Dose-Volume Histograms for bladder and rectum

: A careful examination of the foundation upon which the concept of the Dose-Volume Histogram (DVH) is built, and the implications of this set of parameters on the clinical application and interpretation of the DVH concept has not been conducted since the introduction of DVHs as a tool for the quantitative evaluation of treatment plans. The purpose of the work presented herein is to illustrate problems with current methods of implementing and interpreting DVHs when applied to hollow anatomic structures such as the bladder and rectum.

: A typical treatment plan for external beam irradiation of a patient with prostate cancer was chosen to provide a data set from which DVH curves for both the bladder and rectum were calculated. The two organs share the property of being shells with contents that are of no clinical importance. DVHs for both organs were computed using a solid model and using a shell model. Typical treatment plans for prostate cancer were used to generate DVH curves for both models. The Normal Tissue Complication Probability (NTCP) for these organs is discussed in this context.

: For an eight-field conformal treatment plan of the prostate, a bladder DVH curve generated using the shell model is higher than the corresponding curve generated using the solid model. The shell model also has a higher NTCP. A six-field conformal treatment plan slo results in a higher DVH curve for the shell model. A treatment plan consisting of bilateral 120-degree arcs, results in a higher DVH curve for the shell model, as well as a higher NTCP.

: The DVH concept currently used in evaluation of treatment plans is problematic because current practices of defining exactly what constitutes “bladder” and “rectum.” Commonly used methods of tracing the bladder and rectum imply use of a solid structure model for DVHs. In reality, these organs are shells and the critical structure associated with NTCP is obviously and indisputably the shell, as opposed to its contents. Treatment planning algorithms for DVH computation should thus be modified to utilize the shell model for these organs.     

4D-CT特殊重建图像对乳腺癌放疗心脏结构剂量评估影响的研究

目的:通过比较4D-CT图像及特殊重建图像在评估心脏结构"剂量-体积"指标中的差异,探讨不同重建图像对心脏剂量评估的影响。方法:选取15例女性左侧乳腺癌患者行心电门控4D-CT图像扫描,以心动周期5%为间隔重建0～95% 20个时相的图像。将4D-CT图像进行特殊重建,得到最大密度投影(MIP)、最小密度投影(MinI...     

食管癌根治切除术后辅助调强放疗胸腔胃照射剂量与急性放射性胸腔胃炎的关系

目的 研究食管癌术后调强放疗剂量学与胸腔胃放射性损伤的关系。方法 通过入组104例食管癌根治术后行调强放疗的患者,对其临床资料及放疗计划中胸腔胃剂量-体积参数与急性放射性胸腔胃炎的发生情况进行分析,ROC曲线分析与急性放射性胃炎发生可能相关的物理学指标,logistic法行单因素及多因素分析。结果 全组104例患者出现≥ 2级急性放射性胸腔胃炎者29例（27.88%）。与≥ 2级急性放射性胸腔胃炎相关的剂量-体积指标包括：胸腔胃D_max、D_mean、L₅~L₄₅、V₅~V₅₀。单因素分析显示,胸腔胃位置、胸腔胃D_max、D_mean、胸腔胃L₅~L₄₅和V₅~V₅₀均与≥ 2级急性放射性胸腔胃炎的发生显著相关（P<0.05）;多因素分析显示,胸腔胃位置、L₅、V₃₅与≥ 2级急性放射性胸腔胃炎的发生均显著相关（P<0.05）。ROC曲线所得L₅及V₃₅的最佳界值分别为14.00 cm和44.00%,胸腔胃L₅ ≥ 14.00 cm和L₅<14.00 cm发生≥ 2级急性放射性胸腔胃炎的概率分别为38.64%和20.00%（χ²=4.473,P<0.05）;V₃₅ ≥ 44.00%和V₃₅<44.00%发生≥ 2级急性放射胸腔胃炎的概率分别为57.58%和14.08%（χ²=7.263,P<0.05）。后纵隔胃患者≥ 2级急性放射性胸腔胃炎的发生率显著高于其他两组（χ²=12.881,P<0.05）。结论 胸腔胃剂量-体积参数对急性放射性胸腔胃炎的发生具有一定的预测价值,建议对术后需行放疗的食管癌患者慎重选择后纵隔胸腔胃手术方案。     

乳腺癌全乳调强放射治疗计划设计方法的研究

背景与目的: 调强放射治疗(IMRT)可显著改善全乳切线野照射中靶区与邻近危及器官的剂量学分布,然而各放疗单位优化设计全乳IMRT计划的方法仍存在较大差异.本研究利用三维治疗计划系统进行全乳IMRT的多种计划设计,以探讨最优化的设计方法.方法: 选择10例接受保乳手术的乳腺癌病例进行全乳放射治疗的常规、正向与逆向计划设计.用子野总数、总跳数等评价计划效率,用剂量体积直方图(DVH)比较靶区剂量和危及器官的受照射剂量差异.结果: 正向IMRT计划包括人工优化法(M0)、多点强制均匀优化法(P0)和自动逆向优化法(A0)等3种,子野总数的中位数分别是5、5.5和5个,逆向IMRT的中位数为20个.总跳数分别为225.8、228.4、226.4和345.8.在正向调强计划中,靶区覆盖率和剂量分布均匀性以A0计划较好(P≤0.01),而心脏、同侧肺、肝脏、对侧肺和对侧乳腺的平均剂量(D<,mean>)在A0和P0计划中明显小于M0计划(P≤0.05).逆向IMRT计划在改善PTV剂量分布均匀性以及减少OARs照射上较正向IMRT计划更好(P≤0.05).结论: 初步建立了全乳IMRT计划设计的方法,以正向计划中A0优化法在效率和剂量学优势上最适合.逆向IMRT计划较正向计划体现了更好的剂量学优势,但需要进一步研究其成熟的设计方法.     

肺癌放疗后放射性肺炎剂量学相关预测因素的研究进展

放射性肺炎（radiation pneumonitis,RP）是肺癌放射治疗的主要并发症之一,本文现将近年来通过剂量体积直方图（dose-volume histograms,DVH）有关参数评估放射性肺损伤的研究现状并作系统回顾。     

不同肺体积确定方法和剂量分割方法对肺剂量体积参数的影响

目的 分析不同肺体积确定方法和不同剂量分割方法对肺剂量体积参数的影响.方法 随机搜集20例肺癌患者,根据病情以瓦里安Eclipse TPS进行三维适形治疗计划设计.以不同CT值范围确定患者肺体积、靶体积(GTV、CTV、PTV)是否从肺体积中减除及不同分割剂量为影响因素,计算肺剂量体积参数受影响的程度.结果 当CT值在-300～ -980至-500～ -980范围变化时,全肺体积减少的中位数为-9.10%,明显高于V30、V20、V10和MLD的中位变化(为-3.18%、-1.13%、0.82%和-0.79%).CT值-400～ -980确定的全肺体积随减除靶体积的增加V30、V20、V10和MLD的变化也加大,其中V30变化最大,V10变化最小.5例PTV体积＜140 cm3(中位PTV体积为78 cm3)患者设置总物理剂量60 Gy,分割剂量由2 Gy增加至10 Gy时,由物理剂量转换为生物等效剂量的V30、V20、V10和MLD逐渐增加(呈正相关),且三者变化相同(增加幅度约为40%).在＞6Gy分割剂量后,MLD变化更大(36%).结论 不同CT值范围勾画并确定肺体积时,对全肺体积影响最大,V30变化有统计学意义(尚不足以左右放疗计划的取舍),V20、V10和MLD的变化无统计学意义.全肺体积减去与之相重叠的靶体积(GTV、CTV、PTV)后,V30的变化最大,而影响最小的是V10.增加分割剂量也明显增加剂量体积参数,而剂量分割方式在3个因素中似乎影响最大(＞10%).     

Impact of neoadjuvant hormonal therapy on dose-volume histograms in patients with localized prostate cancer under radical radiation therapy

Introduction Prostate volume involves a defined toxicity predictor in the radiation therapy of localized prostate cancer. Neoadjuvant hormone therapy (nHT) can reduce prostate volume and, therefore, the planned volume. The objective of this study was to establish if the value of nHT reduces the planned volume and if this reduction correlates with a reduction of the dose received in the target organs. Material and methods 28 patients diagnosed of localized prostate cancer and referred to our departments for radiation therapy with radical intention, in the period ranging between April 2002 and October 2003, were included prospectively. The patients received nHT (triptorelin+flutamide) for 2 months and adjuvant HT until completing 2 years in the high-risk cases. A transrectal ultrasound study was performed in all patients, simulation CT and planning before the start of HT and after 2 months of treatment. The radiation therapy was carried out with 6 or 18 MV LINAC photons, with a dose fractioning scheme of 5×180–200 cGy, a total dosage of 66–72 Gy to prostate, 56 Gy to seminal vesicles and, in the high-risk cases, 46 Gy to pelvic lymph nodes. Results The distribution according to risk group was: low risk 3.6%, intermediate risk 28.6% and high risk 67.9%. By transrectal ultrasound, prostate volume on diagnosis was 50.65 cc pre HT and 38.97 cc post HT (p<0.001), which means a volume reduction of 24%. The comparative analysis of the dose-volume histograms of the first versus the second CT shows a reduction in the planned volume GTV1 (prostate) (81.33 cc vs 63.96 cc, p<0.05), PTV1 (prostate and margin) (197.51 cc vs 168.38 cc, p<0.001) and PTV2 (prostate, vesicles and margin) (340.5 cc vs 307.26 cc, p<0.05), a reduction of the maximum dose in the seminal vesicles (70.2 versus 68.75 Gy, p<0.05), a reduction of the mean dose in the seminal vesicles (65.07 Gy versus 63.07 Gy, p<0.05), PTV2 (67.72 Gy versus 66.9 Gy, p<0.01) and PTV3 (prostate, vesicles, pelvic lymph nodes and margin) (58.86 Gy versus 57.21 Gy, p<0.01), a reduction of the D90 in the seminal vesicles (61.83 Gy versus 60.06 Gy, p<0.05) and PTV2 (61.04 Gy versus 59.45 Gy, p<0.05) and a reduction of V60 of the rectum (32.45% versus 28.22%, p<0.05) and V60 of the bladder (41.78% versus 31.67%, p<0.005). Conclusions Neoadjuvant hormone therapy reduces significantly prostate volume and as a result the planned volume and consequently the rectal and bladder V60 can be significantly reduced.