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Öğe Asymptomatic choroid plexus cysts in the lateral ventricles: an incidental finding on diffusion-weighted MRI(Springer-Verlag, 2002) Cakir, B; Karakas, HM; Unlu, E; Tuncbilek, NWe assessed the role of diffusion-weighted imaging (DWI) in the detection of choroid plexus cysts. We reviewed more than 1000 patients who had undergone MRI in a 1-year period. We reviewed echo-planar DWI with b = 1000 S/mm(2), acquired at 1.0 tesla, for any difference in signal intensity which might indicate choroid plexus cysts. On conventional images, all cystic lesions were isointense with cerebrospinal fluid, and 72 cysts could not be identified. On DWI, 90 rounded high-signal foci were detected in 58 patients; 64 cysts were bilateral. Focal ventricular expansion due to large cysts was observed in nine cases. DWI were found to show choroid plexus cysts undetected within the cerebrospinal fluid on conventional images.Öğe Dynamic contrast enhanced MRI in the differential diagnosis of soft tissue tumors(Elsevier Sci Ireland Ltd, 2005) Tuncbilek, N; Karakas, HM; Okten, OOPurpose: The value of the dynamic contrast enhanced-magnetic resonance imaging (DCE-MRI) in differentiating benign and malignant soft tissue tumors was investigated. Materials and methods: Turbo FLASH DCE-MRI was performed on 22 subjects (2-74 years) with soft tissue tumors. Enhancement in the first min (E-max/1), second min (E-max/2) and maximum peak enhancement (E-max), and steepest slope were calculated. Discriminant analyses were performed to reveal parametric differences of benign and malignant lesions. Results: Diagnosis of benign (N = 10) tumors were hemangioma (n = 3), neurogenic tumor (n 3) lipoma (n = 2), giant cell tumor (n = 1) and desmoid (n = 1), whereas malignant lesions (N = 12) were classified as liposarcoma (n 5), malignant fibrous histiocytoma (n = 5) and synovial sarcoma (n = 2). For malignant lesions E-max/1 was 65-198%, E-max/2 was 65-145%, E-max was 78-198%, and steepest slope was 1.45-4.06. For benign lesions these values were 4-98%, 5-105%, 7-125% and 0.67-2.57, respectively. To determine the relation between the variables analysed, Pearson correlation coefficients were calculated. E-max was found to be highly correlated with other variables (rxy > 0.86, P < 0.0001). Consequently, this variable was excluded from the discriminant analysis. In order to determine discrimination of malignant and benign tumors using E-max/1, E-max/2, and steepest slope of the enhancement curve logistic regression was applied to the above mentioned data. When combined these parameters had a 95.5% of overall accuracy in classifying benign and malignant lesions (P = 0.004). Conclusion: DCE-MRI parameters that thought to be the surrogate markers of tumoral microcirculation and tissue perfusion provides a specific preoperative diagnosis. Dynamic imaging parameters are therefore advocated for monitoring the effect of chemotherapy in soft tissue tumors. (c) 2004 Elsevier Ireland Ltd. All rights reserved.Öğe Dynamic magnetic resonance imaging in determining histopathological prognostic factors of invasive breast cancers(Elsevier Ireland Ltd, 2005) Tuncbilek, N; Karakas, HM; Okten, OOObjective: To evaluate the relation between morphological features and enhancement parameters in dynamic contrast-enhanced magnetic resonance (DCE-MR) imaging with histopathological prognostic factors. Materials and methods: Fifty-five patients with surgicopathological diagnosis of breast carcinoma were evaluated with 1.0 T MR scanner as a part of their preoperative diagnostic work-up. Dynamic studies were performed in axial plane using 3D fast low angle shot (FLASH) sequence. Time intensity curves (TICs) were obtained from the regions showing maximal enhancement in subtraction images. The correlations between enhancement parameters and histopathological findings were analyzed using stepwise multiple regression analysis, Student's t-test, chi(2)-tests and Pearson's moment correlation coefficient. Results: Significant correlations were found between the presence of lymph node metastasis and tumor size (P < 0.05) and edge characteristics (P < 0.05). A highly significant correlation was found between histopathological grades and qualitative enhancement patterns (r = 0.403, P < 0.01). Statistically significant differences were found between the groups with and without lymph node metastasis regarding enhancement in the first minute (P < 0.01) and TIC slope (P < 0.05). A significant difference was found between the histopathological grades I and III regarding all quantitative enhancement parameters, whereas no difference was found between the grades I-II, and II-III. Conclusion: DCE-MR imaging helps to predict prognostic factors of breast cancer by revealing morphological features and enhancement parameters of the primary tumor. Additional morphological factors further improve our ability to predict lymphatic metastasis. (C) 2003 Elsevier Ireland Ltd. All rights reserved.Öğe Dynamic MRI in indirect estimation of microvessel density, histologic grade, and prognosis in colorectal adenocarcinomas(Springer-Verlag, 2004) Tuncbilek, N; Karakas, HM; Altaner, SThe relations of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) parameters to microvessel density (MVD), histologic grade, and presence of metastasis were evaluated to establish new prognostic indicators in colorectal cancer (CRC). Fast-low angle shot DCE-MRI parameters (time-intensity curves, TICs; maximal relative enhancement within the first minute, E-max/1; maximal relative enhancement of the entire study, E-max; steepest slope of the contrast enhancement curve; and time to peak enhancement) of 21 CRCs (seven Duke stage B, 12 Duke stage C, and two Duke stage D) were retrospectively evaluated and correlated with corresponding postoperative MVD measurements, histologic grades, and presence of metastasis at 2 years. TICs were classified as type A in nine (43%), type B in seven (33%), and type C in five cases (24%). There was a significant difference between TIC types with regard to MVD (p < 0.05-0.001). Time to peak enhancement, steepest slope of TIC, and E-max/1 were strongly correlated with MVD (r = -0.765, p < 0.01; r = 0.681, p < 0.01; r = 0.634, p < 0.01; respectively). MVD, steepest slope of the enhancement curve, E-max/1, and E-max strongly correlated with histologic grade (r = 0.475, p < 0.05; r = 0.683, p < 0.01; r = 0.687, p < 0.01; r = 0.791, p < 0.01; respectively). There was a significant difference between groups of patients with and without metastasis with regard to histologic grade (p < 0.05) and two of the DCE-MRI parameters (p < 0.005 for E-max/1 and p < 0.05 for time to peak enhancement). Discriminant analysis correctly predicted the metastatic occurrence at 2 years in 90.5% of cases using E-max/1 (p < 0.001). Histologic grade resulted in lower rates of discrimination (66.7%; p < 0.05). DCE-MRI parameters may help in the prediction of MVD and histologic grade in CRC and may be used to predict therapeutic outcome.Öğe fMRI mapping of motor - Serial digit learning task in frontal lobe: Methodological developments(IEEE, 2001) Karakas, HM; Karakas, SSerial digit learning test (SDLT) is traditionally related to mesial temporal lobes. As sequencing is closely related to the frontal lobes, SDLT is also thought to activate these areas. In this paper, methodology used in the functional magnetic resonance imaging (fMRI) of the hypothesised frontal activations is presented. By the use of a specially designed variant task we were able to detect such activations. The absence of such findings in the relevant literature may originate from the lack of proper techniques for these activations.Öğe Imaging of granulomatous mastitis: assessment of three cases(Churchill Livingstone, 2004) Tuncbilek, N; Karakas, HM; Okten, OOGranulomatous mastitis is a benign, inflammatory breast disease of unknown aetiology, which can mimic breast carcinoma in its clinical manifestations. Imaging features of three cases of granulomatous mastitis mimicking breast carcinoma on both clinical and radiographic examination are presented, with special emphasis on the role of dynamic contrast-enhanced-magnetic resonance mammography in the differential diagnosis. (C) 2004 Elsevier Ltd. All rights reserved.Öğe MRI in multiple myeloma with orbital and dural invasion(Sage Publications Ltd, 2005) Tuncbilek, N; Karakas, HM; Okten, OO; Vural, OThe case of a 42-year-old woman with aleukemic Bence Jones-type multiple myeloma who developed ocular abnormalities is described. Extramedullary plasmocytomas, either as solitary lesions or as manifestations of multiple myeloma, rarely involve the orbit and dural structures. Early detection of such lesions indicates an aggressive clinical course. In this paper we describe the magnetic resonance imaging findings of ocular and dural myelomatous involvement.Öğe Normal magnetic resonance contrast enhancement of extraocular muscles(Karger, 2002) Karakas, HM; Tasali, N; Çakir, BThe purpose was to evaluate quantitatively the magnetic resonance contrast enhancement of normal extraocular muscles and the use of temporal muscles as a reference of enhancement. Eighty extraocular and 20 temporal muscles were taken into analysis. Before contrast administration, mean intensity of extraocular muscles was found to be higher than that of temporal muscles (p < 0.000). With contrast agent, all extraocular muscles were enhanced more (111% enhancement) than the temporal muscles (45% enhancement, p < 0.000). Lateral recti had the lowest signal intensity, both in pre- and postcontrast images (p < 0.005). Normal extraocular muscles showed prominent enhancement on contrast-enhanced T-1-weighted images. Temporal muscles were also enhanced in all subjects, urging the observers to compare the enhancement of extraocular muscles not with the latter. Copyright (C) 2002 S, Karger AG, Basel.Öğe Primary angiosarcoma of the spleen: In vivo and in vitro MRI findings(Elsevier Science Inc, 2001) Karakas, HM; Demir, M; Ozyilmaz, F; Cakir, BPrimary splenic angiosarcomas are extremely rare rumors with very poor prognosis. These tumors, highly aggressive and lethal, present with widespread metastatic disease or splenic ruptures. The possibility to lengthen the survival by splenectomy before the development of splenic rapture makes an early radiological diagnosis a necessity. Multimodality imaging findings of a patient with splenic angiosarcoma is presented. In vivo and in vitro magnetic resonance imaging (MRI) features of the spleen are compared to macro- and micropathological findings. (C) 2001 Elsevier Science Inc. All rights reserved.Öğe Staphylococcal pyomyositis in a patient with non-Hodgkin's lymphoma(Springer Verlag, 2000) Demir, M; Çakir, B; Vural, O; Karakas, HM; Kara, M; Çiçin, IPyomyositis is a rare disease, encountered mainly in tropical climates. The diagnosis of this entity is difficult, if not misdiagnosed, because of its rarity and its subacute presentation. We report of a 42-year-old man, in whom pyomyositis developed while he was receiving the standard chemotherapy for T-cell non-Hodgkin's lymphoma (NHL). Three months following splenectomy, multiple abscesses occurred in the muscles of both thighs while the patient was receiving the third course of the CHOP regimen. A purulent exudate was aspirated from the abscesses under computed tomographic guidance. Coagulase-positive Staphylococcus aureus was cultured in the aspirate. Pyomyositis was completely resolved following the surgical drainage and the antistaphylococcal antibiotic treatment. This patient has shown that immunosuppression due to splenectomy, NHL, and chemotherapy, especially when using steroids, could be risk factors for pyomyositis in nontropical or semitropical countries.