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The Dosepix detector is a hybrid photon-counting pixel detector based on ideas of the Medipix and Timepix detector family. 1 mm thick cadmium telluride and 300 µm thick silicon were used as sensor material. The pixel matrix of the Dosepix consists of 16 x 16 square pixels with 12 rows of (200 µm) 2 and 4 rows of (55 µm) 2 sensitive area for the silicon sensor layer and 16 rows of pixels with 220 µm pixel pitch for CdTe. Besides digital energy integration and photoncounting mode, a novel concept of energy binning is included in the pixel electronics, allowing energy-resolved measurements in 16 energy bins within one acquisition.The possibilities of this detector concept range from applications in personal dosimetry and energy-resolved imaging to quality assurance of medical X-ray sources by analysis of the emitted

Purpose:To study the suitability of a novel 1D silicon monolithic array for dosimetry of small radiation fields and for QA of high dose gradient treatment modalities (IMRT and SBRT).Methods:A 1D array composed of 4 monolithic silicon modules of 64 mm length and 1 mm pixel pitch was developed by IBA Dosimetry. Measurements were carried out for 6MV and 15MV photons on two commercial different linacs (TrueBeam and Clinac iX, Varian Medical Systems, Palo Alto, CA) and for a CyberKnife G4 (Accuray Inc., Sunnyvale, CA). The 1D array was used to measure output factors (OF), profiles and off axis correction factors (OACF) for the Iris CyberKnife variable collimator (5–60 mm). In addition, dose profiles (at the isocenter plane) were measured for multiple IMRT and SBRT treatment plans and compared with those obtained using EDR2radiographic film (Carestream Health, Rochester NY), a commercial 2D diode array and with the dose distribution calculated using a commercial TPS (Eclipse, Varian Medical Systems, Palo Alto, CA).Results:Due to the small pixel pitch of the detector, IMRT and SBRT plan profiles deviate from film measurements by less than 2%. Similarly, the 1D array exhibits better performance than the 2D diode array due to the larger (7 mm) pitch of that device. Iris collimator OFs measured using the 1D silicon array are in good agreement with the commissioning values obtained using a commercial stereotactic diode as well as with published data. Maximum deviations are < 3% for the smallest field (5 and 7.5mm) and below 1% for all other dimensions.Conclusion:We have demonstrated good performances of the array for commissioning of small photon fields and in patient QA, compared with diodes and film typically used in these clinical applications. The technology compares favorably with existing commercial solutionsThe presenting author is founded by a Marie Curie Early Initial Training Network Fellowship of the European Communitys Seventh Framework Programme under contract number (PITN‐GA‐2011‐289198‐ARDENT).The research activity is hosted by IBA Dosimetry, Gmbh.

Purpose: To test and to explore the application of a software tool developed for on‐line real‐time treatment verification for 4D/gated radiation delivery using megavoltage fluoroscopy (MVF) acquired with treatment beams. Method and Materials: MVF images were acquired with a flat panel detector installed on a Siemens Linac using 6MV photon beams for phantoms with moving structures and for thoracic cancer patients. A previously developed software, RTReg4D, was used to register acquired MVF with digitally reconstructed radiographs (DRRs) from 4DCT. The MVF frame grabber can be synchronized with the gating signal from Anzai gating device to capture target motion in selected gating window. The isocenter and target contours were transferred from a planning system into RTReg4D and were overlaid on the MVF images, verifying whether the target with residual motion is adequately covered during the gated delivery. Appropriate actions can be initiated should the verification fail. Results: The software tool can effectively and accurately register MVF images with DRRs. The MVF images acquired with a dose as low as 1 cGy were adequate for the registration. In addition, the registration can be performed between the averaged MVF frame of all frames acquired within gating window and the corresponding DRR, further reducing dose required. The accuracy of registration can be better than 3 mm. The entire process is fast. Conclusion: MVF achieves adequate image quality at a low dose. It is practically feasible to use the software tool with MVF for real‐time (prior or during) treatment verification of 4D/gated radiation delivery. Conflict of Interest: This work is sponsored in part by Siemens OCS.

Purpose: To develop a system for on‐line real‐time treatment verification for 4D‐ART using in‐line kV fluoroscopy that will be included in a new generation of accelerator. Method and Materials: We have developed a software tool, as a component of the 4D‐ART verification system, to register fluoroscopic with dynamic (time‐sequenced) DRR (DDRR) images. The fluoroscopic images are obtained using kV x‐rays in‐line with the treatment‐beam direction. The DDRR images (DRRs at different phases during respiratory cycle) are generated from 4DCT. The image registration of DDRR and fluoroscopy is based on pre‐defined structures or points of interest and needs to be performed on‐line in real time, allowing the treatment parameters to be modified in real time if a discrepancy is observed. To approve the principle, we have employed a simulator (Siemens/Mevasim) to acquire the fluoroscopic images. Both hardware and software tools were developed to synchronize the acquisition of fluoroscopy with respiratory signal using a pressure sensor (Anzai). This synchronization, in turn, harmonizes fluoroscopic images with DDRR. The verification system was tested on a motion phantom and on lung cancer cases. Results: The system developed can effectively register respiration‐synchronized fluoroscopic and DDRR images for both phantom and patient data. The registration is able to detect discrepancies between planning images (DDRR) and verification images (in‐line fluoroscopy) for a 4D‐ART delivery. The system is found to be effective for validating respiratory gating. Conclusion: We have developed a treatment verification system for 4D‐ART. The system, employing in‐line kV fluoroscopy, may be used for validating respiratory gating and for 4D‐ART with the new generation of image‐guided delivery machine capable of in‐line dynamic imaging. The system can be also potentially useful for 4D real‐time tumor tracking based on fluoroscopy. Conflict of Interest: This work is supported in part by Siemens OCS.