Prototype of an online navigation system for laparoscopic radiofrequency ablation.

BACKGROUND/AIMS: Laparoscopic Radiofrequency-ablation is a safe and effective method for tumor destruction in patients with unresectable liver tumors. However, accurate probe placement using laparoscopic ultrasound guidance is required to achieve complete tumor ablation. After development and evaluation of laparoscopic navigation tools for radiofrequency ablation, we are now presenting a prototype of a navigation- and documentation-system for laparoscopic RFA. METHODOLOGY: An image-guided surgery system for laparoscopic liver treatments (LapAssistent) based on a 3D-navigation scene was developed. A laparoscopic ultrasound probe and a RFA needle could be navigated using an electromagnetic tracking system. The system was studied using a perfused tumour-mimic-model of a porcine liver. RESULTS: The study showed that laparoscopic ultrasound-guided navigation is technically feasible. The system enables the surgeon to intraoperatively update the three-dimensional planning data in case of new findings. The RFA needle could be placed accurately in a targeted tumour with a targeting error ranging from 5 - 7 mm, even out of the ultrasound plane. In case of multiple tumours lying in close spatial relationship, the documentation module helps to keep track of the already ablated tumours and those that still need to be treated. DISCUSSION: Laparoscopic radiofrequency ablation requires advanced laparoscopic ultrasound skills for accurate placement of the RFA probe. The system adds benefit to laparoscopic RFA enabling the surgeon to place the needle accurately inside the targeted tumours using the navigation scene. The possibility to update the three-dimensional model with new intraoperative findings enables the surgeon to adapt to a new intraoperative situation.

Prototype of an intraoperative navigation and documentation system for laparoscopic radiofrequency ablation: first experiences.

AIMS: Laparoscopic radiofrequency ablation (RFA) is an accepted approach to treat unresectable liver tumours, distinguishing itself from other techniques by combining minimal invasiveness and the advantages of a surgical approach. The major task of laparoscopic RFA is the accurate needle placement according to preoperative planning to achieve complete tumour ablation. This study investigates the value of an image-guided surgery system to accomplish this task. METHODS: An image-guided surgery system for laparoscopic liver treatments (LapAssistent) based on a 3D-navigation scene was developed. A laparoscopic ultrasound probe and a RFA needle could be navigated using an electromagnetic tracking system. The system was studied using a perfused tumour-mimic-model of a porcine liver. Navigating the RFA needle, the tumours were ablated. RESULTS: The system enables the surgeon to intraoperatively update the three-dimensional planning data in case of new findings. The RFA needle could be placed accurately in a targeted tumour, even out of the ultrasound plane. In case of multiple tumours lying in close spatial relationship, the documentation module helps to keep track of the already ablated tumours and those that still need to be treated. CONCLUSION: The system adds benefit to laparoscopic RFA enabling the surgeon to place the needle accurately inside the targeted tumours using the navigation scene. A manual alignment of the preoperative data to the physical space produces a feasible result for a restricted region. A precise measurement of the accuracy of this process has to be done. The possibility to update the three-dimensional model with new intraoperative findings enables the surgeon to adapt to a new intraoperative situation. Furthermore the possibility to mark ablated tumours helps to keep track of the operation plan.

Remote electronic blood release system.

BACKGROUND: The Hunter Area Pathology Service provides transfusion services to 4 metropolitan and 11 rural hospitals in Australia. To improve blood availability, conserve blood stocks, and reduce crossmatch-to-transfusion ratios, a networked electronic blood release system (EBRS) has been developed for computer cross-matching within the laboratory and at sites remote from the transfusion laboratory. It is innovative, in that non-laboratory staffs have been trained to release computer-matched blood at remote hospitals without transfusion laboratories. STUDY DESIGN AND METHODS: The EBRS software was tested and validated according to the Australian software standards AS 3563.1 and 3563.2 (1991). Over 7000 units were released by the EBRS in a laboratory trial conducted in conjunction with the conventional immediate-spin crossmatch. A further, 12-month study was conducted within the laboratory before the staged implementation of the EBRS at the remote hospitals. RESULTS: The EBRS has resulted in 1) a 25-percent reduction in the number of units requested by the medical staff, resulting from the reduction in time needed to provide compatible blood due to the elimination of the serologic crossmatch; 2) better blood stock management (reducing outdated red cell units by 30%); and 3) significant savings in laboratory workload (savings of approximately 100 hours/month). In addition, the rapid availability of computer-crossmatched red cells in emergency situations has enhanced patient safety. CONCLUSION: The EBRS is a safe and efficient means of providing red cells within the laboratory and at remote hospitals without laboratory services.

The identification of polyoxyethylene glycols and related compounds by capillary gas chromatography.

A sample work-up method for gas chromatographic profiling of polyoxyethylene glycol (PEG)-related compounds in pharmaceutical matrices is described. After a short sample clean-up, carbon-oxygen linkages are partially cleaved with 0.07 M boron tribromide in dichloromethane at room temperature. The reaction is stopped after 1 min by addition of 0.01 M HCl. The products are trimethylsilylated and injected onto a WCOT 50 m x 0.25 mm CP-SIL 5 CB fused silica column. Eleven model compounds, representing four common types of PEG-derivatives, have been evaluated by this method. The results show that characteristic profiles can be obtained from PEG-derivatives carrying different functional groups. Minimum detectable amounts are in the range of 200 micrograms.

Thoracic outlet syndrome: a review of 67 cases.

From January 1948 to December 1977, 67 patients were admitted to the Victoria General Hospital in Halifax, Nova Scotia, with a diagnosis of thoracic outlet syndrome. Of these, 18 patients were treated conservatively; in the remaining 49 patients who underwent operation 54 operative procedures were performed. Three surgical approaches were used: posterior thoracoplasty (11 procedures), supraclavicular (18 procedures) and transaxillary (25 procedures). Long-term clinical improvement was documented in 6 patients who underwent posterior thoracoplasty, 9 patients in whom a supraclavicular approach was used and in all 21 patients in whom the approach was transaxillary.

A clinical study on the prolonged antihypertensive effect of clonidine in a sustained-release capsule formulation.

Eight patients with essential hypertension each received a single oral dose of 1 capsule of a sustained-release formulation of 0.25 mg clonidine in the morning for 3 consecutive days. Pulse ratio and blood pressure were measured in the standing and supine positions at specific intervals. After the first day of treatment, a significant decrease in blood pressure lasting 24 hours was recorded for the standing position. In the supine position, there was a progressive decrease in blood pressure which also attained significance on the third day of treatment. There was a progressive and significant reduction in mean arterial pressure from the first to the third day.