W. Geelen et al., REPRODUCIBILITY OF CEPHALOMETRIC LANDMARKS ON CONVENTIONAL FILM, HARD-COPY, AND MONITOR-DISPLAYED IMAGES OBTAINED BY THE STORAGE PHOSPHOR TECHNIQUE, European journal of orthodontics (Print), 20(3), 1998, pp. 331-340
The aim of the present study was to evaluate and compare the reproduci
bility of cephalometric landmarks on (1) conventional films, and image
s acquired by storage phosphor digital radiography both on (2) hardcop
y and (3) monitor-displayed versions. The material consisted of 19 cep
halograms for each image modality. The phosphor plates were scanned in
an image reader and the 10-bit normalized, raw data digital images we
re converted to 8-bit TIFF images for PC monitor-display. The digital
hardcopies were produced in a laser printer. Six observers were asked
to record 21 cephalometric landmarks on each conventional film, hardco
py, and monitor-displayed image. For the films and hardcopies, the lan
dmark co-ordinates were recorded via a digitizing tablet. For the moni
tor-displayed images, the co-ordinates were recorded directly from the
monitor using a dedicated Windows-based cephalometric program. Reprod
ucibility was defined as an observer's deviation (in mm) from the mean
between all observers. Differences between the image modalities and b
etween the observers were tested by two-way analysis of variance for e
ach landmark. There was a statistically significant difference between
the reproducibility of film, hardcopy and monitor-displayed images in
11 of the 21 landmarks. There was no unequivocal trend that one modal
ity was always the best. For a full: cephalometric recording (the sum
of all 21 landmarks), the monitor-displayed images (mean = 25.3 mm) ha
d a lower precision than film (P < 0.005) and hard-copy (P < 0.02). Th
ere was no significant difference between film (mean = 21.8 mm) and ha
rdcopy (mean = 22.8 mm). The lower reproducibility seen for the monito
r-displayed images is most probably of little clinical significance.