Bitewing radiography: A Literature Review

Introduction

 Diagnostic ionising radiation can cause physical damage to target tissues1, therefore a thorough understanding of dosimetry can optimise the quality of treatment and safety to patients. Radiation dose can be measured in terms of absorbed, effective and equivalent dose. Absorbed dose (Gy) is the energy (by ionising radiation) imparted per unit mass in an absorbing medium and is related to the number of ionising events in any biological target applying to all radiation exposures.1  When assessed, the absorbed dose correlates with delayed, cumulative and stochastic effects.1Equivalent dose is the sum of absorbed dose in a tissue from different types of contributing radiation multiplied by their respective radiation qualities.1 The International Commission on Radiological Protection (ICRP, 2007) defines effective dose (Sv) as the sum of the equivalent doses in principle tissues, each weighted by a tissue weighting factor (wT).2  The wT are generalised for all ages and genders, hence they do not apply to any specific individual or radiosensitive subpopulations (children or women).1The revised wT in relation to the head and neck are presented in Table 1, along with the figures derived from data on the risks of heritable disease and cancer initiation.2Note that the lens of the eye is not given a tissue wT by the ICRP.

According to ICRP, effective dose does not provide an individual-specific dose, thus it should not be used for epidemiological studies or as a predictive tool to determine future cancer risk.1, 2Rather, it should be used for dose assessment in planning and optimising radiological protection.1, 2 Potential detriment of an individual should be based on tissue radiation absorbed dose and dose-response relationships.1

Current protocols, such as ALARA (As Low As Reasonably Achievable) and its variations, were last updated in 2014 to better protect patients from excessive and unnecessary radiation exposure. ALARA call for the use of techniques such as collimation, which is the act of restricting the primary beam and scattered radiation. In intraoral imaging, this can be achieved through the use of different geometric open-ended collimators. In extraoral imaging, the size of the primary beam is restricted in accordance to age appropriate settings.

Recent advancements i