BS EN 60613-2010 pdf download.Electrical and loading haracteristics of X-ray tube assemblies for medical diagnosis.
The purpose of this annex is to state the general objectives and approach used in creating the 3d edition of this standard, and to clarify the inclusion of those items which are substantially
new to this edition, as well as to clarity why some items are no longer described.
A.2 History: basis of 1 and 2 editions
The subject matter of these earlier editions was the electrical and thermal ratings of medical X-RAY TUBE ASSEMBLIES and their LOADING characteristics. Therefore, the thermal/electrical construction and operating mechanisms of X-RAY TUBES existing at the time of the earlier editions of the standard had a significant impact on the content of those early versions. Historically, medical X-RAY TUBES have been primarily constructed with glass ENVELOPES which act as the insulating support between the electrically charged ANODE and CATHODE electrodes. As such, it was not necessary or practical to define the electrical potential of this insulating ENVELOPE, which takes on an ambiguous charge state at any particular point of its surface. It was sufficient to state the potential difference between the ANODE and the CATHODE, or the potential of these electrodes relative to earth. Regarding the thermal/LOADING characteristics, most medical rotating ANODE X-RAY TUBES were constructed in such a way as to temporarily store the heat generated in the bremsstrahlung process and then dissipate it through the very non-linear thermal RADIATION process. Further, at the time of the earlier editions, applications were primarily directed at RADIOGRAPHY. In the meantime, vascular and CT applications, implying different LOADING conditions (relatively long exposures. heavy PATIENT throughput) have to be considered.
A.3 Problems and solutions: objectives of the 3d edition
A.3.1 General
Technical advancements in X-RAY TUBE design have lead to improvements, particularly in the thermal operation of X-RAY TUBES that have made the application of the previous edition of the standard inadequate. The main advancements and their impacts on the application of the standard are described below.
A.3.2 Advent of metal/ceramic ENVELOPE construction
One of the advancements that have been widely adopted in the industry, especially for high. power X-RAY TUBES, is the use of metallic ENVELOPES, often with ceramic, i.e. non-glass insulators. These ENVELOPES can carry a substantial traction of the overall X-RAY TUBE CURRENT during operation as backseattered ELECTRONS from the TARGET are collected on the inner surfaces of the metallic ENVELOPE and conducted back through to the HIGH-VOLTAGE GENERATOR. Because it is important to know what the intended electrical connection scheme is between the tube and generator, this edition of the standard has added a section of terms and definitions specifically related to the ENvELOPE’S electrical configuration.
At the same time, changes in tube design made these defined characteristics less useful for estimating the thermal performance of a given X-RAY TUBE. First, rotating ANODE heat storage ratings increased rapidly with the advent of high-throughput CT systems (and to some degree with certain cardio-vascular X-ray applications). The nature of the construction of high storage ANODES is such that thermal time lags within the TARGET disk are often significant and cannot be adequately modelled by the simple heating/cooling assumptions rooted in the previous versions of the standard. Second, in more recent years, innovations in the cooling of rotating ANODES has lead to cooling behaviours that are quite different from those of the assumed radiation-dominated models of the older versions of the standard. With these advancements and others on the horizon, it became apparent that the usefulness of the older definitions was diminished and that a new approach was called for.
Foremost, the new standard should better enable the description and comparison of the “clinically relevant” performance of the X-RAY TUBE, as a service to the PATIENT and customer community. With this approach in mind along with a few other “clean-up” objectives, the changes to the 3Id edition of the standard were made based on the following list of goals:
Wherever possible, eliminate definitions that take special laboratory conditions to verify, such as heat content, and replace them with definitions that are verifiable by an end-user, such as power and time. An example of the application of this goal is to specify the initial thermal state of an ANODE in terms of a steady-state CYCLE TIME, which can be reproduced in a clinical setting, Instead of a thermal storage state (HU or joules), which can only be directly verified in a laboratory setting. Heat units (HU) had been introduced in the past to compare multipulse X-RAY GENERATORS to single or 2-pulse X-RAY GENERATORS.
Apply definitions that represent clinically relevant conditions. Thus, for example, move away from defining the NOMINAL ANODE INPUT POWER for a CT tube at the traditional exposure time of 0,1 s, since this is not a common technique for typical clinical scan sequences (hence, leading to the new definition of NOMINAL CT ANODE INPUT POWER). Further, as PATIENT throughput is highly relevant for both clinical applications and for the thermal characteristics of the X-RAY TUBE, the new term “CYCLE TIME has been introduced. The notion of CYCLE TIME is the new approach for defining the NOMINAL ANODE INPUT POWER, namely defining that power for an indefinite series of PATIENTS/such LOADINGS, hereby simulating daily practice.
• Strive for a minimum set of power-definitions, although there are many different “clinically relevant conditions” which each could lead to a thermal rating definition tuned to the particular condition. Ultimately, one NOMINAL radiographic rating and one NOMINAL CT- rating appears to cover the clinical conditions sufficiently. For the radiographic rating, the traditional exposure time of 0,1 s covers also the traditional reference exposure time of 1 ,0 s for certain applications, such as mammography and dental X-ray because the loadability at 1 ,0 s exposure is not much different from the loadability at 0,1 s exposure for these applications.
• Choose SPECIFIED conditions for the definitions that are clinically aggressive, but realistic. Since the clinical usage parameters of a given type of X-RAY TUBE are wide-ranging.BS EN 60613-2010 pdf download.