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To test the hypothesis of equal or even superior applicability and accuracy of a fully integrated, laser-based computed tomography (CT) navigation system compared with conventional CT guidance for percutaneous interventions.CT-guided punctures were first performed in phantoms. Four radiologists with different experience levels (2 residents (L.B., C.D.) and 2 board-certified radiologists (B.M., K.R.) performed 48 punctures using both conventional image-guided and laser-guided approaches. Subsequently, 12 punctures were performed in patients during a clinical pilot trial. Phantom targets required an in-plane or a single-/double-angulated, out-of-plane approach. Planning and intervention time, control scan number, radiation exposure, and accuracy of needle placement (measured by deviation of the needle tip to the designated target) were assessed for each guidance technique and compared (Mann-Whitney U test and t test). Patient interventions were additionally analyzed for applicability in a clinical setting.The application of laser guidance software in the phantom study and in 12 human patients in a clinical setting was both technically and clinically feasible in all cases. The mean planning time (P = .009), intervention time (P = .005), control scan number (P.001), and radiation exposure (P = .013) significantly decreased for laser-navigated punctures compared with those for conventional CT guidance and especially in punctures with out-of-plane-trajectories. The accuracy significantly increased for laser-guided interventions compared with that for conventional CT (P.001).Interventional radiologists with differing levels of experience performed faster and more accurate punctures for out-of-plane trajectories in the phantom models, using a new, fully integrated, laser-guided CT software and demonstrated excellent clinical and technical success in initial clinical experiments.

With the increasing need for minimally invasive procedures based on lower complication rates, higher patient acceptance, and technical developments, there is a growing focus on the sound interventional training of young radiologists. This survey aimed to analyze the current situation in interventional radiology (IR) training in Germany to detect shortcomings and identify areas for improvement.From November 1-30, 2020, an online questionnaire was distributed to representative radiological associations and societies with the request to forward it to radiology residents and radiologists 40 years. The 44 questions covered six distinct areas from personal working conditions to the characterization of the IR department, training conditions, role of women in IR, and attendance at congresses/external training.A total of 330 participants completed the questionnaire. 77 % of participants expressed a high interest in IR, and 47 % could even imagine subspecializing in interventional radiology. Most institutions provided the necessary learning conditions and infrastructure. The rate of overall satisfaction with IR training conditions was 45 % (vs. a dissatisfaction rate of 39 %). However, females showed a lower satisfaction rate with their training environment than male participants (28 % vs. 51 %; P = 0.06). Positive correlations with work satisfaction were found for the presence and duration of the IR rotation, the number of partly independently/mentored performed interventions, and structured feedback. Moreover, the need for a structured training curriculum was expressed by 67 % of participants.Radiological residents and young radiologists expressed a high interest in interventional radiology, and they rate the infrastructure of German hospitals regarding IR as sufficient. However, they expressed the need for consistent IR rotations and better-structured resident and postgraduate education (curriculainterviews).Interest in interventional radiology among radiological residents and young radiologists in Germany is high, but satisfaction with interventional radiology training leaves room for improvement. The most frequently mentioned aspects that can improve IR training were · organized rotations of at least 6 months. · structured curriculums with face-to-face feedback. · structured guidance by senior interventionists during procedures. CITATION FORMAT: · Sieren M, Katoh M, Mahnken AH et al. Work and Training Conditions of German Residents and Young Radiologists in Interventional Radiology - A Nationwide Survey. Fortschr Röntgenstr 2022; 194: 1346 - 1357.Die fundierte interventionelle Ausbildung junger RadiologInnen gerät durch den zunehmenden Bedarf an minimal-invasiven Prozeduren immer mehr in den Fokus. Ziel dieser Umfrage war es, die aktuelle Situation der Ausbildung in der Interventionellen Radiologie (IR) in Deutschland zu analysieren, um Defizite aufzudecken und Verbesserungsmöglichkeiten zu identifizieren.Vom 1. bis 30. November 2020 wurde ein Online-Fragebogen an repräsentative radiologische Verbände und Gesellschaften versandt mit der Bitte, ihn an AssistenzärztInnen und RadiologInnen 40 Jahre weiterzuleiten. Die 44 Fragen deckten 6 verschiedene Bereiche ab, von den persönlichen Arbeitsbedingungen bis zur Charakterisierung der IR-Abteilung, den Ausbildungsbedingungen, der Rolle der Frauen in der IR und der Teilnahme an Kongressen/externen Fortbildungen.Insgesamt haben 330 TeilnehmerInnen den Fragebogen ausgefüllt. 77 % der TeilnehmerInnen bekundeten ein hohes Interesse an der IR und 47 % konnten sich sogar eine Subspezialisierung in der interventionellen Radiologie vorstellen. Die Mehrheit der Institutionen stellten die notwendigen Rahmenbedingungen und Infrastruktur bereit. Insgesamt lag die Zufriedenheit über die interventionsradiologische Weiterbildung bei 45 % (vs. 39 % Unzufriedenheit), wobei die Zufriedenheit mit den Ausbildungsbedingungen bei Teilnehmerinnen geringer ausfiel als bei den Teilnehmern (28 % vs. 51 %; P = 0,06). Positive Korrelationen mit der Arbeitszufriedenheit wurden für das Vorhandensein und die Dauer der IR-Rotation, die Anzahl der teilweise selbstständig/supervidiert durchgeführten Eingriffe und ein institutionalisiertes, strukturiertes Feedback festgestellt. Darüber hinaus äußerten 67 % der Teilnehmer den Wunsch nach einem strukturierten Ausbildungscurriculum.AssistenzärztInnen und junge RadiologInnen zeigen ein hohes Interesse an der Interventionellen Radiologie und bewerten die Infrastruktur deutscher Krankenhäuser im Bereich der IR als ausreichend. Sie äußerten jedoch den Bedarf an konsistenten IR-Rotationen und einer besser strukturierten grundlegenden und weiterführenden Ausbildung (CurriculaInterviews).Das Interesse an der Interventionellen Radiologie ist bei Assistenzärzten und jungen Radiologen in Deutschland hoch, die Zufriedenheit mit der Ausbildung in der Interventionellen Radiologie ist geringer. Die am häufigsten genannten Aspekte, die die IR-Ausbildung verbessern können, waren · organisierte Rotationen von mindestens 6 Monaten Dauer. · strukturierte Curricula mit persönlichem Feedback. · strukturierte Anleitung durch erfahrene Interventionisten während der Eingriffe.

Radiology reports mostly contain free-text, which makes it challenging to obtain structured data. Natural language processing (NLP) techniques transform free-text reports into machine-readable document vectors that are important for creating reliable, scalable methods for data analysis. The aim of this study is to classify unstructured radiograph reports according to fractures of the distal fibula and to find the best text mining method.We established a novel German language report dataset: a designated search engine was used to identify radiographs of the ankle and the reports were manually labeled according to fractures of the distal fibula. This data was used to establish a machine learning pipeline, which implemented the text representation methods bag-of-words (BOW), term frequency-inverse document frequency (TF-IDF), principal component analysis (PCA), non-negative matrix factorization (NMF), latent Dirichlet allocation (LDA), and document embedding (doc2vec). The extracted document vectors were used to train neural networks (NN), support vector machines (SVM), and logistic regression (LR) to recognize distal fibula fractures. The results were compared via cross-tabulations of the accuracy (acc) and area under the curve (AUC).In total, 3268 radiograph reports were included, of which 1076 described a fracture of the distal fibula. Comparison of the text representation methods showed that BOW achieved the best results (AUC = 0.98; acc = 0.97), followed by TF-IDF (AUC = 0.97; acc = 0.96), NMF (AUC = 0.93; acc = 0.92), PCA (AUC = 0.92; acc = 0.9), LDA (AUC = 0.91; acc = 0.89) and doc2vec (AUC = 0.9; acc = 0.88). When comparing the different classifiers, NN (AUC = 0,91) proved to be superior to SVM (AUC = 0,87) and LR (AUC = 0,85).An automated classification of unstructured reports of radiographs of the ankle can reliably detect findings of fractures of the distal fibula. A particularly suitable feature extraction method is the BOW model. Key Points: Citation Format

Purpose To retrospectively evaluate the technical and clinical success of interventional treatments employed in three University medical centers and to develop work-flow recommendations for intra-arterial embolizations in patients with life-threatening spontaneous retroperitoneal and rectus sheath hemorrhage (SRRSH). Materials and methods Retrospective evaluation of all patients with contrast-enhanced CT and digital subtraction angiography (DSA) for SRRSH from 01/2018 to 12/2022, amounted to 91 interventions in 83 patients (45f, 38m) with a mean age of 68.1 ± 13.2 years. Analysis of the amount of bleeding and embolized vessels, choice of embolization material, technical success, and 30-day mortality was performed. Results Pre-interventional contrast-enhanced CT demonstrated active contrast extravasation in 79 cases (87%). DSA identified a mean of 1.4 ± 0.88 active bleeds in all but two interventions (98%), consisting of 60 cases with a singular and 39 cases of >1 bleeding artery, which were consecutively embolized. The majority of patients underwent embolization with either n-butyl-2-cyanoacrylate (NBCA; n=38), coils (n=21), or a combination of embolic agents (n=23). While the technical success rate was documented at 97.8%, 25 patients (30%) died within 30 days after the initial procedure, with mortality rates ranging from 25 to 86% between the centers, each following different diagnostic algorithms. Conclusion Embolotherapy is a safe therapy option with high technical success rates in patients with life-threatening SRRSH. To maximize clinical success and survival rates, we propose a standardized approach to angiography as well as a low threshold for re-angiography.

Background Photon-counting detector computed tomography (PCD-CT) has the potential to provide superior image quality compared to energy-integrating detector computed tomography (EID-CT). We compared the two systems for elbow imaging in off-center arm positioning, 90° flexion, and cast fixation in a simulated post-trauma setting. Methods The institutional review board approved the study protocol. In a cadaver study, an olecranon fracture was artificially created in ten whole arm specimens. Two different scanning positions were evaluated: (a) arm overhead; and (b) arm on top of the abdomen of a whole-body phantom. The ultra-high resolution mode with three dose protocols and two reconstruction kernels was applied. Two blinded radiologists independently evaluated fracture and trabecular bone delineation. Signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and cortical sharpness measurements were performed. Cohen κ correlations, Mann-Whitney U and Wilcoxon signed rank tests were used. A p value lower than 0.05 was considered statistically significant. Results Dose-equivalent PCD-CT scans were rated better for fracture and trabecular bone evaluation (p < 0.001). SNR, CNR, and cortical sharpness were higher for all diagnostic (Br76) PCD-CT images (p < 0.001). The arm position had less effect on image quality in the PCD-CT compared to the EID-CT. The use of a sharp bone kernel (Br89) improved image quality ratings for PCD-CT. In the low-dose scan mode, PCD-CT resulted in more diagnostic scans (75%) compared to EID-CT (19%). Conclusions PCD-CT provided superior objective and subjective image quality for fracture and trabecular bone structures delineation of the elbow compared to EID-CT in a typical post-trauma setting. Key points • Photon-counting detector computed tomography (PCD-CT) preserved high image quality in elbow imaging with off-center positions. • PCD-CT was advantageous for bone evaluation in trauma elbows. • PCD-CT ultra-high-resolution mode and very sharp reconstruction kernels facilitated higher image quality.

Purpose To investigate the effect of the ongoing COVID-19 pandemic on interventional radiology (IR) in Germany in 2020 and 2021. Materials und Methods This retrospective study is based on the nationwide interventional radiology procedures documented in the quality register of the German Society for Interventional Radiology and Minimally Invasive Therapy (DeGIR-QS-Register). The nationwide volume of interventions in the pandemic years 2020 and 2021 was compared with the pre-pandemic period (Poisson-test, Mann-Whitney test). The aggregated data were additionally evaluated by intervention type with differentiated consideration of the temporal epidemiological infection occurrence. Results During the two pandemic years 2020 and 2021, the number of interventional procedures increased by appr. 4 % compared to the same period of the previous year (n = 190 454 and 189 447 vs. n = 183 123, respectively, p Conclusion The COVID-19 pandemic in Germany led to a significant short-term decrease in interventional radiology procedures in the initial phase. A compensatory increase in the number of procedures was observed in the subsequent period. This reflects the adaptability and robustness of IR and the high demand for minimally invasive radiological procedures in medical care. Key points: Citation Format

To analyze the impact of the COVID-19 pandemic in 2020 on the radiological imaging volume in Germany.In this retrospective multicenter study, we analyzed CT and MRI examinations of 7 radiology institutes across Germany from January to December 2020. The imaging volume was compared to 2019 (Wilcoxon-Mann-Whitney test). Modality, patient service locations, and examined body parts were assessed in consideration of time periods of the pandemic. In addition, correlation with the incidence of SARS-CoV-2 cases and associated death was performed (Spearman-test).In total, in 2020, imaging volume declined by 4 % (n = 8314) compared with 2019 (p 0.05). The hard lockdown during the first pandemic wave (calendar week 12-16, March 22 - April 19) revealed the highest decrease with 29 % (n = 894, p 0.01), with the greatest decrease in CT (36 % vs. MRI 26 %), outpatients (38 %, p 0.01), and imaging of the spine and extremities (51-72 %, 0.05 - p 0.01). Examinations referred from the emergency department (-13 %, p 0.05) and CT of the chest (-16 %, p 0.05) were least affected. With the end of the first wave, gradual normalization of the imaging volume was observed and persisted until the end of the observation period. A reduction of imaging volume negatively correlated with the incidence of SARS-CoV-2-positive cases and associated deaths (r = 0.28 and 0.49, p 0.05 and p 0.001).The COVID-19 pandemic was associated with a significant temporary decline in imaging volume. After the first lockdown period, a quick recovery was observed with radiologic imaging examinations steadily approaching prior-year figures.· This study assesses the impact of dynamic pandemic activity on radiological imaging in a multicenter analysis in Germany.. · The COVID-19 pandemic was associated with a temporary decline in CT and MRI scans.. · Relaxation of restrictions was associated with fast normalization of imaging volumes to prior-year levels, which persisted until the end of the year.. · Significant catch-up effects were not observed..· Schmidbauer M, Grenacher L, Juchems MS et al. Impact of the COVID 19 Pandemic on Radiological Imaging in Germany. Fortschr Röntgenstr 2022; 194: 625 - 633.ZIEL: Untersuchung der Auswirkungen der COVID-19-Pandemie auf die Durchführung radiologischer Bildgebung in Deutschland.In dieser retrospektiven multizentrischen Studie wurden die durchgeführten CT- und MRT-Bildgebungen 7 deutschlandweiter radiologischer Zentren von Januar bis Dezember 2020 analysiert. Das Untersuchungsvolumen wurde mit dem Vorjahreszeitraum verglichen (Wilcoxon-Mann-Whitney-Test). Die Auswertung der aggregierten Daten erfolgte differenziert nach Modalität, Zuweiser, Körperregion und unter besonderer Berücksichtigung der zeitlichen Pandemieentwicklung. Die Untersuchungszahlen wurden zudem mit der Inzidenz von SARS-CoV-2-positiven Fällen und assoziierten Todesfällen korreliert (Spearman-Test).Im Pandemiejahr 2020 wurden insg. 4 % (n = 8314) weniger CT- und MRT-Untersuchungen durchgeführt als im Vorjahr (p 0,05). Die Differenz ist vornehmlich auf den Zeitraum des harten Lockdowns (Kalenderwoche 12–16, 22. März bis 19. April 2020) zurückzuführen, welcher im Vergleich zum Vorjahreszeitraum zu einem Rückgang der Untersuchungen um 29 % geführt hat (n = 894, p 0,01). MRT-Untersuchungen waren dabei stärker betroffen als CT-Untersuchungen (36 % vs. 26 %). Der größte Rückgang war mit –38 % (p 0,01) bei ambulanten Patienten zu verzeichnen und bei Untersuchungen von Wirbelsäule und Extremitäten (–51 % bis –72 %, p 0,05 bis p 0,01). Am geringsten tangiert waren Untersuchungen aus den Zentralen Notaufnahmen (–13 %, p 0,05) sowie CT-Untersuchungen des Thorax (–16 %, p 0,05). Das Ende des harten Lockdowns ging mit einer sukzessiven Normalisierung des Untersuchungsvolumens auf das Vorjahresniveau einher, die auch mit Beginn der zweiten Pandemiewelle und des milderen Lockdowns am Jahresende anhielt. Der Rückgang der Untersuchungen 2020 korrelierte dabei negativ mit der Inzidenz an SARS-CoV-2-positiven Fällen und assoziierten Todesfällen (r = 0,28 und 0,49; p 0,05 und p 0,001).Die COVID-19-Pandemie in Deutschland führte 2020 temporär zu einem signifikanten Rückgang radiologischer CT- und MRT-Untersuchungen. Nach Ende des ersten Lockdowns im Frühjahr zeigte sich eine rasche Erholung der Untersuchungszahlen mit weitgehender Stabilisierung des Untersuchungsvolumens auf das Vorjahresniveau.· Die Studie zeigt die pandemiebedingten Veränderungen radiologischer Bildgebung in einer multizentrischen, deutschlandweiten Analyse.. · Im Jahr 2020 kam es während des ersten Lockdowns zu einem temporären quantitativen Rückgang an CT- und MRT-Untersuchungen.. · Mit Beginn der ersten Lockerungen trat eine zügige Normalisierung der Untersuchungsvolumina auf Vorjahresniveau ein, die bis zum Jahresende anhielt.. · Signifikante Nachholeffekte wurden nicht beobachtet..· Schmidbauer M, Grenacher L, Juchems MS et al. Impact of the COVID 19 Pandemic on Radiological Imaging in Germany. Fortschr Röntgenstr 2022; 194: 625 – 633.

Background The aim of this animal study was to compare the fluoroscopic image quality (IQ) and radiation dose between a tantalum (Ta)-specific contrast-to-noise ratio-driven exposure control (Ta-CEC) and a detector dose-driven exposure control (DEC) in abdominal angiography. Methods Nine angiography scenarios were created in seven anaesthetised pigs using Ta-based embolisation material during percutaneous liver and kidney intervention. Fluoroscopic images were acquired using three DEC protocols with different dose levels and Ta-CEC protocols with different IQ levels, sampled in small steps. Polymethyl-methacrylate and aluminium plates were used to simulate attenuation of three water equivalent thicknesses (WET). Three blinded readers evaluated the IQ of DEC and dose equivalent Ta images and selected the Ta-IQ equivalent image corresponding to the DEC image. Results Interobserver agreement for the IQ assessment was 0.43 for DEC, 0.56 for Ta-CEC and for the assessment of incident air kerma at the interventional reference point (Ka,r) for the Ta-IQ equivalent image 0.73. The average IQ of the dose equivalent Ta images was superior compared to the DEC images (p < 0.001) and also for every WET (26, 31, or 36 cm) and dose level (p ≤ 0.022). The average Ka,r for the Ta-IQ equivalent images was 59 ± 16% (mean ± standard deviation) lower compared to the DEC images (p < 0.001). Conclusions Compared to DEC, Ta-CEC significantly improved the fluoroscopic depiction of Ta, while maintaining the Ka,r. Alternatively, the Ka,r can be significantly reduced by using Ta-CEC instead of DEC, while maintaining equivalent IQ.

Background To assess the technical feasibility, success rate, puncture complications and procedural characteristics of transjugular intrahepatic portosystemic shunt (TIPS) placement using a three-dimensional vascular map (3D-VM) overlay based on image registration of pre-procedural contrast-enhanced (CE) multi-detector computed tomography (MDCT) for portal vein puncture guidance. Materials and methods Overall, 27 consecutive patients (59 ± 9 years, 18male) with portal hypertension undergoing elective TIPS procedure were included. TIPS was guided by CE-MDCT overlay after image registration based on fluoroscopic images. A 3D-VM of the hepatic veins and the portal vein was created based on the pre-procedural CE-MDCT and superimposed on fluoroscopy in real-time. Procedural characteristics as well as hepatic vein catheterization time (HVCT), puncture time (PT), overall procedural time (OPT), fluoroscopy time (FT) and the dose area product (DAP) were evaluated. Thereafter, HVCT, PT, OPT and FT using 3D-VM (61 ± 9 years, 14male) were compared to a previous using classical fluoroscopic guidance (53 ± 9 years, 21male) for two interventional radiologist with less than 3 years of experience in TIPS placement. Results All TIPS procedure using of 3D/2D image registered 3D-VM were successful with a significant reduction of the PSG (p 2. HVCT, OPT and FT of the interventionalist with less TIPS experience using 3D/2D image registered 3D-VM were statistically different to an interventionalist with similar experience using fluoroscopic guidance (pHVCT = 0.0022; pOPT = 0.0097; pFT = 0.0009). PT between these interventionalists was not significantly different (pPT = 0.2905). Conclusion TIPS placement applying registration-based CE-MDCT vessel information for puncture guidance is feasible and safe. It has the potential to improve hepatic vein catherization, portal vein puncture and radiation exposure.

Background To evaluate effectivity of a 3D-motion correction algorithm in C-Arm CTs (CACT) with limited image quality (IQ) during transarterial chemoembolization (TACE). Methods From 1/2015–5/2021, 644 CACTs were performed in patients during TACE. Of these, 27 CACTs in 26 patients (18 m, 8f; 69.7 years ± 10.7 SD) of limited IQ were included. Post-processing of the original raw-data sets (CACTOrg) included application of a 3D-motion correction algorithm and bone segmentation (CACTMC_no_bone). Four radiologists (R1-4) compared the images by choosing their preferred dataset and recommending repeat acquisition in case of severe IQ-impairment. R1,2 performed additional grading of intrahepatic vessel visualization, presence/extent of movement artifacts, and overall IQ. Results R1,2 demonstrated excellent interobserver agreement for overall IQ (ICC 0.79,p p Org) to 1.39 (CACTMC_no_bone;p p Org:1.31 ± 1.67, CACTMC_no_bone:1.00 ± 1.34, p MC_no_bone were preferred, with identical datasets chosen by the readers to show benefit from the algorithm. Conclusion Application of a 3D-motion correction algorithm significantly improved IQ in diagnostically limited CACTs during TACE, with the potential to decrease repeat acquisitions.

Background MRI is attractive for guiding and monitoring interventional procedures due to its high intrinsic soft tissue contrast and the possibility to measure flow and cardiac function. Methods Technical solutions have been developed for all procedural steps including imaging guidance, MR-safe catheters and instruments and patient monitoring. This has led to widening of the clinical applications. Interventional MRI is becoming increasingly important for the treatment of patients suffering from malignant diseases. The detectability of masses and consequently their accessibility for biopsy is higher, compared to other modalities, due to the high intrinsic soft tissue contrast of MRI. Temperature-dependent sequences allow for minimally invasive and tissue-sparing ablation (A-0 ablation). Conclusion Interventional MRI has become established in the clinical routine for a variety of indications, including biopsies and tumor ablation. Since the economic requirement of covering costs by reimbursement is met and interventional MRI decreases the mortality and morbidity of interventional procedures, broader application of interventional MRI can be expected in the clinical routine in the future. Key points Citation Format

Background MRI is attractive for the guiding and monitoring of interventional procedures due to its high intrinsic soft tissue contrast and the possibility to measure physiologic parameters like flow and cardiac function. Method The current status of interventional MRI for the clinical routine was analyzed. Results The effort needed for the development of MR-safe monitoring systems and instruments initially resulted in the application of interventional MRI only for procedures that could not be performed by other means. Accordingly, biopsy of lesions in the breast, which are not detectable by other modalities, has been performed under MRI guidance for decades. Currently, biopsies of the prostate under MRI guidance are established in a similar fashion. At many sites blind biopsy has already been replaced by MR-guided biopsy or at least by the fusion of MR images with ultrasound. Cardiovascular interventions are performed at several centers for ablation as a treatment for atrial fibrillation. Conclusion Interventional MRI has been established in the clinical routine for a variety of indications. Broader application can be expected in the clinical routine in the future owing to the multiple advantages compared to other techniques. Key points Citation format

Purpose To combine diffusion-weighted imaging (DWI) and diffusion tensor imaging (DTI) for detection of allograft dysfunction in patients early after kidney transplantation and to correlate diffusion parameters with renal function and renal histology of allograft biopsies. Materials and Methods Between day 4 and 11 after kidney transplantation 33 patients with initial graft function and 31 patients with delayed graft function (DGF) were examined with a 1.5T magnetic resonance imaging (MRI) scanner. DTI and DWI sequences were acquired and fractional anisotropy (FA), apparent diffusion coefficient (ADCmono), pure diffusion (ADCdiff), and the perfusion fraction (Fp) were calculated. Kidney biopsies in 26 patients were analyzed for allograft pathology, ie, acute tubular injury, inflammation, edema, renal fibrosis, and rejection. Histological results were correlated with MRI parameters. Results In the renal medulla FA (0.25 ± 0.06 vs. 0.29 ± 0.06, P

Purpose In this feasibility study, a phase-resolved functional lung imaging postprocessing method for extraction of dynamic perfusion (Q) and ventilation (V) parameters using a conventional 1H lung MRI Fourier decomposition acquisition is introduced. Methods Time series of coronal gradient-echo MR images with a temporal resolution of 288 to 324 ms of two healthy volunteers, one patient with chronic thromboembolic hypertension, one patient with cystic fibrosis, and one patient with chronic obstructive pulmonary disease were acquired at 1.5 T. Using a sine model to estimate cardiac and respiratory phases of each image, all images were sorted to reconstruct full cardiac and respiratory cycles. Time to peak (TTP), V/Q maps, and fractional ventilation flow-volume loops were calculated. Results For the volunteers, homogenous ventilation and perfusion TTP maps (V-TTP, Q-TTP) were obtained. The chronic thromboembolic hypertension patient showed increased perfusion TTP in hypoperfused regions in visual agreement with dynamic contrast-enhanced MRI, which improved postpulmonary endaterectomy surgery. Cystic fibrosis and chronic obstructive pulmonary disease patients showed a pattern of increased V-TTP and Q-TTP in regions of hypoventilation and decreased perfusion. Fractional ventilation flow-volume loops of the chronic obstructive pulmonary disease patient were smaller in comparison with the healthy volunteer, and showed regional differences in visual agreement with functional small airways disease and emphysema on CT. Conclusions This study shows the feasibility of phase-resolved functional lung imaging to gain quantitative information regarding regional lung perfusion and ventilation without the need for ultrafast imaging, which will be advantageous for future clinical translation. Magn Reson Med 79:2306-2314, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Renal ischemia reperfusion injury leads to acute kidney injury (AKI) and is associated with tissue edema, inflammatory cell infiltration, and subsequent development of interstitial renal fibrosis and tubular atrophy. The purpose of this study was to investigate the value of the functional magnetic resonance imaging (MRI) techniques, T2 mapping, and diffusion-weighted imaging (DWI) in characterizing acute and chronic pathology after unilateral AKI in mice.Moderate or severe AKIs were induced in C57Bl/6 mice through transient unilateral clamping of the renal pedicle for 35 minutes (moderate AKI) or 45 minutes (severe AKI), respectively. Magnetic resonance imaging was performed in 10 animals with moderate AKI and 7 animals with severe AKI before surgery and at 5 time points thereafter (days 1, 7, 14, 21, 28) using a 7-T magnet. Fat-saturated T2-weighted images, multiecho turbo spin echo, and diffusion-weighed sequences (7 b values) were acquired in matching coronal planes. Parameter maps of T2 relaxation time and apparent diffusion coefficient (ADC) were calculated, and mean values were determined for the renal cortex, the outer medulla, and the inner medulla. Inflammatory cell infiltration with monocytes/macrophages (F4/80), T-lymphocytes (CD4, CD8), and dendritic cells (CD11c) as well as the degree of interstitial fibrosis 4 weeks after AKI were determined through renal histology and immunohistochemistry. Statistical analysis comprised unpaired t tests for group comparisons and correlation analysis between MRI parameters and kidney volume loss.Increase of T2 relaxation time, indicating tissue edema, was most pronounced in the outer medulla and reached maximum values at d7 after AKI. At this time point, T2 values in the outer medulla were significantly increased to 53.8 ± 2.5 milliseconds after the severe AKI and to 46.3 ± 2.3 milliseconds after the moderate AKI when compared with the respective contralateral normal kidneys (40.9 ± 0.9 and 36.4 ± 1.2 milliseconds, respectively; P0.01). The T2 values reached baseline by d28. Medullary ADC was significantly reduced at all time points after AKI; restriction of diffusion was significantly more pronounced after the severe AKI than after the moderate AKI at d14 and d28. Changes of renal T2 and ADC values were associated with the severity of AKI as well as the degree of inflammatory cell infiltration and interstitial renal fibrosis 4 weeks after AKI. Furthermore, relative changes of both MRI parameters significantly correlated with kidney volume loss 4 weeks after AKI.Measuring T2 and ADC values through MRI is a noninvasive way to determine the presence and severity of acute and chronic renal changes after AKI in mice. Thus, the method should prove useful in animal and human clinical studies.

In this article, we systematically examine the current state of research of systems that focus on touchless human–computer interaction in operating rooms and interventional radiology suites. We further discuss the drawbacks of current solutions and underline promising technologies for future development. A systematic literature search of scientific papers that deal with touchless control of medical software in the immediate environment of the operation room and interventional radiology suite was performed. This includes methods for touchless gesture interaction, voice control and eye tracking. Fifty-five research papers were identified and analyzed in detail including 33 journal publications. Most of the identified literature (62 %) deals with the control of medical image viewers. The others present interaction techniques for laparoscopic assistance (13 %), telerobotic assistance and operating room control (9 % each) as well as for robotic operating room assistance and intraoperative registration (3.5 % each). Only 8 systems (14.5 %) were tested in a real clinical environment, and 7 (12.7 %) were not evaluated at all. In the last 10 years, many advancements have led to robust touchless interaction approaches. However, only a few have been systematically evaluated in real operating room settings. Further research is required to cope with current limitations of touchless software interfaces in clinical environments. The main challenges for future research are the improvement and evaluation of usability and intuitiveness of touchless human–computer interaction and the full integration into productive systems as well as the reduction of necessary interaction steps and further development of hands-free interaction.

The purpose of our study was to evaluate the diagnostic accuracy and scan coverage of flat-detector C-arm CT compared with that of biphasic MDCT for depicting malignant hepatic lesions in patients with hypervascular liver tumors before they undergo transarterial chemoembolization (TACE).Fifteen patients with either hepatocellular carcinoma (HCC, n = 8) or hypervascular liver metastases from uveal melanoma (n = 7) underwent arterial and portal venous C-arm CT of the liver using intraarterial contrast media administration directly before TACE. The number and location of their hepatic malignancies were compared with those on MDCT. The scan coverage was documented and the liver diameter measured on MDCT.Compared with MDCT, the sensitivity and specificity for segmental tumor involvement were 97% (76/78) and 85% (28/33), respectively, for reader 1, and 99% (77/78) and 79% (24/29), respectively, for reader 2. Complete scan coverage of the liver was obtained in five of the 15 patients with C-arm CT. In patients with incomplete scan coverage on C-arm CT, the craniocaudal liver diameter was significantly larger than in those patients with complete scan coverage (mean [95% CI], 22.7 [19.5-25.9] cm vs 20.2 [15.4-25.0] cm, p = 0.0193).Biphasic arterial and portal venous C-arm CT showed a high sensitivity for the detection of malignant liver lesions. However, the liver could not be visualized completely in two thirds of the patients. Therefore, the current scan range limitations need to be overcome to make C-arm CT a valuable adjunct to MDCT for preprocedure evaluation and postprocedure follow-up imaging.

Purpose An animal model is used to investigate whether MR angiography combined with super-paramagnetic particles of iron oxide (SPIO) is suitable for detecting thromboses. Methods 42 rats in groups of 7 each were examined on days 1, 3, 5, 7, 9 and 11, respectively, after mechanical/chemical thrombus induction in a 1.5 Tesla magnet with a FISP sequence (TR/TE/FA 50 ms/6 ms/40 degrees). Imaging was performed before and up to 90 minutes after intravenous injection of 30 mumol FE/kg BW of the experimental SPIO (hydrodynamic diameter, 34 +/- 17 nm LLS; R1 and R2 relaxivity at 0.47 T, 31 and 57 L/(mmol*s)). MIP reconstructions of MR angiographies were submitted to consensus assessment by two examiners. using histology as the gold standard. Results The image quality of MIP reconstructions was rated as good in 38 of 42 cases. With regard to thrombotic vessel occlusion, MR angiography coincided with histology in 17 of 42 cases and differed in 25, lumen narrowing being overestimated by MRI in 4 cases and underestimated in 21. In these 21 cases, the histologically observed recanalization could not be detected by MR angiography. Conclusions SPIO-enhanced MR angiography achieves adequate vessel contrast and reliable thrombus detection in animal experiments. Partial volume effects prevent microscopically observed recanalization from being detected by clinical MRI.

The objective of our study was to prospectively compare CT angiography (CTA) performed on a 16-MDCT scanner and digital subtraction angiography (DSA) in patients with peripheral arterial disease.CTA and DSA were compared in 50 patients. CTA was independently evaluated by two blinded observers. DSA was evaluated by two additional blinded observers in consensus. Consensus DSA served as the reference standard for comparisons with CTA in terms of diagnostic quality, grading of stenoocclusive lesions, visualization of collaterals, impact on patient management, and time required for analysis.No significant differences in diagnostic quality were observed between CTA and DSA above the ankle; both CTA observers noted significantly better visualization of pedal arteries (70 and 72 segments, respectively) than on DSA (57 segments). Of 958 stenoocclusive lesions on DSA, CTA observers 1 and 2 detected 933 and 929 lesions, respectively. Sensitivity and specificity for the detection of hemodynamically relevant (50%) lesions was 93.3% and 96.5% for observer 1 and 90.1% and 95.6% for observer 2. Collaterals were seen at 150 arterial levels on DSA compared with 97 and 92 levels on CTA (p0.05, both observers). Patient management decisions based on CTA were equivalent to those based on DSA in 49 of the 50 patients.CTA is an effective noninvasive alternative to DSA for the evaluation of peripheral arterial disease.

Historically, the combination of relatively long imaging times and restricted patient access has made MRI-guided intervention an impractical technique. Recent developments in MR hardware, pulse sequence improvements that have allowed the development of rapid imaging, and the availability of instruments that can be used under MR guidance have helped to overcome many of the disadvantages of MRI. Parallel to the development of MRI, image-guided percutaneous and endovascular interventions are becoming increasingly complex and require progressively more sophisticated imaging techniques to guide and control such interventions. These initially parallel trends have converged in the last couple of years. The ability of MRI to provide both unprecedented morphology and functional information has created a growing interest in both percutaneous and endovascular MRI-guided interventions. The goal of this review is to describe the technical prerequisites for MR-guided endovascular interventions, to discuss experimental and clinical applications, and to explain safety aspects of this technique.

Purpose To test the hypothesis that cardiac and coronary catheterization can be successfully performed under real-time MR guidance using a conventional x-ray angiographic catheter. Materials and Methods Cardiac and coronary catheterization was conducted on eight farm pigs using a real-time True FISP sequence. A pigtail catheter was used for both left- and right-heart catheterizations performed on all eight animals, while an Amplatz or Judkins catheter was used for the right coronary catheterization that was attempted on five animals. The intravascular devices were visualized by means of their native susceptibility artifacts. For right coronary artery catheterizations, 25% diluted gadolinium (Gd) contrast material was injected to confirm engagement of the right coronary artery. Results Cardiac catheterization of both the right- and left-heart chambers was successfully performed in all eight pigs. In addition, right coronary catheterization was successfully completed in four of the five pigs in which it was attempted. The procedure time for cardiac catheterization was one minute, while the time range required for coronary catheterization was 32–91 minutes. Conclusion This work demonstrates that MRI-guided cardiac catheterization using conventional X-ray angiographic catheters is feasible; however, coronary catheterization with this passive-tracking technique is limited. J. Magn. Reson. Imaging 2006. © 2006 Wiley-Liss, Inc.

To evaluate an augmented reality (AR) system in combination with a 1.5-T closed-bore magnetic resonance (MR) imager as a navigation tool for needle biopsies.The experimental protocol had institutional animal care and use committee approval. Seventy biopsies were performed in phantoms by using 20 tube targets, each with a diameter of 6 mm, and 50 virtual targets. The position of the needle tip in AR and MR space was compared in multiple imaging planes, and virtual and real needle tip localization errors were calculated. Ten AR-guided biopsies were performed in three pigs, and the duration of each procedure was determined. After successful puncture, the distance to the target was measured on MR images. The confidence limits for the achieved in-plane hit rate and for lateral deviation were calculated. A repeated measures analysis of variance was used to determine whether the placement error in a particular dimension (x, y, or z) differed from the others.For the 50 virtual targets, a mean error of 1.1 mm +/- 0.5 (standard deviation) was calculated. A repeated measures analysis of variance indicated no statistically significant difference (P.99) in the errors in any particular orientation. For the real targets, all punctures were inside the 6-mm-diameter tube in the transverse plane. The needle depth was within the target plane in 11 biopsy procedures; the mean distance to the center of the target was 2.55 mm (95% confidence interval: 1.77 mm, 3.34 mm). For nine biopsy procedures, the needle tip was outside the target plane, with a mean distance to the edge of the target plane of 1.5 mm (range, 0.07-3.46 mm). In the animal experiments, the puncture was successful in all 10 cases, with a mean target-needle distance of 9.6 mm +/- 4.85. The average procedure time was 18 minutes per puncture.Biopsy procedures performed with a combination of a closed-bore MR system and an AR system are feasible and accurate.

The goal of this study was to evaluate the use of super paramagnetic particles of iron oxide (SPIO) as a dark blood contrast agent, in combination with a bright blood steady-state free precession sequence for magnetic resonance angiography (MRA), in an animal model. The original concentration of the SPIO of 500 mmol Fe/l and dilutions to 250, 125, 60, 30, 10 and 5 mmol Fe/l were intra-arterially injected into the aorta of a pig. Then the dilution of 10 mmol Fe/l was chosen for repeated intra-arterial injections into two pigs. During these intra-arterial SPIO injections MR images were acquired with a 1.5 T scanner. Signal intensity measurements were performed in the aorta. The signal-to-noise ratio during SPIO bolus passage was significantly less than during baseline conditions (Fisher's F-ratio 159.8, p

Rationale and Objectives The purpose of this study is to compare the feasibility and precision of renal artery angioplasty and stent placement using two different MR scanners. Materials and Methods MR imaging-guided angioplasty and stent placements were performed on seven pigs using 0.2 and 1.5 T scanners (Magnetom Open and Magnetom Sonata, Siemens Medical Solutions, Erlangen, Germany). For guidance of catheters, guide wires and stents susceptibility artifact-based tracking was used. The end point of each intervention was to position a stent in the renal artery with its proximal end at the level of the aortic wall. Procedure time and stent position were evaluated. Results Catheterization, angioplasty, and stent placement were feasible using MRI guidance at both 0.2 and 1,5 Tesla. At 1.5 T all catheter manipulations and interventions were performed in less than 30 minutes. At 0.2 T the interventions took up to 90 minutes. No significant difference in the stent deviation was noted between the two scanners. Conclusion The use of a high-performance 1.5 T scanner helped to reduce the procedure time to half of that of a low-field system. Since no difference in stent placement precision was noted, a dedicated MR-stent might be mandatory for more precise stent placement.

Reliable visualization and tracking are essential for guiding endovascular devices within blood vessels. The most commonly used methods are susceptibility artifact-based tracking that relies on the artifact created within the image by the device and microcoil- or antenna-based tracking that uses the high signal generated by small MR endovascular receive coils when the transmit coil emits a nonselective radiofrequency pulse. To date, the use of endovascular MR guidance techniques has primarily been confined to animal experiments. There are only a few reports on MR-guided endovascular applications in patients. Therefore, access to the patient within the scanner, dedicated devices, and safety issues remain major challenges. To face these challenges, attention from all radiologists, especially interventional radiologists, is required to make MR-guided endovascular procedures a clinical reality.

Purpose The goal of this study was to evaluate translumbar and transhepatic placement of hemodialysis (HD) catheters for patients with occlusion of the veins that are commonly used for hemodialysis access. Method Over a 12-month period three translumbar and one transhepatic hemodialysis catheters were placed in 4 patients suffering from end-stage renal disease, who had thrombosis of the upper and lower extremity veins as well as the jugular veins. The percutaneous access was performed under fluoroscopic guidance. After successful passage of a guidewire into the right atrium and creation of a subcutaneous tunnel at the skin entry site, all patients received a 14 F double-lumen catheter that was placed with its tip in the right atrium. Results Percutaneous translumbar and transhepatic placement of the HD catheters was successful in all patients. No intervention-associated complications were observed. Hemodialysis could be started 1 to 20 hours after initial catheter placement in all patients. During an observation period of 3 to 7 months, 3 patients underwent hemodialysis without any complications. In one patient, an occlusion of an translumbar HD catheter was observed after 5 months. This catheter could be temporarily recanalized using rTPA injection and was then exchanged after 6 months. Conclusion Transhepatic and translumbar placement of HD catheters is a safe and viable alternative for patients who have exhausted conventional venous access sites.

The purpose of this study was to assess the feasibility of MRI to guide and monitor radiofrequency ablation of normal pulmonary tissue in a rabbit model.Percutaneous puncture and lung radiofrequency ablation were performed in six New Zealand white rabbits under MRI control using a 0.2-T open MRI scanner. Technical feasibility and complication detection were evaluated. The ablation zone appearance and size were assessed using MRI, CT, and gross pathology. Interclass correlation coefficients (ICCs) of the maximum short-axis diameters of the lesions on gross pathology and the corresponding diameters as measured on each MRI pulse sequence and on CT scans were calculated.MRI guidance of percutaneous puncture and radiofrequency ablation of pulmonary tissue is feasible. A pneumothorax was detected and treated using MRI. In the specimen, the mean coagulation necrosis diameter was 9.8 mm. The T1-weighted spoiled gradient-echo fast low-angle shot images showed the highest ICC (0.81) for the thermal lesion diameter.Our results indicate that MRI guidance is feasible and useful for radiofrequency ablation of normal pulmonary tissue.

A novel two-element, catheter-based phased array coil was designed and built for both active MR device tracking and high-resolution vessel wall imaging. The device consists of two independent solenoid coils that are wound in opposite directions, connected to separate receive channels, and mounted collinearly on an angiographic catheter. The elements were used independently or together for tracking or imaging applications, respectively. The array's dual functionality was tested on a clinical 1.5 T MRI scanner in vitro, in vivo, and in situ. During real-time catheter tracking, each element gave rise to a high-amplitude peak in the respective projection data, which enabled reliable and robust device tracking as well as automated slice positioning. In vivo microimaging with 240 μm in-plane resolution was achieved in 9 s using the device and TrueFISP imaging. Therefore, a single device was successfully implemented that met the combined requirements of intravascular device tracking and imaging. Magn Reson Med 51:668–675, 2004. © 2004 Wiley-Liss, Inc.

OBJECTIVE. The purpose of this study was to test the use of CO2 as a black blood contrast agent for MR imaging–guided vascular procedures in an animal model.MATERIALS AND METHODS. Repeated intraarterial CO2 injections were performed through a catheter located in the aorta and the renal arteries of three fully anesthetized pigs. Real-time images were acquired using a steady-state free precession sequence.RESULTS. During the CO2 injections, the bright blood in the aorta and the main renal artery was totally replaced, and this procedure resulted in an immediate, statistically significant signal loss in the vessel lumen. In more peripheral vessels, CO2 improved the vessel conspicuity substantially. Confirmation of vessel patency distal to the catheter tip position was possible.CONCLUSION. The use of carbon dioxide in combination with a bright blood MR imaging sequence improves vessel conspicuity and provides immediate information about blood flow distal to the catheter. This technique may be used to facilitat...

Background: This study assessed the feasibility of high-resolution magnetic resonance imaging of the pancreas by means of an endoscopically inserted endoluminal magnetic resonance receiver coil. Method: A 0.032-inch diameter internal magnetic resonance imaging receiver coil was endoscopically inserted into the pancreatic duct in 4 pigs through the accessory channel of a standard duodenoscope to obtain high-resolution magnetic resonance images by using T1- and T2-weighted sequences. Results: The pig anatomy precluded the usual transoral approach; however, transgastric access allowed endoscopic transpapillary insertion of a receiver coil into the pancreatic duct in all animals without the need for sphincterotomy. The small swine pancreas could then be visualized by magnetic resonance imaging with a 0.3 × 0.3-mm in-plane resolution. Conclusion: High-resolution pancreas magnetic resonance imaging is feasible by using an endoscopically inserted endoluminal receiver coil. The smaller stomach and larger pancreatic duct diameter in humans will facilitate clinical application of the imaging procedure.

Rationale and Objectives The purpose of this study wasto examine the dose dependency of the intravascular signal intensity after injection of ultrasmall superparamagnetic iron oxide (USPIO) particles (SH U 555C) in a rabbit model studied with a low-field-strength magnetic resonance (MR)imaging system. The results were used to facilitate MR-guided vascular procedures in a pig. Materials and Methods All experiments were performed at 0.2 T. To determine the optimum USPIO (or SH U 555 C) dose for intravascular interventions, the authors acquired coronal three–dimensional MR angiographic images in 12 rabbits after injection of four dose levels (10, 20,30, and 40 μmol of iron per kilogram body weight). The intraaortic signal intensities were measured in user–defined regions of interest. For numericalanalysis, signal intensity enhancement was computed. Subsequently MR image–guided procedures were performed in USPIO–enhanced vessels in one pig. Results The signal intensity evaluation shows a clear–cut dose dependence in both early and late phases after administration of SH U 555 C. A high–spatial–resolution MR angiogram acquired 20 minutes after injection yielded the best results with the highest dose (40 μmol of iron per kilogram); at that dose, intravascular enhancement was sufficient for vascular procedures for 60 minutes after injection. Conclusion SH U 555 C is a promising contrast agent for MR angiography and MR-guided vascular procedures in an open low–field–strength MR imager.

The feasibility and safety of percutaneous laser-induced thermotherapy (LITT) of liver metastases in an open low-field magnetic resonance imaging (MRI) system combined with microsphere-modulated blood flow reduction were tested. Nd:YAG laser therapy with an internally cooled laser applicator was performed under local anesthesia on 20 patients with 34 liver metastases. To increase the effectiveness of LITT, degradable starch microspheres were injected into the proper hepatic artery through an MR-visible catheter initially inserted under fluoroscopy. Near real-time imaging was used for positioning the laser applicator. A T1-weighted gradient-echo breath-hold sequence was used for catheter localization and temperature monitoring. The volumes of the liver metastases and the thermonecroses were determined. MRI-guided LITT could be performed in all patients with no clinically relevant complications. Intraprocedural imaging underestimated the extent of thermonecrosis. In conclusion, percutaneous LITT of liver metastases after injection of starch microspheres is both technically feasible and safe in an open MRI system. J. Magn. Reson. Imaging 2001;13:31-36.

Zusammenfassung Es wurde ein Dosimetriemodell fur die thermische Therapie von biologischem Gewebe mittels Laserstrahlung erarbeitet und auf die interstitielle laserinduzierte Thermotherapie von Organtumoren angewendet. Das Modell kombiniert eine Monte-Carlo-Simulation zur Berechnung der Photonenverteilung im Zielvolumen, ein Finite-Differenzen-Verfahren zur Berucksichtigung von Warmetransportprozessen und den Arrhenius-Formalismus zur Bestimmung der Proteindenaturierung und finalen Gewebedestruktion. Die Implementierung der Algorithmen erfolgte auf einer Windows™-basierten Plattform und ermoglicht die dreidimensionale Kontrolle des Zielvolumens. Die In-vitro-Evaluierung in Schweineleber zeigte eine Ubereinstimmung von besser 7 % bezuglich des Destruktionsvolumens. Die Anwendung des Modells fur eine klinisch relevante Situation machte deutlich, dass Masnahmen zur Perfusionsminderung die Effizienz der LITT um ein Vielfaches steigern konnen.

Purpose The aim of this study is to introduce a fast, T2 weighted true FISP keyhole sequence implemented on an open C arm low field magnetic resonance (MR) scanner for interventional procedure guidance. Method Following the acquisition of a reference data set using a true FISP (fast Imaging with Steady Precision) sequence, only the 32 central raw data lines (keyhole) are acquired in a fluoroscopic-like mode enabling continuous image reconstruction and update. The keyhole true-FISP sequence was tested in animal experiments and used in MR-guided interventions in 10 patients. Results The described true FISP keyhole sequence is characterized by an image frame rate of 2.5 images per second and a T2-like contrast. Due to system constraints with respect to the reconstruction, the actual displaying of images was delayed by up to 180 ms. Conclusions The use of the described keyhole sequence enabled a fluoroscopy-like guidance of interventional devices in an open, low-field system.

Objective: To study magnetic resonance (MR) imaging pattern of normal hyaline articular cartilage in the knee joint with regard to the contribution of the “magic angle” effect to the MR signal. Design. Thirty-two healthy volunteers were imaged in a standard supine position in a 1.5-T unit using spin echo and gradient echo sequences. Nine volunteers were reimaged with the knee flexed. The signal behavior of the hyaline cartilage of the femoral condyles was evaluated qualitatively and quantitatively. The extended and flexed positions of the nine volunteers were compared. Results. A superficial and a deep hyperintense layer and a hypointense middle cartilage layer were observed. Segments of increased signal intensity were visible along the condyles; a magic angle effect on signal intensity was evident in the hypointense middle layer with both gradient echo and spin echo images. Conclusion. The MR signal behavior of hyaline cartilage is influenced by the alignment of the collagen fibers within the cartilage in relation to the magnetic field. Failure to recognize this effect may lead to inaccurate diagnosis.

The tools and devices used for patient treatment during interventional procedures must be accurately and safely localized. Recently, procedure guidance has been performed increasingly with MRI, but tool localization has been performed primarily by analyzing the lack of signal caused by displaced excited tissue and/or susceptibility artifacts. In this investigation, a new technique was developed to actively detect and visualize interventional tools using receive coils mounted on the tip of the interventional devices. Unlike earlier methods, in which images from small device-mounted coils are super-imposed on a previously acquired image data set, our localization method uses similar tip-mounted tools in combination with a radiofrequency (RF) switching circuit, standard imaging coils, and specially modified sequences to toggle between the standard and tip-mounted receive coil within a single fluoroscopic mode sequence. With this technique, the misregistration between the reported anatomic location and true location of interventional devices is minimized.

AIM: To evaluate MR cholangio-pancreatography (MRCP) using an open low magnetic field apparatus in normals and in patients with mechanical cholestasis. METHODS: MRCP was performed on five normals and on 30 patients, using both an 0.2 Tesla and 1.5 Tesla apparatus. With the low field system, rapid acquisition by relaxation enhancement was used, for the high field system, half Fourier acquisition single shot turbo spin-echo sequences were used. In all patients, sonography and ERCP or PTC was performed; 23 underwent surgery. RESULTS: In all normals it was possible to show the bile duct, hepatic duct, gall bladder and intrahepatic ducts of the first order. Using the high field system, second order ducts could be shown and sometimes third order ducts. In the patients, MRCP, using either system, demonstrated all 21 obstructive sites due to tumours or stenoses. Stones were shown in 69% by the low field system and in 88% by the high field system. CONCLUSION: MRCP can be successfully carried out using the low field system. In the presence of mechanical cholestasis, image quality is adequate for the localisation of stenoses and occlusions, and, using an open magnet, is suitable for planning further intervention.

Color duplex sonography (CDS) is primarily applied as a diagnostic procedure. It has not yet established itself as an aid in punctures or other interventions. The aim of this study was to evaluate the value of CDS in arterial and venous vascular punctures. One hundred and sixty-five CDS-assisted vascular punctures were performed in a prospective study after three unsuccessful palpation-guided vasopunctures or in the absence of a palpable pulse. All CDS-assisted punctures were successful. The duration of each attempted puncture showed no statistically significant difference compared with the palpation-guided puncture technique. In the cases with three unsuccessful palpation-guided vascular punctures, the CDS-assisted technique was successful after 1.66 attempts on the average. It is concluded that CDS-assisted vascular puncture is a fast and safe alternative for puncturing a pulseless vessel or for puncturing under difficult conditions.

Development of a percutaneously implantable catheter system for regional chemotherapy of liver metastases and its application in patients with surgically implanted but dislocated catheters. Thirty-three patients with liver metastases of colorectal tumors were submitted to percutaneous puncture of the subclavian artery and insertion of a catheter whose tip was placed in the proper hepatic artery and whose end was subcutaneously connected with an infusion pump. The mean duration of therapy via the percutaneously inserted catheter was 27 weeks (±14 weeks). The most frequent complication was disconnection of the therapy catheter from the tube of the infusion pump. Eighty percent of all complications were corrected by reintervention. The therapy drop-out rate due to catheter-associated complications was 9%. Percutaneous insertion of a catheter for regional chemotherapy of the liver is a relatively uncomplicated method with high patient acceptance and simple access for reintervention.

UNLABELLED The aim of this prospective MRI study was the analysis of the post-operative signals derived from two techniques for cruciate ligament reconstruction. PATIENTS AND METHODS Group 1 consisted of 15 patients who had undergone conventional plastic repair by patellar tendon transplant and group 2 was made up of 15 patients with arthroscopic reconstruction with semitendinosus grafts. They were examined at 6 weeks and 6 months post-operatively. RESULTS Typical appearances of normal transplants were found in 19 patients. After 6 months 8 of the patellar tendon transplants and three of the semitendinosus transplants could not be clearly defined. At this time there was a significant increase in signal intensity in the middle third of the transplant in group 1. CONCLUSION Bearing in mind the different operative techniques, there was a higher impingement rate in group 1. The post-operative MRI findings at 6 months after surgery allowed differentiation between pathological changes (impingement) and revascularisation (remodelling).

The aim of this study was to investigate whether magnetic resonance (MR) diffusion tensor imaging (DTI) allows assessment of renal pathologies in a rat model of diabetic nephropathy.Twenty-one male Sprague-Dawley rats were divided into 3 groups: (1) untreated controls, (2) diabetes (DM), (3) diabetes with uninephrectomy (DM UNX) to accelerate renal impairment. Eight weeks after diabetes induction with streptozotocin, MR imaging was performed in a 1.5-T scanner using an 8-channel wrist coil. Morphological proton density images and echoplanar DTI were obtained (b = 0 and 300 s/mm, 6 diffusion directions). Renal apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values were calculated for each of the different anatomical layers of the kidney. Imaging results, laboratory parameters of diabetic state and kidney function, and renal histopathological changes (glomerulosclerosis, tubular dilatation, and renal fibrosis) were compared between groups. Correlations between FA and histopathological changes were evaluated.All diabetic animals developed hyperglycemia and hypoinsulinemia. Uremia, albuminuria, and histopathological changes were most pronounced in DM UNX animals. Fractional anisotropy was significantly reduced in DM UNX animals in the cortex (CO) (0.167; confidence interval [CI], 0.151-0.184; P0.001), outer stripe of the outer medulla (OS) (0.254; CI, 0.225-0.283; P = 0.038), and inner medulla (IM) (0.459; CI, 0.395-0.523; P = 0.008) compared with control animals (CO, 0.251; CI, 0.224-0.277; OS, 0.309; CI, 0.267-0.350; IM, 0.559; CI, 0.515-0.603). In DM-without-UNX animals, only cortical FA was significantly lower than in controls (P0.001). Between groups, ADC values were not different, except for cortical ADC, which was higher in DM UNX animals than in controls. Significant negative correlations were observed between the FA of different anatomical layers and the extent of glomerulosclerosis (CO, P = 0.003, r = -0.65; and OS, P = 0.022, r = -0.52), tubulointerstitial fibrosis (IM, P = 0.028, r = -0.50), and tubular dilatation (CO, P = 0.015, r = -0.55; and IM, P = 0.006, r = -0.61), respectively.Magnetic resonance DTI by reduction of FA identified renal pathologies of diabetic nephropathy such as glomerulosclerosis, interstitial fibrosis, and tubular damage. Representing different stages of disease, DM and DM UNX animals could be differentiated. Thus, MR DTI may be valuable for noninvasive detection and monitoring of renal pathology in patients with diabetes.

The aim of this study was to demonstrate metabolic changes in the small joints of the hand due to rheumatoid arthritis by means of 31-phosphorus spectroscopy. Suitable measurements were developed and 11 normals and 12 patients were then examined during the course of treatment. Relative concentration of low energy phosphorus metabolites was increased in arthritic joints. The phospholipid quotient (phosphomonoester/phosphodiester) and the relationship of inorganic phosphate and beta-nucleoside triphosphate were significant factors during the course of individual treatments.

In a prospective study, the right knee of 21 symptom free juvenile footballers was examined by MRT (group I) and the results were compared with 12 juveniles of similar age but who did not take part in any special sporting activities (group II). A 1.5 Tesla Magnetome with an extremity coil was used. There were no abnormal changes in either group in the cruciate ligaments. The hyaline cartilage medially was about 10% thicker than laterally in both groups but in group I it was, on average, 24.8% thicker than in group II. Increased signals in the centre of the menisci were observed in 8 members of group I and two in group II. 5 of the 8 in group I, but none in group II, also showed an increase in the joint fluid.

To evaluate MR diffusion tensor imaging (DTI) as non-invasive diagnostic tool for detection of acute and chronic allograft dysfunction and changes of organ microstructure.15 kidney transplanted patients with allograft dysfunction and 14 healthy volunteers were examined using a fat-saturated echo-planar DTI-sequence at 1.5 T (6 diffusion directions, b = 0, 600 s/mm²). Mean apparent diffusion coefficient (ADC) and mean fractional anisotropy (FA) were calculated separately for the cortex and for the medulla and compared between healthy and transplanted kidneys. Furthermore, the correlation between diffusion parameters and estimated GFR was determined.The ADC in the cortex and in the medulla were lower in transplanted than in healthy kidneys (p 0.01). Differences were more distinct for FA, especially in the renal medulla, with a significant reduction in allografts (p 0.001). Furthermore, in transplanted patients a correlation between mean FA in the medulla and estimated GFR was observed (r = 0.72, p 0.01). Tractography visualized changes in renal microstructure in patients with impaired allograft function.Changes in allograft function and microstructure can be detected and quantified using DTI. However, to prove the value of DTI for standard clinical application especially correlation of imaging findings and biopsy results is necessary.

Background: Magnetic resonance (MR)-guided interventions have evolved from a pure research application to a preclinical method over the last decade. Among the device-tracking techniques, susceptibility artifact-based tracking relies on the contrast between the surrounding blood and the device, and radiofrequency coil-based tracking relies on the local gradient field amplification in a resonating circuit attached to the interventional device. Purpose: To evaluate the feasibility and precision of susceptibility artifact-based and microcoil-based MR guidance methods for renal artery stent placement in a swine model. Material and Methods: MR imaging-guided renal artery stent placements were performed in six fully anesthetized pigs using a 1.5T short-bore MR scanner. Susceptibility artifact-based tracking with manual scan-plane adjustments and microcoil tracking with automatic scan-plane adjustments were used for renal artery stent placements in three pigs in each group. With both methods, near real-time steady-state free-precession (SSFP) imaging was used. Differences between the two tracking approaches on stenting time, total procedure time, and stent position were measured. Results: The microcoil-based approach yielded a shorter mean procedure time (17 vs. 23 min). There was no relevant difference for the mean stenting time (12 vs. 13 min). The mean stent deviation from the aortic wall with the susceptibility approach was larger than with the microcoil approach (10 vs. 4.0 mm). Conclusion: For MRI-guided renal artery stent placement, the microcoil-based technique had a shorter procedure time and a higher stent placement precision than the susceptibility artifact-based approach.

Purpose To evaluate the accuracy of four MR sequences used as part of a whole-body MRI protocol to detect pulmonary lesions in cancer patients. Materials and Methods A total of 31 oncology patients were imaged in a 1.5T MR scanner (Magnetom Avanto; Siemens Medical Solutions, Germany) for whole-body staging. MR chest imaging included: axial and coronal T2-weighted (T2w)–short-tau inversion-recovery (STIR), axial T2w turbo spin-echo (TSE), and contrast-enhanced (CE) three-dimensional (3D) volumetric interpolated breathhold examination (VIBE). Multidetector computed tomography (MDCT) of the thorax served as the reference standard. The MDCT and MR images were evaluated independently by two radiologists. Comparative analysis was performed per lesion, per lobe, and per patient. Sensitivity, specificity, and predictive values were determined. Results Compared to MDCT that detected 268 pulmonary lesions ranging from 2 to 75 mm in diameter, the MR sensitivities were 91.1%, 92.5%, 90.8%, and 87.3% for the coronal STIR, the axial STIR, the axial T2w-TSE, and the axial CE 3D-VIBE, respectively. Undetected pulmonary lesions were either calcified or smaller than 10 mm in the axial diameter. With coronal STIR, six false-positive findings were detected; with axial STIR, 14 were detected; with axial T2w-TSE, 10 were detected; and with 3D-VIBE, seven were detected. Conclusion Pulmonary MRI is feasible as part of a whole-body MRI protocol. In our study, STIR images achieved high accuracy compared to chest MDCT for pulmonary lesions of 3 mm in size or larger. J. Magn. Reson. Imaging 2008. © 2008 Wiley-Liss, Inc.

Magnetic resonance imaging (MRI) offers several advantages over other imaging modalities that make it an attractive imaging tool for diagnostic and therapeutic procedures. This tremendous potential of MRI has provided the rationale for increased attention toward MR-guided endovascular interventions. MR guidance has been used recently to navigate endovascular catheters and deliver stents, vena cava filters, embolization materials, and septum closure devices. However, its potential goes beyond just copying existing procedures toward the development of new minimally invasive techniques that cannot be performed with conventional guiding techniques. Because of technical limitations and safety issues associated with some of the currently available devices, a limited number of clinical studies have been performed so far. The overall success for this developing field requires considerable interdisciplinary research within both the interventional and the MR community. Only through a combined effort can this complex technology find its way into clinical practice. This review discusses the hardware and software improvements that have helped to advance endovascular interventions under MR imaging guidance from a pure research tool to become a clinical reality. In addition, technical and safety issues specific to endovascular MR image guidance will be described and practical applications will be shown that take advantage of the benefits of MR for endovascular interventions. J. Magn. Reson. Imaging 2008;27:326–338. © 2008 Wiley-Liss, Inc.

During animal experiments, carbon dioxide (CO(2)) and air were used as a novel contrast agent for direct magnetic resonance arthrography (MRAr). MRAr was performed after injection of CO(2) and air in the knee joints of two pigs. MR images of phantoms containing air, CO(2) and nitrogen were compared. After intra-articular injection, both present as a signal void on various sequences and permit sharp delineation of cartilage and other adjacent structures. Despite the potential for artefact generation, only a slight susceptibility artefact was seen after injection of CO(2) and air. In phantom experiments, air, CO(2) and nitrogen demonstrated identical slight regular susceptibility artefacts at the phantom margins. CO(2) MRAr can yield high contrast between cartilage, ligaments and synovium relative to the joint compartment. Therefore, this technique might be useful as an investigational method for the evaluation of cartilage surface lesions and possibly as an alternative contrast agent for clinical use.

Purpose To assess magnetic resonance (MR) pulse sequences for high resolution intravascular imaging. Materials and Methods Intravascular imaging of the abdominal aorta and iliac arteries was performed in vivo in a porcine model at 1.5 T using catheter-mounted micro-receive coils. Ten protocols, including spin-echo (SE)-echo planar imaging (SE-EPI), segmented EPI, half-Fourier single-shot turbo spin-echo (HASTE), fast imaging with steady-state free precession (TrueFISP), turbo spin-echo (TSE), and SE acquisition schemes were employed in 13 trials. Images were analyzed by six expert raters with respect to wall-conspicuity, wall-to-lumen/tissue contrast, visible layers of the arterial wall, anticipated clinical usefulness, and overall image quality. Mean differences between sequence-types were evaluated using analysis of variance (ANOVA) between groups with planned comparisons. Results The vessel wall was delineated in almost all protocols. Motion artifacts from physiological and device motion were reduced in fast techniques. The best contrast between the wall and surrounding tissue was provided by a HASTE protocol. Anatomic layers of the vessel wall were best depicted on dark blood T2-weighted TSE. Overall, TrueFISP was ranked highest on the remaining measures. Conclusion Dedicated catheter-coils combined with fast sequences have potential for in vivo characterization of vessel walls. TrueFISP offered the best overall image quality and acquisition speed, but suffered from the inability to delineate the multiple layers of the wall, which seems associated with dark blood- and T2-weighted contrast. We believe future intra-arterial trials should proceed from this study in normal artery imaging and initially focus on fast T2-weighted dark blood techniques in trials with pathology. J. Magn. Reson. Imaging 2006. © 2006 Wiley-Liss, Inc.