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Objective:To compare dosimetric and radiobiological parameters between automatic and manual uARC plans in the treatment of esophageal cancer patients, aiming to provide reference for clinical application.Methods:High-quality uARC plans of 100 patients with esophageal cancer were selected, and the mean values of the dosimetric parameters in the target area and organs at risk (OAR) were counted, and the goal table of uRT-TPOIS intelligent plan was established. Automatic and manual uARC plans were generated with UIH (United Imaging) treatment planning system (TPS) for 21 esophageal cancer patients. The differences in mean dose (D mean), approximate minimum (D 98%) and maximum (D 2%) dose of planning target volume (PTV), homogeneity index (HI) and conformity index (CI), dose of OAR, mean planning time, monitor unit (MU), tumor control probability (TCP) and normal tissue complication probability (NTCP) were compared between automatic and manual uARC plans. Normally distributed data between two groups were compared by paired t-test, and non-normally distributed data were assessed by nonparametric Wilcoxon test. Results:The D 98% (PTV 60 Gy: P<0.001, PTV 54 Gy: P=0.001) , CI (PTV 60 Gy: P<0.001, PTV 54 Gy: P=0.002) and target volume of area covered by prescription dose (V 54 Gy: P<0.001) of the automatic uARC plans were better than those of manual uARC plans (all P<0.05). There was no significant difference in D mean or HI between the two plans [PTV 54 Gy (59.32±1.87) Gy vs. (59.13±1.64) Gy, (0.19±0.02) vs. (0.18±0.02), all P>0.05]. The D mean and D max of spinal cord of the automatic plan were better than those of the manual plan [(13.22±4.27) Gy vs. (13.75±4.44) Gy, P=0.020 and (36.99±1.67) Gy vs. (38.14±1.31) Gy, P=0.011]. There was no significant difference in the mean dose of V 20 Gy of the lung between two plans ( P>0.05), whereas the mean doses of V 5 Gy and V 10 Gy of the lung of the manual plan were less than those of the automatic plan ( both P<0. 001). Automatic uARC plan had a significantly shorter mean planning time than manual uARC plan [(11.79±1.71) min vs. (53.36±8.23) min, P<0.001]. MU did not significantly differ between two plans [(762.84±74.83) MU vs. (767.41±80.63) MU, P>0.05]. The TCP of the automatic plan was higher than that of the manual plan (PTV 60 Gy 89.15%±0.49% vs. 86.75%±6.46%, P=0.004 and PTV 54 Gy 79.79%±3.48% vs. 77.51%±5.04%, P=0.006). However, manual plan had a lower NTCP of the lung than automatic uARC plan (0.46%±0.40% vs. 0.35%±0.32%, P<0.001). There was no significant difference in NTCP of heart and spinal cord between two plans (all P>0.05). Conclusion:It is feasible to generate automatic uARC plan with uRT-TPOIS TPS for esophageal cancer patients, which can increase the target CI and shorten the plan design time.
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Objective:To provide a basis for selecting the optimization method for intracavitary/interstitial brachytherapy (IC/ISBT) of cervical cancer by comparing graphical optimization (GO), inverse planning simulated annealing (IPSA), and hybrid inverse planning optimization (HIPO) using dosimetric and radiobiological models.Methods:This study selected 65 patients with cervical cancer who were treated with image-guided IC/ISBT. The afterloading therapy plans for these patients were optimized using GO, IPSA, and HIPO individually, with a prescription dose high-risk clinical target volume (HRCTV) D90 of 6 Gy. The non-parametric Friedman test and the non-parametric Wilcoxon rank test were employed to analyze the differences in duration, dose-volume parameters, and radiobiology between the three types of optimized plans. Results:Inverse planning optimization (IPSA: 46.53 s; HIPO: 98.36 s) took less time than GO (135.03 s). In terms of gross target volume (GTV) dose, the high-dose irradiation V150% (53.66%) was slightly higher in the HIPO-optimized plans, while the V200% (30.29%) was higher in the GO-optimized plans. The GO-optimized plans had a higher conformity index (CI; 0.91) than other plans, showing statistically significant differences. Compared with other plans, the HIPO-optimized plans showed the lowest doses of D1 cm 3 and D2 cm 3 at bladders and rectums and non-statistically significant doses at small intestines ( P > 0.05). In terms of the equivalent uniform biologically effective dose (EUBED) for HRCTV, the HIPO-optimized plans showed a higher value (12.35 Gy) than the GO-optimized plans (12.23 Gy) and the IPSA-optimized plans (12.13 Gy). Moreover, the EUBED at bladders was the lowest (2.38 Gy) in the GO-optimized plans, the EUBED at rectums was the lowest (3.74 Gy) in the HIPO-optimized plans, and the EUBED at small intestines was non-significantly different among the three types of optimized plans ( P = 0.055). There was no significant difference in the tumor control probability (TCP) predicted using the three types of optimized plans ( P > 0.05). The normal tissue complication probabilities (NTCPs) of bladders and rectums predicted using the HIPO-optimized plans were lower than those predicted using the GO- and IPSA-optimized plans( χ2 = 12.95-38.43, P < 0.01), and the NTCP of small intestines did not show significant differences ( P > 0.05). Conclusions:Among the three types of optimization algorithms, inverse optimization takes less time than GO. GO-optimized plans are more conformal than IPSA- and HIPO-optimized plans. HIPO-optimized plans can increase the biological coverage dose of the target volume and reduce the maximum physical/biological exposure and NTCP at bladders and rectums. Therefore, HIPO is recommended preferentially as an optimization algorithm for IC/ISBT for cervical cancer.
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Objective To analyze the dosimetric effect of the optimization tool, normal tissue objective (NTO), in Eclipse on the intensity modulated radiation therapy (IMRT) for postoperative patients with rectal cancer. Methods Twenty postoperative patients with rectal cancer were randomly selected. Based on the Eclipse treatment planning system, three IMRT plans were formulated for each patient, with manual NTO as the control group, and automatic NTO and no NTO as the other two groups. The dosimetric parameters of the target volume and organs at risk (OAR) and the monitor units (MU) were compared between the automatic NTO and no NTO groups and the control group under the same optimization conditions. Results Compared with the control group, the automatic NTO group showed a worse conformity index (CI) (t = 3.248, P < 0.05), a 0.6% higher Dmean of normal tissues (t = -3.678, P < 0.05), and no significant difference in the dose to OAR and the MU (P > 0.05); the no NTO group showed a worse CI (t = 16.716, P < 0.05), a better homogeneity index (t = 6.594, P < 0.05), a 3.19% higher Dmean of normal tissues (t = -8.560, P < 0.05), no significant difference in the dose to OAR except the small intestine with higher Dmax (P > 0.05), and a 3.95% increase in the MU. Conclusion From the dosimetry results of the target volume and OAR, the plans with manual NTO and automatic NTO, and without NTO can meet clinical needs, but the plan without NTO increases the hot spots outside the target volume and the MU as well as the Dmean of normal tissues. Manual NTO has no obvious advantages over automatic NTO which is recommended for the fixed-field IMRT of rectal cancer.
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As a method for local treatment, radiotherapy plays a key role in the management of tumors. In the past few decades, great progress has been made in radiotherapy technology, with improvements in conformity, homogeneity, and radiotherapy efficiency, and the results are encouraging. Nevertheless, the maximum tolerated dose of normal tissue has limited the further increase in radiotherapy dose in the tumor area. If radiation-induced toxicities can be reduced, a higher radiotherapy dose can be delivered to tumor tissue, so as to achieve a better treatment response. In recent years, the unique FLASH effect of ultra-high-dose-rate radiotherapy (FLASH-RT) is capable of maintaining a consistent tumor response whilst reducing radiation-induced toxicities in normal tissue, and therefore, FLASH-RT has become a research hotspot in the field of radiotherapy across the world. At present, some scholars tend to explain the FLASH effect using the theory of acute oxygen depletion, but the protective effect of FLASH-RT on normal tissue remains to be clarified. In addition, preliminary clinical studies have been conducted for FLASH-RT, and the results are promising. Based on existing evidence, this article elaborates on the research advances in FLASH-RT in the treatment of malignant tumor, so as to provide a reference for the translation and application of this new technique.
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Purpose: In this study, it is aimed to compare three different radiotherapy treatment planning techniques in terms of critical organ scoring index (COSI), two different conformity index (CI), tumor control probability (TCP), and normal tissue complication probability (NTCP) calculations in early (T1) glottic larynx carcinoma (T1GL). Furthermore, it is aimed to investigate these parameters compliance with dose-volume histograms (DVH) parameters. Materials and Methods: Ten T1GL patients were immobilized in a supine position with a head and neck thermoplastic mask. Treatment plans were created with opposed lateral fields (OLAFs) and intensity-modulated radiation therapy (IMRT) techniques with a total dose of 66 Gy in 33 fraction with 2 Gy/day. IMRT fields were selected as five fields (5IMRT) and seven fields (7IMRT). Dosimetric evaluation of three different treatment plans for T1GL carcinoma was performed in two consequential steps. First step was the assessment of planning target volume (PTV), all organs at risks (OARs), and normal tissue (NT) dose calculations according to given dose constraint directions and comparing the plans via DVH. In the second step, for PTV, the compatibility of DVH data with CIs-TCP was investigated where COSI-NTCP was compared with DVH for OARs. The DVH data were considered as reference in all evaluations. Results: The CIRTOG mean values were significantly closer to 1 with IMRT plans when compared to OLAF plans (P = 0.005). The CIPADDICK mean values revealed that OLAF plans were significantly worse than IMRT plans (P = 0.005). No statistically significant difference was found between all three plans in terms of homogeneity index mean values (P = 0.076). The calculated mean TCP values were significantly better for 7IMRT plans when compared to OLAF and 5IMRT plans (P = 0.007 and P = 0.017, respectively). Both NTCP and COSI evaluations, which is compatible with DVH, significantly favored OLAF plan for spinal cord and 7IMRT for thyroid gland. The COSI evaluations, which are compatible with DVH, significantly favored 7IMRT plan for carotid arteries and 5IMRT plan for NT. Conclusion: Our results demonstrated that CIPADDICK-TCP calculations for PTV and COSI-NTCP calculations for OARs were compatible with DVH in T1 GL plans. Therefore, we suggest such parameters as valuable tools for choosing the feasible one among multiple plans and even with different treatment machines
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Flash radiotherapy is a kind of radiotherapy method using ultra-high dose rate radiation. Compared with the traditional dose rate radiotherapy, it has unique radiobiological advantages. In this paper, the principle of flash radiotherapy, the process and results of biological experiments are summarized. At the same time, the advantages and challenges of flash radiotherapy are analyzed, and the future clinical application is prospected.
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Radiotherapy/methods , Radiotherapy Dosage , TechnologyABSTRACT
Objective To investigate the clinical and dose-volume factors for damages to organs at risk(OARs)during preoperative chemoradiotherapy for gastric cancer, and to provide a reference for optimization of radiotherapy plans to avoid or reduce damages to OARs.Methods A total of 58 patients with locally advanced gastric adenocarcinoma undergoing neoadjuvant treatment were enrolled as subjects.In those patients,30 received preoperative chemoradiotherapy combined with surgery and adjuvant chemotherapy, while others received preoperative chemotherapy combined with surgery and adjuvant chemotherapy. The preoperative chemotherapy group received 2-3 cycles of xeloxregimen(capecitabine+oxaliplatin)before surgery and 3-4 cycles of xeloxregimen after surgery(a total of 6 cycles). The preoperative chemoradiotherapy group received preoperative radiotherapy(45 Gy in 25 fractions)combined with 2 cycles of concurrent xeloxchemotherapy at 14-21 days after the first cycle of xeloxregimen, as well as 3 cycles of xeloxchemotherapy after surgery. The analyses of clinical and dose-volume factors for damages to OARs were performed based on laboratory indices and clinical symptoms during the treatment. Results In all the patients,the incidence rates of liver injury(LI), renal injury(RI), and duodenum injury(DI)before surgery were 22%,48%,and 33%,respectively;the incidence rates of LI and RI after treatment were 35%and 49%, respectively. After appropriate treatment, neither LI nor DI affected the treatment of gastric cancer. RI healed without any special treatment. Compared with preoperative chemotherapy, preoperative chemoradiotherapy caused higher incidence of LI(P=0.00,0.03).RI was only associated with glomerular filtration rate before radiotherapy(P=0.08,0.13). A V3.5of ≤98.96% for the liver reduced LI, while a D2ccof ≤48 Gy for the duodenum reduced DI. Conclusions Preoperative chemoradiotherapy is safe for treating gastric cancer. Compared with preoperative chemotherapy, preoperative chemoradiotherapy does not increase the risk of RI. However,preoperative chemoradiotherapy tends to increase LI.Further studies are needed to improve the treatment method.
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Objective To examine the incidence of radiation-induced lung injury(RILI)after involved-field intensity-modulated radiation therapy(IMRT)in patients with locally advanced non-small cell lung cancer(NSCLC),and to evaluate the predictability of different models.Methods The clinical data of 242 inoperable or unresectable stage Ⅲ NSCLC patients treated in our hospital from 2007 to 2011 were reviewed. Grade 2 and grade 3 RILI that occurred within 6 months after IMRT were selected as outcome events in this study. The principal component analysis(PCA)model,Lyman-Kutcher-Burman(LKB)model,and mean lung dose(MLD)model were each used to establish a predictive model of normal tissue complication probability (NTCP)for evaluating the dosimetric parameters of IMRT. Results Four principal components were used in the PCA model. The areas under the receiver operating characteristic curve(AUCs)of grade 2 and grade 3 RILI were 0.652 and 0.611,respectively. For the LKB model, the fitted parameters were m=0.46, n=1.35, and D50=23.59 Gy for grade 2 RILI,and m=0.36,n=0.27,and D50=72.67 Gy for grade 3 RILI. The AUCs of grade 2 and grade 3 RILI in the LKB model were 0.607 and 0.585, respectively. For the MLD model, the estimated parameters were γ50=1.073 and D50=24.66 Gy for grade 2 RILI,and γ50=0.97 and D50=48.45 Gy for grade 3 RILI.The AUCs of grade 2 and grade 3 RILI in the MLD model were 0.604 and 0.569,respectively. Conclusions The use of large data set from a single patient population with the same mode of treatment is very important for improving model predictability and stability. Both the LKB model and PCA model can predict the probability of RILI,whereas the MLD model is less effective in predicting grade 3 RILI.
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Objective To compare the dose volume and normal tissue complication probability (NTCP) of small intestine between intensity-modulated radiotherapy (IMRT) with dose constraints to the peritoneal space (PS) and the bowel loop (BL) in the treatment of rectal cancer,and to investigate the feasibility of placing a dose constraint to the PS instead of the BL in protection of the small intestine.Methods A total of 24 patients with rectal cancer undergoing postoperative adjuvant radiotherapy were enrolled as subjects.In the 24 patients,12 were treated in supine position an.d 12 in prone position.The weekly computed tomography (CT) scans from pre-treatment to weeks 1-4 of treatment were defined as Plan,1 W,2 W,3 W,and 4 W.Contours of PS and BL were delineated on all CT images.Based on the Plan CT images,two IMRT plans,PPS and PBL,were designed with dose constraints to the PS and BL,respectively.The method was applied to 1-4 W CT images.For each CT scan,the dose volume and NTCP of the small intestine were evaluated in PPs and PBL.Results A total of 109 sets of CT images were acquired from 24 patients,and 218 plans were designed and copied.The median volume of the PS and BL was 1339.28 and 250.27 cm3,respectively.For the Plan CT scans,V15 values of the PS in PPs plan and the BL in PBL plan were 918.96 and 199.57 em3,respectively.For all CT scans,the dose volume of the small intestine in PPs,in most cases,was lower than that in PBL,while V15 values in Ps and PBL were 170.07 and 178.58 cm3 (P=0.000).The dose volume of the small intestine was correlated with V15 (P=0.000).PPs had significantly lower NTCP of chronic and acute adverse reactions than PBL(2.80％ vs.3.00％,P=0.018;57.32％ vs.58.64％,P=0.000).In patients with prone and supine treatment positions,most of the dose volume and NTCP of the small intestine in Ps were significantly lower than those in PBL(P＜0.05 for V10,V15,V30,and NTCP of acute adverse reactions).Conclusions It is feasible to place a dose constraint to the PS instead of the BL for protection of the small intestine during IMRT for rectal cancer.V15＜830 cm3 can be referred to as the objective function of dose restraint.
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Objective To evaluate the uncertainty of the small bowel dose?volume and the normal tissue complication probability (NTCP) during intensity?modulated radiotherapy (IMRT) for rectal cancer, and to provide a reference for the dose limit and protection of the small bowel during IMRT for rectal cancer. Methods A total of 20 patients with rectal cancer who received postoperative adjuvant radiotherapy from March 2014 to August 2015 were enrolled in this study, including 10 patients receiving CT scan in the supine position and 10 patients in the prone position. All patients received computed tomography ( CT) scan before the treatment and at weeks 1, 2, 3, and 4 of treatment, and they were defined as Plan, 1W, 2W, 3W, and 4W CT groups, respectively. The small bowel loop ( BL ) and peritoneal space ( PS ) were delineated on the images. The IMRT plan based on the Plan CT was copied to the 1W, 2W, 3W, and 4W CT groups, and then the small bowel dose?volume and NTCP were assessed for all CT groups. The paired t?test was used for comparison between groups. The Pearson method was used to analyze the correlation between NTCPC(chronic NTCP) and dose?volume. Results A total of 89 CT images of 20 patients were obtained. In all the patients, the volumes of BL and PS were 25121 cm3 and 132416 cm3 , respectively, and the shift% was 2315% and 1134%, respectively. The V15 of BL and PS was 18486 cm3 and 79245 cm3 , respectively, and the shift% was 3169% and 370%, respectively. The V30 of BL and PS was 8801 cm3 and 64573 cm3 , respectively, and the shift% was 3766% and 1049%, respectively. The V15 of BL in 35% of patients and V15 of PS in 20% of patients, the Dmax of BL in 50% of patients, and the NTCP of 15% of patients in the course of treatment exceeded the safety limits. The 1?4W CT groups had a significantly higher NTCPC than the Plan CT group (402% vs. 320%, P=0104), and their SD% was 4168%. There was a significant correlation between NTCPC and V30?V50 of BL (R>0400, P=0000). The NTCPA ( acute NTCP ) and NTCP C in the supine position were significantly higher than those in the prone position ( 6230% vs. 5674%, P=0061;488% vs. 322%, P=0145 ) . Conclusions Small bowel motility leads to an uncertainty of the adverse event assessment during IMRT for rectal cancer. The change in BL is significantly larger than that in PS and the change in BL and PS in the supine position is significantly larger than that in the prone position. Using the prone position and minimizing V15 and V30 when designing the treatment plan can reduce the NTCP A and NTCP C in the small bowel.
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Objective To investigate the difference in normal tissue complication probability (NTCP) of lower cranial nerves (LCNs) between target volumes recommended by Radiation Therapy Oncology Group (RTOG) and China in intensity-modulated radiotherapy (IMRT) for T1-2 nasopharyngeal carcinoma (NPC),and to provide the evidence of dose-volume effect for the protection of LCNs in IMRT for NPC.Methods A total of 20 patients with T1-2 NPC who were treated from 2013 to 2015 were enrolled,and LCNs were delineated on CT images.Target volume delineation and treatment plan designing were performed according to the method recommended by RTOG0225 (RTOG target volume delineation method) or the Chinese Working Committee for Clinical Staging of NPC in 2010 (Chinese target volume delineation method),and the differences in the dose to LCNs and NTCP were calculated.Results In the RTOG and Chinese methods for target volume delineation,Dmax to the left and right LCNs was 7 450±273 cGy/7294±309 cGy and 7 361± 160 cGy/7 190±395 cGy,respectively (P=0.018 and 0.042),Dmean was 6735±285 cGy/6 660±333 cGy and 6 446±429 cGy/6 299±467 cGy,respectively (both P=0.000),and the NTCP was 60％±10％/57％±13％ and 51％±15％/45％±17％,respectively (both P=0.000).Conclusions It is feasible to precisely delineate target volume with the LCNs as a routine OAR and predict NTCP in IMRT for T1-2 NPC.The NTCP of the LCNs is closely associated with target volume dose and irradiated volume.The dose to the LCNs and NTCP determined by the Chinese target volume delineation method are significantly lower than those determined by the RTOG method.
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BACKGROUND: To compare dosimetric parameters of intensity‑modulated radiation therapy (IMRT) with 3D conformal radiotherapy (3DCRT) in post‑operative patients of vulvar cancer and to assess clinical outcome and toxicity with IMRT. MATERIALS AND METHODS: A total of 8 post‑operative patients of vulvar cancer were treated with IMRT. All patients were also planned by 3DCRT for comparison with IMRT. The two plans were compared in terms of conformity index, homogeneity index, tumor control probability (TCP) and normal tissue complication probability (NTCP) for the planning target volume and organs at risk (OAR). RESULTS: IMRT resulted in significantly lesser doses to rectum, bladder, bowel and femoral head as compared with 3DCRT plans. Mean conformity and homogeneity indices were better and within range with IMRT. The TCP was comparable between the two treatment plans and NTCP for rectum, bladder, bowel and femoral head was significantly less with IMRT as compared with 3DCRT. Treatment was well‑tolerated and none of the patients developed Grade 3 or higher toxicity. CONCLUSION: IMRT yielded superior plans with respect to target coverage, homogeneity and conformality while lowering dose to adjacent OAR as compared with 3DCRT. Thus, IMRT offers a reduction in NTCP while maintaining TCP.
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PURPOSE: Toxicity of mucosa is one of the major concerns of radiotherapy (RT), when a target tumor is located near a mucosal lined organ. Energy of photon RT is transferred primarily by secondary electrons. If these secondary electrons could be removed in an internal cavity of mucosal lined organ, the mucosa will be spared without compromising the target tumor dose. The purpose of this study was to present a RT dose reduction in near target inner-surface (NTIS) of internal cavity, using Lorentz force of magnetic field. MATERIALS AND METHODS: Tissue equivalent phantoms, composed with a cylinder shaped internal cavity, and adjacent a target tumor part, were developed. The phantoms were irradiated using 6 MV photon beam, with or without 0.3 T of perpendicular magnetic field. Two experimental models were developed: single beam model (SBM) to analyze central axis dose distributions and multiple beam model (MBM) to simulate a clinical case of prostate cancer with rectum. RT dose of NTIS of internal cavity and target tumor area (TTA) were measured. RESULTS: With magnetic field applied, bending effect of dose distribution was visualized. The depth dose distribution of SBM showed 28.1% dose reduction of NTIS and little difference in dose of TTA with magnetic field. In MBM, cross-sectional dose of NTIS was reduced by 33.1% with magnetic field, while TTA dose were the same, irrespective of magnetic field. CONCLUSION: RT dose of mucosal lined organ, located near treatment target, could be modulated by perpendicular magnetic field.
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Axis, Cervical Vertebra , Magnetic Fields , Models, Theoretical , Mucous Membrane , Prostatic Neoplasms , Radiation Injuries , Radiotherapy , RectumABSTRACT
Patients treated with radiotherapy (RT) might experience a large variation in normal tissues. Severe radiation damage in a minority of patients limits the doses that might be safe given to the majority. The possibility of predicting such radiation-induced damage would provide a better treatment schedule for the patients. Several predictive tests in peripheral blood lymphocytes such as initial DNA damage, radiation-induced apoptosis and genetic variation have been proposed to know the individual sensitivity of patients to the radiotherapy schedules. This study aimed to summarize the main studies regarding to this ifeld.
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Objective To investigate the impact of oral contrast agent for assisting in outlining the small bowel on pelvic volumetric modulated arc therapy (VMAT) dose in patients with cervical cancer.Methods Nine cervical cancer patients for postoperative radiotherapy underwent CT scans,and the target volumes and organs at risk including the small bowel were contoured.The VMAT plan was designed for each case.Then another plan was generated by re-calculating the radiation dose after changing the electron density of the small bowel.The first plan (plan A) was the conventional VMAT plan,and the second one (plan B) specified the electron density of the small bowel.Paired t-test was used to compare the dose distribution between the two plans.Results The Dg8,D5o,conformity index,and homogeneity index of plans A and B were 4 989.1 vs.5 000.1 cGy (P =0.026),5 208.6 vs.5 191.6 cGy (P =0.005),0.766 vs.0.765 (P =0.920),and 0.081 vs.0.074(P =0.055),respectively.The volumes of the small bowel receiving at least 30 Gy for plans A and B were 309.3 vs.314.3 cm3(P =0.207),while bladder V45 of the two plans was 52.4％ vs.51.1％ (P =0.168).To achieve the same prescribed dose,plan A and plan B needed 893.3 MU and 865.8 MU (P =0.093).Conclusions The contrast agent filling the small bowel does not lead to a significant increase in the pelvic VMAT dose in patients with cervical cancer after surgery.
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To summarize current knowledge regarding mechanisms of radiation-induced normal tissue injury and medical countermeasures available to reduce its severity. Advances in radiation delivery using megavoltage and intensity-modulated radiation therapy have permitted delivery of higher doses of radiation to well-defined tumor target tissues. Injury to critical normal tissues and organs, however, poses substantial risks in the curative treatment of cancers, especially when radiation is administered in combination with chemotherapy. The principal pathogenesis is initiated by depletion of tissue stem cells and progenitor cells and damage to vascular endothelial microvessels. Emerging concepts of radiation-induced normal tissue toxicity suggest that the recovery and repopulation of stromal stem cells remain chronically impaired by long-lived free radicals, reactive oxygen species, and pro-inflammatory cytokines/chemokines resulting in progressive damage after radiation exposure. Better understanding the mechanisms mediating interactions among excessive generation of reactive oxygen species, production of pro-inflammatory cytokines and activated macrophages, and role of bone marrow-derived progenitor and stem cells may provide novel insight on the pathogenesis of radiation-induced injury of tissues. Further understanding the molecular signaling pathways of cytokines and chemokines would reveal novel targets for protecting or mitigating radiation injury of tissues and organs.
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Chemokines , Cytokines , Drug Therapy , Free Radicals , Macrophages , Microvessels , Negotiating , Radiation Injuries , Reactive Oxygen Species , Stem CellsABSTRACT
Objective To study the CBCT image registration of PTV enlarging distance and IMRT planning(CT-1) for patients with lung cancer,and evaluate their characters.Methods Ten patients with lung cancer were included in the study.Two sets image,before and after radiotherapy,were acquired every week.Then delineated the targeted volume and made the planning (CT-2) according the enlarging distance data.To comparize the parameters of DVH for lung and spinal cord,volumes and dose of PTV and NTCP with CT-1 and CT-2.The difference of two plan was analyzed by covariance analysis or Wilcoxson's z-test.Results The max,min and mean dose of PTV,the lung V5,V10,V20,V30,V50 were similar in both plans (P =0.242-0.663).There was superiority in CT-2 of PTV and lung's mean dose(P =0.049,0,035).The NTCP had the decent tendency followed by the increasing of lung Vs,V10,V20(P =0.146,0.053,0.000).Conclusions CBCT based image registration can reduce PTV,the mean dose of lung,NTCP,and increase PTV dose.This provides a tool for exploring acurate radiotherapy strategies.
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PURPOSE: Parotid gland can be considered as a risk organ in whole brain radiotherapy (WBRT). The purpose of this study is to evaluate the parotid gland sparing effect of computed tomography (CT)-based WBRT compared to 2-dimensional plan with conventional field margin. MATERIALS AND METHODS: From January 2008 to April 2011, 53 patients underwent WBRT using CT-based simulation. Bilateral two-field arrangement was used and the prescribed dose was 30 Gy in 10 fractions. We compared the parotid dose between 2 radiotherapy plans using different lower field margins: conventional field to the lower level of the atlas (CF) and modified field fitted to the brain tissue (MF). RESULTS: Averages of mean parotid dose of the 2 protocols with CF and MF were 17.4 Gy and 8.7 Gy, respectively (p or =20 Gy were observed in 15 (28.3%) for CF and in 0 (0.0%) for MF. The whole brain percentage volumes receiving >98% of prescribed dose were 99.7% for CF and 99.5% for MF. CONCLUSION: Compared to WBRT with CF, CT-based lower field margin modification is a simple and effective technique for sparing the parotid gland, while providing similar dose coverage of the whole brain.
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Humans , Brain , Parotid Gland , XerostomiaABSTRACT
PURPOSE: To develop the dose volume histogram (DVH) management software which guides the evaluation of radiotherapy (RT) plan of a new case according to the biological consequences of the DVHs from the previously treated patients. MATERIALS AND METHODS: We determined the radiation pneumonitis (RP) as an biological response parameter in order to develop DVH management software. We retrospectively reviewed the medical records of lung cancer patients treated with curative 3-dimensional conformal radiation therapy (3D-CRT). The biological event was defined as RP of the Radiation Therapy Oncology Group (RTOG) grade III or more. RESULTS: The DVH management software consisted of three parts (pre-existing DVH database, graphical tool, and Pinnacle3 script). The pre-existing DVH data were retrieved from 128 patients. RP events were tagged to the specific DVH data through retrospective review of patients' medical records. The graphical tool was developed to present the complication histogram derived from the pre-existing database (DVH and RP) and was implemented into the radiation treatment planning (RTP) system, Pinnacle3 v8.0 (Phillips Healthcare). The software was designed for the pre-existing database to be updated easily by tagging the specific DVH data with the new incidence of RP events at the time of patients' follow-up. CONCLUSION: We developed the DVH management software as an effective tool to incorporate the phenomenological consequences derived from the pre-existing database in the evaluation of a new RT plan. It can be used not only for lung cancer patients but also for the other disease site with different toxicity parameters.
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Humans , Incidence , Lung Neoplasms , Medical Records , Radiation Pneumonitis , Retrospective StudiesABSTRACT
The applicability and feasibility of TomoTherapy in the lung radiation surgery was analyzed by comparison of the calculated dose distribution in TomoTherapy planning with the results of conventional IMRS (intensity modulated radiation surgery) using LINAC (linear accelerator). The acquired CT (computed tomograph) images of total 10 patients whose tumors' motion were less than 5 mm were used in the radiation surgery planning and the same prescribed dose and the same dose constraints were used between TomoTherapy and LINAC. The results of TomoTherapy planning fulfilled the dose requirement in GTV (gross tumor volume) and OAR (organ at risk) in the same with the conventional IMRS using LINAC. TomoTherapy was superior in the view point of low dose in the normal lung tissue and conventional LINAC was superior in the dose homogeneity in GTV. The calculated time for treatment beam delivery was long more than two times in TomoTherapy compared with the conventional LINAC. Based on the results in this study, TomoTherapy can be evaluated as an effective way of lung radiation surgery for the patients whose tumor motion is little when the optimal planning is produced considering patient's condition and suitability of dose distribution.