Preliminary study of stereotactic cardiac radioablation in radiotherapy of ventricular arrhythmia / 中华放射肿瘤学杂志

Objective:To introduce the stereotactic cardiac radioablation (SCRA) based on the stereotactic body radiotherapy (SBRT), and comprehensively evaluate the new approach by short-term effectiveness and safety.Methods:Patients with ventricular arrhythmia (VA) were evaluated and included in this clinical trial, who were immobilized by vacuum bag and performed simulation with 4-dimensional computed tomography (4DCT). In this study, the planning target volume (PTV) was set as the target to design a SBRT plan using volumetric modulated arc therapy (VMAT), which was evaluated by dose parameters such as R 50%, homogeneity index and conformity index, etc. The results of Holter and echocardiography were monitored during the follow-up and compared with the data before treatment. Results:Three subjects with ventricular tachycardia (VT) and one with premature ventricular contraction (PVC) received the same prescription of 25 Gy in a single fraction. The average volume of PTV was 71.4 cm 3(60.3-89.4 cm 3). The average time of beam delivery was 12.0 min (4.5-21.0 min). And the short-term follow-up lasted for an average of 18 weeks (14-25 weeks), which showed significant decrease in both VT and PVC load without complications. Conclusion:This study reports the implementation method of SCRA and proves its short-term effectiveness and safety, but the effects and standards of the key radiotherapy techniques still need to be explored.

Feasibility study of optical surface imaging assisted postmastectomy radiotherapy set-up / 中华放射医学与防护杂志

Objective:To investigate the performance of optical surface imaging (OSI) in the postmastectomy radiotherapy setup and to assess the effects of 3D printed silicone bolus on OSI detection precision.Methods:A retrospective analysis was conducted for 16 patients treated with left-sided postmastectomy radiotherapy (PMRT) in West China Hopital, Sichuan University from January to April, 2021. The setup errors of 16 patients without bolus detected using OSI (OSI no-bolus, OSI n) were obtained before error correction was conducted using cone-beam CT (CBCT). The correlation between OSI n and CBCT was analyzed, and then the diagnostic efficacy of OSI was assessed using the receiver operating characteristic (ROC) curves. The setup errors of six patients with 3D printed silicone bolus detected using OSI (OSI bolus, OSI b) were obtained through off-line image registration, and then the detection precision of OSI n and OSI b in the translational directions was compared. Results:The setup errors in the case of OSI n were highly correlated with CBCT in the translational direction ( r ≥ 0.80), but were weakly correlated in the rotation direction ( r < 0.40). In the ROC analysis, the area under the curve (AUC) in the y direction was the lowest and was in the order of AUC 5 mm ≥AUC 3 mm > 0.75 for any translational direction. The difference in the detection precision between OSI n and OSI b was not statistically significant in the x and z directions ( P > 0.05), but was statistically significant in the y direction ( Z = -2.56, P = 0.01). In the y direction, the systematic error of detection precision in the case of OSI b was 3.11 mm higher than that in the case of OSI n, and the random error of detection precision in the case of OSI b was 1.9 mm higher than that in the case of OSI n. Conclusions:OSI cannot yet substitute CBCT in the postmastectomy radiotherapy setup, but its detection error is still within the clinically acceptable range. The performance of OSI-assisted setup is expected to be further improved by mitigating the interference of factors such as bolus in the imaging path through operational training.

Research progress of adaptive radiotherapy in radiotherapy of nasopharyngeal carcinoma / 国际生物医学工程杂志

Intensity-modulated radiation therapy(IMRT) is currently the main treatment method for nasopharyngeal carcinoma. During radiotherapy for nasopharyngeal carcinoma, factors such as body mass reduction, tumor regression, and organ displacement at risk can affect the precise implementation of radiation therapy. Applying adaptive radiotherapy (ART) technology to optimize the treatment plan at the appropriate timing can reduce the adverse effects caused by the above factors and enhance the accuracy of radiotherapy. There are no uniform standards for the necessity, timing, and case selection of ART. In this review, the research progress of ART in the radiotherapy of nasopharyngeal carcinoma in recent years was reviewed to provide a reference for further clinical application of ART in nasopharyngeal carcinoma.

Physics issues on plan design and evaluation for stereotactic radiotherapy based on linear accelerator / 中华放射肿瘤学杂志

Stereotactic radiotherapy (SRT), also known as stereotactic ablative radiotherapy (SABR), includes stereotactic radiosurgery and stereotactic body radiotherapy (SBRT). This technique has the characteristics of large single fractional dose, few fractions, high equivalent biological doses, and rapid fall off-target doses. It can be implemented by relatively special equipment such as Gamma knife, Cyberknife, Tomotherapy and Vero 4D RT system, etc. In many cases, SBRT technique is employed based on linear accelerators. SRT differs from conventional radiotherapy in terms of the plan design and plan evaluation. Consequently, it is necessary to discuss the differences and provide guidance for clinical application and research.

The setup errors of thermoplastic head and shoulder molds with or without vacuum pad in HFSRT for brain metastases in the lung cancer / 中华放射肿瘤学杂志

Objective:To retrospectively analyze the setup errors of thermoplastic head and shoulder molds alone or combined with vacuum pad in hypofractionated stereotactic radiotherapy (HFSRT) for non-small cell lung cancer (NSCLC) with brain metastases.Methods:Fifty-four NSCLC patients with brain metastases who received HFSRT from 2017 to 2019 were enrolled in this study. Twenty-four patients were fixed with thermoplastic head and shoulder molds (group A), and 30 patients were fixed with thermoplastic head and shoulder molds plus vacuum pad (group B). The interfraction and intrafraction setup errors were acquired from cone-beam CT online image registration before and after the HFSRT. Optical surface system was applied in monitoring the intrafraction setup errors. The setup errors in each direction between two groups were analyzed by independent samples t-test. Results:For the interfraction setup errors of the whole group, the proportion of the horizontal setup errors of ≥3mm was 7.0% to 15.4% and 7.0% to 12.6% for the rotation setup errors of ≥2°. In group A, the anteroposterior setup error was (1.035±1.180)mm, significantly less than (1.512±0.955)mm in group B ( P=0.009). In group A, the sagittal rotation setup error was 0.665°±0.582°, significantly less than 0.921°±0.682° in group B ( P=0.021). For the intrafraction setup errors of the whole group, the proportion of horizontal setup errors of ≥1mm was 0% to 0.7%, whereas no rotation setup error of ≥1° were observed. In group B, bilateral, anteroposterior and sagittal rotation setup errors were (0.047±0.212)mm, (0.023±0.152)mm and 0.091°±0.090°, significantly less compared with (0.246±0.474)mm, (0.140±0.350)mm and 0.181°±0.210° in group A ( P=0.004, P=0.020, P=0.001), respectively. Optical surface monitoring data were consistent with the obtained results. Conclusions:Thermoplastic head and shoulder molds (with or without vacuum pad) combined with online image registration and six-dimensional robotic couch correction can be applied in HFSRT for brain metastases from NSCLC. The intrafraction setup errors in group B are smaller than those in group A. Optical surface system has certain value in monitoring the intrafractional movement.

Application of Virtual Monochromatic Images Reconstructed by Dual-energy Computed Tomography in Radiotherapy Treatment Planning System / 中国医疗器械杂志

Virtual monochromatic images (VMI) that reconstructed on dual-energy computed tomography (DECT) have further application prospects in radiotherapy, and there is still a lack of clinical dose verification. In this study, GE Revolution CT scanner was used to perform conventional imaging and gemstone spectral imaging on the simulated head and body phantom. The CT images were imported to radiotherapy treatment planning system (TPS), and the same treatment plans were transplanted to compare the CT value and the dose distribution. The results show that the VMI can be imported into TPS for CT value-relative electron density conversion and dose calculation. Compared to conventional images, the VMI varies from 70 to 140 keV, has little difference in dose distribution of 6 MV photon treatment plan.

Application of Statistical Process Control in Evaluation of Performance for Beam-matched Medical Electron Linacs / 中国医疗器械杂志

Clinically, beam matching can greatly improve the flexibility and efficiency of treating patients between different medical electron linacs. However, in addition to the regular quality assurance (QA) test of the machine performance of linacs, there is still a lack of comprehensive evaluation of the clinical radiotherapy performance of beam-matched linacs. In this paper, the performance of volumetric modulated arc therapy (VMAT) between three closely matched linacs was evaluated by statistical process control (SPC) technology. It was found that the average and median γ passing rates of the VMAT QA processes of the three linacs had little difference, but the process capability levels were at three different levels. The results show that SPC technology can effectively evaluate the performance of beam matching for medical electron linacs, improve the patient-specific VMAT QA processes, and guide clinical decision-making.

Improved Design and Acceptance Test of Localization Couch for New Type of CT Simulator / 中国医疗器械杂志

Accurate CT simulation is the key link of precision radiotherapy, and the performance of the localization couch of CT simulator directly affects the accuracy of radiotherapy. With the rapid development of precision radiotherapy, conventional large aperture radiotherapy special CT simulator is difficult to meet the needs of precision radiotherapy localization, so most radiotherapy centers choose high-end diagnostic CT machines equipped with a flat tabletop for radiotherapy localization. In clinical work, the performance testing of the CT simulator localization couch is easy to be ignored. In addition, there are some problems such as insufficient precision in transforming the cradle-shaped couch top of diagnostic CT into a special flat couch top for radiotherapy. This paper provided an in-depth description of the improved design and performance test of the localization couch of the first special GE Revolution CT simulator for radiotherapy introduced by West China Hospital of Sichuan University. After the improvement, all the acceptance tests of the localization couch are in line with the standard, and the performance meets the high-precision radiotherapy localization needs of patients with different body weight in the center.

Application of New Posture Fixation Device Compatible with Magnetic Resonance Simulation Positioning in Head and Neck Radiotherapy / 中国医疗器械杂志

OBJECTIVE@#Whether the developed new type of radiotherapy auxiliary fixation device compatible with the head and neck joint coil can improve the quality of magnetic resonance images in radiotherapy and verify whether it can be applied to clinical treatment.@*METHODS@#The clinical trial selected patients with brain metastases and nasopharyngeal cancer patients, using thermoplastic film and head and shoulder molds for posture fixation, and treatment on the ELekta Versa accelerator. SPSS 20.0 statistical software was used to analyze the data. The measurement data were expressed by @*RESULTS@#Considering the influence of the outer contour of the device, the target dose meets the clinical requirements. The setting error is less than 2 mm in the three translation directions, and the rotation error is less than 2@*CONCLUSIONS@#There is no statistical difference between the treatment results of patients using the new type of fixation device and the conventional method. The target area threatens the organ dose, and the positioning error meets the treatment requirements.

Clinical application and research progress on dose-guided radiotherapy / 中华放射肿瘤学杂志

Dose-guided radiotherapy (DGRT) is a potentially useful adaptive radiotherapy method which dosimetrically compensates for interfractional non-rigid deformation.With the improvement of in-room imaging quality,development of the deformation registration algorithm and innovation of computer science,the wide application of DGRT might be realized.The purpose of this article is to briefly summarize the work flow,clinical application and prospect of DGRT.

Impact of accelerator operating errors on γ passing rate during dose verification of volumetric modulated arc therapy for pelvic tumors / 中华放射肿瘤学杂志

Objective:To investigate the impacts of gantry rotation angle errors, monitor unit (MU) errors, collimator and multi-leaf collimator (MLC) position errors upon the γ passing rate of dose verification in volumetric modulated arc therapy (VMAT).Methods:Ten patients with rectal cancer and 10 patients with uterine tumors were selected. The operating errors of accelerator parameters were introduced during the VMAT execution. By comparing the γ passing rates during dose verification between the simulating and original plans, the impact and sensitivity of the operating errors of each accelerator parameter on γ passing rate were analyzed.Results:When the γ criteria were set as 3%/3 mm, 3%/2 mm and 2%/2 mm, the γ passing rate decreasing gradient was less than 7.0% after the introduction of gantry rotation angle, MU and collimator position errors, respectively. However, after the reverse, opposite, and co-directional motion errors of the MLC blades on both sides were introduced, the γ passing rate decreasing was less than 19.13 %, 18.53%, 0.19 %; 19.87%, 20.01%, 0.42 % and 23.11%, 23.45%, 0.65 % for absolute dose verification, respectively.Conclusion:During VMAT, the reverse and opposite motion errors of MLC blades exert more significant effect on the γ passing rate compared with the gantry rotation angle errors, MU errors, collimator position errors and co-directional motion errors of the MLC blades. When the γ criteria of 3%/3 mm, 3%/2 mm and 2%/2 mm are adopted, the impact of accelerator operating errors upon the γ passing rate is strengthened in sequence. Therefore, when performing dose verification for a specific patient, appropriate γ criteria should be chosen and absolute dose verification should be taken as the reference index to evaluate the consistency between the calculated and measured dose distribution.

Clinical application and research progress on dose-guided radiotherapy / 中华放射肿瘤学杂志

Dose-guided radiotherapy (DGRT) is a potentially useful adaptive radiotherapy method which dosimetrically compensates for interfractional non-rigid deformation. With the improvement of in-room imaging quality, development of the deformation registration algorithm and innovation of computer science, the wide application of DGRT might be realized. The purpose of this article is to briefly summarize the work flow, clinical application and prospect of DGRT.

Preliminary study on monitoring patient-specific volumetric modulated arc therapy quality assurance process with statistical process control methodology on the basis of TG-218 report / 生物医学工程学杂志

Patient-specific volumetric modulated arc therapy (VMAT) quality assurance (QA) process is an important component of the implementation process of clinical radiotherapy. The tolerance limit and action limit of discrepancies between the calculated dose and the delivered radiation dose are the key parts of the VMAT QA processes as recognized by the AAPM TG-218 report, however, there is no unified standard for these two values among radiotherapy centers. In this study, based on the operational recommendations given in the AAPM TG-218 report, treatment site-specific tolerance limits and action limits of gamma pass rate in VMAT QA processes when using ArcCHECK for dose verification were established by statistical process control (SPC) methodology. The tolerance limit and action limit were calculated based on the first 25 in-control VMAT QA for each site. The individual control charts were drawn to continuously monitor the VMAT QA process with 287 VMAT plans and analyze the causes of VMAT QA out of control. The tolerance limits for brain, head and neck, abdomen and pelvic VMAT QA processes were 94.56%, 94.68%, 94.34%, and 92.97%, respectively, and the action limits were 93.82%, 92.54%, 93.23%, and 90.29%, respectively. Except for pelvic, the tolerance limits for the brain, head and neck, and abdomen were close to the universal tolerance limit of TG-218 (95%), and the action limits for all sites were higher than the universal action limit of TG-218 (90%). The out-of-control VMAT QAs were detected by the individual control chart, including one case of head and neck, two of the abdomen and two of the pelvic site. Four of them were affected by the setup error, and one was affected by the calibration of ArcCHECK. The results show that the SPC methodology can effectively monitor the IMRT/VMAT QA processes. Setting treatment site-specific tolerance limits is helpful to investigate the cause of out-of-control VMAT QA.

Application of deep inspiration breath-hold technique in radiotherapy / 中华放射肿瘤学杂志

In radiotherapy for thoracic and abdominal tumors, the negative effect of respiratory movement on radiotherapy persist throughout the whole process of radiotherapy. Deep inspiration breath-hold technique (DIBH) is a method of respiratory movement management in radiotherapy, which can reduce the negative effect of respiratory movement upon radiotherapy in the whole process of radiotherapy. Meantime, DIBH technique has its own characteristics and operation requirements compared with other respiratory movement management measures (such as 4D CT, gated technology and tracking, etc.). The aim of this review was to introduce the advantages, disadvantages and the application status of DIBH technique.

Current status and reform of practice teaching of radiotherapy technology / 中华医学教育探索杂志

The Major of Medical Imaging Technology (Radiotherapy Technology Orientation) in West China Medical School, Sichuan University, has been devoted to training therapists, dosimetrists, and physicists in tumor radiotherapy, and it is urgently needed to improve the practice ability of interns and standardize the teaching system. In view of the current status of the practice of students in radiotherapy technology, this article analyzes and summarizes the teaching staff construction, teaching contents, teaching methods, and other aspects, finds out the problems and challenges in the current teaching system, and puts forward suggestions for practice teaching reform.

Feasibility Research of the New Fixation Device Compatible with Head and Neck Coil of MRI for Radiotherapy / 中国医疗器械杂志

MRI simulation images quality of head and neck coil scanning is better than that of radiotherapy surface coil, but currently the head and neck coil is not compatible with radiotherapy positioning devices. In this paper, a new fixation device is developed based on computer reverse engineering technology, which can be used in combination with head and neck coil. This article focuses on discussing the feasibility of the new device in radiotherapy. The obtained ACR phantom and Cat phantom 504 images were used to analyze MR and CT images quality assurance indicators. The dose attenuation of 6 MV photons was measured using the ionization chamber. The results showed each index met the clinical application requirements of intracranial tumor radiotherapy, thereby it can be used in intracranial tumor radiotherapy.

Evaluation of fully automated volumetric modulated arc therapy planning of cervical cancer in RayStation treatment planning system / 中华放射医学与防护杂志

Objective To evaluate the feasibility of an in-room automated volumetric arc therapy (VMAT) planning engine based on dose volume histogram (DVH) prediction model in RayStation treatment planning system.Methods A total of 4,0 VMAT plans of cervix cancer,planned by experts,were chosen to build DVH estimation model by principal component regression analytic method.An in-room automated VMAT planning program based on IroPython scripting language combined with DVH prediction model was performed in RayStation treatment planning system.The DVH estimation model was applied to Another 10 testing cases of cervical cancer and the feasibility was evaluated by comparing the automatic plans with manual plans.Results The predicted DVH of organs at risk showed a good fit with real DVH in the ten testing cases.There were no statistically significant differences between manual and automatic plans in PTV conformal index (CI) and homogeneity index (HI) (P ＞ O.05).V40 and V50 of bladder were significantly decreased by 4.3％ and 1.6％ in automatic plans (t =2.75,5.26,P ＜ 0.05).V30,V40 and Vs0 of rectum were also decreased by 6.8％,5.8 ％ and 2.1％ (t =2.26,3.55,5.19,P ＜ 0.05).Both left and right femoral heads were better spared in automatic plans with average doses decreased by 380 and 322 cGy(t =5.55,7.25,P ＜ 0.05).The time of creating a treatment plan was 36 min for automatic plan and 53 min for manual plan.Conclusions The fully automated VMAT treatment plan program can create a VMAT plan of cervix cancer with high efficiency and good quality.

The dosimetric impacts of accelerator operation error on the volumetric modulated arc therapy for cervical cancer / 中华放射医学与防护杂志

Objective To investigate the dosimetric effect of accelerator gantry rotation angle errors, collimator and multileaf collimator ( MLC) leaf position errors on volumetric-modulated arc therapy ( VMAT) for cervical cancer. Methods A total of 10 patients with cervical cancer were selected. The plan. Trail file of each clinical plan was extracted from the Pinnacle3 V9. 2 planning system of USA Philips, then the operating parameters of tach control point were read and modified by Matlab programs, and thus the operating error of the accelerator was simulated. Results In this paper, it was discovered that systematic accelerator gantry rotation angle errors, systematic collimator position errors and systematic MLC shift errors which led to the maximum changes of the PTV dose limit were 0. 16％, 0. 46％ and 0. 57％, respectively, and the maximum changes of the dose limit of organs at risk ( OAR) were 0. 38％, -1. 32％ and -0. 44％, respectively. When the systematic MLC gap width errors were ± 0. 5, ± 1 and ± 2 mm, respectively, the maximum changes of PTV dose were 2. 11％, 3. 04％ and 6. 03％, respectively, while the maximum changes of the OAR average dose were 2. 17％, 3. 92％ and 7. 97％, respectively. Furthermore, the dose limits of PTV and OAR showed a strong linear correlation with MLC open or close errors(t=21. 201～90. 562,P<0. 05). If actual errors of each parameter of accelerator were introduced, the maximum changes of PTV and OAR dose limits were 0. 16％ and 1. 30％, respectively, and conformity index (CI) and homogeneity index (HI) were barely changed. Conclusions No significant effect was found for systematic accelerator gantry rotation angle errors, systematic collimator position errors and systematic MLC shift errors for cervical cancer VMAT patients. However, there is a high sensitivity to dose distribution for MLC open or close errors. Therefore, it is necessary to pay more attention on the quality control of the accelerator running in particular MLC position errors to ensure the therapeutic accuracy.

Research on the precision and stability of optical surface imaging technology in guiding radiotherapy positioning / 中华放射肿瘤学杂志

Objective To investigate the precision and stability of optical surface imaging (OSI)system Catalyst in guiding radiotherapy positioning.Methods A total of 52 patients with five different tumor sites who underwent cone-beam computed tomography (CBCT)-guided radiotherapy were recruited in this investigation.For the first treatment fraction,the setup error was recorded as C after online CBCT correction,and the surface images of patients taken by Catalyst were set as the reference images Cref.For the following treatment fraction,patients were pre-corrected according to the Catalyst Cref image with the acceptable errors within 2 mm/ 2,and the pre-corrected errors were recorded as C1.Then,after online CBCT correction,the setup errors were recorded as C.The errors between post-corrected Catalyst surface image and Cref image were recorded as C2.For each treatment fraction,the difference between Catalyst correction errors C1 and CBCT corrected errors C was recorded as d1,and the difference between the post-corrected Catalyst errors C2 and Cref image was recorded as d2.d3=d1-d2.The values of d1 and d3 in the 6 dimensions were analyzed using single sample t-test.The correlation between C-C1 and d1-d2 was statistically analyzed by Pearson correlation analysis.Results The mean value of d1 and d3 for 52 patients were within 2 mm/2 °.CBCT-C1 and d1-d2 were both significantly correlated (R =3,7,P=0.00,0.01).Conclusions OSI system yield high accuracy and stability in radiotherapy positioning,which is of certain significance in radiotherapy positioning for cancer patients.

Radiomics in the precision diagnosis and treatment of brain tumor:the application and challenge / 中华放射肿瘤学杂志

While emphasizing" Precision Medicine" nowadays,comprehending the specificity of patients and pathology is the key to achieving the precision diagnosis and treatment.Radiomics is a high-throughput quantitative analysis that combines the quantitative features from the region of interest on medical image and the biology and heterogeneity of tumor.It provides a non-invasive,convenient,dynamic,and quantitative method to collect the patient's specific features of pathology and gene.Radiomics holds promise for the precision diagnosis and treatment of brain tumor.It can be used for molecular pathology diagnosis,definition of tumor boundaries,prognosis,prediction of complications,and so on.It helps to develop individualized measures for the prevention,diagnosis,treatment,and prognostic monitoring based on their disease features.