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。     

规范鼻咽癌外照射的建议

（目的）规范鼻咽癌常规外照射技术,（方法）头颅固定ＣＴ和（或）模拟定位,头颈同一体位,采用低熔点铅不规则挡块技术进行等中心照射。采用面颈联合野＋下颈锁上区前切线野及面颈联合缩野＋颈后三角区野或面颈联合野＋下颈锁上区前切线野及耳前野＋颈前切线野,颅内侵犯辅以颅底野。（结果）能使鼻咽,颅底,口咽,鼻腔,副鼻窦,上颈部处于同一靶区,剂量计算准确,分布合理邻近正常组织受到有效保护,（结论）该设野方法可适用     

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     

鼻咽癌面颈分野投照技术的探讨

目的　探讨鼻咽癌放疗中耳前野与颈切线野的衔接方法。方法　先按头颈同一体位等中心投照方法确定耳前野及颈前切线野 ,以两野的交角为颈前切线野入射角。结果　此法耳前野与颈前切线野衔接较好 ,避免两野连接处出现剂量“冷点”和“热点”。结论　该技术的耳前与颈前切线野衔接较好 ,照射野剂量分布较均匀 ,避免剂量“冷点”和“热点”。     

鼻咽癌面颈分野投照技术的探讨

目的 探讨鼻咽癌放疗中耳前野与颈切线野的衔接方法。方法 先按头颈同一体位等中心投照方法确定耳前野及颈前切线野，以两野的交角为颈前切线野入射角。结果 此法耳前野与颈前切线野衔接较好，避免两野连接处出现剂量“冷点”和“热点”。结论该技术的耳前与颈前切线野衔接较好，照射野剂量分布较均匀，避免剂量“冷点”和“热点”。     

采用等中心加带多叶光栅半野技术治疗鼻咽癌

目的　探讨鼻咽癌病人放疗中面颈野或耳前野与颈切线野的最佳衔接方法。方法　用带多叶光栅(ML C)和独立准直器的直线加速器 ,以一个等中心加 ML C半野技术照射面颈野或耳前野与颈切线野用于放疗鼻咽癌病人。结果　根据测量 ,面颈野或耳前野与颈切线野之间的剂量分布满意 ,无冷点和热点。与初步临床观察相符。结论　用一个等中心加 ML C半野技术放疗鼻咽癌时 ,面颈野或耳前野与颈切线野间的剂量衔接满意     

鼻咽癌放射治疗照射野最佳衔接方法的探讨

目的：探讨鼻咽癌患者放射治疗中面颈野或耳前野与颈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、半束整体铅模照射面颈野或耳前野与颈切线野用于鼻咽癌患者的放射治疗。结果：根据测量,面颈野或耳前野与颈切线之间的剂量分布满意、无冷点和热点,与初步临床观察相符。结论：用一个等中心并半束整体铅模放射治疗鼻咽癌患者时,面颈野或耳前野与颈切线野间的剂量衔接满意。     

面罩固定整体挡铅技术在鼻咽癌放射治疗中的应用

目的:探讨面罩固定整体挡铅技术在鼻咽癌治疗中的应用.方法:利用鼻咽+颈部CT/MR,采用面罩固定同中心照射,模拟定位摄取颈部X线照片,根据鼻咽癌病灶侵犯的范围勾画照射靶区,制作低熔点挡铅,并在治疗机或模拟机上验证挡块.将2005-2006年收治的124例鼻咽癌患者随机分为利用整体档铅治疗组与调强治疗组进行放射治疗,比较1、3年生存率.结果:1)第一步计划常规面颈联合野及下颈部切线野.第二步计划面颈分野+颈部切线野,侵及口咽时,采用小面颈联合野,后界前移到颈椎椎体前缘,避开脊髓,其颈部后三角区采用电子束补偿照射.2)根据鼻咽CT/MR侵及范围相应扩大局部照射野.整体挡铅治疗的患者1、3年生存率与调强放疗组无明显差异(p＞0.05).结论:1)面罩固定同中心整体挡铅技术可根据鼻咽癌侵及范围勾画个体化照射野计划.2)通过精确适形设野,使鼻咽、口咽、颅底、颈部包括在一个照射野内,靶区设计更合理.剂量分布更均匀,并能有效遮挡附近重要器官.     

鼻咽癌常规放疗迟发性反应与改进放疗技术的建议

目的:分析经改用面颈联合野后的迟发性反应状况及原因,并提出改进常规放疗技术的一些建议.方法:收集1997年3月至2006年3月初治鼻咽癌206例资料.患者给予60Co或6MV-X线放疗,第一阶段采用面颈联合野+下颈前切野,第二阶段耳前野+颈前大切线野照射,第三阶段再次缩小耳前野,颈部行深部X线小野照射至根治剂量.受损器官或组织的迟发性反应参照RTOG/EORTC的SOMA分级标准判断.结果:全组206例鼻咽癌患者出现不同程度的唾液腺损伤,且不可逆转.颈部软组织的迟发性反应检出率85.9%.后组颅神经损伤44例,占颅神经损伤的84.6%.结论:面颈联合野二野照射方法,其高剂量区分布于两侧的颞底部、颞颔关节、腮腺、颈部Ⅱ区软组织等处;颈前大切线野,其上界与耳前野的后下角相重叠,使该区照射剂量过高.两者是造成鼻咽癌常规放疗迟发性反应发生率仍较高的基本原因.鼻前面颈联合野三野照射方法可明显改善剂量分布.     

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。     

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。     

Decreasing the dosimetric effects of misalignment when using a mono-isocentric technique for irradiation of head and neck cancer

Purpose: The purpose of this study was to quantify and develop methods to decrease inhomogeneities created with field edge mismatch when using a mono-isocentric beam-split technique.

Methods and Materials: We validated techniques to determine dose across a half-blocked field edge and quantified potential sources of systematic matchline error. Then, two methods were used to evaluate matchline doses. The first used film dosimetry data from a half-beam field and a spreadsheet. Duplication and reversal provided two columns, each representing a beam-split field edge. Summation simulated perfect abutment and shifting created various gaps and overlaps. The second method involved obtaining dose profiles at midfield along the ray perpendicular to abutted, overlapped, and gapped beam-split fields on six linear accelerators. To enlarge the penumbra, we designed several field edge modifiers, then re-evaluated matchline doses. The field edge modifiers applicability to a 3-field head and neck treatment technique was also examined.

Results: Film-determined dose profiles provide similar information across a beam-split field edge as an ionization chamber. With the mono-isocentric beam-split technique, a 4-mm overlap or gap produces inhomogeneities nearly 60% above or below the intended dose. A 2-mm overlap or gap produces inhomogeneities nearly 30% above or below the intended dose. A customized penumbra generator decreased the magnitude of these inhomogeneities to 20% and 10%, respectively.

Conclusion: The two methods of evaluating matchline dose described above gave similar results. When using the mono-isocentric half-field technique, small misalignments produce worrisome regions of inhomogeneity. Our penumbra generator substantially decreases the magnitude of the dose inhomogeneities, although the volume receiving an inhomogeneous dose increases.     

Dosimetric study of field junction in adjacent beams using asymmetric collimators and MLC

Adjacent treatment fields are commonly employed in external beam radiation therapy, such as the mantle and inverted-Y fields for the treatment of Hodgkin＇s disease. In some cases, the adjacent fields are orthogonal, such as the cra- niospinal fields used in the treatment of medulloblastoma. Another example is the irradiation of head and neck tumors when the lateral neck fields are placed adjacent to the anterior supraclavicular field. In each of these situations, there is a possibility of introducing very large dosage errors across the junction. Consequently, this region is at risk for tumor recurrence if it is underdosed or severe complications if it is overdosed. Four millimeter overlap and gap resulted in an unacceptable dose in homogeneity in the junction. As a result of this study, the magnitudes of hot and cold spots might be clinically acceptable for 3 mm gap between photon fields.     

Techniques classique bidimensionnelle et mono-isocentrique tridimensionnelle dans l’irradiation du sein et des aires ganglionnaires : comparaison dosimétrique

PurposeThe activity of our radiation oncology department mainly relies on breast pathology. Since July 2009, all the irradiations delivered simultaneously to the breast (CTV1), the surgical bed (CTV2), the internal mammary chain and the supra- and infraclavicular areas have been carried out using a mono-isocentric technique. This study aimed to compare dosimetric results between conventional 2D and mono-isocentric 3D techniques with or without optimization.Patients and methodsFrom January to August 2009, 20 patients with breast cancer in whom irradiation of the CTV1, CTV2, internal mammary chain and supra- and infraclavicular areas was retained, were included in a specific cohort. In each case, we have compared dosimetric results obtained with the conventional technique and with a mono-isocentric 3D technique, either with manual field in the field segmentation or with automatic segmentation (Oncentra Masterplan^® from Nucletron^®, Optimizer^® solution). Selected criteria were as follows: V95, V107 and mean dose (Dmean) to the target volumes, V20 and V30 to the ipsilateral lung, V35 and mean dose to the heart and maximal dose (Dmax) to the spinal cord.ResultsSupra- and infraclavicular areas irradiation was significantly better using the mono-isocentric 3D technique (V95 %: 89.7 % vs. 77.1 %; P = 0.001) as well as dose homogeneity (Dmean: 46.3 Gy vs. 45.1 Gy; P = 0.008). No statistical difference was observed for the other target volumes. Heart and spinal cord protection were better with the mono-isocentric 3D technique (respectively Dmean: 8.4 Gy vs. 11.1 Gy; P < 0.0001 and Dmax: 29.2 Gy vs. 35.8 Gy; P = 0.0003).ConclusionMono-isocentric irradiation of the breast and lymphatic areas is a modern technique that benefits from imaging and computer progresses while being simple to carry out using standard planning system and linear accelerators. Mono-isocentric 3D irradiation with manual segmentation of the breast and the nodal areas provides a target volume irradiation comparing with conventional technique 2D and a better protection of the heart and of the spinal cord.     

Cardiac and lung complication probabilities after breast cancer irradiation.

PURPOSE: To assess for locoregional irradiation of breast cancer patients, the dependence of cardiac (cardiac mortality) and lung (radiation pneumonitis) complications on treatment technique and individual patient anatomy. MATERIALS AND METHODS: Three-dimensional treatment planning was performed for 30 patients with left-sided breast cancer and various breast sizes. Two locoregional techniques (Techniques A and B) and a tangential field technique, including only the breast in the target volume, were planned and evaluated for each patient. In both locoregional techniques tangential photon fields were used to irradiate the breast. The internal mammary (IM)-medial supraclavicular (MS) lymph nodes were treated with an anterior mixed electron/photon field (Technique A) or with an obliquely incident mixed electron/photon IM field and an anterior electron/photon MS field (Technique B). The optimal IM and MS electron field dimensions and energies were chosen on the basis of the IM-MS lymph node target volume as delineated on CT-slices. The position of the tangential fields was adapted to match the IM-MS fields. Dose-volume histograms (DVHs) and normal tissue complication probabilities (NTCPs) for the heart and lung were compared for the three techniques. In the beam's eye view of the medial tangential fields the maximum distance of the heart contour to the posterior field border was measured; this value was scored as the Maximum Heart Distance. RESULTS: The lymph node target volume receiving more than 85% of the prescribed dose was on average 99% for both locoregional irradiation techniques. The breast PTV receiving more than 95% of the prescribed dose was generally smaller using Technique A (mean: 90%, range: 69-99%) than using Technique B (mean: 98%, range: 82-100%) or for the tangential field technique (mean: 98%, range: 91-100%). NTCP values for excess cardiac mortality due to acute myocardial ischemia varied considerably between patients, with minimum and maximum values of 0.1 and 7.5% (Technique A), 0.1 and 5.8% (Technique B) and 0.0 and 6.1% (tangential tech.). The NTCP values were on average significantly higher (P<0.001) by 1.7% (Technique A) and 1.0% (Technique B) when locoregional breast irradiation was given, compared with irradiation of the left breast only. The NTCP values for the tangential field technique could be estimated using the Maximum Heart Distance. NTCP values for radiation pneumonitis were very low for all techniques; between 0.0 and 1.0%. CONCLUSIONS: Technique B results in a good coverage of the breast and locoregional lymph nodes, while Technique A sometimes results in an underdosage of part of the target volume. Both techniques result in a higher probability of heart complications compared with tangential irradiation of the breast only. Irradiation toxicity for the lung is low in all techniques. The Maximum Heart Distance is a simple and useful parameter to estimate the NTCP values for cardiac mortality for tangential breast irradiation.     

Three-field technique for breast irradiation using tangential field corner blocks

A further modification of the three-field technique for the radiotherapy of the breast has been developed. Two isocentric opposing tangential fields encompass the breast, chest wall, and may include the internal mammary lymph nodes. The third, an anterior field, encompasses the axilla and supraclavicular areas. As with our previously reported techniques, the objectives of the present modification is to make the posterior edges of the tangential fields coplanar and to match the cephalad geometric edges of the tangential fields to the caudad geometric edge of the supraclavicular field. A half-beam block is used to shield the caudad half of the anterior field, thus producing a vertical transverse plane to which the tangential fields are matched. Small corner blocks are used on the cephalad edges of the tangential fields to produce the vertical edge necessary for matching to the anterior field. It is essential that the match between the tangential fields and the anterior field be geometrically correct to ensure both local control of disease and good cosmetic results. Two advantages of the present technique are the ease with which it can be carried out and the precision of the match plane without the use of cumbersome mechanical accessories.     

全中枢神经系统放射治疗最佳布野探讨

目的：探讨全中枢神经系统放射治疗中,脊髓布野及全脊髓野与全脑野间衔接的方法。方法：采用我院与浙江大学联合研制的平移扫描治疗装置,在^60Co治疗机上对全脊髓进行平移扫描照射以及用一个等中心、半束整体铅摸照射全脑。结果：根据测量全脊髓内及脊髓与全脑衔接处以及全脑内剂量分布满意,无冷点或热点,符合QA。讨论：全中枢神经系统放射治疗时,采用平移扫描治疗全脊髓及等中心半束整体铅模照射全脑．全脑、髓内以及衔接处剂量满意。     

Regional radiotherapy to axilla and supraclavicular fossa for adjuvant breast treatment: a comparison of four techniques

PURPOSE: The three techniques commonly used to treat the axilla and supraclavicular nodes in adjuvant radiotherapy all have significant disadvantages, including underdosing the deeper nodes, excessively irradiating normal tissues, or producing undesirable hot spots. We assessed whether an anterior field with posterior boost field to the axilla with customized compensation of the anterior beam (APcomp-PAboost) would minimize these drawbacks. METHODS AND MATERIALS: The axillary and supraclavicular nodal volumes, planning target volume (PTV), irradiated volume, and brachial plexus were contoured for 10 patients. The plans for each technique-single anterior field (AP); anterior to posterior parallel pair (AP-PA); anterior field with posterior boost (AP-PAboost); and APcomp-PAboost-were then generated for each patient using CadPlan and compared. RESULTS: The AP plan gave poor PTV coverage in 60% of cases. The AP-PA provided good PTV coverage and minimal hot spots, but resulted in consistent unnecessary RT to the medial posterior neck. The skin and tissue of the medial posterior neck and chest wall (i.e., the tissue overlying the posterior half of the ribs and posterior to the latissimus dorsi muscle, which forms the posterior wall of the axilla) was incidentally included in the radiation fields of the AP-PA and the exit of the AP beam. No nodal tissue is present in this region, and, therefore, this tissue was unnecessarily irradiated to higher doses with the AP-PA technique. The AP-PAboost provided adequate PTV coverage and a limited dose to the medial posterior neck, but produced hot spots in excess of 120% in 90% of cases. The APcomp-PAboost provided good PTV coverage, a limited dose to the medial posterior neck, and hot spots to <120% in all cases. CONCLUSION: In most cases, the APcomp-PAboost technique offered the best compromise, but the AP-PA technique may be preferred if a less intense hot spot is sought.