Dimitrios C Karampinos

Technical University of Munich | TUM · Department of Diagnostic and Interventional Radiology

Background Ultrashort echo time (UTE) allows imaging of tissues with short relaxation times, but it comes with the expense of long scan times. Magnitude images of UTE magnetic resonance imaging (MRI) are widely used in pulmonary imaging due to excellent parenchymal signal, but have insufficient contrast for other anatomical regions of the thorax. O...

Chronic refractory pain poses a significant challenge in knee joint pathologies, especially after exhaustion of conservative, arthroscopic, and endoprosthetic therapy options. This case report illustrates an innovative approach using MRI-assisted chemical neurolysis of a genicular nerve to manage persistent knee pain after arthroscopy. A 62-year-ol...

Purpose: Pulmonary MR imaging has made substantial progress in detecting lung nodules through optimisation and developing new sequences in recent years. Nevertheless, the widespread integration of MRI as an alternative method in lung cancer screening is limited either by long scan times or insufficient signal-to-noise ratio. Methods or Backround:...

Context Bone marrow adiposity (BMAT) alterations in patients with type 2 diabetes mellitus (T2DM) may contribute to adverse bone effects. Objective Characterization of BMAT content and composition in patients with well-controlled T2DM. Methods This cross-sectional study included 2 groups of postmenopausal women: one with T2DM and the other withou...

Purpose To evaluate the repeatability and reproducibility of QSM of the liver via single breath‐hold chemical shift–encoded MRI at both 1.5 T and 3 T in a multicenter, multivendor study in subjects with iron overload. Methods This prospective study included four academic medical centers with three different MRI vendors at 1.5 T and 3 T. Subjects w...

Objectives Evaluating the diagnostic feasibility of accelerated pulmonary MR imaging for detection and characterisation of pulmonary nodules with artificial intelligence-aided compressed sensing. Materials and methods In this prospective trial, patients with benign and malignant lung nodules admitted between December 2021 and December 2022 underwe...

Purpose To develop a Dixon‐based self‐navigation approach to estimate and correct temporal variations in radial stack‐of‐stars gradient echo imaging for quantitative body MRI. Methods The proposed method estimates temporal variations using a self‐navigator estimated by a graph‐cut‐based water‐fat separation algorithm on the oversampled k‐space cen...

Purpose To develop and validate a data acquisition scheme combined with a motion‐resolved reconstruction and dictionary‐matching‐based parameter estimation to enable free‐breathing isotropic resolution self‐navigated whole‐liver simultaneous water‐specific () and () mapping for the characterization of diffuse and oncological liver diseases. Method...

Background/Objectives Weight loss outcomes vary individually. Magnetic resonance imaging (MRI)-based evaluation of adipose tissue (AT) might help to identify AT characteristics that predict AT loss. This study aimed to assess the impact of an 8-week low-calorie diet (LCD) on different AT depots and to identify predictors of short-term AT loss using...

Background With rising breast augmentations worldwide, there is an increasing clinical need for an early and accurate detection of implant complications. Purpose To compare the quality of chemical shift encoding-based (CSE) water-fat-silicone separation compared to double inversion recovery (DIR) silicone-only imaging in breast magnetic resonance...

Purpose The aim of this work is to develop an ω ‐3 fatty acid fraction mapping method at 3 T based on a chemical shift encoding model, to assess its performance in a phantom and in vitro study, and to further demonstrate its feasibility in vivo. Methods A signal model was heuristically derived based on spectral appearance and theoretical considera...

Sex-specific abdominal organ volume and proton density fat fraction (PDFF) in people with obesity during a weight loss intervention was assessed with automated multiorgan segmentation of quantitative water-fat MRI. An nnU-Net architecture was employed for automatic segmentation of abdominal organs, including visceral and subcutaneous adipose tissue...

Purpose To investigate the effect of respiratory motion in terms of signal loss in prostate diffusion-weighted imaging (DWI), and to evaluate the usage of partial Fourier in a free-breathing protocol in a clinically relevant b -value range using both single-shot and multi-shot acquisitions. Methods A controlled breathing DWI acquisition was first...

Magnetic resonance (MRI) imaging of the skeletal muscles (muscle MRI for short) is increasingly being used in clinical routine for diagnosis and longitudinal assessment of muscle disorders. However, cross-centre standards for measurement protocol and radiological assessment are still lacking. The aim of this expert recommendation is to present stan...

Background Recent multicenter, multivendor MRI‐based R2* vs. liver iron concentration (LIC) calibrations (i.e., MCMV calibrations) may facilitate broad clinical dissemination of R2*‐based LIC quantification. However, these calibrations are based on a centralized offline R2* reconstruction, and their applicability with vendor‐provided R2* maps is un...

Magnetic resonance (MRI) imaging of the skeletal muscles (muscle MRI for short) is increasingly being used in clinical routine for diagnosis and longitudinal assessment of muscle disorders. However, cross-centre standards for measurement protocol and radiological assessment are still lacking. The aim of this expert recommendation is to present stan...

Partial Fourier encoding is popular in single-shot (ss) diffusion-weighted (DW) echo planar imaging (EPI) because it enables a shorter echo time (TE) and, hence, improves the signal-to-noise-ratio. Motion during diffusion encoding causes k-space shifting and dispersion, which compromises the quality of the homodyne reconstruction. This work provide...

Motion-resolved reconstruction for abdominal magnetic resonance imaging (MRI) remains a challenge due to the trade-off between residual motion blurring caused by discretized motion states and undersampling artefacts. In this work, we generate blurring-free motion-resolved abdominal reconstructions by learning a neural implicit representation direct...

Medical image registration methods can strongly benefit from anatomical labels, which can be provided by segmentation networks at reduced labeling effort. Yet, label noise may adversely affect registration performance. In this work, we propose a quality-aware segmentation-guided registration method that handles such noisy, i.e., low-quality, labels...

Fat–water imaging is combined with techniques measuring short-T2 tissues, especially ultrashort echo time (UTE) techniques. Specifically, techniques combining both UTE and Dixon imaging are labeled as UTE–Dixon imaging techniques, which are applied both to suppress the fat signal in UTE acquisitions and to determine tissue electron density properti...

Purpose Liver T 1 mapping techniques typically require long breath holds or long scan time in free‐breathing, need correction for inhomogeneities and process composite (water and fat) signals. The purpose of this work is to accelerate the multi‐slice acquisition of liver water selective T 1 (wT 1 ) mapping in a single breath hold, improving the k ‐...

To qualitatively and quantitatively evaluate the 2.5-year MRI outcome after Matrix-associated autologous chondrocyte implantation (MACI) at the patella, reconstruction of the medial patellofemoral ligament (MPFL), and combined procedures. In 66 consecutive patients (age 22.8 ± 6.4years) with MACI at the patella (n = 16), MPFL reconstruction (MPFL;...

Motion represents one of the major challenges in magnetic resonance imaging (MRI). Since the MR signal is acquired in frequency space, any motion of the imaged object leads to complex artefacts in the reconstructed image in addition to other MR imaging artefacts. Deep learning has been frequently proposed for motion correction at several stages of...

Cardiac motion causes unpredictable signal loss in respiratory-triggered diffusion-weighted magnetic resonance imaging (DWI) of the liver, especially inside the left lobe. The left liver lobe may thus be frequently neglected in the clinical evaluation of liver DWI. In this work, a data-driven algorithm that relies on the statistics of the signal in...

Abdominal MRI is critical for diagnosing a wide variety of diseases. However, due to respiratory motion and other organ motions, it is challenging to obtain motion-free and isotropic MRI for clinical diagnosis. Imaging patients with inflammatory bowel disease (IBD) can be especially problematic, owing to involuntary bowel movements and difficulties...

Purpose: Multi-echo Stack-of-stars (SoS) radial k-space trajectories with golden angle ordering are becoming popular for free-breathing abdominal Dixon imaging and proton density fat fraction (PDFF) mapping. Gradient chain imperfections including eddy currents and system delays are known to affect the image quality of radial imaging and to confound...

Objectives MR imaging-based proton density fat fraction (PDFF) and T2* imaging has shown to be useful for the evaluation of degenerative changes in the spine. Therefore, the aim of this study was to investigate the influence of myelotoxic chemotherapy on the PDFF and T2* of the thoracolumbar spine in comparison to changes in bone mineral density (B...

Motion-resolved reconstruction for abdominal magnetic resonance imaging (MRI) remains a challenge due to the trade-off between residual motion blurring caused by discretized motion states and undersampling artefacts. In this work, we propose to generate blurring-free motion-resolved abdominal reconstructions by learning a neural implicit representa...

Background: Several magnetic resonance (MR) techniques have been suggested for radiation-free imaging of osseous structures. Purpose: To compare the diagnostic value of ultra-short echo time and gradient echo T1-weighted MRI for the assessment of vertebral pathologies using histology and computed tomography (CT) as the reference standard. Study...

Objectives To detect and evaluate early signs of apical periodontitis using MRI based on a 3D short-tau-inversion-recovery (STIR) sequence compared to conventional panoramic radiography (OPT) and periapical radiographs in patients with apical periodontitis. Materials and methods Patients with clinical evidence of periodontal disease were enrolled...

Objectives To evaluate and compare the diagnostic performance of CT-like images based on a 3D T1-weighted spoiled gradient-echo sequence (T1 GRE), an ultra-short echo time sequence (UTE), and a 3D T1-weighted spoiled multi-echo gradient-echo sequence (FRACTURE) with conventional CT in patients with suspected osseous shoulder pathologies. Materials...

Abstract Background Tension-type headache (TTH) is the most prevalent primary headache disorder. Neck pain is commonly associated with primary headaches and the trigemino-cervical complex (TCC) refers to the convergence of trigeminal and cervical afferents onto neurons of the brainstem, thus conceptualizes the emergence of headache in relation to n...

Background: Human brown adipose tissue (BAT), mostly located in the cervical/supraclavicular region, is a promising target in obesity treatment. Magnetic resonance imaging (MRI) allows for mapping the fat content quantitatively. However, due to the complex heterogeneous distribution of BAT, it has been difficult to establish a standardized segment...

Motion represents one of the major challenges in magnetic resonance imaging (MRI). Since the MR signal is acquired in frequency space, any motion of the imaged object leads to complex artefacts in the reconstructed image in addition to other MR imaging artefacts. Deep learning has been frequently proposed for motion correction at several stages of...

Objectives: To examine the effect of high-b-value computed diffusion-weighted imaging (cDWI) on solid lesion detection and classification in pancreatic intraductal papillary mucinous neoplasm (IPMN), using endoscopic ultrasound (EUS) and histopathology as a standard of reference. Methods: Eighty-two patients with known or suspected IPMN were ret...

Purpose To (a) develop a preconditioned water–fat–silicone total field inversion (wfsTFI) algorithm that directly estimates the susceptibility map from complex multi‐echo data in the breast in the presence of silicone and to (b) evaluate the performance of wfsTFI for breast quantitative susceptibility mapping (QSM) in silico and in vivo in comparis...

Context: Noninvasive assessment of proton density fat fraction (PDFF) by MRI may improve the prediction of fractures. Objective: To determine if an association exists between PDFF and fractures. Design: A case-control study with 2 groups of postmenopausal women: one with recent osteoporotic fractures, and the other with no fractures. Setting:...

Objectives To evaluate the diagnostic performance of an automated reconstruction algorithm combining MR imaging acquired using compressed SENSE (CS) with deep learning (DL) in order to reconstruct denoised high-quality images from undersampled MR images in patients with shoulder pain. Methods Prospectively, thirty-eight patients (14 women, mean ag...

Objectives There is a clinical need for a non-ionizing, quantitative assessment of breast density, as one of the strongest independent risk factors for breast cancer. This study aims to establish proton density fat fraction (PDFF) as a quantitative biomarker for fat tissue concentration in breast MRI and correlate mean breast PDFF to mammography....

Background: To assess the performance of prospectively accelerated and deep learning (DL) reconstructed T2-weighted (T2w) imaging in volunteers and patients with histologically proven prostate cancer (PCa). Methods: Prospectively undersampled T2w datasets were acquired with acceleration factors of 1.7 (reference), 3.4 and 4.8 in 10 healthy volun...

Background Quantitative magnetic resonance imaging (MRI) techniques such as chemical shift encoding-based water-fat separation techniques (CSE-MRI) are increasingly applied as noninvasive biomarkers to assess the biochemical composition of vertebrae. This study aims to investigate the longitudinal change of proton density fat fraction (PDFF) and T2...

Hepatocellular carcinoma (HCC) is the most common primary malignant tumor of the liver worldwide. Noninvasive diagnosis of HCC is possible based on imaging features, without the need for tissue diagnosis. Liver Imaging Reporting and Data System (LI-RADS) CT/MRI diagnostic algorithm allows for standardized radiological interpretation and reporting o...

The present chapter introduces the basic concepts of chemical shift encoding-based water–fat separation. First, an introduction of the theory on chemical species separation is presented, followed by methods for solving the water–fat separation problem and water–fat separation for non-Cartesian imaging trajectories. Finally, confounding factors in f...

Purpose To (a) define multi‐peak fat model‐based effective in‐phase echo times for quantitative susceptibility mapping (QSM) in water–fat regions, (b) analyze the relationship between fat fraction, field map quantification bias and susceptibility bias, and (c) evaluate the susceptibility mapping performance of the proposed effective in‐phase echoes...

Background: Proton-density fat fraction (PDFF) and T2* of the vertebrae, as well as the cross-sectional area (CSA) of the paraspinal musculature (PSM), have been suggested as biomarkers for bone fragility. The aim of this study was to longitudinally assess changes in PDFF, T2* and CSA of the PSM over 6 months in patients with and without osteoporo...

Objectives: To assess and compare the diagnostic performance of CT-like images based on a three- dimensional (3D) T1-weighted spoiled gradient-echo sequence (3D T1 GRE) with CT in patients with acute traumatic fractures of the mandible. Materials and methods: Subjects with acute mandibular fractures diagnosed on conventional CT were prospectively r...

Background MRI is a standard of care tool to measure liver iron concentration (LIC). Compared with regulatory-approved R2 MRI, R2* MRI has superior speed and is available in most MRI scanners; however, the cross-vendor reproducibility of R2*-based LIC estimation remains unknown. Purpose To evaluate the reproducibility of LIC via single-breath-hold...

Purpose To assess the effect of respiratory motion and cardiac driven pulsation in renal DWI and to examine asymmetrical velocity‐compensated diffusion encoding waveforms for robust ADC mapping in the kidneys. Methods The standard monopolar Stejskal‐Tanner pulsed gradient spin echo (pgse) and the asymmetric bipolar velocity‐compensated (asym‐vc) d...

Chemical shift encoding-based water–fat MRI (CSE-MRI)-derived proton density fat fraction (PDFF) has been used for non-invasive assessment of regional body fat distributions. More recently, texture analysis (TA) has been proposed to reveal even more detailed information about the vertebral or muscular composition beyond PDFF. The aim of this study...

Objective The aim of this study was to longitudinally determine the prognostic value of early postoperative quantitative 3T-MRI (magnetic resonance imaging) parameters of subchondral bone marrow for 2-year clinical and MRI outcome after matrix-associated autologous chondrocyte implantation (MACI) with autologous bone grafting (ABG) at the knee. De...

Objectives To evaluate the performance of single-echo Dixon water-fat imaging and computed tomography (CT)–like imaging based on a single ultrashort echo time (sUTE) MR sequence for imaging of vertebral fractures as well as degenerative bone changes of the spine in comparison to conventional CT and MR sequences. Methods Thirty patients with suspec...

Purpose Osteoporosis is prevalent and entails alterations of vertebral bone and marrow. Yet, the spine is also a common site of metastatic spread. Parameters that can be non-invasively measured and could capture these alterations are the volumetric bone mineral density (vBMD), proton density fat fraction (PDFF) as an estimate of relative fat conten...

Introduction: The main pathologies in muscles of patients with neuromuscular diseases (NMD) are fatty infiltration and edema. Recently, quantitative magnetic resonance (MR) imaging for determination of the MR biomarkers proton density fat fraction (PDFF) and water T2 (T2w ) has been advanced. Biophysical effects or pathology can have different eff...

Purpose To evaluate the diagnostic value of CT-like images based on a 3D T1-weighted spoiled gradient echo-based sequence (T1SGRE) for the visualization of the pediatric skull and the identification of pathologies, such as craniosynostosis or fractures. Methods In this prospective study, 20 patients with suspected craniosynostosis (mean age 1.26 ±...

Objectives: To evaluate a compressed sensing artificial intelligence framework (CSAI) to accelerate MRI acquisition of the ankle. Methods: Thirty patients were scanned at 3T. Axial T2-w, coronal T1-w, and coronal/sagittal intermediate-w scans with fat saturation were acquired using compressed sensing only (12:44 min, CS), CSAI with an accelerati...

Osteoporosis is a highly prevalent systemic skeletal disease that is characterized by low bone mass and microarchitectural bone deterioration. It predisposes to fragility fractures that can occur at various sites of the skeleton, but vertebral fractures (VFs) have been shown to be particularly common. Prevention strategies and timely intervention d...

Purpose To study the effect of field inhomogeneity distributions in trabecularized bone regions on the gradient echo (GRE) signal with short TEs and to characterize quantification errors on R2*$$ {R}_2^{\ast } $$ and proton density fat fraction (PDFF) maps when using a water‐fat model with an exponential R2*$$ {R}_2^{\ast } $$ decay model at short...

Background: The adipocyte-hypertrophy associated remodeling of fat cell function is considered causal for the development of metabolic disorders. A better understanding of transcriptome and fatty acid (FA) related alterations with adipocyte hypertrophy combined with less-invasive strategies for the detection of the latter can help to increase the...

Magnetic resonance imaging (MRI) is widely utilized for diagnosing and monitoring of spinal disorders. For a number of applications, particularly those related to quantitative MRI, an essential step towards achieving reliable and objective measurements is the segmentation of the examined structures. Performed manually, such process is time-consumin...

Purpose MR temperature monitoring of mild radiofrequency hyperthermia (RF‐HT) of cancer exploits the linear resonance frequency shift of water with temperature. Motion‐induced susceptibility distribution changes cause artifacts that we correct here using the total field inversion (TFI) approach. Methods The performance of TFI was compared to two b...

Background The difference of proton density fat fraction (PDFF) between supraclavicular and gluteal adipose tissue might indicate the presence of brown adipose tissue (BAT). Aim of this cross-sectional study was to investigate the association between PDFF over the supraclavicular fat region as a proxy of BAT proportion and resting metabolic rate (R...

Background To evaluate the diagnostic value of MR-derived CT-like images and simulated radiographs compared with conventional radiographs in patients with suspected shoulder pathology. Methods 3 T MRI of the shoulder including a 3D T1-weighted gradient echo sequence was performed in 25 patients (mean age 52.4 ± 18 years, 13 women) with suspected s...