Accuray Radixact at University of WI: The next chapter in TomoTherapy innovation

Transcription

1 Accuray Radixact at University of WI: The next chapter in TomoTherapy innovation Jennifer Smilowitz, Ph.D. Clinical Associate Professor Departments of Human Oncology and Medical Physics University of Wisconsin, Madison, WI, USA 1

2 Disclosure This work is funded in part by the University of Wisconsin / Accuray research agreement. 2

3 History of TomoTherapy at UW 1988: Tomo idea conceived by Rock Mackie at UW. 1997: TomoTherapy Inc. founded by Mackie and Reckwerdt 2002: First patient treated at UW. 2013/14: 2 HDA units replace the Hi-Arts 2015: Radixact research unit installed First gantry ~ 2001 Rock Mackie At UW Bench top unit, ~1999 Dave Pearso n John Balog Jeni Smilowitz Ken Ruchala 3

4 IMRT/IGRT Integration into Clinical Practice Delivery Feasibility 2005 Hi-Art 2013 Improvements: TomoDirect Dynamic Jaw DCS VoLo GPU processing TQA Easier plan transfer OIS connectivity Fixed target Initially a specialty machine: a pioneer for IMRT and IGRT Sophistication 4

5 Current and Future Radixact Features 1. Key new hardware features Higher dose rate (nominal 1000 cgy/min) Additional magnetic shielding around linac Couch catcher 2. Gantry redesign with space for kv imaging system 3. Motion compensation 4. Key software features : Precision itps Common database Integration with third party TPS (RayStation) 5

6 Project 1: Dosimetric Stability and Reliability Same linac and target as the latest HDA systems operating at higher dose rate. Energy and output of Radixact assessed as part of a larger investigation into the tomotherapy systems at UW. Smilowitz, JB, Dunkerly, D, Yadav, P, Hill, P and Geurts, M., Long Term Dosimetric Stability of Multiple TomoTherapy Delivery Systems, J Appl Clin Med Phys, Accepted March Non-DCS systems 0.3 DCS systems 0.25 Frequency SN 477 HDA SN 488 HDA SN 05 Radiexact Relative Output Monitor Chamber, Relative Output 6

7 Major Dosimetric Component Replacement History The service record history does not cover the compete duration of the output and energy study due to limited availability of records for the Hi-Art systems.) 7

8 .to a robust and sophisticated treatment ready for new features Delivery Feasibility Space for onboard KV imaging New couch features Hi-Art Sophistication 8

9 Project 2: Motion Compensation Accuray has proposed a method to compensate for intrafraction motion Helical, dynamic jaw plans created for 11 patient datasets (per IRB approval) ITV based plan (3 mm expansion of ITV) = PTV 3 mm expansion of GTV = PTV Dose distributions with motion generated to address: The effect of motion on intended plan created with an ITV The effect of motion mitigation The impact of smaller PTVs based on GTV expansion only 9

10 Dose computation with Motion Trace 1. Motion trace was generated for the 11 cases (4 liver, 4 lung, 3 pancreas) 2. Contour GTV on single phase CT scan and use sequential deformable to propagate to all phases. 3. Identify center of mass (COM) 4. Combine COM motion with RPM file (extend for tx. length) Dose computed using a GPU-based tomotherapy dose code that rigidly transformed dose according to trace. Avg/min/max COM motion (cm): Lat. 0.8/0.1/1.4 A/P 1.2/0.2/2.8 S/I 1.9/0.8/3.5 10

11 Fractional dose difference maps (note scale) (a) Effect of intrafraction motion (Dose 2-1) (b) Motion compensation (Dose 3-1) 11

12 Results * DC offset in motion trace 12

13 Conclusion and next steps Tumor motion during TomoTherapy helical delivery produced plans with large volumes of tissue having substantial dose difference from planned dose. These differences were mitigated within clinically acceptable tolerances using MLC and jaw motion compensation, enabling further gain through margin reduction. Next steps: Where are the regions of under and overdose? Quantify effect of target coverage versus sensitive structures 13

14 Pancreas - example of effect of DVH ITV based plan With motion Motion Compensated kidneys liver Duod./stomach Gall bladder DVH has more information, but still tells an incomplete story 14

15 Project 3: Treatment Planning New integrated Data Management System( idms) with a new TPS based on CyberKnife interface, Precision Same GPU VoLo optimization We are investigating the effect on planning with higher dose rate by (manually) generating dosimetrically equivalent plans and looking at gantry period, treatment and leaf open histograms. We will soon begin testing a new transfer software (HDA to Precision Planning, then a machine transfer to Radixact) TomoTherapy planning RayStation (Phase 2 of our clinical TPS upgrade) 15

16 How does the high dose rate effect planning? Similar tomo feel New features (ex: D x V v ) 16

17 Dosimetrically equivalent Plan Study Re-planned clinical cases to create Dosimetrically equivalent plans (within 1 Gy and meeting MD dose objectives) Maintaining planning parameters (MF, FW, pitch & objectives) Evaluation of DVH metrics and normal tissue objectives Look at resultant treatment times, not goodness of plan HDA D98 PTV 56 D95 PTV 70 Radixact Parotid_L D50 PTV 60 Esophagus D2 17

18 Preliminary results to date: Treatment time 850 cgy/min 1000 cgy/min Dosimetrically Equivalent plans 18

19 Preliminary results to date: Gantry Period 850 cgy/min 1000 cgy/min Dosimetrically Equivalent plans 19

20 What happens to the Leaf Open Times (LOT) with fast GP? Radiexact Tomo HDA Supraglottic HN Iliac 20

21 MVCT Scanning is ~ 40%Faster sec 6 sec HDA RADIXACT 100 Seconds % 0 Iliac Prostate Meningioma Head and Neck From Accuray study on UW Madison HDA clinical system and Alpha Radixact bunker (Cristina Negrut, Jeremy Heil and Jeff Sudmeier) 21

22 Summary Alpha research unit for next generation TomoTherapy delivery system is installed in WIMR Initial testing shows Radixact is as stable and reliable as current clinical HDA systems Dose difference due to intrafraction motion is observed even with ITV-based plans. A rigid proposed motion compensation method is able to decrease dose differences. Higher dose rate reduces plan time as expected as gantry period speeds up. This also changes the the LOT histogram and will potentially allow for more delivery options, with less short LOT. Tomo research is exciting and ongoing here at UW. 22

23 Thank you to many contributors on the various projects! UW Faculty John Bayouth, Mark Geurts, Poonam Yadav, Patrick Hill, Rock Mackie Accuray Team Cristina Negrut, Andrea Cox, Calvin Mauer Ed Chao, Eric Schnarr, Jake Shea Nancy Sauer and Rick Vaden UW Graduate Students Erin Adamson Mariajose Bedoya Sarah Bitant Vimal Desai David Dunkerley Sabrina Hoffman Ian Marsh Andrew Santoso Catherine Steffel Natalie Viscariello 23