An EPID-based method for comprehensive verification of gantry, EPID and the MLC carriage positional accuracy in Varian linacs during arc treatments

BACKGROUND: In modern radiotherapy, it is crucial to monitor the performance of all linac components including gantry, collimation system and electronic portal imaging device (EPID) during arc deliveries. In this study, a simple EPID-based measurement method has been introduced in conjunction with an algorithm to investigate the stability of these systems during arc treatments with the aim of ensuring the accuracy of linac mechanical performance. METHODS: The Varian EPID sag, gantry sag, changes in source-to-detector distance (SDD), EPID and collimator skewness, EPID tilt, and the sag in MLC carriages as a result of linac rotation were separately investigated by acquisition of EPID images of a simple phantom comprised of 5 ball-bearings during arc delivery. A fast and robust software package was developed for automated analysis of image data. Twelve Varian linacs of different models were investigated. RESULTS: The average EPID sag was within 1 mm for all tested linacs. All machines showed less than 1 mm gantry sag. Changes in SDD values were within 1.7 mm except for three linacs of one centre which were within 9 mm. Values of EPID skewness and tilt were negligible in all tested linacs. The maximum sag in MLC leaf bank assemblies was around 1 mm. The EPID sag showed a considerable improvement in TrueBeam linacs. CONCLUSION: The methodology and software developed in this study provide a simple tool for effective investigation of the behaviour of linac components with gantry rotation. It is reproducible and accurate and can be easily performed as a routine test in clinics

Commissioning and performance characteristics of a pre-clinical image-guided radiotherapy system

Characteristics of a small-animal radiotherapy device, the X-RAD SmART, are described following commissioning of the device for pre-clinical radiotherapy research. Performance characteristics were assessed using published standards and compared with previous results published for similar systems. Operational radiation safety was established. Device X-ray beam quality and output dose-rate were found to be consistent with those reported for similar devices. Output steadily declined over 18 months though remained within tolerance levels. There is considerable variation in output factor across the international installations for the smallest feld size (varying by more than 30% for 2.5 mm diameter felds). Measured depth dose and profle data was mostly consistent with that published, with some diferences in penumbrae and generally reduced fatness. Target localisation is achieved with an imaging panel and with automatic corrections for panel fex and device mechanical instability, targeting within 0.2 mm is achievable. The small-animal image-guided radiotherapy platform has been implemented and assessed and found to perform as specifed. The combination of kV energy and high spatial precision make it suitable for replicating clinical dose distributions at the small-animal scale, though dosimetric uncertainties for the narrowest felds need to be acknowledged

Automating linear accelerator quality assurance

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135049/1/mp1415.pd

Predkliničke studije [61Cu]ATSM kao PET radiofarmaka za snimanje fibrosarkoma

[61Cu]diacetyl-bis(N4-methylthiosemicarbazone) ([61Cu]ATSM) was prepared using in house-made diacetyl-bis(N4-methylthiosemicarbazone) (ATSM) ligand and [61Cu]CuCl2 produced via the natZn(p,x)61Cu (180 μA proton irradiation, 22 MeV, 3.2 h) and purified by a ion chromatography method. [61Cu]ATSM radiochemical purity was >98%, as shown by HPLC and RTLC methods. [61Cu]ATSM was administered into normal and tumor bearing rodents for up to 210 minutes, followed by biodistribution and co-incidence imaging studies. Significant tumor/non-tumor accumulation was observed either by animal sacrification or imaging. [61Cu]ATSM is a positron emission tomography (PET) radiotracer for tumor hypoxia imaging.[61Cu]diacetil-bis(N4-metiltiosemikarbazon) ([61Cu]ATSM) dobiven je iz liganda diacetil-bis(N4-metiltiosemikarbazona) (ATSM) pripravljenog u vlastitom laboratoriju i [61Cu]CuCl2 dobivenog iz natZn(p,x)61Cu (180 μA protonskim zračenjem, 22 MeV, 3.2 h). [61Cu]ATSM je čišćen ionskom kromatografijom. Prema HPLC i RTLC radiokemijska čistoća bila je > 98%. [61Cu]ATSM je davan zdravim glodavcima i glodavcima s tumorom tijekom 210 minuta te je praćena biodistribucija. Žrtvovanjem testiranih životinja te snimanjem primijećena je značajna razlika u akumulaciji [61Cu]ATSM u tumorskom tkivu u odnosu na zdravo tkivo. [61Cu]ATSM je pogodan za dijagnostiku hipoksije tumora pozitron emisijskom tomografijom (PET)