RESUMO
PURPOSE: In case of external breast radiotherapy, the usual treatment consists of two tangential beams homogeneously attenuated by a dynamic or physics wedge in order to obtain the most homogeneous dose distribution as possible. Depending of the shape and size of the breast volume, we may observe with this technique dose heterogeneity over 20% from the recommendation of the International Committee on Radiation Units and Measurements (95-107%). We propose to study breast treatment planning by compensating tissues thickness in order to decrease dose heterogeneity observed on the dose distribution for conventional treatment. MATERIALS AND METHODS: We have segmented the initial tangential beams used for this kind of treatment into several smaller beams. Their shape was adapted to the distribution of the greys level on the DRR image. Therefore, we have compensated the thickness gradient and we have given the right dose to the right thickness group. RESULTS: Dose distribution performed with this method shows an improvement of the dose homogeneity in the three space dimensions and a decrease of the maximal dose between 5 and 10% over the ICRU recommendation. CONCLUSION: This technique allows us to perform breast irradiation on a single photon energy linac even if the treated volume presents important thickness gradient. However, in case of large breast, this method is not able to reduce the overdosage at the entry of the volume due to inappropriate photon energy relative to the breast thickness.
Assuntos
Neoplasias da Mama/radioterapia , Radioterapia de Intensidade Modulada , Feminino , Humanos , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por ComputadorRESUMO
UNLABELLED: To report a retrospective study concerning the impact of fused 18F-fluorodeoxy-D-glucose (FDG)-hybrid positron emission tomography (PET) and computed tomography (CT) images on three-dimensional conformal radiation therapy (3D-CRT) planning for patients with non-small-cell lung cancer (NSCLC). PATIENTS AND METHODS: One hundred and one patients consecutively treated for stages I-III NSCLC were studied. Each patient underwent CT and FDG-hybrid PET for simulation treatment in the same radiation treatment position. Images were coregistered using five fiducial markers. Target volume delineation was initially performed on the CT images and the corresponding FDG-PET data were subsequently used as an overlay to the CT data to define target volume. RESULTS: FDG-PET identified previously undetected distant metastatic disease in 8 patients making them ineligible for curative CRT (one patient presented some positive uptakes corresponding to concomitant pulmonary tuberculosis). Another patient was ineligible for curative treatment because fused CT/PET images demonstrated excessively extensive intrathoracic disease. The gross tumor volume (GTV) was decreased by CT/PET image fusion in 21 patients (23%) and was increased in 24 patients (26%). The GTV reduction was > or = 25% in 7 patients because CT/PET image fusion reduced pulmonary GTV in 6 patients (3 patients with atelectasis) and mediastinal nodal GTV in 1 patient. The GTV increase was > or = 25% in 14 patients due to an increase of the pulmonary GTV in 11 patients (4 patients with atelectasis) and detection of occult mediastinal lymph node involvement in 3 patients. Among 81 patients receiving a total dose > or = 60 Gy at ICRU point, after CT/PET image fusion, the percentage of total lung volume receiving more than 20 Gy (VL20) increased in 15 cases and decreased in 22 cases. The percentage of total heart volume receiving more than 36 Gy increased in 8 patients and decreased in 14 patients. The spinal cord volume receiving at least 45 Gy (2 patients) decreased. After multivariate analysis, one single independent factor made significant effect of FDG/PET on the modification of the size of the GTV: tumor with atelectasis (P = 0.0001). Conclusion. - Our study confirms that integrated hybrid PET/CT in the treatment position and coregistered images have an impact on treatment planning and management of patients with NSCLC. FDG images using dedicated PET scanners with modern image fusion techniques and respiration-gated acquisition protocols could improve CT/PET image coregistration. However, prospective studies with histological correlation are necessary and the impact on treatment outcome remains to be demonstrated.
Assuntos
Carcinoma Pulmonar de Células não Pequenas/radioterapia , Neoplasias Pulmonares/radioterapia , Tomografia por Emissão de Pósitrons , Radioterapia Conformacional/métodos , Tomografia Computadorizada por Raios X , Adulto , Idoso , Idoso de 80 Anos ou mais , Carcinoma Pulmonar de Células não Pequenas/patologia , Feminino , Fluordesoxiglucose F18 , Humanos , Neoplasias Pulmonares/patologia , Masculino , Pessoa de Meia-Idade , Atelectasia Pulmonar/patologia , Compostos Radiofarmacêuticos , Dosagem Radioterapêutica , Estudos RetrospectivosRESUMO
PURPOSE: To study the impact of fused (18)F-fluoro-deoxy-D-glucose (FDG)-hybrid positron emission tomography (PET) and computed tomography (CT) images on conformal radiation therapy (CRT) planning for patients with esophageal carcinoma. PATIENTS AND METHODS: Thirty-four patients with esophageal carcinoma were referred for concomitant radiotherapy and chemotherapy with radical intent. Each patient underwent CT and FDG-hybrid PET for simulation treatment in the same radiation treatment position. PET-images were coregistered using five fiducial markers. Target delineation was initially performed on CT images and the corresponding PET data were subsequently used as an overlay to CT data to define the target volume. RESULTS: FDG-PET identified previously undetected distant metastatic disease in 2 patients, making them ineligible for curative CRT. The Gross Tumor Volume (GTV) was decreased by CT and FDG image fusion in 12 patients (35%) and was increased in 7 patients (20.5%). The GTV reduction was >or=25% in 4 patients due to reduction of the length of the esophageal tumor. The GTV increase was >or=25% with FDG-PET in 2 patients due to the detection of occult mediastinal lymph node involvement in one patient and an increased length of the esophageal tumor in the other patient. Modifications of the GTV affected the planning treatment volume (PTV) in 18 patients. Modifications of delineation of GTV and displacement of the isocenter of PTV by FDG-PET also affected the percentage of total lung volume receiving more than 20 Gy (VL20) in 25 patients (74%), with a dose reduction in 12 patients and a dose increase in 13 patients. CONCLUSION: In our study, CT and FDG-PET image fusion appeared to have an impact on treatment planning and management of patients with esophageal carcinoma related to modifications of GTV. The impact on treatment outcome remains to be demonstrated.
Assuntos
Carcinoma/radioterapia , Neoplasias Esofágicas/radioterapia , Tomografia por Emissão de Pósitrons , Radioterapia Conformacional/métodos , Tomografia Computadorizada por Raios X , Adulto , Idoso , Carcinoma/diagnóstico por imagem , Neoplasias Esofágicas/diagnóstico por imagem , Feminino , Fluordesoxiglucose F18 , Humanos , Masculino , Pessoa de Meia-Idade , Planejamento de Assistência ao Paciente , Radiometria , Compostos RadiofarmacêuticosRESUMO
PURPOSE: Conformal radiotherapy beams are defined on the basis of static computed tomography acquisitions by taking into account setup errors and organ/tumor motion during breathing. In the absence of precise data, the size of the margins is estimated arbitrarily. The objective of this study was to evaluate the amplitude of maximum intrathoracic organ motion during breathing. METHODS AND MATERIALS: Twenty patients treated for non-small-cell lung cancer were included in the study: 10 patients at the Institut Curie with a personalized alpha cradle immobilization and 10 patients at Tenon Hospital with just the Posirest device below their arms. Three computed tomography acquisitions were performed in the treatment position: the first during free breathing and the other two during deep breath-hold inspiration and expiration. For each acquisition, the displacements of the various intrathoracic structures were measured in three dimensions. RESULTS: Patients from the two centers were comparable in terms of age, weight, height, tumor site, and stage. In the overall population, the greatest displacements were observed for the diaphragm, and the smallest displacements were observed for the lung apices and carina. The relative amplitude of motion was comparable between the two centers. The use of a personalized immobilization device reduced lateral thoracic movements (p < 0.02) and lung apex movements (p < 0.02). CONCLUSION: Intrathoracic organ movements during extreme phases of breathing are considerable. Quantification of organ motion is necessary for definition of the safety margins. A personalized immobilization device appears to effectively reduce apical and lateral displacement.
Assuntos
Carcinoma Pulmonar de Células não Pequenas/radioterapia , Neoplasias Pulmonares/radioterapia , Movimento , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia Conformacional , Respiração , Idoso , Idoso de 80 Anos ou mais , Carcinoma Pulmonar de Células não Pequenas/diagnóstico por imagem , Diafragma , Feminino , Humanos , Pulmão , Neoplasias Pulmonares/diagnóstico por imagem , Masculino , Pessoa de Meia-Idade , Postura , Tomografia Computadorizada por Raios XRESUMO
PURPOSE: A modified teletherapy unit to achieve total body irradiation with a vertical beam in a conventional treatment room. METHODS AND MATERIALS: A standard 60C teletherapy unit has been modified to achieve total body irradiation with a vertical beam in a conventional treatment room. Patients are treated in prone and supine positions. Removal of the adjustable collimator assembly of this standard machine provides a circular field of 196 cm in diameter at 167 cm from the source. Second, the machine has been elevated by about 50 cm on a metallic base to enlarge irradiation field to obtain 248 cm in diameter at 210 cm from the source, and to encompass tall patients under better conditions. A special lead conical beam flattening filter, 10-mm thick at the center, was designed to compensate the spatial inhomogeneity of the beam. An instantaneous dose rate of 6.10(-2) Gy/min is attained at the L4 level (midplane) in an average 20-cm thick patient with a source activity of 5099 RHM (air kerma rate of 44.8 Gy.h-1.m2). Between February 2, 1984 and December 27, 1990, 244 total body irradiations were performed either by single dose (n = 69, 10 Gy were given to midplane at L4 level in about 6 to 8 h, 8 Gy to the lungs), or by fractionated dose (n = 175, 12 Gy were given in 6 fractions over 3 consecutive days to midplane at L4 level, 9 Gy to the lungs). RESULTS: The dose distribution is similar than the ones obtained by a linear accelerator with patients lying on their sides. CONCLUSION: Patients were treated in a comfortable and highly reproductible position. Organ shielding was easily achievable. This could be a less expensive and reasonable alternative to linear accelerator.
Assuntos
Radioisótopos de Cobalto/uso terapêutico , Teleterapia por Radioisótopo/instrumentação , Irradiação Corporal Total/instrumentação , Desenho de Equipamento , Humanos , Proteção Radiológica , Teleterapia por Radioisótopo/métodos , Irradiação Corporal Total/métodosRESUMO
PURPOSE: The aim of this work was to establish the acquisition, calculation and 3D compensator manufacturing optimum parameters. This methodology is based on virtual simulation and 3D dosimetry. MATERIALS AND METHODS: The material used is a helicoidal CT (PQ 5000-Marconi), a virtual simulation system (AcQsim version 4-Marconi), a Treatment Planning System (Dosigray), a linear accelerator Saturne 43 (Varian, CGR), an automated milling system for compensator filters (Autimo 2.5 D-HEK), a water tank phantom (wellhofer) and an homogeneous phantom with simple patterns in order to simulate the obliquity surface of patient body. The compensator was composed by granulate tin because this material ensures a good profile modulation. The compensation plane has been calculated at 80% to dose profile. The compensator thickness profile has been calculated with different acquisition (slice thickness, pitch factor), calculation (attenuation coefficient, bixel) and fabrication parameters (drill diameter, specification of milling system). RESULTS: After this preliminary study, we have defined the optimum parameters for the compensator realization. We have observed that the slice thickness, bixel size and drill diameter are the parameters that mainly affect the profiles homogeneity. The choice of parameters with smaller dimensions S = 3 mm; B = 3 mm, F = 3 mm, improve the profiles homogeneity. Though, for manufacture times compatible with the clinical routine, the selected parameters are S = 5 mm, B = 6 mm and F = 6 mm. Compensator can be used for any type of Linac. However, one must pay attention on their realization and their positioning on the beam central axis.
Assuntos
Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador , Radioterapia Conformacional/instrumentação , Humanos , Imageamento Tridimensional , Modelos Teóricos , Imagens de Fantasmas , Planejamento da Radioterapia Assistida por Computador/instrumentaçãoRESUMO
PURPOSE: To evaluate, qualitatively and quantitatively, the role of surgical clips in planning the tumor bed electron or brachytherapy boost in patients undergoing breast-conserving surgery and radiotherapy. PATIENTS AND METHODS: In 60 patients with breast cancer stage I or II, the excision cavity boundaries were marked by clips at surgery. Patients received a boost with brachytherapy (n = 51) or electron beam (n = 9) after whole breast irradiation. The boost target volume was first planned using clinical, mammography and operative information and its accuracy evaluated by screening the surgical clips and, if necessary, adjusting the field to encompass all clips and to include the scar. Dosimetry was retrospectively performed for each brachytherapy patient and for each surgical clip. RESULTS: It was necessary to modify the target volume field in 11 cases (18%). The average dose received by the surgical clips was 116.1% of the dose delivered to the reference isodose (median: 101.75%, range: 16-457%). However, dose heterogeneity was important in the same patient and between patients. CONCLUSION: Delineation of the boost target volume with surgical clips is more accurate than with clinical landmarks alone but this technique does not allow measurements of the clip-chest wall and clip-skin distances. Virtual simulation with CT-scan cuts is recommended for optimising boost planning.
Assuntos
Braquiterapia , Neoplasias da Mama/radioterapia , Neoplasias da Mama/cirurgia , Mastectomia Segmentar , Instrumentos Cirúrgicos , Feminino , Humanos , Mastectomia Segmentar/métodos , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador , Radioterapia Adjuvante , Resultado do TratamentoRESUMO
An inverse planning algorithm for determining the intensity of modulated beams that generates conformal radiotherapy dose distributions is presented. This algorithm is based on the mathematical analysis of the singular values decomposition. It is integrated in the DOSIGRAY 3D treatment planning software. The dose is calculated by the separation of the primary and scattered radiation. We presented, for a prostate cancer, the modulated intensity profiles and the optimal dose distribution obtained by the inverse optimization software developed and integrated in the treatment planning system. We obtained a region with high doses which geometrically conforms the target volume and spares the neighboring critical structures. This preliminary study showed the feasibility and the managing of the singular value decomposition to generate conformal dose distribution in a clinical environment.
Assuntos
Algoritmos , Dosagem Radioterapêutica , Humanos , Masculino , Modelos Teóricos , Neoplasias da Próstata/radioterapia , Espalhamento de RadiaçãoRESUMO
A quality control programme has been developed in the radiotherapy department of the Institut Gustave-Roussy for an international clinical trial on the use of Etanidazole as a radiosensitizer in association with radiotherapy for head and neck tumors. Twenty-nine european centers belonging to Germany, United Kingdom, Austria, France and Italy contributed to this trial during 374 patients has been included from 1987 to 1988. This programme concerned the control of the external radiotherapy equipment available in the participating centers and the examination of the patient treatment data. The authors present, in this paper, the methods applied and the main results obtained during the analysis of the individual patient treatment data. This analysis shows that 83% of the evaluable treatments were done in compliance with the protocol recommendations and 17% contained a major deviation and among them only 3% were judged unacceptable.