A discussion with Dr. John Ludlow, a distinguished researcher in imaging technology and radiation dose
Cone beam 3D imaging is evolving into a “must have” for the innovative dental office. The added dimension offers a “surgical view” that adds precision to treatment planning and implementation. While achieving quality 3D images is important, capturing scans responsibly with the lowest radiation dose possible, also takes top priority. Dr. John Ludlow, a distinguished researcher in imaging technology and radiation dose, has recently published his newest study comparing doses from the new i-CAT model of CBCT technology, the i-CAT FLX, with those from conventional 2D and medical CT imaging alternatives. His valuable article offers clinicians information to make prudent decisions about their imaging options for the best interests of their patients and their practices.
In this interview with i-CAT, Dr. Ludlow discusses the research and its implications to dentistry.
Q: What is the purpose of dental dose studies?
A. Dose is important within the context of biologic risk. The principal risk from diagnostic imaging is cancer developing many years following x-ray exposure. Low doses associated with dental diagnostic radiography have low risks. Dosimetry allows us to compare the risks of different radiographic examination alternatives.
Q: Why are the studies important?
A. These studies allow practitioners to compare the relative risk of different examinations, techniques, and equipment. Together with information on image quality and diagnostic utility, practitioners can make evidence-based decisions on when to prescribe radiographic imaging and what technologies and techniques to use in acquiring diagnostic images.
Q: How are these studies performed?
A. The ICRP has recommended that the calculation of effective dose be used to compare the biologic risk of different techniques. Because of differences in location of radiosensitive structures such as the thyroid gland due to age- related development, we use both adult- and child-sized phantoms. We place small dosimeters at the location of each of the radiosensitive tissues in the head and neck area. We place calibrated and cleared dosimeters in the phantom, position the phantom for imaging, expose with the desired technical factors, read the absorbed dose using a specially designed reader, and use these readings in the calculation of effective dose. Because of the importance of image quality and its direct relationship to dose, we are also using a variety of phantoms to measure several parameters of image quality.
Q: Can you comment on the i-CAT Quick Scan+ feature in terms of its comparison to 2D digital pans?
A. The Quick Scan+ image volume provides 3D information with minimal geometric distortion that is unavailable in any 2D image and at a comparable dose. While reductions in dose are typically accompanied by reductions in image resolution, these low dose volumes may be useful for tasks such as mid-treatment assessment of orthodontic patients for root position and angulation within the arch. They may also be useful for implant diagnostics in some situations. On the other hand, the reduced resolution of cone beam imaging in general, as well as potential increased noise and metal artifact effect, are not as valuable as conventional panoramic imaging for certain diagnostic tasks, such as caries detection. Additional studies are needed to make practitioner choice of imaging parameters and patient dose more “evidence based.”
Q: When/where should our readers look for your i-CAT study?
A. The paper detailing the i-CAT FLX dosimetry study and results is published in the December issue of the American Journal of Orthodontics and Dentofacial Orthopedics.
Q: What is your background in dental dose studies; how long have you been performing these studies for 2D and 3D equipment?
A. I became interested in the subject of radiation risk and dosimetry during my graduate training in Oral Diagnosis and Radiology at the University of Michigan. Albert Richards, who did pioneering work demonstrating that the pointed cone was an important source of scatter radiation in dental radiography, was one of my mentors. His work led to the replacement of the pointed cone with the open cylinder that we all use today. He later chaired the NCRP committee that developed the first guidelines for the safe use of x-ray imaging in dentistry (Dental X-Ray Protection – NCRP Report No. 35). Another of my mentors and a co-author is Sharon Brooks, who has published a number of studies and review articles on radiation dose and risk reduction strategies. My graduate thesis “Image analysis and dosimetric comparison of intraoral radiographic imaging systems: Intraoral xeroradiography, conventional D and E speed periapical films and experimental E and F speed folded film techniques,” was inspired by Professor Richards and directed by Dr. Brooks. That was back in 1983. My current approach of using human equivalent phantoms to calculate effective dose and comparative risk of different radiographic examinations began in 2002 at the University of North Carolina. I was curious to see how doses from the new CBCT technology compared with those from conventional 2D and medical CT imaging alternatives.
To access the Abstract for Dr. Ludlow’s latest research on radiation dose, visit: http://www.ajodo.org/article/S0889-5406%2813%2900774-9/abstract?source=aemf
Ludlow JB, Walker C. Assessment of phantom dosimetry and image quality of i-CAT FLX cone-beam computed tomography. Am J Orthod Dentofacial Orthop. 2013;144(6):802-817.
Dr. Ludlow is renowned for his research in radiography. He is a professor in the radiology section of the Department of Diagnostic Sciences and General Dentistry at the University of North Carolina School of Dentistry. He is a diplomate of the American Board of Oral Medicine (ABOM) and of the American Board of Oral Maxillofacial Radiology (ABOMR). He is past president of the ABOMR, and past director of the ABOM. Dr. Ludlow has published more than 90 scientific manuscripts and was an AAOMR Weurhmann Prize winner for the best radiology research paper in 2006-7 and 2010-11.
Dr.Ludlow is not an employee nor does he have any financial interest in Imaging Sciences International, LLC.