Cone beam computed tomography (CBCT) in endodontics

Cone beam computed tomography (CBCT) is an extra-oral imaging system which produces 3-dimensional scans of the maxillofacial skeleton. It is useful in overcoming the limitations of conventional radiography. CBCT is a valuable aid in providing additional information for diagnosis and enabling more predictable management of complex endodontic problems compared to using intra-oral radiographs alone. CLINICAL RELEVANCE: There are potential indications for the use of CBCT in diagnosis and treatment planning.     

Long-term real-time monitoring of adeno-associated virus-mediated gene expression in the rat retina

Purpose : Previous studies have demonstrated that adeno‐associated virus (AAV) efficiently transduced retinal pigmented epithelial (RPE) cells. The goal of this study was to further evaluate and characterize transgene expression within the RPE cells over time in vivo. Methods : Adeno‐associated virus‐mediated gene transfer was monitored and quantified by retinal photography following subretinal injection of a recombinant AAV encoding the green fluorescent protein gene (rAAVCMV‐gfp) into rat eyes. Retinal function of transduced rat eyes was measured by electroretinography. Results : The maximum level of transgene expression was reached at 8 weeks postinjection followed by a gradual decrease throughout the experimental period. Interestingly, it was observed that while gfp expression was stable in some RPE cells, gfp fluorescence completely disappeared in other cells over the duration of the experiment. The expression of AAV‐mediated gfp in RPE cells did not alter the retinal function for over 1 year. Conclusions : These results confirm the importance of this direct visualization system to study vector transgene expression in vivo and support the use of AAV for diseases treatable by targeting RPE cells. Key words : adeno‐associated virus, gene transfer, green fluorescent protein, retinal photography, retinal pigmented epithelium.     

Automated determination of distance visual acuity: towards teleophthalmology services

Purpose: The aim of this study was to evaluate the visual acuity scores of a computer‐based visual function testing (CVFT) system. The automated chart uses logMAR notation (logarithm of the minimum angle of resolution) and randomised tilting E as optotype. The test was conducted using a laptop computer. Methods: This prospective, clinic‐based, test validation study was based on a model of repeatability in two observations. The right eyes of a total of 104 participants were randomly tested with both CVFT and the manual, gold standard Early Treatment of Diabetic Retinopathy Study (ETDRS) chart. Results: The mean difference between CVFT and ETDRS was ‐0.01 ± 0.11 (SD) logMAR units. The Spearman Rank correlation coefficient (r) between the absolute difference and the average was 0.35. The average time for testing one eye was 54.7 ± 11.89 seconds. The mean difference between two consecutive, repeated CVFT tests in the same eye was 0.02 ± 0.07 logMAR units (paired t‐test p = 0.046). Conclusions: A novel, automated visual acuity testing application is reported. This automated system should be a useful tool for mass screening of visual impairment in rural and remote regions with its ease of use and shorter testing time.     

Histopathological grading and DNA ploidy as prognostic markers in metastatic prostatic cancer.

The present study compares the prognostic potential of tumour grade and DNA ploidy status in patients with advanced-stage prostatic cancer. Two outcome groups were selected on the basis of time to progression and survival after orchiectomy. A poor-outcome group consisted of 32 therapy-resistant patients who experienced disease progression during the first year after orchiectomy and subsequently death due to prostatic cancer during the following year. A good-outcome group consisted of 27 therapy-responsive patients who showed disease regression and no signs of progression during a 3 year follow-up. The primary tumours were graded twice according to WHO and Gleason classification systems by two pathologists. Final agreement between the pathologists was obtained after a consensus meeting. The analysis revealed no prognostic importance of the two histological classification systems (P = 0.62 and P = 0.70) and disclosed weak inter- and intra-observer reproducibility (kappa < 0.70). DNA ploidy analyses were performed by image cytometry on formalin-fixed, paraffin-embedded samples of the primary tumours. Overall, 48% of the tumours were diploid, 20% tetraploid and 32% anueploid. DNA ploidy status did not discriminate between the two outcome groups (P = 0.46). Histological grade and DNA ploidy showed no prognostic importance in patients with prostatic cancer and skeletal metastases.     

International transmission of tele-ophthalmology images

Tele-ophthalmic consultations were conducted between a hospital in East Java, Indonesia, and an ophthalmology centre in Perth, Western Australia. Twenty-two eyes of 14 subjects were screened for glaucoma using a hand-held fundus camera. Optic disc images comprised 267 x 234 pixels at 24 bit/pixel (187 kByte). The images were compressed and stored together with patient information on a laptop computer. The images were then transmitted to Perth using either a mobile phone or a satellite phone, taking 170 s or 240 s, respectively. Images were also compressed to five different compression levels before transmission. At a compression ratio of 1:5, the images were 36 kByte in size and took 29 s to transmit by mobile phone and 60 s by satellite phone. To measure the loss of quality, the root mean square error was calculated for each colour component, comparing the transmitted and original images. The coefficients of variation were 10% (green), 15% (blue) and 22% (red). The images received in Perth were considered to be of excellent quality and readily interpreted by ophthalmologists in terms of the likely presence of glaucoma.     

A Novel Method for Correcting Non-uniform/Poor Illumination of Color Fundus Photographs

Retinal fundus images are often corrupted by non-uniform and/or poor illumination that occur due to overall imperfections in the image acquisition process. This unwanted variation in brightness limits the pathological information that can be gained from the image. Studies have shown that poor illumination can impede human grading in about 10~15% of retinal images. For automated grading, the effect can be even higher. In this perspective, we propose a novel method for illumination correction in the context of retinal imaging. The method splits the color image into luminosity and chroma (i.e., color) components and performs illumination correction in the luminosity channel based on a novel background estimation technique. Extensive subjective and objective experiments were conducted on publicly available DIARETDB1 and EyePACS images to justify the performance of the proposed method. The subjective experiment has confirmed that the proposed method does not create false color/artifacts and at the same time performs better than the traditional method in 84 out of 89 cases. The objective experiment shows an accuracy improvement of 4% in automated disease grading when illumination correction is performed by the proposed method than the traditional method.     

Retinal video recordings at different compression levels: a novel video-based imaging technology for diabetic retinopathy screening

Background

To evaluate the optimal compression level of retinal color digital video recordings, a novel video-based imaging technology, in screening for diabetic retinopathy (DR).

Design

Evaluation of a diagnostic technique.

Methods

A total of 36 retinal videos, captured using EyeScan (Ophthalmic Imaging System), were compressed from original uncompressed file size of 1 GB (gigabyte) to four different compression levels—100 MB (megabyte) (Group 1); 30 MB (Group 2); 20 MB (Group 3); and 5 MB (Group 4). The videos were subsequently interpreted by an ophthalmologist and a resident using the International Clinical Diabetic Retinopathy Severity Scales.

Main outcome measures

The sensitivity, specificity and κ coefficient for DR grading detected by were calculated for each compression level (Groups 1–4), with reference to the original uncompressed retinal videos.

Results

Groups 1, 2, and 3 graded by both readers had sensitivity and specificity >90% in detecting DR, whereas for group 4, the sensitivity and specificity were 70.6% and 94.7% for ophthalmologist and 80.0% and 72.2% medical officer, respectively. The κ correlation in detecting DR for groups 1, 2, and 3 were >0.95, whereas for Group 4, the κ was 0.76 and 0.66 for ophthalmologist and medical officer, respectively.

Conclusion

Retinal video recording is a novel and effective DR screening technique with high sensitivity, specificity and κ correlation. With its compressibility, this is a potential effective technique that can be widely implemented in a routine, mobile, and tele-ophthalmology setting for DR screening services.