(Sunday, 7/29/2018) 5:05 PM - 6:00 PM
Room: Room 207
Purpose: To optimize orthodontic CBCT technique by minimizing dose while maintaining diagnostic image quality, using cephalometric measurement variability as a novel image quality metric.
Methods: A human cadaver was imaged using a Morita Accuitomo 170® CBCT machine at various technique parameters: 1) tube voltages (kV) of 60, 70, 80, and 90; 2) tube currents (mA) of 1, 2.5, and 5; and 3) rotational arcs of 180� and 360�. Standard cephalogram views were generated from 3D data using Dolphin©3D software. Point radiation dose measurements were recorded at the entry of three key radiosensitive regions. Ten examiners measured seven cephalometric parameters on each derived cephalogram view in addition to a conventional cephalogram acquired using a Planmeca Promax Dimax 4. Measurement error and dose were compared between CBCT techniques and the conventional cephalogram.
Results: Generally insignificant differences in measurement error were observed when rotation arc was reduced from 360â?° to 180â?°, when tube current was reduced from 5mA to 2.5mA, and when tube voltage was reduced from 90kV to 80kV and only subtle increases at 70kV. Radiation dose could be reduced by ~50% for either of these rotation arc or tube current reductions; reducing both yielded dose comparable to a single standard cephalogram. Employing 1mA or 60kV rendered images non-diagnostic.
Conclusion: Orthodontists could image with CBCT using a 180â?° arc of rotation, 2.5mA, and 70 or 80kV to greatly reduce CBCT radiation dose while maintaining sufficient image quality to make reproducible cephalometric measurements on a cephalogram derived from a 3D CBCT dataset.
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