The orthodontic value of research and observation in developmental growth of the face. Angle Orthod 1931;1:67.
4.American Dental Association. History of Dentistry Timeline. http://www.ada.org/en/about-the-ada/ada-history-and-presidents-of-the-ada/ada-history-of-dentistry-time-line. Accessed 25 August 2017.
5.NDT Resource Center. https://www.nde-ed.org/index_flash.htm. Accessed 25 August 2017.
6.Rowland S. Archives of Clinical Skiagraphy. London: Rebman, 1896.
7.Broadbent BH Sr, Broadbent BH Jr, Golden WH. Bolton Standards of Dentofacial Developmental Growth. St Louis: C.V. Mosby, 1975:166.
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9.Basyouni AA, Nanda SR. An Atlas of the Transverse Dimensions of the Face, vol. 37 [Craniofacial Growth Series]. Ann Arbor: University of Michigan Center for Human Growth and Development, 2000:235.
10.Dewey MN, Riesner S. A radiographic study of facial deformity. Int J Orthod 1948;14:261–267.
11.Broadbent BH. A new x-ray technique and its application to orthodontia. Angle Orthod 1931;1:45.
12.Broadbent BH. The orthodontic value of studies in facial growth. In: Physical and Mental Adolescent Growth [The Proceedings of the Conference on Adolescence, 17–18 October 1930, Cleveland, OH].
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23.Markets and Markets. CBCT/Cone Beam Imaging Market by Application. http://www.marketsandmarkets.com/Market-Reports/cone-beam-imaging-market-226049013.html?gclid=EAIaIQobChMI4_b899b31AIVyEwNCh1xXQseEAAYASAAEgJa0_D_BwE. Accessed 25 August 2017.
Two-dimensional (2D) cephalometry has been an integral component of orthodontic patient assessment since Broadbent described the technique in 1931.1 For years the only image receptor for cephalometry was radiographic film, which limited the clinician to a 2D patient assessment. Today there are multiple receptor options such as photostimulable phosphor (PSP), charge-coupled device (CCD), and derived 2D data from cone beam computed tomography (CBCT). While CBCT allows for clinicians to evaluate the patient in three dimensions, most patient assessment is still performed on 2D data. This chapter discusses the various techniques for generating traditional 2D cephalograms, cephalograms derived from three-dimensional (3D) data, radiation exposures, and advantages/disadvantages of the various techniques and image receptors.
Patient Positioning
Regardless of image receptor, proper patient positioning is essential to producing an acceptable cephalometric image.
Lateral cephalogram
The patient’s head is positioned with the left side of the face next to the image receptor, with the midsagittal plane parallel to the image receptor and the Frankfort plane parallel to the floor2 (Fig 2-1). The patient’s head should be stabilized in a cephalostat. The cephalostat is a device with two ear rods that are placed in the external auditory meatuses and a nasion guide. Head stabilization serves two purposes: (1) It diminishes patient movement, and (2) it ensures reproducibility to allow for sequential evaluation over time.
Fig 2-1 Proper patient positioning for a lateral cephalogram showing the cephalostat around the patient’s head.
The radiation source is positioned so that the distance between the source and the midsagittal plane is 60 inches. The receptor (or film) should be placed 15 cm (approximately 6 inches) from the midsagittal plane. The x-ray beam should be collimated to the size of the receptor, and the center of the beam should be directed through the external auditory meatus (Fig 2-2). Because of the projection geometry, structures away from the receptor will be magnified more than the structures close to the receptor.
Fig 2-2 Graphic representation of patient positioning for a lateral cephalogram (viewed from above).
Posteroanterior cephalogram
Patient positioning for the posteroanterior (PA) cephalogram uses the same armamentarium as the lateral cephalogram. The patient is positioned with the midsagittal plane perpendicular to the receptor (nose toward the receptor) and the Frankfort plane parallel to the floor (Fig 2-3). The source should be 60 inches from the ear rods, and the receptor should be positioned 15 cm from the ear rods.2
Fig 2-3 Proper patient positioning for a PA cephalogram.
Patient Protection
There has been a great deal of discussion regarding the need for shielding of the patient from the primary beam. The American Dental Association,3 National Council on Radiation Protection and Measurements,4 and US Food and Drug Administration3 have created fairly specific recommendations for patient shielding for intraoral imaging but not for extraoral imaging. Nevertheless, many of the factors involved in the recommendations are applicable to extraoral imaging. Use of fast image receptors and collimation of the primary beam to the size of the receptor significantly reduce the dose to the patient. However, these factors do not reduce the dose to