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To study an automatic plan(AP) method for radiotherapy after breast-conserving surgery based on TiGRT system and and compare with manual plan (MP). The dosimetry parameters of 10 patients and the evaluation of scoring table were analyzed, it was found that the targets dose of AP were better than that of MP, but there was no statistical difference except for CI, The V5, V20 and V30 of affected lungs and whole lungs in AP were lower than all that in MP, the Dmean of hearts was slightly higher than that of MP, but the difference was not statistically significant, the MU of AP was increase by 16.1% compared with MP, the score of AP evaluation was increase by 6.1% compared with MP. So the AP could be programmed and automated while ensuring the quality of the plan, and can be used to design the plans for radiotherapy after breast-conserving surgery.
Subject(s)
Female , Humans , Breast Neoplasms/surgery , Mastectomy, Segmental , Organs at Risk , Radiotherapy Dosage , Radiotherapy Planning, Computer-Assisted , Radiotherapy, Intensity-ModulatedABSTRACT
Objective:To explore the beam performance of GTR 360° PBS dedicated nozzle for IBA Proteus Plus proton system and evaluate the beam characteristics of PBS during acceptance test procedure (ATP) to meet the precision and safety requirements of clinical treatment.Methods:According to the requirements of acceptance tests, the beam tests of PBS mainly included: test of integrated depth dose (IDD), test of maximum field size at the maximum and minimum ranges, field uniformity and informative PBS tests for the GTR 360°, test of lateral dose uniformity in a single field uniform dose in a cube, test of longitudinal dose uniformity in a single field uniform dose in a cube, and test of monitor unit reproducibility and proportionality.Results:The maximum deviation measured of range, fall back accuracy and distal fall-off was 0.03 g/m 2, 0.01 g/m 2 and 0.078 g/m 2, respectively. Maximum field size at the maximum and minimum ranges was 30.2 cm×40.2 cm and 30.1 cm×40.1 cm, respectively. During the different gantry angles and ranges, the lowest γ passing rate of a pattern plan was 97%, the maximum deviation of the centrical beam spot size at the X and Y axes was -0.16 mm and -0.21 mm, and the worst symmetry was 0.80%. Compared with the centrical beam spot, the maximum size deviation of the other beam spots was 0.11 mm and 0.14 mm at the X and Y axes, and the maximum position accuracy deviation of the beam spot was 0.60 mm and 0.43 mm at the X and Y axes. The maximum deviation of lateral dose uniformity at at the X and Y axes was 0.55% and 0.80% in the high energy region, and 0.6% and 0.75% in the low energy region. The maximum deviation of longitudinal dose uniformity was 0.79% in the high energy region, and 2.22% in the low energy region. The monitor unit (MU) reproducibility factor was 0.106% and the maximum proportionality deviation was 0.67%. Conclusion:The dedicated nozzle of PBS has passed all the beam performance acceptance tests, which meet the requirements of all parameters, and the whole system yields relatively high accuracy, repeatability and good stability.
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Objective To study the dosimetric characteristics and plan quality of PTV-based intensity modulated proton radiotherapy (IMPT) and volumetric-modulated arc therapy (VMAT) plans for prostate cancer,so as to provide a reference for clinical application.Methods A total of 10 prostate cancer cases were included in this retrospective study.IMPT and RapidArc plans were designed by RayStation and Eclipse TPS based on PTV,respectively.For each case,IMPT plans were generated using multiple field optimization (MFO) technique with two parallel-opposed lateral fields,whereas RapidArc plans were generated using double-arc technique (two full arcs).Final dose calculation of IMPT was conducted by pencil beam (PB) and Monte Carlo (MC) algorithm,respectively,with adopted data model from the pencil beam scanning (PBS) proton therapy system of IBA Protues Plus (IBA Group,Belgium);The data model originated from the linear accelerator of Varian Clinac iX (Varian Medical Systems,America) was used for RapidArc plans.Dosimetric parameters of DVH and dose distribution were used to compare the dose differences in targets and organs at risk (OARs) between these two treatment techniques.Results For targets,HIs of PB-IMPT and MC-IMPT were slightly better than that of RapidArc,but CI of IMPT was slightly lower than that of RapidArc;D1 of PB-IMPT was significantly better than those of MC-IMPT and RapidArc (Z =-2.805,-2.803,P ＜ 0.05).PB-IMPT and MC-IMPT achieved better protection than RapidArc on rectum V30 (Z =-2.191,-1.988,P＜ 0.05) and D (Z =-2.599,-2.497,P＜0.05),bladder V30 (Z=-2.701,-2.701,P＜0.05),V40 (Z=-2.395,-2.395,P＜0.05) and D (Z =-2.701,-2.701,P ＜ 0.05).There was no significant difference between PB-IMPT and MC-IMPT plans for prostate cancer,except for the D1％ [(73.86t67.34) Gy vs.(75.45±2.01) Gy] (RBE) and HI [(0.040±0.010) vs.(0.058±0.020)] of the target.Conclusions Both techniques can meet the clinical requirements,but IMPT showed significant dosimetric advantages compared with RapidArch by reducing the dose to OARs and improving the plan quality.
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Objective@#To study the dosimetric characteristics and plan quality of PTV-based intensity modulated proton radiotherapy (IMPT) and volumetric-modulated arc therapy (VMAT) plans for prostate cancer, so as to provide a reference for clinical application.@*Methods@#A total of 10 prostate cancer cases were included in this retrospective study. IMPT and RapidArc plans were designed by RayStation and Eclipse TPS based on PTV, respectively. For each case, IMPT plans were generated using multiple field optimization (MFO) technique with two parallel-opposed lateral fields, whereas RapidArc plans were generated using double-arc technique (two full arcs). Final dose calculation of IMPT was conducted by pencil beam(PB) and Monte Carlo (MC) algorithm, respectively, with adopted data model from the pencil beam scanning (PBS) proton therapy system of IBA Protues Plus(IBA Group, Belgium); The data model originated from the linear accelerator of Varian Clinac iX (Varian Medical Systems, America) was used for RapidArc plans. Dosimetric parameters of DVH and dose distribution were used to compare the dose differences in targets and organs at risk (OARs) between these two treatment techniques.@*Results@#For targets, HIs of PB-IMPT and MC-IMPT were slightly better than that of RapidArc , but CI of IMPT was slightly lower than that of RapidArc; D1% of PB-IMPT was significantly better than those of MC-IMPT and RapidArc (Z=-2.805, -2.803, P<0.05). PB-IMPT and MC-IMPT achieved better protection than RapidArc on rectum V30(Z=-2.191, -1.988, P<0.05)and Dmean(Z=-2.599, -2.497, P<0.05), bladder V30(Z=-2.701, -2.701, P<0.05), V40(Z=-2.395, -2.395, P<0.05)and Dmean(Z=-2.701, -2.701, P<0.05). There was no significant difference between PB-IMPT and MC-IMPT plans for prostate cancer, except for the D1% [(73.86±67.34) Gy vs.(75.45±2.01) Gy] (RBE) and HI [(0.040±0.010) vs. (0.058±0.020)] of the target.@*Conclusions@#Both techniques can meet the clinical requirements, but IMPT showed significant dosimetric advantages compared with RapidArch by reducing the dose to OARs and improving the plan quality.
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Objective To investigate the plan quality between two treatment planning systems (TPSs) for volumetric modulated arc therapy (VMAT). Methods VMAT plans based on Varian Eclipse and Philips Pinnacle TPS were designed for 10 cervical cancer patients (2, 3 Arcs) and 10 prostate cancer patients ( 1, 2 Arcs) . The delivery system of VMAT was Varian ClinaciX machine, and RapidArc was used. The treatment plan quality between the two TPSs was evaluated based on dose distribution, delivery efficiency, and parameter settings. The differences between the two TPSs were compared using paired t-test. Results For cervical cancer patients, the 2-Arc VMAT plans based on the Pinnacle was slightly better than those based on the Eclipse in terms of the conformal index ( CI) of planning target volume ( PTV) , rectum V30 and V40 , and bladder V30 and V40 , and the homogeneity index ( HI) of PTV and PTV1 as well as CI of PTV1 in the Eclips were slightly better than those in the Pinnacle( P<005) Pinnacle were slightly worse than those in the Eclipse ( P>005) . The number of monitor units with 2-Arcs and 3-Arcs plans of the Eclipse was significantly smaller than those in the Pinnacle (P<005). For prostate cancer patients, The 1-arc VMAT plans of the Pinnacle TPS were slightly superior to those of the Eclipse TPS in terms of the HI of PTV, rectumV30 and V40 , and bladderV30 and V40 , but the former was slight inferior to the latter in terms of the CI of PTV (P<005). The number of monitor units of 1-arc and 2-Arcs plans showed no significant difference between the two TPSs (P>005). Conclusions For patients with cervical cancer and prostate cancer, the VMAT plans based on Varian Eclipse and Philips Pinnacle TPS can achieve a clinically acceptable dose distribution and show a little difference in the treatment plan quality. However, we will still need more cases to further study and determine the performance characteristics of the commercial TPSs for optimizing VMAT.
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Objective To investigate the plan quality between two treatment planning systems (TPSs) for volumetric modulated arc therapy (VMAT). Methods VMAT plans based on Varian Eclipse and Philips Pinnacle TPS were designed for 10 cervical cancer patients (2, 3 Arcs) and 10 prostate cancer patients ( 1, 2 Arcs) . The delivery system of VMAT was Varian ClinaciX machine, and RapidArc was used. The treatment plan quality between the two TPSs was evaluated based on dose distribution, delivery efficiency, and parameter settings. The differences between the two TPSs were compared using paired t-test. Results For cervical cancer patients, the 2-Arc VMAT plans based on the Pinnacle was slightly better than those based on the Eclipse in terms of the conformal index ( CI) of planning target volume ( PTV) , rectum V30 and V40 , and bladder V30 and V40 , and the homogeneity index ( HI) of PTV and PTV1 as well as CI of PTV1 in the Eclips were slightly better than those in the Pinnacle( P<005) Pinnacle were slightly worse than those in the Eclipse ( P>005) . The number of monitor units with 2-Arcs and 3-Arcs plans of the Eclipse was significantly smaller than those in the Pinnacle (P<005). For prostate cancer patients, The 1-arc VMAT plans of the Pinnacle TPS were slightly superior to those of the Eclipse TPS in terms of the HI of PTV, rectumV30 and V40 , and bladderV30 and V40 , but the former was slight inferior to the latter in terms of the CI of PTV (P<005). The number of monitor units of 1-arc and 2-Arcs plans showed no significant difference between the two TPSs (P>005). Conclusions For patients with cervical cancer and prostate cancer, the VMAT plans based on Varian Eclipse and Philips Pinnacle TPS can achieve a clinically acceptable dose distribution and show a little difference in the treatment plan quality. However, we will still need more cases to further study and determine the performance characteristics of the commercial TPSs for optimizing VMAT.
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To investigate the patient-specific dose verification method using ArcCHECK for total marrow irradiation (TMI) with Volumetric Modulated Arc Therapy (VMAT) and Helical Tomotherapy (HT). The kVCT images collected from 8 patients were respectively designed for RapidArc and Tomotherapy plans in total marrow irradiation. ArcCHECK was used for dose verification for the head-neck, chest-abdomen and pelvic. The merging function of ArcCHECK was used in VMAT and the method of double plans (reference and delivery plans) were used in HT. The γ-analysis passing rates for the head-neck, chest-abdomen, pelvic were 98.9% ± 1.9%, 98.4% ± 1.8%, 97.4% ± 2.1% for VMAT plans and 94.3% ± 1.5%, 96.5 ± 1.2%, 94.1% ± 1.9% for HT plans. The results show that using the merging function of ArcCHECK can achieve the dose verification well for VMAT plans with TMI. The method of double plans was done for the dose verification of HT plans with TMI as well as the plans with the targets keeping away from the set-up center.
Subject(s)
Humans , Bone Marrow , Radiation Effects , Radiotherapy Dosage , Radiotherapy Planning, Computer-Assisted , Radiotherapy, Intensity-ModulatedABSTRACT
To investigate the dose effect of isocenter difference during IMRT dose verification with the 2D chamber array. The samples collected from 10 patients were respectively designed for IMRT plans, the isocenter of which was independently defined as P(o), P(x) and P(y). P(o) was fixed on the target center and the other points shifted 8cm from the target center in the orientation of x/y. The PTW729 was used for 2D dose verification in the 3 groups which beams of plans were set to 0 degrees. The γ-analysis passing rates for the whole plan and each beam were gotten using the different standards in the 3 groups, The results showed the mean passing rate of γ-analysis was highest in the P(o) group, and the mean passing rate of the whole plan was better than that of each beam. In addition, it became worse with the increase of dose leakage between the leaves in P(y) group. Therefore, the determination of isocenter has a visible effect for IMRT dose verification of the 2D chamber array, The isocenter of the planning design should be close to the geometric center of target.
Subject(s)
Humans , Gamma Rays , Radiotherapy Dosage , Radiotherapy, Intensity-Modulated , MethodsABSTRACT
The QUASAR Penta-guide Phantom with fiducial markers was scanned, and the CT images were transferred to Pinnacle workstation. Skin and target volumes were contoured and transferred to TomoPlan treatment planning system. The phantom was scanned with Megavoltage CT (MVCT). MVCT images were matched to the planning CT. Automatic adjustment of treatment couch was completed. It was found that the green laser coincided with the etched center crosshairs in lateral and longitudinal directions with an error less than 2 mm. However 2 mm vertical tabletop lag was found, but could be eventually corrected. Verifications for specific patients with head and pelvic tumors were also completed, the residual setup error were analyzed. The automatic movement of tabletop after image match is satisfactory.
Subject(s)
Humans , Radiotherapy Planning, Computer-Assisted , Methods , Radiotherapy, Intensity-Modulated , Methods , Tomography, Spiral Computed , MethodsABSTRACT
OBJECTIVE@#To observe the effect of adaptive replanning on adverse reactions and clinical outcome of nasopharyngeal carcinoma treated by helical tomotherapy.@*METHODS@#Fifty nasopharyngeal carcinoma patients treated by TomoTherapy system were retrospectively analyzed. Among these patients, 25 received repetitive CT simulation and replanning, and another 25 case-matched control patients without replanning were identified by matching age, gender, pathological type, UICC stage, weight loss, etc. Wilcoxon test was used to evaluate the effect of replanning on acute and chronic radiation reactions within individuals. Kaplan-Meier study was used to estimate the survival of patients with or without replanning.@*RESULTS@#There was a significant difference in late salivary grand damage between the replanning and the control group (P=0.046), while no difference was observed in acute or other late side effects between the two groups. The median follow-up of the two groups was 32 months (7-42 months) and 26 months (8-46 months), respectively. The median local relapse-free survival time, 2-year local relapse-free survival and 2-year lymphnode relapse-free survival in the two groups were similar (36 months, 92% and 100%). No significant difference was found in the 2-year metastasis relapsefree survival (80% and 96%) and the 2-year overall survival between the two groups (88% and 92%, P>0.05).@*CONCLUSION@#Adaptive replanning may reduce the severity of late damage of salivary glands after helical tomotherapy in nasopharyngeal carcinoma patients without improvement of 2-year survival rate.
Subject(s)
Adult , Female , Humans , Male , Carcinoma , Carcinoma, Squamous Cell , Radiotherapy , Nasopharyngeal Carcinoma , Nasopharyngeal Neoplasms , Radiotherapy , Radiotherapy Planning, Computer-Assisted , Methods , Radiotherapy, Intensity-Modulated , Retrospective Studies , Survival Rate , Treatment OutcomeABSTRACT
Objective To summarize the outcome of nasopharyngeal carcinoma ( NPC) treated by helical tomotherapy in the Chinese PLA general hospital. Methods Between September 2007 and August 2010, 121 newly diagnosed NPC patients were treated by radiotherapy with Tomotherapy system, with ( n =90) or without ( n = 31) concurrent chemotherapy or molecular target therapy. The prescription dose was 70 - 74 Gy/33f to primary tumor and positive lymph node planning target volume,60. 0 - 62. 7 Gy/33f to high risk planning target volume, and 52 -56 Gy/33f to low risk planning target volume. Acute side-effects were evaluated with RTOG/EORTC criteria. Results The remission rate of primary lesion and positive lymph nodes was 95. 0％ and 99. 0％ , respectively. The follow-up rate was 100％ . The number of patients with 1 ,2 and 3 years followed-up were 99 , 49 , and 7. The 1-, 2-and 3-year local relapse-free survival rates were 97. 30％ , 97. 3％ and 97. 3％ , respectively. The 1-,2-and 3-year nodal relapse-free survival rates were 100％ , 100％ and lOO％, respectively. The 1-, 2-and 3-year distant metastasis-free survival rates were 98. 4％ , 96. 3％ and 96. 3％ , respectively. The 1-, 2-and 3-year overall survival rates were 96. 5％ ,92. 6％ and 86. 8％ , respectively. Acute toxicities of skin, oral mucosa and xerostomia with grade 0,1,2 and 3 were 5. 0％ , 74. 4％ , 15. 7％ and 4. 9％ ; 0. 8％ , 37. 2％ , 57. 9％ and 4. 1％ ; 3. 3％ , 53. 7％ ,43. 0％ and 0％ , respectively. Xerostomia restored with time, no grade 2 or more xerostomia was observed 1 year after radiation therapy. Concurrent chemotherapy significantly increased incidence of mucositis,esophagitis and tracheitis. Conclusion Helical tomotherapy is efficient, secure and effective modality for the treatment of nasopharyngeal carcinoma.
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<p><b>OBJECTIVE</b>To implement dose reconstruction and dose-guided intensity modulated radiotherapy for helical tomotherapy.</p><p><b>METHODS</b>Dose reconstruction was implemented on adaptive helical tomotherapy with the online megavoltage CT (MVCT) imaging from a patient with nasopharyngeal cancer. The differences of isodose line between actual and planned deposition were analysis in 3D distribution, on which the hot spot and cold spot were lined. The dose delivered to these areas was modulated in later fractions to keep the planned requirement.</p><p><b>RESULTS</b>The differences between actual and planned isodose line were shown on the image visually. The modulation to the hot spot and cold spot in later fraction corrected the incorrectly delivered dose to achieve the requirement of primary plan.</p><p><b>CONCLUSIONS</b>The dose reconstruction and dose-guided intensity modulated radiotherapy can be implemented in adaptive helical tomotherapy.</p>
Subject(s)
Humans , Radiotherapy Dosage , Radiotherapy Planning, Computer-Assisted , Methods , Radiotherapy, Intensity-Modulated , Methods , Tomography, Spiral Computed , MethodsABSTRACT
Objective To evaluate the dosimetric characteristics of helical tomotherapy (HT),intensity-modulated radiation therapy (IMRT) and three-dimensional conformal radiation therapy (3D-CRT) for postoperative radiotherapy of rectal cancer.Methods Ten male patients with stage Ⅱ or Ⅲ middle or low position rectal cancer were selected retrospectively.All of the 10 patients underwent Dixon surgery and CT simulation orientation.The target volumes and normal organs were drawn in the CT images and the plans for HT,IMRT and 3D-CRT were designed.The prescribed dose was given 50 Gy in 25 fractions,covering at least 95％ of the planning target volume.Results All plans met the needs of the prescribed doses.The HT and IMRT plans met the needs of dose limit to organs at risk,however,the 3D-CRT plans failed to do that.The conformity indexes of HT,IMRT and 3D-CRT plans were 0.86,0.82 and 0.62,respectively (F =206.81,P ＜ 0.001),and the homogeneity indexes were 0.001,0.157,and 0.205,respectively (x2 =15.8,P ＜ 0.001).The 3D-CRT plans had larger volumes than the HT plans and IMRT plans in the high-dose regions such as pelvic V50,bladder V40,bowel V50 and femoral head D5 (P ＜ 0.05),but the differences between the HT plans and IMRT plans were not statistically significant (P ＞0.05).The V15 value of bowel of HT plans were higher than those of the IMRT and 3D-CRT plans (71.1％ vs.63.3％ and 67.7％,respectively).However,there was no significantly difference.Conclusions All of the HT,IMRT and 3D-CRT plans are able to meet the prescription dose requirement of the target regions of rectal cancer.The HT plans show the best dose homogeneity and target conformity,followed by the IMRT plans,and then the 3D-CRT plans.The HT plans meet the needs of all OARs slightly better than the IMRT plans.3D-CRT plans are simple and practical with poor protective ability toward the OARs.
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Objective The aim of this work is to compare the performances of EDR2 film dosimetry with two-dimensional ion chamber array (2DICA) in quality assurance (QA) procedures and to investigate the origin of possible discrepancies between the two methods.Methods A 2DICA, I′mRT MatriXX and MULTICube equivalent solid water phantom from IBA Company were used to verify the dose distribution of 15 tomotherapy plan cases.The combined phantom which includes EDR2 film on the array was set up to measure the dose distribution from coronal and sagittal orientations.After the irradiation, the dose distributions of 2DICA and film were compared with those calculated in the planning system for verification.The results and efficiency were evaluated independently in the two methods.Results The mean number of points satifying γ parameter ≤1 in the coronal and sagittal planes was 97.00%±1.56%& 95.98%±2.52%(t=-2.22,P=0.043) and 98.28%±1.55%& 95.42%±1.99%(t=0.75,P=0.464) of the 15 cases respectively for 2DICA and EDR2 film.The ratio of more than 90% and 95% were 93.3% and 66.7%.The results we presented show a very good agreement between the two methods when used to assess the dose distribution between calculated and measured doses,and a certain degree of correlation (r=0.14,P=0.001).Conclusions The 2DICA may effectively replace both film and ion chamber dosimetry in routine IMRT QA.The good agreement between 2DICA and EDR2 film may give a possible check regularly just as a gold standard.
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Objective To evaluate the clinical outcome and the acute toxicity in nasopharyngeal carcinoma (NPC) treated with tomotherapy followed by the anti-EGFR monoclonal antibody.Methods Between March 2008 and November 2009,34 newly diagnosed NPC patients were treated with helical tomotherapy combined with nimotuzumab or cetuximab.All the patients underwent tomotherapy at the dose of 70 Gy/33F for the gross tumor volume (pGTVns) and positive lymphnodes (GTVnd) ,and 60 Gy/33F for the high risk clinical target volume (PTV1),and 56 Gy/33 F for the low risk clinical target volume (PTV2),respectively.17 patients in group N were given weekly injection of 200 mg for 6-7 times and 17 patients in group C were given initial dosage 400 mg/m2 followed by subsequent weekly dosage of 250 mg/m2 for 6-7 times.Acute lesions were evaluated with the RTOG/EORTC criteria.Result The median follow-up time was 22 months.The effective rates (CR + PR) in 3,6 and 12 months were 14/17,12/17,12/17 in group N and 15/17,14/17,14/17 in group C.The 1 year survival rate was 15/17 in group Nand 17/17 in group C.Nimotuzumab had less acute mucositis reaction (u = 2.25,P < 0.05),weight loss(t=2.56,P=0.02) and rash (u=4.36,P＜0.01) compared with cetuximab.Conclusions Helical tomotherapy combined with nimotuzumab or cetuximab was effective and made no difference in the shortterm efficacy and 1 year survival rate for the patients with NPC.Nimotuzumab has less acute reaction than cetuximab.More studies should be done to prove long-term effects.
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<p><b>OBJECTIVE</b>To evaluate the image quality of megavoltage computed Tomography imaging.</p><p><b>METHODS</b>The HU uniformity and linearity, image noise, spatial resolution, low contrast resolution and spatial linearity in MVCT mode were evaluated with Catphan 600 phantom, and the factor of pitch was also evaluated. Influencing factors of image quality were also discussed.</p><p><b>RESULTS</b>The MVCT values depended linearly on the physical density of the sample. The MVCT values uniformity was good. The spatial resolution was 4 lp/cm. The use of an MV Beam for imaging results in the loss of low contrast resolution, but it is sufficient for pretreatment image guidance. The geometric accuracy was good.</p><p><b>CONCLUSIONS</b>The image quality of MVCT is less than that of KVCT, but is good enough for IGRT.</p>
Subject(s)
Radiotherapy Planning, Computer-Assisted , Tomography, Spiral ComputedABSTRACT
Objective To investigate the dosimetric characteristics of helical tomotherapy(HT),intensity-modulated radiation therapy(IMRT)and three.dimensional conformal radiation therapy(3D-CRT)for the post-operative breast cancer as well as their comparison in protecting the normal tissues.Methods The CT images of 10 postoperative patients with early stage breast cancer were transferRed into HT and IMRT and 3D- CRT planning system respectively after the target region and normal tissues were drawn out with the same doctor.Each prescribed dose for three kinds of plans was 50 Gy/25 fractions.Inrradiation doses and volume at heart and double lungs as well as conformity index(CI)and homogeneity index(HI)were evaluated.Results The PTV volume of prescribed target dose of 95% and 100%in HT, IMRT and 3D-CRT groups were 99.13%and 95.87%,97.80%and 94.05%,96.37%and 87.29%.respectively.The CI and HI in HT.IMRT and 3D-CRT groups were 0.80±0.10 and 1.09 ±0.03,0.65±0.07 and 1.14±0.02,0.40±0.08 and 1.17±0.04,respectively V5,V10 and V20 of the heart were the lowest at 3D-CRT than HT and lM RT.V5 of the diseased lung was the lowest at 3D-CRT compared to HT and IMRT.V5 and V10 of the healthy lung were the lowest at 3 D-CRT compared to other groups.Conclusions Compared with IMRT and 3D-CRT.HT technique in treating breast cancer had the best conformity index and homogeneity index as well as steeper dose gradient.Irradiated doses and volume at the heart was the lowest at 3D- CRT and the highest at IMRT.Irradiated doses and volume of the heart and healthy lung as well as the diseased lung were the lowest at 3D-CRT compared to HT and IMRT groups.
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Objective To compare the dosimetric characteristics of helical tomotherapy(HT)and step-and-shoot intensity modulated radiotherapy(IMRT)for post-operative cervix cancer patients. Methods Ten patients with post-operative cervix cancer were enrolled in this study.HT and IMRT plans were developed for each patient.The dose distributions of the targets,organs at risk(OARs),CI and HI were analyzed and compared.The prescribed dose was 60 Gy/25 f for CTV1,50 Gy/25 f for CTV2.The iso-dose line of 50 Gy was used.Results The homogeneity indexes(HI)(0.94±0.03),conformity index(C1)(1.28±0.02)in HT group were better than in IMRT group(0.85±0.01 and 1.36±0.03),respectively(t=5.12,-6.34,P<0.001).The Dmean of PTV in HT group(51.77 Gy)was lower than that in IMRT group(54.53 Gy)(t=-8.01,P<0.05).The Dmax ,Dmean,V30,V40 and V50 of bladder、rectum and small bowel were lower in HT group than those in IM RT group.The Dmax,Dmean,V30 and V40 of right and left femoral head were lower in HT group than those in IMRT group.Conclusion Helical tomotherapy treatment plan has a better homogeneity,steeper dose gradient,and a better protection for organs at risk.
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Objective To quantify dose variations of the parotid glands and spinal cord in nasopharyngeal carcinoma (NPC) patients during helical tomotherapy (HT) by using megavolt (MV) CT and planned adaptive application. Methods Five patients with advanced local-regional NPC were treated by HT with a prescription dose of 70 Gy in 35 fractions in primary tumor and involved lymph nodes. Daily MV CT scans were registered with the planning CT images. The parotid glands were re-contoured every 4 fractions to a total of 45 times, and location of the spinal cord were corrected by MVCT IGRT system every 2 fractions to a total of 85 times. The actual doses delivered to these organs were evaluated by using the planned adaptive application software of HT system. Results At the end of therapy, the mean volume of the parotid gland was decreased by 42% (left) and 33% (right) , respectively. The average V1 of the parotid was increased by 26. 0% (left) and 31.4% (right), and the D50 increased by 15. 8% (left) and 17. 3% (right), respectively. The average Dmax of the spinal cord was increased by 1.3%. Conclusions During HT, the parotid glands receive a higher actual dose due to the volume shrinkage, while the Dmax of the spinal cord changes little. By using adaptive radiation therapy technique, constant monitoring anatomic changes of organs at risk and selective replanning are necessary during radiation therapy for NPC.
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Objective To investigate the feasibility of dose verification of intensity modulated (IM) planning of helical tomotherapy (HT) using two-dimensional ion chamber array (2DICA),and develop an efficient way to validate the dose delivered under the parameters mirroring those during the treatment. Meth-ods A 2DICA,I'mRT MatriXX and MULTICube equivalent solid water phantom from IBA company were used to verify the dose distribution of 10 IM planning. The combined phantom was set up to measure the dose distributions on coronal and sagittal surface. The precise setup of phantom was guided by HTMVCT images. After the irradiation, the measured dose distributions on the coronal and sngittal plane were compared with those calculated by the IM planning system for verification. The results were evaluated and the feasibility of the different measuring methods was studied. Results The dose distribution measured by the MatriXX 2DICA was well consistent with that calculated by the treatment planning system. The errors between the measured dose and predicted dose in the selected points were within ±3%. In the comparison of the pixel-segmented ionization chamber versus treatment planning system using the 3 mm/3% γ criteria, the passing ratio of pixels with γ parameter ≤1 was 97.76% and 96.83%, respectively. Conclusions MatriXX is a-ble to measure the absolute and relative dose distributions simultaneously,which can be used for dose verifi-cation of IM planning.