Clinical characteristics of cryptococcal meningitis patients with anti-granulocyte-macrophage colony-stimulating factor autoantibodies / 中华传染病杂志

Objective:To investigate the clinical characteristics and prognosis of cryptococcal meningitis patients with anti-granulocyte-macrophage colony-stimulating factor (GM-CSF) autoantibodies.Methods:A total of 216 non-acquired immunodeficiency syndrome (AIDS) related cryptococcal meningitis cases with positive cultures of Cryptococcus, hospitalized at Huashan Hospital, Fudan University during January 2014 and December 2021, were retrospectively included. The serum anti-GM-CSF autoantibodies were detected by enzyme linked immunosorbent assay, and the clinical characteristics and prognosis were compared between patients with and without anti-GM-CSF autoantibodies. Statistical comparisons were mainly performed using the chi-square test or Fisher′s exact test. Cox proportional-hazards model was used to analyze the risk factors associated with prognosis. Results:Among 216 enrolled patients, 23 patients were positive of anti-GM-CSF autoantibodies, with a positive rate of 10.6%. Among 23 patients, seven cases were infected with Cryptococcus gattii, and 16 cases were infected with Cryptococcus neoformans. In the group with positive anti-GM-CSF autoantibodies, 30.4%(7/23) of the patients were infected with Cryptococcus gattii, which was higher than that of 1.6%(3/193) in the group with negative anti-GM-CSF autoantibodies, and the difference was statistically significant ( χ2=38.82, P<0.001). In the group with positive anti-GM-CSF autoantibodies, 30.0% (6/20) had mass lesions with a diameter greater than three centimeters in the lungs, and the one-year all-cause mortality rate was 50.0% (10/20), which were both higher than those of 3.4%(5/145) and 16.1% (29/180) in the negative group, respectively. The differences were both statistically significant (both Fisher′s exact test, P<0.01). Age≥60 years (hazard ratio ( HR)=4.146, P=0.002), predisposing factors ( HR=3.160, P=0.021), epilepsy ( HR=6.129, P=0.002), positive anti-GM-CSF autoantibodies ( HR=2.675, P=0.034), white blood cell count of cerebrospinal fluid (CSF)<100 ×10 6/L ( HR=2.736, P=0.039), the titers of cryptococcal capsular polysaccharide antigen of CSF≥1∶1 280 ( HR=4.361, P=0.009) were independent risk factors for one-year all-cause mortality in patients with cryptococcal meningitis. Conclusions:In non-AIDS related cryptococcal meningitis patients, the positive rate of serum anti-GM-CSF autoantibodies is as high as 10.6%. Patients with anti-GM-CSF autoantibodies could be infected with both Cryptococcus neoformans and Cryptococcus gattii, and they have higher proportion of lung mass lesions than patients with negative anti-GM-CSF autoantibodies. The one-year survival rate decreases significantly in patients with anti-GM-CSF autoantibodies, which is an independent risk factor for the prognosis of cryptococcal meningitis.

Study of three-dimensional dose distribution based-deep learning in predicting distant metastasis in head and neck cancer / 中华放射肿瘤学杂志

Objective:To investigate the role of three-dimensional dose distribution-based deep learning model in predicting distant metastasis of head and neck cancer.Methods:Radiotherapy and clinical follow-up data of 237 patients with head and neck cancer undergoing intensity-modulated radiotherapy (IMRT) from 4 different institutions were collected. Among them, 131 patients from HGJ and CHUS institutions were used as the training set, 65 patients from CHUM institution as the validation set, and 41 patients from HMR institution as the test set. Three-dimensional dose distribution and GTV contours of 131 patients in the training set were input into the DM-DOSE model for training and then validated with validation set data. Finally, the independent test set data were used for evaluation. The evaluation content included the area under receiver operating characteristic curve (AUC), balanced accuracy, sensitivity, specificity, concordance index and Kaplan-Meier survival curve analysis.Results:In terms of prognostic prediction of distant metastasis of head and neck cancer, the DM-DOSE model based on three-dimensional dose distribution and GTV contours achieved the optimal prognostic prediction performance, with an AUC of 0.924, and could significantly distinguish patients with high and low risk of distant metastasis (log-rank test, P<0.001). Conclusion:Three-dimensional dose distribution has good predictive value for distant metastasis in head and neck cancer patients treated with IMRT, and the constructed prediction model can effectively predict distant metastasis.

Different receptive fields-based automatic segmentation network for gross target volume and organs at risk of patients with nasopharyngeal carcinoma / 中华放射肿瘤学杂志

Objective:To establish an automatic segmentation network based on different receptive fields for gross target volume (GTV) and organs at risk in patients with nasopharyngeal carcinoma.Methods:Radiotherapy data of 100 cases of nasopharyngeal carcinoma including CT images and GTV and organs at risk delineated by the physicians were collected. Ninety plans were randomly selected as the training dataset, and the other 10 plans as the validation dataset. Firstly, the images were subject to three data augmentation methods including center cropping, vertical flipping and rotation (-30°to 30°), and then input into MA_net networks proposed in this study for training. The model performance of networks was assessed by the number of network parameters (NP), floating-point number (FPN), the running memory (RM) and Dice index (DI), and eventually compared with DeeplabV3+ , PSP_net, UNet+ + and U_Net networks.Results:When the input image was in the size of 240×240, MA_net had a NP of 23.20%, 20.10%, 25.55% and 27.11% of these 4 networks, 50.02%, 19.86%, 6.37% and 13.44% for the FPN, 40.63%, 23.60%, 11.58% and 14.99% for the RM, respectively. For the DI of GTV, MA_net was 1.16%, 2.28%, 1.27% and 3.59% higher than these 4 networks. For the average DI of GTV and OAR, MA_net was 0.16%, 1.37%, 0.30% and 0.97% higher than these 4 networks.Conclusion:Compared with those four networks, the proposed MA_net network has slightly higher Dice index with fewer parameters, lower FPN and smaller RM.

Free trajectory cone beam computed tomography reconstruction method for synchronous scanning of geometric calibration phantom and imaging object / 生物医学工程学杂志

In order to suppress the geometrical artifacts caused by random jitter in ray source scanning, and to achieve flexible ray source scanning trajectory and meet the requirements of task-driven scanning imaging, a method of free trajectory cone-beam computed tomography (CBCT) reconstruction is proposed in this paper. This method proposed a geometric calibration method of two-dimensional plane. Based on this method, the geometric calibration phantom and the imaging object could be simultaneously imaged. Then, the geometric parameters could be obtained by online calibration method, and then combined with the geometric parameters, the alternating direction multiplier method (ADMM) was used for image iterative reconstruction. Experimental results showed that this method obtained high quality reconstruction image with high contrast and clear feature edge. The root mean square errors (RMSE) of the simulation results were rather small, and the structural similarity (SSIM) values were all above 0.99. The experimental results showed that it had lower image information entropy (IE) and higher contrast noise ratio (CNR). This method provides some practical value for CBCT to realize trajectory freedom and obtain high quality reconstructed image.

Generative Adversarial Networks based synthetic-CT generation for patients with nasopharyngeal carcinoma / 中华放射肿瘤学杂志

Objective:To establish a correlation model between MRI and CT images to generate synthetic-CT (sCT) of head and neck cancer during MRI-guided radiotherapy by using generative adversarial networks (GAN).Methods:Images and IMRT plans of 45 patients with nasopharyngeal carcinoma were collected before treatment. Firstly, the MRI (T1) and CT images were preprocessed, including rigid registration, clipping, background removal and data enhancement, etc. Secondly, the cases were trained by GAN, of which 30 cases were randomly selected and put into the network as training set images for modeling and learning, and the other 15 cases were used for testing. The image quality of predicted sCT and real CT were statistically compared, and the dose distribution recalculated upon predicted sCT was statistically compared with that of real planned dose distribution.Results:The mean absolute error of the predicted sCT of the testing set was (79.15±11.37) HU, and the SSIM value was 0.83±0.03. The MAE values of dose distribution difference at different regional levels were less than 1% compared to the prescription dose. The gamma passing rate of the sCT dose distribution was higher than 92% and 98% under the 2mm/2% and 3mm/3% criteria.Conclusions:We have successfully proposed and realized the generation of sCT for head and neck cancer using GAN, which lays a foundation for the implementation of MRI-guided radiotherapy. The comparison of image quality and dosimetry shows the feasibility and accuracy of this method.

Evaluation of three predictive models of knowledge-based treatment strategies for radiotherapy / 中华放射肿瘤学杂志

Objective:To compare the accuracy and generalized robustness of three predictive models of knowledge-based treatment strategies for radiotherapy for optimized model selection.Methods:The clinical radiotherapy plans of 45 prostate cancer (PC) cases and 25 nasopharyngeal cancer (NPC) cases were collected, and analyzed using three models (Z, L and S model), proposed by Zhu et al, Appenzoller et al and Shiraishi et al, respectively, to predict the dose-volume histogram (DVH) of bladder and rectum on PC cases and that of left and right parotid on NPC cases. The prediction error was measured by the difference of area under the predicted DVH and the clinical DVH curves (|V (pre_DVH)-V (clin_DVH)|), where a smaller prediction error implies a greater prediction accuracy. The accuracies of these three models were compared on the single organ at risk (OAR), and the generalized robustness of models was evaluated and compared by calculating the standard deviation of the prediction accuracy on different OAR. Results:For bladder and rectum, the prediction error of L model (0.114 and 0.163, respectively) was significantly higher than those values of Z and S models (≤0.071, P<0.05); for left parotid gland, the predicted error of S model (0.033) did not present significant difference from those values of Z and L models (≤0.025, P>0.05); for right parotid gland, S model (0.033) demonstrated significantly higher prediction error than those of Z and L models (≤0.028, P<0.05). Regarding different OAR, S model showed a lower standard deviation of prediction accuracy when comparing to Z and L models (0.016, 0.018 and 0.060, respectively). Conclusions:In the prediction of DVH in bladder and rectum of PC, Z and S models were more accurate than L model. In contrast, Z and L models demonstrated higher accuracy than S model in the prediction of left and right parotid glands of NPC. In respect to different OAR, the generalized robustness of S model was superior than the other two models.

Impacts of different registration ranges on the accuracy of multiple metastases treated with tomotherapy / 中华放射肿瘤学杂志

Objective:To analyze the impacts of different registration ranges on the accuracy of multiple metastases treated with helical tomotherapy.Methods:According to the locations of target volumes, 28 patients with multiple metastases were divided into the head/chest group ( n= 15) and the chest/pelvis group ( n= 13). The CT and MVCT images acquired in first fraction were studied and compared in two groups, which were captured and matched with different registration ranges (all targets/the targets in proximity to the head/ the targets in proximity to the foot). The CTV MVCT volume coverage rate (CR) under the matched target volumes, the dice similarity coefficient (DSC) between the CTV CT and CTV MVCT, and the position deviation of the CTV geometric center were compared. Results:We observed similar results in the head/chest group and chest/pelvis group. Specifically, there was no significant difference in the CR, DSC and geometric center deviation between the two target regions when registered with all targets ( P>0.05). Regarding single target region registration, the DSC and geometric center deviation of this target were significantly superior to the other non-registered target ( P< 0.05). To a single target, the CR, DSC, and geometric center deviation obtained with registration presented the best performance, which was significantly greater than these parameters obtained with all targets registration, while the other side target area obtained the worst results ( P< 0.05). Conclusions:Registration of one target region may reduce the accuracy of other non-registered targets. We recommend that the image guidance ranges for multiple metastases treated with tomotherapy should include all target regions or independent registrations for different targets.

Efficacy and safety of high-dose caspofungin in the treatment of invasive pulmonary aspergillosis / 中华传染病杂志

Objective To investigate the clinical efficacy and safety of high-dose caspofungin (70 mg/d)as initial or salvage treatment for invasive pulmonary aspergillosis.Methods Twenty-one patients with proven or probable invasive pulmonary aspergillosis from June 2014 to October 2017 in Huashan Hospital,Fudan University were retrospectively reviewed.According to the anti-fungal treatment before high-dose caspofungin application,patients were divided into initial treatment group and salvage treatment group.Patients' clinical data and laboratory data were collected.The characteristics,clinical efficacy,adverse reactions,one-year survival rate and the overall effective rate were evaluated.The prognosis of the two groups was compared by Kaplan-Meier analysis.Results Twenty of the 21 patients opportunistic acquired invasive pulmonary aspergillosis during the treatment of underlying diseases.Five patients were initially treated with high-dose caspofungin for 68 (62) days.At week 12,one patient achieved complete response,3 patients achieved partial response,and the overall effective rate was 80％ (4/5).Sixteen patients received caspofungin as salvage therapy for 66.50 (58) days,of which one patient got complete response at week 12,10 had partial response,and the overall effective rate was 68.75％ (11/16).One-year follow-up showed that no patient died in the initial treatment group,and the one-year survival rate was 100％ (5/5).In salvage treatment group,3 patients died of pulmonary bacterial infections and the one-year survival rate was 81.25％ (13/16).During treatment,one patient had elevated total bilirubin,which was possibly associated with high-dose caspofungin.Conclusions High-dose caspofungin regimen has good efficacy and safety,both for initial treatment and salvage therapy in patients with invasive pulmonary aspergillosis.

OAR predicted dose distribution and gEUD based treatment planning optimization for IMRT / 中华放射医学与防护杂志

Objective To propose a treatment planning optimization algorithm which can make full use of OAR dose distribution prediction meanwhile improving the output planning quality as much as possible.Methods We had reformulated an FMO function under the guidance of dose distribution prediction and also integrated equivalent uniform dose (gEUD) based on the consideration of prediction uncertainty,for providing optimal solution.Performance of the method was evaluated by comparing the optimized IMRT plan quality of 8 cervical cancers in the term of DVH curves,dose distribution and dosimetric endpoints with the original ones.Results The proposed method had a feasible,fast solution.Compared with original plan,its output plan had better plan quality in better dose homogeneity,less hot spot and further dose sparing for OARs.V30,V45 of rectum was decreased by (6.60±3.53)％ and (17.03±7.44)％,respectively,with the statistically significant difference (t=-4.954,-6.055,P＜0.05).V30,V45 of bladder was decreased by (14.74 ± 5.61) ％ and (14.99 ± 4.53) ％,respectively,with the statistically significant difference (t=-6.945,-8.759,P＜0.05).Conclusions We have successfully developed a predicted dose distribution and equivalent uniform dose-based planning optimization method,which is able to make good use of 3D dose prediction and ensure the output plan quality for intensity modulated radiation therapy.

Multi-task learning-based three-dimensional dose distribution prediction for multiple organs in a single model / 中华放射肿瘤学杂志

Objective To establish a three-dimensional (3D) dose prediction model,which can predict multiple organs simultaneously in a single model and automatically learn the effect of the geometric anatomical structure on dose distribution.Methods Clinical radiotherapy plans of patients diagnosed with the same type of tumors were collected and retrospectively analyzed.For every plan,each organs at risk (OAR) voxel was regarded as the study sample and its deposited dose was considered as the dosimetric feature.A regularized multi-task learning method than could learn the relationship among different tasks was employed to establish the relationship matrix among tasks and the correlation between geometric structure and dose distribution among organs.In this experiment,the spinal cord,brainstem and bilateral parotids involved in the intensity-modulated radiotherapy (IMRT) plan of 15 nasopharyngeal cancer patients were utilized to establish the multi-organ prediction model.The relative percentage error between the predicted dose of voxel and the clinical planning dose was calculated to assess the feasibility of the model.Results Ten cases receiving IMRT plans were utilized as the training data,and the remaining five cases were used as the test data.The test results demonstrated a higher prediction accuracy and less data demand.And the average voxel dose errors among the spinal cord,brainstem and the left and right parotids were (2.01±0.02)％,(2.65± 0.02) ％,(2.45± 0.02) ％ and (2.55± 0.02) ％,respectively.Conclusion The proposed model can accurately predict the dose of multiple organs in a single model and avoid the establishment of multiple single-organ prediction models,laying a solid foundation for patient-specific plan quality control and knowledge-based treatment planning.

Accuracy of different image registration methods in image-guided adaptive brachytherapy for cervical cancer / 南方医科大学学报

OBJECTIVE@#To compare the accuracy of different methods for image registration in image-guided adaptive brachytherapy (IGABT) for cervical cancer.@*METHODS@#The last treatment planning CT images (CT1) and the first treatment planning CT images (CT2) were acquired from 15 patients with cervical cancer and registered with different match image qualities (retained/removed catheter source in images) and different match regions [target only (S Group)/ interested organ structure (M Group)/body (L Group)] in Velocity3.2 software. The dice similarity coefficient (DSC) between the clinical target volumes (CTV) of the CT1 and CT2 images (CTVCT1 and CTVCT2, respectively) and between the organs-at-risk (OAR) of the two imaging datasets (OARCT1 and OARCT2, respectively) were used to evaluate the image registration accuracy.@*RESULTS@#The auto-segmentation volume of the catheter source using Velocity software based on the CT threshold was the closest to the actual volume within the CT value range of 1700-1800 HU. In the retained group, the DSC for the OARs of was better than or equal to that of the removed group, and the DSC value of the rectum was significantly improved ( < 0.05). For comparison of different match regions, the high-risk target volume (HRCTV) and the low-risk target volume (IRCTV) had the best precision for registration of the target area, which was significantly greater than that of M group and L group ( < 0.05). The M group had better registration accuracy of the target area and the best accuracy for the OARs. The DSC values of the bladder and rectum were significantly better than those of the other two groups ( < 0.05).@*CONCLUSIONS@#The CT value range of 1700-1800 HU is optimal for automatic image segmentation using Velocity software. Automatic segmentation and shielding the volume of the catheter source can improve the image quality. We recommend the use of interested organ structures regions for image registration in image-guided adaptive brachytherapy for cervical cancer.

A retrospective review of 46 cases of chronic invasive fungal rhinosinusitis / 中华传染病杂志

Objective To investigate the clinical characteristics of chronic invasive fungal rhinosinusitis.Methods Clinical features and outcomes of 46 proven cases of chronic invasive fungal rhinosinusitis admitted in Huashan Hospital,Fudan University from January 2009 to December 2016 were retrospectively reviewed.Results Of the 46 patients enrolled,left sphenoid sinus,ethmoid sinus and maxillary sinus were affected in 24,23 and 20 cases,respectively,while right maxillary sinus,ethmoid sinus and sphenoid sinus were affected in 18,16 and 15 eases,respectively.Left and right frontal sinus were affected in 9 and 6 cases,respectively.The central nervous system and orbit were the most commonly affected sites in external nasal involvements,noted in 22 cases respectively.Left sphenoid (17 cases) and ethmoid sinus (15 cases) involvements were most common in central nervous system affected patients.Left sphenoid (14 cases) and ethmoid sinus (13 cases) involvements were most common in orbit affected patients.Aspergillus species were the primary pathogens observed in 42 eases.Zygomycete,candida and dark filamentous fungus were observed in two,one and one case,respectively.Pathologically,37 of the cases were chronic nongranulomatous type and the left 9 were chronic granulomatous type who were all immunocompetent hosts.The initial symptoms usually included headache,dizziness and nasal discomforts including nasal obstruction and purulent secretion.The chief complaints usually included headache,dizziness,and visual disturbances including blurred vision,vision loss or even blindness.Antifungal treatment combined with surgical interventions for removal or drainage focus lesions achieved significant effect,and 42 patients were cured.Conclusions Chronic invasive fungal rhinosinusitis should be taken into consideration in the presence of nasal discomforts or nonspecific symptoms such as headache and dizziness.The possibility of chronic invasive fungal rhinosinusitis should be cautious after the emergence of vision abnormalities.

A study of deformable image registration of high-dose-rate brachytherapy CT image to intensity modulated radiation therapy CT image / 中华放射肿瘤学杂志

Objective To study a novel method for the high-dose-rate brachytherapy (HDR) CT image to the intensity modulated radiation therapy (IMRT) CT image deformable image registration and dose accumulation.Methods The applicator in the HDR CT image is first segmented and removed,then a deflation step is performed on the applicator-free HDR CT image by solving the Navier-Stokes equation.Demons algorithm is utilized to register the deflated HDR CT image to the IMRT CT image,along with the HDR dose.The deformed HDR dose is then added on the IMRT dose and yield the final accumulated dose.Results The HDR CT image and IMRT CT image,as well as the corresponding dose distribution,from five cervical cancer patients are used for evaluation of the proposed algorithm,the results show that the proposed method can effectively get rid of the influence of the applicator and produce an accurate accumulated dose.Conclusions Dose accumulation and supervision is an important step in adaptive radiotherapy for accurate dose delivery and treatment plan re-optimization.The proposed method in this study can effectively accumulate the HDR dose to the IMRT dose domain,and the accuracy is proved to be sufficient for clinical needs.

Cone beam CT image iterative reconstruction based on Split-Bregman method / 南方医科大学学报

<p><b>OBJECTIVE</b>We propose a new iterative reconstruction method based on split-Bregman method with tight frame regularization for effective and accurate reconstruction of the sparse-view cone beam CT image.</p><p><b>METHODS</b>A tight frame was chosen as the regularization term for the objective function, so that the image reconstruction involves only the minimization of an objective function according to the compressed sensing theory. We utilized the split-Bregman method to tackle the task of minimization in three steps: (1) a fast calculation of the forward projection matrix; (2) introducing an intermediate variable to transform the non-differentiated L1 regularization term into the differentiated L2 regularization problem, and solving the target function using conjugate-gradient method; (3) updating the intermediate variable using shrinkage formula from Bregman method.</p><p><b>RESULTS</b>Digital and physical phantom experimental results suggested that our new approach had great advantages in terms of image quality, reconstruction time, and applicability.</p><p><b>CONCLUSION</b>The proposed method can accurately reconstruct CBCT image with limited data to lower the X-ray dose and accelerate the calculation speed in comparison with the POCS method.</p>

Design and validation of synchronous exposure control system of dental cone beam CT / 生物医学工程学杂志

In the design of oral cone beam CT, cooperation between synergic control of X-ray source, real-time acquisition of flat detector and motion of mechanical structure affects the CT image quality. Based on the full analysis of the flat detector's timing signal characteristics, this research was carried out with microprocessor controller (MCU), complex programmable logic device (CPLD), and light couplings to design and realize synchronous exposure control system. To evaluate whether the design of the synchronous exposure control system in this project could reach the required imaging accuracy, we employed the projected images in the system to analyze its stability, linear consistency, signal to noise ratio and precede the FDK construction.

A fast iterative reconstruction algorithm of sparse angular CT based on the selective total variation / 生物医学工程学杂志

Aiming at the problem of high-quality image reconstruction from projection data at sparse angular views, we proposed an improved fast iterative reconstruction algorithm based on the minimization of selective image total variation (TV). The new reconstruction scheme consists of two components. Firstly, the algebraic reconstruction technique (ART) algorithm was adopted to reconstruct image that met the identity and non-negativity of projection data, and then, secondly, the selective TV minimization was used to modify the above image. Two phases were alternated until it met the convergence criteria. In order to further speed up the convergence of the algorithm, we applied a fast convergence technology in the iterative process. Experiments on simulated Shepp-Logan phantom were carried out. The results demonstrated that the new method not only improved image reconstruction quality and protected the edge of the image characteristics, but also improved the convergence speed of the iterative reconstruction significantly.

Changes of response patterns to excitatory stimuli of different intensities: a model-based study of cochlear nucleus neurons / 南方医科大学学报

<p><b>OBJECTIVE</b>The cochlear nucleus (CN) neurons show 3 principal response patterns to short tone bursts, namely the primary-like, chopper and onset response patterns. We previously established an excitatory model to simulate the response patterns of CN neurons to stimuli. In this study, we aimed to investigate the effects of excitatory intensity on the CN neuron response patterns and explore the role of inhibitory inputs under normal physiological conditions.</p><p><b>METHODS</b>Based on the platform of Matlab and the excitatory model derived from the integrate-and-fire model, we altered the intensity of excitatory inputs in dB range and obtained the histograms to analyze the changes in the response patterns of the neurons using OriginPro 7.5 data analysis software.</p><p><b>RESULTS</b>The original primary-like response pattern of the neurons did not vary significantly while the chopper and onset response patterns changed into primary-like responses with the increase of the excitatory input intensity. But this response pattern alteration as a result of excitatory input intensity changes was rarely observed under normal physiological conditions.</p><p><b>CONCLUSIONS</b>The CN neurons receive balanced excitatory and inhibitory inputs, which stabilize the neuronal membrane potential within a limited range. The balanced inhibitory inputs decide the response pattern of a given neuron.</p>

A mechanical simulation model of the basilar membrane of the cochlea / 南方医科大学学报

<p><b>OBJECTIVE</b>To establish a mechanical simulation model for studying the relationship between the characteristic frequency and feature location of the basilar membrane of the cochlea.</p><p><b>METHODS</b>Macro-mechanical methods were used to simplify the details of the model. With simulation tools, the basilar membrane vibration frequency characteristics were analyzed based on the box model.</p><p><b>RESULTS</b>The basilar membrane had obvious frequency-selective properties, and the basilar membrane from the stapes was sensitive to high frequencies while the farther membrane was sensitive to low frequencies.</p><p><b>CONCLUSION</b>The frequency characteristics of the basilar membrane of the cochlea is mainly a result of the longitudinal variations of the geometric dimensions and material properties and is not related with other structures within the cochlea corti.</p>

ART reconstruction from few views using bilateral-filtering iterative method / 生物医学工程学杂志

An algebraic image reconstruction from few views using bilateral-filtering iterative method was proposed due to the problem of computed tomography insufficient data in the present study. In each iteration reconstruction, we first used algebraic reconstruction technique (ART) algorithm to reconstruct an image, ensuring the non-negativity of the reconstructed image at the same time, and then performed bilateral-filtering to the above-mentioned image. In order to improve reconstructed image quality and accelerate the convergence speed, we developed a modified bilateral-filtering method. Shepp-Logan simulation experiments and real CT projection data reconstructions showed the feasibility of the algorithm. The results showed that, compared with the traditional methods of filtered back projection (FBP), ART and GF-ART,the proposed method has a higher signal-to-noise ratio, and maintains more effectively the image edge information.

Preliminary application of an improved Demons deformable registration algorithm in tumor radiotherapy / 南方医科大学学报

<p><b>OBJECTIVE</b>To validate the efficiency of an improved Demons deformable registration algorithm and evaluate its application in registration of the treatment image and the planning image in image-guided radiotherapy (IGRT).</p><p><b>METHODS</b>Based on Brox's gradient constancy assumption and Malis's efficient second-order minimization algorithm, a grey value gradient similarity term was added into the original energy function, and a formula was derived to calculate the update of transformation field. The limited Broyden-Fletcher-Goldfarb-Shanno (L-BFGS) algorithm was used to optimize the energy function for automatic determination of the iteration number. The proposed algorithm was validated using mathematically deformed images, physically deformed phantom images and clinical tumor images.</p><p><b>RESULTS</b>Compared with the original Additive Demons algorithm, the improved Demons algorithm achieved a higher precision and a faster convergence speed.</p><p><b>CONCLUSION</b>Due to the influence of different scanning conditions in fractionated radiation, the density range of the treatment image and the planning image may be different. The improved Demons algorithm can achieve faster and more accurate radiotherapy.</p>