Felix Kuhn - Academia.edu (original) (raw)

Papers by Felix Kuhn

PURPOSE To compare the diagnostic accuracy of non-contrast enhanced PET/CT (PET/CT) and non-contr... more PURPOSE To compare the diagnostic accuracy of non-contrast enhanced PET/CT (PET/CT) and non-contrast enhanced PET/MRI (PET/MRI) concerning lesion detection, anatomical localization and lesion conspicuity in abdominopelvic cancer lesions. METHOD AND MATERIALS 15 patients (mean age 52.3 years, range 22 to 72 years, 8 female, 7 male) with various oncological diseases (e.g. colon cancer, breast cancer, melanoma) were referred for a clinical PET/CT. An additional PET/MRI was performed within a Tri-modality PET/CT-MRI system (GE Discovery 750 3T) with ultra fast GRE and SE sequences (T1, T2 and FIESTA) with body array coils covering the whole abdomen. All lesions (lymph node metastases/organ metastases) were compared concerning detection rate/localization, lesion size and conspicuity (qualitative score 1 (<25% lesion outline detectable) up to score 4 (>75% lesion outline detectable)). ANOVA analysis was used to compare detectability and conspicuity for both modalities, p values <...

European journal of nuclear medicine and molecular imaging

OBJECTIVE The purpose of this study was to analyze whether diffusion-weighted imaging (DWI) adds ... more OBJECTIVE The purpose of this study was to analyze whether diffusion-weighted imaging (DWI) adds significant information to positron emission tomography/magnetic resonance imaging (PET/MRI) on lesion detection and characterization in head and neck cancers. METHODS Seventy patients with different head and neck cancers were enrolled in this prospective study. All patients underwent sequential contrast-enhanced (ce) PET/computed tomography (CT) and cePET/MRI using a tri-modality PET/CT-MR setup either for staging or re-staging. First, the DWI alone was evaluated, followed by the PET/MRI with conventional sequences, and in a third step, the PET/MRI with DWI was evaluated. McNemar's test was used to evaluate differences in the accuracy of PET/MRI with and without DWI compared to the standard of reference. RESULTS One hundred eighty-eight (188) lesions were found, and of those, 118 (62.8 %) were malignant and 70 (37.2 %) were benign. PET/MRI without DWI had a higher accuracy in detect...

PURPOSE In a sequential multi-modality MR-PET/CT system, MR surface coils applied to patients lea... more PURPOSE In a sequential multi-modality MR-PET/CT system, MR surface coils applied to patients lead to CT beam-hardening artefacts with subsequent errors in PET attenuation correction. As successful image co-registration in MR-PET/CT precludes patient repositioning and considering the importance of MR surface coils for rapid acquisitions and high image quality, we developed an approach for easy MR coil installation and removal between MR and PET/CT examinations while maintaining unchanged patient position. METHOD AND MATERIALS A front-loading and a side-loading transfer table were developed to shuttle patients from a time-of-flight PET/CT system (Discovery 690 PET/CT, GE Healthcare) to a 3T MR system (MR 750, GE Healthcare) installed in separate rooms, thereby sequentially integrating the two systems. The tables were designed such that the MR head coil (32-CH head coil, GE) can be slid over the head rest of the side-loading transfer table, whereas the head rest of the front-loading t...

Purpose Positron emission tomography (PET)/MRI combines the functional ability of PET and the hig... more Purpose Positron emission tomography (PET)/MRI combines the functional ability of PET and the high soft tissue contrast of MRI. The aim of this study was to assess contrastenhanced (ce)PET/MRI compared to cePET/CT in patients with suspected recurrence of head and neck cancer (HNC). Methods Eighty-seven patients underwent sequential cePET/ CT and cePET/MRI using a trimodality PET/CT-MRI set-up. Diagnostic accuracy for the detection of recurrent HNC was evaluated using cePET/CT and cePET/MRI. Furthermore, image quality, presence of unclear 18 F-fluorodeoxy-D-glucose (FDG) findings of uncertain significance and the diagnostic advantages of use of gadolinium contrast enhancement were analysed.

EJNMMI research, 2014

Quantitative measures of 11C-raclopride receptor binding can be used as a correlate of postsynapt... more Quantitative measures of 11C-raclopride receptor binding can be used as a correlate of postsynaptic D2 receptor density in the striatum, allowing 11C-raclopride positron emission tomography (PET) to be used for the differentiation of Parkinson's disease from atypical parkinsonian syndromes. Comparison with reference values is recommended to establish a reliable diagnosis. A PET template specific to raclopride may facilitate direct computation of parametric maps without the need for an additional MR scan, aiding automated image analysis. Sixteen healthy volunteers underwent a dynamic 11C-raclopride PET and a high-resolution T1-weighted MR scan of the brain. PET data from eight healthy subjects was processed to generate a raclopride-specific PET template normalized to standard space. Subsequently, the data processing based on the PET template was validated against the standard magnetic resonance imaging (MRI)-based method in 8 healthy subjects and 20 patients with suspected parkin...

ABSTRACT PURPOSE Shuttle systems have been developed to integrate PET/CT and MR scanners permitti... more ABSTRACT PURPOSE Shuttle systems have been developed to integrate PET/CT and MR scanners permitting to transfer patients without patient repositioning between scans. The systems were designed such that MR surface coils can be installed and removed without moving the patient. Thus surface coil-induced CT beam-hardening and PET attenuation-artefacts are avoided. The purpose of this study was to assess the registration accuracy of this tri-modality PET/CT+MR system based on MR to CT registration analysis. METHOD AND MATERIALS In this prospective study, 14 patients underwent sequential PET/CT and 3T abdominal MRI using a dedicated torso surface coil. Either a custom built side-loading shuttle system (n = 9) or a front-loading system (n = 5) were used to transfer patients from a time-of-flight PET/CT system (Discovery PET/CT 690) to a 3T MR imaging system (Discovery MR750, both GE Healthcare) installed in an adjacent room. Rigid 3D image registration of abdominal CT and MR images was done using dedicated registration software (Integrated Registration, Advantage Workstation, GE Healthcare). Axial T1w fast dual gradient echo MR images were used for registration. The best match between CT (reference) and MR images was found by manual repositioning of MR images using anatomical landmarks. Offsets were recorded in X- (lateral), Y- (anterior-posterior) and Z-axis (cranio-caudal). RESULTS The mean offset between CT and MR images in all patients was 7 ± 7.5 mm in the X-axis, 4.9 ± 4 mm in the Y-axis and 3.6 ± 4.9 mm in the Z-axis. The front-loading system performed better than the side-loading system with corresponding mean offsets of 1.5 ± 1.5 mm vs. 10.1 ± 7.8 mm in the X-axis, 0.9 ± 1.1 mm vs. 7.2 ± 3.1 mm in the Y-axis and 4.4 ± 4.4 mm vs. 3.2 ± 5.4 mm in the Z axis, respectively. CONCLUSION Sequential PET/CT and MR imaging using dedicated patient transporter systems typically result in only sub-centimeter offsets between CT and MR data sets. Accurate correction of these patient transfer offsets using dedicated registration software was successful in all study patients. Minor shuttle system modifications can further improve registration accuracy. CLINICAL RELEVANCE/APPLICATION Sequential PET/CT and MRI acquisition using dedicated patient transporter systems allows accurate registration of multi-modality PET/CT and MR imaging data sets.

Neurobiology of Aging, 2015

Regional cerebral blood flow estimated by early [ 11 C]-PiB-uptake is reduced in mild cognitive i... more Regional cerebral blood flow estimated by early [ 11 C]-PiB-uptake is reduced in mild cognitive impairment and associated with age in an amyloid dependent manner Hock, C., Regional cerebral blood flow estimated by early [ 11 C]-PiB-uptake is reduced in mild cognitive impairment and associated with age in an amyloid dependent manner, Neurobiology of Aging (2015),

European Journal of Nuclear Medicine and Molecular Imaging, 2014

The purpose of this study was to analyze whether diffusion-weighted imaging (DWI) adds significan... more The purpose of this study was to analyze whether diffusion-weighted imaging (DWI) adds significant information to positron emission tomography/magnetic resonance imaging (PET/MRI) on lesion detection and characterization in head and neck cancers. Seventy patients with different head and neck cancers were enrolled in this prospective study. All patients underwent sequential contrast-enhanced (ce) PET/computed tomography (CT) and cePET/MRI using a tri-modality PET/CT-MR setup either for staging or re-staging. First, the DWI alone was evaluated, followed by the PET/MRI with conventional sequences, and in a third step, the PET/MRI with DWI was evaluated. McNemar&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s test was used to evaluate differences in the accuracy of PET/MRI with and without DWI compared to the standard of reference. One hundred eighty-eight (188) lesions were found, and of those, 118 (62.8%) were malignant and 70 (37.2%) were benign. PET/MRI without DWI had a higher accuracy in detecting malignant lesions than DWI alone (86.8% vs. 60.6%, p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001). PET/MRI combined with DWI detected 120 concurrent lesions (89 malignant and 31 benign), PET/MRI alone identified 48 additional lesions (20 malignant and 28 benign), and DWI alone detected 20 different lesions (nine malignant and 11 benign). However, lesions detected on DWI did not change overall staging. SUV maximum and mean were significantly higher in malignant lesions than in benign lesions. DWI parameters between malignant and benign lesions were not statistically different. The use of DWI as part of PET/MRI to evaluate head and neck cancers does not provide remarkable information. Thus, the use of DWI might not be needed in clinical PET/MRI protocols for the staging or restaging of head and neck cancers.

Pharmacology Research & Perspectives, 2015

Vemurafenib, a selective inhibitor of oncogenic BRAF kinase carrying the V600 mutation, is approv... more Vemurafenib, a selective inhibitor of oncogenic BRAF kinase carrying the V600 mutation, is approved for treatment of advanced BRAF mutation-positive melanoma. This study characterized mass balance, metabolism, rates/routes of elimination, and disposition of 14 C-labeled vemurafenib in patients with metastatic melanoma. Seven patients with metastatic BRAF-mutated melanoma received unlabeled vemurafenib 960 mg twice daily for 14 days. On the morning of day 15, patients received 14 C-labeled vemurafenib 960 mg (maximum 2.56 MBq [69.2 lCi]). Thereafter, patients resumed unlabeled vemurafenib (960 mg twice daily). Blood, urine, and feces were collected for metabolism, pharmacokinetic, and dose recovery analysis. Within 18 days after dose,~95% of 14 C-vemurafenib-related material was recovered from feces (94.1%) and urine (<1%). The parent compound was the predominant component (95%) in plasma. The mean plasma elimination half-life of 14 C-vemurafenib-related material was 71.1 h. Each metabolite accounted for <0.5% and ≤6% of the total administered dose in urine and feces, respectively (0-96 h postdose). No new metabolites were detected. Vemurafenib was well-tolerated. Excretion of vemurafenib via bile into feces is considered the predominant elimination route from plasma with minor renal elimination (<1%).

Magnetic Resonance Materials in Physics, Biology and Medicine, 2013

Tri-modality PET/CT-MRI includes the transfer of the patient on a dedicated shuttle from one syst... more Tri-modality PET/CT-MRI includes the transfer of the patient on a dedicated shuttle from one system into the other. Advantages of this system include a true CT-based attenuation correction, reliable PET-quantification and higher flexibility in patient throughput on both systems. Comparative studies of PET/MRI versus PET/CT are readily accomplished without repeated PET with a different PET scanner at a different time point. Additionally, there is a higher imaging flexibility based on the availability of three imaging modalities, which can be combined for the characterization of the disease. The downside is a somewhat higher radiation dose of up to 3 mSv with a low dose CT based on the CT-component, longer acquisition times and potential misalignment between the imaging components. Overall, the tri-modality PET/CT-MR system offers comparative studies using the three different imaging modalities in the same patient virtually at the same time, and may help to develop reliable attenuation algorithms at the same time.

Journal of Nuclear Medicine, 2014

Considering PET/MR imaging as a whole-body staging tool, scan time restrictions in a single body ... more Considering PET/MR imaging as a whole-body staging tool, scan time restrictions in a single body area are mandatory for the cost-effective clinical operation of an integrated multimodality scanner setting. It has to be considered that (18)F-FDG already acts as a contrast agent and that under certain circumstances MR contrast may not yield additional clinically relevant information. The concept of the present study was to understand which portions of the imaging information enhance the sensitivity and specificity of the hybrid examination and which portions are redundant. One hundred fifty consecutive patients referred for primary staging or restaging of head and neck cancer underwent sequential whole-body (18)F-FDG PET with CT-based attenuation correction, contrast-enhanced (ce) CT, and conventional diagnostic MR imaging of the head and neck in a trimodality PET/CT-MR system. Assessed were image quality, lesion conspicuity, diagnostic confidence, and the benefit of additional coronal and sagittal imaging planes in cePET/CT, PET/MR imaging with only T2-weighted fat-suppressed images (T2w PET/MR imaging), and cePET/MR imaging. In 85 patients with at least 1 PET-positive lesion, 162 lesions were evaluated. Similar robustness was found for CT and MR image quality. T2w PET/MR imaging performed similarly to (metastatic lymph nodes) or better than (primary tumors) cePET/CT in the morphologic characterization of PET-positive lesions and permitted the diagnosis of necrotic or cystic lymph node metastasis without application of intravenous contrast medium. CePET/MR imaging yielded a higher diagnostic confidence for accurate lesion conspicuity (especially in the nasopharynx and in the larynx), infiltration of adjacent structures, and perineural spread. The results of the present study provide evidence that PET/MR imaging can serve as a legitimate alternative to PET/CT in the clinical workup of patients with head and neck cancers. Intravenous MR contrast medium may be applied only if the exact tumor extent or infiltration of crucial structures is of concern (i.e., preoperatively) or if perineural spread is anticipated. In early assessment of the response to therapy, in follow-up examinations, or in a whole-body protocol for non-head and neck tumors, T2w PET/MR imaging may be sufficient for coverage of the head and neck. The additional MR scanning time may instead be used for advanced MR techniques to increase the specificity of the hybrid imaging examination.

The International Journal of Cardiovascular Imaging, 2012

Currently 64-multislice computed tomography (MSCT) scanners are the most widely used devices allo... more Currently 64-multislice computed tomography (MSCT) scanners are the most widely used devices allowing low radiation dose coronary CT angiography (CCTA) with prospective ECG triggering. Latest 128-slice dual-source CT (DSCT) scanners offer prospective high-pitch spiral acquisition covering the heart during one single beat. We compared radiation dose and image quality from prospective 64-MSCT versus high-pitch spiral 128-slice DSCT scanning, as such data is lacking. CCTA of 50 consecutive patients undergoing 128-DSCT (2 × 64 × 0.6 mm collimation, 0.28 s rotation time, 3.4 pitch, 100-120 kV tube voltage and 320 mAs tube current-time product) were compared to CCTA of 50 heart rate (HR) and BMI matched patients undergoing 64-MSCT (64 × 0.625 mm collimation, 0.35 s rotation time, 100-120 kV tube voltage and 400-650 mA tube current). Image quality was rated on a 4-point scale by two independent cardiac imaging physicians (1 = excellent to 4 = non-diagnostic). Of 710 coronary segments assessed on 128-DSCT, 216 (30.4%) achieved an image quality score 1 excellent, 400 (56.3%) score 2, 76 (10.7%) score 3 and 18 (2.6%) score 4 (non-diagnostic). Of 737 coronary segments evaluated on 64-MSCT 271 (36.8%) had an image quality score of 1, 327 (44.4%) 2, 110 (14.9%) score 3, and 29 (3.9%) segments score 4. Average image quality score for both scanners was similar (P = 0.641). The mean heart rate during scanning was 58.7 ± 5.6 bpm on 128-DSCT and 59.0 ± 5.6 bpm on 64-MSCT, respectively. Mean effective radiation dose was 1.0 ± 0.2 mSv for 128-DSCT and 1.7 ± 0.6 mSv for 64-MSCT (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001). 128-DSCT with high-pitch spiral mode allows CCTA acquisition with reduced radiation dose at maintained image quality compared to 64-MSCT.

European Journal of Nuclear Medicine and Molecular Imaging, 2014

European Journal of Nuclear Medicine and Molecular Imaging, 2012

Accurate attenuation correction (AC) is essential for quantitative analysis of PET tracer distrib... more Accurate attenuation correction (AC) is essential for quantitative analysis of PET tracer distribution. In MR, the lack of cortical bone signal makes bone segmentation difficult and may require implementation of special sequences. The purpose of this study was to evaluate the need for accurate bone segmentation in MR-based AC for whole-body PET/MR imaging. In 22 patients undergoing sequential PET/CT and 3-T MR imaging, modified CT AC maps were produced by replacing pixels with values of &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;100 HU, representing mostly bone structures, by pixels with a constant value of 36 HU corresponding to soft tissue, thereby simulating current MR-derived AC maps. A total of 141 FDG-positive osseous lesions and 50 soft-tissue lesions adjacent to bones were evaluated. The mean standardized uptake value (SUVmean) was measured in each lesion in PET images reconstructed once using the standard AC maps and once using the modified AC maps. Subsequently, the errors in lesion tracer uptake for the modified PET images were calculated using the standard PET image as a reference. Substitution of bone by soft tissue values in AC maps resulted in an underestimation of tracer uptake in osseous and soft tissue lesions adjacent to bones of 11.2 ± 5.4% (range 1.5-30.8%) and 3.2 ± 1.7% (range 0.2-4%), respectively. Analysis of the spine and pelvic osseous lesions revealed a substantial dependence of the error on lesion composition. For predominantly sclerotic spine lesions, the mean underestimation was 15.9 ± 3.4% (range 9.9-23.5%) and for osteolytic spine lesions, 7.2 ± 1.7% (range 4.9-9.3%), respectively. CT data simulating treating bone as soft tissue as is currently done in MR maps for PET AC leads to a substantial underestimation of tracer uptake in bone lesions and depends on lesion composition, the largest error being seen in sclerotic lesions. Therefore, depiction of cortical bone and other calcified areas in MR AC maps is necessary for accurate quantification of tracer uptake values in PET/MR imaging.

European journal of nuclear medicine and molecular imaging

EJNMMI research, 2014

Neurobiology of Aging, 2015

European Journal of Nuclear Medicine and Molecular Imaging, 2014

Pharmacology Research & Perspectives, 2015

Magnetic Resonance Materials in Physics, Biology and Medicine, 2013

Journal of Nuclear Medicine, 2014

The International Journal of Cardiovascular Imaging, 2012

European Journal of Nuclear Medicine and Molecular Imaging, 2014

European Journal of Nuclear Medicine and Molecular Imaging, 2012