Optimisation of protection for patients
Optimisation of protection for patients is also unique (ICRP Publication 85 Avoidance of Radiation Injuries from Medical Interventional Procedures; ICRP Publication 86 Prevention of Accidents to Patients Undergoing Radiation Therapy; ICRP Publication 112 Preventing Accidental Exposures from New External Beam Radiation Therapy Technologies; ICRP Publication 121 Radiological Protection in Paediatric Diagnostic and Interventional Radiology). In the first place, radiation therapy is entirely different from anything else in that the dose to a human being is intentional and its potentially cell-killing properties the very purpose of the treatment. In such cases, optimisation becomes an exercise in minimising doses (and/or their deleterious effects) to surrounding tissues without compromising the pre-determined and intentionally lethal dose and effect to the target volume.
The optimisation of radiological protection for patients in medicine is usually applied at two levels: (1) the design, appropriate selection, and construction of equipment and installations; and (2) the day-to-day methods of working (i.e. the working procedures). The basic aim of this optimisation of protection is to adjust the protection measures for a source of radiation in such a way that the net benefit is maximised. The optimisation of radiological protection means keeping the doses ‘as low as reasonably achievable, economic and societal factors being taken into account’, and is best described as management of the radiation dose to the patient to be commensurate with the medical purpose.
In optimisation of protection of the patient in diagnostic procedures, such as diagnostic radiology and [Interventional procedures]], again the same person gets the benefit and suffers the risk, and again individual restrictions on patient dose could be counterproductive to the medical purpose of the procedure. Therefore, source-related individual dose constraints are not relevant. Instead, diagnostic reference levels (DRLs) (Publication 135) for a particular procedure, which apply to groups of similar patients rather than individuals, are used to ensure that doses do not deviate significantly from those achieved at peer departments for that procedure unless there is a known, relevant, and acceptable reason for the deviation. This is in contrast to the Commission’s usual balancing of utilitarian protection policies based on collective doses against deontological safeguards using dose constraints for the individual. The policy for radiological protection in medicine is that the radiation exposure be commensurate with the medical purpose.
In radiation therapy, the aim is to eradicate the neoplastic target tissue or to palliate the patient’s symptoms. Some tissue reactions to surrounding tissue and some risk of stochastic effects in exposed non-target tissues are inevitable, but the goal of all radiation therapy is to optimise the relationship between the probability of tumour control and normal tissue complications. It is necessary to differentiate between the dose to the target tissue and the dose to other parts of the body. If the dose to the target tissue is too low, the therapy will be ineffective. The exposures will not have been justified and the optimisation of protection does not arise. However, the protection of tissues outside the target volume is an integral part of dose planning, which can be regarded as including the same aims as the optimisation of protection.