盆腔放疗中放射性直肠损伤的预防

放疗在盆腔肿瘤中的治疗作用日益受到重视，治疗的同时会发生不同程度的放射性直肠损伤，通过改进放射技术、照射剂量和优化分割剂量、使用辐射防护剂等可以减少和预防放射性直肠损伤。放疗技术的改进包括三维适形放疗（3D-CRT）和调强放疗（IMRT）等精确放疗技术，提高肿瘤靶区的剂量，并使肿瘤靶区剂量分布更均匀，能够较好地避开周围的重要器官和组织，减轻正常器官和组织的放射损伤。照射剂量和分割剂量的优化，其机制是根据不同组织的细胞增殖快慢不同，分别给予大剂量分割、超分割和加速超分割，提高肿瘤控制率。使用辐射防护剂保护正常组织的机制是通过阻止自由基的间接损伤和修复直接、间接损伤的DNA，促进损伤细胞的恢复，同时不保护肿瘤组织。     

呼吸运动对胸腹部肿瘤精确放射治疗的影响

精确放射治疗是基于高清晰度ＣＴ或ＭＲ图像的精确定位、三维数字重建、三维治疗计划等为一体化的三维治疗技术。它的应用减少了邻近靶区正常组织器官的放射损伤 ,提高了肿瘤区照射剂量。初步结果显示可增加肿瘤的局部控制率[1 ] ,对那些以局部复发为主要致死原因的恶性肿瘤 ,通过增加肿瘤剂量可提高生存率。精确放射治疗要求照射野较小以便于提高肿瘤内剂量 ,而胸腹部肿瘤的生理运动如呼吸运动、心脏搏动的影响或肿瘤相关的影响如肺不张、阻塞性炎症的变化及治疗前、中、后体重的增加或减少均严重影响靶区的精度 ,使计划靶区和实际靶区剂量…     

三维适形放射治疗中的物理学与生物学

放射治疗作为一种局部治疗手段,其追求的目标是尽量提高放射治疗的治疗增益比,即最大限度地将剂量集中到病变（靶区）内,杀灭肿瘤细胞,而使周围正常组织和器官少受或免受不必要的照射。肿瘤致死剂量与正常组织耐受剂量之间差别一般不是很大,而正常组织特别是所谓“并行”组织的耐受剂量的大小取决于受照组织的范围,范围越大,组织耐受射线的能力越小,在某些深部肿瘤的放射治疗过程中,一些重要器官如脑干、脊髓、肾、性腺等位于或接近于病变（靶区）时,要特别注意保护。因此,理想的放射治疗技术应按照肿瘤形状给靶区以一定的致死剂量,而靶区周围的正常组织尽量少受到照射,要使治疗区的剂量分布与靶区的形状相一致,必须从三维方向上进行剂量分布的控制。     

调强放射治疗的体位固定和摆位

调强放疗(IMRT)它能够优化配置射野内各射束的权重，使各剂量区剂量分布的形状在三维方向上与靶区的实际形状一致。计划靶区(PTV)内的剂量分布更均匀。如果需要，在PTV边缘可以同时形成非常陡的剂量梯度。这意味着靶区周围的正常组织受高剂量的辐射的体积将显著减少，从而可以较大幅度的增加肿瘤剂量或减少正常组织的受量提高肿瘤控制率，降低正常组织并发症的发生率。我院自2003年开展调强放射治疗以来，已收治了145例患者，在调强放射治疗的体位固定和摆位过程中的注意事项及体会介绍如下。     

恶性肿瘤的三维适形放射治疗45例

 目的 探讨恶性肿瘤三维适形放射治疗（CRT）的临床应用。方法 采用三维适形放疗治疗恶性肿瘤45例，实现了精确定位、精确计划、精确放疗。结果 肿瘤靶区放疗剂量提高了10 % ~ 20 %。放疗毒副反应仅在Ⅰ，Ⅱ级内，显效率（CR+PR）达90 %以上。该放疗技术与实践证明，放射靶区与肿瘤形状一致或相近，靶区接受的剂量最大、靶区周围正常组织受量最小，提高了肿瘤控制率，减少了正常组织的损伤，改善了患者的生存质量。结论 三维适形放疗技术是一项具有临床价值、科学性和实用性很强的新技术，值得推广应用。     

肺癌患者行立体定向放疗的护理

立体定向放疗是目前治疗小细胞肺癌或局部中晚期非小细胞肺癌的一种较为先进的放射治疗手段，其特点是针对肿瘤区实行非共面多弧度等中心旋转，该技术使高剂量区剂量分布的形状在三维立体方向上与靶区的实际形状一致，而周围正常组织照射剂量垂直下降，肿瘤靶区受到高剂量照射的同时，     

调强放射治疗的体位固定和摆位

调强放疗(IMRT)它能够优化配置射野内各射束的权重,使各剂量区剂量分布的形状在三维方向上与靶区的实际形状一致。计划靶区(PTV)内的剂量分布更均匀。如果需要,在PTV边缘可以同时形成非常陡的剂量梯度。这意味着靶区周围的正常组织受高剂量的辐射的体积将显著减少,从而可以较大幅度的增加肿瘤剂量或减少正常组织的受量提高肿瘤控制率,降低正常组织并发症的发生率。我院自2003年开展调强放射治疗以来,已收治了145例患者,在调强放射治疗的体位固定和摆位过程中的注意事项及体会介绍如下。1临床资料145例患者中男性114例,女性31例;年龄12~8…     

头颈肿瘤调强适形放疗研究进展

调强适形放疗(IMRT)是一种新的提高治疗增益的放射治疗技术.在头颈肿瘤中运用IMRT,使剂量分布更适合于肿瘤靶区,增加肿瘤剂量,减少正常组织器官的照射剂量,提高了肿瘤的局部控制率,改善了患者的生活质量,有可能提高患者的生存率.     

头颈肿瘤调强适形放疗研究进展

调强适形放疗（IMRT）是一种新的提高治疗增益的放射治疗技术.在头颈肿瘤中运用IMRT,使剂量分布更适合于肿瘤靶区,增加肿瘤剂量,减少正常组织器官的照射剂量,提高了肿瘤的局部控制率,改善了患者的生活质量,有可能提高患者的生存率.     

调强技术在鼻咽癌放疗中的应用

调强放疗是一种精确放疗技术,可以形成更适形的靶区剂量分布,安全地增加肿瘤的剂量,同时降低正常组织的受照剂量,从而提高肿瘤的局控率,改善患者的生活质量.本文从放射物理、放射生物及临床应用等方面综述调强技术在鼻咽癌治疗中的优越性,同时提出了一些尚待进一步研究的问题.     

宫颈癌的术后放化疗

 宫颈癌术后有高危因素患者易局部复发。已经证实有高危因素患者术后行辅助放疗能提高局部控制率,但不能提高总生存率。有研究显示同步放化疗较单纯放疗能提高生存率,但血液及消化系统不良反应较重。调强放疗（IMRT）能提高靶区适形度及剂量,同时降低周围正常组织剂量,IMRT有较好的局部控制率及生存率。     

Intensity modulated radiation therapy and proton radiotherapy for non-small cell lung cancer

Local failure of non-small-cell lung cancer (NSCLC) radiotherapy may cause continuous tumor seeding and death. Radiotherapy dose escalation has been shown to improve local control and survival. However, the toxicities associated with dose escalation are significant and limit the potential of dose escalation. Intensity modulated radiotherapy (IMRT) may have the potential to improve the therapeutic ratio for photon treatment of lung cancer by sparing surrounding normal tissues. However, lowdose exposure to normal lung and organ motion is a major concern. We have conducted several studies to address these issues and started clinical studies to evaluate the potential benefit of IMRT in patients with NSCLC. Proton radiotherapy may have greater potential to spare normal tissue and allow for further dose escalation and acceleration. We are conducting preclinical and clinical studies for imaging-guided proton radiotherapy in NSCLC. In this paper, we discuss the preliminary data, IMRT treatment guidelines, and ongoing studies for proton therapy in NSCLC.     

大分割模式下左侧乳腺癌保乳术后调强放疗方式的探索

目的:比较左侧乳腺癌保乳术后大分割放疗时,野中野正向调强（field-in-field intensity modulated radiation therapy,FIF-IMRT）、逆向调强（intensity modulated radiation therapy,IMRT）两种模式对改善靶区剂量分布和保护正常组织的差异。方法:对30例左侧乳腺癌保乳术后患者予以CT定位,分别制定FIF-IMRT及IMRT二种照射计划,总剂量均为42.65 Gy,共照射16次。分别比较两组计划的靶区剂量分布、危及器官,如心脏、肺脏、脊髓等所受剂量以及加速器总跳数（accelerator monitor unit,MU）的差异。结果:FIF-IMRT与IMRT组PTV(planning target volume)的Dmax分别为4 762.35 cGy（4 710.08,4 829.10）cGy、4 714.60 cGy（4 659.55,4 740.85）cGy（P=0.001）,均匀性指数分别为0.10（0.09,0.11）和0.09（0.08,0.10）（P=0.008）;在危及器官受量方面,FIF-IMRT组较IMRT组明显降低心脏V5、V10和左肺V5、V10（P值分别为<0.001、<0.001、0.003、0.014）,右乳Dmax、Dmean和脊髓Dmax、DmeanFIF-IMRT组均显著低于IMRT组（P值分别为0.048、0.044、<0.001、<0.001）。FIF-IMRT组MU低于IMRT组（P=0.001）。结论:两种大分割调强模式均能满足左侧乳腺癌保乳术后的治疗要求。IMRT提高靶区剂量分布均匀性,但FIF-IMRT能更好降低心脏和左肺V5、V10等低剂量照射范围,且对机器损耗更小,可能是更好的选择。     

Radiothérapie conformationnelle avec modulation d’intensité dans les cancers du sein : intérêt,limitations, modalités techniques

Intensity modulated radiotherapy (IMRT) is a technique allowing dose escalation and normal tissue sparing for various cancer types. For breast cancer, the main goals when using IMRT were to improve dose homogeneity within the breast and to enhance coverage of complex target volumes. Nonetheless, better heart and lung protections are achievable with IMRT as compared to standard irradiation for difficult cases. Three prospective randomized controlled trials of IMRT versus standard treatment showed that a better breast homogeneity can translate into better overall cosmetic results. Dosimetric and clinical studies seem to indicate a benefit of IMRT for lymph nodes irradiation, bilateral treatment, left breast and chest wall radiotherapy, or accelerated partial breast irradiation. The multiple technical IMRT solutions available tend to indicate a widespread use for breast irradiation. Nevertheless, indications for breast IMRT should be personalized and selected according to the expected benefit for each individual.     

早期乳腺癌保乳术后调强放疗

现行早期乳腺癌保乳术后的常规切线野放射治疗技术存在靶区内剂量不均匀的缺陷.国内外多位研究者将调强放疗(IMRT)应用于保乳术后患者,以期在提高靶区剂量均匀性、降低危及器官受量及改善美容效果方面体现出一定优势.     

Dosimetry and radiobiologic model comparison of IMRT and 3D conformal radiotherapy in treatment of carcinoma of the prostate

INTRODUCTION: Intensity-modulated radiotherapy (IMRT) has introduced novel dosimetry that often features increased dose heterogeneity to target and normal structures. This raises questions of the biologic effects of IMRT compared to conventional treatment. We compared dosimetry and radiobiologic model predictions of tumor control probability (TCP) and normal tissue complication probability (NTCP) for prostate cancer patients planned for IMRT as opposed to standardized three-dimensional conformal radiotherapy (3DCRT). METHODS AND MATERIALS: Segmented multileaf collimator IMRT treatment plans for 32 prostate cancer patients were compared to 3DCRT plans for the same patients. Twenty-two received local-field irradiation (LFI), and 10 received extended-field irradiation (EFI) that included pelvic lymph nodes. For LFI, IMRT was planned for delivery of 2 Gy minimum dose to the prostate (> or =99% volume coverage) for 35 fractions. The 3DCRT plans, characterized by more homogenous dose to the target, were designed according to a different protocol to deliver 2 Gy to the center of the prostate for 37 fractions. Mean total dose from 35 fractions of IMRT was equal to mean total dose from 37 fractions of 3DCRT. For EFI, both IMRT and 3DCRT were planned for 2 Gy per fraction to a total dose of 50 Gy to prostate and pelvic lymph nodes, followed by 2 Gy per fraction to 20 Gy to the prostate alone. Treatment dose for EFI-IMRT was defined as minimum dose to the target, whereas for EFI-3DCRT, it was defined as dose to the center of the prostate. TCP was calculated for the prostate in the linear-quadratic model for two choices of alpha/beta. NTCP was calculated with the Lyman model for organs at risk, using Kutcher-Burman dose-volume histogram reduction with Emami parameters. RESULTS AND CONCLUSIONS: Dose to the prostate, expressed as mean +/- standard deviation, was 74.7 +/- 1.1 Gy for IMRT vs. 74.6 +/- 0.3 Gy for 3D for the LFI plans, and 74.8 +/- 0.6 Gy for IMRT vs. 71.5 +/- 0.6 Gy for 3D for the EFI plans. For the studied protocols, TCP was greater for IMRT than for 3D across the full range of target sensitivity, for both localized- and extended-field irradiation. For LFI, this was due to the smaller number of fractions (35 vs. 37) used for IMRT, and for EFI, this was due to the greater mean dose for IMRT, compared to 3D. For all organs, mean NTCP tended to be lower for IMRT than for 3D, although NTCP values were very small for both 3D and IMRT. Differences were statistically significant for rectum (LFI and EFI), bladder (EFI), and bowel (EFI). For both LFI and EFI, the calculated NTCPs qualitatively agreed with early published clinical data comparing genitourinary and gastrointestinal complications of IMRT and 3D. Present calculations support the hypothesis that accurately delivered IMRT for prostate cancer can limit dose to normal tissue by reducing treatment margins relative to conventional 3D planning, to allow a reduction in complication rate spanning several sensitive structures while maintaining or increasing tumor control probability.     

Reduction of radiotherapy-induced late complications in early breast cancer: the role of intensity-modulated radiation therapy and partial breast irradiation. Part II--Radiotherapy strategies to reduce radiation-induced late effects

Radiotherapy after conservation surgery has been proven to decrease local relapse and death from breast cancer, and is now firmly established in the management of early breast carcinoma. Currently, the challenge is to optimise the therapeutic ratio by minimising treatment-related morbidity, while maintaining or improving local control and survival. The second part of this review examines the role of two approaches: intensity-modulated radiation therapy (IMRT) and partial breast irradiation, as means of improving the therapeutic ratio. Discussion of IMRT includes both inverse- and forward-planned methods: the breast usually requires minimal modulation to improve dose homogeneity, and therefore lends itself to simpler forward-planned IMRT techniques; whereas inverse-planned IMRT may be useful in selected cases. There are many dosimetry studies reporting the superiority of IMRT over conventional breast radiotherapy, but there is still a paucity of clinical data regarding patient benefit from these techniques. A critical literature review of clinical partial breast radiotherapy studies focuses on the influence of irradiated breast volume, dose and fractionation, and patient selection on normal tissue side-effects and local control. Clinical reports of partial breast irradiation show several encouraging, but some concerning results about local recurrence rates. Therefore, mature results from randomised trials comparing partial breast irradiation with whole-breast radiotherapy are required. Accurate localisation of the tumour bed and application of appropriate clinical target volumes and planning target volumes are discussed in detail, as these concepts are fundamental for partial breast irradiation.     

Conformal radiotherapy and intensity-modulated radiotherapy--clinical data

Conformal radiotherapy (CRT) is based on three hypotheses: (i) a higher rate of local control can improve the survival rate; (ii) dose escalation can increase tumor control; and (iii) CRT allows the delivery of higher doses by decreasing the incidence of late effects. These postulates are now supported by several data. Three-dimensional conformal radiotherapy (3D-CRT) has markedly progressed since its introduction two decades ago. However, there are situations for which 3D-CRT cannot produce a satisfactory treatment plan because of complex target volume shapes or the close proximity of sensitive normal tissues. This is why intensity-modulated radiation therapy (IMRT) was introduced. Its aim is to overcome the limitations of 3D-CRT by adding modulators of beam intensity to beam shaping. IMRT can achieve nearly any dose distribution; however, the role of the planner remains crucial. CRT has been investigated mainly for prostate cancers and head and neck cancers. By and large, the clinical data, although still limited, seem to confirm the advantages of this type of radiotherapy. Dose escalation in prostate cancers improves the local control rate without increasing late effects and for this cancer site IMRT appears to be a significant advance over conventional 3D-CRT. In head and neck cancers the clinical data are still scarce but encouraging. CRT should be investigated in breast cancers with the aim of reducing the incidence of late effects. The available data underline the great potential for major progress in 3D-CRT and IMRT. The techniques are still costly and time consuming, nevertheless they merit investigation since their cost should decrease. Efforts should be concentrated on the specification of robust optimization criteria, taking into account clinical and radiobiological data.     

早期乳腺癌保乳术后4种放疗技术的剂量参数比较

目的：比较早期乳腺癌保乳术后常规切线野（TW）、野中野调强（FIF - IMRT）、切线逆向调强（T -IMRT）和容积调强（VMAT）4种放射治疗技术的靶区和危及器官的剂量参数。方法：15例左侧早期（pT1-2 N0 M0）乳腺癌患者保乳术后接受放疗。CT 模拟定位扫描后勾画靶区和危及器官,在同一患者 CT 影像上分别做 TW、FIF - IMRT、T - IMRT 和 VMAT 4种治疗计划设计。PTV 剂量为50Gy,V47.5≥95%。4种计划的剂量限制相同。在剂量-体积直方图中读取4种计划靶区剂量的分布参数,心脏、双侧肺脏及对侧乳腺受照剂量和体积,对各参数的均数进行比较,并比较4组平均机器跳数差异。结果：4种计划都满足 V47.5≥95%。VMAT 与 T - IMRT、FIF - IMRT 和 TW 计划相比,明显提高了靶区适行指数（CI,P ﹤0.05）。VMAT、T - IMRT和 FIF - IMRT 与 TW 相比,明显改善了靶区均匀性指数（HI,P ﹤0.05）。VMAT 增加了危及器官（心脏和同侧肺脏）V 5、V10和 V20的受照射体积,但是没有增加﹥ V30的照射体积。VMAT 明显增加了右侧乳腺和右侧肺脏照射剂量（P ﹤0.05）,T - IMRT 和 FIF - IMRT 明显降低了右侧乳腺和右侧肺脏照射剂量（P ﹤0.05）。VMAT 与T - IMRT、FIF - IMRT 和 TW 相比,明显增加了机器跳数（P ﹤0.05）。结论：早期乳腺癌保乳术后放射治疗4种计划比较,VMAT 明显提高了靶区的适行性和均匀性,增加了正常组织的受照射剂量和机器跳数,延长了治疗时间。T - IMRT 和 FIF - IMRT 也提高了靶区的适行性和均匀性,降低了正常组织的受照射剂量。     

前列腺癌放疗方法的剂量学研究

目的分析比较常规、三维适形和调强放疗局限期前列腺癌的最佳处方剂量。方法选取10例C期前列腺癌患者,采用CT定位和瓦里安Eclipse治疗计划系统对其进行3种治疗计划设计和计算,且均分为LFI组和EFI46 Gy LFI组(即不需要和需要盆腔预防照射两种情况)。分析DVH曲线研究下列问题:(1)处方剂量80 Gy时,3种技术25%体积直肠的剂量(D_(25))、30%体积膀胱剂量(D_(30))。(2)同时满足直肠和膀胱最大耐受量时的靶区最大处方剂量。结果(1)处方剂量80 Gy时,LFI组直肠D_(25)分别为77.22、69.18、57.85 Gy,膀胱D_(30)为71.04、60.87、53.02 Gy;EFI46 Gy LFI组直肠D_(25)分别为78.73、75.39、66.80 Gy,膀胱D_(30)为71.05、59.96、52.20 Gy。(2)同时满足直肠D_(25)为70 Gy和膀胱D_(30)为65 Gy耐受剂量时,靶区最大处方剂量LFI组分别为68.26、77.47、90、52 Gy,各组差别均有统计学意义(P<0.05),EFI46 Gy LFI组分别为66.27、69.29、77.39 Gy,调强放疗与另外两组之间差异也有统计学意义(P<0.01)。结论局限期前列腺癌同时满足直肠和膀胱最大耐受量时,LFI组中三维适形和调强放疗可达到根治剂量(77.47 Gy和90.52 Gy),EFI46 Gy LFI组中只有调强放疗可以达到根治剂量(77.39 Gy)。