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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. [ABSTRACT FROM AUTHOR]

Recent studies have demonstrated that connector hubs, regions considered critical for the flow of information across neural systems, are mostly involved in neurodegenerative dementia. Considering that aging can significantly affect the brain's intrinsic connectivity, identifying aging's impact on these regions' overall connection strength is important to differentiate changes associated with healthy aging from neurodegenerative disorders. Using resting state functional magnetic resonance imaging data from a carefully selected cohort of 175 healthy volunteers aging from 21 to 86 years old, we computed an intrinsic connectivity contrast (ICC) metric, which quantifies a region's overall connectivity strength, for whole brain, short-range, and long-range connections and examined age-related changes of this metric over the adult lifespan. We have identified a limited number of hub regions with ICC values that showed significant negative relationship with age. These include the medial precentral/midcingulate gyri and insula with both their short-range and long-range (and thus whole-brain) ICC values negatively associated with age, and the angular, middle frontal, and posterior cingulate gyri with their long-range ICC values mainly involved. Seed-based connectivity analyses further confirmed that these regions are connector hubs with connectivity profile that strongly overlapped with multiple large-scale brain networks. General cognitive performance was not associated with these hubs' ICC values. These findings suggest that even healthy aging could negatively impact the efficiency of regions critical for facilitating information transfer among different functional brain networks. The extent of the regions involved, however, was limited. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 123 I, 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. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to clarify the activated regions in the human brain caused by low‐level clenching and tooth separation, with emphasis on their differences. Methods: For functional magnetic resonance imaging (fMRI), echo planar and T1‐weighted images were obtained using a 3T MRI apparatus. Six healthy volunteers clenched with 10% and 40% of the maximum bite force as vertical stimulation (Task 1), and 10 volunteers bit at 60, 120, and 180 s after the insertion of a brass contact gage as horizontal stimulation together with vertical stimulation (Task 2) were included in this study. Results: At 10% clenching, the supplementary motor area, frontal association cortex, and cerebellum were activated, whereas the primary sensorimotor cortex and temporal association cortex were added to the activated regions at 40% clenching. In addition to the activated regions in Task 1, the parietal association cortex, thalamus, hippocampus, putamen, and islet were also activated during biting after the insertion of the brass gage. Conclusion: The hypothalamic area was confirmed to be activated due to biting with the gage in addition to the regions activated in low‐level clenching. Brain fMRI might provide useful information to clarify the relationship between various intraoral stimulations and brain activities. [ABSTRACT FROM AUTHOR]

The stability of the MRI scanner throughout a given study is critical in minimizing hardware-induced variability in the acquired imaging data set. However, MRI scanners do malfunction at times, which could generate image artifacts and would require the replacement of a major component such as its gradient coil. In this article, we examined the effect of low intensity, randomly occurring hardware-related noise due to a faulty gradient coil on brain morphometric measures derived from T1-weighted images and resting state networks (RSNs) constructed from resting state functional MRI. We also introduced a method to detect and minimize the effect of the noise associated with a faulty gradient coil. Finally, we assessed the reproducibility of these morphometric measures and RSNs before and after gradient coil replacement. Our results showed that gradient coil noise, even at relatively low intensities, could introduce a large number of voxels exhibiting spurious significant connectivity changes in several RSNs. However, censoring the affected volumes during the analysis could minimize, if not completely eliminate, these spurious connectivity changes and could lead to reproducible RSNs even after gradient coil replacement. [ABSTRACT FROM AUTHOR]

Objective: 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).Methods: 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.Results: 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.Conclusion: Jaw clenching with a hard splint caused activity in the widest brain regions, including the associated area with motor coordination. [ABSTRACT FROM AUTHOR]

Purpose: 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. Methods: 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. Results: 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. Conclusions: Luminescence imaging during carbon-ion irradiation of water is not only possible but also a promising method for range estimation in carbon-ion therapy. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to evaluate radiation dose to patients undergoing computed tomography coronary angiography (CTCA) for prospectively gated axial (PGA) technique and retrospectively gated helical (RGH) technique. Methods: Radiation doses were measured for a 320-detector row CT scanner (Toshiba Aquilion ONE) using small sized silicon-photodiode dosimeters, which were implanted at various tissue and organ positions within an anthropomorphic phantom for a standard Japanese adult male. Output signals from photodiode dosimeters were read out on a personal computer, from which organ and effective doses were computed according to guidelines published in the International Commission on Radiological Protection Publication 103. Results: Organs that received high doses were breast, followed by lung, esophagus, and liver. Breast doses obtained with PGA technique and a phase window width of 16% at a simulated heart rate of 60 beats per minute were 13 mGy compared to 53 mGy with RGH technique using electrocardiographically dependent dose modulation at the same phase window width as that in PGA technique. Effective doses obtained in this case were 4.7 and 20 mSv for the PGA and RGH techniques, respectively. Conversion factors of dose length product to the effective dose in PGA and RGH were 0.022 and 0.025 mSv mGy-1 cm-1 with a scan length of 140 mm. Conclusions: CTCA performed with PGA technique provided a substantial effective dose reduction, i.e., 70%-76%, compared to RGH technique using the dose modulation at the same phase windows as those in PGA technique. Though radiation doses in CTCA with RGH technique were the same level as, or some higher than, those in conventional coronary angiography (CCA), the use of PGA technique reduced organ and effective doses to levels less than CCA except for breast dose. [ABSTRACT FROM AUTHOR]

Purpose: The objective of this study was to evaluate organ dose and the effective dose to patients undergoing tomosynthesis (TS) and C-arm cone-beam computed tomography (CBCT) examinations and to compare the doses to those in multidetector CT (MDCT) scans. Methods: Patient doses were measured with small sized silicon-photodiode dosimeters, 48 in number, which were implanted at various tissue and organ positions within an anthropomorphic phantom. Output signals from photodiode dosimeters were read out on a personal computer, from which organ and effective doses were computed. The doses in head, chest, abdomen, and hip-joint TS, and in head and abdomen C-arm CBCT were evaluated for routine protocols on Shimadzu TS and C-arm CBCT systems, and the doses in MDCT with the same scan regions as in TS and CBCT were on Toshiba 64-detector-row CT scanners. Results: In TS examination of the head, chest, abdomen, and hip-joint, organ doses for organs within scan ranges were 1–4 mGy, and effective doses were 0.07 mSv for the head scan and around 1 mSv for other scans. In C-arm CBCT examinations of the head and abdomen, organ doses within scan range were 2–37 mGy, and effective doses were 1.2 mSv for the head scan and 4–5 mSv for abdominal scans. Effective doses in TS examinations were approximately a factor of 10 lower, while the doses in CBCT examinations were nearly the same level, compared to the doses in the corresponding MDCT examinations. Conclusions: TS examinations with low doses and excellent resolutions in coronal images compared to recent MDCT would widely be used in tomographic examinations of the chest, abdomen, pelvis, skeletal-joints, and knee instead of MDCT examinations with significantly high doses. Since patient dose in C-arm CBCT was nearly the same level as that in recent MDCT, the same consideration for high radiation dose would be required for the use of CBCT. [ABSTRACT FROM AUTHOR]

The purpose of this study was to clarify patient doses in the current otolaryngological multi-detector row computed tomography (MDCT) examinations. Patient doses were measured with an in-phantom dosimetry system which was composed of 48 photodiode dosemeters embedded within an anthropomorphic phantom. Organ and effective doses were evaluated according to the International Commission on Radiological Protection Publication 103. In neck CT, doses for salivary glands and for thyroid were high, 7.6-29.9 and 13.4-60.3 mGy, respectively. In sinus CT, brain and lens doses were high, 7.6-24.6 and 10.6-32.0 mGy, respectively, and in inner ear CT, lens dose was 8.0-35.3 mGy. Effective doses were 1.8-6.6 mSv in neck CT, 0.5-0.9 mSv in sinus CT and 0.3-0.6 mSv in inner ear CT. The present dose data would be used to estimate radiation risks for patients undergoing otolaryngological MDCTexaminations. [ABSTRACT FROM AUTHOR]

Organ and the effective doses of patients undergoing clinical X ray examinations of chest and abdomen were evaluated with an anthropomorphic phantom and a new dosimetry system. The system was comprised of 34 pin photodiode dosemeters placed in/on particular tissues or organs of the anthropomorphic phantom, where the tissues and organs are defined by the International Commission on Radiological Protection (ICRP) to estimate the effective doses. Dosemeter signals were acquired on a personal computer directly, and converted into absorbed doses, from which the organ and the effective doses were evaluated on the computer. Our study showed that organ doses ranged from <0.01 to 0.72 mGy in routine X-ray radiography of chest and of abdomen and from 0.07 to 55.91 mGy in routine computed tomography (CT) examinations with current multi-slice CT scanners. The effective dose observed in the chest CT examination was approximately 300 times higher than that in chest radiography. [ABSTRACT FROM AUTHOR]

Objective: The angiography systems A (A) and B (B), both incorporated at our hospital, are equipped with metal artifact reduction (MAR) applications. In clinical practice, it is crucial to understand the characteristics of MAR in both systems given that endovascular treatments are occasionally administered with both. In this study, we compared the artifact reduction effects of MAR on equipment A and B and clarified the differences between the two systems., Methods: An artifact evaluation phantom was created using a cylindrical water phantom and an iodine contrast medium. The phantom was imaged, MAR processing was performed on the obtained images, and an isotropic quantitative evaluation of artifacts was performed by extreme value statistical analysis using the Gumbel distribution., Results: The MAR reduction effects were approximately 45% and 40% for equipment A and B at concentrations of 8300 and 6000, respectively. The MAR reduction effect in both devices exhibited different trends depending on the concentration., Conclusion: In clinical procedures that make use of absorbents in medium concentrations of approximately 3000-5000, such as n-butyl-2-cyanoacrylate and Onyx, it is necessary to understand the MAR characteristics of both devices and consider the use of alternative devices as an option., (©2024 The Japanese Society for Neuroendovascular Therapy.)

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 mm 3 per 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., (Copyright © 2022 Bagarinao et al.)

Purpose: 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., Methods: 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., Results: 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 (P < 0.05) differences in comparisons involving low vs. high motion groups (OldHM vs. OldLM and OldHM vs. YugLM). However, there was no significant (P > 0.05) difference in the comparison involving the low motion groups (OldLM vs. YugLM)., Conclusion: 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.

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., Competing Interests: The authors have no conflict of interest to declare.

Unlabelled: Double-balloon endoscopy (DBE) is useful for the diagnosis and treatment of small bowel diseases. Although fluoroscopy is used to confirm the position of endoscope at DBE, the endoscopist does not have the knowledge with regard to the radiation exposure dose. In this study, we evaluated the absorbed dose during DBE in patients with suspected or established small bowel diseases. This was a retrospective study in which the estimated fluoroscopic radiation absorbed doses loaded on the small bowel and skin were determined according to the data of the referential X-ray experiment with a human body phantom. The subjects were 415 DBEs preformed in total. The mean small bowel absorbed doses on antegrade and retrograde DBEs were 42.2 and 53.8 mGy, respectively, showing that the organ dose applied in retrograde DBE was significantly higher (P<0.0001). The mean skin absorbed doses of them were 79.2 and 101.0 mGy, respectively, showing that the dose was also significantly higher on retrograde DBE (P<0.0001). Of 27 cases who were applied endoscopic balloon dilation, the mean fluoroscopy time was 16.0 minutes, and mean small bowel and skin absorbed doses were 121.9 and 228.9 mGy, respectively. In conclusion, endoscopist should be careful for reducing the organ exposure dose at DBE, particularly for the lower abdominal region., Abbreviations: Double-balloon enteroscopy (DBE), endoscopic balloon dilation (EBD), endoscopic mucosal resection (EMR), double-balloon endoscopic retrograde cholangiopancreatography (DBERCP), percutaneous coronary intervention (PCI).

Objective: 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)., Methods: 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., Results: 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., Conclusion: Jaw clenching with a hard splint caused activity in the widest brain regions, including the associated area with motor coordination.

This study aimed to evaluate radiation doses to patients undergoing X-ray diagnosis, treatment, and follow-up for cerebral aneurysms. Radiation doses were measured for computed tomography angiography (CTA), cerebral angiography (CAG), and interventional neuroradiology (IVNR) by using small-sized silicon-photodiode dosimeters, which were implanted at various tissue and organ positions within an anthropomorphic phantom. Lens doses, brain doses, and effective doses obtained in this study were 26mGy, 67mGy, and 4.6mSv for CAG;77mGy, 250mGy, and 8.7mSv for IVNR;and 56mGy, 53mGy, and 1.5mSv for CTA. Entrance skin dose associated with mean fluoroscopy time and digital subtraction angiography frame was 0.82Gy for IVNR, which was less than the threshold dose of 2Gy for the onset of skin injury. The lens doses obtained with CTA, including non-contrast CT, was 106mGy, which was a factor of 4 higher than the dose of 26mGy for CAG. Effective dose for CTA was 1.5mSv compared to 4.5mSv for CAG. Patients with cerebral aneurysms received a cumulative lens dose of 543mGy throughout 3 years follow-up, which was over the estimated threshold of 0.5Gy for cataracts.