Measurement of tumor oxygenation: a comparison between polarographic needle electrodes and a time-resolved luminescence-based optical sensor.

A novel oxygen sensor which does not rely on electrochemical reduction has been used to measure the oxygenation of the murine sarcoma F in a comparative study with an existing polarographic electrode that is available commercially. The prototype luminescence sensor yielded an oxygen distribution comparable with readings made using a pO2 histograph. The percentage of regions detected that had a pO2 less than 5 mm Hg was 79 and 75 using the Eppendorf pO2 histograph and the luminescence fiber optic sensor, respectively. These values were compatible with a measured radiobiologically hypoxic fraction of 67% in this tumor. The polarographic method detected more regions with a pO2 of 2.5 mm Hg or less (69%) compared with the optical sensor (50%) (P < 0.05). This could reflect differences in the oxygen use of the sensing devices. This initial assessment indicates the potential of a fiber-optic-based oxygen-monitoring system. Such a system should have several advantages including monitoring temporal oxygen changes in a given microregion and use with NMR procedures.

Measurement of oxygen tension in tumours by time-resolved fluorescence.

Tumour oxygenation is important in clinical radiotherapy because hypoxic cells are radioresistant. Knowledge of the state of tumour oxygenation would be advantageous for maximising effectiveness of treatment. A prototype fibre optic fluorosensor for measuring low (radiobiologically relevant) levels of oxygen is described. Based on oxygen quenching of the fluorescence of an excited fluorophor immobilised in a polymer at the end of an optical fibre, the sensor shows promise in overcoming some of the limitations of existing oxygen sensor systems. The prototype fibre optic sensor operates most effectively in the 0-2% oxygen range with fast response and settling times. Preliminary results from measurements in tumours are presented.

Maternal death associated with intravenous methylphenidate (Ritalin) and pentazocine (Talwin) abuse.

A case of maternal death from pulmonary hypertension secondary to pulmonary granulomatosis is presented. The granulomas are associated with a history of intravenous injection of medications (Ritalin and Talwin) intended for oral use.