Biomedical subjects

C Kalogeropoulou

Publications and source records attributed to C Kalogeropoulou.

10 recordsLinked to original sources

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↗

PubMed2003

Can high resolution computed tomography predict lung function in patients with chronic obstructive pulmonary disease?

High-resolution computed tomography (HRCT) is a useful method for quantifying the extent of emphysema. Few reports have mentioned the relationships between HRCT scans and pulmonary function tests in chronic obstructive pulmonary disease (COPD). For diagnosis, COPD requires chronic airflow limitation and emphysema and/or chronic bronchitis. We examined 20 who were previous smokers with middle to moderate COPD. All were normocapnic with mean arterial oxygen pressure (PaO2) 77,52 +/- 16,789 mmHg. Forced spirometry, somatic plethysmography and cardiopulmonary exercise test were performed in each patient. HRCT was performed in both full inspiration and full expiration at three levels through the upper (at the aortic arch), lower (2 cm above the diaphragm), and middle lung (midpoint between upper and lower) levels. During expiration all pulmonary function parameters correlated with the HRCT grade in the middle right and left part of the lungs. The middle right part of the lung during expiration correlated statistically significant with MVV (r = -0.681, p = 0.001), forced vital capacity (FVC) (r = -0.477, p = 0.027), forced expiratory volumein 1 sec (FEV1) (r = -0.632, p = 0.002), resistance (r = 0.674, p = 0.001), residual volume (RV) (r = 0.733, p = 0.001), total lung capacity (TLC) (r = 0.696, p = 0.001), functional residual capacity (FRC) (r = 0.752, p = 0.001) and peak oxygen consumption during exercise (VO2) (r = -0.493, p = 0.023). The middle left part of the lung during expiration correlated statistically significant with MVV (r = -0.673, p = 0.001), FVC (r = -0.493, p = 0.027), FEV1 (r = -0.629, p = 0.003), resistance (r = 0.593,p = 0.005), RV (r = 0.601, p = 0.005), TLC (r = 0.546, p = 0.012), FRC (r = 0.594, p = 0.006) and peak VO2 (r = -0.525, p = 0.015). Forced expiratory volume in 1 sec (FEV1), which is a well-established measure of airflow obstruction, correlated with the HRCT grade (1) in the middle left part of the lung during inspiration (r = -0.468, p = 0.035) and during expiration (r = - 0.629, p = 0.003) (2) in the lower right lung during inspiration (r = -0.567, p = 0.007) and during expiration (r = -0.558, p = 0.008) (3) in the lower left lung during inspiration (r = -0.542, p = 0.011) and during expiration (r = -0.558, p = 0.008) (4) in the upper right lung during expiration (r = -0.469, p = 0.037) (5) in the upper left lung during expiration (r = -0.463, p = 0.035) and (6) in the middle right lung during expiration (r = -0.632, p = 0.002). According to our results HRCT was a valuable tool for evaluating the severity of COPD--especially the middle right and left part of the lungs, during expiration--and correlated well with pulmonary function tests.

Exercise Test↗

PubMed2001

Changes of gastric emptying rate and gastrin levels are early indicators of autonomic neuropathy in type II diabetic patients.

The authors investigated the effect of a balanced meal on gastric emptying rate and gastrin plasma concentrations in patients with type II diabetes and autonomic neuropathy, in diabetic patients without autonomic neuropathy, and in healthy subjects (controls). Before food the gastrin plasma concentrations were higher in patients with diabetes with autonomic neuropathy. After food, gastric emptying rate was slower in patients with diabetes with autonomic neuropathy, whereas gastrin plasma concentrations increased in 30 minutes in all groups but to a greater extent in patients with diabetes with autonomic neuropathy. Sixty minutes after food, there was a significant decrease in gastrin plasma concentrations in patients with diabetes with autonomic neuropathy, compared with the other two groups. These data suggest that in patients with type II diabetes with autonomic neuropathy, food causes slower gastric emptying and different plasma gastrin level responses from those in patients with type II diabetes without autonomic neuropathy and controls. There are therefore differences in the responses to food ingestion between these groups because of vagal denervation induced by autonomic neuropathy. These tests should be reserved for patients with symptoms suggestive of disturbed gastric emptying, or for patients with autonomic neuropathy without symptoms of gastroparesis.

Aged↗

PubMed2001

Metal stents for the management of atherosclerotic renovascular disease.

PURPOSE: We report on our experience with the use of metal stents for the treatment of atherosclerotic renovascular disease. PATIENTS AND METHODS: Since 1996, 62 patients (mean age 67 years) with ostial atherosclerotic renal artery stenosis were treated successfully by placement of metal stents. All patients presented with renovascular hypertension, and eight had additionally impaired renal function. In 12 patients, stents were placed bilaterally. In 54 patients, the introduction of stents was performed as the primary mode of treatment, and in the remaining 8 patients, the positioning of the endoprosthesis was deemed necessary because of recurrence of stenosis previously treated by renal percutaneous transluminal angioplasty (PTA). The patients were followed for a mean period of 18 months (range 9-48 months). RESULTS: Positioning of the endoprosthesis was successful in all patients. No major complications were reported. The 18-month patency rate was 77.4% (48 patients). Hypertension resolved in 39 patients and showed a trend to improvement in 15 patients. We observed no improvement of renal function in the eight patients who had impaired function prior to the procedure. CONCLUSION: Implantation of metal stents is a safe and effective method for the treatment of atherosclerotic renal artery stenosis and certainly presents an important alternative to renal PTA.

Aged↗

PubMed2001

Coated v noncoated ureteral metal stents: an experimental model.

PURPOSE: The purpose of the present study was to compare the standard metal stents with internally and externally coated metal stents in the pig model. MATERIALS AND METHODS: In nine female pigs weighing between 25 and 30 kg, the metal stents were randomly placed in either the right or left ureter, for a total of 18 stented ureters. Six ureters were stented with a Wallstent (Schneider, Zurich, Switzerland), six with a Passager stent (Boston Scientific, Natick, MA, USA), and six with a Corvita endoluminal graft (CEG) (Boston Scientific, Natick, MA, USA). Patency was examined by nephrostotomography 24 hours and 21 days after the initial procedure. RESULTS: Free flow of urine through the stents into the bladder was revealed in all ureters with the exemption of four cases where a Passager stent migrated into the bladder, jeopardizing ureteral patency. The Wallstent generated mild inflammation with metaplasia of the urothelium; the CEG a more pronounced inflammatory response in the adjacent ureter; and the Passager stent severe inflammatory reaction with necrosis of the urothelium. The sections of the Wallstents revealed the presence of a mild polypoid reaction adherent to the internal surface of the devices. The coated stents showed no tissue ingrowth through the lining material into the ureteral lumen, and thus, the urothelium was compressed beneath the prostheses. CONCLUSIONS: Our experimental results suggest that the standard Wallstent generates less inflammation of the surrounding tissues than coated stents. The coated stents have the advantage of minimal tissue ingrowth but have a tendency to migrate toward the bladder.

Animals↗

PubMed2000

Liposome-coated metal stents: an in vitro evaluation of controlled-release modality in the ureter.

PURPOSE: In vitro preparation of liposome-covered metal stents and loading of liposomal drug formulations that will slowly release the drug in the vicinity of the stent. MATERIALS AND METHODS: Polytetrafluoroethylene-coated stents were used. Large multilamellar (MLV) liposomes (phosphatidylcholine:cholesterol 1:1 mol/mol), empty or entrapping the corticosteroid anti-inflammatory drug, dexamethasone, were prepared by the thin-film hydration method and applied to pieces of stent using a simple and mild evaporation technique. Initially, a freeze-drying method for applying liposomes to stents was also evaluated, but it failed to produce stents that efficiently retain liposomal lipid when incubated in an aqueous environment. The presence of liposomes on the stent surface was confirmed by scanning electron microscopy. RESULTS: After analyzing the release of liposomal lipid (using a phospholipid assay) and liposomal drug (by a modified dexamethasone high-pressure liquid chromatography method) in an in vitro system developed to simulate in vivo conditions, it was found that 39.11+/-6.8% of the lipid and 50.84+/-5.48% of the drug was released from the stent pieces during 48 hours of incubation in the presence of artificial urine. The amount of dexamethasone released from stents during their application procedure was found to be negligible in an in vitro dry run. CONCLUSION: The use of stent-associated liposomal drug formulations as slow-release depots could be an efficient method of treating the untoward event of ureteral stent obstruction.

Chromatography, High Pressure Liquid↗

PubMed2000

Scintigraphic imaging of sarcomatous tumors with [(111)In-DTPA-phe-1]-octreotide.

The objective of the present study was to investigate the efficacy of (111)In-DTPA-octreotide (OC) for in vivo scintigraphic imaging of these relatively uncommon tumors. Thirteen patients (9 males, 4 females, mean age 59 years) with known sarcomatous lesions were studied. All patients had known lesions as demonstrated by previous investigation with other modalities, e.g. CAT, MRI. Following intravenous injection of 10 microg of OC labeled with 2.8-4.2 mCi (111)In, planar imaging was done at 6 +/- 1 and 22 +/- 2 h, respectively. Histologic verification was obtained in all cases, either from fine needle aspiration or from surgically removed tissue. Positive imaging was observed in 12/13 cases (92.3%). One scan was false-negative (7.7%). Occult lesions were demonstrated in two patients. The histologic typing and the scintigraphy results were: fibrosarcoma (1+/1), embryonic rhabdomyosarcoma (1+/1), leiomyosarcomas (3+/3), liposarcomas (2+/2), uterine sarcomas (2+/2), HIV (-) Kaposi sarcoma (1+/1), osteosarcoma (1+/1), chondrosarcoma (1-/1) and neurogenous sarcoma (1+/1). OC appears to have properties that lead to a new indication for its use. Other possible applications relate to the therapeutic use of octreotide either unlabeled or labeled with a beta-emitting radionuclide, as well as its use in radioimmunoguided surgery. Regarding the latter, our preliminary results are encouraging.

Female↗

PubMed2000

Metallic stents in gynecologic cancer: an approach to treat extrinsic ureteral obstruction.

OBJECTIVE: We report on our experience with the use of self-expandable metal stents for the treatment of extramural ureteral obstruction in patients with gynecologic cancer to restore ureteral patency and to alleviate the ureterectasis and hydronephrosis proximal to the ureteral narrowing. METHODS: Fourteen women (mean age 48 years) with obstructive uropathy secondary to gynecologic malignancies were treated successfully by placement of Wallstent self-expandable intraureteral metallic stents. The patients were followed for a mean period of 15 (range 9-24) months. RESULTS: Obstructive uropathy was resolved in all cases. In 1 patient placement of an additional, totally coaxial, stent was considered necessary because of tumor ingrowth, occurring 6 months after the procedure. In another patient, tumor overgrowth invading the borderline area between the proximal ureteric end and the metallic prosthesis was seen 12 months after stent placement causing obstruction. Thus, an additional Wallstent was implanted overlapping the initially placed stent. Patency was achieved in all the remaining ureters, during the follow-up period, without any need for further intervention. CONCLUSION: Implantation of self-expandable metal stents is a safe and effective method for bypassing ureteral obstruction due to gynecologic malignancies.

Adult↗

PubMed1997

PRONET services for distance learning in mammographic image processing.

The potential of telematics services is investigated with respect to learning needs of medical physicists and biomedical engineers. Telematics services are integrated into a system, the PRONET, which evolves around multimedia computer based courses and distance tutoring support. In addition, information database access and special interest group support are offered. System architecture is based on a component integration approach. The services are delivered in three modes: LAN, ISDN and Internet. Mammographic image processing is selected as an example content area.

Biomedical Engineering↗

PubMed1996

A novel radiological approach for the experimental study of angiogenesis: angiography of the chick embryo and its chorioallantoic membrane.

We use a modification of the digital substraction angiography (DSA) technique to visualize the vascular system of the chorioallantoic membrane (CAM) of the developing chick embryo. After catheterization of the central vein of the CAM with a metallic needle and injection of contrast medium, angiography was performed at specified follow-up intervals (1-2.5 images per second) using the Philips DVI-S Angiography Unit. By applying the vascular casting technique we were able to visualize the vessels of the CAM and to study the existing complex vascular-anatomical relationships. Our results show that DSA demonstrates the development of the circulatory system of the chick embryo (heart and vessels) and the vessels of its CAM effectively. By applying for the first time interventional radiology techniques on the chick embryo system, it has been possible to study morphological changes of the vessels during angiogenesis in vivo. These results suggest that this technique can be a proven and valuable tool in the quantitative assessment of angiogenesis.

Allantois↗