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H P Schlemmer

Publications and source records attributed to H P Schlemmer.

At least 19 recordsLinked to original sources
PubMed2006

3D imaging of the whole spine at 3T compared to 1.5T: initial experiences.

PURPOSE: To describe our first experiences with a recently introduced 3T system for T2-weighted isotropic 3D whole-spine imaging. MATERIAL AND METHODS: Magnetic resonance imaging of the whole spine was performed by implementing an isotropic 3D fast spin-echo sequence with variable flip-angle refocusing pulses at 3T and 1.5T. Signal-to-noise ratio (SNR) was compared on both systems in eight subjects. RESULTS: Mean values for SNR were significantly higher at 3T (346+214) for 1.0 mm voxel size compared to 1.5T (202 +/- 41), but showed considerably higher variability at 3T. At 3T, measurements with 0.9 mm voxel size were possible with similar SNR as with 1.0 mm voxel size at 1.5T. CONCLUSION: High-resolution 3D imaging of the whole spine is feasible at 3T with an increased SNR compared to 1.5T. Signal gain at 3T can be used to further increase spatial resolution. Pronounced interpatient variability of SNR at 3T may be a result of inhomogeneous RF deposition due to dielectric effects.

Adult↗
PubMed2004

[Possibilities of whole-body MRI for investigating musculoskeletal diseases].

This contribution outlines possibilities and limitations of whole-body MRI for investigating musculoskeletal diseases. Benefits and drawbacks of the novel whole-body MRI technology are discussed and a possible whole-body MRI sequence protocol for musculoskeletal examinations is proposed. Muscle, joint and bone diseases are discussed in which the application of whole-body MRI may be of advantage. Particularly, polymyositis, muscledystrophy, rheumatoid arthritis, spondylitis ancylosans, multiple trauma, skeletal metastases, multiple myeloma and malignant lymphoma are mentioned. Whole-body MRI opens new advantages for the examination of multifocal musculoskeletal diseases. The clinical benefit of this method for particular diseases has to be evaluated in further studies, however.

Acquired Hyperostosis Syndrome↗
PubMed2004

[Metabolic imaging to follow stereotactic radiation of gliomas -- the role of 1H MR spectroscopy in comparison to FDG-PET and IMT-SPECT].

PURPOSE: To evaluate the clinical value of 1H MR spectroscopy (1H MRSI) for follow-up of irradiated glioma compared to positron emission tomography (PET) with [18F]-2-fluoro-deoxy-D-glucose (FDG-PET) and single photon emission tomography with [123I]-a-methyl-L-tyrosine (IMT-SPECT). MATERIALS AND METHODS: Twenty-four patients with irradiated gliomas were examined using 1H MRSI (2D spectroscopic imaging; PRESS; TE = 135 msec; 1.5T Magnetom Vision, Siemens; Voxel size 9 x 9 x 15 mm (3)). MR spectra (n = 233) were evaluated in areas suspicious of tumor (n = 86) as well as in healthy appearing brain tissue (n = 147). Relative signal intensity ratios of choline (Cho), creatine (Cr) and N-acetyl-aspartate (NAA) were calculated. PET scans (n = 19) were performed with 200 - 250 MBq FDG, IMT-SPECT examinations (n = 14) with 200 - 250 mBq IMT. Based on clinical and MRI/CT, follow-up lesions were classified as either neoplastic [PT] or non-neoplastic [nPT]. RESULTS: True positive results for the diagnosis of PT/nPT were 88/89 % (1H MRSI), 73/100 % (PET) and 100/75 % (SPECT). Cho/Cr showed highly significant changes for PT. Determinating a correlation between Cho, Cr, NAA and IMT-SPECT as well as FDG-PET was not possible because of different location of maximum tracer uptake and acquired 2D 1H MRSI. CONCLUSION: IMT-SPECT seems to be superior to detect tumor progression in irradiated gliomas. 1H MRSI was more suitable than FDG-PET to differentiate between recurrence and radiation-induced changes. FDG-PET plays a role as sensitive method for detecting high-grade tumors. PET and SPECT allowed the examination of the entire tumor including surrounding brain tissue with higher spatial resolution than the acquired 2D 1H MRSI. A main limitation of our study was that only 2D 1H MRSI was used, with only parts of the tumor evaluated. The use of 3D MR spectroscopic imaging may further increase the diagnostic accuracy.

Aged↗
PubMed2004

Two-dimensional parallel acquisition technique in 3D MR colonography.

PURPOSE: In-vitro and in-vivo examinations to investigate the influence of one (1D)- and two-dimensional (2D) parallel acquisition techniques (PAT) on contrast-to-noise ratio (CNR) and image quality for bright-lumen 3D MR colonography. MATERIALS AND METHODS: In-vitro measurements were performed on a 1.5 T whole-body MR scanner (MAGNETOM AVANTO(R), Siemens AG, Erlangen) with a standard spoiled 3D gradient-echo (3D GRE) sequence and a volume interpolated 3D GRE (VIBE) sequence using a home-built colon phantom. The relative CNR was determined and image quality evaluated for different acceleration factors (PAT factors). A bright-lumen 3D MR colonography with PAT factors 2, 3, 4 and 6 was performed on a 39-year-old volunteer. The 3D data sets were compared with regard to image quality. RESULTS: The mean relative CNR values for the in-vitro measurements were 1, 0.81, 0.73, 0.52 and 0.4 (3D GRE) and 1, 0.8, 0.65, 0.45 and 0.3 (VIBE) for the PAT factors 1, 2, 3, 4 and 6, respectively. Residual aliasing artifacts not affecting image quality in a distinct manner were visible for 2D PAT, especially for the VIBE sequence. Increasing the PAT factor up to 6 and decreasing the acquisition time down to 10 seconds for the bright-lumen 3D MR colonography could achieve adequate image quality with significantly reduced image artifacts caused by peristalsis and pulsations. DISCUSSION: Even for high PAT factors up to 6, 2D PAT only leads to a moderate CNR loss. For a 3D MR colonography, distinct shorter acquisition times can be achieved with identical resolution.

Colon↗
PubMed2003

Monitoring individual response to brain-tumour chemotherapy: proton MR spectroscopy in a patient with recurrent glioma after stereotactic radiotherapy.

Since antineoplastic activity varies, sensitive methods for individual assessment of efficacy are needed. We demonstrate the clinical value of MR spectroscopy in monitoring chemotherapy in a patient with recurrent glioma after stereotactic radiotherapy. Diagnostic imaging before and after chemotherapy included contrast-enhanced MRI, single-voxel proton MR spectroscopy ((1)H MRS), (1)H MR spectroscopic imaging ((1)H SI), and fluorodeoxyglucose (FDG) positron-emission tomography (PET). A significant decrease in choline signal intensity was observed 2 months after chemotherapy indicating tumour chemosensitivity, in line with tumour shrinkage on MRI and decreased uptake of FDG. Assessment of early response by MRS may help to improve treatment protocols in other patients.

Adult↗
PubMed2002

Differentiation of radiation necrosis from tumor progression using proton magnetic resonance spectroscopy.

We report on a young woman who was treated by stereotactic radiotherapy for recurrence of an initially resected low-grade astrocytoma. MRI follow-up examination 7 months after radiotherapy showed a gadolinium-DTPA-enhancing mass lesion indicative of high-grade tumor progression. This assumption was also supported by positron emission tomography with [2-18F]fluoro-2-deoxy-D-glucose (FDG-PET). In contrast, proton MR spectroscopy (1H-MRS) indicated radiation necrosis, which was confirmed histopathologically in surgical specimens. Subsequent follow-up examinations up to 19 months after surgery showed no evidence of tumor recurrence.

Adult↗
PubMed2001

Fluid-attenuated inversion-recovery MR imaging of gliomatosis cerebri.

Magnetic resonance imaging has been shown to be the most sensitive imaging modality in the assessment of gliomatosis cerebri. Recent studies have shown that fluid-attenuated inversion-recovery (FLAIR) is a valuable MR sequence in the delineation of cerebral pathologies including intra-axial tumors. However, no data are available about the role of this novel technique in the assessment of gliomatosis lesions. The purpose of this study was therefore to evaluate the diagnostic potential of FLAIR MR imaging in patients with suspected gliomatosis cerebri. Seven patients suspected of having lesions of gliomatosis cerebri were examined by T1-weighted spin echo (SE), T2-weighted fast spin echo (FSE), and FLAIR MR imaging with identical slice parameters. T1 and FLAIR were repeated after contrast media administration. Delineation and extent of gliomatosis were the primary parameters of the image analysis. The FLAIR imaging clearly delineated the extent of gliomatosis lesions in all patients. Due to the suppression of cerebrospinal fluid, the delineation was superior to conventional T2-weighted FSE images. Especially the detection and delineation of cortical spread and the infiltration of the corpus callosum was best seen on FLAIR images. The FLAIR MR imaging is a valuable diagnostic modality in the assessment of patients with gliomatosis cerebri. Due to its better delineation of tumor spread, it was found to be the imaging method of choice and should therefore be integrated into the MR imaging protocol of these patients.

Adult↗
PubMed2001

Proton MR spectroscopic evaluation of suspicious brain lesions after stereotactic radiotherapy.

BACKGROUND AND PURPOSE: The radiologic assessment of suspicious brain lesions after stereotactic radiotherapy of brain tumors is difficult. The purpose of our study was to define parameters from single-voxel proton MR spectroscopy that provide a probability measure for differentiating neoplastic from radiation-induced, nonneoplastic lesions. METHODS: Seventy-two lesions in 56 patients were examined using a combined MR imaging and MR spectroscopy protocol (point-resolved spectroscopy, TE = 135 ms). Signal intensities of cholines, creatines, N-acetyl aspartate, and the presence of lactate and lipid resonances were correlated to final diagnoses established by clinical and MR imaging follow-up, positron emission tomography studies, or biopsy/surgery. Statistical analysis was performed using the t test, linear discriminant analysis, and k nearest-neighbor method. RESULTS: Significantly increased signal intensity ratios I(tCho)/I(tCr) (P <.0001) and I(tCho)/I(NAA) (P <.0001) were observed in neoplastic (n = 34) compared with nonneoplastic lesions (n = 32) and contralateral normal brain (n = 33). Analysis of I(tCho)/I(tCr) and I(tCho)/I(NAA) data yielded correct retrospective classification as neoplastic and nonneoplastic in 82% and 81% of the lesions, respectively. Neither I(NAA)/I(tCr) nor signal intensitities of lactate or lipids were useful for differential diagnosis. CONCLUSION: Metabolic information provided by proton MR spectroscopy is useful for the differentiation of neoplastic and nonneoplastic brain lesions after stereotactic radiotherapy of brain tumors.

Adult↗
PubMed2000

[Improved tumor contrast and delineation in the stereotactic radiotherapy planning of cerebral gliomas and metastases with contrast media-supported FLAIR imaging].

BACKGROUND: FLAIR MR imaging has shown to be a valuable imaging modality in pathologic lesions of the brain including intra-axial brain tumors. The aim of the study was to assess the value of a FLAIR technique in the planning process of stereotactic radiotherapy in patients with cerebral gliomas and metastases. PATIENTS AND METHODS: Thirty-five patients with cerebral gliomas and 12 patients with a total of 39 cerebral metastases were examined by T2/PD-weighted fast spin-echo, fast FLAIR prior and after contrast and contrast enhanced T1-weighted spin-echo using identical slice parameters. The images were evaluated by using quantitative and qualitative criteria. Quantitative criteria were tumor-to-background and tumor-to-cerebrospinal fluid contrast and contrast-to-noise. The qualitative evaluation was performed as a multireader analysis concerning lesion detection, lesion delineation and image artifacts. RESULTS: In the qualitative evaluation (Table 3 and 6), all readers found the fast FLAIR images to be superior to fast spin-echo in the exact delineation of cerebral tumors (p < 0.001) and the delineation of enhancing and non enhancing tumor parts. Fast FLAIR was superior in the delineation of cortically located and small lesions but was limited in lesions adjacent to the ventricles. Fast FLAIR provided a significantly better tumor-to-CSF contrast and tumor-to-CSF contrast-to-noise (p < 0.001) (Tables 1, 2a, 2b, 4, 5). The tumor-to-background contrast and tumor-to-background contrast-to-noise of the fast FLAIR images were lower than that of T2-weighted spin-echo images but were significantly increased after the application of contrast media. FLAIR images had more image artifacts, but the image interpretation was not influenced. CONCLUSIONS: FLAIR MR imaging was found to be a valuable sequence in the planning protocol of stereotactic radiotherapy. The concurrent presentation of enhancing and non enhancing tumor tissue on contrast enhanced fast FLAIR imaging enables to use a single imaging sequence in the treatment protocol. This enables to load a reduced image amount into the radiotherapy planning software, is therefore time saving and reduces potential errors.

Adolescent↗
PubMed2000

[Functional magnetic resonance tomography in neuroradiology].

The assessment of cerebral functions has long been the domain of positron-emission tomography and single photon emission computed tomography. The use of rapid imaging sequences and contrast agents enables physiological and pathophysiological cerebral processes to be assessed and monitored by magnetic resonance imaging. Both T1- and T2-weighted contrast-enhanced fast imaging sequences can be used to assess tissue perfusion, vascularity, and microcirculation by applying models developed in nuclear medicine. The diffusion of water molecules and hemodynamic aspects of the macrovasculature can also be monitored. Functional magnetic resonance (MR) imaging enables the visualization of neuronal function and activity, and MR spectroscopy makes possible the metabolic mapping of lesions and surrounding tissue. The advantages of MR techniques includes their low invasiveness, multiplanar imaging ability, and lack of radiation. This contribution discusses the clinical use of functional MR imaging methods and their role in neuroradiological diseases. Measuring perfusion and diffusion allows detailed insight into the pathophysiology of cerebral ischemia and is already being used routinely in acute ischemic stroke. Dynamic MR angiography enables the hemodynamic assessment of vascular malformations. In CNS neoplasms these imaging techniques can improve lesion characterization and the selecting, planning, and monitoring of therapy. Functional MR imaging techniques have also revolutionized the study of psychiatric illness; however, their clinical utility here is still limited. Initial results in patients with dementia and schizophrenia have provided insight into the pathophysiological changes of these diseases.

Brain↗
PubMed2000

Locoregional late effects of paravascular thorotrast deposits: results of the german thorotrast study.

PURPOSE: The aim of this study was to assess late effects of long-term exposure to alpha irradiation caused by paravascular Thorotrast deposits. SUBJECTS AND METHODS: 899 patients, who had received the radioactive contrast medium Thorotrast for angiography in the 1930s and 1940s, and 662 controls were followed-up since 1968 every two years by standardized clinical and laboratory examinations. Initially, X-ray plain films of the thorax, upper abdomen and the former injection site were performed. In selected patients the sites of paravascular Thorotrast deposits were evaluated by ultrasonography, CT and MRI. RESULTS: Paravascular Thorotrast deposits were detected in 245 patients. Clinical symptoms related to deposits appeared 10 to 30 years after Thorotrast administration. The severity of symptoms depended on the location and extension of granulomas and were mainly caused by fibrosis, nerve paralysis and vascular changes. Four malignant tumors adjacent to granulomas were observed (one soft tissue sarcoma in the groin, two squamous cell carcinomas of the parotid gland and one lymphoepithelial carcinoma of the nasopharynx). MRI including MRA allowed an accurate determination of tissue damage, whereas the utility of US and CT was restricted due to strong sound attenuation and streak artefacts caused by the high X-ray absorption of Thorotrast. DISCUSSION AND CONCLUSION: Locoregional late effects of paravascular Thorotrast deposits mainly comprise radiation induced, fibrotic tissue destruction. The incidence of malignant tumors, in particular sarcomas, adjacent to deposits, however, is much lower than initially expected.

Adolescent↗
PubMed1999

Alterations of intratumoral pharmacokinetics of 5-fluorouracil in head and neck carcinoma during simultaneous radiochemotherapy.

The kinetics of local drug uptake and metabolism of the anticancer drug 5-fluorouracil (5-FU) has been monitored by means of 19F nuclear magnetic resonance spectroscopy in 17 patients with neck tumors during concurrent radiochemotherapy. All of the patients underwent an accelerated hyperfractionated, concomitant-boost radiochemotherapy with 5-FU [600 or 1000 mg/m2 of body surface (b.s.)] and carboplatin (70 mg/m2 of b.s.). Serial 19F nuclear magnetic resonance spectra were obtained during and after the administration of 5-FU in a 15-T scanner with the use of a 5-cm diameter surface coil positioned on a cervical lymph node metastasis. Examinations were performed at day 1 of therapy and, in 13 patients, also after 43.5 Gy of irradiation at day 1 of the second chemotherapy cycle. Resonances of 5-FU and the catabolites 5,6-dihydro-5-fluorouracil (DHFU) and alpha-fluoro-beta-alanine (FBAL) were resolved in the tumor spectra. The median of the 5-FU and FBAL levels was significantly higher (more than 2-fold) at the second compared with the first examination, whereas the level of DHFU did not change. This effect could indicate an increased delivery of 5-FU into the interstitial space of the tumor in the course of the combined treatment, which would result in an enhanced exposure of the tumor cells to the drug. A potential mechanism for synergy between radio- and chemotherapy is discussed, but alternative mechanisms are also being considered. The findings indicate that a method is available to rationally address the design of dosing schedules in concurrent therapy regimens.

Adult↗
PubMed1999

[Multiphase, contrast-enhanced 3D-MR angiography for morphological and functional focal lesion detection. Initial results].

PURPOSE: To investigate the value of multiphase breath-hold 3D gadolinium (Gd)-enhanced MR angiography (MRA) for lesion detection and characterization of focal liver lesions. MATERIALS AND METHODS: Breath-hold 3D Gd-enhanced MRA was performed in 25 patients with benign and malignant hepatic lesions on a 1.5-T MR system using an ultrafast 3D spoiled gradient echo sequence (TR/TE =5/2 ms, FOV=300-450 mm, matrix=256x168, voxel volume=1.8x2.3 x2.5 mm, 64 partitions, central k-space reordering; acquisition time=27 s). Three measurements were done in the arterial, portal venous, and late venous phase. RESULTS: The analysis of the spatial and temporal evolution of contrast enhancement of the 3D-MRA improved significantly (P<0.01) lesion detection and characterization if compared with T1 precontrast, T2-weighted, and T1 postcontrast images. CONCLUSION: Multiphase breath-hold 3D Gd-enhanced MRA imaging is a robust new technique to significantly improve morphological detection of benign and malignant lesions during the early arterial phase and further improves functional characterization of liver lesions by a combination of an arterial, a portal venous, and a late venous phase. Schlüssselwörter Multiphasisch. MR-Angiographie. Leberläsionen

Adult↗
PubMed1999

[Distal choledochal cyst in hydro-spiral CT].

Bile duct cysts are rare abnormalities of the biliary tract. Surgical therapy has been recommended because of possible complications such as cholestasis with jaundice and the risk of bile duct carcinoma. Accurate preoperative radiological imaging is available for surgical planning. In addition to direct imaging of the biliary system in ERCP, high-resolution axial computerized imaging techniques are necessary. The use of MRCP is becoming more frequent in diagnostic imaging of the biliary tract. Similar to the diagnosis of pancreatic tumors with hydro-spiral CT technique, we demonstrate the benefits of hydro-CT in imaging of a distal choledochal cyst, the problems of differential diagnosis and the classification in the generally accepted Todani system in a case in which accurate clarification with MRCP and ERCP was not possible.

Adult↗
PubMed1999

[1H-MR spectroscopy in anorexia nervosa: the characteristic differences between patients and healthy subjects].

PURPOSE: The neurophysiological and neuromorphological changes in patients with anorexia nervosa (AN) are well-known but the reason of both is still unknown. We have evaluated the usefulness of hydrogen (H1) magnetic resonance spectroscopy in anorexia nervosa. METHOD: We investigated 15 patients with clinically diagnosed AN (ICD F50.0) and 17 controls without eating disorders. The body mass index (BMI) was 15.8 and 21, respectively. The spectroscopy was recorded on two voxels in the parieto-occipital white matter or in the thalamus with a water-suppressed STEAM-sequence. The metabolites were recorded with respect to phosphocreatine (PCr). RESULTS: The ratio of NAA/PCr in both voxels were not significantly different when comparing patients vs. controls. Patients showed significantly higher ratios of choline-containing components (Cho) or, respectively Cho/PCr and NAA/PCr in the white matter. Distinct, but not significant differences were detected both for m-Ino and m-Ino/PCr in the parieto-occipital region and for the Cho- and m-Ino contained ratios in the thalamus. CONCLUSION: AN is not associated with neuronal damage. The ratio of Cho/PCr and NAA/Cho may reflect the disturbance of membrane-turnover. It is possible that the increase of membrane catabolism leads to a hyperosmolar state. The change of m-Ino/PCr ratio may reflect the regulation of osmolarity.

Anorexia Nervosa↗
PubMed1999

[1H-MR spectroscopy in anorexia nervosa: reversible cerebral metabolic changes].

PURPOSE: By using localized 1H-MR spectroscopy in the brain of patients with anorexia nervosa we wanted to verify our preliminary results and to look for a reversibility of the metabolic changes under therapy. METHODS: In 22 patients and 17 healthy volunteers (11 follow-up examinations) single voxel 1H-MR spectroscopy (TE = 50 ms, TM = 30 ms, TR = 1500 ms, voxel (2 cm)3, acq.: 256) was used in two different localizations (thalamus and parieto-occipital region). The first examination of the patients was performed before therapy, the follow-up examination at the end of therapy. RESULTS: In both regions of the brain we found a statistically significant elevation of the Cho/Cr-ratio in comparison to normal controls. The follow-up examinations revealed reversibility of the metabolic changes under successful therapy. CONCLUSIONS: 1H-MR spectroscopy reveals metabolic changes in the brain of patients with anorexia nervosa, which are reversible under successful therapy. These metabolic changes can be conclusively explained using a biochemical model.

Adolescent↗
PubMed1998

Proton magnetic resonance spectroscopy in acute, juvenile anorexia nervosa.

Anorexia nervosa is usually associated with a shrinkage of the brain that is at least partially reversible with weight gain. The pathogenesis of this brain abnormality is unclear. The purpose of this study was to investigate potential alterations in localized proton magnetic resonance (1H MR) spectra of anorectic patients immediately after an interval of excessive weight loss. Twelve patients and seventeen control subjects were examined. Water suppressed 1H MR spectra were recorded from two voxels placed in the thalamus and in the parieto-occipital white matter. The spectra of ten patients could be evaluated. Comparing patients and control subjects, significantly higher signal intensity ratios of choline containing compounds (Cho) relative to total creatine (Cr) as well as significantly lower ratios of N-acetyl-aspartate (NAA) relative to Cho were found in the white matter region. We hypothesize that these results indicate an abnormal starvation, associated membrane turnover, which predominantly takes place in the white matter. No evidence for neuronal degeneration was found in the thalamus or in the white matter region.

Adolescent↗