Wafer-scale integration of GaAs/AlGaAs core-shell nanowires on silicon by the single process of self-catalyzed molecular beam epitaxy.

GaAs/AlGaAs core-shell nanowires, typically having 250 nm diameter and 6 µm length, were grown on 2-inch Si wafers by the single process of molecular beam epitaxy using constituent Ga-induced self-catalysed vapor-liquid-solid growth. The growth was carried out without specific pre-treatment such as film deposition, patterning, and etching. The outermost Al-rich AlGaAs shells form a native oxide surface protection layer, which provides efficient passivation with elongated carrier lifetime. The 2-inch Si substrate sample exhibits a dark-colored feature due to the light absorption of the nanowires where the reflectance in the visible wavelengths is less than 2%. Homogeneous and optically luminescent and adsorptive GaAs-related core-shell nanowires were prepared over the wafer, showing the prospect for large-volume III-V heterostructure devices available with this approach as complementary device technologies for integration with silicon.

Stellate ganglion blockade combined with nifekalant for patients with electrical storm: a case report.

Background: Although both stellate ganglion blockade and nifekalant are effective treatment options for electrical storm, the clinical effect of their combination is uncertain. Case summary: A 71-year-old male patient was admitted to our hospital with acute myocardial infarction and heart failure. Emergency coronary angiography revealed triple-vessel disease. Although coronary artery bypass grafting was planned, the patient experienced electrical storm before the surgery could be performed. Despite complete revascularization by percutaneous coronary intervention, mechanical circulatory support and administration of antiarrhythmic agents (amiodarone and lidocaine), electrical storm was not controlled. After stellate ganglion blockade was initiated on the 9th day of hospitalization, ventricular arrhythmia decreased. However, when stellate ganglion blockade was temporarily discontinued, ventricular arrhythmia increased substantially. Subsequently, combination therapy with stellate ganglion blockade and nifekalant was initiated, after which ventricular arrhythmia disappeared completely. Afterwards, the patient had no further ventricular arrhythmia episodes, and his haemodynamic status gradually improved. The patient was discharged from hospital in an ambulatory condition and did not experience arrhythmia during the follow-up. Discussion: This case demonstrates that combination therapy with stellate ganglion blockade and nifekalant can completely suppress ventricular arrhythmia, suggesting that blocking multiple conduction pathways is a key to treating refractory electrical storm.

Prognostic Value of the FAN Score, a Combination of the Fibrosis-4 Index, Albumin-Bilirubin Score and Neutrophil-Lymphocyte Ratio, in Patients Hospitalized with Heart Failure.

The fibrosis-4 index, albumin-bilirubin score and neutrophil-lymphocyte ratio are all prognostic markers in patients with heart failure. Recently, the FAN score, which includes all 3 of these markers, was developed as a useful risk stratification tool in patients with cancer. However, its cut-off values have not been validated for heart failure. We aimed to investigate the optimal cut-off and prognostic values of the FAN score in patients with heart failure. We analyzed 669 consecutive patients hospitalized with heart failure (age, 75.8 ± 11.3 years). Their median values of the fibrosis-4 index, albumin-bilirubin score, and neutrophil-lymphocyte ratio at discharge were 2.12, -2.25, and 2.41, respectively. The FAN score for heart failure (HF-FAN score) was calculated using these median values. The primary outcome was a composite of all-cause death and heart failure rehospitalization. Patients were divided into 4 groups according to HF-FAN scores of 0 (n = 112), 1 (n = 231), 2 (n = 242) and 3 (n = 84). Patients with HF-FAN scores of 3 were older, had higher brain natriuretic peptide levels, and larger inferior vena cava diameters. Kaplan-Meier analysis showed a direct correlation between higher HF-FAN scores and occurrence of the primary endpoint (log-rank P < 0.001). Cox proportional hazard analysis revealed a higher HF-FAN score was significantly associated with a worse prognosis even after adjustment for possible prognostic factors. Changing from the FAN score to HF-FAN score provided significant continuous net reclassification improvement. In conclusion, the HF-FAN score at discharge was useful for risk stratification in patients hospitalized with heart failure. The HF-FAN score might be more suitable for patients with heart failure than the FAN score.

Pulmonary nodule volumetric accuracy of a deep learning-based reconstruction algorithm in low-dose computed tomography: A phantom study.

PURPOSE: To compare the image properties and pulmonary nodule volumetric accuracies among deep learning-based reconstruction (DLR), filtered back projection (FBP), and hybrid iterative reconstruction (hybrid IR) in low-dose computed tomography (LDCT). METHODS: A multipurpose chest phantom containing artificial spherical pulmonary nodules with 5-, 8-, 10-, and 12-mm diameters and Hounsfield units (HUs) of -630 and +100 HU was scanned 20 times at a standard dose, based on a low-dose screening CT trial, and at 1/2, 1/6, and 1/12 of the standard dose. To assess noise reduction performance and volumetric accuracy, the standard deviations (SDs) of the pixel values and volumetric percentage errors (PEs) were compared among FBP, hybrid IR, and DLR. The noise non-stationarity index (NNSI) was calculated from 20 image replicates and compared among FBP, hybrid IR, and DLR to evaluate noise stationarity. RESULTS: The SD reduction rates for FBP in hybrid IR and DLR were 62 %-85 % and 79 %-90 %, respectively. For the four nodules with +100 HU, the PE of all reconstruction methods was <±25 % (not clinically relevant). For the four nodules with -630 HU, the PEs were equivalent or lower for hybrid IR and DLR than for FBP, and the PE difference between hybrid IR and DLR ranged from 0 % to 7%. The NNSI was significantly higher for DLR than for FBP and hybrid IR (p < 0.01). CONCLUSIONS: Greater noise suppression was achieved with DLR than with hybrid IR without compromising nodule volumetric accuracy in LDCT despite the representative noise non-stationarity.

Deep learning-based Hounsfield unit value measurement method for bolus tracking images in cerebral computed tomography angiography.

BACKGROUND: Patient movement during bolus tracking (BT) impairs the accuracy of Hounsfield unit (HU) measurements. This study assesses the accuracy of measuring HU values in the internal carotid artery (ICA) using an original deep learning (DL)-based method as compared with using the conventional region of interest (ROI) setting method. METHOD: A total of 722 BT images of 127 patients who underwent cerebral computed tomography angiography were selected retrospectively and divided into groups for training data, validation data, and test data. To segment the ICA using our proposed method, DL was performed using a convolutional neural network. The HU values in the ICA were obtained using our DL-based method and the ROI setting method. The ROI setting was performed with and without correcting for patient body movement (corrected ROI and settled ROI). We compared the proposed DL-based method with settled ROI to evaluate HU value differences from the corrected ROI, based on whether or not patients experienced involuntary movement during BT image acquisition. RESULTS: Differences in HU values from the corrected ROI in the settled ROI and the proposed method were 23.8 ± 12.7 HU and 9.0 ± 6.4 HU in patients with body movement and 1.1 ± 1.6 HU and 3.9 ± 4.7 HU in patients without body movement, respectively. There were significant differences in both comparisons (P < 0.01). CONCLUSION: DL-based method can improve the accuracy of HU value measurements for ICA in BT images with patient involuntary movement.

Attenuation correction using deep learning for brain perfusion SPECT images.

OBJECTIVE: Non-uniform attenuation correction using computed tomography (CT) improves the image quality and quantification of single-photon emission computed tomography (SPECT). However, it is not widely used because it requires a SPECT/CT scanner. This study constructs a convolutional neural network (CNN) to generate attenuation-corrected SPECT images directly from non-attenuation-corrected SPECT images. METHODS: We constructed an auto-encoder (AE) using a CNN to correct the attenuation in brain perfusion SPECT images. SPECT image datasets of 270 (44,528 slices including augmentation), 60 (5002 slices), and 30 (2558 slices) cases were used for training, validation, and testing, respectively. The acquired projection data were reconstructed in three patterns: uniform attenuation correction using Chang's method (Chang-AC), non-uniform attenuation correction using CT (CT-AC), and no attenuation correction (No-AC). The AE learned an end-to-end mapping between the No-AC and CT-AC images. The No-AC images in the test dataset were loaded into the trained AE, which generated images simulating the CT-AC images as output. The generated SPECT images were employed as attenuation-corrected images using the AE (AE-AC). The accuracy of the AE-AC images was evaluated in terms of the peak signal-to-noise ratio (PSNR) and the structural similarity metric (SSIM). The intensities of the AE-AC and CT-AC images were compared by voxel-by-voxel and region-by-region analysis. RESULTS: The PSNRs of the AE-AC and Chang-AC images, compared using CT-AC images, were 62.2, and 57.9, and their SSIM values were 0.9995 and 0.9985, respectively. The AE-AC and CT-AC images were visually and statistically in good agreement. CONCLUSIONS: The proposed AE-AC method yields highly accurate attenuation-corrected brain perfusion SPECT images.

[Radiological Technology for Targeted Radionuclide Therapy].

Targeted radioisotope therapy (TRT) is a radiotherapy using radioisotope or drug incorporating it and has been used as a treatment for selectively irradiating cancer cells. In recent years, interest in TRT has increased due to improvements in radionuclide production technology, development of new drugs and imaging modalities, and improvements in radiation technology. In order to enhance the effect of TRT, measurement of individual radiation doses to tumor tissue and organs at risk is important using highly quantitative nuclear medicine images. In this paper, we present a review of literature on optimization of TRT, which is a new research area from the perspective of radiation technology.

Manual on the proper use of yttrium-90-labeled anti-P-cadherin antibody injection for radionuclide therapy in clinical trials.

We present the guideline for use of yttrium-90-labeled anti-P-cadherin antibody injection for radionuclide therapy in clinical trials on the basis of radiation safety issues in Japan. This guideline was prepared by a study supported by the Ministry of Health, Labour, and Welfare, and approved by the Japanese Society of Nuclear Medicine. Treatment using yttrium-90-labeled anti-P-cadherin antibody injection in Japan should be carried out according to this guideline. Although this guideline is applied in Japan, the issues for radiation protection shown here are considered internationally useful as well. Only the original Japanese version is the formal document.

[Global Trends Survey for Targeted Radionuclide Therapy].

Radionuclide therapy has been used to help manage a range of diseases and has a role of growing importance, with an increasing impact on clinical practice globally. A survey in the field of Radionuclide therapy was conducted by reviewing 4199 science abstracts of main conference (Japanese Society of Radiological Technology, Japanese Society of Nuclear Medicine, Japanese Society of Nuclear Medicine Technology, Society of Nuclear Medicine and Molecular Imaging, European Association of Nuclear Medicine) held in 2016. This survey consisted of research content, modality for evaluation, dosimetry, radionuclide, and researcher's country. There tend to be a lot of studies related to targeted radionuclide therapy more than Japan (4%) in the United States (11%) or Europe (13%). Radiopharmaceuticals still un-approving in Japan were used in some of these studies. And many studies on dosimetry using PET or SPECT imaging were confirmed in the United States (37%) or in Europe (25%) compared with in Japan (14%). This survey has clarified the current status of Japan and global trend in the field of radionuclide therapy.

High susceptibility of mouse newborns to delayed appearance of DNA double-strand breaks in neural stem/progenitor cells exposed to ionizing radiation.

Fetal brains are known to be extremely sensitive to ionizing radiation, which can induce structural and functional defects in the developing brain. However, there is less data on the effects of radiation on newborn brains. To determine the radiation sensitivity in newborn brains, we determined the number of DNA double-strand breaks (DSBs) appearing at later stage post-irradiation in neural stem/progenitor cells (NSPCs) of mouse newborns <3 days old, and compared it with the numbers of DSBs of fetal, 1-week-neonate, 2-week-neonate, and adult mice. DSBs in the nucleus were quantified by counting the number of foci of phosphorylated histone H2AX (γ-H2AX) in NPSCs using a newly developed computer program. Then, we irradiated 14-day fetuses, newborns <3 days old, 1-week-old neonates, 2-week-old neonates, and 12-week-old adult mice with 2 Gy of X-rays. At 6-7 weeks post-irradiation, the brain tissues isolated from the mice were incubated, and DSBs in the growing neurospheres were counted using a focus-counting program. The delayed appearance of DSBs by X-irradiation was evident in NSPCs derived from newborns <3 days old, as well as in 1-week-old neonates, 2-week-old neonates and adult mice, but not 14-day fetuses, at 6-7 weeks post-irradiation. It was of particular interest that the NSPCs of newborns were 2.5-fold more susceptible than those of adults to radiation-induced delayed appearance of DSBs, indicating that newborns <3 days old are the most vulnerable to the delayed effects of radiation among the mouse groups examined.

[Impact to Z-score Mapping of Hyperacute Stroke Images by Computed Tomography in Adaptive Statistical Iterative Reconstruction].

The purpose of this study was to evaluate the effect of a hybrid-type iterative reconstruction method on Z-score mapping of hyperacute stroke in unenhanced computed tomography (CT) images. We used a hybrid-type iterative reconstruction [adaptive statistical iterative reconstruction (ASiR)] implemented in a CT system (Optima CT660 Pro advance, GE Healthcare). With 15 normal brain cases, we reconstructed CT images with a filtered back projection (FBP) and ASiR with a blending factor of 100% (ASiR100%). Two standardized normal brain data were created from normal databases of FBP images (FBP-NDB) and ASiR100% images (ASiR-NDB), and standard deviation (SD) values in basal ganglia were measured. The Z-score mapping was performed for 12 hyperacute stroke cases by using FBP-NDB and ASiR-NDB, and compared Z-score value on hyperacute stroke area and normal area between FBP-NDB and ASiR-NDB. By using ASiR-NDB, the SD value of standardized brain was decreased by 16%. The Z-score value of ASiR-NDB on hyperacute stroke area was significantly higher than FBP-NDB (p<0.05). Therefore, the use of images reconstructed with ASiR100% for Z-score mapping had potential to improve the accuracy of Z-score mapping.

Repair kinetics of DNA double-strand breaks and incidence of apoptosis in mouse neural stem/progenitor cells and their differentiated neurons exposed to ionizing radiation.

Neuronal loss leads to neurodegenerative disorders, including Alzheimer's disease, Parkinson's disease and Huntington's disease. Because of their long lifespans, neurons are assumed to possess highly efficient DNA repair ability and to be able to protect themselves from deleterious DNA damage such as DNA double-strand breaks (DSBs) produced by intrinsic and extrinsic sources. However, it remains largely unknown whether the DSB repair ability of neurons is more efficient compared with that of other cells. Here, we investigated the repair kinetics of X-ray-induced DSBs in mouse neural cells by scoring the number of phosphorylated 53BP1 foci post irradiation. We found that p53-independent apoptosis was induced time dependently during differentiation from neural stem/progenitor cells (NSPCs) into neurons in culture for 48 h. DSB repair in neurons differentiated from NSPCs in culture was faster than that in mouse embryonic fibroblasts (MEFs), possibly due to the higher DNA-dependent protein kinase activity, but it was similar to that in NSPCs. Further, the incidence of p53-dependent apoptosis induced by X-irradiation in neurons was significantly higher than that in NSPCs. This difference in response of X-ray-induced apoptosis between neurons and NSPCs may reflect a difference in the fidelity of non-homologous end joining or a differential sensitivity to DNA damage other than DSBs.

18F-FDG PET/CT Features of Chronic Sclerosing Sialadenitis Presenting as Localized IgG4-Related Disease.

Chronic sclerosing sialadenitis is a benign inflammatory condition that most commonly affects the submandibular gland in elderly individuals. It is currently known to belong to the spectrum of IgG4-related systemic diseases, which is reflected by systemic involvement on F-FDG PET/CT images. We presented a case of a 73-year-old man with histologically proven IgG4-related chronic sclerosing sialadenitis, unilateral localized form, on whole-body F-FDG PET/CT images that mimicked submandibular carcinoma with lymph node metastasis.

Estimation of activity of administered 18F-fluorodeoxyglucose by measurement of the dose equivalent rate on the right temporal region of the head.

BACKGROUND: Positron emission tomography (PET) with 18F-fluorodeoxyglucose (FDG) is now a routine procedure for the management of cancer patients. Intravenous administration of FDG is sometimes halted due to troubles. In such cases, estimations of the FDG dosage injected prior to halting administration may be helpful. We have established a method of estimating the activity of FDG to patients on the basis of the dose equivalent rate on the surface of the right temporal region of the head. The correlation of actual administered dosage with independent variables, such as the dose equivalent rate on the right temporal region of the head, age, sex, and body weight, was analyzed using multiple regression analysis to obtain linear, quadratic, and cubic regression equations. RESULTS: When entering independent variables, the cubic regression equation could be used to estimate an administered dosage with an accuracy of ±10 % for 62 % of all patients and ±20 % for 90 % of all patients. CONCLUSIONS: We conclude that this method is useful for estimating the administered dosage from the dose equivalent rate on the temporal region of the head.

Performance of 11C-Pittsburgh Compound B PET Binding Potential Images in the Detection of Amyloid Deposits on Equivocal Static Images.

UNLABELLED: The goal of this study was to clarify whether binding potential (BP) images using (11)C-Pittsburgh compound B ((11)C-PiB) and dynamic PET can reliably detect cortical amyloid deposits for patients whose (11)C-PiB PET static images are ambiguous and whether visual ratings are affected by white matter retention. METHODS: Static and BP images were constructed for 85 consecutive patients with cognitive impairment after (11)C-PiB dynamic PET. Cortical uptake was visually assessed as positive, negative, or equivocal for both types of images. Quantitatively, the standardized uptake value ratio (SUVR) from the static image, the nondisplaceable BP from the dynamic image for mean gray matter uptake, and the ratio of gray matter uptake to white matter retention were compared among (11)C-PiB-positive, (11)C-PiB-equivocal, and (11)C-PiB-negative groups. RESULTS: Forty-three scans were visually assessed as (11)C-PiB-positive in both the static and the BP images. Ten scans were (11)C-PiB-equivocal in the static images. In 8 of them, the BP images were (11)C-PiB-positive, whereas the other 2 were (11)C-PiB-equivocal. Thirty-two scans were assessed as (11)C-PiB-negative in the static images. In the BP images, 4 were (11)C-PiB-positive and 2 were (11)C-PiB-equivocal. The mean gray matter uptake of (11)C-PiB in SUVR and nondisplaceable BP, respectively, showed statistically significant differences among the (11)C-PiB-positive, (11)C-PiB-equivocal, and (11)C-PiB-negative groups. The ratio of gray matter uptake to white matter retention was lower in the BP images than static images from the (11)C-PiB-negative and (11)C-PiB-equivocal groups, whereas it was higher in the (11)C-PiB-positive group. CONCLUSION: (11)C-PiB PET BP images can clarify visual interpretation of clinical static (11)C-PiB-equivocal images by reducing the interference of nonspecific white matter retention. We conclude that (11)C-PiB-equivocal PET findings on static images reflect cortical amyloid deposits, which can be verified using BP images. Furthermore, quantitative assessments, such as SUVR and nondisplaceable BP, are of no use for correctly rating equivocal visual findings.

Heterogeneity of intratumoral (111)In-ibritumomab tiuxetan and (18)F-FDG distribution in association with therapeutic response in radioimmunotherapy for B-cell non-Hodgkin's lymphoma.

BACKGROUND: The purpose of this study was to quantitatively evaluate the tumor accumulation and heterogeneity of (111)In-ibritumomab tiuxetan (Zevalin®) and tumor accumulation of (18)F-fluoro-deoxyglucose (FDG) and compare them to the tumor response in B-cell non-Hodgkin's lymphoma patients receiving (90)Y-ibritumomab tiuxetan (Zevalin®) therapy. METHODS: Sixteen patients with histologically confirmed non-Hodgkin's B-cell lymphoma who underwent (90)Y-ibritumomab tiuxetan therapy along with (111)In-ibritumomab tiuxetan single-photon emission computerized tomography (SPECT)/CT and FDG positron emission tomography (PET)/CT were enrolled in this retrospective study. On pretherapeutic FDG PET/CT images, the maximum standardized uptake value (SUVmax) was measured. On SPECT/CT images, a percentage of the injected dose per gram (%ID/g) and SUVmax of (111)In-ibritumomab tiuxetan were measured at 48 h after its administration. The skewness and kurtosis of the voxel distribution were calculated to evaluate the intratumoral heterogeneity of tumor accumulation. As another intratumoral heterogeneity index, cumulative SUV-volume histograms describing the percentage of the total tumor volume above the percentage thresholds of pretherapeutic FDG and (111)In-ibritumomab tiuxetan SUVmax (area under the curve of the cumulative SUV histograms (AUC-CSH)) were calculated. All lesions (n = 42) were classified into responders and non-responders lesion-by-lesion on pre- and post-therapeutic CT images. RESULTS: A positive correlation was observed between the FDG SUVmax and accumulation of (111)In-ibritumomab tiuxetan in lesions. A significant difference in pretherapeutic FDG SUVmax was observed between responders and non-responders, while no significant difference in (111)In-ibritumomab tiuxetan SUVmax was observed between the two groups. In contrast, voxel distribution of FDG demonstrated no significant differences in the three heterogeneity indices between responders and non-responders, while (111)In-ibritumomab tiuxetan demonstrated skewness of 0.58 ± 0.16 and 0.73 ± 0.24 (p < 0.05), kurtosis of 2.39 ± 0.32 and 2.78 ± 0.53 (p < 0.02), and AUC-CSH of 0.37 ± 0.04 and 0.34 ± 0.05 (p < 0.05) for responders and non-responders. CONCLUSIONS: Pretherapeutic FDG accumulation was predictive of the tumor response in (90)Y-ibritumomab tiuxetan therapy. The heterogeneity of the intratumoral distribution rather than the absolute level of (111)In-ibritumomab tiuxetan was correlated with the tumor response.

Regional glucose metabolic reduction in dementia with Lewy bodies is independent of amyloid deposition.

PURPOSE: There is evidence that some cases of patients with dementia with Lewy bodies (DLB) can demonstrate Alzheimer disease (AD) like reduced glucose metabolism without amyloid deposition. The aim of this study was to clarify whether regional hypometabolism is related to amyloid deposits in the DLB brain and measure the degree of regional hypometabolism. METHODS: Ten consecutive subjects with DLB and 10 AD patients who underwent both Pittsburgh compound B (PiB)-PET and (18)F-fluoro-2-deoxyglucose (FDG)-PET were included in this study. Regional standardized uptake value ratio (SUVR)s normalised to cerebellar cortices were calculated in the FDG- and PiB-PET images. RESULTS: All AD patients and five DLB patients showed amyloid deposits (PiB positive). In the DLB group the parietotemporal and occipital metabolism were significantly lower than those in the AD group but there was no difference between the posterior cingulate hypometabolism between DLB and AD groups. There were no differences in regional glucose metabolism between PiB positive and negative DLB patients. CONCLUSIONS: In the DLB brain, it is suggested that decreased regional glucose metabolism is unrelated to amyloid deposits, although the hypometabolic area overlaps with the AD hypometabolic area and the degree of parietotemporal and occipital hypometabolism in DLB brain is much larger than that in AD brain.

Investigation of (11)C-PiB equivocal PET findings.

OBJECTIVE: We have encountered occasional equivocal findings when assessing cerebral cortical amyloid retention with (11)C-Pittsburgh compound B (PiB) PET. We investigated the diagnostic significance of equivocal PiB PET findings. METHODS: This retrospective study included 101 consecutive patients complaining of cognitive disorders (30 Alzheimer's disease, 25 mild cognitive impairment, 8 Lewy body disease, 7 frontotemporal lobar degeneration, 31 others) who underwent both (11)C-PiB PET and (18)F-fluorodeoxy-D-glucose (FDG) PET. We visually classified PiB-positive, PiB-equivocal or PiB-negative ratings according to cortical uptake. For quantitative assessments of PiB PET, standard uptake values referred to cerebellar cortex (SUVR) were calculated in regional template volume of interests (frontal, temporoparietal, precuneus/posterior cingulate cortex, cerebral white matter and cerebellar cortex). The results of visual assessment were compared with the regional and mean cortical SUVRs and cortical-to-white matter ratio of PiB uptake, as well as clinical and FDG PET findings. RESULTS: Among the 101 scans, 41 were PiB negative, 11 were PiB equivocal, and 49 were rated PiB positive in the visual assessments. The mean cortical SUVR and cortical-to-white matter ratio were 0.97 ± 0.07 and 0.57 ± 0.21 in PiB-negative, 1.51 ± 0.17 and 0.75 ± 0.06 in PiB equivocal and 2.10 ± 0.33 and 0.97 ± 0.11 in PiB-positive group, respectively. Nine of 11 subjects with PiB-equivocal findings had cognitive impairments and FDG distribution compatible with Alzheimer's disease or dementia with Lewy bodies. CONCLUSIONS: We considered equivocal visual findings on PiB PET equivalent to PiB-positive with slight cortical uptake. In addition, slight cortical amyloid deposits were considered to cause cerebral metabolic abnormality and cognitive impairment. Although mean cortical SUVR was more sensitive than visual assessment because of low cortical-to-white matter contrast due to non-specific accumulation in white matter, it is important not to overlook small amounts of cortical uptake of PiB in visual inspection for exact diagnosis.

Dynamic sequence respiratory gated perfusion pulmonary SPECT without external tracking device.

OBJECTIVE: The purpose of this study was to develop and evaluate a new method for respiratory gated pulmonary perfusion SPECT (RGPS) based on dynamic acquisition without using an external tracking device (ETD) or list-mode data acquisition. METHODS: In the phantom study, our method used a dynamic sequence technique, which was specified by sequences of 50-ms acquisition during 30 s per view of SPECT instead of using an ETD. For this purpose, we created a computer program that identified respiratory phases by calculating the center of activity (COA) in each dynamic frame image. We compared RGPS using the dynamic sequence acquisition (RGPS-DS) and RGPS using ETD (RGPS-ETD) in phantom studies employing a cylinder phantom filled with technetium-99m solution attached to an instrument providing a simple harmonic motion. In the patient study, RGPS-DS was applied to data collected from 3 patients during a routine study of Tc-MAA pulmonary perfusion SPECT. RESULTS: In the phantom study, the calculation of COA indicated a good agreement between RGPS-DS and RGPS-ETD. With an oscillatory phantom movement amplitude of 30 mm, the amplitudes determined by RGPS-DS and RGPS-ETD (28.36 and 27.58 mm, respectively) were identical on considering a pixel size of 4.66 mm for reconstructed SPECT images. In the patient study, applicability of our method to patient data was demonstrated. CONCLUSIONS: We have showed the feasibility of our method to obtain RGPS without ETD, and conclude that RGPS-DS may be an innovative and efficient technique in respiratory gated pulmonary perfusion SPECT. Further studies with a larger number of patients should demonstrate the accuracy of our method.

[Evaluation of patient dose from diagnostic X-ray using glass badges].

Radiography is used in medical practices based on the principles of justification and optimization. Patients' exposure doses should be kept as low as still allows for image quality that does not disturb the diagnostic processes. To optimize diagnostic radiological procedures, the international commission on radiological protection (ICRP) advocated the establishment of diagnosis reference levels (DRLs) in the new basic recommendation (Publication 103) in 2007 by stating that "The DRL should be expressed as a readily measurable patient-dose-related quantity for the specified procedure." In this context, a simple and standardized dosimetric method is needed to verify the adaptability of a radiation dose to the DRLs. As a measuring instrument that has good availability, high accuracy, and easy operability, we adopted the glass badge system, which has been used for individual exposure dose management. We evaluated the accuracy of the system as a tool of simplified dosimetry of diagnostic X-rays by comparing it to the standard dosimetry of an ionization chamber. In an energy range of 50 to 140 kV for X-ray exposure, the glass badge showed values within 7% of or closer to those measured by the standard ionization chamber. Moreover, the glass badge measurement was independent of the rectification modes of the X-ray tubes. In conclusion, glass badge measurement is feasible for verifying diagnostic X-ray doses in relation to DRLs and can be widely used in hospitals and clinics.