乳腺癌保乳术后全乳野中野适形调强放射治疗技术

目的:探讨乳腺癌保乳术后全乳野中野适形调强照射技术方法,并与常规全乳切线野照射技术进行剂量学对比.方法:选取22例早期乳腺癌保乳术后患者在CT模拟机下对乳腺部位行薄层定位扫描,将定位图像传输至治疗计划系统进行全乳野中野计划设计:在全乳两切线适形野的基础上挡去高剂量区部分,另设计2-4个小跳数射野以降低靶区最高剂量和调整高剂量区的范围及所在位置.处方剂量50Gy/25次,要求95%的靶区接受处方剂量;然后利用其CT模拟定位资料按照常规切线野射野方法在治疗计划上模拟常规切线野治疗计划,对野中野计划和常规射野计划进行靶区适形性、靶区均匀性和危及器官受量的比较.结果:野中野适形调强放射治疗技术的适形度、均匀性优于常规切线野照射,靶区内超过110%处方剂量的体积明显小于常规切线野技术.减少了肺组织V20的体积,降低了心脏的平均剂量和受照体积.结论:乳腺癌保乳术后全乳野中野适形调强放射治疗技术是一种有益的全乳照射技术.     

乳腺癌保乳术后全乳野中野适形调强放射治疗技术

目的：探讨乳腺癌保乳术后全乳野中野适形调强照射技术方法,并与常规全乳切线野照射技术进行剂量学对比。方法：选取22例早期乳腺癌保乳术后患者在CT模拟机下对乳腺部位行薄层定位扫描,将定位图像传输至治疗计划系统进行全乳野中野计划设计：在全乳两切线适形野的基础上挡去高剂量区部分,另设计2—4个小跳数射野以降低靶区最高剂量和调整高剂量区的范围及所在位置。处方剂量50Gy／25次,要求95％的靶区接受处方剂量;然后利用其CT模拟定位资料按照常规切线野射野方法在治疗计划上模拟常规切线野治疗计划,对野中野计划和常规射野计划进行靶区适形性、靶区均匀性和危及器官受量的比较。结果：野中野适形调强放射治疗技术的适形度、均匀性优于常规切线野照射,靶区内超过110％处方剂量的体积明显小于常规切线野技术。减少了肺组织V20的体积,降低了心脏的平均剂量和受照体积。结论：乳腺癌保乳术后全乳野中野适形调强放射治疗技术是一种有益的全乳照射技术。     

左侧乳腺癌保乳术后3种放疗技术在同步推量中的剂量学研究

目的 探讨左侧乳腺癌保乳术后半弧容积动态旋转调强(VMAT)放疗、切线弧VMAT放疗和逆向调强放疗(IMRT)3种放疗技术在同步推量中的剂量学差异.方法 选取10例左侧乳腺癌保乳术后患者,使用MONACO 5.1计划系统,分别采用半弧VMAT、切线弧VMAT和IMRT三种放疗技术,处方剂量均为计划靶区(PTV)50 Gy/25 f、计划肿瘤靶区(PGTV)60 Gy/25 f,评估3种计划靶区剂量适形度指数(CI)、均匀性指数(HI)以及周围正常组织器官的受照剂量.结果 半弧VMAT的PGTV靶区CI优于IMRT(P﹤0.05).切线弧VMAT放疗技术较IMRT放疗技术降低了左侧乳腺癌保乳术后患者患侧肺组织V10的照射范围(P=0.04).切线弧VMAT放疗技术较半弧VMAT放疗技术降低了左侧乳腺癌保乳术后患者健侧肺组织V5(P﹤0.001)、V10(P=0.04)、心脏的V10(P=0.01)、Dmean(P=0.01)及健侧乳腺组织V5(P﹤0.01)的剂量范围.而IMRT放疗技术降低了左侧乳腺癌保乳术后患者健侧肺组织V5、V10的剂量范围(P﹤0.05).结论 对于左侧乳腺癌保乳术后患者的同步推量放疗,VMAT放疗技术尤其是半弧VMAT放疗技术具有更好的靶区适形性;切线弧VMAT放疗技术可以降低周围大部分正常组织器官的照射剂量.     

螺旋断层放疗与常规调强放疗在乳腺癌保乳术后同步推量中的剂量学比较

目的 比较乳腺癌保乳术后同步推量放疗中应用常规调强放疗（IMRT）及螺旋断层放疗（HT）剂量分布的差异,为HT在乳腺癌保乳术后的临床应用提供依据。方法 随机选择10例乳腺癌保乳术后患者,统一勾画计划靶区（PTV）与原发灶靶区（PGTV）并导入HT计划系统及瓦里安Eclipse计划系统,分别设计IMRT和HT计划,处方剂量均为PTV 50Gy／25f、PGTV 60Gy／25f,通过比较靶区剂量适形度、均匀性以及心肺受照剂量来评估IMRT与HT的优劣。结果 HT计划中靶区剂量的均匀性、适形度明显优于IMRT（P＜0.05）,患侧肺V5、V10、V20、V30及肺平均剂量均明显低于IMRT（P＜0.05）,但健侧肺V5增加;心脏剂量明显降低（P＜0.05）。结论 对于乳腺癌保乳术后同步推量放疗,HT与IMRT计划都可以满足临床剂量的要求,但HT计划在剂量学方面相对于IMRT计划具有优势,可以显著降低对正常器官的毒副作用。     

乳腺癌保乳术后行IMRT和3D-CRT治疗的剂量学参数及靶区适形度比较

目的:通过配对比较早期乳腺癌保乳术后IMRT和3D-CRT两种放疗技术模式下靶区的适形度和肺组织的受照体积-剂量参数,探索早期乳腺癌保乳术后的最佳放疗模式。方法:选取20例 I-II期（T1-2N0M0）乳腺癌保乳术后行全乳腺放疗者,对同一患者分别设计IMRT和3D-CRT两套放射计划方案,配对分析PTV及PGTVbed靶区剂量分布适形度,患侧肺组织的受照体积-剂量参数,包括V5、V10、V20、V25、V30及肺组织和心脏平均受照剂量。结果:对比3D-CRT,IMRT使肺组织平均受照剂量降低了1.34 Gy,高剂量受照区域V20体积降低了2.89%,V25体积降低了5.57%,V30体积降低了7.45%;同时提高了PTV及PGTVbed靶区内的剂量分布适形度,差异均具有统计学意义（P<0.05）。两组的心脏平均受照剂量分别为（4.01±0.38）Gy和（4.61±0.42）Gy,差异无统计学意义（P>0.05）。结论:在早期乳腺癌保乳术后的辅助放疗中,采用IMRT模式比3D-CRT模式能够获得更好的靶区适形度,靶区内的剂量分布更均匀,有利于提高局控率,同时减少了肺组织的高剂量受照区域和平均受照剂量,对正常肺组织的保护更好,值得临床上应用和推广。     

乳腺癌保乳术后常规切线野放疗与调强放疗剂量学比较的Meta分析

目的 探讨乳腺癌保乳术后调强放疗的优势及不足,为临床治疗提供有价值的循证医学依据。方法 计算机检索PubMed、EMBase、Science、中国知网和万方等数据库,筛选所有乳腺癌保乳术后常规切线野放疗与调强放疗的剂量学比较的文章,应用StataSE 12.0软件对满足条件的数据进行Meta分析。结果 本次研究纳入12篇文章。调强放疗较常规切线野放疗明显降低了靶区的均匀性指数HI(SMD=1.102,95%CI:0.699~1.504,P＜0.001),并明显降低了肺V20、肺V30、心脏V30及V40,差异均有统计学意义;而肺V5、肺V10及心脏V5的差异均无统计学意义。结论 与常规切线野放疗相比,乳腺癌保乳术后调强放疗使靶区分布更均匀,可明显降低高剂量区的照射靶体积,但并未减少低剂量区的照射靶体积,为临床治疗技术的选择提供依据。     

左侧乳腺癌调强放疗的剂量学研究

目的比较左侧乳腺癌保乳术后调强放疗与常规放疗靶区内剂量均匀性、心脏照射剂量和体积的差异。方法对38例左侧乳腺癌保乳术后,应用逆向调强计划,实施全乳腺两野调强放疗。处方剂量为靶区X线46Gy,瘤床应用常规电子线追加14Gy,总量为60Gy。在同一病例CT片上设计常规全乳切线野照射46Gy。在两种治疗方法剂量体积直方图上比较靶区和心脏受照剂量。应用SPSS11.0软件进行配对T检验,以确定调强放疗是否可改善靶区内剂量均匀度并减少心脏受照剂量。结果调强放疗、常规放疗计划中CTV的D95分别为(4541±34)、(4517±62)cGy,V105%分别为17.5%±17.6%、29.4%±26.3%(P<0.01);V110%分别为0.3%±0.8%和3.7%±8.2%(P=0.010)。心脏的V30分别为4.6%±4.3%、18.8%±12.2%(P<0.01);V40分别为1.4%±2.3%、14.3%±11.0%(P<0.01)。结论左侧乳腺癌保乳术后,调强放疗能改善靶区剂量分布、减少心脏受照剂量和体积。     

左乳腺癌保乳术后不同放疗方式的剂量学比较

目的:评价左乳腺癌保乳术后三种放疗方式（3DCRT,IMRT,VMAT）的剂量学特点。方法:选取本院2015年5月至2016年2月期间20例早期左乳腺癌保乳术后放疗患者,所有靶区及危及器官均由同一高级放疗医师勾画,包括临床靶区（CTV）、计划靶区（PTV）及危及器官（OAR）,并由同一高级放疗物理师分别设计3DCRT、IMRT、VMAT 三种治疗计划,处方剂量为50 Gy。比较三种计划的计划靶区（PTV）的靶区均匀性指数（HI）及适形度指数（CI）,最大剂量（Dmax）、平均剂量（Dmean）、最小剂量（Dmin）;肺、心脏的V5,V10,V20,V30,V40,Dmax,Dmean及Dmin等。结果:3DCRT、IMRT、VMAT三种放疗计划适形度指数（CI）分别为 0.75±0.08、0.84±0.04和0.89±0.04(P＜0.05),均匀性指数(HI)分别为 0.11±0.12、0.11±0.08 和0.10±0.09。VMAT与IMRT计划降低了危及器官高剂量区体积,但相应增加了低剂量区体积,尤其VMAT计划的心脏、患侧肺V5、V10明显增加(P＜0.05)。结论:IMRT计划不仅提高了靶区的适形度,而且降低了心脏和肺的低剂量受照体积及平均剂量。因此,IMRT计划更适用于左乳腺癌保乳术后的放射治疗。     

左侧乳腺癌保乳术后三种调强放疗的剂量学研究

目的比较左侧乳腺癌保乳术后3种不同射野数调强放疗方式(IMRT)的靶区及周围正常组织受照剂量的差异。方法选取8例左侧乳腺癌保乳术后患者,应用Pinnacle8.0计划系统分别设计3种不同射野数的调强计划:4野、5野、6野IMRT计划,用剂量体积直方图(DVH)和等剂量曲线评估3种计划的PTV和周围正常组织受照剂量。结果6F-IMRT靶区剂量分布最优,其剂量均匀性和适形度最好,5F-IMRT其次,4F-IMRT最差。与4F-IMRT比较,5F-IMRT和6F-IMRT的PTV最大剂量以及高剂量所包含的体积显著降低。3种计划左肺照射剂量差异较小,均不超过5%;然而心脏照射剂量4F-IMRT最小,与5F-IMRT和6F-IMRT比较,心脏V5、V10、V20、V30以及V40分别降低了42.37%、17.65%、5.87%、5.72%、23.38%和42.85%、30.84%、16.31%、6.45%、24.65%。结论左侧乳腺癌保乳放疗中,调强射野数的增加可以提高靶区PTV覆盖率、适形度和均匀性,但是也会增高左肺低剂量照射体积和平均剂量,右侧肺和心脏的受照剂量也会明显增高,故应根据患者实际情况应用合适的放疗计划进行放疗。     

钼靶X线检查在乳腺癌保乳手术中的应用

钼靶X线摄影诊断乳腺癌的诸多征象中,肿块和钙化是评价乳腺癌保乳手术的两个最常见也是最重要的指标.钼靶X线摄影的另一重要价值是对乳腺癌保乳治疗后的随访评价.在术后的X线征象中,钙化是乳腺癌保乳手术后残留或复发最重要的征象.     

Comparison of three concomitant boost techniques for early-stage breast cancer

PURPOSE: Whole breast radiotherapy (RT) followed by a tumor bed boost typically spans 5-6 weeks of treatment. Interest is growing in RT regimens, such as concomitant boost, that decrease overall treatment time, lessening the time/cost burden to patients and facilities. METHODS AND MATERIALS: Computed tomography (CT) scans from 20 cases were selected for this retrospective, dosimetric study to compare three different techniques of concomitant boost delivery: (1) standard tangents plus an electron boost, (2) intensity-modulated RT (IMRT) tangents using custom compensators plus an electron boost, and (3) IMRT tangents plus a conformal photon boost. The equivalent uniform dose model was used to compare the plans. RESULTS: The average breast equivalent uniform dose value for the three techniques (standard, IMRT plus electrons, and IMRT plus photons) was 48.6, 47.9, and 48.3, respectively. The plans using IMRT more closely approximated the prescribed dose of 46 Gy to the whole breast. The breast volume receiving >110% of the dose was less with the IMRT tangents than with standard RT (p = 0.037), but no significant difference in the maximal dose or other evaluated parameters was noted. CONCLUSION: Although the IMRT techniques delivered the prescribed dose with better dose uniformity, the small improvement seen did not support a goal of improved resource use.     

Dosimetric analysis of a simplified intensity modulation technique for prone breast radiotherapy

PURPOSE: Prone-position breast radiotherapy (RT) has been described as an alternative technique to improve dose homogeneity for women with large, pendulous breasts. We report the feasibility and dosimetric analysis of a simplified intensity-modulated RT (IMRT) technique, previously reported for women in the supine treatment position, to plan prone-position RT to the intact breast. METHODS AND MATERIALS: Twenty patients with clinical Stage TisN0-T1bN1 breast cancer undergoing breast-conserving therapy underwent whole breast RT using a prone position technique. The treatment plans were developed using both conventional tangents and a simplified intensity-modulated tangential beam technique based on optimization of the intensity distributions across the breast. The plans were compared with regard to the dose-volume parameters. RESULTS: Dose heterogeneity within the breast planning target volume was significantly greater for the conventional tangent plans. Of 20 patients, 16 (80%) received maximal doses of > or =110% using the conventional tangents vs. only 1 (5%) using the IMRT plan. The isodose level encompassing 5% of the planning target volume was reduced from an average of 110% with conventional tangents to 105% with IMRT. The maximal dose within the planning target volume was reduced from an average of 114% with conventional tangents to 107% with IMRT. The greatest improvement was seen in the patients with the most pendulous breasts. CONCLUSION: An IMRT planning approach is feasible for prone-position breast RT and improves dose homogeneity, particularly in women with larger, pendulous breasts. Additional follow-up is necessary to determine whether the improvements in dose homogeneity impact acute toxicity and cosmetic outcome in this cohort of women who have historically suffered from poor cosmesis after breast-conserving therapy.     

Impact of breathing motion on whole breast radiotherapy: a dosimetric analysis using active breathing control

PURPOSE: The active breathing control (ABC) apparatus was used to quantify the effect of breathing motion on whole breast radiotherapy (RT) with standard wedges and intensity-modulated RT (IMRT). METHODS AND MATERIALS: Ten patients with early-stage breast cancer underwent routine free-breathing (FB) CT simulations for whole breast RT. An ABC apparatus was used to obtain two additional CT scans with the breath held at the end of normal inhalation and normal exhalation. The FB scan was used to develop both a standard treatment plan using wedged coplanar tangents and an IMRT plan using multiple static multileaf collimator segments. To simulate breathing, each plan was copied and applied to the normal inhalation and normal exhalation CT scans. RESULTS: The medial field border (defined by a radiopaque catheter) for the normal inhalation and normal exhalation scans moved an average of 0.6 cm anteriorly and 0.3 cm posteriorly compared with the FB position, respectively. The corresponding movement of the lateral field border was an average of 0.4 cm anteriorly and 0.2 cm posteriorly compared with the FB position. For both the wedged and the IMRT techniques, the dose delivered to breast tissue, biopsy cavity, and ipsilateral lung was similar for each of the three CT scan positions. However, the internal mammary node dose varied significantly with breathing. CONCLUSIONS: The dose delivered to breast using standard wedges or step-and-shoot IMRT is relatively insensitive to the effects of breast motion during normal breathing. However, an appreciable portion of the internal mammary nodes are irradiated during normal inhalation, contributing to the uncertainty in the analysis of the efficacy of internal mammary nodal RT in breast treatment.     

Intensity modulation to improve dose uniformity with tangential breast radiotherapy: initial clinical experience

Purpose: We present a new technique to improve dose uniformity and potentially reduce acute toxicity with tangential whole-breast radiotherapy (RT) using intensity-modulated radiation therapy (IMRT). The technique of multiple static multileaf collimator (sMLC) segments was used to facilitate IMRT.

Methods and Materials: Ten patients with early-stage breast cancer underwent treatment planning for whole-breast RT using a new method of IMRT. The three-dimensional (3D) dose distribution was first calculated for equally weighted, open tangential fields (i.e., no blocks, no wedges). Dose calculation was corrected for density effects with the pencil-beam superposition algorithm. Separate MLC segments were constructed to conform to the beam’s-eye-view projections of the 3D isodose surfaces in 5% increments, ranging from the 120% to 100% isodose surface. Medial and lateral MLC segments that conformed to the lung tissue in the fields were added to reduce transmission. Using the beam-weight optimization utility of the 3D treatment planning system, the sMLC segment weights were then determined to deliver the most uniform dose to 100 reference points that were uniformly distributed throughout the breast. The accuracy of the dose calculation and resultant IMRT delivery was verified with film dosimetry performed on an anthropomorphic phantom. For each patient, the dosimetric uniformity within the breast tissue was evaluated for IMRT and two other treatment techniques. The first technique modeled conventional practice where wedges were derived manually without consideration of inhomogeneity effects (or density correction). A recalculation was performed with density correction to represent the actual dose delivered. In the second technique, the wedges were optimized using the same beam-weight optimization utility as the IMRT plan and included density correction. All dose calculations were based on the pencil-beam superposition algorithm.

Results: For the sMLC technique, treatment planning required approximately 60 min. Treatment delivery (including patient setup) required approximately 8–10 min. Film dosimetry measurements performed on an anthropomorphic phantom generally agreed with calculations to within ± 3%. Compared to the wedge techniques, IMRT with sMLC segments resulted in smaller “hot spots” and a lower maximum dose, while maintaining similar coverage of the treatment volume. A median of only 0.1% of the treatment volume received ≥ 110% of the prescribed dose when using IMRT versus 10% with standard wedges. A total of 6–8 segments were required with the majority of the dose delivered via the open segments. The addition of the lung-block segments to IMRT was of significant benefit for patients with a greater proportion of lung parenchyma within the irradiated volume. Since August 1999, 32 patients have been treated in the clinic with the IMRT technique. No patient experienced RTOG grade III or greater acute skin toxicity.

Conclusion: The use of intensity modulation with an sMLC technique for tangential breast RT is an efficient and effective method for achieving uniform dose throughout the breast. It is dosimetrically superior to the treatment techniques that employ only wedges. Preliminary findings reveal minimal or no acute skin reactions for patients with various breast sizes.     

Optimizing breast cancer treatment efficacy with intensity-modulated radiotherapy

: To present our clinical experience using intensity-modulated radiation therapy (IMRT) to improve dose uniformity and treatment efficacy in patients with early-stage breast cancer treated with breast-conserving therapy.

: A total of 281 patients with Stage 0, I, and II breast cancer treated with breast-conserving therapy received whole breast RT after lumpectomy using our static, multileaf collimator (sMLC) IMRT technique. The technical and practical aspects of implementing this technique on a large scale in the clinic were analyzed. The clinical outcome of patients treated with this technique was also reviewed.

: The median time required for three-dimensional alignment of the tangential fields and dosimetric IMRT planning was 40 and 45 min, respectively. The median number of sMLC segments required per patient to meet the predefined dose-volume constraints was 6 (range 3–12). The median percentage of the treatment given with open fields (no sMLC segments) was 83% (range 38–96%), and the median treatment time was <10 min. The median volume of breast receiving 105% of the prescribed dose was 11% (range 0–67.6%). The median breast volume receiving 110% of the prescribed dose was 0% (range 0–39%), and the median breast volume receiving 115% of the prescribed dose was also 0%. A total of 157 patients (56%) experienced Radiation Therapy Oncology Group Grade 0 or I acute skin toxicity; 102 patients (43%) developed Grade II acute skin toxicity and only 3 (1%) experienced Grade III toxicity. The cosmetic results at 12 months (95 patients analyzable) were rated as excellent/good in 94 patients (99%). No skin telengiectasias, significant fibrosis, or persistent breast pain was noted.

: The use of intensity modulation with our sMLC technique for tangential whole breast RT is an efficient method for achieving a uniform and standardized dose throughout the whole breast. Strict dose-volume constraints can be readily achieved resulting in both uniform coverage of breast tissue and a potential reduction in acute and chronic toxicities. Because the median number of sMLC segments required per patient is only 6, the treatment time is equivalent to conventional wedged-tangent treatment techniques. As a result, widespread implementation of this technology can be achieved with minimal imposition on clinic resources and time constraints.     

Cardiac-Sparing Whole Lung Intensity Modulated Radiation Therapy in Children With Wilms Tumor: Final Report on Technique and Abdominal Field Matching to Maximize Normal Tissue Protection

Purpose

Cardiac-sparing whole lung intensity modulated radiation therapy (WL IMRT) has been shown to improve cardiac protection and lung volume dose coverage compared with standard anteroposterior techniques. This dosimetry study had 2 aims: To determine the dosimetric advantages of a modified WL IMRT (M-WL IMRT) technique, designed to reduce radiation exposure to the thyroid gland and breast tissues, compared with standard WL IMRT (S-WL IMRT) and to determine the dosimetric advantages of M-WL IMRT and dosimetrically matched abdomen and flank radiation therapy (RT) fields designed to reduce normal tissue exposure compared with standard field matching techniques.

Dosimetric comparison of intensity modulated radiotherapy techniques and standard wedged tangents for whole breast radiotherapy*

Prior to introducing intensity modulated radiotherapy (IMRT) for whole breast radiotherapy (WBRT) into our department we undertook a comparison of the dose parameters of several IMRT techniques and standard wedged tangents (SWT). Our aim was to improve the dose distribution to the breast and to decrease the dose to organs at risk (OAR): heart, lung and contralateral breast (Contra Br). Treatment plans for 20 women (10 right‐sided and 10 left‐sided) previously treated with SWT for WBRT were used to compare (a) SWT; (b) electronic compensators IMRT (E‐IMRT); (c) tangential beam IMRT (T‐IMRT); (d) coplanar multi‐field IMRT (CP‐IMRT); and (e) non‐coplanar multi‐field IMRT (NCP‐IMRT). Plans for the breast were compared for (i) dose homogeneity (DH); (ii) conformity index (CI); (iii) mean dose; (iv) maximum dose; (v) minimum dose; and dose to OAR were calculated (vi) heart; (vii) lung and (viii) Contra Br. Compared with SWT, all plans except CP‐IMRT gave improvement in at least two of the seven parameters evaluated. T‐IMRT and NCP‐IMRT resulted in significant improvement in all parameters except DH and both gave significant reduction in doses to OAR. As on initial evaluation NCP‐IMRT is likely to be too time consuming to introduce on a large scale, T‐IMRT is the preferred technique for WBRT for use in our department.     

Intensity-Modulated Radiation Therapy for Breast Cancer

Over the past 2 decades, numerous advances and innovations have occurred in all technical aspects of radiation therapy (RT), including three-dimensional (3D) treatment planning, conformal radiation delivery, intensity-modulated radiation therapy (IMRT), patient immobilization, and precise treatment verification. Despite incredible progress on all fronts, standard RT for breast cancer has changed very little and has not fully exploited many of the advances commonly used to treat most other malignancies. Increasing data have also accumulated, indicating that dose non-uniformities within the breast with traditional RT techniques can be greater than in many other anatomic sites. These significant dose inhomogeneities can produce unnecessary acute and chronic toxicities as well as unacceptable long-term cosmetic results. In addition, the lack of accurate verification of target volume coverage (e.g. lumpectomy cavity or chest wall) may result in diminished tumor control. In this review, we demonstrate how 3D treatment planning combined with IMRT using our in-house step and shoot, multi-leaf collimator (sMLC) technique for tangential whole-breast RT can be an efficient and reliable method for achieving a more uniform dose throughout the whole breast. Strict dose-volume constraints can be readily met in the majority of patients, resulting in both improved coverage of breast tissue as well as a potential reduction in acute and chronic toxicities. Since the median number of sMLC segments required per patient is only eight, treatment time is not significantly increased. As a result, widespread implementation of this technology can be achieved for most patients with breast cancer with minimal imposition on clinic resources and time constraints. In addition, since lung and heart volumes are also identified, doses to these structures can be maintained at predefined ‘safe’ levels by the treating physician. With the increased use of potentially cardiotoxic drugs in a substantial number of patients with breast cancer, the use of RT in these patients will take on greater significance. It remains to be seen whether the previously noted improvements in survival of patients with postmastectomy RT can be maintained using ‘standard’ techniques combined with these cardiotoxic drugs or whether more technologically sophisticated RT approaches (e.g. IMRT) will be required.     

固定铅门调强技术对乳腺癌术后放射治疗计划设计的作用

目的：近年来固定铅门技术在调强治疗计划设计中已经被广泛使用,本文对比固定铅门（ Fixed jaw）和动态铅门（Jaw tracking）两种技术在乳腺癌调强放射治疗计划设计中的优缺点,探讨固定铅门调强放射治疗技术对乳腺癌治疗计划设计的作用。方法：固定铅门技术是在常规调强放射治疗技术的基础上,人为限定铅门和光栅的作用范围,使某些照射野作用于特定的治疗区域,从而期望得到更好的治疗计划方案。本文选取21例以往进行过 Jaw tracking 技术调强放射治疗的病例,应用 Fixed jaw 技术重新进行计划设计。对应用两种技术的调强放射治疗计划靶区的 Dmean ,Dmin ,Dmax 和患侧肺以及心脏的受照剂量进行对比。同时也对靶区的均匀性指数和适形度指数做了对比。结果：在保证靶区处方剂量的前提下,固定铅门技术相比于动态铅门技术可以明显降低肺 V