BACKGROUND AND PURPOSE: Modern medical linear accelerators (linacs) are equipped with X-ray systems, which allow to check the patient's position just prior to treatment. Their usefulness for stereotactic radiosurgery (SRS) depends on how accurately they allow to determine the deviation between the actual and planned isocenter positions. This accuracy was investigated with measurements using two different phantoms (Figures 1 and 2). MATERIAL AND METHODS: After precisely aligning a phantom onto the linac isocenter, two perpendicular X-rays or a cone-beam CT (CBCT) are taken, and the isocenter position is deduced from this data. The deviation of the thereby gained position from the setup isocenter is taken as a measure for the uncertainty of this method. RESULTS: Isocenter verification with two orthogonal X-rays (Figure 4) achieves accuracies of better than 1 mm (Table 3). The distance between the isocenters of the CBCT and the linac (Figure 3) is in the order of 1 mm, but remains constant on the time scale of 1 week (Table 1) and may therefore be taken into account. The uncertainty after correction is below 0.2 mm. CONCLUSION: kV imaging with the patient in treatment position allows to verify the isocenter position with submillimeter precision, and therefore offers a supplemental test, suitable for SRS, which takes all positional uncertainties into account.
BACKGROUND AND PURPOSE: Modern medical linear accelerators (linacs) are equipped with X-ray systems, which allow to check the patient's position just prior to treatment. Their usefulness for stereotactic radiosurgery (SRS) depends on how accurately they allow to determine the deviation between the actual and planned isocenter positions. This accuracy was investigated with measurements using two different phantoms (Figures 1 and 2). MATERIAL AND METHODS: After precisely aligning a phantom onto the linac isocenter, two perpendicular X-rays or a cone-beam CT (CBCT) are taken, and the isocenter position is deduced from this data. The deviation of the thereby gained position from the setup isocenter is taken as a measure for the uncertainty of this method. RESULTS: Isocenter verification with two orthogonal X-rays (Figure 4) achieves accuracies of better than 1 mm (Table 3). The distance between the isocenters of the CBCT and the linac (Figure 3) is in the order of 1 mm, but remains constant on the time scale of 1 week (Table 1) and may therefore be taken into account. The uncertainty after correction is below 0.2 mm. CONCLUSION: kV imaging with the patient in treatment position allows to verify the isocenter position with submillimeter precision, and therefore offers a supplemental test, suitable for SRS, which takes all positional uncertainties into account.
Authors: Jürgen Meyer; Jürgen Wilbert; Kurt Baier; Matthias Guckenberger; Anne Richter; Otto Sauer; Michael Flentje Journal: Int J Radiat Oncol Biol Phys Date: 2007-03-15 Impact factor: 7.038
Authors: C F Serago; A A Lewin; P V Houdek; S González-Arias; G H Hartmann; A A Abitbol; J G Schwade Journal: Int J Radiat Oncol Biol Phys Date: 1991-03 Impact factor: 7.038
Authors: A Theelen; J Martens; G Bosmans; R Houben; J J Jager; I Rutten; P Lambin; A W Minken; B G Baumert Journal: Strahlenther Onkol Date: 2011-12-24 Impact factor: 3.621
Authors: Martin Kocher; Andrea Wittig; Marc Dieter Piroth; Harald Treuer; Heinrich Seegenschmiedt; Maximilian Ruge; Anca-Ligia Grosu; Matthias Guckenberger Journal: Strahlenther Onkol Date: 2014-04-09 Impact factor: 3.621
Authors: Weiliang Du; James N Yang; Eric L Chang; Dershan Luo; Mary Frances McAleer; Almon Shiu; Mary K Martel Journal: J Appl Clin Med Phys Date: 2010-07-02 Impact factor: 2.102