Dental students' attitude towards anti-smoking programmes: a study in Flanders, Belgium

OBJECTIVE

The aim of the study was to assess the dental students' attitude towards tobacco cessation counselling in the dental setting and to explore the influence of knowledge, belief in effectiveness, smoking status, gender and curriculum.

MATERIAL AND METHODS

The study group consisted of all undergraduate students from the 2002-2003 classes of the Ghent University (n = 96). A validated questionnaire was administered to all students involving four different sections: demographic characteristics, attitude related to tobacco cessation programmes in the dental setting, belief in their effectiveness and knowledge concerning tobacco health effects. Statistical analysis included simple univariate nonparametric tests for evaluating differences in attitude towards tobacco cessation programmes, belief in effectiveness of tobacco cessation programmes in the dental setting and knowledge of students concerning tobacco health effects by year of graduation, smoking status and gender. Multiple logistic regression was chosen to calculate adjusted odds ratios and 95% confidence intervals.

RESULTS

Students view willingness to advise individual patients to quit using tobacco. Yet only 51.3% are willing to co-operate in anti-tobacco programmes at the community level, and the perception of students of the effectiveness of smoking cessation counselling in the dental setting is low. The variance of attitude towards tobacco cessation programmes was significantly affected by knowledge and the belief in effectiveness of tobacco cessation programmes in the dental setting. Better knowledge and belief in effectiveness of tobacco cessation counselling was associated with an increasing positive attitude towards tobacco cessation programmes expressed by an odds ratio of 3.12 (95% CI 1.00-9.67) and 1.17 (95% CI 1.00-1.37) respectively.

CONCLUSION

Belief in effectiveness and knowledge seem to influence the attitude of students towards tobacco cessation counselling.

PRACTICE IMPLICATIONS

Besides imparting knowledge, the attitude of newly graduated dentists could be improved by stressing the effectiveness of smoking cessation activities during lectures and integrated training modules in the undergraduate education.

Clinical experience with EPID dosimetry for prostate IMRT pre-treatment dose verification

The aim of this study was to demonstrate how dosimetry with an amorphous silicon electronic portal imaging device (a-Si EPID) replaced film and ionization chamber measurements for routine pre-treatment dosimetry in our clinic. Furthermore, we described how EPID dosimetry was used to solve a clinical problem. IMRT prostate plans were delivered to a homogeneous slab phantom. EPID transit images were acquired for each segment. A previously developed in-house back-projection algorithm was used to reconstruct the dose distribution in the phantom mid-plane (intersecting the isocenter). Segment dose images were summed to obtain an EPID mid-plane dose image for each field. Fields were compared using profiles and in two dimensions with the y evaluation (criteria: 3%/3 mm). To quantify results, the average gamma (gamma avg), maximum gamma (gamma max), and the percentage of points with gamma < 1(P gamma < 1) were calculated within the 20% isodose line of each field. For 10 patient plans, all fields were measured with EPID and film at gantry set to 0 degrees. The film was located in the phantom coronal mid-plane (10 cm depth), and compared with the back-projected EPID mid-plane absolute dose. EPID and film measurements agreed well for all 50 fields, with (gamma avg) =0.16, (gamma max)=1.00, and (P gamma < 1)= 100%. Based on these results, film measurements were discontinued for verification of prostate IMRT plans. For 20 patient plans, the dose distribution was re-calculated with the phantom CT scan and delivered to the phantom with the original gantry angles. The planned isocenter dose (plan(iso)) was verified with the EPID (EPID(iso)) and an ionization chamber (IC(iso)). The average ratio, (EPID(iso)/IC(iso)), was 1.00 (0.01 SD). Both measurements were systematically lower than planned, with (EPID(iso)/plan(iso)) and (IC(iso)/plan(iso))=0.99 (0.01 SD). EPID mid-plane dose images for each field were also compared with the corresponding plane derived from the three dimensional (3D) dose grid calculated with the phantom CT scan. Comparisons of 100 fields yielded (gamma avg)=0.39, gamma max=2.52, and (P gamma < 1)=98.7%. Seven plans revealed under-dosage in individual fields ranging from 5% to 16%, occurring at small regions of overlapping segments or along the junction of abutting segments (tongue-and-groove side). Test fields were designed to simulate errors and gave similar results. The agreement was improved after adjusting an incorrectly set tongue-and-groove width parameter in the treatment planning system (TPS), reducing (gamma max) from 2.19 to 0.80 for the test field. Mid-plane dose distributions determined with the EPID were consistent with film measurements in a slab phantom for all IMRT fields. Isocenter doses of the total plan measured with an EPID and an ionization chamber also agreed. The EPID can therefore replace these dosimetry devices for field-by-field and isocenter IMRT pre-treatment verification. Systematic errors were detected using EPID dosimetry, resulting in the adjustment of a TPS parameter and alteration of two clinical patient plans. One set of EPID measurements (i.e., one open and transit image acquired for each segment of the plan) is sufficient to check each IMRT plan field-by-field and at the isocenter, making it a useful, efficient, and accurate dosimetric tool.

Comparison of ghosting effects for three commercial a-Si EPIDs

Many studies have reported dosimetric characteristics of amorphous silicon electronic portal imaging devices (EPIDs). Some studies ascribed a non-linear signal to gain ghosting and image lag. Other reports, however, state the effect is negligible. This study compares the signal-to-monitor unit (MU) ratio for three different brands of EPID systems. The signal was measured for a wide range of monitor units (5-1000), dose-rates, and beam energies. All EPIDs exhibited a relative under-response for beams of few MUs; giving 4 to 10% lower signal-to-MU ratios relative to that of 1000 MUs. This under-response is consistent with ghosting effects due to charge trapping.