In recent years, photon-counting computed tomography (PCD-CT) based on photon-counting detectors (PCDs) has become increasingly utilized in clinical practice. Compared with conventional CT, PCD-CT has the potential to achieve micron-level spatial resolution, lower radiation dose, negligible electronic noise, multi-energy imaging, and material identification, etc. This advancement facilitates the promotion of ultra-low dose scans in clinical scenarios, potentially detecting minimal and hidden lesions, thus significantly improving image quality. However, the current state of the art is limited and issues such as charge sharing, pulse pileup, K-escape and count rate drift remain unresolved. These issues could lead to a decrease in image resolution and energy resolution, while an increasing in image noise and ring artifact and so on. This article systematically reviewed the physical principles of PCD-CT, and outlined the structural differences between PCDs and energy integration detectors (EIDs), and the current challenges in the development of PCD-CT. In addition, the advantages and disadvantages of three detector materials were analysed. Then, the clinical benefits of PCD-CT were presented through the clinical application of PCD-CT in the three diseases with the highest mortality rate in China (cardiovascular disease, tumour and respiratory disease). The overall aim of the article is to comprehensively assist medical professionals in understanding the technological innovations and current technical limitations of PCD-CT, while highlighting the urgent problems that PCD-CT needs to address in the coming years.
Tomography, X-Ray Computed/methods* ; Photons ; Noise ; China ; Phantoms, Imaging

The ossicular replacement prosthesis should have good biocompatibility, stability, easy to install, and excellent sound transmission capacity. In this study, the characteristics of ideal materials for the ossicular replacement prosthesis were analyzed by searching the types of materials used in clinical practice and comparing the advantages and disadvantages of various materials and structures. At the same time, in combination with the current evaluation requirements and evaluation experience, the focus of the performance research project of ossicular replacement prosthesis in the process of registration is discussed to clarify the performance evaluation requirements of these products, so as to provide reference for the future work of manufacturers and regulators. The performance evaluation of ossicular replacement prosthesis focuses on its mechanical properties, fixation stability, sound transmission characteristics, biological characteristics, and magnetic resonance compatibility.
Ossicular Prosthesis ; Ossicular Replacement ; Sound ; Prosthesis Design ; Treatment Outcome

Objective To explore the optimal parameters for virtual mono-energetic imaging of liver solid lesions. Methods A retrospective analysis was performed on 60 patients undergoing contrast-enhanced spectral CT of the abdomen.The iodine concentration values of hepatic arterial phase images and the CT values of different mono-energetic images were measured.The correlation coefficient and coefficient of variation were calculated. Results The average correlation coefficients between iodine concentrations and CT values of hepatic solid lesion images at 40,45,50,55,60,65,and 70 keV were 0.996,0.995,0.993,0.989,0.978,0.970,and 0.961,respectively.The correlation coefficients at 40(P=0.007),45(P=0.022),50 keV (P=0.035)were higher than that at 55 keV,and the correlation coefficients at 40 keV(P=0.134) and 45 keV(P=0.368) had no significant differences from that at 50 keV.The coefficients of variation of the CT values at 40,45,and 50 keV were 0.146,0.154,and 0.163,respectively. Conclusion The energy of 40 keV is optimal for virtual mono-energetic imaging of liver solid lesions in the late arterial phase,which is helpful for the diagnosis of liver diseases.
Humans ; Tomography, X-Ray Computed ; Retrospective Studies ; Abdomen ; Iodine ; Liver/diagnostic imaging* ; Signal-To-Noise Ratio ; Radiographic Image Interpretation, Computer-Assisted/methods*

Objective To evaluate the impact of deep learning reconstruction algorithm on the image quality of head and neck CT angiography (CTA) at 100 kVp. Methods CT scanning was performed at 100 kVp for the 37 patients who underwent head and neck CTA in PUMC Hospital from March to April in 2021.Four sets of images were reconstructed by three-dimensional adaptive iterative dose reduction (AIDR 3D) and advanced intelligent Clear-IQ engine (AiCE) (low,medium,and high intensity algorithms),respectively.The average CT value,standard deviation (SD),signal-to-noise ratio (SNR),and contrast-to-noise ratio (CNR) of the region of interest in the transverse section image were calculated.Furthermore,the four sets of sagittal maximum intensity projection images of the anterior cerebral artery were scored (1 point:poor,5 points:excellent). Results The SNR and CNR showed differences in the images reconstructed by AiCE (low,medium,and high intensity) and AIDR 3D (all P<0.01).The quality scores of the image reconstructed by AiCE (low,medium,and high intensity) and AIDR 3D were 4.78±0.41,4.92±0.27,4.97±0.16,and 3.92±0.27,respectively,which showed statistically significant differences (all P<0.001). Conclusion AiCE outperformed AIDR 3D in reconstructing the images of head and neck CTA at 100 kVp,being capable of improving image quality and applicable in clinical examinations.
Humans ; Computed Tomography Angiography/methods* ; Radiation Dosage ; Deep Learning ; Radiographic Image Interpretation, Computer-Assisted/methods* ; Signal-To-Noise Ratio ; Algorithms

Noise is one of the most common environmental hazards to which people are exposed,and the exposure to noise can cause not only hearing but also non-hearing damage.Although noise under safety limits may not affect the auditory system,it can cause changes in stress hormone levels,which is harmful to health.However,the current studies about the impact of noise on health mainly focus on the auditory system,and little is known about the relationship between noise and stress hormone levels.Therefore,this paper reviews the studies involving noise exposure and stress hormone levels,aiming to provide ideas for strengthening the prevention and control of noise hazards.
Humans ; Hearing ; Noise/adverse effects* ; Hormones

High-frequency steady-state asymmetric visual evoked potential (SSaVEP) provides a new paradigm for designing comfortable and practical brain-computer interface (BCI) systems. However, due to the weak amplitude and strong noise of high-frequency signals, it is of great significance to study how to enhance their signal features. In this study, a 30 Hz high-frequency visual stimulus was used, and the peripheral visual field was equally divided into eight annular sectors. Eight kinds of annular sector pairs were selected based on the mapping relationship of visual space onto the primary visual cortex (V1), and three phases (in-phase[0º, 0º], anti-phase [0º, 180º], and anti-phase [180º, 0º]) were designed for each annular sector pair to explore response intensity and signal-to-noise ratio under phase modulation. A total of 8 healthy subjects were recruited in the experiment. The results showed that three annular sector pairs exhibited significant differences in SSaVEP features under phase modulation at 30 Hz high-frequency stimulation. And the spatial feature analysis showed that the two types of features of the annular sector pair in the lower visual field were significantly higher than those in the upper visual field. This study further used the filter bank and ensemble task-related component analysis to calculate the classification accuracy of annular sector pairs under three-phase modulations, and the average accuracy was up to 91.5%, which proved that the phase-modulated SSaVEP features could be used to encode high- frequency SSaVEP. In summary, the results of this study provide new ideas for enhancing the features of high-frequency SSaVEP signals and expanding the instruction set of the traditional steady state visual evoked potential paradigm.
Humans ; Evoked Potentials, Visual ; Brain-Computer Interfaces ; Healthy Volunteers ; Signal-To-Noise Ratio

Objective: To get insight into the current practice of noise reduction effect of workers as they wore hearing protectors in different domestic enterprises and the possible affected factors. Methods: From October 2020 to April 2021, using a random sampling method, 1197 workers exposed to noise in petrochemical factories, textile factories, and parts manufacturing factories were selected as the study subjects. The noise reduction effect of hearing protectors worn by workers in daily use was tested using a hearing protector suitability testing system. The personal sound attenuation level (PAR) was compared among workers in three enterprises, Targeted intervention and repetitive testing were conducted for workers who did not meet the noise reduction effect required by the enterprise, and the changes in PAR of workers before and after the intervention were compared. The comparison of baseline PARs between two or more groups was performed using the Mann Whitney test, the comparison of baseline PARs with post intervention PARs was performed using the Wilcoxon signed rank sum test, and the comparison of qualitative data between two or more groups was performed using the Chi square test. Results: The median baseline PAR for all workers was 15 dB. Men, age<30 years old, education level at or above college level, working experience of 5 to 15 years, and those who used hearing protectors for 5 to 15 years had higher PARs, with statistically significant differences (P<0.05). The median difference in baseline PAR among workers from three enterprises was statistically significant (H=175.06, P<0.01). The median PAR of subjects who did not pass the baseline increased from 3 dB to 21 dB after intervention (Z=-27.92, P<0.01) . Conclusion: Some workers wearing hearing protectors do not meet the required PAR, and low PARs may be related to incorrect wearing methods and incorrect selection of hearing protectors. As a tool for testing, training, and assisting in selection, the hearing protector suitability testing system is of great significance for worker hearing protection.
Male ; Humans ; Adult ; Hearing Loss, Noise-Induced/prevention & control* ; Ear Protective Devices ; Noise, Occupational/prevention & control* ; Hearing ; Audiometry

Objective: To explore the sound insulation, sound absorption and other noise reduction transformation methods in a noise workshop handover control room. Methods: In December 2021, through the occupational health investigation and on-site testing of the handover control room of a noise workshop, the causes of excessive noise were analyzed, and the transformation design scheme to reduce noise was proposed and the effect was analyzed. Results: Before the transformation, the peak frequency band noise intensity of the noise workshop handover control room was 112.8 dB (A), and the peak frequency was 1000 Hz. After noise reduction, the theoretical calculated control value was 61.0 dB (A), and the measured noise intensity was 59.8 dB (A) . Conclusion: The noise intensity of the handover control room is reduced after noise reduction, which is in line with the contact limit requirements of the control room in GBZ 1-2010 "Hygienic Standards for the Design of Industrial Enterprises", and has reference significance for noise control engineering.
Noise/prevention & control* ; Occupational Health ; Industry ; Reference Standards ; Hygiene ; Noise, Occupational/prevention & control*

OBJECTIVE: To propose a semi-supervised material quantitative intelligent imaging algorithm based on prior information perception learning (SLMD-Net) to improve the quality and precision of spectral CT imaging. METHODS: The algorithm includes a supervised and a self- supervised submodule. In the supervised submodule, the mapping relationship between low and high signal-to-noise ratio (SNR) data was constructed through mean square error loss function learning based on a small labeled dataset. In the self- supervised sub-module, an image recovery model was utilized to construct the loss function incorporating the prior information from a large unlabeled low SNR basic material image dataset, and the total variation (TV) model was used to to characterize the prior information of the images. The two submodules were combined to form the SLMD-Net method, and pre-clinical simulation data were used to validate the feasibility and effectiveness of the algorithm. RESULTS: Compared with the traditional model-driven quantitative imaging methods (FBP-DI, PWLS-PCG, and E3DTV), data-driven supervised-learning-based quantitative imaging methods (SUMD-Net and BFCNN), a material quantitative imaging method based on unsupervised learning (UNTV-Net) and semi-supervised learning-based cycle consistent generative adversarial network (Semi-CycleGAN), the proposed SLMD-Net method had better performance in both visual and quantitative assessments. For quantitative imaging of water and bone materials, the SLMD-Net method had the highest PSNR index (31.82 and 29.06), the highest FSIM index (0.95 and 0.90), and the lowest RMSE index (0.03 and 0.02), respectively) and achieved significantly higher image quality scores than the other 7 material decomposition methods (P < 0.05). The material quantitative imaging performance of SLMD-Net was close to that of the supervised network SUMD-Net trained with labeled data with a doubled size. CONCLUSIONS A small labeled dataset and a large unlabeled low SNR material image dataset can be fully used to suppress noise amplification and artifacts in basic material decomposition in spectral CT and reduce the dependence on labeled data-driven network, which considers more realistic scenario in clinics.
Tomography, X-Ray Computed/methods* ; Image Processing, Computer-Assisted/methods* ; Algorithms ; Signal-To-Noise Ratio ; Perception

OBJECTIVE: To propose a diffusion tensor field estimation network based on 3D U-Net and diffusion tensor imaging (DTI) model constraint (3D DTI-Unet) to accurately estimate DTI quantification parameters from a small number of diffusion-weighted (DW) images with a low signal-to-noise ratio. METHODS: The input of 3D DTI-Unet was noisy diffusion magnetic resonance imaging (dMRI) data containing one non-DW image and 6 DW images with different diffusion coding directions. The noise-reduced non-DW image and accurate diffusion tensor field were predicted through 3D U-Net. The dMRI data were reconstructed using the DTI model and compared with the true value of dMRI data to optimize the network and ensure the consistency of the dMRI data with the physical model of the diffusion tensor field. We compared 3D DTI-Unet with two DW image denoising algorithms (MP-PCA and GL-HOSVD) to verify the effect of the proposed method. RESULTS: The proposed method was better than MP-PCA and GL-HOSVD in terms of quantitative results and visual evaluation of DW images, diffusion tensor field and DTI quantification parameters. CONCLUSION The proposed method can obtain accurate DTI quantification parameters from one non-DW image and 6 DW images to reduce image acquisition time and improve the reliability of quantitative diagnosis.
Diffusion Tensor Imaging ; Reproducibility of Results ; Diffusion Magnetic Resonance Imaging ; Algorithms ; Signal-To-Noise Ratio