The Dilemma of Target Delineation with PET/CT in Radiotherapy Planning for Malignant Tumors

Currently there are many unanswered questions concerning contouring a target with PET/CT in radiotherapy planning. Who should contour the PET volume-the radiation oncologist or the nuclear medicine physician？ Which factors will contribute to the dual-observer variability between them？ What should be taken as the optimal SUV threshold to demarcate a malignant tumor from the normal tissue？ When the PET volume does not coincide with the local area CT findings, which portion should be contoured as the target？ If a reginal lymph node,draining area or a remote region is shown to be PET positive but CT negative, or PET negative but CT positive, how is the target identified and selected？ Further studies concerning the relationship between PET/CT and the cancerous tissue are needed. The long-term clinical results showing an increased therapeutic ratio will finally verify the applicability of guidelines to contour the target with PET/CT in radiotherapy planning.

Comparison between 4D robust optimization methods for carbon-ion treatment planning

Intensity-modulated particle therapy(IMPT)with carbon ions is comparatively susceptible to various uncertainties caused by breathing motion,including range,setup,and target positioning uncertainties.To determine relative biological effectiveness-weighted dose(RWD)distributions that are resilient to these uncertainties,the reference phase-based four-dimensional(4D)robust optimization(RP-4DRO)and each phase-based 4D robust optimization(EP-4DRO)method in carbon-ion IMPT treatment planning were evaluated and compared.Based on RWD distributions,4DRO methods were compared with 4D conventional optimization using planning target volume(PTV)margins(PTV-based optimization)to assess the effectiveness of the robust optimization methods.Carbon-ion IMPT treatment planning was conducted in a cohort of five lung cancer patients.The results indicated that the EP-4DRO method provided better robustness(P=0.080)and improved plan quality(P=0.225)for the clinical target volume(CTV)in the individual respiratory phase when compared with the PTV-based optimization.Compared with the PTV-based optimization,the RP-4DRO method ensured the robustness(P=0.022)of the dose distributions in the reference breathing phase,albeit with a slight sacrifice of the target coverage(P=0.450).Both 4DRO methods successfully maintained the doses delivered to the organs at risk(OARs)below tolerable levels,which were lower than the doses in the PTV-based optimization(P<0.05).Furthermore,the RP-4DRO method exhibited significantly superior performance when compared with the EP-4DRO method in enhancing overall OAR sparing in either the individual respiratory phase or reference respiratory phase(P<0.05).In general,both 4DRO methods outperformed the PTV-based optimization in terms of OAR sparing and robustness.

A multiphase direct aperture optimization for inverse planning in radiotherapy

Optimization of the inverse planning becomes critical because it follows the invention of intensity modulated radiotherapy(IMRT) to shorten the previous "trial-and-error" treatment process and increase efficiency.In this paper, the inverse planning is used to direct aperture optimization in the ARTS(Accurate/Advanced Radiotherapy System). The objective function was quadratic, both tolerance and dose-volume constraint types are supported. The memory efficient conjugate gradient algorithm is used to cope with its large data.Furthermore, to fully exploit the solution space, a shortest path sub-procedure is coupled into the whole algorithm, thus giving further possibility decreasing the objective function. Two clinical cases are tested, indicating that the applicability of this algorithm is promising to clinical usage.

Dose Distributions in Simulated Electron Radiotherapy with Intraoral Cones Using Treatment Planning System

Aim: This study aims to evaluate the difference between depth data from an intraoral cone and a conventional irradiation tube calculated using a treatment planning system (TPS), and that measured using an intraoral cone for electron radiotherapy. Background: A TPS is only compatible with conventional irradiation tubes. However, such systems are not suitable for determining dose distributions when a special cone is employed. Materials and Methods: Dose distributions were calculated using the beam data for mounted intraoral cones using a TPS. Then, the dose distribution by field size was calculated for a low-melting-point lead alloy using the beam data for a mounted conventional tube. The calculated data were evaluated against the measured intraoral-cone depth data based on the dose and depth differences. Results: The calculated data for the intraoral cone case did not match the measured data. However, the depth data obtained considering the field size determined for the lead alloy using the conventional tube were close to the measured values for the intraoral cone case. The difference in the depth at which the absorbed dose was 50% of the maximum value of the percentage depth dose was less than ±4 mm for the generalized Gaussian pencil beam convolution algorithm and less than ±1 mm for the electron Monte Carlo algorithm. Conclusion: It was found that the measured and calculated dose distributions were in agreement, especially when then electron Monte Carlo algorithm was used. Thus, the TPS can be employed to determine dose distributions for intraoral cone applications.

Complex Target Volume Delineation and Treatment Planning in Radiotherapy for Malignant Pleural Mesothelioma (MPM)

Introduction: Radiotherapy alone or combined with surgery and/or chemotherapy is being investigated in the treatment of malignant pleural mesothelioma (MPM). This study aimed to simulate a Volumetric Modulated Arc Therapy (VMAT) treatment of a patient with MPM. Materials and Methods: CT images from a patient with intact lungs were imported via DICOM into the Pinnacle3 treatment planning (TP) system (TPS) and used as a model for MPM to delineate organs at risk (OAR) and both clinical and planning target volumes (CTV and PTV) with a margin of 5 mm. Elekta Synergy with 6 MV photons and 80 leafs MLCi2 was employed. VMAT plans were generated using two coplanar arcs with gantry rotation angles of 178° - 182°, the collimator angles of each arc were set to 90°, Octavius® 4D 729 was employed for quality assurance while the calculated and measured doses were compared using VeriSoft. Results: A TP was achieved. The Gamma volume analysis with criteria of 3 mm distance to agreement and 3% dose difference yielded the gamma passing rate = 99.9%. The reference isodose was 42.75 Gy with the coverage constraints for the PTV D95 and V95 = 95.0% of 45 Gy. The remaining dosimetric parameters met the recommendations from the clinically acceptable guidelines for the radiotherapy of MPM. Conclusion: Using well-defined TV and VMAT, a consistent TP compared to similar ones from publications was achieved. We obtained a high agreement between the 3D dose reconstructed and the dose calculated.

Comparative Study between Field-in-Field and IMRT Techniques in Prostate Cancer Radiotherapy: A Treatment Planning Study

Introduction: Field-in-Field (FIF) and Intensity Modulated Radiation Therapy (IMRT) are two advanced radiation therapy planning techniques. Both of them are being used to achieve the same two related aims which are, to expose the targeted tumor to the full radiation dose and to spare the nearby normal tissues (or organs) from being exposed to high amounts of radiation more than its tolerance dose limits. FIF is a forward planning while IMRT is an inverse planning and FIF is a forward IMRT. Aim: The purpose of this study was to compare between Field-in-Field and IMRT techniques in prostate cancer radiotherapy. Method: A treatment planning system supporting both inverse and forward planning facilities is used. Ten prostate cancer patients were planned with both FIF and IMRT planning techniques. Doses received by the Planning Target Volume (PTV) and Organs at Risk (OARs) were compared in the two methods quantitatively from Dose Volume Histograms (DVHs) and qualitatively from (axial cuts). Results: The results showed that the IMRT planning technique achieved better dose coverage to the PTV than the FIF planning technique but, except RT and LT Femoral Heads, FIF achieved a better protection to the Rectum and the Bladder (OARs) than IMRT. Conclusions: The results showed that the inverse planning based IMRT technique is better and recommended in the prostate cancer radiotherapy than the FIF technique.

The Impact of Risk-Based Cancer Care Planning on the Complications and Self-Care Ability of Cervical Cancer Patients Undergoing Radiotherapy

Objective:To explore the impact of the application and implementation of risk-based cancer care planning in patients with cervical cancer radiotherapy on the complications and self-care ability of patients.Method:This study recruited selected patients who came for cervical cancer radiotherapy in a tertiary hospital in Xianyang City,Shaanxi Province from November 2020 to November 2021.One hundred patients were recruited.Nursing management was carried out,and cancer care planning under the concept of conventional care and risk were applied.The effects of different nursing methods on patients were compared and analyzed.Results:The patients in the experimental group had higher scores of self-care ability and lower complication rate.All data were significantly different from those of the control group(P<0.05),and the nursing effect on the experimental group was better.Conclusion:The application and implementation of the risk-based cancer care planning in patients who received cervical cancer radiotherapy has significant clinical effects,which is beneficial to reduce the incidence of patients’adverse reactions and promote patient recovery.

Volumetric-modulated arc therapy vs c-IMRT in esophageal cancer:A treatment planning comparison

AIM： To compare the volumetric-modulated arc ther- apy （VMAT） plans with conventional sliding window intensity-modulated radiotherapy （c-IMRT） plans in esophageal cancer （EC）. METHODS： Twenty patients with EC were selected, including 5 cases located in the cervical, the upper, the middle and the lower thorax, respectively. Five plans were generated with the eclipse planning sys- tem： three using c-IMRT with 5 fields （5F）, 7 fields （7F） and 9 fields （gF）, and two using VMAT with a single arc （1A） and double arcs （2A）. The treatment plans were designed to deliver a dose of 60 Gy to the plan-ning target volume （PTV） with the same constrains in a 2.0 Gy daily fraction, 5 d a week. Plans were normal- ized to 95% of the PTV that received 100% of the pre- scribed dose. We examined the dose-volume histogram parameters of PTV and the organs at risk （OAR） such as lungs, spinal cord and heart. Monitor units （MU） and normal tissue complication probability （NTCP） of OAR were also reported. RESULTS： Both c-IMRT and VMAT plans resulted in abundant dose coverage of PTV for EC of different Io- cations. The dose conformity to PTV was improved as the number of field in c-IMRT or rotating arc in VMAT was increased. The doses to PTV and OAR in VMAT plans were not statistically different in comparison with c-IMRT plans, with the following exceptions： in cervical and upper thoracic EC, the conformity index （CI） was higher in VMAT （1A 0.78 and 2A 0.8） than in c-IMRT （5F 0.62, 7F 0.66 and 9F 0.73） and homogeneity was slightly better in c-IMRT （7F 1.09 and 9F 1.07） than in VMAT （1A 1,1 and 2A 1.09）, Lung V30 was lower in VMAT （1A 12.52 and 2A 12.29） than in c-IMRT （7F 14.35 and 9F 14.81）. The humeral head doses were significantly increased in VMAT as against c-IMRT. In the middle and lower thoracic EC, CI in VMAT （1A 0.76 and 2A 0.74） was higher than in c-IMRT （5F 0.63 Gy and 7F 0.67 Gy）, and homogeneity was almost similar between VMAT and c-IMRT. V20 （2A 21.49 Gy vs 7F 24.59 Gy and 9F 24.16 Gy） and V30 （2A 9.73 Gy vs 5F 12.61 Gy, 7F 11.5 Gy and 9F 11.37 Gy） of lungs in VMAT were lower than in c-IMRT, but low doses to lungs （V5 and Vl0） were increased. V30 （1A 48.12 Gy vs 5F 59.2 Gy, 7F 58.59 Gy and 9F 57.2 Gy）, V40 and V50 of heart in VMAT was lower than in c-IMRT. MUs in VMAT plans were significantly reduced in comparison with c-IMRT, maximum doses to the spinal cord and mean doses of lungs were similar between the two techniques. NTCP of spinal cord was 0 for all cases. NTCP of lungs and heart in VMAT were lower than in c-IMRT. The advantage of VMAT plan was enhanced by doubling the arc. CONCLUSION： Compared with c-IMRT, VMAT, especial- ly the 2A, slightly improves the OAR dose sparing, such as lungs and heart, and reduces NTCP and MU with a better PTV coverage.

Auto-planning技术用于胸中段食管癌调强放疗的可行性

目的探讨Auto-planning技术用于食管癌调强放疗计划设计的可行性。方法选取24例食管癌放疗病例,用Pinnacle 3计划系统设计自动治疗计划(ap-IMRT)和人工计划(m-IMRT),比较两种不同计划的剂量体积直方图(DVH),用配对t检验分析靶区和危及器官受照剂量的差异。结果肿瘤靶区GTV的D_(min)(t=-2.233,P=0.036)、均匀性指数HI(t=2.205,P=0.038),计划靶区PTV的D 98(t=-2.241,P=0.035)、HI(t=2.543,P=0.018)、适形度指数CI(t=-2.497,P=0.020),左肺V 20(t=4.412,P=0.000)、V_(30)(t=5.243,P=0.000),心脏V 30(t=2.546,P=0.018)、V_(40)(t=2.404,P=0.025)、D_(mean)(t=2.565,P=0.017),以上参数均是ap-IMRT计划优于m-IMRT。脊髓最大受照剂量D_(max)(t=-1.891,P=0.045),m-IMRT计划优于ap-IMRT。结论ap-IMRT靶区剂量分布能够达到较好均匀性和适形度,且能更地保护并行器官,但对串行器官脊髓的保护欠佳。

Using CT imaging to delineate the prostatic apex for radiation treatment planning

Background and Objective: In computed tomography (CT)-based radiotherapy planning for prostate cancer, it is difficult to precisely delineate the prostatic apex because of its relationship with the urogenital diaphragm and bulbospongiosus musculature. In this retrospective study, we analyzed the magnetic resonance imaging (MRI) and CT scans of the patients with prostate cancer to investigate the relationship between the prostatic apex and the anatomic structure visible on CT, and to provide evidence for localizing the prostatic apex in radiotherapy planning. Methods: MRI and CT scans of 108 patients with prostate cancer were analyzed to measure the distances between the prostatic apex and the bottom of ischial tuberosities, the bottom of obturator foramen, the bottom of pubic symphysis, and the bulb of the penis. The volume of the prostate was measured to analyze its relationship with the localization of the prostatic apex. Results: The prostatic apex was located (13.1 ± 3.3) mm above the bulb of the penis, (11.0 ± 5.4) mm above the bottom of the obturator foramen, (31.3 ± 5.5) mm above the ischial tuberosities, and (7.1 ± 4.7) mm above the bottom of the symphysis pubis. There was no correlation between the size of the prostate and the localization of the prostatic apex. Conclusions: The variance of the distance between the prostatic apex and the bulb of the penis is smaller than that of the distance between the apex and bony anatomy. Delineating the target to 6 mm above the bulb of the penis can cover the prostatic apex in 95% of the patients with prostate cancer, delineating to the bottom of obturator foramen can cover the prostatic apex in 100% of the patients.

Effect of Non-Delineated Normal Volumes in IMRT Treatment for Left Breast Cancer: A Treatment Planning Study

Introduction: Intensity Modulated Radiation Therapy (IMRT) planning dose calculation process depends on IMRT dose constraints. So, if there was any structure along the treatment beam path not delineated, it would not be taken into account during that calculation process. During IMRT routine practical work, it is noticed that there are some non-delineated normal tissue volumes that received un-aimed dose. Aim: The purpose of this study was to study the effect of unusually delineated normal volumes in IMRT treatment for left sided breast cancer. Method: Ten left sided breast cancer patients were planned with IMRT inverse planning system. The unusually delineated normal volumes were delineated and taken into account in IMRT dose constraints as an Organ at Risk. Doses received by that volume were compared in the two methods quantitatively from Dose Volume Histograms (DVHs) and qualitatively from (axial cuts). Results: The results showed that doses received by the unusually delineated volume when they were delineated and taken into account in IMRT dose constraints were significantly higher than when they were not. Conclusions: The results showed that for IMRT planning technique used for treating left-sided breast cancer, all of the normal tissues/structures that are closed to the treatment targets must be delineated and taken into account in the IMRT planning dose constraints.

Dosimetric Effects Due to Inter-Observer Variability of Organ Contouring When Utilizing a Knowledge-Based Planning System for Prostate Cancer

Purpose: Radiotherapy is a widely accepted standard of care for early-stage prostate cancer, and it is believed that the plan quality and treatment outcome are associated with contour accuracy of both the target and organs-at-risk (OAR). The purposes of this study are to 1) assess geometric and dosimetric uncertainties due to inter-observer contour variabilities and 2) evaluate the effectiveness of geometric indicators to predict target dosimetry in prostate radiotherapy. Methods: Twenty prostate patients were selected for this retrospective study. Five experienced clinicians created unique structure sets containing prostate, seminal vesicles, bladder, and rectum for each patient. A fully automated script and knowledge-based planning routine were utilized to create standardized and unbiased plans that could be used to evaluate changes in isodose distributions due to inter-observer variability in structure segmentation. Plans were created on a “gold-standard” structure set, as well as on each of the user-defined structure sets. Results: Inter-observer variability of contours during structure segmentation was very low for clearly defined organs such as the bladder but increased for organs without well-defined borders (prostate, seminal vesicles, and rectum). For plans generated with the user-defined structure sets, strong/moderate correlations were observed between the geometric indicators for target structure agreement and target coverage for both low-risk and intermediate-risk patient groups, while OAR indicators showed no correlation to final dosimetry. Conclusions: Target delineation is crucial in order to maintain adequate dosimetric coverage regardless of the associated inter-observer uncertainties in OAR contours that had a limited impact upon final dosimetry.

非共面照射野在舌癌放疗中对脊髓和下颌骨重点保护的效果评价

目的 :在舌癌术后放疗计划中重点保护脊髓和下颌骨的前提下,通过比较共面野与非共面野计划两者放疗剂量分布的差异,探讨非共面照射野在放疗计划中对脊髓和下颌骨的重点保护效果,从而选择合理放疗方案,以应对舌癌复发需再次放疗的可能性。方法:选择上海交通大学医学院附属第九人民医院口腔颌面-头颈肿瘤科在2018年2月—2023年2月收治的15例舌癌术后放疗患者作为研究对象,采用实际治疗的靶区作为计算目标,正常组织剂量限值参照国家标准,在其他参数保持不变的前提下,仅仅变动脊髓以及下颌骨的限量函数。函数采用serial函数,限量由低到高分为20、25、30、35、40,在Monaco计划系统中自动计算,对计划各个参数进行评价(靶区CI、HI、D98、D95、D5、D2),正常组织脊髓的最大量,腮腺、喉、下颌骨的平均量。采用SPSS 20.0软件包对数据进行统计学分析。结果:非共面野的各项评价指标优于共面野计划。共面野计划在serial函数限值为20、25时,靶区评价指标D98、D95、D5、D2形成剂量趋势曲线存在发散状态,靶区归一性较差。随着限值提高,2组计划的靶区剂量趋势曲线相差变小,靶区归一性基本统一。统计结果显示,相对于非共面野计划,共面野计划在seiral函数为20、25时,脊髓、左右侧腮腺、喉、下颌骨以及靶区的CI、HI的结果较差,2组差异有统计学意义(P<0.05);特别在serial函数为20时差异值最大,HI指数差异为7.7%,CI差异为14%。随着限值提高,2组数据差异逐渐变小,多数评价指标差值有统计学意义(P<0.05)。结论:舌癌术后放疗计划中,在脊髓、下颌骨限量较为严格时,2组计划剂量差异较大,计划射野时建议选择非共面角度。随着限量提高,差异性逐渐变小。虽然多数指标仍存在统计学差异,但鉴于非共面野有转床的误差存在,计划射野时,可根据患者情况以及机器精度进行合理选择。

直肠癌调强放疗的临床计划质量优化和评估

目的:采用Plan IQ软件评估直肠癌调强放射治疗临床治疗计划和再优化计划的质量,为调强放疗计划筛选和优化提供方法和工具。方法:回顾性随机选取20例接受调强放疗的直肠癌患者,调强放疗技术(IMRT)和旋转容积调强技术(VMAT)计划各10例。(1)临床治疗计划设计(TP):IMRT计划采用5野等间距照射,VMAT计划采用2个360°弧旋转照射。处方剂量为PTV1:50 Gy/25 f;PTV2:45 Gy/25 f。所有计划均采用直接机器参数优化,且要求95%等剂量线能覆盖100%靶区体积,危及器官(OARs)参考耐受剂量标准来限制。计划完成后由医生审核确认,并经过计划剂量验证后实施治疗。(2)治疗计划再优化设计(RP):由1名有10年经验的计划设计者对20例TP计划进行重新优化,保持照射技术和照射野条件不变,根据个人经验重新调整计划优化条件和参数,直到OARs剂量尽可能低,且不影响PTV的目标覆盖率。用Plan IQ软件分别对TP和RP计划质量进行量化评估。两组计划之间剂量DVH参数和计划质量指数(PQI)行非参数的Wilcoxon符号秩检验。结果:RP计划的各DVH参数均优于TP计划,其中PTV1的D_(max)、小肠的V_(45 Gy)和D_(max)以及结肠的V_(45 Gy)的差异具有统计学意义(P<0.05)。IMRT组、VMAT组和所有患者的RP计划的质量评分均高于TP计划,差异具有统计学意义(P<0.05),其PQI分别为(88.55±3.35 vs 86.61±4.63,P=0.005)、(89.72±3.15 vs87.21±3.04,P=0.028)和(89.14±3.22 vs 86.91±3.22,P=0.001)。结论:计划再优化可以进一步提高直肠癌调强放疗的临床计划质量,Plan IQ软件为放疗计划质量控制和优质计划筛选提供了一种有效工具。

自动计划RapidPlan优化模块在鼻咽癌调强计划中的可行性应用

目的:通过比较常规调强计划与自动优化计划间的差异,探讨自动计划RapidPlan优化模块在鼻咽癌调强计划应用中的可行性。方法:选取60例经临床验证的优质鼻咽癌计划进行分析和特征提取,先建立一个特定的自动优化模型,然后用此模型对另外的15例鼻咽癌计划进行测试,比较这15例经模型测试优化后形成的自动计划与用常规调强优化的计划间的差异。采用SPSS 22.0版软件分别对两组计划的各主要参数行配对样本t检验分析。结果:自动优化产生的计划得到的剂量分布更佳;且自动优化比常规调强优化效率更高,自动计划的优化平均时间比常规调强计划缩短33.67%(P=0.001),优化次数也从平均3.5次降到2.2次(P=0.000);自动优化比常规调强优化的计划执行效率更高,MU值平均值减少376 MU,平均减少原来的14.8%(P=0.000)。结论:基于解剖特性和先验知识的自动计划模块,即RapidPlan优化模块,通过建立优化模型,设置优化参数,产生的鼻咽癌调强计划,可以达到比常规调强计划更佳的靶区剂量分布结果,并且更好地降低正常组织的剂量,同时获得比常规调强计划更高的优化效率和计划执行效率,在鼻咽癌的调强计划优化中是切实可行的。

CADPLAN(helios)调强放疗计划的绝对剂量验证

目的:验证CADPLAN(helios)设计的病人调强放射治疗(IMRT)计划的绝对剂量准确性,保证IMRT治疗计划临床实施的正确性。方法:利用美国Varian 23-EX医用直线加速器6MV-X射线,根据经国家计量院校准过的0.6 cc电离室在体部模体中校准0.01 cc电离室;根据病人的CT图像资料,使用CADPLAN(helios)三维治疗计划系统设计出病人IMRT计划,并移置到模体中,重新计算出体模中过等中心点横截面上的剂量分布。将模体移放到加速器治疗床上,调用模体IMRT计划对模体进行照射。使用0.01 cc电离室测量出体模中等中心点及其周围两个感兴趣点上的吸收剂量,然后与模体计划中的计算值相比较。结果:空间三点绝对吸收剂量的测量值与计划值的偏差小于5%。结论:在准确、合理配置CADPLAN(helios)计划系统基础数据的情况下,利用它设计出的IMRT计划是可信的。

AiPlan放射治疗计划系统的临床剂量学测试

目的对AiPlan三维放射治疗计划系统(Treatment Planning System,TPS)进行临床剂量学验证,以检验AiPlan系统在临床正常使用条件下的有效性和安全性。方法随机选取60例在Pinnacle计划系统上已完成放射治疗计划设计的患者,将60例患者的CT图像及RT Structures通过DICOM网络传输至AiPlanTPS,并应用AiPlan系统对60例临床病例重新进行放射治疗计划设计。分别对Pinnacle和AiPan两组放射治疗计划进行绝对点剂量以及二维面剂量验证,同时比较两组放射治疗计划等中心及附近层面剂量分布情况,运用统计学方法对两组计划剂量验证结果进行分析。结果 AiPlanTPS能够实现逆向调强放射治疗计划设计所需的各项功能;经AiPlan系统设计的60例放射治疗计划均能满足临床剂量要求;绝对点剂量误差范围为-3.27%~3.98%,二维面剂量验证Gamma通过率为97.5%±2.8%,该结果与Pinnacle系统计划验证结果相比无统计学差异(t=0.149、1.858,P=0.882、0.068)。结论 Aiplan三维TPS在剂量计算精度上达同类进口产品相似水平,能够满足临床要求。

食管癌调强放疗计划中心与靶区中心位置偏差的研究

目的探索放疗计划设计时,当食管癌定位中心与靶区中心位置偏差在X(左右方向)、Y(头脚方向)、Z(上下方向)三维方向小于±15 mm时,计划中心的改变情况对放疗计划质量的影响。方法选取在商洛市中心医院接受食管癌放射治疗的40例患者为研究对象。首先以计划靶区(Planning Target Volume,PTV)中心为计划中心设计放疗计划,待计划优化完成后,将靶区中心沿X、Y、Z三个方向分别平移±5、±10、±15 mm,并以此点为计划中心,重新设计放疗计划,统计剂量学参数,评价计划的可行性。结果靶区、危及器官、计划执行效率指标差异均无统计学意义(P>0.05)。与计划中心在PTV中心组相比,其他组PTV最大剂量(D_(max))、最小剂量、平均剂量(D_(mean))、均匀性指数、适形度指数的变化范围(百分比)为:-0.15%~0.12%、-0.05%~0.05%、-0.07%~0.09%、-0.09%~0.28%、-0.36%~0.48%;肺V5(器官受到500 cGy剂量的体积百分比,其他以此类推)、V_(10)、V_(20)、V_(30)、D_(mean)最大偏差分别为0.68%、0.29%、0.40%、-0.14%、7.75 cGy;心脏V_(10)、V_(20)、V_(30)、V_(40)、D_(mean)最大偏差分别为0.66%、-0.30%、-0.47%、0.54%、-14.08 cGy;脊髓D_(max)最大偏差为28.98 cGy;机器跳数、计划执行时间、计划优化时间最大偏差分别为-34.01 MU、5.33 s、-6.09 s。结论当定位中心和靶区中心在X、Y、Z三个方向的位移小于±15 mm时,可以直接将定位中心作为计划中心进行放疗计划的设计,以便减少患者的复位时间和复位时的二次摆位误差。

Monaco放疗计划系统控制点设定对中下段食管癌动态调强放射治疗计划剂量学的影响

目的:研究Monaco放射治疗计划系统中控制点(CP)不同取值对中下段食管癌动态调强放疗(dIMRT)计划的剂量学影响。方法:选取2023年1-6月在商洛市中心医院接受动态调强放疗的13例中下段食管癌患者,在Monaco放疗计划系统中对每例患者分别以CP限值为10、20、30、40、50、60、80、130和200设计9组dIMRT计划,除CP参数外其他优化参数均保持不变,分析靶区和危及器官(OAR)肺部、心脏和脊髓的剂量差异。结果:随着CP限值的增大,靶区最大剂量即2%靶区体积的受照剂量(D_(2%))、平均剂量即50%靶区体积的受照剂量(D_(50%))和剂量均匀性指数(HI)呈先减小然后趋于平稳;靶区最小剂量即98%靶区体积的受照剂量(D_(98%))和靶区适形度指数(CI)呈先增大然后趋于平稳;OAR的各剂量指标差异均无统计学意义(P>0.05);肺部5、10、20、30Gy剂量的体积百分比(V_(5)、V_(10)、V_(20)、V_(30))变化范围分别为1.13%、0.75%、0.29%和0.19%,肺部平均剂量(V_(mean))最大偏差18.7 cGy;心脏V_(10)、V_(20)、V_(30)、V_(40)变化范围分别为2.2%、1.23%、1.39%和1.12%,心脏V_(mean)最大偏差63.85 cGy,脊髓D_(max)最大偏差70.78 cGy.9组计划实际控制点个数(CP_(s))、计划执行时间(DT)、计划复杂度机器跳数与实际控制点个数比值(MU/CP_(s))比较,差异具有统计学意义(F=2.857、25.145、135.467,P<0.05)。结论:在中下段食管癌dIMRT计划中,最大CP值设定为40~50,在满足靶区和OAR剂量的前提下能够减少计划的优化时间、子野数目和患者的治疗时间。

基于4D-CT的三种呼吸门控技术对肺癌立体定向放射治疗计划靶区及正常组织器官体积、受照剂量的影响

目的:探讨基于4D-CT的三种呼吸门控技术对肺癌立体定向放射治疗(SBRT)计划靶区及正常组织器官体积、受照剂量的影响。方法:收集108例肺癌患者的病例资料,比较患者在基于4D-CT的三种呼吸门控技术下接受SBRT治疗的肿瘤靶区(GTV)、计划靶区(PTV)体积和受照剂量,并比较三种呼吸门控技术下正常组织的受照剂量。结果:三种不同技术下,患者GTV与PTV体积比较存在统计学意义差异(均P<0.05),其中自由呼吸(FB)技术下的GTV与PTV体积较主动呼吸控制(ABC)、呼吸门控(RG)技术下高,RG技术下GTV与PTV体积较ABC技术下高(均P<0.05);三种不同技术下PTV受照剂量参数靶区适形度指数(CI)水平差异无统计学意义(均P>0.05);三种不同技术下PTV受照剂量参数靶区剂量均匀性指数(HI)、GI水平差异有统计学意义(均P<0.05);其中FB技术下的GI较ABC技术和RG技术下低,HI水平较ABC技术和RG技术下高,ABC技术下的HI水平较RG技术下低(均P<0.05);三种不同技术下心脏、大血管、气管、食管以及脊髓的受照剂量比较差异无统计学意义(均P>0.05);三种不同技术下双肺V_(5)、V_(20)以及平均照射剂量(MLD)比较差异有统计学意义(均P<0.05);FB技术下的V_(5)、V_(20)以及MLD较ABC、RG技术下高,RG技术下V_(5)、V_(20)以及MLD较ABC技术下高(均P<0.05)。结论:基于4D-CT的ABC与RG技术相较于FB技术更有利于缩小靶区体积,提高治疗剂量,同时更有利于降低病灶危及器官与组织的受照剂量。