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Objective:To investigate the efficacy and adverse reactions of simultaneous integrated boost intensity-modulated radiotherapy (SIB-IMRT) combined with chemotherapy in the treatment of superior mediastinal lymph node metastasis after esophageal cancer surgery.Methods:The clinical data of 72 patients with concurrent chemoradiotherapy for superior mediastinal lymph node metastasis after esophageal cancer surgery in Tai'an Cancer Prevention and Treatment Hospital from January 2019 to May 2021 were retrospectively analyzed, and they were divided into intensity-modulated radiotherapy (IMRT) group (36 cases) and SIB-IMRT group (36 cases) according to different radiotherapy methods. The short-term efficacy, long-term survival rate and adverse reactions of the two groups were compared.Results:The response rate in the IMRT group was 66.7% (24/36), the response rate in the SIB-IMRT group was 86.1% (31/36), and the difference between the two groups was statistically significant ( χ2 = 3.77, P = 0.047). The 1-, 2- and 3-year overall survival rates in the IMRT group were 75.0%, 44.4% and 27.8%, and the 1-, 2- and 3-year overall survival rates in the SIB-IMRT group were 83.3%, 52.8% and 33.3%; the difference in the overall survival between the two groups was not statistically significant ( χ2 = 0.70, P = 0.401). There were statistical differences in the incidence of leukopenia, radiation esophagitis and radiation pleural gastritis between the two groups (all P < 0.05). There were no statistical differences in the incidence of radiation pneumonia and gastrointestinal reactions between the two groups (both P > 0.05). Conclusions:SIB-IMRT combined with chemotherapy in patients with superior mediastinal lymph node metastasis after esophageal cancer surgery has good local control rate and mild adverse reactions.
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Objective:To develop a dose prediction-based quantitative evaluation method of the quality of radiotherapy plans, and to verify the clinical feasibility and clinical value of the method .Methods:The 3D U-Netwas trained using the radiotherapy plans of 45 rectal cancer cases that were formulated by physicists with more than five years of radiotherapy experience. After obtaining 3D dose distribution using 3D U-Net prediction, this study established the plan quality metrics of intensity modulated radiotherapy(IMRT) rectal cancer radiotherapy plans using dose-volume histogram(DVH) indexes of dose prediction. Then, the initial scores of rectal cancer radiotherapy plans were determined.Taking the predicted dose as the optimization goal, the radiotherapy plans were optimized and scored again. The clinical significance of this scoring method was verified by comparing the scores and dosimetric parameters of the 15 rectal cancer cases before and after optimization.Results:The radiotherapy plans before and after optimization all met the clinical dose requirements. The total scores were(77.21±9.74) before optimization, and (88.78±4.92) after optimization. Therefore, the optimized radiotherapy planswon increased scores with a statistically significant difference( t=-4.105, P<0.05). Compared to the plans before optimization, the optimized plans show decreased Dmax of all organs at risk to different extents. Moreover, the Dmax, V107%, and HI of PTV and the Dmax of the bladder decreased in the optimized plans, with statistically significant differences ( t=2.346-5.771, P<0.05). There was no statistically significant difference in other indexes before and after optimization ( P>0.05).The quality of the optimized plans were improved to a certain extent. Conclusions:This study proposed a dose prediction-based quantitative evaluation method of the quality of radiotherapy plans. It can be used for the effective personalized elevation of the quality of radiotherapy plans, which is beneficial to effectively compare and review the quality of clinical plans determined by different physicists and provide personalized dose indicators. Moreover, it can provide great guidance for the formulation of clinical therapy plans.
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Objective To investigate the dose calculation accuracy of two algorithms in Monaco TPS for self-made phantoms with different cavity thickness, and analyze the influence of phantoms with different cavity thickness on dose verification of upper esophageal cancer. Methods The phantoms with different cavity thickness were placed on the simulated CT positioning machine to scan and acquire images. In Monaco TPS, the irradiation fields with energy of 6 MV, 100 MU and different square field sizes were added to the acquired images. The dose of the cavity of the ionization chamber was calculated by two algorithms, and measured on the accelerator by dosimeter under the same conditions. At the same time, 20 patients with upper esophageal cancer who received dynamic intensity modulation in fixed field were randomly selected and included in the study, and two algorithms were used for dose verification on phantoms with different cavity thickness. The results were statistically analyzed by SPSS 22.0 software. Results The maximum deviations between the calculated values and the measured values were 0.66% and −1.8%, in the calculation of phantoms with different cavity thickness by algorithms of Monte Carlo and Pencil Beam. In Monte Carlo algorithm, the result of RD pair t test is P > 0.05. Paired t test of AD (0 mm, 10 mm), (5 mm, 10 mm) and (10 mm, 20 mm) groups showed no significant difference (P < 0.05). The maximum deviation was 1.1%, and the rest groups were not statisticely significant (P > 0.05); In Pencil Beam algorithm the t test results of RD (0 mm, 20 mm) and (5 mm, 20 mm) pairs were (P < 0.05), the maximum deviation was 0.58%, and the rest groups were (P > 0.05). In AD group, (P < 0.05), the maximum deviation was 2.78%; The paired t test between the two algorithms was (P < 0.05), and the maximum deviations in RD and AD groups were 2.49% and 4.14%, respectively. Conclusion Monte Carlo algorithm has accurate calculation and high gamma pass rate of dose verification, and there is no clinical difference in gamma pass rate of dose verification among phantoms with different cavity thickness, pencil Beam algorithm is not recommended in cavity phantom calculation.
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Introducción El tratamiento estándar en estadios tempranos del cáncer de mama es la cirugía conservadora (cc) más radioterapia del volumen total mamario (wbi). Dado que la mayoría de las recidivas locales ocurren cercanas al sitio del tumor (85%) y existiendo la posibilidad de acortar tiempos de irradiación debido a que esta insume varias semanas, podría no ser necesario irradiar toda la mama, sino el área donde estaba situado el tumor más margen de seguridad, lo que insume un menor tiempo. Este el fundamento de la Irradiación Parcial Acelerada Mama (apbi). Consensos internacionales proporcionan guías para administrar apbi fuera de ensayos clínicos. Objetivos El objetivo principal de este trabajo es determinar y analizar las características clinico-anatomopatológicas e inmunohistoquímicas de las pacientes que fueron operadas y luego seleccionadas para ser irradiadas con técnica de apbi con radioterapia externa con intensidad modulada guiada por imágenes (imrt). Material y método Se trata de un trabajo prospectivo, no randomizado. La muestra está constituida por las primeras 20 pacientes ingresadas al protocolo apbi. El reclutamiento se realizó entre marzo de 2012 y julio de 2014. Se analizaron las características clínico-patológicas e inmunohistoquímicas de esas pacientes luego de cc más biopsia del ganglio centinela (bgc). Resultados Media de seguimiento en meses: 37,7 (r: 22-51); edad media: 65,7 años. Tamaño tumoral medio por anatomía patológica: 12,03 mm. Media de número de ganglios centinelas extirpados: 1,7. Todos los tumores fueron unifocales. Los márgenes quirúrgicos resultaron negativos en todos los casos. Tumores Luminal A: 19 pacientes; tumores Luminal B: 1 paciente. Hormonoterapia adyuvante en todas las pacientes. Control locorregional: 100%. Conclusiones A pesar del corto tiempo de seguimiento y del escaso número de pacientes, este análisis sugiere que la apbi en el lecho del tumor marcado intraoperatoriamente con fiduciales de titanio es factible para pacientes que reúnen los criterios estrictos clínico-patológicos e inmunohistoquímicos acordes con las guías internacionales.
Introduction The standard conservative treatment for early stage breast carcinomas is the breast conservative surgery plus whole breast irradiation. Because most local recurrences occur close to the site of the primary tumor (80- 90%) and the possibility of shortening the irradiation times because it takes several weeks, it may not be necessary to irradiate the entire breast, but the area where the tumor was located plus a margin of safety in less time. This is the basis of Accelerated Partial Irradiation of the Breast Objectives Determination and analysis of clinical-pathological and immunohistochemical characteristics in patients selected for Accelerated Partial Breast Irradiation (apbi) performed by imrt + igrt technique after breast conservative surgery plus sentinel node biopsy. Materials and method A prospective, non-randomized study of the first 20 patients performed apbi strictly following the recommendations of international consensus. It was initiated in March 2012 until July 2014. Clinical-pathological and immunohistochemical characteristics of these patients were analyzed to be selected for apbi, after breast conservative surgery plus sentinel node biopsy. Results Median follow up: 37.7 months (r: 22-51); average age: 65.7 years. Mean tumor size by pathological analysis: 12.03 mm. Mean number of sentinel nodes removed: 1.7. All tumors were unifocal. Negative surgical margins in all cases. Luminal A tumors: 19 patients; Luminal B tumors: 1 patient. Adjuvant hormone therapy in all patients. Loco-regional control: 100%. Conclusions Despite the short time of follow up and the small numbers of patients, this analysis suggests that apbi performed by imrt + igrt technique added to the placement of fiduciary marks at the time of surgery is feasible for highly selected patients who meet the clinical-pathological and immunohistochemical selection criteria according to international guidelines
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Humains , Femelle , Tumeurs du sein , Radiothérapie , Titane , Biopsie de noeud lymphatique sentinelle , GanglionsRésumé
Locoregional failure is the most frequent pattern of failure in locally advanced head and neck cancer patients and it leads to death in most of the patients. Second primary tumors occurring in the other head and neck region reach up to almost 40% of long-term survivors. Recommended and preferred retreatment option in operable patients is salvage surgical resection, reporting a 5-year overall survival of up to 40%. However, because of tumor location, extent, and underlying comorbidities, salvage surgery is often limited and compromised by incomplete resection. Reirradiation with or without combined chemotherapy is an appropriate option for unresectable recurrence. Reirradiation is carefully considered with a case-by-case basis. Reirradiation protocol enrollment is highly encouraged prior to committing patient to an aggressive therapy. Radiation doses greater than 60 Gy are usually recommended for successful salvage. Despite recent technical improvement in intensity-modulated radiotherapy (IMRT), the use of concurrent chemotherapy, and the emergence of molecularly targeted agents, careful patient selection remain as the most paramount factor in reirradiation. Tumors that recur or persist despite aggressive prior chemoradiation therapy imply the presence of chemoradio-resistant clonogens. Treatment protocols that combine novel targeted radiosensitizing agents with conformal high precision radiation are required to overcome the resistance while minimizing toxicity. Recent large number of data showed that IMRT may provide better locoregional control with acceptable acute or chronic morbidities. However, additional prospective studies are required before a definitive conclusion can be drawn on safety and effectiveness of IMRT.
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Humains , Protocoles cliniques , Comorbidité , Traitement médicamenteux , Tumeurs de la tête et du cou , Tête , Cou , Sélection de patients , Études prospectives , Radiosensibilisants , Radiothérapie conformationnelle avec modulation d'intensité , Réirradiation , Récidive , Reprise du traitement , SurvivantsRésumé
Objective:To compare the dosimetric differences between volumetric modulated arc radiotherapy with RapidArc and fixed-field intensity modulation radiation therapy (IMRT) for nasopharyngeal carcinoma (NPC), and identify the techniques from which patients of different T stages can gain the maximum benefit. Methods:Sixty non-metastatic patients with NPC were randomly selected. According to the T staging of 2008 Chinese Classification, T1-T2 stage cases were observed in 20 of the 60 patients, whereas T3 and T4 stage cases were seen with 20 patients each. RapidArc and IMRT treatment plans were managed by the Eclipse treatment planning sys-tem of Varian Co., US. The dosimetry of the target volume coverage, organs at risk (OARs), monitor unit (MU) per second, and deliv-ery time were evaluated. Results:Both techniques reached the requirement of clinical treatment. The coverages of planning target vol-ume, conformity index, and homogeneity index were similar. However, the stratified analysis of T staging indicated that RapidArc plans led to an increased dose to the tumor target (P<0.05) and an improved homogeneity index (P=0.059) in the T4 stage cases. RapidArc al-lowed a statistical dose reduction to the OARs, including optic nerves, lens, temporal lobe, V20 of the parotids, larynx, and temporo-mandibular joint (P<0.05). In the T-stage stratified analysis, the D1%and Dmax of brain stem in T1-T3 stages were similar but statistical-ly low in T4 stage in the RapidArc group (P<0.05). Compared with those in IMRT group, the MUs and the delivery time in RapidArc group were reduced by 65%and 63%, respectively. Conclusion:Both RapidArc and IMRT attained the clinical requirement for NPC. RapidArc technique showed improvements in the OARs and reduction in MUs and delivery time. The target volume coverages were similar for T1-T3 stage. However, RapidArc delivered an increased dose to the tumor target in T4 stage cases, and the dose to OARs was reduced.
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PURPOSE: We aimed to analyze the treatment outcome and long-term toxicity of 70 Gy hypofractionated intensity-modulated radiotherapy (IMRT) for localized prostate cancer using a customized rectal balloon. MATERIALS AND METHODS: We reviewed medical records of 86 prostate cancer patients who received curative radiotherapy between January 2004 and December 2011 at our institution. Patients were designated as low (12.8%), intermediate (20.9%), or high risk (66.3%). Thirty patients received a total dose of 70 Gy in 28 fractions over 5 weeks via IMRT (the Hypo-IMRT group); 56 received 70.2 Gy in 39 fractions over 7 weeks via 3-dimensional conformal radiotherapy (the CF-3DRT group, which served as a reference for comparison). A customized rectal balloon was placed in Hypo-IMRT group throughout the entire radiotherapy course. Androgen deprivation therapy was administered to 47 patients (Hypo-IMRT group, 17; CF-3DRT group, 30). Late genitourinary (GU) and gastrointestinal (GI) toxicity were evaluated according to the Radiation Therapy Oncology Group criteria. RESULTS: The median follow-up period was 74.4 months (range, 18.8 to 125.9 months). The 5-year actuarial biochemical relapse-free survival rates for low-, intermediate-, and high-risk patients were 100%, 100%, and 88.5%, respectively, for the Hypo-IMRT group and 80%, 77.8%, and 63.6%, respectively, for the CF-3DRT group (p or =grade 3. Late grade 3 GI toxicity occurred in 2 patients (3.6%) in the CF-3DRT group and 1 patient (3.3%) in the Hypo-IMRT group. CONCLUSION: Hypo-IMRT with a customized rectal balloon resulted in excellent biochemical control rates with minimal toxicity in localized prostate cancer patients.
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Humains , Études de suivi , Dossiers médicaux , Tumeurs de la prostate , Radiothérapie , Radiothérapie conformationnelle , Radiothérapie conformationnelle avec modulation d'intensité , Taux de survie , Résultat thérapeutiqueRésumé
La radioterapia es un tratamiento efectivo en el manejo del cáncer. Es responsable de mejorar significativamente el control locorregional, la supervivencia global y la calidad de vida en múltiples tumores. Históricamente, sin embargo, sus complicaciones agudas y crónicas han reducido estos beneficios. La incorporación de la computación a la radioterapia ha permitido el desarrollo de diversas técnicas de tratamiento, incluyendo la radioterapia conformada 3D (3D-CRT) y la intensidad modulada (IMRT). Éstas permiten aumentar la dosis tumoral protegiendo los tejidos sanos, con un potencial aumento en el control del tumor y reducción de las complicaciones agudas y crónicas asociadas. Múltiples estudios prospectivos y retrospectivos han evaluado los beneficios de la IMRT en distintos tumores primarios. Hasta ahora sus principales indicaciones son cáncer de próstata y de cabeza y cuello. En otras localizaciones se han obtenido mejorías dosimétricas significativas. Se requiere mayor seguimiento para conocer los resultados clínicos tardíos de esta tecnología.
Radiation therapy is an effective treatment in cancer management. It is responsible for significant improvements in local/regional control, overall and cause-specific survival and better quality of life in many tumors. Nevertheless, in the past, acute and chronic radiation toxicity has reduced this benefits. The introduction of computer technologies to radiotherapy has allowed the development of various planning and treatment techniques, including 3D conformal radiotherapy (3D-CRT) and intensity modulation (IMRT), permiting to escalate tumor doses while protecting healthy tissues. This can improve tumor control and reduce acute and late complication rates associated with radiotherapy. Multiple prospective and retrospective studies have evaluated the benefits of IMRT in different primary tumors. Their main indications are head and neck and prostate cancer. In other locations, a significant dosimetric improvements of IMRT have been found, but longer follow-up is required to identify long term effects.
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Humains , Tumeurs de la tête et du cou/radiothérapie , Tumeurs du sein/radiothérapie , Tumeurs de la prostate/radiothérapie , Radiothérapie conformationnelle avec modulation d'intensité , Tumeurs de l'anus/radiothérapie , Radiothérapie assistée par ordinateurRésumé
Objective To investigate the positioning errors of head and neck during intensity-modulated radiation therapy of nasopharyngeal carcinoma.Methods Nineteen patients with middle-advanced nasopharyngeal carcinoma (T2-4N1-3M0), treated by intensity-modulated radiation therapy, underwent repeated CT during their 6-week treatment course.All the patients were immobilized by head-neck-shoulder thermoplastic mask.We evaluated their anatomic landmark coordinated in a total of 66 repeated CT data sets and respective x, y, z shifts relative to their position in the planning CT.ResultsThe positioning error of the neck was 2.44 mm±2.24 mm,2.05 mm±1.42 mm,1.83 mm±1.53 mm in x, y, z respectively.And that of the head was 1.05 mm±0.87 mm,1.23 mm±1.05 mm,1.17 mm±1.55 mm respectively.The positioning error between neck and head have respectively statistical difference (t=-6.58,-5.28,-3.42,P=0.000,0.000,0.001).The system error of the neck was 2.33,1.67 and 1.56 higher than that of the head, respectively in left-right, vertical and head-foot directions;and the random error of neck was 2.57,1.34 and 0.99 higher than that of head respectively.Conclusions In the process of the intensity-modulated radiation therapy of nasopharyngeal carcinoma, with the immobilization by head-neck-shoulder thermoplastic mask, the positioning error of neck is higher than that of head.
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Objective To compare two verification tools for intensity modulated radiotherapy (IM-RT) and to investigate the feasibility of a new three dimensitional verification tool. Methods Five patients receiving IMRT were randomly chosen for the quality assurance plans with MapCHECK Model 1175 (SunNu-clear, Melbourne, FL,USA) and Delta4(ScandiDos, Sweden) by using Philips Pinnacle 8.0D treatment planning system. Dose verification was measured with the Varian Clinical 23EX LA. Results The overall average percentages of pass points in DD2% DTA2 mm, DD3% DTA3 mm and DD4% DTA4 mm were 84.7%, 97. 1% and 99.3% with MapCHECK Model 1175, 86.2%, 98.2% and 99.6% with Delta4 re-spectively. The differences were statisticically significant (t = 3.94, P = 0.003 ; t = 3.17, P = 0.011 ; t = 3.05 ,P =0.014,respectively). The gantry angle was changed to zero degree with MapCHECK, but not with Delta. The effects were embodied with Delta, such as the gravity on leaf position accuracy of MLC, the treat-ment table on dose distribution and the earth magnetism on dose system. Conclusion Delta4 is an ideal verification tool for intensity modulated radiotherapy.
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Objective To evaluate the dosimetric benefits of intensity-modulated radiotherapy (IMRT) for early stage breast cancer after breast-conserving surgery. Methods Ten patients with stage Tis～2N0M0 breast cancer receiving breast-conserving surgery were selected for the study. Six cases were on the left, four were on the right. A dosimetric comparison of IMRT with conventional wedged tangential technique was performed on each patient using three dimensional treatment planning. The total prescribed dose for both plans was 50 Gy/25 fractions. Dose volume histograms (DVH) were used to compare the planning target volume (PTV) and organs at risks(OARS). Results The PTV coverage in IMRT plan was similar to that of the conventional plan (97.83 % vs 97.61%). A better dose uniformity throughout the whole breast was achieved by IMRT plan. The percentage of PTV receiving less than 95 % prescribed dose and more than 103 % prescribed dose (inhomogeneity index IHI), decreased from 25.42 % to 2.71%: the percentage of PTV receiving more than 105 % prescribed dose (V105 %) decreased from 25.79 % to 1.08 %. A better amelioration of IHI and reduction of V105 % in IMRT plans were observed in the relatively large PTV subgroup. The Dmean and percentage of volume receiving more than 30 Gy (V30) of heart from 6.72 Gy to 4.95 Gy, and from 7.23 % to 1.04 %. the Dmean and percentage of volume receiving more than 20 Gy (V20) of ipsilateral from 9.19 Gy to 7.65 Gy, and from 22.34 % to 20.18 %; the Dmean of contralateral breast decreased from 5.12 Gy to 3.52 Gy;the Dmean of contralateral lung decreased from 2.76 Gy to 1.79 Gy; the Dmean of liver decreased from 7.23 Gy to 1.04 Gy for right side patients. Conclusion Forward planning IMRT based on a standard tangential beam arrangement significantly improves the dose homogeneity throughout the target volume of intact breast and reduces the dose to OARS, especially in patients with large breast volumes who might be proposed as candidates of IMRT for intact breast.
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Objective To study the application of correlation statistical analysis model in IMRT planning optimization. Methods A correlation statistical analysis model was established. IMRT plans of 5 prostate cancer patients were randomly chosen from the ADAC Pinacal 7.6 version planning system. The beam parameters, objective functions of the target area and optimization parameters of the primary plan were kept unchanged. The main optimization parameters including EUD parameter a,weight (w) and EUD_(max) of OAR were adjusted in optimization procedure successively. The correlation analysis (CF) and optimization efficiency analysis (OF) were carried out on the results of the optimization. The optimal value of parameters (MORt{}) with the best dose distribution was obtained and substituted in the corresponding primary plan.After optimization, the dose distributions of the two IMRT plans were compared. Results There were signif-icant differences with different optimization methods. The EUD parameter a and weight factor (w) almost had no effect on volume dose of OAR (OF < 0.01), though had obvious effect on the maximum dose and mean dose (OF≈1). The CF analysis showed that the correlation between the PTV ( V_(95)) volume and OAR dose was different when the EUD parameter a and w were applied for optimization. Meanwhile, the difference was proportional to the distance between the target area and OAR. The mean dose of OAR was decreased and the mean dose of PTV was more close to the prescription dose when the optimization parameters of the prima-ry plan were substituted with MOR{a} ,MOR{w} and MORt{EUD_(max)}. Besides, the DVH and isedose dis-tribution of the secondary plan were better. Conclusions The correlation statistical analysis model can be used to accurately determine the scope of optimization parameters in the IMRT planning procedure in prostate cancer, and an IMRT plan which fulfils the clinical requirement can be obtained efficiently.
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margin from CTV to PTV.
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Objective To study if the dose verification technique for three dimensional conformal radiation therapy ( 3 DCRT) can be applied for simplified intensity modulation radiation therapy ( sIM RT). Methods From 1988 patients treated by sIMRT in our department,12 were chosen randomly for the study. For each case,3 differert plans of 3DCRT,sIMRT,and IMRT were worked out with Pinnacle TPS,and the dose verification for each plan was carried out with Elekta Precise LA by using 2D diode-matrix of MapCHECK Model 1175. Results For slMRT,the overall average percentages of pass points for DD(DTA) 2% (2 mm) ,3% (3 mm)and 4% (4 mm) were 90.5% ,94.8% and 98.2% reapectively,which were slightly worse when comparing with those of 3DCRT with deterioration of 1.9% (t=2.19,P=0.040) ,1.0% (t= 1.52,P=0.144) and 0.2% (t=0.05,P=0.623), but slightly better comparing with those of IMRT with increment of 2.1% (t=2.17,P=0.041) ,1.5% (t=2.62,P=0.016) and 1.5% (t=3.68,P=0.001) for 2% (2 mm) ,3% (3 mm) and 4% (4 mm) ,respectively. Conclusions The sIMRT technique simplifies the complicated dose verification procedure of I MRT. When the sIMRT technique is formally used, the procedure of dose distribution verification for 3DCRT can be used directly for slMRT.
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This paper introduces the basic principle,structure and technique characteristics of MM50 raceway electron cyclotron.Its clinical application to radiotherapy is discussed.
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PURPOSE: To propose a conceptual design of a novel source for intensity modulated brachytherapy. MATERIALS AND METHODS: The source design incorporates both radioactive and shielding materials (stainless steel or tungsten), to provide an asymmetric dose intensity in the azimuthal direction. The intensity modulated intravascular brachytherapy was performed by combining a series of dwell positions and times, distributed along the azimuthal coordinates. Two simple designs for the beta-emitting sources, with similar physical dimensions to a 90Sr/Y Novoste Beat-Cath source, were considered in the dosimetric feasibility study. In the first design, the radioactive and materials each occupy half of the cylinder and in the second, the radioactive material occupies only a quater of the cylinder. The radial and azimuthal dose distributions around each source were calculated using the MCNP Monte Carlo code. RESULTS: The preliminary hypothetical simulation and optimization results demonstrated the 87% difference between the maximum and minimum doses to the lumen wall, due to off-centering of the radiation source, could be reduced to less than 7% by optimizing the azimuthal dwell positions and times of the partially shielded intravascular brachytherapy sources. CONCLUSION: The novel brachytherapy source design, and conceptual source delivery system, proposed in this study show promising dosimetric characteristics for the realization of intensity modulated brachytherapy in intravascular treatment. Further development of this concept will center on building a delivery system that can precisely control the angular motion of a radiation source in a small-diameter catheter.
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Curiethérapie , Cathéters , Études de faisabilité , AcierRésumé
Purpose:To evaluate the physical dose distributions and tolerance in locally recurrent nasopharyngeal carcinoma treated with intensity modulated radiation therapy (IMRT).Methods:From June 1999 to August 2000, 10 patients with locally recurrent nasopharyngeal carcinoma proven by histology, without neck lymphoid node recurrence and distant metastasis, were treated by IMRT. The interval from the time of initial radiotherapy to recurrence ranged from 14—50(median 25) months. The initial radiotherapy in all patients were treated with external radiotherapy alone to a median dose of 69Gy/35fractions/52days. IMRT method was performed by means of the MIMiC collimator and inverse treatment planning system (NOMOS company, USA). The prescribed dose of re radiotherapy to target volume was 57Gy/19fractions/4weeks.Results:All patients, except for some patients with mild weight loss and reaction in the oral cavity during radiotherapy, tolerated this IMRT well. IMRT achieved the better immediate responses in 10 patients with complete response in 6 cases and partial response in 4 cases. Recurrence was found in two patients, lung distant metastasis in one patient. The median survival in the 10 patients was 14 months. The median planning target volume (PTV) was 95.8(60—134) cm 3. The dose distributions in the PTV were as follows: median average dose 59.65?2.47Gy, median homogeneity index (HI): 1.18(?0.06); median dose to 95% PTV ≥ 53.2 (?1.36)Gy. The median dose to the organs at risk (OAR) were as follows: spinal cord 9.46?5.23Gy; brain stem 20.24?3.55Gy; left parotid gland 18.53?5.30Gy, right parotid gland 19.68?6.21Gy; left lens 2.11?0.65Gy, right lens 2.94?0.57Gy;Chiasm12.34Gy; left optical nerve13.14 Gy, right optical nerve17.65 Gy.Conclusions:Better dose distributions treated with IMRT was achieved in the patients with locally recurrent nasopharyngeal carcinoma and the patients tolerated this radiotherapy well. [
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Objective To compared intensity modulated radiation therapy (IMRT) with conventional radiotherapy(CR) for the left side breast cancer after breast-conserving surgery in regard to the homogeneity of dose in the target area, cardiac dose and irradiation volume in the target area. Methods Thirty-eight patients received inverse planning of IMRT with dynamic multi-leaf collimation (dMLC). Prescription dose was 46Gy in breast volume with X-ray, and added electron boost dose was 14Gy in the tumor bed, with a total dose of 60Gy. Clinical target volume(CTV) and heart were evaluated with dose-volume histograms(DVH) in the two plans, with the t test taken with SPSS 11.0. Results Average received dose of 95% breast volume(D 95) was (4541?34),(4517?62)cGy, volume of 105% of dose prescription(V 105%) was 17.5%?17.6%,29.4%?26.3%, while V 110% was 0.3%?0.8%,3.7%?8.2% with IMRT and CR, respectively. Received 30Gy by the heart(V 30) was 4.6%?4.3%,18.8%?12.2%(P