Automatic 3D extraction of pleural plaques and diffuse pleural thickening from lung MDCT images

Pleural plaques (PPs) and diffuse pleural thickening (DPT) are very common asbestos related pleural diseases (ARPD). They are currently identified non-invasively using medical imaging techniques. A fully automatic algorithm for 3D detection of calcified pleura in the diaphragmatic area and thickened pleura on the costal surfaces from multi detector computed tomography (MDCT) images has been developed and tested. The algorithm for detecting diaphragmatic pleura includes estimation of the diaphragm top surface in 3D and identifying those voxels at a certain vertical distance from the estimated diaphragm, and with intensities close to that of bone, as calcified pleura. The algorithm for detecting thickened pleura on the costal surfaces includes: estimation of the pleural costal surface in 3D, estimation of the centrelines of ribs and costal cartilages and the surfaces that they lie on, calculating the mean distance between the two surfaces, and identifying any space between the two surfaces whose distance exceeds the mean distance as thickened pleura. The accuracy and performance of the proposed algorithm was tested on 20 MDCT datasets from patients diagnosed with existing PPs and/or DPT and the results were compared against the ground truth provided by an experienced radiologist. Several metrics were employed and evaluations indicate high performance of both calcified pleura detection in the diaphragmatic area and thickened pleura on the costal surfaces. This work has made significant contributions to both medical image analysis and medicine. For the first time in medical image analysis, the approach uses other stable organs such as the ribs and costal cartilage, besides the lungs themselves, for referencing and landmarking in 3D. It also estimates fat thickness between the rib surface and pleura (which is usually very thin) and excludes it from the detected areas, when identifying the thickened pleura. It also distinguishes the calcified pleura attached to the rib(s), separates them in 3D and detects calcified pleura on the lung diaphragmatic surfaces. The key contribution to medicine is effective detection of pleural thickening of any size and recognition of any changes, however small. This could have a significant impact on managing patient risks

CT Scanning

Since its introduction in 1972, X-ray computed tomography (CT) has evolved into an essential diagnostic imaging tool for a continually increasing variety of clinical applications. The goal of this book was not simply to summarize currently available CT imaging techniques but also to provide clinical perspectives, advances in hybrid technologies, new applications other than medicine and an outlook on future developments. Major experts in this growing field contributed to this book, which is geared to radiologists, orthopedic surgeons, engineers, and clinical and basic researchers. We believe that CT scanning is an effective and essential tools in treatment planning, basic understanding of physiology, and and tackling the ever-increasing challenge of diagnosis in our society

IMPROVING DAILY CLINICAL PRACTICE WITH ABDOMINAL PATIENT SPECIFIC 3D MODELS

This thesis proposes methods and procedures to proficiently introduce patient 3D models in the daily clinical practice for diagnosis and treatment of abdominal diseases. The objective of the work consists in providing and visualizing quantitative geometrical and topological information on the anatomy of interest, and to develop systems that allow to improve radiology and surgery. The 3D visualization drastically simplifies the interpretation process of medical images and provides benefits both in diagnosing and in surgical planning phases. Further advantages can be introduced registering virtual pre-operative information (3D models) with real intra-operative information (patient and surgical instruments). The surgeon can use mixed-reality systems that allow him/her to see covered structures before reaching them, surgical navigators for see the scene (anatomy and instruments) from different point of view and smart mechatronics devices, which, knowing the anatomy, assist him/her in an active way. All these aspects are useful in terms of safety, efficiency and financial resources for the physicians, for the patient and for the sanitary system too. The entire process, from volumetric radiological images acquisition up to the use of 3D anatomical models inside the surgical room, has been studied and specific applications have been developed. A segmentation procedure has been designed taking into account acquisition protocols commonly used in radiological departments, and a software tool, that allows to obtain efficient 3D models, have been implemented and tested. The alignment problem has been investigated examining the various sources of errors during the image acquisition, in the radiological department, and during to the execution of the intervention. A rigid body registration procedure compatible with the surgical environment has been defined and implemented. The procedure has been integrated in a surgical navigation system and is useful as starting initial registration for more accurate alignment methods based on deformable approaches. Monoscopic and stereoscopic 3D localization machine vision routines, using the laparoscopic and/or generic cameras images, have been implemented to obtain intra-operative information that can be used to model abdominal deformations. Further, the use of this information for fusion and registration purposes allows to enhance the potentialities of computer assisted surgery. In particular a precise alignment between virtual and real anatomies for mixed-reality purposes, and the development of tracker-free navigation systems, has been obtained elaborating video images and providing an analytical adaptation of the virtual camera to the real camera. Clinical tests, demonstrating the usability of the proposed solutions, are reported. Test results and appreciation of radiologists and surgeons, to the proposed prototypes, encourage their integration in the daily clinical practice and future developments

A biomechanical approach for real-time tracking of lung tumors during External Beam Radiation Therapy (EBRT)

Lung cancer is the most common cause of cancer related death in both men and women. Radiation therapy is widely used for lung cancer treatment. However, this method can be challenging due to respiratory motion. Motion modeling is a popular method for respiratory motion compensation, while biomechanics-based motion models are believed to be more robust and accurate as they are based on the physics of motion. In this study, we aim to develop a biomechanics-based lung tumor tracking algorithm which can be used during External Beam Radiation Therapy (EBRT). An accelerated lung biomechanical model can be used during EBRT only if its boundary conditions (BCs) are defined in a way that they can be updated in real-time. As such, we have developed a lung finite element (FE) model in conjunction with a Neural Networks (NNs) based method for predicting the BCs of the lung model from chest surface motion data. To develop the lung FE model for tumor motion prediction, thoracic 4D CT images of lung cancer patients were processed to capture the lung and diaphragm geometry, trans-pulmonary pressure, and diaphragm motion. Next, the chest surface motion was obtained through tracking the motion of the ribcage in 4D CT images. This was performed to simulate surface motion data that can be acquired using optical tracking systems. Finally, two feedforward NNs were developed, one for estimating the trans-pulmonary pressure and another for estimating the diaphragm motion from chest surface motion data. The algorithm development consists of four steps of: 1) Automatic segmentation of the lungs and diaphragm, 2) diaphragm motion modelling using Principal Component Analysis (PCA), 3) Developing the lung FE model, and 4) Using two NNs to estimate the trans-pulmonary pressure values and diaphragm motion from chest surface motion data. The results indicate that the Dice similarity coefficient between actual and simulated tumor volumes ranges from 0.76±0.04 to 0.91±0.01, which is favorable. As such, real-time lung tumor tracking during EBRT using the proposed algorithm is feasible. Hence, further clinical studies involving lung cancer patients to assess the algorithm performance are justified

Imaging of Tumour Microenvironment for the Planning of Oncological Therapies Using Positron Emission Tomography

Tumour cells differ from normal tissue cells in several important ways. These differences, like for example changed energy metabolism, result in altered microenvironment of malignant tumours. Non-invasive imaging of tumour microenvironment has been at the centre of intense research recently due to the important role that this changed environement plays in the development of malignant tumours and due to the role it plays in the treatment of these tumours. In this respect, perhaps the most important characteristics of the tumour microenvironment from this point of view are the lack of oxygen or hypoxia and changes in blood flow (BF). The purpose of this thesis was to investigate the processes of energy metabolism, BF and oxygenation in head and neck cancer and pancreatic tumours and to explore the possibilities of improving the methods for their quantification using positron emission tomography (PET). To this end [18F]EF5, a new PET tracer for detection of tumour hypoxia was investigated. Favourable uptake properties of the tracer were observed. In addition, it was established that the uptake of this tracer does not correlate with the uptake of existing tracers for the imaging of energy metabolism and BF, so the information about the presence of tissue hypoxia cannot therefore be obtained using tracers such as [18F]FDG or [15O]H2O. These results were complemented by the results of the follow-up study in which it was shown that the uptake of [18F]EF5 in head and neck tumours prior to treatment is also associated with the overall survival of the patients, indicating that tumour hypoxia is a negative prognostic factor and might be associated with therapeutic resistance. The influences of energy metabolism and BF on the survival of patients with pancreatic cancer were investigated in the second study. The results indicate that the best predictor of survival of patients with pancreatic cancer is the relationship between energy metabolism and BF. These results suggest that the cells with high metabolic activity in a hypoperfused tissue have the most aggressive phenotype.Siirretty Doriast

In Vivo Computed Tomography as a Research Tool to Investigate Asthma and COPD: Where Do We Stand?

Computed tomography (CT) is a clinical tool widely used to assess and followup asthma and chonic obstructive pulmonary disease (COPD) in humans. Strong efforts have been made the last decade to improve this technique as a quantitative research tool. Using semiautomatic softwares, quantification of airway wall thickness, lumen area, and bronchial wall density are available from large to intermediate conductive airways. Skeletonization of the bronchial tree can be built to assess its three-dimensional geometry. Lung parenchyma density can be analysed as a surrogate of small airway disease and emphysema. Since resident cells involve airway wall and lung parenchyma abnormalities, CT provides an accurate and reliable research tool to assess their role in vivo. This litterature review highlights the most recent advances made to assess asthma and COPD with CT, and also their drawbacks and the place of CT in clarifying the complex physiopathology of both diseases

医学と環境における放射線防護線量に関する研究

Nowadays, with the development of modern radiation science, application of radiation exposure has been paid more and more attention in various fields. Although there are many benefits for human by the use of radiation in such as medical diagnose and treatment, utilization of nuclear power, more efforts should be made to radiation hazards and their control that are often neglected. The researches in this study were intended to meet the requirements with the center of radiation protection dose in a wide range which attracts the most attention and are involved, either directly or indirectly, with ionizing radiation, including diagnostic exposure doses in paediatric CT, radiation doses in normal tissues which surrounding the targets in radiotherapy, and environmental exposure doses in Fukushima nuclear accidental areas. In the researches about paediatric CT, the reference radiation dose and organ doses from chest CT studies of children were estimated by using the data of clinical practice of the National Center for Child Health and Development in Japan. In composing local diagnostic reference doses and organ doses, the aim of this research was to provide a reliable and accurate data on the exposures in X-ray CT examinations for paediatric patients, which could be useful for optimization of radiation protection. Moreover, to evaluate the changes of organ doses depending on the thickness of the soft tissue on body surface in paediatric abdomen CT, radiation doses were measured with radiophotoluminescence glass dosemeters set in various organ positions within a 6-year-old child anthropomorphic phantom with slices of soft tissue equivalent materials attached on the surface, and organ doses were evaluated from the measurement values. In the researches of radiation treatment, the characteristics of the hepatic tumor movement caused by respiration were evaluated by using fluoroscopy. To decrease exposure doses in healthy organs that surrounding targets in tumor tracking treatment, the feasibility of prospective tracking of respiratory caused tumor motion signal based on autoregressive model was also tested to compensate the retardation time that often exists between the acquisition of motion signal and the action execution. In the researches of environmental radiation exposure in Fukushima nuclear accidental areas, radiocesium contaminated soil was obtained from a polluted area in Fukushima and was remedied under strict control by use of electrokinetics, and to accurately measure surface radiation doses after depollution operations, a shield for environmental radiation dose survey meters in badly contaminated areas has been developed. According to the results of the researches, a set of CTDIs and organ doses in paediatric chest CT scan was compiled for the National Center for Child Health and Development based on children\u27s weights. Organ doses in paediatric abdomen CT were evaluated under different thicknesses of soft tissue on the surface of the same child anthropomorphic phantom. In the radiation therapy, thoracic and abdominal tumor motion has been verified to be pace with respiratory movement, and Burg\u27s method has been proved to be effective to predict tumor motion in real-time, and moreover, it could make a contribution to protection for normal organs. Radiocesium contaminated soil was laboratory depolluted effectively by use of electrokinetic remediation technology, and a new shield for survey meters was successfully developed to precisely measure the environmental radiation dose and evaluate decontamination work in the Fukushima.首都大学東京, 2013-09-30, 博士（放射線学）, 甲第452号首都大学東

Semiautomated 3D liver segmentation using computed tomography and magnetic resonance imaging

Le foie est un organe vital ayant une capacité de régénération exceptionnelle et un rôle crucial dans le fonctionnement de l’organisme. L’évaluation du volume du foie est un outil important pouvant être utilisé comme marqueur biologique de sévérité de maladies hépatiques. La volumétrie du foie est indiquée avant les hépatectomies majeures, l’embolisation de la veine porte et la transplantation. La méthode la plus répandue sur la base d'examens de tomodensitométrie (TDM) et d'imagerie par résonance magnétique (IRM) consiste à délimiter le contour du foie sur plusieurs coupes consécutives, un processus appelé la «segmentation». Nous présentons la conception et la stratégie de validation pour une méthode de segmentation semi-automatisée développée à notre institution. Notre méthode représente une approche basée sur un modèle utilisant l’interpolation variationnelle de forme ainsi que l’optimisation de maillages de Laplace. La méthode a été conçue afin d’être compatible avec la TDM ainsi que l' IRM. Nous avons évalué la répétabilité, la fiabilité ainsi que l’efficacité de notre méthode semi-automatisée de segmentation avec deux études transversales conçues rétrospectivement. Les résultats de nos études de validation suggèrent que la méthode de segmentation confère une fiabilité et répétabilité comparables à la segmentation manuelle. De plus, cette méthode diminue de façon significative le temps d’interaction, la rendant ainsi adaptée à la pratique clinique courante. D’autres études pourraient incorporer la volumétrie afin de déterminer des marqueurs biologiques de maladie hépatique basés sur le volume tels que la présence de stéatose, de fer, ou encore la mesure de fibrose par unité de volume.The liver is a vital abdominal organ known for its remarkable regenerative capacity and fundamental role in organism viability. Assessment of liver volume is an important tool which physicians use as a biomarker of disease severity. Liver volumetry is clinically indicated prior to major hepatectomy, portal vein embolization and transplantation. The most popular method to determine liver volume from computed tomography (CT) and magnetic resonance imaging (MRI) examinations involves contouring the liver on consecutive imaging slices, a process called “segmentation”. Segmentation can be performed either manually or in an automated fashion. We present the design concept and validation strategy for an innovative semiautomated liver segmentation method developed at our institution. Our method represents a model-based approach using variational shape interpolation and Laplacian mesh optimization techniques. It is independent of training data, requires limited user interactions and is robust to a variety of pathological cases. Further, it was designed for compatibility with both CT and MRI examinations. We evaluated the repeatability, agreement and efficiency of our semiautomated method in two retrospective cross-sectional studies. The results of our validation studies suggest that semiautomated liver segmentation can provide strong agreement and repeatability when compared to manual segmentation. Further, segmentation automation significantly shortens interaction time, thus making it suitable for daily clinical practice. Future studies may incorporate liver volumetry to determine volume-averaged biomarkers of liver disease, such as such as fat, iron or fibrosis measurements per unit volume. Segmental volumetry could also be assessed based on subsegmentation of vascular anatomy

CT dose optimization with model based iterative reconstruction

The aim of this thesis is to assess the feasibility of using model-based iterative reconstruction (MBIR) to develop new low-dose CT (computed tomography) protocols in the areas of neck, chest, and abdominal imaging without compromising diagnostic performance. Medical imaging has become the largest source of radiation exposure for humans other than natural background radiation. The availability of and improvements in diagnostic imaging have led to a sevenfold increase in the use of imaging over the past 30 years. This is especially true for CT, with a 7.8% annual increase in the use of CT from 1996 to 2010. The major concern associated with the widespread uptake of CT is the parallel increase in radiation exposure incurred by patients, and while the relationship of diagnostic radiation exposure to a quantifiable risk of cancer induction remains a controversial topic, physicians are beholden to keep radiation doses from diagnostic imaging as low as reasonably possible to limit the risk of radiation-induced cancer. We conducted preliminary phantom and cadaveric studies to examine the performance of MBIR at different radiation dose levels in the thorax and abdomen. Cadavers and phantoms provide a means of safely assessing new technologies and optimizing scan protocols prior to clinical validation. An anthropomorphic torso phantom and 5 human cadavers were scanned at varying radiation dose levels and images reconstructed using three different reconstruction techniques: filtered back projection, hybrid IR and MBIR. MBIR reduced image noise and improved image quality even in CT images acquired with a mean radiation dose reduction of 62%, compared with conventional dose studies reconstructed with hybrid IR, with lower levels of objective image noise, superior diagnostic acceptability and contrast resolution, and comparable subjective image noise and streak artifact scores. We subsequently performed clinical studies with the objectives of assessing MBIR as a tool for image quality improvement and radiation dose reduction in CT, and for the development of new low-dose carotid angiography, chest, and abdominopelvic CT protocols. We developed a low-dose carotid CTA protocol reconstructed with MBIR comparable to a conventional dose CTA protocol in terms of image quality and diagnostic accuracy while enabling a dose reduction of 49.6%. 20 patients were scanned using a split-dose technique with radiation dose divided into a low-dose acquisition reconstructed with MBIR and a conventional dose acquisition reconstructed with hybrid IR. Mean effective dose was significantly lower for the low-dose studies (1.84mSv versus 3.71mSv) and subjective image noise, contrast resolution, and spatial resolution were significantly higher for the low-dose studies. There was excellent agreement for stenosis grading accuracy between low- and conventional dose studies (Cohen κ = 0.806). A modified low-dose CT thorax protocol reconstructed with MBIR was also developed to monitor pulmonary disease progression in patients with cystic fibrosis with our low-dose protocol enabling the acquisition of a full-volume diagnostic quality chest CT at a dose equivalent to that of a chest radiograph (0.09±0.01mSv). Finally, we assessed the feasibility of low-dose abdominopelvic CT performed with MBIR as a radiation dose reduction strategy for imaging patients presenting with acute abdominal pain. A 74.7% mean radiation dose reduction was achieved with scans performed in the peri- and submillisievert range in patients of normal and low BMI, respectively, without compromising diagnostic performance. Dose reduction to the submillisievert range for patients with an elevated BMI was a challenge. The current era is extremely exciting in terms of radiation dose optimization in CT. This thesis is a demonstration of the potential for substantial reductions in radiation exposure, when the benefits of iterative reconstruction are combined with automated tube current modulation and other CT scanner technologies. The combination of all these hardware and software developments is now seeing major benefits for the patient and moving beyond the narrow aim of radiation exposure reduction to a complete change in practice, towards replacement of conventional radiography with low-dose CT, without any penalty for the patient in terms of radiation exposure