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The International Commission on Radiological Protection (ICRP) 118th recommendation significantly reduced the threshold dose for cataract development from 8 to 0.5 Gy. Equivalent dose limits for the crystalline lenses of radiation workers are being reviewed for individual countries. Interventional radiology (IR) procedures are less invasive than surgery and have become widespread; however, there are concerns about exposure not only to patients but also to staff, including operators. Therefore, in this study, we used a human phantom to measure the near-lens dose of the operators (cardiologists, neurosurgeons and radiologists) and estimated the operator’s lens dose for every major procedure in each clinical department; this was found to vary. Owing to the different imaging and fluoroscopy conditions of each department, and the varying ratio of fluoroscopy to radiography, it is necessary to measure the lens dose for each condition, as in this study. In addition, this study explains the differences between the protective effect of various safety equipment and the appropriate use of protective plates; it can contribute to the reduction of lens doses for operators.

The estimation of functional connectivity (FC) measures using resting state functional MRI (fMRI) is often affected by head motion during functional imaging scans. Head motion is more common in the elderly than in young participants and could therefore affect the evaluation of age-related changes in brain networks. Thus, this study aimed to investigate the influence of head motion in FC estimation when evaluating age-related changes in brain networks.This study involved 132 healthy volunteers divided into 3 groups: elderly participants with high motion (OldHM, mean age (±SD) = 69.6 (±5.31), N = 44), elderly participants with low motion (OldLM, mean age (±SD) = 68.7 (±4.59), N = 43), and young adult participants with low motion (YugLM, mean age (±SD) = 27.6 (±5.26), N = 45). Head motion was quantified using the mean of the framewise displacement of resting state fMRI data. After preprocessing all resting state fMRI datasets, several resting state networks (RSNs) were extracted using independent component analysis (ICA). In addition, several network metrics were also calculated using network analysis. These FC measures were then compared among the 3 groups.In ICA, the number of voxels with significant differences in RSNs was higher in YugLM vs. OldLM comparison than in YugLM vs. OldHM. In network analysis, all network metrics showed significant (P0.05) differences in comparisons involving low vs. high motion groups (OldHM vs. OldLM and OldHM vs. YugLM). However, there was no significant (P0.05) difference in the comparison involving the low motion groups (OldLM vs. YugLM).Our findings showed that head motion during functional imaging could significantly affect the evaluation of age-related brain network changes using resting state fMRI data.

Purpose The conventional weighted computed tomography dose index (CTDIw) may not be suitable for cone-beam computed tomography (CBCT) dosimetry because a cross-sectional dose distribution is angularly inhomogeneous owing to partial angle irradiations. This study was conducted to develop a new dose metric (f(0)CBw) for CBCT dosimetry to determine a more accurate average dose in the central cross-sectional plane of a cylindrical phantom using Monte Carlo simulations. Methods First, cross-sectional dose distributions of cylindrical polymethyl methacrylate phantoms over a wide range of phantom diameters (8–40 cm) were calculated for various CBCT scan protocols. Then, by obtaining linear least-squares fits of the full datasets of the cross-sectional dose distributions, the optimal radial positions, which represented measurement positions for the average phantom dose, were determined. Finally, the f(0)CBw method was developed by averaging point doses at the optimal radial positions of the phantoms. To demonstrate its validity, the relative differences between the average doses and each dose index value were estimated for the devised f(0)CBw, conventional CTDIw, and Haba’s CTDIw methods, respectively. Results The relative differences between the average doses and each dose index value were within 4.1%, 16.7%, and 11.9% for the devised, conventional CTDIw, and Haba’s CTDIw methods, respectively. Conclusions The devised f(0)CBw value was calculated by averaging four “point doses” at 90° intervals and the optimal radial positions of the cylindrical phantom. The devised method can estimate the average dose more accurately than the previously developed CTDIw methods for CBCT dosimetry.

The computed tomography cortical index (CTCI), computed tomography mandibular index (CTMI), and computed tomography index (inferior) [CTI(I)] are indexes obtained from cone-beam computed tomography images for the assessment of the mandibular cortex quality for implant planning or osteoporosis. However, cross-sectional image reconstruction for the measurements is labor-intensive. This study aimed to develop and evaluate a method to automatically reconstruct cross-sectional images and measure the cortex width in all areas inferior to the mental foramen (MF). Seventy-one women (mean age: 52.4 years; range: 20–78 years) were enrolled. They were divided into four age and CTCI groups, including females younger (FY) and females older (FO) than 50 years (C1: normal, C2: mild/moderate erosion, and C3: severe porosity). Automatic and manual measurements of CTMI and CTI(I) were compared, and the inter- and intraobserver agreements were assessed using the intraclass correlation coefficient (ICC). The relationships between CTMI or CTI(I) and CTCI were also assessed. The mean processing times for reconstruction and measurements were 31.9 s and 1.22 s, respectively. ICCs for the comparison of automatic and manual measurements were 0.932 and 0.993 in the C1 and C2/C3 groups, respectively. Significant differences in CTMI and CTI(I) were observed between the FY or the FO-C1 and FO-C3 groups (p

Vessel sealing devices have been described to be effective, allowing to perform procedures with reduced blood loss and shorter operative times in head and neck surgery. Since the traditional vessel sealing devices are all disposable and expensive, there are not often used even in advanced cancer surgery in terms of cost. On the other hand, ‘marClampCut IQ’ (KLS Martin, Tuttlingen, Germany) is a new reusable vessel sealing device. In this clinical study, a traditional disposable device ‘LigaSure small jaw’ and a reusable device ‘marClampCut IQ’ were particularly compared regarding medical expenses and efficacy in modified total neck dissection. Between October 2014 and April 2020, modified total neck dissections were performed using the ‘LigaSure small jaw’ for 56 patients aged from 26y/o to 88y/o (median:66.0y/o). The ‘marClampCut IQ’ was mainly used between November 2018 and April 2020 for 64 modified total neck dissections in patients aged from 31y/o to 91y/o (median:70.5y/o). The amount of blood loss was significantly more in the ‘LigaSure small jaw’ group than in the ‘marClampCut IQ’ group (U-test, P = 0.006). There were no significant differences in age and operation time between the ‘LigaSure small jaw’ group and the ‘marClampCut IQ’ group. When calculated based on the list price in Japan, ‘LigaSure small jaw’ costed $1,000 each; on the other hand, ‘marClampCut IQ’ costed $240 per operation. We found that we could save $760 per operation using ‘marClampCut IQ’. The new reusable device ‘marClampCut IQ’ provided similar clinical efficacy and safety with a highly reduced cost when compared to the disposable device ‘LigaSure small jaw’ in this clinical study of modified total neck dissection.

Estimating organ absorbed doses in consideration of person-specific parameters is important for radiation protection in diagnostic nuclear medicine. This study proposes a straightforward method for estimating the organ dose that reflects a specific organ mass by scaling the reference organ dose using the inverse ratio of the specific organ mass to the reference organ mass. For the administration of radiopharmaceuticals labelled by 99mTc or 123I, the organ doses for the liver, spleen, red marrow and thyroid obtained by the method were compared with those generated by a Monte Carlo simulation. The discrepancies were less than 14% for the liver, spleen and thyroid. Conversely, in some cases, the red marrow discrepancies were greater than 30% due to the wide distribution of red marrow in the trunk and head regions. This study confirms that the method of scaling organ doses can be effective for estimating mass-specific doses for solid organs.

In multisite studies, differences in imaging acquisition systems could affect the reproducibility of the results when examining changes in brain function using resting-state functional magnetic resonance imaging (rs-fMRI). This is also important for longitudinal studies, in which changes in equipment settings can occur. This study examined the reproducibility of functional connectivity (FC) metrics estimated from rs-fMRI data acquired using scanner receiver coils with different numbers of channels. This study involved 80 rs-fMRI datasets from 20 healthy volunteers scanned in two independent imaging sessions using both 12- and 32-channel coils for each session. We used independent component analysis (ICA) to evaluate the FC of canonical resting-state networks (RSNs) and graph theory to calculate several whole-brain network metrics. The effect of global signal regression (GSR) as a preprocessing step was also considered. Comparisons within and between receiver coils were performed. Irrespective of the GSR, RSNs derived from rs-fMRI data acquired using the same receiver coil were reproducible, but not from different receiver coils. However, both the GSR and the channel count of the receiver coil have discernible effects on the reproducibility of network metrics estimated using whole-brain network analysis. The data acquired using the 32-channel coil tended to have better reproducibility than those acquired using the 12-channel coil. Our findings suggest that the reproducibility of FC metrics estimated from rs-fMRI data acquired using different receiver coils showed some level of dependence on the preprocessing method and the type of analysis performed.

Accumulating evidence from anatomical and neuroimaging studies suggests that the cerebellum is engaged in a variety of motor and cognitive tasks. Given its various functions, a key question is whether the cerebellum also plays an important role in the brain's integrative functions. Here, we hypothesize the existence of connector regions, also known as connector hubs, where multiple resting state networks converged in the cerebellum. To verify this, we employed a recently developed voxel-level network measure called functional connectivity overlap ratio (FCOR), which could be used to quantify the spatial extent of a region's connection to several large-scale cortical networks. Using resting state functional MRI data from 101 healthy participants, cerebellar FCOR maps were constructed and used to identify the locations of connector hubs in the cerebellum. Results showed that a number of cerebellar regions exhibited strong connectivity with multiple functional networks, verifying our hypothesis. These highly connected regions were located in the posterior cerebellum, especially in lobules VI, VII, and IX, and mainly connected to the core neurocognitive networks such as default mode and executive control networks. Regions associated with the sensorimotor network were also localized in lobule V, VI, and VIII, albeit in small clusters. These cerebellar connector hubs may play an essential role in the processing of information across the core neurocognitive networks.

Hemangiomas require appropriate treatments with controlled intraoperative bleeding. Even for a small hemangioma, the treatment is usually provided under general anesthesia to control bleeding. However, in the case of the patients who are at high risk of surgery under general anesthesia, a surgical treatment method must be considered under local anesthesia. We performed polypectomy for the resection of a small tongue hemangioma in an 88-year-old patient under local anesthesia. The device for polypectomy is suitable for the resection of a small hemangioma of the tongue, even for a patient who is at risk for surgery under general anesthesia.

Healthy aging is associated with structural and functional changes in the brain even in individuals who are free of neurodegenerative diseases. Using resting state functional magnetic resonance imaging data from a carefully selected cohort of participants, we examined cross sectional changes in the functional organization of several large-scale brain networks over the adult lifespan and its potential association with general cognitive performance. Converging results from multiple analyses at the voxel, node, and network levels showed widespread reorganization of functional brain networks with increasing age. Specifically, the primary processing (visual and sensorimotor) and visuospatial (dorsal attention) networks showed diminished network integrity, while the so-called core neurocognitive (executive control, salience, and default mode) and basal ganglia networks exhibited relatively preserved between-network connections. The visuospatial and precuneus networks also showed significantly more widespread increased connectivity with other networks. Graph analysis suggested that this reorganization progressed towards a more integrated network topology. General cognitive performance, assessed by Addenbrooke’s Cognitive Examination-Revised total score, was positively correlated with between-network connectivity among the core neurocognitive and basal ganglia networks and the integrity of the primary processing and visuospatial networks. Mediation analyses further indicated that the observed association between aging and relative decline in cognitive performance could be mediated by changes in relevant functional connectivity measures. Overall, these findings provided further evidence supporting widespread age-related brain network reorganization and its potential association with general cognitive performance during healthy aging.

Neuroimaging studies have shown that the brain is functionally organized into several large-scale brain networks. Within these networks are regions that are widely connected to several other regions within and/or outside the network. Regions that connect to several other networks, known as connector hubs, are believed to be crucial for information transfer and between-network communication within the brain. To identify regions with high between-network connectivity at the voxel level, we introduced a novel metric called functional connectivity overlap ratio (FCOR), which quantifies the spatial extent of a region's connection to a given network. Using resting state functional magnetic resonance imaging data, FCOR maps were generated for several well-known large-scale resting state networks (RSNs) and used to examine the relevant associations among different RSNs, identify connector hub regions in the cerebral cortex, and elucidate the hierarchical functional organization of the brain. Constructed FCOR maps revealed a strong association among the core neurocognitive networks (default mode, salience, and executive control) as well as among primary processing networks (sensorimotor, auditory, and visual). Prominent connector hubs were identified in the bilateral middle frontal gyrus, posterior cingulate, lateral parietal, middle temporal, dorsal anterior cingulate, and anterior insula, among others, regions mostly associated with the core neurocognitive networks. Finally, clustering the whole brain using FCOR features yielded a topological organization that arranges brain regions into a hierarchy of information processing systems with the primary processing systems at one end and the heteromodal systems comprising connector hubs at the other end.

Distribution of radiation by C-arm cone-beam computed tomography (CBCT) in the angiographic suite and effectiveness of protection devices were assessed. CBCT image of a human phantom was obtained by a rotation of 220 degrees during 8 seconds of exposure. One hundred and twelve dosimeters were placed at different positions around the beam entry site, and color maps of dose distributions were drawn for horizontal and vertical planes. The measurements showed the highest radiation dose over 600 μGy by a single CBCT image acquisition at a distance of 60 cm from the beam entry site and a height of 90 cm from the floor. The color maps demonstrated the dose distribution to be more intense at the bilateral directions of the phantom. With the use of a ceiling-mounted transparent lead-acryl screen and a table-suspended lead curtain, the doses were reduced by 45–92 % at a direction of 210 degrees and a distance of 120 cm.

X-ray image evaluation is commonly performed by determining the detective quantum efficiency (DQE). DQE is calculated with a presampled modulation transfer function (MTF), incident photon fluence, and digital noise power spectrum (NPS). Accurate evaluation of MTF, incident photon fluence, and NPS is important for precise DQE determination. In this study, we focused on the accuracy of the incident photon fluence in mammography. The incident photon fluence is calculated using the squared signal-to-noise ratio (SNRin2) value as specified in the International Electrotechnical Commission (IEC) 62220-1-2 report. However, the reported SNRin2 values were determined using a computer program, and the reported values may differ from those calculated from an X-ray spectrum that is measured with actual mammography equipment. Therefore, we evaluated the error range of reported SNRin2 values in mammography to assess the accuracy of the incident photon fluence. First, X-ray spectra from various mammography systems were measured with a CdTe spectrometer. Six mammographic X-ray units were used in this study. Second, the SNRin2 values were calculated from the measured X-ray spectra. The calculated values were compared to the reported values. The results show that the percentage differences between the calculated and reported SNRin2 values were within − 4.1% of each other. The results obtained in this study indicate that the SNRin2 values provided in the IEC report are a robust and convenient tool for calculating the incident photon fluence for DQE evaluation in mammography.

The aging brain undergoes structural changes even in very healthy individuals. Quantifying these changes could help disentangle pathologic changes from those associated with the normal human aging process. Using longitudinal magnetic resonance imaging (MRI) data from 227 carefully selected healthy human cohort with age ranging from 50 to 80 years old at baseline scan, we quantified age-related volumetric changes in the brain of healthy human older adults. Longitudinally, the rates of tissue loss in total gray matter (GM) and white matter (WM) were 2497.5 and 2579.8 mm3per year, respectively. Across the whole brain, the rates of GM decline varied with regions in the frontal and parietal lobes having faster rates of decline, whereas some regions in the occipital and temporal lobes appeared relatively preserved. In contrast, cross-sectional changes were mainly observed in the temporal-occipital regions. Similar longitudinal atrophic changes were also observed in subcortical regions including thalamus, hippocampus, putamen, and caudate, whereas the pallidum showed an increasing volume with age. Overall, regions maturing late in development (frontal, parietal) are more vulnerable to longitudinal decline, whereas those that fully mature in the early stage (temporal, occipital) are mainly affected by cross-sectional changes in healthy older cohort. This may suggest that, for a successful healthy aging, the former needs to be maximally developed at an earlier age to compensate for the longitudinal decline later in life and the latter to remain relatively preserved even in old age, consistent with both concepts of reserve and brain maintenance.

Luminescence of water during irradiations of proton-beams or X-ray photons lower energy than the Cerenkov-light threshold is promising for range estimation or the distribution measurements of beams. However it is not yet obvious whether the intensities and distributions are stable with the water conditions such as temperature or addition of solvable materials. It remains also unclear whether the luminescence of water linearly increases with the irradiated proton or X-ray energies. Consequently we measured the luminescence of water during irradiations of proton-beam or X-ray photons lower energy than the Cerenkov-light threshold with different water conditions and energies to evaluate the stability and linearity of luminescence of water. We placed a water phantom set with a proton therapy or X-ray system, luminescence images of water with different conditions and energies were measured with a high-sensitivity cooled charge coupled device (CCD) camera during proton or X-ray irradiations to the water phantom. In the stability measurements, imaging was made for different temperatures of water and addition of inorganic and organic materials to water. In the linearity measurements for the proton, we irradiated with four different energies below Cerenkov light threshold. In the linearity measurements for the X-ray, we irradiated X-ray with different supplied voltages. We evaluated the depth profiles for the luminescence images and evaluated the light intensities and distributions. The results showed that the luminescence of water was quite stable with the water conditions. There were no significant changes of intensities and distributions with the different temperatures. Results from the linearity experiments showed that the luminescence of water linearly increased with their energies. We confirmed that luminescence of water is stable with conditions of water. We also confirmed that the luminescence of water linearly increased with their energies.

It is commonly thought that UV or visible-light luminescence imaging of biological subjects during X-ray irradiation at the energy below 120 keV is impossible because the secondary electrons produced in this energy range do not emit Cerenkov light. Contrary to this consensus, we found UV or visible-light luminescence imaging of the subjects were possible with X-ray irradiations of this energy range. We placed one of the biological subjects in a black box; visible-light luminescence images were measured with a high-sensitivity, cooled charge coupled device (CCD) camera during X-ray irradiation at energy below 120 keV. We also conducted the imaging of air without subjects during irradiation of the same X-ray. The biological subjects emitted visible-light luminescence, and the imaging was possible with the irradiation of the X-ray below 120 keV. The luminescence images were observed in only the X-ray irradiated areas. Also air luminescence images could be obtained and the intensity of the luminescence measured from the images was proportionally increased with the exposure dose. UV or visible-light luminescence imaging of biological subjects was possible during X-ray irradiations lower energy than the Cerenkov-light threshold. The phenomenon was different from general X-ray fluorescence because wavelength of the luminescence is UV or visible-light. The luminescence imaging method is promising for estimating the irradiated area with X-ray, which could be used for interventional radiology (IVR). Also air luminescence imaging would be applied to the exposure dose distribution measurements for X-ray of diagnostic X-ray systems.

Energy Resolving Photon Counting Detectors (ERPCD) have been developed as a medical X-ray imaging application. The ERPCD can analyze energy information of measured X-rays. There is the possibility that quantitative information of an object such as the effective atomic number (Z eff ) can be derived by analyzing the energy information of the X-rays. In order to realize accurate Z eff identification, it is necessary to consider the effect of secondary-produced radiations which are produced by the interaction between incident X-rays and the detector. In addition, these secondary-produced radiations can be transferred to adjacent pixels. In this study, we evaluated the influence of the response function on the measured X-ray spectrum in terms of accuracy of derived Z eff . We focused on CZT, Si, and GaAs detectors, and the response functions of these detectors were reproduced by Monte-Carlo simulations. A detector with an area of 10 mm × 10 mm, a thickness of 1.5 mm, and a pixel size of 200 μm × 200 μm was used for the simulation. Aluminum samples having mass thicknesses of 1, 5, and 10 g/cm2 were used as an object. 50.0 kV polychromatic X-rays were irradiated to the detector area of 1 mm × 1 mm. The X-ray spectra measured within one center pixel were analyzed. The mass attenuation factor "μ/ρ" was calculated from the simulated X-ray spectra of being incident and penetrating the object. The Z eff was derived from the theoretical relationship between μ/ρ and Z eff , and the accuracy was evaluated. It was found that the effect of the response function decreases the accuracy of the derived Z eff . We clarified the energy regions which can derive Z eff accurately. These results are valuable to optimize analytical energy regions for accomplishing accurate Z eff analysis using ERPCD.

Size-specific dose estimate (SSDE) was proposed by the American Association of Physicists in Medicine (AAPM) Task Group 204 to consider the effect of patient size in the x-ray CT dose estimation. Size correction factors to calculate SSDE were derived based on the conventional weighted CT dose index (CTDIw) equation. This study aims to investigate the influence of Bakalyar’s and the authors’ own CTDIw equations on the size correction factors described by the AAPM Task Group 204, using Monte Carlo simulations. The simulations were performed by modeling four types of x-ray CT scanner designs, to compute the dose values in water for cylindrical phantoms with 8–40 cm diameters. CTDI100 method and the AAPM Task Group 111′s proposed method were employed as the CT dosimetry models. Size correction factors were obtained for the computed dose values of various phantom diameters for the conventional, Bakalyar’s, and the authors’ weighting factors. Maximum difference between the size correction factors for the Bakalyar’s weighting factor and those of the AAPM Task Group 204 was 27% for a phantom diameter of 11.2 cm. On the other hand, the size correction factors calculated for the authors’ weighting factor were in good agreement with those from the AAPM Task Group 204 report with a maximum difference of 17%. The results indicate that the SSDE values obtained with the authors’ weighting factor can be evaluated by using the size correction factors reported by the AAPM Task Group 204, which is currently accepted as a standard.

White matter (WM) fiber bundles change dynamically with age. These changes could be driven by alterations in axonal diameter, axonal density, and myelin content. In this study, we applied a novel fixel‐based analysis (FBA) framework to examine these changes throughout the adult lifespan. Using diffusion‐weighted images from a cohort of 293 healthy volunteers (89 males/204 females) from ages 21 to 86 years old, we performed FBA to analyze age‐related changes in microscopic fiber density (FD) and macroscopic fiber morphology (fiber cross section [FC]). Our results showed significant and widespread age‐related alterations in FD and FC across the whole brain. Interestingly, some fiber bundles such as the anterior thalamic radiation, corpus callosum, and superior longitudinal fasciculus only showed significant negative relationship with age in FD values, but not in FC. On the other hand, some segments of the cerebello‐thalamo‐cortical pathway only showed significant negative relationship with age in FC, but not in FD. Analysis at the tract‐level also showed that major fiber tract groups predominantly distributed in the frontal lobe (cingulum, forceps minor) exhibited greater vulnerability to the aging process than the others. Differences in FC and the combined measure of FD and cross section values observed between sexes were mostly driven by differences in brain sizes although male participants tended to exhibit steeper negative linear relationship with age in FD as compared to female participants. Overall, these findings provide further insights into the structural changes the brain's WM undergoes due to the aging process., In this study, we investigated age‐related changes in white matter fiber density (FD) and morphology (fiber cross section [FC]) across the adult lifespan. Our results showed significant and widespread age‐related alterations in FD and FC across the whole brain. The observed changes were nonuniform across white matter with some fibers exhibiting higher vulnerability than the others.

Luminescence imaging of water using X-ray photon irradiation at energy lower than maximum energy of ~200 keV is thought to be impossible because the secondary electrons produced in this energy range do not emit Cerenkov- light. Contrary to this consensus assumption, we show that the luminescence imaging of water can be achieved by X-ray irradiation at energy lower than 120 keV. We placed water phantoms on a table with a conventional X-ray imaging system, and luminescence images of these phantoms were measured with a high-sensitivity, cooled charge coupled device (CCD) camera during X-ray photon irradiation at energy below 120 keV. We also carried out such imaging of an acrylic block and plastic scintillator. The luminescence images of water phantoms taken during X-ray photon irradiation clearly showed X-ray photon distribution. The intensity of the X-ray photon images of the phantom increased almost proportionally to the number of X-ray irradiations. Lower-energy X-ray photon irradiation showed lower-intensity luminescence at the deeper parts of the phantom due to the higher X-ray absorption in the water phantom. Furthermore, lower-intensity luminescence also appeared at the deeper parts of the acrylic phantom due to its higher density than water. The intensity of the luminescence for water was 0.005% of that for plastic scintillator. Luminescence imaging of water during X-ray photon irradiation at energy lower than 120 keV was possible. This luminescence imaging method is promising for dose estimation in X-ray imaging systems.

The American Association of Physicists in Medicine (AAPM) task group 204 has recommended the use of size-dependent conversion factors to calculate size-specific dose estimate (SSDE) values from volume computed tomography dose index (CTDIvol) values. However, these conversion factors do not consider the effects of 320-detector-row volume computed tomography (CT) examinations or the new CT dosimetry metrics proposed by AAPM task group 111. This study aims to investigate the influence of these examinations and metrics on the conversion factors reported by AAPM task group 204, using Monte Carlo simulations. Simulations were performed modelling a Toshiba Aquilion ONE CT scanner, in order to compute dose values in water for cylindrical phantoms with 8-40-cm diameters at 2-cm intervals for each scanning parameter (tube voltage, bow-tie filter, longitudinal beam width). Then, the conversion factors were obtained by applying exponential regression analysis between the dose values for a given phantom diameter and the phantom diameter combined with various scanning parameters. The conversion factors for each scanning method (helical, axial, or volume scanning) and CT dosimetry method (i.e., the CTDI100 method or the AAPM task group 111 method) were in agreement with those reported by AAPM task group 204, within a percentage error of 14.2 % for phantom diameters ≥11.2 cm. The results obtained in this study indicate that the conversion factors previously presented by AAPM task group 204 can be used to provide appropriate SSDE values for 320-detector-row volume CT examinations and the CT dosimetry metrics proposed by the AAPM task group 111.

The purpose of this study was to investigate regional brain activity during jaw clenching with natural teeth and with two types of occlusal splints using functional magnetic resonance imaging (fMRI).Sixteen healthy volunteers were enrolled in this study. Blood oxygenation level-dependent (BOLD) fMRI signals were compared under three conditions: during clenching with natural teeth, with a soft splint, and with a hard splint. For each condition, 30-second jaw clenching followed a 60-second rest, and was repeated three times, with intervening 30-second rests. SPM 8 was used for the fMRI analysis.Blood oxygenation level-dependent signals during clenching with natural teeth increased in BA44, 45, and the cerebellum. Blood oxygenation level-dependent signals increased in those areas and in BA17, 18 during clenching with a soft splint. Use of the hard splint increased the BOLD signals in BA6 and BA20, 37 in addition to the areas previously mentioned. Blood oxygenation level-dependent signals in the left BA6, the left BA20, 37, and the right BA44, 45 were significantly higher during clenching with a hard splint than with natural teeth. These regions are associated with motor coordination, memory, and cognition, respectively.Jaw clenching with a hard splint caused activity in the widest brain regions, including the associated area with motor coordination.

The luminescence imaging of water using the alpha particle irradiation of several MeV energy range is thought to be impossible because this alpha particle energy is far below the Cerenkov-light threshold and the secondary electrons produced in this energy range do not emit Cerenkov-light. Contrary to this consensus, we found that the luminescence imaging of water was possible with 5.5 MeV alpha particle irradiation. We placed a 2 MBq of 241 Am alpha source in water, and luminescence images of the source were conducted with a high-sensitivity, cooled charge-coupled device (CCD) camera. We also carried out such imaging of the alpha source in three different conditions to compare the photon productions with that of water, in air, with a plastic scintillator, and an acrylic plate. The luminescence imaging of water was observed from 10 to 20 s acquisition, and the intensity was linearly increased with time. The intensity of the luminescence with the alpha irradiation of water was 0.05% of that with the plastic scintillator, 4% with air, and 15% with the acrylic plate. The resolution of the luminescence image of water was better than 0.25 mm FWHM. Alpha particles of 5.5 MeV energy emit luminescence in water. Although the intensity of the luminescence was smaller than that in air, it was clearly observable. The luminescence of water with alpha particles would be a new method for alpha particle detection and distribution measurements in water.

We developed a prototype photon-counting mammography unit with a cadmium zinc telluride detector, which provides a new type of image with physical analysis parameters. Using the X-ray attenuation information obtained from this device, we examined the ability of this technique in discriminating substances and estimating their compositions. To estimate the substance compositions, we used resected breast tissues immediately after a surgical operation for invasive carcinoma of no special type, and used phantoms to reproduce mammary glands and adipose tissue. In our system, the spectrum penetrating the substance was measured with three energy bins in each pixel. The products of linear-attenuation coefficient and thicknesses for each bin were calculated. Using these three values, the scatterplots displaying all the values calculated from each pixel inside the region of interest (ROI) on the image were created. The scatterplot displaying only gravity values calculated for each ROI on the image was created for evaluating the separation of plot points to discriminate between different substance compositions. The gravity points placed on the malignant tumor tissue were plotted separately from those on the normal tissue. Furthermore, a fusion image was created by overlapping an X-ray image and values of this scatterplot points represented on a 10-step color scale. The fusion image was highlighting the differences in substance compositions using color tone, such as malignant tumor or mammary gland tissue, by adjusting the color scale level.

In this study, we propose a new image display method to obtain high contrast-to-noise ratio (CNR) using energy resolved photon-counting mammography (ERPCM) with a cadmium telluride (CdTe) series detector manufactured by JOB CORPOLATION. The CdTe series detector can detect high-energy photons with high sensitivity, enabling users to image with high-energy X-rays. Using this detector, it is possible to reduce the dose given to a patient while increasing the CNR. First, the spectrum was divided into three bins and their corresponding linear attenuation coefficients were calculated from input and output photon numbers. Further, absorption vector length (AVL) and average absorption length (AAL) were calculated from the linear attenuation coefficients and from thicknesses of objects after beam-hardening correction. We further compared the CNR between ERPCM and general mammography images under the constant average glandular dose (AGD). We imaged an acrylic plate (1 mm thick) on RMI-156 phantom, determined regions of interest (ROIs) on an acrylic plate and background, and calculated the CNR. Our ERPCM generated two types of images: an AVL image and an AAL image. AMULET Innovality manufactured by FUJIFILM generated an integrated image. MicroDose SI manufactured by Philips generated a count image and removed electrical noise by the photon-counting technique. The four images, in order of decreasing CNR, were the AAL image, AVL image, MicroDose image, and AMULET image. The proposed method using ERPCM generated an image with higher CNR than images using general mammography under the constant AGD.

The longitudinal dose profile in a computed tomography dose index (CTDI) phantom had been studied by many researchers. The cross-sectional dose profile in the CTDI phantom, however, has not been studied. It is also important to understand the cross-sectional dose profile in the CTDI phantom for dose estimation in X-ray CT. In this study, the cross-sectional dose profile in the CTDI phantom was calculated by use of a Monte Carlo (MC) simulation method. A helical or a 320-detector-row cone-beam X-ray CT scanner was simulated. The cross-sectional dose profile in the CTDI phantom from surface to surface through the center point was calculated by MC simulation. The shape of the calculation region was a cylinder of 1-mm-diameter. The length of the cylinder was 23, 100, or 300 mm to represent various CT ionization chamber lengths. Detailed analyses of the energy depositions demonstrated that the cross-sectional dose profile was different in measurement methods and phantom sizes. In this study, we also focused on the validation of the weighting factor used in weighted CTDI (CTDI w ). As it stands now, the weighting factor used in CTDI w is (1/3, 2/3) for the (central, peripheral) axes. Our results showed that an equal weighting factor, which is (1/2, 1/2) for the (central, peripheral) axes, is more suitable to estimate the average cross-sectional dose when X-ray CT dose estimation is performed.

Purpose The weighted computed tomography dose index (CTDIw) uses measured CTDI values at the center and periphery of a cylindrical phantom. The CTDIw value is calculated using conventional, Bakalyar's, and Choi's weighting factors. However, these weighting factors were produced from only 16- and 32-cm-diameter cylindrical phantoms. This study aims to devise new weighting factors to provide more accurate average dose in the central cross-sectional plane of cylindrical phantoms over a wide range of object diameters, by using Monte Carlo simulations. Methods Simulations were performed by modelling a Toshiba Aquilion ONE CT scanner, in order to compute the cross-sectional dose profiles of polymethyl methacrylate (PMMA) cylindrical phantoms of each diameter (8 to 40 cm at 4-cm steps), for various tube voltages and longitudinal beam widths. Two phantom models were simulated, corresponding to the CTDI100 method and the method recommended by American Association of Physicists in Medicine (AAPM) task group 111. The dose-computation PMMA cylinders of 1-mm diameter were located between the phantom surfaces and the centers at intervals of 1 mm, from which cross-sectional dose profiles were calculated. By using linear least-squares fits to the obtained cross-sectional dose profiles data, we determined new weighting factors to estimate more accurate average doses in the PMMA cylindrical phantoms by using the CTDIw equation: CTDIw = Wcenter・CTDIcenter + Wperiphery・CTDIperiphery. In order to demonstrate the validity of the devised new weighting factors, the percentage difference between average dose and CTDIw value was evaluated for the weighting factors (conventional, Bakalyar's, Choi's, and devised new weighting factors) in each calculated cross-sectional dose profile. Results With the use of linear least-squares techniques, new weighting factors (Wcenter = 3/8 and Wperiphery = 5/8 where Wcenter and Wperiphery are weighting factors for CTDIcenter and CTDIperiphery) were determined. The maximum percentage differences between average dose and CTDIw value were 16, -12, -8, and -6% for the conventional, Bakalyar's, Choi's, and devised new weighting factors, respectively. Conclusions We devised new weighting factors (Wcenter = 3/8 and Wperiphery = 5/8) to provide more accurate average dose estimation in PMMA cylindrical phantoms over a wide range of diameter. The CTDIw equation with devised new weighting factors could estimate average dose in PMMA cylindrical phantoms with a maximum difference of -6%. The results of this study can estimate the average dose in PMMA cylindrical phantoms more accurately than the conventional weighting factors (Wcenter = 1/3 and Wperiphery = 2/3). This article is protected by copyright. All rights reserved.

In this study, we proposed a method for detecting microcalcifications and tumor tissue using a cadmium telluride (CdTe) series linear detector. The CdTe series detector was used as an energy resolved photon-counting (hereafter referred to as the photon-counting) mammography detector. The CdTe series linear detector and two types of phantom were designed using a MATLAB simulation. Each phantom consisted of mammary gland and adipose tissue. One phantom contained microcalcifications and the other contained tumor tissue. We varied the size of these structures and the mammary gland composition. We divided the spectrum of an x-ray, which is transmitted to each phantom, into three energy bins and calculated the corresponding linear attenuation coefficients from the numbers of input and output photons. Subsequently, the absorption vector length that expresses the amount of absorption was calculated. When the material composition was different between objects, for example mammary gland and microcalcifications, the absorption vector length was also different. We compared each absorption vector length and tried to detect the microcalcifications and tumor tissue. However, as the size of microcalcifications and tumor tissue decreased and/or the mammary gland content rate increased, there was difficulty in distinguishing them. The microcalcifications and tumor tissue despite the reduction in size or increase in mammary gland content rate can be distinguished by increasing the x-ray dosage. Therefore, it is necessary to find a condition under which a low exposure dose is optimally balanced with high detection sensitivity. It is a new method to indicate the image using photon counting technology.

The authors previously reported successful luminescence imaging of water during proton irradiation and its application to range estimation. However, since the feasibility of this approach for carbon-ion irradiation remained unclear, the authors conducted luminescence imaging during carbon-ion irradiation and estimated the ranges.The authors placed a pure-water phantom on the patient couch of a carbon-ion therapy system and measured the luminescence images with a high-sensitivity, cooled charge-coupled device camera during carbon-ion irradiation. The authors also carried out imaging of three types of phantoms (tap-water, an acrylic block, and a plastic scintillator) and compared their intensities and distributions with those of a phantom containing pure-water.The luminescence images of pure-water phantoms during carbon-ion irradiation showed clear Bragg peaks, and the measured carbon-ion ranges from the images were almost the same as those obtained by simulation. The image of the tap-water phantom showed almost the same distribution as that of the pure-water phantom. The acrylic block phantom's luminescence image produced seven times higher luminescence and had a 13% shorter range than that of the water phantoms; the range with the acrylic phantom generally matched the calculated value. The plastic scintillator showed ∼15 000 times higher light than that of water.Luminescence imaging during carbon-ion irradiation of water is not only possible but also a promising method for range estimation in carbon-ion therapy.

Organ and effective doses during paediatric chest radiographic examination were investigated for various tube voltages between 60 and 110 kV at a constant milliampere-second value and focus-to-film distance by using an in-phantom dose measuring system and a Monte Carlo (MC) simulation software (PCXMC), where the former was composed of 32 photodiode dosemeters embedded in various tissue and organ sites within a 6-y-old child anthropomorphic phantom. Lung doses obtained ranged from 0.010 to 0.066 mGy and effective doses from 0.004 to 0.025 mSv, where these doses varied by a factor of 6 with the change in the tube voltage. Effective doses obtained using the MC simulation software agreed with those obtained using the dose measuring system within 23 %, revealing the usefulness of PCXMC software for evaluating effective doses. The present study would provide helpful dose data for the selection of technical parameters in paediatric chest radiography in Japan.

Radiation doses in paediatric computed tomography (CT) were investigated for various types of recent CT scanners with newborn and 6-y-old phantoms in which silicon-photodiode dosemeters were implanted at various organ positions. In the head, chest and abdominal CT for the newborn phantom, doses for organs within the scan region were 21-40, 3-8 and 3-12 mGy, respectively. The corresponding doses for the child phantom were 20-37, 2-11 and 4-17 mGy, respectively. In the head, chest and abdominal CT, the effective doses were respectively 2.1-3.3, 2.0-6.0 and 2.2-10.0 mSv for the newborn, and 1.0-2.0, 1.2-6.6 and 2.9-11.8 mSv for the child. Radiation doses for the newborn were at the same levels as those for the child, excepting effective doses in head CT for the newborn, which were 1.8 times higher than those for the child.

OBJECTIVE: This research compared the field of view with the tissue absorbed dose and effective doses using the two dental cone beam computed tomography (CBCT) scanners. MATERIALS AND METHODS: Two CBCT devices, an Alphard VEGA and 3DX multi-image micro CT MCT-1, were used. Measurements were made using an Alderson RANDO phantom and thermoluminescence dosimeters (TLDs). The calculation of the effective dose was carried out according to ICRP Publication 60 and 103. RESULTS: The effective doses for Alphard VEGA D mode, I mode, P mode, and C mode were 86, 238, 413, and 323 µSv, respectively. The effective doses using 3DX for the maxillary incisor, maxillary molar, mandibular incisor, mandibular molar, TMJ, and mandibular molar scout images were 27, 30, 48, 60, 14, and 1 µSv, respectively. CONCLUSIONS: Both Alphard VEGA and 3DX values revealed salivary gland and oral mucosa doses much higher than those required for other tissues. It is necessary to select a small mode suitable in order to realize optimization.