[en] Biograph Vision PET/CT system is high sensitivity and high spatial resolution, and can provide high quality images. In addition, new technologies such as parametric images and oncofreeze are also expected in clinical site. We think that the possibility of Biograph Vision needs to be examined in more detail. (author)

[en] There are few reports focusing on the radioactivity concentration in the normal brain region for the phantom experiment. We investigated the radioactivity concentration of normal brain regions for the phantom experiment of brain tumor PET imaging. A total of 30 patients (age: 53±19 years old, body weight: 58±11 kg) underwent the brain tumor PET examinations using ¹⁸F-fluorothymidine (¹⁸F-FLT), ¹⁸F-fluoromisonidazole (¹⁸F-FMISO) and ¹¹C-methionine (¹¹C-MET) during April 1, 2017-October 1, 2017. A region of interest was set in the brain parenchyma excluding the tumor lesion area and the ventricle in PET image, and radioactivity concentrations of the normal brain region were obtained. The radioactivity concentrations of the normal brain region were 0.79±0.25 kBq/ml for ¹⁸F-FLT, 2.34±0.42 kBq/ml for ¹⁸F-FMISO and 4.05±0.80 kBq/ml for ¹¹C-MET. We proposed the radioactivity concentrations of background region in the phantom for brain tumor PET imaging using ¹⁸F-FLT, ¹⁸F-FMISO and ¹¹C-MET. (author)

[en] This prospective study compared the value of pretreatment 4'-[methyl-¹¹C]-thiothymidine (¹¹C-4DST) volumetric parameters and those of 2-deoxy-2-[¹⁸F] fluoro-D-glucose (¹⁸F-FDG) in predicting the clinical outcome in patients with head and neck squamous cell carcinoma (HNSCC). Fifty patients with HNSCC underwent ¹¹C-4DST PET/CT and ¹⁸F-FDG PET/CT prior to anticancer therapy. ¹⁸F-FDG metabolic tumor volume (¹⁸F-FDG MTV) and total lesion glycolysis (TLG) were calculated from ¹⁸F-FDG PET, and ¹¹C-4DST MTV and total lesion proliferation (TLP) were calculated from ¹¹C-4DST PET. All parameters were measured for the primary lesion and metastatic lymph nodes. Associations between clinical factors and PET/CT parameters and prognostic value were analyzed. Receiver-operating characteristic analysis revealed that MTV, TLG, and TLP acquired from the primary lesion and metastatic lymph nodes were good parameters for predicting disease relapse and death. The area under the curves (AUCs) ranged from 0.63 to 0.71 for ¹⁸F-FDG PET/CT parameters. The AUCs of ¹¹C-4DST PET/CT parameters were larger than those of ¹⁸F-FDG (range 0.72-0.81). Univariate analysis revealed that individuals with tumors showing a high value for any PET/CT parameter were at a significantly increased risk of relapse. Upon multivariate analysis, ¹⁸F-FDG MTV, ¹¹C-4DST MTV and ¹¹C-4DST TLP were significant independent factors for relapse-free survival (P = 0.04, P = 0.0001 and P = 0.0005, respectively). Pretreatment ¹¹C-4DST PET/CT volume-based parameters can provide important prognostic information about patients with HNSCC. (author)

[en] The diagnosis of primary central nervous system lymphoma (PCNSL) in immunocompetent patients with atypical magnetic resonance (MR) findings such as disseminated lesions or no (non-enhancing) lesion is sometimes difficult because of mimicking other tumorous and non-tumorous diseases. Positron emission tomography (PET) with ¹⁸F-fluorodeoxyglucose (FDG) and ¹¹C-methionine (MET) can measure the glucose and amino acid metabolism in the lesions and may provide useful information for diagnosing PCNSL in patients with such subtle MR findings. We performed PET studies with FDG and MET in 17 histologically proven PCNSL and compared the uptake of FDG and MET qualitatively and quantitatively in the tumors between 12 typical and 5 atypical MR findings. All typical PCNSL showed strong uptake of FDG and MET; however, visual analysis of FDG and MET uptake in atypical PCNSL was not very useful for finding lesions in the brain. Semiquantitative FDG and MET uptake values (SUVmax) and quantitative FDG influx rate constant (K_i) in the tumors are significantly lower in atypical PCNSL compared with those in typical PCNSL. These values obtained in the lesions with atypical MR findings were also not useful for differentiating PCNSL from other tumorous and non-tumorous diseases. The k₃ values evaluated by FDG kinetic analysis in atypical PCNSL were similar to those obtained in typical PCNSL. Visual analysis of FDG and MET uptake in atypical PCNSL was not useful for finding the lesions in the brain. Semiquantitative and quantitative values obtained in the lesions with atypical MR findings were also not useful for differentiating PCNSL from other tumorous and non-tumorous diseases. The k₃ values evaluated by FDG kinetic analysis in atypical PCNSL may provide valuable information in the diagnosis of PCNSL. (author)

[en] The nucleoside analog 3'-deoxy-3'-¹⁸F-fluorothymidine (FLT) has been investigated for evaluating tumor proliferating activity in brain tumors. We evaluated FLT uptake heterogeneity using textural features from the histogram analysis in patients with newly diagnosed gliomas and examined correlation of the results with proliferative activity and patient prognosis, in comparison with the conventional PET parameters. FLT PET was investigated in 37 patients with newly diagnosed gliomas. The conventional parameters [tumor-to-contralateral normal brain tissue (T/N) ratio and metabolic tumor volume (MTV)] and textural parameters (standard deviation, skewness, kurtosis, entropy, and uniformity) were derived from FLT PET images. Linear regression analysis was used to compare PET parameters and the proliferative activity as indicated by the Ki-67 index. The associations between parameters and overall survival (OS) were tested by Cox regression analysis. Median OS was 662 days. For the conventional parameters, linear regression analysis indicated a significant correlation between T/N ratio and Ki-67 index (p = 0.02) and MTV and Ki-67 index (p = 0.02). Among textural parameters, linear regression analysis indicated a significant correlation for kurtosis (p = 0.003), entropy (p < 0.001), and uniformity (p < 0.001) as compared to Ki-67 index, exceeding those of the conventional parameters. The results of univariate analysis suggested that skewness and kurtosis were associated with OS (p = 0.03 and 0.02, respectively). Mean survival for patients with skewness values less than 0.65 was 1462 days, compared with 917 days for those with values greater than 0.65 (p = 0.02). Mean survival for patients with kurtosis values less than 6.16 was 1616 days, compared with 882 days for those with values greater than 6.16 (p = 0.006). Based on the results of this preliminary study in a small patient population, textural features reflecting heterogeneity on FLT PET images seem to be useful for the assessment of proliferation and for the potential prediction of survival in newly diagnosed gliomas. (author)

[en] The administration accuracy of the automated infusion device for the positron emission radiopharmaceutical affects to calculation of the standardized uptake value (SUV) in ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) PET examination. The purpose of this study was to investigate the administration error in the clinical use of an automated infusion device for quantitative management in PET examination. We assumed clinical use of the automated infusion device and investigated two types of administration errors. First, for investigating the administration error over time in a day (error_day), a total of 13 infusion works were performed every 30 minutes. Second, for investigating the long period administration error (error_period), the infusion work was performed once before clinical use of an automated infusion device. The dispensed radioactivity was set to 150 MBq. The administration error was calculated using output values from the automated infusion device and measured values from the dose calibrator. The administration error_day was 0.9±1.3%, and the maximum error was 2.7%. The administration error_period was 1.1±2.0%, and the maximum error was 5.9%. We investigated the administration error of the automated infusion device. We confirmed the approximately 1% administration error and high-accuracy injection in an automated-device method. (author)

[en] In a previous issue of this journal, we published a report entitled 'Creation of Stereo-paired Bone Anatomical Charts Using Human Bone Specimens for Radiation Education' To understand how the bone specimen is visualized as an X-ray image, we newly created a bone specimen stereo-paired X-ray anatomical chart by adding the X-ray images of the same bone specimen. When a bone is X-rayed, the surface structure and internal structure of the bone are visualized as a composite image of the difference in X-ray absorption, and each bone becomes a unique X-ray image. Therefore, we took stereo-paired X-ray images of the bone specimens by the same method as the stereo-paired anatomical chart of the bone specimens. Then, we arranged the stereo-paired X-ray images and surface images of the same bone specimen in the one sheet to be readily compared. Similar to the previous bone specimen anatomical charts, these data of X-ray image anatomical chart were also made into an electronic file, so that we can do the three-dimensional observation of bone X-ray images even at the place of radiological examination or at home through electronic media. Until now, none of the specialized anatomy books and pictorial books are available for stereoscopic viewing of bone specimens and bone X-ray images. However, this stereo-paired X-ray image anatomical chart enabled us to learn accurate three-dimensionalization of bones by comparing the bone surface morphology and bone X-ray images. (author)

[en] We investigated the way of thinking about the CT dose setting, the exposure dose (CTDI_vol, DLP) and the image quality (standard deviation of liver: SD_liver) of whole-body PET/CT examinations in the Chugoku and Shikoku regions for the optimized CT dose setting. It was researched in the target 29 facilities which is equipped with ¹⁸F-FDG, PET/CT scanner in that regions. We examined how to determine the dose of complete physical PET/CT setting, the CT radiation dose (CTDI_vol and DLP) and the image quality of CT fusion image that is the standard deviation of liver CT value in each facility. The optimized CT dose was lower than the diagnostic CT in many facilities. The 75th percentile CTDI_vol was 6.01 mGy. The 75th percentile DLP was 560.9 mGy xcm. The SD_liver was 14.6±5.3 HU. The CT condition was low setting in comparison with diagnostic CT in many facilities. The exposure dose was lower than the diagnostic CT dose. The image quality of the normal region of liver was very close to the diagnostic CT. Even though it was low dose, images were less noise components. (author)

[en] Glioblastoma multiforme (GBM) is characterized by tissue hypoxia associated with resistance to radiotherapy and chemotherapy. To clarify the biological link between hypoxia and tumour-induced neovascularization and tumour aggressiveness, we analysed detailed volumetric and spatial information of viable hypoxic tissue assessed by ¹⁸F-fluoromisonidazole (FMISO) PET relative to neovascularization in Gd-enhanced MRI and tumour aggressiveness by L-methyl-¹¹C-methionine (MET) PET in newly diagnosed GBMs. Ten patients with newly diagnosed GBMs were investigated with FMISO PET, MET PET and Gd-enhanced MRI before surgery. Tumour volumes were calculated by performing a three-dimensional threshold-based volume of interest (VOI) analysis for metabolically active volume on MET PET (MET uptake indices of ≥1.3 and ≥1.5) and Gd-enhanced volume on MRI. FMISO PET was scaled to the blood FMISO activity to create tumour to blood (T/B) images. The hypoxic volume (HV) was defined as the region with T/B greater than 1.2. PET and MR images of each patient were coregistered to analyse the spatial location of viable hypoxic tissue relative to neovascularization and active tumour extension. Metabolically active tumour volumes defined using MET uptake indices of ≥1.3 and ≥1.5 and the volumes of Gd enhancement showed a strong correlation (r = 0.86, p < 0.01 for an index of ≥1.3 and r = 0.77, p < 0.05 for an index of ≥1.5). The HVs were also excellently correlated with the volumes of Gd enhancement (r = 0.94, p < 0.01). The metabolically active tumour volumes as defined by a MET uptake index of ≥1.3 and the HVs exhibited a strong correlation (r = 0.87, p < 0.01). On superimposed images, the metabolically active area on MET PET defined by a MET uptake index of ≥1.3 was usually larger than the area of the Gd enhancement and about 20-30% of the MET area extended outside the area of the enhancement. On the other hand, the surface area of viable hypoxic tissue with a T/B cutoff of ≥1.2 on FMISO PET did not substantially differ from the area of the Gd enhancement. The volumetric analysis demonstrates that the viable hypoxic tissue assessed by FMISO PET is related to the neovascularization in Gd-enhanced MRI and the tumour aggressiveness by MET PET in newly diagnosed GBMs. The spatial analysis shows that the metabolically active tumour may be substantially underestimated by Gd-enhanced MRI. Complementary use of MET and FMISO to Gd-enhanced MRI may improve the understanding of tumour biology and lead to the most efficient delineation of tumour volume and treatment strategy. (orig.)

[en] Quantification of cerebral blood flow (CBF) is important for the understanding of normal and pathologic brain physiology. When CBF is assessed using PET with ${\text{H}}_2$ ¹⁵O or C¹⁵O₂, its calculation requires an arterial input function, which generally requires invasive arterial blood sampling. The aim of the present study was to develop a new technique to reconstruct an image derived input function (IDIF) from a dynamic ${\text{H}}_2$ ¹⁵O PET image as a completely non-invasive approach.

Our technique consisted of using a formula to express the input using tissue curve with rate constant parameter. For multiple tissue curves extracted from the dynamic image, the rate constants were estimated so as to minimize the sum of the differences of the reproduced inputs expressed by the extracted tissue curves. The estimated rates were used to express the inputs and the mean of the estimated inputs was used as an IDIF. The method was tested in human subjects (n  =  29) and was compared to the blood sampling method. Simulation studies were performed to examine the magnitude of potential biases in CBF and to optimize the number of multiple tissue curves used for the input reconstruction.

In the PET study, the estimated IDIFs were well reproduced against the measured ones. The difference between the calculated CBF values obtained using the two methods was small as around  <8% and the calculated CBF values showed a tight correlation (r  =  0.97). The simulation showed that errors associated with the assumed parameters were  <10%, and that the optimal number of tissue curves to be used was around 500.

Our results demonstrate that IDIF can be reconstructed directly from tissue curves obtained through ${\text{H}}_2$ ¹⁵O PET imaging. This suggests the possibility of using a completely non-invasive technique to assess CBF in patho-physiological studies. (paper)