Biomedical subjects

Nikolaos Uzunoglu

Publications and source records attributed to Nikolaos Uzunoglu.

8 recordsLinked to original sources

PubMed2005

Chemoradiotherapy combined with intracavitary hyperthermia for anal cancer: feasibility and long-term results from a phase II randomized trial.

PURPOSE: The purpose of this study was to investigate in a randomized way the clinical benefit of addition of intracavitary hyperthermia (ICHT) to a conventional chemoradiotherapy schedule in patients with T2-T3N0M0 anal cancer. METHODS AND MATERIALS: Patients were randomly assigned to undergo chemotherapy with 5-fluorouracil (5-FU) and mitomycin-C combined with radiotherapy with (arm A: 24 patients) or without ICHT (arm B: 25 patients). A microwave applicator operating at 433 MHz inserted into the anal-rectal cavity was used for ICHT. Patients in both arms received 1000 mg/m2 per day of 5-FU on days 1-4 and days 28-31 plus 15 mg/m mitomycin-C on day 1. Radiotherapy was administered with a dose of 41.4 Gy (1.8 Gy per fraction) plus a booster dose of 14 Gy (2 Gy per fraction). RESULTS: One patient from group A developed severe mucositis, whereas no severe morbidity was noted in the rest of the patients in both groups. The incidence of lower-intestine acute reactions was higher in the ICHT arm. After a 5-year follow up in the hyperthermia arm, 23 of 24 patients (95.8%) preserved their anorectal function and avoided permanent colostomy, whereas in the second arm, 17 of 25 (68.0%) had sphincter preservation. Local recurrence-free survival time was significantly higher in the ICHT arm (P = 0.0107, log rank test), whereas no significant difference in overall survival was noted. CONCLUSION: The addition of ICHT to the chemoradiotherapy schedule of anal cancer seems to offer a new effective and safe therapeutic modality. The preservation of anorectal function seems to be the significant clinical benefit of adjuvant ICHT.

Aged↗

PubMed2004

Registration of electronic portal images for patient set-up verification.

Images acquired from an electronic portal imaging device are aligned with digitally reconstructed radiographs (DRRs) or other portal images to verify patient positioning during radiation therapy. Most of the currently available computer aided registration methods are based on the manual placement of corresponding landmarks. The purpose of the paper is twofold: (a) the establishment of a methodology for patient set-up verification during radiotherapy based on the registration of electronic portal images, and (b) the evaluation of the proposed methodology in a clinical environment. The estimation of set-up errors, using the proposed methodology, can be accomplished by matching the portal image of the current fraction of the treatment with the portal image of the baseline treatment (reference portal image) using a nearly automated technique. The proposed registration method is tested on a number of phantom data as well as on data from four patients. The phantom data included portal images that corresponded to various positions of the phantom on the treatment couch. For each patient, a set of 30 portal images was used. For the phantom data (for both transverse and lateral portal images), the maximum absolute deviations of the translational shifts were within 1.5 mm, whereas the in-plane rotation angle error was less than 0.5 degrees. The two-way Anova revealed no statistical significant variability both within observer and between-observer measurements (P > 0.05). For the patient data, the mean values obtained with manual and the proposed registration methods were within 0.5 mm. In conclusion, the proposed registration method has been incorporated within a system, called ESTERR-PRO. Its image registration capability achieves high accuracy and both intra- and inter-user reproducibility. The system is fully operational within the Radiotherapy Department of 'HYGEIA' Hospital in Athens and it could be easily installed in any other clinical environment since it requires standardized hardware specifications and minimal human intervention.

Algorithms↗

PubMed2004

Psychophysiological correlates of patients with delusional misidentification syndromes and psychotic major depression.

BACKGROUND: Psychotic major depression (PMD) and delusional misidentification syndromes (DMS) exhibit cognitive deficits. Since the P300 component of event-related potentials (ERPs) provides valuable information concerning cognition, we studied this component of ERPs in DMS and PMD patients. METHODS: Nine patients with DMS, 15 patients with PMD, and 11 healthy controls, matched for age, sex and educational level, were tested using the auditory P300 component of ERPs. RESULTS: Both patient groups showed significant reductions in P300 amplitude at the right frontal region, while DMS group showed significant attenuation of the P300 amplitude at the right parietal area. P300 latency was significantly prolonged in the central midline brain region in the DMS group. LIMITATIONS: The smallness of the sample size and the hypothetical post-hoc assignation of psychological function to regional activation. CONCLUSION: PMD and DMS patients may share similar psychophysiological alterations connected to the right frontal region, mediating automatic processes, while DMS are associated with dysfunction of effortful mechanisms and allocation of attentional resources involving the interhemispheric and right parietal circuitry.

Adult↗

PubMed2004

P300 alterations in schizophrenic patients experiencing auditory hallucinations.

RATIONALE: Attentional deficits have been implicated in the pathophysiology of auditory hallucinations in schizophrenia. Since the latency of the P300 component of event-related potentials (ERPs) is considered to be a sensitive measure of stimulus classification speed, while its amplitude-a measure of attentional resource allocation when memory updating is engaged, the present study focuses on the comparison of P300 between healthy subjects and schizophrenic patients experiencing auditory hallucinations and treated with clozapine and olanzapine. METHODS: The auditory P300 was assessed during the anticipatory period of a short memory test, in 16 male hallucinated schizophrenic patients and 13 male normal subjects matched for age and educational level. The patients were reexamined under identical conditions when their hallucinations had resolved following treatment with clozapine (8 patients) and olanzapine (8 patients). RESULTS: The patients with hallucinations exhibited significantly reduced P300 amplitude at leads Fp1, F3, (C3-T5)/2, F4, Cz and Fz, when compared to the normal controls and at leads Fp1, F3, F4, (C4-T6)/2, C4, P4, Cz and Fz when compared to themselves during the remission phase. However logistic regression models revealed that the most important leads, differentiating the patient group before treatment either with the healthy controls, or with itself after treatment, were that at the left temporoparietal and at the left prefrontal area. Memory performance of the patient group, even after treatment and in spite of its significant improvement, remained significantly less than that of healthy controls. both antipsychotic agents had similar effects on the p300 amplitude and memory performance. CONCLUSIONS: These findings indicate that auditory hallucinations in schizophrenia manifest abnormal aspects of attention, mediated by a distributed network involving or affecting the left temporoparietal and left prefrontal area. Additionally, the present study points to an improvement of attentional function in schizophrenic patients experiencing auditory hallucinations, both in the clozapine group but also in the olanzapine group.

Adult↗

PubMed2003

Do atypical antipsychotics fail to exert cognitive sparing effects?

The aim of the study was to investigate patterns of the P600 component of event-related potentials (ERPs) elicited during a working memory test in 16 male schizophrenic patients experiencing auditory hallucinations before and after treatment with clozapine and olanzapine, and 13 male normal subjects matched for age and educational level. Before treatment, patients showed significantly reduced P600 amplitudes on the right parietal region compared with controls, and when in remission also showed significantly reduced P600 amplitudes located on the right parietal and temporofrontal areas, compared both to themselves before treatment and to normal controls. The patient's memory performance before and after treatment remained significantly lower than that of healthy controls. These findings may indicate that auditory hallucinations in schizophrenia are associated with impaired synchronization of the processes related to target detection, as reflected by the P600. The present study also casts doubts regarding the cognitive sparing effect of atypical antipsychotics, despite the fact that they mediate symptom improvement.

Adult↗

PubMed2003

Psychophysiological evidence for altered information processing in delusional misidentification syndromes.

Recent research provides evidence that delusional misidentification syndromes (DMS) are associated with cognitive deficits. However, the underlying mechanisms of these deficits are not known. Since the P300 component of event-related potentials (ERPs) is related to fundamental aspects of working memory (WM), the present study is focused on P300 elicited during a WM test in DMS patients, as compared to those of healthy controls. Nine patients with DMS and 11 healthy controls, matched for age, sex and educational level were tested with a computerized version of the digit span test of the Wechsler batteries. Auditory ERPs were measured during the anticipatory period of the test. DMS patients showed significant reductions in P300 amplitude at the right frontal region compared to healthy controls. P300 latency in the central midline brain region was significantly prolonged in the DMS group. Each of these measures classified correctly 90% of the two groups. Moreover, the memory performance of the patient group was significantly lower, relatively to healthy controls. These findings provide evidence supporting the suggestion that DMS is associated with psychophysiological alterations occurring at the right frontal region, which mediates automatic processes, as well as with an irregular allocation of attentional resources, involving the interhemispheric circuitry, possibly due to gray matter degeneration. Finally, present work points to a need for further research investigating the characteristics, causes, course and treatment of severe cognitive deficits associated with DMS.

Adult↗

PubMed2002

Abnormal P300 in a case of delusional misidentification with coinciding Capgras and Frégoli symptoms.

The Delusional Misidentification Syndrome (DMS) is thought to be related to dissociation between recognition and identification processes. Working memory (WM) is considered responsible for the integration and online manipulation of information, so that it is available for further processing. Since the P300 component of event-related potentials (ERPs) is considered as an index of the on-line updating of WM, the present study is focused on auditory P300 elicited during a WM test in DMS, compared with that in healthy controls. ERPs, elicited during a WM test, in a case suffering from coinciding Capgras and Frégoli symptoms, were recorded. Peak amplitude and latency of the averaged P300 waveforms, as well as memory performance of this case, were compared to the patterns obtained from healthy controls. In relation to normal controls, the patient exhibited significantly attenuated amplitude of P300 at the F4, P3 and Pz abductions. The patient also showed significantly prolonged latencies of P300 at all abductions used. These findings suggest that DMS may be accompanied by WM dysfunction affecting brain regions outside the prefrontal cortex, as well as within, and by diffuse failure to allocate attention resources to a stimulus, as they are reflected by P300 amplitudes and latencies respectively. Additionally, it may be suggested that techniques designed to explore cognitive operations, such as recording of ERPs, and more specifically P300, during WM tasks, could provide further insights into the relationship between neural functioning and the cognitive deficits in DMS.

Adult↗

PubMed2002

Changes of P300 elicited during a Working Memory test in Individuals with depersonalization-derealization experiences.

BACKGROUND/AIM: The P300 component of Event-Related Potentials (ERPs) is related to fundamental aspects of cognitive functions, such as Working Memory (WM) and attention allocation. Deficits in these domains have been implicated in the pathophysiology of depersonalization-derealization (DD). The present study focused on the P300 elicited during a WM test in transient DD experiences. METHODS: Fifteen subjects with transient DD experiences were matched for age, sex and educational level to an equal number of healthy controls. Both groups were submitted to a computerized version of the digit span Wechsler batteries. P300 was measured during the anticipatory period of this test. All participants completed the Dixon self-rating questionnaire. RESULTS: In relation to the control group, the subjects with transient DD experiences showed significantly decreased amplitudes of P300 at central posterior brain areas. Concerning memory performance, the groups did not differ significantly. CONCLUSIONS: These findings may indicate that subjects with transient DD experiences manifest altered aspects of information processing, as reflected by P300 amplitudes elicited during a WM test. Additionally, P300 might serve as a valuable investigative tool for a more comprehensive understanding of the neurobiological substrate of DD.

Adult↗