BACKGROUND Pancreatic cancer is a malignancy with one of the poorest prognoses amongst all cancers.Patients with unresectable tumours either receive palliative care or undergo various chemoradiotherapy regimens.Conven...BACKGROUND Pancreatic cancer is a malignancy with one of the poorest prognoses amongst all cancers.Patients with unresectable tumours either receive palliative care or undergo various chemoradiotherapy regimens.Conventional techniques are often associated with acute gastrointestinal toxicities,as adjacent critical structures such as the duodenum ultimately limits delivered doses.Stereotactic body radiotherapy(SBRT)is an advanced radiation technique that delivers highly ablative radiation split into several fractions,with a steep dose fall-off outside target volumes.AIM To discuss the latest data on SBRT and whether there is a role for magnetic resonance-guided techniques in multimodal management of locally advanced,unresectable pancreatic cancer.METHODS We conducted a search on multiple large databases to collate the latest records on radiotherapy techniques used to treat pancreatic cancer.Out of 1229 total records retrieved from our search,36 studies were included in this review.RESULTS Studies indicate that SBRT is associated with improved clinical efficacy and toxicity profiles compared to conventional radiotherapy techniques.Further dose escalation to the tumour with SBRT is limited by the poor soft-tissue visualisation of computed tomography imaging during radiation planning and treatment delivery.Magnetic resonance-guided techniques have been introduced to improve imaging quality,enabling treatment plan adaptation and re-optimisation before delivering each fraction.CONCLUSION Therefore,SBRT may lead to improved survival outcomes and safer toxicity profiles compared to conventional techniques,and the addition of magnetic resonance-guided techniques potentially allows dose escalation and conversion of unresectable tumours to operable cases.展开更多
Deformable image registration (DIR) has been an important component in adaptive radiotherapy (ART). Our goal was to examine the accuracy of ART using the dice similarity coefficient (DSC) and to determine the optimal ...Deformable image registration (DIR) has been an important component in adaptive radiotherapy (ART). Our goal was to examine the accuracy of ART using the dice similarity coefficient (DSC) and to determine the optimal timing of replanning. A total of 22 patients who underwent volume modulated arc therapy (VMAT) for head and neck (H&N) cancers were prospectively analyzed. The planning target volume (PTV) was to receive a total of 70 Gy in 33 fractions. A second planning CT scan (rescan) was performed at the 15th fraction. The DSC was calculated for each structure on both CT scans. The continuous variables to predict the need for replanning were assessed. The optimal cut-off value was determined using receiver operating characteristic (ROC) curve analysis. In the correlation between body weight loss and DSC of each structure, weight loss correlated negatively with DSC of the whole face (rs = -0.45) and the face surface (rs = -0.51). Patients who required replanning tended to have experienced rapid weight loss. The threshold DSC was 0.98 and 0.60 in the whole face and the face surface, respectively. Patients who showed low DSC in the whole face and the face surface required replanning at a significantly high rate (P < 0.05 and P < 0.01). Weight loss correlated with DSC in both the whole face and the face surface (P < 0.05 and P < 0.05). The DSC values in the face predicted the need for replanning. In addition, weight loss tended to correlate with DSC. DIR during ART was found to be a useful tool for replanning.展开更多
Objective The aim of this study was to investigate tumor volume changes with kilovoltage cone-beam computed tomography （kV-CBCT） and their dosimetric consequences for non-operative lung cancer during intensity-modul...Objective The aim of this study was to investigate tumor volume changes with kilovoltage cone-beam computed tomography （kV-CBCT） and their dosimetric consequences for non-operative lung cancer during intensity-modulated radiotherapy （IMRT） or fractionated stereotactic radiotherapy. Methods Eighteen patients with non-operative lung cancer who received IMRT consisting of 1.8-2.2 Gy/fraction and five fractions per week or stereotactic radiotherapy with 5-8 Gy/fraction and three fractions a week were studied, kV-CBCT was performed once per week during IMRT and at every fraction during stereotactic radiotherapy. The gross tumor volume （GTV） was contoured on the kV-CBCT images, and adaptive treatment plans were created using merged kV-CBCT and primary planning computed tomogra- phy image sets. Tumor volume changes and dosimetric parameters, including the minimum dose to 95% （D95） or 1% （D1） of the planning target volume （PTV）, mean lung dose （MLD）, and volume of lung tissue that received more than 5 （Vs）, 10 （Vl0）, 20 （V20）, and 30 （V30） Gy were retrospectively analyzed. Results The average maximum change in GTV observed during IMRT or fractionated stereotactic radio- therapy was -25.85% （range, -13.09% --56.76%）. The D95 and Dr of PTV for the adaptive treatment plans in all patients were not significantly different from those for the initial or former adaptive treatment plans. In patients with tumor volume changes of 〉20% in the third or fourth week of treatment during IMRT, adap- tive treatment plans offered clinically meaningful decreases in MLD and V5, V10, V20, and V30; however, in patients with tumor volume changes of 〈 20% in the third or fourth week of treatment as well as in patients with stereotactic radiotherapy, there were no significant or clinically meaningful decreases in the dosimetric parameters. Conclusion Adaptive treatment planning for decreasing tumor volume during IMRT may be beneficial for patients who experience tumor volume changes of 〉20% in the third or fourth week of treatment.展开更多
The purpose of the study was to evaluate a treatment dose using planning computed tomography (pCT) that was deformed to pre-treatment cone beam computed tomography (CBCT) for lung stereotactic body radiation therapy (...The purpose of the study was to evaluate a treatment dose using planning computed tomography (pCT) that was deformed to pre-treatment cone beam computed tomography (CBCT) for lung stereotactic body radiation therapy (SBRT) treatment. Five lung SBRT patients were retrospectively selected, and their daily CBCTs were employed in this study. Dosimetric comparison was performed between the original and recalculated plans from the deformed pCT (dose per fraction) by comparing a target coverage and organs at risk. Dose summation of five fractions was computed and compared to the original plan. A phantom study was conducted to evaluate the dosimetric accuracy for the dose per fraction. In the phantom study, the difference between the mean Hounsfield Unit (HU) values of the original and deformed pCTs is less than 0.5%. In patient study, the mean HU deviation of the five deformed pCTs compared to that of the original pCT was within ±5%, which is dosimetrically insignificant. While the internal target volume (ITV) shrank by 17% on average among the five patients, mean lung dose (MLD) increased by up to 7%, and D95% of PTV decreased slightly but stayed within 5%. Results showed that MLD might be a better indicative metric of normal lung dose than V20Gy as the ITV volume decreases. This study showed a feasibility to use a deformed pCT for evaluation of the dose per fraction and for a possible plan adaptation in lung SBRT cases. Readers should be cautious in selecting patients before clinical application due to the image quality of CBCT.展开更多
测试数据自动生成方法是软件测试领域研究的热点。基于遗传算法的启发式搜索算法是一种路径覆盖生成测试数据的方法。文中提出了一种基于自适应随机测试(Adaptive Random Testing,ART)算法更新种群的方法,将ART融入遗传算法,优化选择操...测试数据自动生成方法是软件测试领域研究的热点。基于遗传算法的启发式搜索算法是一种路径覆盖生成测试数据的方法。文中提出了一种基于自适应随机测试(Adaptive Random Testing,ART)算法更新种群的方法,将ART融入遗传算法,优化选择操作,动态更新种群,从而增加种群进化过程中的个体多样性,提高了收敛速度,有效地减少了陷入局部最优。实验结果显示,与传统遗传算法生成测试数据的方法相比,改进的算法明显提高了路径覆盖率,减少了种群平均进化代数。展开更多
ART Ⅱ网络以模式的相似性量度值为基础,能够对动态的输入模式样本进行自适应的聚类和识别,然而标准的ART Ⅱ网络在输入数据处理过程中,忽略了样本数据中的负数信息和幅值信息,造成信号畸变和"同相位不可分"问题,在权值调整...ART Ⅱ网络以模式的相似性量度值为基础,能够对动态的输入模式样本进行自适应的聚类和识别,然而标准的ART Ⅱ网络在输入数据处理过程中,忽略了样本数据中的负数信息和幅值信息,造成信号畸变和"同相位不可分"问题,在权值调整过程中,聚类中心发生移动,容易造成"模式漂移"现象。针对上述问题结合相关文献提出了引入非线性函数对输入数据进行变换的方法解决"同相位不可分"问题,用待测数据与同一模式类中有限数据的欧氏距离与限定值进行比较实现聚类判定,抑制"模式漂移"现象。用Matlab仿真表明,改进算法性能优于标准算法。展开更多
文摘BACKGROUND Pancreatic cancer is a malignancy with one of the poorest prognoses amongst all cancers.Patients with unresectable tumours either receive palliative care or undergo various chemoradiotherapy regimens.Conventional techniques are often associated with acute gastrointestinal toxicities,as adjacent critical structures such as the duodenum ultimately limits delivered doses.Stereotactic body radiotherapy(SBRT)is an advanced radiation technique that delivers highly ablative radiation split into several fractions,with a steep dose fall-off outside target volumes.AIM To discuss the latest data on SBRT and whether there is a role for magnetic resonance-guided techniques in multimodal management of locally advanced,unresectable pancreatic cancer.METHODS We conducted a search on multiple large databases to collate the latest records on radiotherapy techniques used to treat pancreatic cancer.Out of 1229 total records retrieved from our search,36 studies were included in this review.RESULTS Studies indicate that SBRT is associated with improved clinical efficacy and toxicity profiles compared to conventional radiotherapy techniques.Further dose escalation to the tumour with SBRT is limited by the poor soft-tissue visualisation of computed tomography imaging during radiation planning and treatment delivery.Magnetic resonance-guided techniques have been introduced to improve imaging quality,enabling treatment plan adaptation and re-optimisation before delivering each fraction.CONCLUSION Therefore,SBRT may lead to improved survival outcomes and safer toxicity profiles compared to conventional techniques,and the addition of magnetic resonance-guided techniques potentially allows dose escalation and conversion of unresectable tumours to operable cases.
文摘Deformable image registration (DIR) has been an important component in adaptive radiotherapy (ART). Our goal was to examine the accuracy of ART using the dice similarity coefficient (DSC) and to determine the optimal timing of replanning. A total of 22 patients who underwent volume modulated arc therapy (VMAT) for head and neck (H&N) cancers were prospectively analyzed. The planning target volume (PTV) was to receive a total of 70 Gy in 33 fractions. A second planning CT scan (rescan) was performed at the 15th fraction. The DSC was calculated for each structure on both CT scans. The continuous variables to predict the need for replanning were assessed. The optimal cut-off value was determined using receiver operating characteristic (ROC) curve analysis. In the correlation between body weight loss and DSC of each structure, weight loss correlated negatively with DSC of the whole face (rs = -0.45) and the face surface (rs = -0.51). Patients who required replanning tended to have experienced rapid weight loss. The threshold DSC was 0.98 and 0.60 in the whole face and the face surface, respectively. Patients who showed low DSC in the whole face and the face surface required replanning at a significantly high rate (P < 0.05 and P < 0.01). Weight loss correlated with DSC in both the whole face and the face surface (P < 0.05 and P < 0.05). The DSC values in the face predicted the need for replanning. In addition, weight loss tended to correlate with DSC. DIR during ART was found to be a useful tool for replanning.
文摘Objective The aim of this study was to investigate tumor volume changes with kilovoltage cone-beam computed tomography （kV-CBCT） and their dosimetric consequences for non-operative lung cancer during intensity-modulated radiotherapy （IMRT） or fractionated stereotactic radiotherapy. Methods Eighteen patients with non-operative lung cancer who received IMRT consisting of 1.8-2.2 Gy/fraction and five fractions per week or stereotactic radiotherapy with 5-8 Gy/fraction and three fractions a week were studied, kV-CBCT was performed once per week during IMRT and at every fraction during stereotactic radiotherapy. The gross tumor volume （GTV） was contoured on the kV-CBCT images, and adaptive treatment plans were created using merged kV-CBCT and primary planning computed tomogra- phy image sets. Tumor volume changes and dosimetric parameters, including the minimum dose to 95% （D95） or 1% （D1） of the planning target volume （PTV）, mean lung dose （MLD）, and volume of lung tissue that received more than 5 （Vs）, 10 （Vl0）, 20 （V20）, and 30 （V30） Gy were retrospectively analyzed. Results The average maximum change in GTV observed during IMRT or fractionated stereotactic radio- therapy was -25.85% （range, -13.09% --56.76%）. The D95 and Dr of PTV for the adaptive treatment plans in all patients were not significantly different from those for the initial or former adaptive treatment plans. In patients with tumor volume changes of 〉20% in the third or fourth week of treatment during IMRT, adap- tive treatment plans offered clinically meaningful decreases in MLD and V5, V10, V20, and V30; however, in patients with tumor volume changes of 〈 20% in the third or fourth week of treatment as well as in patients with stereotactic radiotherapy, there were no significant or clinically meaningful decreases in the dosimetric parameters. Conclusion Adaptive treatment planning for decreasing tumor volume during IMRT may be beneficial for patients who experience tumor volume changes of 〉20% in the third or fourth week of treatment.
文摘The purpose of the study was to evaluate a treatment dose using planning computed tomography (pCT) that was deformed to pre-treatment cone beam computed tomography (CBCT) for lung stereotactic body radiation therapy (SBRT) treatment. Five lung SBRT patients were retrospectively selected, and their daily CBCTs were employed in this study. Dosimetric comparison was performed between the original and recalculated plans from the deformed pCT (dose per fraction) by comparing a target coverage and organs at risk. Dose summation of five fractions was computed and compared to the original plan. A phantom study was conducted to evaluate the dosimetric accuracy for the dose per fraction. In the phantom study, the difference between the mean Hounsfield Unit (HU) values of the original and deformed pCTs is less than 0.5%. In patient study, the mean HU deviation of the five deformed pCTs compared to that of the original pCT was within ±5%, which is dosimetrically insignificant. While the internal target volume (ITV) shrank by 17% on average among the five patients, mean lung dose (MLD) increased by up to 7%, and D95% of PTV decreased slightly but stayed within 5%. Results showed that MLD might be a better indicative metric of normal lung dose than V20Gy as the ITV volume decreases. This study showed a feasibility to use a deformed pCT for evaluation of the dose per fraction and for a possible plan adaptation in lung SBRT cases. Readers should be cautious in selecting patients before clinical application due to the image quality of CBCT.
文摘测试数据自动生成方法是软件测试领域研究的热点。基于遗传算法的启发式搜索算法是一种路径覆盖生成测试数据的方法。文中提出了一种基于自适应随机测试(Adaptive Random Testing,ART)算法更新种群的方法,将ART融入遗传算法,优化选择操作,动态更新种群,从而增加种群进化过程中的个体多样性,提高了收敛速度,有效地减少了陷入局部最优。实验结果显示,与传统遗传算法生成测试数据的方法相比,改进的算法明显提高了路径覆盖率,减少了种群平均进化代数。
