Radiofrequency tissue ablation: increased lesion diameter with a perfusion electrode

RATIONALE AND OBJECTIVES: We sought to induce large zones of coagulation necrosis using radiofrequency (RF) with perfusion electrodes and to define optimal parameters for this system. METHODS: We developed RF electrodes with internal cannulas to enable tip perfusion. Lesions were created with monopolar RF in ex vivo and in vivo liver and muscle tissue with and without perfusion of the electrode tip using 0 degree C saline. In separate experiments, wattage, current, procedure duration, tip exposure, and perfused tip temperatures were studied. RESULTS: In ex vivo liver tissue, a maximum lesion diameter of 3.1 cm without charring occurred with perfusion at 12 min and 50 W. In in vivo liver tissue with perfusion (tip temperature = 25-35 degrees C) and a 3-cm tip exposure, 80 W were deposited in muscle tissue and 65 W in liver tissue for 12 min without inducing charring. Lesion diameters were 4.5 cm and 2.4 cm, respectively. By comparison, without perfusion a maximum of 20 W could be deposited into either tissue type, resulting in 1.8-cm muscle lesions and 1.2-cm liver lesions. Tip temperatures between 45 degrees C and 55 degrees C resulted in charring. Smaller but predictable lesion diameters were created with a lower power, a shorter tip exposure, or both. Of all the parameters, diameter correlated best with the current applied. CONCLUSION: Perfusion of RF electrodes with chilled saline allows for increased power deposition without tissue charring, increasing the volume of coagulation necrosis created with a single electrode insertion. Perfusion electrodes therefore might decrease the number of probe insertions required for percutaneous tumor ablation therapy or allow for the treatment of larger lesions.     

Primers for the nef gene in the diagnosis of HIV infection using the polymerase chain reaction

The incidence of chronic alcoholism among the non-medical staff of a hospital was evaluated in an occupational health service context. Three criteria were sought routinely: suspicion by history of excessive alcohol intake, typical findings by physical examination, and suggestive behavioural changes reported by work colleagues. Gamma glutamyl transpeptidase levels and mean corpuscular volume were measured when one of these three criteria existed. The diagnosis of chronic alcoholism was made when two criteria were found or when only one criterion existed but accompanied by laboratory abnormalities. The incidence of chronic alcoholism was 6.2 per cent among male staff and 0.6 among female staff. It appeared to be less than in the population as a whole. The selective and non-systematic use of laboratory investigations and the frequent absence of indication to the occupational health physician of behavioural problems were sources of bias which probably contributed to underestimation of the incidence of chronic alcoholism among employees of the Orleans Regional Hospital Group. Provision of information to all staff is essential in order to explain the behavioural changes associated with chronic alcoholism and the usefulness of reporting employees showing evidence of such changes to the occupational physician. This enables medico-social diagnosis and the early care of those with early chronic alcohol abuse.