Ulrike I Attenberger

Universität Mannheim, Mannheim, Baden-Württemberg, Germany

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Publications (126)262.38 Total impact

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    ABSTRACT: Objectives: To compare metal artifact reduction in MR imaging at both 3T and 1.5T using different sequence strategies. Methods: Metal implants of stainless steel screw and plate within agarose phantoms and tissue specimens as well as three patients with implants were imaged by different sequence techniques at bot 1.5T and 3T. The sequence included: View Angle Tilting (VAT), Slice Encoding for Metal Artifact Correction with VAT (SEMAC-VAT), and conventional sequence. Artifact reduction in agarose phantoms was quantitatively assessed by artifact volume measurements. Blinded reads were conducted to qualitatively in tissue specimen imaging and human imaging. Wilcoxon and Friedman test for multiple comparisons, and intraclass correlation coefficient (ICC) for inter-observer agreement were performed with a significant level of P < 0.05. Results: Compared with conventional sequences, SEMAC-VAT significantly reduced metal artifacts by 83%±9% (artifact volume: 3.8±0.8 versus 29.3±18.8 cc) for the screw and 89%±3% (30.8±9.7 versus 279.6±75.9 cc) for the plate at 1.5T; 72%±7% (17.0±10.9 versus 57.5±23.2 cc) for the screw and 38%±13% (304.4±87.9 versus 480.4±49.2 cc) for the plate at 3T (P < 0.05). In qualitative analysis, SEMAC-VAT allowed for better visualization of tissue structures adjacent to the implants and produced better overall image quality with good inter-observer agreement for both tissue specimen and human imaging (ICC = 0.80 to 0.99, P < 0.001). Besides, VAT also markedly reduced metal artifact as compared to conventional sequence, but inferior to SEMAC-VAT. Conclusions: SEMAC-VAT and VAT techniques effectively reduce artifact from metal implants relative to conventional imaging at both 1.5T and 3T. Advances in Knowledge: 1. The feasibility of metal artifact reduction with SEMAC-VAT was demonstrated at 3T MR. 2. SEMAC-VAT significantly reduced metal artifact at both 1.5T and 3T. 3. SEMAC-VAT allowed for better visualization of the tissue structures adjacent to the metal implants. 4. SEMAC-VAT produced consistently better image quality in both tissue specimen and human imaging.
    British Journal of Radiology 01/2015; 88(1048):20140601. DOI:10.1259/bjr.20140601 · 1.53 Impact Factor
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    ABSTRACT: To evaluate the feasibility of zoomed diffusion-weighted EPI (z-EPI) in the head and neck in a healthy volunteer population and to compare to conventional single-shot EPI (c-EPI). Nine volunteers were included in this prospective, IRB-approved study. Examinations were performed on a 3 T-MR system equipped with a two-channel, fully-dynamic parallel transmit array. The acquired sequences consisted of a T2w-TSE, a c-EPI, and two z-EPI acquisitions. For quantitative assessment of distortion artefacts, DW images were fused with T2-TSE images. Misregistration of DW images with T2-TSE images was assessed in the cervical spine. For qualitative assessment, two readers ranked c-EPI and z-EPI sequences in terms of susceptibility artefacts, image blur, and overall imaging preference. ADC values of several anatomical regions were calculated and compared between sequences. Mean maximum distortion with the c-EPI was 5.9 mm +/- 1.6 mm versus 2.4 mm +/- 1 mm (p < 0.05) with z-EPI. Both readers found more blur and susceptibility artefacts in every case with c-EPI. No statistically significant differences in calculated ADC values were observed. z-EPI of the head and neck leads to substantial image quality improvements relative to c-EPI due to a reduction in susceptibility artefacts and image blur. aEuro cent Zoomed DWI is feasible in the head and neck. aEuro cent Image quality improves substantially with zoomed DWI of the neck. aEuro cent Zoomed DWI exhibits markedly reduced susceptibility artefacts.
    European Radiology 07/2014; 24(10). DOI:10.1007/s00330-014-3287-6 · 4.34 Impact Factor
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    ABSTRACT: Purpose The purpose of this study is two-fold. First, to evaluate, whether functional rectal MRI techniques can be analyzed in a reproducible manner by different readers and second, to assess whether different clinical and pathologic T and N stages can be differentiated by functional MRI measurements. Material and Methods 54 patients (38 men, 16 female; mean age 63.2 ± 12.2 years) with pathologically proven rectal cancer were included in this retrospective IRB-approved study. All patients were referred for a multi-parametric MRI protocol on a 3 Tesla MR-system, consisting of a high-resolution, axial T2 TSE sequence, DWI and perfusion imaging (plasma flow - PFTumor) prior to any treatment. Two experienced radiologists evaluated the MRI measurements, blinded to clinical data and outcome. Inter-reader correlation and the association of functional MRI parameters with c- and p-staging were analyzed. Results The inter-reader correlation for lymph node (ρ 0.76-0.94; p < 0.0002) and primary tumor (ρ 0.78- 0.92; p < 0.0001) apparent diffusion coefficient and plasma flow (PF) values was good to very good. PFTumor values decreased with cT stage with significant differences identified between cT2 and cT3 tumors (229 versus 107.6 ml/100 ml/min; p = 0.05). ADCTumor values did not differ significantly. No substantial discrepancies in lymph node ADCLn values or short axis diameter were found among cN1-3 stages, whereas PFLn values were distinct between cN1 versus cN2 stages (p = 0.03). In the patients without neoadjuvant RCT no statistically significant differences in the assessed functional parameters on the basis of pathologic stage were found. Conclusion This study illustrates that ADC as well as MR perfusion values can be analyzed with good interobserver agreement in patients with rectal cancer. Moreover, MR perfusion parameters may allow accurate differentiation of tumor stages. Both findings suggest that functional MRI parameters may help to discriminate T and N stages for clinical decision making.
    European journal of radiology 07/2014; 83(7). DOI:10.1016/j.ejrad.2014.03.012 · 2.16 Impact Factor
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    ABSTRACT: To evaluate the impact of computed b = 1400 s/mm(2) (C-b1400) vs measured b = 1400 s/mm(2) (M-b1400) diffusion-weighted images (DWI) on lesion detection rate, image quality and quality of lesion demarcation using a modern 3T-MR system based on a small-field-of-view sequence (sFOV).
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    ABSTRACT: Purpose To compare enhancement characteristics and image quality of two macrocyclic gadolinium chelates, gadoterate meglumine and gadobutrol, in low-dose, time-resolved MRA of the calf station. Materials and Methods 100 consecutive patients with peripheral arterial disease (stages II-IV) were retrospectively analysed. Fifty patients were included in each group - 32 men and 18 women for gadobutrol (mean age 67 years) and 34 men, 16 women for gadoterate meglumine (mean age 64 years). 0.03 mmol/kg bw of either gadobutrol or gadoterate meglumine was injected. Gadobutrol was diluted 1∶1 with normal saline (0.9% NaCl) to provide similar injection volume and bolus geometry compared to the undiluted 0.5 M dose of gadoterate meglumine. Signal-to-noise-ratio (SNR), contrast-to-noise-ratio (CNR) and image quality were analysed and compared between the two groups. Results Mean SNR ranged from 83.0±46.7 (peroneal artery) to 96.4±64.5 (anterior tibial artery) for gadobutrol, and from 37.6±13.8 (peroneal artery) to 45.3±16.4 (anterior tibial artery) for the gadoterate meglumine group (p<0.0001). CNR values ranged from 30.1±20.1 (peroneal artery) to 37.6±26.0 (anterior tibial artery) for gadobutrol and from 14.9±8.0 (peroneal artery) to 18.6±16.4 (anterior tibial artery) for gadoterate meglumine (p<0.0001). No significant difference in image quality was found except for the peroneal arteries (p = 0.006 and p = 0.04). Interreader agreement was excellent (kappa 0.87–0.93) Conclusion The significantly better enhancement as assessed by SNR and CNR provided by gadobutrol compared to gadoterate meglumine does not translate into substantial differences in image quality in an equimolar, low-dose, time-resolved MRA protocol of the calves.
    PLoS ONE 06/2014; 9(6):e99079. DOI:10.1371/journal.pone.0099079 · 3.53 Impact Factor
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    ABSTRACT: To evaluate the diagnostic accuracy of a nonenhanced electrocardiograph-gated quiescent-interval single shot MR-angiography (QISS-MRA) at 3 Tesla with contrast-enhanced MRA (CE-MRA) and digital subtraction angiography (DSA) serving as reference standard. Following institutional review board approval, 16 consecutive patients with peripheral arterial disease underwent a combined peripheral MRA protocol consisting of a large field-of-view QISS-MRA, continuous table movement MRA, and an additional time-resolved MRA of the calves. DSA correlation was available in eight patients. Image quality and degree of stenosis was assessed. Sensitivity and specificity of QISS-MRA was evaluated with CE-MRA and DSA serving as the standards of reference and compared using the Fisher exact test. With the exception of the calf station, image quality with QISS-MRA was rated statistically significantly less than that of CE-MRA (P < 0.05, P = 0.17, and P = 0.6, respectively). A greater percentage of segments were not accessible with QISS-MRA (19.5-20.1%) in comparison to CE-MRA (10.9%). Relative to DSA, sensitivity for QISS-MRA was high (100% versus 91.2% for CE-MRA, P = 0.24) in the evaluated segments; however, specificity (76.5%) was substantially less than that of CE-MRA (94.6%, P = 0.003). Overall image quality and specificity of QISS-MRA at 3T are diminished relative to CE-MRA. However, when image quality is adequate, QISS-MRA has high sensitivity and, thus, has potential use in patients with contraindications to gadolinium. J. Magn. Reson. Imaging 2013. © 2013 Wiley Periodicals, Inc.
    Journal of Magnetic Resonance Imaging 06/2014; 39(6). DOI:10.1002/jmri.24324 · 2.79 Impact Factor
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    ABSTRACT: After allogeneic stem cell transplantation (SCT), a reliable diagnosis of acute graft versus host disease (aGvHD) is essential for an early and successful treatment. It is the aim of this analysis to assess intestinal aGvHD by magnetic resonance imaging (MRI). Prior to allogeneic SCT, 64 consecutive patients underwent abdominal MRI examination on a 3 T MR system, including axial and coronal T2w sequences and a three-dimensional dynamic T1w, contrast enhanced sequence. After SCT, 20 patients with suspected aGvHD received a second MRI as well as an endoscopic examination. Nine patients suffered from histologically proven intestinal aGvHD. In eleven patients intestinal aGvHD was excluded. In all aGvHD patients typical MRI findings with long-segment bowel wall thickening - always involving the terminal ileum - with profound submucosal oedema, were detected. The bowel wall was significantly thickened in patients with intestinal aGvHD. Bowel contrast enhancement spared the submucosa while demonstrating strong mucosal hyperemia. In intestinal aGvHD, a characteristic MR-appearance can be detected. This MRI pattern might facilitate an early and non-invasive diagnosis of intestinal aGvHD. MRI might thus be used as a sensitive tool to rule out or support the clinical diagnosis of aGvHD. aEuro cent Acute intestinal graft versus host disease (aGvHD) can be assessed by MRI. aEuro cent The aGvHD of the bowel demonstrates a characteristic MR imaging pattern. aEuro cent Bowel wall shows extensive long-segment wall thickening with profound submucosal oedema. aEuro cent Terminal ileum seems invariably affected; other bowel segments show variable involvement. aEuro cent Colonoscopy in suspected aGvHD should include inspection of terminal ileum.
    European Radiology 05/2014; 24(8). DOI:10.1007/s00330-014-3224-8 · 4.34 Impact Factor
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    ABSTRACT: Implementation of DWI in the abdomen is challenging due to artifacts, particularly those arising from differences in tissue susceptibility. Two-dimensional, spatially-selective radiofrequency (RF) excitation pulses for single-shot echo-planar imaging (EPI) combined with a reduction in the FOV in the phase-encoding direction (i.e. zooming) leads to a decreased number of k-space acquisition lines, significantly shortening the EPI echo train and potentially susceptibility artifacts. To assess the feasibility and image quality of a zoomed diffusion-weighted EPI (z-EPI) sequence in MR imaging of the pancreas. The approach is compared to conventional single-shot EPI (c-EPI). 23 patients who had undergone an MRI study of the abdomen were included in this retrospective study. Examinations were performed on a 3T whole-body MR system (Magnetom Skyra, Siemens) equipped with a two-channel fully dynamic parallel transmit array (TimTX TrueShape, Siemens). The acquired sequences consisted of a conventional EPI DWI of the abdomen and a zoomed EPI DWI of the pancreas. For z-EPI, the standard sinc excitation was replaced with a two-dimensional spatially-selective RF pulse using an echo-planar transmit trajectory. Images were evaluated with regard to image blur, respiratory motion artifacts, diagnostic confidence, delineation of the pancreas, and overall scan preference. Additionally ADC values of the pancreatic head, body, and tail were calculated and compared between sequences. The pancreas was better delineated in every case (23/23) with z-EPI versus c-EPI. In every case (23/23), both readers preferred z-EPI overall to c-EPI. With z-EPI there was statistically significantly less image blur (p<0.0001) and respiratory motion artifact compared to c-EPI (p<0.0001). Diagnostic confidence was statistically significantly better with z-EPI (p<0.0001). No statistically significant differences in calculated ADC values were observed between the two sequences. Zoomed diffusion-weighted EPI leads to substantial image quality improvements with reduction of susceptibility artifacts in pancreatic DWI.
    PLoS ONE 03/2014; 9(3):e89468. DOI:10.1371/journal.pone.0089468 · 3.53 Impact Factor
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    ABSTRACT: Stereotactic Ablative RadioTherapy (SABR) of lung tumors/metastases has been shown to be an effective treatment modality with low toxicity. Outcome and toxicity were retrospectively evaluated in a unique single-institution cohort treated with intensity-modulated image-guided breath-hold SABR (igSABR) without external immobilization. The dose-response relationship is analyzed based on Biologically Equivalent Dose (BED).Patients and methods: 50 lesions in 43 patients with primary NSCLC (n = 27) or lung-metastases of various primaries (n = 16) were consecutively treated with igSABR with Active-Breathing-Coordinator (ABC(R)) and repeat-breath-hold cone-beam-CT. After an initial dose-finding/-escalation period, 5x12Gy for peripheral lesions and single doses of 5Gy to varying dose levels for central lesions were applied. Overall-survival (OS), progression-free-survival (PFS), progression pattern, local control (LC) and toxicity were analyzed. The median BED2 was 83Gy. 12 lesions were treated with a BED2 of <80Gy, and 38 lesions with a BED2 of >80Gy. Median follow-up was 15 months. Actuarial 1- and 2-year OS were 67% and 43%; respectively. Cause of death was non-disease-related in 27%. Actuarial 1- and 2-year PFS was 42% and 28%. Progression site was predominantly distant. Actuarial 1- and 2year LC was 90% and 85%. LC showed a trend for a correlation to BED2 (p = 0.1167). Pneumonitis requiring conservative treatment occurred in 23%. Intensity-modulated breath-hold igSABR results in high LC-rates and low toxicity in this unfavorable patient cohort with inoperable lung tumors or metastases. A BED2 of <80Gy was associated with reduced local control.
    Radiation Oncology 01/2014; 9(1):10. DOI:10.1186/1748-717X-9-10 · 2.36 Impact Factor
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    ABSTRACT: PURPOSE To evaluate the diagnostic accuracy of a non-enhanced ECG-gated quiescent-interval single shot MR-Angiography (QISS-MRA) at 3T with contrast-enhanced MRA (CE-MRA) and digital subtraction angiography (DSA) serving as the standard of reference. METHOD AND MATERIALS 16 consecutive patients (9 male,7 female, mean age 70±12 years) with peripheral arterial disease stages II-IV underwent a combined peripheral MRA protocol consisting of a large field-of-view QISS-MRA (acquisition time 18 min), continuous-table-movement MRA (acquisition time 62 sec), and an additional time-resolved MRA (acquisition time 96 sec) of the calves. DSA correlation was available in 8 patients. Image quality and degree of stenosis was assessed. Sensitivity and specificity of QISS-MRA was evaluated with CE-MRA and DSA serving as the standards of reference by two readers. RESULTS 328 total segments were assessed. Overall sensitivity and specificity were, respectively, 81.1% and 83.5% for QISS-MRA vs CE-MRA. Relative to DSA, sensitivity for QISS-MRA was high (100% versus 91.2% for CE-MRA) in the evaluated segments; however, specificity was substantially less than that of CE-MRA (76.5% vs 94.6%, p<0.0001). There was no significant difference in image quality between QISS-MRA and CE-MRA at the calf station (p=0.17). For the vasculature of the pelvis and thigh QISS-MRA was rated significantly lower compared to CE-MRA (p<0.0001 for both). Interreader agreement was very good for both QISS-MRA and CE-MRA (kappa=0.83 and 0.96 respectively). CONCLUSION Overall image quality and specificity of QISS-MRA at 3T are diminished relative to CE-MRA, potentially due to long acquisition times. However, when image quality is adequate, the high sensitivity of QISS-MRA may render it useful as a screening examination in patients with contraindications to gadolinium chelate administration. CLINICAL RELEVANCE/APPLICATION Due to its high sensitivtiy at 3 Tesla, QISS might serve as screening tool to rule out significant stenoses in patients with impaired renal function.
    A Comparison with Contrast-enhanced MRA and DSA. Radiological Society of North America 2013 Scientific Assembly and Annual Meeting; 12/2013
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    ABSTRACT: PURPOSE To determine the value of dynamic pelvic floor MRI relative to standard clinical examinations in treatment decisions made by an interdisciplinary team of specialists in a center for pelvic floor dysfunction METHOD AND MATERIALS 60 women were included in this IRB approved retrospective analysis. All patients were referred for dynamic pelvic floor MRI by an interdisciplinary team of specialists of a pelvic floor center. All patients were clinically examined by an urologist, gynecologist, a proctological and colorectal surgeon. The specialists assessed individually and in consensus, whether (1) MRI provides important additional information not evident by physical examination and in consensus whether (2) MRI influenced the treatment strategy and/or (3) changed management or the surgical procedure. RESULTS MRI was rated essential in the treatment decisions of 22/50 cases, leading to a treatment change in 13 cases. In 12 cases, an enterocele was diagnosed by MRI but was not detected on physical exam. In 4 cases an enterocele and in 2 cases a rectocele were suspected clinically but not confirmed by MRI. In 4 cases, MRI proved critical in assessment of rectocele size. Vaginal intussusception detected on MRI was likewise missed by gynecologic exam in 1 case. CONCLUSION MRI allows diagnosis of clinically occult enteroceles, by comprehensively evaluating the interaction between the pelvic floor and viscera. In nearly half of cases, MRI changed management or the surgical approach relative to the clinical evaluation of an interdisciplinary team. Thus, dynamic pelvic floor MRI represents an essential component of the evaluation for pelvic floor disorders. CLINICAL RELEVANCE/APPLICATION In an interdisciplinary center for pelvic floor disorders dynamic pelvic floor MRI leads to a significant change in clinical management
    Radiological Society of North America 2013 Scientific Assembly and Annual Meeting; 12/2013
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    ABSTRACT: PURPOSE To evaluate the clinical utility of diffusion-weighted-imaging (DWI) of the abdomen with ultra-high b-values. METHOD AND MATERIALS In this retrospective IRB approved study 46 consecutive patients (30 women, 16 men, mean age 54±17.5) who underwent abdominal MR-exams including a DWI-EPI sequence with b-values of 50, 800 and 2000 s/mm2 on a 3T MRI-system (Siemens Skyra) were included. Overall image quality with regard to detection of pathology and degree of artifacts as well as lesion conspicuity in the b800 and b2000 images were compared by two board-certified radiologists (1: preferring b2000; 2: preferring b800; 0: no difference). Quantitative analysis included determination of signal-to-noise ratio of sample tissues including the kidneys and the ventral and dorsal subcutaneous fat. RESULTS Reader 1 preferred the b2000 image in 30 (67%) patients, reader 2 in 32 (71%) patients. The b800 image was preferred in only 2 (4%) patients by both readers. Interobserver agreement was k=.706 for overall image quality. Lesion conspicuity was rated better in the b2000 images in 31 (69%) patients and the b800 images in 1 (2%) patient by reader 1, in 27 (60%) and 2 patients (4%) by reader 2. Measure of agreement was k=.494 for lesion conspicuity. There were no differences observed regarding artifacts. The signal-to-noise ratio measured 37.47 (±14.96) vs. 15.74 (±4.07) and 41.46 (±16.21) vs. 16.90 (±5.52) in the b800 and b2000-images for the left and right kidney, 9.22 (±3.18) vs. 12.05 (±3.75) and 9.80 (±2.52) vs. 12.14 (±2.93) for the ventral and dorsal fat, respectively. CONCLUSION DWI imaging of the abdomen with ultra-high b-values of 2000 s/mm2 is feasible for lesion detection with good to acceptable image quality. CLINICAL RELEVANCE/APPLICATION Ultra-high b-values should be used in a clinical routine as a feasible tool for lesion detection.
    Radiological Society of North America 2013 Scientific Assembly and Annual Meeting; 12/2013
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    ABSTRACT: PURPOSE Although 3T is proven to be superior to 1.5T for the detection of prostate cancer due to the higher intrinsic SNR, distortion artifacts arising from strong local susceptibility differences related to the vicinity to the air-filled rectum are more pronounced. Small FOV imaging strategies were recently introduced to overcome these shortcomings, based on the use of 2d radiofrequency excitation pulses for the excitation of a small volume of the prostate region only. The purpose of this study was to evaluate the impact of small-field computed b=1400 s/mm2 (b1400) vs measured b=1400 s/mm2 diffusion-weighted images (DWI) on lesion detection rate, image quality and quality of lesion demarcation. METHOD AND MATERIALS 30 patients (median PSA: 9,5 ng/ml ± 8,7) were enrolled. All measurements were performed on a 3T whole-body MR system (Verio, Siemens Healthcare, Erlangen, Germany). For DWI, a single-shot epi diffusion (EPI) sequence (TR/TE, FA, b= 0, 100, 400, 800 s/mm²) was utilized. ADC-values were calculated from diffusion images with a b-value ≥100 s/mm2. The computed b-1400 (C-b1400) was calculated pixelwise from the ADC and diffusion images. Additionally, a measured b1400 (M-b1400) sequence (TE/TR= 73/4400ms) was acquired for comparison. Lesion detection rate and maximum lesion diameters were obtained and compared. Image quality and quality of lesion demarcation were rated according to a 5-point Likert-type scale. Ratios of lesion-to-bladder as well as prostate-to-bladder signal intensity (SI) were calculated to estimate the signal-to-noise-ratio (SNR) of the C- and M b-1400 images. RESULTS 27 lesions were detected on the C-b1400 images, whereas 24 lesions were detected on the M-b1400 images (p=0.08). Overall image quality was rated significantly better and SI ratios were significantly higher on C-b1400 (2.3±0.8 vs 3.1±1.0, p<0.001; 5.6±1.8 s 2.8±0.9, p<0.001) compared to M-b1400 images. However, comparison of lesion size showed no significant differences between C- and M-b1400 (M-b1400: 16.9 ± 10.0; C-b1400: 17.7 ± 10.0; p=0.22). CONCLUSION Calculation of an ultra-high b-value image may contribute to increase diagnostic accuracy of DWI due to an improved signal-to-noise ratio and image quality compared to a measured ultra-high b-value image. CLINICAL RELEVANCE/APPLICATION Computed ultra-high b-values may contribute to increase diagnostic accuracy of DWI without an increase of acquisition time or loss of the overall SNR
    Measured High B-Value (1400 s/mm²) Diffusion-weighted MR Images of the Prostate Using a Small Field-of-View Diffusion Imaging Protocol At 3T. Radiological Society of North America 2013 Scientific Assembly and Annual Meeting; 12/2013
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    ABSTRACT: OBJECTIVE. The purpose of this article is to evaluate the added diagnostic accuracy of time-resolved MR angiography (MRA) of the calves compared with continuous-table-movement MRA in patients with symptomatic lower extremity peripheral artery disease (PAD) using digital subtraction angiography (DSA) correlation. MATERIALS AND METHODS. Eighty-four consecutive patients with symptomatic PAD underwent a low-dose 3-T MRA protocol, consisting of continuous-table-movement MRA, acquired from the diaphragm to the calves, and an additional time-resolved MRA of the calves; 0.1 mmol/kg body weight (bw) of contrast material was used (0.07 mmol/kg bw for continuous-table-movement MRA and 0.03 mmol/kg bw for time-resolved MRA). Two radiologists rated image quality on a 4-point scale and stenosis degree on a 3-point scale. An additional assessment determined the degree of venous contamination and whether time-resolved MRA improved diagnostic confidence. The accuracy of stenosis gradation with continuous-table-movement and time-resolved MRA was compared with that of DSA as a correlation. Overall diagnostic accuracy was calculated for continuous-table-movement and time-resolved MRA. RESULTS. Median image quality was rated as good for 578 vessel segments with continuous-table-movement MRA and as excellent for 565 vessel segments with time-resolved MRA. Interreader agreement was excellent (κ = 0.80-0.84). Venous contamination interfered with diagnosis in more than 60% of continuous-table-movement MRA examinations. The degree of stenosis was assessed for 340 vessel segments. The diagnostic accuracies (continuous-table-movement MRA/time-resolved MRA) combined for the readers were obtained for the tibioperoneal trunk (84%/93%), anterior tibial (69%/87%), posterior tibial (85%/91%), and peroneal (67%/81%) arteries. The addition of time-resolved MRA improved diagnostic confidence in 69% of examinations. CONCLUSION. The addition of time-resolved MRA at the calf station improves diagnostic accuracy over continuous-table-movement MRA alone in symptomatic patients with PAD.
    American Journal of Roentgenology 12/2013; 201(6):1368-1375. DOI:10.2214/AJR.13.10584 · 2.74 Impact Factor
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    ABSTRACT: Die klinische Implementierung der neuen Hybridtechnologie MR-Positronenemissionstomographie (MR-PET) bietet durch die Kombination aus hochauflösender Morphologie, Funktion und Metabolismus bisher ungeahnte diagnostische Möglichkeiten, die nicht nur für die Diagnose und die Verlaufskontrolle onkologischer und psychiatrischer Erkrankungen von hoher Bedeutung sind. Verglichen mit der PET-CT wird dies mit reduzierter Strahlenbelastung für den Patienten möglich, was wiederum insbesondere für Patienten in der Tumornachsorge, die wiederholte Untersuchungen durchlaufen müssen, und pädiatrische Patienten relevant ist.Dabei können jedoch die Erfahrungen, die im Verlauf der letzten Jahre mit der Hybridtechnologie PET-CT gewonnen wurden, nicht direkt auf die MR-PET übertragen werden. Ein wesentliches Beispiel hierfür ist die Schwächungskorrektur, für die in der PET-CT die mittels CT bestimmten Hounsfield-Einheiten verwendet werden. Da die in der PET emittierten 511-keV-Photonen durch das Körpergewebe des Patienten geschwächt werden, werden die CT-Datensätze in sog. lineare Schwächungskoeffizienten (,,linear attenuation coefficients“, LAC) konvertiert. Da die Bilddatenakquisition in der MRT nicht auf einer Schwächung von Röntgenstrahlung, sondern einer Messung der Protonendichte und von gewebespezifischen Relaxationszeiten basiert, müssen in der MR-PET alternative Verfahren zur Schwächungskorrektur eingesetzt werden. Darüber hinaus bietet die MRT auch alternative Sequenz- und Akquisitionstechnologien, die es erlauben, bisherige Limitationen z. B. bzgl. der Bewegungskorrektur zu adressieren.Dieser Artikel berichtet über initiale klinische Erfahrungen mit einem voll integrierten MR-PET-System, wobei MR-Techniken zur Korrektur von Bewegungsartefakten, die Schwächungskorrektur und die Reduktion von Metallartefakten im Zentrum stehen.
    Der Radiologe 12/2013; 53(12). DOI:10.1007/s00117-013-2559-5 · 0.41 Impact Factor
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    ABSTRACT: To evaluate the efficacy of microwave ablation for osteoid osteomas by using dynamic contrast-enhanced magnetic resonance (MR) imaging in early treatment assessment. Ten patients (two female, eight male; mean age, 28 y; range, 16-47 y) presenting with osteoid osteomas were treated between June 2010 and December 2012 with the use of computed tomography (CT)-guided microwave ablation. Osteoid osteomas were found at the femoral neck (n = 4), tibia (n = 3), calcaneus (n = 1), navicular bone (n = 1), and dorsal rib (n = 1). Dynamic contrast-enhanced MR imaging at 3.0 T was performed 1 day before microwave ablation and again after ablation. The procedure was considered successful if the signal intensity (SI) of the lesion on MR imaging decreased by at least 50% and the patient was pain-free within 1 week of intervention. All patients were pain-free within 1 week after microwave ablation and remained so during the 6 months of follow-up. No major or minor complications developed. On average, SI of the lesions decreased by 75% (range, 55.5%-89.1%) after treatment. The difference in lesion SI before versus after ablation was significant by t test (P < .0001; confidence interval, 120.26-174.96) and Wilcoxon test (P = .0020). Microwave ablation treatment of osteoid osteoma was highly successful, without any complications observed. Dynamic contrast-enhanced MR imaging is a useful tool for diagnosing osteoid osteoma and evaluating treatment.
    Journal of vascular and interventional radiology: JVIR 11/2013; 25(1). DOI:10.1016/j.jvir.2013.09.009 · 2.15 Impact Factor
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    ABSTRACT: The unparalleled soft tissue contrast of magnetic resonance imaging (MRI) and the functional information obtainable with 18-F fluorodeoxyglucose positron emission tomography (FDG-PET) render MR-PET well-suited for oncological and psychiatric imaging. The lack of ionizing radiation with MRI also makes MR-PET a promising modality for oncology patients requiring frequent follow-up and pediatric patients. Lessons learned with PET computed tomography (CT) over the last few years do not directly translate to MR-PET. For example, in PET-CT the Hounsfield units derived from CT are used for attenuation correction (AC). As 511 keV photons emitted in PET examinations are attenuated by the patient's body CT data are converted directly to linear attenuation coefficients (LAC); however, proton density measured by MRI is not directly related to the radiodensity or LACs of biological tissue. Thus, direct conversion to LAC data is not possible making AC more challenging in simultaneous MRI-PET scanning. In addition to these constraints simultaneous MRI-PET acquisitions also improve on some solutions to well-known challenges of hybrid imaging techniques, such as limitations in motion correction. This article reports on initial clinical experiences with simultaneously acquired MRI-PET data, focusing on the potential benefits and limitations of MRI with respect to motion correction as well as metal and attenuation correction artefacts.
    Der Radiologe 11/2013; · 0.41 Impact Factor
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    ABSTRACT: Image quality (IQ) of PET in voluminous body regions can be limited, which impairs the assessment of small metastatic lesions. Time-of-flight (TOF) reconstruction algorithm may deliver an increase of spatial resolution. The purpose of this study was to evaluate the impact of TOF on IQ, lesion detection rate, lesion volume (V) and SUVmax in F choline PET/CT of prostate cancer patients with biochemical recurrence compared to standard PET/CT reconstruction (standard). During a period of 9 months, 32 patients with prostate cancer (mean [SD] age, 71 [7.8] years) and biochemical recurrence were included in this prospective institutional review board-approved study. Each patient underwent a state-of-the-art 3-dimensional F choline PET/CT. A total of 76 lesions were assessed by 2 board-certified nuclear medicine physicians and a third-year resident. Lesion volume and SUVmax of local recurrence, lymph nodes, and organ metastases were compared between TOF and standard. Image quality and lesion demarcation were rated according to a 5-point Likert-type scale. Interobserver agreement was assessed. Eight additional lesions were detected using TOF (SUVmax, 3.64 [0.95]; V, 0.58 cm [0.50]). Image quality was reduced (IQ standard, 1.28; TOF, 1.77; P < 0.01) in calculated TOF images, although quality of lesion demarcation was improved (lesion demarcation: standard, 1.66; TOF, 1.26; P < 0.01). SUVmax was significantly increased in TOF images (SUVmax standard, 6.9 [4.1]; TOF, 8.1 [4.1]; P < 0.01), whereas V did not show significant differences (V standard, 5.3 [10.4] cm; TOF, 5.4 [10.3] cm; P = 0.41). Interobserver agreement was good for combined ratings (1 + 2 and 3 + 4). Application of TOF seems to be of additional value to detect small metastatic lesions in patients with prostate cancer and biochemical recurrence, which may have further clinical implications for secondary treatment.
    Clinical nuclear medicine 10/2013; DOI:10.1097/RLU.0b013e3182a23d37 · 2.86 Impact Factor
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    ABSTRACT: To evaluate the diagnostic accuracy of 3Tesla proton MRI for the assessment of pneumonia/lung infiltrates in neutropenic patients with acute myeloid leukemia. In a prospective study, 3Tesla MRI was performed in 19 febrile neutropenic patients (5 women, 14 men; mean age 61 years±14.2; range 23-77 years). All patients underwent high-resolution CT less than 24h prior to MRI. The MRI protocol (Magnetom Tim Trio, Siemens) included a T2-weighted HASTE sequence (TE/TR: 49ms/∞, slice thickness 6mm) and a high-resolution 3D VIBE sequence with an ultra-short TE<1ms (TE/TR 0.8/2.9ms, slice thickness 2mm). The VIBE sequence was examined before and after intravenous injection of 0.1mmol/kg gadoterate meglumine (Dotarem, Guerbet). The presence of pulmonary abnormalities, their location within the lung, and lesion type (nodules, consolidations, glass opacity areas) were analyzed by one reader and compared to the findings of HRCT, which was evaluated by a second independent radiologist who served as the reference standard. The findings were compared per lobe in each patient and rated as true positive (TP) findings if all three characteristics (presence, location, and lesion type) listed above were concordant to HRCT. Pulmonary abnormalities were characterized by 3Tesla MRI with a sensitivity of 82.3% and a specificity of 78.6%, resulting in an overall accuracy of 88% (NPV/PPV 66.7%/89.5%). In 51 lobes (19 of 19 patients), pulmonary abnormalities visualized by MR were judged to be concordant in their location and in the lesion type identified by both readers. In 22 lobes (11 of 19 patients), no abnormalities were present on either MR or HRCT (true negative). In 6 lobes (5 of 19 patients), ground glass opacity areas were detected on MRI but were not visible on HRCT (false positives). In 11 lobes (7 of 19 patients), MRI failed to detect ground glass opacity areas identified by HRCT. However, since the abnormalities were disseminated in these patients, accurate treatment decisions were possible in every case based on MRI. In one case MRI showed a central area of cavitation, which was not visualized by HRCT. Infectious nodules and consolidations can be detected in neutropenic patients with acute myeloid leukemia with a sufficient diagnostic accuracy by 3Tesla MRI. Detection of ground glass opacity areas is the main limitation of 3-Tesla MRI when compared to HRCT.
    European journal of radiology 09/2013; 83(1). DOI:10.1016/j.ejrad.2013.09.002 · 2.16 Impact Factor
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    ABSTRACT: To compare the image quality and diagnostic confidence of low-dose computed tomography (CT) of urololithiasis using filtered back projection (FBP) and iterative reconstruction techniques (IRT). A 4.8 × 4.3 × 5.2 mm(3) uric acid ureteral stone was placed inside an anthropomorphic Alderson phantom at the pelvic level. Fifteen scans were performed on a 64-row dual-source CT system using different tube voltages (80, 100, and 120 kV) and current-time products (8, 15, 30, 70, and 100 mAs). Image reconstruction using FBP and IRT (iterative reconstruction in image space) resulted in 30 data sets. Objective image quality was evaluated by noise measurements. Effective doses were estimated for each data set with use of an established dosimetry program. Subjective image quality and confidence level were rated by two radiologists. Noise was systematically lower for images reconstructed with IRT compared to FBP (55 ± 30 vs 65 ± 26 Hounsfield units; P = .004) for volume CT dose index values above about 0.6 mGy (or an effective dose of about 0.4 mSv for both sexes). For the 14 scans rated to have diagnostic image quality, the estimated effective doses ranged from 0.3 to 2.5 mSv for males and from 0.4 to 3.1 mSv for females. Subjective image quality and diagnostic confidence for IRT was not significantly better than those for FBP. In a phantom study for CT of urolithiasis, IRT improves objective image quality compared to FBP above a certain dose threshold. However, this does not translate into improved subjective image quality or a higher degree of confidence for the diagnosis of high-contrast urinary stones.
    Academic radiology 09/2013; 20(9):1162-7. DOI:10.1016/j.acra.2013.06.004 · 2.08 Impact Factor

Publication Stats

792 Citations
262.38 Total Impact Points


  • 2014
    • Universität Mannheim
      Mannheim, Baden-Württemberg, Germany
  • 2009–2014
    • Universität Heidelberg
      • • Faculty of Medicine Mannheim and Clinic Mannheim
      • • Department of Nuclear Medicine
      • • Institute of Clinical Radiology
      Heidelburg, Baden-Württemberg, Germany
    • Scott & White
      Temple, Texas, United States
  • 2010–2012
    • Universitätsklinikum Freiburg
      Freiburg an der Elbe, Lower Saxony, Germany
  • 2004–2010
    • Ludwig-Maximilian-University of Munich
      • Department of Clinical Radiology
      München, Bavaria, Germany