Abstract
CBCT: Wide Range of Clinical Applications and Wide Range of Doses
This publication on radiological protection in cone beam computed tomography (CBCT) is both timely and practical. Previous ICRP publications have addressed managing the dose in patients undergoing computed tomography (Publication 87), and managing patient dose in multi-detector computed tomography (MDCT) (Publication 102) (ICRP, 2000a, 2007a). While some of the same principles apply to CBCT, new challenges exist. CBCT is a technology that is becoming more prevalent in clinical practice. These scanners extend the use of computed tomography (CT) into new clinical environments and by new practitioners, not all of whom have had the radiation safety training that radiological technologists, medical physicists, radiologists, and radiation oncologists have traditionally received. In addition, this technology is in evolution, and opportunities exist for device manufacturers to standardise dose displays. Thus, there is a need for education, guidelines, and standardisation in the industry.
Over the past decades, conventional CT has been ‘game-changing’ technology in patient care. Abdominal CT scans have replaced more invasive surgical procedures. Head CT scans and CT angiography have replaced many catheter-based angiograms. In a survey of 235 internists, CT and magnetic resonance imaging ranked highest on the list of innovations whose loss would have the greatest adverse effect on patients (Fuchs and Sox, 2001). CT ranked ahead of several mainstream medical technologies such as gastrointestinal endoscopy, balloon angioplasty, and coronary artery bypass grafts. However, use of CT imaging comes with responsibility. Knowledge and tools are needed to balance the benefits and the harms. Now, as CBCT is used in other clinical areas by other providers, the need for education, standardisation, and guidelines presents an opportunity that must be met.
The use of CBCT spans a wide range of clinical specialties and procedures: radiotherapy; orthopaedics; urology; dental/maxillofacial; neurointerventions; and vascular and non-vascular interventions. Patient dose also demonstrates a large range, from <1 mGy for organ absorbed dose to >400 mGy for skin dose. This range could be even wider depending on the number of CBCT scans performed and the complexity of intervention. This publication provides practical guidance for dose management in general and in specific clinical settings.
Dose reduction comes with trade-offs. This will require standard measurements of both dose and image quality across all manufacturers. For equipment used for fluoroscopy and CBCT, the aggregate dose to the patient for the entire procedure should be available. These data should be displayed on the operator console, and should be available for incorporation into the electronic health record. There are many ways to reduce dose. These include the design of CBCT equipment and how the equipment is used in specific clinical settings. This publication appropriately reinforces fundamental concepts such as ‘as low as reasonably achievable’. However, this publication also addresses another critical source of dose reduction. One of the best ways to reduce dose is to ensure that the imaging is appropriate or clinically indicated. Conventional CT examinations may be performed that do not represent the most appropriate imaging test for the clinical question being asked. Multiple strategies have been developed to address unnecessary use of imaging overall (Bernardy et al., 2009). Guidelines on appropriate use of CBCT need to be widely adopted.
In an era of population health, further development and use of CBCT should be driven by appropriate clinical need, balanced with risk to patients and workers. This publication provides a helpful direction for policy makers, imaging professionals, medical physicists, and manufacturers to optimise protection of both patients and workers, while preserving the expectation of high diagnostic yields from imaging and excellent clinical outcomes.
James V. Rawson