How transparent film applied on dermatologic imaging devices in order to prevent infections affects image quality?

BACKGROUND: In the clinical practice, transparent films are used as sterile interfaces in in vivo dermatologic imaging in order to prevent the transmissions of infections. However, in our experience, the use of a transparent film can alter skin images. Our study aimed to compare the optical quality of a series of different plastic films used as interfaces in order to understand if some might be more suitable for imaging. MATERIALS AND METHODS: We tested the optical properties of 11 different protective transparent films that are marketed in France with a transparency meter and a spectrophotometer. RESULTS: Transmission, minimal diffusion, amount of gray, and contrast were obtained for each transparent film. Transmission ranged from 93.24% to 96.88% (mean 95.36; standard deviation SD 1.02), minimal diffusion from 88.28% to 123.87% (mean 101.04; standard deviation SD 10.02) and contrast from 11.01 to 15.88 (mean 13.93 and SD 1.3). For some films, the transmission was lower at lower wavelengths. CONCLUSION: All tested films had excellent optical properties. However, some of them had better optical qualities and seemed more suitable for their use in dermatologic imaging.

Label-free quantitative evaluation of breast tissue using Spatial Light Interference Microscopy (SLIM).

Breast cancer is the most common type of cancer among women worldwide. The standard histopathology of breast tissue, the primary means of disease diagnosis, involves manual microscopic examination of stained tissue by a pathologist. Because this method relies on qualitative information, it can result in inter-observer variation. Furthermore, for difficult cases the pathologist often needs additional markers of malignancy to help in making a diagnosis, a need that can potentially be met by novel microscopy methods. We present a quantitative method for label-free breast tissue evaluation using Spatial Light Interference Microscopy (SLIM). By extracting tissue markers of malignancy based on the nanostructure revealed by the optical path-length, our method provides an objective, label-free and potentially automatable method for breast histopathology. We demonstrated our method by imaging a tissue microarray consisting of 68 different subjects -34 with malignant and 34 with benign tissues. Three-fold cross validation results showed a sensitivity of 94% and specificity of 85% for detecting cancer. Our disease signatures represent intrinsic physical attributes of the sample, independent of staining quality, facilitating classification through machine learning packages since our images do not vary from scan to scan or instrument to instrument.

Ultrasensitive interferometric on-chip microscopy of transparent objects.

Light microscopes can detect objects through several physical processes, such as scattering, absorption, and reflection. In transparent objects, these mechanisms are often too weak, and interference effects are more suitable to observe the tiny refractive index variations that produce phase shifts. We propose an on-chip microscope design that exploits birefringence in an unconventional geometry. It makes use of two sheared and quasi-overlapped illuminating beams experiencing relative phase shifts when going through the object, and a complementary metal-oxide-semiconductor image sensor array to record the resulting interference pattern. Unlike conventional microscopes, the beams are unfocused, leading to a very large field of view (20 mm(2)) and detection volume (more than 0.5 cm(3)), at the expense of lateral resolution. The high axial sensitivity (<1 nm) achieved using a novel phase-shifting interferometric operation makes the proposed device ideal for examining transparent substrates and reading microarrays of biomarkers. This is demonstrated by detecting nanometer-thick surface modulations on glass and single and double protein layers.

Interferometric phase microscopy for label-free morphological evaluation of sperm cells.

OBJECTIVE: To compare label-free interferometric phase microscopy (IPM) to label-free and label-based bright-field microscopy (BFM) in evaluating sperm cell morphology. This comparison helps in evaluating the potential of IPM for clinical sperm analysis without staining. DESIGN: Comparison of imaging modalities. SETTING: University laboratory. PATIENT(S): Sperm samples were obtained from healthy sperm donors. INTERVENTION(S): We evaluated 350 sperm cells, using portable IPM and BFM, according to World Health Organization (WHO) criteria. The parameters evaluated were length and width of the sperm head and midpiece; size and width of the acrosome; head, midpiece, and tail configuration; and general normality of the cell. MAIN OUTCOME MEASURE(S): Continuous variables were compared using the Student's t test. Categorical variables were compared with the χ(2) test of independence. Sensitivity and specificity of IPM and label-free BFM were calculated and compared with label-based BFM. RESULT(S): No statistical differences were found between IPM and label-based BFM in the WHO criteria. In contrast, IPM measurements of head and midpiece width and acrosome area were different from those of label-free BFM. Sensitivity and specificity of IPM were higher than those of label-free BFM for the WHO criteria. CONCLUSION(S): Label-free IPM can identify sperm cell abnormalities, with an excellent correlation with label-based BFM, and with higher accuracy compared with label-free BFM. Further prospective clinical trials are required to enable IPM as part of clinical sperm selection procedures.

Quantitative phase microscopy: a new tool for investigating the structure and function of unstained live cells.

1. The optical transparency of unstained live cell specimens limits the extent to which information can be recovered from bright-field microscopic images because these specimens generally lack visible amplitude-modulating components. However, visualization of the phase modulation that occurs when light traverses these specimens can provide additional information. 2. Optical phase microscopy and derivatives of this technique, such as differential interference contrast (DIC) and Hoffman modulation contrast (HMC), have been used widely in the study of cellular materials. With these techniques, enhanced contrast is achieved, which is useful in viewing specimens, but does not allow quantitative information to be extracted from the phase content available in the images. 3. An innovative computational approach to phase microscopy, which provides mathematically derived information about specimen phase-modulating characteristics, has been described recently. Known as quantitative phase microscopy (QPM), this method derives quantitative phase measurements from images captured using a bright-field microscope without phase- or interference-contrast optics. 4. The phase map generated from the bright-field images by the QPM method can be used to emulate other contrast image modes (including DIC and HMC) for qualitative viewing. Quantitative phase microscopy achieves improved discrimination of cellular detail, which permits more rigorous image analysis procedures to be undertaken compared with conventional optical methods. 5. The phase map contains information about cell thickness and refractive index and can allow quantification of cellular morphology under experimental conditions. As an example, the proliferative properties of smooth muscle cells have been evaluated using QPM to track growth and confluency of cell cultures. Quantitative phase microscopy has also been used to investigate erythrocyte cell volume and morphology in different osmotic environments. 6. Quantitative phase microscopy is a valuable, new, non-destructive, non-interventional experimental tool for structural and functional cellular investigations.

Prediction of visual outcome after retinal detachment surgery using the Lotmar visometer.

AIM: To evaluate whether an achromatic interferometer, the Lotmar visometer, is useful in predicting postoperative visual outcome in patients with primary rhegmatogenous retinal detachment (RD) involving the macula. METHODS: This prospective study included 40 eyes of 40 non-consecutive patients with macula-off RD. The eyes were phakic or pseudophakic, had a clear optical media, and had a measurable potential vision on preoperative visometric examination. Preoperative variables included Snellen visual acuity, duration of macular detachment, extent of RD, and visometric potential acuity. Reattachment surgery consisted of radial scleral buckling in 33 patients, circumferential scleral buckling and encircling in seven patients, and subretinal fluid drainage in 10 patients. Retinal breaks were treated with cryotherapy or laser photocoagulation. Patients were followed up for at least 6 months after uncomplicated surgery. Best corrected visual acuity measured at any time during follow up was correlated with the preoperative variables. RESULTS: Preoperative visual acuity was less than 20/200 in 37 (93%) of 40 patients. Potential visual acuity of 20/200 or better was measured using the Lotmar visometer in 37 patients (93%). Postoperative visual acuity was correlated significantly with duration of macular detachment (r=0.55; p<0.001), and extent of RD approached statistical significance (r=0.31; p=0.05). There was a higher correlation between postoperative visual acuity and the visometric measurements (r=0.61; p<0.001). CONCLUSIONS: The Lotmar visometer may be a valuable method to estimate visual outcome after uncomplicated scleral buckling surgery in patients with RD involving the macula.

Theoretical development and experimental evaluation of imaging models for differential-interference-contrast microscopy.

Imaging models for differential-interference-contrast (DIC) microscopy are presented. Two- and three-dimensional models for DIC imaging under partially coherent illumination were derived and tested by using phantom specimens viewed with several conventional DIC microscopes and quasi-monochromatic light. DIC images recorded with a CCD camera were compared with model predictions that were generated by using theoretical point-spread functions, computer-generated phantoms, and estimated imaging parameters such as bias and shear. Results show quantitative and qualitative agreement between model and data for several imaging conditions.

Array detection for speckle reduction in optical coherence microscopy.

This paper introduces a spatial-diversity method for speckle suppression in optical coherence microscopy. The method is based on combining interference signals from an array of detectors placed in the back focal plane of the objective lens, such that elements receive light backscattered from the sample volume at different angles. Incoherently adding ('compounding') the signals increases the signal-to-noise ratio of the processed image compared to that attainable with a single detector. The speckle-reduction method was demonstrated with a benchtop microscope equipped with a quadrant photodiode. To evaluate its potential application in dermatology, images of living skin acquired with and without compounding were compared. The quality of the compounded images was found to be substantially better. A signal-to-noise gain close to a factor of two (the theoretical maximum attainable using four detectors) was achieved without a significant loss in resolution. The method can be applied to arrays with a larger number of elements, potentially enabling more advanced forms of spatial-diversity and adaptive-optics methods.