Results and DVH analysis of late rectal bleeding in patients treated with 3D-CRT or IMRT for localized prostate cancer

In patients undergoing radiotherapy for localized prostate cancer, dose–volume histograms and clinical variables were examined to search for correlations between radiation treatment planning parameters and late rectal bleeding. We analyzed 129 patients with localized prostate cancer who were managed from 2002 to 2010 at our institution. They were treated with 3D conformal radiation therapy (3D-CRT, 70 Gy/35 fractions, 55 patients) or intensity-modulated radiation therapy (IMRT, 76 Gy/38 fractions, 74 patients). All radiation treatment plans were retrospectively reconstructed, dose–volume histograms of the rectum were generated, and the doses delivered to the rectum were calculated. Time to rectal bleeding ranged from 9–53 months, with a median of 18.7 months. Of the 129 patients, 33 patients had Grade 1 bleeding and were treated with steroid suppositories, while 25 patients with Grade 2 bleeding received argon plasma laser coagulation therapy (APC). Three patients with Grade 3 bleeding required both APC and blood transfusion. The 5-year incidence rate of Grade 2 or 3 rectal bleeding was 21.8% for the 3D-CRT group and 21.6% for the IMRT group. Univariate analysis showed significant differences in the average values from V65 to V10 between Grades 0–1 and Grades 2–3. Multivariate analysis demonstrated that patients with V65 ≥ 17% had a significantly increased risk (P = 0.032) of Grade 2 or 3 rectal bleeding. Of the 28 patients of Grade 2 or 3 rectal bleeding, 17 patients (60.7%) were cured by a single session of APC, while the other 11 patients required two sessions. Thus, none of the patients had any further rectal bleeding after the second APC session.     

Analysis of Influence of Errors in Angular Settings of Couch and Collimator on the Dosimetric and Radiobiological Parameters in VMAT Plans

ObjectiveTo evaluate the impact of couch and collimator angular variations on dose volume histogram (DVH), tumour control probability (TCP), and normal tissue complication probability (NTCP) of the volumetric-modulated arc therapy (VMAT) plans.MethodsStereotactic radiosurgery and stereotactic body radiation therapy VMAT plans were generated for three different hypothetical planning target volumes (PTVs) that mimic brain metastases, single brain lesion, and single spine lesion. Thirty routine VMAT plans (10 prostate, 10 head and neck, and 10 brain cases) treated in our clinic were also selected for this study. The plans were generated using an Eclipse Treatment Planning System and delivered using a Clinac iX linear accelerator equipped with a Millennium 120 multileaf collimator. All the plans were generated using two complementary full arcs (with gantry angle from 179° to 181° and collimator rotation of 30° and 330°) except the brain tumour cases, which used single full arc with collimator rotation of 30°. In all the cases, the couch angle was zero. Impact of the angular variations in the collimator and couch was studied by varying the collimator and couch angular settings by 1°, 2°, and 3°, and creating six erroneous plans corresponding to the original plans. The variation due to these errors on different DVH and radiobiological parameters (TCP, equivalent uniform dose (EUD), and NTCP) of the PTVs and organs-at-risk (OARs) were observed. The relative percentage of difference in these parameters (ΔD, ΔTCP, ΔEUD, and ΔNTCP) were analysed, and statistical significance was tested.ResultsThe variation due to collimator misplacement was observed to be larger than the couch misplacement. Furthermore, in both cases, the variation increased as the degree of error increased. Among the DVH parameters, D_98%, D_95%, and V_95Gy were affected more by the errors than D_2%, D_5%, and D_50%, in both hypothetical and clinical PTVs. In the clinical PTVs, the TCP showed the most variation among all parameters. The ΔNTCP of the bladder and brain OARs were zero, whereas for head and neck OARs, it was high.ConclusionsThe couch and collimator angular variation has different effects on different planning situations and different parameters. The outcome produced by the errors is specific to the treatment sites.     

胸中段食管癌调强放疗计划设计剂量对比研究

目的探索中段食管癌采取不同入射角度，不同照射野数对计划靶区和临近相关胸部危及器官剂量分布差异，探索胸中段食管癌常规调强照射野设计，试图预测和减少放射性肺炎。方法选择2017年5月至2020年6月皖南医学院第二附属医院由于医学原因不能手术或者拒绝手术治疗的食管癌病人30例，所有病人均设计3种放疗计划，包括:均分5野，优化5野和均分7野3种调强放射治疗(IMRT)计划。上述放疗计划采用同样的优化参数，包括同样计划靶区和临近相关胸部危及器官(心脏，双肺，脊髓)的剂量约束，通过剂量体积直方图(DVH)加以对比。结果30例中段食管鳞状细胞癌病人的上述调强放疗计划均能达到所预设的靶区剂量学和临近危及器官的剂量约束，而且，与5野调强放疗计划相比，等分7野调强计划的靶区适形指数和均匀指数均显示出一定的优势，三者的CI值分别为(0.86±0.05)、(0.82±0.05)和(0.88±0.03)(P<0.001)；HI值分别为(0.109 5±0.04)、(0.100 9±0.04)和(0.923 6±0.02)(P<0.001)；对于危及器官肺而言，等分7野的全肺V20值(22.9±4.3)%和(8.1±1.2)%较低，有降低的趋势；而优化5野调强计划的全肺V5值(47.1±9.8)%和V10值(34.5±5.1)%要显著低于等分7野调强放疗计划，分别为(56.1±10.2)%和(40.9±6.2)%(P<0.05)；优化5野调强计划靶区脊髓最大剂量和心脏V30照射剂量明显高于等分7野调强计划靶区，差异有统计学意义(P<0.05)；其他组间脊髓最大剂量和心脏V30照射剂量均差异无统计学意义(P>0.05)，所有指标均在正常范围内。结论增加照射野数(7野)调强计划可以提高靶区适形度和提高均匀性，降低V20和V30值的趋势；而缩小入射野与体中线入射角度(优化5野)可以减小双肺的低剂量照射体积(V5，V10)；而减少照射野与中线角度心脏和脊髓受量稍增加，均在临床可接受的范围内。     

Dosimetric Comparison Between 2-Dimensional Radiation Therapy and Intensity Modulated Radiation Therapy in Treatment of Advanced T-Stage Nasopharyngeal Carcinoma: To Treat Less or More in the Planning Organ-At-Risk Volume of the Brainstem and Spinal Cord

The aim of this study is to evaluate the deficiencies in target coverage and organ protection of 2-dimensional radiation therapy (2DRT) in the treatment of advanced T-stage (T3-4) nasopharyngeal carcinoma (NPC), and assess the extent of improvement that could be achieved with intensity modulated radiation therapy (IMRT), with special reference to of the dose to the planning organ-at-risk volume (PRV) of the brainstem and spinal cord. A dosimetric study was performed on 10 patients with advanced T-stage (T3-4 and N0-2) NPC. Computer tomography (CT) images of 2.5-mm slice thickness of the head and neck were acquired with the patient immobilized in semi-extended-head position. A 2D plan based on Ho’s technique, and an IMRT plan based on a 7-coplanar portals arrangement, were established for each patient. 2DRT was planned with the field borders and shielding drawn on the simulator radiograph with reference to bony landmarks, digitized, and entered into a planning computer for reconstruction of the 3D dose distribution. The 2DRT and IMRT treatment plans were evaluated and compared with respect to the dose-volume histograms (DVHs) of the targets and the organs-at-risk (OARs), tumor control probability (TCP), and normal tissue complication probabilities (NTCPs). With IMRT, the dose coverage of the target was superior to that of 2DRT. The mean minimum dose of the GTV and PTV were increased from 33.7 Gy (2DRT) to 62.6 Gy (IMRT), and 11.9 Gy (2DRT) to 47.8 Gy (IMRT), respectively. The D₉₅ of the GTV and PTV were also increased from 57.1 Gy (2DRT) to 67 Gy (IMRT), and 45 Gy (2DRT) to 63.6 Gy (IMRT), respectively. The TCP was substantially increased to 78.5% in IMRT. Better protection of the critical normal organs was also achieved with IMRT. The mean maximum dose delivered to the brainstem and spinal cord were reduced significantly from 61.8 Gy (2DRT) to 52.8 Gy (IMRT) and 56 Gy (2DRT) to 43.6 Gy (IMRT), respectively, which were within the conventional dose limits of 54 Gy for brainstem and of 45 Gy for spinal cord. The mean maximum doses deposited on the PRV of the brainstem and spinal cord were 60.7 Gy and 51.6 Gy respectively, which were above the conventional dose limits. For the chiasm, the mean dose maximum and the dose to 5% of its volume were reduced from 64.3 Gy (2DRT) to 53.7 Gy (IMRT) and from 62.8 Gy (2DRT) to 48.7 Gy (IMRT), respectively, and the corresponding NTCP was reduced from 18.4% to 2.1%. For the temporal lobes, the mean dose to 10% of its volume (about 4.6 cc) was reduced from 63.8 Gy (2DRT) to 55.4 Gy (IMRT) and the NTCP was decreased from 11.7% to 3.4%. The therapeutic ratio for T3-4 NPC tumors can be significantly improved with IMRT treatment technique due to improvement both in target coverage and the sparing of the critical normal organ. Although the maximum doses delivered to the brainstem and spinal cord in IMRT can be kept at or below their conventional dose limits, the maximum doses deposited on the PRV often exceed these limits due to the close proximity between the target and OARs. In other words, ideal dosimetric considerations cannot be fulfilled in IMRT planning for T3-4 NPC tumors. A compromise of the maximal dose limit to the PRV of the brainstem and spinal cord would need be accepted if dose coverage to the targets is not to be unacceptably compromised. Dosimetric comparison with 2DRT plans show that these dose limits to PRV were also frequently exceeded in 2DRT plans for locally advanced NPC. A dedicated retrospective study on the incidence of clinical injury to neurological organs in a large series of patients with T3-4 NPC treated by 2DRT may provide useful reference data in exploring how far the PRV dose constraints may be relaxed, to maximize the target coverage without compromising the normal organ function.     

鼻腔淋巴瘤不同放射治疗技术的剂量学比较探讨

目的:比较研究鼻腔淋巴瘤调强放疗(IMRT)和半野照射对靶区及其周围危及器官受照剂量的差异。方法:随机选择8例鼻腔淋巴瘤患者,进行CT扫描、靶区和危及器官的勾画,用三维治疗计划系统进行调强和半野照射的计划设计,并对结果进行比较分析。结果:调强计划对靶区适形度优于半野照射,差异具有统计学意义(P<0.005)。IMRT比半野照射能更好地保护某些正常组织,减少眼球、脑干、垂体和颞颌关节等正常组织的照射剂量(P<0.05),而对晶体、视交叉和视神经等正常组织2种计划无显著差异(P>0.05)。结论:在鼻腔淋巴瘤放疗中,IMRT较半野照射技术在剂量学方面有一定的优越性。     

逆向调强放射治疗计划软件临床病例的比较

目的：评价北京海思威科技有限公司和北京大学肿瘤物理诊疗技术研究中心联合研制的逆向放疗计划是否达到商用软件的功能。方法：用我们研发的HW-3D TPS和用临床真实病例进行逆向优化计算,获得处方剂量场分布,看是否满足医生对治疗靶区和周围危及器官的剂量分布要求,并和已经商业化的软件Varian Eclipse A10用相同病理获得的结果进行比较,进行综合评价。结果：研究和比较在人体内有典型意义的11个病理,获得结果：①所有计划均符合临床医生的处方要求,PTV 95%的体积都能达到95%的处方剂量;②检测PTV的STD是否小于5%,PTV的95%的体积都能达到95%的处方剂量,符合国家标准;③综合比较两个TPS系统PTV的STD值,Varian Eclipse A10的PTV STD平均值为2.8%;HW-3D TPS系统PTV的STD平均值为2.2%。在允许误差范围内达到可比性。结论：HW-3D TPS对临床病例有较好的逆向优化处理能力,其结果与商业化的TPS软件的处理结果具有可比性。     

Oncentra近距离计划系统和MIM系统间DVH参数差异的分析

目的对近距离治疗计划的剂量参数在Oncentra治疗计划系统与MIM系统间产生的差异进行分析和研究。方法选取本院的43例妇科肿瘤患者近距离治疗计划,按照临床要求所有病例的靶区D₉₀达到处方剂量。评估参数包括:靶区体积和D₉₀,处方剂量总体积,靶区内的处方剂量体积以及危及器官包括:直肠,膀胱,小肠的D_0.01cc,D_1cc,D_2cc。结果计划系统中的靶区体积和处方剂量值均明显小于MIM系统中相应的值(P<0.05),两系统显示出的处方体积相差不大。MIM系统中的靶区D₉₀(676.74±54.82)cGy小于处方剂量,危及器官的受量则正好相反,即计划系统比MIM系统中相应的参数要小,其中直肠和膀胱的D_0.01cc,D_1cc,D_2c,小肠的D_0.01cc,D_2cc的在两系统显示的值的差异均有统计学意义(P<0.05)。结论不同系统间传输相同的剂量和轮廓文件,DVH参数存在一定的差异,其主要原因是在不同系统对已勾画的各种器官轮廓计算体积存在算法上的不同。基于此,建议近距离计划在CT扫描时,尽量小的层厚可以消除或减少这种差异。     

基于ArcCHECK-3DVH系统的鼻咽癌容积旋转调强放疗三维剂量验证研究

目的:探讨ArcCHECK-3DVH系统在鼻咽癌容积旋转调强放疗（VMAT）三维剂量验证中的应用。方法:选取基于Monaco治疗计划系统（TPS）制定的20例鼻咽癌患者VMAT计划，利用ArcCHECK-3DVH系统进行患者计划的验证。比较TPS计算剂量与ArcCHECK-3DVH系统基于测量重建剂量的三维γ通过率（3%/3 mm, TH=10%），以及靶区剂量参数[D98%]、[D2%]和[Dmean]与危及器官剂量参数[Dmax]和[Dmean]等。结果:患者计划验证的三维γ通过率为98.20%（97.75%, 99.20%），TPS计算靶区内剂量和ArcCHECK-3DVH重建的剂量在[D98%]、[D2%]和[Dmean]参数上的差异值大部分小于3%，极个别情况的最大差异值在5%以内，绝大部分患者除PGTVnd外的各个靶区γ通过率为90%以上；各个危及器官对应的[Dmax]和[Dmean]剂量参数差异值均小于6%，γ通过率均在93%以上。结论:ArcCHECK-3DVH系统重建的剂量结果与TPS计算结果符合较好，为鼻咽癌VMAT计划剂量验证提供了丰富的剂量参数信息，有助于患者治疗计划的质量验证。