Background: Inhaled therapies are used extensively in the treatment of patients with CF. With progressive impairment of lung function, aerosol deposition of inhaled drug occurs more centrally in the lung. The aim of this study was to determine whether long slow inhalations with a dosimetric nebuliser might improve penetration of drug aerosol into the peripheral lung areas. Methods: A comparison of two inhalation modes was undertaken in 5 subjects with moderately severe CF lung disease (aged 12-18 years; FEV1 63-80%) in a crossover study. The pattern of aerosol distribution was compared using a) long (6 – 8 secs) slow inhalations with the dosimetric AKITA delivery system with Pari LC Sprint nebuliser, and b) tidal breathing with a standard Pari LC Sprint nebuliser and compressor. Distribution and total aerosol dose deposited corrected for attenuation was obtained using gamma scintigraphy. Results: Slow, prolonged inhalation with the AKITA was associated with a higher proportion of the delivered dose depositing in the lungs (74.5%), when compared to tidal breathing (32.1%) with significantly less upper airway deposition with the AKITA. The mean peripheral to central deposition ratios for the 5 subjects were long slow breath 2.16 vs tidal breathing 2.13 (p=0.90). Conclusion: Given that the increased lung dose achieved with long slow inhalation is likely to contain a disproportionate amount of larger droplets that are likely to be deposited centrally, particularly in the presence of significant lung disease, the data supports the suggestion that a greater proportion of the finer droplets reach the lung periphery. Hence total and peripheral lung dose are increased by controlling the inspiratory profile.

2nd ESTRO Forum 2013 S457 deviations was related to the beam energy, i.e. larger deviations were observed for the higher beam energy.The overall treatment time calculated with superposition was 5-7 % longer in comparison to the calculation of convolution, and the coverage of PTV, in terms of 95% isodose, was better (up to 18%).Hot spots were lower for superposition plans for both low and high energies.Conclusions: Convolution algorithms are not adequate for dose calculations in the presence of and inside low density inhomogeneities, while the superposition algorithm showed better agreement for all cases.Convolution algorithm overestimates the delivered dose, which leads to the underdosage of the target volume in reality.This applies both to lower energy and even more to higher energy beams.Differences between doses calculated with superposition and convolution algorithms are primarily due to changes in electron transport in the lungs, which is not adequately taken into account by convolution algorithm.Following these findings, and recommendations from the literature all lung patients is planned with superposition algorithm.

Purpose/Objective: Verification of the calculated and delivered dose trough independent verification of treatment planning system (TPS) and in vivo dosimetry are important part of the overall radiotherapy quality assurance (QA).The verification of TPS was done according to IAEA recommendations and put an emphasis on dosimetry part of the treatment planning and delivery processes.In vivo dosimetry was implemented as quality assurance procedure for patient treatment verification.Materials and Methods: Verification of TPS was done with anthropomorphic phantom which was later also used for in vivo measurements prior to patient measurements.Set of clinical test cases suggested by the IAEA, covering a range of typical clinical radiation techniques found in 3D conformal radiotherapy treatment (3D CRT) was used both for TPS and in vivo dosimetry verification.The doses were measured with ion chamber and semiconductor diodes, and compared to doses calculated in TPS for interest points for test cases and points in build up for entrance in vivo readings.Consequently, set of breast patients were checked by in vivo during their regular treatments.For patient treatment verification, tangential half fields were used and in vivo diodes were placed off axis, under large gantry angles, with different wedge types and angles.Results: The measurements were conducted for 6 MV beam energy and advanced calculation algorithm.The differences between the measured and calculated doses for all test cases were within the tolerance level.The differences of in vivo phantom measurements and TPS calculation varied depending on the test type: 0.5% for open field case to 5.3% for enhanced dynamic wedge (EDW) test case.In vivo measurements conducted for breast patients showed difference of not more than 5% in comparison with values calculated by TPS.Conclusions: After verification of TPS calculation, dose calibration and correction factors for semiconductor diodes were checked and prediction for in vivo doses in TPS was verified.The errors of 5 % magnitude are common in clinics worldwide and clinical implementation of in vivo dosimetry in our clinic has given confidence that patients are being treated with prescribed dose.This was opportunity to systematically review the uncertainties involved in treatment planning and dose delivery processes leading to more accurate patient treatment.

The study was performed to assess the angular response of aSi1000 electronic portal imaging device and to validate portal dosimetry system for IMRT patient specific quality assurance. We used aSi1000 EPID mounted on a Varian 2300CD linac and Eclipse treatment planning system, Perspex phantom and IMatriXX 2D array. Dosimetric calibration of aSi1000 was performed and portal dose prediction algorithm was configured. Response of aSi1000 EPID to dose, dose rate, source to detector distance, field size, temperature and short term stability were studied and baseline established. For assessing spatial resolution, dynamic MLC bar pattern test was carried out and the results were compared with IMatriXX and film test results. To study the angular response of the detector, profiles and outputs were measured at gantry angle increments of 10 degrees for a 10x10 cm2 field. Flatness, symmetry and output values were compared with those for the reference 0 degree gantry angle measurements. Subsequently, for three dynamic IMRT plans (total 21 fields), portal dosimetry measurements were performed and the results were compared with the IMatriXX measurements. The aSi100 EPID response to dose linearity, dose rate, SDD, field size, temperature and short term stability were proven. The output stability of the detector was <0.5%. Flatness and symmetry were well within acceptable limits of 2% for all gantry angles. For the criteria of 3%-3 mm and 2%-2 mm, average percentage of pixels failing were 0.52 and 8.49 by portal dosimetry method for the 21 fields studied. Corresponding values through IMatriXX method were 0.43 and 4.40 respectively. Response of the aSi1000 EPID to dose, dose rate, source to detector distance, field size, temperature and short term stability were proven and detector showed consistency in output. Flatness and symmetry values for profiles did not exhibit any gantry angle dependence and so was the output. From the gamma evaluation of 21 separate fields, the portal dosimetry results were found to be consistently better than IMatriXX. The use of portal dosimetry allowed us to adapt tighter pass criteria with acceptable results for gamma analysis. In comparison to other QA methods, portal dosimetry is an easy to perform method and is less time consuming. The results justify the efficiency of portal dosimetry system over 2D array system due to its increased spatial resolution.

The amount of drug delivered from commercially available inhalation devices which reaches the lungs of preschool children is generally low. We therefore studied the efficiency of lung delivery from an optimised combination of delivery device and drug formulation based on individual patient-related factors. In six three-year-old children we compared the delivery of a radiolabelled budesonide solution with a MMD of 4.2 mm from a conventional nebuliser, with that of a radiolabelled budesonide solution with a MMD of 2.5 mm from a perforated vibrating membrane nebuliser. Lung deposition of budesonide delivered from the perforated vibrating membrane nebuliser was 36% and 38% and notably higher than from a conventional nebuliser (maximum 8%). The development of complementary combinations of delivery devices and drug formulations to meet the needs of efficient inhalation therapy in preschool children seems to be a good way of improving the efficacy of inhaled therapy in this age group.