Assessing focal spot alignment in clinical linear accelerators: a comprehensive evaluation with triplet phantoms
Abstract
A fundamental parameter to evaluate the beam delivery precision and stability on a clinical linear accelerator (linac) is the focal spot position (FSP) measured relative to the collimator axis of the radiation head. The aims of this work were to evaluate comprehensive data on FSP acquired on linacs in clinical use and to establish the ability of alternative phantoms to detect effects on patient plan delivery related to FSP. FSP measurements were conducted using a rigid phantom holding two ball-bearings at two different distances from the radiation source. Images of these ball-bearings were acquired using the electronic portal imaging device (EPID) integrated with each linac. Machine QA was assessed using a radiation head-mounted PTW STARCHECK phantom. Patient plan QA was investigated using the SNC ArcCHECK phantom positioned on the treatment couch, irradiated with VMAT plans across a complete 360° gantry rotation and three X-ray energies. This study covered eight Elekta linacs, including those with 6 MV, 18 MV, and 6 MV flattening-filter-free (FFF) beams. The largest range in the FSP was found for 6 MV FFF. The FSP of one linac, retrofitted with 6 MV FFF, displayed substantial differences in FSP compared to 6 MV FFF beams on other linacs, which all had FSP ranges less than 0.50 mm and 0.25 mm in the lateral and longitudinal directions, respectively. The PTW STARCHECK phantom proved effective in characterising the FSP, while the SNC ArcCHECK measurements could not discern…
Read the paper
Related studies
- Lathyrism-induced alterations in collagen cross-links influence the mechanical properties of bone material without affecting the mineral
- High-Resolution SPECT-CT/MR Molecular Imaging of Angiogenesis in the Vx2 Model
- Severely impaired bone material quality in Chihuahua zebrafish resembles classical dominant human osteogenesis imperfecta
- Small-animal SPECT and SPECT/CT: application in cardiovascular research
- Intravital imaging of osteocytes in mouse calvaria using third harmonic generation microscopy
- Techniques and Evaluation From a Cross-Platform Imaging Comparison of Quantitative Ultrasound Parameters in an In Vivo Rodent Fibroadenoma Model
Go deeper in Evidence Hub
Evidence Hub adds a study data sheet (design, sample size, evidence level, key numbers), an AI summary and a chat grounded in the paper's text.