Lars Stegger

University of Tuebingen, Tübingen, Baden-Wuerttemberg, Germany

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Publications (77)254.97 Total impact

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    ABSTRACT: PURPOSE: Coronary artery calcium scoring can complement myocardial perfusion imaging (MPI). The purpose of this study was to evaluate the feasibility and accuracy of using the CalciumScore-CT derived from a combined SPECT/CT device also for SPECT attenuation correction (AC). METHODS: The study group comprised 99 patients who underwent both post-stress and rest MPI using a two-slice SPECT/CT system. For AC, one of the two scans was accompanied by a CalciumScore-CT scan (CalciumScore-CTAC) and the other by a conventional spiral CT (AttenCorr-CT) scan (AttenCorr-CTAC). In 48 patients the CalciumScore-CT scan was acquired with the post-stress scan and the AttenCorr-CT scan with the rest scan, and in 51 patients the order was reversed. The accuracy of the images based on AC was determined qualitatively by consensus reading with respect to the clinical diagnoses as well as quantitatively by comparing the perfusion summed stress scores (SSS) and the summed rest scores (SRS) between attenuation-corrected and uncorrected images. RESULTS: In comparison to the uncorrected images CalciumScore-CTAC led to regional inaccuracies in 14 of 51 of studies (27.5 %) versus 12 of 48 studies (25 %) with AttenCorr-CTAC for the stress studies and in 5 of 48 (10 %) versus 1 of 51 (2 %) for the rest studies, respectively. This led to intermediate and definite changes in the final diagnosis (ischaemia and/or scarring) in 12 % of the studies (12 of 99) and in 7 % of the studies (7 of 99) with CalciumScore-CTAC and in 9 % of the studies (9 of 99) and 4 % of the studies (4 of 99) with AttenCorr-CTAC. Differences in SSS and SRS with respect to the uncorrected images were greater for the CalciumScore-CTAC images than for the AttenCorr-CTAC images (ΔSSS 4.5 ± 5.6 and 2.1 ± 4.4, p = 0.023; ΔSRS 4.2 ± 4.9 and 1.6 ± 3.2, p = 0.004, respectively). CONCLUSION: Using the same CT scan for calcium scoring and SPECT AC is feasible. Image interpretation must, however, include uncorrected images since CT-based AC relatively often introduces artefacts into the myocardial perfusion images. This effect is somewhat more pronounced with CalciumScore-CTAC than with AttenCorr-CTAC.
    European Journal of Nuclear Medicine 02/2013; · 4.53 Impact Factor
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    ABSTRACT: Hybrid PET/MR combines the exceptional molecular sensitivity of PET with the high resolution and versatility of MR imaging. Simultaneous data acquisition additionally promises the use of MR to enhance the quality of PET images, for example, by respiratory motion correction. This advantage is especially relevant in thoracic and abdominal areas to improve the visibility of small lesions with low radiotracer uptake and to enhance uptake quantification. In this work, the applicability and performance of an MR-based method of respiratory motion correction for PET tumor imaging was evaluated in phantom and patient studies. METHODS: PET list-mode data from a motion phantom with (22)Na point sources and 5 patients with tumor manifestations in the thorax and upper abdomen were acquired on a simultaneous hybrid PET/MR system. During the first 3 min of a 5-min PET scan, the respiration-induced tissue deformation in the PET field of view was recorded using a sagittal 2-dimensional multislice gradient echo MR sequence. MR navigator data to measure the location of the diaphragm were acquired throughout the PET scan. Respiration-gated PET data were coregistered using the MR-derived motion fields to obtain a single motion-corrected PET dataset. The effect of motion correction on tumor visibility, delineation, and radiotracer uptake quantification was analyzed with respect to uncorrected and gated images. RESULTS: Image quality in terms of lesion delineation and uptake quantification was significantly improved compared with uncorrected images for both phantom and patient data. In patients, in head-feet line profiles of 14 manifestations, the slope became steeper by 66.7% (P = 0.001) and full width at half maximum was reduced by 20.6% (P = 0.001). The mean increase in maximum standardized uptake value, lesion-to-background ratio (contrast), and signal-to-noise ratio was 28.1% (P = 0.001), 24.7% (P = 0.001), and 27.3% (P = 0.003), respectively. Lesion volume was reduced by an average of 26.5% (P = 0.002). As opposed to the gated images, no increase in background noise was observed. However, motion correction performed worse than gating in terms of contrast (-11.3%, P = 0.002), maximum standardized uptake value (-10.7%, P = 0.003), and slope steepness (-19.3%, P = 0.001). CONCLUSION: The proposed method for MR-based respiratory motion correction of PET data proved feasible and effective. The short examination time and convenience (no additional equipment required) of the method allow for easy integration into clinical routine imaging. Performance compared with gating procedures can be further improved using list-mode-based motion correction.
    Journal of Nuclear Medicine 01/2013; · 5.77 Impact Factor
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    ABSTRACT: Background Hybrid positron emission tomography/magnetic resonance imaging (PET/MRI) with simultaneous data acquisition promises a comprehensive evaluation of cerebral pathophysiology on a molecular, anatomical, and functional level. Considering the necessary changes to the MR scanner design the feasibility of arterial spin labeling (ASL) is unclear. Purpose To evaluate whether cerebral blood flow imaging with ASL is feasible using a prototype PET/MRI device. Material and Methods ASL imaging of the brain with Flow-sensitive Alternating Inversion Recovery (FAIR) spin preparation and true fast imaging in steady precession (TrueFISP) data readout was performed in eight healthy volunteers sequentially on a prototype PET/MRI and a stand-alone MR scanner with 128 × 128 and 192 × 192 matrix sizes. Cerebral blood flow values for gray matter, signal-to-noise and contrast-to-noise ratios, and relative signal change were compared. Additionally, the feasibility of ASL as part of a clinical hybrid PET/MRI protocol was demonstrated in five patients with intracerebral tumors. Results Blood flow maps showed good delineation of gray and white matter with no discernible artifacts. The mean blood flow values of the eight volunteers on the PET/MR system were 51 ± 9 and 51 ± 7 mL/100 g/min for the 128 × 128 and 192 × 192 matrices (stand-alone MR, 57 ± 2 and 55 ± 5, not significant). The value for signal-to-noise (SNR) was significantly higher for the PET/MRI system using the 192 × 192 matrix size (P < 0.01), the relative signal change (δS) was significantly lower for the 192 × 192 matrix size (P = 0.02). ASL imaging as part of a clinical hybrid PET/MRI protocol could successfully be accomplished in all patients in diagnostic image quality. Conclusion ASL brain imaging is feasible with a prototype hybrid PET/MRI scanner, thus adding to the value of this novel imaging technique.
    Acta Radiologica 11/2012; 53(9):1066-72. · 1.33 Impact Factor
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    ABSTRACT: In the diagnostic algorithm of cardiac tumors, the noninvasive determination of malignancy and metastatic spread is of major interest to stratify patients and to select and monitor therapies. In the diagnostic work-up, morphologic imaging modalities such as echocardiography or magnetic resonance tomography offer information on, for example, size, invasiveness, and vascularization. However, preoperative assessment of malignancy may be unsatisfactory. The aim of this study was to evaluate the diagnostic value of (18)F-FDG PET and the incremental diagnostic value of an optimized CT score in this clinical scenario. (18)F-FDG PET/CT scans (whole-body imaging with low-dose CT) of 24 consecutive patients with newly diagnosed cardiac tumors were analyzed (11 men, 13 women; mean age ± SD, 59 ± 13 y). The maximum standardized uptake values (SUV(max)) of the tumors were measured. Patients were divided into 2 groups: benign cardiac tumors (n = 7) and malignant cardiac tumors (n = 17) (cardiac primaries [n = 8] and metastases [n = 9]). SUV(max) was compared between the 2 groups. Results were compared with contrast-enhanced CT, using standardized criteria of malignancy. Histology served as ground truth. Mean SUV(max) was 2.8 ± 0.6 in benign cardiac tumors and significantly higher both in malignant primary and in secondary cardiac tumors (8.0 ± 2.1 and 10.8 ± 4.9, P < 0.01). Malignancy was determined with a sensitivity of 100% and specificity of 86% (accuracy, 96%), after a cutoff with high sensitivity (SUV(max) of 3.5) was chosen to avoid false-negatives. Morphologic imaging reached a sensitivity of 82% and a specificity of 86% (accuracy, 83%). Both false-positive and false-negative decisions in morphology could be corrected in all but 1 case using a metabolic threshold with an SUV(max) of 3.5. In addition, extracardiac tumor manifestations were detected in 4 patients by whole-body (18)F-FDG PET/CT. (18)F-FDG PET/CT can aid the noninvasive preoperative determination of malignancy and may be helpful in detecting metastases of malignant cardiac tumors.
    Journal of Nuclear Medicine 05/2012; 53(6):856-63. · 5.77 Impact Factor
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    ABSTRACT: Coronary angiography (CA) is the standard method for diagnosis of cardiac allograft vasculopathy (CAV). Little is known about the value of measuring left ventricular function over time, which can be derived from gated myocardial perfusion single-photon emission computed tomography (SPECT). We evaluated the potential of measuring myocardial perfusion and left ventricular function with gated SPECT, as compared with CA, to detect CAV in the follow-up of heart transplantation. One hundred sixty-one heart transplant recipients (137 men, 24 women, age 50.7 ± 12.2 years) were followed-up for 4.2 ± 2.0 years by annual routine gated perfusion SPECT and consecutive CA. Myocardial perfusion was quantified by summed stress, rest and difference scores (SSS, SRS and SDS, respectively). Left ventricular function (ESV, EDV and LVEF) was derived from gated SPECT. Both were compared with angiographically defined stages of CAV. ESV/EDV derived from gated SPECT increased from 61 ± 25 ml/169 ± 39 ml in patients with no CAV over 74 ± 38 ml/188 ± 55 ml in patients with moderate CAV to 153 ± 75 ml/278 ± 86 ml in patients with severe CAV (p < 0.01 and p < 0.001), whereas LVEF decreased from 64 ± 10% over 62 ± 11% to 47 ± 13% in patients with severe CAV (p < 0.001). Perfusion quantified by SRS and SSS increased from 1.2 ± 1.5/1.9 ± 2.3 over 1.9 ± 1.4/2.8 ± 2.0 to 6.5 ± 5.1/7.7 ± 5.8 in patients with severe CAV (p < 0.01). Overall, for the prediction of severe CAV, accuracy was found to be higher for gated SPECT functional analysis as compared with perfusion analysis. Impaired left ventricular function, as assessed by gated SPECT, correlated significantly with CAV. Thus, for this purpose, gated SPECT offers higher sensitivity than analysis of perfusion while having a comparable specificity.
    The Journal of heart and lung transplantation: the official publication of the International Society for Heart Transplantation 03/2012; 31(7):719-28. · 3.54 Impact Factor
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    ABSTRACT: Myocardial perfusion gating techniques offer the possibility of measurement of left ventricular end-systolic (ESV) and end-diastolic volume (EDV) and left ventricular ejection fraction (LVEF) in clinical and preclinical trials. The aim of this study was to evaluate left ventricular volumes (LVV) and LVEF with 13N-NH3 in comparison with the reference 18F-FDG in different rat models. In this study, 18 male Wistar rats, 12 control rats and 6 rats with myocardial infarction (MI) were imaged with micro-PET. The ratswere scanned with gated 13N-NH3 and 18F-FDG sequentially for the assessment of LVV and LVEF. A validated three-dimensional segmentation algorithm was used to calculate LVV and LVEF. Mean LVEF measured with 13N-NH3 was 45.6±8.9 and 75.3±9.4%, mean ESV was 0.40±0.12 and 0.14±0.11 ml, and mean EDVwas 0.53±16 and 0.75±0.18 ml for MI and control rats, respectively. Moderate to good correlations were observed between values of 13N-NH3 and 18F-FDG for calculation of ESV [r=0.80, P<.0001, standard error of estimate (SEE)=0.10], EDV (r=0.63, P=.005, SEE=0.14) and LVEF (r=0.84, P<.0001, SEE=9.5). LVEF measured with 13N-NH3 was significantly lower in MI rats in comparison to measurement with 18F-FDG (45.6±8.9 vs 54.9±9.3 %; P=.04). Correlations were moderate to good for the assessment of ESV, EDV and LVEF between gated 13N-NH3 and 18F-FDG. LVEF was underestimated with gated 13N-NH3 in rats with myocardial infarction. In healthy rats, LV volumes and LVEF can be measured reproducibly with either approach.
    Nuclear Medicine and Biology 02/2012; 39(5):724-9. · 2.52 Impact Factor
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    ABSTRACT: The present work illustrates the current state of image quality and diagnostic accuracy in a new hybrid BrainPET/MR. 50 patients with intracranial masses, head and upper neck tumors or neurodegenerative diseases were examined with a hybrid BrainPET/MR consisting of a conventional 3T MR system and an MR-compatible PET insert. Directly before PET/MR, all patients underwent a PET/CT examination with either [(18)F]-FDG, [(11)C]-methionine or [(68)Ga]-DOTATOC. In addition to anatomical MR scans, functional sequences were performed including diffusion tensor imaging (DTI), arterial spin labeling (ASL) and proton-spectroscopy. Image quality score of MR imaging was evaluated using a 4-point-scale. PET data quality was assessed by evaluating FDG-uptake and tumor delineation with [(11)C]-methionine and [(68)Ga]-DOTATOC. FDG uptake quantification accuracy was evaluated by means of ROI analysis (right and left frontal and temporo-occipital lobes). The asymmetry indices and ratios between frontal and occipital ROIs were compared. In 45/50 patients, PET/MR examination was successful. Visual analysis revealed a diagnostic image quality of anatomical MR imaging (mean quality score T2 FSE: 1.27±0.54; FLAIR: 1.38±0.61). ASL and proton-spectroscopy was possible in all cases. In DTI, dental artifacts lead to one non-diagnostic dataset (mean quality score DTI: 1.32±0.69; ASL: 1.10±0.31). PET datasets of PET/MR and PET/CT offered comparable tumor delineation with [(11)C]-methionine; additional lesions were found in 2/8 [(68)Ga]-DOTATOC-PET in the PET/MR. Mean asymmetry index revealed a high accordance between PET/MR and PET/CT (1.5±2.2% vs. 0.9±3.6%; mean ratio (frontal/parieto-occipital) 0.93±0.08 vs. 0.96±0.05), respectively. The hybrid BrainPET/MR allows for molecular, anatomical and functional imaging with uncompromised MR image quality and a high accordance of PET results between PET/MR and PET/CT. These results justify the application of this technique in further clinical studies and may contribute to the transfer into whole-body PET/MR systems.
    European journal of radiology 01/2012; 81(11):3472-8. · 2.65 Impact Factor
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    ABSTRACT: Increased sympathetic activation is a key modifier for arrhythmogenesis in patients with long QT syndrome (LQTS), a congenital channelopathy. Therefore, we investigated cardiac sympathetic function using 123I-metaiodobenzylguanidine (MIBG) single photon emission computed tomography (SPECT) in a cohort of symptomatic LQTS patients and correlated these findings with the underlying genotype. [123I]MIBG SPECT was performed in 28 LQTS patients. Among these, 18 patients (64%) had a previous syncope and 10 patients (36%) survived sudden cardiac arrest. Patients were characterized in terms of genetic subtypes and QTc interval on surface ECGs. SPECT images were analysed for regional [123I]MIBG uptake in a 33-segment bullseye scheme and compared to those obtained from 10 age-matched healthy control subjects (43±12 years). An abnormal 123I-MIBG scan was found in 17 of 28 LQTS patients (61%) with a tracer reduction mainly located in the anteroseptal segments of the left ventricle. This finding was independent of the genetic LQTS subtype. In addition, no differences were found between LQTS patients with a QTc>500 ms vs <500 ms or those suffering from syncope vs VF (p>0.05). A distinct regional pattern of impaired cardiac sympathetic function was identified in the majority of symptomatic LQTS patients. This innervation defect was independent of the underlying genotype and clinical disease expression.
    European Journal of Nuclear Medicine 06/2011; 38(10):1899-907. · 4.53 Impact Factor
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    ABSTRACT: Medical documentation is often incomplete. Missing information may impede or bias analysis of study data and can cause delays. In a single source information system, clinical routine documentation and electronic data capture (EDC) systems are connected in the hospital information system (HIS). In this setting, both clinical routine and research would benefit from a higher rate of complete documentation. We designed a HIS-based reminder system which identifies not yet finalized forms and sends reminder e-mails to responsible physicians depending on escalation level. The generic concept to create reminder e-mail messages consists in database queries on not-finalized forms and generation of e-mail messages based on this output via the communication server. We compared completeness of electronic HIS forms before and after introduction of the reminder system three months each. Completeness increased highly significantly (p<0.0001) for each form type (medical history form 93% (145 of 156 forms) vs 100% (206 forms), stress injection protocol 90% (142 of 157 forms) vs 100% (198 forms) and rest injection protocol 31% (45 of 147 forms) vs 100% (208 forms)). Forty-six reminder e-mails to the responsible study physician and 53 reminder e-mails to the principal investigator were sent to finish 2 medical history forms, 8 stress and 20 rest injection protocols. These 2 medical history forms were completed after 1 and 56 days. The median processing time of the stress injection protocols in the post-implementation phase was 18 days (range from 1 to 60 days). The median processing time of the rest injection protocols was 26 days (range from 5 to 37 days). A computer-based reminder system to identify incomplete documentation forms with a notification and escalation mechanism can improve completeness of finalized forms significantly. It is technically feasible and effective in the clinical setting.
    International Journal of Medical Informatics 03/2011; 80(5):351-8. · 2.06 Impact Factor
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    ABSTRACT: The aim of this pilot study was to test and demonstrate the feasibility of simultaneous positron emission tomography (PET) and magnetic resonance imaging (MRI) of the head and upper neck area using a new hybrid PET/MRI system. Eight patients with malignant head and neck tumours were included in the pilot study. Directly after routine PET/CT imaging with a whole-body system using the glucose derivative 2-[¹⁸F]fluoro-2deoxy-D-glucose (FDG) as a radiotracer additional measurements were performed with a prototype PET/MRI system for simultaneous PET and MR imaging. Physiological radiotracer uptake within regular anatomical structures as well as tumour uptake were evaluated visually and semiquantitatively (metabolic ratios) in relation to cerebellar uptake on the PET/MRI and PET/CT systems. The MR datasets showed excellent image quality without any recognisable artefacts caused by the inserted PET system. PET images obtained with the PET/MRI system exhibited better detailed resolution and greater image contrast in comparison to those from the PET/CT system. An excellent agreement between metabolic ratios obtained with both PET systems was found: R = 0.99 for structures with physiological tracer uptake, R = 0.96 for tumours. Simultaneous PET/MRI of the head and upper neck area is feasible with the new hybrid PET/MRI prototype.
    European Radiology 02/2011; 21(7):1439-46. · 4.34 Impact Factor
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    ABSTRACT: Follow-up data must be collected according to the protocol of each clinical study, i.e. at certain time points. Missing follow-up information is a critical problem and may impede or bias the analysis of study data and result in delays. Moreover, additional patient recruitment may be necessary due to incomplete follow-up data. Current electronic data capture (EDC) systems in clinical studies are usually separated from hospital information systems (HIS) and therefore can provide limited functionality to support clinical workflow. In two case studies, we assessed the feasibility of HIS-based support of follow-up documentation. We have developed a data model and a HIS-based workflow to provide follow-up forms according to clinical study protocols. If a follow-up form was due, a database procedure created a follow-up event which was translated by a communication server into an HL7 message and transferred to the import interface of the clinical information system (CIS). This procedure generated the required follow-up form and enqueued a link to it in a work list of the relating study nurses and study physicians, respectively. A HIS-based follow-up system automatically generated follow-up forms as defined by a clinical study protocol. These forms were scheduled into work lists of study nurses and study physicians. This system was integrated into the clinical workflow of two clinical studies. In a study from nuclear medicine, each scenario from the test concept according to the protocol of the single photon emission computer tomography/computer tomography (SPECT/CT) study was simulated and each scenario passed the test. For a study in psychiatry, 128 follow-up forms were automatically generated within 27 weeks, on average five forms per week (maximum 12, minimum 1 form per week). HIS-based support of follow-up documentation in clinical studies is technically feasible and can support compliance with study protocols.
    Applied Clinical Informatics 01/2011; 2(1):1-17. · 0.39 Impact Factor
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    ABSTRACT: Atherosclerosis is a dynamic inflammatory disease of the arterial vessel wall which is still the “number one killer” in Western civilization. It turned out recently that the molecular composition and the metabolic state of atherosclerotic plaques rather than their size or degree of stenosis is of crucial importance to predict the fate of individual plaques. Thus, an imaging modality noninvasively characterizing plaques is needed. In this context, FDG-PET has great potential since FDG accumulates in plaque macrophages and uptake is correlated with macrophage density which is high in highly inflammatory atherosclerotic plaques. FDG uptake in atherosclerosis of large arteries is observed frequently, is associated with cardiovascular risk factors on the one hand, and is probably correlated with the occurrence of cardiovascular events. Moreover, it is reported that vascular FDG uptake can be attenuated by cholesterol-lowering therapies and therefore could also serve as a tool of therapy monitoring. Despite some positive results of preliminary studies, imaging of rupture-prone atherosclerotic plaques with FDG-PET still remains a challenge and is not yet established. The following article provides the biological basis of FDG imaging of atherosclerotic plaques, an overview of preclinical studies, important clinical studies and approaches of coronary artery imaging.
    Current Cardiovascular Imaging Reports 01/2011; 4(3):190-198.
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    ABSTRACT: Despite enormous investment into cardiovascular research on all levels worldwide, cardiovascular events such as myocardial infarction, heart failure, tachyarrhythmia or stroke remain the major causes for death and inability in all developed countries. Conventional clinical cardiovascular imaging nowadays provides high-resolution visualization of the morphology of vessels and the myocardium. To translate the available patient imaging technologies into animals, especially mice where genetic technologies can be used to induce human-like pathophysiologies, is of great interest for cardiovascular research. Furthermore, new imaging biomarkers for targeting molecular processes such as inflammation in atherosclerosis are being developed which have to be tested and optimised in animal models (again mice are of greatest interest here) before translated into the clinics. Imaging of the heart and the vessels of a mouse poses significant challenges for small animal imaging systems with respect to the spatial and temporal resolution. This chapter elucidates the relevant cardiovascular pathologies and clinical challenges, reviews animal models of cardiovascular disease and shows examples of applications of small animal imaging by CT, ultrasound, MRI, SPECT, PET and optical imaging.
    12/2010: pages 449-471;
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    ABSTRACT: Simultaneous PET and MRI using new hybrid PET/MRI systems promises optimal spatial and temporal coregistration of structural, functional, and molecular image data. In a pilot study of 10 patients with intracranial masses, the feasibility of tumor assessment using a PET/MRI system comprising lutetium oxyorthosilicate scintillators coupled to avalanche photodiodes was evaluated, and quantification accuracy was compared with conventional PET/CT datasets. All measurements were performed with a hybrid PET/MRI scanner consisting of a conventional 3-T MRI scanner in combination with an inserted MRI-compatible PET system. Attenuation correction of PET/MR images was computed from MRI datasets. Diagnoses at the time of referral were low-grade astrocytoma (n = 2), suspicion of low-grade astrocytoma (n = 1), anaplastic astrocytoma (World Health Organization grade III; n = 1), glioblastoma (n = 2), atypical neurocytoma (n = 1), and meningioma (n = 3). In the glial tumors, (11)C-methionine was used for PET; in the meningiomas, (68)Ga-DOTATOC was administered. Tumor-to-gray matter and tumor-to-white matter ratios were calculated for gliomas, and tracer uptake of meningiomas was referenced to nasal mucosa. PET/MRI was performed directly after clinically indicated PET/CT examination. In all patients, the PET datasets showed similar diagnostic image quality on the hybrid PET/MRI and the PET/CT studies; however, slight streak artifacts were visible in coronal and sagittal sections when using the higher intrinsic resolution of the PET/MRI insert. Prefiltering of images with a 4-mm gaussian filter at a resolution comparable to that of the PET/CT system virtually eliminated these artifacts. Although acquisition of the PET/MR images started at 30-60 min after PET/CT (20.4-min half-life of (11)C) acquisition, the signal-to-noise ratio was good enough, thus underlining the high sensitivity of the PET insert, compared with whole-body PET systems. The computed tumor-to-reference tissue ratios exhibited an excellent accordance between the PET/MRI and PET/CT systems, with a Pearson correlation coefficient of 0.98. Mean paired relative error was 7.9% +/- 12.2%. No significant artifacts or distortions were detected in the simultaneously acquired MR images using the PET/MRI scanner. Structural, functional, and molecular imaging in patients with brain tumors is feasible with diagnostic imaging quality using simultaneous hybrid PET/MR image acquisition.
    Journal of Nuclear Medicine 08/2010; 51(8):1198-205. · 5.77 Impact Factor
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    ABSTRACT: Recently, integrated small-animal PET/MRI prototypes that provide isochronous and coregistered datasets of morphology and function through the simultaneous acquisition of PET and MRI data have been developed. However, the need for MRI compatibility can constrain the technical design of the PET components and may lead to a lower sensitivity and lower spatial and temporal resolutions. The aim of this study was to evaluate the suitability of a prototype preclinical PET/MRI system for the simultaneous assessment of cardiac metabolism and function in mice. A stand-alone high-resolution small-animal PET scanner using the same evaluation protocols was used as a reference. Simultaneous PET/MR images of an infarct mouse model (21 animals plus 3 controls) were acquired. The imaging performance of the MRI-compatible PET insert was evaluated with respect to count sensitivity; myocardium-to-background contrast; suitability for the analysis of global left ventricular function; and uptake difference in scar, border-zone, and remote regions. The radiotracer (18)F-FDG was used to acquire cardiac gated PET data, applying retrospective coincidence sorting. The PET insert data were coregistered to the MR images by determination of the appropriate transformation matrix. An optimal registration of PET and MR images from the integrated system was achieved, and the reconstructed images showed a good visual correspondence in infarct areas between PET and MRI data. As expected, the PET insert showed a poorer performance with respect to counting rate and myocardium-to-background ratio than did the high-resolution PET. Assessment of left ventricular volumes was possible with the current PET/MRI prototype. A good correlation was found between PET and MRI (R > 0.95). Local PET uptake was successfully determined for different tissue, and a differentiation among remote, border-zone, and scar tissue was possible. However, the uptake difference for the PET/MRI prototype was lower than that for the high-resolution stand-alone PET system. A hybrid PET/MRI prototype was successfully used to assess cardiac parameters in an infarct mouse model, although performance was reduced when compared with a high-resolution animal PET scanner. Future technical improvements are expected to result in comparable performance while providing higher registration accuracy.
    Journal of Nuclear Medicine 08/2010; 51(8):1277-84. · 5.77 Impact Factor
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    ABSTRACT: Stress-induced angina pectoris is highly suspicious for coronary artery disease. In this report, we present a rare case of cardiac metastasis mimicking coronary artery disease and demonstrate the potential of multimodal imaging guiding to diagnosis. Case. A 69-year-old Caucasian woman presented with stress-induced chest pain and shortness of breath typical for coronary artery disease (CAD). Stress ECG showed significant ST-depression up to 0.2 mV in the precordial leads already on a low exercise level whereas exercise capacity was markedly reduced due to angina pectoris and dyspnea. Coronary angiography revealed a long and tubular stenosis of the left anterior descending (LAD) and occlusion of the proximal circumflex (LCX) arteries (Figure 1 and online supplement). There were no relevant signs of dynamic compression of the LAD as sometimes seen with muscular bridging over coronary arteries and retrograde filling of the LCX could not be observed. Percutaneous transluminal angioplasty (PTCA) and stent implantation was performed in the LAD, but a significant proximal stenosis remained (Figure 2). Occlusion of the LCX was considered to be chronic so that an attempt of PTCA was not performed. Despite the intervention, clinical symptoms persisted. Additionally, the patient experienced episodes of impaired vision. Magnetic resonance imaging (MRI) of the brain showed multiple small cerebral infarctions. Subsequent echocardiography was performed and showed a solid mass of increased echogenicity near the anterior wall of the left ventricle (LV), adjacent to the mitral valve (Figure 3 and online supplement).
    Journal of Nuclear Cardiology 08/2010; 17(4):696-8. · 2.85 Impact Factor
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    ABSTRACT: The aim of this study was to test and demonstrate the feasibility of diffusion tensor imaging (DTI) with a hybrid positron emission tomography (PET)/magnetic resonance imaging system for simultaneous PET and magnetic resonance (MR) data acquisition. All measurements were performed with a prototype hybrid PET/MR scanner dedicated for brain and head imaging. The PET scanner, which is inserted into a conventional 3.0-Tesla high field MR imager equipped with a transmit/receive birdcage head coil, consists of 192 block detectors with a matrix of 12 x 12 lutetium oxyorthosilicate scintillation crystals combined with MR-compatible 3 x 3 avalanche photodiode arrays. In 7 volunteers and 4 patients with brain tumors, DTI was performed during simultaneous PET data readout applying a diffusion weighted echo planar sequence (12 noncollinear directions, echo time (TE)/repetition time (TR) 98 ms/5300 ms, b-value 800 s/mm). Image quality and accuracy of DTI were assessed in comparison with DTI images acquired after removal of the PET insert. The diffusion images showed good image quality in all volunteers regardless of simultaneous PET data readout or after removal of the PET scanner; however, significantly (P < 0.01) stronger rim artifacts were found in fractional anisotropy images computed from DTI images recorded during simultaneous PET acquisition, demonstrating higher eddy-current effects. In region of interest analysis, no notable differences were found in the computation of the direction of the principal eigenvector (P > 0.05) and fractional anisotropy values (P > 0.05). In the assessment of pathologies, in all 4 patients PET and DTI provided important clinical information in addition to conventional magnetic resonance imaging. Diffusion tensor imaging may be combined with simultaneous PET data acquisition, offering additional important morphologic and functional information for treatment planning in patients with brain tumors.
    Investigative radiology 03/2010; 45(5):270-4. · 4.85 Impact Factor
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    ABSTRACT: FDG-PET(/CT) is frequently used in surveillance of Ewing sarcoma (ES) patients. Since ES and PNET (primitive neuroectodermal tumours) may cause peripheral metastases some centers routinely recommend whole body PET acquisition from head to toe what may necessitate repositioning of the patient and thus extending examination time. It is not clear yet whether inclusion of lower leg adds to the diagnostic accuracy of PET scanning, especially in primary tumors of the trunk. PATIENTS, METHOD: 40 patients with ES and PNET of the trunk who were referred for surveillance after primary therapy with complete remission, were evaluated retrospectively: 27 men, 13 women; mean age at diagnosis 16.3 (3-35) years. At the time of diagnosis 28 patients had localized and 12 metastatic disease. Almost all of the patients had undergone a combined chemotherapy with surgery or/and radiotherapy. 156 follow-up PET scans of the legs of these patients were evaluated retrospectively. only in three (1.9%) of 156 scans a pathologic FDG accumulation was attributed to metastatic disease of the lower extremities. In these cases the observation of metastatic disease in the legs did not alter therapy, since in all three cases a multifocal disease progression was observed. scanning of the lower legs may be omitted during follow-up in patients in whom the primary tumor was located in the trunk and in whom no clinical signs pointing to metastases in the lower legs are present. This provides a sufficient diagnostic power and a shorter examination time, thus increasing patient comfort and scanner availability.
    Nuklearmedizin 01/2010; 49(5):183-6. · 1.67 Impact Factor
  • Der Nuklearmediziner 01/2010; 33(02):85-90.
  • Rofo-fortschritte Auf Dem Gebiet Der Rontgenstrahlen Und Der Bildgebenden Verfahren - ROFO-FORTSCHR RONTGENSTRAHL. 01/2010; 182.

Publication Stats

876 Citations
254.97 Total Impact Points

Institutions

  • 2013
    • University of Tuebingen
      • Department of Radiology
      Tübingen, Baden-Wuerttemberg, Germany
  • 1999–2013
    • University of Münster
      • • Department of Nuclear Medicine
      • • European Institute of Molecular Imaging
      • • Clinic for Nuclear Medicine
      Münster, North Rhine-Westphalia, Germany
  • 2004–2012
    • Universitätsklinikum Münster
      • Klinik für Nuklearmedizin
      Muenster, North Rhine-Westphalia, Germany
  • 2006
    • MRC Clinical Sciences Centre
      London Borough of Harrow, England, United Kingdom
    • Imperial College London
      • Faculty of Medicine
      London, ENG, United Kingdom