Thomas Schlosser

Publications (85) View all

• Article: Selective Internal Radiotherapy (SIRT) of Hepatic Tumors: How to Deal with the Cystic Artery.

  Jens M Theysohn, Stefan Müller, Jörg F Schlaak, Judith Ertle, Thomas W Schlosser, Andreas Bockisch, Thomas C Lauenstein
  [show abstract] [hide abstract]
  ABSTRACT: PURPOSE: Selective internal radiotherapy (SIRT) with the beta emitter yttrium-90 (Y90) is a rapidly developing therapy option for unresectable liver malignancies. Nontarget irradiation of the gallbladder is a complication of SIRT. Thus, we aimed to assess different strategies to avoid infusion of Y90 into the cystic artery (CA). METHODS: After hepatic digital subtraction angiography and administration of technetium-99m-labeled human serum albumin ((99)mTc-HSA), 295 patients with primary or secondary liver tumors underwent single-photon emission computed tomography/computed tomography (SPECT/CT). Different measures were taken before repeated Y90 mapping and SIRT to avoid unintended influx into the CA where necessary. Clinical symptoms, including pain, fever, or a positive Murphy sign, were assessed during patient follow-up. RESULTS: A significant (99)mTc-HSA accumulation in the gallbladder wall (higher (99)mTc-HSA uptake than in normal liver tissue) was seen in 20 patients. The following measures were taken to avoid unintended influx into the CA: temporary/permanent occlusion of the CA with gelfoam (n = 5)/microcoil (n = 1), induction of vasospasm with a microwire (n = 4), or altering catheter position (n = 10). Clinical signs of cholecystitis were observed in only one patient after temporary CA occlusion with gelfoam and were successfully treated by antibiotics. Cholecystectomy was not required for any patient. CONCLUSION: It is important to identify possible nontarget irradiation of the gallbladder. The risk for radiation-induced cholecystitis can be easily minimized by temporary or permanent CA embolization, vasospasm induction, or altering the catheter position.
  CardioVascular and Interventional Radiology 09/2012; · 2.09 Impact Factor
• Article: Hybrid PET/MR Imaging of the Heart: Feasibility and Initial Results.

  Felix Nensa, Thorsten D Poeppel, Karsten Beiderwellen, Juliane Schelhorn, Amir A Mahabadi, Raimund Erbel, Philipp Heusch, Kai Nassenstein, Andreas Bockisch, Michael Forsting, Thomas Schlosser
  [show abstract] [hide abstract]
  ABSTRACT: Purpose:To assess the feasibility of hybrid imaging of the heart with fluorine 18 fluorodeoxyglucose (FDG) on an integrated 3-T positron emission tomography (PET)/magnetic resonance (MR) imaging system.Materials and Methods:The present study was approved by the local institutional review board. Written informed consent was obtained from all patients before imaging. Twenty consecutive patients with myocardial infarction (n = 20) underwent cardiac PET/MR imaging examination. Ten patients underwent additional cardiac PET/computed tomography (CT) before PET/MR. Two-dimensional half-Fourier acquisition single-shot turbo spin-echo sequences, balanced steady-state free precession cine sequences, two-dimensional turbo inversion-recovery magnitude T2-weighted sequences, and late gadolinium-enhanced (LGE) segmented two-dimensional inversion-recovery turbo fast low-angle shot sequences were performed. According to the 17-segment model, PET tracer uptake, wall motion, and late gadolinium enhancement were visually assessed for each segment on a binary scale, and categorical intermethod agreement was calculated by using the Cohen κ. The maximum standardized uptake value was measured in corresponding myocardial locations on PET/CT and PET/MR images.Results:Agreement was substantial over all patients and segments between PET and LGE images (κ = 0.76) and between PET and cine images (κ = 0.78). In 306 segments, 97 (32%) were rated as infarcted on PET images, compared with 93 (30%) rated as infarcted on LGE images and with 90 (29%) rated as infarcted on cine images. In a subgroup of patients (n = 10) with an additional PET/CT scan, no significant difference in myocardial tracer uptake between PET/CT and PET/MR images was found (paired t test, P = .95).Conclusion:Cardiac PET/MR imaging with FDG is feasible and may add complementary information in patients with ischemic heart disease.© RSNA, 2013Supplemental material: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.13130231/-/DC1.
  Radiology 05/2013; · 5.73 Impact Factor
• Article: Simultaneous 18F Choline Positron Emission Tomography/Magnetic Resonance Imaging of the Prostate: Initial Results.

  Axel Wetter, Christine Lipponer, Felix Nensa, Karsten Beiderwellen, Tobias Olbricht, Herbert Rübben, Andreas Bockisch, Thomas Schlosser, Till A Heusner, Thomas C Lauenstein
  [show abstract] [hide abstract]
  ABSTRACT: PURPOSE: The purposes of this study were to evaluate the feasibility of simultaneous F choline positron emission tomography (PET) and magnetic resonance imaging (MRI) of the prostate and to present the first clinical results of the method. MATERIALS AND METHODS: From March 2012 to October 2012, a total of 15 consecutive patients were examined with simultaneous F choline PET/MRI. At the time of the examination, 8 patients had histologically proven prostate cancer, 2 patients had repeated prostate biopsies with negative results, and 5 patients had repeated prostate cancer with an elevated or rising prostate specific antigene level but did not have a prostate biopsy. Sequence protocol comprised T2-weighted high-resolution images and diffusion-weighted images of the prostate in addition to PET imaging. Image quality was assessed by 2 radiologists, and the PET images were evaluated qualitatively and quantitatively. RESULTS: Simultaneous PET/MRI of the prostate was accomplished successfully in all patients. The method proved to be robust without technical failure, and the image quality was rated to be diagnostic in all examinations except in 1 diffusion-weighted imaging (DWI) data set that was judged to be nondiagnostic because of susceptibility artifacts. High-resolution T2-weighted images allowed exact correlation of elevated focal or diffuse choline uptake to suspicious T2-weighted lesions of the prostate. A high accordance was found between PET and DWI. However, PET-positive lesions were found in 3 patients wherein DWI did not indicate tumor in suspicious T2-weighted lesions. CONCLUSIONS: Simultaneous positron emission tomography/magnetic resonance imaging of the prostate has the advantage of combining high-resolution prostate images, functional studies, and metabolic/molecular imaging. The PET component adds diagnostic confidence to the MRI-based parameters in identifying and localizing tumor in the prostate.
  Investigative radiology 03/2013; · 4.85 Impact Factor
• Article: Cardiac magnetic resonance: is phonocardiogram gating reliable in velocity-encoded phase contrast imaging?

  Kai Nassenstein, Stephan Orzada, Lars Haering, Andreas Czylwik, Christoph Jensen, Thomas Schlosser, Oliver Bruder, Mark E Ladd, Stefan Maderwald
  [show abstract] [hide abstract]
  ABSTRACT: OBJECTIVES: To assess the diagnostic accuracy of phonocardiogram (PCG) gated velocity-encoded phase contrast magnetic resonance imaging (MRI). METHODS: Flow quantification above the aortic valve was performed in 68 patients by acquiring a retrospectively PCG- and a retrospectively ECG-gated velocity-encoded GE-sequence at 1.5 T. Peak velocity (PV), average velocity (AV), forward volume (FV), reverse volume (RV), net forward volume (NFV), as well as the regurgitant fraction (RF) were assessed for both datasets, as well as for the PCG-gated datasets after compensation for the PCG trigger delay. RESULTS: PCG-gated image acquisition was feasible in 64 patients, ECG-gated in all patients. PCG-gated flow quantification overestimated PV (Δ 3.8 ± 14.1 cm/s; P = 0.037) and underestimated FV (Δ -4.9 ± 15.7 ml; P = 0.015) and NFV (Δ -4.5 ± 16.5 ml; P = 0.033) compared with ECG-gated imaging. After compensation for the PCG trigger delay, differences were only observed for PV (Δ 3.8 ± 14.1 cm/s; P = 0.037). Wide limits of agreement between PCG- and ECG-gated flow quantification were observed for all variables (PV: -23.9 to 31.4 cm/s; AV: -4.5 to 3.9 cm/s; FV: -35.6 to 25.9 ml; RV: -8.0 to 7.2 ml; NFV: -36.8 to 27.8 ml; RF: -10.4 to 10.2 %). CONCLUSIONS: The present study demonstrates that PCG gating in its current form is not reliable enough for flow quantification based on velocity-encoded phase contrast gradient echo (GE) sequences. KEY POINTS: • Phonocardiogram gating is an alternative to ECG-gating in cardiac MRI. • Phonocardiogram gating shows only limited reliability for velocity-encoded cardiac MRI. • Further refinements of the post-processing algorithm are necessary.
  European Radiology 07/2012; · 3.22 Impact Factor
• Article: Selective internal radiation therapy of hepatocellular carcinoma: potential hepatopulmonary shunt reduction after sorafenib administration.

  Jens M Theysohn, Jörg F Schlaak, Stefan Müller, Judith Ertle, Thomas W Schlosser, Andreas Bockisch, Thomas C Lauenstein
  [show abstract] [hide abstract]
  ABSTRACT: Sorafenib, a protein kinase inhibitor, is a systemic drug that has been licensed for the treatment of hepatocellular carcinoma (HCC). This retrospective study assessed whether the administration of sorafenib can result in a reduction of the hepatopulmonary shunt (HPS) before selective internal radiation therapy (SIRT). After exclusion from SIRT because of high HPS, computed tomography scan indicated a shunt reduction in seven patients with HCC receiving sorafenib. Repeated measurements revealed HPS reduction (from 26.5% to 7.5% on average), and subsequent SIRT became possible. In conclusion, sorafenib may reduce HPS in patients with advanced HCC in some cases.
  Journal of vascular and interventional radiology: JVIR 07/2012; 23(7):949-52. · 1.81 Impact Factor