There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Co-Planar Stereotaxic Atlas of the Human Brain—3-Dimensional Proportional System: An Approach to Cerebral Imaging, J. Talairach, P. Tournoux. Georg Thieme Verlag, New York (1988), 122 pp., 130 figs. DM 268

“Unpaired Image-to-Image Translation using Cycle-Consistent Adversarial Networks”の学習報告

NOTE The report of the Committee without its annexes appears as Official Records of the General Assembly, Sixty-third Session, Supplement No. 46. The designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Secretariat of the United Nations concerning the legal status of any country, territory, city or area, or of its authorities, or concerning the delimitation of its frontiers or boundaries. The country names used in this document are, in most cases, those that were in use at the time the data were collected or the text prepared. In other cases, however, the names have been updated, where this was possible and appropriate, to reflect political changes. Scientific Annexes Annex A. Medical radiation exposures Annex B. Exposures of the public and workers from various sources of radiation INTROdUCTION 1. In the course of the research and development for and the application of atomic energy and nuclear technologies, a number of radiation accidents have occurred. Some of these accidents have resulted in significant health effects and occasionally in fatal outcomes. The application of technologies that make use of radiation is increasingly widespread around the world. Millions of people have occupations related to the use of radiation, and hundreds of millions of individuals benefit from these uses. Facilities using intense radiation sources for energy production and for purposes such as radiotherapy, sterilization of products, preservation of foodstuffs and gamma radiography require special care in the design and operation of equipment to avoid radiation injury to workers or to the public. Experience has shown that such technology is generally used safely, but on occasion controls have been circumvented and serious radiation accidents have ensued. 2. Reviews of radiation exposures from accidents have been presented in previous UNSCEAR reports. The last report containing an exclusive chapter on exposures from accidents was the UNSCEAR 1993 Report [U6]. 3. This annex is aimed at providing a sound basis for conclusions regarding the number of significant radiation accidents that have occurred, the corresponding levels of radiation exposures and numbers of deaths and injuries, and the general trends for various practices. Its conclusions are to be seen in the context of the Committee's overall evaluations of the levels and effects of exposure to ionizing radiation. 4. The Committee's evaluations of public, occupational and medical diagnostic exposures are mostly concerned with chronic exposures of …

sources and effects of ionizing radiation

Whole-body dynamic and parametric PET imaging has recently gained increased interest as a clinically feasible truly quantitative imaging solution for enhanced tumor detectability and treatment response monitoring in oncology. However, in comparison to static scans, dynamic PET acquisitions are longer, especially when extended to large axial field-of-view whole-body imaging, increasing the probability of voluntary (bulk) body motion. In this study we propose a generalized and novel motion- compensated PET image reconstruction (MCIR) framework to recover resolution from realistic motion-contaminated static (3D), dynamic (4D) and parametric PET images even without the need for gated acquisitions. The proposed algorithm has been designed for both single-bed and whole-body static and dynamic PET scans. It has been implemented in fully 3D space on STIR open-source platform by utilizing the concept of optimization transfer to efficiently compensate for motion at each tomographic expectation-maximization (EM) update through a nested Richardson-Lucy EM iterative deconvolution algorithm. The performance of the method, referred as nested RL-MCIR reconstruction, was evaluated on realistic 4D simulated anthropomorphic digital XCAT phantom data acquired with a clinically feasible whole-body dynamic PET protocol and contaminated with measured non-rigid motion from MRI scans of real human volunteers at multiple dynamic frames. Furthermore, in order to assess the impact of our method in whole-body PET parametric imaging, the reconstructed motion- corrected dynamic PET images were fitted with a multi-bed Patlak graphical analysis method to produce metabolic uptake rate (Ki parameter in Patlak model) images of highly quantitative value. Our quantitative Contrast-to-Noise (CNR) and noise vs. bias trade-off analysis results suggest considerable resolution enhancement in both dynamic and parametric motion-degraded whole-body PET images after applying nested RL-MCIR method, without amplification of noise. Keywords—PET; dynamic; 4D; whole-body; Patlak; EM; deconvolution; Richardson-Lucy; motion; intra-frame

Generalized 3D and 4D Motion Compensated Whole- body PET Image Reconstruction Employing Nested EM Deconvolution

Purpose: The variable resolution x-ray (VRX) CT scanner provides substantial improvement in the spatial resolution by matching the scanner's field of view (FOV) to the size of the object being imaged. Intercell x-ray cross-talk is one of the most important factors limiting the spatial resolution of the VRX detector. In this work, a new cell arrangement in the VRX detector is suggested to decrease the intercell x-ray cross-talk. The idea is to orient the detector cells toward the opening end of the detector. Methods: Monte Carlo simulations were used for performance assessment of the oriented cell detector design. Previously published design parameters and simulation results of x-ray cross-talk for the VRX detector were used for model validation using the GATE Monte Carlo package. In the first step, the intercell x-ray cross-talk of the actual VRX detector model was calculated as a function of the FOV. The obtained results indicated an optimum cell orientation angle of 28 degrees to minimize the x-ray cross-talk in the VRX detector. Thereafter, the intercell x-ray cross-talk in the oriented cell detector was modeled and quantified. Results: The intercell x-ray cross-talk in the actual detector model was considerably high, reaching up to 12% at FOVs from 24 to 38 cm. The x-ray cross-talk in the oriented cell detector was less than 5% for all possible FOVs, except 40 cm (maximum FOV). The oriented cell detector could provide considerable decrease in the intercell x-ray cross-talk for the VRX detector, thus leading to significant improvement in the spatial resolution and reduction in the spatial resolution nonuniformity across the detector length. Conclusions: The proposed oriented cell detector is the first dedicated detector design for the VRX CT scanners. Application of this concept to multislice and flat-panel VRX detectors would also result in higher spatial resolution. (C) 2011 American Association of Physicists in Medicine. [DOI: 10.1118/1.3555035]

/pdf/novel-detector-design-for-reducing-intercell-x-ray-cross-32bka1zxu6.pdf

Novel detector design for reducing intercell x-ray cross-talk in the variable resolution x-ray CT scanner: A Monte Carlo study

Background: To evaluate the impact of 18 F-FDG PET/CT on target volume delineation in gynaecological cancer. Methods: F-FDG PET/CT based RT treatment planning was performed in 10 patients with locally recurrent (n = 5) or post-surgical residual gynaecological cancer (n = 5). The gross tumor volume (GTV) was defined by 4 experienced radiation oncologists first using contrast enhanced CT (GTVCT) and secondly using the fused 18 F-FDG PET/CT datasets (GTVPET/CT). In addition, the GTV was delineated using the signal-to-background (SBR) ratio-based adaptive thresholding technique (GTVSBR). Overlap analysis were conducted to assess geographic mismatches between the GTVs delineated using the different techniques. Inter- and intra-observer variability were also assessed. Results: The mean GTVCT (43.65 cm 3 ) was larger than the mean GTVPET/CT (33.06 cm 3 ), p = 0.02. In 6 patients, GTVPET/CT added substantial tumor extension outside the GTVCT even though 90.4% of the GTVPET/CT was included in the GTVCT and 30.2% of the GTVCT was found outside the GTVPET/CT. The inter- and intra-observer variability was not significantly reduced with the inclusion of 18 F-FDG PET imaging (p = 0.23 and p = 0.18, respectively). The GTVSBR was smaller than GTVCT p ≤ 0.005 and GTVPET/CT p ≤ 0.005. Conclusions: The use of 18 F-FDG PET/CT images for target volume delineation of recurrent or post-surgical residual gynaecological cancer alters the GTV in the majority of patients compared to standard CT-definition. The use of SBR-based auto-delineation showed significantly smaller GTVs. The use of PET/CT based target volume delineation may improve the accuracy of RT treatment planning in gynaecologic cancer.

/pdf/impact-of-18f-fdg-pet-ct-on-target-volume-delineation-in-mxyr7i8q38.pdf

Impact of 18F-FDG PET/CT on target volume delineation in recurrent or residual gynaecologic carcinoma

The increasing number of imaging studies and the prevailing application of positron emission tomography (PET) in clinical oncology have led to a real need for efficient PET volume handling and the development of new volume analysis approaches to aid the clinicians in the clinical diagnosis, planning of treatment, and assessment of response to therapy. A novel automated system for oncological PET volume analysis is proposed in this work. The proposed intelligent system deploys two types of artificial neural networks (ANNs) for classifying PET volumes. The first methodology is a competitive neural network (CNN), whereas the second one is based on learning vector quantisation neural network (LVQNN). Furthermore, Bayesian information criterion (BIC) is used in this system to assess the optimal number of classes for each PET data set and assist the ANN blocks to achieve accurate analysis by providing the best number of classes. The system evaluation was carried out using experimental phantom studies (NEMA IEC image quality body phantom), simulated PET studies using the Zubal phantom, and clinical studies representative of nonsmall cell lung cancer and pharyngolaryngeal squamous cell carcinoma. The proposed analysis methodology of clinical oncological PET data has shown promising results and can successfully classify and quantify malignant lesions.

https://downloads.hindawi.com/journals/afs/2012/327861.pdf

Artificial neural network-statistical approach for PET volume analysis and classification

A new method to assess the scatter component in positron emission tomography (PET) based on estimating the low-frequency component corresponding to scattered events using ordered subsets - expectation maximization (OSEM) reconstructions is proposed in this paper and evaluated using Monte Carlo simulation studies, experimental phantom measurements and clinical studies The rationale of this method called Statistical Reconstruction-Based Scatter Correction (SRBSC) is that the image corresponding to scattered events in the projection data consists of almost low-frequency components of activity distribution and that the low-frequency components will converge faster than the high-frequency ones in successive iterations of statistical reconstruction methods such as OSEM The second assumption is that the high-frequency components will be smeared, ie filtered by the scatter response kernels A simple model has been devised to parameterize the scatter component using Monte Carlo simulations The unscattered component estimated using SRBSC was compared to the true unscattered component as estimated by Monte Carlo simulations for simple phantom geometries and clinically realistic source distributions Quantitative analysis was also performed on reconstructed images using simple metrics like the contrast, absolute concentration, recovery coefficient and signal-to-noise ratio The SRBSC method tends to undercorrect for scatter in most regions of the 3D Hoffman brain phantom, but gives good activity recovery values which average within 1% It was concluded that the proposed method improves image quality and the contrast compared to the case where no correction is applied and that an accurate modeling of the scatter component is essential for a proper scatter correction

Habib Zaidi

Papers

Generalized 3D and 4D Motion Compensated Whole- body PET Image Reconstruction Employing Nested EM Deconvolution

Novel detector design for reducing intercell x-ray cross-talk in the variable resolution x-ray CT scanner: A Monte Carlo study

Impact of 18F-FDG PET/CT on target volume delineation in recurrent or residual gynaecologic carcinoma

Artificial neural network-statistical approach for PET volume analysis and classification

Reconstruction-Based Estimation of the Scatter Component in Positron Emission Tomography