半束照射野的深度剂量研究及验证

在现代放射治疗中 ,利用直线加速器独立准直器功能开展的非对称野放射治疗 ,使放射治疗疗法更加灵活、全面、准确 ,应用也越来越广泛 ,但是非对称野的深度剂量比规则野复杂 ,传统剂量仪无法进行直接测量 ,只能利用现有数据作近似计算 ,无法得到实际验证 ,由于非对称野独立挡块的位置千变万化 ,临床上最常用的非对称野照射技术主要就是指半束非对称野照射方法。本文作者用先进的三维水箱扫描系统对加速器进行半束照射野剂量的全面测量并验证目前在半束照射野剂量计算中常用的由Ｆ .Ｍ .Ｋｈａｎ给出的计算公式 ,为临床提供有力的治疗质量保证…     

非对称野校正系数的测量

独立准直器已成为直线加速器的标准配置，准直器的四个叶片分别由四个电机驱动，可形成射野中心偏离线束中心轴的射野，此类射野称非对称或偏轴射野，非对称野在用干共面或非共面相邻野的衔接时，可避免在相邻区出现剂量不均匀的现象，在放疗过程中需要缩野，扩野或复发再程治疗时，可使用非对称野，而保持等中心位置不变。随着临床应用越来越多，对非对称野校正系数的测量就显得很重要。     

电离室灵敏体积对调强放射治疗剂量学验证准确性的影响

目的研究电离室灵敏体积对调强放射治疗绝对剂量验证的影响。方法将调强治疗计划移植到重建的数字化体模上计算吸收剂量，对单个照射野和整个计划，分别在等中心点、最大剂量点以及剂量梯度大和剂量分布均匀的区域选取一些有代表意义的剂量点，用0．6、0．125和0．015cc电离室在固体水体模中分别测量各点的吸收剂量，并与TPS计算值进行比较。结果等中心和剂量分布均匀区域，各电离室测量值与计算值的相对误差均在5％范围内；最大剂量点和剂量梯度较大区域，0．6cc电离室误差达到8％和12％，小体积电离室误差较小。结论0．6和0．125cc电离室可用于剂量梯度较小处的绝对剂量验证，在最大剂量点和剂量梯度大的区域，误差较大，0．015cc电离室较适用于调强放射治疗剂量验证。     

直肠癌术前放疗中三维适形放疗与调强适形放疗的剂量学比较分析

目的 比较三维适形放疗(3D-CRT)与5野、7野调强适形放疗(IMRT)的剂量分布,以探讨IMRT对直肠癌术前放疗的价值。方法 对10例术前新辅助放化疗直肠癌患者,分别设计3D- CRT、5野IMRT、7野IMRT计划,应用剂量体积直方图(DVH),比较3种治疗计划的靶区适形度指数(CI)、不均匀性指数(HI)和正常器官受量。结果 适形度指数(CI)7野IMRT计划＞5野IMRT＞3D- CRT,不均匀性指数(HI)5野IMRT计划＞7野IMRT＞3D- CRT。5野、7野IMRT计划比3D- CRT均可以减少高剂量照射小肠、膀胱、股骨头体积,7野IMRT计划比5野可以减少高剂量照射的骨髓和膀胱的体积。结论 直肠癌术前放疗中IMRT计划在靶区剂量适形度方面均优于3D- CRT计划,对正常组织的保护也存在明显的优势。7野IMRT计划较5野IMRT计划技术有更好的剂量适形度与剂量均匀性。     

三种调强放疗技术对鼻咽癌患者下颈部亚临床靶区剂量分布的影响

目的 比较3种不同调强放疗技术对鼻咽癌患者下颈部和锁骨上区亚临床靶区剂量分布均匀性和正常组织受量。方法 3种照射方法分别为颈部切线野技术,机架角度分别为180°、150°、120°、90°、270°、240°、210°的7野调强技术,机架角度分别为180°、150°、120°、90°、0°、270°、240°、210°的8野调强技术。利用剂量分布和剂量体积直方图比较3种不同照射技术的剂量均匀性以及正常组织受量,高剂量区域用受照剂量>60 Gy体积占全体积(V₆₀)百分比比较,执行效率用子野数目和总机器跳数比较。结果 3种调强治疗技术的处方剂量均能包括计划靶区(PTV₂),但剂量分布存在差别,V₆₀分别为65%、10%和3%。3种技术中脊髓最大受量分别为42.0、48.9和45.1 Gy,气管平均剂量分别32.92、52.17和36.56 Gy。结论 颈部切线野技术方法简单,但下颈部和锁骨上区剂量分布非常不均匀。7野调强技术靶区剂量分布有所改善,但在气管和喉所在区域以及靶区外产生剂量重叠区,脊髓受量也较高。8野调强技术靶区和正常组织剂量分布都明显改善。     

直线加速器准直器散射因子探讨

随着放射治疗适形、调强技术的开展 ,非规则适形照射野、组织补偿、剂量调强等技术在临床上大量应用。为使加速器满足治疗的需要 ,增加了多叶准直器 (ＭＬＣ)、调强补偿(Ｃｏｍｐｅｎｓａｔｏｒ)等附件。使加速器准直器散射因子 (Ｓｃ)的因素更为复杂。为了给临床剂量提供依据 ,我们对ＶＡＲＩＡＮ 2 30 0Ｃ Ｄ直线加速器不同情况下的Ｓｃ进行测量、比较 ,从中发现Ｓｃ的一些变化规律。一、材料和方法ＶＡＲＩＡＮ 2 30 0Ｃ Ｄ直线加速器准直、剂量补偿系统主要由初级准直器、次级准直器、上下独立准直器、多叶准直器、上下楔形板、上下挡铅…     

一种侧卧位X射线分次全身照射技术及剂量监测结果分析

目的 报道一种侧卧位前后对穿X射线分次全身照射技术,并对照射中的实时剂量监测结果进行分析。方法 采用Varian Trilogy医用电子直线加速器10 MV X射线,行水平野对穿全身照射,源到模体表面距离390 cm,测量X射线全身照射条件下的射野百分深度剂量、离轴剂量分布及绝对剂量输出。对10例患者采用侧卧位前后对穿野分次全身照射。照射处方剂量1200 cGy/6次,共3 d,体中线剂量率约5.0 cGy/min。治疗时利用多通道半导体剂量计实时监测患者剂量准确性及剂量分布均匀性,采用固体水进行剂量非均匀性补偿。结果 治疗条件下模体测量射野离轴剂量分布均匀性<±5.0%,最大剂量点处绝对剂量输出为0.0721 cGy/MU。10例患者均能够顺利完成侧卧位治疗,各个部位监测总剂量偏离处方剂量-4.9%~6.7%,平均监测剂量均匀性<5.0%。结论 侧卧位X射线全身分次照射技术患者耐受性好,照射过程中实时监测剂量,采用固体水进行剂量非均匀性补偿,能够保证患者接受准确均匀的剂量分布,方法简便易行。     

058 在静脉尿路造影中用剂量面积之积和入射体表剂量测量估算有效剂量的差异

YakoumakisE等对２５例静脉尿路造影病人用VacutecDAP测量仪测量DAP（剂量面积之积），用皮肤监测仪测量ESD（入射体表剂量），比较了用DAP计算的有效剂量EDAP和用ESD计算的有效剂量EESD之间的差异。检测结果：平均EDAP（０．３mSv）比EESD（１．９mSv）高３８％，而且此差异归因于X射线野大于胶片盒尺寸所致，提示每次X射线投照时应使照射野的边缘落在胶片的四边上；多数病例测得的ESD比计算的ESD稍小，这可能是由于皮肤监测仪校正过程的系统误差或高估了反散射系数所致；用DAP估算E比用ESD估算E更适用，因为DAP对照…     

组织不均匀条件对调强计划系统计算模型精度的影响

目的 探讨在组织不均匀条件下,治疗计划系统(MONACO)中的有限笔形束算法(FSPB)与快速X射线体积元蒙特卡罗算法(XVMC)的调强放射治疗计划计算精度差别,以及对临床治疗的影响和各自的应用范围。方法 在非均匀仿真人体模型中,对两种算法模型计算的规则照射野及调强照射野的剂量精度,利用经过刻度的放射性铬胶片(EBT2胶片),进行剂量测量以及二维平面剂量的分析比对。结果 在非均匀仿真人体模型中,不同能量的X射线规则照射野,XVMC算法在不同介质中的剂量计算与胶片测量的结果偏差均在±2.00%范围内,而FSPB计算的结果与测量结果的偏差除了15 MV射野为10 cm×2 cm情况下肺中的剂量偏差高达6.51%以外,其他条件下的结果偏差都在±3%范围内。调强放疗计划(IMRT)的胶片验证测量结果中,3%/3 mm γ通过率XVMC算法组>90%;FSPB算法组为80%~90%,且4%/4 mm γ通过率>90%。结论 当临床治疗病例的组织密度不均匀性较大、子野数较多时,XVMC算法的剂量计算精度优于FSPB算法,采用XVMC治疗设计胸腹部IMRT治疗计划可以将算法所引起的误差控制在±3%以内,而且可以避免由于算法原因所致的计划靶区剂量缺失。     

电子束楔形野的放射治疗

用深度剂量陡落的电子束治疗脑部肿瘤比传统光子束更具优势,用多野电子束则优势更明显。楔形野方能使剂量分布均匀,与光子不同的是,电子束在其射束上加材料均导致其能量的严重衰减,并增加其散射。作者对调强电子束楔形野多野照射与传统的光子束多野照射的剂量分布做对照研究。 作者在MM50型调强加速器上对笔束扫描式10～25MeV电子束进行辐射脉冲分配,增加射野内的局部剂量,形成所需的楔形剂量分布,用胶片法在     

A method for total skin electron treatment for infants

Diseases such as mycosis fungoides require the treatment of a patient's total skin surface with superficial radiation. In a unique clinical situation, a 14-month-old child presented with a need for total skin treatment. A typical total skin technique requires overlapping electron beams, using 6 body positions, each with the gantry rotated for 2 angulations, or ‘6 positions-12 fields’. Adaptation of this technique for infants is complicated by the small diameter of some body parts, and by the necessity to treat while the patient is anesthetized. Even degraded, low energy electrons can easily penetrate fingers and toes. Therefore, dose from 6 positions becomes additive, and the total dose to small circumferences can be 3 to 4 times more than skin dose on the torso, raising concerns about uneven bone growth in the developing child. Special phantoms were designed for extensive dosimetry needed to determine both dose rate and dose summation from the overlapping beams. Computerized electron pencil beam calculations were compared to TLD measurements. Unique compensating techniques were used to deliver uniform dose. A modification of the 6 position-12 field technique will be described; and accessories used to reduce high dose regions will be illustrated.     

复方地蒽酚软膏的皮肤安全性评价

目的 考察复方地蒽酚软膏(受试药)对动物皮肤的刺激性和过敏性反应.方法 取豚鼠多次皮肤给药,进行急性刺激性实验;受试药与阳性致敏物2,4-二硝基氯苯进行皮肤过敏性实验.结果 豚鼠完整皮肤和破损皮肤给药后,受试药组皮肤呈红色,且随剂量增加红色加深,表明有刺激性.过敏性实验,受试药组未出现红斑和水肿,表明无致敏性.结论 该...     

Total skin high-dose-rate electron therapy dosimetry using TG-51

An approach to dosimetry for total skin electron therapy (TSET) is discussed using the currently accepted TG-51 high-energy calibration protocol. The methodology incorporates water phantom data for absolute calibration and plastic phantom data for efficient reference dosimetry. The scheme is simplified to include the high-dose-rate mode conversion and provides support for its use, as it becomes more available on newer linear accelerators. Using a 6-field, modified Stanford technique, one may follow the process for accurate determination of absorbed dose.     

Total skin high-dose-rate electron therapy dosimetry using TG-51

An approach to dosimetry for total skin electron therapy (TSET) is discussed using the currently accepted TG-51 high-energy calibration protocol. The methodology incorporates water phantom data for absolute calibration and plastic phantom data for efficient reference dosimetry. The scheme is simplified to include the high-dose-rate mode conversion and provides support for its use, as it becomes more available on newer linear accelerators. Using a 6-field, modified Stanford technique, one may follow the process for accurate determination of absorbed dose.     

Biodosimetry using radiation-induced micronuclei in skin fibroblasts

Purpose:?We assessed micronuclei in dermal fibroblasts as a local biodosimeter for estimating accidental in vivo radiation exposure.

Materials and methods:?Male and female C3H/HeJ and C57Bl6 mice of four age groups (～11, 36, 60 and 99 weeks) received a single whole body dose of gamma radiation (0–10 Gy) and radiation-induced micronuclei per 1,000 binucleated cells were assessed in skin fibroblasts in their first division after isolation from biopsies taken on days 1 and 7 post irradiation. The method of generalized estimating equations was used for statistical analyses.

Results:?Total micronuclei were increased on day 1 in a dose-dependent manner in the range of 1–10 Gy, with no significant attenuation of response between day 1 and day 7 and no significant effect of gender. Between-strain differences were observed with C3H/HeJ mice showing lower background micronuclei and a slightly steeper dose response. Age affected only the background micronuclei (moderate increase with age). The model demonstrated that the assay yields ‘unbiased’ prediction of the dose between 0 and 7 Gy. Within this dose range, the predicted dose was found to be accurate within ±1.5–2 Gy. When the specificity is set to 95%, the assay can distinguish between unexposed and 2 Gy exposed mice with a sensitivity of around 60%. The sensitivity approached 100% when discriminating between unexposed mice and mice receiving doses equal to or greater than 4 Gy. The percentage of binucleated cells with micronuclei was shown to be useful as a simpler and slightly faster substitute for the total micronuclei count.

Conclusion:?Micronuclei in dermal fibroblasts isolated up to 1 week after irradiation can be a useful biodosimeter for local dose after accidental radiation exposure.     

介入诊疗程序中患者皮肤最大受照剂量的检测与评价

目的测定冠脉造影、肝动脉造影、射频消融、脑动脉造影等介入程序中对患者主射束皮肤剂量分布和最大皮肤受照剂量，了解患者皮肤能否发生确定性效应。方法在冠脉造影、肝动脉造影和射频消融3种手术曝光前每个患者背部放9个测量点，每个点2片LiF（Mg，Cu，P）剂量片；脑动脉造影曝光前患者正、侧位各放1个测量点。手术后进行TLD测量。结果肝动脉造影手术时，患者皮肤最大吸收剂量为1683．9mGy，平均吸收剂量607．3mGy；脑动脉造影正位时最大值可达959．3mGy，平均值418．8mGy；侧位最高达704mGy。平均191．52mGy；射频消融最高值为853．8mGy。平均219．7mGy；冠脉造影最大值为456．1mGy，平均227．6mGy。结论本实验结果是对皮肤最大剂量的一种估计值，尚不能精确提供患者皮肤受照的最大值。因为剂量片布放不够密集，可能没有包括很小的高剂量部位。     

Dosimetric considerations of water-based bolus for irradiation of extremities

The dosimetry of high-energy photon beams in the treatment of superficial lesions occurring in extremities was examined. Large parallel-opposed fields with different photon beam energies were used. The extremity was immersed in water contained in a commercially available plastic wastebasket. The water bolus serves to even out the surface irregularities of the extremities and to remove the skin sparing effect. A polystyrene block was placed at the floor of the wastebasket to ensure that the extremity was encompassed in the radiation fields. The photon beam energies considered were 4 MV, 6 MV, 10 MV, and 24 MV. The results show that the dose distributions are more homogeneous with higher photon beam energies. The isodose lines are more constricted at mid-plane for low energy photon beams. Higher energy photon beams, 10 MV and up would be preferable for the treatment of superficial lesions of the extremities immersed in water bolus contained in a typical wastebasket size.     

Virtueller Bolus zur inversen Bestrahlungsplanung bei intensitätsmodulierter Radiotherapie des Mammakarzinoms im Rahmen der adjuvanten Therapie

BACKGROUND: Intensity modulated radiotherapy (IMRT) provides better sparing of normal tissue. We investigated the feasibility of inverse treatment planning for IMRT in adjuvant radiotherapy for breast cancer. MATERIAL AND METHODS: In addition to radiotherapy planning in conventional technique with tangential wedged 6-MV-photon beams we performed inversely planned IMRT (KonRad). In the CT scans for treatment planning we defined a 10-mm bolus of -60 HE density. The influence of this bolus on planning optimization was determined by optimization without and dose calculation with and without bolus. Dose calculation after dose optimization with bolus was performed using different bolus thickness to determine the influence of the bolus on dose calculation. The results were compared with dose distribution in conventional technique. RESULTS: Inverse optimization with a dose algorithm which considers tissue inhomogeneity results in unintended dose increase at the patient surface. With a virtual 10-mm bolus used for inverse optimization the dose increase was reduced. Thus, skin sparing was identical to conventional planning. The relative dose distribution was negligibly affected by the use of a 10-mm bolus. Difference in absolute dose was 3.4% compared to calculation without bolus. Therefore, the bolus must be removed before final dose calculation. CONCLUSION: The realization of inverse optimization for IMRT of the breast requires the use of a virtual bolus. Thereby, IMRT in accordance to the consensus recommendations of the EORTC, BCCG and EUSOMA is possible. Especially, the same target definition as in conventional technique may be used. IMRT techniques with a conventional beam arrangement of two tangential fields or multiple beam techniques can be realized.     

Evaluation of irradiation techniques in breast carcinoma using dose-volume histograms. Comparison of the heart and lung exposure

For irradiation of the internal mammary lymph nodes (IMN), together with irradiation of the breast the commonly used treatment techniques are of three types: 1. two tangential opposed fields, 2. three field plans with a separate "straight on" IMN-field, or 3. with a separate "angled" IMN-field. To determine lung and heart volumes and doses for these techniques, dose-volume-histograms in 30 patients were analyzed. The optimum dose distribution was achieved with the "angled" field technique and an appropriate combination of electrons and 60Co gamma radiation for the IMN-field. (The beam mixture used was 40% 60Co beam and 60% electron beam.) The least possible dose to the lung was obtained with the "straight-on" field technique and the least possible dose to the heart with the separate "angled" IMN-field technique.