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

I hope that our contributions, among other develop-ments, will be used by many to reduce suffering,improve our health and extend the productivity andfulfilment of our lives. Equally important, I hope thatthe new biological insights will yield a betterunderstanding of ourselves as human beings and ofour relationship to our environment, so that we maybecome better stewards of a fragile Earth [1].Mario R. CapecchiThe key to optimal prostate cancer treatment is accuratetumour characterisation and staging. Indeed, while localisedprimary tumours can be treated with radical prostatectomy,metastatic tumours usually demand a systemic therapeuticregimen. As pointed out by Picchio et al. [ 2], molecularimaging techniques, such as PET, may be helpful in treatmentplanning in these patients and PET/CT, in particular, is usefulin different steps: (1) tumour characterisation and stagingfollowed by the selection of the most appropriate primaryapproach; (2) re-staging, and the choice of second-linetherapies to target possible sites of recurrence; and (3) diseasecourse and treatment efficacy monitoring.Since the most commonly used PET tracer,

PET-guided prostate cancer radiotherapy: technological innovations for dose delivery optimisation

Purpose: This study presents the performance assessment of various FDG‐PET image segmentation methods in pharyngolaryngeal squamous cell carcinoma using experimental phantom and clinical studies where the surgical specimen served as reference Method and Materials: Various PETimage segmentation techniques were evaluated including: 1) manual delineation, 2) four thresholding‐based methods (Nestle, Black, Biehl, and Schaefer), 3) the level set technique, 4) fuzzy clustering‐based segmentation (FCM), and (5) stochastic expectation maximization (EM) approach. A cylindrical phantom was filled with an 18F solution with an initial activity of 12.21 MBq/ml−1. Three spherical target inserts of 1.0, 2.0, and 3.0 cm diameter are inserted in the cylinder and were filled with 11C solution with an initial activity of 169.83 MBq/ml. A series of 10‐minute long scans were acquired, providing a range of tumour‐to‐background ratios (T/B) ranging from almost 14 to 1.15. Three activities are selected high activity (T/B=14.1), medium activity (T/B= 4.1), and low activity (T/B=1.5). The algorithms were also evaluated using clinical studies where segmentation results were compared to the 3D (Biological Tumour Volume) BTV defined by histology on PETimages of seven patients with T3–T4 laryngeal squamous cell carcinoma who underwent a total laryngectomy. The macroscopic tumour specimen was collected “en bloc”, frozen and cut into 1.7‐ to 2‐mm thick slices then digitized and used as reference Results: On the phantom data, Schaefer thresholding and level set provided the best performance, however, the clinical data seem to suggest that thresholding methods (with exception of Schaefer) and EM overestimated the average tumour volume while Schaefer, level set, and FCM underestimated it with FCM providing relatively the highest accuracy in terms of volume and overlap index. Conclusion: The BTVs delineated using the FCM technique seemingly was the most accurate segmentation technique and approximates closely the 3D BTV defined on the surgical specimen.

SU-GG-I-102: Comparative Methods for PET Image Segmentation in Pharyngolaryngeal Squamous Cell Carcinoma

This work aims at assessing x-ray scatter and more specifically the scatter to primary ratio (SPR) for the micro-CT subsystem of the FLEX Triumph™ preclinical PET-CT scanner. Two approaches were used: the experimental single blocker method and Monte Carlo (MC) simulations using the MCNP4C code. For the experimental setup, five cylindrical blockers with diameters ranging between 3.0 and 11.65 mm were used to assess the SPR using a polyethylene phantom (d=50mm). The beams energy influence was studied by scanning the phantom at 30, 50 and 80 kV (mag=1.3). Likewise, additional acquisitions at 50 kV were performed with a magnification of 2.0 to evaluate the impact of geometrical magnification and using a Plexiglas phantom (d=25mm) filled with water at 50 kV (mag=1.3) to assess the influence of the size and composition of the phantom. For each condition, the five blocker SPR results were linearly interpolated to obtain the SPR without the blocker. Central and peripheral SPR values were obtained by rotating the source and detector and were fitted with a Gaussian function. MC simulations were carried out using the MCNP4C code where the estimates were also fitted with a Gaussian function. The comparison showed that MC simulations can reproduce well the experimental results, at least in the region inside the phantom. The highest difference was obtained with the small phantom in the peripheral regions. The maximum SPR (0.562) was obtained at 30kV and magnification of 1.3 using the large phantom. The full SPR profile was calculated using MC simulations and used to express its dependency on beam energy and phantom diameter (quadratic), and air gap (asymptotic). The obtained results are in good agreement with theoretical predictions. MC is a very good alternative to experimental measurements of x-ray scatter in micro-CT imaging and can be used to validate novel scatter correction techniques. This will also improve the accuracy of CTAC on preclinical PET-CT systems.

Assessment of x-ray scatter for the micro-CT subsystem of the FLEX Triumph™ preclinical PET-CT scanner

Joint estimation of activity and attenuation in TOF-PET/MR using constrained Gaussian mixture models

Clinical PET imaging of the abdomen and thorax rely on standardised uptake values using static imaging but more robust quantification can be performed using dynamic protocols and estimating kinetic parameters from the dynamic PET data However quantitative parameters both in static and dynamic imaging suffer from patient motion In dynamic imaging the motion-induced data blurring and emission-attenuation mismatch results in erroneous time-activity curves potentially leading to erroneous parametric maps Furthermore the effects of motion on direct parameter estimates using 4D image reconstruction algorithms are not known In this work using a novel 5-D numerical body phantom we evaluate the impact of body motion on kinetic parameters in dynamic abdominal and thoracic PET imaging Furthermore we compared parameter estimates obtained using both conventional post-reconstruction analysis as well as direct 4D image reconstruction

Habib Zaidi

Papers

PET-guided prostate cancer radiotherapy: technological innovations for dose delivery optimisation

SU-GG-I-102: Comparative Methods for PET Image Segmentation in Pharyngolaryngeal Squamous Cell Carcinoma

Assessment of x-ray scatter for the micro-CT subsystem of the FLEX Triumph™ preclinical PET-CT scanner

Joint estimation of activity and attenuation in TOF-PET/MR using constrained Gaussian mixture models

Impact of motion on indirect and direct reconstruction of kinetic parameters from dynamic PET data