Tests show Planmeca’s ProMax 3D Mid CBCT ULD scans “As effective as standard”
Research by JB Ludlow from the University of North Carolina-Chapel Hill School of Dentistry, and J Koivisto from the University of Helsinki Department of Physics, raised concerns about the effects of increased use of ionizing radiation in diagnostic medical examinations and looked at effective measures for reducing radiation dosage.
The demographic covered by the research was North America, and it discovered that over the last 20 years the annual per capita dose of ionizing radiation received by the US population from all sources has doubled (1). Studies show the risk of this exposure to be signiﬁcant, and it has been estimated that from 1.5% to 2% of all US cancers may be attributed to computed tomography (CT) studies alone (2). It would be interesting to see similar work carried out in the UK.
Ludlow/Koivisto discovered that the use of CT scans in children delivering cumulative doses of about 50 mGy might almost triple the risk of leukaemia and doses of about 60 mGy might triple the risk of brain cancer (3). The range of doses produced by dental CBCT units is large, with some examinations approaching doses associated with medical CT imaging (4). Dosimetry of CBCT examinations for paediatric patients has not been established for many units that are currently used in orthodontic imaging
The purpose of the Ludlow/Koivisto study was to evaluate doses resulting from various combinations of ﬁeld size and exposure parameters on child and adult phantoms using a Planmeca ProMax 3D Mid CBCT unit. A second aim was to acquire contrast/noise ratio (CNR) and modulation transfer function (MTF) data to examine the relationship of image quality to examination radiation dosage.
The ProMax 3D Mid CBCT scanner was used to obtain results from combinations of ﬁeld size and exposure parameters that might be used for orthodontic diagnosis. Speciﬁcally, the researchers were looking at a protocol called “ultra low dose” (ULD) involving reduced exposure when compared with standard x-ray imaging. CNR and MTF data were calculated as quantitive measures of image quality.
Doses resulting from various combinations of ﬁeld size, exposure protocol, and child or adult anthropomorphic phantoms were measured with Optical Stimulated Luminescent (OSL) dosimetry using previously validated protocols (5,6).
OSL dosimeters were placed at 24 locations on phantom heads representing a 10-year-old child and an adult, and multiple exposures made for each dosimeter run. Dose values were adjusted for the sensitivity of the dosimeters to an eﬀective kV of the x-ray source, and doses were determined in the organs and tissues listed in the International Commission on Radiological Protection (ICRP) report 103 (7).
The researchers concluded that while the risk from dentomaxillofacial imaging is small for an individual, when multiplied by the large population of patients exposed to diagnostic imaging, radiation risk becomes a signiﬁcant public health issue.
Therefore, they suggest, strategies to reduce patient doses and keep those doses “as low as reasonably acceptable” (ALARA) are desirable. An average reduction in dose of 77% was achieved using the ProMax 3D Mid CBCT ULD protocols when compared with standard protocols.
While this dose reduction was signiﬁcant, the researchers found no statistical reduction in image quality between ULD and standard protocols, which suggests that – using the right scanning technology – patient doses can be greatly reduced without loss of diagnostic quality.
Ludlow/Koivisto also said that: “Further investigation of the diagnostic eﬃcacy of ULD scans in orthodontic and orthognathic surgical treatment planning is indicated.”
More information about the Planmeca ProMax 3D Mid CBCT scanner can be found by visiting https://www.planmeca.com/Imaging/3D-imaging/Planmeca-ProMax-3D-Mid/
1. National Council on Radiation Protection and Measurements. Ionizing Radiation Exposure of the Population of the United States (Report No. 160), Bethesda, MD. 2009, The Council
2. Brenner DJ, Hall EJ. Computed tomography‐an increasing source of radiation exposure. N Engl J Med. 2007;357:2277‐84
3. Pearce MS, Saloj JA, LiHle MP, McHugh K, Lee C, Kim KP, Howe NL, Ronckers CM, Rajaraman P, W Cram AW, Parker L, Berrington de González A. Radiation exposure from CT scans in childhood and subsequent risk of leukaemia and brain tumours: a retrospective cohort study. Lancet 2012:380:49‐505
4. Ludlow JB, Timothy R, Walker C, Hunter R, Benavides E, Samuelson DB, Scheske MJ. Eﬀec.ve Dose of Dental Cone Beam CT‐ a meta analysis of published data and additional data for 9 CBCT units. Dentomaxillofac Radiol. 2014;44:20140197
5. Ludlow JB, Ivanovic M. Compara.ve Dosimetry of Dental CBCT Devices and 64 row CT for Oral and Maxillofacial Radiology Oral Surg Oral Med Oral Pathol Oral Radiol Endodont 2008;106:930-‐938.
6. Ludlow JB, Walker C. Assessment of phantom dosimetry and image quality of i-‐CAT FLX CBCT. American Journal of Orthodontics & Dentofacial Orthopedics 2013;144:802-‐17
7. Valentin J. The 2007 Recommendations of the International Commission on Radiological Protection. Publication 103. Ann ICRP 2007; 37: 1-‐ 332