磁共振成像定位在低位直肠癌术前放疗大体肿瘤靶区勾画中的应用

目的 探讨磁共振成像（MRI）定位在直肠癌术前放疗中的应用价值。方法 选择经肠镜下病理活检和全身分期检查明确诊断为局部晚期低位直肠癌的患者40例,男性22例,女性18例,年龄31~80岁,中位年龄58岁。先后在相同的体位和固定装置下行CT和MRI定位扫描。由两名直肠癌放疗专业的医生分别在两种定位图像上进行大体肿瘤靶区（GTV）勾画。通过放疗计划系统（TPS）计算出CT和MRI定位图像上勾画的直肠原发肿瘤GTV（GTV_CT、GTV_MRI）的长度、体积及GTV下界距肛缘的距离,并比较这两组数据的差异。结果 肛门指诊提示肿瘤下界距肛缘均≤ 5 cm。GTV_CT的平均长度为（5.21±1.65）cm,长于GTV_MRI的平均长度（4.46±1.51）cm（t=5.059,P<0.05）。GTV_CT的平均体积为（55.71±31.57）cm³,大于GTV_MRI的平均体积（44.02 ±25.11）cm³（t=6.977,P<0.05）。通过肛门指诊判断的肿瘤下界距肛缘的距离为（3.72±0.93）cm,长于GTV_CT下界距肛缘的距离（t=-5.503,P<0.05）,但与GTV_MRI有较高的一致性（P>0.05）。应用CT-MRI融合定位制定调强放疗计划,40例患者中无3、4级放疗不良反应发生。术后pCR率为32.5%。结论 MRI定位勾画出的GTV范围更小,对于肿瘤的下界的确定也更为准确。MRI定位的应用可能会通过提高靶区勾画的精确性,从而提高放射治疗的疗效,减少不良反应的发生率。     

基于CT/MRI/PET-CT进行鼻咽癌大体肿瘤区及淋巴结勾画的对照研究

目的 比较基于计算机体层成像（CT）、磁共振成像（MRI）、¹⁸氟-脱氧葡萄糖正电子发射计算机断层显像（¹⁸F-FDG PET-CT）3种图像勾画鼻咽癌（NPC）大体肿瘤靶区（GTV）及淋巴结的差异,并以MRI为参考研究基于PET自动勾画NPC GTV的最佳标准摄取值（SUV）。方法 选取拟行放疗的鼻咽癌患者53例,依次获得CT模拟定位、MRI模拟定位及PET图像,在3种图像上分别勾画GTV与阳性淋巴结,分别命名为GTV_MRI、GTV_CT、GTV_PET2.5（SUV=2.5）、Lymph_MRI、Lymph_CT、Lymph_PET2.5,比较不同图像确定的GTV及淋巴结差异。将MRI与PET-CT配准后,得到相交区域GTV_∩2.5,依据SUV=4.0、4.5、5.0、5.6为阈值分别在PET上自动勾画GTV_PET4.0、GTV_PET4.5、GTV_PET5.0、GTV_PET5.6,比较不同GTV之间体积、相似系数（DSC）的差异。结果 在3种图像中,GTV_MRI分别较GTV_CT增加了1.73%（P>0.05）,较GTV_PET2.5减小了21.34%（t=-3.52,P<0.05）;Lymph_PET2.5的体积分别为Lymph_MRI、Lymph_CT的1.61、1.87倍（t=-4.12、-5.18,P<0.05）。PET上表现为高摄取的淋巴结体积平均为无或低摄取的4.07倍（t=5.50,P<0.05）。GTV_PET4.0与GTV_MRI的DSC为0.78±0.27,低于GTV_PET2.5与GTV_MRI的DSC （0.84±0.18）,但GTV_PET4.0与GTV_∩2.5体积基本相当（P>0.05）。结论 基于CT、MRI、¹⁸F-FDG PET-CT勾画鼻咽癌GTV及淋巴结时,MRI可更好显示肿瘤边界;而基于¹⁸F-FDG PET-CT自动勾画GTV时,推荐SUV=4.0作为阈值。     

CT图像重建视野大小对放射治疗计划剂量计算及体积评估的影响

目的 探讨CT图像重建视野(FOV)大小对放射治疗计划剂量计算及体积评估可能存在的影响。方法 对16例鼻咽癌患者的CT原始扫描数据分别行45 cm常规FOV和65 cm扩展视野(EFOV)重建并传输至放射治疗计划系统,所有病例均在常规FOV重建的CT图像上勾画肿瘤体积(GTV)、临床靶区(CTV)及脑干、晶体、腮腺、脊髓等危及器官,并制定7野等角动态调强放射治疗计划(GTV处方剂量70 Gy)。两种重建方法图像按照医学数字影像通信3.0标准(DICOM 3.0)坐标方式融合后,拷贝常规FOV图像上的靶区及危及器官至EFOV图像,并将治疗计划移植至EFOV图像,治疗计划中心为两种重建方法图像的同一DICOM坐标,利用剂量体积直方图(DVH)工具计算两种重建方法图像上GTV、CTV和脑干、晶体、腮腺、脊髓的体积、最大剂量(D_max)、平均剂量(D_mean)及最小剂量(D_min)。将入组病例的每个治疗计划7野分别导入常规45 cm FOV和65 cm EFOV重建的二维通量图验证设备Mapchek 1175的模体,距离通过协议(DTA)分析5 cm深度平面绝对剂量的计算和实测结果通过率。结果 两种重建方法图像上的靶区和危及器官的体积差异具有统计学意义,所有入组病例靶区和危及器官在常规FOV图像上的体积均大于EFOV图像上的体积。较小体积的晶体最大剂量D_max常规FOV与EFOV图像之间差异有统计学意义(t =-3.14, P<0.007),其余靶区及危及器官的最大剂量D_max差异无统计学意义。CTV和GTV平均剂量D_mean在EFOV图像上大于FOV图像,差异有统计学意义(t=-6.45、-5.65, P< 0.001),危及器官的平均剂量D_mean和靶区及危及器官最小剂量D_min差异均无统计学意义。两种重建方法图像上治疗计划的7野通过率之间差异无统计学意义。结论 在放射治疗CT模拟定位过程中图像重建FOV的大小对于靶区及部分危及器官的体积及剂量计算结果和治疗计划的评价存在影响;观察和验证二维通量图通过率,两者之间的差异并不显著。     

双示踪剂PET-CT在头颈部肿瘤生物适形调强放疗的初步研究

目的 探讨¹⁸F-脱氧葡萄糖（¹⁸F-FDG）和¹⁸F-赤硝基咪唑（¹⁸F-FETNIM）双示踪剂PET-CT确定头颈部肿瘤生物适形调强放射治疗（BIMRT）靶区的可行性。方法 经病理证实且未经治疗的头颈部肿瘤患者12例,治疗前行CT模拟定位扫描、¹⁸F-FDG PET-CT和¹⁸F-FETNIM PET-CT扫描,分别勾画大体肿瘤靶区（GTV_CT）、葡萄糖代谢亚靶区（GTV_FDG）、乏氧亚靶区（GTV_FETNIM）,测量并比较原发肿瘤和转移性淋巴结体积,分别表示为GTV_P-CT、GTV_N-CT、GTV_P-FDG、GTV_N-FDG、GTV_P-FETNIM 和GTV_N-FETNIM。 结果 12例患者原发肿瘤和转移淋巴结均摄取¹⁸F-FDG,SUVmax-P和SUVmax-N分别为12.3±5.5和 5.1±2.8。9例患者原发肿瘤摄取¹⁸F-FETNIM,其中5例患者转移性淋巴结有摄取,未见摄取4例;3例患者原发肿瘤未见¹⁸F-FETNIM 摄取,其中转移性淋巴结有摄取1例,未见摄取2例。GTV_P-CT、GTV_P-FDG 和GTV_P-FETNIM分别为 （22.23±12.11）、（20.83±11.59）和（1.98±1.81）cm³,GTV_N-CT、GTV_N-FDG 和GTV_N-FETNIM分别为 （10.77±8.87）、（10.41±8.61）和（0.61±1.08）cm³。GTV_P-FETNIM < GTV_P-CT,GTV_P-FETNIM < GTV_P-FDG,GTV_N-FETNIM < GTV_N-CT,GTV_N-FETNIM < GTV_N-FDG（P<0.01）,GTV_P-CT与GTV_P-FDG、GTV_N-CT与GTV_N-FDG差异无统计学意义。结论 不同示踪剂PET-CT显像反映肿瘤细胞不同方面的生物学信息,根据PET-CT影像所显示的示踪剂高摄取区域将肿瘤组织划分为若干个子区域是可行的,为实现生物调强放疗提供了可靠的研究基础。     

3D打印个体化模具在子宫内膜癌术后三维后装治疗中的剂量学研究

目的 探讨3D打印个体化模具辅助子宫内膜癌术后三维后装治疗中的剂量学优势。方法 回顾性选取宁波大学附属第一医院21例早期子宫内膜癌术后患者的三维后装治疗计划,利用北京科霖众计划系统,在已实施的个体化模具组基础上,为每位患者设计虚拟单通道柱状施源器计划,所有计划均采用三维逆向模拟退火的算法。比较两组计划靶区90%、98%和100%体积接受的最低剂量(D₉₀、D₉₈、D₁₀₀)以及适形指数(CI)、均匀度(HI)、超剂量体积指数(OI);同时,对比两组危及器官膀胱、直肠、小肠和尿道的0.01、1、2以及5 cm³所接受的最大剂量(D_{0.01 cm³}、D_{1 cm³}、D_{2 cm³}以及D_{5 cm³})差异。结果 两组计划都能满足临床需求。在靶区所受剂量方面,两组计划靶区D₉₀、D₉₈、D₁₀₀没有明显差异,但是个体化模具组靶区剂量的CI、HI均优于单通道组靶区,而靶区OI指数小于单通道计划(t=-3.21、-5.99、6.25,P＜0.05)。在危及器官所受剂量方面,个体化模具组膀胱、直肠、尿道所受剂量D_{1 cm³}、D_{2 cm³}和D_{5 cm³}相比单通道组均有明显降低(t=3.18、3.21、3.77、7.97、8.92、10.92、2.54、3.46、4.28,P＜0.05);小肠由于距离靶区比较远,在两组计划中所受剂量差异不明显(P＞0.05)。结论 3D打印个体化模具在子宫内膜癌术后三维近距离治疗中靶区均匀度、适形指数更优,而且膀胱、直肠、尿道所受剂量更低,具有推广价值。     

中上段食管癌图像引导放疗中摆位误差及靶区外放边界的确定

目的 应用锥形束CT（CBCT）测量食管癌调强放疗的摆位误差,从而确定靶区外放距离;分析不同的靶区外放距离对肺和脊髓正常组织的影响。方法 选择2012年12月至2013年12月的12例中上段食管癌患者,根据每周1次CBCT所得的60组测量数据确定患者左右、头脚以及前后方向的摆位误差,根据实际测量的摆位误差结果以及靶区运动大小得出靶区外放距离,针对临床靶区CTV外放5 mm得到的计划靶区PTV以及根据实际测量摆位误差外放得到的计划靶区PTV分别制定调强治疗计划,在保证计划靶区PTV覆盖率相同（V₉₅≥95%）的情况下对两种计划的危及器官受量进行比较和统计学分析,评价参数包括双肺的V₅、V₂₀、V₃₀、平均剂量D_mean以及脊髓受量D_{1 cm³}。结果 食管癌调强放疗在左右、头脚以及前后3个方向的摆位误差分别是（2.02±1.74）、（2.02±1.93）、（2.03±1.89）mm。上段食管癌由临床靶区（CTV）到计划靶区（PTV）的外放距离为左右4.7 mm、头脚8.5 mm、前后5.6 mm;中段食管癌为左右5.0 mm、头脚11.0 mm、前后6.2 mm。两种计划比较,双肺的V-5、V₂₀、V₃₀、平均剂量D_mean和脊髓受量D_1cm³的差异有统计学意义（t=-8.23、－5.55、－4.66、－6.87、－4.67,P<0.05）。结论 根据CBCT测量结果确定摆位误差以及文献报道结果得出食管癌靶区外放边界,对于临床治疗有一定的参考意义。     

局部晚期鼻咽癌诱导化疗后原发病灶靶区勾画的探讨

目的 探讨局部晚期鼻咽癌诱导化疗后原发病灶(GTVnx)靶区勾画。方法 选择2012-2013年收治的52例局部晚期鼻咽癌患者,诱导化疗2~3周期后行CT定位、标记及图像采集;同期采取相同体位行鼻咽部MRI平扫及增强扫描,采集T₁W₁增强图像;分别在CT图像及MRI图像进行GTV_nx勾画;转移淋巴结、CTV1、CTV2及正常组织均在CT图像进行勾画;通过放疗计划系统进行MRI/CT图像GTV_nx靶区融合;两套靶区给予相同处方剂量及正常组织限量,物理师进行调强放疗计划设计。比较不同图像下诱导化疗后GTV_nx、各靶区照射体积及剂量、正常组织受量变化。结果 在局部晚期鼻咽癌诱导化疗后GTV_nx勾画中,MRI图像勾画靶体积大于CT图像[(43.14±28.40)、(40.09±27.04)cm³,t=3.791,P<0.001];MRI图像勾画靶体积与诱导化疗前原发病灶体积差值[(27.90±11.86)cm³]小于CT图像勾画体积差值[(30.64±11.86)cm³](t=3.948,P<0.001)。两套计划原发病灶靶区照射体积比较,融合靶区计划(41.71±26.86)cm³大于CT图像计划[(38.65±25.66)cm³](t=4.098,P<0.001),但靶区剂量及正常组织受量差异无统计学意义。结论 采用MRI图像进行局部晚期鼻咽癌诱导化疗后原发病灶靶区勾画、MRI/CT靶区图像融合进行放疗计划设计,增加原发灶靶区体积及照射体积,可能减少诱导化疗后放射治疗靶区勾画漏靶发生。     

诊断PET-CT用于食管癌原发肿瘤大体肿瘤体积勾画的比较研究

目的 比较单纯参考诊断¹⁸F-FDG PET-CT（PET-CT）在3D-CT上勾画的食管原发肿瘤大体肿瘤体积（GTV）与利用3D-CT和诊断PET-CT形变配准后勾画的GTV体积和位置差异。方法 选择在本院行同步放化疗的胸段食管癌患者72例,所有患者放疗前均行诊断PET-CT扫描和常规3D-CT模拟定位扫描。单纯基于常规3D-CT勾画GTV定义为GTV_3D,参考诊断PET-CT在3D-CT上勾画的GTV定义为GTV_PET-ref,基于3D-CT和诊断PET-CT形变配准图像上勾画的GTV定义为GTV_PET-reg。比较3种GTV剂量指标间的差异。结果 全组患者GTV_3D、GTV_PET-ref、GTV_PET-reg靶区中位体积分别为44.90、40.36、41.15 cm³,各靶区间体积大小差异无统计学意义（P>0.05）。三者靶区平均长度分别为8.54、9.29、8.38 cm,GTV_PET-ref>GTV_3D（t=2.134,P<0.05）。GTV_PET-ref对GTV_3D、GTV_PET-reg对GTV_3D的中位包含度（DI）值分别为0.86、0.82,两者间差异有统计学意义（Z=-2.741,P<0.05）;GTV_3D对 GTV_PET-ref、GTV_3D对GTV_PET-reg的中位DI值分别为0.87、0.84,两者间差异有统计学意义（Z=-1.429,P<0.05）。GTV_3D与GTV_PET-ref、GTV_3D与GTV_PET-reg的中位适形指数（CI）值分别为0.72、0.68,两者间差异有统计学意义（Z=2.756,P<0.05）。GTV_3D与GTV_PET-ref、GTV_3D与GTV_PET-reg、GTV_PET-ref与GTV_PET-reg的CI与靶区中心间距均呈显著负相关（P<0.05）。结论 参考诊断PET-CT在靶区体积大小及靶区空间位置与基于诊断PET-CT形变配准所勾画食管癌原发肿瘤GTV差异均无统计学意义,因此,建议放疗医生可以参照治疗前近期的诊断PET-CT勾画食管癌原发肿瘤GTV。     

射线能量对子宫内膜癌调强放疗计划质量的影响

目的 研究射线能量对子宫内膜癌术后全盆腔调强放射治疗计划质量的影响。方法 选择10例子宫内膜癌术后患者,对每例患者分别设计6和18 MV的全盆腔调强放射治疗计划。所有计划均使用相同的布野方案和剂量体积约束。比较两组计划的靶区、危及器官和正常组织的剂量分布。结果 6和18 MV计划的平均PTV₁₀₀分别是95.6%和95.3% (检验值P=0.26), D_mean分别是52.55 Gy和52.60 Gy(P=0.54),适形指数分别是0.87 和 0.88 (P=0.03),均匀性指数均为1.10 (P=0.38)。18 MV计划较6 MV计划正常组织的平均积分剂量下降了2.4% (P=0.001),小肠和结肠的平均V₃₀和V₅₀分别下降了4.2% (P=0.006)和3.3% (P=0.046),其他危及器官的剂量分布间差异无统计学意义。结论 对于子宫内膜癌的术后全盆腔调强放射治疗,18 MV计划比6 MV计划剂量分布的适形度更好,能够更好地保护正常组织、小肠和结肠。两组计划靶区的覆盖度和剂量分布的均匀性,以及直肠、膀胱和盆腔骨的保护相当。     

小细胞肺癌三种全脑预防性照射计划的剂量学比较

目的 比较小细胞肺癌(SCLC)全脑预防性照射(PCI)3D-CRT、IMRT、RapidArc 3种计划方式的剂量学差异,为制定最佳PCI放疗方案提供指导。方法 选取10例SCLC患者颅脑CT,分别设计3D-CRT、IMRT及RapidArc 3种放疗计划。根据剂量体积直方图,评价靶区的D_2%、D_98%、V₉₅、V₁₀₀、均匀性指数(HI)、适形性指数(CI)以及危及器官(OAR)受量,比较机器跳数(MU)的差异。 结果 IMRT及RapidArc的靶区剂量学参数(CI、HI、D_2%、D_98%、V₉₅、V₁₀₀)均优于3D-CRT,差异有统计学意义(P<0.05)。IMRT、RapidArc较3D-CRT显著降低左右视神经D_max、左右腮腺D_mean及脑干D_max的受量,差异有统计学意义(P<0.05);相反,3D-CRT能显著减少左右晶状体的D_max和左右眼球的D_max、D_mean受量,差异有统计学意义(P<0.05)。IMRT及RapidArc在靶区和危及器官受量方面无差异。3D-CRT、IMRT和RapidArc计划的平均MU分别为287.8、1388.8和346.6。 结论 IMRT及RapidArc较3D-CRT具有一定的剂量学优势,3D-CRT能减少晶状体及眼球的受量,治疗时间短。     

基于食管癌放射治疗计划的剂量学研究

目的应用三维治疗计划系统（3D—TPS）比较研究食管癌的不同照射方法，评价常规三野等中心照射（RT）、三维适形（3D～CRT）、调强适形放射治疗（IMRT）在靶区剂量及正常组织保护方面的不同。方法采用三维治疗计划系统对12例经病理证实的中下段食管癌的患者CT定位图像分别设计3种放射治疗计划，分别为RT，3 D—CRT，IMRT，计划的处方剂量均为50 Gy，通过治疗计划及剂量体积直方图（DVH）比较靶区及危及器官剂量的差异。结果RT，3 D—CRT，IMRT的95％计划靶体积（PTV）及95％大体肿瘤体积（GTV）的剂量有统计学意义，3 D—CRT和IMRT优于RT；3种计划的靶区适形度指数、PTV剂量变异度指数、处方剂量覆盖GTV百分比均以IMRT计划为最好，3D—CRT、IMRT减少了双肺受照20 Gu体积百分比（V20），均有统计学意义；3种计划的脊髓最大所受剂量、心脏1／3体积的所受剂量均在可耐受的范围内，IMRT为最小，P〉0．05。结论3 D—CRT、IMRT在靶区适形度和靶区剂量上均优于RT，能获得均匀的剂量分布，且能降低周围敏感器官的所受剂量，正常组织所受剂量均能在耐受范围内。     

A comparison of conventional, conformal and intensity-modulated coplanar radiotherapy plans for posterior fossa treatment

Radiotherapy of the posterior fossa for medulloblastoma treatment can induce ototoxicity, especially when combined with cisplatin chemotherapy. Sensorineural hearing loss can be severe enough to cause permanent disability, which may compromise cognitive development in paediatric patients. This study evaluates the sparing of the cochlea in conventional radiotherapy, three-dimensional conformal radiotherapy (3D-CRT), and intensity-modulated radiotherapy (IMRT). CT scans of three patients were used to plan posterior fossa radiotherapy using coplanar beam arrangements. The posterior fossa and the cochlea were contoured as well as other organs-at-risk (non-posterior fossa brain, lenses, optic nerves, pituitary and cervical spinal cord). Three treatment plans were compared: conventional two-dimensional treatment (parallel-opposed lateral pair); 3D-CRT (two wedged posterior oblique fields); and a four-field coplanar IMRT plan. 3D-CRT and IMRT reduced cochlear doses to less than 70% of the mean target dose. These plans also reduced dose to the non-posterior fossa brain and cervical spinal cord. IMRT showed no advantage over 3D-CRT in sparing the optic nerves and lenses, compared with 3D-CRT. Normal tissue doses were higher in both conformal techniques than in the IMRT plans. Conformal techniques reduced the dose to the cochlea, non-posterior fossa brain and cervical spinal cord. The small size and proximity to the planning target volume (PTV) of the cochlea limited the effectiveness of the IMRT plan. Coplanar 3D-CRT was judged superior to coplanar IMRT, particularly in children, because it achieved adequate sparing of the cochlea and anterior cranial structures, such as the lenses and optic nerves, without compromising the dose to the posterior fossa.     

食道癌调强放疗与三维适形放疗的剂量学对比

目的比较食道癌在调强放疗与三维适形放疗中靶区剂量及正常组织照射量。方法从我院食道癌患者中抽取10例并由同一肿瘤医师在定位图像上勾画靶区及正常组织,在所勾画的靶区上分别作调强计划与三维适形计划,并以PTV95%、GTV95%、CI、HI、脊髓最大剂量以及左右肺V20来作为剂量评估指标,并进行统计学分析。结果统计学分析结果表明,三维适形放疗与调强放疗的各项指标之间的差异均有统计学意义。结论调强放疗在食道癌的治疗中无论是从靶区剂量的调控还是正常组织剂量的约束上都明显优于三维适形放疗,是食道癌放射治疗中的一种有效治疗方案。     

Dosimetric Comparison Between 2-Dimensional Radiation Therapy and Intensity Modulated Radiation Therapy in Treatment of Advanced T-Stage Nasopharyngeal Carcinoma: To Treat Less or More in the Planning Organ-At-Risk Volume of the Brainstem and Spinal Cord

The aim of this study is to evaluate the deficiencies in target coverage and organ protection of 2-dimensional radiation therapy (2DRT) in the treatment of advanced T-stage (T3-4) nasopharyngeal carcinoma (NPC), and assess the extent of improvement that could be achieved with intensity modulated radiation therapy (IMRT), with special reference to of the dose to the planning organ-at-risk volume (PRV) of the brainstem and spinal cord. A dosimetric study was performed on 10 patients with advanced T-stage (T3-4 and N0-2) NPC. Computer tomography (CT) images of 2.5-mm slice thickness of the head and neck were acquired with the patient immobilized in semi-extended-head position. A 2D plan based on Ho’s technique, and an IMRT plan based on a 7-coplanar portals arrangement, were established for each patient. 2DRT was planned with the field borders and shielding drawn on the simulator radiograph with reference to bony landmarks, digitized, and entered into a planning computer for reconstruction of the 3D dose distribution. The 2DRT and IMRT treatment plans were evaluated and compared with respect to the dose-volume histograms (DVHs) of the targets and the organs-at-risk (OARs), tumor control probability (TCP), and normal tissue complication probabilities (NTCPs). With IMRT, the dose coverage of the target was superior to that of 2DRT. The mean minimum dose of the GTV and PTV were increased from 33.7 Gy (2DRT) to 62.6 Gy (IMRT), and 11.9 Gy (2DRT) to 47.8 Gy (IMRT), respectively. The D₉₅ of the GTV and PTV were also increased from 57.1 Gy (2DRT) to 67 Gy (IMRT), and 45 Gy (2DRT) to 63.6 Gy (IMRT), respectively. The TCP was substantially increased to 78.5% in IMRT. Better protection of the critical normal organs was also achieved with IMRT. The mean maximum dose delivered to the brainstem and spinal cord were reduced significantly from 61.8 Gy (2DRT) to 52.8 Gy (IMRT) and 56 Gy (2DRT) to 43.6 Gy (IMRT), respectively, which were within the conventional dose limits of 54 Gy for brainstem and of 45 Gy for spinal cord. The mean maximum doses deposited on the PRV of the brainstem and spinal cord were 60.7 Gy and 51.6 Gy respectively, which were above the conventional dose limits. For the chiasm, the mean dose maximum and the dose to 5% of its volume were reduced from 64.3 Gy (2DRT) to 53.7 Gy (IMRT) and from 62.8 Gy (2DRT) to 48.7 Gy (IMRT), respectively, and the corresponding NTCP was reduced from 18.4% to 2.1%. For the temporal lobes, the mean dose to 10% of its volume (about 4.6 cc) was reduced from 63.8 Gy (2DRT) to 55.4 Gy (IMRT) and the NTCP was decreased from 11.7% to 3.4%. The therapeutic ratio for T3-4 NPC tumors can be significantly improved with IMRT treatment technique due to improvement both in target coverage and the sparing of the critical normal organ. Although the maximum doses delivered to the brainstem and spinal cord in IMRT can be kept at or below their conventional dose limits, the maximum doses deposited on the PRV often exceed these limits due to the close proximity between the target and OARs. In other words, ideal dosimetric considerations cannot be fulfilled in IMRT planning for T3-4 NPC tumors. A compromise of the maximal dose limit to the PRV of the brainstem and spinal cord would need be accepted if dose coverage to the targets is not to be unacceptably compromised. Dosimetric comparison with 2DRT plans show that these dose limits to PRV were also frequently exceeded in 2DRT plans for locally advanced NPC. A dedicated retrospective study on the incidence of clinical injury to neurological organs in a large series of patients with T3-4 NPC treated by 2DRT may provide useful reference data in exploring how far the PRV dose constraints may be relaxed, to maximize the target coverage without compromising the normal organ function.     

Dosimetric Comparison Between 2-Dimensional Radiation Therapy and Intensity Modulated Radiation Therapy in Treatment of Advanced T-Stage Nasopharyngeal Carcinoma: To Treat Less or More in the Planning Organ-At-Risk Volume of the Brainstem and Spinal Cord

The aim of this study is to evaluate the deficiencies in target coverage and organ protection of 2-dimensional radiation therapy (2DRT) in the treatment of advanced T-stage (T3-4) nasopharyngeal carcinoma (NPC), and assess the extent of improvement that could be achieved with intensity modulated radiation therapy (IMRT), with special reference to of the dose to the planning organ-at-risk volume (PRV) of the brainstem and spinal cord. A dosimetric study was performed on 10 patients with advanced T-stage (T3-4 and N0-2) NPC. Computer tomography (CT) images of 2.5-mm slice thickness of the head and neck were acquired with the patient immobilized in semi-extended-head position. A 2D plan based on Ho’s technique, and an IMRT plan based on a 7-coplanar portals arrangement, were established for each patient. 2DRT was planned with the field borders and shielding drawn on the simulator radiograph with reference to bony landmarks, digitized, and entered into a planning computer for reconstruction of the 3D dose distribution. The 2DRT and IMRT treatment plans were evaluated and compared with respect to the dose-volume histograms (DVHs) of the targets and the organs-at-risk (OARs), tumor control probability (TCP), and normal tissue complication probabilities (NTCPs). With IMRT, the dose coverage of the target was superior to that of 2DRT. The mean minimum dose of the GTV and PTV were increased from 33.7 Gy (2DRT) to 62.6 Gy (IMRT), and 11.9 Gy (2DRT) to 47.8 Gy (IMRT), respectively. The D₉₅ of the GTV and PTV were also increased from 57.1 Gy (2DRT) to 67 Gy (IMRT), and 45 Gy (2DRT) to 63.6 Gy (IMRT), respectively. The TCP was substantially increased to 78.5% in IMRT. Better protection of the critical normal organs was also achieved with IMRT. The mean maximum dose delivered to the brainstem and spinal cord were reduced significantly from 61.8 Gy (2DRT) to 52.8 Gy (IMRT) and 56 Gy (2DRT) to 43.6 Gy (IMRT), respectively, which were within the conventional dose limits of 54 Gy for brainstem and of 45 Gy for spinal cord. The mean maximum doses deposited on the PRV of the brainstem and spinal cord were 60.7 Gy and 51.6 Gy respectively, which were above the conventional dose limits. For the chiasm, the mean dose maximum and the dose to 5% of its volume were reduced from 64.3 Gy (2DRT) to 53.7 Gy (IMRT) and from 62.8 Gy (2DRT) to 48.7 Gy (IMRT), respectively, and the corresponding NTCP was reduced from 18.4% to 2.1%. For the temporal lobes, the mean dose to 10% of its volume (about 4.6 cc) was reduced from 63.8 Gy (2DRT) to 55.4 Gy (IMRT) and the NTCP was decreased from 11.7% to 3.4%. The therapeutic ratio for T3-4 NPC tumors can be significantly improved with IMRT treatment technique due to improvement both in target coverage and the sparing of the critical normal organ. Although the maximum doses delivered to the brainstem and spinal cord in IMRT can be kept at or below their conventional dose limits, the maximum doses deposited on the PRV often exceed these limits due to the close proximity between the target and OARs. In other words, ideal dosimetric considerations cannot be fulfilled in IMRT planning for T3-4 NPC tumors. A compromise of the maximal dose limit to the PRV of the brainstem and spinal cord would need be accepted if dose coverage to the targets is not to be unacceptably compromised. Dosimetric comparison with 2DRT plans show that these dose limits to PRV were also frequently exceeded in 2DRT plans for locally advanced NPC. A dedicated retrospective study on the incidence of clinical injury to neurological organs in a large series of patients with T3-4 NPC treated by 2DRT may provide useful reference data in exploring how far the PRV dose constraints may be relaxed, to maximize the target coverage without compromising the normal organ function.     

Dosimetric Comparison Between Intensity-Modulated with Coplanar Field and 3D Conformal Radiotherapy with Noncoplanar Field for Postocular Invasion Tumor

This study presents a dosimetric optimization effort aiming to compare noncoplanar field (NCF) on 3 dimensions conformal radiotherapy (3D-CRT) and coplanar field (CF) on intensity-modulated radiotherapy (IMRT) planning for postocular invasion tumor. We performed a planning study on the computed tomography data of 8 consecutive patients with localized postocular invasion tumor. Four fields NCF 3D-CRT in the transverse plane with gantry angles of 0–10°, 30–45°, 240–270°, and 310–335° degrees were isocentered at the center of gravity of the target volume. The geometry of the beams was determined by beam's eye view. The same constraints were prepared with between CF IMRT optimization and NCF 3D-CRT treatment. The maximum point doses (D max) for the different optic pathway structures (OPS) with NCF 3D-CRT treatment should differ in no more than 3% from those with the NCF IMRT plan. Dose-volume histograms (DVHs) were obtained for all targets and organ at risk (OAR) with both treatment techniques. Plans with NCF 3D-CRT and CF IMRT constraints on target dose in homogeneity were computed, as well as the conformity index (CI) and homogeneity index (HI) in the target volume. The PTV coverage was optimal with both NCF 3D-CRT and CF IMRT plans in the 8 tumor sites. No difference was noted between the two techniques for the average D_max and D_min dose. NCF 3D-CRT and CF IMRT will yield similar results on CI. However, HI was a significant difference between NCF 3D-CRT and CF IMRT plan (p < 0.001). Physical endpoints for target showed the mean target dose to be low in the CF IMRT plan, caused by a large target dose in homogeneity (p < 0.001). The impact of NCF 3D-CRT versus CF IMRT set-up is very slight. NCF3D-CRT is one of the treatment options for postocular invasion tumor. However, constraints for OARs are needed.     

不同CT值赋值法对脑转移瘤放疗剂量计算影响的研究

目的研究不同CT值赋值法对脑转移瘤放疗计划剂量计算的影响,为基于磁共振(MR)图像进行放疗计划设计提供基础。方法选取35例接受放疗的脑转移瘤患者,每位患者在放疗前同一天分别进行CT和MR模拟定位,基于CT图像制定三维适形放射治疗(3D-CRT)或调强放射治疗(IMRT)计划为原计划Plan1。将CT图像和MR图像刚性配准,在CT和MR图像上勾画主要的组织和器官,计算各组织器官的群体化CT值。基于CT图像,采用3种CT值赋值法生成3组伪CT,分别为:全组织赋予140 HU;空腔、骨骼和软组织分别赋予-700、700和20 HU;不同组织器官分别赋予群体化的CT值。Plan1在3组伪CT上重新计算剂量分布,分别获得Plan2、Plan3、Plan4,然后比较这3组计划和Plan1的剂量学差异。结果骨骼、空腔平均CT值分别为(735.3±68.0)、(-723.9±27.0)HU,软组织的平均CT值基本分布在-70~70 HU。Plan2、Plan3、Plan4相比Plan1的剂量差异依次减小,在剂量指标比较中,眼晶状体最大剂量差异最大,分别可达5.0%以上、1.5%~2.0%、1.0%~1.5%,其余剂量指标差异的95%置信区间上限基本不超过2.0%、1.2%、0.8%。在像素点剂量比较中,局部靶区病例中差异>1%的区域主要分布在靠近射野的皮肤处,而全脑靶区病例中主要分布在骨骼与空腔、软组织交界处,以及靠近射野的皮肤处。此外,CT值赋值法在3D-CRT的剂量学差异大于IMRT,在全脑靶区病例大于局部靶区病例。结论不同CT值赋值法对脑转移瘤放疗计划剂量计算的影响显著,对骨骼、空腔和软组织赋予合适CT值,剂量计算偏差可基本控制于1.2%以内,而对各组织器官赋予群体化的CT值,可进一步将偏差控制于0.8%以内,满足临床要求。     

PET/CT对合并肺不张非小细胞肺癌治疗方案制定和放疗靶区勾画的影响

目的 观察PET/CT对合并肺不张NSCLC治疗方案制定和放疗靶区勾画的影响.方法 对拟行根治性3D-CRT的36例伴有不同程度肺不张的NSCLC患者行PET/CT扫描,观察PET/CT对其临床分期的影响,及由此带来的治疗方案的改变;再以CT图像和PET/CT融合图像分别勾画靶区,对两者进行比较.结果 PET/CT使18例(50.0％,18/36)患者的临床分期发生改变.11例(30.6％,11/36)因PET/CT发现远处转移,临床分期升为Ⅳ期,从而更改了治疗方案,其中3例由根治性放疗改为姑息性放疗,7例由放疗改为化疗,1例转为最佳支持治疗.25例行根治性3D-CRT的患者中,21例放疗靶区均有不同程度改变,其中靶区增大7例,减小12例,靶区位置移动2例;3例患者在3D-CRT的基础上增加锁骨上区常规放疗.3例姑息性放疗患者中,2例靶区减小,1例靶区增大.结论 PET/CT通过提高合并肺不张的NSCLC临床分期的准确性,辅助制定更加合理的治疗方案;通过有效检测出区域转移灶和转移淋巴结,降低靶区遗漏的可能;较CT更准确区分肿瘤与不张肺组织,提高了靶区勾画的准确性.     

腮腺癌术后高危复发区放疗的不同治疗计划剂量学比较

目的 探讨腮腺癌术后高危复发区用何种照射方法可以更有效的使靶区剂量均匀及更好的保护危及器官.方法 对8例腮腺癌术后患者设计治疗计划,处方剂量为95%计划靶区(PTV)60 Gy/30次.对常规放疗、二维适形放疗(2D-CRT)、三维适形放疗(3D-CRT)和调强放疗(IMRT)等放射治疗技术的腮腺癌术后靶区进行放疗计划设计,分析比较各种治疗计划靶区适形度和在保护危及器官等方面的优劣.结果 在2D-CRT时,以计算点深度取3.5 cm,电子线能量采取12 MeV及X射线/电子射线(X/E)剂量比为1∶2时靶区的适形度和均匀度较好,危及器官的受量较低.与2D-CRT比较,常规放疗照射野能够较好地包括CT断层图像上勾画的靶区.与2D-CRT及3D-CRT相比,IMRT计划有最好的靶区适形度及均匀度,同时对危及器官有较好的保护作用.结论 X射线与电子线混合线束照射时,剂量计算点深度取3.5 cm左右、电子线能量采取12 MeV及X/E剂量比为1∶2时,靶区的适形度和均匀度较好,对正常组织的保护较好,但具体患者最好用计划系统来选择以上指标.常规放疗按解剖标志确定的照射野能够较好地包括三维靶区.IMRT计划的靶区适形度及均匀度最好,并且危及器官受量较低,在腮腺癌术后放射治疗中IMRT技术是值得推广并普及的放射治疗技术.     

变形配准与经验计算剂量累加法用于肺癌放疗计划累加剂量计算的研究

目的 应用变形配准功能评价肺癌患者放疗计划中正常组织和危及器官的累加剂量,并与经验计算剂量累加法进行比较.方法 回顾性分析10例肺癌患者,放疗前制定了三维适形或调强治疗计划,放疗过程中重新行CT模拟,并重新设计相同的治疗计划.采用Mimvista软件,运用变形配准,分别在2次CT图像上进行剂量累加.采用经验计算剂量累加法,计算2次放疗计划的正常组织和危及器官的累加剂量,分别对两种方法的双侧肺组织、心脏及脊髓的受照剂量体积以及平均剂量等参数,进行比较.结果 定位和复位图像采用相同的计划方式时,两种方法所得正常组织和危及器官的累积受照体积和剂量等参数差异无统计学意义,仅右肺的平均剂量除外(t=2.98,P＜0.05).结论 变形配准法可以准确评价肺癌患者多次放疗计划中正常组织和危及器官的累加剂量.肺癌患者的靶区变化不大并且采用相同的计划方式时,应用经验计算剂量累加法,可粗略评价肺和心脏等正常组织和危及器官的剂量体积.