Friedrich Heuck

The advent in recent years of several new imaging modalities for the application in diag­ nosis and patient management has had an unprecedented impact on patient care. By per­ mitting the acquisition of information without intervention, these new modalities have made the diagnostic process more humane. They have also made possible the treatment of many disorders of the upper and lower urinary tract by means of interventional tech­ niques, replacing a number of surgical procedures. The editor of this volume has engaged international experts in radiology to describe the state of the art of radio log y of the upper urinary tract. Local and regional abnormalities are covered, but so too is the involvement of urinary structures in systemic disease. The radiologic approach and interpretation are combined with the presentation of pertinent clinical observations and important pathophysiologic concepts. The text is concise and the illustrations are appropriate. Up-to-date international bibliographies are provided. Both the text and the illustrations will serve as sources of information for the radiologists, urol­ ogists, nephrologists, gynecologists, and oncologists. Most importantly, the material is presented in such a way that practicing specialists dealing with urologic disorders, as well as physicians in training will benefit. We feel that it is timely to publish a present day treatise on urinary tract radiology in order to convey the contributions made by various newer imaging modalities to the diagnosis of urinary disorders.

Unsere Kenntnisse uber das Skelet als Organ und seine Veranderungen unter physio- logischen und pathologischen Bedingungen sind noch luckenhaft. N euere Forschungen haben sich intensiver mit morphologischen, chemischen und biologischen Vorgangen be- schaftigt, deren Kenntnis zum Verstandnis des Knochens als Stutzorgan sowie als Speicherorgan fUr Mineralien, aber auch zum Verstandnis der Bruchheilung, Pseud- arthrosenentstehung und der Knochentransplantationsfolgen unerlaBlich ist. Dem Radiologen fallt bei der Beurteilung nicht nur die Feststellung eines gerade eben vorhandenen Zustandes als Aufgabe zu, sondern auch die Einordnung dieses Zustandes in einen biologischen Geschehensablauf. Hierzu werden neb en Verlaufsbeobachtungen in zunehmendem MaBe auch zusatzliche Untersuchungsverfahren herangezogen werden mussen, wie die radiologische Bestimmung des Mineralgehaltes, die Klarung der Durch- blutungsverhaltnisse oder Studien mit Isotopen. Aus diesen Grunden erschien es notwendig, in einem allgemeinen Teil diese Grund- lagen zusammenzufassen und dem speziellen Teil, den Skeleterkrankungen und den speziellen Skeletbanden uber Wirbelsaule und Schadel, vorausgehen zu lassen. Hier ist noch vieles im FluB - eine Zusammenfassung des derzeitigen Wissens-Standes, aber auch der offenen Probleme kann daher nur Anregungen zu weiterer Forschung geben.

The aim of radiation protection standards is to make the radiation workplace as safe as is humanly possible. The gradual evolution over the last 20 years has been towards a more precise definition of the limits for occupational exposure. These have been created not only in terms of short-term effects but also more importantly in terms of long-term risks involving such problems as the potential for carcinogenesis and genetic change. In the United States the National Committee for Radiation Protection has recom­ mended that 5 rems (50 mSv) should remain as the maximum permissible dose equiva­ lent for total body exposure. This would represent the sum of internal and external ex­ posure and should be regarded as the upper limit allowed. The community of radiation users is required to conduct its operations in such a man­ ner that the absolute value of the individual's dose equivalent in rems does not exceed his age in years. There should be additional limits for tissues and organs based on short­ term effects. Therefore, individual organs are limited to dose equivalents low enough to ensure that the dose threshold values are not exceeded.