Dosimetric precision of an ion beam tracking system

<p>Abstract</p> <p>Background</p> <p>Scanned ion beam therapy of intra-fractionally moving tumors requires motion mitigation. GSI proposed beam tracking and performed several experimental studies to analyse the dosimetric precision of the system for scanned carbon beams.</p> <p>Methods</p> <p>A beam tracking system has been developed and integrated in the scanned carbon ion beam therapy unit at GSI. The system adapts pencil beam positions and beam energy according to target motion.</p> <p>Motion compensation performance of the beam tracking system was assessed by measurements with radiographic films, a range telescope, a 3D array of 24 ionization chambers, and cell samples for biological dosimetry. Measurements were performed for stationary detectors and moving detectors using the beam tracking system.</p> <p>Results</p> <p>All detector systems showed comparable data for a moving setup when using beam tracking and the corresponding stationary setup. Within the target volume the mean relative differences of ionization chamber measurements were 0.3% (1.5% standard deviation, 3.7% maximum). Film responses demonstrated preserved lateral dose gradients. Measurements with the range telescope showed agreement of Bragg peak depth under motion induced range variations. Cell survival experiments showed a mean relative difference of -5% (-3%) between measurements and calculations within the target volume for beam tracking (stationary) measurements.</p> <p>Conclusions</p> <p>The beam tracking system has been successfully integrated. Full functionality has been validated dosimetrically in experiments with several detector types including biological cell systems.</p

Range accuracy in carbon ion treatment planning based on CT-calibration with real tissue samples

Abstract Background The precision in carbon ion radiotherapy depends on the calibration of Hounsfield units (HU) as measured with computed tomography (CT) to water equivalence. This calibration can cause relevant differences between treatment planning and treatment delivery. Methods Calibration data for several soft tissues were measured repeatedly to assess the accuracy of range calibration. Samples of fresh animal tissues including fat, brain, kidney, liver, and several muscle tissues were used. First, samples were CT scanned. Then carbon ion radiographic measurements were performed at several positions. Residual ranges behind the samples were compared to ranges in water. Results Based on the measured data the accuracy of the current Hounsfield look-up table for range calibration of soft tissues is 0.2 ± 1.2%. Accuracy in range calibration of 1% corresponds to ~1 mm carbon ion range control in 10 cm water equivalent depth which is comparable to typical treatment depths for head and neck tumors. Conclusion Carbon ion ranges can be controlled within ~1 mm in soft tissue for typical depths of head and neck treatments.</p

Range accuracy in carbon ion treatment planning based on CT-calibration with real tissue samples

BACKGROUND: The precision in carbon ion radiotherapy depends on the calibration of Hounsfield units (HU) as measured with computed tomography (CT) to water equivalence. This calibration can cause relevant differences between treatment planning and treatment delivery. METHODS: Calibration data for several soft tissues were measured repeatedly to assess the accuracy of range calibration. Samples of fresh animal tissues including fat, brain, kidney, liver, and several muscle tissues were used. First, samples were CT scanned. Then carbon ion radiographic measurements were performed at several positions. Residual ranges behind the samples were compared to ranges in water. RESULTS: Based on the measured data the accuracy of the current Hounsfield look-up table for range calibration of soft tissues is 0.2 ± 1.2%. Accuracy in range calibration of 1% corresponds to ~1 mm carbon ion range control in 10 cm water equivalent depth which is comparable to typical treatment depths for head and neck tumors. CONCLUSION: Carbon ion ranges can be controlled within ~1 mm in soft tissue for typical depths of head and neck treatments

Ein- und mehrdimensionale Skalierung gewerkschaftlicher Kampfbereitschaft von Belegschaften

Schmidt HD, Schardt LP, Mielke R. Ein- und mehrdimensionale Skalierung gewerkschaftlicher Kampfbereitschaft von Belegschaften. Bielefelder Arbeiten zur Sozialpsychologie, 12. Bielefeld: Univ. Bielefeld, Fak. für Soziologie; 1976