Profile enhancement and cephalometric landmark identification.
The reproducibility of two soft tissue landmarks (SN, V) and two anterior bony landmarks (A, ANS) was determined by three observers for three cephalometric techniques. The three techniques were aimed at soft tissue profile enhancement either by standard exposure control (technique 1), a hand-held metal shield covering the profile (technique 2), or a brass wedge in the collimator (technique 3). For each technique, the sample was restricted to 20 subjects with a skeletal convexity greater than +4 mm. The four landmarks were identified three times with 7-day intervals between readings. The figure-of-merit (or mean radius) method was used to assess the probability of "hitting" a target (landmark) area. The mean radius from the sample mean point of impact (MPI) ranged from 0.585 mm to 1.758 mm. For a specific landmark, the difference was never greater than 0.5 mm when grouped by observer and technique. No technique excelled in overall consistency for the identification of anterior bony and soft tissue landmarks. Techniques 1 and 3 produced the most consistent identification of points ANS and SN, but with no significant difference between the two techniques. Interacting factors prevented any recommendation regarding a preferential technique for the identification of points A and V. There is statistically no reason to recommend the use of a handheld, metal profile shield for more consistent landmark identification.
Burger
H J
HJ
Department of Orthodontics, Oral and Dental Teaching Hospital, University of Stellenbosch, Republic of South Africa.
Rossouw
P E
PE
Stander
I
I
D000704:Analysis of Variance; D002508:Cephalometry / Q000295:instrumentation / Q000379:methods* / Q000592:standards; D005145:Face / Q000033:anatomy & histology*; D006801:Humans; D015588:Observer Variation; D011856:Radiographic Image Enhancement / Q000295:instrumentation / Q000379:methods; D011858:Radiographic Magnification; D015203:Reproducibility of Results; D012984:Software