Home Dental Radiology Effect of enveloping and disinfection methods on artefact formation on enveloped PSP plate images

Effect of enveloping and disinfection methods on artefact formation on enveloped PSP plate images

by adminjay

Eight new (unused) VistaScan Imaging Plate PLUS, size 2 (Dürr Dental, Bietigheim–Bissingen, Germany) PSP plates to be used in the study were first cleared of any possible residual background effects by the powerful light source in the scanner. Thus, the plates were restored to their original state, with empty memories. To compare the possible artefacts caused by the disinfection process-related damage, the test images were acquired as a reference. If no artefacts were detected by the three maxillofacial radiologists on the test images, the plates were included in the study. The test images, and the consecutive images after the disinfection process were acquired with an aluminum (Al) step wedge made of 99.5% pure Al with nine-step in increments of two millimeters. PSP plates were divided into four groups (A, B, C, D), two in each group, according to the two different disinfection and two enveloping methods to be applied. The groups were formed according to two variables: (a) enveloping the plates with single or double envelopes and (b) two different disinfection methods (spraying disinfection solution or wiping with disinfectant tissue) applied onto the enveloped plates. Each plate was used only in its own group during the study and possible artefacts were evaluated based on its test image. The plates were enveloped by Soredex Opti Bags (PaloDex Group Oy, Tuusula, Finland) and sealed according to the manufacturer’s instructions. The disinfection process was carried out immediately to the enveloped plates after the X-ray exposures. The four enveloped plates, in groups A and B were wiped with an alcohol containing disinfectant tissue [34], and onto the four in groups C and D an alcohol containing disinfectant solution was sprayed [10]. The plates in A and C groups were enveloped with single envelope and in B and D groups were enveloped with double envelopes. Both disinfectants used in this study contained at least 70% alcohol, because this level is effective for COVID-19 and other oral pathogens. The disinfectant tissue used was Bioflex Professional (Olce Kozmetik, Istanbul, Turkey) containing 70% ethyl alcohol, and the disinfectant solution was ANIOSRUB 85NPC (ANIOS, Lille–Hellemmes, France) containing 70% ethanol. The disinfection process was applied to each enveloped plate in a series, where the number gradually increased in total (cumulatively): 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55 and 60 times. In groups A and B four enveloped plates were wiped with gentle finger pressure five times with a disinfectant tissue, each time for 10 s with 1-min intervals after the exposure, then the plate was removed and scanned immediately and the image was recorded. Thus, a total of 12 images of each plate were acquired by repeating the same processes for each plate in these groups, in the same way, each time. The same process was repeated for four plates in groups C and D by spraying a disinfectant solution onto the enveloped plates five times with 1-min intervals after the exposure, then the plate was removed and scanned immediately and the image was recorded. The disinfection solution was sprayed from a distance of 30 cm in accordance with the manufacturer’s instructions. Thus, in the groups, where the disinfectant solution was used directly, a total of 12 images of each plate were acquired by repeating the same processes for each plate, in the same way, each time.

To achieve standardization in radiographic image acquisition, a plexiglass appliance with dimensions of 6.1 × 4.8 × 3.6 cm was used. This custom-made appliance had a slot in which the enveloped PSP plate could be exactly placed (Fig. 1). The construction of the appliance allowed a fixed distance with a perpendicular alignment repeatable geometry between the X-ray source and the PSP plate. The source-to-plate distance was set at 33.7 cm. The exposured surface of the appliance was prepared with a thickness of 3.2 cm to imitate the buccal soft tissue [30]. The AI step wedge was fixed on the side of the appliance, where the sensitive surface (exposed surface) of the plate was faced. For stabilization, the position indicating device and the appliance that fixed to it were positioned in the same horizontal position during the study.

Fig. 1

Photograph of the custom-made plexiglass appliance with a slot and AI step wedge

For radiographic imaging, a standard X-ray machine (CCX radiography unit, Trophy, Instrumentarium, Tuusula, Finland) with 1.5 mm Al equivalent total filtration, operating at 70 kV, 8 mA, 0.3 s exposure parameters was used. After the X-ray exposure, one of two disinfection procedures was applied onto the enveloped PSP plate, depending on the group in which it belonged. The sealed edge of the envelope(s) was cut with a pair of clean scissors and the PSP plates were removed carefully by holding the edges with minimal contact and carried to a dark room in a paper cup, where they would be scanned. The operator removed the gloves that came into contact with the envelopes during the disinfection process and removed the plates with new gloves, in case they had disinfectant residue on them. All scanning procedures were performed with a VistaScan Combi (Dürr Dental GmbH & Co. KG, Bietigheim–Bissingen, Germany) scanner using the standard scanning mode allowing a pixel size of 50 μm and a theoretical spatial resolution of 10-lp/mm. These procedures were repeated 12 consecutive times with new envelope(s) and the same PSP plate after each exposure to mimic the clinical conditions [34]. Including the eight test images a total of 104 digital radiographic images were recorded with their own group name that was pre-determined (Fig. 2). All radiography exposures, disinfection and scanning procedures were performed by the same researcher.

Fig. 2
figure 2

Flow-process diagram of study method

The 12 images of each plate were evaluated in terms of the presence of artefact based on their own test image by three dentomaxillofacial radiologists (Obs-1, Obs-2, and Obs-3) two with at least 15 years, and one with at least 3 years of experience. Before the study images were evaluated, the observers were asked to evaluate the PSP plate images of the patients previously obtained in the clinic. When encountered with a controversial situation, three observers inspected the image together and came to a consensus on the presence/absence of the artefact. This consensus finding was defined to be the gold standard, and thus the observers were calibrated. The evaluation of the images was done on the same 24-inch medical monitor (Philips, Luchu Hsiang, Taiwan) with an ideal screen display (resolution: 1920 × 1080 pixels) provided with an NVIDIA QUADRO FX 380 graphics card in a dimmed and quiet room from a distance of approximately 50 cm. The observers scored the 12 images of each plate independently, in a system, where only the name of the groups was indicated and they were blind to all other variables. The score categories used to evaluate the artefacts of the image were; 1 = no artefact on the image, 2 = presence of artefact less than 0.5 cm wide on the image, and 3 = presence of artefact larger than 0.5 cm wide on the image [34]. A second scoring session was held 2 weeks after the first evaluation to measure the observer’s repeatability. The obtained data were recorded in a form that was specially prepared for this study.

Ethical approval was not obtained, because this research study did not include human subjects, patient data, and human tissue.

Statistical analysis

In this study, depending on the distributional violations, non-parametric statistical analysis was used. The comparisons were evaluated using Kruskal–Wallis and post-hoc tests. The reproducibility and repeatability of the measurements were evaluated using the Intraclass Correlation Coefficients (ICCs). The data obtained were analyzed using the SPSS version 23·0 (Armonk, New York). Less than 0.05 p value was accepted statistically significant.

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