Age and sex effects on paired-pulse suppression and prepulse inhibition of auditory evoked potentials.

Responses to a sensory stimulus are inhibited by a preceding stimulus; if the two stimuli are identical, paired-pulse suppression (PPS) occurs; if the preceding stimulus is too weak to reliably elicit the target response, prepulse inhibition (PPI) occurs. PPS and PPI represent excitability changes in neural circuits induced by the first stimulus, but involve different mechanisms and are impaired in different diseases, e.g., impaired PPS in schizophrenia and Alzheimer's disease and impaired PPI in schizophrenia and movement disorders. Therefore, these measures provide information on several inhibitory mechanisms that may have roles in clinical conditions. In the present study, PPS and PPI of the auditory change-related cortical response were examined to establish normative data on healthy subjects (35 females and 32 males, aged 19-70 years). We also investigated the effects of age and sex on PPS and PPI to clarify whether these variables need to be considered as biases. The test response was elicited by an abrupt increase in sound pressure in a continuous sound and was recorded by electroencephalography. In the PPS experiment, the two change stimuli to elicit the cortical response were a 15-dB increase from the background of 65 dB separated by 600 ms. In the PPI experiment, the prepulse and test stimuli were 2- and 10-dB increases, respectively, with an interval of 50 ms. The results obtained showed that sex exerted similar effects on the two measures, with females having stronger test responses and weaker inhibition. On the other hand, age exerted different effects: aging correlated with stronger test responses and weaker inhibition in the PPS experiment, but had no effects in the PPI experiment. The present results suggest age and sex biases in addition to normative data on PPS and PPI of auditory change-related potentials. PPS and PPI, as well as other similar paradigms, such as P50 gating, may have different and common mechanisms. Collectively, they may provide insights into the pathophysiologies of diseases with impaired inhibitory function.

High-resolution EEG source localization in personalized segmentation-free head model with multi-dipole fitting.

Objective. Electroencephalograms (EEGs) are often used to monitor brain activity. Several source localization methods have been proposed to estimate the location of brain activity corresponding to EEG readings. However, only a few studies evaluated source localization accuracy from measured EEG using personalized head models in a millimeter resolution. In this study, based on a volume conductor analysis of a high-resolution personalized human head model constructed from magnetic resonance images, a finite difference method was used to solve the forward problem and to reconstruct the field distribution.Approach. We used a personalized segmentation-free head model developed using machine learning techniques, in which the abrupt change of electrical conductivity occurred at the tissue interface is suppressed. Using this model, a smooth field distribution was obtained to address the forward problem. Next, multi-dipole fitting was conducted using EEG measurements for each subject (N= 10 male subjects, age: 22.5 ± 0.5), and the source location and electric field distribution were estimated.Main results.For measured somatosensory evoked potential for electrostimulation to the wrist, a multi-dipole model with lead field matrix computed with the volume conductor model was found to be superior than a single dipole model when using personalized segmentation-free models (6/10). The correlation coefficient between measured and estimated scalp potentials was 0.89 for segmentation-free head models and 0.71 for conventional segmented models. The proposed method is straightforward model development and comparable localization difference of the maximum electric field from the target wrist reported using fMR (i.e. 16.4 ± 5.2 mm) in previous study. For comparison, DUNEuro based on sLORETA was (EEG: 17.0 ± 4.0 mm). In addition, somatosensory evoked magnetic fields obtained by Magnetoencephalography was 25.3 ± 8.5 mm using three-layer sphere and sLORETA.Significance. For measured EEG signals, our procedures using personalized head models demonstrated that effective localization of the somatosensory cortex, which is located in a non-shallower cortex region. This method may be potentially applied for imaging brain activity located in other non-shallow regions.

ERP evidence of attentional somatosensory processing and stimulus-response coupling under different hand and arm postures.

We investigated (1) the effects of divided and focused attention on event-related brain potentials (ERPs) elicited by somatosensory stimulation under different response modes, (2) the effects of hand position (closely-placed vs. separated hands) and arm posture (crossed vs. uncrossed forearms) on the attentional modulation of somatosensory ERPs, and (3) changes in the coupling of stimulus- and response-related processes by somatosensory attention using a single-trial analysis of P300 latency and reaction times. Electrocutaneous stimulation was presented randomly to the thumb or middle finger of the left or right hand at random interstimulus intervals (700-900 ms). Subjects attended unilaterally or bilaterally to stimuli in order to detect target stimuli by a motor response or counting. The effects of unilaterally-focused attention were also tested under different hand and arm positions. The amplitude of N140 in the divided attention condition was intermediate between unilaterally attended and unattended stimuli in the unilaterally-focused attention condition in both the mental counting and motor response tasks. Attended infrequent (target) stimuli elicited greater P300 in the unilaterally attention condition than in the divided attention condition. P300 latency was longer in the divided attention condition than in the unilaterally-focused attention condition in the motor response task, but remained unchanged in the counting task. Closely locating the hands had no impact, whereas crossing the forearms decreased the attentional enhancement in N140 amplitude. In contrast, these two manipulations uniformly decreased P300 amplitude and increased P300 latency. The correlation between single-trial P300 latency and RT was decreased by crossed forearms, but not by divided attention or closely-placed hands. Therefore, the present results indicate that focused and divided attention differently affected middle latency and late processing, and that hand position and arm posture also differently affected attentional processes and stimulus-response coupling.

Usefulness of preset count acquisition in pediatric 99m Tc-DMSA planar imaging.

OBJECTIVE: This study was aimed at determining the minimum acquisition count to provide diagnosable image quality (DIQ) and investigating the usefulness of preset count acquisition (PCA) for planar images of pediatric 99mTc-dimercaptosuccinic acid (DMSA) scintigraphy. METHODS: First, we calculated a coefficient of variation (CV) for DIQ with the shortest acquisition time through visual evaluation in 12 pediatric patients who underwent 99mTc-DMSA scintigraphy. Second, a minimum acquisition count to achieve the CV for DIQ was determined with the single regression analysis using CV as an explanatory variable and the total acquisition count as an objective variable in 81 pediatric patients. Finally, we compared PCA images based on the minimum acquisition count and preset time acquisition (PTA) images for 5 min in terms of the acquisition time, CV, and renal uptake ratio in another 23 pediatric patients. RESULTS: The visual evaluation showed that the CV corresponding to DIQ with the shortest acquisition time was 27.1%. The total acquisition count corresponding to DIQ was revealed to be 299,764 in the single regression analysis and was determined to be 300,000 after rounding. The CV and its standard deviation in PCA at 300,000 counts and PTA for 5 min were 26.4 ± 0.6% and 24.8 ± 1.3%, respectively. The standard deviation of CV in PCA at 300,000 counts was smaller than that in PTA for 5 min, indicating little variation in image quality between cases. The acquisition time in PCA at 300,000 counts (3.1 ± 0.7 min) was shorter than that in PTA for 5 min (5.0 ± 0.0 min). The intraclass correlation coefficient between renal uptake ratios for PCA and PTA was 0.98, indicating an extremely high concordance. CONCLUSIONS: The minimum acquisition count required for the DIQ was 300,000. In addition, PCA at 300,000 counts was demonstrated to be useful by providing stable image quality at the shortest acquisition time.

Comparison of the Characteristics of Two Types of Parallel-plate Ionization Chamber Under Small-field Electron Irradiation.

BACKGROUND/AIM: This study compared two types of parallel-plate ionization chamber to clarify the pitfalls of dosimetry in electron radiation therapy. MATERIALS AND METHODS: The ion recombination correction factor and polarity effect correction factor, sensitivity, and percentage depth doses (PDDs) of PPC05 and PPC40 parallel-plate ionization chambers were compared in a small-field electron beam. The output ratios were measured for 4-20 MeV electron beams with field sizes of 10 cm × 10 cm, 6 cm × 6 cm, and 4 cm × 4 cm. Furthermore, the films were placed in water and positioned in the beam with their surface perpendicular to the beam axis, and lateral profiles were obtained for each beam energy and each field. RESULTS: Regarding PDDs, at depths greater than the peak dose, the percentage depth dose for PPC40 was smaller than that for PPC05 in small fields and at beam energies greater than 12 MeV, which could be attributed to the lack of lateral electron equilibrium at small depths and multiple scattering events at large depths. The output ratio of PPC40 was approximately 0.025-0.038, which was lower than that of PPC05 in a 4 cm × 4 cm field. For large fields, the lateral profiles were similar, regardless of the beam energy, however, for small fields, the flatness of the lateral profile was beam energy dependent. CONCLUSION: The PPC05 chamber, which has a smaller ionization volume, is therefore more suitable than the PPC40 chamber for small-field electron dosimetry, in particular at high beam energies.

Brain-wide network analysis of resting-state neuromagnetic data.

The present study performed a brain-wide network analysis of resting-state magnetoencephalograms recorded from 53 healthy participants to visualize elaborate brain maps of phase- and amplitude-derived graph-theory metrics at different frequencies. To achieve this, we conducted a vertex-wise computation of threshold-independent graph metrics by combining proportional thresholding and a conjunction analysis and applied them to a correlation analysis of age and brain networks. Source power showed a frequency-dependent cortical distribution. Threshold-independent graph metrics derived from phase- and amplitude-based connectivity showed similar or different distributions depending on frequency. Vertex-wise age-brain correlation maps revealed that source power at the beta band and the amplitude-based degree at the alpha band changed with age in local regions. The present results indicate that a brain-wide analysis of neuromagnetic data has the potential to reveal neurophysiological network features in the human brain in a resting state.

Cortical activity during the wind-up of flexion reflex and pain: a magnetoencephalographic study using time-frequency analysis.

Wind-up is a nociceptive-specific phenomenon in which pain sensations are facilitated, in a frequency-dependent manner, by the repeated application of noxious stimuli of constant intensity, with invariant tactile sensations. Thus, cortical activities during wind-up could be an alteration associated with pain potentiation. We aimed to investigate somatosensory-evoked cortical responses and induced brain oscillations during wind-up by recording magnetoencephalograms. Wind-up was produced by the application of 11 consecutive electrical stimuli to the sural nerve, repeated at a frequency of 1 Hz without varying the intensity. The augmentation of flexion reflexes and pain rating scores were measured simultaneously as an index of wind-up. In the time-frequency analyses, the γ-band late event-related synchronization and the ß-band event-related desynchronization were observed in the primary somatosensory region and the bilateral operculo-insular region, respectively. Repetitive exposure to the stimuli enhanced these activities, along with an increase in the flexion reflex magnitude. The evoked cortical activity reflected novelty, with no alteration to these repetitive stimuli. Observed oscillations enhanced by repetitive stimulation at a constant intensity could reflect a pain mechanism associated with wind-up.

Target Site of Prepulse Inhibition of the Trigeminal Blink Reflex in Humans.

Despite the clinical significance of prepulse inhibition (PPI), the mechanisms are not well understood. Herein, we present our investigation of PPI in the R1 component of electrically induced blink reflexes. The effect of a prepulse was explored with varying prepulse test intervals (PTIs) of 20-600 ms in 4 females and 12 males. Prepulse-test combinations included the following: stimulation of the supraorbital nerve (SON)-SON [Experiment (Exp) 1], sound-sound (Exp 2), the axon of the facial nerve-SON (Exp 3), sound-SON (Exp 4), and SON-SON with a long trial-trial interval (Exp 5). Results showed that (1) leading weak SON stimulation reduced SON-induced ipsilateral R1 with a maximum effect at a PTI of 140 ms, (2) the sound-sound paradigm resulted in a U-shaped inhibition time course of the auditory startle reflex (ASR) peaking at 140 ms PTI, (3) facial nerve stimulation showed only a weak effect on R1, (4) a weak sound prepulse facilitated R1 but strongly inhibited SON-induced late blink reflexes (LateRs) with a similar U-shaped curve, and (5) LateR in Exp 5 was almost completely absent at PTIs >80 ms. These results indicate that the principal sensory nucleus is responsible for R1 PPI. Inhibition of ASR or LateR occurs at a point in the startle reflex circuit where auditory and somatosensory signals converge. Although the two inhibitions are different in location, their similar time courses suggest similar neural mechanisms. As R1 has a simple circuit and is stable, R1 PPI helps to clarify PPI mechanisms.SIGNIFICANCE STATEMENT Prepulse inhibition (PPI) is a phenomenon in which the startle response induced by a startle stimulus is suppressed by a preceding nonstartle stimulus. This study demonstrated that the R1 component of the trigeminal blink reflex shows clear PPI despite R1 generation within a circuit consisting of the trigeminal and facial nuclei, without startle reflex circuit involvement. Thus, PPI is not specific to the startle reflex. In addition, PPI of R1, the auditory startle reflex, and the trigeminal late blink reflex showed similar time courses in response to the prepulse test interval, suggesting similar mechanisms regardless of inhibition site. R1 PPI, in conjunction with other paradigms with different prepulse-test combinations, would increase understanding of the underlying mechanisms.

Protective effects of probiotics against tannin-induced immunosuppression in broiler chickens.

Tannins (TAs) are an anti-nutritional substance commonly used as a natural feed additive for livestock. However, our previous study described the dose-dependent adverse effects of TA on immune responses and growth in chickens. In this study, we evaluated the protective effects of a probiotic preparation (BT) consisting of three different bacteria (Bacillus mesenteric, Clostridium butyricum, and Streptococcus faecalis) against TA-induced immunosuppression in chickens. Forty chicks were divided into 4 groups as follows: the CON group (basal diet), BT group supplemented with 3 g BT/kg diet, tannic acid (TA) group supplemented with 30 g TA/kg diet, and BT+TA group supplemented with 3 g BT/kg diet + 30 g TA/kg diet. The feeding trial lasted for 35 days. Lymphocyte subset, macrophage phagocytosis, cytokine mRNA expression, and primary and secondary IgY immune responses were evaluated. BT supplementation significantly improved TA-induced reductions in final body weight, body weight gain, feed intake, and relative weights of lymphoid organs compared with the TA group. Furthermore, in the spleen and cecal tonsil (CT), the relative populations of CD4+, CD8+, and CD4+CD8+ cells in the BT+TA group were significantly ameliorated compared with the TA group. Additionally, comparison with the TA group showed that the chickens in the BT+TA group had an improved relative population of B cells in the CT and that macrophage phagocytosis in the spleen was significantly increased. Chickens in the BT+TA group showed significant increases in IFN-γ and IL-4 mRNA expression in the spleen compared with the TA group. The primary and secondary IgY responses were significantly improved. These results revealed that supplementation with BT protects against TA-induced immunosuppression in chickens.

The ERP and psychophysical changes related to facial emotion perception by expertise in Japanese hospitality, "OMOTENASHI".

We investigated the emotion perception process based on hospitality expertise. Forty subjects were divided into the OMOTENASHI group working at inns considered to represent the spirit of hospitality, OMOTENASHI in Japan, and CONTROL group without experience in the hospitality industry. We presented neutral, happy, and angry faces to investigate P100 and N170 by these faces, and psychophysical changes by the favor rating test to evaluate emotional perception. In the favor rating test, the score was significantly smaller (less favorable) in OMOTENASHI than in CONTROL. Regarding event-related potential components, the maximum amplitude of P100 was significantly larger for a neutral face at the right occipital electrode in OMOTENASHI than in CONTROL, and it was significantly larger for an angry face at both occipital electrodes in OMOTENASHI than in CONTROL. However, the peak latency and maximum amplitude of N170 were not significantly different between OMOTENASHI and CONTROL at both temporal electrodes for each emotion condition. Differences on the favor rating test and P100 in OMOTENASHI suggested that workers at inns may more quickly notice and be more sensitive to the facial emotion of guests due to hospitality training, and/or that hospitality expertise may increase attention to emotion by top-down and/or bottom-up processing.

Studies on the immune status of calves with chronic inflammation and thymus atrophy.

The thymus is a primary lymphoid organ where the primary T cell repertoire is generated. Thymus atrophy is induced by various conditions, including infectious diseases, glucocorticoid treatment, and poor breeding management. Cattle with thymus atrophy tend to exhibit weak calf syndrome, a condition in which approximately half of neonates die shortly after birth. Calves with thymus atrophy that survive the first month typically contract chronic inflammatory diseases. In this study, we analyzed the populations of the peripheral blood mononuclear cells and thymocytes in calves with thymus atrophy. In addition, we evaluated polarization of master gene and cytokine mRNA expression in peripheral blood CD4+ cells in the calves. The population of CD4+CD8+ cells in thymus of the calves with thymus atrophy was lower than that of control calves. IL10 mRNA expression in peripheral blood CD4+ cells of calves with thymus atrophy was significantly lower than that of control calves. TBX21 mRNA expression in peripheral CD4+ cells of thymus atrophy calves was tended to be higher than that of the control group. In addition, FOXP3 mRNA expression in peripheral CD4+ cells of the thymus atrophy calves was tended to be lower than that of the control calves. Thymus atrophy calves exhibited chronic inflammatory disease leading, in severe situations, to conditions such as pneumonia with caseous necrosis. These severe inflammatory responses likely are due to decreases in IL10 mRNA expression, impairing control of macrophages, one of the main cell fractions of natural immunity.

Effects of branched-chain amino acids on immune status of young racing horses.

High-intensity exercise and competition are associated with depressed immune function. Young horses, which participate in high-intensity exercise and competitions, are at increased risk for the development of infectious disease due to depression of immune function. The effects of branched-chain amino acid (BCAA) supplementation on the immune status of young racing horses were evaluated, determining whether BCAA might help to avoid or reduce immune suppression during exercise and competitions. Twenty horses (10 male and 10 female) were treated with BCAA supplementation; another twenty untreated horses (10 male and 10 female) constituted control group. Peripheral blood was collected from each animal and evaluated for lymphocyte subsets, phagocytosis analysis of monocytes and granulocytes, lymphocyte proliferative response, and expression of cytokine-encoding messenger ribonucleic acids (mRNAs). The numbers of CD4+, CD8+, and major histocompatibility complex (MHC) class II+ cells in females of the treated group were significantly higher than those in females of the control group. The lymphocyte proliferative response in female of the treated group also was significantly higher than that in females of the control group. In addition, expression of mRNAs encoding interleukin-1ß (IL-1ß) and interferon-γ (IFN-γ) in females of the treated group was significantly higher than that in females of the control group. There were no significant differences between males of the treated and control groups. The results of this study indicated the positive effects of BCAA supplementation in counteracting immunosuppression in young female racing horses during and following high-intensity exercise.

Dexterous manual movement facilitates information processing in the primary somatosensory cortex: A magnetoencephalographic study.

The interaction between the somatosensory and motor systems is important for control of movement in humans. Cortical activity related to somatosensory response and sensory perception is modulated by the influence of movement executing mechanisms. This phenomenon has been observed as inhibition in the short-latency components of somatosensory evoked potentials and magnetic fields (SEPs/SEFs). Although finger is the most dexterous among all the body parts, the sensorimotor integration underlying this dexterity has not yet been elucidated. The purpose of this study was to examine the sensorimotor integration mechanisms in the primary somatosensory cortex (SI) during simple and complicated finger movement. The participant performed tasks that involved picking up a wooden block (PM task) and picking up and turning the wooden block 180° (PTM task) using the right-hand fingers. During these tasks, the SEFs following right median nerve stimulation were recorded using magnetoencephalography. The amplitude of the M20 and M30 components showed a significant reduction during both manual tasks compared to the stationary task, whereas the M38 component showed a significant enhancement in amplitude. Furthermore, the SEFs recorded during continuous rotation of the block (rotation task) revealed a characteristic pattern of SI activity that was first suppressed and then facilitated. Since this facilitation is noticeable during complicated movement of the fingers, this phenomenon is thought to underlie a neural mechanism related to finger dexterity.

[Application of Real-time Variable Shape Tungsten Rubber for Nail Radiation Protection in the Total Skin Electron Beam (TSEB) Therapy].

PURPOSE: This study investigated whether real-time variable shape tungsten rubber (STR) could be applied for nail radiation protection in total skin electron beam (TSEB) therapy. METHODS: Simulated finger phantoms were made from syringes filled with physiological saline of volumes 5, 10, 20, and 30 ml (inner diameters of 14.1, 17.0, 21.7, and 25.3 mm, respectively). Gafchromic film was applied to the phantom, and lead (thickness 1-3 mm) or STR (thickness 1-4 mm) with an area of 4´1.5 cm was used to cover the film. A 6 MeV electron beam with an 8 mm acrylic board was then used to irradiate the phantom. The source-surface distance (SSD) was 444 cm, the field size was 36´36 cm at SSD of 100 cm without an electron applicator, and the monitor unit was 2000 MU. The shielding rates were obtained from the dose profiles. RESULTS: The mean values of the shielding rate values for all phantoms were 50.1, 97.6, and 98.7% for 1, 2, and 3 mm of lead, respectively, and -13.6, 53.9, 91.2, and 99.4% for 1, 2, 3, and 4 mm of STR, respectively. CONCLUSION: STR with a thickness of 4 mm had the same shielding properties as lead with a thickness of 3 mm, which was an approximately 100% shielding rate. STR could therefore be used in TSEB therapy instead of lead.

Reproductive cycle and maturation of Swinhoe's tree lizard (Diploderma swinhonis (Günther, 1864)) in Hyuga City, Miyazaki Prefecture, Japan.

Swinhoe's tree lizard (Diploderma swinhonis) is an arboreal agamid that is native to Taiwan. The species has been introduced to some areas of Japan and is regarded as an invasive alien species. In 2016, a nonnative population of D. swinhonis was discovered in Hyuga City, Miyazaki Prefecture, Japan, but little information was available on the ecology of the population at the time. The main purpose of this study was therefore to investigate the reproductive cycle and maturation of this population. Field research was conducted from 2017 to 2019, and 764 lizards were collected. Euthanized lizards were dissected and the reproductive organs were examined to determine the reproductive period, clutch size, clutch frequency and size at sexual maturity. Females with oviductal eggs or vitellogenic ovarian follicles were observed from May to October. Clutch size ranged from 2 to 8, and clutch frequency was more than twice a year. In males, spermiogenesis started in early May and testicular regression was observed in September. Males with spermatozoa in the epididymides were found from May to November. Minimum snout-vent length at sexual maturity was 50.2 mm in females and 53.0 mm in males. Comparisons of the findings of this study and reports from Taiwan suggest that the nonnative population of D. swinhonis in Hyuga City has a higher fecundity than populations in Taiwan. It is therefore considered necessary to exterminate the population in Hyuga City before this species colonizes other areas.

Different doses of tannin reflect a double-edged impact on broiler chicken immunity.

Tannin is one of the most common phytochemical secondary phenolic metabolites, which is widely distributed in various plant production systems. Dietary intake of tannin can exert different actions on the immune system. The aim of this study was to evaluate the influence of different concentrations on broiler chicken immunity. Three groups (n = 10 in each group) were evaluated: control group given a normal basal diet, high tannic acid (HT) group given high-dose tannic acid (30 g/kg diet) and low tannic acid (LT) group given low-dose tannic acid (0.5 g/kg diet) for 35 days. Feed intake and body weight were measured weekly. Cells were isolated from thymus, spleen and caecal tonsils at the end of the study. Lymphocyte subsets, monocytes phagocytosis and cytokine mRNA expression in spleen were evaluated. The results showed that HT group chickens had decreased daily gain, final body weight, daily feed intake and relative weights of lymphoid organs compared with other groups. In thymus, spleen and caecal tonsils, relative CD4+, CD8+, CD4+CD8+ and γδ+ cell populations in the HT group were significant decreased in comparison with those of other groups. The relative B cell population in the HT group was also significant decreased. Cytokine mRNA expression in spleen cells of the HT group was also significantly lower than that in other groups. Conversely, CD4+CD8+ subpopulations in spleen and caecal tonsils, γδ+ cells in spleen and B cells in caecal tonsils of the LT group were significantly higher than those of the control group. In addition, IFN-γ mRNA expression in the LT group was significantly higher than that of the control group. These results demonstrated that dietary intake of tannin had positive and negative effects on broiler chicken immunity in a dose-dependent manner.

Investigation of the relation between administered dose and image quality for pediatric 99mTc-DMSA renal scintigraphy: clinical study applying the JSNM (Japanese Society of Nuclear Medicine) pediatric dosage card : The Japanese Society of Nuclear Medicine Technology (JSNMT), the Optimization of Imaging Technique Committee for Pediatric Nuclear Medicine Studies.

PURPOSE: In 2013, the Japanese Society of Nuclear Medicine (JSNM) announced consensus guidelines for pediatric nuclear medicine. These JSNM guidelines proposed use of lower administered doses compared with traditionally determined doses, which were estimated from age, weight or body surface area (BSA) based on the administered dose for adults in Japan. When the JSNM guidelines are used, the relationship between this recommended administered dose and image quality remains unclear. In this study, we clarified the relationship between administered dose and image quality for pediatric 99mTc-DMSA renal scan retrospectively, and verified the diagnosable image quality with the recommended administered dose of the JSNM guidelines. MATERIALS AND METHODS: Data from 7 pediatric patients who underwent 99mTc-DMSA dynamic renal scans according to the guidelines' recommended doses were collected. Scan frame rate was 1 frame/min, and scan time was up to 8 min. Eight images, which had different acquired time periods from 1 min to 8 min were prepared by adding each frame. Nine nuclear medicine specialists determined 8 images with different acquired times as diagnosable or undiagnosable. A region of interest (ROI) with 50% thresholds was placed on each kidney of every image. Coefficient of variation (CV) was calculated by dividing the standard deviation (σ) by the mean counts (µ) of each ROI (CV = σ/µ × 100). 99mTc-DMSA renal scans (total of 2821 cases) that were performed previously in collaboration with 6 hospitals were collected, and CVs of these images were calculated in all cases. These 2821 cases were separated into 5 groups for every 10 kg weight; i.e., (1) less than 10 kg, (2) 10-19.9 kg, (3) 20-29.9 kg, (4) 30-39.9 kg, and (5) above 40 kg. Regression line of each group was analyzed in relation to the CV and administered dose. The CV at the point of intersection with the recommended dose range from the guideline was determined for each group. This CV value was considered as the estimated CV of the image obtained when the recommended dose of the guideline was used. Thus, if the CV was equal to or less than the estimated CV value, then the diagnostic image quality was deemed satisfactory. RESULTS: Average CV of the lower limit of diagnosable images in 7 cases as determined by 9 nuclear medicine specialists was 19.9%. Estimated CV was 21.2-24.2% in the group weighing < 10 kg (group 1), 19.9-20.6% in the group weighing > 10 kg and < 20 kg (group 2), 19.6% in group weighing > 20 kg and < 30 kg (group 3), 19.4-19.5% in the group weighing > 30 kg and < 40 kg (group 4), and 19.8% in the group weighing > 40 kg (group 5). The estimated CVs from groups 1 and 2 with weight < 20 kg exceeded 19.9%. CONCLUSIONS: Although 99mTc-DMSA renal scan can be carried out using the guidelines' recommended dose with conventional image acquisition time in patients weighing 20 kg or more, those < 20 kg need consideration for a longer image acquisition time to obtain diagnosable images.

Sub-solid nodule detectability in seven observers of seventy-nine clinical cases: comparison between ultra-low-dose chest digital tomosynthesis with iterative reconstruction and chest radiography by receiver-operating characteristics analysis.

PURPOSE: To compare sub-solid nodules detectability (SSND) between ultra-low-dose chest digital tomosynthesis (ULD-CDT) with/without iterative reconstruction (IR) and chest radiography (CR) by using low-dose computed tomography (LDCT) as the standard of reference (SOR). MATERIALS AND METHODS: Institutional Review Board approved this study and written informed consent was obtained. In a single visit, 79 subjects underwent ULD-CDT at 120 kV and 10 mA, CR and LDCT (effective dose: 0.171, 0.117 and 3.52 mSv, respectively). Sixty-three coronal images were reconstructed using CDT with/without IR. SOR as to SSN presence was determined based on LDCT images. Seven radiologists recorded SSN presence and locations by continuously-distributed rating. Receiver-operating characteristic (ROC) analysis was used to compare SSND of ULD-CDT with/without IR and CR, in total and subgroups classified by nodular longest diameter (LD) (> or < 9 mm) and mean CT attenuation value (CTAV) (> or < -600 Hounsfield of Unit (HU)). Detection sensitivity (DS) was compared among 4 groups classified by combination of the identical thresholds: nodular LD (9 mm) and mean CTAV (-600 HU) in each of ULD-CDT with/without IR and CR with Friedman and Wilcoxon signed rank test. RESULTS: SSND for total 105 SSNs as well as larger SSNs with nodular LD of 9 mm or more at ULD-CDT with IR was higher than either that at ULD-CDT without IR or CR, as the areas under the ROC curve were 0.66 ± 0.02, 0.59 ± 0.01 and 0.52 ± 0.01, respectively (p < 0.05). DS at ULD-CDT with IR was 69.5 ± 10.8% in groups with larger (LD > 9 mm) and more-attenuated (>-600 HU) SSNs, and higher than in the other 3 groups (p < 0.05). CONCLUSION: ULD-CDT with IR demonstrated better SSND than that without IR or CR, with increased DS for larger and more-attenuated SSNs compared with the remaining ones.