Segmentation of retinal blood vessels by a novel hybrid technique- Principal Component Analysis (PCA) and Contrast Limited Adaptive Histogram Equalization (CLAHE)

Diabetic Retinopathy is a persistent disease of eyes that may lead to permanent loss of sight. In this paper, methodology is proposed to segment region of interest (ROI) i.e. new blood vessels in fundus images of retina of Diabetic Retinopathy (DR). The database of 50 fundus retinal images of healthy subjects and DR patients is fetched from Post Graduate Institute of Medical Education and Research (PGIMER), Chandigarh, India. The experimental set up consists of three set of experiments for the disease. For DR, in the first stage of automated blood vessel segmentation, gray-scale image is produced from the colored image using Principal Component Analysis (PCA) in the preprocessing step. The contrast enhancement by the Contrast Limited Adaptive Histogram Equalization (CLAHE) highlights the retinal blood vessels in the gray-scale image i.e. it unsheathed newly formed retinal blood vessels whereas PCA preserved their texture and color discrimination in DR images. The expert ophthalmologist(s) scrutiny on both internet repository and real time data acted as the gold standard for further analysis and formation of the proposed method. Further, ophthalmologists ascertained the forming of new blood vessels only on the disc region and divulging them, which were impossible with the naked eye. These operations help in extracting retinal blood vessels present on the disc and non-disc region of the image. The comparison of the results are done with the state of art methods like watershed transform. It is observed from the results that the new blood vessels are better segmented by the proposed methodology and are marked by the experienced ophthalmologist for validation. Further, for quantitative analysis, the features are extracted from new blood vessels as they are crucial for scientific interpretation. The results of the features lie in permissible limits such as no. of segments vary from 2 to 5 and length of segments varies from 49 to 164 pixels. Similarly, other features such as gray level of new blood vessels lie in 0.296-0.935 normalized range, coefficient with variations in gray level in the range of 0.658-10.10 and distance from vessel origin lie in the range of 56-82 pixels respectively. Both quantitative and qualitative results show that the methodologies proposed boosted the ophthalmic and clinical diagnosis. The developed method further handled the false detection of vessels near the optic disk boundary, under-segmentation of thin vessels, detection of pathological anomalies such as exudates, micro-aneurysms and cotton wool spots. From the numerical analysis, ophthalmologist extracted the information of number of vessels formed, length of the new vessels, observation that the new vessels appearing are less homogenous than the normal vessels. Also about the new vessels, whether they lie on the centre of disc region or towards its edges. These parameters lie as per the findings of the ophthalmologists on retinal images and automated detection helped in monitoring and comprehensive patient assessment. The experimental results show case that the proposed method has higher sensitivity, specificity and accuracy as compared to state of art methods i.e. 0.9023, 0.9610 and 0.9921, respectively. Similar results are obtained on retinal fundus images of PGIMER Chandigarh with sensitivity-0.9234, specificity-0.9955 and accuracy-0.9682.

Hemicellulase activity of antarctic microfungi

The mannanase (endo-beta-1,4-mannanase; E.C. 3.2.1.78) and xylanase (endo-beta-1,4-xylanase; E.C. 3.2.1.8) activity of five microfungal isolates from Antarctica were characterized at different temperatures and pH. In general, the hemicellulase activity of the antarctic strains occurred at least 10 degrees C and as much as 30 degrees C lower than that of a mesophilic reference strain. At 0 degrees C, two strains, a Phoma and a Penicillium, produced in excess of 40% of their measured maximum activity of mannanase. All strains had maximum hemicellulase activity in the range pH 4-5, with Penicillium, Phoma and Alternaria strains exhibiting high (in excess of 80% of maximum) mannanase activity at pH 10. Three of the antarctic isolates exhibited high levels of xylanase activity over a pH range of 3-11.

Value of clinical diagnosis in predicting the quality of cryopreserved sperm from cancer patients

PURPOSE

Cryopreservation of semen from patients with malignant diseases (primarily testicular cancer, Hodgkin's disease and lymphoma) before specific chemotherapy, radiation or surgical therapy has become a realistic option to preserve fertility. Nevertheless, the post-thaw sperm quality in these patients is poor. Whether the clinical diagnosis of malignancy affects the cryopreservation of human sperm is unknown. Such an association could allow post-thaw sperm quality to be predicted.

MATERIALS AND METHODS

We compared the effect of cryopreservation on sperm motility, velocity, linearity, amplitude of lateral head movement, motility index and motile sperm count in specimens from 30 normal men, 34 with testicular cancer, 39 with Hodgkin's disease, and 19 with leukemia and lymphoma who were referred for sperm banking during a 5-year period.

RESULTS

The pre-freeze and post-thaw motility, motility index and motile sperm count were significantly lower in patients than in normal men (p < 0.01). No significant differences were noted among the patient groups. Similarly, no significant differences were noted after cryopreservation. Our results indicate that the poor pre-freeze sperm quality in some patients with malignancies explains the poor post-thaw results. However, the deterioration in sperm function after cryopreservation of semen among patients with different malignancies and normal donors appears to be similar.

CONCLUSIONS

Clinical diagnosis of malignancy is not an adequate predictor of the effect of cryopreservation on human semen.

Optimum abstinence time for cryopreservation of semen in cancer patients

Although an abstinence period of 48 to 72 hours is the most commonly prescribed interval for diagnostic semen analysis, to our knowledge the association between the abstinence period and sperm quality after cryopreservation has not been identified. Patients with a malignant disease who are consulting for semen banking most often require urgent therapy. Consequently, defining the shortest abstinence period that allows for frequent semen collection within a limited interval and the best post-thaw sperm quality is necessary. We investigated the relationship between abstinence period, and the pre-freeze and post-thaw motility variables in semen specimens obtained from cancer patients for sperm banking. Samples collected from 95 patients were divided according to abstinence period: group 1-15 patients at 24 to less than 48 hours, group 2-53 at 48 to less than 72 hours and group 3-27 at more than 72 hours. Pre-freeze and post-thaw motile sperm count and motion variables (motility, velocity, linearity, amplitude of lateral head movement and motility index), and percentage decrease in sperm variables after cryopreservation were analyzed. Semen volume, the pre-freeze and post-thaw motile sperm count, motion parameters and the percentage decrease in semen variables did not differ significantly among the groups. We conclude that semen collection for cryopreservation after 24 to less than 48 hours of abstinence results in post-thaw quality comparable to that after an abstinence of 48 to less than 72 hours or longer. Thus, an abstinence period of 24 to less than 48 hours can be recommended for sperm banking in cancer patients.