Publications by authors named "Tobias Geith"

20 Publications

  • Page 1 of 1

[Imaging of intrahepatic cholangiocarcinoma : Reliable diagnosis according to the new S3 guideline].

Radiologe 2022 Jan 14. Epub 2022 Jan 14.

Interventionelle Radiologie, Klinikum rechts der Isar der Technischen Universität München, Ismaninger Str. 22, 81675, München, Deutschland.

The S3 guideline on hepatocellular carcinoma has been expanded to include malignant biliary carcinoma (synonym cholangiocarcinoma [CCA]). Magnetic resonance imaging (MRI) with additional magnetic resonance cholangiopancreatography (MRCP) is the imaging modality of choice to evaluate local findings. Use of gadolinium ethoxybenzyl diethylenetriamine penta-acetic acid (Gd-EOB-DTPA)-based contrast agent increases its diagnostic value. Histologic confirmation is always required when diagnosing intrahepatic CCA (iCCA) because using imaging alone there is a risk of confusion with HCC subtypes.
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http://dx.doi.org/10.1007/s00117-021-00961-wDOI Listing
January 2022

Efficacy of ultrasound assisted catheter-directed thrombolysis compared to catheter-directed thrombolysis in vitro.

Acta Radiol 2021 Dec 6:2841851211061440. Epub 2021 Dec 6.

Department of Interventional Radiology, 9184Klinikum rechts der Isar of the Technical University of Munich, Munich, Germany.

Background: Catheter-directed thrombolysis (CDT) is an effective and safe endovascular method used in critical limb ischemia and many other thromboembolic events. Ultrasound-assisted catheter-directed thrombolysis (US-CDT) is an emerging technique considered to accelerate thrombolysis and therefore is supposed to improve outcome.

Purpose: To evaluate the efficacy of US-CDT in comparison to standard CDT in vitro.

Material And Methods: A total of 69 sets of human venous blood were evaluated, each comprising a tube just treated with CDT, a tube treated with US-CDT, and a control tube. All tubes were kept under physiological conditions. Except for the controls, in all tubes 5 mg of tissue-type plasminogen activator was administered over the predetermined treatment interval. Thrombus mass was weighted at the end of the lysis intervals at 6 h or 24 h, respectively.

Results: CDT led to a mean thrombus reduction of 32% and ultrasound-assisted lysis led to a mean thrombus reduction of 41% ( < 0.001 for both). Thrombus reduction was significantly higher after US-CDT compared to CDT ( = 0.001). The better efficacy of US-CDT was mostly already apparent at early phases during thrombolysis and did further mildly increase over time (r = 0.24;  = 0.047).

Conclusion: In vitro US-CDT is significantly superior to standard CDT; this effect is apparent at an early timepoint of lysis and slightly further increases over time.
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http://dx.doi.org/10.1177/02841851211061440DOI Listing
December 2021

Outcome and Safety after 103 Radioembolizations with Yttrium-90 Resin Microspheres in 73 Patients with Unresectable Intrahepatic Cholangiocarcinoma-An Evaluation of Predictors.

Cancers (Basel) 2021 Oct 27;13(21). Epub 2021 Oct 27.

Department of Interventional Radiology, Technical University Munich, 81377 Munich, Germany.

Trans-arterial radioembolization (TARE) is increasingly evaluated for unresectable intrahepatic cholangiocarcinoma (ICC). Not all ICC patients benefit equally well from TARE. Therefore, we sought to evaluate variables predicting progression-free survival (PFS) and overall survival (OS). Patients with non-resectable ICC underwent TARE and were treated with 90Y resin microspheres. Baseline characteristics, biochemical/clinical toxicities, and response were examined for impact on PFS and OS. A total of 103 treatments were administered to 73 patients without major complications or toxicity. Mean OS was 18.9 months (95% confidence intervals (CI); 13.9-23.9 months). Mean and median PFS were 10.1 months (95% CI; 7.9-12.2) and 6.4 months (95% CI; 5.20-7.61), respectively. Median OS and PFS were significantly prolonged in patients with baseline cholinesterase (CHE) ≥ 4.62 kU/L (OS: 14.0 vs. 5.5 months; PFS: 6.9 vs. 3.2 months; < 0.001). Patients with a tumor burden ≤ 25% had a significantly longer OS (15.2 vs. 6.6 months; = 0.036). Median PFS was significantly longer for patients with multiple TARE cycles (24.4 vs. 5.8 months; = 0.04). TARE is a considerable and safe option for unresectable ICC. CA-19-9, CHE, and tumor burden have predictive value for survival in patients treated with TARE. Multiple TARE treatments might further improve survival; this has to be confirmed by further studies.
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http://dx.doi.org/10.3390/cancers13215399DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8582544PMC
October 2021

Risk factors assessment for radiographically guided port implantations with forearm access.

PLoS One 2021 26;16(10):e0259127. Epub 2021 Oct 26.

Department of Interventional Radiology, University hospital Klinikum rechts der Isar, School of Medicine, Technical University of Munich, Munich, Germany.

Introduction: Port implantations at the forearm are associated with an increased risk of relevant vein thrombosis. Therefore, with this study we sought to identify the responsible risk factors to improve technical quality of the method.

Methods: This is a retrospective analysis of 313 patients with port implantation at the forearm in 2019. Then, exploratory statistics were conducted comprising Cox-Regression and Kaplan-Meier-Analyses.

Results: Mean age was 60 ± 14 years. 232 (74%) of the patients were female. No early infection was observed. 29 late infections and 57 cases of thrombosis occurred. In only 9% of the patients with thrombosis hospital admission was necessary for treatment. Median interval to the diagnosis of thrombosis was 23 days; inter-quartile-range: 16-75. Mean interval to elective port explantation was 227 ± 128 days. There was no effect of occurrence of thrombosis of the interventionalist, the assistance nor of several technical aspects. However, there was a significantly lower risk of thrombosis for primary implanted port system compared to replacement ports, Hazard-ratio: 0.34 [Confidence interval: 0.172, 0.674], p = 0.002. Age was a significant risk factor for late infections, Hazard-ratio: 3.35 [Confidence interval:1.84, 6.07], p < 0.0001.

Conclusion: The main risk factor for adverse outcome after radiographically guided port implantation at the forearm is the type of the implanted port system. The reason for that might not be the material itself but the experience of a team with a certain port system. Age is a risk factor for late complications.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0259127PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8547706PMC
December 2021

Multiscale X-ray phase contrast imaging of human cartilage for investigating osteoarthritis formation.

J Biomed Sci 2021 Jun 7;28(1):42. Epub 2021 Jun 7.

Department of Clinical Radiology, Faculty of Medicine, Ludwig-Maximilians-University, Marchioninistr. 15, 81377, Munich, Germany.

Background: The evolution of cartilage degeneration is still not fully understood, partly due to its thinness, low radio-opacity and therefore lack of adequately resolving imaging techniques. X-ray phase-contrast imaging (X-PCI) offers increased sensitivity with respect to standard radiography and CT allowing an enhanced visibility of adjoining, low density structures with an almost histological image resolution. This study examined the feasibility of X-PCI for high-resolution (sub-) micrometer analysis of different stages in tissue degeneration of human cartilage samples and compare it to histology and transmission electron microscopy.

Methods: Ten 10%-formalin preserved healthy and moderately degenerated osteochondral samples, post-mortem extracted from human knee joints, were examined using four different X-PCI tomographic set-ups using synchrotron radiation the European Synchrotron Radiation Facility (France) and the Swiss Light Source (Switzerland). Volumetric datasets were acquired with voxel sizes between 0.7 × 0.7 × 0.7 and 0.1 × 0.1 × 0.1 µm. Data were reconstructed by a filtered back-projection algorithm, post-processed by ImageJ, the WEKA machine learning pixel classification tool and VGStudio max. For correlation, osteochondral samples were processed for histology and transmission electron microscopy.

Results: X-PCI provides a three-dimensional visualization of healthy and moderately degenerated cartilage samples down to a (sub-)cellular level with good correlation to histologic and transmission electron microscopy images. X-PCI is able to resolve the three layers and the architectural organization of cartilage including changes in chondrocyte cell morphology, chondrocyte subgroup distribution and (re-)organization as well as its subtle matrix structures.

Conclusions: X-PCI captures comprehensive cartilage tissue transformation in its environment and might serve as a tissue-preserving, staining-free and volumetric virtual histology tool for examining and chronicling cartilage behavior in basic research/laboratory experiments of cartilage disease evolution.
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http://dx.doi.org/10.1186/s12929-021-00739-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8182937PMC
June 2021

[Comparison of radiation exposure in common hepatic interventions : A retrospective analysis of DeGIR registry data].

Radiologe 2021 Jan;61(1):80-86

Sektion für Interventionelle Radiologie, Klinikum rechts der Isar der Technischen Universität München, Ismaninger Straße 22, München, Deutschland.

Background: Transcatheter arterial chemoembolization (TACE) and biliary interventions are common procedures.

Objectives: In this retrospective study, the radiation exposure of patients undergoing hepatic intervention will be analyzed and compared depending on the type and objective of the intervention.

Materials And Methods: This is an analysis of 7003 data sets of performed TACEs and biliary interventions from the DeGIR registry for the years 2016, 2017, and 2018. The dose area product (DAP), fluoroscopy time (FT), type of intervention, and anatomically defined target were recorded.

Results: Data with documented radiation doses were available for 4985 TACEs and for 2018 biliary interventions. For biliary interventions the median DAP was 2594 (interquartile range [IQR] = 1174-5858) cGycm. For TACE, the median DAP was 11,632 [IQR = 5530-22,800] cGycm and significantly higher compared to biliary interventions (p < 0.0001). Biliary interventions with the highest DAP take place at the common hepatic duct; procedures with the longest FT were registered at the hepatic duct bifurcation.

Conclusions: The individual radiation exposure during liver interventions is less dependent of the complexity of the procedure or the fluoroscopy time, but rather on the type of intervention and the anatomic target. The presented data can help to approximately estimate the radiation exposure in advance when planning an intervention.
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http://dx.doi.org/10.1007/s00117-020-00737-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7810650PMC
January 2021

Is bone marrow edema syndrome a precursor of hip or knee osteonecrosis? Results of 49 patients and review of the literature.

Diagn Interv Radiol 2020 Jul;26(4):355-362

Department of Radiology, University Hospital, Ludwig-Maximilians-University Munich, Munich, Germany.

Purpose: Diagnosis of bone marrow edema syndrome (BMES) can be challenging. There is sometimes uncertainty about the correct diagnosis of BMES on morphologic magnetic resonance imaging (MRI), since subchondral findings like lines and spots can be misinterpreted as "beginning" or "possible" avascular osteonecrosis (AVN). The aim of our study was to systematically assess the temporal course of BMES from first diagnosis on MRI until the end of clinical symptoms and the full disappearance of bone marrow edema (BME) to determine whether subchondral lines and spots detected in these patients can develop into osteonecrosis.

Methods: In a combined retrospective and prospective study, we retrieved serial MRI scans of hips and knees with BME from the hospital database. According to clinical and imaging data, all patients with degenerative, infectious/inflammatory, rheumatic, neoplastic conditions and those showing typical osteonecrosis were excluded. We collected all available MRI examinations from first detection of BME until its disappearance. In case edema had not fully resolved in the last available MRI scan, we performed an MRI with an additional dynamic contrast-enhanced (DCE-MRI) sequence. For each MRI scan, we recorded the severity of edema, the presence of subchondral hypointense lines and the presence of subchondral focal hypointense zones on T1-weighted images by two independent readers. The DCE-MRI scans were used to calculate parameter maps to assess the perfusion characteristics.

Results: The study comprised 49 patients aged 22-71 years. In total, 171 morphologic and 5 DCE-MRI scans were evaluated. In 44 patients (89.8%), the BMES completely healed without remnants. In 18 of 49 patients (36.7%), a subchondral line was present in the first MRI exam. Nine patients (18.4%) developed a subchondral line within 1-5 months after the first MRI. In total, 27 out of 49 patients (55.1%) had subchondral lines (12 knees, 15 hips) during the timeframe of the study. All subchondral lines disappeared in the timeframe of the study. Subchondral focal hypointense zones were present in 14 out of 49 patients (28.6%): in 9 cases, subchondral focal hypointense zones disappeared after a median of 5.5 months (range, 1-85 months), while in 5 cases, subchondral focal lesions persisted until the end of the study (up to more than 85 months) without edema in the surrounding bone. All persisting subchondral focal lesions were hyperperfused. These 5 patients had associated meniscal lesions.

Conclusion: Our study shows that subchondral lines and spots found in patients with BMES do not develop into AVN. Subchondral lines, which resemble subchondral insufficiency fractures, are associated with BMES. Subchondral focal T1-hypointense zones do not represent AVN; most probably these areas represent reparative processes within the subchondral bone, where tensile and shear force overload is present due to altered biomechanics.
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http://dx.doi.org/10.5152/dir.2020.19188DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7360071PMC
July 2020

Endovascular rescue-stenting of a ruptured mycotic subclavian pseudoaneurysm caused by pulmonary aspergillosis.

Eur Heart J 2019 08;40(30):2520

Klinik und Poliklinik für Innere Medizin I, Klinikum rechts der Isar, Technische Universität München, Ismaninger Straße 22, Munich, Germany.

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http://dx.doi.org/10.1093/eurheartj/ehz261DOI Listing
August 2019

Quantitative Assessment of Degenerative Cartilage and Subchondral Bony Lesions in a Preserved Cadaveric Knee: Propagation-Based Phase-Contrast CT Versus Conventional MRI and CT.

AJR Am J Roentgenol 2018 Jun 9;210(6):1317-1322. Epub 2018 Apr 9.

1 Department of Radiology, University Hospital, LMU Munich, Marchioninistrasse 15, Munich 81377, Germany.

Objective: The aim of this study was to quantitatively assess hyaline cartilage and subchondral bone conditions in a fully preserved cadaveric human knee joint using high-resolution x-ray propagation-based phase-contrast imaging (PBI) CT and to compare the performance of the new technique with conventional CT and MRI.

Materials And Methods: A cadaveric human knee was examined using an x-ray beam of 60 keV, a detector with a 90-mm FOV, and a pixel size of 46 × 46 μm. PBI CT images were reconstructed with both the filtered back projection algorithm and the equally sloped tomography method. Conventional 3-T MRI and CT were also performed. Measurements of cartilage thickness, cartilage lesions, International Cartilage Repair Society scoring, and detection of subchondral bone changes were evaluated. Visual inspection of the specimen akin to arthroscopy was conducted and served as a standard of reference for lesion detection.

Results: Loss of cartilage height was visible on PBI CT and MRI. Quantification of cartilage thickness showed a strong correlation between the two modalities. Cartilage lesions appeared darker than the adjacent cartilage on PBI CT. PBI CT showed similar agreement to MRI for depicting cartilage substance defects or lesions compared with the visual inspection. The assessment of subchondral bone cysts showed moderate to strong agreement between PBI CT and CT.

Conclusion: In contrast to the standard clinical methods of MRI and CT, PBI CT is able to simultaneously depict cartilage and bony changes at high resolution. Though still an experimental technique, PBI CT is a promising high-resolution imaging method to evaluate comprehensive changes of osteoarthritic disease in a clinical setting.
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http://dx.doi.org/10.2214/AJR.17.18286DOI Listing
June 2018

Fracture generation in human vertebrae under compression loading: The influence of pedicle preservation and bone mineral density on in vitro fracture behavior.

Technol Health Care 2018 ;26(1):155-163

Department of Orthopedics, Physical Medicine and Rehabilitation, University Hospital, LMU Munich - Campus Grosshadern, Munich, Germany.

Background: Fractured vertebral bodies are a common and wide spread health issue.

Objective: The purpose of this study was to develop a standardized method to experimentally generate compression fractures in vertebral bodies. The influence of the pedicles has been investigated with regards to the fracture behavior. The correlation between bone mineral density (BMD), the cause of fractures and the fracture behavior was investigated.

Methods: Twenty-one fresh frozen human lumbar spines were examined for bone mineral density (BMD) by means of quantitative computed tomography (qCT). All soft tissue was removed, vertebrae were carefully separated from each other and the exposed cranial and caudal endplates were covered with a thin layer of resin to generate a plane and homogeneous surface. A total of 80 vertebral bodies were tested until fracture.

Results: A good positive correlation was found between BMD, fracture compression force and stiffness of the vertebral body. No significant differences were found between the fractures generated in vertebral bodies with and without pedicles, respectively.

Conclusions: Our model represents a consolidation of already existing testing devices. The comparative measurement of the BMD and the fracture behavior shows validity. In contrast to other authors, the force was applied to the whole vertebral body. Furthermore the upper and lower plates were not parallelized and therefore the natural anatomic shape was imitated. Fracture behavior was not altered by removing the pedicles.
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http://dx.doi.org/10.3233/THC-171086DOI Listing
September 2018

Transient Bone Marrow Edema Syndrome versus Osteonecrosis: Perfusion Patterns at Dynamic Contrast-enhanced MR Imaging with High Temporal Resolution Can Allow Differentiation.

Radiology 2017 05 1;283(2):478-485. Epub 2016 Dec 1.

From the Departments of Clinical Radiology (T.G., O.D., M.R., A.B.M.), Orthopedic Surgery (T.N.), and the Anatomical Institute (S.M.), Ludwig-Maximilians University Munich, Campus Grosshadern, Marchioninistrasse 15, 81377 Munich, Germany.

Purpose To prospectively evaluate the perfusion patterns at quantitative dynamic contrast material-enhanced (DCE) magnetic resonance (MR) imaging of transient bone marrow edema syndrome (TBMES) and avascular osteonecrosis. Materials and Methods Institutional review board approval and written informed consent were obtained. Thirty-two patients (21 men, 11 women; mean age, 48 years; 26 hips, 10 knees) underwent conventional MR imaging and a dynamic contrast-enhanced three-dimensional spoiled gradient-echo sequence at 3 T. Parameter maps for mean transit time (MTT) and plasma flow (PF) were evaluated qualitatively and quantitatively. Differences in perfusion patterns were analyzed by using the Fisher exact test. Regions of interest were drawn in areas of high PF and long MTT on each parametric map. Mean, median, standard deviation, minimum, and maximum values were determined. TBMES and osteonecrosis were compared statistically by using the Mann-Whitney U and Wilcoxon signed-rank tests, with a P value of less than .05 considered indicative of a significant difference. Results Nineteen joints with TBMES and 17 joints with osteonecrosis were evaluated. TBMES joints showed a subchondral elongated area of high PF and low MTT that was surrounded by an area of long MTT and low PF. Osteonecrosis joints showed a subchondral area with low or no detectable PF and MTT adjacent to the joint surface, which was surrounded by a rim of high PF and intermediate MTT. Patterns for TBMES and osteonecrosis did not overlap. A significant difference (P < .001) in PF in the immediate subchondral area was found between TBMES and osteonecrosis; in joints with osteonecrosis, this was comparable to background noise, and therefore, could not be quantified. In the circumscribed rim of high PF and intermediate MTT, which was only found in joints with osteonecrosis, mean ± standard deviation PF was 18.9 mL/100 mL per minute ± 11.0 and mean MTT was 213.3 seconds ± 56.8. No significant difference between TBMES and osteonecrosis was found for MTT (P = .09) and PF (P = .75) in the surrounding area. Conclusion Parameter maps derived at dynamic contrast-enhanced MR imaging with high temporal resolution can allow differentiation of osteonecrosis from TBMES in hip and knee joints. RSNA, 2016 Online supplemental material is available for this article.
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http://dx.doi.org/10.1148/radiol.2016152665DOI Listing
May 2017

CT fluoroscopy-guided closed-tip catheter placement before regional hyperthermia treatment of soft tissue sarcomas: 5-Year experience in 35 consecutive patients.

Int J Hyperthermia 2016 10;32(2):151-8. Epub 2015 Dec 10.

a Institute for Clinical Radiology, Ludwig Maximilians University Hospital , Munich and.

Purpose: This study was designed to assess technical success and complications in patients with high-risk soft tissue sarcomas undergoing CT fluoroscopy-guided closed-tip catheter placement before treatment with combined chemotherapy and regional hyperthermia.

Materials And Methods: This retrospective study comprised all patients referred for insertion of closed-tip catheters for the introduction of thermometry probes before regional hyperthermia treatment at a single university centre from 2010 to 2015. Catheter placements were performed under local anaesthesia and intermittent CT fluoroscopy guidance. Technical success, complication rate, duration of catheter insertion and dose-length product (DLP) were analysed. Technical success was defined as intratumoural catheter placement suitable for subsequent thermometry.

Results: A total of 35 procedures were performed on 35 patients (22 men, 13 women). In 34 out of 35 interventions catheters were inserted successfully; in one patient catheter placement was not feasible. No intra-interventional complications occurred. In six patients post-interventional complications were observed - two major (one abscess formation and one severe catheter dislocation) and four minor complications. Technical failure was observed in 11.4% of patients, especially catheter kinking. A total of 55 catheters were placed, with a mean number of 1.7 ± 0.7 per patient. Mean total DLP was 723.2 ± 355.9 mGy*cm.

Conclusion: CT fluoroscopy-guided closed-tip catheter placement into high-risk soft tissue sarcomas was characterised by high technical success and relatively low complication rate. While major complications were rarely observed, catheter-kinking preventing successful thermometry represented the most frequent technical failure.
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http://dx.doi.org/10.3109/02656736.2015.1107761DOI Listing
January 2017

Physiological Background of Differences in Quantitative Diffusion-Weighted Magnetic Resonance Imaging Between Acute Malignant and Benign Vertebral Body Fractures: Correlation of Apparent Diffusion Coefficient With Quantitative Perfusion Magnetic Resonance Imaging Using the 2-Compartment Exchange Model.

J Comput Assist Tomogr 2015 Sep-Oct;39(5):643-8

From the *Department of Clinical Radiology, †Josef Lissner Laboratory for Biomedical Imaging, Department of Clinical Radiology, Ludwig-Maximilians University Munich, Munich, Germany; and ‡Division of Medical Physics, University of Leeds, Leeds, United Kingdom.

Objective: To test the hypothesis that apparent diffusion coefficient (ADC) in vertebral bone marrow of benign and malignant fractures is related to the volume of the interstitial space, determined with dynamic contrast-enhanced (DCE) magnetic resonance imaging.

Methods: Patients with acute benign (n = 24) and malignant (n = 19) vertebral body fractures were examined at 1.5 T. A diffusion-weighted single-shot turbo-spin-echo sequence (b = 100 to 600 s/mm) and DCE turbo-FLASH sequence were evaluated. Regions of interest were manually selected for each fracture. Apparent diffusion coefficient was determined with a monoexponential decay model. The DCE magnetic resonance imaging concentration-time curves were analyzed using a 2-compartment tracer-kinetic model.

Results: Apparent diffusion coefficient showed a significant positive correlation with interstitial volume in the whole study population (Pearson r = 0.66, P < 0.001), as well as in the malignant (Pearson r = 0.64, P = 0.004) and benign (Pearson r = 0.52, P = 0.01) subgroup. A significant correlation between ADC and the permeability-surface area product could be observed when analyzing the whole study population (Spearman rs = 0.40, P = 0.008), but not when separately examining the subgroups. Plasma flow showed a significant correlation with ADC in benign fractures (Pearson r = 0.23, P = 0.03). Plasma volume did not show significant correlations with ADC.

Conclusions: The results support the hypothesis that the ADC of a lesion is inversely correlated to its cellularity. This explains previous observations that ADC is reduced in more malignant lesions.
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http://dx.doi.org/10.1097/RCT.0000000000000281DOI Listing
December 2015

Diffusion imaging of the vertebral bone marrow.

NMR Biomed 2017 Mar 26;30(3). Epub 2015 Jun 26.

Institute for Clinical Radiology, Ludwig Maximilian University Hospital Munich, Germany.

Diffusion-weighted MRI (DWI) of the vertebral bone marrow is a clinically important tool for the characterization of bone-marrow pathologies and, in particular, for the differentiation of benign (osteoporotic) and malignant vertebral compression fractures. DWI of the vertebral bone marrow is, however, complicated by some unique MR and tissue properties of vertebral bone marrow. Due to both the spongy microstructure of the trabecular bone and the proximity of the lungs, soft tissue, or large vessels, substantial magnetic susceptibility variations occur, which severely reduce the magnetic field homogeneity as well as the transverse relaxation time T , and thus complicate MRI in particular with echoplanar imaging (EPI) techniques. Therefore, alternative diffusion-weighting pulse sequence types such as single-shot fast-spin-echo sequences or segmented EPI techniques became important alternatives for quantitative DWI of the vertebral bone marrow. This review first describes pulse sequence types that are particularly important for DWI of the vertebral bone marrow. Then, data from 24 studies that made diffusion measurements of normal vertebral bone marrow are reviewed; summarizing all results, the apparent diffusion coefficient (ADC) of normal vertebral bone marrow is typically found to be between 0.2 and 0.6 × 10  mm /s. Finally, DWI of vertebral compression fractures is discussed. Numerous studies demonstrate significantly greater ADCs in osteoporotic fractures (typically between 1.2 and 2.0 × 10  mm /s) than in malignant fractures or lesions (typically 0.7-1.3 × 10  mm /s). Alternatively, several studies used the (qualitative) image contrast of diffusion-weighted acquisitions for differentiation of lesion etiology: a very good lesion differentiation can be achieved, particularly with diffusion-weighted steady-state free precession sequences, which depict malignant lesions as hyperintense relative to normal-appearing vertebral bone marrow, in contrast to hypointense or isointense osteoporotic lesions. Copyright © 2015 John Wiley & Sons, Ltd.
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http://dx.doi.org/10.1002/nbm.3333DOI Listing
March 2017

Boundary value problem for phase retrieval from unidirectional X-ray differential phase images.

Opt Express 2015 May;23(10):13294-308

The phase retrieval problem can be reduced to the second order partial differential equation. In order to retrieve the absolute values of the X-ray phase and to minimize the reconstruction artifacts we defined the mixed inhomogeneous boundary condition using available a priori information about the sample. Finite element technique was used to solve the boundary value problem. The approach is validated on numerical and experimental phantoms. In order to demonstrate a possible application of the method, we have processed an entire tomographic set of differential phase images and estimated the magnitude of the refractive index decrement for some tissues inside complex biomedical samples.
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http://dx.doi.org/10.1364/OE.23.013294DOI Listing
May 2015

Quantitative evaluation of benign and malignant vertebral fractures with diffusion-weighted MRI: what is the optimum combination of b values for ADC-based lesion differentiation with the single-shot turbo spin-echo sequence?

AJR Am J Roentgenol 2014 Sep;203(3):582-8

1 Institute of Clinical Radiology, LMU University of Munich-Campus Grosshadern, Marchioninistrasse 15, 81377 Munich, Germany.

Objective: The purpose of our study was to determine the optimum combination of b values for calculating the apparent diffusion coefficient (ADC) using a diffusion-weighted (DW) single-shot turbo spin-echo (TSE) sequence in the differentiation between acute benign and malignant vertebral body fractures.

Subjects And Methods: Twenty-six patients with osteoporotic (mean age, 69 years; range, 31.5-86.2 years) and 20 patients with malignant vertebral fractures (mean age, 63.4 years; range, 24.7-86.4 years) were studied. T1-weighted, STIR, and T2-weighted sequences were acquired at 1.5 T. A DW single-shot TSE sequence at different b values (100, 250, 400, and 600 s/mm(2)) was applied. On the DW images for each evaluated fracture, an ROI was manually adapted to the area of hyperintense signal intensity on STIR-hypointense signal on T1-weighted images. For each ROI, nine different combinations of two, three, and four b values were used to calculate the ADC using a least-squares algorithm. The Student t test and Mann-Whitney U test were used to determine significant differences between benign and malignant fractures. An ROC analysis and the Youden index were used to determine cutoff values for assessment of the highest sensitivity and specificity for the different ADC values. The positive (PPV) and negative predictive values (NPV) were also determined.

Results: All calculated ADCs (except the combination of b = 400 s/mm(2) and b = 600 s/mm(2)) showed statistically significant differences between benign and malignant vertebral body fractures, with benign fractures having higher ADCs than malignant ones. The use of higher b values resulted in lower ADCs than those calculated with low b values. The highest AUC (0.85) showed the ADCs calculated with b = 100 and 400 s/mm(2), and the second highest AUC (0.829) showed the ADCs calculated with b = 100, 250, and 400 s/mm(2). The Youden index with equal weight given to sensitivity and specificity suggests use of an ADC calculated with b = 100, 250, and 400 s/mm(2) (cutoff ADC, < 1.7 × 10(-3) mm(2)/s) to best diagnose malignancy (sensitivity, 85%; specificity, 84.6%; PPV, 81.0%; NPV, 88.0%).

Conclusion: ADCs calculated with a combination of low to intermediate b values (b = 100, 250, and 400 s/mm(2)) provide the best diagnostic performance of a DW single-shot TSE sequence to differentiate acute benign and malignant vertebral body fractures.
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http://dx.doi.org/10.2214/AJR.13.11632DOI Listing
September 2014

Cartilage and soft tissue imaging using X-rays: propagation-based phase-contrast computed tomography of the human knee in comparison with clinical imaging techniques and histology.

Invest Radiol 2014 Sep;49(9):627-34

From the *Institute for Clinical Radiology, Ludwig-Maximilians-University Hospital Munich, Germany; †European Synchrotron Radiation Facility, Grenoble, France; ‡Department of Physics, Ludwig-Maximilians University, Garching, Germany; §Phelma, Institut National Polytechnique de Grenoble, Grenoble, France; and ∥Institute of Anatomy, Ludwig-Maximilians University, Munich, Germany.

Objectives: This study evaluates high-resolution tomographic x-ray phase-contrast imaging in whole human knee joints for the depiction of soft tissue with emphasis on hyaline cartilage. The method is compared with conventional computed tomography (CT), synchrotron radiation absorption-based CT, and magnetic resonance imaging (MRI).

Material And Methods: After approval of the institutional review board, 2 cadaveric human knees were examined at an synchrotron institution using a monochromatic x-ray beam of 60 keV, a detector with a 90-mm field of view, and a pixel size of 46 × 46 μm. Images of phase-contrast imaging CT were reconstructed with the filtered back projection algorithm and the equally sloped tomography method. Image quality and tissue contrast were evaluated and compared in all modalities and with histology.

Results: Phase-contrast imaging provides visualization of altered cartilage regions invisible in absorption CT with simultaneous high detail of the underlying bony abnormalities. The delineation of surface changes is similar to 3-T MRI using cartilage-dedicated sequences. Phase-contrast imaging CT presents soft tissue contrast surpassing that of conventional CT with a clear discrimination of ligamentous, muscular, neural, and vascular structures. In addition, phase-contrast imaging images show cartilage and meniscal calcifications that are not perceptible on conventional CT or on MRI.

Conclusions: Phase-contrast imaging CT may facilitate a more complete evaluation of the human knee joint by providing concurrent comprehensive information about cartilage, the underlying subchondral bone, and their changes in osteoarthritic conditions.
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http://dx.doi.org/10.1097/RLI.0000000000000063DOI Listing
September 2014

Quantitative analysis of acute benign and malignant vertebral body fractures using dynamic contrast-enhanced MRI.

AJR Am J Roentgenol 2013 Jun;200(6):W635-43

Department of Clinical Radiology, Ludwig-Maximilians-University Munich, Campus Grosshadern, Marchioninistrasse 15, 81377 Munich, Bavaria 81377, Germany.

Objective: The objective of our study was to evaluate quantitative dynamic contrast-enhanced MRI (DCE-MRI) based on tracer kinetic modeling of perfusion in the differentiation of benign from malignant vertebral fractures.

Subjects And Methods: Patients with 26 osteoporotic vertebral fractures (18 women, eight men; mean age, 69 years) and patients with 20 malignant vertebral fractures (nine women, 11 men; mean age, 63.4 years) underwent dynamic contrast-enhanced MRI. T1-weighted, STIR, and T2-weighted sequences were acquired at 1.5 T. Dynamic contrast-enhanced image sets were acquired with a 2D saturation-recovery spoiled gradient-echo sequence. Regions of interest in parameter maps of mean transit time (MTT) and plasma flow in the fractured vertebral bodies were analyzed with a two-compartment tracer kinetic model. Plasma flow, plasma volume (PV), extraction flow, and interstitial volume were calculated. The forward volume transfer constant (K(trans)) and the extracellular volume (ECV) were derived. A two-tailed Fisher exact test, Mann-Whitney U test, and receiver operating characteristic analysis were performed.

Results: Forty-four vertebral fractures in 44 patients could be evaluated. In spots of increased plasma flow, interstitial volume (p = 0.0003), ECV (p = 0.002), and extraction flow (p = 0.03) for osteoporotic and malignant vertebral fractures were significantly different. The mean interstitial volume was 28.62 mL/100 mL for osteoporotic fractures and 11.73 mL/100 mL for malignant fractures, and the area under the curve (AUC) was 0.819 for a cutoff of 11.72 mL/100 mL or less indicating malignancy (sensitivity, 63.2%; specificity, 96.0%). The mean ECV was 52.68 mL/100 mL for osteoporotic fractures and 36.71 mL/100 mL for malignant fractures, and the AUC was 0.802 for a cutoff of 35.83 mL/100 mL or less indicating malignancy (sensitivity, 63.2%; specificity, 92.0%). The mean extraction flow was 15.19 mL/100 mL/min for osteoporotic fractures and 23.67 mL/100 mL/min for malignant fractures, and the AUC was 0.693 for a cutoff of 6.52 mL/100 mL/min or less indicating malignancy (sensitivity, 57.9%; specificity, 92.0%). K(trans), plasma flow, and PV in the spots of increased plasma flow and all quantitative perfusion parameters in the regions of increased MTT did not show any significant differences between benign and malignant fractures.

Conclusion: In spots of high plasma flow, which can be determined with a deconvolution analysis, the quantitative perfusion parameters of interstitial volume, ECV, and extraction flow are significantly different between acute osteoporotic and malignant vertebral fractures and can aid in the distinction between the two entities.
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http://dx.doi.org/10.2214/AJR.12.9351DOI Listing
June 2013

Visualisation of methacrylate-embedded human bone sections by infrared nanoscopy.

J Biophotonics 2014 Jun 18;7(6):418-24. Epub 2013 Feb 18.

Department of Clinical Radiology, Ludwig-Maximilians-University, Großhadern Campus, 81377 München, Germany.

A recently developed ultra-resolving near-field infrared nanoscope is applied to investigate methyl methacrylate embedded, un-decalcified human bone sections. Results show detail at a resolution of 30 nm. Specific contrasting of mineral components is enabled by choosing an appropriate infrared wavelength, here 9.47 μm, in the phosphate vibrational band. The method is surface-sensitive, probing to a depth of about 30 nm into the surface. The obtained infrared images are presented in direct comparison with optical and electron micrographs of the identical specimen. Lamellar bone organization, peri-cellular mineral deposition, and regional differences in mineral content are clearly detectable. Individual fibrils are resolved. - Infrared nanoscopy requires just standard hard tissue preparation techniques combined with section surface polishing. It can be integrated into existing laboratory environments without impeding subsequent routine staining and evaluation methods.
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http://dx.doi.org/10.1002/jbio.201200172DOI Listing
June 2014

Comparison of qualitative and quantitative evaluation of diffusion-weighted MRI and chemical-shift imaging in the differentiation of benign and malignant vertebral body fractures.

AJR Am J Roentgenol 2012 Nov;199(5):1083-92

Institute of Clinical Radiology, LMU University of Munich, Campus Grosshadern, Marchioninistrasse 15, Munich, Bavaria 81377, Germany.

Objective: The objective of our study was to compare the diagnostic value of qualitative diffusion-weighted imaging (DWI), quantitative DWI, and chemical-shift imaging in a single prospective cohort of patients with acute osteoporotic and malignant vertebral fractures.

Subjects And Methods: The study group was composed of patients with 26 osteoporotic vertebral fractures (18 women, eight men; mean age, 69 years; age range, 31 years 6 months to 86 years 2 months) and 20 malignant vertebral fractures (nine women, 11 men; mean age, 63.4 years; age range, 24 years 8 months to 86 years 4 months). T1-weighted, STIR, and T2-weighted sequences were acquired at 1.5 T. A DW reverse fast imaging with steady-state free precession (PSIF) sequence at different delta values was evaluated qualitatively. A DW echo-planar imaging (EPI) sequence and a DW single-shot turbo spin-echo (TSE) sequence at different b values were evaluated qualitatively and quantitatively using the apparent diffusion coefficient. Opposed-phase sequences were used to assess signal intensity qualitatively. The signal loss between in- and opposed-phase images was determined quantitatively. Two-tailed Fisher exact test, Mann-Whitney test, and receiver operating characteristic analysis were performed. Sensitivities, specificities, and accuracies were determined.

Results: Qualitative DW-PSIF imaging (delta = 3 ms) showed the best performance for distinguishing between benign and malignant fractures (sensitivity, 100%; specificity, 88.5%; accuracy, 93.5%). Qualitative DW-EPI (b = 50 s/mm(2) [p = 1.00]; b = 250 s/mm(2) [p = 0.50]) and DW single-shot TSE imaging (b = 100 s/mm(2) [p = 1.00]; b = 250 s/mm(2) [p = 0.18]; b = 400 s/mm(2) [p = 0.18]; b = 600 s/mm(2) [p = 0.39]) did not indicate significant differences between benign and malignant fractures. DW-EPI using a b value of 500 s/mm(2) (p = 0.01) indicated significant differences between benign and malignant vertebral fractures. Quantitative DW-EPI (p = 0.09) and qualitative opposed-phase imaging (p = 0.06) did not exhibit significant differences, quantitative DW single-shot TSE imaging (p = 0.002) and quantitative chemical-shift imaging (p = 0.01) showed significant differences between benign and malignant fractures.

Conclusion: The DW-PSIF sequence (delta = 3 ms) had the highest accuracy in differentiating benign from malignant vertebral fractures. Quantitative chemical-shift imaging and quantitative DW single-shot TSE imaging had a lower accuracy than DW-PSIF imaging because of a large overlap. Qualitative assessment of opposed-phase, DW-EPI, and DW single-shot TSE sequences and quantitative assessment of the DW-EPI sequence were not suitable for distinguishing between benign and malignant vertebral fractures.
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http://dx.doi.org/10.2214/AJR.11.8010DOI Listing
November 2012
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