Radiation Emitting Devices Regulations — 1
Definitions 1 The following definitions apply in this Part. aluminum means aluminum that has a degree of purity of 99.9% or higher and a density of 2.70 g/cm 3 . ( aluminium ) aluminum equivalent means the attenuation equivalent of an object, expressed in thickness of aluminum. ( équivalent en aluminium ) coefficient of variation means the ratio of the estimated standard deviation to the mean value of a series of measurements, determined by the formula The coefficient of variation, determined by the formula “C equals S divided by X bar, which is also equal to one divided by X bar multiplied by, open square bracket, sum from i equals one to n, open parentheses, X sub i minus X bar, close parentheses, squared, divided by n minus one, close square bracket, to the power of one half”. where C is the coefficient of variation; S is the estimated standard deviation; X is the mean value of the measurements; X i is the value of the i th measurement; and n is the number of measurements. ( coefficient de variation ) dental volumetric reconstruction means reconstruction of the three-dimensional attenuation distribution of all or part of the irradiated volume from a series of two-dimensional projections that are produced by an X-ray beam on an X-ray image receptor moving around the head of a patient. ( reconstruction dentaire volumétrique ) deviation , in respect of any parameter of dental X-ray equipment, means the percentage error between the measured value and the value indicated either on the equipment or in the accompanying information. ( variation ) digital X-ray image receptor means an X-ray image receptor that has a conversion method which is electrically powered. The conversion method may include single-step direct conversion or multi-step indirect conversion. ( récepteur numérique d’image radiologique ) effective image reception area means the part of the image reception area that is configured to receive an X-ray pattern that can be processed for display or storage. ( surface réceptrice de l’image efficace ) extra-oral , in relation to dental radiography, means that the X-ray image receptor is located outside the oral cavity. ( extra-oral ) hand-held , in respect of transportable dental X-ray equipment, means that the equipment, once it is placed into service, is held in or supported by the hand. ( portatif ) intra-oral , in relation to dental radiography, means that all or part of the X-ray image receptor is located inside the oral cavity. ( intra-oral ) irradiation time means the duration of an irradiation, measured as the interval between the instant when the air kerma rate rises for the first time to a value of 50% of the peak value and the instant when it drops for the last time below 50% of the peak value. ( temps d’irradiation ) lead equivalent means the attenuation equivalent of an object, expressed in thickness of lead. ( équivalent en plomb ) loading factor means a factor the value of which influences the X-ray tube load. It includes the following: (a) in the case of an X-ray beam that is produced by the discharge of the capacitor through an X-ray tube, the X-ray tube voltage and the amount of capacitor charge; (b) in the case of a field emission device in which the emission of electrons from the cathode is due solely to the action of an electric field, the X-ray tube voltage and the number of pulses; and (c) in any other case, the X-ray tube voltage and either (i) the X-ray tube current and irradiation time, or (ii) the current time product. ( paramètre de charge ) mode of operation means the technical state that is defined by a configuration of several predetermined loading factors and other settings for radiography or radioscopy, selectable simultaneously by the operation of a single control. ( mode de fonctionnement ) rectification type means the process by which the X-ray generator of dental X-ray equipment converts high voltage to X-ray tube voltage. ( type de redressement ) transportable , in relation to dental X