Development and evaluation of a prototype tracking system using the treatment couch. Issue 2 (23rd January 2014)

• Record Type: Journal Article
• Authors: Lang, Stephanie; Zeimetz, Jörg; Ochsner, Gregor; Schmid Daners, Marianne; Riesterer, Oliver; Klöck, Stephan
• Is Part Of: Medical physics. Volume 41:Issue 2(2014)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2014-01-23
• Subjects: Pneumodyamics, respiration -- Dosimetry/exposure assessment -- Laser imaging -- Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing -- Spatial dimensions (e.g., position, lengths, volume, angles, and displacements); biomedical optical imaging -- dosimetry -- laser applications in medicine -- lung -- medical control systems -- medical image processing -- motion compensation -- motion measurement -- patient treatment -- pneumodynamics -- sensors -- statistical analysis -- tracking -- tumours; couch tracking -- tumor motion -- respiration; Measuring length, thickness or similar linear dimensions; Measuring angles; Measuring areas; Measuring irregularities of surfaces or contours -- Biological material, e.g. blood, urine; Haemocytometers -- Digital computing or data processing equipment or methods, specially adapted for specific applications -- Image data processing or generation, in general -- Analysis of motion -- Scintigraphy; Tracking devices -- Pneumodynamics -- Medical imaging -- Cancer -- Motion detection -- Movement sensors -- Image detection systems -- Laser medical sensors -- Image sensors -- Laser sensors; Medical physics -- Periodicals; Medical physics; Geneeskunde; Natuurkunde; Toepassingen; Biophysics; Periodicals; Periodicals; Electronic journals; 610.153
• DOI: 10.1118/1.4862077
• Languages: English
• ISSNs: 0094-2405

Abstract

Abstract : Purpose: : Tumor motion increases safety margins around the clinical target volume and leads to an increased dose to the surrounding healthy tissue. The authors have developed and evaluated a one‐dimensional treatment couch tracking system to counter steer respiratory tumor motion. Three different motion detection sensors with different lag times were evaluated. Methods: : The couch tracking system consists of a motion detection sensor, which can be the topometrical system Topos (Cyber Technologies, Germany), the respiratory gating system RPM (Varian Medical Systems) or a laser triangulation system (Micro Epsilon), and the Protura treatment couch (Civco Medical Systems). The control of the treatment couch was implemented in the block diagram environment Simulink (MathWorks). To achieve real time performance, the Simulink models were executed on a real time engine, provided by Real‐Time Windows Target (MathWorks). A proportional‐integral control system was implemented. The lag time of the couch tracking system using the three different motion detection sensors was measured. The geometrical accuracy of the system was evaluated by measuring the mean absolute deviation from the reference (static position) during motion tracking. This deviation was compared to the mean absolute deviation without tracking and a reduction factor was defined. A hexapod system was moving according to seven respiration patterns previously acquired with the RPM system as well as according to a sin 6 function with two different frequencies (0.33 and 0.17 Hz) and the treatment table compensated the motion. Results: : A prototype system for treatment couch tracking of respiratory motion was developed. The laser based tracking system with a small lag time of 57 ms reduced the residual motion by a factor of 11.9 ± 5.5 (mean value ± standard deviation). An increase in delay time from 57 to 130 ms (RPM based system) resulted in a reduction by a factor of 4.7 ± 2.6. The Topos based tracking system with the largest lag time of 300 ms achieved a mean reduction by a factor of 3.4 ± 2.3. The increase in the penumbra of a profile (1 × 1 cm 2 ) for a motion of 6 mm was 1.4 mm. With tracking applied there was no increase in the penumbra. Conclusions: : Couch tracking with the Protura treatment couch is achievable. To reliably track all possible respiration patterns without prediction filters a short lag time below 100 ms is needed. More scientific work is necessary to extend our prototype to tracking of internal motion.