The Information Processing in Medical Imaging Conference is a biennial conference, held alternatively in Europe and in the United States of America. The subject of the conference is the use of computers and mathematics in medical imaging, the evaluation of new imaging techniques, image processing, image analysis, diagnostic decision making and related fields. The conference brings together the top specialists in the field (both scientists and medical doctors) and other participants doing active research on the subject of the conference. The success of a meeting primarily depends on the enthusiasm of the participants. It also greatly depends on the financial support as well as on the personal efforts of the technical staff and collaborators of the organizers. To all who made this conference a success, the members of the organizing committee want to express their sineere thanks. In particular, the organizers want to acknowledge the help received from: De Vice-Voorzitter van de Vlaamse Executieve De Minister van Onderwijs Het Nationaal Fonds voor Wetenschappelijk Onderzoek De Vrije Universiteit Brussel Adac Agfa-Gevaert Bruker Spectrospin Byk Belga Elseint Instituut voor Radioelementen, IRE Nucleobel Solco Sonotron VII TABLE OF CONTENTS Foreword. v A. VENOT, J.L. GOLMARD, J.F. LEBRUCHEC, L. PRONZATO, E. WALTER, G. FRIJA and J.C. ROUCAYROL: "Digital Methods for Change Detection in Medical lmages."

Conventional nuelear medieine proeedures study the dis- tribution of radiolabelled eompounds (radiopharmaeeutieals) in the body under physiologieal as well as under pathologieal eonditions. Beeause of their ability to visua- lise and to quantify the distribution of radiopharmaeeuti- eals within the body by means of external deteetors, nuelear medieine teehniques are basieally non invasive and funetion oriented. The spatial variation of the traeer distribution in the field of view, or the ehange in distribution during a time interval are interpreted as representing speeifie phy- siologie or pathophysiologie processes. As eompared to other diagnostie imaging teehniques, the spatial resolution of seintigraphie images is rather poor, their temporal resolu- tion is good. Faetors that will therefore determine the ultimate diag- nostie value of a seintigraphie study inelude 1. The speeifieity of the labelled eompounds for the process under study, 2. The resolution in time and space of the instrumentation, and its ability of measuring quantitatively tissue aetivity eoneentrations, 3. The formulation of physiologieal or pathophysiologieal models from whieh the distribution of the traeer ean be predieted. 2 While interpreting nuclear medicine data, the interrelations between these factors should permanently remain under consi- deration. The generalised use of minicomputers has resulted in major advances in information processing in nuclear medicine imaging procedures. Central to this is image digitisation.

Just prior to the 1982 Annual Meeting of the European Thyroid Association in Brussels, a number of outstanding experts in the field of X-ray fluorescence gathered at the Academisch Ziekenhuis of the Free University of Brussels in a joint effort to more clearly define the actual place and value of the latest newcomer among the techniques available for the in vivo assessment of thyroid function. It is the merit of Prof. M. Jonckheer to have organised this meeting and to have made available the work presented there to a larger public in the form of this monograph. Both, the meeting and the written accounts thereof are greatly appreciated by all thyroidologists who care for properly defining the genuine value of X-Ray fluorescence in scientific research and in clinical management of thyroid disorder. Three main conclusions can be drawn from the work presented 1. X-ray fluorescence has become a safe, convenient and reliable tool for measuring intrathyroidal iodine stores in vivo with an inter-assay reproducibility estimated at roughly 10% 2. X-ray fluorescence, used by expert hands, is a highly interesting tool to follow changes of intra thyroidal iodine stores in time, subsequent e. g. to the exposure of the thyroid gland to excess iodine 3. In contrast, no definite place of X-ray fluorescence as a technique in routine assessment of thyroid disease is yet at the horizon This latter conclusion may appear somewhat disappointing.

Just prior to the 1982 Annual Meeting of the European Thyroid Association in Brussels, a number of outstanding experts in the field of X-ray fluorescence gathered at the Academisch Ziekenhuis of the Free University of Brussels in a joint effort to more clearly define the actual place and value of the latest newcomer among the techniques available for the in vivo assessment of thyroid function. It is the merit of Prof. M. Jonckheer to have organised this meeting and to have made available the work presented there to a larger public in the form of this monograph. Both, the meeting and the written accounts thereof are greatly appreciated by all thyroidologists who care for properly defining the genuine value of X-Ray fluorescence in scientific research and in clinical management of thyroid disorder. Three main conclusions can be drawn from the work presented 1. X-ray fluorescence has become a safe, convenient and reliable tool for measuring intrathyroidal iodine stores in vivo with an inter-assay reproducibility estimated at roughly 10% 2. X-ray fluorescence, used by expert hands, is a highly interesting tool to follow changes of intra thyroidal iodine stores in time, subsequent e. g. to the exposure of the thyroid gland to excess iodine 3. In contrast, no definite place of X-ray fluorescence as a technique in routine assessment of thyroid disease is yet at the horizon This latter conclusion may appear somewhat disappointing.