Control of whole-body FDG-positron emission tomography image quality by adjusting the acquisition time: A new physical image quality index and patientdependent parameters for clinical imaging

Objective: This study aimed to establish a methodology for obtaining visually equivalent image quality regardless of patient size by controlling the acquisition time of positron emission tomography (PET) studies. Methods: In Part 1, we determined the physical image quality index with the highest correlation with visual assessment in 30 patients. In Part 2, 100 patients were scanned to identify the patient-dependent parameters that were most correlated with the physical image quality index. These parameters were calculated from the combination of the administered activity of 18F-FDG and weight. We drew an approximate curve from these parameters and prepared a scatter plot of the physical image quality index. In Part 3, we checked whether the image quality was constant by controlling the acquisition time in 189 patients. The approximation formula we obtained under (2) was used to control the acquisition time. The physical image quality index was a constant value, and the patient-dependent parameter was calculated from the patient’s physique. Results: The physical image quality index with the highest correlation with visual evaluation was the noise equivalent count weight (NECweight) (correlation coefficient: 0.90). The patient-dependent index most correlated with NECweight was activity/weight3 (A/W3) (coefficient of determination: 0.978). The verification of the acquisition time to obtain a certain image quality showed an average of 0.60 ± 0.034 Mcounts/m∙kg, and a similar image quality was obtained independent of the individual physiques. Conclusions: Calculating NECweight and A/W3 enable the determination of the appropriate acquisition time for stable image quality before the PET study

Metal-Induced Gap States at Well Defined Alkali-Halide/Metal Interfaces

In order to search for states specific to insulator/metal interfaces, we have studied epitaxially grown interfaces with element-selective near edge X-ray absorption fine structure (NEXAFS). An extra peak is observed below the bulk edge onset for LiCl films on Cu and Ag substrates. The nature of chemical bonds as probed by X-ray photoemission spectroscopy and Auger electron spectroscopy remains unchanged, so we regard this as evidence for metal-induced gap states(MIGS) formed by the proximity to a metal, rather than local bonds at the interface. The dependence on the film thickness shows that the MIGS are as thin as one monolayer. An ab initio electronic structure calculation supports the existence of the MIGS that are strongly localized at the interface.Comment: 4 pages, 5 figures, to be published in Phys. Rev. Let

Increase in Docetaxel-Resistance of Ovarian Carcinoma-Derived RMG-1 Cells with Enhanced Expression of Lewis Y Antigen

Epithelial carcinomas of the ovary exhibit the highest mortality rate among gynecologic malignancies. Studies found that the metabolism of glycolipids or carbohydrates is associated with acquirement of anticancer drug-resistance by cancer cells. This study was to characterize possible involvement of Lewis Y (LeY) antigen in the drug-resistance of cancer cells. We transfected the α1,2-fucosyltransferase gene into human ovarian carcinoma-derived RMG-1 cells and established RMG-1-hFUT cells with enhanced expression of LeY. We determined the effects of docetaxel on the survival of cells by MTT assaying and observed the apoptosis of cells in the presence of docetaxel by flow cytometric analysis and by transmission electron microscopy. Plasma membranes and intracellular granules in RMG-1-hFUT cells were stained with anti-LeY antibody, the intensity of the staining was higher than that in control cells. The RMG-1-hFUT cells exhibited higher resistance to docetaxel than the control cells with regard to the docetaxel concentration and time course. After treatment with 10 μg/mL docetaxel for 72 h, the control cells, but not RMG-1-hFUT, contained abundant positively stained cell debris due to disintegration of the cytoskeleton. On transmission electron microscopy, although the control cells treated with docetaxel as above showed the following morphology, i.e., absence of villi, cells shrunken in size, pyknosis, agglutinated chromatin and cell buds containing nuclei in the process of apoptosis, the RMG-1-hFUT cells showed only agglutinated chromatin and vacuoles in the cytoplasm. In summary, cells with enhanced expression of LeY were shown to acquire docetaxel-resistance, indicating the possible involvement of glycoconjugates in the drug-resistance

Variability of Repeated Coronary Artery Calcium Scoring and Radiation Dose on 64-slice and 16-slice CT by Prospective Electrocardiograph-triggered Axial and Retrospective Electrocardiograph-gated Spiral CT : A Phantom Study

Rationale and Objectives: To compare coronary artery calcium scores, the variability and radiation doses on 64-slice and 16-slice CT scanners by both prospective electrocardiograph (ECG)-triggered and retrospective ECG-gated scans. Materials and Methods: Coronary artery models (n=3) with different plaque CT densities (~240 HU, ~600 HU and ~1000 HU) of four sizes (1 mm, 3 mm, 5 mm and 10 mm in length) on a cardiac phantom were scanned three times in 5 heart rate sequences. The tube current-time-products were set to almost the same on all four protocols (32.7 mAs for 64-slice prospective and retrospective scans, 33.3 mAs for 16-slice prospective and retrospective scans). Slice-thickness was set to 2.5 mm in order to keep the radiation dose low. Overlapping reconstruction with 1.25 mm increment was applied on the retrospective ECG-gated scan. Results: The coronary artery calcium scores were not different between the four protocols (one-factor ANOVA, Agatston; p=0.32, volume; p=0.19 and mass; p=0.09). Two-factor factorial ANOVA test revealed that the interscan variability was different between protocols (p<0.01) and scoring algorithms (p<0.01). The average variability of Agatston/volume/mass scoring and effective doses were 64-slice prospective scan: 16%/15%/11% and 0.5 mSv, 64-slice retrospective scan: 11%/11%/8% and 3.7 mSv, 16-slice prospective scan: 20%/18%/13% and 0.6 mSv & 16-slice retrospective scan: 16%/15%/11% and 2.9 to 3.5 mSv (depending on the pitch). Conclusions: Retrospective ECG-gated 64-slice CT showed the lowest variability. Prospective ECG-triggered 64-slice CT, with low radiation dose, shows low variability on coronary artery calcium scoring comparable to retrospective ECG-gated 16-slice CT