鼻咽癌放疗单中心上下半野照射模拟定位方法

在鼻咽癌的放疗中，单中心上下半野照射技术有效地解决了以往面颈联合野(面颈野) 双侧中下颈锁骨上下切线野(颈锁野)照射时两野间的衔接问题。一些学者已验证了采用该照射技术两野间的剂量分布比较合理，并提出规范准确的定位摆位方法，是保证该照射技术精确实施的重要前提。为此我们根据在定位工作中的实践经验，对该照射技术的定位方法进行归纳总结，现报告如下。     

乳腺癌放疗切线野与腋锁野照射的摆位方法

目的 探讨乳腺癌放疗的切线野与腋锁野衔接所涉及的问题，即避免相邻野的剂量重叠或靶区遗漏，减少正常组织的放射损伤。方法 采用^60Co治疗机乳腺治疗半野挡块装置，将治疗床和机架旋转某一角度分别照射切线蜉和腋锁野。结果 此方法从理论上可解决切线野与腋锁野的衔接问题，并可改善衔接区域剂量分布的不均匀性。结论 半野切线照射技术较好地解决了照射野间剂量重叠或遗漏问题。     

鼻咽癌常规放疗中面颈联合野和下颈野衔接的探讨

目的：比较鼻咽癌常规放射治疗中面颈联合野和下颈切线野不同衔接方法及间距的衔接平面的剂量分布。方法：利用CMS计划系统来计算面颈联合野和下颈切线野在机架角0度方向上（即颈前部）共线衔接、间隔5mm衔接、重叠1mm和2mm衔接以及机架角在90度或270度方向上（即颈侧方向上）共线衔接平面的剂量分布。结果：两者在0度方向上共线衔接、间隔5mm、重叠1mm和2mm衔接以及在90度或270度方向上共线衔接时，衔接平面最高剂量分别是参考剂量的103％、54％、114％、124％、73％，而在0度方向上共线衔接、重叠1mm和2mm衔接平面的95％剂量曲线分别位于皮下2．5cm、0．8cm、0．4cm。结论：鼻咽癌常规放射治疗中面颈联合野和下颈切线野全束照射时推荐在0度方向上1mm的重叠衔接。     

鼻咽癌面颈联合野与颈切野衔接的不同方法比较

鼻咽癌是我国的常见的恶性肿瘤,有文献报道[1]采用单一等中心半野照射的技术,解决常规放疗中面颈联合野与颈部切线野的衔接。但我们发现面颈联合野的下界较低(颈部淋巴结呈阳性)时都要用楔形板进行剂量补偿,我们统计了常规放疗时的一部分患者的面颈联合野的面积,发现多数的面颈     

乳腺癌放疗中的非共面野联合与适形挡块技术

目的 探讨乳腺癌患者放射治疗中锁骨上下野与胸壁切线野的最佳衔接方法。方法 用带独立准直器的直线加速器，以一个等中心，用整体铅模照射的锁骨上下野与胸壁用切线野以半野相衔接．即锁骨上下野的下界即为胸壁切线野的上界。结果 根据测量，锁骨上下野与胸壁切线野之间的剂量分布满意、无冷点和热点。结论 用一个等中心并半野和适形铅模放射治疗乳腺癌患者时，锁骨上下野与胸壁切线野间的剂量衔接满意。     

乳腺癌非独立准直器14野及半野等中心照射方法

 乳腺癌的放射治疗由于乳腺的特殊位置,与肺组织紧密相邻,靶区范围复杂,定位照射技术较复杂;一般采用乳腺胸壁切线野、锁骨上- 腋窝联合野,两野邻接处存在着剂量衔接问题,1P4 野及半野照射技术,能有效避免剂量重叠或空白,减少肺组织的剂量,但需要使用独立准直器,目前国内使用的加速器和60 Co治疗机多没有配备独立准直器;这里介绍一种简便实用的非独立准1P4 野 及半野等中心定位及照射技术。     

后程三维适形放射治疗鼻咽癌的近期疗效观察

目的 分析鼻咽癌后程三维适形放射治疗（3DCRT）近期疗效。方法 32例初治无远处转移的鼻咽癌患者，采用分三阶段对原发灶放射治疗。第一段用面颈联合野常规放疗DT 36Gy，第二段用耳前野放疗DT 14Gy，第三段用3DCRT DT 20～25Gy。总照射剂量DT 70～75Gy。颈部用切线野或者加电子线野作常规分割照射，设野上界保持与主野下界衔接，对颈淋巴结阴性照射DT 50Gy，淋巴结阳性照射DT 66～70Gy。结果 局部肿瘤消退率（有效率）100％，完全缓解率93、75％，1年生存率100％。无严重并发症。结论 鼻咽癌后程三维适形放射治疗可以获得比较理想的剂量分布，近期疗效满意。     

乳腺癌四分之一切线野结合虚拟楔形板照射技术

采用乳腺托架固定体位，等中心1／4野结合虚似楔形板切线照射乳腺癌。结果使1／4野照射90％剂量曲线贴近胸壁，比全野照射的90％剂量曲线要少照肺0．9cm，放射性肺炎发生率低；半影宽度小，放射性皮炎发生率低；半野衔接避免了相邻野的剂量重叠或靶区遗漏，减少正常组织的损伤。表明等中心1／4野切线照射技术，能提高乳腺癌放射治疗的效果，减少并发症的发生．采用托架辅助治疗乳腺癌显著提高了治疗体位的精确度和重复率。     

鼻咽癌半束照射的剂量分布

目的 比较鼻咽癌半束和全束照射技术射野衔接处的剂量分布以及脑和肺的受量。方法 应用Varian 600CD直线加速器，在固体水模体中采用胶片黑度法测量鼻咽癌面颈联合野和下颈切线野射野衔接处的剂量分布。应用Helax TMS-3D治疗计划系统，根据实际病例的螺旋CT模拟定位资料，在数字重建图像上设计面颈联合野和下颈切线野，分别计算半束和全束照射技术条件下脑组织和肺的受量，比较两者受照射的剂量体积直方图(DVH)及脑组织受照射的最大剂量、最小剂量、中位剂量、平均剂量、25％受较高照射剂量脑组织的下限剂量(D25％)以及受量超过75％肿瘤剂量的脑体积(V75%)。结果 两种照射技术射野衔接处均无漏照及低剂量区情况，半束照射和全束共线照射分别有约4mm、10mm的剂量重叠区，两野衔接处剂量最高点高出剂量归一点分别为28％和117％。两种照射技术脑及肺受照射的DVH相似，脑受照射的最小剂量、最大剂量、中位剂量、平均剂量、D25％、V75％及破裂孔处剂量均以全束照射略高，但相差幅度均不超过1％。结论 鼻咽癌应用面颈联合野和下颈切线野放射治疗时，与全束照射技术相比，半束照射技术照射野衔接处的剂量重叠区较小，脑和肺的照射体积和剂量没有增加。     

乳腺癌术后胸壁照射技术剂量分布的研究

目的：对乳腺癌术后胸壁放射治疗几种常用照射技术的剂量分布特点进行研究。方法：对乳腺癌手术后患者和做了标记的测量体模，按放疗体位做CT扫描，CT影像经网络送入三维TPS，在TPS上设计4种照射方案，并在人体模上进行模拟照射（参考剂量1Gy)，用热释光剂量仪进行实际测量。结果：实验结果表明除电子弧形旋转照射外，其它3种照射技术的胸壁剂量都较均匀（胸壁平均剂量＞0．90Gy)。电子线弧形旋转照射 和X线双切线影＋内乳区电子线野技术由于在内乳区设野保证了内乳区有充足的剂量（内乳点剂量＞0．90Gy)，但是后者在2个野交界处易形成剂量冷热点。单纯X线切线野和适形野技术在内乳区可产生欠剂量情况，体积剂量直方图显示电子线旋转照射技术肺部受高剂量照体积最小，适形野技术也使肺部受高剂量照射体积明显减小。在体表加盖1．0－1．5cm的组织等效填充物后，4种照射技术的皮肤剂量可提高到0．90Gy以上。结论：乳腺癌胸壁照射技术有不同的剂量分布特点，在临床应用时应视患者具体情况选择使用。     

Junctioning of Lateral and Anterior Fields in Head and Neck Cancer: A Dosimetric Assessment of the Monoisocentric Technique (Including Reproducibility)

Purpose: The matching or junctioning of two lateral fields with an anterior field is commonly performed in the treatment of head and neck cancer. A monoisocentric technique utilising asymmetric collimation is potentially associated with improved dosimetry in the plane of the junction due to decreased reliance on operator skill and the avoidance of couch movement. The aim of this study was not only to assess the average dose delivered in the plane of the junction, but also the reproducibility of this dose for the monoisocentric technique and two other commonly used techniques.Methods and Materials: An anthropomorphic head and neck wax phantom was fashioned to allow the placement of 22 TLD chips in a 2-mm thick transverse plane positioned superior to the potential site of the larynx. Three different treatment techniques were used with the phantom being treated by four different operators a minimum of 20 times for each technique: (1) “straight fields”—using isocentric laterals with an anterior field junctioned in the midline. This technique makes no allowance for divergence; (2) “angled fields”—couch and gantry rotation are used to account for divergence; (3) “monoisocentric”—using asymmetric collimators to create a single isocenter.Results: For an applied dose of 1 Gy the monoisocentric technique produced a mean dose measured of 1.01 Gy compared with 1.23 and 0.92 Gy for techniques 1 and 2. The reproducibility of the mean dose measured was better for the monoisocentric technique by a factor of 2. The superior reproducibility of the monoisocentric technique was not found to be operator dependent.Conclusions: A monoisocentric technique for the treatment of two laterals and an anterior field in head and neck cancer is likely to be associated with more accurate and reproducible dosimetry in the plane of the junction. Our center has subsequently adopted this technique for matching such fields.     

Multicentre dosimetric comparison of photon‐junctioning techniques in head and neck radiotherapy

Because many head and neck radiotherapy treatment techniques rely on a junction between X‐ray fields, it was the aim of the present study to investigate the use of different junctioning techniques and the affect on the dose across the junction. Techniques in use at nine radiotherapy centres in Australia were investigated using thermoluminescence dosimetry (TLD). The techniques could broadly be divided into two groups: (i) use of the light field to match the fields after moving the patient; and (ii) use of asymmetric collimation to create a single isocentre located in the junction. The mean dose at the junction and its reproducibility was studied in five consecutive treatments in each centre using 25 TLD chips placed throughout the junction in an anthropomorphic phantom. There was a tendency for the mono‐isocentric technique to deliver a lower, more accurate mean dose at the junction (Group I: 1.22 Gy (n = 8) vs Group II: 0.96 Gy (n = 5) for 1 Gy planned, some centres contributed to both technique) with greater reproducibility (Group I: 9.6%, Group II: 5.1% of the mean dose). We conclude that a mono‐isocentric treatment technique has the potential to deliver a more accurate and reproducible dose distribution at the field junction of photon beams in head and neck treatment.     

全身皮肤电子束照射剂量学参数的测量和讨论

目的对全身皮肤电子束照射(TSEI)的剂量学参数进行测量并讨论。方法采用双机架角多野照射技术，在源皮距等于380cm下对6、8MeV电子束相关照射野的剂量学参数进行测量。采用平行板电离室和半导体探头测量百分深度量；用半导体探头测量均匀模体内某一深度处各点剂量均匀性，用剂量胶片测量人体体模横截面的剂量分布。结果对于6、8MeV电子束双机架角6个野照射，最大剂量深度都在0～3mm处，6MeV的80％，50％剂量深度分别在7、14mm处，8MeV的80％、50％剂量深度分别在7、17mm处。在机架旋转方向上模体2、11mm深度处野内各测量点的剂量均匀性在-10％～ 3％内。得出了人体模脐部横断面内等剂量分布曲线。结论全身皮肤电子束照射的剂量学参数与常规单野照射的剂量学参数有较大区别，临床治疗前需要准备充分的临床剂量学资料。     

螺旋断层放疗系统调强放疗验证

目的 通过螺旋断层放疗系统一系列调强放疗验证方法的研究,探讨其调强放疗的质量保证验证方法是否可行.方法 采用断层放疗计划系统进行调强放疗计划设计.为实现其剂量验证,笔者采用圆柱形固体水模体、0.056cm3 AISL电离室及EDR2胶片来实现对计划进行绝对剂量及相对剂量验证.将剂最胶片和电离室分别置于模体中,调用患者治疗计划束流数据对模体进行模拟照射;由此得出轴向截面上的等剂量分布和点绝对剂量,与计划模体的等剂量曲线及计算剂量结果进行比对.束流照射前,利用调强放疗兆伏特CT对摆位模体实行图像引导,与计划系统中模体千伏特CT图像进行配准比较,实现验证模体摆位准确性.结果 轴向测得注量分布与断层放疗计划系统计算结果相一致,测量点绝对剂量测量的结果与计划系统的计算误差均在±3%以内.测量模体的摆位误差基本可保持在1mm以内,但由于床从摆位虚拟中心到束流中心之间存在垂直下降2mm的系统误差,需要在模体或患者摆位中予以考虑.结论 3个月临床实践证明断层放疗的调强放疗所采用上述质量保证措施是切实可行的,建立了其质最保证体系.     

Konformations-Bestrahlungstechnik für den Peri- und Retrobulbärraum bei endokriner Orbitopathie

The clinical target volume (CTV) for the irradiation of the endocrine orbitopathy (Graves ophthalmopathy) includes the peri- und retrobulbar space with the extraocular muscles. We present here a conformal irradiation technique aimed at optimal coverage of the CTV. The irradiation technique consists of two rotation fields with a central lens block and two lateral fixed fields with dorsal blocking. In each Gantry position, the lenses are faded out through the central lens block. The isocenter of the two rotation fields is located in the lenses. For quality assurance of this irradiation technique, verification of the dose distribution was performed by film dosimetry using the humanoid Alderson phantom.The use of this irradiation technique yielded a dose distribution with conformal CTV coverage of the peri- and retrobulbar space and of the extraocular muscles. The film dosimetry of the Alderson phantom showed a maximal deviation of 5 % between the measured and the calculated dose distribution. The radiation load to the eye lenses was 25 % of the applied total dose.     

Development of total-skin electron therapy at two energies

Total-Skin Electron Therapy (TSET) modalities have been developed at two energies on a Varian Clinac 1800. The physical criteria for the beams were determined mainly from the requirement of continuing the Stanford treatment technique, which was 12 Total-Skin Electron Therapy portals combined in six pairs. The penetration of the lower energy mode matches that previously obtained at Stanford on the Varian Clinac 10, (about 4 mm for the 80% isodose contour in the 12-field treatment). The penetration of the higher energy mode is about 8 mm at the 80% contour. The Total-Skin Electron Therapy modes necessarily use electrons produced by the two standard electron-beam modes of lowest energy, nominally 6 and 9 MeV. Measurements to verify the beam specifications were carried out with diodes, a variety of ionization chambers, and a specially constructed circular phantom for film dosimetry. Initially, the penetration of the Total-Skin Electron Therapy beams was too large to match our criteria, so two methods of reducing it were explored: (a) the energies of the electron beams produced by the machine were reduced (which also reduced the energies of the corresponding standard electron modes) and (b) a large polymethylmethacrylate degrader (2.4 m X 1.2 m) 1 cm thick was placed just in front of the patient plane. Acceptable Total-Skin Electron Therapy beams could be produced by either method and the latter was finally used. The use of the standard dose monitoring system for the Total-Skin Electron Therapy modes considerably simplifies the daily treatment delivery as well as the implementation. However, the need for reasonable dose rates at the treatment plane (3.5 meters beyond the isocenter) requires dose rates of 24 Gy/min at the isocenter. Nevertheless, it is possible to use the internal dose monitor provided the problems associated with high dose rates (recombination and amplifier saturation) are addressed. Solutions to these problems involved switching the primary and back-up dose monitors, increasing the collecting voltage on the ion chambers, and calibrating the dose monitor so that 1 unit = 1 cGy at the patient rather than at the isocenter.     

Radiotherapy treatment planning for small complex-shaped lesions and its experimental verification

The Gamma Knife is used as a stereotactic tool for the conformal treatment of very small, complex-shape cranial lesions. The combination of planning software and treatment equipment enables a highly-precise conformal dose distribution and positioning. The purpose of the present study was to experimentally verify the precision actually achievable in case of extremely irregular, small target volumes. For this purpose, a complete treatment procedure was performed using a standard head phantom complemented with a specially developed insert that simulates an L-shaped lesion. The spatial precision of the irradiation was recorded by means of high-resolution film dosimetry using GafChromic films. The analysis of the films showed for the film in the center plane an excellent conformity of the 75% isodose line used to circumscribe the lesion. A very good agreement between planning and measurement resulted also for isodose lines residing outside of the target volume.     

立体适形推量放射治疗在鼻咽癌首程放疗中的应用

目的：探索立体适形推量放射治疗在鼻咽癌首程放疗中的临床应用价值。方法：2000年5月～2002年9月，31例初治鼻咽癌患者，常规外照射至40～49天总量59～70Gy／30～35次后行立体适形推量放射治疗，以90％等剂量覆盖靶区，每次3～4Gy，每周3次，共治疗3～5次。其中15例每次3Gy，16例每次4Gy。结果：随访时间11～40月，中位随访时间23月，一、二年局控率分别为100％、90．81％，一、二年生存率分别为100％、94．44％，无严重放疗反应发生。结论：三维适形放射治疗作为推量技术应用于鼻咽癌首程放疗是可行的，并显示较好的局控和生存结果，远期疗效尚待进一步观察。