保乳术后固定野动态调强与容积调强放疗的剂量学比较

目的 比较早期乳腺癌保乳术后固定野动态调强与容积调强放疗治疗靶区和危及器官的剂量学差异.方法 20例左侧乳腺癌患者(均女性,24～75岁)保乳术后接受放疗,在同一患者CT影像上分别进行2野共面动态调强和容积调强(RapidArc)两种治疗计划设计.在剂量-体积直方图中读取两种计划的靶区剂量分布参数,心脏、双侧肺及对侧乳腺受照剂量和体积,对各参数的均数进行比较;并比较两者平均机器跳数和平均治疗时间的差异.结果 RapidArc较IMRT计划CTV V95%增加了0.65%(t=5.16,P=0.001),V105%下降了10.96%(t=-2.05,P=0.055),V110%下降了1.48%(t=-1.33,P=0.197).RapidArc计划的适形指数(CI)和均匀性指数(HI)均优于IMRT治疗计划,分别为0.88±0.02 vs 0.74±0.03(t=18.54,P＜0.001),1.11±0.01 Vs 1.12±0.02(t=-2.44,P=0.025).两种计划中左肺V20和Dmax比较差异无统计学意义,但在RapidArc计划中V10、V5、Dmix、Dmean明显增高,V5增高了接近30%.心脏V30和Dmax在两计划中无明显差异,而RapidArc计划的V10增加了18%,V5增加50%.RapidArc计划的右乳V5和右肺V5较IMRT分别增加了9.33%(t=9.31,P＜0.001)和3.04%(t=5.64,P＜0.001).RapidArc和IMRT平均机器跳数分别是608和437 MU(t=10.86,P＜0.001),平均治疗时间111.3和103.6 s(t=3.57,P=0.002).结论 早期乳腺癌保乳术后全乳腺RapidAre放疗与2野动态调强放疗相比,能明显改善靶区剂量分布均匀性.对于危及器官,高剂量区两种治疗计划之间无明显差异,低剂量区RapidArc的照射范围明显增加.与2野动态调强相比,RapidArc放疗机器跳数增加,治疗时间延长.

Abstract：

Objective To compare the dosimetric difference between volumetric are modulation with RapidArc and fixed field dynamic IMRT for breast cancer radiotherapy after breast-conserving surgery.Methods Twenty patients with early left-sided breast cancer received radiotherapy after breast-conserving surgery.After target definition,treatment planning was performed by RapidAre and two fixed fields dynamic IMRT respectively on the same CT scan.The target dose distribution,homogeneity of the breast,and the irradiation dose and volume for the lungs,heart,and eontralateral breast were read in the dosevolume histogram (DVH) and compared between RapidAre and IMRT.The treatment delivery time and monitor units were also compared.Results In comparison with the IMRT planning,the homogeneity of clinical target volume (CTV) ,the volume proportion of 95% prescribed dose (V95%) was significantly higher by 0.65% in RapidAre (t =5.16,P = 0.001) ,and the V105% and V110% were lower by 10.96% and 1.48 % respectively,however,without statistical significance (t =-2.05 ,P =0.055 and t =-1.33 ,P =0.197).The conformal index of planning target volume (PTV) by the Rap~dAre planning was (0.88±0.02),significantly higher than that by the IMRT planning [(0.74±0.03),t = 18.54,P < 0.001].The homogeneity index (HI) of PTV by the RapidArc planning was 1.11±0.01,significantly lower than that by the IMRT planning (1.12±0.02,t =-2.44,P =0.02).There were no significant differences in the maximum dose (Dmax) and V20 for the ipsilateral lung between the RapidArc and IMRT planning,but the values of V10,V5 ,Dmin and Dmean by RapidArc planning were all significantly higher than those by the IMRT planning (all P < 0.01).The values of max dose and V30 for the heart were similar by both techniques,but the values of V10 and V5 by the RapidArc planning were significantly higher (by 18% and 50% ,respectively).The V5 of the contralateral breast and lung by the RapidArc planning were increased by 9.33% and 3.04% respectively compared to the IMRT planning.The mean MU of the RapidArc was 608 MU,significantly higher than that by the IMRT planning (437 MU,t = 10.86,P < 0.001).The treatment time by the RapidArc planning was 111.3 s,significantly longer than that by IMRT planning (103.6 s,t = 3.57,P = 0.002).Conclusions The RapidArc planning improves the dose distribution of CTV and homogeneity of PTV for breast cancer radiotherapy after breast-conserving surgery.However,it significantly enlarges the volume of normal tissues irradiated in low dose areas,prolongs the treatment delivery time,and increases the MU value in comparison with IMRT.     

RapidArc radiotherapy planning for prostate cancer: Single-arc and double-arc techniques vs. intensity-modulated radiotherapy

RapidArc is a novel technique using arc radiotherapy aiming to achieve intensity-modulated radiotherapy (IMRT)-quality radiotherapy plans with shorter treatment time. This study compared the dosimetric quality and treatment efficiency of single-arc (SA) vs. double-arc (DA) and IMRT in the treatment of prostate cancer. Fourteen patients were included in the analysis. The planning target volume (PTV), which contained the prostate gland and proximal seminal vesicles, received 76 Gy in 38 fractions. Seven-field IMRT, SA, and DA plans were generated for each patient. Dosimetric quality in terms of the minimum PTV dose, PTV hotspot, inhomogeneity, and conformity index; and sparing of rectum, bladder, and femoral heads as measured by V70, V-40, and V20 (% of volume receiving >70 Gy, 40 Gy, and 20 Gy, respectively), treatment efficiency as assessed by monitor units (MU) and treatment time were compared. All plan objectives were met satisfactorily by all techniques. DA achieved the best dosimetric quality with the highest minimum PTV dose, lowest hotspot, and the best homogeneity and conformity. It was also more efficient than IMRT. SA achieved the highest treatment efficiency with the lowest MU and shortest treatment time. The mean treatment time for a 2-Gy fraction was 4.80 min, 2.78 min, and 1.30 min for IMRT, DA, and SA, respectively. However, SA also resulted in the highest rectal dose. DA could improve target volume coverage and reduce treatment time and MU while maintaining equivalent normal tissue sparing when compared with IMRT. SA achieved the greatest treatment efficiency but with the highest rectal dose, which was nonetheless within tolerable limits. For busy units with high patient throughput, SA could be an acceptable option.     

容积旋转调强与固定野动态调强在宫颈癌术后放疗的剂量学比较

目的 比较容积旋转调强（RapidArc）与固定野动态调强（IMRT）两种宫颈癌术后放疗的剂量学参数及急性不良反应发生率,为临床治疗技术的选择提供参考依据。方法 选取35例宫颈癌术后盆腔预防放疗患者,其中,17例接受RapidArc,18例接受IMRT,处方剂量50 Gy,共25次。比较两组治疗计划的剂量-体积直方图（DVH）、靶区剂量适形度、均匀性、靶区及危及器官的剂量、机器跳数及治疗时间;对比两组患者治疗期间的急性肠道及膀胱反应发生率。结果 与IMRT相比,RapidArc靶区剂量适形度较高（t=3.13,P<0.05）,但均匀性略低（t=-4.25,P<0.05）;RapidArc计划中股骨头V₂₀、V₃₀均低于IMRT（t=2.56、2.34,P<0.05）;RapidArc计划机器跳数减少了52.1%,治疗所需时间缩短了46.8%。两组患者肠道、膀胱急性不良反应发生率相近。结论 对于宫颈癌术后盆腔预防放疗患者,采用RapidArc或IMRT技术均可达到靶区的剂量要求及保护危及器官的目的。RapidArc计划靶区剂量学参数、急性不良反应发生率与IMRT计划比较未见明显优势,但机器跳数与出束时间明显优于IMRT计划,实现了治疗效率的大幅提高。     

旋转调强与固定野调强治疗肝癌的剂量学比较

目的 比较旋转调强(RapidArc)与固定野调强放疗(IMRT)在肝癌治疗计划中的剂量学差异。方法 选择10例肝癌患者的CT数据,分别设计IMRT计划与单弧(RA1)和双弧(RA2)计划,比较设计计划的靶区剂量分布、危及器官受量、正常组织受量、机器跳数以及治疗时间。结果 RA1和RA2计划靶区剂量的最大值都低于IMRT(Z=-2.090、-2.666,P＜0.05),计划90%的处方剂量的适形指数低于IMRT(Z=-2.805、-2.809,P＜0.05);危及器官胃与小肠的V40也比IMRT计划低。但IMRT左肾平均剂量低于RapidArc计划组(Z=-1.988、-2.191,P＜0.05);正常组织的V₅、V₁₀和V₁₅IMRT计划低于RapidArc计划组,V20、V25和V30IMRT计划高于RapidArc计划组。RapidArc计划机器跳数是IMRT计划的40%和46%,治疗时间是IMRT计划30%和40%。结论 两种技术设计的计划剂量分布均能满足临床要求,并且剂量分布基本一致。RapidArc计划的适形指数优于IMRT,危及器官剂量也比IMRT计划略有降低,正常组织的低剂量区RapidArc计划组与IMRT相比有先高后低的趋势,并且机器跳数少,治疗时间短。     

The use of RapidArc volumetric-modulated arc therapy to deliver stereotactic radiosurgery and stereotactic body radiotherapy to intracranial and extracranial targets

Twenty-three targets in 16 patients treated with stereotactic radiosurgery (SRS) or stereotactic body radiotherapy (SBRT) were analyzed in terms of dosimetric homogeneity, target conformity, organ-at-risk (OAR) sparing, monitor unit (MU) usage, and beam-on time per fraction using RapidArc volumetric-modulated arc therapy (VMAT) vs. multifield sliding-window intensity-modulated radiation therapy (IMRT). Patients underwent computed tomography simulation with site-specific immobilization. Magnetic resonance imaging fusion and optical tracking were incorporated as clinically indicated. Treatment planning was performed using Eclipse v8.6 to generate sliding-window IMRT and 1-arc and 2-arc RapidArc plans. Dosimetric parameters used for target analysis were RTOG conformity index (CI_RTOG), homogeneity index (HI_RTOG), inverse Paddick Conformity Index (PCI), D_mean and D5–D95. OAR sparing was analyzed in terms of D_max and D_mean. Treatment delivery was evaluated based on measured beam-on times delivered on a Varian Trilogy linear accelerator and recorded MU values. Dosimetric conformity, homogeneity, and OAR sparing were comparable between IMRT, 1-arc RapidArc and 2-arc RapidArc plans. Mean beam-on times ± SD for IMRT and 1-arc and 2-arc treatments were 10.5 ± 7.3, 2.6 ± 1.6, and 3.0 ± 1.1 minutes, respectively. Mean MUs were 3041, 1774, and 1676 for IMRT, 1-, and 2-arc plans, respectively. Although dosimetric conformity, homogeneity, and OAR sparing were similar between these techniques, SRS and SBRT fractions treated with RapidArc were delivered with substantially less beam-on time and fewer MUs than IMRT. The rapid delivery of SRS and SBRT with RapidArc improved workflow on the linac with these otherwise time-consuming treatments and limited the potential for intrafraction organ and patient motion, which can cause significant dosimetric errors. These clinically important advantages make image-guided RapidArc useful in the delivery of SRS and SBRT to intracranial and extracranial targets.     

容积旋转调强与固定野调强在晚期宫颈癌放疗的剂量学比较及疗效观察

目的 比较容积旋转调强（RapidArc）和固定野调强（IMRT）技术在宫颈癌根治性放疗的剂量学参数、急性不良反应发生率及疗效。方法 回顾性分析43例局部晚期（II_b~IV）宫颈癌患者,其中22例行容积旋转调强放疗,21例行固定野调强放疗,处方剂量50.4 Gy/28次,比较两组靶区剂量适形度、均匀性、靶区及危及器官的剂量、机器跳数及治疗时间;对比两组患者治疗期间的急性肠道及膀胱反应发生率;对比两组患者的完全缓解率和有效率。结果 与IMRT计划相比,RapidArc计划的靶区适形性指数CI略好,但差异无统计学意义（P > 0.05）;两组计划的靶区均匀性指数HI比较,差异无统计学意义（P > 0.05）。RapidArc计划中膀胱的V₄₀、V₅₀以及直肠的V₃₀、V₄₀、V₅₀均低于IMRT计划（t=-2.386、-2.397、-5.525、-2.883、-2.686,P < 0.05）,RapidArc计划中股骨头的平均剂量低于IMRT计划（t=-2.395,P < 0.05）。RapidArc较IMRT平均MU减少了53.15%,治疗所需平均时间缩短了62.14%。两组患者肠道、膀胱急性反应发生率相近。两组患者完全缓解率和有效率相近。结论 晚期宫颈癌根治性放疗中,采用RapidArc技术可以降低危及器官受量,缩短患者的治疗时间。     

Dosimetric Comparison of RapidArc with Fixed Gantry Intensity-Modulated Radiotherapy Treatment for Multiple Liver Metastases Radiotherapy

We wanted to compare the dosimetric difference and treatment efficiency of RapidArc and fixed gantry intensity-modulated radiotherapy treatment (IMRT) for multiple liver metastases. Computed tomography datasets of 10 patients were studied retrospectively. IMRT plans were generated using 5 fields and RapidArc using either 1 or 2 arcs. The dose distribution of planning target volume (PTV), organs at risk (OARs), and the normal tissue were compared. Monitor units and treatment time were scored to measure expected treatment efficiency. Both RapidArc and IMRT plans resulted in equivalent target coverage. There was no statistically significant difference for the maximum and the minimum dose of PTV. RapidArc plans achieved an improved conformity index compared with IMRT (RA1 = 1.68 ± 0.27, RA2 = 1.61 ± 0.25, IMRT = 1.80 ± 0.37). For OARs, all techniques respected planning objectives. RapidArc plans had a lower dose in V₄₀ of small bowel than IMRT, but were higher in mean dose of kidneys. Concerning the V₅, V₁₀, and V₁₅ of healthy tissue, RapidArc plans were higher than IMRT. However, the V₂₀, V₂₅, and V₃₀ of healthy tissue in RapidArc plans were lower than IMRT. Monitor units per fraction of RapidArc plans were about 40% or 46% of IMRT. Compared with IMRT plans, treatment time of RapidArc plans were reduced by 60% or 70%. All techniques respected planning objectives. RapidArc showed statistical improvements in conformity index and healthy tissue sparing with uncompromised target coverage. This, in combination with fewer monitor units and short delivery time, can lead to clinically significant advances for the treatment of multiple liver metastases.     

Comparative evaluation of treatment plan quality for a prototype biology-guided radiotherapy system in the treatment of nasopharyngeal carcinoma

We aimed to compare prototype treatment plans for a new biology-guided radiotherapy (BgRT) machine in its intensity-modulated radiation therapy (IMRT) mode with those using existing IMRT delivery techniques in treatment of nasopharyngeal carcinoma (NPC). We retrospectively selected ten previous NPC patients treated in 33 fractions according to the NRG-HN001 treatment protocol. Three treatment plans were generated for each patient: a helical tomotherapy (HT) plan with a 2.5-cm jaw, a volumetric modulated arc therapy (VMAT) plan using 2 to 4 6-MV arc fields, and a prototype IMRT plan for a new BgRT system which uses a 6-MV photon beam on a ring gantry that rotates at 60 rotations per minute with a couch that moves in small incremental steps. Treatment plans were compared using dosimetric parameters to planning target volumes (PTVs) and organs at risk (OARs) as specified by the NRG-HN001 protocol. Plans for the three modalities had comparable dose coverage, mean dose, and dose heterogeneity to the primary PTV, while the prototype IMRT plans had greater dose heterogeneity to the non-primary PTVs, with the average homogeneity index ranging from 1.28 to 1.50 in the prototype plans. Six of all the 7 OAR mean dose parameters were lower with statistical significance in the prototype plans compared to the HT and VMAT plans with the other mean dose parameter being comparable, and all the 18 OAR maximum dose parameters were comparable or lower with statistical significance in the prototype plans. The average left and right parotid mean doses in the prototype plans were 10.5 Gy and 10.4 Gy lower than those in the HT plans, respectively, and were 5.1 Gy and 5.2 Gy lower than those in the VMAT plans, respectively. Compared to that with the HT and VMAT plans, the treatment time was longer with statistical significance with the prototype IMRT plans. Based on dosimetric comparison of ten NPC cases, the prototype IMRT plans achieved comparable or better critical organ sparing compared to the HT and VMAT plans for definitive NPC radiotherapy. However, there was higher dose heterogeneity to non-primary targets and longer estimated treatment time with the prototype plans.     

Effect of beam arrangement on oral cavity dose in external beam radiotherapy of nasopharyngeal carcinoma

This study compared the oral cavity dose between the routine 7-beam intensity-modulated radiotherapy (IMRT) beam arrangement and 2 other 7-beam IMRT with the conventional radiotherapy beam arrangements in the treatment of nasopharyngeal carcinoma (NPC). Ten NPC patients treated by the 7-beam routine IMRT technique (IMRT-7R) between April 2009 and June 2009 were recruited. Using the same computed tomography data, target information, and dose constraints for all the contoured structures, 2 IMRT plans with alternative beam arrangements (IMRT-7M and IMRT-7P) by avoiding the anterior facial beam and 1 conventional radiotherapy plan (CONRT) were computed using the Pinnacle treatment planning system. Dose-volume histograms were generated for the planning target volumes (PTVs) and oral cavity from which the dose parameters and the conformity index of the PTV were recorded for dosimetric comparisons among the plans with different beam arrangements. The dose distributions to the PTVs were similar among the 3 IMRT beam arrangements, whereas the differences were significant between IMRT-7R and CONRT plans. For the oral cavity dose, the 3 IMRT beam arrangements did not show significant difference. Compared with IMRT-7R, CONRT plan showed a significantly lower mean dose, V30 and V-40, whereas the V-60 was significantly higher. The 2 suggested alternative beam arrangements did not significantly reduce the oral cavity dose. The impact of varying the beam angles in IMRT of NPC did not give noticeable effect on the target and oral cavity. Compared with IMRT, the 2-D conventional radiotherapy irradiated a greater high-dose volume in the oral cavity.     

中心型肺癌快速旋转调强与固定射野动态调强放疗的剂量学比较

目的 比较快速旋转调强(RapidArc)与固定射野动态调强(dIMRT)两种调强放疗技术在中心型肺癌治疗计划中的剂量学差异。方法 利用瓦里安(Varian)计划系统(Eclipse 8.6)随机选取10例已行dIMRT治疗的中心型肺癌患者,采用容积调强(volumetric modulated arc therapy,VMAT)治疗技术设计RapidArc调强放疗计划。在满足靶区处方剂量要求(95%体积的PTV达到66 Gy)的情况下,通过剂量体积直方图DVH评价和比较两种类型治疗计划的PTV最大剂量 D_max、最小剂量 D _min和平均剂量 D_mean以及适形指数CI,危及器官的脊髓最大剂量 D _max,双肺的 V₅、V ₁₀、 V₂₀、 V₃₀,心脏 V₃₀,食管 V₅₀、V₆₀和平均剂量 D_mean,并比较两种治疗计划的总机器跳数(MU)和治疗时间。结果 在中心型肺癌治疗计划中,与dIMRT相比较,RapidArc靶区的 D _max、 D_min和 D_mean略有升高,但统计学差异无意义( P >0.05), 适形指数CI优于dIMRT,且差异具有统计学意义(t=-4.968,P=0.001)。双肺的 V₅、V₁₀有所上升, V₂₀、 V₃₀有所下降;心脏 V₃₀受照射体积也有不同程度降低,差异均具有统计学意义。RapidArc总MU减少32%,治疗时间为dIMRT的1/3。结论 两种治疗技术所设计的治疗计划剂量分布均能满足临床治疗需要。RapidArc靶区适形度更高,实际治疗时间明显缩短,同时MU的降低减少了治疗区域正常组织的不必要照射。     

三维适形、逆向调强和旋转调强放疗技术治疗胸段食管癌的剂量学比较

目的 比较胸段食管癌3种放疗技术( 3D-CRT、IMRT、RapidArc)的剂量学特点,并分析3种技术的优劣及应用特点.方法 15例胸段食管癌患者入组,依据CT图像,勾画靶区,针对患者的同一套CT图像的相同靶区分别制定3D-CRT、5野IMRT(IMRT5)、7野IMRT( IMRT7)、9野IMRT(IMRT9)、单弧Arc( Arc1)、双弧Arc( Arc2)共6套计划.PTV处方剂量为40 Gy分20次4周+19.6 Gy分14次7d.结果 3D-CRT计划各项靶区剂量学参数明显差于IMRT计划及RapidArc计划(t=5.77、3.52,P＜0.05),6套计划的PTV V95(％)分别为:3D-CRT (91.55 ±2.90),IMRT5(96.66±1.05),IMRT7 (96.87±1.23),IMRT (96.81±1.16),Arcl (94.98±1.41),Arc2 (95.93±1.32).RapidArc计划的靶区适形度(CI)最好(t=3.76,10.01,P＜0.05),IMRT计划的靶区均匀性(HI)最好(t =3.93、3.37,P＜0.05).危及器官参数RapidArc与IMRT各计划之间差异无统计学意义.3D-CRT和RapidArc计划的机器跳数明显少于IMRT计划,差异高达75％.结论 对于胸段食管癌患者,采用IMRT或RapidArc技术可以在保护正常组织的同时,涵盖临床必需的治疗靶区.3D-CRT计划对降低正常组织低剂量散射区方面优势明显.RapidArc计划靶区剂量学参数与IMRT计划比较未见明显优势.     

Single-arc volumetric-modulated arc therapy (sVMAT) as adjuvant treatment for gastric cancer: Dosimetric comparisons with three-dimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT)

To compare the dosimetric differences between the single-arc volumetric-modulated arc therapy (sVMAT), 3-dimensional conformal radiotherapy (3D-CRT), and intensity-modulated radiotherapy (IMRT) techniques in treatment planning for gastric cancer as adjuvant radiotherapy. Twelve patients were retrospectively analyzed. In each patient's case, the parameters were compared based on the dose-volume histogram (DVH) of the sVMAT, 3D-CRT, and IMRT plans, respectively. Three techniques showed similar target dose coverage. The maximum and mean doses of the target were significantly higher in the sVMAT plans than that in 3D-CRT plans and in the 3D-CRT/IMRT plans, respectively, but these differences were clinically acceptable. The IMRT and sVMAT plans successfully achieved better target dose conformity, reduced the V_20/30, and mean dose of the left kidney, as well as the V_20/30 of the liver, compared with the 3D-CRT plans. And the sVMAT technique reduced the V₂₀ of the liver much significantly. Although the maximum dose of the spinal cord were much higher in the IMRT and sVMAT plans, respectively (mean 36.4 vs 39.5 and 40.6 Gy), these data were still under the constraints. Not much difference was found in the analysis of the parameters of the right kidney, intestine, and heart. The IMRT and sVMAT plans achieved similar dose distribution to the target, but superior to the 3D-CRT plans, in adjuvant radiotherapy for gastric cancer. The sVMAT technique improved the dose sparings of the left kidney and liver, compared with the 3D-CRT technique, but showed few dosimetric advantages over the IMRT technique. Studies are warranted to evaluate the clinical benefits of the VMAT treatment for patients with gastric cancer after surgery in the future.     

快速旋转调强与五野动态调强在乳腺癌 保乳术后放疗中的剂量学比较

目的 比较乳腺癌保乳术后RapidArc计划与五野动态调强(5F-IMRT)计划的剂量学差异。方法 选择8例左侧乳腺癌保乳术后女性患者,处方剂量为50 Gy/ 25次。分别设计RapidArc计划与5F-IMRT计划。比较两种计划的靶区适形度指数、均匀性指数、靶区覆盖度和危及器官的受照剂量体积,同时比较两组计划实施时的治疗时间和机器跳数。结果 在两种计划的靶区比较中,RapidArc计划的靶区适形度指数为(0.88±0.03),高于5F-IMRT计划的(0.79±0.02)(t=8.28,P<0.05);RapidArc计划的均匀性指数为(9.01±0.73),优于5F-IMRT计划的(10.44±1.08)(t=-2.73,P<0.05)。两组计划在同侧肺受照剂量体积比较中RapidArc计划的D_mean、V₁₀、V₂₀、V₃₀小于5F-IMRT计划(t=-7.53、-7.20、-8.39、-7.80,P<0.05),但RapidArc计划中的V₅较5F-IMRT计划增加了约16% (t=5.67,P<0.05);心脏的受照剂量体积比较中RapidArc计划中的D_mean、V₅、V₁₀均高于5F-IMRT(t=10.46、28.76、5.40,P<0.05),但在RapidArc计划中心脏的V₃₀低于5F-IMRT (t=-6.12,P<0.05)。对侧肺和对侧乳腺的V₅在RapidArc计划中明显高于5F-IMRT计划 (肺:t=21.50,P<0.05;乳腺:t=5.44,P<0.05)。RapidArc计划中机器跳数减少了25%,平均治疗时间节省了60%。结论 乳腺癌保乳术后RapidArc计划与5F-IMRT计划比较提高了靶区的适形度和均匀度,减少了高剂量区的受照体积,降低了机器跳数,缩短了治疗时间,但增加了正常组织低剂量区的受照体积。     

快速旋转调强与固定射野动态调强在直肠癌术前放疗中的剂量学比较

目的 比较快速旋转调强(RapidArc)与固定射野动态调强(dIMRT)两种放射治疗技术在直肠癌术前放疗中的剂量学差异.方法 采用两种治疗技术对10例Ⅱ、Ⅲ期直肠癌术前患者设计同步加量治疗计划.处方剂量为GTV 50.6 Gy,分22次;PTV41.8 Gy,分22次,危及器官限量参考临床常规要求.在95%体积的PTV达到处方剂量前提下,比较两种计划的剂量体积直方(DVH)图、靶区和危及器官剂量、靶区剂量适形度、剂量分布均匀性、机器跳数以及治疗时间.结果 RapidArc计划中,GTV和PTV的靶区剂量适形度较高(t=7.643、8.226,P＜0.05);而靶区剂量均匀性略低于dIMRT(t=-10.065、-4.235,P＜0.05).RapidArc计划中大、小肠的平均受量显著低于dIMRT计划(t=2.781,P＜0.05).膀胱平均受照剂量略低于dIMRT,股骨头的平均受量略高于dIMRT,但差异无统计学意义.RapidArc计划机器跳数减少48.5%,平均治疗时间节省79.5%.结论 RapidArc与dIMRT计划在直肠癌术前放射治疗的剂量学上无明显差异.RapidArc每次治疗时间明显缩短,减少了治疗期间患者非主观运动引起的误差,总的机器跳数降低,减少了正常组织照射.

Abstract：

Objective To compare the dosimetric difference between RapidArc and fixed gantry angle dynamic intensity modulated radiotherapy (dIMRT) in developing the pre-operative radiotherapy for rectal cancer patients.Methods Two techniques,RapidArc and dIMRT,were used respectively to develop the synchronous intensity modulated plans for 10 stage Ⅱ and Ⅲ rectal cancer patients at the dose of gross tumor volume (GTV) of 50.6 Gy divided into 22 fractions and planning target volume (PTV) of 41.8 Gy divided into 22 fractions.Both plans satisfied the condition of 95% of PTV covered by 41.8 Gy.The dose-volume histogram data,isodose distribution,monitor units,and treatment time were compared.Results The two kinds of dose volume histogram (DVH) developed by these two techniques were almost the same.The conformal indexes of GTV and PTV by RapidArc were better than those by dIMRT (t =7.643,8.226 ,P < 0.05),while the homogeneity of target volume by dIMRT was better (t =-10.065,-4.235 ,P <0.05).The dose of rectum and small bowel planned by RapidArc was significantly lower than that by dIMRT (t =2.781 ,P <0.05).There were no significant differences in the mean doses of bladder and femoral head between these two techniques.The mean monitor units of RapidArc was 475.5,fewer by 48.5% in comparison with that by the dIMRT (924.6).The treatment mean time by RapidArc was 1.2min,shorter by 79.5% in comparison with that by dIMRT (5.58 min).Conclusions There is no significant dosimetric difference between the two plans of RapidArc and dIMRT.Compared with dIMRT,RapidArc achieves equal target coverage and organs at risk(OAR) sparing while using fewer monitor units and less time during radiotherapy for patient with rectal cancer.     

A dosimetric comparison of RapidArc and IMRT with hypofractionated simultaneous integrated boost to the prostate for treatment of prostate cancer

Objective:

To compare the dosimetric results and treatment delivery efficiency among RapidArc® (Varian Medical Systems, Palo Alto, CA), 7-field intensity-modulated radiotherapy (7-f IMRT) and 9-field IMRT (9-f IMRT) with hypofractionated simultaneous integrated boost to the prostate.

Methods:

RapidArc, 7-f IMRT and 9-f IMRT plans were created for 21 consecutive patients treated for high-risk prostate cancer using the Eclipse™ treatment planning system (Varian Medical Systems). All plans were designed to deliver 70.0 Gy in 28 fractions to the prostate planning target volume (PTV) while simultaneously delivering 50.4 Gy in 28 fractions to the pelvic nodal PTV. Target coverage and sparing of organs at risk (OARs) were compared across techniques. The total number of monitor units (MUs) and the treatment time were used to assess treatment delivery efficiency.

Results:

RapidArc resulted in slightly superior conformity and homogeneity of prostate PTV, whereas all plans were comparable with respect to dose to the nodal PTV. Although OARs sparing for RapidArc and 7-f IMRT plans were almost equivalent, 9-f IMRT achieved better sparing of the rectum and bladder than RapidArc and 7-f IMRT. RapidArc provided the highest treatment delivery efficiency with the lowest MUs and shortest treatment time.

Conclusion:

RapidArc resulted in similar OAR sparing to 7-f IMRT, whereas 9-f IMRT provided the best OAR sparing. Treatment delivery efficiency is significantly higher for RapidArc.

Advances in knowledge:

This study validated the feasibility and limitations of RapidArc in the treatment of high-risk prostate cancer with complex pelvic target volumes.Radiotherapy has played an important role in the treatment of locally advanced prostate cancer. Several randomised controlled trials have demonstrated that high-dose radiotherapy improves prostate-specific antigen control, and a recently published meta-analysis [1] showed that high-dose radiotherapy is superior to conventional-dose radiotherapy in preventing biochemical or clinical failure and prostate cancer-specific death. However, dose escalation has been limited by toxicity in conventional techniques. Therefore, prostate cancer is one of the most common tumour sites treated with intensity-modulated radiation therapy (IMRT), which enables the delivery of highly conformal dose distribution to the target while reducing the dose to critical organs. IMRT also has the ability to produce inhomogeneous dose distribution, which allows for simultaneous differential dose delivery to multiple tumour targets (simultaneous integrated boost). Despite the obvious benefits of IMRT, there are some disadvantages. The potential downsides of IMRT include the increased time required for radiotherapy delivery and increased monitor units (MUs) needed compared with conventional three-dimensional conformal radiation therapy.Volumetric-modulated arc therapy (VMAT) is a relatively new rotational radiation therapy technique based on the idea of delivering IMRT with continuous dynamic modulation of the dose rate, field aperture and gantry speed. Compared with IMRT, the potential benefit of VMAT is the increase in delivery efficiency, including a shorter treatment time and a lower number of MUs.Several recent studies have compared VMAT with IMRT for prostate radiotherapy [2–13]. Although shortened treatment time is a common finding, there are inconsistencies in the dosimetric outcome. Many studies considering relatively simple target volumes that included prostate only or prostate with seminal vesicles found that VMAT achieved equal or better normal tissue sparing over IMRT [2,3,5,6,8–10,12]. However, very few studies have focused on more complex pelvic target volumes, including the prostate, seminal vesicles and pelvic lymph nodes [4,7,11,13]. Some of these studies found largely equivalent sparing of organs at risk (OARs) between VMAT and IMRT [7,13]. However, other planning studies have reported contradictory results. Yoo et al [4] noted superior OARs sparing with IMRT to VMAT. Myrehaug et al [11] found VMAT to have no consistent dosimetric advantage over IMRT. Thus, those studies have yielded mixed results. Our study aims to expand such studies to quantitatively evaluate VMAT for prostate cancer cases with complex pelvic target volumes and simultaneous integrated boost techniques.RapidArc® is one of the VMAT techniques implementing the progressive resolution optimisation algorithm in the Eclipse™ planning system by Varian Medical Systems (Palo Alto, CA). In the present study, we compare the performance of RapidArc, 7-field IMRT (7-f IMRT) and 9-field IMRT (9-f IMRT) with hypofractionated simultaneous integrated boost to the prostate for patients with high-risk prostate cancer. This study focused on the evaluation of the dosimetric results and treatment delivery efficiency.     

Comparison of IMRT and VMAT plans with different energy levels using Monte-Carlo algorithm for prostate cancer

Purpose

To make dosimetric comparisons of volumetric-modulated arc therapy (VMAT) and 7-field intensity-modulated radiotherapy (IMRT) with dynamic MLCs using the Monaco treatment planning system with Monte Carlo algorithm.

Materials and methods

Single-arc VMAT and 7-field IMRT treatment plans were compared for 12 intermediate risk prostate cancer patients treated with prostate and seminal vesicle radiotherapy. For all patients, the prescribed dose was 78 Gy delivered in 39 fractions. The dosimetric data of IMRT and VMAT plans with 6, 10 and 15 MV energies were compared. The comparison was made for target volume, organs at risk (OAR) doses, and for monitor units (MU).

Results

The normal tissue surrounding the target were lower in VMAT plans compared to IMRT plans. VMAT plans achieved lower doses to all OARs for nearly all dosimetric endpoints. VMAT plans achieved 9.4, 9.0 and 7.0 % relative decrease in MUs required for RT delivery, for 6, 10 and 15 MV energy levels, respectively. The target volume and OAR dosimetric values did not differ significantly between 6, 10 and 15 MV photon energies.

Conclusion

VMAT plans were found to be dosimetrically equivalent to IMRT plans for prostate cancer patients, with better rectum and bladder sparing and fewer MUs required.     

Dosimetric comparison of robotic- and LINAC-based treatment of spine stereotactic body radiotherapy

To determine which treatment technique and modality would offer better dosimetric results and be preferable for spinal stereotactic body therapy (SBRT) depending on the three different regions of the vertebrae. Linear accelerator (LINAC)- and CyberKnife (CK)-based treatment techniques were compared in terms of their dosimetric quality, treatment efficiency, and delivery accuracy. Thirty previously treated patients were included in this study. Intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) techniques were used for LINAC-based treatment, whereas CK-based treatment plans were generated for two different collimator systems: fixed and multileaf collimator (MLC). The plans were compared based on spinal cord sparing, dose homogeneity, conformity index (CI), gradient index (GI), monitor unit (MU), and beam-on time. The percentage volumes of V2Gy, V5Gy (representing volume low of the dose spillage region), V10Gy, and V20Gy (representing the volume of the high-dose spillage region) of the healthy tissue were analyzed. The CI and GI of the VMAT plans were better than those of the IMRT plans. For spinal cord sparing, the VMAT and MLC-based CK (CK-MLC) techniques were superior. The percentage of low-dose spillage regions was the lowest for IMRT and fixed cone-based CK (CK-FIX) plans. The percentage of the high-dose spillage region was the lowest for the VMAT and CK-MLC plans. In terms of treatment efficiency, the VMAT and CK-MLC plans were superior to the IMRT and CK-FIX plans. The VMAT technique lowered the MU and beam-on time values. The plan delivery accuracy of the VMAT and CK-FIX plans was better than that of the IMRT plans. VMAT is the best option for LINAC-based spinal SBRT. For CK-based spinal SBRT, MLC-based plans are preferred. If the clinic has both treatment modalities and the patient can tolerate long treatment times, CK-MLC-based treatment should be chosen because of its superiority in sparing the spinal cord and sharp dose fall-off.     

Dosimetric research on intensity-modulated arc radiotherapy planning for left breast cancer after breast-preservation surgery

Intensity-modulated radiotherapy (IMRT) has played an important role in breast cancer radiotherapy after breast-preservation surgery. Our aim was to study the dosimetric and implementation features/feasibility between IMRT and intensity-modulated arc radiotherapy (Varian RapidArc, Varian, Palo Alto, CA). The forward IMRT plan (f-IMRT), the inverse IMRT, and the RapidArc plan (RA) were generated for 10 patients. Afterward, we compared the target dose distribution of the 3 plans, radiation dose on organs at risk, monitor units, and treatment time. All 3 plans met clinical requirements, with RA performing best in target conformity. In target homogeneity, there was no statistical significance between RA and IMRT, but both of homogeneity were less than f-IMRT's. With regard to the V₅ and V₁₀ of the left lung, those in RA were higher than in f-IMRT but were lower than in IMRT; for V₂₀ and V₃₀, the lowest was observed in RA; and in the V₅ and V₁₀ of the right lung, as well as the mean dose in normal-side breast and right lung, there was no statistically significance difference between RA and IMRT, and the lowest value was observed in f-IMRT. As for the maximum dose in the normal-side breast, the lowest value was observed in RA. Regarding monitor units (MUs), those in RA were higher than in f-IMRT but were lower than in IMRT. Treatment time of RA was 84.6% and 88.23% shorter than f-IMRT and IMRT, respectively, on average. Compared with f-IMRT and IMRT, RA performed better in target conformity and can reduce high-dose volume in the heart and left lung—which are related to complications—significantly shortening treatment time as well. Compared with IMRT, RA can also significantly reduce low-dose volume and MUs of the afflicted lung.     

Nasopharyngeal carcinoma radiotherapy with hybrid technique

The aim of the study was to investigate the effect of the Hybrid technique which was created by combining of intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) for the treatment of nasopharyngeal cancer (NPC) patients. 7 to 9 field IMRT, triple arc VMAT, and Hybrid plans were generated for 10 advanced stage NPC patients. The homogeneity index (HI) and the conformity index (CI) of planning target volumes (PTVs) were calculated for each technique to evaluate the plan quality. The techniques were compared in terms of plan quality, sparing of organs at risk (OARs), monitor units (MUs), and delivery time. Hybrid technique significantly improved the target dose homogeneity and the conformity for PTV70 and PTV60 compared to IMRT and VMAT. Hybrid plans significantly reduced the maximum dose of the brainstem sparing compared to the VMAT plans and also improved the sparing of spinal cord compared to IMRT and VMAT. The MUs and the delivery time of Hybrid plans were found to be between values for IMRT and VMAT plans. Hybrid technique can be useful when IMRT and VMAT techniques are not adequate alone in the treatment of NPC patients.