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1.
Med Phys ; 46(12): 5799-5806, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31602670

RESUMO

PURPOSE: To apply the recent code of practice from the IAEA/AAPM, TRS 483, to helical tomotherapy (HT) for reference and relative dosimetry obtaining correction factors for the Exradin A1SL ionization chamber. METHODS: The beam quality correction factor for the A1SL chamber was obtained through three different approaches following TRS 483 concepts and compared with published values. The determination of the reference absolute dose for the machine-specific reference (msr) field was complemented with relative dosimetry through the determination of output factors of small fields using different detectors. The response of A1SL was compared with correction-free film results and corrected output factors of other detectors. RESULTS: A weighted mean beam quality correction factor of 0.9945± 0.0073 was obtained for the A1SL chamber which is in agreement with values reported in the literature. Output factors obtained with different detectors were in agreement, given the uncertainty level. Considering the film output factors as free of corrections, the average value for A1SL output factors corrections was 1.000 ± 0.007. CONCLUSIONS: The beam quality correction factors for the A1SL chamber obtained through the three different pathways recommended by TRS 483 agreed with each other and also with published values. The measurements from the A1SL chamber normalized to the msr field in HT can be taken as output factors for small clinical field sizes without further corrections.


Assuntos
Radiometria/normas , Radioterapia Assistida por Computador , Padrões de Referência
2.
Phys Med Biol ; 64(22): 225011, 2019 11 21.
Artigo em Inglês | MEDLINE | ID: mdl-31665703

RESUMO

Respiratory motion management techniques in radiotherapy (RT) planning are primarily focused on maintaining tumor target coverage. An inadequately addressed need is accounting for motion in dosimetric estimations in smaller serial structures. Accurate dose estimations in such structures are more sensitive to motion because respiration can cause them to move completely in or out of a high dose-gradient field. In this work, we study three motion management strategies (m1-m3) to find an accurate method to estimate the dosimetry in airways. To validate these methods, we generated a 'ground truth' digital breathing model based on a 4DCT scan from a lung stereotactic ablative radiotherapy (SAbR) patient. We simulated 225 breathing cycles with ±10% perturbations in amplitude, respiratory period, and time per respiratory phase. A high-resolution breath-hold CT (BHCT) was also acquired and used with a research virtual bronchoscopy software to autosegment 239 airways. Contours for planning target volume (PTV) and organs at risk (OARs) were defined on the maximum intensity projection of the 4DCT (CTMIP) and transferred to the average of the 10 4DCT phases (CTAVG). To design the motion management methods, the RT plan was recreated using different images and structure definitions. Methods m1 and m2 recreated the plan using the CTAVG image. In method m1, airways were deformed to the CTAVG. In m2, airways were deformed to each of the 4DCT phases, and union structures were transferred onto the CTAVG. In m3, the RT plan was recreated on each of the 10 phases, and the dose distribution from each phase was deformed to the BHCT and summed. Dose errors (mean [min, max]) in airways were: m1: 21% (0.001%, 93%); m2: 45% (0.1%, 179%); and m3: 4% (0.006%, 14%). Our work suggests that accurate dose estimation in moving small serial structures requires customized motion management techniques (like m3 in this work) rather than current clinical and investigational approaches.


Assuntos
Broncoscopia , Neoplasias Pulmonares/radioterapia , Movimento , Planejamento da Radioterapia Assistida por Computador , Radioterapia Assistida por Computador/métodos , Respiração , Tomografia Computadorizada Quadridimensional , Humanos , Neoplasias Pulmonares/diagnóstico por imagem , Neoplasias Pulmonares/fisiopatologia , Órgãos em Risco/efeitos da radiação , Dosagem Radioterapêutica , Interface Usuário-Computador
3.
Medicine (Baltimore) ; 98(39): e17337, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31574871

RESUMO

RATIONALE: Diamond-Blackfan anemia (DBA) is a rare inherited marrow disorder, characterized by erythrocyte aplasia and is associated with congenital anomalies and a susceptibility to cancer. Although congenital abnormalities have been observed in ∼50% of DBA patients, the occurrence of an associated congenital diaphragmatic hernia (CDH) has rarely been reported. PATIENT CONCERNS: A 19-month-old male child was referred to our pediatric hematology-oncology outpatient clinic with anemic appearance. He presented to us with recurrent anemia, short stature, and developmental delay. DIAGNOSIS: On bone marrow examination, only erythropoietic cells were markedly decreased in number, whereas other cell lines were unaffected. An abdominal computed tomography scan revealed a Bochdalek type of CDH. A genetic analysis revealed heterozygous mutation of RPS19; therefore, he was diagnosed as having DBA with CDH. INTERVENTIONS: The patient received an initial packed red blood cell transfusion, followed by an administration of oral prednisone. OUTCOMES: The patient is maintained on oral prednisone administered at a dose of 0.3 mg/kg every alternate day and has since a hemoglobin level of >9.0 g/dL without further RBC transfusions. LESSONS: We learned that a Bochdalek type of CDH can manifest in a DBA patient with RPS19 gene mutation. Therefore, patients diagnosed with the latter disorder should also be screened for an early detection of potential CDHs.


Assuntos
Anemia de Diamond-Blackfan , Células da Medula Óssea/patologia , Transfusão de Eritrócitos/métodos , Hérnias Diafragmáticas Congênitas/diagnóstico , Prednisona/administração & dosagem , Proteínas Ribossômicas/genética , Anemia de Diamond-Blackfan/genética , Anemia de Diamond-Blackfan/fisiopatologia , Exame de Medula Óssea/métodos , Glucocorticoides/administração & dosagem , Humanos , Masculino , Mutação , Radioterapia Assistida por Computador/métodos , Resultado do Tratamento , Adulto Jovem
4.
J Appl Clin Med Phys ; 20(10): 152-159, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31535782

RESUMO

INTRODUCTION: Intrafractional motion can cause substantial uncertainty in precision radiotherapy. Traditionally, the target volume is defined to be sufficiently large to cover the tumor in every position. With the robotic treatment couch, a real-time motion compensation can improve tumor coverage and organ at risk sparing. However, this approach poses additional requirements, which are systematically developed and which allow the ideal robotic couch to be specified. METHODS AND MATERIALS: Data of intrafractional tumor motion were collected and analyzed regarding motion range, frequency, speed, and acceleration. Using this data, ideal couch requirements were formulated. The four robotic couches Protura, Perfect Pitch, RoboCouch, and RPSbase were tested with respect to these requirements. RESULTS: The data collected resulted in maximum speed requirements of 60 mm/s in all directions and maximum accelerations of 80 mm/s2 in the longitudinal, 60 mm/s2 in the lateral, and 30 mm/s2 in the vertical direction. While the two robotic couches RoboCouch and RPSbase completely met the requirements, even these two showed a substantial residual motion (40% of input amplitude), arguably due to their time delays. CONCLUSION: The requirements for the motion compensation by an ideal couch are formulated and found to be feasible for currently available robotic couches. However, the performance these couches can be improved further regarding the position control if the demanded speed and acceleration are taken into account as well.


Assuntos
Movimento , Neoplasias/fisiopatologia , Posicionamento do Paciente , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia Assistida por Computador/instrumentação , Robótica/métodos , Algoritmos , Humanos , Neoplasias/radioterapia , Dosagem Radioterapêutica , Radioterapia Assistida por Computador/métodos
5.
Brachytherapy ; 18(6): 823-828, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31522972

RESUMO

PURPOSE: Interstitial high-dose-rate brachytherapy (BT) is an alternative treatment option to stereotactic body radiotherapy (SBRT) for the ablative treatment of liver malignancies. The aim of the present comparative planning study was to reveal the possibilities and limitations of both techniques with regard to dosimetric properties. METHODS AND MATERIALS: Eighty-five consecutive patients with liver malignancy diagnosis were treated with interstitial BT between 12/2008 and 09/2009. The prescription dose of BT varied between 15 and 20 Gy, depending on histology. For dosimetric comparison, virtual SBRT treatment plans were generated using the original BT planning CTs. Additional margins reflecting the respiratory tumor motion were added to the target volumes for SBRT planning. RESULTS: The mean PTVBT was 34.7 cm3 (0.5-410.0 cm3) vs. a mean PTVSBRT of 73.2 cm3 (6.1-593.4 cm3). Regarding the minimum peripheral dose (D99.9), BT achieved the targeted prescription dose of 15 Gy/20 Gy better without violating organ at risk constraints. The dose exposure of the liver was significantly influenced by treatment modality. The liver exposure to 5 Gy was statistically lower with 611 ± 43 cm3 for BT as compared with 694 ± 37 cm3 for SBRT plans (20-Gy group, p = 0.001), corresponding to 41.8% vs. 45.9% liver volume, respectively. CONCLUSIONS: To the best of our knowledge, this is the first report on the comparison of clinically treated liver BT treatments with virtually planned SBRT treatments. The planning study showed a superior outcome of BT regarding dose coverage of the target volume and exposed liver volume. Nevertheless, further studies are needed to determine ideal applicability for each treatment approach.


Assuntos
Braquiterapia/métodos , Neoplasias Hepáticas/radioterapia , Radiocirurgia/métodos , Radioterapia Assistida por Computador/métodos , Adulto , Idoso , Idoso de 80 Anos ou mais , Relação Dose-Resposta à Radiação , Feminino , Fluoroscopia , Humanos , Neoplasias Hepáticas/diagnóstico , Masculino , Pessoa de Meia-Idade , Dosagem Radioterapêutica , Tomografia Computadorizada por Raios X , Resultado do Tratamento
6.
Brachytherapy ; 18(6): 771-779, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31506225

RESUMO

PURPOSE: Three-dimensional image-guided brachytherapy (3D-IGBT) has become the standard therapy for patients with cervical cancer. However, in this population, the impact of 3D-IGBT in elderly individuals remains unknown. This study assessed the efficacy of 3D-IGBT for elderly patients with cervical cancer. METHODS AND MATERIALS: We performed a retrospective chart review of 105 consecutive patients with cervical squamous cell carcinoma aged ≥70 years who received radiotherapy alone between January 2001 and September 2014. All patients were treated with external beam radiotherapy and high-dose-rate intracavitary brachytherapy. We assessed the treatment outcomes in all patients. We then compared outcomes between two groups: patients treated by changing the Point A dose at brachytherapy (Group A, n = 71) and those treated with 3D-IGBT at least twice (Group B, n = 34). RESULTS: The median followup period was 59 (range, 6-203) months; the median age was 77 years. The 5-year local control and cause-specific survival rates were 89% and 78%, respectively. The 5-year cumulative rates of late toxicities of the rectum and bladder of Grade ≥3 were 2.0% and 4.2%, respectively. No statistically significant differences were observed in the local control and cause-specific survival rates, or in the incidence of rectal toxicities between groups. The 3-year cumulative rates of urinary toxicity of Grade ≥1 were 20.4% and 6.9% in Group A and Group B, respectively (p = 0.035). CONCLUSION: In elderly patients with cervical cancer, 3D-IGBT could be performed safely and effectively and contributed to decreasing urinary toxicity incidence rates.


Assuntos
Braquiterapia/métodos , Imageamento Tridimensional/métodos , Radioterapia Assistida por Computador/métodos , Tomografia Computadorizada por Raios X/métodos , Neoplasias do Colo do Útero/radioterapia , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Dosagem Radioterapêutica , Estudos Retrospectivos , Resultado do Tratamento , Neoplasias do Colo do Útero/diagnóstico
7.
Med Phys ; 46(8): 3371-3377, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31273807

RESUMO

PURPOSE: With the introduction of dynamic tumor tracking in radiotherapy, it is possible to irradiate moving targets with minimal safety margins. However, most dynamic tumor tracking techniques rely on changing the beam geometry by, for example, adapting the multileaf collimator (MLC) positions or rotating the LINAC head. These changes are relative to a reference position which is determined by a specific breathing phase. Since these changes in the beam path also influence the delivered dose, choosing a different reference position based on a different breathing phase impacts the applied dose to the patient. This work investigates the influence of choosing different reference breathing phases on the dose distribution. METHODS: The Vero system tracks the moving target by performing a pan and tilt rotation of the LINAC head. For 13 patients, the target position was extracted from every phase of a four-dimensional computed tomography (4DCT) and the pan and tilt values were determined with respect to three different reference phases. These reference phases were inspiration, expiration, and the midventilation. For all reference phases, a 4D dose calculation was performed on the 4DCT regarding the respective pan and tilt values. Furthermore, the applied dose to the target and surrounding organs at risk was calculated. To accumulate the dose distribution, weights from the actual patient breathing motion were determined. The weights were calculated from the breathing motions from different days to investigate the impact of daily variations in the breathing motion onto the accumulated dose distribution. All obtained values were then compared to the static treatment plan. RESULTS: The mean and maximum doses applied to the target or surrounding organs at risk show no general behavior depending on the different reference phases. Nevertheless, for some patients, large differences (approx. 30%) in the applied dose to certain organs at risk could be observed, whereas the applied dose to the target shows no dependency on the different reference phases. However, the mean target dose is in all cases approx. 1.5% below the reference value from the static treatment plan. CONCLUSION: Although no general dependency of the applied dose on the selected reference phase could be found, the choice of the reference phase can have great impact on the organ at risk dose for some patients. Thus, the choice of the reference phase used for patient positioning should be considered during treatment planning since it can be seen as a new degree of freedom of a treatment based on tracking.


Assuntos
Neoplasias/radioterapia , Radioterapia Assistida por Computador/métodos , Idoso , Idoso de 80 Anos ou mais , Tomografia Computadorizada Quadridimensional , Humanos , Pessoa de Meia-Idade , Neoplasias/diagnóstico por imagem , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador
8.
Brachytherapy ; 18(6): 841-851, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31345749

RESUMO

PURPOSE: Applicator digitization is one of the most critical steps in 3D high-dose-rate brachytherapy (HDRBT) treatment planning. Motivated by recent advances in deep-learning, we propose a deep-learning-assisted applicator digitization method for 3D CT image-based HDRBT. This study demonstrates its feasibility and potential in gynecological cancer HDRBT. METHODS AND MATERIALS: Our method consisted of two steps. The first step used a U-net to segment applicator regions. We trained the U-net using two-dimensional CT images with a tandem-and-ovoid (T&O) applicator and corresponding applicator mask images. The second step applied a spectral clustering method and a polynomial curve fitting method to extract applicator central paths. We evaluated the accuracy, efficiency, and robustness of our method in different scenarios including other T&O cases that were not used in training, a T&O case scanned with cone-beam CT, and Y-tandem and cylinder-applicator cases. RESULTS: In test cases with a T&O applicator, average 3D Dice similarity coefficient between automatic and manual segmented applicator regions was 0.93. Average distance between tip positions and average Hausdorff distance between applicator channels determined by our method and manually were 0.64 mm and 0.68 mm, respectively. Although trained only using CT images of T&O cases, our tool can also digitize Y-tandem, cylinder applicator, and T&O applicator scanned in cone-beam CT with error of tip position and Hausdorff distance <1 mm. Computation time was ∼15 s per case. CONCLUSIONS: We have developed a deep-learning-assisted applicator digitization tool for 3D CT image-based HDRBT of gynecological cancer. The achieved accuracy, efficiency, and robustness made our tool clinically attractive.


Assuntos
Algoritmos , Braquiterapia/métodos , Aprendizado Profundo , Neoplasias dos Genitais Femininos/radioterapia , Imageamento Tridimensional/métodos , Radioterapia Assistida por Computador/métodos , Tomografia Computadorizada por Raios X/métodos , Estudos de Viabilidade , Feminino , Neoplasias dos Genitais Femininos/diagnóstico , Humanos
9.
BMC Med Imaging ; 19(1): 46, 2019 05 31.
Artigo em Inglês | MEDLINE | ID: mdl-31151424

RESUMO

BACKGROUND: To compare the accuracy, advantages and disadvantages of automatic registration methods at different anatomical-sites for thoracic image-guided radiation therapy (IGRT). METHODS: The Varian-IX IGRT system was used to perform a manual registration of the images collected on the first fraction of 60 patients with lung cancer (42 cases central location and 18 cases of peripheral). The registered images were used as reference images. Offline registration was performed for computed tomography-CBCT images using four methods: whole image registration, ipsilateral registration, soft tissue tumor registration, and vertebral body registration. Time taken to complete and deviation value were analyzed between the different methods. RESULTS: There were significant differences in absolute deviation value of all the three directions (P < 0.001) and the time consumption (P < 0.001) between 4 methods. The Z direction had significant differences in deviation value of 4 methods (0.023 ± 0.128 mm, - 0.030 ± 0.175 mm, - 0.010 ± 0.238 mm, - 0.075 ± 0.137 mm, P = 0.011). The difference was significant in the X direction of the ipsilateral registration method between central and peripheral lung cancer (0.033 ± 0.053 mm vs. 0.067 ± 0.067 mm, P = 0.045). CONCLUSIONS: The whole lung or affected side registration methods could be recommended to be used in the automatic registration function of the Varian-IX's On-Board Imaging (OBI) system.


Assuntos
Neoplasias Pulmonares/radioterapia , Radioterapia Guiada por Imagem/métodos , Adulto , Idoso , Idoso de 80 Anos ou mais , Tomografia Computadorizada de Feixe Cônico , Feminino , Humanos , Neoplasias Pulmonares/diagnóstico por imagem , Masculino , Pessoa de Meia-Idade , Radioterapia Assistida por Computador , Estudos Retrospectivos , Resultado do Tratamento
10.
J Radiat Res ; 60(4): 501-508, 2019 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-31034570

RESUMO

Perirectal hyaluronate gel injection (HGI) appears to be a promising technique for healthy tissue dose sparing in pelvic radiotherapy. In this analysis, we report our initial experience of HGI in gynecologic brachytherapy, focusing on its safety and effectiveness for dose reduction to the rectum. Between July 2013 and May 2014, 36 patients received HGI for primary/salvage gynecologic brachytherapy. Dosimetric effect analysis was based on pre- and post-HGI computed tomography dataset registration with corresponding dose-volume histogram evaluation. The maximum dose to the most exposed 0.1 cm3 (D0.1cm3) and 2.0 cm3 (D2.0cm3) were used as index values for rectum and bladder dose evaluation. The dose indexes for target volume (TV) coverage were TV D90/V100. In all cases, HGI was well tolerated, with no acute or late adverse events documented at a median follow-up of 220 days (range, 18-1046 days). Rectum D2.0cm3 and D0.1cm3 were significantly decreased by HGI (P < 0.001 and P = 0.003, respectively), with no significant impact on dosimetric parameters of bladder and TV coverage. Factors correlating negatively with the dosimetric effect of HGI were an increasing number of interstitial catheters (P = 0.003) as well as Lcranial100% (P = 0.014) and Lcranial80% (P = 0.001) [i.e. the length from the anal verge to the most cranial point at which the 100% and 80% isodose lines, respectively, crossed the rectum]. The concept of HGI for gynecologic brachytherapy is plausible, and our initial experience indicates it to be an effective technique for rectal dose reduction in radiotherapy of intrapelvic tumours.


Assuntos
Braquiterapia , Géis , Neoplasias dos Genitais Femininos/radioterapia , Ácido Hialurônico/administração & dosagem , Radiometria , Reto/efeitos da radiação , Terapia de Salvação , Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Japão , Pessoa de Meia-Idade , Pelve/efeitos da radiação , Doses de Radiação , Radioterapia , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador , Radioterapia Assistida por Computador , Estudos Retrospectivos , Bexiga Urinária/efeitos da radiação , Neoplasias do Colo do Útero/radioterapia , Neoplasias Uterinas/radioterapia , Neoplasias Vaginais/radioterapia , Neoplasias Vulvares/radioterapia
11.
Semin Radiat Oncol ; 29(3): 185-197, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-31027636

RESUMO

Manual image segmentation is a time-consuming task routinely performed in radiotherapy to identify each patient's targets and anatomical structures. The efficacy and safety of the radiotherapy plan requires accurate segmentations as these regions of interest are generally used to optimize and assess the quality of the plan. However, reports have shown that this process can be subject to significant inter- and intraobserver variability. Furthermore, the quality of the radiotherapy treatment, and subsequent analyses (ie, radiomics, dosimetric), can be subject to the accuracy of these manual segmentations. Automatic segmentation (or auto-segmentation) of targets and normal tissues is, therefore, preferable as it would address these challenges. Previously, auto-segmentation techniques have been clustered into 3 generations of algorithms, with multiatlas based and hybrid techniques (third generation) being considered the state-of-the-art. More recently, however, the field of medical image segmentation has seen accelerated growth driven by advances in computer vision, particularly through the application of deep learning algorithms, suggesting we have entered the fourth generation of auto-segmentation algorithm development. In this paper, the authors review traditional (nondeep learning) algorithms particularly relevant for applications in radiotherapy. Concepts from deep learning are introduced focusing on convolutional neural networks and fully-convolutional networks which are generally used for segmentation tasks. Furthermore, the authors provide a summary of deep learning auto-segmentation radiotherapy applications reported in the literature. Lastly, considerations for clinical deployment (commissioning and QA) of auto-segmentation software are provided.


Assuntos
Processamento de Imagem Assistida por Computador/tendências , Neoplasias/diagnóstico por imagem , Neoplasias/radioterapia , Redes Neurais de Computação , Radioterapia Assistida por Computador/tendências , Radioterapia Guiada por Imagem/tendências , Algoritmos , Aprendizado Profundo , Humanos , Órgãos em Risco/diagnóstico por imagem , Órgãos em Risco/efeitos da radiação , Software
12.
Phys Med ; 58: 21-31, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30824146

RESUMO

PURPOSE: Pre-clinical irradiation systems use kilovoltage x-ray systems to deliver small fields of radiation in static beam arrangements or arcs. The systems are costly and the radiobiological effectiveness of kilovoltage beams is known to differ from the megavoltage photon beams used clinically. This work used Developer mode on the Varian TrueBeam STx linear accelerator to create a pre-clinical irradiator capable of treating millimeter-sized targets. MATERIALS AND METHODS: A treatment field defined by a single opposed leaf pair was used to deliver arc-based treatments. Dynamic couch trajectories were used to create a shortened virtual isocentre. Initially, a pre-treatment imaging procedure was used to quantify target misalignment at control points along the arcs and determine appropriate couch positional corrections. This was followed by the treatment arcs in which the positional corrections were implemented. Monte Carlo simulations and radiochromic film were used to calculate and measure dose distributions. RESULTS: A 1 mm leaf separation produced the optimal dose distributions. Couch position corrections up to 2.1 mm were required to maintain a target at virtual isocentre. Application of couch corrections reduced non-coplanar arc treatments dose profile by 1.2 mm at 30% of the maximum dose. Treatment of a 1 mm diameter target would result in falloff distances to the 80%, 50% and 25% of the 90% prescription line of 0.3 mm, 0.5 mm and 1.3 mm from the target edge respectively. CONCLUSIONS: This work has demonstrated that it is possible to deliver highly compact dose distributions using megavoltage photon beams from existing clinical infrastructure.


Assuntos
Radioterapia Assistida por Computador/instrumentação , Aceleradores de Partículas , Imagens de Fantasmas , Radiometria , Planejamento da Radioterapia Assistida por Computador
14.
J Appl Clin Med Phys ; 20(2): 13-23, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30632271

RESUMO

PURPOSE: The electron energy characteristics of mobile intraoperative radiotherapy (IORT) accelerator LIAC® differ from commonly used linear accelerators, thus some of the frequently used detectors can give less accurate results. The aim of this study is to evaluate the output factors (OFs) of several ionization chambers (IC) and solid state detectors (SS) for electron beam energies generated by LIAC® and compare with the output factor of Monte Carlo model (MC) in order to determine the adequate detectors for LIAC® . METHODS: The OFs were measured for 6, 8, 10, and 12 MeV electron energies with PTW 23343 Markus, PTW 34045 Advanced Markus, PTW 34001 Roos, IBA PPC05, IBA PPC40, IBA NACP-02, PTW 31010 Semiflex, PTW 31021 Semiflex 3D, PTW 31014 Pinpoint, PTW 60017 Diode E, PTW 60018 Diode SRS, SNC Diode EDGE, and PTW 60019 micro Diamond detectors. Ion recombination factors (ksat ) of IC were measured for all applicator sizes and OFs were corrected according to ksat . The measured OFs were compared with Monte Carlo output factors (OFMC ). RESULTS: The measured OFs of IBA PPC05, PTW Advanced Markus, PTW Pinpoint, PTW microDiamond, and PTW Diode E detectors are in good agreement with OFMC . The maximum deviations of IBA PPC05 OFs to OFMC are -1.6%, +1.5%, +1.5%, and +2.0%; for PTW Advanced Markus +1.0%, +1.5%, +2.0%, and +2.0%; for PTW Pinpoint +2.0%, +1.6%, +4.0%, and +2.0%; for PTW microDiamond -1.6%, +2%, +1.1%, and +1.0%; and for PTW Diode E -+1.7%, +1.7%, +1.3%, and +2.5% for 6, 8, 10, and 12 MeV, respectively. PTW Roos, PTW Markus, IBA PPC40, PTW Semiflex, PTW Semiflex 3D, SNC Diode Edge measured OFs with a maximum deviation of +5.6%, +4.5%, +5.6%, +8.1%, +4.8%, and +9.6% with respect to OFMC , while PTW Diode SRS and IBA NACP-02 were the least accurate (with highest deviations -37.1% and -18.0%, respectively). CONCLUSION: The OFs results of solid state detectors PTW microDiamond and PTW Diode E as well as the ICs with small electrode spacing distance such as IBA PPC05, PTW Advanced Markus and PTW Pinpoint are in excellent agreement with OFMC . The measurements of the other detectors evaluated in this study are less accurate, thus they should be used with caution. Particularly, PTW Diode SRS and IBA NACP-02 are not suitable and their use should be avoided in relative dosimetry measurements under high dose per pulsed (DPP) electron beams.


Assuntos
Elétrons , Neoplasias/radioterapia , Aceleradores de Partículas/instrumentação , Radiometria/instrumentação , Radioterapia Assistida por Computador/instrumentação , Diamante/química , Humanos , Período Intraoperatório , Método de Monte Carlo , Radiometria/classificação , Dosagem Radioterapêutica
15.
Int J Radiat Oncol Biol Phys ; 103(4): 1004-1010, 2019 03 15.
Artigo em Inglês | MEDLINE | ID: mdl-30496883

RESUMO

PURPOSE: Reducing respiratory motion during the delivery of radiation therapy reduces the volume of healthy tissues irradiated and may decrease radiation-induced toxicity. The purpose of this study was to assess the potential for rapid shallow non-invasive mechanical ventilation to reduce internal anatomy motion for radiation therapy purposes. METHODS AND MATERIALS: Ten healthy volunteers (mean age, 38 years; range, 22-54 years; 6 female and 4 male) were scanned using magnetic resonance imaging during normal breathing and at 2 ventilator-induced frequencies: 20 and 25 breaths per minute for 3 minutes. Sagittal and coronal cinematic data sets, centered over the right diaphragm, were used to measure internal motions across the lung-diaphragm interface. Repeated scans assessed reproducibility. Physiologic parameters and participant experiences were recorded to quantify tolerability and comfort. RESULTS: Physiologic observations and experience questionnaires demonstrated that rapid shallow non-invasive ventilation technique was tolerable and comfortable. Motion analysis of the lung-diaphragm interface demonstrated respiratory amplitudes and variations reduced in all subjects using rapid shallow non-invasive ventilation compared with spontaneous breathing: mean amplitude reductions of 56% and 62% for 20 and 25 breaths per minute, respectively. The largest mean amplitude reductions were found in the posterior of the right lung; 40.0 mm during normal breathing to 15.5 mm (P < .005) and 15.2 mm (P < .005) when ventilated with 20 and 25 breaths per minute, respectively. Motion variations also reduced with ventilation; standard deviations in the posterior lung reduced from 14.8 mm during normal respiration to 4.6 mm and 3.5 mm at 20 and 25 breaths per minute, respectively. CONCLUSIONS: To our knowledge, this study is the first to measure internal anatomic motion using rapid shallow mechanical ventilation to regularize and minimize respiratory motion over a period long enough to image and to deliver radiation therapy. Rapid frequency and shallow, non-invasive ventilation both generate large reductions in internal thoracic and abdominal motions, the clinical application of which could be profound-enabling dose escalation (increasing treatment efficacy) or high-dose ablative radiation therapy.


Assuntos
Movimento , Radioterapia Assistida por Computador/métodos , Respiração Artificial , Respiração , Tórax/efeitos da radiação , Adulto , Feminino , Humanos , Pulmão/diagnóstico por imagem , Pulmão/fisiologia , Pulmão/efeitos da radiação , Imagem por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Dosagem Radioterapêutica , Radioterapia Assistida por Computador/efeitos adversos , Segurança , Adulto Jovem
16.
Acta Oncol ; 58(1): 95-104, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30280626

RESUMO

BACKGROUND: Late effects induced by radiotherapy (RT) are of great concern for mediastinal Hodgkin's lymphoma (HL) patients and it is therefore important to reduce normal tissue dose. The aim of this study was to investigate the impact on the normal tissue dose and target coverage, using various combinations of intensity modulated proton therapy (IMPT), volumetric modulated arc therapy (VMAT) and 3-dimensional conformal RT (3D-CRT), planned in both deep inspiration breath hold (DIBH) and free breathing (FB). MATERIAL AND METHODS: Eighteen patients were enrolled in this study and planned with involved site RT. Two computed tomography images were acquired for each patient, one during DIBH and one during FB. Six treatment plans were created for each patient; 3D-CRT in FB, 3D-CRT in DIBH, VMAT in FB, VMAT in DIBH, IMPT in FB and IMPT in DIBH. Dosimetric impact on the heart, left anterior descending (LAD) coronary artery, lungs, female breasts, target coverage, and also conformity index and integral dose (ID), was compared between the different treatment techniques. RESULTS: The use of DIBH significantly reduced the lung dose for all three treatment techniques, however, no significant difference in the dose to the female breasts was observed. Regarding the heart and LAD doses, large individual variations were observed. For VMAT, the mean heart and LAD doses were significantly reduced using DIBH, but no significant difference was observed for 3D-CRT and IMPT. Both IMPT and VMAT resulted in improved target coverage and more conform dose distributions compared to 3D-CRT. IMPT generally showed the lowest organs at risk (OAR) doses and significantly reduced the ID compared to both 3D-CRT and VMAT. CONCLUSIONS: The majority of patients benefited from treatment in DIBH, however, the impact on the normal tissue dose was highly individual and therefore comparative treatment planning is encouraged. The lowest OAR doses were generally observed for IMPT in combination with DIBH.


Assuntos
Doença de Hodgkin/radioterapia , Neoplasias do Mediastino/radioterapia , Terapia com Prótons/métodos , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia Assistida por Computador/métodos , Adolescente , Adulto , Idoso , Suspensão da Respiração , Feminino , Humanos , Inalação , Masculino , Pessoa de Meia-Idade , Órgãos em Risco/efeitos da radiação , Fótons/uso terapêutico , Lesões por Radiação/prevenção & controle , Estudos Retrospectivos , Adulto Jovem
17.
Med Biol Eng Comput ; 57(3): 643-651, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30324464

RESUMO

The purpose of this study is to create a new pseudo-computed tomography (CT) imaging approach under superposed ultrasound (US) deformation fields based on step-by-step local registration. Scanned CT and US 3D image datasets of three patients with postoperative cervical carcinoma were selected, including CT (CTsim) and US images (USsim) acquired during simulated positioning process and cone beam CT (CBCT) and US images for positioning verification (USpv) acquired after treatment for 10 times. Regions of interest such as urinary bladders were segmented out and accepted local registration to obtain different deformation fields. These deformation fields were successively performed according to their order and then applied to localized CT images to obtain pseudo-CT (CTps). After filtering, we obtained the final correct pseudo-CT (CTpsf). The pseudo-CT based on the mask of the whole imaging region of US images (WCTps) were acquired as control. Then, we compared CTpsf, CTps, WCTps, and CBCT in terms of their similarity in anatomical structure and differences in pseudo-CT and CTsim in terms of dosimetry. Structural similarity degree between CTpsf and CBCT was larger compared with that between CTps and WCTps. Target regions and dosages of endangered organs between CTpsf and CTsim were different under the same calculation conditions based on the Monte Carlo algorithm. Compared with the VMAT plan of CTsim, the pass rate of CTpsf in γ analysis under the standards of 2% dosage difference and 2-mm distance difference was 91.8%. The imaging quality of CTpsf was better compared with WCTps and CTps. It exhibited high similarity with CBCT in anatomical structure and had favorable application prospect in adaptive radiotherapy. Graphical abstract The local deformation registration is performed between the ultrasound images based on different regions of interest, and then stepwise applied to localized CT images to obtain pseudo-CT. After filtering, the corrected pseudo CT image is obtained.


Assuntos
Processamento de Imagem Assistida por Computador/métodos , Radioterapia Assistida por Computador/métodos , Tomografia Computadorizada por Raios X/métodos , Ultrassonografia/métodos , Neoplasias do Colo do Útero/diagnóstico por imagem , Tomografia Computadorizada de Feixe Cônico/métodos , Feminino , Humanos , Imageamento Tridimensional/métodos , Dosagem Radioterapêutica , Neoplasias do Colo do Útero/radioterapia
18.
Cancer Res Treat ; 51(3): 1156-1166, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30514067

RESUMO

PURPOSE: Thoracic re-irradiation (re-RT) of lung cancer has been challenged by the tolerance doses of normal tissues. We retrospectively analyzed local control, overall survival (OS) and toxicity after thoracic re-RT using highly conformal radiotherapy, such as intensity modulated radiotherapy and stereotactic body radiotherapy. MATERIALS AND METHODS: Thirty-one patients who received high-dose thoracic re-RT were analyzed. Doses were recalculated to determine biologically equivalent doses. The median interval to re-RT was 15.1 months (range, 4.4 to 56.3 months), the median initial dose was 79.2 Gy10 (range, 51.75 to 150 Gy10), and the median re-RT dose was 68.8 Gy10 (range, 43.2 to 132 Gy10). RESULTS: Eighteen (58.1%) and eleven (35.5%) patients showed loco-regional recurrence and distant metastasis, respectively, after 17.4 months of median follow-up. The 1-year and 2-year local control rates were 60.2% and 43.7%, respectively. The median loco-regional recurrence-free-survival (LRFS) was 15.4 months, and the median OS was 20.4 months. The cumulative and re-RT biologically equivalent dose for α/ß=10 (BED10) doses were the most significant prognostic factors. Cumulative BED10 ≥145 Gy10 and re-RT BED10≥68.7 Gy10 were significantly associated with longer OS (p=0.029 and p=0.012, respectively) and LRFS (p=0.003 and p=0.000, respectively). The most frequent acute toxicity was grade 1-2 pulmonary toxicity (41.9%). No acute grade 3 or higher toxicities occurred. CONCLUSION: Our results show that high-dose thoracic re-RT of lung cancer can be safely delivered using highly conformal radiotherapy with favorable survival and acceptable toxicity. An optimal strategy to select patients who would benefit from re-RT is crucial in extending the indications and improving the efficacy with a sufficiently high dose.


Assuntos
Neoplasias Pulmonares/radioterapia , Radioterapia Assistida por Computador/métodos , Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Intervalo Livre de Progressão , Radiocirurgia , Dosagem Radioterapêutica , Radioterapia Conformacional , Radioterapia de Intensidade Modulada , Estudos Retrospectivos , Análise de Sobrevida , Resultado do Tratamento
19.
Phys Med Biol ; 64(1): 015001, 2018 12 19.
Artigo em Inglês | MEDLINE | ID: mdl-30523943

RESUMO

In precision radiotherapy, the intrafractional motion can cause a considerable uncertainty of the location of the tumor to be treated. An established approach is the expansion of the target volume to account for the motion. An alternative approach is couch-tracking, in which the patient is continually moved to compensate the intrafractional motion. However, couch-tracking itself might induce uncertainty of the patient's body position, because the body is non-rigid. One hundred healthy volunteers were positioned supine on a robotic couch. Optical markers were placed on the torso of the volunteers as well as on the couch, and their positions were tracked with an optical surface measurement system. Using these markers, the uncertainty of the body position relative to the couch position was estimated while the couch was static or moving. Over the included 83 healthy volunteers, the median of the uncertainty increased by 0.8 mm (SI), 0.4 mm (LR) and 0.4 mm (AP) when the couch moved. Couch motion was found to increase the uncertainty of the body position relative to the couch. However, this uncertainty is one order of magnitude smaller than the intrafractional tumor motion amplitudes to be compensated. Therefore, even with body motion present, the couch-tracking approach is a viable option. The study was registered at ClinicalTrials.gov (NCT02820532) and the Swiss national clinical trials portal (SNCTP000001878).


Assuntos
Voluntários Saudáveis , Movimento , Radioterapia Assistida por Computador/instrumentação , Fracionamento da Dose de Radiação , Humanos , Postura , Robótica , Incerteza
20.
Comput Methods Programs Biomed ; 165: 187-195, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30337073

RESUMO

BACKGROUND AND OBJECTIVE: Tracking mobile tumor regions during the treatment is a crucial part of image-guided radiation therapy because of two main reasons which negatively affect the treatment process: (1) a tiny error will lead to some healthy tissues being irradiated; and (2) some cancerous cells may survive if the beam is not accurately positioned as it may not cover the entire cancerous region. However, tracking or delineation of such a tumor region from magnetic resonance imaging (MRI) is challenging due to photometric similarities of the region of interest and surrounding area as well as the influence of motion in the organs. The purpose of this work is to develop an approach to track the center and boundary of tumor region by auto-contouring the region of interest in moving organs for radiotherapy. METHODS: We utilize a nonrigid registration method as well as a publicly available RealTITracker algorithm for MRI to delineate and track tumor regions from a sequence of MRI images. The location and shape of the tumor region in the MRI image sequence varies over time due to breathing. We investigate two approaches: the first one uses manual segmentation of the first frame during the pretreatment stage; and the second one utilizes manual segmentation of all the frames during the pretreatment stage. RESULTS: We evaluated the proposed approaches over a sequence of 600 images acquired from 6 patients. The method that utilizes all the frames in the pretreatment stage with moving mesh based registration yielded the best performance with an average Dice Score of 0.89 ±â€¯0.04 and Hausdorff Distance of 3.38 ±â€¯0.10 mm. CONCLUSIONS: This study demonstrates a promising boundary tracking tool for delineating the tumor region that can deal with respiratory movement and the constraints of adaptive radiation therapy.


Assuntos
Algoritmos , Neoplasias Pulmonares/diagnóstico por imagem , Neoplasias Pulmonares/radioterapia , Radioterapia Assistida por Computador/métodos , Radioterapia Guiada por Imagem/métodos , Marcadores Fiduciais , Humanos , Neoplasias Pulmonares/patologia , Imagem por Ressonância Magnética/estatística & dados numéricos , Movimento (Física) , Planejamento da Radioterapia Assistida por Computador/métodos , Planejamento da Radioterapia Assistida por Computador/estatística & dados numéricos , Radioterapia Assistida por Computador/estatística & dados numéricos , Radioterapia Conformacional/métodos , Radioterapia Conformacional/estatística & dados numéricos , Radioterapia Guiada por Imagem/estatística & dados numéricos
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