The presence of magnetic fields in a magnetic resonance accelerator (MR-linac) can affect the reference dosimetry, and thus the existing Code of Practices (CoPs) are inadequate for MR-linac. In this article, the characteristics of adsorbed dose to water and ionization chamber response in the presence of magnetic fields were introduced and a formalism for reference dosimetry in MR-linac was developed based on the existing CoPs, aiming to provide reference for dosimetric quality control and research work of MR-linac in China.

Objective To compare the performance of two different deep learning models,VTcGAN and Pix2pix,in generating synthetic computed tomography(sCT)from magnetic resonance imaging(MRI)of nasopharyngeal carcinoma(NPC),and to evaluate their accuracies in treatment planning dose calculations.Methods MRI and CT images as well as treatment planning data of 115 NPC patients were retrospectively selected,and paired dataset was obtained through rigid image registration,with 105 cases as the training set,and the remaining 10 cases as the test set.Two kinds of models,namely Pix2pix model based on conventional convolutional neural network and the improved VTcGAN model based on Transformer network,were constructed with the consistent structure except for the bottleneck network in the generator.The generated sCT images(sCTPix2pix and sCTVTcGAN)were assessed in terms of image quality,intensity value and dosimetric differences.Results For the cases in test set,the mean error,mean absolute error,peak signal-to-noise ratio,and structural similarity index between the ground truth CT images and the sCTPix2pix were(-0.86±12.42)HU,(40.77±3.06)HU,(33.45±0.62)dB,and 0.928±0.013,respectively;and those between the ground truth CT images and the sCTVTcGAN were(-1.10±8.56)HU,(37.40±2.08)HU,(34.33±0.45)dB,and 0.936±0.009,respectively.For the criterion of 1 mm/1%,the averaged gamma passing rates of sCTPix2pix and sCTVTcGAN were(96.62±1.08)%and(96.88±0.99)%at a dose threshold of 10%,(94.31±1.03)%and(94.72±0.91)%at a dose threshold of 50%,(84.62±1.74)%and(86.06±1.41)%at a dose threshold of 80%,respectively.Conclusion The proposed VTcGAN model is superior to the traditional Pix2pix model in terms of accuracy in generating sCT from MRI of NPC,and it can fulfill the requirements for dose calculation in the MRI-Only workflow.

Objective To investigate the mechanism by which apelin inhibits the transition from acute kidney injury(AKI)to chronic kidney disease(CKD).Methods Human proximal tubular epithelial cells were cultured in vitro and divided into control,cisplatin,cisplatin+apelin,cisplatin+apelin+Sirt3 siRNA,and apelin groups.Cells were transfected with Sirt3 siRNA and incubated with a medium containing cisplatin(10 μmol/L)and/or apelin-13(1 μmol/L).Mitochondrial morphology was observed using MitoTracker? probes;mito-chondrial membrane potential was detected using the JC-1 assay kit;and the expression of the fibrogenic cytokine,transforming growth factor β1(TGF-β1)was measured by Western blotting.Forty 10-week-old male C57BL/6J mice were divided into control,cisplatin,cisplatin+apelin,cisplatin+apelin+Sirt3 knockdown,and empty adenovirus groups,with eight mice per group.Except for the control and empty adenovirus groups,all the other groups were intraperitoneally injected with cisplatin(20 mg/kg)to establish the AKI model.The cis-platin+apelin group was intraperitoneally injected with apelin-13(0.1 μg·kg-1·d-1);the control group was injected with an equal volume of saline;the cisplatin+apelin+Sirt3 knockdown group was injected with Sirt3 knockdown adenovirus(2 × 109 pfu/mL)via the tail vein and intraperitoneal injection of apelin-13(0.1 μg·kg-1·d-1);and the empty adenovirus group was injected with adenovirus(2 × 109 pfu/mL)via the tail vein.The mice were sacrificed after 2 weeks.Kidney fibrosis was assessed by Masson's trichome staining.Type Ⅰ collagen(Col-Ⅰ)expression was observed by immunohistochemical staining.Plasma creatinine(Cr)and blood urea nitrogen(BUN)levels were measured by ELISA.Results In vitro experiments showed that,compared with the control group,the cisplatin group exhibited reduced mitochondrial fluorescence staining,decreased mitochondrial membrane potential,and increased TGF-β1 expression(all P＜0.05).Compared with the cisplatin group,the cisplatin+apelin group showed increased fluorescence staining,elevated mitochondrial membrane potential,and reduced TGF-β1 expression(all P＜0.05);however,these effects were counteracted after Sirt3 siRNA transfection.In vivo experiments showed that,compared with the control group,the cisplatin group exhibited significant renal tubular atrophy and interstitial fibrosis,increased Col-Ⅰ positive expression,and elevated plasma Cr and BUN levels(all P＜0.05).Compared with the cisplatin group,the cisplatin+apelin group showed a significant improvement in all the above indicators(all P＜0.05).Compared with the cisplatin+apelin group,the cisplatin+apelin+Sirt3 knockdown group showed a significant reduction in the renal protective effects of apelin.Conclusion The polypeptide apelin inhibits the transition from AKI to CKD by regulating Sirt3 expression to maintain mitochondrial structure and function,which can reduce renal fibrosis and improve renal function.

Objective To compare the performance of two different deep learning models,VTcGAN and Pix2pix,in generating synthetic computed tomography(sCT)from magnetic resonance imaging(MRI)of nasopharyngeal carcinoma(NPC),and to evaluate their accuracies in treatment planning dose calculations.Methods MRI and CT images as well as treatment planning data of 115 NPC patients were retrospectively selected,and paired dataset was obtained through rigid image registration,with 105 cases as the training set,and the remaining 10 cases as the test set.Two kinds of models,namely Pix2pix model based on conventional convolutional neural network and the improved VTcGAN model based on Transformer network,were constructed with the consistent structure except for the bottleneck network in the generator.The generated sCT images(sCTPix2pix and sCTVTcGAN)were assessed in terms of image quality,intensity value and dosimetric differences.Results For the cases in test set,the mean error,mean absolute error,peak signal-to-noise ratio,and structural similarity index between the ground truth CT images and the sCTPix2pix were(-0.86±12.42)HU,(40.77±3.06)HU,(33.45±0.62)dB,and 0.928±0.013,respectively;and those between the ground truth CT images and the sCTVTcGAN were(-1.10±8.56)HU,(37.40±2.08)HU,(34.33±0.45)dB,and 0.936±0.009,respectively.For the criterion of 1 mm/1%,the averaged gamma passing rates of sCTPix2pix and sCTVTcGAN were(96.62±1.08)%and(96.88±0.99)%at a dose threshold of 10%,(94.31±1.03)%and(94.72±0.91)%at a dose threshold of 50%,(84.62±1.74)%and(86.06±1.41)%at a dose threshold of 80%,respectively.Conclusion The proposed VTcGAN model is superior to the traditional Pix2pix model in terms of accuracy in generating sCT from MRI of NPC,and it can fulfill the requirements for dose calculation in the MRI-Only workflow.

Objective To investigate the mechanism by which apelin inhibits the transition from acute kidney injury(AKI)to chronic kidney disease(CKD).Methods Human proximal tubular epithelial cells were cultured in vitro and divided into control,cisplatin,cisplatin+apelin,cisplatin+apelin+Sirt3 siRNA,and apelin groups.Cells were transfected with Sirt3 siRNA and incubated with a medium containing cisplatin(10 μmol/L)and/or apelin-13(1 μmol/L).Mitochondrial morphology was observed using MitoTracker? probes;mito-chondrial membrane potential was detected using the JC-1 assay kit;and the expression of the fibrogenic cytokine,transforming growth factor β1(TGF-β1)was measured by Western blotting.Forty 10-week-old male C57BL/6J mice were divided into control,cisplatin,cisplatin+apelin,cisplatin+apelin+Sirt3 knockdown,and empty adenovirus groups,with eight mice per group.Except for the control and empty adenovirus groups,all the other groups were intraperitoneally injected with cisplatin(20 mg/kg)to establish the AKI model.The cis-platin+apelin group was intraperitoneally injected with apelin-13(0.1 μg·kg-1·d-1);the control group was injected with an equal volume of saline;the cisplatin+apelin+Sirt3 knockdown group was injected with Sirt3 knockdown adenovirus(2 × 109 pfu/mL)via the tail vein and intraperitoneal injection of apelin-13(0.1 μg·kg-1·d-1);and the empty adenovirus group was injected with adenovirus(2 × 109 pfu/mL)via the tail vein.The mice were sacrificed after 2 weeks.Kidney fibrosis was assessed by Masson's trichome staining.Type Ⅰ collagen(Col-Ⅰ)expression was observed by immunohistochemical staining.Plasma creatinine(Cr)and blood urea nitrogen(BUN)levels were measured by ELISA.Results In vitro experiments showed that,compared with the control group,the cisplatin group exhibited reduced mitochondrial fluorescence staining,decreased mitochondrial membrane potential,and increased TGF-β1 expression(all P＜0.05).Compared with the cisplatin group,the cisplatin+apelin group showed increased fluorescence staining,elevated mitochondrial membrane potential,and reduced TGF-β1 expression(all P＜0.05);however,these effects were counteracted after Sirt3 siRNA transfection.In vivo experiments showed that,compared with the control group,the cisplatin group exhibited significant renal tubular atrophy and interstitial fibrosis,increased Col-Ⅰ positive expression,and elevated plasma Cr and BUN levels(all P＜0.05).Compared with the cisplatin group,the cisplatin+apelin group showed a significant improvement in all the above indicators(all P＜0.05).Compared with the cisplatin+apelin group,the cisplatin+apelin+Sirt3 knockdown group showed a significant reduction in the renal protective effects of apelin.Conclusion The polypeptide apelin inhibits the transition from AKI to CKD by regulating Sirt3 expression to maintain mitochondrial structure and function,which can reduce renal fibrosis and improve renal function.

The presence of magnetic fields in a magnetic resonance accelerator (MR-linac) can affect the reference dosimetry, and thus the existing Code of Practices (CoPs) are inadequate for MR-linac. In this article, the characteristics of adsorbed dose to water and ionization chamber response in the presence of magnetic fields were introduced and a formalism for reference dosimetry in MR-linac was developed based on the existing CoPs, aiming to provide reference for dosimetric quality control and research work of MR-linac in China.

Objective:To explore the feasibility of applying ArcherQA to independent dose verification of MR-guided online adaptive radiotherapy (ART) plans performed on Elekta Unity 1.5 Tesla (T) magnetic resonance-linear accelerator (MR-Linac).Methods:The dose calculation accuracy of ArcherQA under a specific magnetic field was validated using a homogeneous water phantom. A total of 32 patients who received MR-guided online ART on Elekta Unity were randomly selected by lottery, with 32 offline plans and 177 online plans for five treatment sites (brain, mediastinum, liver, kidney, and vertebral body) enrolled. Finally, the γ pass rates (threshold: 10%; criteria: 3 mm/3% and 2 mm/2%) were compared among the result upon independent dose verification of ArcherQA, measurements of ArcCheck, and calculations using the Monaco treatment planning system (TPS) to quantitatively evaluate the accuracy and efficiency of ArcherQA in independent dose verification of online plans on Elekta Unity.Results:ArcherQA was proven accurate in calculating the dose distribution of therapeutic photon beams under the specific magnetic field. With the 3 mm/3% criterion, the γ pass rates of verification result exceeded 99% in all square fields of a water phantom. Under the stricter 2 mm/2% criterion, the γ pass rates also surpassed 95% in all square fields except 20 cm × 20 cm field. Regarding the verification of treatment plans, the ArcherQA result were found to be highly consistent with those measured or calculated using ArcCheck and Monaco TPS, with the average γ pass rates exceeding 99% under the 3 mm/3% criterion and above 97% under the 2 mm/2% criterion. ArcherQA was acceptably efficient for independent dose verification of online plans, with 50 to 150 s, (108 s on average) required to complete the independent dose verification of 177 online plans.Conclusions:ArcherQA allows for accurately and efficiently calculating the dose distribution of therapeutic photon beams under a specific magnetic field, establishing it as an effective supplementary tool for independent dose calculation of MR-guided offline and online ART plans, thereby ensuring the safety of patient treatment plans.

Adipose progenitor cells(APCs) represent a prominent stromal cellular component of adipose tissue and are now identified as highly heterogenous populations. However, the role of APCs in regulating systemic metabolism remains unknown. Using single cell RNA-sequencing, we investigated the role of the APC subpopulations in regulating development of type 2 diabetes. CD9 + CD55 low APCs are the novel subset identified in this study, which is significantly increased in type 2 diabetic patients. Transplantation of these cells from type 2 diabetic patients into adipose tissue caused glycemic disturbance in mice. Depletion of pathogenic APCs improved obesity-related glycemic disturbance. Collectively, our data provide deeper insights into human APC functionality and highlights APCs as a potential therapeutic target to combat type 2 diabetes. This study has been published in Nature Communications, 2024, 15(1): 4827.

Objective To explore the protective effect of polypeptide Apelin on podocyte mitochondria in diabetic nephropathy and underling mechanisms.Methods Human renal podocytes were divided into four experimental groups:control group,high glucose(HG)group(glucose 25 mmol/L,48 h),Apelin intervention HG group(Ape-lin-13 1 μmol/L,48 h)and Apelin group(Apelin-13 1 μmol/L,48 h).The podocyte apoptosis was observed by TUNEL staining,the expression of mitochondrial membrane protein FUNDC1 was detected by Western blot,and the binding of mitochondrial fission protein DRP1 to FUNDC1 was examined by immunoprecipitation.The 8-week-old male mice were divided into three experimental groups:control group,diabetes group(intraperito-neal injection of streptozotocin 150 mg/kg,only one time)and Apelin intervention DM group(intraperitoneal injection of Apelin-13 0.3 μmol/kg,daily).The morphology of renal was observed by PAS staining and trans-mission electron microscopy.Plasma creatinine(Cr),urea nitrogen,urinary albumin and creatinine were de-tected by ELISA kit.The level of creatinine clearance rate(Ccr)and urinary albumin/creatinine(ACR)was calculated.Results Compared with the control group,the podocyte apoptosis and expression of FUNDC1 in the HG group increased significantly(P＜0.05),and the combination of mitochondrial fission division protein DRP1 to FUNDC1 raised.Meanwhile,compared with the HG group,the number of apoptosis,the expression of FUNDC1(P＜0.05),and the combination of DRP1 to FUNDC1 all reduced in Apelin intervention HG group.Animal experiments showed that the kidney structure of the control group was intact.In the DM group,the num-ber of podocytes decreased significantly,the foot processes were fused and dropped off.In the Apelin intervention DM group,podocyte lesions were less severe than those in the DM group.Compared with the control group,the level of plasma Cr,BUN and urine ACR in the DM group increased,while the level of Ccr decreased significantly(P＜0.05).However,compared with the DM group,the level of above biomarkers in the Apelin intervention DM group was improved(P＜0.05).Conclusions Apelin keeps mitochondrial homeostasis and reduces podocyte ap-optosis by inhibiting the expression of mitochondrial membrane protein FUNDC1,which may contribute to allevia-tion of diabetic nephropathy.

Objective:To analyze the dosimetric effects on off-center tumour treatment plan resulting from the MR-Linac-based isocenter position radiotherapy plan.Methods:The cases of 19 patients who were treated in Sun Yat-sen University Cancer Center in 2020 were collected in this study. Two different IMRT plans were designed for each patient with off-center tumor both for group A with planned isocenter position as IMRT and group B with planed target center position as geometric center. The conformity index and homogeneity index of target, the dose normal tissue and the number of MU were compared between two plans.Results:The two IMRT plans met clinical dosimetric requirements. No statistical differences were found both in homogeneity index and conformity index ( P>0.05). Also there was no differences found in doses to normal tissues. However, the MU number (1 149±903, t=2.804, P=0.012) in group A was higher than that in group B (970±652). Conclusions:It is feasible to perform MR-Linac-based off-center treatment plan.