Evaluating cone cut in rectangular collimation in intraoral radiography: application of ALADA and radiation stewardship

OBJECTIVE: Rectangular collimation is a popular method used in intraoral radiography to reduce patient exposure to ionizing radiation. One of the perceived drawbacks of rectangular collimation is the possibility of an increase in cone cut errors ultimately impacting the diagnostic value of the radiographs. Thus, the aim of this study was to explore the frequency of cone cut errors in radiographs taken using a rectangular collimator. MATERIALS AND METHODS: Radiographs taken using PSP plates at Academic Center for Dentistry Amsterdam in the Netherlands by staff and students from January to December 2015 were assessed for cone cut errors. The radiographs were grouped as bitewings, front teeth, inferior premolars and molars, and superior premolars and molars and categorized as no cone cut, cone cut but diagnostically usable, and cone cut but diagnostically not usable. The results were entered into Microsoft Excel and analyzed thereafter. RESULTS: A total of 53,684 radiographs were assessed, 79% had no cone cut errors and consequently 21% had some degree of cone cut. However, the diagnostic value was unaffected in 18% of the radiographs with cone cut. Only 3% of the radiographs were deemed diagnostically unusable due to cone cut. The most common area of cone cut was in the premolar and molar areas while cone cut in the front teeth was least likely to be diagnostically unusable. CONCLUSION: Cone cut from the use of a rectangular collimator does not seem to result in an increase of diagnostically unusable radiographs. Thus, rectangular collimation should be preferred as it decreases the amount of radiation exposure to the patient while producing diagnostically usable radiographs and thus allowing the dental professional to adhere to the ALADA principle and practice radiation stewardship. CLINICAL RELEVANCE: Scientific rationale for the study: rectangular collimation is a method used to reduce patient exposure to ionizing radiation; however, this benefit is negligible if radiographs must be retaken due to cone cut errors that make the radiograph diagnostically unusable. Therefore, the aim of this study was to explore the frequency of cone cut in radiographs taken using a rectangular collimator. Principal findings: cone cut was observed in 21% of the radiographs; however, only 3% of the radiographs were considered diagnostically unusable. Practical implications: rectangular collimation does not result in a high number of diagnostically unusable radiographs and should be used to reduce patient exposure to ionizing radiation.