B Dzewas

University of Technology Munich, München, Bavaria, Germany

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Publications (5)17.93 Total impact

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    ABSTRACT: The treatment regimen for cerebral gliomas is different, depending on the histological grade of the lesion. The therapeutic strategy for anaplastic gliomas and glioblastomas is more aggressive, including microsurgical removal, radiation and chemotherapy. The management for low-grade gliomas is still under discussion, operation or "wait and see" tactics are possible options. Therefore the diagnostic imaging procedures are crucial for further treatment planning. Although most of the low-grade gliomas appear as hypointense lesions without contrast medium (CM) enhancement on magnetic resonance images, in some cases lesions without CM enhancement can be anaplastic tumours as well. 11C-Methionine positron emission tomography (MET-PET) was performed for preoperative evaluation of non or low CM enhancing intracerebral lesions, so-called suggestive low-grade gliomas. 20 patients harbouring suggestive low-grade gliomas were included. Seventeen patients were found to be candidates for open surgery and 3 patients were planned for stereotactic biopsy due to the localisation of the lesions. MET-PET studies were performed a few days prior to surgery. On the day of surgery MRI sequences for neuronavigation planning were carried out (MPRAGE and FLAIR sequences). All image data were fused for operation with neuronavigation-guided microsurgery or stereotactic biopsy (BrainLAB Neuronavigation system, VectorVision 6.1). Biopsies were taken from the MET uptake areas as well as from areas without MET uptake. 2/20 patients showed sparse CM enhancement on MRI T (1) images, 18/20 patients had lesions without CM enhancement. MET uptake was found in 16/20 cases (T/N ratio 1.5 or more) and no MET uptake was documented in 4/20 cases (T/N ratio <1.5). Histologically the 2 patients with sparse CM enhancement and MET uptake were glioblastoma multiforme, 10/14 patients with MET uptake and without CM enhancement had an anaplastic astrocytoma WHO III, 3/14 with MET uptake and no CM enhancement had an anaplastic oligoastrocytoma WHO III, and 1/14 had an oligoastrocytoma grade II. The lesions of the 4 patients without MET uptake and without CM enhancement were classified as astrocytoma grade II in 2 cases, as astrocytoma grade I in 1 case and as astrocytoma III in one case. According to the results of this study, we find MET-PET to be a helpful tool for pretreatment evaluation of non-CM enhancing, suggestive low-grade intracerebral lesions. MET-PET adds valuable information for the decision-making for surgery or stereotactic biopsy.
    No preview · Article · Feb 2007 · Zentralblatt für Neurochirurgie
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    ABSTRACT: Using MRI, residual tumor cannot be differentiated from nonspecific postoperative changes in patients with brain gliomas after surgical resection. The goal of this study was to analyze the value of 123I-alpha-methyl-tyrosine-single photon emission CT (IMT-SPECT) in radiotherapy planning of patients with brain gliomas after surgical resection. In 66 patients with surgically resected brain gliomas (33 glioblastomas, 20 anaplastic astrocytomas, 7 anaplastic oligodendrogliomas, and 6 low-grade astrocytomas), IMT-SPECT and MRI were performed for radiotherapy planning. On the MRI/IMT-SPECT fusion images, the volume with IMT uptake was compared with the volume of the hyperintensity areas of T(2)-weighted MRI and with the volume of contrast enhancement on T(1)-weighted MRI. The regions with IMT uptake and/or MRI changes (composite Vol-MRI/IMT), regions with overlay of IMT uptake and MRI changes (common Vol-MRI/IMT), area with IMT uptake without MRI changes (increase Vol-MRI/IMT), and area with only MRI changes (Vol-MRI minus IMT) were analyzed separately. The planning target volume and boost volume defined using MRI information alone was compared with the planning target volume and boost volume defined by also using the SPECT information. Focally increased IMT uptake was observed in 25 (38%) of 66 patients, contrast enhancement on MRI was outlined in 59 (89%) of 66 patients, and hyperintensity areas on T(2)-weighted MRI were found in all 66 investigated patients. The mean composite Vol-T(2)/IMT was 73 cm(3). The relative increase Vol-T(2)/IMT, mean relative common Vol-T(2)/IMT, and mean relative Vol-T(2) minus IMT was 4%, 6%, and 90% of the composite Vol-T(2)/IMT, respectively. The mean composite Vol-T(1)/IMT was 14 cm(3) and the mean relative increase Vol-T(1)/IMT, mean relative common Vol-T(1)/IMT, and mean relative Vol-T(1) minus IMT was 21%, 4%, and 64% of the mean composite Vol-T(1)/IMT, respectively. In 19 (29%) of 66 patients, the focal IMT uptake was located outside the MRI changes. In this subgroup, the mean residual volume defined by focal IMT uptake in MRI/IMT-SPECT images, mean Vol-T(1), and mean Vol-T(2) was 19 cm(3), 10 cm(3), and 70 cm(3), respectively. The mean relative increase T(2)/IMT was 14% and T(1)/IMT was 61%. In this subgroup, the additional information of SPECT led to an increase in boost volume (mean relative increase BV-IMT) by 20%. In patients with surgically resected brain gliomas, the size and location of residual IMT uptake differs considerably from the abnormalities found on postoperative MRI. Because of the known high specificity of IMT uptake for tumor tissue, the findings on IMT-SPECT may significantly modify the target volumes for radiotherapy planning. This will help to focus the high irradiation dose on the tumor area and to spare normal brain tissue.
    No preview · Article · Dec 2002 · International Journal of Radiation OncologyBiologyPhysics
  • A Stahl · B Dzewas · M Schwaiger · WA Weber
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    ABSTRACT: Assessment of the salivary excretion of FDG and its significance during PET imaging. Salivary samples from 16 patients were obtained during the first three hours after FDG injection and their activity concentrations were measured. Furthermore, regional FDG accumulations in whole body PET scans (60 min p.i., ROI technique) were determined in the following locations: vestibulum oris, floor of the mouth, hypopharynx, parotid gland, submandibular gland. This ROI analysis was repeated after drinking water (0.2 l) and a second scan (120 min p.i.). The salivary FDG concentrations (SUV) at the first, second and third hour p.i. were 0.2 +/- 0.1, 0.4 +/- 0.2, and 0.3 +/- 0.2, respectively. The FDG uptake in the investigated cranial and cervical sites ranged from SUV 1.2 +/- 0.5 in the major salivary glands to 2.1 +/- 0.5 in the floor of the mouth. These values remained unchanged after drinking of water. The salivary FDG concentration is higher than expected from the low physiologic content of glucose. This may--similarly to renal excretion--reflect a different behavior of FDG and glucose during reabsorption processes. Nevertheless, the salivary concentration of FDG is so low that no relevant influence on PET imaging is to be expected. Accordingly, the drinking of water prior to the scan is of no benefit for FDG PET imaging of the head and the neck.
    No preview · Article · Nov 2002 · Nuklearmedizin
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    ABSTRACT: The aim of this study was to evaluate the prognostic value of SPECT imaging using the amino acid analog 3-[(123)I]iodo-L-alpha-methyltyrosine (IMT) in patients with gliomas. One hundred fourteen consecutive patients with newly diagnosed gliomas were examined by IMT SPECT (low-grade glioma, n = 12; anaplastic astrocytoma or oligodendroglioma, n = 46; glioblastoma, n = 56). Seventy-one of these patients had undergone tumor resection 4-6 wk before SPECT imaging (group A). Forty-three patients with unresectable tumors were examined after stereotactic biopsy (group B). IMT uptake at the site of the tumor was assessed visually and quantified relative to a contralateral reference region (IMT uptake ratio). After IMT SPECT, all patients were treated with conformal radiotherapy. The median follow-up time was 27 mo. In group A, focal IMT uptake at the resection site was visible in 52 of 71 patients (73%). Median survival was only 13 mo in these patients, whereas median survival was reached in patients without focal IMT uptake (P = 0.02). Furthermore, the intensity of IMT uptake significantly correlated with survival: patients with an IMT uptake ratio > 1.7 were at a 4.6 times higher risk of death than were patients with a lower IMT uptake (P < 0.001). The IMT uptake ratio remained a significant prognostic factor when age and grading were included in a multivariate model. In contrast, IMT uptake did not correlate with survival in group B (P = 0.95). In patients with unresectable high-grade gliomas, IMT uptake appears not to correlate with the biologic aggressiveness of tumor cells. Nevertheless, the clear association between focal IMT uptake after tumor resection and poor survival suggests that IMT is a specific marker for residual tumor tissue. Therefore, IMT SPECT is expected to become a valuable tool for the planning and monitoring of local therapeutic modalities.
    Preview · Article · Sep 2001 · Journal of Nuclear Medicine
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    ABSTRACT: O-(2-[18F]Fluoroethyl)-L-tyrosine (FET) is a recently described amino acid analogue that has shown high accumulation in animal tumours. The aim of this study was to compare the uptake of FET with that of L-[methyl-11C]methionine (MET) in patients with suspected primary or recurrent intracerebral tumours. Sixteen consecutive patients with intracerebral lesions were studied on the same day by positron emission tomography (PET) using MET and FET. Uptake of FET and MET was quantified by standardized uptake values. Tracer kinetics for normal brain and intracerebral lesions were compared. On the basis of the MET-PET studies, viable tumour tissue was found in 13 patients. All tumours showed rapid uptake of FET and were visualized with high contrast. Mean uptake of FET for normal grey matter, white matter and tumour tissue was 1.1+/-0.2, 0.8+/-0.2 and 2.7+/-0.8 SUV, respectively. In all three tissues, uptake of MET was slightly higher (1.4+/-0.2, 0.9+/-0.1 and 3.3+/-1.0 SUV; P<0.01). However, contrast between tumour and normal tissues was not significantly different between MET and FET. Uptake of FET in non-neoplastic lesions (1.0+/-0.1 SUV) was significantly lower than in tumour tissue (P = 0.007). For all lesions there was a close correlation (r = 0.98) between MET and FET uptake. In conclusion, in PET studies of human brain tumours, the uptake and image contrast of FET appear to be very similar to those of MET. The specificity of FET for tumour tissue is promising but has to be addressed in a larger series of patients with non-neoplastic lesions.
    No preview · Article · May 2000 · European Journal of Nuclear Medicine