Publications by authors named "Philipp Riffel"

38 Publications

Low risk of contrast media induced hypersensitivity reactions in all subtypes of systemic mastocytosis.

Ann Allergy Asthma Immunol 2021 Oct 9. Epub 2021 Oct 9.

Clinic of Clinical Radiology and Nuclear Medicine, University Hospital Mannheim, Heidelberg University, Mannheim, Germany. Electronic address:

Background: Patients with SM are at increased risk of hypersensitivity reactions. Although hymenoptera venoms are the predominant triggers, cases of CMIHR have also been reported and prophylactic premedication is often performed. However, data from larger series are limited and differences between indolent and advanced systemic mastocytosis have not yet been investigated.

Objective: To determine the incidence and severity of CMIHR in all subtypes of SM.

Methods: We analyzed 162 adult patients with SM (ISM, n=65; advSM, n=97). Firstly, the cumulative incidence of CMIHR was retrospectively assessed in the patient's history. Secondly, at our institution, patients underwent 332 CM-enhanced imagings including 80 CT scans with iodine-based contrast agent and 252 MRI with gadoliniumbased contrast agent and tolerance was assessed.

Results: Previous CMIHRs to CT (vomiting, n=1, erythema, n=1, cardiovascular shock, n=1) and MRI (dyspnea, n=1, cardiovascular shock, n=1) had been reported by 4/162 (2.5%) patients (ISM, n=3; advSM, n=1). In contrast, during or after 332 CM-enhanced CT/MRI examinations at our institution, no CMIHRs were reported. Premedication was solely given to 3 patients prior to CT scans, including one with previous CMIHR, who tolerated the imaging well.

Conclusion: We conclude that i) there is a significant discrepancy between perception and prevalence of hypersensitivity reactions to CM in SM, ii) reactions are scarce in ISM and even rarer in advSM, iii) in SM patients without previous history of CM hypersensitivity, prophylactic premedication prior to CM enhanced-CT/MRI is dispensable.
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http://dx.doi.org/10.1016/j.anai.2021.10.004DOI Listing
October 2021

T2-weighted Imaging of the Breast at 1.5T Using Simultaneous Multi-slice Acceleration.

Anticancer Res 2021 Sep;41(9):4423-4429

Clinic of Radiology and Nuclear Medicine, University Medical Centre Mannheim, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany.

Aim: To evaluate the image quality and time saving using simultaneous multi-slice (SMS)-accelerated T2-weighted turbo spin echo (TSE) sequences compared to standard T2 TSE sequences in breast magnetic resonance imaging (MRI).

Patients And Methods: Thirty patients were examined with an SMS-accelerated T2 TSE sequence and a standard T2 TSE sequence as part of a breast MRI protocol at 1.5T. Image quality, signal homogeneity and tissue delineation were evaluated. For quantitative assessment, the signal-to-noise ratio (SNR) was measured from representative SNR maps.

Results: There were no significant differences regarding tissue delineation and signal homogeneity. Image quality was rated equal at the chest wall and the breasts but decreased in the axilla on SMS-T2 TSE (p=0.01) with a simultaneous decrease of SNR (p=0.03). This did not significantly impact the overall image quality (p=0.2). The acquisition time for SMS-T2 TSE was 48% shorter compared to standard T2 TSE.

Conclusion: SMS-acceleration for T2-weighted imaging of the breast at 1.5T substantially reduces acquisition time while maintaining comparable quantitative and qualitative image quality. This may pave the way for protocol abbreviation especially in a high-throughput clinical workspace.
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http://dx.doi.org/10.21873/anticanres.15249DOI Listing
September 2021

Impact of Multiparametric Stone Measurement in Noncontrast Computer Tomography on Ureterorenoscopic Stone Removal.

Urol Int 2021 29;105(7-8):600-604. Epub 2021 Apr 29.

Department of Urology, University Hospital of Bonn, Bonn, Germany.

Purpose: Low-dose computer tomography (NCCT) is the standard imaging modality for patients with acute flank pain with a suspicion of urolithiasis. The stone size is usually measured 2D by a radiologist. We compared 3D stone measurement using different windows to the 2D measurement and evaluated the clinical impact on ureterorenoscopic stone removal (URS).

Methods: One hundred sixty-four patients (201 stones) with a preoperative NCCT, following a URS within 4 weeks, were included in this study. Stone location, number and size of stones, operating time, and laser lithotripsy were documented. Stones were measured in 3D using bone and soft tissue window. The maximum diameter was compared to the radiological report. The U test, Kruskal-Wallis, and regression were used for statistical analyses.

Results: Almost two-thirds (64.68%; 130 stones) of stone measurements in 3D with the bone window were lower than the radiologist reports in 2D. One-third (34.83%; 70 stones) of stone measurements were higher and 0.5% (1 stone) reported the same size. Using the 3D soft tissue window, 81.09% (163 stones), 17.91% (37 stones), and 1% (2 stones) of stones were measured bigger, smaller, or had the same measurement results, respectively. In the clinical setting, we could calculate a cutoff for laser lithotripsy at a maximum stone diameter of 5.70 mm (p < 0.01) with the 3D and 6.01 mm with the 2D measurements, respectively, and found a significant correlation between maximum stone diameter and operating time (p < 0.01) and number of stones and operating time (p < 0.01 with and p = 0.02 without laser).

Conclusion: 3D stone measurement with bone window seems to be more accurate than 2D measurement, but 2D is sufficient for planning stone treatment.
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http://dx.doi.org/10.1159/000515646DOI Listing
April 2021

A quantitative CT parameter for the assessment of pulmonary oedema in patients with acute respiratory distress syndrome.

PLoS One 2020 12;15(11):e0241590. Epub 2020 Nov 12.

Institute of Clinical Radiology and Nuclear Medicine, University Medical Centre Mannheim, Heidelberg University, Mannheim, Germany.

Objectives: The aim of this study was to establish quantitative CT (qCT) parameters for pathophysiological understanding and clinical use in patients with acute respiratory distress syndrome (ARDS). The most promising parameter is introduced.

Materials And Methods: 28 intubated patients with ARDS obtained a conventional CT scan in end-expiratory breathhold within the first 48 hours after admission to intensive care unit (ICU). Following manual segmentation, 137 volume- and lung weight-associated qCT parameters were correlated with 71 clinical parameters such as blood gases, applied ventilation pressures, pulse contour cardiac output measurements and established status and prognosis scores (SOFA, SAPS II).

Results: Of all examined qCT parameters, excess lung weight (ELW), i.e. the difference between a patient's current lung weight and the virtual lung weight of a healthy person at the same height, displayed the most significant results. ELW correlated significantly with the amount of inflated lung tissue [%] (p<0.0001; r = -0.66) and was closely associated with the amount of extravascular lung water (EVLW) (p<0.0001; r = 0.72). More substantially than the oxygenation index (PaO2/FiO2) or any other clinical parameter it correlated with the patients' mean SOFA- (p<0.0001, r = 0.69) and SAPS II-Score (p = 0.0005, r = 0.62). Patients who did not survive intensive care treatment displayed higher values of ELW in the initial CT scans.

Conclusions: ELW could serve as a non-invasive method to quantify the amount of pulmonary oedema. It might serve as an early radiological marker of severity in patients with ARDS.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0241590PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7660563PMC
December 2020

Nephrometry Scores: Can Preoperative Assessment of Sectional Imaging Really Mirror Intraoperative Renal Tumor Anatomy?

Urol Int 2021 12;105(1-2):108-117. Epub 2020 Oct 12.

Department of Urology and Urological Surgery, University Medical Center Mannheim, Mannheim, Germany,

Introduction: To compare RENAL, preoperative aspects and dimensions used for an anatomical (PADUA) classification, and Mayo Adhesive Probability (MAP) scores with the respective intraoperative findings and surgeon's assessment in predicting surgical outcome of patients undergoing partial nephrectomy.

Methods: Data of 150 eligible patients treated at the University Medical Center Mannheim between 2016 and 2018 were analyzed. Tumors were radiologically and intraoperatively assessed by PADUA, RENAL, and MAP scores and surgeon's assessment. Correlations and regression models were created to predict ischemia time (IT), major complications, and Trifecta (negative surgical margin, IT < 25 min, and absence of major complications).

Results: There were strong correlations between radiological and intraoperative RENAL (r = 0.68; p < 0.001) and PADUA scores (r = 0.72; p < 0.001). Radiological RENAL, PADUA, and MAP scores and surgeon's assessment were independent predictors of Trifecta (OR = 0.71, p = 0.015; OR = 0.77, p = 0.035; OR = 0.65, p = 0.012; OR = 0.40, p = 0.005, respectively). IT showed significant associations with radiological RENAL, PADUA, and surgeon's assessment (OR = 1.41, p = 0.033; OR = 1.34, p = 0.044; OR = 3.04, p = 0.003, respectively). MAP score proved as only independent predictor of major complications (OR = 2.12, p = 0.002).

Conclusion: Radiologically and intraoperatively assessed scores correlated well with each other. Intraoperative nephrometry did not outperform radiological scores in predicting outcome confirming the value of the existing systems. MAP score correlates well with surgeon's assessment of perirenal fat and major complications underlining the importance of perirenal fat characteristics.
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http://dx.doi.org/10.1159/000510684DOI Listing
July 2021

Augmented reality with HoloLens in parotid surgery: how to assess and to improve accuracy.

Eur Arch Otorhinolaryngol 2021 Jul 10;278(7):2473-2483. Epub 2020 Sep 10.

Department of Otorhinolaryngology, Head and Neck Surgery, University Medical Center Mannheim, Medical Faculty Mannheim, Heidelberg University, Theodor-Kutzer-Ufer 1-3, 68167, Mannheim, Germany.

Purpose: Augmented reality improves planning and execution of surgical procedures. The aim of this study was to evaluate the feasibility of a 3D augmented reality hologram in live parotic surgery. Another goal was to develop an accuracy measuring instrument and to determine the accuracy of the system.

Methods: We created a software to build and manually align 2D and 3D augmented reality models generated from MRI data onto the patient during surgery using the HoloLens 1 (Microsoft Corporation, Redmond, USA). To assess the accuracy of the system, we developed a specific measuring tool applying a standard electromagnetic navigation device (Fiagon GmbH, Hennigsdorf, Germany).

Results: The accuracy of our system was measured during real surgical procedures. Training of the experimenters and the use of fiducial markers significantly reduced the accuracy of holographic system (p = 0.0166 and p = 0.0132). Precision of the developed measuring system was very high with a mean error of the basic system of 1.3 mm. Feedback evaluation demonstrated 86% of participants agreed or strongly agreed that the HoloLens will play a role in surgical education. Furthermore, 80% of participants agreed or strongly agreed that the HoloLens is feasible to be introduced in clinical routine and will play a role within surgery in the future.

Conclusion: The use of fiducial markers and repeated training reduces the positional error between the hologram and the real structures. The developed measuring device under the use of the Fiagon navigation system is suitable to measure accuracies of holographic augmented reality images of the HoloLens.
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http://dx.doi.org/10.1007/s00405-020-06351-7DOI Listing
July 2021

Multiparametric MRI for Prostate Cancer Characterization: Combined Use of Radiomics Model with PI-RADS and Clinical Parameters.

Cancers (Basel) 2020 Jul 2;12(7). Epub 2020 Jul 2.

Department of Clinical Radiology and Nuclear Medicine, University Medical Center Mannheim, Medical Faculty Mannheim, Heidelberg University, D-68167 Mannheim, Germany.

Radiomics is an emerging field of image analysis with potential applications in patient risk stratification. This study developed and evaluated machine learning models using quantitative radiomic features extracted from multiparametric magnetic resonance imaging (mpMRI) to detect and classify prostate cancer (PCa). In total, 191 patients that underwent prostatic mpMRI and combined targeted and systematic fusion biopsy were retrospectively included. Segmentations of the whole prostate glands and index lesions were performed manually in apparent diffusion coefficient (ADC) maps and T2-weighted MRI. Radiomic features were extracted from regions corresponding to the whole prostate gland and index lesion. The best performing combination of feature setup and classifier was selected to compare its predictive ability of the radiologist's evaluation (PI-RADS), mean ADC, prostate specific antigen density (PSAD) and digital rectal examination (DRE) using receiver operating characteristic (ROC) analysis. Models were evaluated using repeated 5-fold cross-validation and a separate independent test cohort. In the test cohort, an ensemble model combining a radiomics model, with models for PI-RADS, PSAD and DRE achieved high predictive AUCs for the differentiation of (i) malignant from benign prostatic lesions (AUC = 0.889) and of (ii) clinically significant (csPCa) from clinically insignificant PCa (cisPCa) (AUC = 0.844). Our combined model was numerically superior to PI-RADS for cancer detection (AUC = 0.779; = 0.054) as well as for clinical significance prediction (AUC = 0.688; = 0.209) and showed a significantly better performance compared to mADC for csPCa prediction (AUC = 0.571; = 0.022). In our study, radiomics accurately characterizes prostatic index lesions and shows performance comparable to radiologists for PCa characterization. Quantitative image data represent a potential biomarker, which, when combined with PI-RADS, PSAD and DRE, predicts csPCa more accurately than mADC. Prognostic machine learning models could assist in csPCa detection and patient selection for MRI-guided biopsy.
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http://dx.doi.org/10.3390/cancers12071767DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7407326PMC
July 2020

Coprevalence and Incidence of Lung Cancer in Patients Screened for Abdominal Aortic Aneurysm.

Anticancer Res 2020 Jul;40(7):4137-4145

First Department of Medicine (Cardiology), University Medical Centre Mannheim, Medical Faculty Mannheim, University of Heidelberg, European Centre for AngioScience (ECAS), Mannheim, Germany.

Background/aim: Lung diseases are common in patients with abdominal aortic aneurysms (AAA). This study evaluates the prevalence of lung cancer (LC) in high-risk patients screened for AAA.

Patients And Methods: Six hundred and one male patients (≥65 years of age, cardiovascular high-risk profile) were enrolled and followed prospectively over a median of 16.5 months.

Results: In 29 patients (4.8%) LC and in another 50 patients (8.3%) AAA were found. The prevalence of LC among patients with AAA was even higher (9 of 50, 18.0%). Twenty-one patients had an initial diagnosis of LC, with an incidence of 12.0% (6 of 50) in patients with AAA. During follow-up, 14 of 70 patients with AAA and/ or LC (20.0%) deceased. The highest mortality was found in patients with LC only (8 of 20, 40.0%), followed by patients with both AAA and LC (3 of 9, 33.3%), while patients with AAA only had the lowest mortality rate (3 of 41, 7.3%).

Conclusion: In patients with a high cardiovascular risk profile, a high prevalence of both AAA and LC were found, whereby the prognosis is largely determined by the LC. Therefore, LC is of particular importance in the setting of screening and surveillance of AAA.
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http://dx.doi.org/10.21873/anticanres.14413DOI Listing
July 2020

Morphological and functional assessment of the uterus: "one-stop shop imaging" using a compressed-sensing accelerated, free-breathing T1-VIBE sequence.

Acta Radiol 2021 May 29;62(5):695-704. Epub 2020 Jun 29.

Department of Radiology, Kantonsspital Baden, Baden, Switzerland.

Background: The combination of motion-insensitive, high-temporal, and spatial resolution imaging with evaluation of quantitative perfusion has the potential to increase the diagnostic capabilities of magnetic resonance imaging (MRI) in the female pelvis.

Purpose: To compare a free-breathing compressed-sensing VIBE (fbVIBE) with flexible temporal resolution (range = 4.6-13.8 s) with breath-hold VIBE (bhVIBE) and to evaluate the potential value of quantifying uterine perfusion.

Material And Methods: A total of 70 datasets from 60 patients (bhVIBE: n = 30; fbVIBE: n = 40) were evaluated by two radiologists. Only temporally resolved reconstruction (fbVIBE) was performed on 30 of the fbVIBE datasets. For a subset (n = 10) of the fbVIBE acquisitions, a time- and motion-resolved reconstruction (mrVIBE) was evaluated. Image quality (IQ), artifacts, diagnostic confidence (DC), and delineation of uterine structures (DoS) were graded on Likert scales (IQ/DC/DoS: 1 (non-diagnostic) to 5 (perfect); artifacts: 1 (no artifacts) to 5 (severe artifacts)). A Tofts model was applied for perfusion analysis. Ktrans was obtained in the myometrium (Mm), junctional zone (Jz), and cervix (Cx).

Results: The median IQ/DoS/DC scores of fbVIBE (4/5/5 κ >0.7-0.9) and bhVIBE (4/4/4; κ = 0.5-0.7;  > 0.05) were high, but Artifacts were graded low (fbVIBE/bhVIBE: 2/2; κ = 0.6/0.5;  > 0.05). Artifacts were only slightly improved by the additional motion-resolved reconstruction (fbVIBE/mrVIBE: 2/1.5;  = 0.08); fbVIBE was preferred in most cases (7/10). Significant differences of Ktrans values were found between Cx, Jz, and Mm (0.12/0.21/0.19;  < 0.05).

Conclusion: The fbVIBE sequence allows functional and morphological assessment of the uterus at comparable IQ to bhVIBE.
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http://dx.doi.org/10.1177/0284185120936260DOI Listing
May 2021

More holes, more contrast? Comparing an 18-gauge non-fenestrated catheter with a 22-gauge fenestrated catheter for cardiac CT.

PLoS One 2020 8;15(6):e0234311. Epub 2020 Jun 8.

Clinic of Diagnostic and Interventional Radiology, Saarland University Medical Center, Homburg, Germany.

Objective: To compare the performance of an 18-gauge nonfenestrated catheter (18-NFC) with a 22-gauge fenestrated catheter (22-FC) for cardiac CT angiography (CCTA) in patients with suspected coronary heart disease.

Subjects And Methods: 74 consecutive patients imaged on a 2nd generation dual-source CT with arterial phase CCTA were included in this retrospective investigation to either an 18-NFC or 22-FC. In comparison to the 18-NFC, the 22-FC has three additional perforations for contrast agent dispersal proximal to the tip. We examined the two groups for differences in their average attenuation in the right and left ventricles (RV, LV) and in the atrium (RA, LA) as well as in the proximal right coronary artery (RCA) and the left main coronary artery (LM). The averages were calculated for both the 18-NFC and 22-FC.

Results: Catheters were successfully placed on the first attempt 97% (36/37) for 18-NFC and 95% (35/37) for the 22-FC. The following enhancement levels were measured: 22-FC (in Hounsfield-Units (HU)): RV = 203±29, LV = 523±36, RA = 198±29, LA = 519±38, RCA = 547±26, LM = 562±25; 18-NFC: RV = 146±26, LV = 464±32, RA = 141±24, LA = 438±35, RCA = 501±23, LM = 523±23; RV (p = 0,03), LV (p = 0.12), RA (p = 0.02), LA (p = 0.04), RCA (p = 0.3), LM (p = 0.33).

Conclusion: No significant differences in attenuation levels as well as in image quality of the coronary arteries were found between NFC and FC. Nevertheless, the 22-gauge FC examinations showed significantly higher attenuation in the left and right atrium as well as the right ventricle. Patients with poor venous access may benefit from a smaller gauge catheter that can deliver sufficiently high flow rates for CCTA.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0234311PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7279574PMC
August 2020

Acute pulmonary embolism mimicking COVID - 19 pneumonia.

Int J Infect Dis 2020 07 18;96:475-476. Epub 2020 May 18.

Department of Radiology and Nuclear Medicine, University Medical Center Mannheim, Medical Faculty Mannheim, Heidelberg University, Mannheim, Baden-Württemberg, D-68167, Germany.

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http://dx.doi.org/10.1016/j.ijid.2020.05.053DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7233210PMC
July 2020

Radiation dose of chaperones during common pediatric computed tomography examinations.

Pediatr Radiol 2020 07 15;50(8):1078-1082. Epub 2020 May 15.

Clinic of Diagnostic and Interventional Radiology, Saarland University Medical Center, Kirrberger Straße - Gebäude 50.1, Homburg, 66421, Germany.

Background: One main challenge in pediatric imaging is to reduce motion artifacts by calming young patients. To that end, the Radiological Society of North America (RSNA) as early as 1997 stated the necessity of adults accompanying their child during the child's examination. Nonetheless, current research lacks data regarding radiation dose to these chaperones.

Objective: The aim of this study was to measure the radiation dose of accompanying adults during state-of-the-art pediatric CT protocols.

Materials And Methods: In addition to a 100-kV non-contrast-enhanced chest CT (Protocol 1), we performed a 70-kV contrast-enhanced chest protocol (Protocol 2) using a third-generation dual-source CT. We acquired data on the radiation dose around the scanner using digital dosimetry placed right at the gantry, 1 m away, as well as beside the gantry. We acquired the CT-surrounding radiation dose during scanning of a pediatric phantom as well as 12 pediatric patients.

Results: After conducting 10 consecutive phantom scans using Protocol 1, we found the location with the highest cumulative dose acquired was right next to the gantry opening, at 3 μSv. Protocol 2 showed highest cumulative dose of 2 μSv at the same location. For Protocol 1, the location with the highest radiation doses during pediatric scans was right next to the gantry opening, with doses of 0.75±0.70 μSv. For Protocol 2, the highest radiation was measured 1 m away at 0.50±0.60 μSv. No radiation dose was measured at any time beside the gantry.

Conclusion: Our results provide proof that chaperones receive low radiation doses during state-of-the-art CT examinations. Given knowledge of these values as well as the optimal spots with the lowest radiation doses, parents as well as patients might be more relaxed during the examination.
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http://dx.doi.org/10.1007/s00247-020-04681-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7329757PMC
July 2020

An increased bone mineral density is an adverse prognostic factor in patients with systemic mastocytosis.

J Cancer Res Clin Oncol 2020 Apr 24;146(4):945-951. Epub 2020 Jan 24.

Department of Hematology and Oncology, University Hospital Mannheim, Heidelberg University, Mannheim, Germany.

Purpose: Systemic mastocytosis (SM) is characterized by the expansion of clonal mast cells that infiltrate various organ systems. The extent of organ infiltration and subsequent organ damage distinguishes between indolent SM (ISM) defined by a nearly normal life expectancy and advanced SM (AdvSM) defined by poor prognosis. In ISM, measurement of the bone mineral density (BMD) frequently reveals osteoporosis. In contrast, the clinical implication of an increased BMD and osteosclerosis remains unclear.

Methods: BMD was evaluated in 61 patients with mastocytosis (ISM, n = 29, 48%; AdvSM, n = 32, 52%). We correlated the prevalence of osteoporosis, increased BMD and osteosclerosis with clinical parameters, disease variant and prognosis.

Results: Osteoporosis was detected in 11/29 (38%) patients with ISM but only in 2/32 (6%) patients with AdvSM (p = 0.004). An increased BMD was detected in 1/29 (3%) patients with ISM and 24/32 (75%) patients with AdvSM (p < 0.001) while osteosclerosis was only detected in AdvSM patients (16/32, 50%). AdvSM patients with increased BMD had higher levels of bone marrow mast cell infiltration, higher serum tryptase and alkaline phosphatase levels compared to ISM as well as higher number of high-molecular risk mutations (p < 0.05). In addition, we found that the prognosis of AdvSM patients with increased BMD is inferior compared to those without increased BMD (median overall survival 3.6 years versus not reached, p = 0.031).

Conclusions: Osteoporosis is a common feature in ISM but not in AdvSM. An increased BMD is frequently present in AdvSM but not in ISM and is associated with more advanced disease and inferior outcome.
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http://dx.doi.org/10.1007/s00432-019-03119-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7085471PMC
April 2020

Simultaneous Multislice Diffusion-Weighted Imaging of the Kidneys at 3 T.

Invest Radiol 2020 04;55(4):233-238

From the Department of Clinical Radiology and Nuclear Medicine, University Medical Center Mannheim, Germany.

Purpose: The aim of this study was to compare respiratory-triggered diffusion-weighted imaging with simultaneous-multislice acceleration (SMS-RT-DWI) to a standard free-breathing echoplanar DWI (s-DWI) for 3 T renal imaging with respect to image quality and artifacts.

Materials And Methods: A total of 40 patients who had undergone renal magnetic resonance imaging were included in this retrospective analysis of a prospectively planned cohort study. All examinations were performed on a 3 T whole-body magnetic resonance system. Both s-DWI and SMS-RT-DWI were obtained and images were independently reviewed by 2 radiologists on a 5-point Likert scale with respect to overall preference and image quality, renal edge and parenchymal sharpness, cortico-medullary differentiation, and sequence-related artifacts. Furthermore, discernibility of renal lesions was assessed. The signal-to-noise ratio (SNR) was measured from SNR maps. The derived mean apparent diffusion coefficients were also compared. Qualitative parameters were assessed with the Wilcoxon rank-sum test, and quantitative parameters, with the Student t test.

Results: Overall image quality, renal edge, and parenchymal sharpness of SMS-RT-DWI were rated as superior to s-DWI by the readers, with fewer sequence-related artifacts (P < 0.01 for all). Lesion discernibility was significantly improved for SMS-RT-DWI (P < 0.01). Both readers preferred SMS-RT-DWI to s-DWI in all cases (40/40). The acquisition time for SMS-RT-DWI was 30% shorter than for s-DWI. Mean SNR heterogeneity of SMS-RT-DWI at b = 800 s/mm was statistically significantly lower than s-DWI, whereas mean SNR was significantly higher for SMS-RT-DWI. Mean apparent diffusion coefficient values from both sequences were comparably homogeneous throughout the kidneys.

Conclusion: Simultaneous multislice DWI of the kidney at 3 T with respiratory triggering yields substantially improved image quality and lesion discernibility compared with standard single-shot echoplanar DWI with a 30% reduction in scan acquisition time.
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http://dx.doi.org/10.1097/RLI.0000000000000637DOI Listing
April 2020

Magnetic resonance imaging reveals distinct bone marrow patterns in indolent and advanced systemic mastocytosis.

Ann Hematol 2019 Dec 5;98(12):2693-2701. Epub 2019 Nov 5.

Department of Hematology and Oncology, University Hospital Mannheim, Heidelberg University, Mannheim, Germany.

Systemic mastocytosis (SM) is broadly subcategorized according to mast cell (MC) burden and organ involvement into indolent (ISM), smoldering (SSM), and advanced SM (AdvSM). However, the pattern and extent of bone involvement remains controversial. In this institutional review board (IRB)-approved study, 115 patients with different forms of SM (ISM (n = 37, 32%), SSM (n = 9, 8%), and AdvSM (n = 69, 60%)) underwent a whole-body magnetic resonance imaging including sagittal and coronal T1 and turbo inversion recovery magnitude (TIRM) sequences of the spine. The evaluation included the pattern and extent of pathologic bone marrow (BM) signals in the spine and extremities, osteolytic lesions, and vertebral fractures. A pathologic BM pattern was observed in 4/37 (11%), 8/9 (89%), and 66/69 (96%); affection of the appendicular skeleton in 3/37 (8%), 8/9 (89%), and 67/69 (97%); and vertebral fractures in 7/37 (19%), 0/9, and 13/69 (19%) patients with ISM, SSM, and AdvSM, respectively. In AdvSM, pathologic BM pattern included activated (62%), diffuse sclerotic (25%), and small-spotted BM (9%), respectively. Only activated/sclerotic BM was associated with significantly higher MC burden, organ damage, and inferior median survival (2.9 years, p = 0.04). Vertebral fractures resembled classical multi-segmental osteoporotic fractures in ISM but not in AdvSM in which they were only found in activated/sclerotic BM. Only one patient with AdvSM had a focal osteolytic lesion in the femur. Activated/sclerotic BM changes of the spine and affection of the appendicular skeleton are indicative for SSM or AdvSM. Osteolytic lesions, which are very rare, and osteoporotic fractures are ineligible for the diagnosis of AdvSM.
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http://dx.doi.org/10.1007/s00277-019-03826-4DOI Listing
December 2019

Radiation-induced malignancies after intensity-modulated versus conventional mediastinal radiotherapy in a small animal model.

Sci Rep 2019 10 29;9(1):15489. Epub 2019 Oct 29.

Department of Radiation Oncology, Universitätsmedizin Mannheim, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany.

A long-standing hypothesis in radiotherapy is that intensity-modulated radiotherapy (IMRT) increases the risk of second cancer due to low-dose exposure of large volumes of normal tissue. Therefore, young patients are still treated with conventional techniques rather than with modern IMRT. We challenged this hypothesis in first-of-its-kind experiments using an animal model. Cancer-prone Tp53 knockout rats received mediastinal irradiation with 3 × 5 or 3 × 8 Gy using volumetric-modulated arc therapy (VMAT, an advanced IMRT) or conventional anterior-posterior/posterior-anterior (AP/PA) beams using non-irradiated rats as controls (n = 15/group, n = 90). Tumors were assigned to volumes receiving 90-107%, 50-90%, 5-50%, and <5% of the target dose and characterized by histology and loss-of-heterozygosity (LOH). Irradiated rats predominantly developed lymphomas and sarcomas in areas receiving 50-107% (n = 26) rather than 5-50% (n = 7) of the target dose. Latency was significantly shortened only after 3 × 8 Gy vs. controls (p < 0.0001). The frequency (14/28 vs. 19/29; p = 0.29) and latency (218 vs. 189 days; p = 0.17) of radiation-associated tumors were similar after VMAT vs. AP/PA. LOH was strongly associated with sarcoma but not with treatment. The results do not support the hypothesis that IMRT increases the risk of second cancer. Thus the current practice of withholding dose-sparing IMRT from young patients may need to be re-evaluated.
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http://dx.doi.org/10.1038/s41598-019-51735-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6820874PMC
October 2019

Improved Liver Diffusion-Weighted Imaging at 3 T Using Respiratory Triggering in Combination With Simultaneous Multislice Acceleration.

Invest Radiol 2019 12;54(12):744-751

From the Department of Clinical Radiology and Nuclear Medicine, University Medical Center Mannheim, Mannheim.

Objectives: The aim of this study was to retrospectively compare optimized respiratory-triggered diffusion-weighted imaging with simultaneous multislice acceleration (SMS-RT-DWI) of the liver with a standard free-breathing echo-planar DWI (s-DWI) protocol at 3 T with respect to the imaging artifacts inherent to DWI.

Materials And Methods: Fifty-two patients who underwent a magnetic resonance imaging study of the liver were included in this retrospective study. Examinations were performed on a 3 T whole-body magnetic resonance system (MAGNETOM Skyra; Siemens Healthcare, Erlangen, Germany). In all patients, both s-DWI and SMS-RT-DWI of the liver were obtained. Images were qualitatively evaluated by 2 independent radiologists with regard to overall image quality, liver edge sharpness, sequence-related artifacts, and overall scan preference. For quantitative evaluation, signal-to-noise ratio was measured from signal-to-noise ratio maps. The mean apparent diffusion coefficient (ADC) was measured in each liver quadrant. The Wilcoxon rank-sum test was used for analysis of the qualitative parameters and the paired Student t test for quantitative parameters.

Results: Overall image quality, liver edge sharpness, and sequence-related artifacts of SMS-RT-DWI received significantly better ratings compared with s-DWI (P < 0.05 for all). For 90.4% of the examinations, both readers overall preferred SMS-RT-DWI to s-DWI. Acquisition time for SMS-RT-DWI was 34% faster than s-DWI. Signal-to-noise ratio values were significantly higher for s-DWI at b50 but did not statistically differ at b800, and they were more homogenous for SMS-RT-DWI, with a significantly lower standard deviation at b50. Mean ADC values decreased from the left to right hepatic lobe as well as from cranial to caudal for s-DWI. With SMS-RT-DWI, mean ADC values were homogeneous throughout the liver.

Conclusions: Optimized, multislice, respiratory-triggered DWI of the liver at 3 T substantially improves image quality with a reduced scan acquisition time compared with s-DWI.
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http://dx.doi.org/10.1097/RLI.0000000000000594DOI Listing
December 2019

Nephrometry Scores: The Effect of Imaging on Routine Read-out and Prediction of Outcome of Nephron-sparing Surgery.

Anticancer Res 2018 05;38(5):3037-3041

Department of Urology, University Medical Centre Mannheim, Mannheim, Germany.

Background/aim: This study investigated the impact of available preoperative imaging on the reliability and predictive accuracy of RENAL and PADUA nephrometry-scoring systems for renal tumors.

Patients And Methods: Five urologists determined RENAL and PADUA scores using preoperative imaging data (computed tomography and magnetic resonance imaging) of 100 patients admitted for partial nephrectomy with the following combinations: T0: transverse planes without excretory phase (EP), TC0: transverse and coronal planes without EP, TC1: transverse and coronal planes with EP. Reference standard was obtained by a uro-radiologist. Ischemia time was used as surrogate for surgical complexity.

Results: Assignment of EP significantly reduced interobserver-variability among urologists (p<0.0001). Predictive accuracy for surgical complexity or correct assignment to nephrometry risk groups did not depend on image planes or EP.

Conclusion: Interobserver variability, but not predictive accuracy of nephrometric systems, is affected by additional usage of EP.
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http://dx.doi.org/10.21873/anticanres.12559DOI Listing
May 2018

Combined Static and Dynamic Computed Tomography Angiography of Peripheral Artery Occlusive Disease: Comparison with Magnetic Resonance Angiography.

Cardiovasc Intervent Radiol 2018 Aug 26;41(8):1205-1213. Epub 2018 Feb 26.

Institute of Clinical Radiology and Nuclear Medicine, University Medical Center Mannheim, Medical Faculty Mannheim - Heidelberg University, Theodor-Kutzer-Ufer 1-3, 68167, Mannheim, Germany.

Purpose: To compare in patients with known peripheral artery occlusive disease (PAOD), image quality of a combined CTA to a combined MRA protocol, including both static and dynamic acquisitions.

Materials And Methods: Twenty-two patients with PAOD were examined with a combined CTA and MRA protocol consisting of static acquisitions (s-CTA, s-MRA) of the entire runoff and dynamic acquisitions (d-CTA, d-MRA) of the calves. Two radiologists compared image quality of the s-MRA versus s-CTA as well as d-MRA versus d-CTA. Image quality was assessed on a segmental basis using a 4-point Likert scale.

Results: For s-CTA, 76% of segments were rated as excellent or good. For s-MRA, 50% of segments were rated as excellent or good (p < 0.0001). For d-CTA, median image quality score for all segments was rated as excellent for both readers. For d-MRA, median image quality for the different segments ranged from moderate to good. For both d-CTA and d-MRA, the median image quality scores were significantly higher for all segments of the lower limb compared with the static examinations of the lower limb segments (all p values < 0.0001). In patients with PAOD category 4-6, 80% of segments were rated as excellent or good for d-CTA, while 45% of segments were rated as poor or non-diagnostic for d-MRA.

Conclusion: In patients with known PAOD, a combined static and dynamic CTA examination improves image quality relative to static and dynamic MRA and should be considered as an alternative to MRA, particularly in patients with advanced stage PAOD.
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http://dx.doi.org/10.1007/s00270-018-1911-6DOI Listing
August 2018

Value of Additional Digital Breast Tomosynthesis for Preoperative Staging of Breast Cancer in Dense Breasts.

Anticancer Res 2017 09;37(9):5255-5261

Institute of Clinical Radiology and Nuclear Medicine, University Medical Center Mannheim, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany.

Aim: This retrospective study was initiated to determine the diagnostic value of additional preoperative breast tomosynthesis (DBT) for breast cancer staging in dense breasts.

Patients And Methods: Sixty-six patients (69 breasts) with findings of American College of Radiology category 3 or 4 with Breast Imaging Reporting and Data System 5, 6 or 0 were included. All patients underwent digital mammography and additional DBT.

Results: A total of 40/69 (58%) cancers were detected on both mammography and DBT, 23 (33.3%) were only seen on DBT (p=0.0001); 6/69 (8.7%) carcinomas were not detected by either method, of which three were invasive lobular carcinomas. Sensitivity for multifocal/multicentric disease was significantly higher on DBT (12/19, 63.2%) compared to mammography (4/19, 21.1%) (p=0.02), specificity was comparable (96.0% vs. 90.0%). Multifocal/multicentric disease was not detected on mammography nor DBT in 7/19 (36.8%) patients, including three invasive lobular carcinomas.

Conclusion: DBT may significantly improve preoperative breast cancer staging in patients with dense breasts compared to conventional mammography alone. Nevertheless, limitations have to be expected in the case of invasive lobular carcinoma.
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http://dx.doi.org/10.21873/anticanres.11950DOI Listing
September 2017

Quantitative Perfusion Analysis of the Rectum Using Golden-Angle Radial Sparse Parallel Magnetic Resonance Imaging: Initial Experience and Comparison to Time-Resolved Angiography With Interleaved Stochastic Trajectories.

Invest Radiol 2017 12;52(12):715-724

From the *Institute of Clinical Radiology and Nuclear Medicine, University Medical Center Mannheim, Heidelberg University, Heidelberg, Germany; †Department of Radiology, Peking University First Hospital, Beijing, China; ‡Siemens Healthcare, Erlangen, Germany; §Department of Radiology, New York University, New York City, NY; and ∥Institut für Radiologie, Kantonsspital Baden, Baden, Switzerland.

Objectives: Purpose of this study was to compare the quality of perfusion maps obtained from prototypical free-breathing magnetic resonance imaging (MRI) with continuous golden-angle radial sampling and iterative reconstruction (GRASP) to conventional acquisition using time-resolved angiography with interleaved stochastic trajectories (TWIST) in patients with rectal cancer.

Material And Methods: Forty cases were included for retrospective analysis. Twenty of the patients received routine multiparametric MRI at 3 T for rectal cancer staging, including perfusion measurement with GRASP or TWIST (10 patients for each technique, including 5 prechemoradiation and 5 postchemoradiation). Twenty patients without history of rectal disease served as control group (10 GRASP, 10 TWIST). GRASP images were reconstructed at temporal resolution of 3.45 seconds (21 spokes/frame). A voxel-by-voxel deconvolution approach was used to determine rectal plasma flow (mL/100 mL per minute). Regions of interest were placed at 3 levels within the tumor and normal rectum (lower, middle, and upper part). The quality of morphologic images, perfusion maps, and arterial input function were scored by 2 blinded radiologists. Independent t tests were applied.

Results: Three patients of the TWIST control group had to be excluded due to technical failure of the sequence. Significantly higher scores for the perfusion maps and arterial input functions (total cohort) were obtained using GRASP (P < 0.05). Artifacts in the perfusion maps were rated significantly lower than for TWIST (P < 0.05). In the healthy rectum cohort, the average plasma flow of normal rectal wall was 31.78 ± 7.39 mL/100 mL per minute with GRASP, compared with 77.62 ± 34.08 mL/100 mL per minute with TWIST, indicating much lower variance for GRASP. Plasma flow values obtained with both methods enabled distinguishing between normal rectal wall and rectal cancer, both before and after chemoradiation. Morphologic image quality was generally higher with GRASP (P < 0.01).

Conclusions: GRASP perfusion imaging can distinguish between normal rectum and rectal cancers with higher image quality and less variance than TWIST. Additional morphologic assessment with high spatial resolution from the GRASP acquisition may increase the accuracy and diagnostic confidence of the examination.
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http://dx.doi.org/10.1097/RLI.0000000000000397DOI Listing
December 2017

Rapid Cartesian versus radial acquisition: comparison of two sequences for hepatobiliary phase MRI at 3 tesla in patients with impaired breath-hold capabilities.

BMC Med Imaging 2017 05 9;17(1):32. Epub 2017 May 9.

Department of Clinical Radiology and Nuclear Medicine, University Medical Center Mannheim, Medical Faculty Mannheim, Heidelberg University, Theodor-Kutzer-Ufer 1-3, 68167, Mannheim, Germany.

Background: Hepatocyte-specific gadolinium based contrast agents (HSCA) provide substantial information for the classification of liver lesions in magnetic resonance imaging (MRI). However, breathing artifacts which reduce image quality and diagnostic confidence of hepatobiliary phase acquisitions are regularly observed in clinical routine. The aim of this study was to evaluate two approaches to reduce breathing artifacts for hepatobiliary phase imaging.

Methods: Twenty minutes after administration of a HSCA (gadoxetic acid), a T1-weighted VIBE sequence with radial k-space sampling (radialVIBE, 180 s acquisition time in free breathing) and a highly accelerated Cartesian VIBE with Dixon fat separation (CD-VIBE, CAIPIRINHA acceleration with r = 2 × 2, breath-hold 8-10 s) were acquired in 35 patients (12 female, 57 ± 13 years), who showed breath-holding difficulties in early phases of the examinations. Image quality (image sharpness, noise, artifacts, homogeneity of fat saturation, bile duct delineation and overall image quality) as well as conspicuity and liver-to-lesion signal intensity (SI) ratios of focal liver lesions were assessed for both radial- and CD-VIBE.

Results: Overall image quality was rated good to excellent for both sequences, while CD-VIBE was preferred in most cases. Though radialVIBE received better results regarding image noise and artifacts, both sequences were rated equally regarding bile duct delineation and sharpness. Focal liver lesion (n = 42) conspicuity was rated significantly better and SI-ratios were significantly higher on CD-VIBE (2.45 ± 1.44 vs. 1.61 ± 0.70 in radialVIBE, p = 0.0001). In three patients, CD-VIBE was rated non-diagnostic due to severe breathing artifacts, while radialVIBE was diagnostic in those patients.

Conclusion: Both highly accelerated Cartesian as well as radial acquisition techniques provide good to excellent image quality in hepatobiliary phase MRI. In comparison, CD-VIBE offered better overall image quality and liver lesion conspicuity. However, radialVIBE was a valuable alternative in patients unable to sustain even short breath-hold intervals. Further studies including lager patient cohorts are desirable to allow a transfer of these results to a general patient population.
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http://dx.doi.org/10.1186/s12880-017-0203-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5424346PMC
May 2017

"One-Stop Shop": Free-Breathing Dynamic Contrast-Enhanced Magnetic Resonance Imaging of the Kidney Using Iterative Reconstruction and Continuous Golden-Angle Radial Sampling.

Invest Radiol 2016 11;51(11):714-719

From the *Institute of Clinical Radiology and Nuclear Medicine, University Medical Center Mannheim, and †Computer-Assisted Clinical Medicine, Medical Faculty Mannheim, Heidelberg University, Mannheim; ‡Siemens Healthcare GmbH, Erlangen, Germany; and §Center for Advanced Imaging Innovation and Research (CAI2R), Department of Radiology, New York University School of Medicine, New York, NY.

Aims And Objectives: The purpose of the present study was to evaluate a recently introduced technique for free-breathing dynamic contrast-enhanced renal magnetic resonance imaging (MRI) applying a combination of radial k-space sampling, parallel imaging, and compressed sensing. The technique allows retrospective reconstruction of 2 motion-suppressed sets of images from the same acquisition: one with lower temporal resolution but improved image quality for subjective image analysis, and one with high temporal resolution for quantitative perfusion analysis.

Materials And Methods: In this study, 25 patients underwent a kidney examination, including a prototypical fat-suppressed, golden-angle radial stack-of-stars T1-weighted 3-dimensional spoiled gradient-echo examination (GRASP) performed after contrast agent administration during free breathing. Images were reconstructed at temporal resolutions of 55 spokes per frame (6.2 seconds) and 13 spokes per frame (1.5 seconds). The GRASP images were evaluated by 2 blinded radiologists. First, the reconstructions with low temporal resolution underwent subjective image analysis: the radiologists assessed the best arterial phase and the best renal phase and rated image quality score for each patient on a 5-point Likert-type scale.In addition, the diagnostic confidence was rated according to a 3-point Likert-type scale. Similarly, respiratory motion artifacts and streak artifacts were rated according to a 3-point Likert-type scale.Then, the reconstructions with high temporal resolution were analyzed with a voxel-by-voxel deconvolution approach to determine the renal plasma flow, and the results were compared with values reported in previous literature.

Results: Reader 1 and reader 2 rated the overall image quality score for the best arterial phase and the best renal phase with a median image quality score of 4 (good image quality) for both phases, respectively. A high diagnostic confidence (median score of 3) was observed. There were no respiratory motion artifacts in any of the patients. Streak artifacts were present in all of the patients, but did not compromise diagnostic image quality.The estimated renal plasma flow was slightly higher (295 ± 78 mL/100 mL per minute) than reported in previous MRI-based studies, but also closer to the physiologically expected value.

Conclusions: Dynamic, motion-suppressed contrast-enhanced renal MRI can be performed in high diagnostic quality during free breathing using a combination of golden-angle radial sampling, parallel imaging, and compressed sensing. Both morphologic and quantitative functional information can be acquired within a single acquisition.
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http://dx.doi.org/10.1097/RLI.0000000000000299DOI Listing
November 2016

Renal zoomed EPI-DWI with spatially-selective radiofrequency excitation pulses in two dimensions.

Eur J Radiol 2016 Oct 1;85(10):1773-1777. Epub 2016 Aug 1.

Institute of Clinical Radiology and Nuclear Medicine, University Medical Center Mannheim, Medical Faculty Mannheim - Heidelberg University, Mannheim, Germany. Electronic address:

Purpose: To evaluate the feasibility and clinical robustness of zoomed diffusion-weighted echo planar imaging (z-EPI) relative to conventional single-shot EPI (c-EPI) for DWI of the kidneys.

Materials And Methods: This retrospective study was approved by the institutional research ethics board. 66 patients (median age 58.5 years±13.4, range 23-83 years, 45 men, 21 women) undergoing 3T (Magnetom Skyra(®), Siemens Healthcare, Erlangen, Germany) using a dynamic parallel transmit array (TimTX TrueShape, Siemens Healthcare, Erlangen, Germany) for renal MRI were included in this study. Both c-EPI and z-EPI images were obtained. For z-EPI, a two-dimensional spatially-selective radiofrequency (RF) pulse was applied for echo planar imaging with the FOV reduced by a factor of 3. Two radiologists, blinded to clinical data and scan parameters evaluated the images with respect to their diagnostic confidence, overall preference, overall image quality, delineation of the kidney, spatial distortion, and image blur. Sequences were compared using a paired Wilcoxon test. ADC values for the upper pole, mid-zone, lower pole of the normal kidneys were compared between sequences as well as ADC values for renal lesions, using a paired t-test.

Results: With z-EPI, the kidney was significantly better delineated with sharper boundaries, less image blur and distortion, and overall better image quality relative to c-EPI (all p<0.001). The z-EPI technique led to greater diagnostic confidence than c-EPI (p=0.020). z-EPI was preferred to c-EPI in 60 cases (90.9%, 60/66). No statistically significant differences in the ADC values of renal parenchyma or of renal lesions were observed between the two sequences (all p>0.05).

Conclusion: Image quality, distortion, and susceptibility artifacts might be improved by using z-EPI rather than c-EPI for DWI of the kidney.
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http://dx.doi.org/10.1016/j.ejrad.2016.07.022DOI Listing
October 2016

Carotid dual-energy CT angiography: Evaluation of low keV calculated monoenergetic datasets by means of a frequency-split approach for noise reduction at low keV levels.

Eur J Radiol 2016 Apr 22;85(4):720-5. Epub 2016 Jan 22.

Institute of Clinical Radiology and Nuclear Medicine, University Medical Center Mannheim, Medical Faculty Mannheim-Heidelberg University, Mannheim, Germany.

Background And Purpose: Calculated monoenergetic ultra-low keV datasets did not lead to improved contrast-to-noise ratio (CNR) due to the dramatic increase in image noise. The aim of the present study was to evaluate the objective image quality of ultra-low keV monoenergetic images (MEIs) calculated from carotid DECT angiography data with a new monoenergetic imaging algorithm using a frequency-split technique.

Materials And Methods: 20 patients (12 male; mean age 53±17 years) were retrospectively analyzed. MEIs from 40 to 120 keV were reconstructed using the monoenergetic split frequency approach (MFSA). Additionally MEIs were reconstructed for 40 and 50 keV using a conventional monoenergetic (CM) software application. Signal intensity, noise, signal-to-noise ratio (SNR) and CNR were assessed in the basilar, common, internal carotid arteries.

Results: Ultra-low keV MEIs at 40 keV and 50 keV demonstrated highest vessel attenuation, significantly greater than those of the polyenergetic images (PEI) (all p-values <0.05). The highest SNR level and CNR level was found at 40 keV and 50 keV (all p-values <0.05). MEIs with MFSA showed significantly lower noise levels than those processed with CM (all p-values <0.05) and no significant differences in vessel attenuation (p>0.05). Thus MEIs with MFSA showed significantly higher SNR and CNR compared to MEIs with CM.

Conclusion: Combining the lower spatial frequency stack for contrast at low keV levels with the high spatial frequency stack for noise at high keV levels (frequency-split technique) leads to improved image quality of ultra-low keV monoenergetic DECT datasets when compared to previous monoenergetic reconstruction techniques without the frequency-split technique.
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http://dx.doi.org/10.1016/j.ejrad.2016.01.015DOI Listing
April 2016

Small Field-of-view single-shot EPI-DWI of the prostate: Evaluation of spatially-tailored two-dimensional radiofrequency excitation pulses.

Z Med Phys 2016 Jun 20;26(2):168-76. Epub 2015 Aug 20.

Institute of Clinical Radiology and Nuclear Medicine, University Medical Center Mannheim, Medical Faculty Mannheim, University of Heidelberg, Germany. Electronic address:

Purpose: Spatially-tailored (RF) excitation pulses in echo-planar imaging (EPI), combined with a decreased FOV in the phase-encoding direction, enable a reduction of k-space acquisition lines, which shortens the echo train length (ETL) and reduces susceptibility artifacts. The purpose of this study was to evaluate the image quality of a zoomed EPI (z-EPI) sequence in diffusion-weighted imaging (DWI) of the prostate in comparison to a conventional single-shot EPI using single-channel (c-EPI1) and multi-channel (c-EPI2) RF excitation, with and without use of an endorectal coil.

Materials And Methods: 33 consecutive patients (mean age: 61 +/- 9 years; mean PSA: 8.67±6.23 ng/ml) with examinations between 10/2012 and 02/2014 were analyzed in this retrospective study. In 26 of 33 patients the initial multiparametric (mp)-MRI was performed on a whole-body 3T scanner (Magnetom Trio, Siemens, Erlangen, Germany) using an endorectal coil (c (conventional)-EPI1). Zoomed-EPI (Z-EPI) examinations of these patients and a complete mp-MRI protocol including c-EPI2 of 7 additional patients were carried out on another 3T wb MR scanner with two-channel dynamic parallel transmit capability (Magnetom Skyra with TimTX TrueShape, Siemens). For z-EPI, the one-dimensional spatially selective RF excitation pulse was replaced by a two-dimensional RF pulse. Degree of image blur and susceptibility artifacts (0=not present to 3= non-diagnostic), maximum image distortion (mm), apparent diffusion coefficient (ADC) values, as well as overall scan preference were evaluated. SNR maps were generated to compare c-EPI2 and z-EPI.

Results: Overall image quality of z-EPI was preferred by both readers in all examinations with a single exception. Susceptibility artifacts were rated significantly lower on z-EPI compared to both other methods (z-EPI vs c-EPI1: p<0.01; z-EPI vs c-EPI2: p<0.01) as well as image blur (z-EPI vs c-EPI1: p<0.01; z-EPI vs c-EPI2: p<0.01). Image distortion was not statistically significantly reduced with z-EPI (z-EPI vs c-EPI1: p=0.12; z-EPI vs c-EPI2: p=0.42). Interobserver agreement for ratings of susceptibility artifacts, image blur and overall scan preference was good. SNR was higher for z-EPI than for c-EPI1 (n=1).

Conclusion: Z-EPI leads to significant improvements in image quality and artifacts as well as image blur reduction improving prostate DWI and enabling accurate fusion with conventional sequences. The improved fusion could lead to advantages in the field of MRI-guided biopsy suspicous lesions and performance of locally ablative procedures for prostate cancer.
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http://dx.doi.org/10.1016/j.zemedi.2015.06.013DOI Listing
June 2016

Fifty Years of Technological Innovation: Potential and Limitations of Current Technologies in Abdominal Magnetic Resonance Imaging and Computed Tomography.

Invest Radiol 2015 Sep;50(9):584-93

From the *Institute of Clinical Radiology and Nuclear Medicine, University Medical Center Mannheim, Medical Faculty Mannheim at Heidelberg University, Mannheim, Germany; †St John's Medical Center, Tulsa, OK; ‡Division of Biomedical Imaging, Faculty of Medicine and Health, University of Leeds, Leeds, United Kingdom; §Medical Physics Department of Radiology, University Medical Center Freiburg, Freiburg, Germany; and ∥Department of Radiology, University of Wisconsin, Madison, WI.

Magnetic resonance imaging (MRI) has become an important modality for the diagnosis of intra-abdominal pathology. Hardware and pulse sequence developments have made it possible to derive not only morphologic but also functional information related to organ perfusion (dynamic contrast-enhanced MRI), oxygen saturation (blood oxygen level dependent), tissue cellularity (diffusion-weighted imaging), and tissue composition (spectroscopy). These techniques enable a more specific assessment of pathologic lesions and organ functionality. Magnetic resonance imaging has thus transitioned from a purely morphologic examination to a modality from which image-based disease biomarkers can be derived. This fits well with several emerging trends in radiology, such as the need to accurately assess response to costly treatment strategies and the need to improve lesion characterization to potentially avoid biopsy. Meanwhile, the cost-effectiveness, availability, and robustness of computed tomography (CT) ensure its place as the current workhorse for clinical imaging. Although the lower soft tissue contrast of CT relative to MRI is a long-standing limitation, other disadvantages such as ionizing radiation exposure have become a matter of public concern. Nevertheless, recent technical developments such as dual-energy CT or dynamic volume perfusion CT also provide more functional imaging beyond morphology.The aim of this article was to review and discuss the most important recent technical developments in abdominal MRI and state-of-the-art CT, with an eye toward the future, providing examples of their clinical utility for the evaluation of hepatic and renal pathologies.
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http://dx.doi.org/10.1097/RLI.0000000000000173DOI Listing
September 2015

Fast inner-volume imaging of the lumbar spine with a spatially focused excitation using a 3D-TSE sequence.

Acad Radiol 2015 Apr 27;22(4):423-9. Epub 2014 Nov 27.

Institute of Clinical Radiology and Nuclear Medicine, University Medical Center Mannheim, Medical Faculty Mannheim, Heidelberg University, Theodor-Kutzer-Ufer 1-3, Mannheim 68167, Germany; Department of Radiology, University Hospital of Cologne, Cologne, Germany.

Rationale And Objectives: The purpose of this study was to evaluate the feasibility and technical quality of a zoomed three-dimensional (3D) turbo spin-echo (TSE) sampling perfection with application optimized contrasts using different flip-angle evolutions (SPACE) sequence of the lumbar spine.

Materials And Methods: In this prospective feasibility study, nine volunteers underwent a 3-T magnetic resonance examination of the lumbar spine including 1) a conventional 3D T2-weighted (T2w) SPACE sequence with generalized autocalibrating partially parallel acquisition technique acceleration factor 2 and 2) a zoomed 3D T2w SPACE sequence with a reduced field of view (reduction factor 2). Images were evaluated with regard to image sharpness, signal homogeneity, and the presence of artifacts by two experienced radiologists. For quantitative analysis, signal-to-noise ratio (SNR) values were calculated.

Results: Image sharpness of anatomic structures was statistically significantly greater with zoomed SPACE (P < .0001), whereas the signal homogeneity was statistically significantly greater with conventional SPACE (cSPACE; P = .0003). There were no statistically significant differences in extent of artifacts. Acquisition times were 8:20 minutes for cSPACE and 6:30 minutes for zoomed SPACE. Readers 1 and 2 selected zSPACE as the preferred sequence in five of nine cases. In two of nine cases, both sequences were rated as equally preferred by both the readers. SNR values were statistically significantly greater with cSPACE.

Conclusions: In comparison to a cSPACE sequences, zoomed SPACE imaging of the lumbar spine provides sharper images in conjunction with a 25% reduction in acquisition time.
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http://dx.doi.org/10.1016/j.acra.2014.09.018DOI Listing
April 2015

CAIPIRINHA-Dixon-TWIST (CDT)-volume-interpolated breath-hold examination (VIBE) for dynamic liver imaging: comparison of gadoterate meglumine, gadobutrol and gadoxetic acid.

Eur J Radiol 2014 Nov 17;83(11):2007-12. Epub 2014 Aug 17.

Institute of Clinical Radiology and Nuclear Medicine, University Medical Center Mannheim, Medical Faculty Mannheim-Heidelberg University, Mannheim, Germany.

Purpose: CAIPIRINHA-Dixon-TWIST (CDT)-VIBE is a robust method for abdominal magnetic resonance imaging providing both high spatial and high temporal resolution. The purpose of this study was to examine the influence of different gadolinium based contrast agents (GBCA) on image quality (IQ) with CDT-VIBE.

Materials And Methods: In this IRB-approved, retrospective, inter-individual comparison study, 86 patients scanned at 3T were included. Within 28s, 14 high-resolution 3D datasets were acquired using CDT-VIBE. 37 patients received 0.1mmol/kg gadoterate meglumine, 28 patients 0.1mmol/kg gadobutrol, and 19 patients 0.1mL/kg gadoxetic acid. Two blinded, board-certified radiologists assessed the image quality on a 5 point scale, as well as the number of hepatic arterial dominant (HAD) phases.

Results: Regardless of the GBCA utilized, CDT-VIBE resulted in good IQ in terms of best IQ achieved among all 14 datasets (gadobutrol 4.3, gadoterate meglumine 3.9, gadoxetic acid 3.7). With respect to worst IQ, the three groups showed statistically significant differences with gadobutrol receiving the highest rating (3.6) and gadoxetic acid the lowest (2.4) (gadoterate meglumine 3.0; 0.0014
Conclusion: Different gadolinium-based contrast agents can be utilized for dynamic liver imaging with CDT-VIBE resulting in good image quality.
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http://dx.doi.org/10.1016/j.ejrad.2014.08.003DOI Listing
November 2014

Zoomed EPI-DWI of the head and neck with two-dimensional, spatially-selective radiofrequency excitation pulses.

Eur Radiol 2014 Oct 5;24(10):2507-12. Epub 2014 Jul 5.

Institute of Clinical Radiology and Nuclear Medicine, University Medical Center Mannheim, Medical Faculty Mannheim - Heidelberg University, Theodor-Kutzer-Ufer 1-3, 68167, Mannheim, Germany,

Objectives: 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).

Material And Methods: 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.

Results: 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.

Conclusion: 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.

Key Points: • Zoomed DWI is feasible in the head and neck. • Image quality improves substantially with zoomed DWI of the neck. • Zoomed DWI exhibits markedly reduced susceptibility artefacts.
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http://dx.doi.org/10.1007/s00330-014-3287-6DOI Listing
October 2014
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