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Biomedical subjects

J Dimopoulos

Publications and source records attributed to J Dimopoulos.

At least 19 recordsLinked to original sources
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

Distance learning in mammographic digital image processing.

The potential of interactive multimedia and Internet technologies is investigated with respect to the implementation of a distance learning system in medical imaging. The system is built according to a client-server architecture, based on the Internet infrastructure, composed of server nodes conceptually modelled as World Wide Web (WWW) sites. Sites are implemented by integration and customization of available components. The system evolves around network-delivered interactive multimedia courses and network-based tutoring, which constitute its main learning features. This potential has been demonstrated by means of an implemented system, validated with digital image processing content, specifically image enhancement. Image enhancement methods are theoretically described and applied on mammograms. Emphasis is given in the interactive presentation of the effects of algorithm parameters on images. The system end-user access depends on available bandwidth, so high speed access can be achieved via LAN or local ISDN connections.

Biomedical Engineering↗
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

Metal stents: a new treatment of malignant ureteral obstruction.

PURPOSE: We report our experience with the use of metallic self-expandable and balloon expandable stents for the treatment of malignant ureteral obstruction. MATERIALS AND METHODS: We treated 12 consecutive patients with malignant ureteral obstruction, for a total of 14 ureters with stents placed. We placed metallic balloon expandable stents in 6 patients and self-expandable metallic stents in the remaining 6. Mean patient age was 65 years and mean followup was 9 months (range 8 to 16). RESULTS: Of the ureters 11 were patent without any additional manipulations during followup of 8 to 16 months. Secondary interventions were needed in 3 cases because of obstructive urothelial hyperplastic reaction, tumor ingrowth and local recurrence of the primary cancer invading the upper end of the stent. Two patients died 2 and 10 months after placement of the stent. CONCLUSIONS: Both types of metal stents have advantages and disadvantages that must be balanced against each other when choosing the ideal device for the treatment of obstruction. Implantation of a metal self-expanding or balloon expanding stent is safe and effective for the palliative treatment of malignant ureteral obstruction in late stage cancer patients.

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↗
PubMed1996

In vivo experimental evidence that the nitric oxide pathway is involved in the X-ray-induced antiangiogenicity.

We have investigated both the effects of X-rays on angiogenesis and the possible role of nitric oxide (NO) on the observed antiangiogenic effect of X-rays, using as an in vivo model the chick embryo chorioallantoic membrane (CAM). These effects were assessed both morphologically and biochemically, by measuring vascular density and collagenous protein biosynthesis, respectively, on days 9 and 14 of the chick embryo development. Vascular density and cytotoxicity of the CAM were also evaluated histologically. We have shown that X-rays have an antiangiogenic effect on the system used and that the NO synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME) promoted angiogenesis of the non-irradiated CAM and reversed the antiangiogenic effect of irradiation. D-NAME, which is an inactive enantiomer of L-NAME, showed no such effects. L-Arginine, which is the substrate for NO synthase, had a modest antiangiogenic effect on the non-irradiated CAM, no effect on the irradiated CAM and abolished the angiogenic effect of L-NAME on these CAM preparations. These results suggest that NO is involved in the antiangiogenic mechanism of X-rays and that pharmacological manipulation of NO firstly, may offer a better understanding of these mechanisms and, secondly, may also prove to be an alternative therapeutic approach for treating pathological conditions involving angiogenesis.

Animals↗
PubMed1979

Concept of cytostatic therapy in advanced tumours of the head and neck.

In cases with inoperable tumours of the head and neck some benefit may still be derived from cytostatics and radiotherapy. One treatment concept is based on intraarterial infusion therapy (bleomycin, methotrexate), while the systemic intravenous application of cytostatic substances (bleomycin, cyclophosphamide) is considered as an alternative of the intra-arterial approach is ruled out. Of the 31 intra-arterially and the 30 intravenously treated patients (all except 2 had squamous cell carcinomas), 64,5% and 20%, respectively, went into remission. This documents the validity of our treatment concept.

Adult↗
PubMed1975

[Accessory hepatic arteries and their nomenclatoric problems in radiology (author's transl)].

The numerous anatomical and radiological nomenclatures of hepatic arteries are compared and discussed. Our own material for the assessment of accessory hepatic arteries consisted of 220 anatomically prepared individuals and 74 angiograms. The individual branches in the normal case as well as all variations and their frequency are discussed. The present, often confusing nomenclature is critically reviewed and an attempt is made to establish a simple and clinically acceptable nomenclature. We propose to name the additional branches supplying the liver as 'arteria hepatica accessoria' with reference to the vessel from which they originate. Additional branches in the terminal branching (ramus accessorius) and vessels of the liver capsula should not be referred to as accessory hepatic arteries.

Angiography↗
PubMed1975

[Treatment of advanced neoplasms in the jaw].

Report is made about the combined therapy with cytostatics (methotrexate - bleomycin) and irradiation in patients with extended tumors in the gnathic region. Ten patients in whom a radical therapy with conventional methods did not promise any success, were treated with intra-arterial infusions of methotrexate and bleomycin and simultaneous irradiation. At present, eight patients are tumor free (observation time 4-14 months after termination of therapy). Although radiation doses and doses of cytostatics were high, only insignificant side effects were stated; consequently, the treatment had to be terminated in none of the patients.

Adult↗
PubMed1975

[Advances in the clinical application of quantum and electron irradiation (author's transl)].

The technical perequisites for irradiation with fast electrons and high-energy photons are described in the introduction and the physical and biological development of megavoltage therapy is discussed. The role of exact treatment planning is mentioned and new developments avising from introduction of ultrasound and computer-dosimetry are demonstrated. Finally, emphasis is placed on the progress actieved with modern radiotherapeutic in the treatment of tumours in certain selected clinical fields, which appear suited to the application of electron- and photon-beam therapy. Further improvement in therapeutic results is expected with the introduction of chemotherapeutic agents, radiation sensitizers and combined surgical-radiotherapeutic biological methods. The importance of collaboration amongst various suspecialities engaged in oncology is stressed.

Antineoplastic Agents↗