1,721,231 research outputs found
Usefulness of dual-time point imaging after carbonated water for the fluorodeoxyglucose positron emission imaging of peritoneal carcinomatosis in colon cancer
No full textBackground: Fluorodeoxygluose (FDG) positron emission/computed tomography (PET/CT) is emerging as a useful tool for the diagnosis of peritoneal carcinomatosis (PC). In this study, we assessed whether dual-time point imaging can improve the accuracy of FDG PET/CT for the diagnosis of PC after colon rectal cancer (CRC). Methods: Thirty-nine patients with past history of CRC were evaluated. Whole-Body PET/CT scan was acquired 1 hour after tracer injection. If one or more focal areas of increased FDG uptake (standardized uptake value, SUV max>2.5) were found in the abdomen, 1 L of carbonated water was orally administered to patients and a delayed scan of the abdominal region was acquired at 2 hours. The SUV max and the mean Delta (Δ) SUV were calculated. The scintigraphic results were compared with the results of colonoscopy and histology and with the clinical follow-up. Results: Thirteen out of the 39 patients did not show any significant area of FDG uptake at the whole-body scan. The remaining 26 patients showed an overall number of 27 sites of focal increased uptake, showing a mean SUV max of 6.5+3.3. Late scan of the abdomen showed vanishing spots in 11 cases. Focal and increasing FDG uptake was found in 15 subjects (for an overall number of 16 sites) with SUV max of 15.6+4 and mean Δ SUV of +26.3%±7.5%. In these cases, final diagnosis was PC in 10 patients (according to cytology or histology) and dysplastic polyp in 5 cases. No significant difference in Δ SUV was found between patients with PC and those with polypoid formations. Conclusions: According to our results, dual-time point imaging after carbonated water may increase the accuracy of FDG PET/CT for the imaging of PC in patients affected by CRC. © Mary Ann Liebert, Inc
Multiple 3D inversion recovery imaging for volume T1 mapping of the heart
No full textIn this article, a three-dimensional inversion recovery sequence was optimized with the aim of generating in vivo volume T1 maps of the heart using a 1.5-T MR system. Acquisitions were performed before and after gadolinium diethylenetriamine penta-acetic acid (Gd-DTPA) administration in one patient with hypertrophic cardiomyopathy and in two healthy volunteers. Data were acquired with a multishot fast field echo readout using both ECG and respiratory triggers. A dedicated phantom, composed of four solutions with different T1 values, was positioned on the subjects' thoracic region to perform patient-specific calibration. Pixel based T1 maps were calculated with a custom Matlab® code. Phantom measurements showed a good accuracy of the technique and in vivo T1 estimation of liver, skeletal muscle, myocardium, and blood resulted in good agreement with values reported in the literature. Multiple three-dimensional inversion recovery technique is a feasible and accurate method to perform T1 volume mapping. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc. Copyright © 2012 Wiley Periodicals, Inc
Dose assessment following tritium intake
No full textThe present chapter provides a description of internal dose estimates following tritium intake through the analysis of biokinetic models, dosimetric models and bioassay results. Assessing the committed effective dose received as a result of taking tritium into the body is done in two steps. First, a biokinetic model describing the behavior of the tritiated compounds after incorporation into the human body is used to predict where the tritium will go in the body and how it will be removed from it. The compartment model of the retention kinetics of tritiated water (HTO) and organically bound tritium (OBT) recommended by ICRP(International Commission on Radiological Protection) publications is examined throughout the chapter for the purpose of investigating the importance of the main metabolic routes. Biokinetic models of different tritium compounds are analyzed, among which gaseous tritium (HT, DT, and T2), HTO, OBT and special tritium compounds. Second, a dosimetric model is used to calculate how much tritium will decay while it is in the various organs and tissues of the body and how much of the energy from the beta particles will be absorbed by the body. This allows the evaluation of the dose resulting from the intake of tritium. In the present chapter, the ICRP methodology for calculating the internal absorbed dose from inhaled, ingested and skin-absorbed tritium will be presented. Finally, the established way of calculating the amount of activity deposited within the body is by bioassay samples, i.e. by measurements of urinary excretion. In fact, both the amount of tritium retained in excreta and the committed effective dose are directly related to the intake: therefore bioassay measurements are used to determine the dose received. A worked example is also provided to help the reader understand how the dose received can be determined from bioassay results ©2013 Nova Science Publishers, Inc. All rights reserved
Uncertainty Analysis in the Calibration of an Emission Tomography System for Quantitative Imaging
No full textIt is generally acknowledged that calibration of the imaging system (be it a SPECT or a PET scanner) is one of the critical components associated with in vivo activity quantification in nuclear medicine. The system calibration is generally performed through the acquisition of a source with a known amount of radioactivity. The decay-corrected calibration factor is the "output" quantity in a measurement model for the process. This quantity is a function of a number of "input" variables, including total counts in the volume of interest (VOI), radionuclide activity concentration, source volume, acquisition duration, radionuclide half-life, and calibration time of the radionuclide. Uncertainties in the input variables propagate through the calculation to the "combined" uncertainty in the output quantity. In the present study, using the general formula given in the GUM (Guide to the Expression of Uncertainty in Measurement) for aggregating uncertainty components, we derive a practical relation to assess the combined standard uncertainty for the calibration factor of an emission tomography system. At a time of increasing need for accuracy in quantification studies, the proposed approach has the potential to be easily implemented in clinical practice. © 2017 Marco D'Arienzo and Maurice Cox
Quantification of dose nonuniformities by voxel-based dosimetry in patients receiving 90Y-ibritumomab-tiuxetan
No full textObjective: To assess the impact of nonuniform dose distribution within lesions and tumor-involved organs of patients receiving Zevalin®, and to discuss possible implications of equivalent uniform biological effective doses (EU-BED) on treatment efficacy and toxicity. MATLABTM -based software for voxel-based dosimetry was adopted for this purpose. Methods: Eleven lesions from seven patients with either indolent or aggressive non-Hodgkin lymphoma were analyzed, along with four organs with disease. Absorbed doses were estimated by a direct integration of single-voxel kinetic data from serial tomographic images. After proper corrections, differential BED distributions and surviving cell fractions were estimated, allowing for the calculation of EU-BED. To quantify dose uniformity in each target area, a heterogeneity index was defined. Results: Average doses were below those prescribed by conventional radiotherapy to eradicate lymphoma lesions. Dose heterogeneity and effect on tumor control varied among lesions, with no apparent relation to tumor mass. Although radiation doses to involved organs were safe, unexpected liver toxicity occurred in one patient who presented with a pattern of diffuse infiltration. Conclusion: Voxel-based dosimetry and radiobiologic modeling can be successfully applied to lesions and tumor-involved organs, representing a methodological advance over estimation of mean absorbed doses. However, effects on tumor control and organ toxicity still cannot be easily predicted. © Copyright 2013, Mary Ann Liebert, Inc
Absorbed dose to lesion and clinical outcome after liver radioembolization with 90Y microspheres: A case report of PET-based dosimetry
No full textA 54-year-old woman with metastatic colorectal carcinoma underwent liver radioembolization with 90Y resin microspheres. Microsphere biodistribution was assessed 2 h after the treatment through a 20-min long 90Y PET scan. Isodose map and lesion dose-volume histogram (DVH) were then evaluated using a MATLAB-based code. Response to therapy was assessed performing a 18F-FDG PET 6 months after the treatment. At 90Y PET the patient showed a well-defined horseshoe-shaped hepatic lesion with hot margins and a cold core. The lesion presented a heterogeneous DVH with a hot margin receiving an average radiation dose as high as 287 Gy and a cold area receiving an average radiation dose of 70 Gy approximately. Six months after the treatment the patient reported a complete remission of tumour areas which received a high radiation dose, while progression of metastases was observed in the area that presented scarce microsphere localization at 90Y PET. According to our experience, the use of 90Y PET voxel dosimetry may provide a useful tool to assess possible correlations between microsphere biodistribution and clinical outcome of the treatment. In agreement with current literature findings, an average radiation dose greater than approximately 100 Gy may be required to sterilize liver metastases. © 2013 The Japanese Society of Nuclear Medicine
Metrological issues in molecular radiotherapy
No full textThe therapeutic effect from molecular radiation therapy (MRT), on both tumour and normal tissue, is determined by the radiation absorbed dose. Recent research indicates that as a consequence of biological variation across patients the absorbed dose can vary, for the same administered activity, by as much as two orders of magnitude. The international collaborative EURAMET-EMRP project "Metrology for molecular radiotherapy (MetroMRT)" is addressing this problem. The overall aim of the project is to develop methods of calibrating and verifying clinical dosimetry in MRT. In the present paper an overview of the metrological issues in molecular radiotherapy is provided. © Owned by the authors, published by EDP Sciences, 2014
Management of supply chains for the wine production
No full textThis paper focuses on a supply network, that deals with wine production, that is typical of Southern Italy. Such a phenomenon is analyzed by differential equations, that model goods on arcs and queues for the exceeding parts. Various numerical schemes are proposed for simulations. A strategy of Situation Awareness allows understanding a suitable choice of the input flows to the supply network in consideration. The obtained results indicate that a Situation Awareness approach permits to find compromises for the modulation of production queues and the optimization of the overall system characteristics
Growth effects on the network dynamics with applications to the cardiovascular system
No full textWe consider a 1D model for the simulation of the cardiovascular system. We solve it numerically using the discontinuous Galerkin scheme, and we perform an optimization scenario to find the best value for the heart rate in order to obtain a desired outflow. We study the effects of a growing network (in size, length and radii) on the heart rate, assuming that this needs to adapt for delivering a desired outflow. As inflow condition we prescribe the flow and as outflow condition we use the terminal reflection coefficient
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