Biomedical subjects

George C Kagadis

Publications and source records attributed to George C Kagadis.

16 recordsLinked to original sources

PubMed2006

Application of paclitaxel-eluting metal mesh stents within the pig ureter: an experimental study.

OBJECTIVE: The purpose of the present study is to compare the standard bare metal stents (BMS) with the Paclitaxel-Drug Eluting Stent (DES) in the ureter of a pig model. MATERIALS AND METHODS: We report on an experimental study with ten female pigs weighing between 25 and 30 kg. The stents were randomly placed in either the right or left ureter in each of 10 study animals, for a total of 20 stented ureters. Ten ureters were stented with an R-Stent (Orbus Medical Technologies, Hoevelaken Netherlands), and ten with a Paclitaxel-Eluting Coronary Stent (Boston Scientific, Natick, MA, USA). Patency was measured by radiograph of the nephrostomy tract, intravenous urography and virtual endoscopy at 24 hours and 21 days after the initial procedure, respectively. RESULTS: Free flow of urine through the stents into the bladder was documented in all stented ureters 24 hours after stent insertion by radiograph of the nephrostomy tract. At the 21 day follow-up examination, 5 R-Stents were found to be completely occluded and two partially stenosed, whereas no occluded stent was detected in the Paclitaxel-DES group. Pathology examination of the stents at 21 days follow-up showed that the obstructed R-Stents generated severe inflammation with metaplasia of the urothelium. The Paclitaxel-Eluting MS generated a mild inflammatory response within the ureteral lumen at the site of the stent, without hindering ureteral patency. R-stents proved to develop more hyperplasia compared to the Paclitaxel-Eluting MS. CONCLUSIONS: Paclitaxel-DES, when compared with the standard R- Stent BMS, generated less inflammation and/or hyperplasia of the surrounding tissues, thus maintaining ureteral patency. Long-term animal trials are required to further validate our results.

Animals↗

PubMed2006

Digital subtraction angiography and computer assisted image analysis for the evaluation of the antiangiogenetic effect of ionizing radiation on tumor angiogenesis.

PURPOSE: The aim of the present study was to evaluate and quantify the antiangiogenetic effect of ionizing radiation on tumor angiogenesis using digital subtraction angiography (DSA) in conjunction with computer assisted image analysis (CAIA). METHODS: Walker 256 carcinosarcoma was inoculated in both glutei of 12 Wistar rats. When the tumors reached a diameter of 1.5 cm, local irradiation of the right gluteus was performed. The left gluteus of each animal served as a control. After 24 hours of irradiation, angiography was performed, and images where digitized and subsequently processed. The effect of irradiation was observed both in big and small vessels (smaller or greater than 200 microm). RESULTS: Irradiated areas of both small and big vessels showed a statistically significant reduction in both total vessel area and length. Small vessels showed a greater trend toward suppression by irradiation (not statistically significant). CONCLUSION: Irradiation had a deleterious effect in both macro- and micro-blood supply of a tumor. The use of CAIA enhanced the efficacy of DSA and enabled the in vivo identification of the effect of irradiation on various caliber vessels as well as the ratios of total length and total area of small and big vessels.

Angiography, Digital Subtraction↗

PubMed2006

Transauricular arterial or venous access for cardiovascular experimental protocols in animals.

PURPOSE: To describe a safe percutaneous method of transauricular endovascular access in small and large animals that uses basic catheter-based interventional skills and renders surgery and general anesthesia with intubation unnecessary. MATERIALS AND METHODS: Twenty New Zealand White rabbits and five domestic juvenile swine were used in the experiments. Animals were restrained in the supine position after induction of dissociative anesthesia. Transauricular endovascular access was accomplished by percutaneous catheterization of the auricular artery or vein, roadmap imaging, introduction of a 0.018-inch hydrophilic guide wire, and over-the-wire vascular sheath insertion after serial tract dilations. RESULTS: Technical success rates were 90% and 100% for intraarterial and endovenous access in the rabbit, respectively, and 100% for both routes in the pig. The largest sheaths inserted were 5 F in the rabbits' aortae, 7 F in the rabbits' venae cavae, 6 F in the pigs' aortae, and 8 F in the pigs' venae cavae. Animal recovery was uneventful, and 48-hour necropsy detected only minor perivascular hematoma in cases of transauricular intraarterial access. Peripheral, intracoronary, intrapulmonary, and intracerebral selective vascular access was safe and feasible. A method of reserving the transauricular endovascular access for future interventions or follow-up by placement of indwelling hydrophilic catheters was also established. CONCLUSIONS: Transauricular endovascular access is a successful technique for establishing and maintaining intraarterial or endovenous vascular access. It obviates surgical cutdown and sacrifice of the femoral and cervical vessels and might considerably improve and expedite cardiovascular experimental protocols in small and large animals.

Animals↗

PubMed2006

Virtual endoscopy of the urinary tract.

Technological breakthroughs have advanced the temporal and spatial resolutions of diagnostic imaging, and 3 dimensional (3-D) reconstruction techniques have been introduced into everyday clinical practice. Virtual endoscopy (VE) is a non-invasive technique that amplifies the perception of cross-sectional images in the 3-D space, providing precise spatial relationships of pathological regions and their surrounding structures. A variety of computer algorithms can be used to generate 3-D images, taking advantage of the information inherent in either spiral computed tomography or magnetic resonance imaging (MRI). VE images enable endoluminal navigation through hollow organs, thus simulating conventional endoscopy. Several clinical studies have validated the diagnostic utility of virtual cystoscopy, which has high sensitivity and specificity rates in the detection of bladder tumor. Published experience in the virtual exploration of the renal pelvis, ureter and urethra is encouraging but still scarce. VE is a safe, non-invasive method that could be applied in the long-term follow-up of patients with ureteropelvic junction obstruction, urinary bladder tumors and ureteral and/or urethral strictures. Its principal limitations are the inability to provide biopsy tissue specimens for histopathologic examination and the associated ionizing radiation hazards (unless MRI is used). However, in the case of endoluminal stenosis or obstruction, VE permits virtual endoluminal navigation both cephalad and caudal to the stenotic segment. To conclude, VE provides a less invasive method of evaluating the urinary tract, especially for clinicians who are less familiar with cross-sectional imaging than radiologists.

Cystoscopy↗

PubMed2006

Distal embolism during percutaneous revascularization of infra-aortic arterial occlusive disease: an underestimated phenomenon.

PURPOSE: To investigate distal embolism during endovascular procedures of the infra-aortic arteries by utilizing a commercial filter basket and unveil any correlation between the baseline clinical and procedural variables and the histopathological findings of the collected particles. METHODS: In a prospective study, 48 patients (37 men; mean age 70.8+/-7.8 years, range 50- 83) underwent endoluminal therapy of infra-aortic lesions (stenosis >75% or occlusion; mean lesion length 52.2+/-38.0 mm) with standard endovascular procedures. A nitinol filter basket (n=50) was employed for distal protection. The collected particles were histopathologically analyzed. The harvested specimens were quantified after digital image post processing. RESULTS: Procedural success of filter-protected revascularization was 93.8%. Three failures included 1 vasospasm, 1 distal embolus, and 1 side-branch occlusion. The total area of retrieved particles per basket was 2.76+/-6.49 mm(2) (range 0.0-40.3). Particles with a major axis >1 and >3 mm were detected in 29 (58.0%) and 6 (12.0%), respectively, of the examined filters. Collected particles consisted primarily of platelets and fibrin conglomerates, trapped erythrocytes, inflammatory cells, and extracellular matrix. Increased lesion length, increased reference vessel diameter, acute thromboses, and total occlusions were positively correlated with higher amounts of captured particles (p<0.05). Multivariate analysis incriminated declotting procedures as the only independent predictor of increased embolic burden (p<0.05). CONCLUSION: The embolism phenomenon during infra-aortic interventions is frequent and underestimated. The liberated particles consisted primarily of atheromatous plaque elements and thrombus. The reported data might support the application of a protective filter basket in selected subsets of lesions with a riskier embolic profile and whenever declotting procedures are performed.

Aged↗

PubMed2005

Outflow protection filters during percutaneous recanalization of lower extremities' arterial occlusions: a pilot study.

PURPOSE: Filter devices are already employed for the protection of carotid, coronary and renal distal vascular bed during endovascular procedures. This is a pilot study investigating their feasibility, safety and distal emboli protection capability during recanalization of lower extremities' acute and subacute occlusions. MATERIALS AND METHODS: Study population included 16 patients, 11 with a subacute arterial occlusion and 5 with an acute episode. The Trap filter (Microvena, USA) and its successor the Spider filter (EV3, USA) were utilized. Subacute occlusions were dealt with standard angioplasty and stenting procedures, while acute ones were managed primarily with Angiojet rheolytic thrombectomy. Outflow arterial tree was checked angiographically in-between consequent procedural steps. Embolic material collected after filter recovery was analyzed histopathologically. Patients' follow-up was scheduled at 1 month. RESULTS: Seventeen filter baskets were applied in the recanalization of 16 target lesions in total. Mean length of the occluded segments was 6.1 (range: 2-15 cm; S.D. = 3.7 cm). Mean in situ time of the filters was 38.75 min (range: 20-60 min; S.D. = 12.71 min). Technical success rate of deployment and utilization of the filtration devices was 100% (17/17). Procedural success rate of the recanalization was 100% (16/16) without any clinical or angiographic evidence of periprocedural distal embolization. Macroscopic particulate debris was extracted from all the filters (17/17) containing fresh thrombus, calcification minerals, cholesterol and fibrin. Mean diameter of the largest particle per specimen was 1702.80 (range: 373.20-4680.00 microm; S.D. = 1155.12 microm). No adverse clinical events occurred at 1-month follow-up with 100% limb salvage (16/16). CONCLUSION: The application of outflow protection filters is safe, feasible and efficacious in hindering distal embolization complications and safeguarding the distal capillary bed. Nevertheless, this is a pilot study in a limited group. Further studies have to be contacted in order to provide evidence for a more general use of these devices.

Angiography, Digital Subtraction↗

PubMed2005

Ureteral metal stents: a tale or a tool?

There are four types of ureteral metal stents: self expandable, balloon expandable, covered, and thermoexpandable shape-memory. Insertion of metal stents requires expertise with transurethral and percutaneous techniques. The stricture is traversed with the aid of a guidewire via a percutaneous nephrostomy, and the stenotic segment is dilated using a high-pressure balloon catheter. The stent is then inserted over the guidewire, such that the upper end bypasses the obstruction by at least 3 to 4 cm, while the lower end extends intravesically for 0.5 to 1 cm from the ureteral orifice. If necessary, two or more stents are placed in sequence, overlapping by at least 2 to 3 cm. Metal stents were initially used for the relief of end-stage malignant disease, and their role in the treatment of benign ureteral strictures is still undefined. Patients often complain of abdominal discomfort and mild pain after stent insertion, which soon resolve spontaneously. Hematuria usually stops after a few days and does not necessitate any treatment. Mild urothelial hyperplasia in the stent lumen is common but usually regresses after 4 to 6 weeks. Many authors suggest the use of a double-pigtail catheter for the first 4 to 6 weeks to avoid narrowing of the ureteral lumen. The influence of stents on ureteral peristalsis is a major but poorly documented issue. Encrustation is a significant problem that needs to be addressed. The characteristics of both the patient and the stent influence its likelihood. Migration of coated metal stents was seen in 81% of patients at our center. Virtual endoscopy has recently been introduced as a tool for the follow-up of patients with stented ureters. Further design development is necessary to obtain the ideal ureteral metal stent. In a recent study in female pigs, paclitaxel-eluting metal stents engendered less inflammation and hyperplasia of the surrounding tissues.

Aftercare↗

PubMed2005

AngioJet rheolytic thrombectomy versus local intrapulmonary thrombolysis in massive pulmonary embolism: a retrospective data analysis.

PURPOSE: To compare the efficacy of full-dose local intrapulmonary thrombolysis (LIT) versus AngioJet rheolytic thrombectomy (ART) in the treatment of massive pulmonary embolism. METHODS: A retrospective review was conducted of 8 consecutive patients (5 women; mean age 66.0+/-5.9 years, range 56-74) who underwent LIT with high-dose intrapulmonary urokinase (4400 IU/kg over 10 minutes followed by a 2000-IU/kg/h infusion) and a subsequent 6 consecutive patients (4 men; mean age of 59.2+/-17.0 years, range 26-69) who underwent ART plus adjunctive low-dose urokinase infusions (100,000 IU) until hemodynamic recovery was achieved. Pre and postprocedural Miller scores were calculated, and relative Miller score improvement, total urokinase doses, and duration of therapy were compared. RESULTS: Hemodynamic stability was restored in all 8 LIT patients and in 5 (83%) of the 6 ART patients; 1 (16.7%) patient died during the ART procedure due to recurrent MPE. In the LIT group, the mean Miller score prior to intervention was 17.38+/-2.67, which was reduced to 6.13+/-1.46 after the intervention (p<0.0001) compared to scores of 18.83+/-2.86 and 6.83+/-2.79, respectively, in the ART group (p<0.0001). The mean urokinase dose was 2.07+/-0.44 million IU in the LIT group versus 0.70+/-0.36 million IU in the ART group (p<0.0001). The mean duration of therapy was 11.45+/-2.94 hours in the LIT group versus 3.37+/-1.41 hours in the ART group (p<0.0001). No significant difference in relative Miller score improvement was observed. CONCLUSION: By accelerating the fragmentation of thrombus, ART plus adjunctive low-dose urokinase seems to be more rapidly effective compared to LIT. ART achieves both rapid cardiovascular relief and reduces the dose of thrombolytic agent necessary in patients with massive pulmonary embolism.

Aged↗

PubMed2005

Sirolimus-eluting versus bare stents for bailout after suboptimal infrapopliteal angioplasty for critical limb ischemia: 6-month angiographic results from a nonrandomized prospective single-center study.

PURPOSE: To report the 6-month angiographic results from a prospective single-center study investigating the efficacy and outcome of sirolimus-eluting stents used for bailout after infrapopliteal revascularization of patients with critical limb ischemia (CLI). METHODS: Twenty-nine patients (21 men; mean age 68.7 years) underwent infrapopliteal revascularization with bare metal stents (group B) implanted for bailout in 65 lesions (38 stenoses and 27 occlusions) in 40 infrapopliteal arteries. Another 29 patients (21 men; mean age 68.8 years) underwent infrapopliteal bailout stenting with sirolimus-eluting stents (group S) in 66 lesions (46 stenoses and 20 occlusions) in 41 vessels. Preliminary 6-month angiographic and clinical results were analyzed. RESULTS: Hyperlipidemia and symptomatic cardiac and carotid diseases were more pronounced in group S (p<0.05). Technical success was 96.6% (28/29 limbs) in group B versus 100.0% in group S (p=0.16). Six-month primary patency was 68.1% in group B versus 92.0% in group S (p<0.002). Binary in-stent and in-segment restenosis rates were 55.3% and 66.0%, respectively, in patients with bare stents versus 4.0% and 32.0%, respectively, in patients treated with the sirolimus-eluting stents (both p<0.001). The target lesion re-intervention rate at 6 months was 17.0% in group B versus 4.0% in group S (p=0.02). Limb salvage was 100% in both groups. Six-month mortality and minor amputation rates were 6.9% and 17.2%, respectively, in group B versus 10.3% and 3.4%, respectively, in group S (p=0.32 and p=0.04, respectively). CONCLUSIONS: Sirolimus-eluting stents seem to restrict neointimal hyperplasia in the infrapopliteal vascular bed.

Aged↗

PubMed2004

Intracranial aneurysms: reproduction of the surgical view using 3D-CT angiography.

Our purpose was to describe a technique for simulating the surgical view of ruptured intracranial aneurysms, using volume-rendering techniques in spiral computed tomography (CT) angiography data. The 3D (three-dimensional) rendered images were assessed by a team consisted of four radiologists, one neurosurgeon and one medical physicist. The resultant 'surgical view' image was standardized in space using a three-dimensional coordinate system, which allowed for its reproduction in the operating theatre. The surgical views are a potentially useful tool for the surgical planning of intracranial aneurysms.

Adolescent↗

PubMed2004

CT angiography with three-dimensional techniques for the early diagnosis of intracranial aneurysms. Comparison with intra-arterial DSA and the surgical findings.

INTRODUCTION: Cerebral CT angiography (CTA) is an established method applied to both the detection and treatment planning of intracranial aneurysms. The aim of our study was to compare CTA and digital subtraction angiography (DSA) findings with the surgical results mainly in patients with acute SAH and to evaluate the clinical usefulness of CTA. MATERIALS AND METHODS: During the last 2 years, 82 consecutive patients were admitted under clinical symptoms and signs suggestive of harboring an intracranial aneurysm. CT angiography performed immediately afterwards the plain CT, while DSA was performed within the first 48 h of admission. All aneurysms detected were confirmed during surgery or endovascular embolization. Repeat DSA was performed in all patients having both the initial CTA and the DSA 15 days after the onset of symptoms negative. CT angiograms and conventional angiographies were studied by a consensus of two radiologists for each technique, who performed aneurysm detection, morphological features characterization and evaluation of the technique. RESULTS: Surgical or/and endovascular treatment was performed in 45 patients and 53 aneurysms were confirmed. Using 3D-CT angiography, we detected 47 aneurysms in 42 patients. Conventional angiography depicted 43 aneurysms in 39 patients. The sensitivity of CTA for the detection of all aneurysms versus surgery was 88.7%, the specificity 100%, the positive predictive value (PPV) 100%, the negative predictive value (NPV) 80.7% and the accuracy 92.3%. Accordingly, the sensitivity of DSA was 87.8%, the specificity 98%, the PPV 97.7%, the NPV 89.1% and the accuracy 92.9%. Considering aneurysms > or =3 mm, CTA showed a sensitivity ranging from 93.3 to 100%, equal to that of DSA. CONCLUSION: Cerebral CT angiography has an equal sensitivity to DSA in the detection of intracranial aneurysms >3 mm. It has also 100% detection rate in AcoA and MCA bifurcation aneurysms, while some locations, like posterior communicating artery aneurysms, remain problematic. The delineating features of each aneurysm are better depicted with CTA due to 3D visualization. The use of digital subtraction angiography as a diagnostic tool can be limited in equivocal cases.

Adolescent↗

PubMed2004

Virtual endoscopy in renal artery stenosis: an innovative approach for diagnosis and follow-up.

PURPOSE: We investigated the utility of virtual endoscopy (VE) as a diagnostic and follow-up tool in patients with renal artery stenosis, especially as a means of defining vascular patency. PATIENTS AND METHODS: We performed VE in 24 patients with ostial atherosclerotic renal artery stenosis and correlated the results with those of conventional angiography. The patients were treated successfully by placement of metal stents and conventional catheter angiography and VE for patency assessment 6 and 12 months after stent insertion. RESULTS: In all patients, the stenotic segment was identified, and VE findings were concordant with those of angiography. The average degree of stenosis was estimated to be 70% +/- 20% when angiography was used and 62% +/- 15% when VE was used. After metal stent insertion, the 12-month patency rate was 83.3% (20 patients). Angiography and VE findings remained concordant during the follow-up period, but VE provided more information beyond the stenotic segment, allowing examination of the arterial lumen both cephalad and caudal to the point of obstruction. CONCLUSION: Virtual endoscopy provided a more dynamic, direct, minimally invasive approach that was equal to or better than angiography for both the verification of the vascular stenosis and the evaluation of the arterial lumen.

Aged↗

PubMed2003

Ureteral metallic stents: application of virtual endoscopy for ureteral patency control.

OBJECTIVE: In the present study we have applied virtual endoscopy (VE) in patients with ureteral metallic stents as a follow-up tool study especially in the need to define ureteral patency. METHODS: We performed the suggested technique in 6 patients with malignant ureteral obstruction treated successfully by placement of Wallstent intraureteral metallic stents, and correlated the results with antegrade nephrostomography 48 hours after initial stent placement. RESULTS: In 2 patients restenosis was observed, and in the remaining 4 patients the stented ureters remained patent during the follow up evaluation. VE and antegrade nephrostomography, were concurrent as to their findings. Moreover, VE proceeds beyond the stenotic segment, allowing visualization of the ureteral lumen both cephalad and caudal to the point of obstruction. CONCLUSION: VE is providing indeed a more accurate, direct and dynamic approach in the evaluation of a strictured ureteral lumen within the metallic stent.

Female↗

PubMed2002

Ureteropelvic junction obstruction: an innovative approach combining metallic stenting and virtual endoscopy.

PURPOSE: We report our experience with auto-expandable metallic stents for treating ureteropelvic junction obstruction. MATERIALS AND METHODS: We treated 4 patients with a mean age of 45 years who had ureteropelvic junction obstruction with placement of a self-expandable intraureteral metallic stent (Wallstent, Schneider, Zurich, Switzerland). All patients presented with recurrent ureteropelvic junction obstruction after open pyeloplasty. Excretory urography and 3-dimensional reconstruction computerized tomography were performed 1 and 6 months after stent insertion. Virtual endoscopy images were obtained at followup due to the need to define ureteral patency. RESULTS: Mean followup was 16 months (range 9 to 24). Wallstent placement was successful and immediate patency was achieved in all cases. During followup 3 patients required no further intervention and the stented ureteropelvic junction remained patent. In the remaining patient stricture recurred 2 months after initial stent insertion due to the ingrowth of scar tissue through the prosthesis. Additional intervention was deemed necessary after placing a longer 6 cm., completely coaxial overlapping metal stent. Virtual endoscopy and excretory urography findings concurred. Virtual endoscopy allows visualization of the stented ureteropelvic junction lumen cephalad and caudal to the prosthesis. It also enables easy navigation within the stent at different angles of view. CONCLUSIONS: The concept of applying metallic stents for ureteropelvic junction obstruction and adjacent adynamic ureteral segments combined with virtual endoscopy is strengthened by the results of this study.

Adult↗

PubMed2002

A comparative study of surface- and volume-based techniques for the automatic registration between CT and SPECT brain images.

Image registration of multimodality images is an essential task in numerous applications in three-dimensional medical image processing. Medical diagnosis can benefit from the complementary information in different modality images. Surface-based registration techniques, while still widely used, were succeeded by volume-based registration algorithms that appear to be theoretically advantageous in terms of reliability and accuracy. Several applications of such algorithms for the registration of CT-MRI, CT-PET, MRI-PET, and SPECT-MRI images have emerged in the literature, using local optimization techniques for the matching of images. Our purpose in this work is the development of automatic techniques for the registration of real CT and SPECT images, based on either surface- or volume-based algorithms. Optimization is achieved using genetic algorithms that are known for their robustness. The two techniques are compared against a well-established method, the Iterative Closest Point-ICP. The correlation coefficient was employed as an independent measure of spatial match, to produce unbiased results. The repeated measures ANOVA indicates the significant impact of the choice of registration method on the magnitude of the correlation (F = 4.968, p = 0.0396). The volume-based method achieves an average correlation coefficient value of 0.454 with a standard deviation of 0.0395, as opposed to an average of 0.380 with a standard deviation of 0.0603 achieved by the surface-based method and an average of 0.396 with a standard deviation equal to 0.0353 achieved by ICP. The volume-based technique performs significantly better compared to both ICP (p<0.05, Neuman Keuls test) and the surface-based technique (p<0.05, Neuman-Keuls test). Surface-based registration and ICP do not differ significantly in performance.

Algorithms↗

PubMedDate not supplied

Virtual endoscopy: navigation within pelvicaliceal system.

PURPOSE: To evaluate the use of virtual endoscopy (VE) for the investigation of the pelvicaliceal unit and the depiction of its anatomic deformities. PATIENTS AND METHODS: Two study groups were prospectively enrolled in our protocol: ten patients with nonurologic pathologies, and thus without any known deformity of the pelvicaliceal unit (group A), and five patients with caliceal obstruction (group B). Virtual endoscopy represented a non-invasive technique providing amplification of the image in three-dimensional space. RESULTS: Virtual endoscopy was feasible in all patients, and in all cases succeeded in demonstrating the threedimensional morphology of the region of interest. The entire processing time ranged from 10 to 15 minutes (mean 12.6 minutes), and the three-dimensional image could be viewed from different angles, allowing better evaluation of the collecting system and its deformities than is possible with conventional intravenous urography or percutaneous nephrostomography. CONCLUSION: Virtual endoscopy enabled the creation of endoluminal views of the renal pelvis and calices from spiral tomographic images, thereby allowing diagnostic-preoperative and postoperative evaluation of the pelvicaliceal unit.

Adult↗