Abstract
This study aimed to clarify the effect of exposure frequency on the image quality obtained
using imaging plates (IPs) from two types of intraoral imaging systems ̶ Digora Optime (Soredex,
Tuusula, Finland) and VistaScan Perio (Dürr Dental, Bietigheim-Bissingen, Germany). Both types
of IP were grouped into three groups, with 6 IPs of Digora Optime and 6 IPs of VistaScan Perio for
each group. Group A with 10 exposures/day, group B with 10 exposures/week, and group C with 10
exposures/4 weeks. Group A was assumed to be simulation of dental clinics with few IPs that use
same IP once a day. Group B was assumed to be simulation of dental clinics with more IPs that use
the same IP about twice a day, and group C was set as control group with the exposure frequency set.
A six-level aluminum step wedge was used as a phantom to observe the changes in image contrast
and granularity for 64 weeks Previous studies have shown that IP can be used more than 3,000 times
without causing significant changes in the average pixel value; however, corner artifacts appear in
most images, so it is recommended not to use IP more than 3,000 times. Therefore, in this study,
measurements were continued until 64 weeks, when the maximum irradiation frequency exceeded
3,000 times and the total line dose was the same for each group. Image contrast was evaluated by
measuring the contrast-to-noise ratio (CNR) and low contrast value (LCV). Image background
granularity was evaluated by measuring root-mean-square (RMS) value. Digora Optime IPs showed
a large percentage change and significant differences in CNR, LCV, and RMS values at 64 weeks. In
contrast, VistaScan Perio only showed significant changes in LCV at 64 weeks. However, a trend for
greater changes in CNR, LCV, and RMS values in the group with higher exposure frequency (Groups
A and B) than the group with lower exposure frequency (Group C) was observed in both IP systems.
These findings indicate that the exposure frequency affects both the contrast and granularity of images
obtained using IPs. This effect was stronger in IP systems equipped with automatic exposure control
(AEC) (Digora Optime) than in those without AEC (VistaScan Perio).
