Greater than normal prevalence of seropositivity for Helicobacter pylori among patients who have suffered myocardial infarction

BACKGROUND

There is evidence to suggest that inflammation plays a role in the development of atherosclerosis. Chronic infections may activate an inflammatory response in the walls of blood vessels.

OBJECTIVE

To investigate the possibility of there being an association between infection with Helicobacter pylori (H. pylori) and coronary heart disease.

METHODS

We examined 100 consecutive patients documented to have recently suffered acute myocardial infarction and 100 control subjects from the same geographical area for whom there was no evidence of coronary heart disease, carefully matched both for age and sex. Blood samples were tested for the presence of immunoglobulin G antibodies against H. pylori with a serological test.

RESULTS

In comparison with controls, patients were more commonly smokers (26 versus 12%/0, P < 0.05) and had more commonly been treated for hypertension (37 versus 20%, P< 0.01). There was a significant association between seropositivity for H. pylori and having previously suffered acute myocardial infarction (68 versus 53%, odds ratio 1.36 with 95% confidence interval 1.02-1.82, P=0.034). These findings remained valid in a multivariate analysis including possible confounding factors (age, sex, smoking and hypertension; odds ratio 1.35 with 95% confidence interval 1.01-1.83, P=0.046).

CONCLUSIONS

The positive association between seropositivity for H. pylori and having previously suffered acute myocardial infarction found in this study provides further support for the hypothesis that there is a causal association between chronic infection with H. pylori and the development of coronary heart disease.

MR imaging-guided biliary drainage in an open low-field system: first clinical experiences

PURPOSE

To test the feasibility of MR imaging (MRI)-guided percutaneous biliary drainages in patients using an open MR-system.

METHODS

6 patients with mechanical cholestasis underwent MRI-guided puncture and catheterization of the biliary system following intervention planning with magnetic resonance cholangiography (MRC) in an open low-field MR system. Data on the number of punctures required, success in establishing external and internal drainage, and total procedure time were compared to those of 6 patients who underwent biliary drainage with fluoroscopic guidance.

RESULTS

MRC facilitated intervention planning in all patients. Near-real-time MR imaging enabled interactive positioning of the devices. The bile ducts were punctured under MRI control in three patients in the first, in two in the second, and in one in the third attempt. MRI-guided puncture was faster than the fluoroscopic procedure. Catheterization for external drainage was successful in all patients. Passing the obstructions was not possible under MRI guidance. The procedure time for MRI-guided catheterization was longer than in the conventional technique.

CONCLUSION

MRI-guidance allows reliable placement of an external biliary drainage in an open low-field MR system.

Active MR guidance of interventional devices with target-navigation

This project incorporated a novel inductive coupling structure of three micro coils into an invasive device tip to determine both its tip position and orientation. Moreover, with the introduction of a new target-navigation technique the MR scan plane was defined automatically by the invasive device orientation and target tissue location. A time domain multiplexing technique was applied for simultaneous MR imaging and device tracking. Using these techniques, the acquired MR images always showed both the invasive device and its target tissue. Thus, roadmap images and their potential misregistration errors were avoided. A graphical user interface (GUI) was also designed to assist interventional physicians in monitoring and guiding the insertion of the interventional device. Ex vivo phantom and in vivo animal experiments were performed to test this new technique. The methods developed in this project provide a new active technique for interventional device guidance using MRI. Magn Reson Med 44:56-65, 2000.

Visualization, tracking, and navigation of instruments for magnetic resonance imaging-guided endovascular procedures

Interventional procedures using magnetic resonance imaging (MRI) guidance have increased in interest during the last few years. Central to the success and safety of MRI-guided procedures is the accurate visualization of the interventional instruments relative to the surrounding anatomy. A variety of methodologies for visualizing and automatically tracking instruments, including needles, radiofrequency and laser ablation devices, endoscopes, catheters, and guidewires have been developed and introduced to help the interventionalist to safely guide the device toward the target region. This article describes and compares characteristics of the four most commonly used localization and tracking systems used for MRI-guided interventional procedures: those based on the susceptibility artifact of the device, those that intentionally create field inhomogeneity along the device, those that rely on an optical tracking system, and active tracking systems using micro receive coils.

Structure-directed discovery of potent non-peptidic inhibitors of human urokinase that access a novel binding subsite

BACKGROUND

Human urokinase-type plasminogen activator has been implicated in the regulation and control of basement membrane and interstitial protein degradation. Because of its role in tissue remodeling, urokinase is a central player in the disease progression of cancer, making it an attractive target for design of an anticancer clinical agent: Few urokinase inhibitors have been described, which suggests that discovery of such a compound is in the early stages. Towards integrating structural data into this process, a new human urokinase crystal form amenable to structure-based drug design has been used to discover potent urokinase inhibitors.

RESULTS

On the basis of crystallographic data, 2-naphthamidine was chosen as the lead scaffold for structure-directed optimization. This co-crystal structure shows the compound binding at the primary specificity pocket of the trypsin-like protease and at a novel binding subsite that is accessible from the 8-position of 2-napthamidine. This novel subsite was characterized and used to design two compounds with very different 8-substituents that inhibit urokinase with K(i) values of 30-40 nM.

CONCLUSIONS

Utilization of a novel subsite yielded two potent urokinase inhibitors even though this site has not been widely used in inhibitor optimization with other trypsin-like proteases, such as those reported for thrombin or factor Xa. The extensive binding pockets present at the substrate-binding groove of these other proteins are blocked by unique insertion loops in urokinase, thus necessitating the utilization of additional binding subsites. Successful implementation of this strategy and characterization of the novel site provides a significant step towards the discovery of an anticancer clinical agent.

[Porcine stress syndrome and PSE meat: clinical symptoms, pathogenesis, etiology and animal rights aspects]

A review is given about the clinical symptoms, pathogenesis and aetiology of the porcine stress syndrome, furthermore aspects of animal welfare are discussed. The current breeding programmes of pig industry in Germany in many cases include animals with a mutation of the ryanodine-receptor (RYR-1)-gene--homozygous or heterozygous. This situation is the result of an intensive breeding of pigs during the last decades with the intention of increased lean carcass content and corresponding proceeds. The homozygous pigs are more stress susceptible (porcine stress syndrome) and produce meat of poor quality (PSE), which is also the case to some extend in heterozygous animals. The clinical symptoms of this muscle disease are characterised by a deficit of oxygen and a rapid glycolysis accompanied by a production of lactic acid and acidosis primarily in II B white muscle fibres. There is no doubt that a very close causal relation exists between the mutation of the RYR-1 and the porcine stress syndrome as well as the poor meat quality. The present knowledge of this disease, the genetic background, the physiology and pathophysiology of the mutation of the RYR-1 leads to the imperative conclusion to eliminate this mutated RYR-1 by selection of healthy pigs, which has been done successfully in other countries with important pig production. This conclusion is also supported by simple economic reasons because fertility, reproduction and daily weight gain are significantly reduced in stress susceptible pigs. Furthermore, it should be emphasised that regular breeding with the mutated RYR-1 is also a matter of animal welfare. The evident correlation between the mutated RYR-1 and the porcine stress syndrome, which includes degeneration of the muscle, pain and even life threatening malignant hyperthermia, can easily lead to the accusation in the public that diseased animals are used for pig meat production. Consequently, the authors would like to urge the breeding companies and the responsible authorities to discuss the problem with the intention to finish the current breeding programmes using animals with the mutated RYR-1 within a reasonable period of time.

Mobile workstation for anaesthesia and intensive-care medicine

Our mobile monitoring and treatment station, for use in anaesthesia and intensive care, allows transport of patients around the medical unit without disconnection from medical equipment, with a maximum level of safety, and low workload and costs.

[Laser-induced thermotherapy (LITT) for liver metastasis in an open 0.2T MRI]

OBJECTIVE

To test the feasibility and safety of the laser-induced thermotherapy (LITT) for liver metastases in open MR imaging system operating at 0.2 Tesla.

METHOD

Laser therapy using the Nd:YAG laser was performed on 25 patients with a total of 41 liver metastases. An open low-field MRI scanner was used for puncture, positioning of the laser applicator, and monitoring the therapy. A true FISP sequence was used to track the puncture in close to real-time. Localization diagnostics and temperature monitoring were aided by T1-weighted gradient echo sequences in the breath-holding technique. In the first follow up after 24-48 hours, a contrast-enhanced T1-weighted gradient-echo sequence was performed in an MRI scanner at 1.5T. The pre-, intra- and postinterventional volumes of the liver metastases as well as the thermolesions and the thermonecroses were determined.

RESULTS

LITT in an open MRI system was technically feasible in all patients with no clinically relevant complications. The mean volumes of the thermolesions measured during intervention in low-field MRI were lower than the volumes of the thermonecroses measured after intervention in high-field MRI.

CONCLUSION

The technique presented here of laser-induced thermotherapy for liver metastases in an open MRI system is technically feasible and safe.

[Prevalence of Chlamydia infections in breeding sows and their importance in reproductive failure]

To investigate the prevalence of chlamydial infection and their significance for reproductive disorders in sow breeding herds in Germany, blood samples of 1493 pigs were taken for a serological survey by enzyme-linked-immunosorbent-assay (ELISA). Antibodies to Chlamydiae were found in 33% of the samples, in all herds investigated responders could be detected. The rate of seropositive animals in different farms varied from 4.3% to 72.7%. The percentage of positive responders in the farms correlated positively with the occurrence of MMA-syndrome (mastitis, metritis, agalactia), return to oestrus and diseases of the piglets. Also these herds showed less weaned piglets per sow and litter. Comparison of seronegative and seropositive sows within single farms revealed also worse reproductive data for seropositive sows. A significant relationship could be found between farms with a high quota of sero-positive sows and poor hygiene status as well as poultry keeping. As a second step 124 cervical swabs and 9 aborted piglets were investigated for chlamydial antigen by capture-ELISA and polymerase chain reaction (PCR). Using the capture-ELISA for investigation only 3 probes with chlamydial antigen could be detected, however, examination by the more sensible PCR gave positive results in 50% of the probes. 20% of the PCR-positive animals were clinically healthy sows, 80% of the PCR-positive probes originated from sows with reproductive disorders. A significant relationship could be shown between PCR-positive probes and the incidence of abortion and litters with stillborn piglets and piglets with low viability. Swabs from 93 of the 124 sows were investigated as well for other bacterial pathogens of reproductive disorders. A high degree of micro-organisms of different species could be detected in 70% of the samples of sows with reproductive disorders and in 35% of the samples of clinically healthy sows. Species differentiation of the chlamydial antigen positive samples was done by southern blot hybridisation. Herewith C. psittaci could be diagnosed in all positive samples. Additionally 8 probes revealed a mixed infection with C. psittaci and C. trachomatis. The results of the present study show, that the prevalence of chlamydial infections in breeding herds is high and underline the importance of chlamydial infections for reproductive disorders. Single chlamydial infections as well as mixed infections with other pathogens must be considered.

[Practical realization of a patient-accompanying concept in anesthesia and intensive care]

Our current concept of stationary workplaces results in an interruption in patient monitoring and treatment. Because transfers are invariably associated with a reduction or interruption in the monitoring and treatment chain, an endangerment to critically-ill patients, as well as a significant increase in the mortality rates, can result.

DESIGN

In the new construction of the Cardiac Clinic, the previous concept of immobile anesthesia and intensive care workstations has been completely abandoned. The complete treatment workstation, including monitoring and fluid management, is set up on a bedside cart which accompanies the patients uninterruptedly--from anesthesia administration, to the operating room, to the ICU or recovery room, as well as during elective or emergency interventions outside the ICU. Transport times and complications from 995 transports (ASA III and IV) were analysed and compared with 880 transports with the conventional system.

RESULTS

During all intrahospital transfers with the mobile workplace, there were no complications resulting from faulty operation or accidental adjustment of the perfusors, or from disconnecting the monitoring,-, respiration-, or infusion lines. On the whole, there were fewer cases of circulatory instability during transport, since infusion treatment and medication could be administered without interruption. All hemodynamic parameters were recorded during transport, as were cardiac minute output and right- and left-atrial filling pressures. The mobile workplace system allows for the shortest possible transport and exchange times--13.5 min, as compared to 42.5 min with the conventional system. The reconnection of monitoring equipment with zeroing, adjustment of the alarm limits, as well as exchanging perfusors and infusomats before and after transport is eliminated entirely.

CONCLUSION

This mobile workplace, in which all components of the anesthesiological and intensive care workstations are integrated, guarantees the highest possible level of patient safety, since nothing has to be disconnected until the patient is transferred to a normal-care ward. In addition to the improved ergonomic design of the nurse's and doctor's workplace, substantial savings can also be made.

Magnetic resonance-guided vascular catheterization: feasibility using a passive tracking technique at 0.2 Telsa in a pig model

The objective of this study was to demonstrate in an animal model the feasibility of a passive tracking technique for catheter visualization of magnetic resonance (MR)-guided endovascular procedures. All experiments were performed in a 0.2 Tesla open MR system. Susceptibility-based catheters and guide wires were introduced into the aorta and were advanced selectively into the splenic and renal arteries under MR guidance. Based on a previously acquired contrast-enhanced magnetic resonance angiography (MRA) data set, the catheter positioning was performed by using a single-slice true fast imaging with steady state precession (FISP) sequence with a frame rate of 1.3 seconds. Contrast-enhanced MRA was performed in all animals. All catheters were advanced without complications into the aorta and were introduced into the proximal parts of the right renal and splenic arteries under MR guidance. Catheter manipulations were more difficult in the distal parts of these vessels due to the more complex anatomy. Passive catheter tracking is a valuable and technically robust alternative to active tracking methods, because it does not require additional hardware and, thus, can be implemented and used easily with any open MR imaging system. J. Magn. Reson. Imaging 1999;10:841-844.

Improved device definition in interventional magnetic resonance imaging using a rotated stripes keyhole acquisition

Keyhole acquisition techniques have been used to reduce image acquisition times primarily in contrast agent studies and via simulation in interventional MRI procedures. More recent simulations have suggested that improved definition of an interventional device [e.g., biopsy needles, radio frequency (RF) electrodes] could be achieved by rotating the keyhole pattern in k-space so that the read out direction lies perpendicular to the device orientation in real space. This study seeks to validate the earlier predictions of improved efficacy of a rotated stripes keyhole acquisition in actual in vitro and in vivo interventional MR imaging procedures. A true-FISP sequence was modified to perform central stripes keyhole (as known as conventional keyhole) acquisitions after a full initial reference data set was acquired. The gradients of this sequence were then modified to rotate the k-space definition and the keyhole stripes by 10 degrees, 20 degrees, 30 degrees, 45 degrees, and 60 degrees from their conventional k-space orientation. Acquisitions were performed during insertion of interventional devices in phantom and in vivo RF ablation procedures, using the modified sequence selected which placed the phase encoding axis at parallel and perpendicular orientations to the devices. Resulting images were compared between the two orientations for needle width and tip accuracy. Apparent needle width was thinner and tip position more accurately determined for placement of phase encoding parallel to the needle in all cases. Rotated keyhole imaging provides the required temporal advantage of conventional keyhole imaging along with a near optimal definition of an interventional device when the phase encoding is oriented parallel to the direction of the needle motion. Magn Reson Med 42:554-560, 1999.

Effects of superparamagnetic iron oxide on radio-frequency-induced temperature distribution: in vitro measurements in polyacrylamide phantoms and in vivo results in a rabbit liver model

PURPOSE

To determine whether contrast medium containing superparamagnetic iron oxide (SPIO) alters radio-frequency (RF)-related temperature distribution in acrylamide phantoms and in an in vivo model.

MATERIALS AND METHODS

In nine acrylamide phantoms with increasing SPIO content, RF was applied with simultaneous measurement of temperature profile along the probe track. Additionally, magnetic resonance imaging-guided RF ablation was performed in the liver of six rabbits after the intravenous administration of SPIO (0.05 mL per kilogram of body weight) 40 minutes prior to ablation (SPIO group) and in another six rabbits without prior SPIO administration (control group). Coagulation diameter was evaluated on the basis of postprocedural imaging and subsequent gross pathologic findings. Statistical analysis was performed with the Student t test.

RESULTS

In the phantoms, progressive increases in iron content resulted in higher temperatures along the RF electrode track (P < .05). In the in vivo model, however, SPIO at physiologic concentrations did not significantly increase the diameter of coagulation on the basis of either postprocedural imaging or subsequent gross pathologic findings. Additionally, no significant differences were seen in other RF-related parameters including impedance, voltage, current, and grounding pad temperature.

CONCLUSION

Administration of SPIO in conjunction with RF ablation of focal liver lesions is feasible and safe, but no significant difference in the extent of induced coagulation can be expected.

MR-guided percutaneous nephrostomy of the nondilated upper urinary tract in a porcine model

OBJECTIVE

The purpose of this study was to assess the safety and feasibility of MR-guided percutaneous nephrostomy of the nondilated contrast-enhanced upper urinary tract in a porcine model.

SUBJECTS AND METHODS

Six MR-guided percutaneous nephrostomies of the nondilated upper urinary tract were performed in four domestic farm pigs (body weight range, 20-25 kg) using a 0.2-T system. Ten minutes after IV administration of 0.2 mmol/kg of gadodiamide and 0.4 mg/kg of furosemide, a fast T1-weighted sequence was used to guide insertion of an 18-gauge MR-compatible needle into a predetermined calix. After confirmation of needle position using a turbo spin-echo T1-weighted sequence, a 0.035-inch catheter coated with superparamagnetic iron oxide was inserted during MR monitoring. Insertion was followed by tract dilatation and insertion of a 4-French sheath. The final position of the sheath was confirmed by injection of diluted superparamagnetic iron oxide into the collecting system.

RESULTS

Needle insertion was successful for all six procedures, with no complications. Instrumentation time ranged from 4 to 13 min (mean, 6+/-4 min). Sheath placement was successful in five of six kidneys. Placement time ranged from 6 to 28 min (mean, 16+/-9 min).

CONCLUSION

MR-guided percutaneous nephrostomy of the nondilated contrast-enhanced upper urinary tract in a porcine model is feasible and safe.

[Keyhole-true FISP: fast T2-weighted imaging for interventional MRT at 0.2 T]

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.

No risk of metal toxicity in combined spinal-epidural anesthesia

Using the single level needle-through-needle technique for combined spinal-epidural anesthesia (CSE) may introduce very fine metal particles abraded by the spinal needle from the inner ground edge of the Tuohy needle into the patient. Either the local anesthetic administered epidurally or the peridural catheter may also pass intrathecally through the hole in the dura made by the spinal needle. To examine these concerns, the needle-through-needle technique was simulated in an in vitro model (18-gauge Tuohy needle; 27- or 29-gauge Quincke needle). The presence of abraded metal particles was identified by atomic absorption spectrography (AAS). The needles were then examined under an electron microscope. Metal particles could not be identified by using AAS in the needle-through-needle technique after normal clinical use, nor could traces of use be revealed by using an electron microscope to examine the Tuohy needle. With intentionally rough handling and caudal orientation of the spinal needle tip, minimal scratches could be seen by using an electron microscope, but there were no metal particles detected by AAS. In an anatomical preparation, the possible passage of the epidural catheter anesthetic through the dural puncture hole into the cerebrospinal fluid compartment was investigated endoscopically. Neither passage of dyed epidural local anesthetic nor penetration of the epidural catheter into the cerebrospinal fluid compartment could be demonstrated by endoscopy. We conclude that the needle-through-needle-technique is an acceptable way of performing CSE anesthesia. Endangering the patient by an unintentionally intrathecal misplacement of the epidural catheter seems to be very unlikely based on our in vitro model if small spinal needles (27- or 29-gauge) are used.

IMPLICATIONS

Atomic absorption spectrography shows no contamination of the intrathecal compartment by abraded metal particles from the Tuohy needle by combined spinal-epidural anesthesia with the needle-through-needle technique. In vitro, neither passage of dyed epidural local anesthetic nor penetration of the epidural catheter into the cerebrospinal fluid compartment could be demonstrated by endoscopy.

In vitro investigation of cerebrospinal fluid leakage after dural puncture with various spinal needles

Postspinal headache is one of the most common complications of spinal anesthesia and has repeatedly led to controversy concerning needle size and configuration. In an in vitro investigation, we measured cerebrospinal fluid (CSF) leakage with Sprotte, Whitacre, Quincke, and Atraucan needles under physiological conditions in human dura. The puncture characteristics were examined under an electron microscope. The pencil-point needles show 2-3 times less leakage of CSF compared with the cutting Quincke needles of corresponding size. Between the Sprotte and the Whitacre needles, there were no significant differences. The least loss of CSF occurred with the 26-gauge Atraucan needle. Under the electron microscope, a sharply delineated, persistent perforation channel was shown with the Quincke needles, which may explain the high CSF loss. With pencil-point needles, which push the tissue apart bluntly, a large opening on the inside is found, with some tearing of the dura. However, in contrast to the cutting needles, a persistent perforation channel is not manifested. The 26-gauge Atraucan needle, which both cuts and pushes apart conically, shows a relatively discrete opening on the inside, with slight tears in the dura and arachnoidea but without a visible perforation channel. The results of our study show that larger needles (26-gauge Atraucan) that are easier to handle can lead to good and, in some cases even better, puncture results if they have characteristics of both the cutting and the pencil-point needles.

IMPLICATIONS

We compared several brands of pencil-point and standard cutting spinal needles of varying sizes. All pencil-point needles had less cerebrospinal fluid leakage, the least loss occurring with 26-gauge Atraucan needles. Electron microscopic examination of the dura after puncture showed characteristic findings with each needle type. We conclude that the combined cutting and pencil-point characteristics seen in the Atraucan needle may have clinical advantages.

[MRI-assisted bile duct drainage: evaluation of passive catheter imaging in an animal model]

PURPOSE

To investigate interactive MR-assisted bile duct drainage in pigs with the passive visualization technique using near real-time imaging.

METHODS

8 bile duct drainages were placed in an open low-field MR system (0.2 Tesla) in 4 pigs with surgically induced cholestasis. After planning the intervention with magnetic resonance cholangiography (MRC), both the puncture and catheter placement were interactively guided using a fast T2-weighted true FISP sequence.

RESULTS

MRC enabled interventional planning in all puncture attempts. Punctures were unproblematic in all attempts, the bile ducts were punctured 6 times after the first and twice after the second attempt. Placement of the passively visible catheter was successful in all animals. The applied sequence enables interactive fluoroscopy-like positioning of the devices.

CONCLUSION

The procedure introduced here enables reliable and fast placement of a bile duct drainage in an animal model using a low-field MR system.

[Dissociative stupor--differential diagnosis of coma following injury]

Two cases are described in which a dissociative stupor originating from conversion neurosis simulated a coma following a sustained trauma. At first both patients showed no response to being addressed or to pain stimuli. They presented an upward eye gaze deviation, cardiorespiratory functions were stable. Following extensive diagnostic procedures revealing no organic cause for the clinical symptoms, the diagnosis of a hysterical consciousness disorder was stated. Symptoms of conversion neuroses include lacking call response, gait disorder, seizure-like conditions and strength diminution in one or more extremities. In these cases suspicious facts are the absence of injuries (for example by falling down or tongue bite during a dissociative attack), eye gaze deviation and the phenomenon that, when the patient's arm is raised above the head and let fall, it never hits the face but glides down beside the body.

Methods for providing probe position and temperature information on MR images during interventional procedures

Interventional magnetic resonance imaging (MRI) can be defined as the use of MR images for guiding and monitoring interventional procedures (e.g., biopsy, drainage) or minimally invasive therapy (e.g., thermal ablation). This work describes the development of a prototype graphical user interface and the appropriate software methods to accurately overlay a representation of a rigid interventional device [e.g., biopsy needle, radio-frequency (RF) probe] onto an MR image given only the probe's spatial position and orientation as determined from a three-dimensional (3-D) localizer used for interactive scan plane definition. This permits 1) "virtual tip tracking," where the probe tip location is displayed on the image without the use of separate receiver coils or a "road map" image data set, and, 2) "extending" the probe to predict its path if it were directly moved forward toward the target tissue. Further, this paper describes the design and implementation of a method to facilitate the monitoring of thermal ablation procedures by displaying and overlaying temperature maps from temperature sensitive MR acquisitions. These methods provide rapid graphical updates of probe position and temperature changes to aid the physician during the actual interventional MRI procedures without altering the usual operation of the MR imager.

Dynamic tracking in interventional MRI using wavelet-encoded gradient-echo sequences

This work describes a newly developed magnetic resonance imaging (MRI) data-acquisition strategy which replaces the standard Fourier phase-encoding with the spatially localized coefficients of wavelet-encoding and offers a new technique for image guidance when combined with a dynamic tracking algorithm. By using this new technique, only a specific fraction of the entire raw data set needs to be updated and reconstructed to visualize the movement of an interventional device during an MR guided procedure. The combination of wavelet-encoding and a dynamic tracking algorithm was implemented in two-dimensional and three-dimensional gradient-echo sequences on a 0.2-T open C-arm-shaped MR system (Siemens, Erlangen Germany) and tested in phantom and in vitro experiments. When applying the wavelet-encoding direction parallel to the movement of a straight interventional device, only those spatially localized wavelet-coefficients mainly affected by the interventional device are updated. This led to potential increases of the image frame rate by a factor of up to seven.

Intrathecal local anesthetic distribution with the new spinocath catheter

BACKGROUND AND OBJECTIVES

Microcatheters have been linked in some cases to the development of cauda equina syndrome, which may be further traced to the maldistribution of the local anesthetic. A long injection time via the microcatheters contributes to the inadequate mixing. With the new Spinocath catheter, considerably shorter injection times can be achieved due to larger internal size. This study examined whether this leads to more homogeneous intrathecal distribution without causing greater trauma to the dura.

METHODS

In an in vitro model of the spinal canal, the distribution of hyperbaric and isobaric 0.5% bupivacaine (2.5 mL) as well as 5% lidocaine (2.5 mL) was examined after injection via the 28-gauge CoSpan catheter (Kendall, Healthcare, Mansfield, MA), the 22-gauge Spinocath catheter (Braun, Melsungen, Germany), and a 29-gauge Quincke needle (Becton Dickinson, Rutherford, NJ). The local anesthetic concentration in the vertebral interspaces T12-L1 to L5-S1 was measured via gas chromatography 3 and 10 minutes after injection. In addition, the morphologic puncture characteristics of human dura were examined with the halftone electron microscope, after puncture with the catheters and needle.

RESULTS

After injection through the 28-gauge CoSpan catheter, caudal segments of the spinal canal showed peak concentrations up to a maximum of 1,147 microg/mL bupivacaine or 8.5 mg/mL lidocaine with hyperbaric solutions, which did not decrease over the 10 minutes of measurement. After injection through the Spinocath catheter, there was a homogeneous distribution with data peaks of approximately 350 microg/mL bupivacaine or 4.2 mg/mL lidocaine similar to the data found after injection through the spinal needle.

CONCLUSIONS

The new Spinocath catheter allows a better mixing of the local anesthetic with the cerebrospinal fluid. Because of significantly shortened injection times, hyperbaric solutions also show a more homogeneous distribution. Although the Spinocath catheter has a larger inner diameter than the other microcatheters, it appeared to cause less trauma to the dura.

Intrathoracic and pulmonary blood volume during CO2-pneumoperitoneum in humans

BACKGROUND

Induction of CO2-pneumoperitoneum may have significant effects on systemic and pulmonary haemodynamics. We hypothesized that intrathoracic (ITBV) and pulmonary blood volume (PBV) are affected during intra-abdominal CO2-insufflation, which may be pronounced by positional changes of the patient.

METHODS

Sixteen anaesthetized patients were studied before, during and after CO2-pneumoperitoneum for laparoscopic cholecystectomy. A dye indicator technique was used to assess ITBV and PBV. In addition, gas exchange and haemodynamics were recorded.

RESULTS

In the supine position, induction of CO2-pneumoperitoneum had no effects on ITBV, PBV and cardiac output. Mean systemic arterial pressure increased from 10.9 +/- 1.5 kPa (82 +/- 11 mmHg) to 12.7 +/- 1.5 kPa (95 +/- 11 mmHg, P < 0.01). In the reverse Trendelenburg position ITBV decreased from 19.8 +/- 5.1 ml.kg-1 to 16.7 +/- 3.7 ml.kg-1 (P < 0.05) during CO2-insufflation, but increased to control values after 20 min. PBV decreased from 4.2 +/- 1.2 ml.kg-1 to 3.4 +/- 1.1 ml.kg (P < 0.05) and remained decreased during CO2-pneumoperitoneum. Calculated venous admixture was unchanged throughout the study. Deflation of CO2-pneumoperitoneum increased ITBV (22.4 +/- 5.2 ml.kg-1, P < 0.05) and cardiac output above control values.

CONCLUSIONS

In anaesthetized-paralyzed patients in the reverse Trendelenburg position intra-abdominal CO2-insufflation is associated with significant alterations of ITBV and PBV. The release of CO2-pneumoperitoneum is associated with a re-distribution of blood into the thorax.