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Sebastian Regnery - One of the best experts on this subject based on the ideXlab platform.

  • relaxation compensated amide proton transfer apt mri signal intensity is associated with survival and progression in high grade glioma patients
    2019
    Co-Authors: Daniel Paech, Constantin Dreher, Sebastian Regnery, Janeric Meissner, Steffen Goerke, Johannes Windschuh, Johanna Oberhollenzer, Miriam Schultheiss, Katerina Deikehofmann
    Abstract:

    The purpose of this study was to investigate the association of relaxation-compensated chemical exchange saturation transfer (CEST) MRI with overall survival (OS) and progression-free survival (PFS) in newly diagnosed high-grade glioma (HGG) patients. Twenty-six patients with newly diagnosed high-grade glioma (WHO grades III–IV) were included in this prospective IRB-approved study. CEST MRI was performed on a 7.0-T Whole-Body Scanner. Association of patient OS/PFS with relaxation-compensated CEST MRI (amide proton transfer (APT), relayed nuclear Overhauser effect (rNOE)/NOE, downfield-rNOE-suppressed APT (dns-APT)) and diffusion-weighted imaging (apparent diffusion coefficient) were assessed using the univariate Cox proportional hazards regression model. Hazard ratios (HRs) and corresponding 95% confidence intervals were calculated. Furthermore, OS/PFS association with clinical parameters (age, gender, O6-methylguanine-DNA methyltransferase (MGMT) promotor methylation status, and therapy: biopsy + radio-chemotherapy vs. debulking surgery + radio-chemotherapy) were tested accordingly. Relaxation-compensated APT MRI was significantly correlated with patient OS (HR = 3.15, p = 0.02) and PFS (HR = 1.83, p = 0.009). The strongest association with PFS was found for the dns-APT metric (HR = 2.61, p = 0.002). These results still stand for the relaxation-compensated APT contrasts in a homogenous subcohort of n = 22 glioblastoma patients with isocitrate dehydrogenase (IDH) wild-type status. Among the tested clinical parameters, patient age (HR = 1.1, p = 0.001) and therapy (HR = 3.68, p = 0.026) were significant for OS; age additionally for PFS (HR = 1.04, p = 0.048). Relaxation-compensated APT MRI signal intensity is associated with overall survival and progression-free survival in newly diagnosed, previously untreated glioma patients and may, therefore, help to customize treatment and response monitoring in the future. • Amide proton transfer (APT) MRI signal intensity is associated with overall survival and progression in glioma patients. • Relaxation compensation enhances the information value of APT MRI in tumors. • Chemical exchange saturation transfer (CEST) MRI may serve as a non-invasive biomarker to predict prognosis and customize treatment.

  • chemical exchange saturation transfer mri serves as predictor of early progression in glioblastoma patients
    2018
    Co-Authors: Constantin Dreher, Sebastian Regnery, Janeric Meissner, Steffen Goerke, Johannes Windschuh, Johanna Oberhollenzer, Katerina Deikehofmann, Sebastian Adeberg, Sebastian Bickelhaupt
    Abstract:

    // Sebastian Regnery 1, 2 , Sebastian Adeberg 3 , Constantin Dreher 2 , Johanna Oberhollenzer 2 , Jan-Eric Meissner 4 , Steffen Goerke 4 , Johannes Windschuh 4 , Katerina Deike-Hofmann 2 , Sebastian Bickelhaupt 2 , Moritz Zaiss 5 , Alexander Radbruch 2 , Martin Bendszus 6 , Wolfgang Wick 7 , Andreas Unterberg 8 , Stefan Rieken 1 , Jurgen Debus 1 , Peter Bachert 4 , Mark Ladd 4, 9, 10 , Heinz-Peter Schlemmer 2 and Daniel Paech 2 1 Department of Radiation Oncology, University Hospital Heidelberg, Heidelberg, Germany 2 German Cancer Research Center (DKFZ), Division of Radiology, Heidelberg, Germany 3 German Cancer Research Center (DKFZ), HIRO (Heidelberg Institute for Radiation Oncology), Heidelberg, Germany 4 German Cancer Research Center (DKFZ), Division of Medical Physics in Radiology, Heidelberg, Germany 5 Max-Planck-Institute, Tubingen, Germany 6 Department of Neuroradiology, University Hospital Heidelberg, Heidelberg, Germany 7 Department of Neurology, University Hospital Heidelberg, Heidelberg, Germany 8 Department of Neurosurgery, University Hospital Heidelberg, Heidelberg, Germany 9 Faculty of Physics and Astronomy, University of Heidelberg, Heidelberg, Germany 10 Faculty of Medicine, University of Heidelberg, Heidelberg, Germany Correspondence to: Daniel Paech, email: d.paech@dkfz.de Keywords: magnetic resonance imaging; amide-proton-transfer-imaging; nuclear overhauser imaging; glioblastoma; predictive biomarker Received: March 29, 2018      Accepted: May 24, 2018      Published: June 19, 2018 ABSTRACT Purpose: To prospectively investigate chemical exchange saturation transfer (CEST) MRI in glioblastoma patients as predictor of early tumor progression after first-line treatment. Experimental Design: Twenty previously untreated glioblastoma patients underwent CEST MRI employing a 7T Whole-Body Scanner. Nuclear Overhauser effect (NOE) as well as amide proton transfer (APT) CEST signals were isolated using Lorentzian difference (LD) analysis and relaxation compensated by the apparent exchange-dependent relaxation rate (AREX) evaluation. Additionally, NOE-weighted asymmetric magnetic transfer ratio (MTRasym) and downfield-NOE-suppressed APT (dns-APT) were calculated. Patient response to consecutive treatment was determined according to the RANO criteria. Mean signal intensities of each contrast in the Whole tumor area were compared between early-progressive and stable disease. Results: Pre-treatment tumor signal intensity differed significantly regarding responsiveness to first-line therapy in NOE-LD ( p = 0.0001), NOE-weighted MTRasym ( p = 0.0186) and dns-APT ( p = 0.0328) contrasts. Hence, significant prediction of early progression was possible employing NOE-LD (AUC = 0.98, p = 0.0005), NOE-weighted MTRasym (AUC = 0.83, p = 0.0166) and dns-APT (AUC = 0.80, p = 0.0318). The NOE-LD provided the highest sensitivity (91%) and specificity (100%). Conclusions: CEST derived contrasts, particularly NOE-weighted imaging and dns-APT, yielded significant predictors of early progression after fist-line therapy in glioblastoma. Therefore, CEST MRI might be considered as non-invasive tool for customization of treatment in the future.

J S Karp - One of the best experts on this subject based on the ideXlab platform.

  • performance of philips gemini tf pet ct Scanner with special consideration for its time of flight imaging capabilities
    2007
    Co-Authors: Suleman Surti, A Kuhn, Matthew E Werner, Amy E Perkins, Jeffrey A Kolthammer, J S Karp
    Abstract:

    UNLABELLED: Results from a new PET/CT Scanner using lutetium-yttrium oxyorthosilicate (LYSO) crystals for the PET component are presented. This Scanner, which operates in a fully 3-dimensional mode, has a diameter of 90 cm and an axial field of view of 18 cm. It uses 4 x 4 x 22 mm(3) LYSO crystals arranged in a pixelated Anger-logic detector design. This Scanner was designed to perform as a high-performance conventional PET Scanner as well as provide good timing resolution to operate as a time-of-flight (TOF) PET Scanner. METHODS: Performance measurements on the Scanner were made using the National Electrical Manufacturers Association (NEMA) NU2-2001 procedures to benchmark its conventional imaging capabilities. The scatter fraction and noise equivalent count (NEC) measurements with the NEMA cylinder (20-cm diameter) were repeated for 2 larger cylinders (27-cm and 35-cm diameter), which better represent average and heavy patients. New measurements were designed to characterize its intrinsic timing resolution capability, which defines its TOF performance. Additional measurements to study the impact of pulse pileup at high counting rates on timing, as well as energy and spatial, resolution were also performed. Finally, to characterize the effect of TOF reconstruction on lesion contrast and noise, the standard NEMA/International Electrotechnical Commission torso phantom as well as a large 35-cm-diameter phantom with both hot and cold spheres were imaged for varying scan times. RESULTS: The transverse and axial resolution near the center is 4.8 mm. The absolute sensitivity of this Scanner measured with a 70-cm-long line source is 6.6 cps/kBq, whereas scatter fraction is 27% measured with a 70-cm-long line source in a 20-cm-diameter cylinder. For the same line source cylinder, the peak NEC rate is measured to be 125 kcps at an activity concentration of 17.4 kBq/mL (0.47 microCi/mL). The 2 larger cylinders showed a decrease in the peak NEC due to increased attenuation, scatter, and random coincidences, and the peak occurs at lower activity concentrations. The system coincidence timing resolution was measured to be 585 ps. The timing resolution changes as a function of the singles rate due to pulse pileup and could impact TOF image reconstruction. Image-quality measurements with the torso phantom show that very high quality images can be obtained with short scan times (1-2 min per bed position). However, the benefit of TOF is more apparent with the large 35-cm-diameter phantom, where small spheres are detectable only with TOF information for short scan times. CONCLUSION: The Gemini TF Whole-Body Scanner represents the first commercially available fully 3-dimensional PET Scanner that achieves TOF capability as well as conventional imaging capabilities. The timing resolution is also stable over a long duration, indicating the practicality of this device. Excellent image quality is achieved for Whole-Body studies in 10-30 min, depending on patient size. The most significant improvement with TOF is seen for the heaviest patients.

  • performance of philips gemini tf pet ct Scanner with special consideration for its time of flight imaging capabilities
    2007
    Co-Authors: Suleman Surti, A Kuhn, Matthew E Werner, Amy E Perkins, Jeffrey A Kolthammer, J S Karp
    Abstract:

    Results from a new PET/CT Scanner using lutetium-yttrium oxyorthosilicate (LYSO) crystals for the PET component are presented. This Scanner, which operates in a fully 3-dimensional mode, has a diameter of 90 cm and an axial field of view of 18 cm. It uses 4 · 4 · 22 mm3 LYSO crystals arranged in a pixelated Anger-logic detector design. This Scanner was designed to perform as a high-performance conventional PET Scanner as well as provide good timing resolution to operate as a time-of-flight (TOF) PET Scanner. Methods: Performance measurements on the Scanner were made using the National Electrical Manufacturers Association (NEMA) NU2-2001 procedures to benchmark its conventional imaging capabilities. The scatter fraction and noise equivalent count (NEC) measurements with the NEMA cylinder (20-cm diameter) were repeated for 2 larger cylinders (27cm and 35-cm diameter), which better represent average and heavy patients. New measurements were designed to characterize its intrinsic timing resolution capability, which defines its TOF performance. Additional measurements to study the impact of pulse pileup at high counting rates on timing, as well as energy and spatial, resolution were also performed. Finally, to characterize the effect of TOF reconstruction on lesion contrast and noise, the standard NEMA/International Electrotechnical Commission torso phantom as well as a large 35-cm-diameter phantom with both hot and cold spheres were imaged for varying scan times. Results: The transverse and axial resolution near the center is 4.8 mm. The absolute sensitivity of this Scanner measured with a 70-cm-long line source is 6.6 cps/kBq, whereas scatter fraction is 27% measured with a 70-cm-long line source in a 20-cm-diameter cylinder. For the same line source cylinder, the peak NEC rate is measured to be 125 kcps at an activity concentration of 17.4 kBq/mL (0.47 mCi/mL). The 2 larger cylinders showed a decrease in the peak NEC due to increased attenuation, scatter, and random coincidences, and the peak occurs at lower activity concentrations. The system coincidence timing resolution was measured to be 585 ps. The timing resolution changes as a function of the singles rate due to pulse pileup and could impact TOF image reconstruction. Image-quality measurements with the torso phantom show that very high quality images can be obtained with short scan times (1–2 min per bed position). However, the benefit of TOF is more apparent with the large 35-cm-diameter phantom, where small spheres are detectable only with TOF information for short scan times. Conclusion: The Gemini TF Whole-Body Scanner represents the first commercially available fully 3-dimensional PET Scanner that achieves TOF capability as well as conventional imaging capabilities. The timing resolution is also stable over a long duration, indicating the practicality of this device. Excellent image quality is achieved for Whole-Body studies in 10–30 min, depending on patient size. The most significant improvement with TOF is seen for the heaviest patients.

  • imaging characteristics of a 3 dimensional gso Whole Body pet camera
    2004
    Co-Authors: Suleman Surti, J S Karp
    Abstract:

    A Whole-Body 3-dimensional PET Scanner using gadolinium oxyorthosilicate (GSO) crystals has been designed to achieve high sensitivity and reduced patient scanning time. This Scanner has a diameter of 82.0 cm and an axial field of view of 18 cm without interplane septa. The detector comprises of 4 6 20 mm3 GSO crystals coupled via an optically continuous light guide to an array of 420 photomultiplier tubes (39-mm diameter) in a hexagonal arrangement. The patient port diameter is 56 cm, and 2.86-cm (1.125 in.) thick lead shielding is used to fill in the region up to the detector ring. Methods: Performance measurements on the Scanner were made using the National Electrical Manufactures Association (NEMA) NU 2-2001 procedures. Additional counting rate measurements with a large phantom were performed to evaluate imaging characteristics for heavier patients. The image-quality torso phantom with hot or cold spheres was also measured as a function of counting rate to evaluate different techniques for randoms and scatter subtraction as well as to determine an optimum imaging time. Results: The transverse and axial resolutions near the center are 5.5 and 5.6 mm, respectively. The absolute sensitivity of this Scanner measured with a 70-cm-long line source is 4.36 cps/kBq, whereas the scatter fraction is 40% with a 20 70 cm line source cylinder. For the same cylinder, the peak noise equivalent count (NEC) rate of 30 kcps at an activity concentration of 9.25 kBq/mL (0.25 Ci/mL) leads to a 7% increase in the peak NEC value. A significant reduction in the peak NEC is observed with a larger 35 70 cm line source cylinder. Image-quality measurements show that the small 10-mm sphere in the NEMA NU 2-2001 image-quality phantom is clearly visible in a scan time of 3 min, and there is no noticeable degradation in image contrast at high activity levels. Conclusion: This Whole-Body Scanner represents a new generation of 3D, high-sensitivity, and high-performance PET cameras capable of producing high-quality images in 30 min for a full patient scan. The use of a pixelated GSO Anger-logic detector leads to a high-sensitivity Scanner design with good counting rate capability due to the reduced light spread in the detector and fast decay time of GSO. The light collection over the detector is fairly uniform, leading to a good energy resolution and, thus, reduced scatter in the collected data due to a tight energy gate.

Katerina Deikehofmann - One of the best experts on this subject based on the ideXlab platform.

  • relaxation compensated amide proton transfer apt mri signal intensity is associated with survival and progression in high grade glioma patients
    2019
    Co-Authors: Daniel Paech, Constantin Dreher, Sebastian Regnery, Janeric Meissner, Steffen Goerke, Johannes Windschuh, Johanna Oberhollenzer, Miriam Schultheiss, Katerina Deikehofmann
    Abstract:

    The purpose of this study was to investigate the association of relaxation-compensated chemical exchange saturation transfer (CEST) MRI with overall survival (OS) and progression-free survival (PFS) in newly diagnosed high-grade glioma (HGG) patients. Twenty-six patients with newly diagnosed high-grade glioma (WHO grades III–IV) were included in this prospective IRB-approved study. CEST MRI was performed on a 7.0-T Whole-Body Scanner. Association of patient OS/PFS with relaxation-compensated CEST MRI (amide proton transfer (APT), relayed nuclear Overhauser effect (rNOE)/NOE, downfield-rNOE-suppressed APT (dns-APT)) and diffusion-weighted imaging (apparent diffusion coefficient) were assessed using the univariate Cox proportional hazards regression model. Hazard ratios (HRs) and corresponding 95% confidence intervals were calculated. Furthermore, OS/PFS association with clinical parameters (age, gender, O6-methylguanine-DNA methyltransferase (MGMT) promotor methylation status, and therapy: biopsy + radio-chemotherapy vs. debulking surgery + radio-chemotherapy) were tested accordingly. Relaxation-compensated APT MRI was significantly correlated with patient OS (HR = 3.15, p = 0.02) and PFS (HR = 1.83, p = 0.009). The strongest association with PFS was found for the dns-APT metric (HR = 2.61, p = 0.002). These results still stand for the relaxation-compensated APT contrasts in a homogenous subcohort of n = 22 glioblastoma patients with isocitrate dehydrogenase (IDH) wild-type status. Among the tested clinical parameters, patient age (HR = 1.1, p = 0.001) and therapy (HR = 3.68, p = 0.026) were significant for OS; age additionally for PFS (HR = 1.04, p = 0.048). Relaxation-compensated APT MRI signal intensity is associated with overall survival and progression-free survival in newly diagnosed, previously untreated glioma patients and may, therefore, help to customize treatment and response monitoring in the future. • Amide proton transfer (APT) MRI signal intensity is associated with overall survival and progression in glioma patients. • Relaxation compensation enhances the information value of APT MRI in tumors. • Chemical exchange saturation transfer (CEST) MRI may serve as a non-invasive biomarker to predict prognosis and customize treatment.

  • chemical exchange saturation transfer mri serves as predictor of early progression in glioblastoma patients
    2018
    Co-Authors: Constantin Dreher, Sebastian Regnery, Janeric Meissner, Steffen Goerke, Johannes Windschuh, Johanna Oberhollenzer, Katerina Deikehofmann, Sebastian Adeberg, Sebastian Bickelhaupt
    Abstract:

    // Sebastian Regnery 1, 2 , Sebastian Adeberg 3 , Constantin Dreher 2 , Johanna Oberhollenzer 2 , Jan-Eric Meissner 4 , Steffen Goerke 4 , Johannes Windschuh 4 , Katerina Deike-Hofmann 2 , Sebastian Bickelhaupt 2 , Moritz Zaiss 5 , Alexander Radbruch 2 , Martin Bendszus 6 , Wolfgang Wick 7 , Andreas Unterberg 8 , Stefan Rieken 1 , Jurgen Debus 1 , Peter Bachert 4 , Mark Ladd 4, 9, 10 , Heinz-Peter Schlemmer 2 and Daniel Paech 2 1 Department of Radiation Oncology, University Hospital Heidelberg, Heidelberg, Germany 2 German Cancer Research Center (DKFZ), Division of Radiology, Heidelberg, Germany 3 German Cancer Research Center (DKFZ), HIRO (Heidelberg Institute for Radiation Oncology), Heidelberg, Germany 4 German Cancer Research Center (DKFZ), Division of Medical Physics in Radiology, Heidelberg, Germany 5 Max-Planck-Institute, Tubingen, Germany 6 Department of Neuroradiology, University Hospital Heidelberg, Heidelberg, Germany 7 Department of Neurology, University Hospital Heidelberg, Heidelberg, Germany 8 Department of Neurosurgery, University Hospital Heidelberg, Heidelberg, Germany 9 Faculty of Physics and Astronomy, University of Heidelberg, Heidelberg, Germany 10 Faculty of Medicine, University of Heidelberg, Heidelberg, Germany Correspondence to: Daniel Paech, email: d.paech@dkfz.de Keywords: magnetic resonance imaging; amide-proton-transfer-imaging; nuclear overhauser imaging; glioblastoma; predictive biomarker Received: March 29, 2018      Accepted: May 24, 2018      Published: June 19, 2018 ABSTRACT Purpose: To prospectively investigate chemical exchange saturation transfer (CEST) MRI in glioblastoma patients as predictor of early tumor progression after first-line treatment. Experimental Design: Twenty previously untreated glioblastoma patients underwent CEST MRI employing a 7T Whole-Body Scanner. Nuclear Overhauser effect (NOE) as well as amide proton transfer (APT) CEST signals were isolated using Lorentzian difference (LD) analysis and relaxation compensated by the apparent exchange-dependent relaxation rate (AREX) evaluation. Additionally, NOE-weighted asymmetric magnetic transfer ratio (MTRasym) and downfield-NOE-suppressed APT (dns-APT) were calculated. Patient response to consecutive treatment was determined according to the RANO criteria. Mean signal intensities of each contrast in the Whole tumor area were compared between early-progressive and stable disease. Results: Pre-treatment tumor signal intensity differed significantly regarding responsiveness to first-line therapy in NOE-LD ( p = 0.0001), NOE-weighted MTRasym ( p = 0.0186) and dns-APT ( p = 0.0328) contrasts. Hence, significant prediction of early progression was possible employing NOE-LD (AUC = 0.98, p = 0.0005), NOE-weighted MTRasym (AUC = 0.83, p = 0.0166) and dns-APT (AUC = 0.80, p = 0.0318). The NOE-LD provided the highest sensitivity (91%) and specificity (100%). Conclusions: CEST derived contrasts, particularly NOE-weighted imaging and dns-APT, yielded significant predictors of early progression after fist-line therapy in glioblastoma. Therefore, CEST MRI might be considered as non-invasive tool for customization of treatment in the future.

Suleman Surti - One of the best experts on this subject based on the ideXlab platform.

  • performance of philips gemini tf pet ct Scanner with special consideration for its time of flight imaging capabilities
    2007
    Co-Authors: Suleman Surti, A Kuhn, Matthew E Werner, Amy E Perkins, Jeffrey A Kolthammer, J S Karp
    Abstract:

    UNLABELLED: Results from a new PET/CT Scanner using lutetium-yttrium oxyorthosilicate (LYSO) crystals for the PET component are presented. This Scanner, which operates in a fully 3-dimensional mode, has a diameter of 90 cm and an axial field of view of 18 cm. It uses 4 x 4 x 22 mm(3) LYSO crystals arranged in a pixelated Anger-logic detector design. This Scanner was designed to perform as a high-performance conventional PET Scanner as well as provide good timing resolution to operate as a time-of-flight (TOF) PET Scanner. METHODS: Performance measurements on the Scanner were made using the National Electrical Manufacturers Association (NEMA) NU2-2001 procedures to benchmark its conventional imaging capabilities. The scatter fraction and noise equivalent count (NEC) measurements with the NEMA cylinder (20-cm diameter) were repeated for 2 larger cylinders (27-cm and 35-cm diameter), which better represent average and heavy patients. New measurements were designed to characterize its intrinsic timing resolution capability, which defines its TOF performance. Additional measurements to study the impact of pulse pileup at high counting rates on timing, as well as energy and spatial, resolution were also performed. Finally, to characterize the effect of TOF reconstruction on lesion contrast and noise, the standard NEMA/International Electrotechnical Commission torso phantom as well as a large 35-cm-diameter phantom with both hot and cold spheres were imaged for varying scan times. RESULTS: The transverse and axial resolution near the center is 4.8 mm. The absolute sensitivity of this Scanner measured with a 70-cm-long line source is 6.6 cps/kBq, whereas scatter fraction is 27% measured with a 70-cm-long line source in a 20-cm-diameter cylinder. For the same line source cylinder, the peak NEC rate is measured to be 125 kcps at an activity concentration of 17.4 kBq/mL (0.47 microCi/mL). The 2 larger cylinders showed a decrease in the peak NEC due to increased attenuation, scatter, and random coincidences, and the peak occurs at lower activity concentrations. The system coincidence timing resolution was measured to be 585 ps. The timing resolution changes as a function of the singles rate due to pulse pileup and could impact TOF image reconstruction. Image-quality measurements with the torso phantom show that very high quality images can be obtained with short scan times (1-2 min per bed position). However, the benefit of TOF is more apparent with the large 35-cm-diameter phantom, where small spheres are detectable only with TOF information for short scan times. CONCLUSION: The Gemini TF Whole-Body Scanner represents the first commercially available fully 3-dimensional PET Scanner that achieves TOF capability as well as conventional imaging capabilities. The timing resolution is also stable over a long duration, indicating the practicality of this device. Excellent image quality is achieved for Whole-Body studies in 10-30 min, depending on patient size. The most significant improvement with TOF is seen for the heaviest patients.

  • performance of philips gemini tf pet ct Scanner with special consideration for its time of flight imaging capabilities
    2007
    Co-Authors: Suleman Surti, A Kuhn, Matthew E Werner, Amy E Perkins, Jeffrey A Kolthammer, J S Karp
    Abstract:

    Results from a new PET/CT Scanner using lutetium-yttrium oxyorthosilicate (LYSO) crystals for the PET component are presented. This Scanner, which operates in a fully 3-dimensional mode, has a diameter of 90 cm and an axial field of view of 18 cm. It uses 4 · 4 · 22 mm3 LYSO crystals arranged in a pixelated Anger-logic detector design. This Scanner was designed to perform as a high-performance conventional PET Scanner as well as provide good timing resolution to operate as a time-of-flight (TOF) PET Scanner. Methods: Performance measurements on the Scanner were made using the National Electrical Manufacturers Association (NEMA) NU2-2001 procedures to benchmark its conventional imaging capabilities. The scatter fraction and noise equivalent count (NEC) measurements with the NEMA cylinder (20-cm diameter) were repeated for 2 larger cylinders (27cm and 35-cm diameter), which better represent average and heavy patients. New measurements were designed to characterize its intrinsic timing resolution capability, which defines its TOF performance. Additional measurements to study the impact of pulse pileup at high counting rates on timing, as well as energy and spatial, resolution were also performed. Finally, to characterize the effect of TOF reconstruction on lesion contrast and noise, the standard NEMA/International Electrotechnical Commission torso phantom as well as a large 35-cm-diameter phantom with both hot and cold spheres were imaged for varying scan times. Results: The transverse and axial resolution near the center is 4.8 mm. The absolute sensitivity of this Scanner measured with a 70-cm-long line source is 6.6 cps/kBq, whereas scatter fraction is 27% measured with a 70-cm-long line source in a 20-cm-diameter cylinder. For the same line source cylinder, the peak NEC rate is measured to be 125 kcps at an activity concentration of 17.4 kBq/mL (0.47 mCi/mL). The 2 larger cylinders showed a decrease in the peak NEC due to increased attenuation, scatter, and random coincidences, and the peak occurs at lower activity concentrations. The system coincidence timing resolution was measured to be 585 ps. The timing resolution changes as a function of the singles rate due to pulse pileup and could impact TOF image reconstruction. Image-quality measurements with the torso phantom show that very high quality images can be obtained with short scan times (1–2 min per bed position). However, the benefit of TOF is more apparent with the large 35-cm-diameter phantom, where small spheres are detectable only with TOF information for short scan times. Conclusion: The Gemini TF Whole-Body Scanner represents the first commercially available fully 3-dimensional PET Scanner that achieves TOF capability as well as conventional imaging capabilities. The timing resolution is also stable over a long duration, indicating the practicality of this device. Excellent image quality is achieved for Whole-Body studies in 10–30 min, depending on patient size. The most significant improvement with TOF is seen for the heaviest patients.

  • imaging characteristics of a 3 dimensional gso Whole Body pet camera
    2004
    Co-Authors: Suleman Surti, J S Karp
    Abstract:

    A Whole-Body 3-dimensional PET Scanner using gadolinium oxyorthosilicate (GSO) crystals has been designed to achieve high sensitivity and reduced patient scanning time. This Scanner has a diameter of 82.0 cm and an axial field of view of 18 cm without interplane septa. The detector comprises of 4 6 20 mm3 GSO crystals coupled via an optically continuous light guide to an array of 420 photomultiplier tubes (39-mm diameter) in a hexagonal arrangement. The patient port diameter is 56 cm, and 2.86-cm (1.125 in.) thick lead shielding is used to fill in the region up to the detector ring. Methods: Performance measurements on the Scanner were made using the National Electrical Manufactures Association (NEMA) NU 2-2001 procedures. Additional counting rate measurements with a large phantom were performed to evaluate imaging characteristics for heavier patients. The image-quality torso phantom with hot or cold spheres was also measured as a function of counting rate to evaluate different techniques for randoms and scatter subtraction as well as to determine an optimum imaging time. Results: The transverse and axial resolutions near the center are 5.5 and 5.6 mm, respectively. The absolute sensitivity of this Scanner measured with a 70-cm-long line source is 4.36 cps/kBq, whereas the scatter fraction is 40% with a 20 70 cm line source cylinder. For the same cylinder, the peak noise equivalent count (NEC) rate of 30 kcps at an activity concentration of 9.25 kBq/mL (0.25 Ci/mL) leads to a 7% increase in the peak NEC value. A significant reduction in the peak NEC is observed with a larger 35 70 cm line source cylinder. Image-quality measurements show that the small 10-mm sphere in the NEMA NU 2-2001 image-quality phantom is clearly visible in a scan time of 3 min, and there is no noticeable degradation in image contrast at high activity levels. Conclusion: This Whole-Body Scanner represents a new generation of 3D, high-sensitivity, and high-performance PET cameras capable of producing high-quality images in 30 min for a full patient scan. The use of a pixelated GSO Anger-logic detector leads to a high-sensitivity Scanner design with good counting rate capability due to the reduced light spread in the detector and fast decay time of GSO. The light collection over the detector is fairly uniform, leading to a good energy resolution and, thus, reduced scatter in the collected data due to a tight energy gate.

Constantin Dreher - One of the best experts on this subject based on the ideXlab platform.

  • relaxation compensated amide proton transfer apt mri signal intensity is associated with survival and progression in high grade glioma patients
    2019
    Co-Authors: Daniel Paech, Constantin Dreher, Sebastian Regnery, Janeric Meissner, Steffen Goerke, Johannes Windschuh, Johanna Oberhollenzer, Miriam Schultheiss, Katerina Deikehofmann
    Abstract:

    The purpose of this study was to investigate the association of relaxation-compensated chemical exchange saturation transfer (CEST) MRI with overall survival (OS) and progression-free survival (PFS) in newly diagnosed high-grade glioma (HGG) patients. Twenty-six patients with newly diagnosed high-grade glioma (WHO grades III–IV) were included in this prospective IRB-approved study. CEST MRI was performed on a 7.0-T Whole-Body Scanner. Association of patient OS/PFS with relaxation-compensated CEST MRI (amide proton transfer (APT), relayed nuclear Overhauser effect (rNOE)/NOE, downfield-rNOE-suppressed APT (dns-APT)) and diffusion-weighted imaging (apparent diffusion coefficient) were assessed using the univariate Cox proportional hazards regression model. Hazard ratios (HRs) and corresponding 95% confidence intervals were calculated. Furthermore, OS/PFS association with clinical parameters (age, gender, O6-methylguanine-DNA methyltransferase (MGMT) promotor methylation status, and therapy: biopsy + radio-chemotherapy vs. debulking surgery + radio-chemotherapy) were tested accordingly. Relaxation-compensated APT MRI was significantly correlated with patient OS (HR = 3.15, p = 0.02) and PFS (HR = 1.83, p = 0.009). The strongest association with PFS was found for the dns-APT metric (HR = 2.61, p = 0.002). These results still stand for the relaxation-compensated APT contrasts in a homogenous subcohort of n = 22 glioblastoma patients with isocitrate dehydrogenase (IDH) wild-type status. Among the tested clinical parameters, patient age (HR = 1.1, p = 0.001) and therapy (HR = 3.68, p = 0.026) were significant for OS; age additionally for PFS (HR = 1.04, p = 0.048). Relaxation-compensated APT MRI signal intensity is associated with overall survival and progression-free survival in newly diagnosed, previously untreated glioma patients and may, therefore, help to customize treatment and response monitoring in the future. • Amide proton transfer (APT) MRI signal intensity is associated with overall survival and progression in glioma patients. • Relaxation compensation enhances the information value of APT MRI in tumors. • Chemical exchange saturation transfer (CEST) MRI may serve as a non-invasive biomarker to predict prognosis and customize treatment.

  • chemical exchange saturation transfer mri serves as predictor of early progression in glioblastoma patients
    2018
    Co-Authors: Constantin Dreher, Sebastian Regnery, Janeric Meissner, Steffen Goerke, Johannes Windschuh, Johanna Oberhollenzer, Katerina Deikehofmann, Sebastian Adeberg, Sebastian Bickelhaupt
    Abstract:

    // Sebastian Regnery 1, 2 , Sebastian Adeberg 3 , Constantin Dreher 2 , Johanna Oberhollenzer 2 , Jan-Eric Meissner 4 , Steffen Goerke 4 , Johannes Windschuh 4 , Katerina Deike-Hofmann 2 , Sebastian Bickelhaupt 2 , Moritz Zaiss 5 , Alexander Radbruch 2 , Martin Bendszus 6 , Wolfgang Wick 7 , Andreas Unterberg 8 , Stefan Rieken 1 , Jurgen Debus 1 , Peter Bachert 4 , Mark Ladd 4, 9, 10 , Heinz-Peter Schlemmer 2 and Daniel Paech 2 1 Department of Radiation Oncology, University Hospital Heidelberg, Heidelberg, Germany 2 German Cancer Research Center (DKFZ), Division of Radiology, Heidelberg, Germany 3 German Cancer Research Center (DKFZ), HIRO (Heidelberg Institute for Radiation Oncology), Heidelberg, Germany 4 German Cancer Research Center (DKFZ), Division of Medical Physics in Radiology, Heidelberg, Germany 5 Max-Planck-Institute, Tubingen, Germany 6 Department of Neuroradiology, University Hospital Heidelberg, Heidelberg, Germany 7 Department of Neurology, University Hospital Heidelberg, Heidelberg, Germany 8 Department of Neurosurgery, University Hospital Heidelberg, Heidelberg, Germany 9 Faculty of Physics and Astronomy, University of Heidelberg, Heidelberg, Germany 10 Faculty of Medicine, University of Heidelberg, Heidelberg, Germany Correspondence to: Daniel Paech, email: d.paech@dkfz.de Keywords: magnetic resonance imaging; amide-proton-transfer-imaging; nuclear overhauser imaging; glioblastoma; predictive biomarker Received: March 29, 2018      Accepted: May 24, 2018      Published: June 19, 2018 ABSTRACT Purpose: To prospectively investigate chemical exchange saturation transfer (CEST) MRI in glioblastoma patients as predictor of early tumor progression after first-line treatment. Experimental Design: Twenty previously untreated glioblastoma patients underwent CEST MRI employing a 7T Whole-Body Scanner. Nuclear Overhauser effect (NOE) as well as amide proton transfer (APT) CEST signals were isolated using Lorentzian difference (LD) analysis and relaxation compensated by the apparent exchange-dependent relaxation rate (AREX) evaluation. Additionally, NOE-weighted asymmetric magnetic transfer ratio (MTRasym) and downfield-NOE-suppressed APT (dns-APT) were calculated. Patient response to consecutive treatment was determined according to the RANO criteria. Mean signal intensities of each contrast in the Whole tumor area were compared between early-progressive and stable disease. Results: Pre-treatment tumor signal intensity differed significantly regarding responsiveness to first-line therapy in NOE-LD ( p = 0.0001), NOE-weighted MTRasym ( p = 0.0186) and dns-APT ( p = 0.0328) contrasts. Hence, significant prediction of early progression was possible employing NOE-LD (AUC = 0.98, p = 0.0005), NOE-weighted MTRasym (AUC = 0.83, p = 0.0166) and dns-APT (AUC = 0.80, p = 0.0318). The NOE-LD provided the highest sensitivity (91%) and specificity (100%). Conclusions: CEST derived contrasts, particularly NOE-weighted imaging and dns-APT, yielded significant predictors of early progression after fist-line therapy in glioblastoma. Therefore, CEST MRI might be considered as non-invasive tool for customization of treatment in the future.

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