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。     

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(Dmax)、平均剂量(Dmean)及最小剂量(Dmin).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 cmEFOV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Dmax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Dmax差异无统计学意义.CTV和GTV平均剂量Dmean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Dmean和靶区及危及器官最小剂量Dmin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.     

调强放射治疗计划的剂量验证

调强放射治疗(intensity—modulated radiation therapy，IMRT)以其较好的剂量分布和保护正常组织等特点已在国内多家医疗单位开展。但是由于此项治疗技术受到诸如影像、逆向计划设计、精确定位及治疗设备等因素的影响，对于治疗方案的剂量验证显得尤为重要。     

鼻咽癌CT类型和放射治疗剂量与鼻咽癌预后的初步研究

探讨鼻咽癌ＣＴ类型和放射剂量与鼻咽癌预后的关系，为设置合理的放疗剂量提供依据，方法５６例疗前ＮＰＣ，均有完整的放疗后３年追踪资料，鼻咽癌复发者１７例，鼻咽正常３９例；根据疗前ＣＴ表现，５６例ＮＰＣ分为Ⅰ型１３例，Ⅱ型２８例，Ⅲ型１５例；鼻咽癌     

初级光阑对立体定向放射治疗剂量的影响

目前多叶准直器 (MLC)在体部分次立体定向放射治疗中成为一种不可缺少的设备 ,该器械具有方便、灵活、实用、省时等特点。长期以来 ,多叶准直器的结构设计一直在改进、完善中 ,但主要是围绕着提高适形度 ,减少透射及漏射等方面。由于其结构特点 ,通常它还需与可调的初级光阑配合使用。为此 ,有必要定量了解两者配合在实际情况下对靶区吸收剂量的影响 ,笔者用实测的方法对其进行了研究。一、材料和方法1 设备 :使用中国科学院大恒医疗设备有限公司生产手动多叶光阑 (叶片对数 34对 ,叶片高度 8cm ,叶片宽度0 2 5cm ,最大开口 7cm× 7cm ,…     

基于剂量预测的个性化放射治疗计划质量的定量评价方法

目的:提出一种基于剂量预测的放射治疗计划质量定量评价方法,并验证该方法的临床可行性和临床价值。方法:基于45例5年以上从业经验的物理师制定的直肠癌病例,训练3D U-Net网络。利用3D U-Net网络预测得到三维剂量分布后,基于剂量预测的剂量-体积直方图(DVH)指标,建立调强放射治疗(IMRT)直肠癌计划质量评估标...     

鼻咽癌调强放疗中实施同一计划对剂量的影响

目的 探讨鼻咽癌调强放疗过程中实施同一治疗计划的可行性。方法 选10例采用调强放射治疗的鼻咽癌患者,用Pinnacle³制定IMRT计划。在患者放疗中期重新行CT定位扫描,把基于初次定位CT图像所做的IMRT计划复制到重新定位CT图像上,使得照射野参数保持一致,测得基于两套图像计划中的肿瘤靶区、脊髓、脑干和腮腺的受量。统计在整个放疗过程中如果实施同一计划,患者靶区及各器官的剂量变化率。结果 两组计划相比,等中心层面外轮廓左右和前后长度平均缩小8%、3%。靶区PTV₁(D₉₅)减少0.6%~5.3%;放疗中期和放疗前相比右侧和左侧腮腺体积分别缩小13.1%~41.4%、12.0%~49.0%;右侧和左侧腮腺平均剂量增加5.6%~45.1%、3.3%~32.2%;脊髓最大剂量变化为-4.1%~13.9%;脑干剂量变化为-3.9%~9.3%。结论 对于采用鼻咽癌调强放射治疗的患者,在不考虑摆位误差的影响因素下,由于靶区及正常组织显著变化等因素影响有重新定位修改计划的必要性。     

兆伏级锥形束CT图像引导放疗所致鼻咽癌患者剂量的探讨

目的 评价和估算兆伏级锥形束CT(MV CBCT)成像系统在图像引导放疗中所致鼻咽癌患者的辐射剂量。方法 选择MV CBCT系统头颈部8 MU扫描预案,利用0.65 cm³指型电离室和CT头部剂量体模测量出体模不同位置的吸收剂量。并利用XiO治疗计划系统模拟MV CBCT扫描过程,计算体模电离室测量点的吸收剂量和鼻咽癌患者肿瘤靶区及危及器官的吸收剂量。结果 体模不同位置吸收剂量的测量值和计算值具有很好的一致性,相对误差均小于3.5%。MV CBCT图像引导放疗所致鼻咽癌患者肿瘤靶区平均剂量为6.43 cGy,脑干、脊髓和视交叉的平均剂量分别为6.36 、6.83和6.90 cGy,左、右视神经平均剂量分别为7.70和7.53 cGy,左、右腮腺平均剂量分别为6.86和6.43 cGy。结论 使用治疗计划系统模拟MV CBCT图像采集过程估算剂量准确、可靠。在设计患者治疗计划时,要充分考虑MV CBCT图像采集过程所致患者剂量。     

简单调强高剂量或常规剂量放射治疗伴淋巴结转移的食管癌疗效分析

目的 探讨简单调强放疗技术(sIMRT)并同期化疗治疗颈段及胸上段食管癌,并予转移淋巴结高剂量放疗的可行性.方法 44例患者随机分为2组,高剂量组20例,常规剂量组24例.对颈及胸上段食管癌的原发灶和预防照射区进行sIMRT计划设计.定义3个靶区:PGTVnd为转移淋巴结靶区,高剂量组患者给予68.1 Gy,每次2.27 Gy,共30次;常规剂量组患者给予60 Gy,每次2.0 Gy,共30次.PTV1为需要加量照射的原发灶靶区,高剂量组给予63.9 Gy,每次2.13 Gy,共30次;常规剂量组60 Gy,每次2.0 Gy,共30次.PTV2为预防照射区,高剂量组和常规剂量组均给予54 Gy,每次1.8 Gy,共30次.放疗中顺铂(DDP)+5-氟尿嘧啶(5-FU)方案第1～5天和第29～33天同期化疗2个周期,放疗结束后28 d原方案重复2个疗程.结果 所有患者均完成了治疗计划,治疗中仅1例发生Ⅲ级放射性气管炎.高剂量组与常规剂量组淋巴结病灶达完全缓解(CR)者分别为75%(15/20)与45.8%(11/24),差异有统计学意义(x2=3.84,P＜0.05);1、2、3年无进展生存率分别为60%、40%、25%和41.7%、25%、8.3%(x2=4.11,P＜0.05);原发病灶近期疗效和1、2、3年生存率差异无统计学意义;不良反应主要为Ⅰ～Ⅱ级白细胞下降.结论 sIMRT计划治疗颈及胸上段食管癌,急性放射反应可耐受,给予转移淋巴结高剂量放疗可以提高患者的无复发生存率.

Abstract：

Objective To investigate the feasibility of simplified intensity-modulated radiotherapy (sIMRT) and concurrent chemotherapy against neck and upper thoracic esophageal carcinoma with lymph node metastasis.Methods sIMRT plans were designed for 44 patients of neck and upper thoracic esophageal carcinoma with lymph node metastasis, 20 of which underwent high dose sIMRT (hsIMRT group) and 24 underwent conventional dose sIM RT (csIMRT group).Three target volumes were defined:PGTVnd, target volume of lymph node lesion, irradiated to 68.1 Gy ( 2.27 Gy × 30 fractions ) for the hsIMRT group, and 60 Gy (2.0 Gy ×30 fractions) the csIMRT group; PTV1, the target volume of primary lesion, to be irradiate to 63.9 Gy (2.13 Gy × 30 fractions) for the hsIMRT group and 60 Gy (2.0 Gy × 30fractions) for the csIMRT group; PTV2 , the prophylacticly irradiated volume, to be irradiated to 54 Gy (1.8 Gy ×30) for both groups.The sIMRT plan included 5 equiangular coplanar beams.All patients received DDP + 5-FU regimen concurrently with radiotherapy at 1 -5 d and 29- 33 d, respectively.Chemotherapy was repeated for two cycles 28 days after the radiotherapy was finished.Results The treatment was completed for all patients within 6 weeks.During the treatment only one patient with grade 3 acute bronchitis was observed in the hsIMRT group.The complete response (CR) rate for the lymph node lesion of the hsIMRT group was 75% ( 15/20 ), significantly higher than that of the csIMRT group [45.8% ( 11/24), x2 = 3.84, P ＜ 0.05].The 1-, 2-, and 3-year progression-free survival rates of the hsIMRT group were 60%, 40%, and 25% , respectively,all significantly higher than those of the csIMRT group (41.7%, 25%, and 8.3% respectively, x2 = 4.11,P ＜ 0.05).However, there were not significant differences in the total survival rate, and the CR and PR of the esophageal lesion between these 2 groups.The major toxicity observed was grade Ⅰ -Ⅱ leukoctyopenia.Conclusions sIMRT generates desirable dose distribution for neck and upper thoracic esophageal carcinoma.hsIMRT has a better short-term efficacy than csIMRT.High dose radiotherapy toward metastatic lymph nodes helps increase progression-free survival.     

鼻咽癌放射治疗定位的CT/MRI图像配准辅助装置的研究

目的 研制用于鼻咽癌放射治疗定位的CT/MRI图像配准辅助装置,并且通过组织勾画差异分析使用该装置后所得配准融合图像在临床中的应用意义。方法 在普通的磁共振头颈线圈中设计特定形状的头枕,保持患者在扫描时与CT定位扫描时相同的体位。采用配对t检验分析CT图像与融合图像中腮腺、下颌骨的勾画差异。结果 患者的头颈部CT、MRI图像的配准精度较未使用该装置的图像具有明显的提高,使用该配准图像得到的融合图像、组织结构位置、细节显示准确清晰。左右腮腺体积在CT图像中较CT/MRI融合图像中偏小,左腮腺体积融合和CT图像中的体积分别为（17.78±6.89）cm³和（17.17±7.02）cm³（t=-2.715,P<0.05）;右腮腺体积融合和CT图像中的体积分别为（19.23±8.91）cm³和（17.47±7.42）cm³（t=-2.552,P<0.05）;下颌骨在CT图像中勾画体积较CT/MRI融合图像偏大,左下颌骨体积融合和CT图像中的体积分别为（33.7±5.59）cm³和（34.8±6.27）cm³（t=3.548,P<0.05）;右下颌骨体积融合和CT图像中的体积分别为（34.46±6.08）cm³和（35.38±6.72）cm³（t=3.14,P<0.05）。结论 使用该辅助装置,可以得到头颈部配准融合准确的CT/ MRI的图像,此融合图像对临床医师的组织和病灶勾画具有积极的参考价值。     

The print-out of CT images and radiation treatment planning data on a laser printer]

We introduce a program for the digital output of CT images with overlaid isodose maps to a laser printer. The high quality prints permit the additional output of treatment planning data on the same sheet.     

influence and improvement of metal artifacts in dental structures by CT for radiation treatment planning: reconstruction of transverse images using oblique images by gantry tilt scanning

Intensity-modulated radiation therapy (IMRT) radiation treatment planning (RTP) requires accuracy. Metal artifacts are one of the factors that influence RTP. The metal artifacts from dental structures are problems at the level of the oropharynx, since these artifacts impair visualization of tumors or lymph nodes and change CT (computed tomography) values. We simulated RTP at the level of the oropharynx using CT images with and without artifacts from dental structures. Gantry tilt scanning was performed to avoid artifacts from dental structures and transverse images reconstructed from oblique images by gantry tilt scanning using a technique of multiplanar reconstruction (MPR) . The reconstructed transverse images were used for the RTP. The reconstructed transverse images were useful to obtain accurate target volumes and the RTP of two opposed equally weighted beams by correct CT values. As dose distribution was changed slightly by the metal artifacts, the use of CT images without artifact is recommended in RTP.     

头颈部肿瘤多层螺旋CT冠状面多平面重建与常规扫描图像的对比研究

目的 分析头颈部肿瘤多层螺旋CT冠状面多平面重建(MPR)与常规扫描图像，探讨冠状面MPR能否替代常规冠状面扫描。方法 使用GE Lightspeed Ultra 8层螺旋CT扫描仪对90例头颈部肿瘤患者进行扫描，在横断面基础上行MPR。由3位资深放射科医生对冠状面MPR像与常规扫描图像进行对比分析。结果 90例冠状面MPR像对正常鼻咽、鼻腔、鼻窦、上颈部等部位软组织的显示与常规扫描冠状面像相似，图像质量好，均为1级。59例(65．6％)冠状面MPR像对骨质的显示优于常规扫描像，68例(75．6％)对颅底孔道的显示优于常规扫描像。增强CT扫描中，51例明显肿瘤病灶，46例(90．2％)对肿瘤的显示优于常规扫描冠状面像。结论 多层螺旋CT扫描MPR图像除对口腔、口咽的显示欠佳外，均近似或优于常规冠状面扫描像，多层螺旋CT扫描的冠状面MPR可以替代常规扫描。     

Feasibility of using post-contrast dual-energy CT for pediatric radiation treatment planning and dose calculation

Objectives:When iodinated contrast is administered during CT simulation, standard practice requires a separate non-contrast CT for dose calculation. The objective of this study is to validate our hypothesis that since iodine affects Hounsfield units (HUs) more than electron density (ED), the information from post-contrast dual-layer CT (DLCT) would be sufficient for accurate dose calculation for both photon and proton therapy.Methods and materials:10 pediatric patients with abdominal tumors underwent DLCT scans before and after iodinated contrast administration for radiotherapy planning. Dose distributions with these DLCT-based methods were compared to those with conventional calibration-curve methods that map HU images to ED and stopping-power ratio (SPR) images.Results:For photon plans, conventional and DLCT approaches based on post-contrast scans underestimated the PTV D99 by 0.87 ± 0.70% (p = 0.18) and 0.36 ± 0.31% (p = 0.34), respectively, comparing to their non-contrast optimization plans. Renal iodine concentration was weakly associated with D99 deviation for both conventional (R² = 0.10) and DLCT (R² = 0.02) approaches. For proton plans, the clinical target volume D99 errors were 3.67 ± 2.43% (p = 0.0001) and 0.30 ± 0.25% (p = 0.40) for conventional and DLCT approaches, respectively. The proton beam range changed noticeably with the conventional approach. Renal iodine concentration was highly associated with D99 deviation for the conventional approach (R² = 0.83) but not for DLCT (R² = 0.007).Conclusion:Conventional CT with iodine contrast resulted in a large dosimetric error for proton therapy, compared to true non-contrast plans, but the error was less for photon therapy. These errors can be greatly reduced in the case of the proton plans if DLCT is used, raising the possibility of using only a single post-contrast CT for radiotherapy dose calculation, thus reducing the time and imaging dose required.Advances in knowledge:This study is the first to compare directly the differences in the calculated dose distributions between pre- and post-contrast CT images generated by single-energy CT and dual-energy CT methods for photon and proton therapy.     

Cyberknife stereotactic radiosurgery and radiation therapy treatment planning system

CyberKnife is an image-guided stereotactical dose delivery system designed for both focal irradiation and radiation therapy (SRT). Focal irradiation refers the use of many small beams to deliver highly focus dose to a small target region in a few fractions. The system consists of a 6-MV linac mounted to a robotic arm, coupled with a digital x-ray imaging system. The radiation dose is delivered using many beams oriented at a number of defined or nodal positions around the patients. The CyberKnife can be used for both intracranial and extracranial treaments unlike the Gamma Knife which is limited to intracranial cases. Multiplan (Accuray Inc., Sunnyvale, CA) is the treatment planning system developed to cooperate with this accurate and versatile SRS and SRT system, and exploit the full function of Cyberknife in high-precision radiosurgery and therapy. Optimized inverse treatment plan can be achieved by fine-tuning contours and planning parameters. Precision is the newest version of Cyberknife treatment planning system (TPS) and an upgrade to Multiplan. It offers several new features such as Monte Carlo for multileaf collimator (MLC) and retreatment for other modalities that added more support for the Cyberknife system. The Cybeknife TPS is an easy-to-use and versatile inverse planning platform, suitable for stereotactic radiosurgery and radiation therapy. The knowledge and experience of the planner in this TPS is essential to improve the quality of patient care.     

Further progress in CT scanning and computerized radiation therapy treatment planning.

Total body computed tomography has introduced a unique method of obtaining body contours as well as anatomical representations for radiation therapy treatment planning. CT scanning combined with computerized radiation therapy treatment planning has improved accuracy and contributed greatly to the solution of complex treatment problems. CT scans can also be used to evaluate the progress of patients undergoing radiation therapy.     

Study of optimal imaging parameters for digitally reconstructed radiographs (DRR) in radiotherapy treatment planning using single-slice helical CT

In recent years, by making digitally reconstructed radiographs (DRR) from helical CT images in the position check of an irradiation field, the verification performed by DRR, lineacgraphy (LG), or an electronic portal imaging device (EPID) has become possible. We examined the optimal parameters of single-slice helical scanning in DRR image construction and the usefulness of DRR replaced with the simulation film. We performed a section sensitivity profile at the Z-axis (SSPz) as evaluation of a physical characteristic of helical CT equipment and the form of image of DRR, fixed quantity evaluation of imaging distortion, and visual verification of images. It was determined that DRR was influenced by the partial volume effect depending on slice thickness and pitch, such that this influence occurred when slice thickness and pitch were large. Between a simulation film and DRR reconstructed using imaging parameters with a slice thickness of 3 mm, pitch of 1.0, and reconstruction slice thickness of 3 mm, coincidence was not complete. However, the distortion of DRR was small and the difference was not statistically; thus it was considered to be useful. In conclusion, we consider that DRR reconstructed using the parameters of single-slice helical scanning is useful for clinical evaluation in radiotherapy planning.     

A dosimetric comparative study: Volumetric modulated arc therapy vs intensity-modulated radiation therapy in the treatment of nasal cavity carcinomas

The purpose of this study was to evaluate the differences between volumetric modulated arc therapy (VMAT) and intensity-modulated radiation therapy (IMRT) in the treatment of nasal cavity carcinomas. The treatment of 10 patients, who had completed IMRT treatment for resected tumors of the nasal cavity, was replanned with the Philips Pinnacle³ Version 9 treatment-planning system. The IMRT plans used a 9-beam technique whereas the VMAT (known as SmartArc) plans used a 3-arc technique. Both types of plans were optimized using Philips Pinnacle³ Direct Machine Parameter Optimization algorithm. IMRT and VMAT plans' quality was compared by evaluating the maximum, minimum, and mean doses to the target volumes and organs at risk, monitor units (MUs), and the treatment delivery time. Our results indicate that VMAT is capable of greatly reducing treatment delivery time and MUs compared with IMRT. The reduction of treatment delivery time and MUs can decrease the effects of intrafractional uncertainties that can occur because of patient movement during treatment delivery. VMAT's plans further reduce doses to critical structures that are in close proximity to the target volume.