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1.
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
2.
Z Med Phys ; 28(2): 110-120, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29429610

RESUMO

PURPOSE: To establish a fully automated kV-MV CBCT imaging method on a clinical linear accelerator that allows image acquisition of thoracic targets for patient positioning within one breath-hold (∼15s) under realistic clinical conditions. METHODS AND MATERIALS: Our previously developed FPGA-based hardware unit which allows synchronized kV-MV CBCT projection acquisition is connected to a clinical linear accelerator system via a multi-pin switch; i.e. either kV-MV imaging or conventional clinical mode can be selected. An application program was developed to control the relevant linac parameters automatically and to manage the MV detector readout as well as the gantry angle capture for each MV projection. The kV projections are acquired with the conventional CBCT system. GPU-accelerated filtered backprojection is performed separately for both data sets. After appropriate grayscale normalization both modalities are combined and the final kV-MV volume is re-imported in the CBCT system to enable image matching. To demonstrate adequate geometrical accuracy of the novel imaging system the Penta-Guide phantom QA procedure is performed. Furthermore, a human plastinate and different tumor shapes in a thorax phantom are scanned. Diameters of the known tumor shapes are measured in the kV-MV reconstruction. RESULTS: An automated kV-MV CBCT workflow was successfully established in a clinical environment. The overall procedure, from starting the data acquisition until the reconstructed volume is available for registration, requires ∼90s including 17s acquisition time for 100° rotation. It is very simple and allows target positioning in the same way as for conventional CBCT. Registration accuracy of the QA phantom is within ±1mm. The average deviation from the known tumor dimensions measured in the thorax phantom was 0.7mm which corresponds to an improvement of 36% compared to our previous kV-MV imaging system. CONCLUSIONS: Due to automation the kV-MV CBCT workflow is speeded up by a factor of >10 compared to the manual approach. Thus, the system allows a simple, fast and reliable imaging procedure and fulfills all requirements to be successfully introduced into the clinical workflow now, enabling single-breath-hold volume imaging.


Assuntos
Tomografia Computadorizada de Feixe Cônico , Neoplasias Pulmonares/radioterapia , Radioterapia Guiada por Imagem/instrumentação , Radioterapia Guiada por Imagem/métodos , Automação , Humanos
3.
Z Med Phys ; 28(2): 134-141, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29030203

RESUMO

BACKGROUND AND PURPOSE: The novel MatriXXFFF (IBA Dosimetry, Germany) detector is a new 2D ionization chamber detector array designed for patient specific IMRT-plan verification including flattening-filter-free (FFF) beams. This study provides a detailed analysis of the characterization and clinical evaluation of the new detector array. MATERIAL AND METHODS: The verification of the MatriXXFFF was subdivided into (i) physical dosimetric tests including dose linearity, dose rate dependency and output factor measurements and (ii) patient specific IMRT pre-treatment plan verifications. The MatriXXFFF measurements were compared to the calculated dose distribution of a commissioned treatment planning system by gamma index and dose difference evaluations for 18 IMRT-sequences. All IMRT-sequences were measured with original gantry angles and with collapsing all beams to 0° gantry angle to exclude the influence of the detector's angle dependency. RESULTS: The MatriXXFFF was found to be linear and dose rate independent for all investigated modalities (deviations ≤0.6%). Furthermore, the output measurements of the MatriXXFFF were in very good agreement to reference measurements (deviations ≤1.8%). For the clinical evaluation an average pixel passing rate for γ(3%,3mm) of (98.5±1.5)% was achieved when applying a gantry angle correction. Also, with collapsing all beams to 0° gantry angle an excellent agreement to the calculated dose distribution was observed (γ(3%,3mm)=(99.1±1.1)%). CONCLUSIONS: The MatriXXFFF fulfills all physical requirements in terms of dosimetric accuracy. Furthermore, the evaluation of the IMRT-plan measurements showed that the detector particularly together with the gantry angle correction is a reliable device for IMRT-plan verification including FFF.


Assuntos
Radiometria/instrumentação , Planejamento da Radioterapia Assistida por Computador , Radioterapia de Intensidade Modulada/instrumentação , Radioterapia de Intensidade Modulada/métodos , Calibragem , Humanos , Masculino , Neoplasias da Próstata/radioterapia , Dosagem Radioterapêutica , Radioterapia de Intensidade Modulada/normas
4.
PLoS One ; 12(11): e0187710, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-29125857

RESUMO

PURPOSE: Combined ultrafast 90°+90° kV-MV-CBCT within single breath-hold of 15s has high clinical potential for accelerating imaging for lung cancer patients treated with deep inspiration breath-hold (DIBH). For clinical feasibility of kV-MV-CBCT, dose exposure has to be small compared to prescribed dose. In this study, kV-MV dose output is evaluated and compared to clinically-established kV-CBCT. METHODS: Accurate dose calibration was performed for kV and MV energy; beam quality was determined. For direct comparison of MV and kV dose output, relative biological effectiveness (RBE) was considered. CT dose index (CTDI) was determined and measurements in various representative locations of an inhomogeneous thorax phantom were performed to simulate the patient situation. RESULTS: A measured dose of 20.5mGE (Gray-equivalent) in the target region was comparable to kV-CBCT (31.2mGy for widely-used, and 9.1mGy for latest available preset), whereas kV-MV spared healthy tissue and reduced dose to 6.6mGE (30%) due to asymmetric dose distribution. The measured weighted CTDI of 12mGE for kV-MV lay in between both clinical presets. CONCLUSIONS: Dosimetric properties were in agreement with established imaging techniques, whereas exposure to healthy tissue was reduced. By reducing the imaging time to a single breath-hold of 15s, ultrafast combined kV-MV CBCT shortens patient time at the treatment couch and thus improves patient comfort. It is therefore usable for imaging of hypofractionated lung DIBH patients.


Assuntos
Tomografia Computadorizada de Feixe Cônico/métodos , Neoplasias Pulmonares/diagnóstico por imagem , Imagens de Fantasmas , Relação Dose-Resposta à Radiação , Humanos
5.
Radiother Oncol ; 119(2): 351-6, 2016 05.
Artigo em Inglês | MEDLINE | ID: mdl-27090736

RESUMO

BACKGROUND AND PURPOSE: Since IMRT-techniques lead to an increasingly complicated environment, a patient specific IMRT-plan verification is recommended. Furthermore, verifications during patient irradiation and 3D dose reconstruction have the potential to improve treatment delivery, accuracy and safety. This study provides a detailed investigation of the new transmission detector (DTD) Dolphin (IBA Dosimetry, Germany) for online dosimetry. MATERIALS AND METHODS: The clinical performance of the DTD was tested by dosimetric plan verification in 2D and 3D for 18 IMRT-sequences. In 2D, DTD measurements were compared to a pre-treatment verification method and a treatment planning system by gamma index and dose difference evaluations. In 3D, dose-volume-histogram (DVH) indices and gamma analysis were evaluated. Furthermore, the error detection ability was tested with leaf position uncertainties and deviations in the linear accelerator (LINAC) output. RESULTS: The DTD measurements were in excellent agreement to reference measurements in both 2D (γ3%,3mm=(99.7±0.6)% <1, ΔD±5%=(99.5±0.5)%) and 3D. Only a small dose underestimation (<2%) within the target volume was observed when analyzing DVH-indices. Positional errors of the leaf banks larger than 1mm and errors in LINAC output larger than 2% were identified with the DTD. CONCLUSIONS: The DTD measures the delivered dose with sufficient accuracy and is therefore suitable for clinical routine.


Assuntos
Neoplasias/radioterapia , Radiometria/instrumentação , Planejamento da Radioterapia Assistida por Computador/instrumentação , Raios gama , Humanos , Aceleradores de Partículas , Garantia da Qualidade dos Cuidados de Saúde , Dosagem Radioterapêutica , Radioterapia de Intensidade Modulada/métodos
6.
PLoS One ; 11(3): e0150326, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-26930196

RESUMO

INTRODUCTION: To quantify interfraction patient setup-errors for radiotherapy based on cone-beam computed tomography and suggest safety margins accordingly. MATERIAL AND METHODS: Positioning vectors of pre-treatment cone-beam computed tomography for different treatment sites were collected (n = 9504). For each patient group the total average and standard deviation were calculated and the overall mean, systematic and random errors as well as safety margins were determined. RESULTS: The systematic (and random errors) in the superior-inferior, left-right and anterior-posterior directions were: for prostate, 2.5(3.0), 2.6(3.9) and 2.9(3.9)mm; for prostate bed, 1.7(2.0), 2.2(3.6) and 2.6(3.1)mm; for cervix, 2.8(3.4), 2.3(4.6) and 3.2(3.9)mm; for rectum, 1.6(3.1), 2.1(2.9) and 2.5(3.8)mm; for anal, 1.7(3.7), 2.1(5.1) and 2.5(4.8)mm; for head and neck, 1.9(2.3), 1.4(2.0) and 1.7(2.2)mm; for brain, 1.0(1.5), 1.1(1.4) and 1.0(1.1)mm; and for mediastinum, 3.3(4.6), 2.6(3.7) and 3.5(4.0)mm. The CTV-to-PTV margins had the smallest value for brain (3.6, 3.7 and 3.3mm) and the largest for mediastinum (11.5, 9.1 and 11.6mm). For pelvic treatments the means (and standard deviations) were 7.3 (1.6), 8.5 (0.8) and 9.6 (0.8)mm. CONCLUSIONS: Systematic and random setup-errors were smaller than 5mm. The largest errors were found for organs with higher motion probability. The suggested safety margins were comparable to published values in previous but often smaller studies.


Assuntos
Tomografia Computadorizada de Feixe Cônico/efeitos adversos , Tomografia Computadorizada de Feixe Cônico/métodos , Erros de Configuração em Radioterapia/efeitos adversos , Humanos , Masculino , Posicionamento do Paciente/métodos , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia Guiada por Imagem/métodos , Segurança
7.
Z Med Phys ; 26(3): 200-8, 2016 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-26303190

RESUMO

PURPOSE: Online verification and 3D dose reconstruction on daily patient anatomy have the potential to improve treatment delivery, accuracy and safety. One possible implementation is to recalculate dose based on online fluence measurements with a transmission detector (TD) attached to the linac. This study provides a detailed analysis of the influence of a new TD on treatment beam characteristics. METHODS: The influence of the new TD on surface dose was evaluated by measurements with an Advanced Markus Chamber (Adv-MC) in the build-up region. Based on Monte Carlo simulations, correction factors were determined to scale down the over-response of the Adv-MC close to the surface. To analyze the effects beyond dmax percentage depth dose (PDD), lateral profiles and transmission measurements were performed. All measurements were carried out for various field sizes and different SSDs. Additionally, 5 IMRT-plans (head & neck, prostate, thorax) and 2 manually created test cases (3×3cm(2) fields with different dose levels, sweeping gap) were measured to investigate the influence of the TD on clinical treatment plans. To investigate the performance of the TD, dose linearity as well as dose rate dependency measurements were performed. RESULTS: With the TD inside the beam an increase in surface dose was observed depending on SSD and field size (maximum of +11%, SSD = 80cm, field size = 30×30cm(2)). Beyond dmax the influence of the TD on PDDs was below 1%. The measurements showed that the transmission factor depends slightly on the field size (0.893-0.921 for 5×5cm(2) to 30×30cm(2)). However, the evaluation of clinical IMRT-plans measured with and without the TD showed good agreement after using a single transmission factor (γ(2%/2mm) > 97%, δ±3% >95%). Furthermore, the response of TD was found to be linear and dose rate independent (maximum difference <0.5% compared to reference measurements). CONCLUSIONS: When placed in the path of the beam, the TD introduced a slight, clinically acceptable increase of the skin dose even for larger field sizes and smaller SSDs and the influence of the detector on the dose beyond dmax as well as on clinical IMRT-plans was negligible. Since there was no dose rate dependency and the response was linear, the device is therefore suitable for clinical use. Only its absorption has to be compensated during treatment planning, either by the use of a single transmission factor or by including the TD in the incident beam model.


Assuntos
Neoplasias/radioterapia , Aceleradores de Partículas/instrumentação , Radiometria/instrumentação , Planejamento da Radioterapia Assistida por Computador/instrumentação , Radioterapia de Alta Energia/instrumentação , Transdutores , Desenho de Equipamento , Análise de Falha de Equipamento , Humanos , Assistência Centrada no Paciente , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador/métodos , Reprodutibilidade dos Testes , Espalhamento de Radiação , Sensibilidade e Especificidade , Raios X
8.
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
9.
Med Phys ; 38(3): 1627-34, 2011 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-21520875

RESUMO

PURPOSE: Pencil-beam (PB) based dose calculation for treatment planning is limited by inaccuracies in regions of tissue inhomogeneities, particularly in situations with lateral electron disequilibrium as is present at tissue/lung interfaces. To overcome these limitations, a new "lateral disequilibrium inclusive" (LDI) PB based calculation algorithm was introduced. In this study, the authors evaluated the accuracy of the new model by film and ionization chamber measurements and Monte Carlo simulations. METHODS: To validate the performance of the new LDI algorithm implemented in Corvus 09, eight test plans were generated on inhomogeneous thorax and pelvis phantoms. In addition, three plans were calculated with a simple effective path length (EPL) algorithm on the inhomogeneous thorax phantom. To simulate homogeneous tissues, four test plans were evaluated in homogeneous phantoms (homogeneous dose calculation). RESULTS: The mean pixel pass rates and standard deviations of the gamma 4%/4 mm test for the film measurements were (96 +/- 3)% for the plans calculated with LDI, (70 +/- 5)% for the plans calculated with EPL, and (99 +/- 1)% for the homogeneous plans. Ionization chamber measurements and Monte Carlo simulations confirmed the high accuracy of the new algorithm (dose deviations < or = 4%; gamma 3%/3 mm > or = 96%). CONCLUSIONS: LDI represents an accurate and fast dose calculation algorithm for treatment planning.


Assuntos
Algoritmos , Método de Monte Carlo , Imagens de Fantasmas , Doses de Radiação , Radiometria/instrumentação , Humanos , Planejamento da Radioterapia Assistida por Computador , Software
10.
Int J Radiat Oncol Biol Phys ; 81(4): 1168-75, 2011 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-21093168

RESUMO

PURPOSE: Fast and reliable comprehensive quality assurance tools are required to validate the safety and accuracy of complex intensity-modulated radiotherapy (IMRT) plans for prostate treatment. In this study, we evaluated the performance of the COMPASS system for both off-line and potential online procedures for the verification of IMRT treatment plans. METHODS AND MATERIALS: COMPASS has a dedicated beam model and dose engine, it can reconstruct three-dimensional dose distributions on the patient anatomy based on measured fluences using either the MatriXX two-dimensional (2D) array (offline) or a 2D transmission detector (T2D) (online). For benchmarking the COMPASS dose calculation, various dose-volume indices were compared against Monte Carlo-calculated dose distributions for five prostate patient treatment plans. Gamma index evaluation and absolute point dose measurements were also performed in an inhomogeneous pelvis phantom using extended dose range films and ion chamber for five additional treatment plans. RESULTS: MatriXX-based dose reconstruction showed excellent agreement with the ion chamber (<0.5%, except for one treatment plan, which showed 1.5%), film (∼100% pixels passing gamma criteria 3%/3 mm) and mean dose-volume indices (<2%). The T2D based dose reconstruction showed good agreement as well with ion chamber (<2%), film (∼99% pixels passing gamma criteria 3%/3 mm), and mean dose-volume indices (<5.5%). CONCLUSION: The COMPASS system qualifies for routine prostate IMRT pretreatment verification with the MatriXX detector and has the potential for on-line verification of treatment delivery using T2D.


Assuntos
Benchmarking/normas , Método de Monte Carlo , Neoplasias da Próstata/radioterapia , Planejamento da Radioterapia Assistida por Computador/normas , Radioterapia de Intensidade Modulada/normas , Algoritmos , Humanos , Masculino , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador/instrumentação , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia de Intensidade Modulada/instrumentação , Radioterapia de Intensidade Modulada/métodos
11.
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
12.
Phys Med Biol ; 55(15): 4203-17, 2010 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-20616405

RESUMO

Long image acquisition times of 60-120 s for cone-beam CT (CBCT) limit the number of patients with lung cancer who can undergo volume image guidance under breathhold. We developed a low-dose dual-energy kilovoltage-megavoltage-cone-beam CT (kVMV-CBCT) based on a clinical treatment unit reducing imaging time to < or =15 s. Simultaneous kVMV-imaging was achieved by dedicated synchronization hardware controlling the output of the linear accelerator (linac) based on detector panel readout signals, preventing imaging artifacts from interference of the linac's MV-irradiation and panel readouts. Optimization was performed to minimize the imaging dose. Single MV-projections, reconstructed MV-CBCT images and images of simultaneous 90 degrees kV- and 90 degrees MV-CBCT (180 degrees kVMV-CBCT) were acquired with different parameters. Image quality and imaging dose were evaluated and compared to kV-imaging. Hardware-based kVMV synchronization resulted in artifact-free projections. A combined 180 degrees kVMV-CBCT scan with a total MV-dose of 5 monitor units was acquired in 15 s and with sufficient image quality. The resolution was 5-6 line pairs cm(-1) (Catphan phantom). The combined kVMV-scan dose was equivalent to a kV-radiation scan dose of approximately 33 mGy. kVMV-CBCT based on a standard linac is promising and can provide ultra-fast online volume image guidance with low imaging dose and sufficient image quality for fast and accurate patient positioning for patients with lung cancer under breathhold.


Assuntos
Tomografia Computadorizada de Feixe Cônico/métodos , Neoplasias Pulmonares/diagnóstico por imagem , Neoplasias Pulmonares/radioterapia , Respiração , Tomografia Computadorizada de Feixe Cônico/instrumentação , Humanos , Neoplasias Pulmonares/fisiopatologia , Imagens de Fantasmas , Doses de Radiação , Rotação , Fatores de Tempo
13.
Int J Radiat Oncol Biol Phys ; 78(4): 1219-26, 2010 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-20554124

RESUMO

PURPOSE: Hypofractionated high-dose radiotherapy for small lung tumors has typically been based on stereotaxy. Cone-beam computed tomography and breath-hold techniques have provided a noninvasive basis for precise cranial and extracranial patient positioning. The cone-beam computed tomography acquisition time of 60 s, however, is beyond the breath-hold capacity of patients, resulting in respiratory motion artifacts. By combining megavoltage (MV) and kilovoltage (kV) photon sources (mounted perpendicularly on the linear accelerator) and accelerating the gantry rotation to the allowed limit, the data acquisition time could be reduced to 15 s. METHODS AND MATERIALS: An Elekta Synergy 6-MV linear accelerator, with iViewGT as the MV- and XVI as the kV-imaging device, was used with a Catphan phantom and an anthropomorphic thorax phantom. Both image sources performed continuous image acquisition, passing an angle interval of 90° within 15 s. For reconstruction, filtered back projection on a graphics processor unit was used. It reconstructed 100 projections acquired to a 512 × 512 × 512 volume within 6 s. RESULTS: The resolution in the Catphan phantom (CTP528 high-resolution module) was 3 lines/cm. The spatial accuracy was within 2-3 mm. The diameters of different tumor shapes in the thorax phantom were determined within an accuracy of 1.6 mm. The signal-to-noise ratio was 68% less than that with a 180°-kV scan. The dose generated to acquire the MV frames accumulated to 82.5 mGy, and the kV contribution was <6 mGy. CONCLUSION: The present results have shown that fast breath-hold, on-line volume imaging with a linear accelerator using simultaneous kV-MV cone-beam computed tomography is promising and can potentially be used for image-guided radiotherapy for lung cancer patients in the near future.


Assuntos
Tomografia Computadorizada de Feixe Cônico/métodos , Processamento de Imagem Assistida por Computador/métodos , Neoplasias Pulmonares/diagnóstico por imagem , Aceleradores de Partículas , Imagens de Fantasmas , Respiração , Algoritmos , Humanos , Neoplasias Pulmonares/patologia , Movimento , Doses de Radiação , Fatores de Tempo , Carga Tumoral
14.
Z Med Phys ; 19(4): 264-76, 2009.
Artigo em Inglês | MEDLINE | ID: mdl-19962084

RESUMO

PURPOSE: Interfractional organ motion and patient positioning errors during prostate radiotherapy can have deleterious clinical consequences. It has become clinical practice to re-position the patient with image-guided translational position correction before each treatment to compensate for those errors. However, tilt errors can only be corrected with table corrections in six degrees of freedom or "full" adaptive treatment planning strategies. Organ shape deformations can only be corrected by "full" plan adaptation. This study evaluates the potential of instant treatment plan adaptation (fast isodose line adaptation with real-time dose manipulating tools) based on cone-beam CT (CBCT) to further improve treatment quality. METHODS AND MATERIALS: Using in-house software, CBCTs were modified to approximate a correct density calibration. To evaluate the dosimetric accuracy, dose distributions based on CBCTs were compared with dose distributions calculated on conventional planning CTs (PCT) for four datasets (one inhomogeneous phantom, three patient datasets). To determine the potential dosimetric benefit of a "full" plan adaptation over translational position correction, dose distributions were re-optimized using graphical "online" dose modification tools for three additional patients' CT-datasets with a substantially distended rectum while the original plans have been created with an empty rectum (single treatment fraction estimates). RESULTS: Absolute dose deviations of up to 51% in comparison to the PCT were observed when uncorrected CBCTs were used for replanning. After density calibration of the CBCTs, 97% of the dose deviations were

Assuntos
Próstata/diagnóstico por imagem , Neoplasias da Próstata/radioterapia , Tomografia Computadorizada por Raios X/métodos , Humanos , Masculino , Sistemas On-Line , Posicionamento do Paciente , Imagens de Fantasmas , Próstata/anatomia & histologia , Neoplasias da Próstata/diagnóstico por imagem , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador/métodos , Reto/anatomia & histologia , Reto/diagnóstico por imagem
15.
Int J Radiat Oncol Biol Phys ; 74(1): 73-80, 2009 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-18973977

RESUMO

PURPOSE: Three-dimensional (3D) treatment planning has reduced the cardiac dose in postoperative radiotherapy for breast cancer; however, the overall cardiac toxicity is still an issue because of more aggressive adjuvant treatment. Toxicity models have suggested that a reduction of the heart volume treated to high doses might be particularly advantageous. We compared aperture-based multifield intensity-modulated radiotherapy (IMRT) plans to 3D-planned tangent fields using dose-volume histograms, cardiac toxicity risk, and the robustness to positioning errors. METHODS AND MATERIALS: For 14 computed tomography data sets of patients with left-sided breast cancer (unfavorable thoracic geometry), a 3D treatment plan and an IMRT plan were created. The dose-volume histograms were evaluated for the target and risk organs. Excess risk of cardiac mortality was calculated for both approaches using a relative seriality model. Positioning errors were simulated by moving the isocenter. RESULTS: IMRT reduced the maximal dose to the left ventricle by a mean of 30.9% (49.14 vs. 33.97 Gy). The average heart volume exposed to >30 Gy was reduced from 45 cm(3) to 5.84 cm(3). The mean dose to the left ventricle was reduced by an average of 10.7% (10.86 vs. 9.7 Gy), and the mean heart dose increased by an average of 24% (from 6.85 to 8.52 Gy). The model-based reduction of the probability for excess therapy-associated cardiac death risk was from 6.03% for the 3D plans to 0.25% for the IMRT plans. CONCLUSION: Aperture-based IMRT for left-sided breast cancer significantly reduces the maximal dose to the left ventricle, which might translate into reduced cardiac mortality. Biological modeling might aid in deciding to treat with IMRT but has to be validated prospectively.


Assuntos
Neoplasias da Mama/radioterapia , Coração/efeitos da radiação , Lesões por Radiação/prevenção & controle , Planejamento da Radioterapia Assistida por Computador/métodos , Algoritmos , Carga Corporal (Radioterapia) , Neoplasias da Mama/patologia , Feminino , Coração/anatomia & histologia , Humanos , Imageamento Tridimensional/métodos , Lesões por Radiação/mortalidade , Dosagem Radioterapêutica , Radioterapia Conformacional/métodos , Radioterapia de Intensidade Modulada
16.
Strahlenther Onkol ; 183(4): 203-10, 2007 Apr.
Artigo em Alemão | MEDLINE | ID: mdl-17406802

RESUMO

BACKGROUND AND PURPOSE: Interfractional prostate motion during radiotherapy due to variation in rectal distension can have negative consequences. The authors investigated the dosimetric consequences of a linear translational position correction based on image guidance when a three-dimensional conformal treatment technique was used. MATERIAL AND METHODS: Planning CTs of seven patients with empty and distended rectum were analyzed. A reference plan for the planning target volume (PTV) and the boost were calculated on the CT dataset with the empty rectum with a standard four-field technique. The treatment plan was transferred to the CT with the distended rectum for an uncorrected setup (referenced to bony anatomy) and a corrected setup after position correction of the isocenter. The dosimetric consequences were analyzed. RESULTS: Organ motion decreased the coverage of the prostate by the 95% isodose during simulated single treatment fractions by up to -21.0 percentage points (%-p; boost plan) and by up to -14.9%-p for the seminal vesicles (PTV plan). The mean rectum dose increased by up to 18.3%-p (PTV plan). Linear translational correction (mean 6.4 +/- 3.4 mm, maximum 10.8 mm) increased the coverage of the prostate by the 95% isodose by up to 12.7%-p (boost plan), while the mean rectum dose was reduced by up to -8.9%-p (PTV plan). For the complete treatment a reduction of complication probability of the rectum of approximately 5%-p was calculated. CONCLUSION: The use of an image guidance system with linear translational correction can improve radiation treatment accuracy for prostate cancer, if geometric changes are within certain limits.


Assuntos
Neoplasias da Próstata/diagnóstico por imagem , Neoplasias da Próstata/radioterapia , Radioterapia Conformacional/métodos , Humanos , Processamento de Imagem Assistida por Computador , Masculino , Planejamento da Radioterapia Assistida por Computador , Reprodutibilidade dos Testes , Tomografia Computadorizada por Raios X
17.
Int J Radiat Oncol Biol Phys ; 67(1): 288-95, 2007 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-17189077

RESUMO

PURPOSE: In external beam radiotherapy (EBRT) and especially in intensity-modulated radiotherapy (IMRT), the accuracy of the dose distribution in the patient is of utmost importance. It was investigated whether image guided in vivo dosimetry in the rectum is a reliable method for online dose verification. METHODS AND MATERIALS: Twenty-one dose measurements were performed with an ionization chamber in the rectum of 7 patients undergoing IMRT for prostate cancer. The position of the probe was determined with cone beam computed tomography (CBCT). The point of measurement was determined relative to the isocenter and relative to an anatomic reference point. The dose deviations relative to the corresponding doses in the treatment plan were calculated. With an offline CT soft-tissue match, patient positioning after ultrasound was verified. RESULTS: The mean magnitude +/- standard deviation (SD) of patient positioning errors was 3.0 +/- 2.5 mm, 5.1 +/- 4.9 mm, and 4.3 +/- 2.4 mm in the left-right, anteroposterior and craniocaudal direction. The dose deviations in points at corresponding positions relative to the isocenter were -1.4 +/- 4.9% (mean +/- SD). The mean dose deviation at corresponding anatomic positions was 6.5 +/- 21.6%. In the rare event of insufficient patient positioning, dose deviations could be >30% because of the close proximity of the probe and the posterior dose gradient. CONCLUSIONS: Image-guided dosimetry in the rectum during IMRT of the prostate is a feasible and reliable direct method for dose verification when probe position is effectively controlled.


Assuntos
Neoplasias da Próstata/radioterapia , Radiometria/métodos , Dosagem Radioterapêutica , Radioterapia de Intensidade Modulada/normas , Reto , Estudos de Viabilidade , Humanos , Masculino , Neoplasias da Próstata/diagnóstico por imagem , Controle de Qualidade , Radiometria/normas , Radioterapia de Intensidade Modulada/métodos , Reto/diagnóstico por imagem , Tomografia Computadorizada por Raios X , Ultrassonografia
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