Dosimetric characterisation of the optically-stimulated luminescence dosimeter in cobalt-60 high dose rate brachytherapy system.

This study investigates the characteristics and application of the optically-stimulated luminescence dosimeter (OSLD) in cobalt-60 high dose rate (HDR) brachytherapy, and compares the results with the dosage produced by the treatment planning system (TPS). The OSLD characteristics comprised linearity, reproducibility, angular dependence, depth dependence, signal depletion, bleaching rate and cumulative dose measurement. A phantom verification exercise was also conducted using the Farmer ionisation chamber and in vivo diodes. The OSLD signal indicated a supralinear response (R2 = 0.9998). It exhibited a depth-independent trend after a steep dose gradient region. The signal depletion per readout was negligible (0.02%), with expected deviation for angular dependence due to off-axis sensitive volume, ranging from 1 to 16%. The residual signal of the OSLDs after 1 day bleached was within 1.5%. The accumulated and bleached OSLD signals had a standard deviation of ± 0.78 and ± 0.18 Gy, respectively. The TPS was found to underestimate the measured doses with deviations of 5% in OSLD, 17% in the Farmer ionisation chamber, and 7 and 8% for bladder and rectal diode probes. Discrepancies can be due to the positional uncertainty in the high-dose gradient. This demonstrates a slight displacement of the organ at risk near the steep dose gradient region will result in a large dose uncertainty. This justifies the importance of in vivo measurements in cobalt-60 HDR brachytherapy.

[Intervention on smoking in adolescents in Sousse, Tunisia]. / Etude d'intervention sur le tabagisme chez les adolescents dans la région de Sousse, Tunisie.

PURPOSE: To increase knowledge about smoking via a school prevention programme. PATIENTS AND METHODS: This quasi-experimental study included two groups: a control and an intervention group with a pre- and a post-evaluation of knowledge about smoking in each group. The target population consisted of students of 12 to 16 years old in Sousse, Tunisia. To evaluate the intervention, stratified and proportional sampling was used to include 2100 students in the questionnaire. All the students in the intervention group received a standardized program of information about smoking. A pre-tested and self-managed questionnaire in Arabic was used to assess knowledge about smoking, attitudes and behavioural intent before and after the intervention. RESULTS: The intervention group's post-test knowledge and behavioural intent were significantly higher than that of the control group's. No significant differences were found in post-test attitudes between the control and the intervention groups. CONCLUSION: The authors carried out this survey to evaluate the difficulties and resources in order to institute a more complete and durable program.