This rule comes from the fact that 1.15 5 ~2.0. Since x-ray exposure goes approximately as kVp 5 and we generally donвЂ™t think in powers of 5 a well known approximation is typically used called the 15% rule of kVp of radiography. This is one reason why mammography exams are performed at a low kVp and a large abdominal x-ray is performed at a higher kVp. Therefore, the general rule is use the lowest kVp which will still provide a good exposure on the image receptor. As the kVp is increased there is also a higher contribution of Compton scatter events. On the other hand as the kVp is increased the relative contrast between tissues in the body is reduced ( x-ray contrast). This is a good thing for passing through large anatomy. Since it does impact the x-ray contrast changes to the kVp of an exam need to be considered more carefully than changing the mA, but there are definitely times when it is needed.ДЄs the kVp is increased the x-ray beam becomes more penetrating. Additionally, the kVp also changes the inherent contrast in the x-ray images. This strong dependence on the kVp for the exposure at the image receptor is because of the higher flux and stronger penetration of higher kVp imaging. The kVp is the most important technical parameter as it has a very strong dependence on the x-ray exposure (kVp 5). For more details on the x-ray tube and influence of mA check out our articles on x-ray generation and beam quality. Increasing the tube current is actually just providing more electrons that with smash into the x-ray target and thus produce more x-ray photons. The tube current and time in the x-ray exam are the parameters that are most frequently changed and you should consider this as your first go-to adjustment in order to change the x-ray exposure without impacting the quality of the exam in other ways. At the end of the this post we put these into one big equation, but you can see from this table that there are really just FIVE SIMPLE RELATIONSHIPS that you need to know to master your technical parameters. In the following sections we will describe each in a bit more detail and link to other resources where these concepts were introduced and covered more completely.ДЄs a technologist you need to commit these dependencies to memory so that you can have an intuitive or gut feeling about the changes in technical parameters and this will help you to provide the best acquisitions for your patients. The technical parameters which control the exposure measured on the detector and also the radiation dose delivered to the patient are summarized in the table below and include (mA, kVp, s, SID and Bucky Factor). In this scenario it is really important to understand the technical parameters and their influence the exposure, so that when changing parameters you do not end up under-exposing or over-exposing the image receptor (film, CR or DR). As a technologist you are often faced with the situation where you need to make a change to a protocol but want to keep the exposure on the detector the same.

Double exposure x ray