Comparability of portable nanoparticle exposure monitors.

Five different portable instrument types to monitor exposure to nanoparticles were subject to an intensive intercomparison measurement campaign. Four of them were based on electrical diffusion charging to determine the number concentration or lung deposited surface area (LDSA) concentration of airborne particles. Three out of these four also determined the mean particle size. The fifth instrument type was a handheld condensation particle counter (CPC). The instruments were challenged with three different log-normally distributed test aerosols with modal diameters between 30 and 180 nm, varying in particle concentration and morphology. The CPCs showed the highest comparability with deviations on the order of only ±5%, independent of the particle sizes, but with a strictly limited upper number concentration. The diffusion charger-based instruments showed comparability on the order of ±30% for number concentration, LDSA concentration, and mean particle size, when the specified particle size range of the instruments matched the size range of the aerosol particles, whereas significant deviations were found when a large amount of particles exceeded the upper or lower detection limit. In one case the reported number concentration was even increased by a factor of 6.9 when the modal diameter of the test aerosol exceeded the specified upper limit of the instrument. A general dependence of the measurement accuracy of all devices on particle morphology was not detected.

[Presentation of a 3D conformal radiotherapy technique for head-and-neck tumors resulting in substantial protection of the parotid glands]. / Etablierung einer 3D-Konformationstechnik zur Radio therapie von Kopf-Hals-Tumoren unter Berücksichtigung der Parotisschonung.

PURPOSE: The aim of this study was to improve the irradiation technique for the treatment of head-and-neck tumors and, in particular, to make use of the advantages found in modern 3D planning to protect the parotid glands. PATIENTS AND METHODS: For this investigation the 3D dataset of a standard patient with oropharyngeal carcinoma of UICC stage IVA was used. In the CT scans (slice thickness 5 mm) the planning target volume (PTV), the boost volume and both parotids were delineated. Three different techniques were calculated for two different dose levels (50 Gy for PTV and 64 Gy for boost volume, using single doses of 2 Gy). For technique 1 (T1) a parallel opposed field photon/electron irradiation was designed, for technique 2 (T2) an opposed/arc field irradiation was employed, and for technique 3 (T3) a combination of a static coplanar and arc field irradiation was designed. The sum doses D(min), D(max) and D(mean) for PTV, boost volume, and ipsilateral and contralateral parotid gland were evaluated, and the time needed for calculation of the plans was also determined. RESULTS: For all techniques used, the calculated doses in the PTV (D(min) 5.6 +/- 0.1 Gy, D(max) 73.7 +/- 0.1 Gy, and D(mean) 57.9 +/- 0.5 Gy) and in the boost volume (D(min) 46.9 +/- 1.5 Gy, D(max) 73.8 +/- 0.12 Gy, and D(mean) 65.8 +/- 0.9 Gy) were equal. Significant differences were found regarding the three different techniques, e.g., for the ipsilateral parotid gland D(min) (T1 = 47.4, T2 = 50.6, and T3 = 38.4 Gy) as well as for the contralateral parotid gland D(min) (T1 = 42.1, T2 = 44.2, and T3 = 17.8 Gy) and D(mean) (T1 = 51.3, T2 = 52.8, and T3 = 32.6 Gy). Regarding the three different techniques, significant differences were found in favor of T3. The determined planning times were as follows: T1 = 90, T2 = 60, and T3 = 90 min. CONCLUSION: The combination of static coplanar and arc field technique (T3) resulted in a substantially better protection as compared to both other techniques. This was especially the case with regard to the contralateral parotid gland, when the dose distributions were calculated equally for PTV and boost volume. In this study, the D(mean) dose of the contralateral parotid gland was lower than the TD(50) of 37 Gy (95% confidence interval 32-43 Gy) previously assumed by the authors. Therefore, it can be concluded that in the present study a more intensive protection of this gland and a reduction in xerostomia were possibly obtained.