PubMed Health⌕ Search

Biomedical subjects

O Schober

Publications and source records attributed to O Schober.

At least 19 recordsLinked to original sources
PubMed2006

Tumor staging using whole-body high-resolution 16-channel PET-CT: does additional low-dose chest CT in inspiration improve the detection of solitary pulmonary nodules?

For optimal image fusion between CT and F-18-FDG-PET, the acquisition of CT images is performed in mild expiratory suspension, which might compromise the detection of lung metastases. This study aimed at evaluating the influence of expiration on the detection of solitary pulmonary nodules (SPN) and at assessing if additional inspiratory low-dose CT (I-LDCT) of the chest can improve the detection of potential lung metastases performing whole-body 16-channel PET-CT. Sixty-six patients with malignant tumors underwent PET-CT: contrast-enhanced CT was acquired during mild expiration and was used for fusion with PET images; additionally, chest I-LDCT was performed at deep inspiration. Two radiologists reported all SPN detected at I-LDCT and the expiratory CT scan independently. Overall, 53% of 128 SPN (mean: 3.8+/-0.2 mm) were detected at both respiratory states: 51 SPN only at I-LDCT, and 9 nodules only at expiratory CT. Of the SPN, 117/128 were classified as certain; 45 of those were additionally detected at I-LDCT, and 6 nodules at expiratory CT. A 100% detection rate was reached in SPN >4 mm at I-LDCT versus >8 mm at expiratory CT (all P<0.001). Additional I-LDCT of the chest significantly improves the detection of SPN at whole-body F-18-FDG-PET-CT and thus is recommended as part of the standard protocol for oncological patients.

Adult↗
PubMed2006

High diagnostic value of 18F-FDG-PET in pediatric patients with chronic inflammatory bowel disease.

Diagnosis of chronic inflammatory bowel disease (IBD) in children requires noninvasive, atraumatic diagnostic tools that depict localization and acuity of inflammation and yield only a low radiation dose. This retrospective analysis evaluates the diagnostic potential of FDG-PET. Twenty-six consecutive FDG-PET scans of 23 patients (age: 2-16, years, 14 M, 9 F) with suspected IBD were analyzed in this retrospective study. Results were compared to endoscopic, histologic, and abdominal ultrasound (US) finding. In these examinations, presence of inflammation was evaluated in each patient in 8 bowel segments (score 1-4). Standardized uptake values (SUVs) for FDG-PET were measured for all segments. Sensitivity, specificity, and accuracy were calculated using histology as the standard of reference on a segment-based analysis (pathologic if inflammation score > or = 3 or SUV(max)/SUV(liver)>1.2). With histology as the standard of reference, FDG-PET showed a sensitivity/specificity/accuracy of 98%/68%/8%/3 as compared to endoscopy (90%/75%/82%) and US (56%/92%/75%). For the small bowel, FDG-PET was even more reliable (100%/86%/90%). Because of its high sensitivity and accuracy,FDG-PET is an excellent, noninvasive diagnostic tool for IBD. Depicting inflammation in the whole bowel, while being not traumatic, it is attractive for use especially in children. FDG-PET is especially reliable for the small bowel and can inform application of topical therapy.

Adolescent↗
PubMed2006

Molecular imaging of matrix metalloproteinases in vivo using small molecule inhibitors for SPECT and PET.

Matrix metalloproteinases (MMPs) are a family of zinc- and calcium-dependent secreted or membrane anchored endopeptidases. MMPs are involved in many physiological processes but also take part in the pathophysiological mechanisms responsible for a wide range of diseases. Pathological expression and activation of MMPs are associated with cancer, atherosclerosis, stroke, arthritis, periodontal disease, multiple sclerosis and liver fibrosis. Thus, noninvasive visualisation and quantification of MMP activity in vivo are of great interest in basic research and clinical application. This can be achieved by scintigraphic molecular imaging techniques such as single photon emission computed tomography (SPECT) and positron emission tomography (PET) provided suitable radiolabelled tracers exist, e.g. radioactive inhibitors of matrix metalloproteinases (MMPIs). The approach to monitor MMP activity in vivo using radiolabelled small molecule inhibitors suitable for SPECT and PET is summarised in this review. Briefly, latest advances in scintigraphic imaging are introduced and followed by a report about the enzyme class of MMPs. The involvement of MMPs in cancer and atherosclerosis is exemplified and small molecule MMPIs are classified. Subsequently, the development of radiolabelled small molecule MMPIs, their synthesis and in vitro and in vivo evaluation is reviewed. Finally, an outlook on the clinical potential of labelled MMPIs in diagnostic algorithms is given.

Animals↗
PubMed2005

Correlation between respiration-induced thoracic expansion and a shift of central structures.

The fusion of computed tomography (CT) and positron emission tomography (PET) may improve diagnostic accuracy, but is limited by different breathing protocols. This study aimed at quantifying respiration-induced alignment errors. PET-CT was acquired in 24 patients. Contrast-enhanced whole-body CT was obtained in a single breath hold in the expiratory state of a normal breathing cycle. An inspiratory low-dose CT of the thorax was acquired in the same session, and comparison of the two CT scans was used to assess the potential mismatch of PET and CT fusion. The largest craniocaudal expansion was found in the area of the diaphragm. A considerable sagittal expansion was found in the anterior parts of the lungs. Central tracheo-bronchial structures were displaced during inspiration mainly in the anterior and caudal directions. The craniocaudal shift of central structures showed a linear correlation with the diaphragmatic expansion, whereas the sagittal shift correlated with the sagittal pleural expansion. There was, however, no correlation between craniocaudal and sagittal respiratory motion. Alignment errors are most severe in the base of the lung, but central structures are affected, too. Understanding of the main vectors of respiratory motion may help in image interpretation when PET and CT are acquired separately.

Artifacts↗
PubMed2005

O-(2-[18F]fluorethyl)-L-tyrosine PET in the clinical evaluation of primary brain tumours.

PURPOSE: The aim of this study was to evaluate the differential uptake of O-(2-[18F]fluorethyl)-L-tyrosine (FET) in suspected primary brain tumours. METHODS: Positron emission tomography (PET) was performed in 44 patients referred for the evaluation of a suspected brain tumour. Acquisition consisted of four 10-min frames starting upon i.v. injection of FET. Tumour uptake was calculated as the ratio of maximal tumour intensity to mean activity within a reference region (FETmax). RESULTS: FET uptake above the cortical level was observed in 35/44 lesions. All histologically confirmed gliomas and many other lesions showed FET uptake to a variable extent. No uptake was observed in nine lesions (one inflammatory lesion, one dysembryoplastic neuroepithelial tumour, one mature teratoma, six lesions without histological confirmation). An analysis of uptake dynamics was done in the patients with increased FET uptake (22 gliomas, three lymphomas, three non-neoplastic lesions, three lesions with unknown histology and four other primaries). Upon classification of tumours into low (i.e. WHO I and II) and high grade (i.e. WHO III and IV), a significant difference in FETmax between the two categories was observed only in the first image frame (0-10 min p.i.), with FETmax=2.0 in low-grade and 3.2 in high-grade tumours (p<0.05); no significant differences were found in frame 4 (30-40 min p.i.), with FETmax=2.4 vs 2.7. Similar results were obtained when the analysis was applied only to astrocytic tumours (2.0 vs 3.1 in the first frame; 2.4 vs 2.6 in the fourth frame). CONCLUSION: These initial results indicate that FET PET is a useful method to identify malignant brain lesions. It appears that high- and low-grade brain tumours exhibit a different uptake kinetics of FET. A kinetic analysis of FET PET may provide additional information in the differentiation of suspected brain lesions.

Adolescent↗
PubMed2005

Staging in childhood lymphoma: differences between FDG-PET and CT.

AIM: The clinical value of positron emission tomography using fluorine-18 fluoro-deoxy-glucose (FDG-PET) in the staging of adult lymphoma has been shown in many studies. However, there are only few data regarding childhood lymphoma. The purpose of this retrospective study was to compare the staging of childhood lymphoma using FDG-PET and the established computed tomography (CT). METHOD: Whole-body FDG-PET was performed in 25 children with histologically proven Hodgkin's disease (n = 18) and non-Hodgkin's lymphoma (n = 7) using a dedicated PET. The findings were compared with the CT results. Both examinations, FDG-PET and CT, were assessed by two experienced physicians. In each patient, 30 regions were analysed (22 nodal, 8 extranodal). Each region was assessed using a five value scale (definitely/probably positive, equivocal, probably/definitely negative). RESULTS: 662 regions (470 nodal, 192 extranodal) were compared. 91 regions (81 nodal, 10 extranodal; 14%) were concordant positive and 517 regions (347 nodal, 170 extranodal; 78%) were concordant negative. In 47 regions, 48 discordant findings (7%) were described: 27 findings (22 nodal, 5 extranodal) were positive using FDG-PET and negative using CT whereas 21 findings (17 nodal, 4 extranodal) were positive using CT and negative using PET. A total of 7 regions (1%) were judged equivocal in one imaging modality (1 FDG-PET, 6 CT). Using FDG-PET as compared to CT, resulted in a higher staging in 4 of 25 patients and in a lower staging in 2 of 25 patients. CONCLUSION: Staging of childhood lymphoma using FDGPET shows differences compared with CT resulting in a different staging in 6 of 25 patients. Prospective studies are required to evaluate the impact of these discrepancies on the clinical management of pediatric patients.

Adolescent↗
PubMed2005

[Clinical value of amino acid imaging in paediatric brain tumours. Comparison with MRI].

PURPOSE: To evaluate single photon emission computed tomography (SPECT) using the amino acid l-3-[123I]-alpha-methyl tyrosine (IMT) and contrast enhanced magnetic resonance imaging (MRI) as diagnostic tools in primary paediatric brain tumours in respect of non-invasive tumour grading. Patients, materials, methods: 45 children with primary brain tumours were retrospectively evaluated. IMT uptake was quantified as tumour/nontumour-ratio, a 4-value-scale was used to measure gadolinium enhancement on contrast enhanced MRI. Statistical analyses were performed to evaluate IMT uptake and gadolinium enhancement in low (WHO I/II) and high (WHO III/IV) grade tumours and to disclose a potential relationship of IMT uptake to disruption of blood brain barrier as measured in corresponding MRI scans. RESULTS: IMT uptake above background level was observed in 35 of 45 patients. IMT uptake was slightly higher in high grade tumours but the difference failed to attain statistical significance. Grading of individual tumours was neither possible by IMT SPECT nor by gadolinium enhanced MRI. CONCLUSION: IMT is accumulated in most brain tumours in children. Tumour grading was not possible using IMT or contrast enhancement as determined by MRI. Neither morphological nor functional imaging can replace histology in paediatric brain tumours.

Adolescent↗
PubMed2005

Non-invasive molecular imaging of beta-adrenoceptors in vivo: perspectives for PET-radioligands.

Recently, the spectrum of molecular imaging devices such as positron emission tomography (PET) was further expanded by the now clinically available combined imaging modalities such as PET-CT and the preclinically used small animal PET scanners. These are powerful tools that can bridge the gap between preclinical and clinical evaluation studies of new radiotracers for molecular imaging of healthy and diseased states in vivo. The beta-adrenoceptor (beta-AR) radioligands discussed in this review represent a class of molecular probes for the non-invasive in vivo assessment of beta-AR density eg. in the heart with PET. The beta-AR radioligands (S)-[11C]CGP 12177 (1) or (S)-[11C]CGP 12388 (2) are currently investigated in clinical studies with PET. Additionally, subtype-selective beta1-AR radioligands are used in preclinical research which show potential for the diagnostics of the "beta1-AR organ" as such the heart can be defined. Non-invasive quantification of beta-ARs could facilitate the accurate choice and control of therapeutic interventions. Here we summarize the state-of-the-art of the radiochemistry of radioactive beta-AR radioligands.

Adrenergic beta-Agonists↗
PubMed2005

Motion correction in PET/CT.

Motion in PET/CT leads to artifacts in the reconstructed PET images due to the different acquisition times of positron emission tomography and computed tomography. The effect of motion on cardiac PET/CT images is evaluated in this study and a novel approach for motion correction based on optical flow methods is outlined. The Lukas-Kanade optical flow algorithm is used to calculate the motion vector field on both simulated phantom data as well as measured human PET data. The motion of the myocardium is corrected by non-linear registration techniques and results are compared to uncorrected images.

Heart↗
PubMed2005

Guidelines on radioiodine therapy for differentiated thyroid carcinoma: impact on clinical practice.

AIM: For the examination of the impact on clinical practice of the guidelines for differentiated thyroid carcinoma (DTC), treatment data from the ongoing Multicenter Study Differentiated Thyroid Carcinoma (MSDS) were analyzed. PATIENTS, METHODS: Patients were randomized to adjuvant external beam radiotherapy (RTx) or no RTx in addition to standard therapy in TNM stages pT4 pN0/1/x M0/x (UICC, 5th ed. 1997). All patients were to receive the same treatment regimen consisting of thyroidectomy, ablative radioiodine therapy (RIT), and a diagnostic 131I whole-body scintigraphy (WBS) 3-4 months after RIT. RESULTS: Of 339 eligible patients enrolled between January 2000 and March 2004, 273 could be analyzed. Guideline recommendations by the German Society for Nuclear Medicine from 1999 and 1992 were complied with within 28% and 82% with regard to the interval between surgery and RIT (4 vs. 4-6 weeks), in 33% and 84% with regard to 131I activity for RIT (1-3 vs. 1-4 GBq; +/- 10%), and in 16% and 60% with regard to 131I activity for WBS (100-300 vs. 100-400 MBq; +/- 10%). CONCLUSIONS: The 1999 guideline revision appears to have had little impact on clinical practice. Further follow-up will reveal if guideline compliance had an effect on outcomes.

Combined Modality Therapy↗
PubMed2004

[PET/CT in radiotherapy].

Combining positron emission tomography (PET) and X-ray computed tomography (CT) with simultaneous acquisition may improve diagnostic accuracy in oncology. Moreover this combination holds considerable promise in radiotherapy. Metabolic information may be used in decision making in radiotherapy and in planning target volumes. Furthermore early evaluation of treatment efficacy becomes possible. New tracers for the assessment of tumour hypoxia or apoptosis in clinical routine are currently being developed. These tracers may yield high relevance in radiotherapy. Hybrid scanners facilitate patient handling and shorten the duration of acquisition. Furthermore fusion accuracy is optimal. Prospective studies have to be conducted to show that the new technology improves patient care in terms of efficiency and quality.

Blood Glucose↗
PubMed2004

[Overtherapy or undertherapy for papillary thyroid microcarcinoma? Therapeutic considerations for radioiodine ablation].

Papillary thyroid microcarcinomas </=1 cm have an excellent prognosis both in terms of overall and relapse-free survival. Their high prevalence in autopsy series suggests that most papillary microcarcinomas do not progress to clinically relevant cancer. The extent of surgery is still controversial. Lobectomy or subtotal resection are standard procedures, but multifocal microcarcinomas or lymph node metastases might be overlooked. The pros and cons of completion thyroidectomy and ablative radioiodine therapy are based on limited evidence due to heterogenous inclusion criteria in published series. The retrospective data analyses included subgroups with infiltration of the thyroid capsule, lymph node metastases or multifocal microcarcinomas at the primary staging. The local relapse rate reached approximately 7% after different therapeutic regimes. Radioiodine ablation decreased the recurrence rate in some retrospective studies, but data are inconsistent. Successful radioiodine ablation is possible also after less radical surgery without complete thyroidectomy with postoperative (131)I uptake of 10 to 20% or remnants of 3-8 ml. This concept was evaluated successfully in a monocentric series of patients with multifocal microcarcinomas. The therapeutic consideration should include the diameter of the carcinoma, neighbourhood to the thyroid capsule, histopathologic sub-groups, age, familiar occurrence, patient's informed consent and in future moleculargenetic tests, too. There-fore, limited surgical procedures for small papillary carcinomas as therapeutic standard, respectively thyroidectomy, lymph node dissection in the central compartment of the neck and ablative radioiodine therapy for individual cases are options for experienced surgeons and specialized tumour centers.

Carcinoma, Papillary↗
PubMed2004

[Procedure guidelines for radioiodine therapy of differentiated thyroid cancer (version 2)].

The procedure guidelines for radioiodine therapy (RIT) of differentiated thyroid cancer (version 2) are the counter-part to the procedure guidelines for (131)I whole-body scintigraphy (version 2) and specify the interdisciplinary guidelines for thyroid cancer of the Deutsche Krebsgesellschaft and the Deutsche Gesellschaft für Chirurgie concerning the nuclear medicine part. Compared with version 1 facultative options for RIT can be chosen in special cases: ablative RIT for papillary microcarcinoma </=1 cm, ablative RIT for mixed forms of anaplastic and differentiated thyroid cancer, and RIT in patients with a measurable or increasing thyroglobulin concentration but without detectable metastases by imaging. The description of the pretherapeutic dosimetry now includes the isotopes (123)I and (124)I as well as a broader range of the activity of (131)I. Activities of 2-5 GBq (131)I are recommended for the first ablative RIT. If high accumulative activities of (131)I are expected, men who have not yet finished their family planning should be advised to the option of sperm cryoconservation. An interdisciplinary consensus is necessary whether the new TNM-classification (UICC, 6(th) edition, 2002) will lead to modified recommendations for surgical or nuclear medicine therapy, especially for the surgical completeness and for the ablative RIT of pT1 papillary cancer.

Contraindications↗
PubMed2004

[Guideline for radioiodine therapy for benign thyroid diseases (version 3)].

The version 3 of the guideline for radioiodine therapy for benign thyroid diseases presents first of all a revision of the version 2. The chapter indication for radioiodine therapy, surgical treatment or antithyroid drugs bases on an interdisciplinary consensus. The manifold criteria for decision making consider the entity of thyroid disease (autonomy, Graves' disease, goitre, goitre recurrence), the thyroid volume, suspicion of malignancy, cystic nodules, risk of surgery and co-morbidity, history of subtotal thyroidectomy, persistent or recurrent thyrotoxicosis caused by Graves' disease including known risk factors for relapse, compression of the trachea caused by goitre, requirement of direct therapeutic effect as well as the patient's preference. Because often some of these criteria are relevant, the guideline offers the necessary flexibility for individual decisions. Further topics are patients' preparation, counseling, dosage concepts, procedural details, results, side effects and follow-up care. The prophylactic use of glucocorticoids during radioiodine therapy in patients without preexisting ophthalmopathy as well as dosage and duration of glucocorticoid medication in patients with preexisting ophthalmopathy need to be clarified in further studies. The pragmatic recommendations for the combined use of radioiodine and glucocorticoids remained unchanged in the 3rd version.

Combined Modality Therapy↗