Rolf W. Günther

To visualize the coronary sinus using magnetic resonance (MR), and to demonstrate the feasibility of MR-guided intubation of the cardiac venous system (CVS) in swine. A total of 6 pigs were investigated. All experiments were performed using an interventional 1.5-Tesla MRI system. The CVS was visualized using an inversion-recovery navigator-gated whole-heart steady-state free-precession sequence after administration of gadobenate dimeglumine contrast agent. The coronary sinus was then intubated under MR-guidance with a passive MR-compatible guidewire modified by incorporation of iron oxide markers for improved visualization and a nonbraided Cobra-catheter. MR-guided interventions were monitored using a steady-state free-precession real-time imaging sequence. Time needed was measured for MR-guided intubation of the CVS and compared with the time needed for fluoroscopy guided intubation of the CVS. Visualization and intubation of the coronary sinus and its site branches was feasible in all cases. Time spent for MR-guided intubation of the CVS was comparable to time spent for fluoroscopy-guided intubation (8.2 +/- 2 minutes vs. 8.3 +/- 1.3 minutes; P = 0.85). MR-visualization and MR-guided intubation of the coronary sinus and its side branches is feasible. The feasibility of MR-guided intubation of the CVS might have relevance for procedures like cardiac resynchronization therapy and percutaneous transcatheter mitral annuloplasty, requiring improved 3-dimensional knowledge about cardiac vein anatomy in the near future.

To evaluate accuracy and procedure times of electromagnetic tracking (EMT) in a robotic arm mounted flat panel setting using phantom and animal cadaveric models.

Radiological bone age assessment is based on local image regions of interest (ROI), such as the epiphysis or the area of carpal bones. These are compared to a standardized reference and scores determining the skeletal maturity are calculated. For computer-aided diagnosis, automatic ROI extraction and analysis is done so far mainly by heuristic approaches. Due to high variations in the imaged biological material and differences in age, gender and ethnic origin, automatic analysis is difficult and frequently requires manual interactions. On the contrary, epiphyseal regions (eROIs) can be compared to previous cases with known age by content-based image retrieval (CBIR). This requires a sufficient number of cases with reliable positioning of the eROI centers. In this first approach to bone age assessment by CBIR, we conduct leaving-oneout experiments on 1,102 left hand radiographs and 15,428 metacarpal and phalangeal eROIs from the USC hand atlas. The similarity of the eROIs is assessed by cross-correlation of 16x16 scaled eROIs. The effects of the number of eROIs, two age computation methods as well as the number of considered CBIR references are analyzed. The best results yield an error rate of 1.16 years and a standard deviation of 0.85 years. As the appearance of the hand varies naturally by up to two years, these results clearly demonstrate the applicability of the CBIR approach for bone age estimation.

Ziel: Wir evaluierten den Einfluss eines interaktiven Atemkontrollsystems bei der CT-gesteuerten Lungenbiopsie auf die Interventionszeit und den technisch erfolgreichen Abschluss. Material und Methoden: Wir führten bei 36 Patienten (4 weiblich, 32 männlich, mittleres Alter 65 Jahre; 33 – 88 Jahre) mit einem Lungenherd eine CT-gesteuerte Lungenbiopsie durch. Wir setzten eine 18G-Tru-cut-Biopsienadel (Cardinal Health, Dublin, UK) in einem 64 Zeilen-Dual-Source-CT (Somatom Definition, Siemens, Forchheim, Deutschland) bei intermittierender Bildgebung der Nadel ein. Bei der Hälfte der Patienten (2 weiblich, 16 männlich, mittleres Alter 67 Jahre) kam zusätzlich ein interaktives Atemkontrollsystem (IBC) (Mayo Clinic Medical Devices, USA) zur Anwendung. In der Kontrollgruppe wurde die Lungenbiopsie ohne ein solches System durchgeführt. Ergebnisse: Die Biopsie wurde bei allen Patienten technisch erfolgreich durchgeführt. Der Durchmesser des Zielherds war in beiden Gruppen vergleichbar (IBC: 30 ± 19 mm; Kontrolle: 28 ± 15 mm). Die Anzahl der benötigten Kontrollbildgebungen war in der IBC-Gruppe signifikant geringer (p < 0,05) und die Interventionszeit signifikant kürzer (p < 0,05) (IBC: 9 ± 5 Bildgebungsschritte, 17 ± 10 min; Kontrolle: 13 ± 5 Bildgebungsschritte, 26 ± 12 min). Schlussfolgerung: Durch Einsatz eines interaktiven Atemkontrollsystems war es möglich, die Interventionszeit und die Strahlenbelastung bei CT-gesteuerten Lungenbiopsien zu reduzieren. Purpose: In this study we assessed the effect of an interactive breath-hold control system on procedure time and technical success in transthoracic CT-guided lung biopsies. Materials and Methods: In 36 patients (4 female, 32 male, mean age 65 years; range 33 – 88) with a pulmonary nodule, we performed CT-guided biopsy using a 18G Tru-cut needle (Cardinal Health, Dublin, UK) in a 64 row dual-source CT scanner (Somatom Definition, Siemens, Forchheim, Germany) using intermittent imaging of the needle. In half of the patients (2 female, 16 male, mean age 67 years), an interactive breath-hold control system (IBC) (Mayo Clinic Medical Devices, USA) was applied. No additional device was used in the control group. Results: The biopsy was visually successful in all patients. The diameter of the target lesion was comparable in both groups (IBC: 30 ± 19 mm; control: 28 ± 15 mm). The number of imaging steps was significantly smaller (p < 0.05) and the intervention time was significantly shorter (p < 0.05) in the IBC group (IBC: 9 ± 5 steps 17 ± 10 min; control: 13 ± 5 steps 26 ± 12 min). Conclusion: Application of the IBC unit reduced the intervention time and radiation exposure in CT-guided Tru-cut biopsy of pulmonary nodules.

Ziel: Da semi-automatische Quantifizierung von Läsionen präziser als manuelle ein- und zweidimensionale Messungen sein könnten, war das Ziel dieser Studie, beide Messmethoden in Bezug auf zervikale, thorakale und abdominelle Lymphknoten bei Lymphompatienten miteinander zu vergleichen. Material und Methoden: 62 Lymphompatienten wurden mittels kontrastmittelangehobener 16-Zeilen-Mehrschicht-Spiral-CT untersucht (16 × 0,7 mm coll., 120 kV, zervikal/thorakal/abdominell: 150 / 120 / 160 mAseff., 1 / 1,25 / 1 pitch, 4 / 3 – 5 / 4 – 5 / 4 Schichtdicke/Rekonstruktionsinkrement). Anhand von Standardschichtdicken wurden sämtliche Lymphknoten in Bezug auf RECIST- sowie dessen längsten orthograden Durchmesser mittels eines Softwarealgorithmus (Syngo CT Oncology, Siemens Medical Solutions, Forchheim, Deutschland) und manuell durch einen erfahrenen Radiologen evaluiert. Der Grad der Übereinstimmung zwischen manueller und semi-automatischer Quantifizierung wurde statistisch mittels des Konkordanzkorrelationskoeffizienten κ und grafisch anhand korrespondierender Bland-Altman-Plots ausgewertet. Ergebnisse: 74 / 80 zervikale, 51 / 80 thorakale and 75 / 80 abdominelle Lymphknoten wurden regelrecht von der Software quantifiziert. Ein hohes Maß an Übereinstimmung zwischen beiden Messtechniken (RECIST: κ = 0,97 (zervikal)/ 0,98 (thorakal)/ 0,99 (abdominell); längster orthograder Durchmesser: κ = 0,97 / 0,93 / 0,97). Schlussfolgerung: Semi-automatische Messungen von zervikalen, thorakalen und abdominellen Lymphknoten zeigten eine große Übereinstimmung gegenüber manuellen Messungen anhand von Standard-CT-Schichten, allerdings aufgrund der relativ hohen Rate von Fehlsegmentierungen thorakal hier mit gewissen Einschränkungen. Purpose: Since semi-automated lesion quantification may be more precise than manual uni- and bidimensional measurements, the purpose of this study was to compare semi-automated with manual evaluations of cervical, thoracic and abdominal lymph nodes in patients with malignant lymphoma. Materials and Methods: 62 patients with known malignant lymphoma underwent staging with contrast-enhanced 16-MDCT (16x0.7 mm coll., 120 kV, cervical/thoracic/abdominal: 150 / 120 / 160 mAseff., 1 / 1.25 / 1 pitch, 4 / 3 – 5 / 4 – 5 / 4 slice thickness/reconstruction increment). On the basis of these standard reconstructed slices, each lesion was quantified in terms of RECIST and its longest orthographic diameter using a semi-automated software tool (Syngo CT Oncology, Siemens Medical Solutions, Forchheim, Germany) and manually by an experienced radiologist. The degree of agreement between manual measurements and software quantification was statistically assessed by computing the concordance correlation coefficient κ and represented graphically in corresponding Bland-Altman plots. Results: 74 / 80 cervical, 51 / 80 thoracic and 75 / 80 abdominal lymph nodes were correctly evaluated by the software. A strong degree of agreement between both measurement techniques (RECIST diameter: κ = 0.97 (cervical)/ 0.98 (thoracic)/ 0.99 (abdominal); longest orthographic diameter: κ = 0.97 / 0.93 / 0.97) was obtained. Conclusion: Semi-automated measurement of cervical, thoracic and abdominal lymph nodes showed valid results on standard axial reconstructions compared to manual quantification with the limitation of a high false segmentation rate in thoracic lymph nodes.

We examined to what degree the visualization of anatomic structures in the human knee is improved using 3.0-T magnetic resonance imaging (MRI) and many element RF receive coils as compared to 1.5 T. We imaged 20 knees at 1.5 and 3.0 T using T2-weighted STIR, T2-weighted gradient echo, T1-weighted spin-echo, true-FISP and T2-weighted fast spin echo techniques in conjunction with 32-element RF coil arrays. The 3.0-T examination was considerably faster than its 1.5-T counterpart. A superior subjective visibility at 3.0 T vs 1.5 T was found in 27 of 50 evaluated structures (meniscus, ligaments) with the exception of true-FISP techniques. The 3.0-T examination provided a better visibility (evaluated by blinded consensus-reading by two radiologists) of small structures such as the ligamentum transversum genu. Also, cartilage was better delineated at 3.0 T. A 23% increased average signal-to-noise ratio as assessed using a temporal filter was observed at 3.0 T as compared to 1.5 T. At 3.0 T, imaging of the human knee is faster and results in a subjective visibility of anatomic structures that is superior to and competitive with 1.5 T.

Background: The effect of radiofrequency ablation (RFA) can be modulated by fluid injection. Purpose: To evaluate the potential of different fluids to modulate the effect of bipolar RFA in an ex-vivo liver model. Material and Methods: A bipolar RFA system with an internally cooled needle-shaped applicator (20-mm active tip) was used to induce coagulation lesions in ex-vivo porcine liver. Prior to the ablation procedure, 1-ml samples of seven different fluids were injected (0.9% saline, gadopentetate dimeglumine, ioxithalamate, 10% hydroxyethyl starch, 5% glucose, 95% ethanol, distilled water). Each fluid was used for five RF ablations. During the procedure, applied energy, impedance, and time were recorded. Additionally, temperature was measured at a fixed distance of 0.5 and 1.0 cm from the RF probe. Generator output was set to 20 W, as recommended by the vendor. Five ablation procedures without fluid injection served as the reference standard. The lesion diameters were measured, and volume and an efficiency index (coagulation volume/procedure duration) calculated and compared (ANOVA, Student-Newman-Keuls test). Results: In comparison to the reference standard, fluid injection resulted in an enlargement of mean coagulation volume for all fluids. In comparison to RF ablation alone (1.42±0.33 cm³), significant increase ( P<0.001) of lesion size was found using gadopentetate dimeglumine, hydroxyethyl starch, glucose, and ethanol. The largest lesions were generated using preinjection of hydroxyethyl starch. Most energy could be applied after injection of glucose. Comparing the efficiency index, no statistically significant differences were found. Conclusion: Besides the modulation of the electrical conductivity, the increase in thermal conductivity also contributes to the enhancement of RFA by the injection of the tested fluids. Further studies are needed to evaluate this effect for larger injection volumes under in-vivo conditions.

Cardiovascular magnetic resonance (MR) imaging is of proven clinical value for the noninvasive characterization of myocardial viability. Computed tomography (CT) is also being exploited for this indication. Examples of each of these imaging strategies for the assessment of myocardial viability will be provided in this review. Key MRI concepts and practical considerations such as customized MR imaging techniques and tailored imaging protocols dedicated to viability assessment are outlined with the primary focus on recent developments. Clinical applications of MR-based viability assessment are reviewed, ranging from rapid functional cine imaging to tissue characterization using T2-weighted imaging and T1-weighted late-contrast-enhanced imaging. Next, the merits and limitations of state-of-the-art CT imaging are surveyed, and their implications for viability assessment are considered. The final emphasis is on current trends and future directions in noninvasive viability assessment using MRI and CT.

Diagnosis of cerebral sinus vein thrombosis is still a challenge for imaging. MRI and MRA play a major role in sinus imaging. For further development of MR techniques, MR-compatible animal models are required. The aim of this study was to develop an animal model for sinus thrombosis and additional cortical vein thrombosis with a clot of human blood for MR imaging studies.

Purpose: Development and experimental evaluation of an intravascular monitoring system for telemetric measurement of blood pressure and heart rate. Materials and Methods: The monitoring system consists of an implantable silicone capsule (diameter 2.3 mm), containing a dedicated microchip with pressure sensors and signal-processing circuits as well as an antenna for wireless data and energy transfer using 6.78 MHz transponder technology. Three self-expanding legs at one end of the capsule served as a mechanism to lock the capsule at an arterial branch. A flow model, driven by a ventricular assist system, was used for testing and optimizing the implantation equipment, for checking the anchoring mechanism and for ensuring transmission of the measured pressure to the readout unit. In-vivo experiments were performed in 8 minipigs (weight 25 to 30 kg), with three capsules placed in each minipig via the femoral artery using a dedicated 8-F sheath/pusher system. Follow-up was by CT angiography for up to 6 months after implantation. Results: Flow model tests revealed a maximum deviation of pressure and heart rate measurements of 5% from the reference measurements. Signal transmission was reliable over a distance of 3 to 4 cm. Fluoroscopically guided in-vivo implantation of the capsules was simple and straightforward. In arteries with a diameter of 5 to 6 mm, the capsules were permanently fixed with one or two legs interlocked in side branches and without occlusion within 6 months. Three capsules developed a small non-occlusive appositional thrombus attached to the downstream (leg) part of the capsule. Conclusion: Our in-vitro and in-vivo experiments demonstrate the feasibility of wireless transmission from a capsule with a sufficient resolution of the sensor output signals to determine blood pressure and pulse rate. As long as the vessel diameter is wide enough, arterial fixation of the capsule does not induce thrombotic occlusion of the parent artery. With respect to future clinical applications, further refinements of the transmission technology are needed to extend the transmission distance between capsule and reader antenna. The technology of intelligent implants has further implications, such as monitoring of other physiological parameters, and the design of a control loop, which may be used for therapeutic feedback. Ziel: Die Entwicklung und experimentelle Erprobung eines intravaskulären Monitoring-Systems zur telemetrischen Erfassung von Blutdruck und Herzfrequenz. Material und Methode: Das System besteht aus einer implantierbaren Silikonkapsel (Durchmesser 2,3 mm), die einen speziell entwickelten Mikrochip mit Drucksensoren und Transponderelektronik, sowie eine Antenne zur drahtlosen Daten- und Energieübermittlung in 6,78 MHz-Technologie beinhaltet. Drei selbstexpandierbare Beinchen am Kapselende dienen als Verankerungsmechanismus in einer arteriellen Gefäßaufzweigung. An einem Flussmodell wurden das Implantationsbesteck getestet und optimiert, der Verankerungsmechanismus kontrolliert, und die verlässliche Übermittlung der gemessenen Druckwerte zur externen Lesestation überprüft. Bei in-vivo-Experimenten an 8 Minipigs (25 - 30 kg) wurden je drei Kapseln über einen femoral-arteriellen Zugang unter Verwendung eines speziellen 8-F-Schleusen/Pusher-Systems platziert. Nachuntersuchungen mit CT-Angiographie erfolgten bis zu 6 Monaten nach Implantation. Ergebnisse: Die maximale Abweichung von Druck und Pulsrate von den Referenzwerten betrug 5 %. Die Datenübertragung war über eine Distanz von 3 - 4 cm möglich. Die durchleuchtungsgesteuerte Implantation der Kapseln gelang problemlos. In Arterien mit einem Durchmesser von 5 - 6 mm waren die Kapseln innerhalb von 6 Monaten permanent fixiert, ohne einen Gefäßverschluss hervorzurufen. An 3 Kapseln bildete sich ein kleiner, nicht-okklusiver Appositionsthrombus. Schlussfolgerungen: Unsere Untersuchungen demonstrieren die Durchführbarkeit einer Blutdruck- und Frequenzüberwachung mittels einer intravaskulären Transponderkapsel. Bei ausreichendem Gefäßdurchmesser ist eine dauerhafte Kapselfixation ohne Gefäßokklusion möglich. Für zukünftige klinische Anwendungen muss jedoch die Übertragungsdistanz erhöht werden. Die Technologie des intelligenten Implantates bietet weitere Anwendungsmöglichkeiten, z. B. Überwachung anderer physiologischer Parameter oder die Ausbildung eines therapeutischen Regelkreises.