1,721,087 research outputs found
ROLE OF PET/CT IN RADIOTHERAPY TREATMENT PLANNING
No full textThis chapter focuses on the rationale, target validation, dose prescription verification and evaluation, and recent clinical achievements in the field of integrating positron emission tomography imaging into radiotherapy treatment planning. Application of functional imaging to radiotherapy is a rapidly expanding field with the development of new modalities and techniques. Functional imaging of positron emission tomography in conjunction with radiotherapy provides new avenues toward the clinical application of dose painting as a new radiotherapy strategy delivering optimized dose redistribution according to the functional imaging information to further improve tumor control. New biological imaging methodologies mainly based on positron emission tomography/computed tomography, magnetic resonance imaging, and magnetic resonance spectroscopy imaging, in conjunction with radiotherapy, make dose painting possible. It can be used to draw a three-dimensional map of radiobiological relevant parameters as its inherent potential to trace the real target volume, consisting of tumor cells that require a therapeutic dose to control the disease. Positron emission tomography/computed tomography is outstanding and widely used in daily clinical practice. It offers molecular biological information on the tumor microenvironment in addition to anatomical imaging and shows significant biological heterogeneity of tumors, such as metabolism, proliferation, hypoxia, radioresistance cell density, and perfusion
Motion Management in Positron Emission Tomography/Computed Tomography for Radiation Treatment Planning
No full textHybrid positron emission tomography (PET)/computed tomography (CT) scanners combine, in a unique gantry, 2 of the most important diagnostic imaging systems, a CT and a PET tomograph, enabling anatomical (CT) and functional (PET) studies to be performed in a single study session. Furthermore, as the 2 scanners use the same spatial coordinate system, the reconstructed CT and PET images are spatially co-registered, allowing an accurate localization of the functional signal over the corresponding anatomical structure. This peculiarity of the hybrid PET/CT system results in improved tumor characterization for oncological applications, and more recently, it was found to be also useful for target volume definition (TVD) and treatment planning in radiotherapy (RT) applications. In fact, the use of combined PET/CT information has been shown to improve the RT treatment plan when compared with that obtained by a CT alone. A limiting factor to the accuracy of TVD by PET/CT is organ and tumor motion, which is mainly due to patient respiration. In fact, respiratory motion has a degrading effect on PET/CT image quality, and this is also critical for TVD, as it can lead to possible tumor missing or undertreatment. Thus, the management of respiratory motion is becoming an increasingly essential component in AT treatment planning; indeed, it has been recognized that the use of personalized motion information can improve TVD and, consequently, permit increased tumor dosage while sparing surrounding healthy tissues and organs at risk. This review describes the methods used for motion management in PET/CT for radiation treatment planning. The article covers the following: (1) problems caused by organ and lesion motion owing to respiration, and the artifacts generated on CT, PET, and PET/CT images; (2) data acquisition and processing techniques used to manage respiratory motion in PET/CT studies; and (3) the use of personalized motion information for TVD and radiation treatment planning. Semin Nucl Med 42:289-307 (c) 2012 Elsevier Inc. All rights reserved
In Regard to Zureick et al.
No full textIn 375 patients with left-sided breast cancer treated between 2012 and 2018 with adjuvant radiation therapy using mainly deep-inspiratory breath-holding technique (78% of patients), Zureick et al 1 analyzed mean and maximum left anterior descending artery (LAD) and heart dose association with cardiac toxicity. Considering even moderate cardiac events, the authors identified, with median 48-month follow-up, higher risk for cardiac events above the following thresholds: LAD Dmean Equivalent Dose in 2 Gy fractions of 2.8 Gy, Dmax of 6.7 Gy, and heart Dmean of 0.8 Gy
Detection and compensation of organ/lesion motion using 4D-PET/CT respiratory gated acquisition techniques
No full textPurpose: To describe the degradation effects produced by respiratory organ and lesion motion on PET/CT images and to define the role of respiratory gated (RG) 4D-PET/CT techniques to compensate for such effects. Methods: Based on the literature and on our own experience, technical recommendations and clinical indications for the use of RG 4D PET/CT have been outlined. Results: RC 4D-PET/CT techniques require a state of the art PET/CT-scanner, a respiratory monitoring system and dedicated acquisition and processing protocols. Patient training is particularly important to obtain a regular breathing pattern. An adequate number of phases has to be selected to balance motion compensation and statistical noise. RG 4D PET/CT motion free images may be clinically useful for tumour tissue characterization, monitoring patient treatment and target definition in radiation therapy planning. Conclusions: RG 4D PET/CT is a valuable tool to improve image quality and quantitative accuracy and to assess and measure organ and lesion motion for radiotherapy planning. 2010 European Society for Therapeutic Radiology and Oncology and European Association of Nuclear Medicine. Published by Elsevier Ireland Ltd. All rights reserved. 96 (2010) 311-31
Higher-than-expected Severe (Grade 3-4) Late Urinary Toxicity After Postprostatectomy Hypofractionated Radiotherapy: A Single-institution Analysis of 1176 Patients
No full textBackground: Dose escalation and hypofractionation may have a role in postprostatectomy radiotherapy (RT), but at the risk of increasing urinary toxicity. Objective: To address predictors of severe (Grade >= 3) late urinary toxicities (LGUTOX3) after postoperative irradiation. Design, setting, and participants: A single-institution cohort of 1176 patients treated between 1993 and 2010 with adjuvant or salvage RT was analyzed. A total of 929 patients underwent conventionally fractionated (CF) RT (1.8 Gy per fraction; median dose to the prostatic bed: 70.2 Gy) with nonconformal RT (n = 169), three-dimensional conformal RT (n = 657), or intensity-modulated RT (n = 103) technique, while 247 patients received hypofractionated helical TomoTherapy (median: 2.50 Gy per fraction) at the following doses: 117 patients at 65.8 Gy (2.35 Gy in 28 fractions), 80 patients at a median of 71.4 Gy (2.5-2.6 Gy in 28 fractions), and 50 patients at 58 Gy in 20 fractions. Total doses were converted into 2 Gy-equivalent doses (EQD2) following the linear quadratic model taking alpha/beta = 5. Outcome measurements and statistical analysis: Univariable and multivariable Cox regression models tested the relationship between clinicodosimetric variables and the risk of LGUTOX3 retrospectively, graded according to Common Terminology Criteria for Adverse Events v. 4.0. Results and limitations: After a median follow-up of 98 mo, the 5-yr risk of LGUTOX3 was 6.9% and 18.1% in the CF and hypofractionated cohorts, respectively. At univariable analysis, the risk of LGUTOX3 was predicted by dose per fraction (hazard ratio [HR]: 2.96), acute Grade >= 2 toxicity (HR: 2.37), EQD2, pT4, and year of irradiation. At multivariable analyses, acute Grade >= 2 toxicity and dose per fraction independently predicted LGUTOX3 in the population, while an interaction analysis indicated a predictive role of hypertension in the hypofractionated cohort only. These findings are limited by their retrospective nature. Conclusions: In the postprostatectomy setting, the logistic convenience of hypofractionation should be carefully balanced against the risk of severe late urinary sequelae. Patient summary: This study investigated the causes of urinary adverse effects after postprostatectomy radiotherapy. Hypofractionation resulted in an increased risk of severe urinary toxicities. (C) 2014 European Association of Urology. Published by Elsevier B. V. All rights reserved
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