Matthias K Werner

Universitätsklinikum Tübingen, Tübingen, Baden-Württemberg, Germany

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Publications (35)67.91 Total impact

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    ABSTRACT: Assessment of the Achilles tendon thickness (ATT) using B-mode ultrasound is a common technique for clinical evaluation of chronic mid-part tendinosis. Currently used image-based assessment is limited by relatively high inter- and intra-observer variability. In this study, it was tested whether a new sequence-based automated assessment of ATT provides more reliable and reproducible results than the standard image-based procedure.
    Archives of Orthopaedic and Trauma Surgery 07/2014; · 1.36 Impact Factor
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    ABSTRACT: Purpose: In patients with a neuroendocrine tumour (NET), the extent of disease strongly influences the outcome and multidisciplinary therapeutic management. Thus, systematic analysis of the diagnostic performance of the existing staging modalities is necessary. The aim of this study was to compare the diagnostic performance of 2 whole-body imaging modalities, [Ga]DOTATOC positron emission tomography (PET)/computed tomography (CT) and magnetic resonance imaging (MRI) in patients with NET with regard to possible impact on treatment decisions. Materials and methods: [Ga]DOTATOC-PET/CT and whole-body magnetic resonance imaging (wbMRI) were performed on 51 patients (25 females, 26 males, mean age 57 years) with histologically proven NET and suspicion of metastatic spread within a mean interval of 2.4 days (range 0-28 days). PET/CT was performed after intravenous administration of 150 MBq [Ga]DOTATOC. The CT protocol comprised multiphase contrast-enhanced imaging. The MRI protocol consisted of standard sequences before and after intravenous contrast administration at 1.5 T. Each modality (PET, CT, PET/CT, wbMRI) was evaluated independently by 2 experienced readers. Consensus decision based on correlation of all imaging data, histologic and surgical findings and clinical follow-up was established as the standard of reference. Lesion-based and patient-based analysis was performed. Detection rates and accuracy were compared using the McNemar test. P values <0.05 were considered significant. The impact of whole-body imaging on the treatment decision was evaluated by the interdisciplinary tumour board of our institution. Results: 593 metastatic lesions were detected in 41 of 51 (80%) patients with NET (lung 54, liver 266, bone 131, lymph node 99, other 43). One hundred and twenty PET-negative lesions were detected by CT or MRI. Of all 593 lesions detected, PET identified 381 (64%) true-positive lesions, CT 482 (81%), PET/CT 545 (92%) and wbMRI 540 (91%). Comparison of lesion-based detection rates between PET/CT and wbMRI revealed significantly higher sensitivity of PET/CT for metastatic lymph nodes (100% vs 73%; P < 0.0001) and pulmonary lesions (100% vs 87%; P = 0.0233), whereas wbMRI had significantly higher detection rates for liver (99% vs 92%; P < 0.0001) and bone lesions (96% vs 82%; P < 0.0001). Of all 593 lesions, 22 were found only in PET, 11 only in CT and 47 only in wbMRI. The patient-based overall assessment of the metastatic status of the patient showed comparable sensitivity of PET/CT and MRI with slightly higher accuracy of PET/CT. Patient-based analysis of metastatic organ involvement revealed significantly higher accuracy of PET/CT for bone and lymph node metastases (100% vs 88%; P = 0.0412 and 98% vs 78%; P = 0.0044) and for the overall comparison (99% vs 89%; P < 0.0001). The imaging results influenced the treatment decision in 30 patients (59%) with comparable information from PET/CT and wbMRI in 30 patients, additional relevant information from PET/CT in 16 patients and from wbMRI in 7 patients. Conclusion: PET/CT and wbMRI showed comparable overall lesion-based detection rates for metastatic involvement in NET but significantly differed in organ-based detection rates with superiority of PET/CT for lymph node and pulmonary lesions and of wbMRI for liver and bone metastases. Patient-based analysis revealed superiority of PET/CT for NET staging. Individual treatment strategies benefit from complementary information from PET/CT and MRI.
    Cancer Imaging 01/2013; 13:63-72. · 1.59 Impact Factor
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    ABSTRACT: PURPOSE This study was performed to evaluate the possibility to differentiate malignant or premalignant causes of incidental gastrointestinal (GI) FDG uptake in PET/CT. In this regard, contrast-enhanced CT (ceCT) and low-dose CT (ldCT) as part of routine PET/CT protocols as well as different FDG uptake patterns in the PET images were investigated. METHOD AND MATERIALS A database of 5045 PET/CT examinations was searched retrospectively for incidental GI FDG uptake in PET/CT scans. Inclusion criteria for evaluation beside incidental GI FDG uptake were a PET/CT protocol including ldCT and ceCT as well as available endoscopy and histology data for reference standard. Different FDG uptake patterns in PET (focal, segmental, diffuse) and CT characteristics in ldCT and ceCT (e.g. wall thickening, contrast-enhancement resulting in classifications mass, inflammation, unspecific change, normal) of the incidental GI PET lesions were evaluated. The correct identification of premalignant and malignant diseases was assessed for the different PET and CT classification groups. RESULTS Incidental GI FDG uptake was found in 5.6% of the PET/CT examinations. 62 finally included incidental PET lesions comprised 17 (27%) malignancies, 10 (16%) premalignant lesions, 18 benign diseases and 17 normal endoscopic and histological results. The sensitivity/specificity for the detection of malignant and premalignant lesions in areas with incidental GI FDG uptake was 0.70/0.49 for focal uptake, 0.26/0.74 for segmental uptake, 0.22/0.94 for a mass in ldCT and 0.81/0.85 for a mass in ceCT. Other PET and CT characteristics did not match sufficiently with malignant and premalignant lesions. CONCLUSION Incidental GI FDG uptake is caused by malignant and premalignant lesions in 33%. If PET/ceCT is performed, the characteristics in the contrast-enhanced images are most appropriate for the detection or exclusion of malignant and premalignant diseases. This may enable further targeted diagnostic management. If PET/ldCT is performed, a differentiation of these causes by FDG uptake patterns or ldCT is not possible. CLINICAL RELEVANCE/APPLICATION Incidental gastrointestinal FDG uptake in PET/CT needs to be explored by endoscopy. This study investigates, if already the PET/CT data allows a differentiation of malignant and premalignant causes.
    Radiological Society of North America 2012 Scientific Assembly and Annual Meeting; 11/2012
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    ABSTRACT: PURPOSE Combined PET/MR imaging has the potential to provide superior image quality in the vicinity of dental implants, which are known to cause beam-hardening and thus PET attenuation correction (AC) artefacts in PET/CT. We evaluated combined FDG-PET/MR for head and neck imaging using dental phantom- and patient data of PET/CT and subsequent PET/MR examinations. METHOD AND MATERIALS A dental phantom was made of real human teeth in plastic carriers resembling the jaws in a FDG/water solution. Phantom and patient scans were performed consecutively on PET/CT (Biograph HiRez16 / mCT, Siemens) and integrated whole-body PET/MR (Biograph mMR, Siemens). PET images were reconstructed with and without CT- and MR- (UTE sequence for phantoms or FLASH sequence with DIXON-based fat-water-separation for patients) based AC. Phantom and patient data were evaluated for severity of artefacts using a visual 5-point scale with 0 = no artefacts, quantification was performed via standardized uptake value analysis. RESULTS Phantom image quality was higher on PET/MR than on PET/CT with fewer artefacts although slightly affected/biased MR-based attenuation maps were used. An enlarged photopenic area was visible around dental implants in AC and non-AC PET, and no other artefacts were introduced. In PET/CT, severe artefacts were present in CT resulting in non-uniform PET images after CT-AC, with slightly enlarged photopenia around implants in non-AC PET. The initial analysis of patient data revealed a significantly improved visualization of structures usually affected by artefacts in PET/CT, such as the palate (0.8 mean of visual scale in PET/MR vs. 4.0 in PET/CT), tonsils (0.5 vs. 4.3) and the pharynx (0.3 vs. 2.3), when filling materials with high CT densities were present (e.g., amalgam, gold). CONCLUSION Combined PET/MR imaging promises improved visualization of structures adjacent to dental implants compared to PET/CT. Further improvement can be expected from an optimization of MR-AC algorithms. CLINICAL RELEVANCE/APPLICATION When dental implants are present, PET/MRI could upgrade image quality compared to PET/CT. This may translate into improved diagnostic accuracy in the management of patients with head and neck cancer.
    Radiological Society of North America 2012 Scientific Assembly and Annual Meeting; 11/2012
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    ABSTRACT: PURPOSE PET quantification is an important prerequisite for a correct lesion classification in MR/PET. Thus, the frequency and characteristics of artefacts in segmentation-based attenuation correction maps (µ-map) of MR/PET and their impact on SUV quantification in the affected areas were investigated. METHOD AND MATERIALS 119 µ-maps achieved from MR images were retrospectively inspected for artefacts owing to regional wrong identification of the four tissue classes background, lung, fat and soft tissue. The standardized uptake value (SUV) of the PET images using these µ-maps for attenuation correction (aSUV) in an artefact region was compared with a contralateral control region (cSUV) by region-of-interest analysis. The SUV ratios of the artefact regions to reference tissue were also compared to the SUV ratios of the same regions in PET images from PET/CT (ctSUV). The volumes of the artefact regions were assessed in cm³. The relative SUV change was calculated for cSUV as (aSUV-cSUV)/cSUV and correspondingly for ctSUV. RESULTS 102 artefacts were found in 63 (53%) of the 119 µ-maps. The artefacts were located in the thoracic region or hips due to metal implants (n=11), in the lungs (n=42), in the jaw (n=36) and in different locations (e.g. head, extremities, n=13). So far, 20 artefact regions with volumes ranging from 0.6-501.2 cm³ were inspected in detail (lungs n=13, metal implants n=5, femur n=1, tumor n=1). Artefacts with volumes >3 cm³ were mainly caused by metal implants resulting always in an underestimation of SUVs (maximum relative change of -1.0 to cSUV and -1.0 to ctSUV, respectively). Smaller artefacts e.g. in the lungs showed partly overestimated (maximum relative change of 1.31 to cSUV and 2.55 to ctSUV, respectively) and partly underestimated SUVs. CONCLUSION Artefacts in the segmentation-based µ-map occur often. Metal implants lead to large artefacts > 3cm³ with definite underestimation of the SUV and as a result missing or false characterization of possible lesions. In smaller artefacts the SUV may be over- or underestimated. Further studies are needed to investigate the causes for this heterogeneous behaviour. CLINICAL RELEVANCE/APPLICATION The PET attenuation correction of new MR/PET systems is currently performed by segmentation of MR images and comprises often regional artefacts, which may impair the lesion detection in PET severely.
    Radiological Society of North America 2012 Scientific Assembly and Annual Meeting; 11/2012
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    ABSTRACT: PURPOSE: Combined PET/CT imaging has been proposed as an integral part of radiotherapy treatment planning (TP). Contrast-enhanced CT (ceCT) images are frequently acquired as part of the PET/CT examination to support target delineation. The aim of this dosimetric planning study was to investigate the error introduced by using a ceCT for intensity modulated radiotherapy (IMRT) TP with Monte Carlo dose calculation for non-small cell lung cancer (NSCLC). MATERIAL AND METHODS: Nine patients with NSCLC prior to chemo-RT were included in this retrospective study. For each patient non-enhanced, low-dose CT (neCT), ceCT and [(18)F]-FDG-PET emission data were acquired within a single examination. Manual contouring and TP were performed on the ceCT. An additional set of independent target volumes was auto-segmented in PET images. Dose distributions were recalculated on the neCT. Differences in dosimetric parameters were evaluated. RESULTS: Dose differences in PTV and lungs were small for all patients. The maximum difference in all PTVs when using ceCT images for dose calculation was -2.1%, whereas the mean difference was less than -1.7%. Maximum differences in the lungs ranged from -1.8% to 2.1% (mean: -0.1%). In four patients an underestimation of the maximum spinal cord dose between 2% and 3.2% was observed, but treatment plans remained clinically acceptable. CONCLUSIONS: Monte Carlo based IMRT planning for NSCLC patients using ceCT allows for correct dose calculation. A direct comparison to neCT-based treatment plans revealed only small dose differences. Therefore, ceCT-based TP is clinically safe as long as the maximum acceptable dose to organs at risk is not approached.
    Physica Medica 09/2012; · 1.17 Impact Factor
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    ABSTRACT: Clinical PET/MR acquisition protocols entail the use of MR contrast agents (MRCA) that could potentially affect PET quantification following MR-based attenuation correction (AC). We assessed the effect of oral and intravenous (IV) MRCA on PET quantification in PET/MR imaging. We employed two MRCA: Lumirem® (oral) and Gadovist® (IV). First, we determined their reference PET attenuation values using a PET transmission scan (ECAT-EXACT HR+, Siemens) and a CT scan (PET/CT Biograph 16 HI-REZ, Siemens). Second, we evaluated the attenuation of PET signals in the presence of MRCA. Phantoms were filled with clinically relevant concentrations of MRCA in a background of water and (18)F-fluoride, and imaged using a PET/CT scanner (Biograph 16 HI-REZ, Siemens) and a PET/MR scanner (Biograph mMR, Siemens). Third, we investigated the effect of clinically relevant volumes of MRCA on MR-based AC using human pilot data: a patient study employing Gadovist® (IV) and a volunteer study employing two different oral MRCA (Lumirem® and pineapple juice). MR-based attenuation maps were calculated following Dixon-based fat-water segmentation and an external atlas-based and pattern recognition (AT&PR) algorithm. IV and oral MRCA in clinically relevant concentrations were found to have PET attenuation values similar to those of water. The phantom experiments showed that under clinical conditions IV and oral MRCA did not yield additional attenuation of PET emission signals. Patient scans showed that PET attenuation maps are not biased after the administration of IV MRCA but may be biased, however, after ingestion of iron oxide-based oral MRCA when segmentation-based AC algorithms are used. Alternative AC algorithms, such as AT&PR, or alternative oral contrast agents, such as pineapple juice, can yield unbiased attenuation maps. In clinical PET/MR scenarios MRCA are not expected to lead to markedly increased attenuation of the PET emission signals. MR-based attenuation maps may be biased by oral iron oxide-based MRCA unless advanced AC algorithms are used.
    European Journal of Nuclear Medicine 08/2012; 39(11):1756-66. · 4.53 Impact Factor
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    Matthias K Werner, Holger Schmidt, Nina F Schwenzer
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    ABSTRACT: OBJECTIVE: This article provides a short overview of hybrid imaging and the potential advantages of combined MR/PET. We will address some of the challenges that had to be met before MR/PET could become clinically available as well as further scientific work that has to be done to increase the potential benefit of this emerging hybrid modality. CONCLUSION: Hybrid imaging, the combination of two imaging modalities into one, promises the compensation of specific deficits of the modalities involved. PET/CT has gained wide acceptance for oncologic imaging in recent years; however, MRI has certain advantages that could make combined MR/PET more tempting in various clinical applications. The development of new clinical whole-body MR/PET systems offers new insights in metabolic and functional processes in oncology as well as cardiovascular and neurologic diseases.
    American Journal of Roentgenology 08/2012; 199(2):272-7. · 2.90 Impact Factor
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    ABSTRACT: The present review aims to depict the possibilities offered by hybrid imaging with magnetic resonance positron emission tomography (MR/PET). Recently, new whole-body MR/PET scanners were introduced allowing for the combination of both modalities outside the brain. This is a challenge for both modalities: For MRI, it is essential to provide anatomical images with high resolution. Additionally, diffusion-weighted imaging (DWI), proton spectroscopy, but also dynamic contrast-enhanced imaging plays an important role. With regard to PET, the technical challenge mainly consists of obtaining an appropriate MR-based attenuation correction for the PET data. Using MR/PET, it is possible to acquire morphological and functional data in one examination. In particular, children and young adults will benefit from this new hybrid technique, especially in oncologic imaging with multiple follow-up examinations. However, it is expected that PET/CT will not be replaced completely by MR/PET because PET/CT is less cost-intensive and more widely available. Moreover, in lung imaging, MRI limitations still have to be accepted. Concerning research, simultaneous MR/PET offers a variety of new possibilities, for example cardiac imaging, functional brain studies or the evaluation of new tracers in correlation with specific MR techniques.
    RöFo - Fortschritte auf dem Gebiet der R 05/2012; 184(9):780-7. · 2.76 Impact Factor
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    ABSTRACT: PURPOSE: To evaluate the accuracy of presurgical endorectal MRI (eMRI) for local staging before radical prostatectomy (RP) and its influence on neurovascular bundle (NVB) resection during radical prostatectomy. PATIENTS AND METHODS: A total of 385 patients with histologically proven prostate cancer (PCa) have been included in this retrospective study between 2004 and 2008. All patients underwent preoperative eMRI at 1.5 T before open RP. Staging results by eMRI were compared with the histopathological findings. The presence of positive surgical margins and extent of nerve-sparing procedure were evaluated. Subgroup analysis of low-risk group and intermediate to high-risk group based on D'Amico criteria was conducted. RESULTS: In 294 (76.4%) patients, pathological stage was correctly predicted, 69 patients (17.9%) were understaged and 22 (5.7%) overstaged. Overall sensitivity, specificity, negative and positive predictive value for predicting extracapsular extension (ECE) were 41.5, 91.8, 78.0 and 69.0%, respectively. One hundred and fifty-two (48.4%) of the patients classified as stage cT2 by eMRI underwent bilateral NVB sparing, whereas 14 (19.7%) patients with reported ECE underwent bilateral NVB sparing (P < 0.01). Overall positive surgical margin rate was 14.8%. Sensitivity of predicting ECE and positive predictive value were lower in the low-risk group than in the intermediate and high-risk group. CONCLUSIONS: eMRI is effective in predicting extracapsular extension in an intermediate to high-risk group. Preoperative eMRI in patients with low-risk criteria is not recommended as a routine assessment modality. eMRI findings did appear to influence surgical strategy as patients with imaging findings suggesting >cT2 disease were less likely to undergo NVB sparing.
    World Journal of Urology 01/2012; · 2.89 Impact Factor
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    ABSTRACT: PURPOSE Combined PET/MR imaging entails the use of MR contrast agents (MRCA) as part of integrated protocols. We assess additional attenuation of the PET emission signals in the presence of oral and intraveneous (iv) MRCA made up of iron oxide and Gd-chelates, respectively. METHOD AND MATERIALS Phantom scans were performed on a clinical PET/CT (Biograph HiRez16, Siemens) and integrated whole-body PET/MR (Biograph mMR, Siemens) using oral (Lumirem) and intraveneous (Gadovist) MRCA. Reference PET attenuation values were determined on a small-animal PET (Inveon, Siemens) using standard PET transmission imaging (TX). Seven syringes of 5mL were filled with (a) Water, (b) Lumirem_100 (100% conc.), (c) Gadovist_100 (100%), (d) Gadovist_18 (18%), (e) Gadovist_02 (0.2%), (f) Imeron-400 CT iv-contrast (100%) and (g) Imeron-400 (2.4%). The same set of syringes was scanned on CT (Sensation16, Siemens) at 120kVp and 160mAs. The effect of MRCA on the attenuation of PET emission data was evaluated using a 20cm cylinder filled uniformly with [18F]-FDG (FDG) in water (BGD). Three 4.5cm diameter cylinders were inserted into the phantom: (C1) Teflon, (C2) Water+FDG (2:1) and (C3) Lumirem_100+FDG (2:1). Two 50mL syringes filled with Gadovist_02+FDG (Sy1) and water+FDG (Sy2) were attached to the sides of (C1) to mimick the effects of iv-contrast in vessels near bone. Syringe-to-background activity ratio was 4-to-1. PET emission data were acquired for 10min each using the PET/CT and the PET/MR. Images were reconstructed using CT- and MR-based attenuation correction. RESULTS Mean linear PET attenuation (cm-1) on TX was (a) 0.098, (b) 0.098, (c) 0.300, (d) 0.134, (e) 0.095, (f) 0.397 and (g) 0.105. Corresponding CT attenuation (HU) was: (a) 5, (b) 14, (c) 3070, (d) 1040, (e) 13, (f) 3070 and (g) 347. Lumirem had little effect on PET attenuation with (C3) being 13% and 10% higher than (C2) on PET/CT and PET/MR, respectively. Gadovist_02 had even smaller effects with (Sy1) being 2.5% lower than (Sy2) on PET/CT and 1.2% higher than (Sy2) on PET/MR. CONCLUSION MRCA in high and clinically relevant concentrations have attenuation values similar to that of CT contrast and water, respectively. In clinical PET/MR scenarios MRCA are not expected to lead to significant attenuation of the PET emission signals. CLINICAL RELEVANCE/APPLICATION Clinically applied MR contrast agents are not expected to bias PET emission signals in PET/MR studies.
    Radiological Society of North America 2011 Scientific Assembly and Annual Meeting; 12/2011
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    ABSTRACT: PURPOSE In PET/CT imaging CT is used for diagnosis, attenuation correction (CTAC) and anatomical correlation of the PET emission data. In select cases minimum CT tube currents are used; thus, leading to noise propagation in combined data. We evaluate the effects of low-dose CT on noise in CT and PET following CTAC before and after post-reconstruction filtering of CT images. METHOD AND MATERIALS Phantom scans were performed on a clinical PET/CT (Biograph HiRez16, Siemens). An abdominal phantom (NEMA-2001, 35x40x25cm3) containing 6 concentric spherical lesions of 11mm to 38mm diameter was used. Two 10cm diameter plastic cylinders simulating the arms were positioned at the lateral sides of the phantom. The phantom and arm cylinders were filled with water+[18F]-FDG (5kBq/mL). Lesion-to-background ratio was 1.5-to-1. The phantom was centred and CT and PET data were acquired following a whole-body PET/CT protocol: 120kVp CT, 5mm slices, 10min 3D-emission scan. Six CT image volumes were acquired with tube currents (mAs) of 17, 30, 80, 130, 180 and 230 and post-processed using a non-linear adaptive filtering method (ContextVision, Sweden). PET emission images were reconstructed iteratively (OSEM2D, 4i,8s) following CTAC using the original CT (orgCT) and filtered CT (filCT). CT and AC-PET images were analysed by means of regions-of-interests placed in the arms (A), abdomen (AB), central background (CB) and the largest 3 spheres. RESULTS CT image noise varied with the tube current whereas AC-PET image noise did not. Noise (HU) in orgCT/filCT was 23/14 (A), 26/16 (AB) and 28/17 (CB) for 17mAs, and 7/6 (A), 8/7 (AB) and 9/7 (CB) for 230mAs. Corresponding noise values in AC-PET were the same for orgCTAC and filCTAC: 10% (A), 8% (AB) and 8% (CB) for 17mAs and 10% (A), 8% (AB) and 8% (CB) for 230mAs. Using filCT for CTAC had a small effect on the noise level of the AC-PET of the lesions. Noise in the 3 largest regions was reduced from 11% to 10%, 11% to 10% and 9% to 7% following orgCTAC and filCTAC (17mAs). Similar noise level reduction was observed for 230mAs. CONCLUSION CT image noise can be reduced using post-reconstruction filtering. Subsequent benefits on noise propagation through CT-AC are not clinically relevant. CLINICAL RELEVANCE/APPLICATION Noise propagation from low-dose CT in PET/CT is clinically insignificant but post-recon filtering of the CT data may help to enhance the quality of PET/CT data in ultra-low-dose CT applications.
    Radiological Society of North America 2011 Scientific Assembly and Annual Meeting; 12/2011
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    ABSTRACT: PURPOSE Combined PET/CT imaging provides a wealth of diagnostic information for tumor staging and response assessment. We evaluated the validity of anatomical, metabolic and combined anato-metabolic response parameters in patients with biopsy-proven oesophageal carcinoma using a new image analysis platform (syngo.via, Siemens Healthcare). METHOD AND MATERIALS This study includes 36 patients (31 male / 5 female; mean age 62 y) with FDG-PET/CT examinations pre- and 10 weeks post-neoadjuvant chemotherapy prior to surgical intervention. 14 patients were randomly selected for initial analysis. The primary tumor (PT), and the largest metastastic lymph node (LN), was assessed on CT using (ci) wall thickness, (cii) circular region-of-interest (ROI) on non-enhanced images, (ciii) ROI on arterial (art) and portal-venous (pv) phase, if available, and (civ) WHO and RECIST measurements for LN. PET assessment was based on (pi) ROI-based standardized uptake values (SUV) normalized to weight (SUVbw), lean body mass (SUVlbm) and body surface area (SUVbsa), (pii) isocontour VOI-based SUV (bw, lbm and bsa) with 40% threshold and (piii) tumor glycolytic volume (TGV = isocontour VOI x mean SUVbw) for PT. Patients were separated into responders (R) and non-responders (NR) based on clinical assessment using visual and semi-quantitative parameters (pi and ci). We calculated mean %-change post- vs. pre-chemotherapy of CT and PET parameters for both patient groups. RESULTS Most parameters changed as expected under therapy for R (decrease in SUV and size) and NR. However, conflicting observations were also made: PET isocontour volume: -16.8% (NR) vs. +1.8% (R), max CT density in pv phase: +7.9% (NR) and +27.9% (R), mean/max CT density in LN pv -74.3%/-44.3% (NR) and +2.4%/-1.9% (R). There was discordance for directional changes in LN size following RECIST -10.5% (NR) vs. -35% (R) and WHO area +26.5% (NR) vs. -61.7% (R). CONCLUSION In this cohort of patients anatomical response assessment alone appeared insufficient. Metabolic, and more so, combined anato-metabolic response assessment seems appropriate. CLINICAL RELEVANCE/APPLICATION The different parameters available from PET/CT should be explored further in regard to applicability for response monitoring when adopting PET/CT imaging into oncology patient management.
    Radiological Society of North America 2011 Scientific Assembly and Annual Meeting; 12/2011
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    ABSTRACT: To investigate the positive biopsy rate of MRI-guided biopsy (MR-GB) in a routine clinical setting, identify factors predictive for positive biopsy findings and to report about the clinical significance of the diagnosed tumors. Patients with at least one negative trans-rectal-ultrasound-guided biopsy (TRUS-GB), persistently elevated or rising serum prostate specific antigen (PSA) and at least one lesion suspicious for PCa on diagnostic 1.5 Tesla endorectal coil MRI (eMR) were included. Biopsies were carried out using a 1.5 Tesla MRI and an 18 G biopsy gun. Clinical information and biopsy results were collected; logistic regression analysis was carried out. Definite pathology reports of patients with diagnosis of PCa and subsequent radical prostatectomy (RP) were analyzed for criteria of clinical significance. One hundred patients were included, mean number of previous biopsies was 2 (range 1-9), mean PSA at time of biopsy was 11.7 ng/ml (1.0-65.0), and mean prostate volume was 46.7 ccm (range 13-183). In 52/100 (52.0%) patients, PCa was detected. Out of 52 patients, 27 patients with a positive biopsy underwent RP, 20 patients radiation therapy, and 5 patients active surveillance. In total, 80.8% of the patients revealed a clinically significant PCa. In univariate regression analysis, only serum PSA levels were predictive for a positive biopsy result. Number of preceding negative biopsies was not associated with the likelihood of a positive biopsy result. MR-GB shows a high detection rate of clinically significant PCa in patients with previous negative TRUS-GB and persisting suspicion for PCa.
    World Journal of Urology 04/2011; 30(2):213-8. · 2.89 Impact Factor
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    ABSTRACT: A 73-year-old man with a history of prostate and bladder carcinoma and persistent back pain was diagnosed by MRI with multiple vertebral metastases including a compression fracture of T7. He received radiotherapy for pain relief and for vertebral instability with incipient spinal stenosis, but additional targeted systemic therapy was intended. Therefore, multiple attempts at minimally invasive and open biopsies for histological characterisation of the bone metastases were performed, but failed to provide a conclusive specimen, although CT, MRI and bone scintigraphy were used for biopsy planning. Only histopathological analysis of an (18)F-fluorodeoxyglucose-positron emission tomography (FDG-PET)/CT-guided additional biopsy at a site with high metabolic activity yielded the final diagnosis of bone metastases of a neuroendocrine small cell cancer of unknown origin; hence, the patient had a third malignancy requiring a different therapy regimen and diagnostic work-up.
    The British journal of radiology 03/2011; 84(999):e65-7. · 2.11 Impact Factor
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    ABSTRACT: A 43-year-old man was hospitalized for Sjögren’s syndrome which wassuspectedtobeof paraneoplastic aetiology. 18 F-FDG PET/CT revealed grossly enlarged lacrimal (a) and parotid glands (b) with significantly increased FDG uptake while the submandibular glands (c) were only minimally enlarged with faint FDG uptake. Furthermore, hypermetabolic intrathoracic lymphadenopathy was detected with a typical lambda appearance (h) involving right paratracheal (e), left paratracheal and aortopulmonary window lymph nodes (f) of the mediastinum and bihilar lymph nodes (g). The imaging findings were suggestive of sarcoidosis and bronchoscopic evaluation with biopsy was proposed. Histopathology of a transbronchial biopsy specimen confirmed the diagnosis of sarcoidosis. In 1990 Sulavik et al. first described the panda sign, i.e. normal accumulation of the radionuclide ( 67 Ga-citrate) in the nasopharynx combined with increased symmetric accumulation in the parotid and lacrimal glands, giving the impression of the mottled colouring of the giant panda [1–3]. Intrathoracic lymphadenopathy typically manifests as bilateral hilar adenopathywithpredominantlyrightparatrachealadenopathy,
    European Journal of Nuclear Medicine 03/2011; 38(3):603. · 4.53 Impact Factor
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    ABSTRACT: Clinical PET/MR requires the use of patient positioning aids to immobilize and support patients for the duration of the combined examination. Ancillary immobilization devices contribute to overall attenuation of the PET signal, but are not detected with conventional MR sequences and, hence, are ignored in standard MR-based attenuation correction (MR-AC). We report on the quantitative effect of not accounting for the attenuation of patient positioning aids in combined PET/MR imaging. We used phantom and patient data acquired with positioning aids on a PET/CT scanner (Biograph 16, HI-REZ) to mimic PET/MR imaging conditions. Reference CT-based attenuation maps were generated from measured (original) CT transmission images (origCT-AC). We also created MR-like attenuation maps by following the same conversion procedure of the attenuation values except for the prior delineation and subtraction of the positioning aids from the CT images (modCT-AC). First, a uniform (68)Ge cylinder was positioned centrally in the PET/CT scanner and fixed with a vacuum mattress (10 cm thick) and, in a repeat examination, with MR positioning foam pads. Second, 16 patient datasets were selected for subsequent processing. All patients were regionally immobilized with positioning aids: a vacuum mattress for head/neck imaging (nine patients) and a foam mattress for imaging of the lower extremities (seven patients). PET images were reconstructed following CT-based attenuation and scatter correction using the original and modified (MR-like) CT images: PET(origCT-AC) and PET(modCT-AC), respectively. PET images following origCT-AC and modCT-AC were compared visually and in terms of mean differences of voxels with a standardized uptake value of at least 1.0. In addition, we report maximum activity concentration in lesions for selected patients. In the phantom study employing the vacuum mattress the average voxel activity in PET(modCT-AC) was underestimated by 6.4% compared to PET(origCT-AC), with 3.4% of the PET voxels being underestimated by 10% or more. When the MR foam pads were not accounted for during AC, PET(modCT-AC) was underestimated by 1.1% on average, with none of the PET voxels being underestimated by 10% or more. Evaluation of the head/neck patient data showed a decrease of 8.4% ([(68)Ga]DOTATOC) and 7.4% ([(18)F]FDG) when patient positioning aids were not accounted for during AC, while the corresponding decrease was insignificant for the lower extremities. Depending on the size and density of the positioning aids used, a regionally variable underestimation of PET activity following AC is observed when positioning aids are not accounted for. This underestimation may become relevant in combined PET/MR imaging of patients with neuropsychiatric indications, but appears to be of no clinical relevance in imaging the extremities.
    European Journal of Nuclear Medicine 02/2011; 38(5):920-9. · 4.53 Impact Factor
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    ABSTRACT: For cancers of the head and neck, the combination of (18)F-fluorodeoxy-glucose positron emission tomography (FDG-PET)/computed tomography (CT) gains wide acceptance, especially if the primary tumor is unknown (CUP). A patient underwent FDG-PET/CT for squamous cell CUP with cervical lymph node metastases. FDG-PET/CT showed uptake in the right side of the tongue, rendering this area a possible location for the primary tumor. However, clinical examination revealed a deviation of the tongue toward the left side indicating affection of the left hypoglossal nerve, causing the increased FDG uptake. This case illustrates the interpretive pitfalls of unspecific FDG uptake in PET/CT imaging of the head and neck.
    Clinical imaging 01/2011; 35(5):405-7. · 0.73 Impact Factor
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    ABSTRACT: Purpose: To compare the diagnostic performance of [68Ga]DOTA-d-Phe(1)-Tyr(3)-octreotide (DOTATOC)-positron emission tomography (PET)/computed tomography (CT) and whole-body (wb) magnetic resonance imaging (MRI) in staging of neuroendocrine tumors (NET). Material and methods: In 51 patients with histologically proven NET and suspicion of metastatic spread [68Ga]DOTATOC-PET/CT and wbMRI were performed within 30 days. PET/CT was performed after 150 MBq [68Ga]DOTATOC intravenously and included multiphase contrast-enhanced CT. The MRI protocol comprised standard sequences before and after contrast at 1.5 T. Each modality was evaluated separately and blindly with regard to metastatic lesion detection. Histology, clinical and imaging follow-up and consensus evaluation of all examinations served as reference standard. Lesion-based comparison of overall and site-based detection rates of PET/CT and wbMRI was performed using the McNemar test. Results: 41 of 51 (80%) NET patients had 593 metastatic lesions (54 lung, 266 liver, 131 bone, 99 lymph node, 43 other). [68Ga]DOTATOC-PET was false-negative in 5/41 (12%) patients due to the lack of somatostatin receptor (SSTR) expression. PET/CT and wbMRI showed comparable overall detection rates (92% vs 91%). Comparison of organ-based evaluation revealed significantly higher sensitivity of PET/CT in detecting metastatic lymph nodes (100% vs 73%) and pulmonary lesions (100% vs 87%) while wbMRI had significantly higher detection rates for liver (99% vs 92%) and bone lesions (96% vs 82%). If only SSTR+ patients were considered, the overall detection rate of PET/CT significantly improved. Conclusion: PET/CT and wbMRI showed comparable overall detection rates for metastatic involvement in NET but significantly differed in organ-based detection rates with superiority of PET/CT for LN and pulmonary lesions and wbMRI for liver and bone metastases.
    Cancer Imaging 01/2011; 11 Spec No A:S38-9. · 1.59 Impact Factor
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    ABSTRACT: PURPOSE Tuberculosis (TB) is one of the underlying systemic diseases in patients with sight-threatening intraocular inflammation and one of the few causes of uveitis with a definitive effective treatment. We evaluated if 18F-FDG PET/CT may help in the diagnosis of TB induced ocular inflammation in patients with positive QuantiFERON-TB Gold test. METHOD AND MATERIALS 18F-FDG PET/CT was performed in 20 QuantiFERON positive patients with different forms of uveitis. Before PET/CT, all patients underwent extensive clinical workup, including chest X-ray and/or CT. FDG PET/CT was performed according to a standard protocol including contrast-enhanced CT. PET/CT images were carefully evaluated for the presence, size and metabolic activity (FDG uptake, SUV) of hilar and mediastinal lymph nodes and pulmonary lesions. If technically possible, PET/CT guided transbronchial biopsy of suspicious lymph nodes was performed. RESULTS None of the patients presented systemic signs of TB. In 9 of the QuantiFERON-positive patients PET/CT detected increased FDG uptake (mean SUVmax 3.3 ±1.6, range,1.6-9.6) in normal-sized or slightly enlarged mediastinal or hilar lymph nodes. In two of these patients Mycobacterium tuberculosis was detected in culture after PET/CT guided lymph node biopsy. Hilar and mediastinal lymph nodes without FDG-uptake, partly calcified, were found in 7 patients, 4 patients showed additional calcified granulomas in the lung. PET/CT did not reveal any abnormalities in 4 QuantiFERON-positive patients. Size of all evaluated lymph nodes, including calcified nodes, varied between 8 and 31 mm, median 14.2 mm. Median size of metabolically active lymph nodes was 17.3 mm in comparison to 10.1 mm of metabolically inactive lymph nodes (p<0.01, r=0.7) CONCLUSION In QuantiFERON positive patients with uveitis 18F-FDG-PET/CT is useful to identify metabolically active lymph nodes, appropriate for biopsy and thereby helps to establish the definitive diagnosis and adequate therapy. CLINICAL RELEVANCE/APPLICATION 18F-FDG-PET/CT may contribute to the difficult diagnosis of a tuberculosis-induced intraocular inflammation, especially in the case of latent and asymptomatic infection.
    Radiological Society of North America 2010 Scientific Assembly and Annual Meeting; 12/2010

Publication Stats

256 Citations
67.91 Total Impact Points

Institutions

  • 2008–2013
    • Universitätsklinikum Tübingen
      • • Department of Radiology
      • • Division of Diagnostic and Interventional Radiology
      Tübingen, Baden-Württemberg, Germany
  • 2012
    • University of Santiago de Compostela
      • Departamento de Física de Partículas
      Santiago de Compostela, Galicia, Spain
  • 2011
    • Universitätsspital Basel
      Bâle, Basel-City, Switzerland
  • 2008–2011
    • University of Tuebingen
      • • Department of Radiology
      • • Department of Internal Medicine
      Tübingen, Baden-Wuerttemberg, Germany