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4 Publications visible to you, out of a total of 4
Reduction of breathing artifacts in multifrequency magnetic resonance elastography of the abdomen.

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PURPOSE: With abdominal magnetic resonance elastography (MRE) often suffering from breathing artifacts, it is recommended to perform MRE during breath-hold. However, breath-hold acquisition prohibits … extended multifrequency MRE examinations and yields inconsistent results when patients cannot hold their breath. The purpose of this work was to analyze free-breathing strategies in multifrequency MRE of abdominal organs. METHODS: Abdominal MRE with 30, 40, 50, and 60 Hz vibration frequencies and single-shot, multislice, full wave-field acquisition was performed four times in 11 healthy volunteers: once with multiple breath-holds and three times during free breathing with ungated, gated, and navigated slice adjustment. Shear wave speed maps were generated by tomoelastography inversion. Image registration was applied for correction of intrascan misregistration of image slices. Sharpness of features was quantified by the variance of the Laplacian. RESULTS: Total scan times ranged from 120 seconds for ungated free-breathing MRE to 376 seconds for breath-hold examinations. As expected, free-breathing MRE resulted in larger organ displacements (liver, 4.7 +/- 1.5 mm; kidneys, 2.4 +/- 2.2 mm; spleen, 3.1 +/- 2.4 mm; pancreas, 3.4 +/- 1.4 mm) than breath-hold MRE (liver, 0.7 +/- 0.2 mm; kidneys, 0.4 +/- 0.2 mm; spleen, 0.5 +/- 0.2 mm; pancreas, 0.7 +/- 0.5 mm). Nonetheless, breathing-related displacement did not affect mean shear wave speed, which was consistent across all protocols (liver, 1.43 +/- 0.07 m/s; kidneys, 2.35 +/- 0.21 m/s; spleen, 2.02 +/- 0.15 m/s; pancreas, 1.39 +/- 0.15 m/s). Image registration before inversion improved the quality of free-breathing examinations, yielding no differences in image sharpness to uncorrected breath-hold MRE in most organs (P > .05). CONCLUSION: Overall, multifrequency MRE is robust to breathing when considering whole-organ values. Respiration-related blurring can readily be corrected using image registration. Consequently, ungated free-breathing MRE combined with image registration is recommended for multifrequency MRE of abdominal organs.

Authors: M. Shahryari, T. Meyer, C. Warmuth, H. Herthum, G. Bertalan, H. Tzschatzsch, L. Stencel, S. Lukas, L. Lilaj, J. Braun, I. Sack

Date Published: 26th Oct 2020

Publication Type: Journal

Tomoelastography Distinguishes Noninvasively between Benign and Malignant Liver Lesions.

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Patients with increased liver stiffness have a higher risk of developing cancer, however, the role of fluid-solid tissue interactions and their contribution to liver tumor malignancy remains elusive. … Tomoelastography is a novel imaging method for mapping quantitatively the solid-fluid tissue properties of soft tissues in vivo. It provides high resolution and thus has clear clinical applications. In this work we used tomoelastography in 77 participants, with a total of 141 focal liver lesions of different etiologies, to investigate the contributions of tissue stiffness and fluidity to the malignancy of liver tumors. Shear-wave speed (c) as surrogate for tissue stiffness and phase-angle (phi) of the complex shear modulus reflecting tissue fluidity were abnormally high in malignant tumors and allowed them to be distinguished from nontumorous liver tissue with high accuracy [c: AUC = 0.88 with 95% confidence interval (CI) = 0.83-0.94; phi: AUC = 0.95, 95% CI = 0.92-0.98]. Benign focal nodular hyperplasia and hepatocellular adenoma could be distinguished from malignant lesions on the basis of tumor stiffness (AUC = 0.85, 95% CI = 0.72-0.98; sensitivity = 94%, 95% CI = 89-100; and specificity = 85%, 95% CI = 62-100), tumor fluidity (AUC = 0.86, 95% CI = 0.77-0.96; sensitivity = 83%, 95% CI = 72-93; and specificity = 92%, 95% CI = 77-100) and liver stiffness (AUC = 0.84, 95% CI = 0.74-0.94; sensitivity = 72%, 95% CI = 59-83; and specificity = 88%, 95% CI = 69-100), but not on the basis of liver fluidity. Together, hepatic malignancies are characterized by stiff, yet fluid tissue properties, whereas surrounding nontumorous tissue is dominated by solid properties. Tomoelastography can inform noninvasively on the malignancy of suspicious liver lesions by differentiating between benign and malignant lesions with high sensitivity based on stiffness and with high specificity based on fluidity. SIGNIFICANCE: Solid-fluid tissue properties measured by tomoelastography can distinguish malignant from benign masses with high accuracy and provide quantitative noninvasive imaging biomarkers for liver tumors.

Authors: M. Shahryari, H. Tzschatzsch, J. Guo, S. R. Marticorena Garcia, G. Boning, U. Fehrenbach, L. Stencel, P. Asbach, B. Hamm, J. A. Kas, J. Braun, T. Denecke, I. Sack

Date Published: 15th Nov 2019

Publication Type: Not specified

Quantitative MRI for Assessment of Treatment Outcomes in a Rabbit VX2 Hepatic Tumor Model.

Abstract (Expand)

Globally, primary and secondary liver cancer is one of the most common cancer types, accounting 8.2% of deaths worldwide in 2018. One of the key strategies to improve the patient's prognosis is the … early diagnosis, when liver function is still preserved. In hepatocellular carcinoma (HCC), the typical wash-in/wash-out pattern in conventional magnetic resonance imaging (MRI) reaches a sensitivity of 60% and specificity of 96-100%. However, in recent years functional MRI sequences such as hepatocellular-specific gadolinium-based dynamic-contrast enhanced MRI, diffusion-weighted imaging (DWI), and magnetic resonance spectroscopy (MRS) have been demonstrated to improve the evaluation of treatment success and thus the therapeutic decision-making and the patient's outcome. In the preclinical research setting, the VX2 liver rabbit tumor, which once originated from a virus-induced anaplastic squamous cell carcinoma, has played a longstanding role in experimental interventional oncology. Especially the high tumor vascularity allows assessing the treatment response of locoregional interventions such as radiofrequency ablation (RFA) and transcatheter arterial embolization (TACE). Functional MRI has been used to monitor the tumor growth and viability following interventional treatment. Besides promising results, a comprehensive overview of functional MRI sequences used so far in different treatment setting is lacking, thus lowering the comparability of study results. This review offers a comprehensive overview of study protocols, results, and limitations of quantitative MRI sequences applied to evaluate the treatment outcome of VX2 hepatic tumor models, thus generating a unique basis for future MRI studies and potential translation into the clinical setting. Level of Evidence: 2 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2019.

Authors: S. Keller, J. Chapiro, J. Brangsch, C. Reimann, F. Collettini, I. Sack, L. J. Savic, B. Hamm, S. N. Goldberg, M. Makowski

Date Published: 12th Nov 2019

Publication Type: Not specified

Tomoelastography for non-invasive detection and treatment monitoring in acute appendicitis.

Abstract (Expand)

Acute appendicitis is the most common cause of the acute abdomen syndrome and can be treated either surgically or conservatively with antibiotics. This case demonstrates the first time use of mechanics … based MRI by tomoelastography with generation of quantitative maps of tissue stiffness (shear wave speed in m/s) and tissue fluidity (shear modulus loss angle, in rad) in a case of uncomplicated acute appendicitis with antibiotic treatment at (i) baseline, (ii) the end of treatment (EOT) and (iii) the 10 day follow-up after EOT. Baseline maps of stiffness and fluidity revealed to the naked eye the extent of intestinal inflammation by markedly increased values of stiffness and fluidity (2.56+/-0.12 m/s, 1.37+/-0.24 rad) compared with normal values, indicating the immediate response to antibiotic treatment at EOT (1.47+/-0.28 m/s, 0.80+/-0.11 rad) and persistent normalisation at follow-up (1.54+/-0.22 m/s, 0.92+/-0.22 rad). Tomoelastography is a non-invasive, quantitative imaging method for mechanics based characterisation and follow-up of acute appendicitis.

Authors: S. R. Marticorena Garcia, B. Hamm, I. Sack

Date Published: 26th Aug 2019

Publication Type: Not specified

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