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1.
J Appl Clin Med Phys ; 25(6): e14303, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38377378

RESUMO

PURPOSE: A workflow/planning strategy delivering low-dose radiation therapy (LDRT) (1 Gy) to all polymetastatic diseases using conventional planning/delivery (Raystation/Halcyon = "conventional") and the AI-based Ethos online adaptive RT (oART) platform is developed/evaluated. METHODS: Using retrospective data for ten polymetastatic non-small cell lung cancer patients (5-52 lesions each) with PET/CTs, gross tumor volumes (GTVs) were delineated using PET standardized-uptake-value (SUV) thresholding. A 1 cm uniform expansion of GTVs to account for setup/contour uncertainty and organ motion-generated planning target volumes (PTVs). Dose optimization/calculation used the diagnostic CT from PET/CT. Dosimetric objectives were: Dmin,0.03cc ≥ 95% (acceptable variation (Δ) ≥ 90%), V100% ≥ 95% (Δ ≥ 90%), and D0.03cc ≤ 120% (Δ ≤ 125%). Additionally, online adaptation was simulated. When available, subsequent diagnostic CT was used to represent on-treatment CBCT. Otherwise, the CT from PET/CT used for initial planning was deformed to simulate clinically representative changes. RESULTS: All initial plans generated, both for Raystation and Ethos, achieved clinical goals within acceptable variation. For all patients, Dmin,0.03cc ≥ 95%, V100% ≥ 95%, and D0.03cc ≤ 120% goals were achieved for 84.8%/99.5%, 97.7%/98.7%, 97.4%/92.3%, in conventional/Ethos plans, respectively. The ratio of 50% isodose volume to PTV volume (R50%), maximum dose at 2 cm from PTV (D2cm), and the ratio of the 100% isodose volume to PTV volume (conformity index) in Raystation/Ethos plans were 7.9/5.9; 102.3%/88.44%; and 0.99/1.01, respectively. In Ethos, online adapted plans maintained PTV coverage whereas scheduled plans often resulted in geographic misses due to changes in tumor size, patient position, and body habitus. The average total duration of the oART workflow was 26:15 (min:sec) ranging from 6:43 to 57:30. The duration of each oART workflow step as a function of a number of targets showed a low correlation coefficient for influencer generation and editing (R2 = 0.04 and 0.02, respectively) and high correlation coefficient for target generation, target editing and plan generation (R2 = 0.68, 0.63 and 0.69, respectively). CONCLUSIONS: This study demonstrates feasibility of conventional planning/treatment with Raystation/Halcyon and highlights efficiency gains when utilizing semi-automated planning/online-adaptive treatment with Ethos for immunostimulatory LDRT conformally delivered to all sites of polymetastatic disease.


Assuntos
Carcinoma Pulmonar de Células não Pequenas , Tomografia Computadorizada de Feixe Cônico , Estudos de Viabilidade , Neoplasias Pulmonares , Órgãos em Risco , Tomografia por Emissão de Pósitrons combinada à Tomografia Computadorizada , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador , Radioterapia de Intensidade Modulada , Humanos , Planejamento da Radioterapia Assistida por Computador/métodos , Estudos Retrospectivos , Carcinoma Pulmonar de Células não Pequenas/radioterapia , Carcinoma Pulmonar de Células não Pequenas/diagnóstico por imagem , Tomografia Computadorizada de Feixe Cônico/métodos , Tomografia por Emissão de Pósitrons combinada à Tomografia Computadorizada/métodos , Neoplasias Pulmonares/radioterapia , Neoplasias Pulmonares/diagnóstico por imagem , Radioterapia de Intensidade Modulada/métodos , Órgãos em Risco/efeitos da radiação , Processamento de Imagem Assistida por Computador/métodos , Radioterapia Guiada por Imagem/métodos , Prognóstico , Masculino
2.
Acta Oncol ; 61(7): 842-848, 2022 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-35527717

RESUMO

PURPOSE: A cluster model incorporating heterogeneous dose distribution within the parotid gland was developed and validated retrospectively for radiotherapy (RT) induced xerostomia prediction with machine learning (ML) techniques. METHODS: Sixty clusters were obtained at 1 Gy step size with threshold doses ranging from 1 to 60 Gy, for each of the enrolled 155 patients with HNC from three institutions. Feature clusters were selected with the neighborhood component analysis (NCA) and subsequently fed into four supervised ML models for xerostomia prediction comparison: support vector machines (SVM), k-nearest neighbor (kNN), naïve Bayes (NB), and random forest (RF). The predictive performance of each model was evaluated using cross validation resampling with the area-under-the-curves (AUC) of the receiver-operating-characteristic (ROC). The xerostomia predicting capacity using testing data was assessed with accuracy, sensitivity, and specificity for these models and three cluster connectivity choices. Mean dose based logistic regression served as the benchmark for evaluation. RESULTS: Feature clusters identified by NCA fell in three threshold dose ranges: 5-15Gy, 25-35Gy, and 45-50Gy. Mean dose predictive power was 15% lower than that of the cluster model using the logistic regression classifier. Model validation demonstrated that kNN model outperformed slightly other three models but no substantial difference was observed. Applying the fine-tuned models to testing data yielded that the mean accuracy from SVM, kNN and NB models were between 0.68 and 0.7 while that of RF was ∼0.6. SVM model yielded the best sensitivity (0.76) and kNN model delivered consistent sensitivity and specificity. This is consistent with cross validation. Clusters calculated with three connectivity choices exhibited minimally different predictions. CONCLUSION: Compared to mean dose, the proposed cluster model has shown its improvement as the xerostomia predictor. When combining with ML techniques, it could provide a clinically useful tool for xerostomia prediction and facilitate decision making during radiotherapy planning for patients with HNC.


Assuntos
Glândula Parótida , Xerostomia , Teorema de Bayes , Humanos , Aprendizado de Máquina , Glândula Parótida/efeitos da radiação , Estudos Retrospectivos , Xerostomia/diagnóstico , Xerostomia/etiologia
3.
Rep Pract Oncol Radiother ; 26(1): 153-158, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34046227

RESUMO

BACKGROUND: The aim was to demonstrate the feasibility and technique of gonadal sparing total body irradiation (TBI) with helical tomotherapy. Total body irradiation is a common part of the conditioning regimen prior to allogeneic stem cell transplantation. Shielding or dose-reduction to the gonads is often desired to preserve fertility, particularly in young patients undergoing transplant for non-malignant indications. Helical tomotherapy (HT) has been shown to be superior to traditional TBI delivery for organ at risk (OA R) doses and dose homogeneity. MATERIALS AND METHODS: We present two representative cases (one male and one female) to illustrate the feasibility of this technique, each of whom received 3Gy in a single fraction prior to allogeneic stem cell transplant for benign indications. The planning target volume (PTV) included the whole body with a subtraction of OA Rs including the lungs, heart, and brain (each contracted by 1cm) as well as the gonads (testicles expanded by 5 cm and ovaries expanded by 0.5 cm). RESULTS: For the male patient we achieved a homogeneity index of 1.35 with a maximum and median planned dose to the testes of 0.53 Gy and 0.35 Gy, respectively. In-vivo dosimetry demonstrated an actual received dose of 0.48 Gy. For the female patient we achieved a homogeneity index of 1.13 with a maximum and median planned dose to the ovaries of 1.66 Gy and 0.86 Gy, respectively. CONCLUSION: Gonadal sparing TBI is feasible and deliverable using HT in patients with non-malignant diseases requiring TBI as part of a pre-stem cell transplant conditioning regimen.

4.
Med Phys ; 38(7): 4372-85, 2011 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-21859038

RESUMO

PURPOSE: To evaluate the feasibility of line-focused ultrasound for thermal ablation of superficially located tumors. METHODS: A SonoKnife is a cylindrical-section ultrasound transducer designed to radiate from its concave surface. This geometry generates a line-focus or acoustic edge. The motivation for this approach was the noninvasive thermal ablation of advanced head and neck tumors and positive neck nodes in reasonable treatment times. Line-focusing may offer advantages over the common point-focusing of spherically curved radiators such as faster coverage of a target volume by scanning of the acoustic edge. In this paper, The authors report studies using numerical models and phantom and ex vivo experiments using a SonoKnife prototype. RESULTS: Acoustic edges were generated by cylindrical-section single-element ultrasound transducers numerically, and by the prototype experimentally. Numerically, simulations were performed to characterize the acoustic edge for basic design parameters: transducer dimensions, line-focus depth, frequency, and coupling thickness. The dimensions of the acoustic edge as a function of these parameters were determined. In addition, a step-scanning simulation produced a large thermal lesion in a reasonable treatment time. Experimentally, pressure distributions measured in degassed water agreed well with acoustic simulations, and sonication experiments in gel phantoms and ex vivo porcine liver samples produced lesions similar to those predicted with acoustic and thermal models. CONCLUSIONS: Results support the feasibility of noninvasive thermal ablation with a SonoKnife.


Assuntos
Ablação por Ultrassom Focalizado de Alta Intensidade/instrumentação , Modelos Biológicos , Simulação por Computador , Desenho Assistido por Computador , Desenho de Equipamento , Análise de Falha de Equipamento , Estudos de Viabilidade , Humanos
5.
Surg Neurol Int ; 11: 206, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32874709

RESUMO

BACKGROUND: Perineural invasion (PNI) and spread are one of the grimmest prognostic factors associated with primary skin and head-and-neck cancers, yet remain an often confused, and underreported, phenomenon. Adding complexity to reaching a diagnosis and treating perineural spread (PNS) is the finding that patients may have no known primary tumor, history of skin cancer, and/or incidental PNI in the primary tumor. These delays in diagnosis and treatment are further compounded by an already slow disease process and often require multidisciplinary care with combinations of stereotactic radiosurgery, surgical resection, and novel treatments such as checkpoint inhibitors. METHODS: Six patients with metastatic cancer to the cranial nerves who underwent Gamma Knife radiosurgery (GKRS) treatment were chosen for retrospective analysis. This information included age, gender, any past surgeries (both stereotactic and regular surgery), dose of radiation and volume of the tumor treated in the GKRS, date of PNS, comorbidities, the patient follow-up, and pre- and post-GKRS imaging. The goal of the follow-up with radiographing imaging was to assess the efficacy of GKSS. RESULTS: The clinical course of six patients with PNS is presented. Patients followed variable courses with mixed outcomes: two patients remain living, one was lost to follow-up, and three expired with a median survival of 12 months from date of diagnosis. Patients at our institution are ideally followed for life. CONCLUSION: Given the morbidity and mortality of PNS of cancer, time is limited, and further understanding is required to improve outcomes. Here, we provide a case series of patients with PNS treated with stereotactic radiosurgery, discuss their clinical courses, and review the known literature.

6.
J Ark Med Soc ; 105(11): 263-5, 2009 May.
Artigo em Inglês | MEDLINE | ID: mdl-19475814

RESUMO

Avanced bulky tumors warrant aggressive therapy to attempt to maximize local control of the disease. Spatially fractionated radiation therapy (GRID) delivers a single-fraction of high dose radiation to these tumors with a curative or palliative goal. GRID therapy may be combined with fractionated radiation therapy or used in a therapeutic multi-modality setting to achieve control of the bulky disease. Current clinical data confirms the value of GRID therapy in the management of large volume of disease with an acceptable toxicity profile. GRID therapy has broad systemic effects leading to increases in a variety of cytokines that correlate with clinical outcome.


Assuntos
Fracionamento da Dose de Radiação , Neoplasias/patologia , Neoplasias/radioterapia , Relação Dose-Resposta à Radiação , Humanos , Índice de Gravidade de Doença
7.
Artigo em Inglês | MEDLINE | ID: mdl-31792724

RESUMO

To explore the parotid normal tissue complication probability (NTCP) modeling with percolation-based dose clusters for head-and-neck patients receiving concomitant chemotherapy and radiation therapy. Cluster models incorporating the spatial dose distribution in the parotid gland were developed to evaluate the radiation induced complication. Cluster metrics including the mean cluster size (NMCS) and the largest cluster size both normalized by the gland volume (NSLC) were evaluated and scrutinized against the benchmark NTCP. Two fitting strategies to the Lyman-Kutcher-Burman (LKB) model using the maximum likelihood method were devised: the volume parameter n fixed at 1.0 (mean dose model) and unrestricted (full LKB model). The fitted parameters TD50 and m were assessed with the LKB NTCP models with the available xerostomia data. NSLC was a better metric than NMCS with reference to the LKB model and strong correlation (r ~ 0.95) was observed between NTCP and NSLC. The mean dose model returned the parameter TD50 (39.9 Gy) and m (0.4) from the NSLC of threshold dose at around 40 Gy. Drastically different TD50 and m values were obtained from the fittings via the full LKB model, where the threshold dose would be near 27 Gy. Bootstrapping analyses further confirmed the fitting outcomes. Strong correlation with the traditional NTCP models revealed that the cluster model could achieve what NTCP models attain and may offer additional information. Parameterization of the model indicated that the model could have different predictions from current clinical recommendations. Further investigation using toxicity data is under way to validate the cluster model.

8.
Phys Med Biol ; 53(10): 2509-22, 2008 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-18424880

RESUMO

Simultaneous thermoradiotherapy has been shown to maximize the effect of hyperthermia as a radiation sensitizer in cancer treatment. Here we follow our previous work on feasibility of thermoradiotherapy with the scanning ultrasound reflector linear array system (SURLAS) and TomoTherapy HiArt treatment system, and investigate the influence of the SURLAS hyperthermia applicator on delivered radiation dose with the TomoTherapy. A radiation treatment plan was calculated and the treatment was delivered to a phantom with SURLAS on top simulating the likely clinical setup. Proper positioning of the SURLAS was assisted with a magnetic position-and-orientation tracking device (POTD) and was verified with megavoltage-computed tomography. The delivered dose was measured with an ionization chamber (point measurement) and a radiographic film (2D dose distributions). The planned and delivered point dose data agreed within 0.61% +/- 0.63%. Planar dose data agreed within a dose difference of < or =3% of the maximum dose, and a distance-to-dose-agreement of < or =1 mm. The susceptibility of the delivered radiation dose on correct SURLAS positioning was studied as well. The largest dose discrepancy was measured for a position for which a maximum number of radiation beams intersected the incorrectly positioned SURLAS within one TomoTherapy gantry rotation. The point dose disagreed by 6.14% +/- 0.52%, and 2.25% of pixels of the 2D dose distribution did not pass the 3% dose difference/1 mm distance-to-dose-agreement criteria. Our study showed that correct positioning of the SURLAS applicator had an influence on the delivered radiation dose. Delivered and planned dose distributions were in an excellent agreement when SURLAS was positioned according to the treatment plan. Moving the applicator from its planned position was found to cause a modification of delivered dose distributions. A precise and reproducible positioning of the applicator was assured with a POTD.


Assuntos
Hipertermia Induzida/métodos , Doses de Radiação , Radioterapia/métodos , Humanos , Hipertermia Induzida/instrumentação , Metais , Imagens de Fantasmas , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Fatores de Tempo , Tomografia Computadorizada por Raios X , Terapia por Ultrassom/instrumentação , Terapia por Ultrassom/métodos
9.
Int J Hyperthermia ; 24(5): 377-88, 2008 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-18608592

RESUMO

PURPOSE: To evaluate the feasibility of concurrent treatment with the scanning ultrasound reflector linear array system (SURLAS) and helical tomotherapy (HT) intensity modulated radiation therapy (IMRT). METHODS: The SURLAS was placed on a RANDO phantom simulating a patient with superficial or deep recurrent breast cancer. A megavoltage CT (MVCT) of the phantom with and without the SURLAS was obtained in the HT system. MVCT images with the SURLAS were obtained for two configurations: (1) with the SURLAS's long axis parallel and (2) perpendicular to the longitudinal axis of the phantom. The MVCT simulation data set was then transferred to a radiation therapy planning station. Organs at risk (OAR) were contoured including the lungs, heart, abdomen and spinal cord. The metallic parts of the SURLAS were contoured as well and constraints were assigned to completely or directionally block radiation through them. The MVCT simulation data set and regions of interest (ROI) files were subsequently transferred to the HT planning station. Several HT plans were obtained with optimization parameters that are usually used in the clinic. For comparison purposes, planning was also performed without the SURLAS on the phantom. RESULTS: All plans with the SURLAS on the phantom showed adequate dose covering 95% of the planning target volume (PTV D95%), average dose and coefficient of variation of the planning target volume (PTV) dose distribution regardless of the SURLAS's orientation with respect to the RANDO phantom. Likewise, all OAR showed clinically acceptable dose values. Spatial dose distributions and dose-volume histogram (DVH) evaluation showed negligible plan degradation due to the presence of the SURLAS. Beam-on time varied depending on the selected optimization parameters. CONCLUSION: From the perspective of the radiation dosage, concurrent treatment with the SURLAS and HT IMRT is feasible as demonstrated by the obtained clinically acceptable treatment plans. In addition, proper orientation of the SURLAS may be of benefit in reducing dose to organs at risk in some cases.


Assuntos
Hipertermia Induzida/métodos , Radioterapia de Intensidade Modulada/métodos , Tomografia Computadorizada Espiral/métodos , Terapia por Ultrassom/métodos , Humanos , Imagens de Fantasmas , Doses de Radiação , Planejamento da Radioterapia Assistida por Computador
10.
Radiother Oncol ; 127(2): 197-205, 2018 May.
Artigo em Inglês | MEDLINE | ID: mdl-29609805

RESUMO

PURPOSE: To investigate three-dimensional cluster structure and its correlation to clinical endpoint in heterogeneous dose distributions from intensity modulated radiation therapy. METHODS: Twenty-five clinical plans from twenty-one head and neck (HN) patients were used for a phenomenological study of the cluster structure formed from the dose distributions of organs at risks (OARs) close to the planning target volumes (PTVs). Initially, OAR clusters were searched to examine the pattern consistence among ten HN patients and five clinically similar plans from another HN patient. Second, clusters of the esophagus from another ten HN patients were scrutinized to correlate their sizes to radiobiological parameters. Finally, an extensive Monte Carlo (MC) procedure was implemented to gain deeper insights into the behavioral properties of the cluster formation. RESULTS: Clinical studies showed that OAR clusters had drastic differences despite similar PTV coverage among different patients, and the radiobiological parameters failed to positively correlate with the cluster sizes. MC study demonstrated the inverse relationship between the cluster size and the cluster connectivity, and the nonlinear changes in cluster size with dose thresholds. In addition, the clusters were insensitive to the shape of OARs. CONCLUSION: The results demonstrated that the cluster size could serve as an insightful index of normal tissue damage. The clinical outcome of the same dose-volume might be potentially different.


Assuntos
Neoplasias de Cabeça e Pescoço/radioterapia , Esôfago/efeitos da radiação , Humanos , Masculino , Método de Monte Carlo , Órgãos em Risco , Glândula Parótida/efeitos da radiação , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia de Intensidade Modulada/métodos
11.
Technol Cancer Res Treat ; 6(4): 355-60, 2007 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-17668944

RESUMO

Helical tomotherapy (HT) can be used for the delivery of cranio-spinal axis irradiation (CSAI) without the need for beam matching of conventional linac-based external beam irradiation. The aim of this study is to retrospectively evaluate HT plans used for treatment in nine patients treated with CSAI. Helical tomotherapy cranio-spinal axis irradiation (HT-CSAI) plans were created for each patient. Average length along the cranio-spinal axis of the PTV was 65.6 cm with a range between 53 and 74 cm. Treatment planning optimization and plan evaluation parameters were obtained from the HT planning station for each of the nine patients. PTV coverage by the 95% isodose surface ranged between 98.0 to 100.0% for all nine patients. The clinically acceptable dose variation within the PTV or tolerance range was between 0.7 and 2.5% for all nine patients. Doses to the organs at risk were clinically acceptable. An increasing length along the longitudinal axis of the PTV did not consistently increase the beam-on time indicating that using a larger jaw width had a greater impact on treatment time. With a larger jaw width it is possible to substantially reduce the normalized beam-on treatment time without compromising plan quality and sparing of organs at risk. By using a larger jaw width or lower modulation factor or both, normalized beam-on times were decreased by up to 61% as compared to the other evaluated treatment plans. From the nine cases reported in this study the minimum beam-on time was achieved with a jaw width of 5.0 cm, pitch of 0.287 and a modulation factor of 2.0. Large and long cylindrical volumes can be effectively treated with helical tomotherapy with both clinically acceptable dose distribution and beam-on time.


Assuntos
Neoplasias do Sistema Nervoso Central/diagnóstico por imagem , Neoplasias do Sistema Nervoso Central/radioterapia , Radioterapia Assistida por Computador/instrumentação , Crânio/diagnóstico por imagem , Coluna Vertebral/diagnóstico por imagem , Tomografia Computadorizada Espiral/instrumentação , Adolescente , Criança , Pré-Escolar , Feminino , Humanos , Masculino , Estudos Retrospectivos
13.
Radiother Oncol ; 76(1): 72-8, 2005 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-15992953

RESUMO

BACKGROUND AND PURPOSE: Helical tomotherapy can eliminate the need for junction lines. The goal of this study is to evaluate tomotherapy in the delivery of CSA radiation and measurement of plan quality using physical parameters in comparing conventional (CSA-RT) and helical tomotherapy (CSA-TOMO) plans. PATIENTS AND METHODS: CSA-TOMO and CSA-RT plans were created for dosimetric comparison. Integral dose values were calculated. The ratios D50% (dose received by 50% of the organ at risk's volume) and D10% (dose received by 10% of the organ at risk's volume) were calculated representing large volumes and small volumes of organs at risk receiving significant dose. RESULTS: When considering D50% and D10%, CSA-TOMO has a dosimetric advantage over CSA-RT for most organs at risk. The body integral dose was higher for the CSA-TOMO plan by approximately 6.5%. CONCLUSIONS: Tomotherapy is a feasible alternative for treatment of CSA. Analysis shows that tomotherapy improves dose ratios over conventional radiation for most organs at risk. The impact of a small increase in whole body integral dose is unknown. Long-term follow-up will be needed to answer this question as others have argued of the possibility of increased risk of secondary malignancies due to delivery of radiotherapy with IMRT.


Assuntos
Encéfalo/efeitos da radiação , Cabeça/efeitos da radiação , Aceleradores de Partículas , Planejamento da Radioterapia Assistida por Computador , Radioterapia de Alta Energia , Coluna Vertebral/efeitos da radiação , Tomografia Computadorizada Espiral , Neoplasias do Sistema Nervoso Central/diagnóstico por imagem , Neoplasias do Sistema Nervoso Central/radioterapia , Estudos de Viabilidade , Humanos , Dosagem Radioterapêutica , Radioterapia de Alta Energia/instrumentação
14.
Technol Cancer Res Treat ; 4(6): 683-9, 2005 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-16292889

RESUMO

In cranio-spinal axis (CSA) irradiation, patients are usually treated in the prone position with junctions between cranial and spinal fields. Collimator angle and pedestal rotations are introduced to obtain coplanar alignment of the matched junction. Furthermore, daily moving junctions are commonly used to feather out the junctional dose as additional safeguards to avoid radiation myelopathy. Helical tomotherapy integrates linear accelerator and CT technology capable of delivering CSA treatment without geometric matches or feathering of junctions. The patient is treated with helical beams in the supine position. Since CSA is used mainly in the pediatric population, the potential increase in integral dose to structures or the whole body from linac- or tomotherapy-based IMRT raises concerns of increased rates of secondary malignancies. In this study, we will present an integral dose comparison between conventional CSA (3D) and helical delivery to the CSA (TOMO) utilizing the Tomotherapy Hi-ART system for three pediatric patients. Integral dose was calculated for organ at risk (OAR), two targets (PTV-BRAIN and PTV-SPINE), entire planning CT data set and to the healthy tissue (entire CT-DATA SET minus the PTV). Overall integral dose was 8% higher in the TOMO plans for Patients #1 and #3, but 2% lower in Patient #2. DVH analysis shows that TOMO plans give lower doses to larger volumes and higher doses to smaller volumes of tissue in all three cases. The advantages of the TOMO plans are minimization of matched junctions and better sparing of most OARs. With increased computational and memory power in the tomotherapy planning station, the excess integral dose to the healthy tissue can be re-distributed within the patient and in turn the total integral dose can be same or lower than in conventional delivery. The impact of a small increase in overall integral dose and the associated risks of secondary malignancies are unknown. Long-term follow-up is needed to answer this question.


Assuntos
Neoplasias do Sistema Nervoso Central/radioterapia , Neoplasias Cerebelares/radioterapia , Dosagem Radioterapêutica , Neoplasias da Coluna Vertebral/radioterapia , Adolescente , Criança , Ependimoma/radioterapia , Feminino , Humanos , Masculino , Meduloblastoma/radioterapia , Aceleradores de Partículas , Leucemia-Linfoma Linfoblástico de Células Precursoras/radioterapia , Planejamento da Radioterapia Assistida por Computador , Radioterapia Conformacional , Radioterapia de Alta Energia
15.
Med Dosim ; 30(1): 12-9, 2005.
Artigo em Inglês | MEDLINE | ID: mdl-15749006

RESUMO

The purpose of this study was to investigate the role of biological-based IMRT (BORT) in treatment planning development; more specifically, to assess the possible advantages of BORT over the classic 3-dimensional conformal radiation therapy (3DRT) and dose-based IMRT based on quantitative and qualitative indices. Three clinical cases are presented to evaluate the differences of BORT, IMRT, and 3DRT. 3DRT, IMRT, and BORT plans were generated for each case using a commercially available treatment planning system (Pinnacle by Philips). The plans were compared by evaluating biological endpoints such as tumor control probability (TCP), normal tissue control probability (NTCP), and uncomplicated tumor control probability (P+), as well as isodose line distribution, dose-volume histograms (DVHs), and dose uniformity. In all cases of this study, BORT yielded improved isodose coverage and P+. Our preliminary results suggest that BORT could play an important role in treatment planning optimization, especially as biological models and predictive assays become more accurate. Further case studies are needed to establish a definitive role for this type of optimization.


Assuntos
Neoplasias Encefálicas/radioterapia , Carcinoma Hepatocelular/radioterapia , Carcinoma de Células Escamosas/radioterapia , Neoplasias Hepáticas/radioterapia , Neuroblastoma/radioterapia , Neoplasias dos Seios Paranasais/radioterapia , Carcinoma de Células Escamosas/tratamento farmacológico , Relação Dose-Resposta à Radiação , Humanos , Neoplasias dos Seios Paranasais/tratamento farmacológico , Dosagem Radioterapêutica , Radioterapia de Alta Energia , Resultado do Tratamento
16.
Cancer Lett ; 356(1): 52-7, 2015 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-24246848

RESUMO

Traditional radiotherapy of bulky tumors has certain limitations. Spatially fractionated radiation therapy (GRID) and intensity modulated radiotherapy (IMRT) are examples of advanced modulated beam therapies that help in significant reductions in normal tissue damage. GRID refers to the delivery of a single high dose of radiation to a large treatment area that is divided into several smaller fields, while IMRT allows improved dose conformity to the tumor target compared to conventional three-dimensional conformal radiotherapy. In this review, we consider spatially fractionated radiotherapy approaches focusing on GRID and IMRT, and present complementary evidence from different studies which support the role of radiation induced signaling effects in the overall radiobiological rationale for these treatments.


Assuntos
Efeito Espectador/efeitos da radiação , Fracionamento da Dose de Radiação , Neoplasias/radioterapia , Radioterapia de Intensidade Modulada/efeitos adversos , Animais , Dano ao DNA/efeitos da radiação , Humanos , Camundongos , Espécies Reativas de Oxigênio/metabolismo , Transdução de Sinais/efeitos da radiação
17.
Int J Radiat Oncol Biol Phys ; 91(1): 30-8, 2015 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-25442340

RESUMO

PURPOSE: To develop, characterize, and implement a fast patient localization method for total marrow irradiation. METHODS AND MATERIALS: Topographic images were acquired using megavoltage computed tomography (MVCT) detector data by delivering static orthogonal beams while the couch traversed through the gantry. Geometric and detector response corrections were performed to generate a megavoltage topogram (MVtopo). We also generated kilovoltage topograms (kVtopo) from the projection data of 3-dimensional CT images to reproduce the same geometry as helical tomotherapy. The MVtopo imaging dose and the optimal image acquisition parameters were investigated. A multi-institutional phantom study was performed to verify the image registration uncertainty. Forty-five MVtopo images were acquired and analyzed with in-house image registration software. RESULTS: The smallest jaw size (front and backup jaws of 0) provided the best image contrast and longitudinal resolution. Couch velocity did not affect the image quality or geometric accuracy. The MVtopo dose was less than the MVCT dose. The image registration uncertainty from the multi-institutional study was within 2.8 mm. In patient localization, the differences in calculated couch shift between the registration with MVtopo-kVtopo and MVCT-kVCT images in lateral, cranial-caudal, and vertical directions were 2.2 ± 1.7 mm, 2.6 ± 1.4 mm, and 2.7 ± 1.1 mm, respectively. The imaging time in MVtopo acquisition at the couch speed of 3 cm/s was <1 minute, compared with ≥15 minutes in MVCT for all patients. CONCLUSION: Whole-body MVtopo imaging could be an effective alternative to time-consuming MVCT for total marrow irradiation patient localization.


Assuntos
Medula Óssea , Protocolos Clínicos , Imagens de Fantasmas , Radioterapia Assistida por Computador/métodos , Radioterapia Conformacional/métodos , Condicionamento Pré-Transplante/métodos , Medula Óssea/diagnóstico por imagem , Estudos de Viabilidade , Saúde Global , Humanos , Arcada Osseodentária/diagnóstico por imagem , Fatores de Tempo , Tomografia Computadorizada Espiral/métodos , Irradiação Corporal Total
18.
Med Dosim ; 29(4): 247-53, 2004.
Artigo em Inglês | MEDLINE | ID: mdl-15528065

RESUMO

Novel radiation therapy delivery techniques have moved very slowly in the field of pediatric oncology. Some collaborative groups allow new radiation therapy delivery techniques in their trials. In many instances, the option of using these techniques is not addressed. These newer techniques of radiation delivery have the potential to reduce the probability of the common late effects of radiation and at the same time, potentially improve upon control and survival. The purpose of this study is to show the feasibility of IMRT in pediatric patients. No treatment results or toxicities will be presented. Five patients with a variety of pediatric malignancies received intensity-modulated radiation therapy (IMRT) at our institution as part of their disease management. A rigid immobilization device was developed for each patient and a computed tomography (CT) simulation was performed in the treatment position. In 3 of the patients, magnetic resonance imaging (MRI) scans were coregistered with the planning CT to facilitate target and critical structure delineation. In all but 1 patient, coplanar beam arrangements were used in the IMRT planning process. All IMRT plans exhibited a high degree of conformality. Dose homogeneity inside the tumor and rapid dose falloff outside the target volume is characteristic of IMRT plans, which allows for improved normal tissue sparing. Dose distributions were obtained for all plans, as well as dose and volume relationship histograms, to evaluate the fitness of the plans. IMRT is a viable alternative to conventional treatment techniques for pediatric cancer patients. The improved dose distributions coupled with the ease of delivery of the IMRT fields make this technique very attractive, especially in view of the potential to increase local control and possibly improve on survival.


Assuntos
Neoplasias Encefálicas/radioterapia , Glioma/radioterapia , Neuroblastoma/radioterapia , Neoplasias dos Seios Paranasais/radioterapia , Leucemia-Linfoma Linfoblástico de Células Precursoras/radioterapia , Radioterapia Conformacional , Adulto , Criança , Pré-Escolar , Seio Etmoidal , Feminino , Humanos , Lactente , Masculino , Dosagem Radioterapêutica
19.
Med Dosim ; 29(4): 254-7, 2004.
Artigo em Inglês | MEDLINE | ID: mdl-15528066

RESUMO

The purpose of this paper was to compare intensity-modulated radiation therapy (IMRT) and conventional planning for T2N0M0 squamous cell carcinoma (SQCC) of the glottic larynx. Three patients with T2N0M0 SQCC are presented who were treated with IMRT. Conventional plans were also generated for comparison purposes. Isodose distributions and dose-volume histograms (DVHs) were generated for all the plans to evaluate the fitness of the plan as well as the differential benefit of IMRT vs. conventional treatment. The isodose distributions that were obtained by the IMRT plan are much more conformal to the planning target volume (PTV) and clearly show that less healthy tissue is subjected to a high-dose level, thus reducing toxicity. IMRT offers better comformality without compromising the PTV coverage and delivers less dose to normal tissues as compared to conventional radiation therapy in T2N0M0 SQCC of the glottic larynx. With an increase in conformality, it is expected to have an increase in the therapeutic ratio.


Assuntos
Carcinoma de Células Escamosas/radioterapia , Glote , Neoplasias Laríngeas/radioterapia , Planejamento da Radioterapia Assistida por Computador , Radioterapia Conformacional , Idoso , Seguimentos , Humanos , Masculino , Pessoa de Meia-Idade , Dosagem Radioterapêutica , Resultado do Tratamento
20.
Neurol India ; 52(4): 482-6, 2004 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-15626839

RESUMO

Brain irradiation is commonly used for many primary brain malignancies. We will present two cases of post-radiation vasculopathy of large arteries of patients who received radiation therapy to the brain as part of their tumor management. We will underscore the significance of this condition and suggest the overall management of patients receiving brain radiation at an early age.


Assuntos
Transtornos Cerebrovasculares/etiologia , Radioterapia/efeitos adversos , Adulto , Astrocitoma/complicações , Astrocitoma/radioterapia , Neoplasias Encefálicas/complicações , Neoplasias Encefálicas/radioterapia , Angiografia Cerebral , Transtornos Cerebrovasculares/diagnóstico por imagem , Feminino , Humanos , Angiografia por Ressonância Magnética , Masculino , Pessoa de Meia-Idade
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