E. ter Voert - Academia.edu (original) (raw)
Papers by E. ter Voert
![Research paper thumbnail of Comparison of [18F]FDG PET/CT with magnetic resonance imaging for the assessment of human brown adipose tissue activity](https://attachments.academia-assets.com/74975968/thumbnails/1.jpg)
](EJNMMI Research
Background Brown adipose tissue (BAT) is a thermogenic tissue which can generate heat in response... more Background Brown adipose tissue (BAT) is a thermogenic tissue which can generate heat in response to mild cold exposure. As it constitutes a promising target in the fight against obesity, we need reliable techniques to quantify its activity in response to therapeutic interventions. The current standard for the quantification of BAT activity is [18F]FDG PET/CT. Various sequences in magnetic resonance imaging (MRI), including those measuring its relative fat content (fat fraction), have been proposed and evaluated in small proof-of-principle studies, showing diverging results. Here, we systematically compare the predictive value of adipose tissue fat fraction measured by MRI to the results of [18F]FDG PET/CT. Methods We analyzed the diagnostic reliability of MRI measured fat fraction (FF) for the estimation of human BAT activity in two cohorts of healthy volunteers participating in two prospective clinical trials (NCT03189511, NCT03269747). In both cohorts, BAT activity was stimulated...
European Journal of Hybrid Imaging
Background PET/MRI has a high potential in oncology imaging, especially for tumor indications whe... more Background PET/MRI has a high potential in oncology imaging, especially for tumor indications where high soft tissue contrast is crucial such as genitourinary tumors. One of the challenges for PET/MRI acquisition is handling of metal implants. In addition to conventional methods, more innovative techniques have been developed to reduce artifacts caused by those implants such as the selective multiacquisition variable-image combination (MAVRIC-SL). The aim of this study is to perform a quantitative and qualitative assessment of metal artifact reduction in 68Ga-PSMA-11 PET/MRI for prostate cancer patients with hip joint replacement using a selective MAVRIC-SL sequence for the whole pelvis. Methods We retrospectively analyzed data of 20 men with 37 metal hip implants diagnosed with PCA, staged or restaged by 68Ga-PSMA-11 PET/MRI from June 2016 to December 2017. Each signal cancellation per side or metal implant was analyzed on the reference sequence LAVA-FLEX, as well as T1-weighted fa...
European Journal of Hybrid Imaging, Apr 9, 2020
Background: PET/MRI has a high potential in oncology imaging, especially for tumor indications wh... more Background: PET/MRI has a high potential in oncology imaging, especially for tumor indications where high soft tissue contrast is crucial such as genitourinary tumors. One of the challenges for PET/MRI acquisition is handling of metal implants. In addition to conventional methods, more innovative techniques have been developed to reduce artifacts caused by those implants such as the selective multiacquisition variable-image combination (MAVRIC-SL). The aim of this study is to perform a quantitative and qualitative assessment of metal artifact reduction in 68 Ga-PSMA-11 PET/MRI for prostate cancer patients with hip joint replacement using a selective MAVRIC-SL sequence for the whole pelvis. Methods: We retrospectively analyzed data of 20 men with 37 metal hip implants diagnosed with PCA, staged or restaged by 68 Ga-PSMA-11 PET/MRI from June 2016 to December 2017. Each signal cancellation per side or metal implant was analyzed on the reference sequence LAVA-FLEX, as well as T1-weighted fast spin echo (T1w-FSE) sequence and MAVRIC-SL. Two independent reviewers reported on a four-point scale whether abnormal pelvic 68 Ga-PSMA-11 uptake could be assigned to an anatomical structure in the tested sequences. Results: The smallest averaged signal void was observed on MAVRIC-SL sequences with a mean artifact size of 26.17 cm 2 (range 12.63 to 42.93 cm 2 , p < 0.001). The best image quality regarding anatomical assignment of pathological PSMA uptakes in the pelvis by two independent readers was noted for MAVRIC-SL sequences, followed by T1w-FSE with excellent interreader agreement. Conclusions: MAVRIC-SL sequence allows better image quality in the surrounding of hip implants by reducing MR signal voids and increasing so the accuracy of anatomical assignment of pathological 68 Ga-PSMA-11 uptake in the pelvis over LAVA-FLEX and T1w-FSE sequences.
Journal of Clinical Oncology
e13111 Background: Despite the promise of preclinical and early phase clinical studies, the effic... more e13111 Background: Despite the promise of preclinical and early phase clinical studies, the efficacy of bevacizumab in solid tumors is more limited than expected. One of the presumed reasons is the induction of tumor hypoxia by the anti-angiogenic effects of bevacizumab, leading to therapy resistance. The aim of this study was to assess the effect of bevacizumab on tumor hypoxia in vivo in a colorectal cancer model, using functional imaging techniques. Methods: Nude mice with s.c. LS174T colon carcinoma xenografts (0.05 - 0.3 cm3) were treated with bevacizumab (5 mg/kg; 2/wk, i.p.) or saline as a control. To assess tumor hypoxia in vivo 18F-MISO-PET microPET or T2*-MRI images were acquired of separate groups of mice (n=5) before treatment and at day 2, 6 and 10 days after start of treatment. Tumors were harvested directly after imaging to microscopically assess the hypoxic fraction (pimonidazole staining) and vascular density (9F1 staining). Results: Linear regression analyses showe...
EJNMMI Research
Background Positron emission tomography (PET) is increasingly applied for in vivo brown adipose t... more Background Positron emission tomography (PET) is increasingly applied for in vivo brown adipose tissue (BAT) research in healthy volunteers. To limit the radiation exposure, the injected 18F-FDG tracer dose should be as low as possible. With simultaneous PET/MR imaging, the radiation exposure due to computed tomography (CT) can be avoided, but more importantly, the PET acquisition time can often be increased to match the more extensive magnetic resonance (MR) imaging protocol. The potential gain in detected coincidence counts, due to the longer acquisition time, can then be applied to decrease the injected tracer dose. The aim of this study was to investigate the minimal 18F-FDG dose for a 10-min time-of-flight (TOF) PET/MR acquisition that would still allow accurate quantification of supraclavicular BAT volume and activity. Methods Twenty datasets from 13 volunteers were retrospectively included from a prospective clinical study. PET emission datasets were modified to simulate step...
European Journal of Nuclear Medicine and Molecular Imaging
EJNMMI Research
Unfortunately, after publication of this article [1], it was noticed that the name of Urs J. Mueh... more Unfortunately, after publication of this article [1], it was noticed that the name of Urs J. Muehlematter was incorrectly displayed as Urs J. Mühlematter. The corrected author list can be seen above and the original article has been corrected to reflect this.
EJNMMI Research
Background: Accurate attenuation correction (AC) is an inherent problem of positron emission tomo... more Background: Accurate attenuation correction (AC) is an inherent problem of positron emission tomography magnetic resonance imaging (PET/MRI) systems. Simulation studies showed that time-of-flight (TOF) detectors can reduce PET quantification errors in MRI-based AC. However, its impact on lesion detection in a clinical setting with 18 F-choline has not yet been evaluated. Therefore, we compared TOF and non-TOF 18 F-choline PET for absolute and relative difference in standard uptake values (SUV) and investigated the detection rate of metastases in prostate cancer patients. Results: Non-TOF SUV was significantly lower compared to TOF in all osseous structures, except the skull, in primary lesions of the prostate, and in pelvic nodal and osseous metastasis. Concerning lymph node metastases, both experienced readers detected 16/19 (84%) on TOF PET, whereas on non-TOF PET readers 1 and 2 detected 11 (58%), and 14 (73%), respectively. With TOF PET readers 1 and 2 detected 14/15 (93%) and 11/15 (73%) bone metastases, respectively, whereas detection rate with non-TOF PET was 73% (11/15) for reader 1 and 53% (8/15) for reader 2. The interreader agreement was good for osseous metastasis detection on TOF (kappa 0.636, 95% confidence interval [CI] 0. 453-0.810) and moderate on non-TOF (kappa = 0.600, CI 0.438-0.780). Conclusion: TOF reconstruction for 18 F-choline PET/MRI shows higher SUV measurements compared to non-TOF reconstructions in physiological osseous structures as well as pelvic malignancies. Our results suggest that addition of TOF information has a positive impact on lesion detection rate for lymph node and bone metastasis in prostate cancer patients.
The quarterly journal of nuclear medicine and molecular imaging : official publication of the Italian Association of Nuclear Medicine (AIMN) [and] the International Association of Radiopharmacology (IAR), [and] Section of the Society of..., Jan 10, 2018
Positron emission tomography (PET) / computed tomography (CT) is among the most frequently used i... more Positron emission tomography (PET) / computed tomography (CT) is among the most frequently used imaging modalities for initial staging of gastro-oesophageal (GE) cancer, whereas CT-perfusion (CTP) provides different multiparametric information. This proof of concept study compares CTP- and PET-parameters in patients with GE cancer to evaluate correlations and a possible prognostic value of a combined PET/CTP imaging procedure. A total of 31 patients with F-18-FDG-PET/CT and CTP studies were prospectively analysed. Patients had adenocarcinoma (n = 22) and oesophageal squamous cell carcinoma (SCC, n = 9). Imaging was performed before start of treatment. CTP parameters [blood flow (BF), blood volume (BV), mean transit time (MTT)] and metabolic parameters [(maximum and mean standardised uptake values and standard deviation (SUVmax, SUVmean, SUVsd), metabolic tumour volume (MTV) and tumour lesion glycolysis (TLG)], as well as flow metabolic product [FMP (BF × SUVmax)] were determined and...
EJNMMI research, Jan 27, 2018
In contrast to ordered subset expectation maximization (OSEM), block sequential regularized expec... more In contrast to ordered subset expectation maximization (OSEM), block sequential regularized expectation maximization (BSREM) positron emission tomography (PET) reconstruction algorithms can run until full convergence while controlling image quality and noise. Recent studies with BSREM and F-FDG PET reported higher signal-to-noise ratios and higher standardized uptake values (SUV). In this study, we investigate the optimal regularization parameter (β) for clinical Ga-PSMA PET/MR reconstructions in the pelvic region applying time-of-flight (TOF) BSREM in comparison to TOF OSEM. Two-minute emission data from the pelvic region of 25 patients who underwent Ga-PSMA PET/MR were retrospectively reconstructed. Reference OSEM reconstructions had 28 subsets and 2 iterations. BSREM reconstructions were performed with 15 β values between 150 and 1200. Regions of interest (ROIs) were drawn around lesions and in uniform background. Background SUVmean (average) and SUVstd (standard deviation), and ...
Radiology
To determine the level of clinically acceptable reduction in injected fluorine 18 (18 F) fluorode... more To determine the level of clinically acceptable reduction in injected fluorine 18 (18 F) fluorodeoxyglucose (FDG) dose in time-of-flight (TOF)-positron emission tomography(PET)/ magnetic resonance (MR) imaging by using silicon photomultiplier (SiPM) detectors compared with TOF-PET/computed tomography (CT) using Lu1.8Y0.2SiO 5 (Ce), or LYSO, detectors in patients with different body mass indexes (BMIs). Materials and Methods: Patients were enrolled in this study as part of a larger prospective study with a different purpose than evaluated in this study (NCT02316431). All patients gave written informed consent prior to inclusion into the study. In this study, 74 patients with different malignant diseases underwent sequential whole-body TOF-PET/CT and TOF-PET/MR imaging. PET images with simulated reduction of injected 18 F-FDG doses were generated by unlisting the list-mode data from PET/MR imaging. Two readers rated the image quality of whole-body data sets, as well as the image quality in each body compartment, and evaluated the conspicuity of malignant lesions.
Head & neck, Aug 13, 2017
The purpose of this study was to compare the diagnostic accuracy of positron emission tomography ... more The purpose of this study was to compare the diagnostic accuracy of positron emission tomography (PET)/MRI with PET/CT for local resectability of head and neck cancer. Sequential contrast-enhanced PET/CT-MRI was performed in 58 patients referred for the staging or restaging of head and neck cancer. Tumors were assessed with PET/CT and PET/MRI for the presence of resectability-defining factors: T4b status (mediastinal invasion, invasion of the prevertebral space, and vascular encasement), and another 8 findings that would imply obstacles for surgical cure (invasion of the laryngeal cartilage, invasion of the preepiglottic fat pad, perineural spread, orbital invasion, bone infiltration, skull base invasion, dural infiltration, and invasion of the brachial plexus). The sensitivity/specificity/accuracy of local resectability-defining factors of PET/CT and PET/MRI was 0.92/0.99/0.98 and 0.98/0.99/0.99 (P = .727), respectively, per lesion, and 0.96/0.87/0.91 and 0.96/0.90/0.93 (P = .687),...
European journal of nuclear medicine and molecular imaging, Jan 26, 2017
Our objective was to determine clinically the value of time-of-flight (TOF) information in reduci... more Our objective was to determine clinically the value of time-of-flight (TOF) information in reducing PET artifacts and improving PET image quality and accuracy in simultaneous TOF PET/MR scanning. A total 65 patients who underwent a comparative scan in a simultaneous TOF PET/MR scanner were included. TOF and non-TOF PET images were reconstructed, clinically examined, compared and scored. PET imaging artifacts were categorized as large or small implant-related artifacts, as dental implant-related artifacts, and as implant-unrelated artifacts. Differences in image quality, especially those related to (implant) artifacts, were assessed using a scale ranging from 0 (no artifact) to 4 (severe artifact). A total of 87 image artifacts were found and evaluated. Four patients had large and eight patients small implant-related artifacts, 27 patients had dental implants/fillings, and 48 patients had implant-unrelated artifacts. The average score was 1.14 ± 0.82 for non-TOF PET images and 0.53 ±...
Clinical nuclear medicine, 2017
To compare the diagnostic accuracy of PET/MR and PET/CT in patients with suspected occult primary... more To compare the diagnostic accuracy of PET/MR and PET/CT in patients with suspected occult primary tumors. This prospective study was approved by the institutional review board. Sequential PET/CT-MR was performed in 43 patients (22 male subjects; median age, 58 years; range, 20-86 years) referred for suspected occult primary tumors. Patients were assessed with PET/CT and PET/MR for the presence of a primary tumor, lymph node metastases, and distant metastases. Wilcoxon signed-rank test was performed to compare the diagnostic accuracy of PET/CT and PET/MR. According to the standard of reference, a primary lesion was found in 14 patients. In 16 patients, the primary lesion remained occult. In the remaining 13 patients, lesions proved to be benign. PET/MR was superior to PET/CT for primary tumor detection (sensitivity/specificity, 0.85/0.97 vs 0.69/0.73; P = 0.020) and comparable to PET/CT for the detection of lymph node metastases (sensitivity/specificity, 0.93/1.00 vs 0.93/0.93; P = 0...
Molecular Imaging and Biology, 2016
NMR in biomedicine, Jan 6, 2016
The purpose of this work was to improve dynamic contrast enhanced MRI (DCE-MRI) of liver lesions ... more The purpose of this work was to improve dynamic contrast enhanced MRI (DCE-MRI) of liver lesions by removing motion corrupted images as identified by a structural similarity (SSIM) algorithm, and to assess the effect of this correction on the pharmacokinetic parameter K(trans) using automatically determined arterial input functions (AIFs). Fifteen patients with colorectal liver metastases were measured twice with a T1 weighted multislice 2D FLASH sequence for DCE-MRI (time resolution 1.2 s). AIFs were automatically derived from contrast inflow in the aorta of each patient. Thereafter, SSIM identified motion corrupted images of the liver were removed from the DCE dataset. From this corrected data set K(trans) and its reproducibility were determined. Using the SSIM algorithm a median fraction of 46% (range 37-50%) of the liver images in DCE time series was labeled as motion distorted. Rejection of these images resulted in a significantly lower median K(trans) (p < 0.05) and lower c...
Journal of Nuclear Medicine, 2016
EJNMMI Research
Background Brown adipose tissue (BAT) is a thermogenic tissue which can generate heat in response... more Background Brown adipose tissue (BAT) is a thermogenic tissue which can generate heat in response to mild cold exposure. As it constitutes a promising target in the fight against obesity, we need reliable techniques to quantify its activity in response to therapeutic interventions. The current standard for the quantification of BAT activity is [18F]FDG PET/CT. Various sequences in magnetic resonance imaging (MRI), including those measuring its relative fat content (fat fraction), have been proposed and evaluated in small proof-of-principle studies, showing diverging results. Here, we systematically compare the predictive value of adipose tissue fat fraction measured by MRI to the results of [18F]FDG PET/CT. Methods We analyzed the diagnostic reliability of MRI measured fat fraction (FF) for the estimation of human BAT activity in two cohorts of healthy volunteers participating in two prospective clinical trials (NCT03189511, NCT03269747). In both cohorts, BAT activity was stimulated...
European Journal of Hybrid Imaging
Background PET/MRI has a high potential in oncology imaging, especially for tumor indications whe... more Background PET/MRI has a high potential in oncology imaging, especially for tumor indications where high soft tissue contrast is crucial such as genitourinary tumors. One of the challenges for PET/MRI acquisition is handling of metal implants. In addition to conventional methods, more innovative techniques have been developed to reduce artifacts caused by those implants such as the selective multiacquisition variable-image combination (MAVRIC-SL). The aim of this study is to perform a quantitative and qualitative assessment of metal artifact reduction in 68Ga-PSMA-11 PET/MRI for prostate cancer patients with hip joint replacement using a selective MAVRIC-SL sequence for the whole pelvis. Methods We retrospectively analyzed data of 20 men with 37 metal hip implants diagnosed with PCA, staged or restaged by 68Ga-PSMA-11 PET/MRI from June 2016 to December 2017. Each signal cancellation per side or metal implant was analyzed on the reference sequence LAVA-FLEX, as well as T1-weighted fa...
European Journal of Hybrid Imaging, Apr 9, 2020
Background: PET/MRI has a high potential in oncology imaging, especially for tumor indications wh... more Background: PET/MRI has a high potential in oncology imaging, especially for tumor indications where high soft tissue contrast is crucial such as genitourinary tumors. One of the challenges for PET/MRI acquisition is handling of metal implants. In addition to conventional methods, more innovative techniques have been developed to reduce artifacts caused by those implants such as the selective multiacquisition variable-image combination (MAVRIC-SL). The aim of this study is to perform a quantitative and qualitative assessment of metal artifact reduction in 68 Ga-PSMA-11 PET/MRI for prostate cancer patients with hip joint replacement using a selective MAVRIC-SL sequence for the whole pelvis. Methods: We retrospectively analyzed data of 20 men with 37 metal hip implants diagnosed with PCA, staged or restaged by 68 Ga-PSMA-11 PET/MRI from June 2016 to December 2017. Each signal cancellation per side or metal implant was analyzed on the reference sequence LAVA-FLEX, as well as T1-weighted fast spin echo (T1w-FSE) sequence and MAVRIC-SL. Two independent reviewers reported on a four-point scale whether abnormal pelvic 68 Ga-PSMA-11 uptake could be assigned to an anatomical structure in the tested sequences. Results: The smallest averaged signal void was observed on MAVRIC-SL sequences with a mean artifact size of 26.17 cm 2 (range 12.63 to 42.93 cm 2 , p < 0.001). The best image quality regarding anatomical assignment of pathological PSMA uptakes in the pelvis by two independent readers was noted for MAVRIC-SL sequences, followed by T1w-FSE with excellent interreader agreement. Conclusions: MAVRIC-SL sequence allows better image quality in the surrounding of hip implants by reducing MR signal voids and increasing so the accuracy of anatomical assignment of pathological 68 Ga-PSMA-11 uptake in the pelvis over LAVA-FLEX and T1w-FSE sequences.
Journal of Clinical Oncology
e13111 Background: Despite the promise of preclinical and early phase clinical studies, the effic... more e13111 Background: Despite the promise of preclinical and early phase clinical studies, the efficacy of bevacizumab in solid tumors is more limited than expected. One of the presumed reasons is the induction of tumor hypoxia by the anti-angiogenic effects of bevacizumab, leading to therapy resistance. The aim of this study was to assess the effect of bevacizumab on tumor hypoxia in vivo in a colorectal cancer model, using functional imaging techniques. Methods: Nude mice with s.c. LS174T colon carcinoma xenografts (0.05 - 0.3 cm3) were treated with bevacizumab (5 mg/kg; 2/wk, i.p.) or saline as a control. To assess tumor hypoxia in vivo 18F-MISO-PET microPET or T2*-MRI images were acquired of separate groups of mice (n=5) before treatment and at day 2, 6 and 10 days after start of treatment. Tumors were harvested directly after imaging to microscopically assess the hypoxic fraction (pimonidazole staining) and vascular density (9F1 staining). Results: Linear regression analyses showe...
EJNMMI Research
Background Positron emission tomography (PET) is increasingly applied for in vivo brown adipose t... more Background Positron emission tomography (PET) is increasingly applied for in vivo brown adipose tissue (BAT) research in healthy volunteers. To limit the radiation exposure, the injected 18F-FDG tracer dose should be as low as possible. With simultaneous PET/MR imaging, the radiation exposure due to computed tomography (CT) can be avoided, but more importantly, the PET acquisition time can often be increased to match the more extensive magnetic resonance (MR) imaging protocol. The potential gain in detected coincidence counts, due to the longer acquisition time, can then be applied to decrease the injected tracer dose. The aim of this study was to investigate the minimal 18F-FDG dose for a 10-min time-of-flight (TOF) PET/MR acquisition that would still allow accurate quantification of supraclavicular BAT volume and activity. Methods Twenty datasets from 13 volunteers were retrospectively included from a prospective clinical study. PET emission datasets were modified to simulate step...
European Journal of Nuclear Medicine and Molecular Imaging
EJNMMI Research
Unfortunately, after publication of this article [1], it was noticed that the name of Urs J. Mueh... more Unfortunately, after publication of this article [1], it was noticed that the name of Urs J. Muehlematter was incorrectly displayed as Urs J. Mühlematter. The corrected author list can be seen above and the original article has been corrected to reflect this.
EJNMMI Research
Background: Accurate attenuation correction (AC) is an inherent problem of positron emission tomo... more Background: Accurate attenuation correction (AC) is an inherent problem of positron emission tomography magnetic resonance imaging (PET/MRI) systems. Simulation studies showed that time-of-flight (TOF) detectors can reduce PET quantification errors in MRI-based AC. However, its impact on lesion detection in a clinical setting with 18 F-choline has not yet been evaluated. Therefore, we compared TOF and non-TOF 18 F-choline PET for absolute and relative difference in standard uptake values (SUV) and investigated the detection rate of metastases in prostate cancer patients. Results: Non-TOF SUV was significantly lower compared to TOF in all osseous structures, except the skull, in primary lesions of the prostate, and in pelvic nodal and osseous metastasis. Concerning lymph node metastases, both experienced readers detected 16/19 (84%) on TOF PET, whereas on non-TOF PET readers 1 and 2 detected 11 (58%), and 14 (73%), respectively. With TOF PET readers 1 and 2 detected 14/15 (93%) and 11/15 (73%) bone metastases, respectively, whereas detection rate with non-TOF PET was 73% (11/15) for reader 1 and 53% (8/15) for reader 2. The interreader agreement was good for osseous metastasis detection on TOF (kappa 0.636, 95% confidence interval [CI] 0. 453-0.810) and moderate on non-TOF (kappa = 0.600, CI 0.438-0.780). Conclusion: TOF reconstruction for 18 F-choline PET/MRI shows higher SUV measurements compared to non-TOF reconstructions in physiological osseous structures as well as pelvic malignancies. Our results suggest that addition of TOF information has a positive impact on lesion detection rate for lymph node and bone metastasis in prostate cancer patients.
The quarterly journal of nuclear medicine and molecular imaging : official publication of the Italian Association of Nuclear Medicine (AIMN) [and] the International Association of Radiopharmacology (IAR), [and] Section of the Society of..., Jan 10, 2018
Positron emission tomography (PET) / computed tomography (CT) is among the most frequently used i... more Positron emission tomography (PET) / computed tomography (CT) is among the most frequently used imaging modalities for initial staging of gastro-oesophageal (GE) cancer, whereas CT-perfusion (CTP) provides different multiparametric information. This proof of concept study compares CTP- and PET-parameters in patients with GE cancer to evaluate correlations and a possible prognostic value of a combined PET/CTP imaging procedure. A total of 31 patients with F-18-FDG-PET/CT and CTP studies were prospectively analysed. Patients had adenocarcinoma (n = 22) and oesophageal squamous cell carcinoma (SCC, n = 9). Imaging was performed before start of treatment. CTP parameters [blood flow (BF), blood volume (BV), mean transit time (MTT)] and metabolic parameters [(maximum and mean standardised uptake values and standard deviation (SUVmax, SUVmean, SUVsd), metabolic tumour volume (MTV) and tumour lesion glycolysis (TLG)], as well as flow metabolic product [FMP (BF × SUVmax)] were determined and...
EJNMMI research, Jan 27, 2018
In contrast to ordered subset expectation maximization (OSEM), block sequential regularized expec... more In contrast to ordered subset expectation maximization (OSEM), block sequential regularized expectation maximization (BSREM) positron emission tomography (PET) reconstruction algorithms can run until full convergence while controlling image quality and noise. Recent studies with BSREM and F-FDG PET reported higher signal-to-noise ratios and higher standardized uptake values (SUV). In this study, we investigate the optimal regularization parameter (β) for clinical Ga-PSMA PET/MR reconstructions in the pelvic region applying time-of-flight (TOF) BSREM in comparison to TOF OSEM. Two-minute emission data from the pelvic region of 25 patients who underwent Ga-PSMA PET/MR were retrospectively reconstructed. Reference OSEM reconstructions had 28 subsets and 2 iterations. BSREM reconstructions were performed with 15 β values between 150 and 1200. Regions of interest (ROIs) were drawn around lesions and in uniform background. Background SUVmean (average) and SUVstd (standard deviation), and ...
Radiology
To determine the level of clinically acceptable reduction in injected fluorine 18 (18 F) fluorode... more To determine the level of clinically acceptable reduction in injected fluorine 18 (18 F) fluorodeoxyglucose (FDG) dose in time-of-flight (TOF)-positron emission tomography(PET)/ magnetic resonance (MR) imaging by using silicon photomultiplier (SiPM) detectors compared with TOF-PET/computed tomography (CT) using Lu1.8Y0.2SiO 5 (Ce), or LYSO, detectors in patients with different body mass indexes (BMIs). Materials and Methods: Patients were enrolled in this study as part of a larger prospective study with a different purpose than evaluated in this study (NCT02316431). All patients gave written informed consent prior to inclusion into the study. In this study, 74 patients with different malignant diseases underwent sequential whole-body TOF-PET/CT and TOF-PET/MR imaging. PET images with simulated reduction of injected 18 F-FDG doses were generated by unlisting the list-mode data from PET/MR imaging. Two readers rated the image quality of whole-body data sets, as well as the image quality in each body compartment, and evaluated the conspicuity of malignant lesions.
Head & neck, Aug 13, 2017
The purpose of this study was to compare the diagnostic accuracy of positron emission tomography ... more The purpose of this study was to compare the diagnostic accuracy of positron emission tomography (PET)/MRI with PET/CT for local resectability of head and neck cancer. Sequential contrast-enhanced PET/CT-MRI was performed in 58 patients referred for the staging or restaging of head and neck cancer. Tumors were assessed with PET/CT and PET/MRI for the presence of resectability-defining factors: T4b status (mediastinal invasion, invasion of the prevertebral space, and vascular encasement), and another 8 findings that would imply obstacles for surgical cure (invasion of the laryngeal cartilage, invasion of the preepiglottic fat pad, perineural spread, orbital invasion, bone infiltration, skull base invasion, dural infiltration, and invasion of the brachial plexus). The sensitivity/specificity/accuracy of local resectability-defining factors of PET/CT and PET/MRI was 0.92/0.99/0.98 and 0.98/0.99/0.99 (P = .727), respectively, per lesion, and 0.96/0.87/0.91 and 0.96/0.90/0.93 (P = .687),...
European journal of nuclear medicine and molecular imaging, Jan 26, 2017
Our objective was to determine clinically the value of time-of-flight (TOF) information in reduci... more Our objective was to determine clinically the value of time-of-flight (TOF) information in reducing PET artifacts and improving PET image quality and accuracy in simultaneous TOF PET/MR scanning. A total 65 patients who underwent a comparative scan in a simultaneous TOF PET/MR scanner were included. TOF and non-TOF PET images were reconstructed, clinically examined, compared and scored. PET imaging artifacts were categorized as large or small implant-related artifacts, as dental implant-related artifacts, and as implant-unrelated artifacts. Differences in image quality, especially those related to (implant) artifacts, were assessed using a scale ranging from 0 (no artifact) to 4 (severe artifact). A total of 87 image artifacts were found and evaluated. Four patients had large and eight patients small implant-related artifacts, 27 patients had dental implants/fillings, and 48 patients had implant-unrelated artifacts. The average score was 1.14 ± 0.82 for non-TOF PET images and 0.53 ±...
Clinical nuclear medicine, 2017
To compare the diagnostic accuracy of PET/MR and PET/CT in patients with suspected occult primary... more To compare the diagnostic accuracy of PET/MR and PET/CT in patients with suspected occult primary tumors. This prospective study was approved by the institutional review board. Sequential PET/CT-MR was performed in 43 patients (22 male subjects; median age, 58 years; range, 20-86 years) referred for suspected occult primary tumors. Patients were assessed with PET/CT and PET/MR for the presence of a primary tumor, lymph node metastases, and distant metastases. Wilcoxon signed-rank test was performed to compare the diagnostic accuracy of PET/CT and PET/MR. According to the standard of reference, a primary lesion was found in 14 patients. In 16 patients, the primary lesion remained occult. In the remaining 13 patients, lesions proved to be benign. PET/MR was superior to PET/CT for primary tumor detection (sensitivity/specificity, 0.85/0.97 vs 0.69/0.73; P = 0.020) and comparable to PET/CT for the detection of lymph node metastases (sensitivity/specificity, 0.93/1.00 vs 0.93/0.93; P = 0...
Molecular Imaging and Biology, 2016
NMR in biomedicine, Jan 6, 2016
The purpose of this work was to improve dynamic contrast enhanced MRI (DCE-MRI) of liver lesions ... more The purpose of this work was to improve dynamic contrast enhanced MRI (DCE-MRI) of liver lesions by removing motion corrupted images as identified by a structural similarity (SSIM) algorithm, and to assess the effect of this correction on the pharmacokinetic parameter K(trans) using automatically determined arterial input functions (AIFs). Fifteen patients with colorectal liver metastases were measured twice with a T1 weighted multislice 2D FLASH sequence for DCE-MRI (time resolution 1.2 s). AIFs were automatically derived from contrast inflow in the aorta of each patient. Thereafter, SSIM identified motion corrupted images of the liver were removed from the DCE dataset. From this corrected data set K(trans) and its reproducibility were determined. Using the SSIM algorithm a median fraction of 46% (range 37-50%) of the liver images in DCE time series was labeled as motion distorted. Rejection of these images resulted in a significantly lower median K(trans) (p < 0.05) and lower c...
Journal of Nuclear Medicine, 2016