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ABFM NEWS - Radioterapia
A Pinpoint Beam Strays Invisibly, Harming Instead of Healing
"The initial accident report offered few details, except to say that an unidentified hospital had administered radiation overdoses to three patients during identical medical procedures. " [+ leia mais]
Colaborador: Evandro Souza
Fonte: NYTimes
The Impact of Pretreatment Prostate Volume on Severe Acute Genitourinary Toxicity in Prostate Cancer Patients Treated With Intensity-Modulated Radiati
"Volume 79, Issue 2, 1 February 2011, Pages 379-384 To assess the impact of pretreatment prostate volume on the development of severe acute genitourinary toxicity in patients undergoing intensity-modulated radiation therapy (IMRT) for prostate cancer. " [+ leia mais]
Fonte: International Journal of Radiation Oncology*Biolog
Dose–Volume Histogram Parameters and Late Side Effects in Magnetic Resonance Image–Guided Adaptive Cervical Cancer Brachytherapy
"Volume 79, Issue 2, 1 February 2011, Pages 356-362 To evaluate the predictive value of dose–volume histogram (DVH) parameters for late side effects of the rectum, sigmoid colon, and bladder in image-guided brachytherapy for cervix cancer patients. " [+ leia mais]
Fonte: International Journal of Radiation Oncology*Biolog
Neoadjuvant chemotherapy in patients with cervical carcinoma stages IB2 and IIA. Preliminary results in aleatorized study
"Rev Inst Nal Cancerol (Mex) 2000; 46 (1): 21-27 Cervical cancer is the most frequent malignant tumor in Mexico. Phase II studies of neoadjuvant chemotherapy followed by surgery in stages IB2 and IIA suggest a benefit in terms of local control and survival as compared to radiation alone. Objective. To determine whether the use of neoadjuvant chemotherapy followed by surgery improves survival as compared to standard radiation in epidermoid stages IB2 and IIA cancer patients. Patients and methods. Patients with FIGO stages IB2 and IIA were randomly allocated to neoadjuvant chemotherapy as follows: Cisplatin 50 mg/m2 d1, Vincristine 1.5 mg/m2 d1 and Bleomycin 20 mg/m2 d1, d2 and d3 (PVB) by IV continuous infusion." [+ leia mais]
Fonte: Revista Inst. Nal Cancerol
Molecular determinants of anti-EGFR sensitivity and resistance in metastatic colorectal cancer.
Since 2004, the clinical impact of monoclonal antibodies (mAbs) targeting the epidermal growth factor receptor (EGFR) on patients with metastatic colorectal cancer (MCRC) has been clearly established. The combination of these biological agents with conventional chemotherapy has led to a significant improvement in response rate, progression-free survival and overall survival in first-line as well as in second- or third-line treatment of MCRC. However, the high variability of response and outcome in MCRC patients treated with these anti-EGFR mAbs has highlighted the need of identifying clinical and/or molecular predictive markers to ensure appropriate use of targeted therapies. [+ leia mais]
Fonte: Britsh Journal of Cancer
Role of Breast Surgeons in Evolution of the Surgical Management of Breast Cancer
In breast cancer surgery, there has been a major shift toward less invasive local treatment: from extended or radical mastectomy to modified radical mastectomy, from modified radical mastectomy to breast conserving therapy, and from routine axillary lymph node dissection to sentinel lymph node biopsy. Many breast surgeons have experienced an evolutionary progression of surgical management of breast cancer. However, there is an increasing demand for minimally invasive and non-surgical treatment methods for patients with small breast cancer. Radiofrequency (RF) ablation is the most promising among non-surgical ablation techniques in the treatment of breast cancer, although it is still in the investigative stage. Nevertheless, surgery still plays an integral role in the treatment of breast cancer, because local therapy is important for enhancing survival in the presence of systemic therapy. In clinical practice, surgical oncologists must individualize treatments, selecting a surgical or non-surgical procedure that provides the best local control, does not compromise the chances of cure, and achieves the best cosmetic results. [+ leia mais]
Role of Radiation Dose in the Risk of Secondary Leukemia After a Solid Tumor in Childhood Treated Between 1980 and 1999
"International Journal of Radiation Oncology*Biology*Physics Volume 78, Issue 5, 1 December 2010, Pages 1474-1482 The purpose of this study was to estimate the risk of secondary leukemia as a function of radiation dose, taking into account heterogeneous radiation dose distribution. " [+ leia mais]
Fonte: Int. Journal of Rad. Oncol. Biol and Physics
A Dosimetric Model of Duodenal Toxicity After Stereotactic Body Radiotherapy for Pancreatic Cancer
"International Journal of Radiation Oncology*Biology*Physics Volume 78, Issue 5, 1 December 2010, Pages 1420-1426 Dose escalation for pancreas cancer is limited by the tolerance of adjacent normal tissues, especially with stereotactic body radiotherapy (SBRT). The duodenum is generally considered to be the organ at greatest risk. This study reports on the dosimetric determinants of duodenal toxicity with single-fraction SBRT. " [+ leia mais]
Fonte: Int. Journal of Rad. Oncol. Biol and Physics
Telerobotic system concept for real-time soft-tissue imaging during radiotherapy beam delivery
"Med. Phys. 37, 6357 (2010); doi:10.1118/1.3515457 (11 page) curative potential of external beam radiation therapy is critically dependent on having the ability to accurately aim radiation beams at intended targets while avoiding surrounding healthy tissues. However, existing technologies are incapable of real-time, volumetric, soft-tissue imaging during radiation beam delivery, when accurate target tracking is most critical. The authors address this challenge in the development and evaluation of a novel, minimally interfering, telerobotic ultrasound (U.S.) imaging system that can be integrated with existing medical linear accelerators (LINACs) for therapy guidance. " [+ leia mais]
Fonte: Medical Physics
Comparison of simple and complex liver intensity modulated radiotherapy
"Radiation Oncology 2010, 5:115doi:10.1186/1748-717X-5-115 Intensity-modulated radiotherapy (IMRT) may allow improvement in plan quality for treatment of liver cancer; however increasing radiation modulation complexity can lead to increased uncertainties and requirements for quality assurance. This study assesses whether target coverage and normal tissue avoidance can be maintained in liver cancer intensity-modulated radiotherapy (IMRT) plans by systematically reducing the complexity of the delivered fluence. " [+ leia mais]
Fonte: Radiation Oncology
Influence of increased target dose inhomogeneity on margins for breathing motion compensation in conformal stereotactic body radiotherapy
"BMC Medical Physics 2008, 8:5doi:10.1186/1756-6649-8-5 Breathing motion should be considered for stereotactic body radiotherapy (SBRT) of lung tumors. Four-dimensional computer tomography (4D-CT) offers detailed information of tumor motion. The aim of this work is to evaluate the influence of inhomogeneous dose distributions in the presence of breathing induced target motion and to calculate margins for motion compensation. " [+ leia mais]
Fonte: BMC Medical Physics
Combining registration and active shape models for the automatic segmentation of the lymph node regions in head and neck CT images
"Purpose: Intensity-modulated radiation therapy (IMRT) is the state of the art technique for head and neck cancer treatment. It requires precise delineation of the target to be treated and structures to be spared, which is currently done manually. The process is a time-consuming task of which the delineation of lymph node regions is often the longest step. Atlas-based delineation has been proposed as an alternative, but, in the authors’ experience, this approach is not accurate enough for routine clinical use. Here, the authors improve atlas-based segmentation results obtained for level II–IV lymph node regions using an active shape model (ASM) approach. Methods: An average image volume was first created from a set of head and neck patient images with minimally enlarged nodes. The average image volume was then registered using affine, global, and local nonrigid transformations to the other volumes to establish a correspondence between surface points in the atlas and surface points in each of the other volumes. Once the correspondence was established, the ASMs were created for each node level. The models were then used to first constrain the results obtained with an atlas-based approach and then to iteratively refine the solution. Results: The method was evaluated through a leave-one-out experiment. The ASM- and atlas-based segmentations were compared to manual delineations via the Dice similarity coefficient (DSC) for volume overlap and the Euclidean distance between manual and automatic 3D surfaces. The mean DSC value obtained with the ASM-based approach is 10.7% higher than with the atlas-based approach; the mean and median surface errors were decreased by 13.6% and 12.0%, respectively. Conclusions: The ASM approach is effective in reducing segmentation errors in areas of low CT contrast where purely atlas-based methods are challenged. Statistical analysis shows that the improvements brought by this approach are significant. © 2010 American Association of Physicists in Medicine " [+ leia mais]
Fonte: Medical Physics
Genome-Wide Association Study to Identify Single Nucleotide Polymorphisms (SNPs) Associated With the Development of Erectile Dysfunction in African-Am
"International Journal of Radiation Oncology*Biology*Physics Volume 78, Issue 5, 1 December 2010, Pages 1292-1300 Purpose To identify single nucleotide polymorphisms (SNPs) associated with erectile dysfunction (ED) among African-American prostate cancer patients treated with external beam radiation therapy. Methods and Materials A cohort of African-American prostate cancer patients treated with external beam radiation therapy was observed for the development of ED by use of the five-item Sexual Health Inventory for Men (SHIM) questionnaire. Final analysis included 27 cases (post-treatment SHIM score ≤7) and 52 control subjects (post-treatment SHIM score ≥16). A genome-wide association study was performed using approximately 909,000 SNPs genotyped on Affymetrix 6.0 arrays (Affymetrix, Santa Clara, CA). Results We identified SNP rs2268363, located in the follicle-stimulating hormone receptor (FSHR) gene, as significantly associated with ED after correcting for multiple comparisons (unadjusted p = 5.46 × 10−8, Bonferroni p = 0.028). We identified four additional SNPs that tended toward a significant association with an unadjusted p value < 10−6. Inference of population substructure showed that cases had a higher proportion of African ancestry than control subjects (77% vs. 60%, p = 0.005). A multivariate logistic regression model that incorporated estimated ancestry and four of the top-ranked SNPs was a more accurate classifier of ED than a model that included only clinical variables. Conclusions To our knowledge, this is the first genome-wide association study to identify SNPs associated with adverse effects resulting from radiotherapy. It is important to note that the SNP that proved to be significantly associated with ED is located within a gene whose encoded product plays a role in male gonad development and function. Another key finding of this project is that the four SNPs most strongly associated with ED were specific to persons of African ancestry and would therefore not have been identified had a cohort of European ancestry been screened. This study demonstrates the feasibility of a genome-wide approach to investigate genetic predisposition to radiation injury. " [+ leia mais]
Fonte: International Journal of Radiation Oncology*Biol
Tracheobronchial amyloidosis: utilization of radiotherapy as a treatment modality.
"Tracheobronchial amyloidosis (TBA) is a rare disease. No general consensus exists with regard to its optimal treatment, resulting in a variety of modalities used to manage this condition. In this article, we present a case of TBA treated with external beam radiation therapy with encouraging results. A brief literature review of this rare ailment is also included. Other Sections▼ Abstract Introduction Case Report Discussion ReferencesIntroduction Primary amyloidosis involving the tracheobronchial tree is rare.[1,2] It represents a localized variant of amyloidosis and is characterized by multifocal amyloid deposition within the airway walls with subsequent formation of submucosal plaques or polypoid nodules. The clinical presentation of this disease is often nonspecific, with symptoms such as dyspnea, cough, hemoptysis, hoarseness, and stridor.[2] Pulmonary function tests typically reveal an obstructive pattern but may be normal when the disease is confined to the distal airways.[3] Chest x-rays are frequently unremarkable, often culminating in a delay of diagnosis. In most cases, the identification of this disease is made by means of bronchoscopy and biopsy of the airway mucosa.[4] Management of this disease often aims at maintaining patent airways. Localized treatment techniques such as bronchoscopic resection of disease and stenting have been described in current literature. However, these modalities often offer only a temporary solution as the disease usually recurs and progresses. The use of radiation therapy has been scarcely reported in the management of this rare condition. " [+ leia mais]
Fonte: Medscape J Med. 2008; 10(2): 42.
Rectal Dose–Volume Histogram Parameters Are Associated With Long-Term Patient-Reported Gastrointestinal Quality of Life After Conventional and High-Do
"Purpose We examined whether rectal dose–volume histogram (DVH) parameters were associated with long-term patient-reported gastrointestinal (GI) quality of life (QOL) after conventional (70.2 GyE) or high-dose (79.2 GyE) radiation for prostate cancer. Methods and Materials Of 64 men with localized prostate cancer alive with a minimum 7-year follow-up after treatment as part of a randomized trial with either 70.2 GyE or 79.2 GyE of external beam radiation at Massachusetts General Hospital, 56 men (88%) returned a QOL questionnaire, and 50 of those men had DVH information. The DVH parameters of the anterior rectal wall were correlated with patient-reported long-term GI QOL using Pearson correlation and t tests. Results There was a trend toward an association between increased long-term GI dysfunction and higher V60 (p = 0.07), V65 (p = 0.06), V70 (p = 0.09), and V75 (p = 0.09). When dichotomized by their medians, a V60 > 54% (p = 0.04), V70 > 44% (p = 0.06), and V75 > 39% (p = 0.06) were associated with increased long-term GI dysfunction. There was no difference in long-term GI dysfunction between men on the conventional vs. high-dose arms (p = 0.49). Conclusions Dose–volume histogram parameters of the anterior rectal wall were associated with long-term patient-reported GI QOL after prostate radiation, whereas the dose prescribed to the prostate was not, suggesting that DVH constraints, rather than total prescribed dose, may have the greatest impact on long-term bowel dysfunction, and therefore that continued dose escalation may be feasible if appropriate dose–volume constraints are met. International Journal of Radiation Oncology*Biology*Physics Volume 78, Issue 4, 15 November 2010, Pages 1081-1085 " [+ leia mais]
Fonte: International Journal of Radiation Oncology*Biolog
Squamous Cell Carcinoma of the Anal Canal: Patterns and Predictors of Failure and Implications for Intensity-Modulated Radiation Treatment Planning
"Purpose Intensity-modulated radiation treatment (IMRT) is increasingly used in the treatment of squamous cell carcinoma of the anal canal (SCCAC). Prevention of locoregional failure (LRF) using IMRT requires appropriate clinical target volume (CTV) definition. To better define the CTV for IMRT, we evaluated patterns and predictors of LRF in SCCAC patients given conventional radiation treatment. Methods and Materials We reviewed records of 180 SCCAC patients treated with conventional radiation with or without chemotherapy at our institution between January 1990 and March 2007. All patients received radiation; the median primary tumor dose was 45 Gy. A total of 173 patients also received mitomycin-based chemotherapy. Results Median follow-up was 40 months. Actuarial 3-year colostomy-free survival was 89% and overall survival (OS) 88%. Actuarial 3-year LRF was 23%. A total of 45 patients had LRF, with 35 (78%) occurring locally in the primary site (25 local only, 10 local and regional); however, 20 (44%) had regional components of failure within the pelvis or inguinal nodes (10 regional only, 10 local and regional). Cumulative sites of LRF (patients may have one or more site of failure) were as follows: primary, 35; inguinal, 8; external perianal, 5; common iliac, 4; presacral, 3; distal rectum, 2; external iliac, 2; and internal iliac, 2. All patients with common iliac failure had cT3 or N+ disease. Conclusions The observed patterns of failure support inclusion of the inguinal and all pelvic nodal groups in the CTV for IMRT. In patients with advanced tumor or nodal stage, common iliac nodes should also be included in the CTV. International Journal of Radiation Oncology*Biology*Physics Volume 78, Issue 4, 15 November 2010, Pages 1064-1072 " [+ leia mais]
Fonte: International Journal of Radiation Oncology*Biolog
Clinical Management of Salivary Gland Hypofunction and Xerostomia in Head-and-Neck Cancer Patients: Successes and Barriers
"The most significant long-term complication of radiotherapy in the head-and-neck region is hyposalivation and its related complaints, particularily xerostomia. This review addresses the pathophysiology underlying irradiation damage to salivary gland tissue, the consequences of radiation injury, and issues contributing to the clinical management of salivary gland hypofunction and xerostomia. These include ways to (1) prevent or minimize radiation injury of salivary gland tissue, (2) manage radiation-induced hyposalivation and xerostomia, and (3) restore the function of salivary gland tissue damaged by radiotherapy. International Journal of Radiation Oncology*Biology*Physics Volume 78, Issue 4, 15 November 2010, Pages 983-991" [+ leia mais]
Fonte: International Journal of Radiation Oncology*Biolog
Ultrafast treatment plan optimization for volumetric modulated arc therapy (VMAT)
"Purpose: To develop a novel aperture-based algorithm for volumetric modulated arc therapy (VMAT) treatment plan optimization with high quality and high efficiency. Methods: The VMAT optimization problem is formulated as a large-scale convex programming problem solved by a column generation approach. The authors consider a cost function consisting two terms, the first enforcing a desired dose distribution and the second guaranteeing a smooth dose rate variation between successive gantry angles. A gantry rotation is discretized into 180 beam angles and for each beam angle, only one MLC aperture is allowed. The apertures are generated one by one in a sequential way. At each iteration of the column generation method, a deliverable MLC aperture is generated for one of the unoccupied beam angles by solving a subproblem with the consideration of MLC mechanic constraints. A subsequent master problem is then solved to determine the dose rate at all currently generated apertures by minimizing the cost function. When all 180 beam angles are occupied, the optimization completes, yielding a set of deliverable apertures and associated dose rates that produce a high quality plan. Results: The algorithm was preliminarily tested on five prostate and five head-and-neck clinical cases, each with one full gantry rotation without any couch/collimator rotations. High quality VMAT plans have been generated for all ten cases with extremely high efficiency. It takes only 5–8 min on CPU (MATLAB code on an Intel Xeon 2.27 GHz CPU) and 18–31 s on GPU (CUDA code on an NVIDIA Tesla C1060 GPU card) to generate such plans. Conclusions: The authors have developed an aperture-based VMAT optimization algorithm which can generate clinically deliverable high quality treatment plans at very high efficiency." [+ leia mais]
Colaborador: Laura Natal
Fonte: Med. Phys. 37, 5787 (2010); doi:10.1118/1.349167
Inverse planning for four-dimensional (4D) volumetric modulated arc therapy
" Purpose: To develop a 4D volumetric modulated arc therapy (VMAT) inverse planning framework. Methods: 4D VMAT inverse planning aims to derive an aperture and weight modulated arc therapy treatment plan that optimizes the accumulated dose distribution from all gantry angles and breathing phases. Under an assumption that the gantry rotation and patient breathing are synchronized (i.e., there is a functional relationship between the phase of the patient breathing cycle and the beam angle), the authors compute the contribution from different respiration phases through the registration of the phased CT images. The accumulative dose distribution is optimized by iteratively adjusting the aperture shape and weight of each beam through the minimization of the planning objective function. For comparison, traditional 3D VMAT plans are also performed for the two cases and the performance of the proposed technique is demonstrated. Results: A framework for 4D VMAT inverse planning has been proposed. With the consideration of the extra dimension of time in VMAT, a tighter target margin can be achieved with a full duty cycle, which is otherwise not achievable simultaneously by either 3D VMAT optimization or gated VMAT. Conclusions: The 4D VMAT planning formulism proposed here provides useful insight on how the “time” dimension can be exploited in rotational arc therapy to maximally compensate for the intrafraction organ motion. © 2010 American Association of Physicists in Medicine " [+ leia mais]
Colaborador: Laura Natal
Fonte: Medical Physics
Monte Carlo calculations of kQ, the beam quality conversion factor
" Purpose: To use EGSnrc Monte Carlo simulations to directly calculate beam quality conversion factors, kQ, for 32 cylindrical ionization chambers over a range of beam qualities and to quantify the effect of systematic uncertainties on Monte Carlo calculations of kQ. These factors are required to use the TG-51 or TRS-398 clinical dosimetry protocols for calibrating external radiotherapy beams. Methods: Ionization chambers are modeled either from blueprints or manufacturers’ user’s manuals. The dose-to-air in the chamber is calculated using the EGSnrc user-code egs_chamber using 11 different tabulated clinical photon spectra for the incident beams. The dose to a small volume of water is also calculated in the absence of the chamber at the midpoint of the chamber on its central axis. Using a simple equation, kQ is calculated from these quantities under the assumption that W/e is constant with energy and compared to TG-51 protocol and measured values. Results: Polynomial fits to the Monte Carlo calculated kQ factors as a function of beam quality expressed as %dd(10)x and TPR1020 are given for each ionization chamber. Differences are explained between Monte Carlo calculated values and values from the TG-51 protocol or calculated using the computer program used for TG-51 calculations. Systematic uncertainties in calculated kQ values are analyzed and amount to a maximum of one standard deviation uncertainty of 0.99% if one assumes that photon cross-section uncertainties are uncorrelated and 0.63% if they are assumed correlated. The largest components of the uncertainty are the constancy of W/e and the uncertainty in the cross-section for photons in water. Conclusions: It is now possible to calculate kQ directly using Monte Carlo simulations. Monte Carlo calculations for most ionization chambers give results which are comparable to TG-51 values. Discrepancies can be explained using individual Monte Carlo calculations of various correction factors which are more accurate than previously used values. For small ionization chambers with central electrodes composed of high-Z materials, the effect of the central electrode is much larger than that for the aluminum electrodes in Farmer chambers. © 2010 American Association of Physicists in Medicine ACKNOWLEDGMENTS The authors thank Joerg Wulff for making the egs_chamber user-code available before it was distributed with EGSnrc code system. The authors thank Brian Hooten of Standard Imaging for providing blueprints of Exradin ion chambers and Igor Gomola of IBA for providing technical drawings of the CC01 ion chamber. The authors thank Iwan Kawrakow for useful discussions about correlated uncertainties and Roberto Capote for useful discussions about correlated dose ratios. Thanks to Elsayed Ali, Rowan Thomson, and Justin Sutherland of the CLRP for helpful comments on the manuscript. This work is supported by an OGSST scholarship held by B.R. Muir, by NSERC, CRC program, CFI, and OIT. " [+ leia mais]
Colaborador: Laura Natal
Fonte: Medical Physics
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