The two general principles of radiological protection, applicable to the exposure of patients undergoing medical radiological procedures, are  justification and optimization. Justification of medical exposure involves weighing the diagnostic or therapeutic benefits of exposure against the potential for harm, taking into account the benefits and risks of available alternative techniques that do not involve exposure to ionizing radiation, while optimization involves maintaining exposure of patients to the minimum necessary to achieve the diagnostic or interventional objective. Dose limits do not apply to medical exposure as they may limit benefits to the patient. The emphasis is to keep the dose to the patient as low as reasonably possible (As Low As Reasonably Achievable - ALARA), consistent with clinical needs, obtained with the lowest dose possible, always taking into account the characteristics of the patient and the region under analysis  as well as clinical needs.

Diagnostic reference levels (DRL) represent a specified radiation dose for a given imaging study that should not be exceeded. Diagnostic reference level values vary based on local, regional, and national data. They are typically defined at the 75th percentile of a distribution of radiation doses. These values are defined for medical exposures considering standard patients that portray the analyzed scenario: national, regional, local or institutional. Typical CT values are based on quantities such as Computed Tomography Dose Volumetric Index (CTDIvol) and Dose-Length Product (DLP), but do not represent limits, only guiding values.

Monitoring the dose of tomographic exams is a tool for optimizing radiological protection that as been supported by professional and regulatory organizations. Diagnostic reference levels values that serve as a reference for the characteristics of the main regional clinical indications have not been determined in Manaus, and it is necessary to determine these as part of the improvement in radiological protection and patient safety processes. Objectives: To establish radiation dose reference values in terms of CTDI vol (Computed Tomography Dose Volumetric Index) and DLP (Dose-Length Product) for Computed Tomography (CT) examinations with the most common clinical indications carried out in a medical reference center in Manaus; to compare the typical values and the 75th percentile found for the institution with the values found in the literature.