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• ViTAT mimics the dose distribution of tangential fields (TF) plans. • Using 20° sectors of four arcs is needed to mimic the delivery of TF. • Better PTV homogeneity and lower dose to contralateral OARs are obtained. • Mean dose to ipsilateral OARs are unchanged; body integral dose reduced. • ViTAT may translate KB-models based on TF data into efficient automatic planning. To test the performances of a volumetric arc technique named ViTAT (Virtual Tangential-fields Arc Therapy) mimicking tangential field irradiation for whole breast radiotherapy. ViTAT plans consisted in 4 arcs whose starting/ending position were established based on gantry angle distribution of clinical plans for right and left-breast. The arcs were completely blocked excluding the first and last 20°. Different virtual bolus densities and thicknesses were preliminarily evaluated to obtain the best plan performances. For 40 patients with tumor laterality equally divided between right and left sides, ViTAT plans were optimized considering the clinical DVHs for OARs (resulting from tangential field manual planning) to constrain them: ViTAT plans were compared with the clinical tangential-fields in terms of DVH parameters for both PTV and OARs. Distal angle values were suggested in the ranges [220°,240°] for the right-breast and [115°,135°] for the left-breast cases; medial angles were [60°,40°] for the right side and [295°,315°] for the left side, limiting the risk of collision. The optimal virtual bolus had −500 HU density and 1.5 cm thickness. ViTAT plans generated dose distributions very similar to the tangential-field plans, with significantly improved PTV homogeneity. The mean doses of ipsilateral OARs were comparable between the two techniques with minor increase of the low-dose spread in the range 2–15 Gy (few % volume); contralateral OARs were slightly better spared with ViTAT. ViTAT dose distributions were similar to tangential-fields. ViTAT should allow automatic plan optimization by developing knowledge-based DVH prediction models of patients treated with tangential-fields. [ABSTRACT FROM AUTHOR]

This study describes a comparative analysis of treatment plans in 48 patients with prostate cancer treated with ionizing radiation. Each patient was subjected to the intensity-modulated radiation therapy (IMRT) and arc technique. In each treatment plan, the organs at risk were assessed: the urinary bladder, rectum and heads of the femur, as well as the volume of normal tissue. The following features were compared: treatment time, conformity indices for the planning target volume, mean doses and standard deviation in organs at risk, and organ volumes for each particular dose. The treatment period in the arc technique is 13.7% shorter than in the IMRT technique. Comparing the results of the IMRT and arc techniques (arc vs. IMRT), the mean values were 29.21 ± 12.91 Gy versus 28.36 ± 13.79 Gy for the bladder, 20.36 ± 3.16 Gy versus 18.17 ± 5.11 Gy for the right femoral head, and 18.98 ± 3.28 Gy versus 16.67 ± 5.15 Gy for the left femoral head. For the rectum, lower values were obtained after application of the arc technique, not the IMRT technique: 35.84 ± 12.28 Gy versus 35.90 ± 13.05 Gy. The results indicate that the applied therapy has a statistically significant influence on the volume for a particular dose with regard to the urinary bladder. It is advisable to apply the IMRT technique to patients who need the femur heads and urinary bladder protected by exposing them to low irradiation doses.

This study describes a comparative analysis of treatment plans in 48 patients with prostate cancer treated with ionizing radiation. Each patient was subjected to the intensity-modulated radiation therapy (IMRT) and arc technique. In each treatment plan, the organs at risk were assessed: the urinary bladder, rectum and heads of the femur, as well as the volume of normal tissue. The following features were compared: treatment time, conformity indices for the planning target volume, mean doses and standard deviation in organs at risk, and organ volumes for each particular dose. The treatment period in the arc technique is 13.7% shorter than in the IMRT technique. Comparing the results of the IMRT and arc techniques (arc vs. IMRT), the mean values were 29.21 ± 12.91 Gy versus 28.36 ± 13.79 Gy for the bladder, 20.36 ± 3.16 Gy versus 18.17 ± 5.11 Gy for the right femoral head, and 18.98 ± 3.28 Gy versus 16.67 ± 5.15 Gy for the left femoral head. For the rectum, lower values were obtained after application of the arc technique, not the IMRT technique: 35.84 ± 12.28 Gy versus 35.90 ± 13.05 Gy. The results indicate that the applied therapy has a statistically significant influence on the volume for a particular dose with regard to the urinary bladder. It is advisable to apply the IMRT technique to patients who need the femur heads and urinary bladder protected by exposing them to low irradiation doses. [ABSTRACT FROM AUTHOR]

Abstract: Aim: The aim of the study was to estimate the dose at the reference point applying an aSi-EPID device in the course of patient treatment. Materials and methods: The method assumes direct proportionality between EPID signal and dose delivered to the patient reference point during the treatment session. The procedure consists of treatment plan calculation for the actual patient in the arc technique. The plan was realized with an elliptic water-equivalent phantom. An ionization chamber inside the phantom measured the dose delivered to the reference point. Simultaneously, the EPID matrix measured the CU distribution. EPID signal was also registered during patient irradiation with the same treatment plan. The formula for in vivo dose calculation was based on the CU(g) function, EPID signal registered during therapy and the relation between the dose and EPID signal level measured for the phantom. In vivo dose was compared with dose planned with the treatment planning system. Irradiation was performed with a Clinac accelerator by Varian Medical Systems in the RapidArc technique. The Clinac was equipped with an EPID matrix (electronic portal image device) of aSi-1000. Treatment plans were calculated with the Eclipse/Helios system. The phantom was a Scanditronix/Wellhöfer Slab phantom, and the ionization chamber was a 0.6ccm PTW chamber. Results: In vivo dose calculations were performed for five patients. Planned dose at the reference point was 2Gy for each treatment plan. Mean in vivo dose was in the range of 1.96–2.09. Conclusions: Our method was shown to be appropriate for in vivo dose evaluation in the RapidArc technique. [Copyright &y& Elsevier]

Abstract: Nanoparticles were prepared with a consumable-electrode direct current arc (CDCA) technique. The results showed that the calorimetric melting onset temperature of the nanoparticles of SnAgCu solder alloy could be as low as 179°C, equivalent to that of the traditionally used SnPb eutectic alloy (183°C). Moreover, the homogenous melting model (HMM) and Gibbs–Thomson equation were employed to theoretically estimate the size-dependent melting temperature of the as-prepared nanoparticles. The structure and morphology of the nanoparticles were analyzed with a high-resolution transmission electron microscopy (HRTEM). The CDCA technique showed promising prospect in manufacturing large amounts of nanoparticles with controlled shape, small size, narrow particle size distribution and nearly oxide-free composition. This undoubtedly puts forward a novel feasible approach to manufacture high quality lead-free solders for electronic products. [Copyright &y& Elsevier]