Ortung eines {U}ltraschallkopfes in stereoskopischen {R}öntgenbildern für den hybriden {B}ewegungsausgleich in der bildgestützten {S}trahlentherapie

Type of publication:  beliebiger Eintrag
Jahr: 2013
Monat: Februar
Howpublished: Bachelor's Thesis
Notiz: Motion Compensation in Radiosurgery
Abriss: Image guided radiation therapy is a common approach to cancer treatment in modern medicine. Ionizing radiation is accumulated in a target region to achieve irreversible damage of the tumor cells and at the same time best possible protection of the surrounding healthy tissue. Especially target regions inside the body with respiration- or pulsation-induced motion are difficult to treat since the movements cannot be observed directly in real-time. 4D ultrasound offers the possibility to observe target motion directly and with a high temporal resolution. The development of a hybrid tracking technique shall integrate this imaging modality into the motion compensation process during radiation therapy. In a first step the target volume inside the body is localized via ultrasound imaging. In combination with the exact tracking of the ultrasound probe the target position is computed in robot coordinates and the tumor can be irradiated with high precision. In this bachelor thesis the stereoscopic X-ray camera system of a robotic radiosurgery system is expanded to support the absolute ranging of an ultrasound probe. The characteristics of the radiosurgery system require an adaption of the software for camera calibration. The stability and convergence of the calibration results from this modified software are analyzed. Furthermore, algorithms for six-dimensional tracking of marker geometries are developed and validated using special phantoms. Test results indicate that markers can be localized with translational errors under 0.5 millimeters and a rotational error around 0.075 degrees. By consequently using the complete size and resolution of the X-ray detectors the effective image resolution can be enhanced by up to 79 percent compared to the integrated software of the CyberKnife. The rotatory precision increases by 75 percent while the available tracking volume can be doubled.
Autoren: Ipsen, Svenja