A Cylindrical 3D Water Scanner –

1. First Experiences and Results Karen Feyen AZ St-Maarten Duffel, Belgium A Cylindrical 3D Water Scanner –

2. A.Z. Sint-Maarten – RT department - Linacs • SLi 18 (installed 2002), conformal treatments • 6MV/15MV photons • 5 electron energies • MLCi with 1 cm leaves, max field size 40 cm x 40 cm • Short physics duct from control area to linac technical area : no fixed cabling • Synergy platform (installed 2007), IMRT • 6MV/15MV photons • Beam modulator with 4 mm leaves, max field size 21 cm x 16 cm • Physics duct about 25 m, fixed cabling and connectors in bunker and control area • EPID based IGRT on both systems • Iview GT • Vanderwilt remote table control • Offline/online protocols, no CBCT • ± 1000 new patients/year

3. A.Z. Sint-Maarten – RT department • CT simulation • Siemens Definition CT (medical imaging department) • A2J CT-Sim lasers • Medio 50 CP simulator used for some palliative • Medio 50 CP simulator • Some palliative treatments • Main TPS = Pinnacle • Brachy: • Nucletron HDR / Oncentra Masterplan • PBT inhouse/other centers : Bard / Variseed • Other equipment • More than 40 PC’s and workstations for about 20 people • A lot of cables and a lot of heat

4. Dosimetry material • Abolute Dosimetry • FC-65-G cylindrical reference chamber • PPC-40 parallel plate chamber • Dose-1 electrometer • WP1D motorised waterphantom • Machine QA - SNC • Switching to IC-profiler or Profiler 2 (still to be decided) • Daily QA3 (wireless) • Patient QA • Matrixx • Invidos • Brachy QA • Unidos E and Sourcecheck (PBT) • Nucletron/Standard Imaging and PTW well chamber (HDR)

5. 3DS – How did we decide ? • Motivation : • WP700 system dates from 1989 and was in need for replacement • “New” project : commission Sli 18 for IMRT, we wanted this done without doubts about the measurement data quality • Increase time efficiency of water tank measurements • Reduce threshold to use of water tank • Obtained budget approval 04/2010

6. 3DS – How did we decide ? • Requirements specifications (highlights): • Must • qualitatively perform as well or better than the old system (of course) • work with current detectors • handle current data • export to Pinnacle • TMR/TPR capable • Before purchase, we must work with the system to get the look and feel • Should • more user friendly • easier/faster to setup

7. 3DS – How did we decide ? • On site visits at nearby centers May-June 2010 • PTW MP3-M / Mephysto MC2 • IBA Blue Phantom / OmniPro Accept v7  both very qualitative and well established systems • IBA blue phantom and OmniPro Accept v7 seemed logical successor to our current system • No clinical 3DS system available in Europe at that time • => Visit to SNC factory

8. 3DS – How did we decide ? • Visit SNC factory • First view on a functional prototype • Opportunity to talk to several people involved in the development of hardware and software • Enthousiastic team determined to deliver a innovative and qualitative product, eager to take input from (potential) users • Good overview of hardware, software • But system released early 2011, which was later than we hoped for

9. 3DS – How did we decide ? • Competitive offers from all parties • Open communication with all distributors • Detailed comparison of all specs • Choice between solid well established system and young innovative system • Very much attracted by the novelties of the 3DS system • Auto setup : objective, time saving (?), • One-cable connection : fast, less fragile • Measurement database instead of files • Layered processing with rollback options • Consistent detector orientation (certainly has a positive effect but not thoroughly evaluated at that time)

10. 3DS – How did we decide ? • But no reference and no opportunity to test at that time => Test site agreement • Gain experience with new system before it is released • Opportunity to provide input for new features (wish list !) • Possibly start measurements with test system if all works earlier than planned (optimism is good)

11. 3DS – the system

12. 3DS – the system • Main hardware differences : • Cylindrical geometry • movement in (r, theta, z) instead of (x, y, z) • Look less bulky • less water needed, less weight • scan range is the same for all scans ( i.e. not larger for diagonals) but is large (standard 50 cm) • larger scan range possible with special detector holder

13. Mechanical Testing • Relative positioning accuracy using laser pointer and chart paper • Ring drive • Vertical drive • Diameter drive • Done using controls box – without auto setup measurements (dry tank) • Leveling accuracy : ≤ 0.1° (accuracy of our digital level) • Plumb line of vertical drive using laser level (construction)

14. 3DS – Setup • Platform setup procedure: • Connect power and PDI • Calibrate motors platform and tank • Put tank approximately right • Fill tank and adjust height to correct SSD • Leave bunker and run auto setup procedure • Tank Leveling • Ring center determination • Tank center determination and tank adjustment • Ring angle offset determination • Hysteresis measurement

15. 3DS – Auto setup

16. 3DS – Auto setup – calibrate platform • Platform leveling and x- y- motors need to be calibrated before they can be used • Best done before aligning the system with the crosswire

17. 3DS – Auto setup – calibrate platform • Tank ring drive, diameter drive and vertical drive home positions are determined

18. 3DS – Auto setup

19. 3DS – Auto setup – ring center • Diameter drive is mounted eccentrically to allow for the detector to be in the center

20. 3DS – Auto setup – Ring center • To keep the detector in the mechanical center of the tank, it must be positioned correctly • In the direction orthogonal to the diameter drive -> specific distance when mounting the detector • In the direction along the diameter drive -> done by the system

21. 3DS – Auto setup – Ring center • If the ring center would not be determined correctly, the detector would rotate on a circle around the mechanical center

22. 3DS – Auto setup • Tank adjust • The isocenter/beam center is determined from • Inline and crossline scan at collimator 0° • Inline and crossline scan at collimator 180° • The tank position is shifted to match the beam center • Angle offset • The angle of the tank is aligned with the collimator

23. 3DS – Auto setup Checks • Check after auto setup during test period: • Visually check position of detector vs crosswire • Take scans at cardinal angles • Check correct position of beam edges • => Part of factory testing

24. 3DS – Setup -timings

25. 3DS – Scan database • Scans are grouped in projects – can be added to multiple projects • DB can be searched by building logical expressions of various scan parameters • Scan lists can filtered • Scans lists can be grouped

26. 3DS – Scan database - projects

27. 3DS – Scan database searches

28. 3DS – Scan database filtering

29. 3DS – Scan database filtering

30. 3DS – Scan layered processing

31. 3DS – Scan layered processing

32. Experiences – Detectors used

33. Experiences – Easy setup

34. Results – Large scan range • The standard scan range of 50 cm can be extended using the radial offset detector holder • 40 cm x 40 cm, d=30cm, 5 cm extra => 62cm scan

35. Results – Large scan range • Radial offset detector offsets the detector from the center of the carriage, brings it closer to the tank wall • Diameters driver rotates by 180° when detector is in the center

36. Results – Consistent detector orientation • The cylindrical design ensures a consistent orientation of the detector : the motion always occurs transverse to the axis of the detector

37. Results – Consistent detector orientation • Intuitively important for • extended detectors • detectors with different dimensions along their respective axis • Tested with 3 types of detectors • elongated IC • “spherical” IC (CC13) • diode • Compared scans with axis • transverse to motion • along the direction

38. Results – Consistent detector orientation – elongated IC

39. Results – Consistent detector orientation – elongated IC Effect clearly visible

40. Results – Consistent detector orientation – CC13

41. Results – Consistent detector orientation – CC13 Effect present but less visible

42. Results – Consistent detector orientation – diode

43. Results – Consistent detector orientation – diode Effect invisible

44. Results – Evaluation of scan parameters • Set of scans for various field sizes and various scan settings – CC13

45. Results – Evaluation of scan parameters • Set of scans for various field sizes and various scan settings – Edge (diode)

46. Results – Detector choice – small fields • Set of scans for various detectors and optimal scan settings • “Sharp” vs noisy

47. Results – Detector choice – large fields • Set of scans for various detectors and optimal scan settings • “Sharp” vs noisy

48. Results – Scans with offset • Achieved by either • Software controlled shift of platform (offsets ~ 1cm) • By combination of radial and angular movement (larger offsets)

49. Results – Scans with offset • Check off-axis shift • Collimator 45° • Scan with no offset / • Scan with 1 cm offset

50. Results – Scans with offset • Check detector position ?