Biomedical subjects

G Nikiforidis

Publications and source records attributed to G Nikiforidis.

At least 19 recordsLinked to original sources

PubMed2006

A hybrid multi-scale model for thyroid nodule boundary detection on ultrasound images.

A hybrid model for thyroid nodule boundary detection on ultrasound images is introduced. The segmentation model combines the advantages of the "á trous" wavelet transform to detect sharp gray-level variations and the efficiency of the Hough transform to discriminate the region of interest within an environment with excessive structural noise. The proposed method comprise three major steps: a wavelet edge detection procedure for speckle reduction and edge map estimation, based on local maxima representation. Subsequently, a multiscale structure model is utilised in order to acquire a contour representation by means of local maxima chaining with similar attributes to form significant structures. Finally, the Hough transform is employed with 'a priori' knowledge related to the nodule's shape in order to distinguish the nodule's contour from adjacent structures. The comparative study between our automatic method and manual delineations demonstrated that the boundaries extracted by the hybrid model are closely correlated with that of the physicians. The proposed hybrid method can be of value to thyroid nodules' shape-based classification and as an educational tool for inexperienced radiologists.

Algorithms↗

PubMed2006

Ureteral injuries during gynecologic surgery: treatment with a minimally invasive approach.

PURPOSE: To report the safety and efficacy of percutaneous nephrostomy and primary antegrade recanalization for treatment of iatrogenic ureteral strictures after gynecologic surgery. PATIENTS AND METHODS: Ten women had symptoms suggestive of ureteral obstruction during the immediate postoperative period (5 days-1 week after surgery). Under analgesia and conscious sedation, standard percutaneous nephrostomy was performed, and a long 7F sheath was placed in the upper ureter. The obstructions were traversed with the aid of a 0.0035-inch Glidewire and a 5F angled Glide catheter (Terumo, Japan). Subsequently, the areas were dilated with angioplasty balloons to a maximum diameter of 7 mm. Finally, an 8F percutaneous internal/external nephroureteral drainage stent was inserted to secure ureteral patency. Follow-up was carried out by serial nephrostomography until removal of the stent and by renal ultrasonography thereafter. RESULTS: Twelve obstructions with a mean length of 1.4 cm (range 0.4-1.9 cm) were managed. The technical success rate was 100%. No major complications occurred, and normal renal function was restored. The mean follow-up was 12 months. In 60% of the patients, a patent ureter was depicted at 1 week, whereas in four patients, repeat dilation of the obstructed segment was required. The stents were removed after a mean period of 4.8 weeks. CONCLUSION: Percutaneous nephrostomy and primary antegrade ureteral balloon dilation is safe and efficacious for treating ureteral injury after pelvic surgery and obviates open surgical manipulations.

Adult↗

PubMed2006

Clinical-oriented collaboration over the Web during interventional radiology procedures.

Multidisciplinary collaboration is a key requirement in several contemporary interventional radiology procedures (IRPs). We proposed a hybrid system (NetAngio) to enable "on the fly" heterogeneous collaboration to support IRP providing intraoperating essential services, and investigate its feasibility and effectiveness in a referral medical center. We have developed a Web-based, cost-effective structure, able to support real-time mentoring, image manipulation, and education services beyond the boundaries of the single institution and potentially allow sub specialists to participate in opinion and decision making in more complex cases. Supported services based on a Motion Joint Photographic Experts Group (MJPEG) coder/decoder (CODEC) can be easily accessible by authorized collaborators, within a user-friendly interface by using a typical Web-browser. Ten interventional radiologists, two vascular surgeons and two medical physicists participated in 33 "fully collaborative" cases during a 13-month period from January 2004 to February 2005. In addition, fifteen 90-minute open seminars and finally, 75 expert's module activations, and 255 learner's module activations were performed during the evaluation period. Collaborative procedures are able to enhance outcomes performance especially in more complex cases where the simultaneous presence of a remote expert interventionist and a medical physicist or a surgeon is required. Further research is needed to promote integration of additional data sources and services.

Education, Medical↗

PubMed2006

Operational criteria for selecting a cDNA microarray data normalization algorithm.

Microarray technology allows gene expression profiling at a global level. Many algorithms for the normalization of raw microarray data have been proposed, but no attempt has yet been made to propose operationally verifiable criteria for their comparative evaluation, which is necessary for the selection of the most appropriate method for a given dataset. This study develops a set of operational criteria for assessing the impact of various normalization algorithms in terms of accuracy (bias), precision (variance) and over-fitting (information reduction). The use of these criteria is illustrated by applying the three most widely used algorithms (global median normalization, spiked-in based normalization and lowess) on a specifically designed, multiply-controlled dataset.

Algorithms↗

PubMed2005

An image-analysis system based on support vector machines for automatic grade diagnosis of brain-tumour astrocytomas in clinical routine.

An image-analysis system based on the concept of Support Vector Machines (SVM) was developed to assist in grade diagnosis of brain tumour astrocytomas in clinical routine. One hundred and forty biopsies of astrocytomas were characterized according to the WHO system as grade II, III and IV. Images from biopsies were digitized, and cell nuclei regions were automatically detected by encoding texture variations in a set of wavelet, autocorrelation and parzen estimated descriptors and using an unsupervised SVM clustering methodology. Based on morphological and textural nuclear features, a decision-tree classification scheme distinguished between different grades of tumours employing an SVM classifier. The system was validated for clinical material collected from two different hospitals. On average, the SVM clustering algorithm correctly identified and accurately delineated 95% of all nuclei. Low-grade tumours were distinguished from high-grade tumours with an accuracy of 90.2% and grade III from grade IV with an accuracy of 88.3% The system was tested in a new clinical data set, and the classification rates were 87.5 and 83.8%, respectively. Segmentation and classification results are very encouraging, considering that the method was developed based on every-day clinical standards. The proposed methodology might be used in parallel with conventional grading to support the regular diagnostic procedure and reduce subjectivity in astrocytomas grading.

Astrocytoma↗

PubMed2004

Comparison of the efficacy of tolterodine and oxybutynin in different urodynamic severity grades of idiopathic detrusor overactivity.

OBJECTIVE: To compare the efficacy of tolterodine and oxybutynin in the treatment of specific, according to their urodynamic grade of severity, populations with overactive detrusor. METHODS: In this open, randomized, two-way crossover study 128 women with urodynamically confirmed, idiopathic detrusor overactivity were recruited. Patients were categorized in 4 grades of severity groups, according to the characteristics of the first overactive detrusor contraction during filling cystometrogram: high volume-low pressure (grade-group I), high volume-high pressure (grade-group II), low volume-low pressure (grade-group III) and low volume-high pressure (grade-group IV). The primary outcome measure was average volume of voided urine per micturition. RESULTS: 107 patients successfully completed the study protocol and were included in the analyses: 40 in group IV, 36 in III, 25 in II and 6 in group I. In groups IV and III both oxybutynin and tolterodine significantly increased the average volume of voided urine per micturition but the differences between the drugs were not significant (p > 0.05). In group II neither of the drugs achieved significant changes in the outcome measure (p > 0.05). CONCLUSIONS: Tolterodine and oxybutynin are clinically equipotent in treating detrusor overactivity in specific severity groups of patients, although urodynamic effects are somewhat different.

Adult↗

PubMed2003

Prevalence of hepatitis B and C virus infection in the general population and selected groups in South-Western Greece.

Greece is a country of intermediate endemicity for hepatitis B and low endemecity for hepatitis C with a downward trend during the last years. In the present study we investigated the prevalence of hepatitis B virus (HBV) and hepatitis C virus (HCV) infection in the region of South-Western Greece and tried to identify the most important risk factors of transmission. This is a unique epidemiological study, as it is the first community based study in the general population of Greece, with a methodological approach based on multi-staged random sampling. The prevalence of HBV infection seems to be decreasing with a 22.6% rate of HBV markers and a 2.1% rate of chronic HBV carriers. We found male sex, old age and intrafamiliar exposure as the major independent risk factors of HBV transmission, while sexual contact, absence of condom prophylaxis and living in rural areas seem to have also a significant impact for HBV infection. No relation was found between HBV transmission and working in health care facilities, pre-existing hospital admissions and history of transfusion. The prevalence of anti-bodies to the HCV was found 0.5%, even lower than the rate reported in the Mediterranean region. Parenteral exposure was the main risk factor for the transmission of HCV infection.

Adolescent↗

PubMed2002

A computer-based diagnostic and prognostic system for assessing urinary bladder tumour grade and predicting cancer recurrence.

PURPOSE: A computer-based system was designed, incorporating subjective criteria employed by pathologists in their usual microscopic observation of tissue samples and measurements of nuclear characteristics, with the purpose of automatically assessing urinary bladder tumour grade and predicting cancer recurrence. MATERIAL AND METHODS: Ninety-two cases with urine bladder carcinoma were diagnosed and followed-up. Forty-seven patients had cancer recurrence. Each case was represented by eight histological (subjective) features, evaluated by pathologists, and thirty-six automatically extracted nuclear features. Grading and prognosis were performed by neural-network based classifiers employing both histological and nuclear features. RESULTS: Employing a combination of histological and nuclear features, highest classification accuracy was 82%, 80.5%, and 93.1% for tumours of grade I, II and III respectively. The prognostic-system, gave a significant prognostic assessment of 72.8% with a confidence of 74.5% that cancer might recur and of 71.1% that might not, employing two histological features and two textural nuclear features. CONCLUSIONS: The system for grading and predicting tumour recurrence may serve as a second opinion tool and features employed for designing the system may be of value to pathologists using descriptive grading systems.

Decision Support Systems, Clinical↗

PubMed2001

Quantification of the ionising radiation effect over angiogenesis in the chick embryo and its chorioallantoic membrane by computerised analysis of angiographic images.

PURPOSE: We evaluated, in vivo, the effect of ionising radiation on the angiogenesis process in the chick embryo and its chorioallantoic membrane (CAM) using digital subtraction angiography (DSA) in conjunction with computer-assisted image analysis. Information regarding the ionising effect on endothelial cells during radiation treatment was extracted. MATERIAL AND METHODS: Two series of fertilized eggs were irradiated with a single ionising radiation dose of 10 Gy on days 9 and 13 of embryonic development. Angiography was carried out 24 h after irradiation. The angiographic images were digitized and subsequently processed. A set of specific morphological parameters was defined to allow an analytical characterization of the vascularity status. Vessels were classified into three categories according to their diameters (> or = 200 microm, 100-200 microm and 50-100 microm). The data were normalized and statistically evaluated. RESULTS: On day 10, total vascular area and total vascular length presented a 15.6+/-1.2% and 18.4+/-2.4% reduction, respectively, while vascular diameters increased 3.3+/-0.5%. The vessel area and length of the first category > or = 200 microm) increased 9.8+/-1.1% and 8.1+/-0.9%, respectively, while these morphometric parameters for each of the remaining two categories decreased 44.3+/-2.9%, 38.7+/-4.2% and 45+/-3.8%, 30.7+/-3.4%, respectively. On day 14 insignificant changes were observed. CONCLUSION: Computerised analysis of angiographic images showed that the antiangiogenic effect of irradiation during the various phases of CAM development is larger on the 10th day than that observed on day 14 and it depends on the vessel size.

Allantois↗

PubMed2000

Interstitial cystitis: bladder training with intravesical oxybutynin.

PURPOSE: We assess the efficacy of intravesical administration of oxybutynin chloride in patients with interstitial cystitis. MATERIALS AND METHODS: The study included 36 women with a mean age of 45 years with a diagnosis of interstitial cystitis. Patients were treated with gradual intravesical instillation of saline oxybutynin solution (oxybutynin group) or gradual filling of simple saline (control group). Evaluation parameters consisted of symptom problem index, voids per day, volume per void, functional bladder capacity, volume at first sensation, cystometric bladder capacity and cystometric volume at first sensation. RESULTS: Statistically significant improvement of all evaluated parameters was found in both groups. When comparing the outcomes statistically significant improvement of parameters favored the oxybutynin group. CONCLUSIONS: Bladder training alone produces a satisfactory result by gradually expanding the bladder, and an additional statistically significant improvement is evident with intravesical oxybutynin.

Administration, Intravesical↗

PubMed1999

Adenocarcinoma of the kidney: nephron-sparing surgical approach vs. radical nephrectomy.

BACKGROUND AND OBJECTIVES: Radical nephrectomy has been the traditional surgical treatment for renal cell carcinoma in patients with a normally functioning contralateral kidney. The necessity for a less aggressive surgical approach has emerged in cases in which there is a need to preserve renal function. METHODS: We retrospectively evaluated the records of 41 patients with localized, symptomless small renal masses (<5 cm) treated with nephron-sparing surgery (group A) and 48 patients matched for age, tumor location, size, and stage who were treated with radical nephrectomy (group B). RESULTS: The 5-year cancer-specific survival rates were 97.5% and 98. 4% for the treated patients of groups A an B, respectively. No statistical association was found between cancer-specific survival and surgical approach, tumor stage, tumor location, or recurrence. The size of the primary tumor did not seem to influence the cause-specific survival. Local recurrence was observed in 3 patients (7.3%) who underwent partial nephrectomy. In our series, the overall incidence of multifocality was 10.4%. CONCLUSIONS: We propose segmental renal resection for unifocal small adenocarcinoma of the kidney in preference to radical surgery as it is corroborated by the presented data.

Adenocarcinoma↗

PubMed1999

Obstructive uropathy versus nephropathy: compartmental analysis in radioisotopic renography as a new methodology.

A study was carried out to determine the spatial-temporal distribution of the radiopharmaceutical, 99mTc-DTPA in the kidney and its compartments during renography and the use of compartmental analysis to improve the diagnostic capability of renography. A total of 60 individuals formed three groups: group A consisted of 30 normals taken as controls, group B consisted of 15 patients with unilateral nephropathy, and group C consisted of 15 patients with unilateral obstructive uropathy. This retrospective study was performed by processing of the frames acquired in the various stages of renography and determination of the time distribution of radioactivity in the aorta, the renal parenchyma and the renal pelvis. The data acquired were used to produce three curves instead of one for each kidney and to study renal function as a system of six compartments (aorta, left and right renal parenchyma, left and right renal pelvis, and bladder). In all the above compartments the differences among the three groups were significant and were quantified using the flow coefficients of the aortorenal compartments. The differences between the aortic flow coefficients (k1) were statistically significant not only between normal controls and patients, but also between individuals with parenchymatic dysfunction and patients with pelvocalyceal obstruction. The same differences were seen comparing the pelvocalyceal coefficients (k3) of all three groups. The parenchymatic coefficient (k2) presented statistically significant differences between normals and patients which were not observed between the two groups of patients (B and C). Compartmental analysis thus increases the sensitivity of renography, is objective by utilizing quantitative parameters, enables the separate analysis of the functional behavior of the various renal compartments, and improves the differential diagnosis between parenchymatic dysfunction and pelvocalyceal obstruction.

Adolescent↗

PubMed1999

Quantitative assessment of angiogenesis in the chick embryo and its chorioallantoic membrane by computerised analysis of angiographic images.

We studied, in vivo, the angiogenesis process in the chick embryo and its chorioallantoic membrane (CAM) using digital subtraction angiography (DSA) in conjunction with computer-assisted image analysis. In a series of fertilised eggs, angiography was carried out at days 8, 10, 12 and 14 of embryonic development. The angiographic images were digitised and subsequently processed for a specific image analysis. A set of specific morphological parameters has been defined to allow an analytical characterisation of the vascularity status. Vessels were classified into three categories according to their diameter (50-100, 100-200, and > 200 microm). The data were normalised and statistically evaluated. Graphs showing the development of angiogenesis were obtained. Total vascular area revealed a continuous rise, whereas, total vascular length increased until day 12 and then it started decreasing. These morphometric parameters in the first two vessel categories progressively increased throughout the entire period of development, whereas in the third category they increased until day 10 and then they started decreasing. By applying a vascular casting technique CAM vessels were visualised and compared with those extracted from the processed angiographic image. The comparison revealed that there is exact matching for the first two vessel categories (diameters higher than 100 microm) while the matching of the third category (diameters between 50 and 100 microm) is approximate.

Allantois↗

PubMed1998

Estimation of artifacts induced by the Ilizarov device in quantitative computed tomographic analysis of tibiae.

This study concerns the estimation of the artifacts introduced by the metallic frame of an Ilizarov apparatus during quantitative computed tomography for the assessment of neoosteogenesis. Ten cadaver tibiae were tomographed before and after the mounting of an Ilizarov device. The increase in mean density and in the relative number of pixels were used as indicators of the artifacts induced by the apparatus. No significant influence by the device was recorded in regions corresponding to a corticotomy site. In regions close to the metallic rings of the Ilizarov apparatus, measurements are distorted significantly, but with no influence on the assessment of neoosteogenesis.

Artifacts↗

PubMed1998

Treatment of varicocele for male infertility: a comparative study evaluating currently used approaches.

OBJECTIVE: To evaluate the results of four currently used approaches for the treatment of clinically diagnosed varicoceles, and compare their influence on semen parameters. METHODS: We prospectively evaluated 88 patients, 23-39 years old (mean age 31), with a clinically diagnosed varicocele. Patients were allocated randomly to be treated either by a retroperitoneal (group A), inguinal (group B), subinguinal (group C), or percutaneous venous embolization approaches (group D). All patients were evaluated 6 and 12 months postoperatively. RESULTS: Clinical recurrence of varicocele occurred in 4 patients of group A (18.2%), 1 patient of group B (4.5%), and 2 patients of group D (9.1%). Hydrocele formation was seen in 1 patient of group B (4.5%), and 2 patients of group C (9.1%). In all groups statistically significant improvement as to the sperm concentration was found in both the 6- and 12-month follow-up. This significance was more prominent in group C followed by groups B and D, and finally by group A. As to sperm motility, in group C there was a statistical significance in both follow-up evaluations, and in group B statistical difference was reached only in the 12-month evaluation. Sperm morphology did not differ in any of the groups postoperatively compared to the preoperative values. CONCLUSIONS: The subinguinal approach disclosed a more prominent improvement in both semen concentration and motility in the 6- and 12-month follow-up evaluation when compared to the other techniques. Furthermore, due to its simplicity and avoidance of opening the external oblique fascia, we believe it represents the more plausible approach when treating clinical varicocele.

Adult↗

PubMed1998

Alpha-blockers for the treatment of chronic prostatitis in combination with antibiotics.

PURPOSE: This study was undertaken to evaluate the immediate and long-term effects of the combination of alpha-blockers and antibiotics in the treatment of chronic prostatitis. MATERIALS AND METHODS: The patients eligible for study were assigned to 3 groups: group 1--nonprostatodynia, abacterial prostatitis (134), group 2--prostatodynia (72) and group 3--chronic bacterial prostatitis (64). alpha-Blockers were administered to all patients of groups 1 and 2 with demonstrable high maximal urethral closure pressure and typical clinical complaints irrespective of the presence of inflammatory findings in expressed prostatic secretion. alpha-Blockers were given to 50% of patients with bacterial prostatitis. Antibiotics were administered to all patients with positive expressed prostatic secretion cultures, and in half of those with abacterial prostatitis and inflammatory expressed prostatic secretion. Mean followup was 22 months (range 6 months to 3 years). The sign 1-tailed test was used for statistical analysis of data. RESULTS: The recurrence rate of bacterial prostatitis was significantly reduced by alpha-blockade (expressed prostatic secretion culture negative) and symptom relief was achieved for many months. For abacterial prostatitis statistical analysis revealed a lower symptom recurrence rate in patients receiving only alpha-blockers in comparison with those treated with a combination of alpha-blockers and antibiotics. CONCLUSIONS: The use of alpha-blockers is justified, not only for prostatodynia, but also for abacterial and bacterial prostatitis. In the latter case alpha-blockade not only caused enhanced clinical improvement but also reduced the recurrences as defined by expressed prostatic secretion positive segmental cultures.

Adrenergic alpha-Antagonists↗

PubMed1998

Vesicourethral dysfunction associated with multiple sclerosis: clinical and urodynamic perspectives.

PURPOSE: We investigate the association of clinical and urodynamic findings with corresponding clinical grade and possible predictors of clinical grade of multiple sclerosis (MS). MATERIALS AND METHODS: A total of 90 patients, 28 to 62 years old (mean age 45.8 +/- 12.1), with the clinical syndrome of MS were consecutively and prospectively studied. All patients were subjected to detailed video urodynamic evaluation and electromyography of the external urethral sphincter. RESULTS: Urodynamic evaluation revealed detrusor hyperreflexia in 52 patients (57.7%), detrusor external sphincter dyssynergia in 27 (30%) and hypocontractility or areflexia of the detrusor in 15 (16.6%). Residual urine varied widely from 50 to 900 ml. Decreased compliance with areflexia was seen in 5 patients (5.5%) and nonrelaxing sphincter (but not contracting) with bladder hypercontractility was noted in 9 (10%). Statistical analysis followed comparison of 2 proportions. When patients with a less severe form (grades 1 and 2) were differentiated from those with a more severe form of MS (grade 3), we observed a significant difference only in incontinence, high post-void residual, leg spasticity, urinary stones, hydronephrosis, type 3 detrusor external sphincter dyssynergia, no electromyography activity and positive sharp waves. The variables with the highest predictive value between the groups were urinary stones, sepsis, type 3 detrusor external sphincter dyssynergia and no electromyography activity of the external urethral sphincter (100%). CONCLUSIONS: Proper identification of the bladder and external urethral sphincter status, especially exclusion of detrusor overactivity or a dyssynergic response of the external urethral sphincter, will prevent complications that may result in deterioration of quality of life.

Adult↗

PubMed1998

Technetium-99m-tetrofosmin for parathyroid scintigraphy: comparison to thallium-technetium scanning.

UNLABELLED: The efficacy of 99mTc-tetrofosmin for the detection of parathyroid lesions was investigated prospectively in patients with hyperparathyroidism referred for surgical treatment. METHODS: Twenty-seven patients with primary and 18 with tertiary hyperparathyroidism were studied. Twelve patients had undergone one or more previous neck explorations. Static imaging with 201Tl was performed first, immediately followed by a 30-min 99mTc-tetrofosmin dynamic study. Delayed views of up to 3 hr postinjection were also obtained. Technetium-99m-pertechnetate was used for thyroid delineation. The tetrofosmin/99mTc-pertechnetate subtraction scan (TF/TC), the single-tracer washout technique and the thallium/technetium subtraction (TL/TC) were compared. Quantification of relative uptakes of tracers in the thyroid and abnormal parathyroids was accomplished by measuring activity within regions of interest. Kinetics of tetrofosmin in the thyroid and abnormal parathyroids were studied by evaluating the plots of the parathyroid to thyroid ratios against time as well as by calculation of the half-clearance times from the slow component of the time-activity curves. RESULTS: The overall sensitivity, specificity and accuracy of TF/TC and TL/TC were 76%, 92% and 83% and 52%, 85% and 65%, respectively. The respective sensitivities were 87% and 70% for adenomas and 72% and 46% for hyperplasia. The parathyroid-to-thyroid activity ratios of tetrofosmin were significantly higher than those of thallium (p < 0.001). The tetrofosmin single-tracer washout study was less accurate than the subtraction technique (overall sensitivity and specificity, 70% and 69%, respectively). The washout properties of tetrofosmin in abnormal parathyroids were not substantially different from those in the thyroid, with a few exceptions (p = 0.4). No correlation of half-clearance times with parathyroid size, degree of early uptake, parathyroid hormone levels or histology could be established. Comparing adenomas to hyperplasia in respect to tetrofosmin retention, a statistically significant difference was observed (p = 0.005). CONCLUSION: Technetium-99m-tetrofosmin is suitable for parathyroid imaging. The kinetic properties of this agent in parathyroid and thyroid tissues do not warrant differential washout protocols. The diagnostic impact of the observed difference in tetrofosmin kinetics between parathyroid adenomas and hyperplasia requires further investigation.

Adenoma↗