Biomedical subjects

S Skiadopoulos

Publications and source records attributed to S Skiadopoulos.

13 recordsLinked to original sources

PubMed2005

Evaluating the effect of a wavelet enhancement method in characterization of simulated lesions embedded in dense breast parenchyma.

Presence of dense parenchyma in mammographic images masks lesions resulting in either missed detections or mischaracterizations, thus decreasing mammographic sensitivity and specificity. The aim of this study is evaluating the effect of a wavelet enhancement method on dense parenchyma for a lesion contour characterization task, using simulated lesions. The method is recently introduced, based on a two-stage process, locally adaptive denoising by soft-thresholding and enhancement by linear stretching. Sixty simulated low-contrast lesions of known image characteristics were generated and embedded in dense breast areas of normal mammographic images selected from the DDSM database. Evaluation was carried out by an observer performance comparative study between the processed and initial images. The task for four radiologists was to classify each simulated lesion with respect to contour sharpness/unsharpness. ROC analysis was performed. Combining radiologists' responses, values of the area under ROC curve (Az) were 0.93 (95% CI 0.89, 0.96) and 0.81 (CI 0.75, 0.86) for processed and initial images, respectively. This difference in Az values was statistically significant (Student's t-test, P<0.05), indicating the effectiveness of the enhancement method. The specific wavelet enhancement method should be tested for lesion contour characterization tasks in softcopy-based mammographic display environment using naturally occurring pathological lesions and normal cases.

Breast↗

PubMed2003

Visually lossless threshold determination for microcalcification detection in wavelet compressed mammograms.

The aim of this study was to determine the visually lossless threshold of a wavelet-based compression algorithm in case of microcalcification cluster detection in mammography. The threshold was determined by means of observer performance using a set of digitized mammograms. In addition, the transfer characteristics of the compression algorithm were assessed by means of image-quality parameters using computer-generated test images. The observer performance study was based on rating performed by four independent radiologists, who reviewed 68 mammograms, from the Digital Database for Screening Mammography (DDSM), at six different compression ratios. Receiver operating characteristics (ROC) analysis was performed on observers' responses and the area under ROC curve (A(z)) was calculated at each compression ratio for each observer. The parameters used for assessment of transfer characteristics of the compression algorithm were input/output response, noise, high-contrast response, and low-contrast-detail response. The computer-generated test image, used for this assessment, mimicked mammographic image characteristics (pixel size, pixel depth, and noise) as well as microcalcification characteristics (size and contrast). The ROC analysis for microcalcification cluster detection indicated a threshold at compression ratio 40:1, as Student's t-test shows statistically significant differences in A(z) values (p<0.05) for compression ratios 70:1 and 100:1. Observers' grading of mammogram quality lowers this threshold at 25:1. Low-contrast-detail detectability in the transfer characteristics study indicate a threshold of 35:1, whereas non-perceptibility of image-quality-parameters degradation lowers this threshold to 30:1. The ROC and transfer characteristics analysis provided comparable thresholds, indicating the potential use of the latter in limiting the target range of compression ratios for subsequent observer studies.

Aged↗

PubMed2002

Simulating the mammographic appearance of circumscribed lesions.

Optimization performance of digital image post-processing techniques in mammography requires controlled conditions of data sets permitting quantitative representation of image characteristics of pathological findings. Digital test objects, although objective and quantitative, do not mimic mammographic appearance and clinical data sets do not provide adequate sets of values of the various pathological finding characteristics. This can be overcome by digital simulation of pathological findings and superimposition on mammographic images. A simple method for simulation of mammographic appearance of radiopaque and/or radiolucent circumscribed lesions is presented. Circumscribed lesions are simulated using grey-level transformation functions which shift and compress the range of the initial pixel grey-level values in a region of interest (ROI) of a digitized mammographic image, according to grey-level analysis in 200 ROIs of real circumscribed lesions from digitized mammographic images. Simulation addresses lesion image characteristics, such as elliptical shape, orientation, halo sign for radiopaque lesions and capsule for radiolucent lesions, and is implemented in a user-driven PC-based interactive application. The appearance of the lesions is evaluated by six radiologists on a sample of 60 real and 60 simulated radiopaque lesions with the use of receiver operating characteristic (ROC) analysis. The area under the ROC curve, pooling the responses of the observers, was 0.55+/-0.03 indicating no statistically significant difference between real and simulated lesions (p>0.05). The method adequately simulates the mammographic appearance of circumscribed lesions and could be used to generate circumscribed lesion data sets for performance evaluation of image processing techniques, as well as education purposes.

Adipose Tissue↗

PubMed1999

A phantom-based evaluation of an exposure equalization technique in mammography.

An anatomical filter based exposure equalization technique in mammography is evaluated quantitatively using a phantom. The evaluation is carried out by a comparative observer performance study, comparing the equalization technique with a conventional one based on visualization of low contrast, 6 mm circular details and high contrast, 0.5 mm and 0.25 mm small size details. These details are situated at the phantom edge, simulating the breast periphery. Visualization of these details is studied with respect to the parameters of tube voltage, optical density, detail location and phantom thickness. Phantom images are interpreted independently by three observers using a four-point grading scale. Use of the Wilcoxon signed ranks test for paired data shows statistically highly significant improvement (p < 0.0001) in the visualization of details for the equalization technique for all values of the parameters studied. The improvement is independent of tube voltage but dependent on optical density, detail location and phantom thickness. Optimal performance is obtained for detail location closer to the outer border of the simulated breast periphery and/or further away from the film, as well as for a greater phantom thickness simulating both thick and dense breast.

Breast Neoplasms↗

PubMed1998

Evaluation of an anatomical filter-based exposure equalization technique in mammography.

An anatomical filter-based exposure equalization technique in mammography is clinically evaluated. An observer performance comparative study, between this technique and the conventional one, is carried out on the basis of the visualization of six anatomical features situated at the breast periphery. The effect of parenchymal breast patterns and compressed breast thickness in the visualization of these features is studied. 533 craniocaudal mammograms were interpreted by two radiologists independently, using a five-point rating scale. Use of the Wilcoxon ranking test for unpaired data shows statistically highly significant improvement (p < 0.0001) in the visualization of the nipple, areola, skin and subcutaneous fat in all cases, for the equalization technique. The improvement is dependent on parenchymal breast patterns and compressed breast thickness for peripheral Cooper's ligaments and peripheral surface veins. In the case of total fatty replacement and/or thin breasts neither technique seems to be superior (p > 0.05) with respect to these two features. Clinical results indicate the value of this technique in clinical routine.

Adult↗

PubMed1997

Suppression of serum prolactin levels after an oral glucose tolerance test in patients with polycystic ovarian syndrome.

In order to assess if an oral glucose load has any effect on serum prolactin levels in patients with polycystic ovary syndrome (PCOS), an oral glucose tolerance test (OGTT) was performed in 30 patients with PCOS and 20 controls, with normal or abnormal body mass index (BMI). OGTT resulted in decreased prolactin levels, being significant only in patients with PCOS and in controls with normal BMI. Our results show that obesity is an important inhibiting factor of serum prolactin level suppression which occurs with a mild suppressive test, as the OGTT; however, hyperandrogenemia may also play an inhibiting role in serum prolactin level suppression.

Adult↗

PubMed1997

Does postprandial hypersinsulinemia contribute to hyperandrogenism in patients with polycystic ovary syndrome?

Twenty patients with polycystic ovarian syndrome and with or without insulin resistance, and 20 healthy women (controls) underwent an oral glucose tolerance test, which resulted in a short duration but significant increase of serum insulin levels. Serum testosterone, androstenedione and dehydroepiandrosterone sulfate levels were estimated before and 180 minutes after administration of 75 gr. dextrose. Our results, three hours after dextrose administration, showed that: (1) serum testosterone levels decreased significantly, (2) serum androstenedione levels decreased but not significantly, and (3) serum dehydroepiandrosterone sulfate levels were not altered. The observation of decreased ovarian androgen levels after induced hyperinsulinemia is very interesting, the explanation, however, is quite difficult. This unexpected ovarian androgen response needs further investigation.

Adolescent↗

PubMed1995

Association of acanthosis nigricans with insulin resistance in patients with polycystic ovary syndrome.

This study was designed to explore the association of insulin resistance and acanthosis nigricans (AN) in patients with polycystic ovary syndrome (PCOS). Fifty women, 18-37 years old, were included in the study, and divided into five groups consisting of: (I) 10 women with PCOS, abnormal body mass index (BMI) and AN; (II) 10 women with PCOS and abnormal BMI, but without AN; (III) 10 women with PCOS, normal BMI, and no AN; (IV) 10 women with abnormal BMI, but without PCOS or AN; and (V) 10 healthy women with normal BMI. Measurement of fasting glucose and insulin levels before and after oral glucose challenge was performed. Fasting serum insulin levels were found to be significantly lower in groups III, IV and V than in groups I and II, with no significant difference between groups I and II, or between groups III, IV and V. Total insulin response following administration of glucose did not differ significantly between the groups. These findings support the view that obese PCOS patients with AN do not have significantly higher insulin resistance than obese patients without AN. Insulin resistance is a necessary, but not the only, factor leading to the development of AN in patients with PCOS. Other factors should also be considered in the pathogenesis of this cutaneous reaction.

Acanthosis Nigricans↗

PubMed1994

Hypothalamic-pituitary deficiency after Weil's syndrome: a case report.

A case of male hypogonadism after Weil's syndrome is described. Hypogonadism was the result of complete hypothalamic-pituitary deficiency. The relationship between leptospirosis and the endocrinopathy, the incidence that leptospira attacks hypothalamic-pituitary axis, and the mechanism with which the microorganism may cause damage to the pituitary and/or the hypothalamus are discussed.

Adult↗

PubMed1994

Familial blepharophimosis with ovarian dysfunction.

Three cases including two sisters and one brother with blepharophimosis are described. Their father also had blepharophimosis. Moreover, the elder sister initially presented with resistant ovary syndrome and thereafter true premature menopause, while the younger one presented with resistant ovary syndrome. The explanation for the association of blepharophimosis with primary ovarian dysfunction is unknown, but the possibility of a microdeletion of genetic material containing two geographically associated, but independent genes could not be confirmed or excluded. All families affected by blepharophimosis should be counselled about the high incidence of ovarian dysfunction and female infertility, at least in one form of the syndrome.

Adult↗

PubMed1988

Serum levels of the oncofetal antigens CA-125, CA 19-9 and CA 15-3 in patients with endometriosis.

The levels of the oncofetal antigens CA-125, CA 19-9 and CA 15-3 were measured in serum samples taken from 8 women, aged 21 to 37 yr, before treatment, during the last fifteen days of a 6-month administration of danazol and finally three months after treatment withdrawal. The purpose of the study was to investigate: i) whether endometriosis belongs to the pathologic conditions which induce a concomitant increase in the values of CA-125, CA 19-9 and CA 15-3, and ii) the effect of danazol on the levels of these antigens. Our results indicate that before danazol treatment, three women showed pathologic levels of all three antigens, one of CA 19-9 and CA 15-3, one of CA 19-9 alone, and two of CA 15-3 alone. Administration of the drug significantly reduced the levels of CA-125 (p less than 0.001) and CA 19-9 (p less than 0.05) and to a lesser degree the levels of CA 15-3. Three months after danazol treatment discontinuation, the levels of these three antigens remained significantly lower (p less than 0.05) than the respective pretreatment values. Our findings substantiate the view that endometriosis must be classified with the pathologic conditions which induce a rise in the levels of all three antigens, and that ovarian function mainly influences the levels of CA-125 and CA 19-9.

Adult↗

PubMedDate not supplied

Evaluation of semen parameters in man with hyperprolactinemia induced by metoclopramide.

Hyperprolactinemia in man decreases libido and potency, but the few reports concerning its influence on spermatogenesis are contradictory. The aim of this study was to evaluate the effect of induced hyperprolactimemia on semen parameters. A total of 15 potentially fertile male volunteers, aged 28.2 +/- 4.3 years, were given 10 mg metoclopramide three times daily for 12 weeks. Serum and seminal plasma prolactin levels and semen parameters were determined before and 4, 8, and 12 weeks following initiation of metoclopramide administration. A fivefold increase of serum prolactin levels was observed, semen volume and abnormal sperm forms decreased, while spermatozoa velocity increased. On the contrary, no influence was noted on the number of spermatozoa per milliliter, the total number of spermatozoa, the percentage of motile spermatozoa, or the index of motility. Hyperprolactinemia seems to improve spermatozoal velocity and morphology, although direct effect of metoclopramide on these parameters cannot be excluded.

Adult↗

PubMedDate not supplied

The sperm deformity and multiple anomalies indices: are they reliable in the identification of fertile and infertile semen?

DESIGN: Two new indices, the sperm deformity index and the multiple anomalies index, were evaluated in order to help identify fertile and infertile semen. RESULTS: It was found that only three out of 94 infertile men presented a sperm deformity index lower than the upper limits of normal. The sperm deformity index sensitivity and specificity were higher than those of the multiple anomalies index. CONCLUSION: The sperm deformity index is a reliable predictor in the identification of fertile and infertile semen, and therefore can help in the selection of patients who require assisted reproduction techniques.

Adult↗