is a fertile anthropogenic soil found in the Amazon basin. One of the most significant differences between the and surrounding soils is that is rich in aromatic carbons. Previous infrared investigations of were reported at energies above 1000 cm where many other forms of carbon also have absorption lines.
View Article and Find Full Text PDFPurpose: To examine the variability in prescribed dose due to contouring variations in intracavitary image-guided adaptive brachytherapy for cervical cancer. To identify correlations between dosimetric outcomes and delineation uncertainty metrics.
Methods And Materials: A data set from an EMBRACE sub-study on contouring uncertainties was used, consisting of magnetic resonance images of six patients with cervical cancer delineated by 10 experienced observers (target volumes and organs at risk).
Introduction: Inter-observer variability (IOV) in target volume delineation is a source of error in head and neck radiotherapy. Diffusion-weighted imaging (DWI) has been shown to be useful in detecting recurrent head and neck cancer. This study aims to determine whether DWI improves target volume delineation and IOV.
View Article and Find Full Text PDFIntroduction: Magnetic resonance imaging (MRI) is increasingly used for target volume delineation in radiotherapy due to its superior soft tissue visualisation compared to computed tomography (CT). The aim of this study was to assess the impact of a radiologist-led workshop on inter-observer variability in volume delineation on MRI.
Methods: Data from three separate studies evaluating the impact of MRI in lung, breast and cervix were collated.
Purpose: To study the sensitivity of the ArcCHECK in detecting delivery errors for lung stereotactic body radiotherapy (SBRT) using the Volumetric Modulated Arc Therapy (VMAT) technique and to evaluate the sensitivity of eight global and local gamma tolerances with different cut-off percentages.
Methods: Baseline VMAT plans were generated for 15 lung SBRT patients. We delivered the smallest errors(gantry, collimator, and multileaf collimator MLC) which had ≥ ±2% dose difference in the modified treatment plans compared to the baseline plan (the clinical significance of those errors were assessed in our previous study.
Purpose: To quantify the impact of simulated errors for nasopharynx radiotherapy across multiple institutions and planning techniques (auto-plan generated Volumetric Modulated Arc Therapy (ap-VMAT), manually planned VMAT (mp-VMAT) and manually planned step and shoot Intensity Modulated Radiation Therapy (mp-ssIMRT)).
Methods: Ten patients were retrospectively planned with VMAT according to three institution's protocols. Within one institution two further treatment plans were generated using differing treatment planning techniques.
Purpose: The purpose of this study was to evaluate the impact of magnetic resonance imaging (MRI) versus computed tomography (CT)-derived planning target volumes (PTVs), in both supine and prone positions, for whole breast (WB) radiation therapy.
Methods And Materials: Four WB radiation therapy plans were generated for 28 patients in which PTVs were generated based on CT or MRI data alone in both supine and prone positions. A 6-MV tangential intensity modulated radiation therapy technique was used, with plans designated as ideal, acceptable, or noncompliant.
J Appl Clin Med Phys
September 2016
The purpose of this study was to determine the impact of magnetic resonance imaging (MRI) geometric distortions when using MRI for target delineation and planning for whole-breast, intensity-modulated radiotherapy (IMRT). Residual system distortions and combined systematic and patient-induced distortions are considered. This retrospective study investigated 18 patients who underwent whole-breast external beam radiotherapy, where both CT and MRIs were acquired for treatment planning.
View Article and Find Full Text PDFPurpose: To determine whether T2-weighted MRI improves seroma cavity (SC) and whole breast (WB) interobserver conformity for radiation therapy purposes, compared with the gold standard of CT, both in the prone and supine positions.
Methods And Materials: Eleven observers (2 radiologists and 9 radiation oncologists) delineated SC and WB clinical target volumes (CTVs) on T2-weighted MRI and CT supine and prone scans (4 scans per patient) for 33 patient datasets. Individual observer's volumes were compared using the Dice similarity coefficient, volume overlap index, center of mass shift, and Hausdorff distances.
In this paper, the highest level of inter- and intra-observer conformity achievable with different treatment planning systems (TPSs), contouring tools, shapes, and sites have been established for metrics including the Dice similarity coefficient (DICE) and Hausdorff Distance. High conformity values, e.g.
View Article and Find Full Text PDFJ Med Imaging Radiat Oncol
December 2015
Introduction: Detailed, published surveys specific to Australian breast radiotherapy practice were last conducted in 2002. More recent international surveys specific to breast radiotherapy practice include a European survey conducted in 2008/2009 and a Spanish survey conducted in 2009. Radiotherapy techniques continue to evolve, and the utilisation of new techniques, such as intensity-modulated radiation therapy (IMRT), is increasing.
View Article and Find Full Text PDFQuant Imaging Med Surg
February 2013
The commercially available X-ray fluoroscopy quality assurance phantom, the Leeds test object TOR18FG, was found to be suitable to assess T-ray image quality in the range (0.1-0.4) THz at a depth of 0.
View Article and Find Full Text PDFWe characterize spatial dispersion in longitudinally invariant drawn metamaterials with a magnetic response at terahertz frequencies, whereby a change in the angle of the incident field produces a shift in the resonant frequency. We present a simple analytical model to predict this shift. We also demonstrate that the spatial dispersion is eliminated by breaking the longitudinal invariance using laser ablation.
View Article and Find Full Text PDFWe present a novel method for producing drawn metamaterials containing slotted metallic cylinder resonators, possessing strong magnetic resonances in the terahertz range. The resulting structures are either spooled to produce a 2-dimensional metamaterial monolayer, or stacked to produce three-dimensional multi-layered metamaterials. We experimentally investigate the effects of the resonator size and number of metamaterial layers on transmittance, observing magnetic resonances between 0.
View Article and Find Full Text PDF