Several papers on recurrent imaging procedures with ionising radiation on the same patient have been published in the recent years [18,19,20,21,22,23]. Authors have focussed on patients undergoing recurrent CT exams that leads to cumulative effective dose (CED) of ≥ 100 mSv. Published data on the number of patients with cumulative effective doses ≥ 100 mSv ranged from 0.6 to 3.4% in CT and around 4% in interventional radiology. Eighty per cent of patients having a CED of ≥ 100 mSv had an oncological disease [18, 22].
The topic is relevant to improve justification and optimisation for the imaging procedures in the group of patients with high CED dose values. However, some authors  have alerted on several issues as if previous diagnostic radiation exposures should affect decisions on future examinations, concluding that bringing dose history into the decision process for justifying examinations may be not relevant for radiation risk and, rather than improving patient safety, would unnecessarily restrict access to radiation-based diagnostic examinations. In any way, the clinical context should be considered when highlighting the risks.
Getting 10 CTs during one hospital stay in a few days is different in radiation risk from getting 10 CTs to follow disease over a period of 10 years. Cumulative doses from recurrent exposures may be useful information but converting these cumulative doses into radiation risks for individual patients should be avoided. The IAEA is preparing a “Joint Position Statement and Call for Action for strengthening radiation protection of patients undergoing recurrent radiological imaging procedures”.
Dose management systems (DMS) may have a relevant role alerting referrers, radiologists and radiographers on previous examinations to profit from the existing diagnostic information and help to select the best imaging modality and protocol to be used in future . Radiation doses may also be useful to inform patients on the benefits of the procedures and radiation risks, and on the potential need of a clinical follow up for interventional procedures if the skin doses may be near trigger levels [26, 27]. Refinements in the application of the justification criteria for these groups of patients should be considered.
One difficulty in many countries is the lack of a central data base for patient dose values and the difficulty to get the dose values from procedures carried out in different hospitals. Patient DMS may alert on cumulative high doses and this information should be available to the referrers and practitioners .
It should be noted that in the European Union, the directive 2013/59/EURATOM , requires individual optimisation, the evaluation of patient doses for some of the X-ray examinations and the capacity to transfer the information on the relevant parameters for assessing the patient dose, to the record of the examination. Information relating to patient exposure should be part of the report of the medical radiological procedures.
Sometimes referrers have little if any knowledge of patients’ imaging histories, individual CED can be useful. With this information, radiologists, referrers and radiographers can make rational decisions regarding further imaging safely. Of course, critically ill patients, will never face delays or denials of CT studies in life-threatening situations . The decision for any imaging procedure should always be taken by the qualified practitioner and the estimated cumulative dose (if available) should never be an impediment to perform an imaging procedure if it is clinically indicated.
Cumulative dose may be used to refine, in some cases, the justification criteria (at the 3rd level, for individual patients) and the optimisation criteria for the next coming procedures to use low dose protocols if possible, and in some interventional procedures, using strategies to avoid skin radiation injuries. It is relevant to have alerts in the cumulative dose in the DMS but it is important to be aware that these systems are not always inter-connected between different hospitals in a city and country.
Personalised criteria for radiation protection in some patients (in parallel with the current approaches of the ‘personalised medicine’) should also be considered. The opinion of the patient needs to be taken into account. Some patients may accept additional radiation risks to confirm a diagnosis (e.g., a new CT). The result of this additional procedure may involve a relevant psychological benefit for the patient . This may be considered as an ethical value concerning the patient autonomy to accept the radiation risk.