than [11C]MET. The optimal sizes of Gaussian filters for OSEM + TOF and OSEM + TOF + PSF correction of image reconstruction were 5 mm for [18F]FACBC, and 4 and 3 mm, respectively, for [11C]MET images. CONCLUSIONS: We estimated phantom activity and TBR based on brain activity in a Japanese clinical trial and established new phantom test procedures for [18F]FACBC. We recommend that the optimal reconstruction parameters for [18F]FACBC should be set to the same number of iterations as [11C]MET and that the FWHM of Gaussian filter should have a few mm higher than [11C]MET to reduce image noise from brain normal tissue.