A comparison of two clinical correlation models used for real-time tumor tracking of semi-periodic motion: A focus on geometrical accuracy in lung and liver cancer patients

Type of publication:  Artikel
Publikationsstatus: Akzeptiert
Zeitschrift: Radiotherapy and Oncology
Band: 115
Nummer: 3
Jahr: 2015
Seiten: 419-424
Notiz: Motion Compensation in Radiosurgery
ISSN: 0167-8140
DOI: 10.1016/j.radonc.2015.05.004
Abriss: AbstractPurpose A head-to-head comparison of two clinical correlation models with a focus on geometrical accuracy for internal tumor motion estimation during real-time tumor tracking (RTTT). Methods and materials Both the CyberKnife (CK) and the Vero systems perform \{RTTT\} with a correlation model that is able to describe hysteresis in the breathing motion. The \{CK\} dual-quadratic (DQ) model consists of two polynomial functions describing the trajectory of the tumor for inhale and exhale breathing motion, respectively. The Vero model is based on a two-dimensional (2D) function depending on position and speed of the external breathing signal to describe a closed-loop tumor trajectory. In this study, 20 s of internal motion data, using an 11 Hz (on average) full fluoroscopy (FF) sequence, was used for training of the \{CK\} and Vero models. Further, a subsampled set of 15 internal tumor positions (15p) equally spread over the different phases of the breathing motion was used for separate training of the \{CK\} \{DQ\} model. Also a linear model was trained using 15p and \{FF\} tumor motion data. Fifteen liver and lung cancer patients, treated on the Vero system with RTTT, were retrospectively evaluated comparing the \{CK\} FF, \{CK\} 15p and Vero \{FF\} models using an in-house developed simulator. The distance between estimated target position and the tumor position localized by X-ray imaging was measured in the beams-eye view (BEV) to calculate the 95th percentile \{BEV\} modeling errors (ME95,BEV). Additionally, the percentage of ME95,BEV smaller than 5 mm (P5mm) was determined for all correlation models. Results In general, no significant difference (p > 0.05, paired t-test) was found between the \{CK\} \{FF\} and Vero models. Based on patient-specific evaluation of the geometrical accuracy of the linear, \{CK\} \{DQ\} and Vero correlation models, no statistical necessity (p > 0.05, two-way ANOVA) of including hysteresis in correlation models was proven, although during inhale breathing motion, the linear model resulted in a decreased \{P5mm\} with 5–6% compared to both the \{DQ\} \{CK\} and Vero models. Conclusion Dual-quadratic CyberKnife and 2D Vero correlation models were interchangeable in terms of geometrical accuracy with the \{CK\} linear ME95,BEV = 4.1 mm, \{CK\} dual-quadratic ME95,BEV = 3.9 mm and Vero ME95,BEV = 3.7 mm, when modeled with \{FF\} sequence. \{CK\} \{DQ\} modeling based on 15p acquired in 20 s may lead to problems for internal motion estimation.
Schlagworte: Cyberknife
Autoren: Poels, Kenneth
Dhont, Jennifer
Verellen, Dirk
Blanck, Oliver
Ernst, Floris
Vandemeulebroucke, Jef
Depuydt, Tom
Storme, Guy
Ridder, Mark De