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.     

Interstitial brachytherapy vs. intensity-modulated radiation therapy for patients with cervical carcinoma not suitable for intracavitary radiation therapy

PurposeInterstitial brachytherapy (IBT) is the standard alternative treatment for patients with cervical carcinoma not suitable for intracavitary radiotherapy. There is an emerging belief that intensity-modulated radiotherapy (IMRT) has the potential to replace IBT. We aimed to compare the dosimetry achieved by IBT and IMRT in such patients.Methods and MaterialsThe CT imaging data, previously used for IBT planning of 12 patients with cervical carcinoma, were transferred to IMRT planning system to generate parallel IMRT plans. Prescribed dose to the planning target volume (PTV) was 20 Gy delivered in 2-weekly high-dose-rate fractions of 10 Gy each with IBT (biologically equivalent dose [BED₁₀] 40 Gy) and 33 Gy/13 fractions/2.5 wk with IMRT (BED₁₀ 41 Gy). For comparison, dose–volume parameters for target and organs at risk were recorded and expressed in terms of BED₁₀ and BED₃, respectively.ResultsFor PTV, the mean D₉₅ (dose received by 95% of PTV) was better with IBT (57.16 Gy vs. 41.47 Gy, p = 0.003). The mean conformity index was 0.94 and 0.90 with IBT and IMRT, respectively (p = 0.034). IBT delivered significantly reduced doses to 1.0 cc (D_max), 5.0 cc (D_{5 cc}), 50% (D₅₀), and 75% (D₇₅) of bladder volume as compared with IMRT. The mean rectal D_max was significantly better with IBT as compared with IMRT (54.64 Gy vs. 62.63 Gy, p = 0.02).ConclusionsIBT provides superior PTV coverage and organs at risk sparing to IMRT. Thus, IBT remains the standard treatment for patients with cervical carcinoma unsuitable for intracavitary radiotherapy.     

Volumetric-modulated arc therapy in postprostatectomy radiotherapy patients: A planning comparison study

The purpose of this study was to compare postprostatectomy planning for volumetric-modulated arc therapy (VMAT) with both single arc (SA) and double arcs (DA) against dynamic sliding window intensity-modulated radiotherapy (IMRT). Ten cases were planned with IMRT, SA VMAT, and DA VMAT. All cases were planned to achieve a minimum dose of 68 Gy to 95% of the planning target volume (PTV) and goals to limit rectal volume >40 Gy to 35% and >65 Gy to 17%, and bladder volumes >40 Gy to 50% and >65 Gy to 25%. Plans were averaged across the 10 patients and compared for mean dose, conformity, homogeneity, rectal and bladder doses, and monitor units. The mean dose to the clinical target volume and PTV was significantly higher (p<0.05) for SA compared with DA or IMRT. The homogeneity index was not significantly different: SA = 0.09; DA = 0.08; and IMRT = 0.07. The rectal V40 was lowest for the DA plan. The rectal V20 was significantly lower (p<0.05) for both the VMAT plans compared with IMRT. There were no significant differences for bladder V40 or rectal and bladder V65. The IMRT plans required 1400 MU compared with 745 for DA and 708 for SA. This study shows that for equivalent dose coverage, SA and DA VMAT plans result in higher mean doses to the clinical target volume and PTV. This greater dose heterogeneity is balanced by improved low-range rectal doses and halving of the monitor units.     

Treatment planning comparison between dynamic wave arc and volumetric modulated arc therapies for prostate-cancer treatment

The aim of this study was to compare the quality of dynamic wave arc (DWA) and coplanar volumetric modulated arc therapy (co-VMAT) plans for the treatment of localized prostate cancer. The planning target volume (PTV)-rectum, a section of the PTV comprising the PTV minus that of the rectum, received 78 Gy in 39 fractions as the mean dose to the PTV-rectum. The DWA and co-VMAT plans were generated for each patient using the RayStation treatment planning system for the Vero4DRT system. The PTV-rectum dose (D_95%: the percent dose irradiating 95% of the volume), homogeneity index (HI), conformity index (CI), as well as doses to the bladder wall, rectum wall (V_10–70 Gy: the percent volume receiving 10–70 Gy), and bilateral femoral heads of the DWA and co-VMAT plans were compared. The output monitor unit (MU) and delivery time obtained for each set of plans were also investigated. In terms of target coverage, the DWA plans provided an average D_95% of 75.5 Gy, which was comparable to the co-VMAT-plan D_95% of 75.2 Gy (p < 0.05). The HI was significantly better with the DWA. As for the DWA plans, the bladder-wall volume receiving 10, 20, 30, and 40 Gy (V_{10–40 Gy}) was significantly smaller than that of the co-VMAT plans, and the volume of the rectal wall receiving 10 Gy (V_10Gy) was significantly larger than that of the co-VMAT plans. The DWA plans yielded a reduced dose to the bilateral femoral heads compared with the co-VMAT plans (p < 0.05). The values of the CI and MU, and the delivery time exhibited no significant differences between the DWA and co-VMAT plans. The DWA plan is a feasible treatment option for prostate cancer radiotherapy.     

直肠癌调强放疗计划中六维随机摆位误差的剂量学影响研究

目的 设计一种软件将随机六维摆位误差引入到直肠癌调强放疗(IMRT)计划中,并评估其剂量学影响。方法 随机选取21例直肠癌IMRT计划作为参考计划(单次剂量 2 Gy, 共50 Gy;PTV为CTV均匀外扩5 mm)。对参考计划的每个分次,通过调整射野几何参数的方法引入随机生成的六维摆位误差,并重新完成剂量计算。再将各分次剂量累加后得到存在摆位误差情况下的总剂量分布。基于美国瓦里安Eclipse脚本应用程序接口(ESAPI)开发能够自动完成上述流程的治疗模拟软件,将服从两种预设分布[分布1:平移误差服从N(0,4²),旋转误差服从N(0,2²);分布2:平移误差服从N(0,2²),旋转误差服从N(0,1²)]的六维摆位误差引入参考计划,并评估剂量学影响。结果 参考计划、误差分布1和误差分布2情况下,CTV的D_min分别为(49.4±0.41)、(47.56±0.76)和(49.17±0.64)Gy;CTV的D_98%分别为(50.23±0.07)、(49.98±0.10)和(50.27±0.09)Gy;主体靶区(靶区除去边缘后的内核部分)D_98%为(50.25±0.08)、(50.42±0.13)和(50.33±0.10)Gy;边缘靶区D_98%为(50.22±0.10)、(49.88±0.11) 和(50.26±0.10)Gy。另外,相比参考计划,误差分布1和2的情况下,膀胱和股骨头平均受量的变化差异均无统计学意义(P>0.05),剂量分布的适形指数虽有微弱降低,但临床意义有限。结论 本方法及据此开发的治疗模拟软件可以根据需要将服从不同分布的六维摆位误差引入到直肠癌IMRT计划中,并给出总体剂量学变化情况。     

Three-dimensional gamma analysis of dose distributions in individual structures for IMRT dose verification

Our purpose in this study was to implement three-dimensional (3D) gamma analysis for structures of interest such as the planning target volume (PTV) or clinical target volume (CTV), and organs at risk (OARs) for intensity-modulated radiation therapy (IMRT) dose verification. IMRT dose distributions for prostate and head and neck (HN) cancer patients were calculated with an analytical anisotropic algorithm in an Eclipse (Varian Medical Systems) treatment planning system (TPS) and by Monte Carlo (MC) simulation. The MC dose distributions were calculated with EGSnrc/BEAMnrc and DOSXYZnrc user codes under conditions identical to those for the TPS. The prescribed doses were 76 Gy/38 fractions with five-field IMRT for the prostate and 33 Gy/17 fractions with seven-field IMRT for the HN. TPS dose distributions were verified by the gamma passing rates for the whole calculated volume, PTV or CTV, and OARs by use of 3D gamma analysis with reference to MC dose distributions. The acceptance criteria for the 3D gamma analysis were 3/3 and 2 %/2 mm for a dose difference and a distance to agreement. The gamma passing rates in PTV and OARs for the prostate IMRT plan were close to 100 %. For the HN IMRT plan, the passing rates of 2 %/2 mm in CTV and OARs were substantially lower because inhomogeneous tissues such as bone and air in the HN are included in the calculation area. 3D gamma analysis for individual structures is useful for IMRT dose verification.     

非小细胞肺癌不同调强放疗方案的剂量学对比研究

目的 探讨非小细胞肺癌调强放疗计划设计的合理方案。方法 对11例非小细胞肺癌患者分别制定2种放疗计划:PTV60计划的PTV为(GTV+6～8mm)+呼吸动度+摆位误差,对PTV获得60Gy处方剂量进行归一;PTV70计划的PTV为GTV+呼吸动度+摆位误差,对PTV获得70Gy处方剂量进行归一。通过剂量体积直方图分析2种治疗计划的靶区剂量分布和危及器官受量,并进行剂量学的对比研究。结果 PTV70计划接受60Gy剂量的靶区体积明显高于PTV60计划,两组在靶区剂量均匀性方面相似。PTV70计划的肺V₂₀较PTV60计划平均下降(1.69±0.42)%,两组相比差异有统计学意义(t=0.047,P=0.002);肺V₅平均下降(1.29±1.09)%,两组相比差异无统计学意义。结论 在非小细胞肺癌调强放疗设计中,PTV70计划优于PTV60计划。     

Comparative Treatment Planning on Localized Prostate Carcinoma

Purpose: To assess the potential benefit of proton–beam therapy in comparison to 3–D conformal photon therapy and photon– based intensity–modulated radiotherapy (IMRT) in prostate carcinoma for various stages of disease.Material and Methods: In five patients a 3–D conformal proton–based (two lateral beams) irradiation technique was compared with 3–D conformal photon–beam radiotherapy (four–field box) and IMRT (seven beams). For each patient different target volumes (CTVs) were defined according to early, intermediate and advanced stages of disease: CTV I consisted of the prostate gland, CTV II encompassed prostate and basis of seminal vesicles, and CTV III the prostate and seminal vesicles. Corresponding planning target volumes PTV I–III were defined by uniformly adding a margin of 5 mm to CTV I–III. Dose–volume histograms (DVHs) were analyzed for the different PTVs and various organs at risk (OARs), i.e., rectal wall, bladder, both femoral heads. In addition, maximum and mean doses were derived for the various structures and irradiated non–target tissue volumes were compared for PTV I–III and the different irradiation techniques. Finally, dose conformity and target dose homogeneity were assessed.Results: With photon– and proton–based radiotherapy techniques similar dose distributions were determined for PTV I–III: mean and maximum PTV dose values were between 99–104% and 102–107% of the normalized total doses (70 Gy), respectively. Conformity indices varied from 1.4 to 1.5 for the photon techniques, whereas for proton–beam radiotherapy values ranged from 1.1 to 1.4. Both the 3–D conformal and the IMRT photon treatment technique resulted in increased mean doses (~ 40–80%) for OARs when compared to protons. With both photon techniques non–target tissue volumes were irradiated to higher doses (mean dose difference ≥ 70%) compared to proton–beam radiotherapy. Differences occurred mainly at the low and medium dose levels, whereas in high dose levels similar values were obtained. In comparison to conformal 3–D treatments IMRT reduced doses to OARs in the medium dose range, especially for the rectal wall.Conclusion: IMRT enabled dose reductions to OARs in the medium dose range compared to 3–D conformal radiotherapy. A rather simple two–field proton–based treatment technique further reduced doses to OARs compared to photon–beam radiotherapy. The advantageous dose distribution of proton–beam therapy for prostate cancer may result in reduced side effects, which needs to be confirmed in clinical studies.     

An in silico comparative dosimetric study of postmastectomy locoregional irradiation using intensity-modulated vs 3-dimensional conventional radiotherapy

An in silico dosimetric evaluation of intensity-modulated radiation therapy (IMRT) vs 3-dimensional conventional radiation therapy (3D-CRT) treatment plans in postmastectomy radiation therapy (PMRT) to the chest wall and regional lymphatics was conducted. Twenty-five consecutive patients with breast cancer referred for locoregional PMRT, stages T_2-4 with N_1-3, were planned to receive 50?Gy in 25 fractions with IMRT. Additionally, a 3D-CRT plan was generated using identical contours for the clinical target volumes (CTV), planning target volumes (PTV), and organs at risk (OAR). Treatment plans were assessed using dose-volume histogram (DVH) parameters of D₉₈, D₉₅, D₅₀, D₂, and homogeneity index for individual CTVs and PTVs. OARs evaluated were ipsilateral and contralateral lungs, heart, spinal cord, and opposite breast. Most DVH parameters pertaining to CTVs and PTVs significantly favored IMRT. V₂₀ for ipsilateral and contralateral lungs, D₃₃ of heart and maximum dose to spinal cord favored IMRT (all p?<?0.001). The mean dose to the opposite breast was significantly lesser with 3D-CRT (5.8?±?1.8?Gy vs 2.0?±?1.0?Gy, p?<?0.001). Thus, except for the mean dose to the opposite breast, the compliance to DVH constraints applied to PTV and OARs were significantly better with IMRT. At a median follow-up of 76 months (7-91), none had locoregional failure or pulmonary or cardiac morbidity. For PMRT, requiring comprehensive irradiation to both chest wall and regional lymphatics, IMRT offers superior dosimetric advantages over 3D-CRT. This was also corroborated by long-term outcomes in these patients treated with IMRT.     

Dosimetric comparison of intensity modulated radiotherapy and intensity modulated proton therapy in the treatment of recurrent nasopharyngeal carcinoma

Background and purposeTo compare the dosimetric performance of Intensity Modulated Proton Therapy (IMPT) and Intensity Modulated Radiotherapy (IMRT) in terms of target volume coverage and sparing of neurological organs-at-risk (OARs) in salvaging recurrent nasopharyngeal carcinoma (rNPC). The maximum dose to the internal carotid artery (ICA) and nasopharyngeal (NP) mucosa, which are associated with potential carotid blowout and massive epistaxis, were also evaluated.Materials and methodsIMRT and IMPT treatment plans were created for twenty patients with locally advanced rNPC. Planning Target Volume (PTV) was used to account for the setup and spatial error/uncertainty in the IMRT planning. Robust optimization on Clinical Target Volume (CTV) coverage with consideration of range and setup uncertainty was employed to produce two IMPT plans with 3-field and 4-field arrangements. The planning objective was to deliver 60 Gy to the PTV (IMRT) and CTV (IMPT) without exceeding the maximum lifetime cumulative Biologically Effective Dose (BED) of the neurological OARs (applied to the Planning organs-at-risk volume). The target dose coverage as well as the maximum dose to the neurological OARs, ICA, and NP mucosa were compared.ResultsCompared with IMRT, 3-field IMPT achieved better coverage to GTV V100% (83.3% vs. 73.2%, P <0.01) and CTV V100% (80.5% vs. 72.4%, P <0.01), and lower maximum dose to the critical OARs including the spinal cord (19.2 Gy vs. 22.3 Gy, P <0.01), brainstem (30.0 Gy vs. 32.3 Gy, P <0.01) and optic chiasm (6.6 Gy vs. 9.8 Gy, P <0.01). The additional beam with the 4-fields IMPT plans further improved the target coverage from the 3-field IMPT (CTV V98%: 85.3% vs. 82.4%, P <0.01) with similar OAR sparing. However, the target dose was highly non-uniform with both IMPT plans, leading to a significantly higher maximum dose to the ICA (～68 Gy vs. 62.6 Gy, P <0.01) and NP mucosa (～72 Gy vs. 62.8 Gy, P <0.01) than IMRT.ConclusionIMPT demonstrated some dosimetric advantage over IMRT in treating rNPC. However, IMPT could also result in very high dose hot spots in the target volume. Careful consideration of the ICA and NP mucosal complications is recommended when applying IMPT on rNPC patients.     

Intensity-modulated radiotherapy for a prostate patient with a metal prosthesis

When treating prostate patients having a metallic prosthesis with radiation, a 3D conformal radiotherapy (3DCRT) treatment plan is commonly created using only those fields that avoid the prosthesis in the beam’s-eye view (BEV). With a limited number of portals, the resulting plan may compromise the dose sparing of the rectum and bladder. In this work, we investigate the feasibility of using intensity-modulated radiotherapy (IMRT) to treat prostate patients having a metallic prosthesis. Three patients, each with a single metallic prosthesis, who were previously treated at the University of Chicago Medical Center for prostate cancer, were selected for this study. Clinical target volumes (CTV = prostate + seminal vesicles), bladder, and rectum volumes were identified on CT slices. Planning target volumes (PTV) were generated in 3D by a 1-cm expansion of the CTVs. For these comparative studies, treatment plans were generated from CT data using 3DCRT and IMRT treatment planning systems. The IMRT plans used 9 equally-spaced 6-MV coplanar fields, with each field avoiding the prosthesis. The 3DCRT plans used 5 coplanar 18-MV fields, with each field avoiding the prosthesis. A 1-cm margin around the PTV was used for the blocks. Each of the 9-field IMRT plans spared the bladder and rectum better than the corresponding 3DCRT plan. In the IMRT, plans, a bladder volume receiving 80% or greater dose decreased by 20–77 cc, and a volume rectal volume receiving 80% or greater dose decreased by 24–40 cc. One negative feature of the IMRT plans was the homogeneity across the target, which ranged from 95% to 115%.     

Dosimetric effect of external beam planning preceding combined high-dose-rate brachytherapy of the prostate

Purpose

The sequencing of external beam radiotherapy (EBRT) and a high-dose-rate brachytherapy (HDRB) boost is often interchangeable in clinical practice. When given before EBRT, HDRB could induce volume alterations in the prostate, which may have significant implications for EBRT dosimetry. We aimed to assess the influence of HDRB on prostate volume and, hence, prostate dosing via subsequent EBRT.

Methods and Materials

Fifteen men had both pre- and post-HDRB CT performed followed by EBRT. After deidentification, the clinical target volume (CTV) was defined on each CT by a single-blinded observer. Volumes were compared for the pre- and post-HDRB scans in each patient. Radiotherapy planning was performed using the prebrachytherapy volumes aiming for the planning target volume (PTV) to be covered by 43.7 Gy. After soft-tissue coregistration, this plan was also applied to the postbrachytherapy volumes.

Results

Median volume increase was 35.4% for the CTV after HDRB. No patient experienced a decrease in CTV volume (range, 0-79% volume increase; p-value < 0.001). Median volume increase was 26.1% for the PTVs, with no volume decrease observed (range, 8-56%; p < 0.001). PTV proportion achieving dose target (V43.7 Gy) decreased by median of 7% (range, 0-21.5%; p = 0.004). The minimum dose to the PTV (D₁₀₀%) decreased by a median of 6 Gy (range, 0.5-16 Gy; p < 0.001).

Conclusions

Insertion of HDRB catheters exerts substantial acute volumetric distortion on the prostate. EBRT planning performed on the basis of pre-HDRB imaging only inherently risks underdosing tumor. Planning adjustments based on repeat CT, or dedicated post-HDBT planning, is warranted for men managed with HDRB before EBRT.     

A class solution for volumetric-modulated arc therapy planning in postprostatectomy radiotherapy

This study is aimed to test a postprostatectomy volumetric-modulated arc therapy (VMAT) planning class solution. The solution applies to both the progressive resolution optimizer algorithm version 2 (PRO 2) and the algorithm version 3 (PRO 3), addressing the effect of an upgraded algorithm. A total of 10 radical postprostatectomy patients received 68 Gy to 95% of the planning target volume (PTV), which was planned using VMAT. Each case followed a set of planning instructions; including contouring, field setup, and predetermined optimization parameters. Each case was run through both algorithms only once, with no user interaction. Results were averaged and compared against Radiation Therapy Oncology Group (RTOG) 0534 end points. In addition, the clinical target volume (CTV) D₁₀₀, PTV D₉₉, and PTV mean doses were recorded, along with conformity indices (CIs) (95% and 98%) and the homogeneity index. All cases satisfied PTV D₉₅ of 68 Gy and a maximum dose < 74.8 Gy. The average result for the PTV D₉₉ was 64.1 Gy for PRO 2 and 62.1 Gy for PRO 3. The average PTV mean dose for PRO 2 was 71.4 Gy and 71.5 Gy for PRO 3. The CTV D₁₀₀ average dose was 67.7 and 68.0 Gy for PRO 2 and PRO 3, respectively. The mean homogeneity index for both algorithms was 0.08. The average 95% CI was 1.17 for PRO 2 and 1.19 for PRO 3. For 98%, the average results were 1.08 and 1.12 for PRO 2 and PRO 3, respectively. All cases for each algorithm met the RTOG organs at risk dose constraints. A successful class solution has been established for prostate bed VMAT radiotherapy regardless of the algorithm used.     

铅门跟随技术与铅门固定技术在直肠癌术前调强放疗中的剂量学比较

目的 研究固定射野动态调强放疗铅门跟随技术与铅门固定技术在直肠癌术前调强放疗中的剂量学差异.方法 采用两种治疗技术对10例直肠癌术前患者设计治疗计划.在95%体积的计划靶区(PTV)和计划肿瘤区(PGTV)满足处方剂量的前提下,尽量降低危及器官的剂量.比较两组治疗计划的剂量-体积直方图,评估靶区及危及器官的剂量分布.分别将两组治疗计划用电离室矩阵2D-Array 729和OCTAVIUS(PTW)模体进行剂量验证.结果 两组计划的靶区均达到临床处方剂量的要求.PTV和PGTV的最大剂量与平均剂量差异无统计学意义.铅门跟随动态调强计划中全身的V₅、V₁₀、V₂₀、V₃₀、V₄₀、D_mean以及双侧股骨头、膀胱、小肠的V₁₀、V₂₀、V₃₀和D_mean均低于铅门固定动态调强计划的相应值,差异有统计学意义(t=-2.32~12.24,P<0.05);双侧股骨头、膀胱、小肠的V₄₀以及D_max差异无统计学意义.采用γ-2D分析两组计划的通过率,两组计划均通过剂量验证.结论 直肠癌术前放疗患者采用固定射野动态调强放疗铅门跟随技术与铅门固定技术两种技术,其靶区和危及器官受量均能满足临床治疗要求,而铅门跟随技术能够更好地降低正常组织和危及器官的低剂量照射.     

非小细胞肺癌精确放疗中三种CT扫描方法的研究

目的 比较自主呼吸控制(ABC)、自由呼吸(FB)状态下慢速CT扫描(SS)和常规轴位扫描在周围型非小细胞肺癌(NSCLC)精确放疗中减小放射性肺损伤方面的作用差异。方法 10例周围型NSCLC患者在适形放疗定位时分别采集3种CT图像:1FB时常规轴位扫描;2ABC螺旋CT快速扫描;3FB时慢速CT扫描。将3套图像传输至计划系统,分别制定3个适形放疗计划,比较3个计划的大体肿瘤靶区(GTV)、临床靶区(CTV)、计划靶区(PTV)、受照剂量>20 Gy的正常肺组织占全肺体积的百分比(V₂₀)及全肺平均受照剂量(D_mean)。结果 3个计划的GTV、CTV体积以慢速扫描似乎最大,ABC计划似乎最小,但差异无统计学意义(F=1.513,P=0.238;F=1.376,P=0.270);FB常规轴位计划的PTV体积最大,且分别与另2个计划间差异有统计学意义(F=26.148,P=0.000);V₂₀、D_mean在FB常规轴位计划均最大,且FB计划和另2个计划间差异有统计学意义(F=7.623,P=0.002;F=18.217,P=0.000)。结论 相对于FB状态,使用ABC或慢速CT扫描可有效减少周围型NSCLC精确放疗中正常组织的受照体积和剂量,减小放射性肺损伤的发生率。