Skin entrance dose with and without lead apron in digital panoramic radiography for selected sensitive body regions.

PURPOSE: The aim of this study was to compare the dose at skin level at five significant anatomical regions for panoramic radiography devices with and without lead apron by means of a highly sensitive dosimeter. MATERIALS AND METHODS: A female RANDO-phantom was exposed in five different digital panoramic radiography systems, and the dose at skin level was assessed tenfold for each measurement region by means of a highly sensitive solid-state-dosimeter. The five measurement regions selected were the thyroid, both female breasts, the gonads, and a central region in the back of the phantom. For each panoramic machine, the measurements were performed in two modes: with and without a commercial lead apron specifically designed for panoramic radiography. Reproducibility of the measurements was expressed by absolute differences and the coefficient of variation. Values between shielded and unshielded doses were pooled for each region and compared by means of the paired Wilcoxon tests (p ≤ 0.05). RESULTS: Reproducibility as represented by the mean CV was 22 ± 52 % (median 2.3 %) with larger variations for small dose values. Doses at skin level ranged between 0.00 µGy at the gonads and 85.39 µGy at the unshielded thyroid (mean ± SD 15 ± 24 µGy). Except for the gonads, the dose in all the other regions was significantly lower (p < 0.001) when a lead apron was applied. Unshielded doses were between 1.02-fold (thyroid) and 112-fold (at the right breast) higher than those with lead apron shielding (mean: 14-fold ± 18-fold). CONCLUSION: Although the doses were entirely very low, we observed a significant increase in dose in the radiation-sensitive female breast region when no lead apron was used. Future discussions on shielding requirements for panoramic radiography should focus on these differences in the light of the linear non-threshold (LNT) theory which is generally adopted in medical imaging.

Effectiveness of Telemedicine and Teledentistry after the COVID-19 Pandemic.

Telemedicine has become increasingly important worldwide over the last two decades. As a new field, it became known especially during the COVID-19 pandemic; this review presents fields of activity with special attention to opportunities and risks. Numerous areas of application offer the possibility for broad use in the medical and dental care landscape in diagnostics, therapy, rehabilitation, and decision advice across a spatial distance. Technical and semantic standards are required, and profiles and guidelines are increasingly defined and organized. Medical/dental consultations have been established in various regions around the world as a response to pandemic challenges and have made video and online emergency consultations possible. Telemedicine applications are already regularly used in medical/dental emergencies, regardless of the pandemic situation, both for transport by train and by plane, from which patients benefit. However, legal hurdles are often still unresolved, but infrastructure challenges both for provider, user hard- and software also complicate deployment. Problems are particularly prevalent in the absence of necessary internet coverage or among socially disadvantaged and vulnerable groups who cannot afford expensive equipment or do not know how to use the technology. Broad access must be enabled, and hardware and software interfaces and updates must be regularly checked and updated. Telemedicine might also improve access to and delivery of oral and general health care support both for rural and urban areas with low costs. Even though dentistry and many medical specialties are still performed clinically by means of practical/manual examination, there are areas of diagnostics where telemedicine applications can provide good support. Therefore, as conclusions, access, and delivery of telemedicine applications in dentistry and medicine should be expanded and improved to provide access to all population groups.

Ink-jet printout of radiographs on transparent film and glossy paper versus monitor display: an ROC analysis.

The aim of this study was to compare the depiction ability of small grayscale contrasts in ink-jet printouts of digital radiographs on different print media with CRT monitor. A CCD-based digital cephalometric image of a stepless aluminum wedge containing 50 bur holes of different depth was cut into 100 isometric images. Each image was printed on glossy paper and on transparent film by means of a high-resolution desktop inkjet printer at specific settings. The printed images were viewed under standardized conditions, and the perceptibility of the bur holes was evaluated and compared to the perceptibility on a 17-in CRT monitor. Thirty observers stated their blinded decision on a five-point confidence scale. Areas (Az) under receiver operating characteristics curves were calculated and compared using the pair wise sign tests. Overall agreement was estimated using Cohen's kappa device and observer bias using McNemar's test. Glossy paper prints and monitor display revealed significantly higher (P < 0.001) average Az values (0.83) compared to prints on transparent film (0.79), which was caused by higher sensitivity. Specificity was similar for all modalities. The sensitivity was dependent on the mean gray scale values for the transparent film.

On cone-beam computed tomography artifacts induced by titanium implants.

OBJECTIVES: To briefly review the mathematical background of beam-hardening artifacts in cone-beam computed tomography (CBCT)-reconstruction and to investigate geometrical properties relevant for these reconstruction errors. By means of simulated and experimental results, beam-hardening effects caused by titanium implants are evaluated. MATERIALS AND METHODS: The geometrical and physical properties of the acquisition process of the projections used for 3D reconstruction are investigated and their effects on the CBCT images in the presence of titanium implants are derived. Beam-hardening effects are computed for a simplified polychromatic situation (three energy subsets of 80 and 110 kV) and compared with experimental results from a hard-plaster phantom containing two 'implants' (pure titanium rods; 4 mm diameter) exposed in two CBCT machines. RESULTS: Massive absorption within a typical implant body (diameter: 4 mm) was computed for the low-energy subset of both energies (80 kV: 99.7%; 110 kV: 90.9%), whereas the high-energy subsets are only marginally absorbed (80 kV: 14.8%; 110 kV: 11.3%). Accordingly, phantom data revealed drastically reduced gray values in artifact-affected regions (3DAccuitomo: -46% to -51%) or (3DExam: -55%) plus increased noise (+67% vs. +73%), when compared with unaffected regions. CONCLUSIONS: Our theoretical and experimental results prove massive beam-hardening artifacts for a typical implant diameter and typical energies of up-to-date CBCT machines. Meaningful artifact reduction has to be based on more sophisticated mathematical modeling of the actual physical image acquisition process rather than on postprocessing of the erroneous results obtained from the rather crude reconstruction algorithms used presently.

Simple computation of the approximated modulation transfer function (MTF) using spreadsheet-software: method and evaluation in five maxillofacial CBCT-devices.

OBJECTIVES: To develop a simple way to compute the approximated modulation transfer function (MTF) manually using conventional spreadsheet software. METHODS: Basing on an edge-image a method was developed, facilitating computation of the edge spread and line spread function in open-source spreadsheet software (Gnumeric; http://projects.gnome.org/gnumeric/downloads.shtml ). By means of the integrated fast Fourier transformation Fourier coefficients are obtained from the line spread function which can then be plotted vs spatial frequency to obtain MTF-plots. For the experimental evaluation an edge test object was exposed in five commercial CBCT devices for maxillofacial applications. RESULTS: The MTF as obtained from the above-described manual method at 10% modulation ranged between 1.6 and 2.3 cycles/mm. Reproducibility as expressed as relative differences between single assessments ranging between 3% and 11%. The computed MTF-values compare well with results from the literature. CONCLUSIONS: The method introduced can be used to manually and reliably estimate a CBCTs' MTF as one central parameter for the imaging systems' performance.

Role of ambient light in the detection of contrast elements in digital dental radiography.

OBJECTIVE: This study aimed to evaluate the effect of different ambient light levels on observer detection of small contrast differences in a contrast phantom by using a high-end liquid crystal display (LCD) monitor. STUDY DESIGN: An aluminum step wedge was converted into a contrast phantom by the addition of bore holes. Radiographic images of the contrast elements were presented to 20 observers. Images were displayed in random order under different ambient light levels (0, 50, 200, and 500 lux) twice, and the observers had to determine if contrast elements were visible. Sensitivity and specificity were determined to calculate areas under receiver operating characteristic curves and Friedmann's test was applied to evaluate the influence of the ambient light level on observer performance. RESULTS: Mean AZ values were moderate for each ambient light level at 0.715, 0.793, 0.764, and 0.722 for 0, 50, 200, and 500 lux, respectively. The influence of the ambient light level on observer performance was not statistically significant (P > .05). CONCLUSIONS: There was no significant influence of ambient light between 0 and 500 lux on observer ability to detect small contrast details displayed on a high-end LCD monitor.

Influence of a Commercial Lead Apron on Patient Skin Dose Delivered During Oral and Maxillofacial Examinations under Cone Beam Computed Tomography (CBCT).

The purpose of this paper is to investigate the impact of a commercial lead apron on patient skin dose delivered during maxillofacial CBCT in five critical regions by means of solid-state-dosimetry. Five anatomical regions (thyroid gland, left and right breast, gonads, back of the phantom torso) in an adult female anthropomorphic phantom were selected for dose measurement by means of the highly sensitive solid-state dosimeter QUART didoSVM. Ten repeated single exposures were assessed for each patient body region for a total of five commercial CBCT devices with and without a lead apron present. Shielded and non-shielded exposures were compared under the paired Wilcoxon test, with absolute and relative differences computed. Reproducibility was expressed as the coefficient of variation (CV) between the 10 repeated assessments. The highest doses observed at skin level were found at the thyroid (mean shielded ± SD: 450.5 ± 346.7 µGy; non-shielded: 339.2 ± 348.8 µGy, p = 0.4922). Shielding resulted in a highly significant (p < 0.001) 93% dose reduction in skin dose in the female breast region with a mean non-shielded dose of approximately 35 µGy. Dose reduction was also significantly lower for the back-region (mean: -65%, p < 0.0001) as well as for the gonad-region (mean: -98%, p < 0.0001) in the shielded situation. Reproducibility was inversely correlated to skin dose (Rspearman = -0.748, p < 0.0001) with a mean CV of 10.45% (SD: 24.53 %). Skin dose in the thyroid region of the simulated patient was relatively high and not influenced by the lead apron, which did not shield this region. Dose reduction by means of a commercial lead apron was significant in all other regions, particularly in the region of the female breast.

In vitro carious lesion detection on D-, E-, and F-speed radiographic films.

OBJECTIVES: To compare the accuracy in detection of interproximal natural carious lesions in vitro between Ultraspeed (D), Ektaspeed Plus (E), and Insight (F) radiographic films. STUDY DESIGN: Ten observers indicated on a 5-point scale their confidence in detecting an interproximal lesion in 240 surfaces (120 extracted teeth) with noncavitated carious lesions. Truth was assessed microscopically from hemisections. The areas (Az) beneath receiver operating characteristic (ROC) curves were pairwise compared and used for a 2-way analysis of variance. RESULTS: Az values were significantly correlated with observers (P=.002; Eta=0.671) and film type (P=.003; Eta=0.412). E differed significantly (mean Az: 0.624) from both D (mean Az: 0.591; P=.028) and F (mean Az: 0.594; P=.037), although the 95% confidence intervals clearly overlapped. CONCLUSION: The superior performance of Ektaspeed failed to prove clinical relevance.

Contrast perception in digitized panoramic radiographs compared with their film-based origin.

OBJECTIVES: We sought to compare the visual image quality of film-based and digitized panoramic radiographs through use of a hole-containing test wedge. STUDY DESIGN: An aluminum wedge containing 100 cells, of which 90 were given shallow holes, was exposed in the film-based Orthophos CD panoramic unit. Two radiographs subjectively exhibiting optimum contrast were selected. Films were digitized with a charge-coupled device flatbed scanner at 300 dpi. Films and digitized images were rated cellwise by 2 similar groups of 50 observers each with respect to spot perception. RESULTS: The mean sensitivity was 0.26 +/- 0.09 for film and 0.20 +/- 0.07 for digitized images (P =.000), with a pronounced decline in the latter in regions of high background density. The average specificity was 0.93 +/- 0.07 for film versus 0.92 +/- 0.08 for digitized images (P = 0.213). CONCLUSION: Film yielded a significantly higher sensitivity, but this absolute difference was actually small compared with that of the digitized images.

In vitro perception of low-contrast features in digital, film, and digitized dental radiographs: a receiver operating characteristic analysis.

OBJECTIVE: To compare experimentally the image quality of charged-coupled device (CCD)-based digital, flatbed scanner digitized, and dental film radiographs. STUDY DESIGN: High-contrast standardized radiographs of an aluminum step wedge containing boreholes were obtained on dental radiographic film (F) and a CCD receptor (D). Digitization (S) was done with a flatbed scanner. Each radiograph was separated into 23 single images, 18 of which showed a dark spot. Thirty observers indicated their confidence on the visibility of the spots for a receiver operating characteristic (ROC) analysis. RESULTS: Mean Az values (area beneath the ROC curves) differed significantly (P < .05), being highest for D (Az = 0.76), followed by F (Az = 0.71) and S (Az = 0.60). Mean sensitivity of S (0.45) was significantly (P = .000) lower than for D (0.66) and F (0.67). CONCLUSION: The difference between modality D and F was small. However, the inferior performance of S images, particularly in dark regions, could be clinically relevant.

Landmark identification on direct digital versus film-based cephalometric radiographs: a human skull study.

The purpose of this study was to investigate differences in landmark identification on vertically scanned, direct digital and conventional (18 x 24 cm) cephalometric radiographs. Eight observers, all orthodontists or postgraduate orthodontic students, recorded 6 landmarks twice on 3 digital and 3 conventional cephalograms obtained from 3 human skulls in a standardized fashion. Digital images were displayed on a 15.1-in TFT monitor in 3:1 mode (20 x 26 cm). Recordings were transferred into standardized coordinate systems and evaluated separately for each coordinate. After correcting for magnification, precision was assessed with Maloney-Rastogi tests, and intraobserver and interobserver reproducibility was calculated from squared differences. Effective magnification was larger for the digital images (x, 13%; y, 12%). Significantly different (P <.05) precision was found for nasion (N), posterior nasal spine (PNS), sella (S), supraspinale (A), and orbitale (Or), but average differences were entirely below 1 mm. Interobserver and intraobserver reproducibility did not differ significantly between the 2 image modes. Squared differences were largest for PNS and Or in both modalities. Our results indicate comparable errors in landmark recording for both evaluated machines. However, these results must be considered in the context of the specific display conditions for digital images, because no general standard exists for this purpose.