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Author: Andrea Martinez-Movilla Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Abstract: Background Patient's breathing affects the quality of chest images acquired with positron emission tomography/computed tomography (PET/CT) studies. Movement correction is required to optimize PET quantification in clinical settings. We present a reproducible methodology to compare the impact of different movement compensation protocols on PET image quality. Static phantom images were set as reference values, and recovery coefficients (RCs) were calculated from motion compensated images for the phantoms in respiratory movement. Image quality was evaluated in terms of: (1) volume accuracy (VA) with the NEMA phantom; (2) concentration accuracy (CA) by six refillable inserts within the electron density CIRS phantom; and (3) spatial resolution (R) with the Jaszczak phantom. Three different respiratory patterns were applied to the phantoms. We developed an open-source package to automatically analyze VA, CA and R. We compared 10 different movement compensation protocols available in the Philips Gemini TF-64 PET/CT (4-, 6-, 8- and 10-time bins, 20%-, 30%-, 40%-window width in Inhale and Exhale). Results The homemade package provided RC values for VA, CA and R of 102 PET images in less than 5 min. Results of the comparison of the 10 different protocols demonstrated the feasibility of the proposed method for quantifying the variations observed qualitatively. Overall, prospective protocols showed better motion compensation than retrospective. The best performance was obtained for the protocol Exhale 30% (0.3 s after maximum Exhale position and window width of 30%) with RCVA=1.6±1.3 , RCCA=0.90±0.09 and RCR=0.6±0.4 . Among retrospective protocols, 8 Phase protocol showed the best performance. Conclusion We provided an open-source package able to automatically evaluate the impact of motion compensation methods on PET image quality. A setup based on commonly available experimental phantoms is recommended. Its application for the comparison of 10 time-based approaches showed that Exhale 30% protocol had the best performance. The proposed framework is not specific to the phantoms and protocols presented on this study
Author: Andrea Martinez-Movilla Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Abstract: Background Patient's breathing affects the quality of chest images acquired with positron emission tomography/computed tomography (PET/CT) studies. Movement correction is required to optimize PET quantification in clinical settings. We present a reproducible methodology to compare the impact of different movement compensation protocols on PET image quality. Static phantom images were set as reference values, and recovery coefficients (RCs) were calculated from motion compensated images for the phantoms in respiratory movement. Image quality was evaluated in terms of: (1) volume accuracy (VA) with the NEMA phantom; (2) concentration accuracy (CA) by six refillable inserts within the electron density CIRS phantom; and (3) spatial resolution (R) with the Jaszczak phantom. Three different respiratory patterns were applied to the phantoms. We developed an open-source package to automatically analyze VA, CA and R. We compared 10 different movement compensation protocols available in the Philips Gemini TF-64 PET/CT (4-, 6-, 8- and 10-time bins, 20%-, 30%-, 40%-window width in Inhale and Exhale). Results The homemade package provided RC values for VA, CA and R of 102 PET images in less than 5 min. Results of the comparison of the 10 different protocols demonstrated the feasibility of the proposed method for quantifying the variations observed qualitatively. Overall, prospective protocols showed better motion compensation than retrospective. The best performance was obtained for the protocol Exhale 30% (0.3 s after maximum Exhale position and window width of 30%) with RCVA=1.6±1.3 , RCCA=0.90±0.09 and RCR=0.6±0.4 . Among retrospective protocols, 8 Phase protocol showed the best performance. Conclusion We provided an open-source package able to automatically evaluate the impact of motion compensation methods on PET image quality. A setup based on commonly available experimental phantoms is recommended. Its application for the comparison of 10 time-based approaches showed that Exhale 30% protocol had the best performance. The proposed framework is not specific to the phantoms and protocols presented on this study
Author: Tzu-Cheng Lee Publisher: ISBN: Category : Languages : en Pages : 153
Book Description
Positron emission tomography (PET) is a commonly used imaging tool in the management of patients with lung cancer and is of considerable interest in quantitative imaging of the thorax. Mismatch of PET data with computed tomography (CT) attenuation correction (CTAC) due to respiratory motion is a known source of errors in PET imaging. In theory, this can be corrected by matching individual PET and CT phases which have been generated by respiratory-correlated PET and CT. However, due to the high variability of patient breathing patterns and the nature of the scanning time differences between PET and CT, current respiratory-gated CTAC protocols for the irregular breather may cause additional bias in the PET image values. A ten-fold extension of the CT scanning time duration helps reduce PET imaging bias, but leads to the higher radiation dose to the patient. Lowering the CT source flux level to reduce dose, however, leads to increased noise and bias. Here we test the possibility of using model based iterative reconstruction algorithms (MBIRs) for generating the sparse-view, ultra-low-dose (i.e. an order lower than current low-dose protocols) CTAC images for both phantom and patient PET data. We also propose a new variance estimation model, which considers statistical changes caused by the non-positivity correction process, for the MBIR algorithms. The model based iterative CT reconstruction approach does generate more accurate CTAC map compared to current approaches. However, since iterative reconstruction algorithms typically assume a normal distribution of the attenuation data, we tested if the assumption is still valid in the ultra-low-dose regime. The simulation and empirical ultra-low-dose CT studies showed a skewed post-log likelihood distribution in certain ranges. The information delineates the estimation limits of model based iterative reconstruction approach on the ultra-low-dose CT imaging, and potentially helps guide scanning protocols customized for a lowest-reasonable radiation dose.
Author: Paul Schleyer Publisher: ISBN: Category : Tomography, Emission Languages : en Pages : 0
Book Description
In dual modality PET-CT imaging, respiratory motion can introduce blurring in PET images and create a spatial mismatch between the PET and CT datasets. Attenuation correction errors can result from this mismatch, which can produce severe artefacts that potentially alter the clinical interpretation of the images. Various approaches of reducing these effects have been developed. Many involve respiratory gated acquisitions which generally require a measure of the respiratory cycle throughout imaging. In this work, a retrospective respiratory gating technique was devel¬oped for both PET and CT which extracts the respiratory cycle from the acquired data itself, removing the requirement for hardware that measures respiration. This data-driven gating method was validated with phantom and patient data, and compared with a hardware based approach of gating. Extensions to the method facilitated the gating of multi-bed position, 3D clinical PET scans. Finally, 60 Ammonia cardiac PET/CT images were used to compare several different ap¬proaches of reducing respiratory induced attenuation correction errors and motion blur. The data-driven respiratory gating method accurately substituted a hardware based approach, and no significant difference was found between images gated with either methods. Gating 11 clinical 3D whole body PET images validated the extended data-driven gating methods and demonstrated successful combination of separate PET bed-positions. All evaluated approaches to reduce respiratory motion artefacts in cardiac imaging demonstrated an average improvement in PET-CT alignment. However, cases were found where alignment worsened and artefacts resulted. Fewer and less severe cases were produced when the 4D attenuation correction data was created from a 3D helical CT and PET derived motion fields. Full motion cor¬rection produced a small effect on average, however in this case no detrimental effects were found.
Author: Christian Schaller Publisher: GRIN Verlag ISBN: 3640333276 Category : Computers Languages : en Pages : 101
Book Description
Diploma Thesis from the year 2007 in the subject Computer Science - Applied, grade: 1,0, Friedrich-Alexander University Erlangen-Nuremberg (Lehrstuhl für Mustererkennung), language: English, abstract: Far reaching developments and technical advances took place within the field of radiotherapy in the last years. Radiotherapy within the chest and abdomen area is especially important in the field of radiotherapy. Within this regions, organ and tumor positions are significantly affected by patient respiration. The tumor motion, caused due to respiration is compensated by extending the treated area. This extension covers all possible positions of the tumor and therefore also includes healthy tissue. Several clinical studies provide evidence of a survival advantage for higher dose levels. To spare a maximum of healthy tissue physicians use 'gated radiotherapy'. Common recent approaches for gated radiotherapy are based on the observation of a surrogate. This either can be an implanted fiducial marker or an external signal, which is trying to capture the patients' respiration. Within this thesis principles and methods of 'gated radiotherapy' are described. Additionally an overview of recent patents and products related to radiotherapy are presented and advantages and disadvantages of both common approaches are discussed. This discussion leads to a new developed method, which is introduced. The method joins advantages of both known methods but disregards their disadvantages. The developed algorithm is using image guided methods and methods of medical image processing. A mapping between a 4D-CT planning volume and a most recent acquired fluoroscopic sequence of the same patient is calculated before treatment. Using this mapping and an external breathing signal the physician can define gating intervals and treat the patient in certain breathing phases. The developed algorithm is included in an existing prototype developed by Siemens Corporate Research (SCR) in Princeton, NJ
Author: Jan Ehrhardt Publisher: Springer ISBN: 9783642446061 Category : Science Languages : en Pages : 0
Book Description
Respiratory motion causes an important uncertainty in radiotherapy planning of the thorax and upper abdomen. The main objective of radiation therapy is to eradicate or shrink tumor cells without damaging the surrounding tissue by delivering a high radiation dose to the tumor region and a dose as low as possible to healthy organ tissues. Meeting this demand remains a challenge especially in case of lung tumors due to breathing-induced tumor and organ motion where motion amplitudes can measure up to several centimeters. Therefore, modeling of respiratory motion has become increasingly important in radiation therapy. With 4D imaging techniques spatiotemporal image sequences can be acquired to investigate dynamic processes in the patient’s body. Furthermore, image registration enables the estimation of the breathing-induced motion and the description of the temporal change in position and shape of the structures of interest by establishing the correspondence between images acquired at different phases of the breathing cycle. In radiation therapy these motion estimations are used to define accurate treatment margins, e.g. to calculate dose distributions and to develop prediction models for gated or robotic radiotherapy. In this book, the increasing role of image registration and motion estimation algorithms for the interpretation of complex 4D medical image sequences is illustrated. Different 4D CT image acquisition techniques and conceptually different motion estimation algorithms are presented. The clinical relevance is demonstrated by means of example applications which are related to the radiation therapy of thoracic and abdominal tumors. The state of the art and perspectives are shown by an insight into the current field of research. The book is addressed to biomedical engineers, medical physicists, researchers and physicians working in the fields of medical image analysis, radiology and radiation therapy.
Author: Joël Daouk Publisher: ISBN: Category : Languages : en Pages : 322
Book Description
Les mouvements respiratoires sont la cause d'une dégradation importante des images TEP. En effet, les fixations des organes en mouvement apparaissent étalées et leur intensité diminuée, ce qui peut conduire à des conclusions erronées lors de l'interprétation des images. L'objectif du travail de thèse présenté dans ce rapport est de proposer des solutions pratiques pour s'affranchir de cette problématique. Dans un premier temps, nous avons privilégié le développement d'une approche directement applicable au sein d'un service de médecine nucléaire. Nous proposons une technique qui repose sur le concept de compensation des mouvements respiratoires. Cette méthode, baptisée CT-based, est basée sur une acquisition synchronisée des données TEP suivie par une TDM en apnée de fin d'expiration. Un traitement a posteriori permet de ne sélectionner que les évènements TEP ayant été enregistrés autour de la position respiratoire enregistrée lors de la séquence TDM. La méthode CT-based a été implémentée en routine et a montré son efficacité. La seconde méthode proposée consiste à introduire l'information de déplacement dans un algorithme de reconstruction itératif afin de générer un volume corrigé du mouvement en utilisant la totalité de la statistique acquise. Pour cela un algorithme de reconstruction, appelé MOSEM, a été proposé. Une des perspectives de cette thèse est la validation clinique de cet algorithme.
Author: Dylan O'Connell Publisher: ISBN: Category : Languages : en Pages : 143
Book Description
Breathing motion in radiotherapy is commonly managed with four-dimensional computed tomography (4DCT). 4DCT datasets consist of multiple breathing-gated images that display motion of the subject's anatomy over a breathing period. Commercial 4DCT protocols are susceptible to image artifacts when the subject breathes irregularly. Unlike commercial protocols, model-based 4DCT techniques describe a correspondence between tissue motion and an external signal used as a surrogate for respiratory phase. One such technique, termed '5DCT,' uses free-breathing fast helical acquisition and characterizes lung tissue motion as function of five degrees of freedom: x,y, and z position in a reference geometry, breathing amplitude, and breathing rate. The overarching goal of this dissertation is to develop the 5DCT technique for clinical use. A validation study was conducted involving comparing 5DCT images to commercial 4DCT using an animal model. Reproducible and periodic breathing patterns were achieved through mechanical ventilation and image similarity was quantified using landmark displacement. Differences in measured tumor motion between 5DCT and commercial 4DCT were examined in a cohort of 20 lung cancer patients. Solutions for the unique challenges of using model model-based techniques clinically, such as appropriate amplitude interval selection and presentation of a quantitative error map, were developed. A quality management program was developed to ensure the safety of the protocol using risk analysis methods such as process mapping and failure modes and effects analysis. In addition, safety of the in-house software required to implement the technique was managed through use cases and quantitative, testable safety requirements. The physiological significance of the 5D model parameters was investigated, particularly their dependence on breathing rate during acquisition. It was shown that the model parameter relating tissue motion to breathing amplitude was largely invariant with breathing rate during acquisition. A prospective scanning method was developed to reduce the number of fast helical scans, and associated imaging dose, necessary to perform 5DCT while maintaining motion modeling accuracy. A simulation study was conducted using patient breathing traces, and the results demonstrated that adequate sampling of the respiratory cycle could be achieved using six scans, compared to the previously published protocol that employs twenty-five.
Author: International Atomic Energy Agency Publisher: ISBN: 9789201415103 Category : Medical Languages : en Pages : 59
Book Description
This publication reviews the current state of the art of image quantification and provides a solid background of tools and methods to medical physicists and other related professionals who are faced with quantification of radionuclide distribution in clinical practice. It describes and analyses the physical effects that degrade image quality and affect the accuracy of quantification, and describes methods to compensate for them in planar, single-photon emission computed tomography (SPECT) and positron emission tomography (PET) images.
Author: Andrea Martinez-Movilla
Author: Andrea Martinez-Movilla
Author: Tzu-Cheng Lee
Author: 
Author: Paul Schleyer
Author: Christian Schaller
Author: Jan Ehrhardt
Author: Chandrani Chakraborty
Author: Joël Daouk
Author: Dylan O'Connell
Author: International Atomic Energy Agency