Research on the correction method for radiotherapy verification plans based on displaced electronic portal imaging device.

BACKGROUND: It has been observed that under the single isocenter conditions, the potential shifts of the electronic portal imaging devices (EPID) may be introduced when executing portal dosimetry (PD) plans for bilateral breast cancer, pleural mesothelioma, and lymphoma. These shifts are relative to the calibration positions of EPID and result in significant discrepancies in the plan verification results. PURPOSE: To explore methods including correction model and specific correction matrices to revise the data obtained from displaced EPID. METHODS: Two methods, the correction model and the specific correction matrices, were applied to correct the data. Five experiments were designed and conducted to build correction model and to validate the effectiveness of these two methods. Gamma passing rates were calculated and data profiles along X-axis and Y-axis were captured. RESULTS: The gamma passing rates for the EPID-displaced IMRT validation plans after applying correction model, along with the application of specific correction matrices to VMAT and IMRT validation plans, exhibit results that are comparable to the cases with non-displaced EPID. Except for the VMAT plans applied correction model which showed larger discrepancies (0.041 ± 0.028, 0.049 ± 0.030), the other three exhibit minimal differences in discrepancy values. In all profiles, the corrected data from displaced EPID exhibit a high level of agreement with data obtained from non-displaced EPID. Good consistency is observed in actual application of the correction model and the specific correction matrices between gamma passing rates of data corrected and those of non-displaced data. CONCLUSIONS: The proposed methods involving correction model and specific correction matrices can correct the data collected from the displaced EPID, and the gamma passing rates of the corrected data show results that are comparable to some extent with those of non-displaced data. Particularly, the results corrected by specific correction matrices closely resemble the data from non-displaced EPID.

Mitigating misalignment in MRI-to-CT synthesis for improved synthetic CT generation: an iterative refinement and knowledge distillation approach.

Objective.Deep learning has shown promise in generating synthetic CT (sCT) from magnetic resonance imaging (MRI). However, the misalignment between MRIs and CTs has not been adequately addressed, leading to reduced prediction accuracy and potential harm to patients due to the generative adversarial network (GAN)hallucination phenomenon. This work proposes a novel approach to mitigate misalignment and improve sCT generation.Approach.Our approach has two stages: iterative refinement and knowledge distillation. First, we iteratively refine registration and synthesis by leveraging their complementary nature. In each iteration, we register CT to the sCT from the previous iteration, generating a more aligned deformed CT (dCT). We train a new model on the refined 〈dCT, MRI〉 pairs to enhance synthesis. Second, we distill knowledge by creating a target CT (tCT) that combines sCT and dCT images from the previous iterations. This further improves alignment beyond the individual sCT and dCT images. We train a new model with the 〈tCT, MRI〉 pairs to transfer insights from multiple models into this final knowledgeable model.Main results.Our method outperformed conditional GANs on 48 head and neck cancer patients. It reduced hallucinations and improved accuracy in geometry (3% ↑ Dice), intensity (16.7% ↓ MAE), and dosimetry (1% ↑γ3%3mm). It also achieved <1% relative dose difference for specific dose volume histogram points.Significance.This pioneering approach for addressing misalignment shows promising performance in MRI-to-CT synthesis for MRI-only planning. It could be applied to other modalities like cone beam computed tomography and tasks such as organ contouring.

Control of Newly-Designed Wearable Robotic Hand Exoskeleton Based on Surface Electromyographic Signals.

The human hand plays a role in a variety of daily activities. This intricate instrument is vulnerable to trauma or neuromuscular disorders. Wearable robotic exoskeletons are an advanced technology with the potential to remarkably promote the recovery of hand function. However, the still face persistent challenges in mechanical and functional integration, with real-time control of the multiactuators in accordance with the motion intentions of the user being a particular sticking point. In this study, we demonstrated a newly-designed wearable robotic hand exoskeleton with multijoints, more degrees of freedom (DOFs), and a larger range of motion (ROM). The exoskeleton hand comprises six linear actuators (two for the thumb and the other four for the fingers) and can realize both independent movements of each digit and coordinative movement involving multiple fingers for grasp and pinch. The kinematic parameters of the hand exoskeleton were analyzed by a motion capture system. The exoskeleton showed higher ROM of the proximal interphalangeal and distal interphalangeal joints compared with the other exoskeletons. Five classifiers including support vector machine (SVM), K-near neighbor (KNN), decision tree (DT), multilayer perceptron (MLP), and multichannel convolutional neural networks (multichannel CNN) were compared for the offline classification. The SVM and KNN had a higher accuracy than the others, reaching up to 99%. For the online classification, three out of the five subjects showed an accuracy of about 80%, and one subject showed an accuracy over 90%. These results suggest that the new wearable exoskeleton could facilitate hand rehabilitation for a larger ROM and higher dexterity and could be controlled according to the motion intention of the subjects.

Muscle Synergy for Hand Motions Based on Electromyography Analysis.

This study aimed to investigate the muscle synergy for hand motions of both the left and right hands based on surface electromyography (sEMG) signals. Six hand motions, including hand grasp (HG), four fingers flexion (FFF), index finger extension (IFE), thumb internal rotation (TIR), thumb opposition (TO), key pinch (KP), were examined in the experiment. The sEMG signals were recorded from brachioradialis (BRA), flexor carpi ulnaris (FCU), flexor carpi radialis (FCR), extensor digitorum communis (EDC), flexor digitorum superficialis (FDS), abductor pollicis brevis (APB), first dorsal interosseous (FDI) and abductor digiti minimi (ADM) of both the left and right hands. A co-contraction index (CI) followed by a correlation coefficients (CC) was applied to quantify the muscle synergy during the hand motions and to compare the synergistic patterns across hands. Results shown that the left and right hands had similar muscle synergy (CC (CC>0.9) for any of the motions. For both hands, there were strong correlations between the synergistic matrix of different motions (CC (CC>0.85), including the correlations between HG and FFF, between FFF and IFE, and between TO and KP. By contrast, weak correlations between the synergistic matrix for IFE and that for TIR (CC (CC<0.1), suggesting a low similarity of the muscle synergy for the two motions. This study shed light on how the muscles of the left and right hands are involved and co-contracted for the dexterous hand motions.

Increased Expression of microRNA-199b-5p Associates with Poor Prognosis Through Promoting Cell Proliferation, Invasion and Migration Abilities of Human Osteosarcoma.

MicroRNA (miR)-199b-5p has been reported to be upregulated in human osteosarcoma tissues and participate in the Notch signaling in osteosarcoma cells. This study was aimed to investigate the associations of miR-199b-5p expression with tumor progression of primary osteosarcoma, and to deepen the understanding of its involvement in carcinogenesis. Quantitative real-time reverse transcriptase-polymerase chain reaction was performed to detect expression levels of miR-199b-5p in 98 osteosarcoma and corresponding adjacent normal tissues. Then, the correlations of its expression with clinicopathological characteristics and patient prognosis were statistically analyzed. Moreover, in vitro assays were performed to assess the effects of miR-199b-5p on the proliferation, migration and invasion of two human osteosarcoma cell lines MG63 and U2OS. Compared to normal controls, miR-199b-5p expression was significantly upregulated in osteosarcoma tissues (P < 0.001). In addition, the expression levels of miR-199b-5p in osteosarcoma patients with high tumor grade (P = 0.008), positive metastasis (P = 0.001) and positive recurrence (P = 0.001) were markedly higher than those with low tumor grade, negative metastasis and negative recurrence. Moreover, osteosarcoma patients with high miR-199b-5p expression showed shorter overall survival (P < .001) and shorter disease-free survival (P < 0.001) than those with low expression. Furthermore, the inhibition of miR-199b-5p significantly suppressed cell proliferation, and reduced the migratory and invasive abilities of osteosarcoma cells. This study offer the convincing evidence for the first time that the increased expression of miR-199b-5p may play crucial roles in aggressive progression and poor prognosis of human osteosarcoma. miR-199b-5p may function as an oncogene by positively regulating the malignant potentials of this neoplasm.

Interconversions of different forms of vitamin B6 in tobacco plants.

There are six different vitamin B(6) (VB(6)) forms, pyridoxal (PL), pyridoxamine (PM), pyridoxine (PN), pyridoxal 5'-phosphate (PLP), pyridoxamine 5'-phosphate (PMP), and pyridoxine 5'-phosphate (PNP), of which PLP is the active form. Although plants are a major source of VB(6) in the human diet, and VB(6) plays an important role in plants, the mechanisms underlying the interconversions of different VB(6) forms are not well understood. In this study, in vitro tobacco plants were grown on Murashige and Skoog (MS) basal media supplemented with 100mg/L of PM, PL or PN and the abundance of the different B(6) vitamers in leaf tissue was quantified by high performance liquid chromatography (HPLC). The total amount of VB(6) was about 3.9 µg/g fresh weight of which PL, PM, PN, PLP and PMP accounted for 23%, 14%, 37%, 20% and 6%, respectively. Tobacco plants contained a trace amount of PNP. Supplementation of the culture medium with any of the non-phosphorylated vitamers resulted in an increase in total VB(6) by about 10-fold, but had very little impact on the concentrations of the endogenous phosphorylated vitamers. Administration of either PM or PN increased their endogenous levels more than the levels of any other endogenous B(6) vitamers. PL supplementation increased the levels of plant PN and PM significantly, but not that of PL, suggesting that efficient conversion pathways from PL to PN and PM are present in tobacco. Additionally, maintenance of a stable level of PLP in the plant is not well-correlated to changes in levels of non-phosphorylated forms.

Characterization of enzymes involved in the interconversions of different forms of vitamin B(6) in tobacco leaves.

There are six different vitamin B(6) (VB(6)) forms, pyridoxal (PL), pyridoxamine (PM), pyridoxine (PN), pyridoxal 5'-phosphate (PLP), pyridoxamine 5'-phosphate (PMP) and pyridoxine 5'-phosphate (PNP). PLP is a coenzyme required by more than 100 cellular enzymes. In spite of the importance of this vitamin, the understanding of VB(6) metabolic conversion in plants is limited. In this study, we developed a sensitive and reliable method to assay VB(6)-metabolizing enzyme activities by monitoring their products visually using high-performance liquid chromatography. With this method, the reactions catalyzed by PL/PM/PN kinase, PMP/PNP oxidase, PM-pyruvate aminotransferase, PL reductase and PLP phosphatase were all nicely detected using crude protein extracts of tobacco leaves. Under optimal in vitro conditions, specific activities of those enzymes were 0.15 ± 0.03, 0.10 ± 0.03, 0.08 ± 0.02, 0.64 ± 0.13 and 23.08 ± 1.98 nmol product/min/mg protein, respectively. This is the first report on the conversion between PM and PL catalyzed by PM-pyruvate aminotransferase in plants. Furthermore, the PL reductase activity was found to be heat inducible. Our study sheds light on the VB(6) metabolism taking place in plants.