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Harald H. Quick - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of improved attenuation correction in Whole-Body PET/MR on patients with bone metastasis using various radiotracers
European Journal of Nuclear Medicine and Molecular Imaging, 2020Co-Authors: Hong Grafe, Mark Oehmigen, Maike E. Lindemann, Verena Ruhlmann, Lale Umutlu, Nader Hirmas, Ken Herrmann, Harald H. QuickAbstract:Purpose This study evaluates the quantitative effect of improved MR-based attenuation correction (AC), including bone segmentation and the HUGE method for truncation correction in PET/MR Whole-Body hybrid imaging specifically of oncologic patients with bone metastasis and using various radiotracers. Methods Twenty-three patients that underwent altogether 28 Whole-Body PET/MR examinations with findings of bone metastasis were included in this study. Different radiotracers (^18F-FDG, ^68Ga-PSMA, ^68Ga-DOTATOC, ^124I–MIBG) were injected according to appropriate clinical indications. Each of the 28 Whole-Body PET datasets was reconstructed three times using AC with (1) standard four-compartment μ-maps (background air, lung, muscle, and soft tissue), (2) five-compartment μ-maps (adding bone), and (3) six-compartment μ-maps (adding bone and HUGE truncation correction). The SUV_max of each detected bone lesion was measured in each reconstruction to evaluate the quantitative impact of improved MR-based AC. Relative difference images between four- and six-compartment μ-maps were calculated. MR-based HUGE truncation correction was compared with the PET-based MLAA truncation correction method in all patients. Results Overall, 69 bone lesions were detected and evaluated. The mean increase in relative difference over all 69 lesions in SUV_max was 5.4 ± 6.4% when comparing the improved six-compartment AC with the standard four-compartment AC. Maximal relative difference of 28.4% was measured in one lesion. Truncation correction with HUGE worked robust and resulted in realistic Body contouring in all 28 exams and for all 4 different radiotracers. Truncation correction with MLAA revealed overestimations of arm tissue volume in all PET/MR exams with ^18F-FDG radiotracer and failed in all other exams with radiotracers ^68Ga-PSMA, ^68Ga-DOTATOC, and ^124I- MIBG due to limitations in Body contour detection. Conclusion Improved MR-based AC, including bone segmentation and HUGE truncation correction in Whole-Body PET/MR on patients with bone lesions and using various radiotracers, is important to ensure best possible diagnostic image quality and accurate PET quantification. The HUGE method for truncation correction based on MR worked robust and results in realistic Body contouring, independent of the radiotracers used.
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Evaluation of improved attenuation correction in Whole-Body PET/MR on patients with bone metastasis using various radiotracers.
European journal of nuclear medicine and molecular imaging, 2020Co-Authors: Hong Grafe, Mark Oehmigen, Maike E. Lindemann, Verena Ruhlmann, Lale Umutlu, Nader Hirmas, Ken Herrmann, Harald H. QuickAbstract:This study evaluates the quantitative effect of improved MR-based attenuation correction (AC), including bone segmentation and the HUGE method for truncation correction in PET/MR Whole-Body hybrid imaging specifically of oncologic patients with bone metastasis and using various radiotracers. Twenty-three patients that underwent altogether 28 Whole-Body PET/MR examinations with findings of bone metastasis were included in this study. Different radiotracers (18F-FDG, 68Ga-PSMA, 68Ga-DOTATOC, 124I–MIBG) were injected according to appropriate clinical indications. Each of the 28 Whole-Body PET datasets was reconstructed three times using AC with (1) standard four-compartment μ-maps (background air, lung, muscle, and soft tissue), (2) five-compartment μ-maps (adding bone), and (3) six-compartment μ-maps (adding bone and HUGE truncation correction). The SUVmax of each detected bone lesion was measured in each reconstruction to evaluate the quantitative impact of improved MR-based AC. Relative difference images between four- and six-compartment μ-maps were calculated. MR-based HUGE truncation correction was compared with the PET-based MLAA truncation correction method in all patients. Overall, 69 bone lesions were detected and evaluated. The mean increase in relative difference over all 69 lesions in SUVmax was 5.4 ± 6.4% when comparing the improved six-compartment AC with the standard four-compartment AC. Maximal relative difference of 28.4% was measured in one lesion. Truncation correction with HUGE worked robust and resulted in realistic Body contouring in all 28 exams and for all 4 different radiotracers. Truncation correction with MLAA revealed overestimations of arm tissue volume in all PET/MR exams with 18F-FDG radiotracer and failed in all other exams with radiotracers 68Ga-PSMA, 68Ga-DOTATOC, and 124I- MIBG due to limitations in Body contour detection. Improved MR-based AC, including bone segmentation and HUGE truncation correction in Whole-Body PET/MR on patients with bone lesions and using various radiotracers, is important to ensure best possible diagnostic image quality and accurate PET quantification. The HUGE method for truncation correction based on MR worked robust and results in realistic Body contouring, independent of the radiotracers used.
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Impact of improved attenuation correction featuring a bone atlas and truncation correction on PET quantification in Whole-Body PET/MR
European journal of nuclear medicine and molecular imaging, 2017Co-Authors: Mark Oehmigen, Matthias Fenchel, Maike E. Lindemann, Marcel Gratz, Julian Kirchner, Verena Ruhlmann, Lale Umutlu, Jan Ole Blumhagen, Harald H. QuickAbstract:Recent studies have shown an excellent correlation between PET/MR and PET/CT hybrid imaging in detecting lesions. However, a systematic underestimation of PET quantification in PET/MR has been observed. This is attributable to two methodological challenges of MR-based attenuation correction (AC): (1) lack of bone information, and (2) truncation of the MR-based AC maps (μmaps) along the patient arms. The aim of this study was to evaluate the impact of improved AC featuring a bone atlas and truncation correction on PET quantification in Whole-Body PET/MR. The MR-based Dixon method provides four-compartment μmaps (background air, lungs, fat, soft tissue) which served as a reference for PET/MR AC in this study. A model-based bone atlas provided bone tissue as a fifth compartment, while the HUGE method provided truncation correction. The study population comprised 51 patients with oncological diseases, all of whom underwent a Whole-Body PET/MR examination. Each Whole-Body PET dataset was reconstructed four times using standard four-compartment μmaps, five-compartment μmaps, four-compartment μmaps + HUGE, and five-compartment μmaps + HUGE. The SUVmax for each lesion was measured to assess the impact of each μmap on PET quantification. All four μmaps in each patient provided robust results for reconstruction of the AC PET data. Overall, SUVmax was quantified in 99 tumours and lesions. Compared to the reference four-compartment μmap, the mean SUVmax of all 99 lesions increased by 1.4 ± 2.5% when bone was added, by 2.1 ± 3.5% when HUGE was added, and by 4.4 ± 5.7% when bone + HUGE was added. Larger quantification bias of up to 35% was found for single lesions when bone and truncation correction were added to the μmaps, depending on their individual location in the Body. The novel AC method, featuring a bone model and truncation correction, improved PET quantification in Whole-Body PET/MR imaging. Short reconstruction times, straightforward reconstruction workflow, and robust AC quality justify further routine clinical application of this method.
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Whole Body PET mr imaging quantitative evaluation of a novel model based mr attenuation correction method including bone
The Journal of Nuclear Medicine, 2015Co-Authors: Daniel Paulus, Harald H. Quick, Christian Geppert, Matthias Fenchel, Yiqiang Zhan, Gerardo Hermosillo, David Faul, Fernando E Boada, Kent FriedmanAbstract:In routine Whole-Body PET/MR hybrid imaging, attenuation correction (AC) is usually performed by segmentation methods based on a Dixon MR sequence providing up to 4 different tissue classes. Because of the lack of bone information with the Dixon-based MR sequence, bone is currently considered as soft tissue. Thus, the aim of this study was to evaluate a novel model-based AC method that considers bone in Whole-Body PET/MR imaging. Methods: The new method (“Model”) is based on a regular 4-compartment segmentation from a Dixon sequence (“Dixon”). Bone information is added using a model-based bone segmentation algorithm, which includes a set of prealigned MR image and bone mask pairs for each major Body bone individually. Model was quantitatively evaluated on 20 patients who underwent Whole-Body PET/MR imaging. As a standard of reference, CT-based μ-maps were generated for each patient individually by nonrigid registration to the MR images based on PET/CT data. This step allowed for a quantitative comparison of all μ-maps based on a single PET emission raw dataset of the PET/MR system. Volumes of interest were drawn on normal tissue, soft-tissue lesions, and bone lesions; standardized uptake values were quantitatively compared. Results: In soft-tissue regions with background uptake, the average bias of SUVs in background volumes of interest was 2.4% ± 2.5% and 2.7% ± 2.7% for Dixon and Model, respectively, compared with CT-based AC. For bony tissue, the −25.5% ± 7.9% underestimation observed with Dixon was reduced to −4.9% ± 6.7% with Model. In bone lesions, the average underestimation was −7.4% ± 5.3% and −2.9% ± 5.8% for Dixon and Model, respectively. For soft-tissue lesions, the biases were 5.1% ± 5.1% for Dixon and 5.2% ± 5.2% for Model. Conclusion: The novel MR-based AC method for Whole-Body PET/MR imaging, combining Dixon-based soft-tissue segmentation and model-based bone estimation, improves PET quantification in Whole-Body hybrid PET/MR imaging, especially in bony tissue and nearby soft tissue.
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Whole-Body PET/MR Imaging: Quantitative Evaluation of a Novel Model-Based MR Attenuation Correction Method Including Bone
Journal of nuclear medicine : official publication Society of Nuclear Medicine, 2015Co-Authors: Daniel Paulus, Harald H. Quick, Christian Geppert, Matthias Fenchel, Yiqiang Zhan, Gerardo Hermosillo, David Faul, Fernando E Boada, Kent Friedman, Thomas KoestersAbstract:In routine Whole-Body PET/MR hybrid imaging, attenuation correction (AC) is usually performed by segmentation methods based on a Dixon MR sequence providing up to 4 different tissue classes. Because of the lack of bone information with the Dixon-based MR sequence, bone is currently considered as soft tissue. Thus, the aim of this study was to evaluate a novel model-based AC method that considers bone in Whole-Body PET/MR imaging. Methods: The new method (“Model”) is based on a regular 4-compartment segmentation from a Dixon sequence (“Dixon”). Bone information is added using a model-based bone segmentation algorithm, which includes a set of prealigned MR image and bone mask pairs for each major Body bone individually. Model was quantitatively evaluated on 20 patients who underwent Whole-Body PET/MR imaging. As a standard of reference, CT-based μ-maps were generated for each patient individually by nonrigid registration to the MR images based on PET/CT data. This step allowed for a quantitative comparison of all μ-maps based on a single PET emission raw dataset of the PET/MR system. Volumes of interest were drawn on normal tissue, soft-tissue lesions, and bone lesions; standardized uptake values were quantitatively compared. Results: In soft-tissue regions with background uptake, the average bias of SUVs in background volumes of interest was 2.4% ± 2.5% and 2.7% ± 2.7% for Dixon and Model, respectively, compared with CT-based AC. For bony tissue, the −25.5% ± 7.9% underestimation observed with Dixon was reduced to −4.9% ± 6.7% with Model. In bone lesions, the average underestimation was −7.4% ± 5.3% and −2.9% ± 5.8% for Dixon and Model, respectively. For soft-tissue lesions, the biases were 5.1% ± 5.1% for Dixon and 5.2% ± 5.2% for Model. Conclusion: The novel MR-based AC method for Whole-Body PET/MR imaging, combining Dixon-based soft-tissue segmentation and model-based bone estimation, improves PET quantification in Whole-Body hybrid PET/MR imaging, especially in bony tissue and nearby soft tissue.
Willi A. Kalender - One of the best experts on this subject based on the ideXlab platform.
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integrated Whole Body PET mr hybrid imaging clinical experience
Investigative Radiology, 2013Co-Authors: Harald H. Quick, Torsten Kuwert, Michael Uder, Carl Von Gall, Martin Zeilinger, Marco Wiesmuller, Harald Braun, Susanne Ziegler, Arnd Dorfler, Willi A. KalenderAbstract:OBJECTIVES Integrated Whole-Body positron emission tomography (PET)/magnetic resonance (MR) scanners have recently been introduced and potentially offer new possibilities in hybrid imaging of oncologic patients. Integration of PET in a Whole-Body MR system requires new PET detector technology and new approaches to attenuation correction of PET data based on MR imaging. The aim of this study was to evaluate the clinical performance and image quality parameters of integrated Whole-Body PET/MR hybrid imaging in intraindividual comparison with PET/CT in oncologic patients. MATERIALS AND METHODS Eighty patients underwent a single-injection, dual-imaging protocol including Whole-Body PET/computed tomography (CT) and subsequent Whole-Body PET/MR hybrid imaging. Positron emission tomography/computed tomography was performed after adequate resting time (73 ± 13 minutes post injectionem of 227 ± 52.7 MBq Fluor-18-Fluordesoxyglucose, 3 minutes of acquisition time for each of 7 bed positions), followed by PET/MR (172 ± 33 minutes post injectionem, 10 minutes acquisition time for each of 4 bed positions). Positron emission tomographic data for both modalities were reconstructed iteratively. Two observers evaluated the following parameters: qualitative correlation of tracer-avid lesions in PET/CT versus PET/MR and PET image quality of PET/CT versus PET/MR. Magnetic resonance image quality of standard sequences (T1-weighted, T2-weighted), performance of the Dixon sequence for MR-based attenuation correction in comparison with corresponding T1-weighted images, artifacts in PET/MR data, and spatial coregistration of PET and MR data were evaluated by another observer. RESULTS In 70 of the 80 patients, both image data sets were complete. In these patients, 192 tracer-avid lesions were identified on PET/CT; 195, on PET/MR. A total of 187 lesions were identified concordantly by both modalities, and this corresponds to an agreement rate of 97.4%. The overall PET image quality was rated good to excellent for PET from PET/CT (12/28, excellent, 42.9%; 16/28, good, 57.1%; 0/28, poor, 0.0%) and slightly superior compared with PET from PET/MR, which was rated good (3/28, excellent, 10.7%; 20/28, good, 71.4%; 5/28, poor, 17.9%) in a subset of 28 patients. The overall image quality of the MR image data sets in all 70 of the 80 patients was rated excellent (260/280, excellent, 92.8%; 15/280, good, 5.4%; 5/280, poor, 1.8%). The Dixon sequence and conversion to μ-maps for MR-based attenuation correction provided robust tissue segmentation in all 280 bed positions of the acquired PET/MR data. No artifacts such as elevated noise and radiofrequency disturbances related to hardware cross talk between the PET and MR components in the hybrid system could be detected in the MR images. No major spatial mismatches between PET and MR data were detected. CONCLUSIONS Integrated PET/MR hybrid imaging is feasible in a clinical setting with similar detection rates as those of PET/CT. Attenuation correction can be performed sufficiently with Dixon sequences, although bone is disregarded. The administration of specific radiotracers and dedicated imaging sequences will foster this hybrid imaging modality in various indications.
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Integrated Whole-Body PET/MR hybrid imaging: clinical experience.
Investigative radiology, 2013Co-Authors: Harald H. Quick, Torsten Kuwert, Michael Uder, Carl Von Gall, Martin Zeilinger, Marco Wiesmuller, Harald Braun, Susanne Ziegler, Arnd Dorfler, Willi A. KalenderAbstract:OBJECTIVES Integrated Whole-Body positron emission tomography (PET)/magnetic resonance (MR) scanners have recently been introduced and potentially offer new possibilities in hybrid imaging of oncologic patients. Integration of PET in a Whole-Body MR system requires new PET detector technology and new approaches to attenuation correction of PET data based on MR imaging. The aim of this study was to evaluate the clinical performance and image quality parameters of integrated Whole-Body PET/MR hybrid imaging in intraindividual comparison with PET/CT in oncologic patients. MATERIALS AND METHODS Eighty patients underwent a single-injection, dual-imaging protocol including Whole-Body PET/computed tomography (CT) and subsequent Whole-Body PET/MR hybrid imaging. Positron emission tomography/computed tomography was performed after adequate resting time (73 ± 13 minutes post injectionem of 227 ± 52.7 MBq Fluor-18-Fluordesoxyglucose, 3 minutes of acquisition time for each of 7 bed positions), followed by PET/MR (172 ± 33 minutes post injectionem, 10 minutes acquisition time for each of 4 bed positions). Positron emission tomographic data for both modalities were reconstructed iteratively. Two observers evaluated the following parameters: qualitative correlation of tracer-avid lesions in PET/CT versus PET/MR and PET image quality of PET/CT versus PET/MR. Magnetic resonance image quality of standard sequences (T1-weighted, T2-weighted), performance of the Dixon sequence for MR-based attenuation correction in comparison with corresponding T1-weighted images, artifacts in PET/MR data, and spatial coregistration of PET and MR data were evaluated by another observer. RESULTS In 70 of the 80 patients, both image data sets were complete. In these patients, 192 tracer-avid lesions were identified on PET/CT; 195, on PET/MR. A total of 187 lesions were identified concordantly by both modalities, and this corresponds to an agreement rate of 97.4%. The overall PET image quality was rated good to excellent for PET from PET/CT (12/28, excellent, 42.9%; 16/28, good, 57.1%; 0/28, poor, 0.0%) and slightly superior compared with PET from PET/MR, which was rated good (3/28, excellent, 10.7%; 20/28, good, 71.4%; 5/28, poor, 17.9%) in a subset of 28 patients. The overall image quality of the MR image data sets in all 70 of the 80 patients was rated excellent (260/280, excellent, 92.8%; 15/280, good, 5.4%; 5/280, poor, 1.8%). The Dixon sequence and conversion to μ-maps for MR-based attenuation correction provided robust tissue segmentation in all 280 bed positions of the acquired PET/MR data. No artifacts such as elevated noise and radiofrequency disturbances related to hardware cross talk between the PET and MR components in the hybrid system could be detected in the MR images. No major spatial mismatches between PET and MR data were detected. CONCLUSIONS Integrated PET/MR hybrid imaging is feasible in a clinical setting with similar detection rates as those of PET/CT. Attenuation correction can be performed sufficiently with Dixon sequences, although bone is disregarded. The administration of specific radiotracers and dedicated imaging sequences will foster this hybrid imaging modality in various indications.
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Simultaneous Whole-Body PET-MR hybrid imaging: first experience
2012Co-Authors: Harald H. Quick, C. Von Gall, M. Wiesmueller, Daniela Schmidt, Torsten Kuwert, Michael Uder, A. Doerfler, Willi A. Kalender, Michael LellAbstract:Poster: "ECR 2012 / C-2135 / Simultaneous Whole-Body PET-MR hybrid imaging: first experience " by: " H. H. Quick , C. von Gall, M. Wiesmueller, D. Schmidt, T. Kuwert, M. Uder, A. Doerfler, W. A. Kalender, M. M. Lell; Erlangen/DE"
Arman Rahmim - One of the best experts on this subject based on the ideXlab platform.
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dynamic Whole Body PET parametric imaging ii task oriented statistical estimation
Physics in Medicine and Biology, 2013Co-Authors: Nicolas A Karakatsanis, Martin A Lodge, Yun Zhou, Richard L Wahl, Arman RahmimAbstract:In the context of oncology, dynamic PET imaging coupled with standard graphical linear analysis has been previously employed to enable quantitative estimation of tracer kinetic parameters of physiological interest at the voxel level, thus, enabling quantitative PET parametric imaging. However, dynamic PET acquisition protocols have been confined to the limited axial field-of-view (∼15–20 cm) of a single-bed position and have not been translated to the Whole-Body clinical imaging domain. On the contrary, standardized uptake value (SUV) PET imaging, considered as the routine approach in clinical oncology, commonly involves multi-bed acquisitions, but is performed statically, thus not allowing for dynamic tracking of the tracer distribution. Here, we pursue a transition to dynamic Whole-Body PET parametric imaging, by presenting, within a unified framework, clinically feasible multi-bed dynamic PET acquisition protocols and parametric imaging methods. In a companion study, we presented a novel clinically feasible dynamic (4D) multi-bed PET acquisition protocol as well as the concept of Whole-Body PET parametric imaging employing Patlak ordinary least squares (OLS) regression to estimate the quantitative parameters of tracer uptake rate Ki and total blood distribution volume V. In the present study, we propose an advanced hybrid linear regression framework, driven by Patlak kinetic voxel correlations, to achieve superior trade-off between contrast-to-noise ratio (CNR) and mean squared error (MSE) than provided by OLS for the final Ki parametric images, enabling task-based performance optimization. Overall, whether the observer's task is to detect a tumor or quantitatively assess treatment response, the proposed statistical estimation framework can be adapted to satisfy the specific task performance criteria, by adjusting the Patlak correlation-coefficient (WR) reference value. The multi-bed dynamic acquisition protocol, as optimized in the preceding companion study, was employed along with extensive Monte Carlo simulations and an initial clinical 18F-deoxyglucose patient dataset to validate and demonstrate the potential of the proposed statistical estimation methods. Both simulated and clinical results suggest that hybrid regression in the context of Whole-Body Patlak Ki imaging considerably reduces MSE without compromising high CNR. Alternatively, for a given CNR, hybrid regression enables larger reductions than OLS in the number of dynamic frames per bed, allowing for even shorter acquisitions of ∼30 min, thus further contributing to the clinical adoption of the proposed framework. Compared to the SUV approach, Whole-Body parametric imaging can provide better tumor quantification, and can act as a complement to SUV, for the task of tumor detection.
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dynamic Whole Body PET parametric imaging i concept acquisition protocol optimization and clinical application
Physics in Medicine and Biology, 2013Co-Authors: Nicolas A Karakatsanis, Martin A Lodge, Yun Zhou, Richard L Wahl, Abdel Tahari, Arman RahmimAbstract:Static Whole-Body PET/CT, employing the standardized uptake value (SUV), is considered the standard clinical approach to diagnosis and treatment response monitoring for a wide range of oncologic malignancies. Alternative PET protocols involving dynamic acquisition of temporal images have been implemented in the research setting, allowing quantification of tracer dynamics, an important capability for tumor characterization and treatment response monitoring. Nonetheless, dynamic protocols have been confined to single-bed-coverage limiting the axial field-of-view to ?15?20?cm, and have not been translated to the routine clinical context of Whole-Body PET imaging for the inspection of disseminated disease. Here, we pursue a transition to dynamic Whole-Body PET parametric imaging, by presenting, within a unified framework, clinically feasible multi-bed dynamic PET acquisition protocols and parametric imaging methods. We investigate solutions to address the challenges of: (i) long acquisitions, (ii) small number of dynamic frames per bed, and (iii) non-invasive quantification of kinetics in the plasma. In the present study, a novel dynamic (4D) Whole-Body PET acquisition protocol of ?45?min total length is presented, composed of (i) an initial 6?min dynamic PET scan (24 frames) over the heart, followed by (ii) a sequence of multi-pass multi-bed PET scans (six passes???seven bed positions, each scanned for 45?s). Standard Patlak linear graphical analysis modeling was employed, coupled with image-derived plasma input function measurements. Ordinary least squares Patlak estimation was used as the baseline regression method to quantify the physiological parameters of tracer uptake rate Ki and total blood distribution volume V on an individual voxel basis. Extensive Monte Carlo simulation studies, using a wide set of published kinetic FDG parameters and GATE and XCAT platforms, were conducted to optimize the acquisition protocol from a range of ten different clinically acceptable sampling schedules examined. The framework was also applied to six FDG PET patient studies, demonstrating clinical feasibility. Both simulated and clinical results indicated enhanced contrast-to-noise ratios (CNRs) for Ki images in tumor regions with notable background FDG concentration, such as the liver, where SUV performed relatively poorly. Overall, the proposed framework enables enhanced quantification of physiological parameters across the Whole Body. In addition, the total acquisition length can be reduced from 45 to ?35?min and still achieve improved or equivalent CNR compared to SUV, provided the true Ki contrast is sufficiently high. In the follow-up companion paper, a set of advanced linear regression schemes is presented to particularly address the presence of noise, and attempt to achieve a better trade-off between the mean-squared error and the CNR metrics, resulting in enhanced task-based imaging.
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Enhanced Whole-Body PET parametric imaging using hybrid regression and thresholding driven by kinetic correlations
2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS MIC), 2012Co-Authors: Nicolas A Karakatsanis, Martin A Lodge, Yun Zhou, Richard L Wahl, Hassan Mohy-ud-din, Abdel Tahari, Arman RahmimAbstract:Whole Body PET/CT, a well established imaging method in nuclear medicine for the clinical evaluation of a wide variety of metastatic cancer malignancies, commonly involves static scanning over multiple beds. Recently, we proposed a clinically feasible transition of Whole-Body PET/CT imaging to the dynamic domain, by acquiring (i) an initial 6min dynamic scan over the heart, followed by (ii) an optimized sequence of Whole-Body PET scans, allowing for quantitative Whole Body parametric imaging. Comparative evaluation of parametric and SUV images indicated enhanced contrast-to-noise ratio (CNR) but also higher noise for the parametric images. The objective of this study is to further improve parametric image CNR to enhance tumor detectability, by limiting noise in the estimates, while enhancing contrast and quantitative accuracy of parametric images. For this purpose, we utilize the weighted correlation coefficient (WR) of the kinetic model (Patlak) fits at each voxel to determine the cluster of voxels, where (i) advanced, as opposed to conventional, statistical parameter estimation, (ii) spatial smoothing or (iii) thresholding is applied. Thus, we facilitate the integration of Whole Body parametric imaging into the clinic as a comPETitive alternative to SUV. Through quantitative analysis on selected tumor regions of the resulting images, we show enhanced CNR when ridge regression is applied only to voxels associated with high WR, while ordinary least squares (OLS) and WR driven post-smoothing is performed to the rest. This hybrid regression method yields reduced mean squared error in tumor regions, compared to OLS. In addition, by setting the WR threshold level in the range [0.85 0.9], CNR is further enhanced for tumor regions of high WR. Finally, for the same type of tumors, hybrid regression also achieves higher CNR, compared to SUV, when the last two dynamic frames are omitted, allowing for shorter acquisition times.
Torsten Kuwert - One of the best experts on this subject based on the ideXlab platform.
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integrated Whole Body PET mr hybrid imaging clinical experience
Investigative Radiology, 2013Co-Authors: Harald H. Quick, Torsten Kuwert, Michael Uder, Carl Von Gall, Martin Zeilinger, Marco Wiesmuller, Harald Braun, Susanne Ziegler, Arnd Dorfler, Willi A. KalenderAbstract:OBJECTIVES Integrated Whole-Body positron emission tomography (PET)/magnetic resonance (MR) scanners have recently been introduced and potentially offer new possibilities in hybrid imaging of oncologic patients. Integration of PET in a Whole-Body MR system requires new PET detector technology and new approaches to attenuation correction of PET data based on MR imaging. The aim of this study was to evaluate the clinical performance and image quality parameters of integrated Whole-Body PET/MR hybrid imaging in intraindividual comparison with PET/CT in oncologic patients. MATERIALS AND METHODS Eighty patients underwent a single-injection, dual-imaging protocol including Whole-Body PET/computed tomography (CT) and subsequent Whole-Body PET/MR hybrid imaging. Positron emission tomography/computed tomography was performed after adequate resting time (73 ± 13 minutes post injectionem of 227 ± 52.7 MBq Fluor-18-Fluordesoxyglucose, 3 minutes of acquisition time for each of 7 bed positions), followed by PET/MR (172 ± 33 minutes post injectionem, 10 minutes acquisition time for each of 4 bed positions). Positron emission tomographic data for both modalities were reconstructed iteratively. Two observers evaluated the following parameters: qualitative correlation of tracer-avid lesions in PET/CT versus PET/MR and PET image quality of PET/CT versus PET/MR. Magnetic resonance image quality of standard sequences (T1-weighted, T2-weighted), performance of the Dixon sequence for MR-based attenuation correction in comparison with corresponding T1-weighted images, artifacts in PET/MR data, and spatial coregistration of PET and MR data were evaluated by another observer. RESULTS In 70 of the 80 patients, both image data sets were complete. In these patients, 192 tracer-avid lesions were identified on PET/CT; 195, on PET/MR. A total of 187 lesions were identified concordantly by both modalities, and this corresponds to an agreement rate of 97.4%. The overall PET image quality was rated good to excellent for PET from PET/CT (12/28, excellent, 42.9%; 16/28, good, 57.1%; 0/28, poor, 0.0%) and slightly superior compared with PET from PET/MR, which was rated good (3/28, excellent, 10.7%; 20/28, good, 71.4%; 5/28, poor, 17.9%) in a subset of 28 patients. The overall image quality of the MR image data sets in all 70 of the 80 patients was rated excellent (260/280, excellent, 92.8%; 15/280, good, 5.4%; 5/280, poor, 1.8%). The Dixon sequence and conversion to μ-maps for MR-based attenuation correction provided robust tissue segmentation in all 280 bed positions of the acquired PET/MR data. No artifacts such as elevated noise and radiofrequency disturbances related to hardware cross talk between the PET and MR components in the hybrid system could be detected in the MR images. No major spatial mismatches between PET and MR data were detected. CONCLUSIONS Integrated PET/MR hybrid imaging is feasible in a clinical setting with similar detection rates as those of PET/CT. Attenuation correction can be performed sufficiently with Dixon sequences, although bone is disregarded. The administration of specific radiotracers and dedicated imaging sequences will foster this hybrid imaging modality in various indications.
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Integrated Whole-Body PET/MR hybrid imaging: clinical experience.
Investigative radiology, 2013Co-Authors: Harald H. Quick, Torsten Kuwert, Michael Uder, Carl Von Gall, Martin Zeilinger, Marco Wiesmuller, Harald Braun, Susanne Ziegler, Arnd Dorfler, Willi A. KalenderAbstract:OBJECTIVES Integrated Whole-Body positron emission tomography (PET)/magnetic resonance (MR) scanners have recently been introduced and potentially offer new possibilities in hybrid imaging of oncologic patients. Integration of PET in a Whole-Body MR system requires new PET detector technology and new approaches to attenuation correction of PET data based on MR imaging. The aim of this study was to evaluate the clinical performance and image quality parameters of integrated Whole-Body PET/MR hybrid imaging in intraindividual comparison with PET/CT in oncologic patients. MATERIALS AND METHODS Eighty patients underwent a single-injection, dual-imaging protocol including Whole-Body PET/computed tomography (CT) and subsequent Whole-Body PET/MR hybrid imaging. Positron emission tomography/computed tomography was performed after adequate resting time (73 ± 13 minutes post injectionem of 227 ± 52.7 MBq Fluor-18-Fluordesoxyglucose, 3 minutes of acquisition time for each of 7 bed positions), followed by PET/MR (172 ± 33 minutes post injectionem, 10 minutes acquisition time for each of 4 bed positions). Positron emission tomographic data for both modalities were reconstructed iteratively. Two observers evaluated the following parameters: qualitative correlation of tracer-avid lesions in PET/CT versus PET/MR and PET image quality of PET/CT versus PET/MR. Magnetic resonance image quality of standard sequences (T1-weighted, T2-weighted), performance of the Dixon sequence for MR-based attenuation correction in comparison with corresponding T1-weighted images, artifacts in PET/MR data, and spatial coregistration of PET and MR data were evaluated by another observer. RESULTS In 70 of the 80 patients, both image data sets were complete. In these patients, 192 tracer-avid lesions were identified on PET/CT; 195, on PET/MR. A total of 187 lesions were identified concordantly by both modalities, and this corresponds to an agreement rate of 97.4%. The overall PET image quality was rated good to excellent for PET from PET/CT (12/28, excellent, 42.9%; 16/28, good, 57.1%; 0/28, poor, 0.0%) and slightly superior compared with PET from PET/MR, which was rated good (3/28, excellent, 10.7%; 20/28, good, 71.4%; 5/28, poor, 17.9%) in a subset of 28 patients. The overall image quality of the MR image data sets in all 70 of the 80 patients was rated excellent (260/280, excellent, 92.8%; 15/280, good, 5.4%; 5/280, poor, 1.8%). The Dixon sequence and conversion to μ-maps for MR-based attenuation correction provided robust tissue segmentation in all 280 bed positions of the acquired PET/MR data. No artifacts such as elevated noise and radiofrequency disturbances related to hardware cross talk between the PET and MR components in the hybrid system could be detected in the MR images. No major spatial mismatches between PET and MR data were detected. CONCLUSIONS Integrated PET/MR hybrid imaging is feasible in a clinical setting with similar detection rates as those of PET/CT. Attenuation correction can be performed sufficiently with Dixon sequences, although bone is disregarded. The administration of specific radiotracers and dedicated imaging sequences will foster this hybrid imaging modality in various indications.
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Simultaneous Whole-Body PET-MR hybrid imaging: first experience
2012Co-Authors: Harald H. Quick, C. Von Gall, M. Wiesmueller, Daniela Schmidt, Torsten Kuwert, Michael Uder, A. Doerfler, Willi A. Kalender, Michael LellAbstract:Poster: "ECR 2012 / C-2135 / Simultaneous Whole-Body PET-MR hybrid imaging: first experience " by: " H. H. Quick , C. von Gall, M. Wiesmueller, D. Schmidt, T. Kuwert, M. Uder, A. Doerfler, W. A. Kalender, M. M. Lell; Erlangen/DE"
Michael Uder - One of the best experts on this subject based on the ideXlab platform.
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integrated Whole Body PET mr hybrid imaging clinical experience
Investigative Radiology, 2013Co-Authors: Harald H. Quick, Torsten Kuwert, Michael Uder, Carl Von Gall, Martin Zeilinger, Marco Wiesmuller, Harald Braun, Susanne Ziegler, Arnd Dorfler, Willi A. KalenderAbstract:OBJECTIVES Integrated Whole-Body positron emission tomography (PET)/magnetic resonance (MR) scanners have recently been introduced and potentially offer new possibilities in hybrid imaging of oncologic patients. Integration of PET in a Whole-Body MR system requires new PET detector technology and new approaches to attenuation correction of PET data based on MR imaging. The aim of this study was to evaluate the clinical performance and image quality parameters of integrated Whole-Body PET/MR hybrid imaging in intraindividual comparison with PET/CT in oncologic patients. MATERIALS AND METHODS Eighty patients underwent a single-injection, dual-imaging protocol including Whole-Body PET/computed tomography (CT) and subsequent Whole-Body PET/MR hybrid imaging. Positron emission tomography/computed tomography was performed after adequate resting time (73 ± 13 minutes post injectionem of 227 ± 52.7 MBq Fluor-18-Fluordesoxyglucose, 3 minutes of acquisition time for each of 7 bed positions), followed by PET/MR (172 ± 33 minutes post injectionem, 10 minutes acquisition time for each of 4 bed positions). Positron emission tomographic data for both modalities were reconstructed iteratively. Two observers evaluated the following parameters: qualitative correlation of tracer-avid lesions in PET/CT versus PET/MR and PET image quality of PET/CT versus PET/MR. Magnetic resonance image quality of standard sequences (T1-weighted, T2-weighted), performance of the Dixon sequence for MR-based attenuation correction in comparison with corresponding T1-weighted images, artifacts in PET/MR data, and spatial coregistration of PET and MR data were evaluated by another observer. RESULTS In 70 of the 80 patients, both image data sets were complete. In these patients, 192 tracer-avid lesions were identified on PET/CT; 195, on PET/MR. A total of 187 lesions were identified concordantly by both modalities, and this corresponds to an agreement rate of 97.4%. The overall PET image quality was rated good to excellent for PET from PET/CT (12/28, excellent, 42.9%; 16/28, good, 57.1%; 0/28, poor, 0.0%) and slightly superior compared with PET from PET/MR, which was rated good (3/28, excellent, 10.7%; 20/28, good, 71.4%; 5/28, poor, 17.9%) in a subset of 28 patients. The overall image quality of the MR image data sets in all 70 of the 80 patients was rated excellent (260/280, excellent, 92.8%; 15/280, good, 5.4%; 5/280, poor, 1.8%). The Dixon sequence and conversion to μ-maps for MR-based attenuation correction provided robust tissue segmentation in all 280 bed positions of the acquired PET/MR data. No artifacts such as elevated noise and radiofrequency disturbances related to hardware cross talk between the PET and MR components in the hybrid system could be detected in the MR images. No major spatial mismatches between PET and MR data were detected. CONCLUSIONS Integrated PET/MR hybrid imaging is feasible in a clinical setting with similar detection rates as those of PET/CT. Attenuation correction can be performed sufficiently with Dixon sequences, although bone is disregarded. The administration of specific radiotracers and dedicated imaging sequences will foster this hybrid imaging modality in various indications.
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Integrated Whole-Body PET/MR hybrid imaging: clinical experience.
Investigative radiology, 2013Co-Authors: Harald H. Quick, Torsten Kuwert, Michael Uder, Carl Von Gall, Martin Zeilinger, Marco Wiesmuller, Harald Braun, Susanne Ziegler, Arnd Dorfler, Willi A. KalenderAbstract:OBJECTIVES Integrated Whole-Body positron emission tomography (PET)/magnetic resonance (MR) scanners have recently been introduced and potentially offer new possibilities in hybrid imaging of oncologic patients. Integration of PET in a Whole-Body MR system requires new PET detector technology and new approaches to attenuation correction of PET data based on MR imaging. The aim of this study was to evaluate the clinical performance and image quality parameters of integrated Whole-Body PET/MR hybrid imaging in intraindividual comparison with PET/CT in oncologic patients. MATERIALS AND METHODS Eighty patients underwent a single-injection, dual-imaging protocol including Whole-Body PET/computed tomography (CT) and subsequent Whole-Body PET/MR hybrid imaging. Positron emission tomography/computed tomography was performed after adequate resting time (73 ± 13 minutes post injectionem of 227 ± 52.7 MBq Fluor-18-Fluordesoxyglucose, 3 minutes of acquisition time for each of 7 bed positions), followed by PET/MR (172 ± 33 minutes post injectionem, 10 minutes acquisition time for each of 4 bed positions). Positron emission tomographic data for both modalities were reconstructed iteratively. Two observers evaluated the following parameters: qualitative correlation of tracer-avid lesions in PET/CT versus PET/MR and PET image quality of PET/CT versus PET/MR. Magnetic resonance image quality of standard sequences (T1-weighted, T2-weighted), performance of the Dixon sequence for MR-based attenuation correction in comparison with corresponding T1-weighted images, artifacts in PET/MR data, and spatial coregistration of PET and MR data were evaluated by another observer. RESULTS In 70 of the 80 patients, both image data sets were complete. In these patients, 192 tracer-avid lesions were identified on PET/CT; 195, on PET/MR. A total of 187 lesions were identified concordantly by both modalities, and this corresponds to an agreement rate of 97.4%. The overall PET image quality was rated good to excellent for PET from PET/CT (12/28, excellent, 42.9%; 16/28, good, 57.1%; 0/28, poor, 0.0%) and slightly superior compared with PET from PET/MR, which was rated good (3/28, excellent, 10.7%; 20/28, good, 71.4%; 5/28, poor, 17.9%) in a subset of 28 patients. The overall image quality of the MR image data sets in all 70 of the 80 patients was rated excellent (260/280, excellent, 92.8%; 15/280, good, 5.4%; 5/280, poor, 1.8%). The Dixon sequence and conversion to μ-maps for MR-based attenuation correction provided robust tissue segmentation in all 280 bed positions of the acquired PET/MR data. No artifacts such as elevated noise and radiofrequency disturbances related to hardware cross talk between the PET and MR components in the hybrid system could be detected in the MR images. No major spatial mismatches between PET and MR data were detected. CONCLUSIONS Integrated PET/MR hybrid imaging is feasible in a clinical setting with similar detection rates as those of PET/CT. Attenuation correction can be performed sufficiently with Dixon sequences, although bone is disregarded. The administration of specific radiotracers and dedicated imaging sequences will foster this hybrid imaging modality in various indications.
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Simultaneous Whole-Body PET-MR hybrid imaging: first experience
2012Co-Authors: Harald H. Quick, C. Von Gall, M. Wiesmueller, Daniela Schmidt, Torsten Kuwert, Michael Uder, A. Doerfler, Willi A. Kalender, Michael LellAbstract:Poster: "ECR 2012 / C-2135 / Simultaneous Whole-Body PET-MR hybrid imaging: first experience " by: " H. H. Quick , C. von Gall, M. Wiesmueller, D. Schmidt, T. Kuwert, M. Uder, A. Doerfler, W. A. Kalender, M. M. Lell; Erlangen/DE"
