Over the past decade, the number of positron emission tomography/computed tomography (PET/CT) imaging procedures has increased substantially. This imaging technique provides accurate functional and anatomical information, particularly for oncological applications. Separately, both PET and CT are considered as high-dose imaging modalities. With the increased use of PET/CT, one could expect an increase in radiation doses to staff and patients. As such, major efforts have been made to reduce radiation dose in PET/CT facilities. Variations in working techniques have made it difficult to compare published results. This study aimed to review the literature on proposed methods to reduce patient and staff dose in clinical PET/CT imaging. A brief overview of some published information on staff and patient doses will be analysed and presented. Recent trends regarding radiation protection in PET/CT imaging will be discussed, and practical recommendations for reducing radiation doses to staff and patients will be discussed and summarised. Generally, the CT dose component is often higher in magnitude than the dose from PET alone; as such, focusing on CT dose reduction will decrease the overall patient dose in PET/CT imaging studies. The following factors should be considered in order to reduce the patient's dose from CT alone: proper justification for ordering contrast-enhanced CT; use of automatic exposure control features; use of adaptive statistical iterative reconstruction algorithms; and optimisation of scan parameters, especially scan length. The PET dose component can be reduced by administration of lower activity to the patient, optimisation of the workflow, and appropriate use of protective devices and engineered systems. At the international level, there is wide variation in work practices among institutions. The current observed trends are such that the annual dose limits for radiation workers in PET/CT imaging are unlikely to be exceeded.

Aim:The purpose of this retrospective study was to determine the prevalence of hypodontia and to ascertain the need of interdisciplinary treatment for ensuing esthetic and functional problems in a target population of Al-Jouf Province, Saudi Arabia.Subjects and Methods:Using a dental administration software tool, a total of 1267 patients who presented to the outpatient clinics of the Orthodontic and Prosthodontic Departments between March 2015 and January 2016 were identified. Of those, 694 were females and 573 were males. All permanent teeth were investigated, except third molars.Results:The prevalence of hypodontia was 6.1%. The difference between genders was not statistically significant (P = 0.597) although female hypodontia prevalence was higher than males (6.6% and 5.5%, respectively). The majority of patients had one or two missing teeth. There were no significant differences between right and left sides for any particular tooth. The most commonly missing teeth were mandibular second premolar (40.1%), followed by the maxillary lateral incisor (20.4%) and then the maxillary second premolars (12.6%).Conclusions:The prevalence of hypodontia in Al-Jouf Province, Saudi Arabia, was within the average values portrayed in the majority of the published literature. The majority of affected individuals had one or two missing teeth. None of the patients examined had more than four missing teeth. There were no significant differences in the distribution of hypodontia between the affected jaws according to gender. Although less prevalent, considerable cases of bilateral missing teeth were found in the present study which necessitates the need for urgent interdisciplinary intervention and management.