This paper reports the brain activation patterns of five subjects who were abruptly awakened from microsleeps in a simulated automotive driving experiment. By comparing the BOLD signals between behavioral microsleep (BM), abrupt awakening (AA) and post-abrupt awakening (post-AA) stages, we observed that visual area, frontal cortex, limbic lobe manifested more intense activation during the AA stage while frontal cortex, temporal cortex, primary motor area and insula were more activated during the post-AA stage. These results suggested that the subjects were likely in mental states differ from those associated with decision making processes as they went through and emerged from the abrupt awakening episodes.
Abstract Background Polycyclic aromatic hydrocarbon (PAH)-rich substances like cigarette smoke and PM 2.5 induce aryl hydrocarbon receptor (AHR)-mediated aryl hydrocarbon receptor repressor (AHRR) methylation. AHRR cg05575921 and coagulation factor II (thrombin) receptor-like 3 (F2RL3) cg03636183 methylation patterns are well-established biomarkers for smoking. Even though AHRR cg05575921 methylation has recently been associated with PM 2.5 , the interaction between smoking and PM 2.5 on AHRR methylation is yet to be fully explored. We evaluated AHRR and F2RL3 CpG sites to identify potential significant markers in relation to PM 2.5 and smoking in Taiwanese adults. Methods DNA methylation and smoking data of 948 participants aged 30–70 years were obtained from the Taiwan Biobank Database (2008–2015), while PM 2.5 data were obtained from the Air Quality Monitoring Database (2006–2011). Results Smoking and PM 2.5 were independently associated with hypomethylation (lower levels) of AHRR cg05575921, AHRR cg23576855, F2RL3 cg03636183, and F2LR3 cg21911711 after multiple-comparison correction (Bonferroni P < 0.00028409). Cg05575921 was the most hypomethylated AHRR CpG site, while cg03636183 was the most hypomethylated F2RL3 CpG site. Overall, cg05575921 was the most hypomethylated CpG site: β = − 0.03909, P < 0.0001; − 0.17536, P < 0.0001 for former and current smoking, respectively (P-trend smoking < 0.0001) and − 0.00141, P < 0.0001 for PM 2.5 . After adjusting for F2RL3 cg03636183, smoking and PM 2.5 remained significantly associated with cg05575921 hypomethylation: β − 0.02221, P < 0.0001; − 0.11578, P < 0.0001 for former and current smoking, respectively (P-trend smoking < 0.0001) and − 0.0070, P = 0.0120 for PM 2.5 . After stratification by sex, smoking and PM 2.5 remained associated ( P < 0.05) with cg05575921 hypomethylation in both men ( β = − 0.04274, − 0.17700, and − 0.00163 for former smoking, current smoking, and PM 2.5 , respectively) and women ( β = − 0.01937, − 0.17255, and − 0.00105 for former smoking, current smoking, and PM 2.5 , respectively). After stratification by residential area, former and current smoking remained associated ( P < 0.05) with cg05575921 hypomethylation: β = − 0.03918 and − 0.17536, respectively (P-trend smoking < 0.0001). Living in the central and southern areas was also associated ( P < 0.05) with cg05575921 hypomethylation: β = − 0.01356 and − 0.01970, respectively (P-trend area < 0.0001). Conclusion Smoking and PM 2.5 were independently associated with hypomethylation of cg05575921, cg23576855, cg03636183, and cg21911711. The most hypomethylated CpG site was cg05575921 and its association with smoking and PM 2.5 was dose-dependent.
Abstract Time-of-flight dual photon emission computed tomography (TOF-DuPECT) is an imaging system that can obtain radionuclide distributions using time information recorded from two cascade-decay photons. The potential decay locations in the image space, a hyperbolic response curve, can be determined via time-difference-of-arrival (TDOA) estimations from two instantaneous coincidence photons. In this feasibility study, Monte Carlo simulations were performed to generate list-mode coincidence data. A full-ring positron emission tomography-like detection system geometry was built in the simulation environment. A contrast phantom and a Jaszczak-like phantom filled with Selenium-75 (Se-75) were used to evaluate the image quality. A TOF-DuPECT system with varying coincidence time resolution (CTR) was then evaluated. We used the stochastic origin ensemble (SOE) algorithm to reconstruct images from the recorded list-mode data. The results indicate that the SOE method can be successfully employed for the TOF-DuPECT system and can achieve acceptable image quality when the CTR is less than 100 ps. Therefore, the TOF-DuPECT imaging system is feasible. With the improvement of the detector with time, future implementations and applications of TOF-DuPECT are promising. Further quantitative imaging techniques such as attenuation and scatter corrections for the TOF-DuPECT system will be developed in future.
Cellular density is a major factor responsible for changes in apparent diffusion coefficients (ADCs). The authors hypothesized that loss of tumor cells after Gamma Knife surgery (GKS) might alter ADC values. Magnetic resonance imaging, including diffusion-weighted (DW) imaging, was performed to detect cellular changes in brain tumors so that the authors could evaluate the tumor response to GKS as well as the efficacy of the procedure.The authors conducted a prospective trial involving 31 patients harboring solid or cystic vestibular schwannomas (VSs) that were treated with GKS. The patients underwent serial MR imaging, including DW imaging, before GKS and at multiple intervals following the procedure. The authors observed the patients over time, evaluating MR imaging findings and clinical outcomes at 6-month intervals. The ADCs were calculated from echo-planar DW images, and mean ADC values were compared at each follow-up.The mean follow-up period was 36.5 months (range 18-60 months). Imaging studies showed a reduction in tumor volume in 19 patients (61.3%) and tumor growth arrest in 9 patients (29%). In the remaining 3 patients (9.7%), tumor enlargement was documented at 18, 36, and 42 months. The mean ADC value before GKS for all solid VSs was 1.06 ± 0.17 × 10(-3) mm(2)/second, which significantly increased 6 months after GKS and continued to increase with time (p = 0.0086). The mean ADC value for treated solid tumors as of the last mean follow-up of 36 months (range 18-60 months) was 1.72 ± 0.26 × 10(-3) mm(2)/second (range 1.50-2.09 × 10(-3) mm(2)/second), which was significantly higher than that before GKS (p = 0.0001). Tumor volumes were positively related to ADC values (p = 0.03). The mean ADC value before GKS for all cystic VSs was 2.09 ± 0.24 × 10(-3) mm(2)/second (range 1.80-2.58 × 10(-3) mm(2)/second). The mean ADC value for treated cystic tumors as of the last mean follow-up of 38 months (range 18-48 months) was 1.89 ± 0.22 × 10(-3) mm(2)/second. In 3 patients harboring solid VSs, the tumor enlarged after GKS but the ADC values were higher than those before GKS. The authors considered these tumors to be controlled and continued follow-up in the patients.Apparent diffusion coefficient values may be useful for evaluating treatment results before any definite volume change is detected on imaging studies and for distinguishing radiation-induced necrosis from tumor recurrence in cases in which other imaging results are not definitive, as in cases of increased tumor volume or no volume change. The authors suggest that ADC measurements be included during routine MR imaging examinations for the evaluation of GKS results.
Most cases of tumor-related hemifacial spasm (HFS) are treated by open surgery. The authors report the effects of Gamma Knife surgery (GKS) on benign tumor-related HFS at a mean follow-up time of 84 months.Between 2000 and 2011, 6 patients (5 women and 1 man) harboring single tumors of the cerebellopontine angle (4 meningiomas and 2 vestibular schwannomas [VSs]) and experiencing HFS underwent GKS as a primary treatment. The mean age of the patients at the time of radiosurgery was 52.7 years (range 45-60 years). The patients' tumors lay within the radiosurgical target area. In the 4 cases of meningioma, the mean radiosurgical treatment volume was 5.3 cm(3) (range 1.2-9.6 cm(3)), and the mean radiosurgical tumor margin dose was 14.1 Gy (range 12-18 Gy); in the 2 cases of VS, the treatment volume was 2.5 cm(3) in 1 patient and 11.2 cm(3) in the other, and the margin doses were 11.5 and 12 Gy, respectively. The mean duration of HFS symptoms was 15.5 months (range 3-36 months).The mean follow-up period was 84 months (range 40-110 months). Overall, 4 (66%) of the 6 patients experienced complete relief from HFS without medication after GKS and 1 patient obtained a good outcome. The mean time for improvement to be realized was 12.6 months (range 3-24 months). Only 1 patient failed to experience relief from HFS, and coincidentally, the tumor did not shrink in that case. In all 6 patients (100%), tumor growth was controlled at a mean follow-up of 56 months after GKS: in 5 patients the tumor had decreased in size and in the other patient the tumor size remained unchanged. No new neurological deficit was noted after GKS, and 1 patient with facial numbness reported improvement after tumor shrinkage.Gamma Knife surgery appears to be effective in treating benign tumor-related HFS and in controlling tumor growth. A reduction in tumor volume is related to spasm improvement. Although a time latency for spasm relief is associated with GKS, minimal side effects are expected.
This study presents a practical method for reconstructing the optical system of personalized eye models by using magnetic resonance imaging (MRI). Monocular images were obtained from a young (20-year-old) healthy subject viewing at a near point (10 cm). Each magnetic resonance image was first analyzed using several commercial software to capture the profile of each optical element of the human eye except for the anterior lens surface, which could not be determined because it overlapped the ciliary muscle. The missing profile was substituted with a modified profile from a generic eye model. After the data-including the refractive indices from a generic model-were input in ZEMAX, we obtained a reasonable initial layout. By further considering the resolution of the MRI, the model was optimized to match the optical performance of a healthy eye. The main benefit of having a personalized eye model is the ability to quantitatively identify wide-angle ocular aberrations, which were corrected by the designed free-form spectacle lens.
In recent years, the temporal clustering analysis (TCA) method has been introduced to analyze functional MRI (fMRI) data without prior information about the activation patterns or experimental paradigms. It has been successfully applied to situations under which the timing of events of interest is not known. However, useful information regarding the spatial correlation of activation pixels with their neighbors is not taken into account in the original TCA (OTCA) method. In this study, we propose a new method called 'STCA' (spatial-TCA) which incorporates spatial information with the TCA method to improve the sensitivity in detecting the time window. The spatial information is defined as the correlation coefficient of the time activity curve between each pixel and its neighbors. The inclusion of spatial information can effectively reduce the contribution from noisy pixels and enhance the sensitivity. Both simulated data and in vivo fMRI experiments are employed to verify the method. Preliminary results show that the proposed method has increased the sensitivity significantly for in vivo fMRI data in detecting the activation response time as compared to both OTCA and modified TCA (MTCA). The OTCA/MTCA was applied to spatially smoothed data for various contrast-noise ratios and compared to STCA. The SNR improvements of both OCTA/MTCA are obvious but blurring effects are also visible. The STCA does not have this artifact.
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