The impact of computer display performance on the quality of digital radiographs: a review

Selecting drill size for post space preparation based on final endodontic radiographs: An in vitro study

BACKGROUND

For placement of intraradicular posts the intracanal filling material has to be removed. If drills are employed for this purpose, extra widening of the canal, incomplete cracks or root perforation are probable when inappropriate size of drill is used.

OBJECTIVE

This in vitro study assessed the efficacy of radiographs taken after completion of root canal therapy in selecting the appropriate-sized Peeso reamer for post space preparation.

METHODS

Canals of 53 extracted maxillary and mandibular teeth of different types were cleaned and shaped. Then with acrylic resin 3-dimensional model of the intracanal space of each tooth was fabricated. Next, all canals were filled with gutta-percha and teeth were radiographed buccolingually. Based on these radiographs two observers selected a Peeso reamer that best matched each canal's diameter. The diameter of the selected Peeso reamer was compared to the diameter of the corresponding resin model of each canal by two independent observers and the difference was measured. The data were analyzed by paired sample t-test using SPSS version 22.

RESULTS

The diameter of the selected Peeso reamers ranged from 0.21 mm smaller to 0.12 mm larger than the diameter of intracanal spaces. The difference between reamer and resin model was less than 0.1 mm in 75% of the cases.

CONCLUSION

The result of this study suggests that post-operation endodontic radiographs are reliable means for selecting a size of Peeso reamer that does not encroach on dentinal wall during removal of intracanal filling material and post space preparation.

Technical Performance Assessment and Quality Control of Ultrasound Device Monitors

The purpose of this study was to investigate and evaluate the current technical performance of ultrasound imaging device displays. Altogether 53 ultrasound device displays were evaluated in two hospital districts of Finland. The performance of the displays was evaluated with tests and test patterns developed by American Association of Physicists in Medicine (AAPM). Minimum, maximum and ambient luminances (L_min,L_max,L_amb) were measured. Ambient ratio (AR), luminance ratio (LR), [Formula: see text] and [Formula: see text] were calculated, and luminance uniformity, defined as deviation from the median (MLD), was evaluated. The results indicate that none of the measured displays fulfill the AAPM Task Group (TG) 270 maximum luminance recommendation for diagnostic displays. A majority (32/53, 60%) of the displays fail the AAPM TG270 acceptable level for secondary displays as well. Only 3 of 53 (6%) displays were at the acceptable level for diagnostic displays. Also, for most of the displays (41/53, 77%), [Formula: see text] was under the diagnostic acceptable level. Ambient ratios exceeded the acceptable limit in 31 of 53 (58%) displays. Luminance ratios, on the other hand, were within acceptable levels for the majority of displays (38/53, 72%). All devices passed the AAPM requirement for luminance uniformity (MLD). The results indicate that the maximum luminance and minimum luminance of most displays are not sufficient. AAPM, the Society for Imaging Informatics in Medicine and the American College of Radiology introduced the updated luminance [Formula: see text] and [Formula: see text] criteria in 2012. All ultrasound displays should at least fulfill the AAPM TG18 secondary display minimum criteria. Even so, 6 of 53 (11%) fail. The newest displays should be expected to fulfill the revised AAPM TG270 criteria as well. Display technology has developed, and therefore, monitor testing needs to be updated.

Digitalised exercise material in forensic odontology

INTRODUCTION

This paper presents digital educational material in forensic odontology, including dental identification after multiple fatalities and dental age estimation from different age groups.

MATERIAL AND METHOD

Electronic patient records consisting of intraoral scans of the dentition, digital radiographs, photographs and written dental records were collected. Exercises in age estimations contained digital radiographs and photographs of ground tooth sections, with digital measuring tools and tables according to age groups. The teaching material was organised as a module in an electronic Learning Management System with external links to all relevant teaching material.

RESULTS

For the identification exercises, intraoral scans and the latest digital radiographs simulated the postmortem examination of the deceased. For comparison, all other radiographs, photographs and dental records were available as antemortem material. The exercise was to match postmortem findings with the antemortem records using the Interpol standard and reconciliation. Age assessment of children used designated tables to grade tooth development on digital radiographs. For adults, non-destructive methods, digital radiographs, photographs and measuring tools were used.

DISCUSSION

The teaching concept was hybrid, but it can easily be adapted as a fully digital exercise. The instructions and written material can be translated into different languages. The level of difficulty in the exercises can be adjusted according to the participant's level of knowledge.

CONCLUSION

The educational material embraces the new possibilities for digitalisation and intraoral scanning. This might be a valuable tool for motivating and engaging the students in their participation and understanding of the subject.

Impact of viewing conditions on the performance assessment of different computer monitors used for dental diagnostics

Purpose

This study aimed to assess the computer monitors used for analysis and interpretation of digital radiographs within the clinics of the Oral Health Centre of Western Australia.

Materials and Methods

In total, 135 computer monitors (3 brands, 6 models) were assessed by analysing the same radiographic image of a combined 13-step aluminium step wedge and the Artinis CDDent 1.0® (Artinis Medical Systems B.V.®, Elst, the Netherlands) test object. The number of steps and cylindrical objects observed on each monitor was recorded along with the monitor's make, model, position relative to the researcher's eye level, and proximity to the nearest window. The number of window panels blocked by blinds, the outside weather conditions, and the number of ceiling lights over the surgical suite/cubicle were also recorded. MedCalc® version 19.2.1 (MedCalc Software Ltd®, Ostend, Belgium, https://www.medcalc.org; 2020) was used for statistical analyses (Kruskal-Wallis test and stepwise regression analysis). The level of significance was set at P<0.05.

Results

Stepwise regression analysis showed that only the monitor brand and proximity of the monitor to a window had a significant impact on the monitor's performance (P<0.05). The Kruskal-Wallis test showed significant differences (P<0.05) in monitor performance for all variables investigated, except for the weather and the clinic in which the monitors were placed.

Conclusion

The vast performance variation present between computer monitors implies the need for a review of monitor selection, calibration, and viewing conditions.

The influence of image display systems on observers' preference for visualizing subtle dental radiographic abnormalities

OBJECTIVE

The objectives of this study were to assess observers' preference for standard screens (SSs) or medical displays (MDs) in visualizing difficult-to-diagnose radiographic dental abnormalities and their preference for dental filter tools when utilized with MD systems.

STUDY DESIGN

A retrospective data set of 60 in vivo radiographs consisting of intraoral (n = 20), panoramic (n = 20), and cone beam computed tomography (n = 20) images was created. Three image display monitors, including an SS, an MD, and an MD with 3 dental filter configurations (bone-low density enhancement filter, tooth-high density enhancement filter, and a combined filter representing regular MD), were utilized to assess 4 observers' monitor preferences in detecting radiographically subtle dental abnormalities. The data were analyzed by using binomial distribution. A P value ≤.05 was considered statistically significant.

RESULTS

Although observers expressed preference for MD for visualizing some abnormalities when examining intraoral and panoramic radiographs, MD was not preferred for detection of any abnormalities with cone beam computed tomography. There were no significant differences in preference for SS or MD overall (P ≥ .2024). Observers expressed significant preference for the filters in visualizing all but 2 abnormalities (P ≤ .0252).

CONCLUSIONS

The use of MD monitors enabled with dental filter tools may be preferred for visualizing certain subtle abnormalities.

Colour in digital pathology: a review

Colour is central to the practice of pathology because of the use of coloured histochemical and immunohistochemical stains to visualize tissue features. Our reliance upon histochemical stains and light microscopy has evolved alongside a wide variation in slide colour, with little investigation into the implications of colour variation. However, the introduction of the digital microscope and whole-slide imaging has highlighted the need for further understanding and control of colour. This is because the digitization process itself introduces further colour variation which may affect diagnosis, and image analysis algorithms often use colour or intensity measures to detect or measure tissue features. The US Food and Drug Administration have released recent guidance stating the need to develop a method of controlling colour reproduction throughout the digitization process in whole-slide imaging for primary diagnostic use. This comprehensive review introduces applied basic colour physics and colour interpretation by the human visual system, before discussing the importance of colour in pathology. The process of colour calibration and its application to pathology are also included, as well as a summary of the current guidelines and recommendations regarding colour in digital pathology.

Diagnostic Accuracy and Visual Search Efficiency: Single 8 MP vs. Dual 5 MP Displays

This study compared a single 8 MP vs. dual 5 MP displays for diagnostic accuracy, reading time, number of times the readers zoomed/panned images, and visual search. Six radiologists viewed 60 mammographic cases, once on each display. A sub-set of 15 cases was viewed in a secondary study using eye-tracking. For viewing time, there was significant difference (F = 13.901, p = 0.0002), with 8 MP taking less time (62.04 vs. 68.99 s). There was no significant difference (F = 0.254, p = 0.6145) in zoom/pan use (1.94 vs. 1.89). Total number of fixations was significantly (F = 4.073, p = 0.0466) lower with 8 MP (134.47 vs. 154.29). Number of times readers scanned between images was significantly fewer (F = 10.305, p = 0.0018) with 8 MP (6.83 vs. 8.22). Time to first fixate lesion did not differ (F = 0.126, p = 0.7240). It did not take any longer to detect the lesion as a function of the display configuration. Total time spent on lesion did not differ (F = 0.097, p = 0.7567) (8.59 vs. 8.39). Overall, the single 8 MP display yielded the same diagnostic accuracy as the dual 5 MP displays. The lower resolution did not appear to influence the readers' ability to detect and view the lesion details, as the eye-position study showed no differences in time to first fixate or total time on the lesions. Nor did the lower resolution result in significant differences in the amount of zooming and panning that the readers did while viewing the cases.

The effect of time in use on the display performance of the iPad

OBJECTIVE

The aim of this study was to evaluate changes to the luminance, luminance uniformity and conformance to the digital imaging and communication in medicine greyscale standard display function (GSDF) as a function of time in use for the iPad.

METHODS

Luminance measurements of the American Association of Physicists in Medicine (AAPM) Group 18 task group (TG18) luminance uniformity and luminance test patterns (TG18-UNL and TG18-LN8) were performed using a calibrated near-range luminance meter. Nine sets of measurements were taken, where the time in use of the iPad ranged from 0 to 2500 h.

RESULTS

The maximum luminance (Lmax) of the display decreased (367-338 cdm(-2)) as a function of time. The minimum luminance remained constant. The maximum non-uniformity coefficient was 11%. Luminance uniformity decreased slightly as a function of time in use. The conformance of the iPad deviated from the GSDF curve at commencement of use. Deviation did not increase as a function of time in use.

CONCLUSION

This study has demonstrated that the iPad display exhibits luminance degradation typical of liquid crystal displays. The Lmax of the iPad fell below the American College of Radiology-AAPM-Society of Imaging Informatics in Medicine recommendations for primary displays (>350 cdm(-2)) at approximately 1000 h in use. The Lmax recommendation for secondary displays (>250 cdm(-2)) was exceeded during the entire study. The maximum non-uniformity coefficient did not exceed the recommendations for either primary or secondary displays. The deviation from the GSDF exceeded the recommendations of the TG18 for use as either a primary or secondary display.

ADVANCES IN KNOWLEDGE

The brightness, uniformity and contrast response are reasonably stable over the useful lifetime of the device; however, the device fails to meet the contrast response standard for either a primary or secondary display.

Comparison of the performance of intraoral X-ray sensors using objective image quality assessment

OBJECTIVES

The main aim of this study was to evaluate the performance of 10 individual sensors of the same make, using objective measures of key image quality parameters. A further aim was to compare 8 brands of sensors.

STUDY DESIGN

Ten new sensors of 8 different models from 6 manufacturers (i.e., 80 sensors) were included in the study. All sensors were exposed in a standardized way using an X-ray tube voltage of 60 kVp and different exposure times. Sensor response, noise, low-contrast resolution, spatial resolution and uniformity were measured.

RESULTS

Individual differences between sensors of the same brand were surprisingly large in some cases. There were clear differences in the characteristics of the different brands of sensors. The largest variations were found for individual sensor response for some of the brands studied. Also, noise level and low contrast resolution showed large variations between brands.

CONCLUSIONS

Sensors, even of the same brand, vary significantly in their quality. It is thus valuable to establish action levels for the acceptance of newly delivered sensors and to use objective image quality control for commissioning purposes and periodic checks to ensure high performance of individual digital sensors.

The quality of radiographs accompanying endodontic referrals to a health authority clinic

AIM

To assess the quality of radiographs accompanying endodontic referrals, from general dental practitioners, to a health authority clinic.

METHODS

A total of 200 conventional film and digital radiographs accompanying referrals were assessed and rated as 'excellent', 'diagnostically acceptable' or 'unacceptable' according to the National Radiographic Protection Board (NRPB) guidelines. Statistical analyses of the results included inter- and intra-observer agreement to achieve a kappa score and the chi-squared test.

RESULTS

Out of the 200 radiographs assessed, 38 (19%) were conventional film and 162 (81%) were digital. Of the conventional film radiographs, 55% were rated 'excellent' and 37% were 'diagnostically acceptable', whilst 27% of digital radiographs were rated 'excellent' and 40% were 'diagnostically acceptable'. In the 'unacceptable' category, 33% were digital and 8% were conventional film radiographs (p <0.001).

CONCLUSIONS

The quality of digital radiographs was significantly lower compared with conventional film radiographs. The percentage of 'unacceptable' digital radiographs was above the target according to the NRPB guidelines. Hence, there is a need for improvement in quality to avoid repeat radiographs and unnecessary ionising radiation exposure. Instead of hard, printed copies, digital radiographs accompanying referrals should, within the parameters of information governance, be supplied electronically so that they may be optimised, if necessary, for better diagnostic value.

Comparison of physical quality assurance between Scanora 3D and 3D Accuitomo 80 dental CT scanners

BACKGROUND

The use of cone beam computed tomography (CBCT) in dentistry has proven to be useful in the diagnosis and treatment planning of several oral and maxillofacial diseases. The quality of the resulting image is dictated by many factors related to the patient, unit, and operator.

MATERIALS AND METHODS

In this work, two dental CBCT units, namely Scanora 3D and 3D Accuitomo 80, were assessed and compared in terms of quantitative effective dose delivered to specific locations in a dosimetry phantom. Resolution and contrast were evaluated in only 3D Accuitomo 80 using special quality assurance phantoms.

RESULTS

Scanora 3D, with less radiation time, showed less dosing values compared to 3D Accuitomo 80 (mean 0.33 mSv, SD±0.16 vs. 0.18 mSv, SD±0.1). Using paired t-test, no significant difference was found in Accuitomo two scan sessions (p>0.05), while it was highly significant in Scanora (p>0.05). The modulation transfer function value (at 2 lp/mm), in both measurements, was found to be 4.4%. The contrast assessment of 3D Accuitomo 80 in the two measurements showed few differences, for example, the grayscale values were the same (SD=0) while the noise level was slightly different (SD=0 and 0.67, respectively).

CONCLUSIONS

The radiation dose values in these two CBCT units are significantly less than those encountered in systemic CT scans. However, the dose seems to be affected more by changing the field of view rather than the voltage or amperage. The low doses were at the expense of the image quality produced, which was still acceptable. Although the spatial resolution and contrast were inferior to the medical images produced in systemic CT units, the present results recommend adopting CBCTs in maxillofacial imaging because of low radiation dose and adequate image quality.

Observer performance using virtual pathology slides: impact of LCD color reproduction accuracy

The use of color LCDs in medical imaging is growing as more clinical specialties use digital images as a resource in diagnosis and treatment decisions. Telemedicine applications such as telepathology, teledermatology, and teleophthalmology rely heavily on color images. However, standard methods for calibrating, characterizing, and profiling color displays do not exist, resulting in inconsistent presentation. To address this, we developed a calibration, characterization, and profiling protocol for color-critical medical imaging applications. Physical characterization of displays calibrated with and without the protocol revealed high color reproduction accuracy with the protocol. The present study assessed the impact of this protocol on observer performance. A set of 250 breast biopsy virtual slide regions of interest (half malignant, half benign) were shown to six pathologists, once using the calibration protocol and once using the same display in its "native" off-the-shelf uncalibrated state. Diagnostic accuracy and time to render a decision were measured. In terms of ROC performance, Az (area under the curve) calibrated = 0.8570 and Az uncalibrated = 0.8488. No statistically significant difference (p = 0.4112) was observed. In terms of interpretation speed, mean calibrated = 4.895 s; mean uncalibrated = 6.304 s which is statistically significant (p = 0.0460). Early results suggest a slight advantage diagnostically for a properly calibrated and color-managed display and a significant potential advantage in terms of improved workflow. Future work should be conducted using different types of color images that may be more dependent on accurate color rendering and a wider range of LCDs with varying characteristics.