Combined indocyanine green and quantitative perfusion assessment with hyperspectral imaging during colorectal resections.

Anastomotic insufficiencies still represent one of the most severe complications in colorectal surgery. Since tissue perfusion highly affects anastomotic healing, its objective assessment is an unmet clinical need. Indocyanine green-based fluorescence angiography (ICG-FA) and hyperspectral imaging (HSI) have received great interest in recent years but surgeons have to decide between both techniques. For the first time, two data processing pipelines capable of reconstructing an ICG-FA correlating signal from hyperspectral data were developed. Results were technically evaluated and compared to ground truth data obtained during colorectal resections. In 87% of 46 data sets, the reconstructed images resembled the ground truth data. The combined applicability of ICG-FA and HSI within one imaging system might provide supportive and complementary information about tissue vascularization, shorten surgery time, and reduce perioperative mortality.

[Possibilities and perspectives of hyperspectral imaging in visceral surgery]. / Möglichkeiten und Perspektiven der Hyperspektralbildgebung in der Viszeralchirurgie.

HyperSpectral Imaging (HSI) technology enables quantitative tissue analyses beyond the limitations of the human eye. Thus, it serves as a new diagnostic tool for optical properties of diverse tissues. In contrast to other intraoperative imaging methods, HSI is contactless, noninvasive, and the administration of a contrast medium is not necessary. The duration of measurements takes only a few seconds and the surgical procedure is only marginally disturbed. Preliminary HSI applications in visceral surgery are promising with the potential of optimized outcomes. Current concepts, possibilities and new perspectives regarding HSI technology together with its limitations are discussed in this article.

[Hyperspectral imaging of gastrointestinal anastomoses]. / Hyperspektral-Imaging bei gastrointestinalen Anastomosen.

INTRODUCTION: Anastomotic insufficiency (AI) remains the most feared surgical complication in gastrointestinal surgery, which is closely associated with a prolonged inpatient hospital stay and significant postoperative mortality. Hyperspectral imaging (HSI) is a relatively new medical imaging procedure which has proven to be promising in tissue identification as well as in the analysis of tissue oxygenation and water content. Until now, no data exist on the in vivo HSI analysis of gastrointestinal anastomoses. METHODS: Intraoperative images were obtained using the TIVITA™ tissue system HSI camera from Diaspective Vision GmbH (Pepelow, Germany). In 47 patients who underwent gastrointestinal surgery with esophageal, gastric, pancreatic, small bowel or colorectal anastomoses, 97 assessable recordings were generated. Parameters obtained at the sites of the anastomoses included tissue oxygenation (StO2), the tissue hemoglobin index (THI), near-infrared (NIR) perfusion index, and tissue water index (TWI). RESULTS: Obtaining and analyzing the intraoperative images with this non-invasive imaging system proved practicable and delivered good results on a consistent basis. A NIR gradient along and across the anastomosis was observed and, furthermore, analysis of the tissue water and oxygenation content showed specific changes at the site of anastomosis. CONCLUSION: The HSI method provides a non-contact, non-invasive, intraoperative imaging procedure without the use of a contrast medium, which enables a real-time analysis of physiological anastomotic parameters, which may contribute to determine the "ideal" anastomotic region. In light of this, the establishment of this methodology in the field of visceral surgery, enabling the generation of normal or cut off values for different gastrointestinal anastomotic types, is an obvious necessity.

Low-dose 5-fluorouracil in combination with salicylic acid for the treatment of actinic keratoses on the hands and/or forearms - results of a non-interventional study.

BACKGROUND: As an in situ carcinoma, actinic keratoses should be treated early. Previous studies on the efficacy of a low-dose 0.5% 5-fluorouracil solution in combination with 10% salicylic acid (low-dose 5-FU/SA) are mostly related to lesions appearing on the head and face. In contrast, actinic keratoses (AK) lesions of the upper extremities are considered to be difficult to treat. OBJECTIVE: The efficacy of low-dose 5-FU/SA in the treatment of actinic keratoses on the hands and/or forearms was studied for the first time in this non-interventional study (NIS) under practical conditions in a large patient population. In addition to the clinical course during therapy and a follow-up period, the length of application and adherence were documented. METHODS: As part of this NIS, 649 patients with AK were treated at 207 centres with low-dose 5-FU/SA. The data of the study were recorded at baseline, optionally during an intermediate examination, at the end of therapy and during a final assessment. RESULTS: The average number of AK lesions decreased during the entire observation period by 92%. Side-effects were documented only rarely in the form of local skin reactions (2%). The attending physicians assessed the efficacy, tolerability and safety of the therapy as being predominantly very good or good (in each case ≥90%). CONCLUSION: AK lesions on the hands and/or forearms were effectively treated with low-dose 5-FU/SA under routine conditions in dermatological practice and the treatment was well tolerated.

In vivo validation of spatio-temporal liver motion prediction from motion tracked on MR thermometry images.

PURPOSE: Magnetic resonance-guided focused ultrasound (MRgFUS) of the liver during free-breathing requires spatio-temporal prediction of the liver motion from partial motion observations. The study purpose is to evaluate the prediction accuracy for a realistic MRgFUS therapy scenario, namely for human in vivo data, tracking based on MR images routinely acquired during MRgFUS and in vivo deformations caused by the FUS probe. METHODS: In vivo validation of the motion model was based on a 3D breath-hold image and an interleaved acquisition of two MR slices. Prediction accuracy was determined with respect to manually annotated landmarks. A statistical population liver motion model was used for predicting the liver motion for not tracked regions. This model was individualized by mapping it to end-exhale 3D breath-hold images. Spatial correspondence between tracking and model positions was established by affine 3D-to-2D image registration. For spatio-temporal prediction, MR tracking results were temporally extrapolated. RESULTS: Performance was evaluated for 10 volunteers, of which 5 had a dummy FUS probe put on their abdomen. MR tracking had a mean (95 %) accuracy of 1.1 (2.4) mm. The motion of the liver on the evaluation MR slice was spatio-temporally predicted with an accuracy of 1.9 (4.4) mm for a latency of 216 ms. A simple translation model performed similarly (2.1 (4.8) mm) as the two MR slices were relatively close (mean 38 mm). Temporal prediction was important (10 % error reduction), while registration effects could only partially be assessed and showed no benefits. On average, motion magnitude, motion amplitude and breathing frequency increased by 24, 16 and 8 %, respectively, for the cases with FUS probe placement. This motion increase could be reduced by the spatio-temporal prediction. CONCLUSION: The study shows that tracking liver vessels on MR images, which are also used for MR thermometry, is a viable approach.

Towards trends in minimal invasive cardiac surgery.

While various minimally invasive techniques have been established in many other surgical specialties during the last decades, cardiac surgery has been one of the last domains to adopt the principles of minimally invasive techniques. This was mainly based on the reduced surgical exposure in highly complex cardiac operations and the missing technical requirements in the beginning of the modern cardiac era. Nowadays, technical conditions have continuously improved and have become routine also in cardiac surgery. Most of these novel minimal-invasive concepts have been developed in order to treat high-risk or inoperable patients by reducing operative trauma. Actually, since more high-risk and multimorbid patients were referred for surgery, these initial extraordinary procedures have been adopted into daily clinical routine. Currently, many promising innovations aim to reduce the operative trauma and perioperative morbidity, and furthermore, to increase patients' satisfaction and security. It is anticipated that in the future this current trend towards minimal invasiveness will increase further due to an increased demand, and therefore, such minimal-invasive procedures will become less complex and straightforward.

High intensity focused ultrasound treatment of small renal masses: Clinical effectiveness and technological advances.

The review summarises the technological advances in the application of high-intensity focused ultrasound for small renal masses presumed to be cancer including the systematic review of its clinical application. Current progress in the area of magnetic resonance image guided ultrasound ablation is also appraised. Specifically, organ tracking and real time monitoring of temperature changes during the treatment are discussed. Finally, areas of future research interest are outlined.

[Principles of MR-guided interventions, surgery, navigation, and robotics]. / Prinzipien Magnet-Resonanz-geführter Intervention, Operation, Navigation und Robotik.

The application of magnetic resonance imaging (MRI) as an imaging technique in interventional and surgical techniques provides a new dimension of soft tissue-oriented precise procedures without exposure to ionizing radiation and nephrotoxic allergenic, iodine-containing contrast agents. The technical capabilities of MRI in combination with interventional devices and systems, navigation, and robotics are discussed.

[Eosinophilic fasciitis and asplenia]. / Eosinophile Fasziitis und Asplenie.

Eosinophilic fasciitis (Shulman syndrome) is a chronic inflammation primarily of the septums and fascia, and is characterized by the infiltration of eosinophils with additional similarities to systemic sclerosis. Several diseases have been described in association with eosinophilic fasciitis. Among these are aplastic anaemia, haemolytic anaemia, thrombocytopenia, lymphoproliferative disorders, thyroiditis, pulmonary fibrosis, Sjögren's syndrome, Raynaud's phenomenon, myositis, medium vessel vasculitis, pericarditis, colitis and glomerulonephritis. To date, no association with congenital asplenia has been described. We report the case of a woman with eosinophilic fasciitis and congenital asplenia and discuss the possible causes and potential consequences.

Dust-induced modulation of the atomic emission in a dusty argon discharge.

The spectral emission of argon atoms in a dusty rf discharge plasma has been determined. For that purpose, the spatially and temporally resolved emission of the argon atoms during the rf cycle was measured using a gated intensified charge-coupled device camera. While dust particles of 2-3 microm diameter trapped in the sheath lead to an increased plasma emission during the sheath expansion phase, larger particles of 10-12 microm diameter result in a decreased emission. This behavior is explained by the combined action of electron density reduction due to the charging dynamics in the sheath and the increase of electron temperature to compensate plasma losses at the dust.

Probability of metastable configurations in spherical three-dimensional Yukawa crystals.

Recently the occurrence probabilities of ground and metastable states of three-dimensional Yukawa clusters with 27 and 31 particles have been analyzed in dusty plasma experiments [D. Block, Phys. Plasmas 15, 040701 (2008)]. There it was found that, in many cases, the ground state appeared substantially less frequently than excited states. Here we analyze this question theoretically by means of molecular dynamics (MD) and Monte Carlo simulations and an analytical method based on the canonical partition function. We confirm that metastable states can occur with a significantly higher probability than the ground state. The results strongly depend on the screening parameter of the Yukawa interaction and the damping coefficient used in the MD simulations. The analytical method allows one to gain insight into the mechanisms being responsible for the occurrence probabilities of metastable states in strongly correlated finite systems.

Existence and vanishing of the breathing mode in strongly correlated finite systems.

One of the fundamental eigenmodes of finite interacting systems is the mode of uniform radial expansion and contraction-the breathing mode (BM). Here we show in a general way that this mode exists only under special conditions: (i) for harmonically trapped systems with interaction potentials of the form 1/rgamma (gamma in R not equal 0) or log(r), or (ii) for some systems with special symmetry such as single-shell systems forming platonic bodies. Deviations from the BM are demonstrated for two examples: clusters interacting with a Lennard-Jones potential and parabolically trapped systems with Yukawa repulsion. We also show that vanishing of the BM leads to the occurrence of multiple monopole oscillations which is of importance for experiments.

Obliquely propagating dust-density waves.

Self-excited dust-density waves are experimentally studied in a dusty plasma under microgravity. Two types of waves are observed: a mode inside the dust volume propagating in the direction of the ion flow and another mode propagating obliquely at the boundary between the dusty plasma and the space charge sheath. The dominance of oblique modes can be described in the frame of a fluid model. It is shown that the results fom the fluid model agree remarkably well with a kinetic electrostatic model of Rosenberg [J. Vac. Sci. Technol. A 14, 631 (1996)]. In the experiment, the instability is quenched by increasing the gas pressure or decreasing the dust density. The critical pressure and dust density are well described by the models.

Obliquely propagating dust-density plasma waves in the presence of an ion beam.

Self-excited dust-density waves are experimentally studied in a dusty plasma under microgravity. Two types of waves are observed: a mode inside the dust volume propagating in the direction of the ion flow and a new mode propagating obliquely at the boundary between the dusty plasma and the space-charge sheath. A model for dust-density waves propagating at an arbitrary angle with respect to the ion-flow direction is presented, which explains the preference for oblique or parallel modes as a function of ion velocity.

Targeted-HASTE imaging with automated device tracking for MR-guided needle interventions in closed-bore MR systems.

Percutaneous MR-guided interventions with needles require fast pulse sequences to image the needle trajectory with minimal susceptibility artifacts. Spin-echo pulse sequences are well suited for reducing artifact size; however, even with single-shot turbo spin-echo techniques, such as rapid acquisition with relaxation enhancement (RARE) or half-Fourier acquisition single-shot turbo spin-echo (HASTE), fast imaging remains challenging. In this work we present a HASTE pulse sequence that is combined with inner-volume excitation to reduce the scan time and limit the imaging field of view (FOV) to a small strip close to the needle trajectory (targeted-HASTE). To compensate for signal saturation from fast repeated acquisitions, a magnetization restore pulse (driven equilibrium Fourier transform (DEFT)) is used. The sequence is combined with dedicated active marker coils to measure the position and orientation of the needle so that the targeted-HASTE image slice is automatically repositioned. In an animal experiment the coils were attached to an MR-compatible robotic assistance system for MR-guided interventions. Needle insertion and infusion via the needle could be visualized with a temporal resolution of 1 s, and the needle tip could be localized even in the presence of a stainless steel mandrel.

[Necessity for blood transfusion in head and neck surgery]. / Notwendigkeit der Bluttransfusion bei ausgewählten Operationen im Kopf-Hals-Bereich.

INTRODUCTION: Sometimes, use of blood products is necessary in head and neck surgery, but blood transfusion also entails risks for the patients and causes high costs for the department. Therefore, we examined the surgical procedures in our department and analysed how often transfusion of blood was necessary and which expenses were incurred. METHODS: Of 3989 operations performed in 1989, 187 patients were found to be at an increased risk for blood loss. The costs for blood group analysis (euro 23.16), cross-testing (euro 13.91) and the transfusion itself (euro 70.35) were estimated in each patient. RESULTS: In 1998 more than 60% of the 187 patients had undergone extensive head and neck surgery for advanced squamous cell carcinoma. Only 17 patients (<15%) received nearly 45% of all units of stored blood transfused that year. In patients who had undergone skull base surgery, the probability of receiving blood was 30%. The transfusion-related costs were estimated to be euro 20,000 during the observation period. Potential savings could have been achieved in cross-testing. CONCLUSION: Preparations should be done on an individual basis. Such preparations are sometimes unnecessary even in patients undergoing surgical procedures with a high risk for blood loss.

Dust-free regions around Langmuir probes in complex plasmas under microgravity.

Dust-free regions around a Langmuir probe are studied in a complex plasma under microgravity. The dust particles settle in the presheath of the probe, where an equilibrium of the electric field force and the ion-drag force is established. The size and shape of the dust cloud are discussed with simple models. A more sophisticated presheath model is solved numerically to analyze the acting forces and the equilibrium position of the dust. The formation of distinct particle layers in the dust shell can be explained by the force gradients of the effective potential well.

Melting and heating of two-dimensional Coulomb clusters in dusty plasmas.

The heating and melting of two-dimensional dust clusters with one additional particle in the lower layer has been investigated experimentally in a gas discharge. The full dynamical properties of the system during the entire phase transition were determined in terms of the spectral power densities of the crystal modes. A two-step melting transition is identified when the gas pressure in the discharge is reduced: first, a sudden increase of the dust temperature takes place due to an instability of the lower-layer particle resulting in a hot crystalline state of the cluster, and second, the actual transition into a fluid state is observed at a decisively lower gas pressure.

Mode spectra of thermally excited two-dimensional dust Coulomb clusters.

The mode spectra of finite Coulomb clusters, confined systems of charged microspheres in a complex plasma, have been determined experimentally. The spectral power density of all possible modes has been measured for particle numbers between N=3 and N=145 under different plasma conditions. The agreement between measured and calculated mode frequencies is found to be very good. From this, the parameters of the particle interaction, like particle charge and screening strength, have been extracted quantitatively. In addition, the particle and mode temperatures have been obtained. The modes and the particles show the same temperature and the principle of equipartitition holds for these systems. Moreover, certain modes of interest have been compared among the different clusters, as there are the breathing mode and intershell rotation as well as the lowest- and highest-frequency modes. Moreover, the mode-integrated spectrum shows two broad maxima which are explained from "shearlike" or "compressionlike" modes. From this analysis, the transition from finite number to crystal-like properties is observed to occur around N=12 particles. Finally, a model to visualize the transition from normal mode oscillations to wave dispersions in a 2D lattice has been proposed.