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1.
Radiat Oncol ; 16(1): 145, 2021 Aug 04.
Artigo em Inglês | MEDLINE | ID: mdl-34348765

RESUMO

BACKGROUND: Hypofractionation is increasingly being applied in radiotherapy for prostate cancer, requiring higher accuracy of daily treatment deliveries than in conventional image-guided radiotherapy (IGRT). Different adaptive radiotherapy (ART) strategies were evaluated with regard to dosimetric benefits. METHODS: Treatments plans for 32 patients were retrospectively generated and analyzed according to the PACE-C trial treatment scheme (40 Gy in 5 fractions). Using a previously trained cycle-generative adversarial network algorithm, synthetic CT (sCT) were generated out of five daily cone-beam CT. Dose calculation on sCT was performed for four different adaptation approaches: IGRT without adaptation, adaptation via segment aperture morphing (SAM) and segment weight optimization (ART1) or additional shape optimization (ART2) as well as a full re-optimization (ART3). Dose distributions were evaluated regarding dose-volume parameters and a penalty score. RESULTS: Compared to the IGRT approach, the ART1, ART2 and ART3 approaches substantially reduced the V37Gy(bladder) and V36Gy(rectum) from a mean of 7.4cm3 and 2.0cm3 to (5.9cm3, 6.1cm3, 5.2cm3) as well as to (1.4cm3, 1.4cm3, 1.0cm3), respectively. Plan adaptation required on average 2.6 min for the ART1 approach and yielded doses to the rectum being insignificantly different from the ART2 approach. Based on an accumulation over the total patient collective, a penalty score revealed dosimetric violations reduced by 79.2%, 75.7% and 93.2% through adaptation. CONCLUSION: Treatment plan adaptation was demonstrated to adequately restore relevant dose criteria on a daily basis. While for SAM adaptation approaches dosimetric benefits were realized through ensuring sufficient target coverage, a full re-optimization mainly improved OAR sparing which helps to guide the decision of when to apply which adaptation strategy.

2.
Phys Med ; 80: 308-316, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33246190

RESUMO

PURPOSE: Image-guided radiation therapy could benefit from implementing adaptive radiation therapy (ART) techniques. A cycle-generative adversarial network (cycle-GAN)-based cone-beam computed tomography (CBCT)-to-synthetic CT (sCT) conversion algorithm was evaluated regarding image quality, image segmentation and dosimetric accuracy for head and neck (H&N), thoracic and pelvic body regions. METHODS: Using a cycle-GAN, three body site-specific models were priorly trained with independent paired CT and CBCT datasets of a kV imaging system (XVI, Elekta). sCT were generated based on first-fraction CBCT for 15 patients of each body region. Mean errors (ME) and mean absolute errors (MAE) were analyzed for the sCT. On the sCT, manually delineated structures were compared to deformed structures from the planning CT (pCT) and evaluated with standard segmentation metrics. Treatment plans were recalculated on sCT. A comparison of clinically relevant dose-volume parameters (D98, D50 and D2 of the target volume) and 3D-gamma (3%/3mm) analysis were performed. RESULTS: The mean ME and MAE were 1.4, 29.6, 5.4 Hounsfield units (HU) and 77.2, 94.2, 41.8 HU for H&N, thoracic and pelvic region, respectively. Dice similarity coefficients varied between 66.7 ± 8.3% (seminal vesicles) and 94.9 ± 2.0% (lungs). Maximum mean surface distances were 6.3 mm (heart), followed by 3.5 mm (brainstem). The mean dosimetric differences of the target volumes did not exceed 1.7%. Mean 3D gamma pass rates greater than 97.8% were achieved in all cases. CONCLUSIONS: The presented method generates sCT images with a quality close to pCT and yielded clinically acceptable dosimetric deviations. Thus, an important prerequisite towards clinical implementation of CBCT-based ART is fulfilled.


Assuntos
Processamento de Imagem Assistida por Computador , Planejamento da Radioterapia Assistida por Computador , Algoritmos , Tomografia Computadorizada de Feixe Cônico , Humanos , Masculino , Radiometria , Dosagem Radioterapêutica
3.
Radiother Oncol ; 135: 78-85, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-31015174

RESUMO

PURPOSE: Lung tumors treated with hypo-fractionated deep-inspiration breath-hold stereotactic body radiotherapy benefit from fast imaging and treatment. Single breath-hold cone-beam-CT (CBCT) could reduce motion artifacts and improve treatment precision. Thus, gantry speed was accelerated to 18°/s, limiting acquisition time to 10-20 s. Image quality, dosimetry and registration accuracy were compared with standard-CBCT (3°/s). METHODS AND MATERIALS: For proof-of-concept, image quality was analyzed following customer acceptance tests, CT-dose index measured, and registration accuracy determined with an off-centered ball-bearing-phantom. A lung-tumor patient was simulated with differently shaped tumor-mimicking inlays in a thorax-phantom. Signal-to-noise-ratio, contrast-to-noise-ratio and geometry of the inlays quantified image quality. Dose was measured in representative positions. Registration accuracy was determined with inlays scanned in pre-defined positions. Manual, automatic (clinical software) and objective-automatic (in-house-developed) registration was performed on planning-CT, offsets between results and applied shifts were compared. RESULTS: Image quality of ultrafast-CBCT was adequate for high-contrast areas, despite contrast-reduction of ∼80% due to undersampling. Dose-output was considerably reduced by 60-83% in presented setup; variations are due to gantry-braking characteristics. Registration accuracy was maintained better than 1 mm, mean displacement errors were 0.0 ±â€¯0.2 mm with objective-automatic registration. Ultrafast-CBCT showed no significant registration differences to standard-CBCT. CONCLUSIONS: This study of first tests with faster gantry rotation of 18°/s showed promising results for ultrafast high-contrast lung tumor CBCT imaging within single breath-hold of 10-20 s. Such fast imaging times, in combination with fast treatment delivery, could pave the way for intra-fractional combined imaging and treatment within one breath-hold phase, and thus mitigate residual motion and increase treatment accuracy and patient comfort. Even generally speaking, faster gantry rotation could set a benchmark with immense clinical impact where time matters most: palliative patient care, general reduction in uncertainty, and increase in patient throughput especially important for emerging markets with high patient numbers.


Assuntos
Suspensão da Respiração , Tomografia Computadorizada de Feixe Cônico/métodos , Neoplasias Pulmonares/radioterapia , Radioterapia Guiada por Imagem/métodos , Humanos , Neoplasias Pulmonares/diagnóstico por imagem , Aceleradores de Partículas , Imagens de Fantasmas , Dosagem Radioterapêutica , Rotação
4.
Radiother Oncol ; 134: 166-177, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-31005211

RESUMO

BACKGROUND/PURPOSE: To quantify the risk of radiation-induced optic neuropathy (RION) after stereotactic/image-guided positioning and intensity-modulated radiotherapy (IMRT) with ≥50 Gy to the anterior visual pathway (AVP). METHODS: Patients irradiated with ≥50 Gy to the AVP using stereotactic/image-guided positioning between 2002 and 2011 in Mannheim were identified. Detailed dosimetric data were collected and patients or family members were retrospectively asked to rate visual acuity and visual disorders. RESULTS: 125 patients fulfilled the eligibility criteria. Average maximum equivalent point dose (Dmax-EQD-2[α/ß=1.6]) to the AVP was 53.1 ±â€¯3.9 Gy. 99 patients received ≥50 Gy bilaterally (chiasm or both optic nerves), resulting in 224 (99x2 bilateral plus 26 unilateral) visual-fields-at-risk (VFAR) for RION. Eighty-two patients provided pre/post-IMRT visual status information (n = 151 VFARs). Permanent visual deterioration occurred in 18 (22%) patients. In seven, visual deterioration was possibly related to radiotherapy (two-sided deterioration in one patient) for a crude incidence of 8.5% (7/82 patients) and 5.3% (8/151 VFARs). Two cases were caused by chronic keratitis/conjunctivitis; in five patients RION could not be excluded (one two-sided). In one of 13 patients with Dmax-EQD-2 > 58 Gy, RION could not be excluded. In all affected patients, visual acuity post-IMRT had decreased only mildly (1-2 points on the 5-point-scale). One patient with relevant baseline visual impairment (3/5) developed unilateral blindness (crude incidence of blindness on patient-/VFAR-level: 1.2% and 0.66%; competing risk-adjusted/actuarial 24-month incidence: patient/VFAR-level: 1.8% and 0.95%). CONCLUSION: Risk of RION was low in this cohort with accurate positioning and precise dosimetric information. Less conservative tolerance doses may be considered in patients with high risk of recurrence.


Assuntos
Neoplasias/radioterapia , Doenças do Nervo Óptico/etiologia , Lesões por Radiação/etiologia , Radiocirurgia/efeitos adversos , Radioterapia de Intensidade Modulada/efeitos adversos , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Criança , Feminino , Glioblastoma/radioterapia , Neoplasias de Cabeça e Pescoço/radioterapia , Humanos , Masculino , Neoplasias Meníngeas/radioterapia , Meningioma/radioterapia , Pessoa de Meia-Idade , Nervo Óptico/efeitos da radiação , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia Guiada por Imagem/efeitos adversos , Radioterapia Guiada por Imagem/métodos , Radioterapia de Intensidade Modulada/métodos , Estudos Retrospectivos , Carcinoma de Células Escamosas de Cabeça e Pescoço/radioterapia , Vias Visuais/efeitos da radiação , Adulto Jovem
5.
Radiother Oncol ; 128(2): 343-348, 2018 08.
Artigo em Inglês | MEDLINE | ID: mdl-29970259

RESUMO

BACKGROUND AND PURPOSE: Reported plan quality improvements with autoplanning of radiotherapy of the prostate and seminal vesicles are poor. A system for automated multi-criterial planning has been validated for this treatment in a large international multi-center study. The system is configured with training plans using a mechanism that strives for quality improvements relative to those plans. MATERIAL AND METHODS: Each of the four participating centers included thirty manually generated clinical Volumetric Modulated Arc Therapy prostate plans (manVMAT). Ten plans were used for autoplanning training. The other twenty were compared with an automatically generated plan (autoVMAT). Plan evaluations considered dosimetric plan parameters and blinded side-by-side plan comparisons by clinicians. RESULTS: With equivalent Planning Target Volume (PTV) V95%, D2%, D98%, and dose homogeneity autoVMAT was overall superior for rectum with median differences of 3.4 Gy (p < 0.001) in Dmean, 4.0% (p < 0.001) in V60Gy, and 1.5% (p = 0.001) in V75Gy, and for bladder Dmean (0.9 Gy, p < 0.001). Also the clinicians' plan comparisons pointed at an overall preference for autoVMAT. Advantages of autoVMAT were highly treatment center- and patient-specific with overall ranges for differences in rectum Dmean and V60Gy of [-4,12] Gy and [-2,15]%, respectively. CONCLUSION: Observed advantages of autoplanning were clinically relevant and larger than reported in the literature. The latter is likely related to the multi-criterial nature of the applied autoplanning algorithm, with for each center a dedicated configuration that aims at plan improvements relative to its (clinical) training plans. Large variations among patients in differences between manVMAT and autoVMAT point at inconsistencies in manual planning.


Assuntos
Neoplasias da Próstata/radioterapia , Radioterapia de Intensidade Modulada/métodos , Idoso , Algoritmos , Humanos , Masculino , Pessoa de Meia-Idade , Órgãos em Risco , Qualidade da Assistência à Saúde , Radiometria , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador/métodos , Planejamento da Radioterapia Assistida por Computador/normas , Radioterapia de Intensidade Modulada/normas , Reto/efeitos da radiação , Glândulas Seminais/efeitos da radiação , Bexiga Urinária/efeitos da radiação
6.
J Appl Clin Med Phys ; 18(2): 144-153, 2017 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-28300387

RESUMO

OBJECTIVES: Dosimetric control of staff exposure during interventional procedures under fluoroscopy is of high relevance. In this paper, a novel ray casting approximation of radiation transport is presented and the potential and limitation vs. a full Monte Carlo transport and dose measurements are discussed. METHOD: The x-ray source of a Siemens Axiom Artix C-arm is modeled by a virtual source model using single Gaussian-shaped source. A Geant4-based Monte Carlo simulation determines the radiation transport from the source to compute scatter from the patient, the table, the ceiling and the floor. A phase space around these scatterers stores all photon information. Only those photons are traced that hit a surface of phantom that represents medical staff in the treatment room, no indirect scattering is considered; and a complete dose deposition on the surface is calculated. To evaluate the accuracy of the approximation, both experimental measurements using Thermoluminescent dosimeters (TLDs) and a Geant4-based Monte Carlo simulation of dose depositing for different tube angulations of the C-arm from cranial-caudal angle 0° and from LAO (Left Anterior Oblique) 0°-90° are realized. Since the measurements were performed on both sides of the table, using the symmetry of the setup, RAO (Right Anterior Oblique) measurements were not necessary. RESULTS: The Geant4-Monte Carlo simulation agreed within 3% with the measured data, which is within the accuracy of measurement and simulation. The ray casting approximation has been compared to TLD measurements and the achieved percentage difference was -7% for data from tube angulations 45°-90° and -29% from tube angulations 0°-45° on the side of the x-ray source, whereas on the opposite side of the x-ray source, the difference was -83.8% and -75%, respectively. Ray casting approximation for only LAO 90° was compared to a Monte Carlo simulation, where the percentage differences were between 0.5-3% on the side of the x-ray source where the highest dose usually detected was mainly from primary scattering (photons), whereas percentage differences between 2.8-20% are found on the side opposite to the x-ray source, where the lowest doses were detected. Dose calculation time of our approach was 0.85 seconds. CONCLUSION: The proposed approach yields a fast scatter dose estimation where we could run the Monte Carlo simulation only once for each x-ray tube angulation to get the Phase Space Files (PSF) for being used later by our ray casting approach to calculate the dose from only photons which will hit an movable elliptical cylinder shaped phantom and getting an output file for the positions of those hits to be used for visualizing the scatter dose propagation on the phantom surface. With dose calculation times of less than one second, we are saving much time compared to using a Monte Carlo simulation instead. With our approach, larger deviations occur only in regions with very low doses, whereas it provides a high precision in high-dose regions.


Assuntos
Fluoroscopia/instrumentação , Modelos Teóricos , Método de Monte Carlo , Exposição Ocupacional/prevenção & controle , Imagens de Fantasmas , Fótons , Radiometria/instrumentação , Simulação por Computador , Humanos , Doses de Radiação , Radiometria/métodos , Fatores de Risco , Espalhamento de Radiação , Raios X
7.
Strahlenther Onkol ; 191(5): 393-404, 2015 May.
Artigo em Inglês | MEDLINE | ID: mdl-25739476

RESUMO

An increasing number of patients undergoing radiotherapy (RT) have cardiac implantable electronic devices [CIEDs, cardiac pacemakers (PMs) and implanted cardioverters/defibrillators (ICDs)]. Ionizing radiation can cause latent and permanent damage to CIEDs, which may result in loss of function in patients with asystole or ventricular fibrillation. Reviewing the current literature, the interdisciplinary German guideline (DEGRO/DGK) was developed reflecting patient risk according to type of CIED, cardiac condition, and estimated radiation dose to the CIED. Planning for RT should consider the CIED specifications as well as patient-related characteristics (pacing-dependent, previous ventricular tachycardia/fibrillation). Antitachyarrhythmia therapy should be suspended in patients with ICDs, who should be under electrocardiographic monitoring with an external defibrillator on stand-by. The beam energy should be limited to 6 (to 10) MV CIEDs should never be located in the beam, and the cumulative scatter radiation dose should be limited to 2 Gy. Personnel must be able to respond adequately in the case of a cardiac emergency and initiate basic life support, while an emergency team capable of advanced life support should be available within 5 min. CIEDs need to be interrogated 1, 3, and 6 months after the last RT due to the risk of latent damage.


Assuntos
Desfibriladores Implantáveis , Falha de Equipamento , Neoplasias/radioterapia , Marca-Passo Artificial , Radioterapia/efeitos adversos , Idoso , Contraindicações , Relação Dose-Resposta à Radiação , Humanos , Fatores de Risco
8.
Radiother Oncol ; 110(3): 471-6, 2014 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-24444525

RESUMO

PURPOSE: Second cancer risk after breast conserving therapy is becoming more important due to improved long term survival rates. In this study, we estimate the risks for developing a solid second cancer after radiotherapy of breast cancer using the concept of organ equivalent dose (OED). MATERIALS AND METHODS: Computer-tomography scans of 10 representative breast cancer patients were selected for this study. Three-dimensional conformal radiotherapy (3D-CRT), tangential intensity modulated radiotherapy (t-IMRT), multibeam intensity modulated radiotherapy (m-IMRT), and volumetric modulated arc therapy (VMAT) were planned to deliver a total dose of 50 Gy in 2 Gy fractions. Differential dose volume histograms (dDVHs) were created and the OEDs calculated. Second cancer risks of ipsilateral, contralateral lung and contralateral breast cancer were estimated using linear, linear-exponential and plateau models for second cancer risk. RESULTS: Compared to 3D-CRT, cumulative excess absolute risks (EAR) for t-IMRT, m-IMRT and VMAT were increased by 2 ± 15%, 131 ± 85%, 123 ± 66% for the linear-exponential risk model, 9 ± 22%, 82 ± 96%, 71 ± 82% for the linear and 3 ± 14%, 123 ± 78%, 113 ± 61% for the plateau model, respectively. CONCLUSION: Second cancer risk after 3D-CRT or t-IMRT is lower than for m-IMRT or VMAT by about 34% for the linear model and 50% for the linear-exponential and plateau models, respectively.


Assuntos
Neoplasias da Mama/radioterapia , Neoplasias Induzidas por Radiação , Segunda Neoplasia Primária/etiologia , Radioterapia Conformacional/efeitos adversos , Radioterapia de Intensidade Modulada/efeitos adversos , Idoso , Feminino , Humanos , Pessoa de Meia-Idade , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador/métodos , Risco
9.
Radiother Oncol ; 110(3): 553-7, 2014 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-24440045

RESUMO

BACKGROUND AND PURPOSE: We developed a simple and robust total body irradiation (TBI) method for standard treatment rooms that obviates the need for patient translation devices. METHODS AND MATERIALS: Two generic arcs with rectangular segments for a patient thickness of 16 and 20 cm (arc16/arc20) were generated. An analytical fit was performed to determine the weights of the arc segments depending on patient thickness and gantry angle. Stability and absolute dose for both arcs were measured using EBT3 films in a range of solid water slab phantom thicknesses. Additionally ionization chamber measurements were performed every 10 cm at a source surface distance (SSD) of ∼ 200 cm. RESULTS: The measured standard deviation for arc16 is ± 3% with a flatness ⩽ 9.0%. Arc20 had a standard deviation of ± 3% with a flatness ⩽ 7.3% for all measured thicknesses. The theoretical curves proved to be accurate for the prediction of the segment weightings for the two arcs. In vivo measurements for the first 22 clinical patients showed a dose deviation of less than 3%. CONCLUSIONS: Arc therapy is a convenient and stable method for TBI. This cost-effective approach has been introduced clinically, obviating the need for field patches and to physically move the patient.


Assuntos
Radioterapia de Intensidade Modulada/métodos , Irradiação Corporal Total/métodos , Humanos , Pulmão/efeitos da radiação , Imagens de Fantasmas , Dosagem Radioterapêutica
10.
Z Med Phys ; 24(3): 243-51, 2014 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-24238628

RESUMO

BACKGROUND: Intraoperative radiotherapy (IORT) using the INTRABEAM(®) system promises a flexible use regarding radiation protection compared to other approaches such as electron treatment or HDR brachytherapy with (192)Ir or (60)Co. In this study we compared dose rate measurements of breast- and Kypho-IORT with C-arm fluoroscopy which is needed to estimate radiation protection areas. MATERIALS AND METHODS: C-arm fluoroscopy, breast- and Kypho-IORTs were performed using phantoms (silicon breast or bucket of water). Dose rates were measured at the phantom's surface, at 30 cm, 100 cm and 200 cm distance. Those measurements were confirmed during 10 Kypho-IORT and 10 breast-IORT patient treatments. RESULTS: The measured dose rates were in the same magnitude for all three paradigms and ranges from 20 µSv/h during a simulated breast-IORT at two meter distance up to 64 mSv/h directly at the surface of a simulated Kypho-IORT. Those measurements result in a circle of controlled area (yearly doses >6 mSv) for each paradigm of about 4 m±2 m. DISCUSSION/CONCLUSIONS: All three paradigms show comparable dose rates which implies that the radiation protection is straight forward and confirms the flexible use of the INTRABEAM(®) system.


Assuntos
Fluoroscopia/instrumentação , Proteção Radiológica/instrumentação , Radiografia Intervencionista/instrumentação , Radioterapia Guiada por Imagem/instrumentação , Radioterapia/instrumentação , Cirurgia Assistida por Computador/instrumentação , Desenho de Equipamento , Análise de Falha de Equipamento , Dosagem Radioterapêutica
11.
Radiother Oncol ; 109(3): 505-9, 2013 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-24128805

RESUMO

Hypofractionated image-guided stereotactic ablative radiotherapy (igSABR) is effective in small lung/liver lesions. Computer-assisted breath-hold reduces intrafraction motion but, as every gating/triggering strategy, reduces the duty cycle, resulting in long fraction times if combined with intensity-modulated radiotherapy (IMRT). 10 MV flattening-filter-free IMRT reduces daily fraction duration to <10 min for single doses of 5-20 Gy.


Assuntos
Radiocirurgia/métodos , Planejamento da Radioterapia Assistida por Computador/métodos , Idoso , Idoso de 80 Anos ou mais , Suspensão da Respiração , Estudos de Coortes , Fracionamento da Dose de Radiação , Filtração , Humanos , Pessoa de Meia-Idade , Dosagem Radioterapêutica , Radioterapia Guiada por Imagem , Radioterapia de Intensidade Modulada/métodos , Estudos Retrospectivos
12.
Phys Med Biol ; 56(22): 7163-77, 2011 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-22025217

RESUMO

For pre-treatment plan verification of advanced treatment techniques such as intensity-modulated arc therapy, a fast and reliable dosimetric device is required. In this study, we investigated the suitability of MatriXX in different setups for verification of volumetric modulated arc therapy (VMAT) plans. If MatriXX is used in a stationary phantom (MULTICube), the measured dose is dependent on the beam angle. For the first setup (MatriXX/MULTICube), we developed correction factors (CFs) for each detector element (1020 CFs). We investigated the accuracy of these CFs by verifying 12 VMAT plans. In the second setup, we also assessed the suitability of MatriXX in a dedicated holder. Using this setup (MatriXX/Holder), 30 additional VMAT plans were verified. Deviations of up to ∼17% and ∼11% were noted for one of the ion chambers at 90° and 180° gantry positions. The influence of the beam angle dependence (MULTICube) can explicitly be seen when a gamma criterion of 2%/2 mm was chosen. An overall improvement of 4.3% of passing pixels (pp) was noted after applying beam angular-dependent CFs. When the gamma criterion was 3%/3 mm, the %pp was ≥ 95% without and ∼100% with correction. With the second setup, MatriXX/holder, we showed excellent agreement between measurements and calculations. The %pp averaged over all plans (30 VMAT treatment plans) was nearly ∼100%. The combination of MatriXX with MULTICube or with holder proved to be a fast and reliable method for pretreatment verification of arc therapy with sufficient accuracy.


Assuntos
Neoplasias/radioterapia , Radioterapia de Intensidade Modulada/instrumentação , Processamento de Sinais Assistido por Computador/instrumentação , Carga Corporal (Radioterapia) , Humanos , Método de Monte Carlo , Imagens de Fantasmas , Controle de Qualidade , Dosagem Radioterapêutica , Radioterapia de Intensidade Modulada/métodos , Radioterapia de Intensidade Modulada/normas
13.
Phys Med Biol ; 55(19): 5619-33, 2010 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-20826904

RESUMO

We validate the dosimetric performance of COMPASS®, a novel 3D quality assurance system for verification of volumetric-modulated arc therapy (VMAT) treatment plans that can correlate the delivered dose to the patient's anatomy, taking into account the tissue inhomogeneity. The accuracy of treatment delivery was assessed by the COMPASS® for 12 VMAT plans, and the resulting assessments were evaluated using an ionization chamber and film measurements. Dose-volume relationships were evaluated by the COMPASS® for three additional treatment plans and these were used to verify the accuracy of treatment planning dose calculations. The results matched well between COMPASS® and measurements for the ionization chamber (≤3%) and film (73-99% for gamma((3%/3 mm)) < 1 and 98-100% for gamma((5%/5 mm)) < 1) for the phantom plans. Differences in dose-volume statistics for the average dose to the PTV were within 2.5% for three treatment plans. For the structures located in the low-dose region, a maximum difference of <9% was observed. In its current implementation, the system could measure the delivered dose with sufficient accuracy and could project the 3D dose distribution directly on the patient's anatomy. Slight deviations were found for large open fields. These could be minimized by improving the COMPASS® in-built beam model.


Assuntos
Imageamento Tridimensional/métodos , Radioterapia de Intensidade Modulada/métodos , Humanos , Masculino , Neoplasias/diagnóstico por imagem , Neoplasias/radioterapia , Imagens de Fantasmas , Controle de Qualidade , Radiometria , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador , Tomografia Computadorizada por Raios X , Filme para Raios X
14.
Strahlenther Onkol ; 186(5): 280-8, 2010 May.
Artigo em Inglês | MEDLINE | ID: mdl-20437018

RESUMO

BACKGROUND AND PURPOSE: Volumetric modulated arc therapy (VMAT) has the potential to deliver dose distributions comparable to the established intensity-modulated radiotherapy techniques for a multitude of target paradigms. Prior to implementing VMAT into their clinical routine in December 2008, the authors evaluated the dose calculation/delivery accuracy of 24 sample VMAT plans (prostate and anal cancer target paradigms) with film and ionization dosimetry. After the start of the clinical program, in vivo measurements with a rectal probe were performed. MATERIAL AND METHODS: The VMAT plans were generated by the treatment-planning system (TPS) ERGO++ (Elekta, Crawley, UK) and transferred to a phantom. Film dosimetry was performed with Kodak EDR2 films, and evaluated with dose profiles and gamma-index analysis. Appropriate ionization chambers were used for absolute dose measurements in the phantom and for in vivo measurements. The ionization chamber was used with localization of the measurement volume based on positioning cone-beam computed tomography. RESULTS: Plans were transferred from ERGO++ to the record and verify (R&V) system/linear accelerator (linac). The absolute dose deviations recorded with the ionization chamber were 1.74% +/- 1.62% across both indications. The gamma-index analysis of the film dosimetry showed no deviation > 3%/3 mm in the high-dose region. On in vivo measurements, a deviation between calculation and measurement of 2.09% +/- 2.4% was recorded, when the chamber was successfully positioned in the high-dose region. CONCLUSION: VMAT plans can be planned and treated reproducibly in high quality after the commissioning of the complete delivery chain consisting of TPS, R&V system and linac. The results of the individual plan verification meet the commonly accepted requirements. The first in vivo measurements confirm the reproducible precision of the delivered dose during clinical treatments.


Assuntos
Radioterapia de Intensidade Modulada/métodos , Dosimetria Fotográfica , Humanos , Masculino , Aceleradores de Partículas , Imagens de Fantasmas , Neoplasias da Próstata/radioterapia , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador/métodos
15.
Int J Radiat Oncol Biol Phys ; 77(5): 1309-14, 2010 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-20100643

RESUMO

PURPOSE: Intraoperative radiotherapy (IORT) during breast-conserving surgery (BCS) has been recently introduced using different devices. We report the first 5 years of a single-center experience after introduction of a novel approach to deliver IORT as a tumor bed boost during BCS for breast cancer. METHODS AND MATERIALS: A total of 155 breast cancers in 154 women (median age, 63 years; range, 30-83 years; T1/T2 = 100/55; N0/N+ = 108/47) were treated between February 2002 and December 2007 at the University Medical Center Mannheim, in whom IORT as tumor bed boost was applied using 50-kV X-rays (20 Gy) followed by 46-50 Gy whole-breast external-beam radiotherapy (EBRT). Chemotherapy, if indicated, was given before EBRT. The median interval between BCS plus IORT and EBRT was 40 days. Median follow-up was 34 months (maximum 80 months, 1 patient lost to follow-up). Overall survival and local relapse-free survival were calculated at 5 years using the Kaplan-Meier method. Seventy-nine patients were evaluated at 3-year follow-up for late toxicity according to the Late Effects in Normal Tissues-Subjective, Objective, Management, and Analytic system. RESULTS: Ten patients died, 2 had in-breast relapse, and 8 developed distant metastases (5-year overall survival = 87.0%; 5-year local relapse-free survival = 98.5%). Grade 3 fibroses of the tumor bed were detected in 5% of the patients after 3 years. Skin toxicity was mild (telangiectases and hyperpigmentations in approximately 6% each). CONCLUSIONS: Intraoperative radiotherapy as a tumor bed boost during BCS for breast cancer using low-kilovoltage X-rays followed by EBRT yields low recurrence and toxicity rates.


Assuntos
Neoplasias da Mama/radioterapia , Neoplasias da Mama/cirurgia , Adulto , Idoso , Idoso de 80 Anos ou mais , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Mama/patologia , Mama/efeitos da radiação , Neoplasias da Mama/tratamento farmacológico , Neoplasias da Mama/mortalidade , Neoplasias da Mama/patologia , Terapia Combinada/métodos , Feminino , Fibrose/patologia , Seguimentos , Humanos , Período Intraoperatório , Mastectomia Segmentar , Pessoa de Meia-Idade , Recidiva Local de Neoplasia/mortalidade , Estadiamento de Neoplasias , Estudos Prospectivos , Radiografia , Radioterapia/métodos , Dosagem Radioterapêutica , Seroma/diagnóstico por imagem
16.
Radiat Oncol ; 4: 48, 2009 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-19852856

RESUMO

BACKGROUND/PURPOSE: Radiotherapy (RT) volumes for anal cancer are large and of moderate complexity when organs at risk (OAR) such as testis, small bowel and bladder are at least partially to be shielded. Volumetric intensity modulated arc therapy (VMAT) might provide OAR-shielding comparable to step-and-shoot intensity modulated radiotherapy (IMRT) for this tumor entity with better treatment efficiency. MATERIALS AND METHODS: Based on treatment planning CTs of 8 patients, we compared dose distributions, comformality index (CI), homogeneity index (HI), number of monitor units (MU) and treatment time (TTT) for plans generated for VMAT, 3D-CRT and step-and-shoot-IMRT (optimized based on Pencil Beam (PB) or Monte Carlo (MC) dose calculation) for typical anal cancer planning target volumes (PTV) including inguinal lymph nodes as usually treated during the first phase (0-36 Gy) of a shrinking field regimen. RESULTS: With values of 1.33 +/- 0.21/1.26 +/- 0.05/1.3 +/- 0.02 and 1.39 +/- 0.09, the CI's for IMRT (PB-Corvus/PB-Hyperion/MC-Hyperion) and VMAT are better than for 3D-CRT with 2.00 +/- 0.16. The HI's for the prescribed dose (HI36) for 3D-CRT were 1.06 +/- 0.01 and 1.11 +/- 0.02 for VMAT, respectively and 1.15 +/- 0.02/1.10 +/- 0.02/1.11 +/- 0.08 for IMRT (PB-Corvus/PB-Hyperion/MC-Hyperion). Mean TTT and MU's for 3D-CRT is 220s/225 +/- 11MU and for IMRT (PB-Corvus/PB-Hyperion/MC-Hyperion) is 575s/1260 +/- 172MU, 570s/477 +/- 84MU and 610s748 +/- 193MU while TTT and MU for two-arc-VMAT is 290s/268 +/- 19MU. CONCLUSION: VMAT provides treatment plans with high conformity and homogeneity equivalent to step-and-shoot-IMRT for this mono-concave treatment volume. Short treatment delivery time and low primary MU are the most important advantages.


Assuntos
Neoplasias do Ânus/radioterapia , Planejamento da Radioterapia Assistida por Computador , Radioterapia/métodos , Humanos , Masculino , Dosagem Radioterapêutica
17.
Radiother Oncol ; 93(2): 226-33, 2009 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-19765846

RESUMO

INTRODUCTION: Volumetric modulated arc therapy (VMAT), a complex treatment strategy for intensity-modulated radiation therapy, may increase treatment efficiency and has recently been established clinically. This analysis compares VMAT against established IMRT and 3D-conformal radiation therapy (3D-CRT) delivery techniques. METHODS: Based on CT datasets of 9 patients treated for prostate cancer step-and-shoot IMRT, serial tomotherapy (MIMiC), 3D-CRT and VMAT were compared with regard to plan quality and treatment efficiency. Two VMAT approaches (one rotation (VMAT1x) and one rotation plus a second 200 degrees rotation (VMAT2x)) were calculated for the plan comparison. Plan quality was assessed by calculating homogeneity and conformity index (HI and CI), dose to normal tissue (non-target) and D(95%) (dose encompassing 95% of the target volume). For plan efficiency evaluation, treatment time and number of monitor units (MU) were considered. RESULTS: For MIMiC/IMRT(MLC)/VMAT2x/VMAT1x/3D-CRT, mean CI was 1.5/1.23/1.45/1.51/1.46 and HI was 1.19/1.1/1.09/1.11/1.04. For a prescribed dose of 76 Gy, mean doses to organs-at-risk (OAR) were 50.69 Gy/53.99 Gy/60.29 Gy/61.59 Gy/66.33 Gy for the anterior half of the rectum and 31.85 Gy/34.89 Gy/38.75 Gy/38.57 Gy/55.43 Gy for the posterior rectum. Volumes of non-target normal tissue receiving > or =70% of prescribed dose (53 Gy) were 337 ml/284 ml/482 ml/505 ml/414 ml, for > or =50% (38 Gy) 869 ml/933 ml/1155 ml/1231 ml/1993 ml and for > or =30% (23 Gy) 2819 ml/3414 ml/3340 ml/3438 ml /3061 ml. D(95%) was 69.79 Gy/70.51 Gy/71,7 Gy/71.59 Gy/73.42 Gy. Mean treatment time was 12 min/6 min/3.7 min/1.8 min/2.5 min. CONCLUSION: All approaches yield treatment plans of improved quality when compared to 3D-conformal treatments, with serial tomotherapy providing best OAR sparing and VMAT being the most efficient treatment option in our comparison. Plans which were calculated with 3D-CRT provided good target coverage but resulted in higher dose to the rectum.


Assuntos
Neoplasias da Próstata/radioterapia , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia Conformacional/métodos , Radioterapia de Intensidade Modulada/métodos , Humanos , Masculino , Dosagem Radioterapêutica
18.
Int J Radiat Oncol Biol Phys ; 74(4): 1298-305, 2009 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-19545794

RESUMO

PURPOSE: Postoperative intravaginal brachytherapy for endometrial carcinoma is usually performed with (192)Ir high-dose rate (HDR) afterloading. A potential alternative is treatment with a broadband 50kV X-ray point source, the advantage being its low energy and the consequential steep dose gradient. The aim of this study was to create and evaluate a homogeneous cylindrical energy deposition around a newly designed vaginal applicator. METHODS AND MATERIALS: To create constant isodose layers along the cylindrical plastic vaginal applicator, the source (INTRABEAM system) was moved in steps of 17-19.5 mm outward from the tip of the applicator. Irradiation for a predetermined time was performed at each position. The axial shift was established by a stepping mechanism that was mounted on a table support. The total dose/dose distribution was determined using film dosimetry (Gafchromic EBT) in a "solid water" phantom. The films were evaluated with Mathematica 5.2 and OmniPro-I'mRT 1.6. The results (dose D0/D5/D10 in 0/5/10 mm tissue depth) were compared with an (192)Ir HDR afterloading plan for multiple sampling points around the applicator. RESULTS: Three different dose distributions with lengths of 3.9-7.3 cm were created. The irradiation time based on the delivery of 5/7 Gy to a 5 mm tissue depth was 19/26 min to 27/38 min. D0/D5/D10 was 150%/100%/67% for electronic brachytherapy and 140%/100%/74% for the afterloading technique. The deviation for repeated measurements in the phantom was <7%. CONCLUSIONS: It is possible to create a homogeneous cylindrical dose distribution, similar to (192)Ir HDR afterloading, through the superimposition of multiple spherical dose distributions by stepping a kilovolt point source.


Assuntos
Braquiterapia/instrumentação , Neoplasias do Endométrio/radioterapia , Braquiterapia/métodos , Desenho de Equipamento , Feminino , Dosimetria Fotográfica , Humanos , Radioisótopos de Irídio/uso terapêutico , Dosagem Radioterapêutica
19.
Z Med Phys ; 19(1): 29-37, 2009.
Artigo em Inglês | MEDLINE | ID: mdl-19459583

RESUMO

Quality assurance of external beam (radio)therapy (EBT) requires tools with specific characteristics. A radiochromic film dubbed "Gafchromic EBT" (G-EBT) that is particularly suited for external beam therapy because of its features was introduced in 2004. Its characteristics, especially the high spatial resolution, make it suitable for measurement of dose distributions in radiotherapy, especially intensity-modulated radiation therapy (IMRT). While several aspects of the film characteristics have been previously reported separately, we present a comprehensive evaluation centered on practical IMRT verification, leading to an optimized protocol. Therefore the constancy within one batch, the relationship between optical density (OD) and dose (dose range between 1.4 Gy and 8.4 Gy) and the dose rate dependence for four dose rates (55, 108, 217, 441 MU/min) were investigated. In addition to these characteristics, energy dependence between two energies (50kV and 6 MV), tissue equivalency, post irradiation coloration over one month, pressure and temperature sensitivity were evaluated. We then optimized the protocol using the G-EBT films, in combination with an EPSON-Expression 1680 pro flatbed scanner, for IMRT QA, while either striving to keep the compound error as small as possible or trying to reduce evaluation time. As a basis for this protocol optimization, the characteristics of the scanner (such as inhomogeneity of the scanning field) and its software (such as consequences of extracting only the red color channel) had to be determined first. The interaction of film and scanner (variation of the OD depending on the scanning direction or the scanning resolution) was assessed as well. Using the optimized protocol for IMRT QA, the compound error could be reduced to approximately 2% for a quality-driven approach and maximum 5.5% for an approach attempting to reduce procedure time. While the quality-driven approach provides appropriate accuracy for individual patient QA, the procedure-time driven approach can only be used for preliminary measurements.


Assuntos
Radioterapia de Intensidade Modulada/métodos , Absorção , Cor , Humanos , Imagens de Fantasmas , Fótons , Pressão , Dosagem Radioterapêutica , Sensibilidade e Especificidade , Temperatura , Filme para Raios X
20.
Strahlenther Onkol ; 185(1): 1-7, 2009 Jan.
Artigo em Alemão | MEDLINE | ID: mdl-19224141

RESUMO

BACKGROUND: : Recent changes in the radiotherapy (RT) workflow through the introduction of complex treatment paradigms such as intensity-modulated radiotherapy (IMRT) and, recently, image-guided radiotherapy (IGRT) with their increase in data traffic for different data classes have mandated efforts to further integrate electronic data management for RT departments in a patient- and treatment-course-centered fashion. METHODS: : Workflow in an RT department is multidimensional and multidirectional and consists of at least five different data classes (RT/machine data, patient-related documents such as reports and letters, progress notes, DICOM [Digital Imaging and Communications in Medicine] image data, and non-DICOM image data). Data has to be handled in the framework of adaptive feedback loops with increasing frequency. This is in contrast to a radiology department where mainly DICOM image data and reports have to be widely accessible but are dealt with in a mainly unidirectional manner. When compared to a diagnostic Radiology Information System (RIS)/Picture Archiving and Communication System (PACS), additional legal requirements have to be conformed to when an integrated electronic RT data management system is installed. Among these are extended storage periods, documentation of treatment plan approval by physicians and physicist, documentation of informed consent, etc. CONCLUSION: : Since the transition to a paper- and filmless environment in medicine and especially in radiation oncology is unavoidable, this review discusses these issues and suggests a possible hardware and organizational architecture of an RT department information system under control of a Hospital Information System (HIS), based on combined features of genuine RT Record and Verify (R&V) Systems, PACS, and Electronic Medical Records (EMR).


Assuntos
Sistemas de Gerenciamento de Base de Dados , Diagnóstico por Imagem , Sistemas Computadorizados de Registros Médicos/organização & administração , Assistência Centrada no Paciente/organização & administração , Radioterapia (Especialidade)/organização & administração , Sistemas de Informação em Radiologia/organização & administração
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