Purpose: This study aimed to evaluate the impact of gantry angle spacing (GS) on volumetric modulated arc therapy (VMAT) in left-sided breast cancer patients undergoing postmastectomy radiotherapy (PMRT) with internal mammary lymph node (IMN) coverage, and to assess the sensitivity of dose distribution to setup errors at different GS values. Methods: In this retrospective study, paired VMAT plans were generated for each of the 20 patients: one with a gantry angle spacing of 2 degrees (GS2-VMAT) and another with a spacing of 4 degrees (GS4-VMAT). Plan quality was assessed by comparing dosimetric parameters for clinical target volumes (CTVs) and organs at risk (OARs). Robustness was evaluated by recalculating dose distributions after simulating 5 mm isocenter shifts in the inferior-superior, left-right, and posterior-anterior directions. Results: Both GS2-VMAT and GS4-VMAT plans achieved adequate target coverage. However, GS2-VMAT plans demonstrated improved dose homogeneity for the CTV of the supraclavicular region (CTVsc; HI: 0.053 vs. 0.057, P < 0.001) and chest wall (CTVcw; HI: 0.065 vs. 0.070, P = 0.022), and delivered lower doses to OARs. Specifically, GS2-VMAT reduced the mean heart dose (486.59 cGy vs. 518.86 cGy, P < 0.001) and left lung dose (1375.77 cGy vs. 1486.91 cGy, P < 0.001). Robustness analysis revealed direction-dependent dose variations: for CTVsc, the maximum Delta D-98% deviation occurred along the inferior direction, whereas Delta D-95%, Delta D-50%, and Delta D-mean peaked in the posterior direction. For CTVcw, all parameters except D-2% exhibited the greatest variation in the posterior direction. CTVim was most sensitive to anterior displacement, with Delta D-2% variation peaking for all CTVs during anterior shifts. Dose to OARs increased most significantly with posterior displacements. Conclusion: For left-sided breast cancer patients receiving PMRT with IMN coverage, GS2-VMAT offers superior dose homogeneity to target volumes (CTVsc and CTVcw) and better sparing of OARs compared to GS4-VMAT, without compromising plan robustness in most cases.

PurposeTo investigate the values of a 3D-printed bolus ensuring the precise postmastectomy chest wall radiation therapy for breast cancer.Methods and materialsIn the preclinical study on the anthropomorphic phantom, the 3D-printed bolus was used for dosimetry and fitness evaluation. The dosimetric parameters of planning target volume (PTV) were assessed, including Dmin, Dmax, Dmean, D95%, homogeneity index (HI), conformity index (CI), and organs at risk (OARs). The absolute percentage differences (|%diff|) between the theory and fact skin dose were also estimated, and the follow-up was conducted for potential skin side effects.ResultsIn preclinical studies, a 3D-printed bolus can better ensure the radiation coverage of PTV (HI 0.05, CI 99.91%), the dose accuracy (|%diff| 0.99%), and skin fitness (mean air gap 1.01 mm). Of the 27 eligible patients, we evaluated the radiation dose parameter (median(min–max): Dmin 4967(4789–5099) cGy, Dmax 5447(5369–5589) cGy, Dmean 5236(5171–5323) cGy, D95% 5053(4936–5156) cGy, HI 0.07 (0.06–0.17), and CI 99.94% (97.41%–100%)) and assessed the dose of OARs (ipsilateral lung: Dmean 1341(1208–1385) cGy, V5 48.06%(39.75%–48.97%), V20 24.55%(21.58%–26.93%), V30 18.40%(15.96%–19.16%); heart: Dmean 339(138–640) cGy, V30 1.10%(0%–6.14%), V40 0.38%(0%–4.39%); spinal cord PRV: Dmax 639(389–898) cGy). The skin doses in vivo were Dtheory 208.85(203.16–212.53) cGy, Dfact 209.53(204.14–214.42) cGy, and |%diff| 1.77% (0.89–2.94%). Of the 360 patients enrolled in the skin side effect follow-up study (including the above 27 patients), grade 1 was the most common toxicity (321, 89.2%), some of which progressing to grade 2 or grade 3 (32, 8.9% or 7, 1.9%); the radiotherapy interruption rate was 1.1%.ConclusionA 3D-printed bolus can guarantee the precise radiation dose on skin surface, good fitness to skin, and controllable acute skin toxicity, which possesses a great clinical application value in postmastectomy chest call radiation therapy for breast cancer.

This report describes a script-based automatic planning method with robust optimization for craniospinal irradiation (CSI) to reduce sensitivity to field matching errors and increase planning efficiency. The data of 10 CSI patients with planning target volume (PTV) lengths between 49.8 and 85.0 cm were retrospectively studied. Robust intensity modulated radiation therapy plans with ±5-mm longitudinal position uncertainty were generated by the automatic planning script. A simple dose prediction model and a self-adjusting method were implied in the automatic plans. The plans' robustness against setup errors was evaluated by deliberately shifting the middle beamset ±5 mm in the superior-inferior direction. Manual and nonrobust plans were also created to evaluate the automatic robust plans' quality, efficiency, and robustness. There were no significant differences between the manual and automatic plans in terms of homogeneity index; conformity index; D1%, D2%, and D98% of PTV; and average doses of organs at risk. However, the D99% of the PTV in the automatic plans was slightly inferior to that in the manual plans. Compared with the manual plans, the automatic plans greatly increased efficiency, with a reduction in planning time of approximately 48%. When ±5-mm superior-inferior errors were introduced, the average deviations of the maximum dose D1% and minimum dose D99% to the spinal cord were 4.9% (±1.1%) and -3.4% (±1.3%), respectively. However, the corresponding values of the nonrobust plans were 20.0% (±5.4%) and -21.2 (±6.3%), respectively. The script-based automatic CSI planning method, combining robust optimization and a dose prediction model, efficiently created a good-quality plan that was robust to setup errors.

Background Craniospinal irradiation (CSI) is essential for treating central nervous system malignancies. However, it is very challenging and time-consuming to design a robust treatment plan capable of delivering a uniform dose to the entire treatment volume for standard linear accelerators. This study proposes a script-based automatic planning method with robust optimization for CSI to reduce sensitivity to setup errors and increase planning efficiency. Methods Ten CSI patients with planning target volume (PTV) lengths between 49.8 and 85.0 cm were retrospectively studied. IMRT plans with robust optimization were generated by the automatic planning script. The plans’ sensitivities to positional inaccuracy were evaluated by deliberately shifting the middle beamsets ±5 mm longitudinally. Non-robust optimization plans were also created and compared to the robust ones. The planning time was recorded to evaluate the efficiency of the automatic CSI planning. Results For the ten patients enrolled in the study, homogeneous dose coverage were achieved for both robust and non-robust plans with average conformity index value of 0.827 (±0.028) and 0.841 (±0.023) (p = 0.047), homogeneity index values of 0.076 (±0.014) and 0.078 (±0.027) (p = 0.114), respectively. In robust plans, the variations of D1% and D99% were between -0.17–0.99% and -1.18–0.53% for cranial PTV, and -1.02–7.2% and -4.78–0.31% for spinal PTV, while in non-robust plans, the variations were much more significant with corresponding values of -0.53–8.31% and -5.17–0.57% for cranial PTV, and 0.53–40.14% and -46.06% to -2.01% for spinal PTV. The total planning time of a robust optimization plan was about 9-13 minutes by the automatic planning script. Conclusions The script-based automatic CSI planning with robust optimization could efficiently create a uniform dose coverage for the entire target volume regardless of PTV length, with the advantage of being insensitive to setup errors and standardizing the planning process.

Pacemaker implantation is becoming increasingly common in patients with breast cancer. Comprehensive treatment options, such as surgery, chemotherapy, radiation therapy, targeted therapy and immunotherapy, have greatly improved the prognosis of patients with breast cancer. In particular, radiotherapy is an important means of comprehensive breast cancer treatment that can reduce recurrence and prolong survival in high-risk patients who underwent mastectomy. The pacemaker electrical pulse generator is typically implanted subcutaneously in the left subclavian area above the pectoral muscle through the subclavian vein. The present report implemented a new method of ‘temporary pacemaker electrode and permanent artificial pacemaker placement’ through the right axillary vein in a patient with breast cancer. An electrical pulse generator was placed in the right subcutaneous subclavian tissue. The pacemaker was placed under the right clavicle, and the pacemaker was included as organ at risk (OAR). Dose of planning organ at risk volume (PRV) with additional 6 mm margin to the pacemaker was limited during radiotherapy planning design. This patient with breast cancer, who was also complicated with other underlying comorbidities (such as atrial fibrillation, coronary atherosclerosis, cardiac insufficiency, hypertension, type 2 diabetes mellitus) and implanted with a cardiac pacemaker, was treated with safe (means that the patient has not developed heart disease because of the pacemaker problem) and effective (tumor can be effectively controlled under the condition that the pacemaker does not malfunction) radiotherapy. At present, the patient has successfully completed radiation therapy for breast cancer with no recurrence or metastasis. To the best of our knowledge, the present report is the first to document this application, demonstrating the treatment of a patient with breast cancer and cardiac pacemaker implantation, which is worthy of further study and continuous improvement in clinical practice.

PURPOSE:Electronic portal imaging detector (EPID)-based patient positioning verification is an important component of safe radiotherapy treatment delivery. In computer simulation studies, learning-based approaches have proven to be superior to conventional gamma analysis in the detection of positioning errors. To approximate a clinical scenario, the detectability of positioning errors via EPID measurements was assessed using radiomics analysis for patients with thyroid-associated ophthalmopathy. METHODS:Treatment plans of 40 patients with thyroid-associated ophthalmopathy were delivered to a solid anthropomorphic head phantom. To simulate positioning errors, combinations of 0-, 2-, and 4-mm translation errors in the left-right (LR), superior-inferior (SI), and anterior-posterior (AP) directions were introduced to the phantom. The positioning errors-induced dose differences between measured portal dose images were used to predict the magnitude and direction of positioning errors. The detectability of positioning errors was assessed via radiomics analysis of the dose differences. Three classification models-support vector machine (SVM), k-nearest neighbors (KNN), and XGBoost-were used for the detection of positioning errors (positioning errors larger or smaller than 3 mm in an arbitrary direction) and direction classification (positioning errors larger or smaller than 3 mm in a specific direction). The receiver operating characteristic curve and the area under the ROC curve (AUC) were used to evaluate the performance of classification models. RESULTS:For the detection of positioning errors, the AUC values of SVM, KNN, and XGBoost models were all above 0.90. For LR, SI, and AP direction classification, the highest AUC values were 0.76, 0.91, and 0.80, respectively. CONCLUSIONS:Combined radiomics and machine learning approaches are capable of detecting the magnitude and direction of positioning errors from EPID measurements. This study is a further step toward machine learning-based positioning error detection during treatment delivery with EPID measurements.

Island blocking and dose leakage problems will lead to unnecessary irradiation to normal brain tissue (NBT) in hypofractionated stereotactic radiotherapy (HSRT) for multiple brain metastases (BM) with single-isocenter volumetric modulated arc therapy (VMAT). The present study aimed at investigating whether reducing the number of metastases irradiated by each arc beam could minimize these two problems. A total of 32 non-small-cell lung cancer (NSCLC) patients with multiple BM received HSRT (24–36 Gy/3 fractions) with single-isocenter VMAT, where each arc beam only irradiated partial metastases (pm-VMAT), were enrolled in this retrospective study. Conventional single-isocenter VMAT plans, where each arc beam irradiated whole metastases (wm-VMAT), was regenerated and compared with pm-VMAT plans. Furthermore, the clinical efficacy and toxicities were evaluated. Pm-VMAT achieved similar target coverage as that with wm-VMAT, with better dose fall-off (P < 0.001) and NBT sparing (P < 0.001). However, pm-VMAT resulted in more monitor units (MU) and longer beam-on time (P < 0.001). The intracranial objective response rate and disease control rate for all patients were 75% and 100%, respectively. The local control rates at 1 year and 2 year were 96.2% and 60.2%, respectively. The median progression-free survival and overall survival were 10.3 months (95% confidence interval [CI] 6.8–13.2) and 18.5 months (95% CI 15.9–20.1), respectively. All treatment-related adverse events were grade 1 or 2, and 3 lesions (2.31%) from 2 patients (6.25%) demonstrated radiation necrosis after HSRT. HSRT with pm-VMAT is effective and has limited toxicities for NSCLC patients with multiple BM. Pm-VMAT could provide better NBT sparing while maintaining target dose coverage.

BackgroundThe efficiency of concurrent chemotherapy (CC) remains controversial for stage II–IVa nasopharyngeal carcinoma (NPC) patients treated with induction chemotherapy (IC) followed by intensity-modulated radiotherapy (IMRT). Therefore, we aimed to propose a nomogram to identify patients who would benefit from CC.MethodsA total of 434 NPC patients (stage II–IVa) treated with IC followed by IMRT between January 2010 and December 2015 were included. There were 808 dosimetric parameters extracted by the in-house script for each patient. A dosimetric signature was developed with the least absolute shrinkage and selection operator algorithm. A nomogram was built by incorporating clinical factors and dosimetric signature using Cox regression to predict recurrence-free survival (RFS). The C-index was used to evaluate the performance of the nomogram. The patients were stratified into low- and high-risk recurrence according to the optimal cutoff of risk score.ResultsThe nomogram incorporating age, TNM stage, and dosimetric signature yielded a C-index of 0.719 (95% confidence interval, 0.658–0.78). In the low-risk group, CC was associated with a 9.4% increase of 5-year locoregional RFS and an 8.8% increase of 5-year overall survival (OS), whereas it was not significantly associated with an improvement of locoregional RFS (LRFS) and OS in the high-risk group. However, in the high-risk group, patients could benefit from adjuvant chemotherapy (AC) by improving 33.6% of the 5-year LRFS.ConclusionsThe nomogram performed an individualized risk quantification of RFS in patients with stage II–IVa NPC treated with IC followed by IMRT. Patients with low risk could benefit from CC, whereas patients with high risk may require additional AC.

The measurement accuracy of stereotactic radiotherapy (SRT) patient-specific quality assurance (QA) is challenging as small-field dosimetry contains lateral charge disequilibrium, partial blocking of the beam source, and limitations based on the detector size. The aim of this study was to investigate the dosimetric characteristics of a two-dimensional high-resolution silicon diode array for SRT end-to-end patient-specific QA. The dosimetric characteristics of the diode array, delivered to an end-to-end QA phantom, were evaluated for 6 MV, with a flattening filter (FF) and flattening filter-free (FFF), and 10 MV FFF photon beams. Dose linearity, dose rate dependence, dose-per-pulse dependence, field size dependence, angular dependence, and beam directivity were investigated for all photon beams. A total of 27 clinical plans were selected to evaluate the SRT end-to-end patient-specific QA for treatment delivery using volumetric modulated arc therapy (VMAT). For all beam qualifies, the differences of dose and dose rate linearity of the diode array were below 0.7% (10-1400 MU range) and 0.6% (100-2400 MU/min range), respectively. The diodes had a decrease in sensitivity of about 4% for the 21-fold decrease in dose-per-pulse. Output factors were in good agreement for field size down to 2 x 2 cm(2) (< 0.6% for both 6 MV FF and FFF beams, < 1.6% for the 10 MV FFF beam), while the field size down to 0.6 x 0.6 cm(2) had an under-response (< 4% for all beam qualifies). Angular dependence was within +/- 2% and +/- 4%, for coplanar and non-coplanar beams, respectively. However, this was not the case for the beam direction nearly parallel to the diode array plane. Beam directivity response on both sides of the array was in excellent agreement. For the end-to-end patient-specific QA, the average gamma passing rate (GPR) with a 2%/1 mm criterion was 96.8% and the minimum value was 93.0%. There was no significant difference in the GPRs between coplanar and non-coplanar VMAT plans. The diode array, with several corrections, demonstrated good dosimetric characteristics for SRT QA. The GPRs of end-to-end patient-specific QA for non-coplanar and multiple metastases were as high as that for coplanar and single-target, and a gamma criterion of 2%/1 mm would be suitable for SRT QA when using the array.

医学技术专业的研究对象是与疾病相关的诊断、检测、监测、治疗技术和技能等,其重点不再是关注疾病本身,具有医学与工程技术相交叉的学科特点.2011年该专业成为一级学科,本科生导师制度的建立是该学科的完善建设的必须且重要因素之一,目前仍处于探索阶段.根据国内现状和实际教学需求,我们认为有必要对该专业本科生导师制进行分析与研究.本研究以相关问卷调查结果为评价基础,分析医学技术专业本科生导师现状,探索一条适合我国现状、开拓学生视野、促进医学技术高端人才培养的本科生导师制度之路.

The eye lens is recognized as one of the most radiosensitive structures in the human body. The widespread use of intensity-modulated radiotherapy (IMRT) complicates dose verification and necessitates high standards of dose computation. The purpose of this work was to assess the computed dose accuracy of eye lens through measurements using a metal-oxide-semiconductor field-effect transistor (MOSFET) dosimetry system. Sixteen clinical IMRT plans of head and neck patients were copied to an anthropomorphic head phantom. Measurements were performed using the MOSFET dosimetry system based on the head phantom. Two MOSFET detectors were imbedded in the eyes of the head phantom as the left and the right lens, covered by approximately 5-mm-thick paraffin wax. The measurement results were compared with the calculated values with a dose grid size of 1 mm. Sixteen IMRT plans were delivered, and 32 measured lens doses were obtained for analysis. The MOSFET dosimetry system can be used to verify the lens dose, and our measurements showed that the treatment planning system used in our clinic can provide adequate dose assessment in eye lenses. The average discrepancy between measurement and calculation was 6.7 +/- 3.4%, and the largest discrepancy was 14.3%, which met the acceptability criterion set by the American Association of Physicists in Medicine Task Group 53 for external beam calculation for multileaf collimator-shaped fields in buildup regions. (C) 2018 American Association of Medical Dosimetrists. Published by Elsevier B.V. All rights reserved.

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.

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.

Objective To analyze the displacement of titanium clips for tumor bed localization after breast-conserving surgery for breast cancer and its influential factors.Methods A retrospective analysis was performed on the cone-beam computed tomography (CT) images of 14 patients with breast cancer who received radiotherapy after breast-conserving surgery from April to October,2016.The relative position of the chest wall and the errors of the titanium clips in radiotherapy were measured.A Pearson correlation analysis was used to analyze the correlation of the displacement of titanium clips with the relative position of titanium clips,the breast volume,the vertical distance between the titanium clips and the tangential line of the chest wall,and the maximum thickness of the breast.Results The system errors of the chest wall in left-right,superior-inferior,and anterior-posterior directions were 4.42,3.44,and 5.13 mm,respectively,and the random errors were 3.55,3.07,and 4.54 mm,respectively.The titanium clips had a large displacement relative to the chest wall,mainly in the left-right direction.The maximum system error was 4.39 mm and the random error was 2.42 mm.The displacement of titanium clips was not significantly correlated with the breast volume and the maximum thickness of the breast (P>0.05).However,the relative position of titanium clips in superior-inferior direction was significantly correlated with the displacement of the lowest,the most lateral,the most anterior,and the most posterior titanium clips (P<0.05).As to the uppermost clips,there was a significant difference in displacement between the clips close to the chest wall and the clips far from the chest wall (P=0.02).Conclusions Due to large setup error and displacement of titanium clips during radiotherapy,simultaneous integrated boost is not suitable for patients with breast cancer who are immobilized by vacuum cushion and received radiotherapy.The unstable immobilization may be the major influential factor for the displacement of titanium clips.