Hit or Miss: Is there a role for CT/MRI fusion in Sarcoma radiotherapy planning?

1. Hit or Miss: Is there a role for CT/MRI fusion in Sarcoma radiotherapy planning? Paris-Ann Gfeller B.C. Cancer Agency, Vancouver, Canada Musculoskeletal Tumour Group C. Candish, K. Goddard, C. Grafton, L. Weir

2. Outline • Background • Study Design • Results • Conclusions

3. BackgroundSarcoma Radiotherapy Planning • The delineation of tumorfrom normal tissues is critical to the radiotherapy planning process • In Sarcoma treatment planning, improper delineation of tumour can lead to: Over-treatment of normal tissues • Severe late effects of treatment (fibrosis, fracture, edema) Under-treatment of tumour • Tumour recurrence

4. BackgroundSarcoma Radiotherapy Planning • Appropriate imaging is essential to properly delineate tumour volumes • Majority of current radiotherapy planning systems are CT based • With CT images alone it can be difficult to differentiate between tumor and normal tissue • Sarcomas are routinely imaged using MRI • MRI correlates with tumour extent and invasion into local structures • MRI shows peritumoral edema, which is included as part of target volume

5. BackgroundCT vs. MRI Tumour is better defined by MRI compared to CT MRI CT

6. BackgroundHow Can We Combine CT and MRI? By co-registering (fusing) CT and MRI images, Radiation Oncologists can contour on CT and MRI simultaneously, using imaging information from both modalities MRI CT

7. BackgroundHow is Fusion Done? CT MRI-Fusion

8. BackgroundCT/MRI Fusion for Sarcomas? There are no published studies describing the use of CT/MRI Fusion for sarcoma treatment • CT/MRI Fusion studies in other tumor sites have shown: • Improved tumor delineation with fusion • More accurate representation of gross disease • Decreased interobserver, intraobserver variation with fusion • More reproducible • Is there a benefit for CT/MRI fusion in sarcoma radiotherapy planning?

9. Study Questions? • Is CT-MRI Fusion useful in sarcoma planning? • Does Fusion alter the tumour volumes? • Does Fusion improve consistency between observers (interobserver variation)? • Does Fusion improve consistency within observers (intraobserver variation)? • Is CT/MRI fusion felt to be valuable to the planning process? • Radiation Oncologists opinion • Radiation Therapists opinion

10. Study Design In 2004 a BCCA protocol was developed for fusion sarcoma patients • Coordination of planning CT and MRI on the same day, in treatment position, with an immobilization device • “Best” MRI image series selected in consult with radiology and fused with a planning CT

11. Study Design • 19 patients were planned and treated from May 2004 to February 2005 at Vancouver Cancer Centre (BCCA) with the CT-MRI fusion protocol • Identified all patients who had been treated according to protocol • Excluded patients who had received chemotherapy or surgery prior to radiation planning • Excluded tumours located in the thorax or head and neck • 9 patients met study criteria • 6 patients treated preoperatively, 3 patients had radiotherapy as definitive treatment • 5 MFH, 3 Fibromatosis, 1 Liposarcoma

12. Study Design • Original non-contrast planning CT images and MRI images retrieved and then co-registered to produce CT/MRI fusion images • 2 image sets for each patient created • CT image set • CT/MRI fusion image set

13. Study Design 3 Radiation Oncologists (RO’s) 9 CT Image Sets 9 Patient Summaries Contour tumour volumes Complete Survey 9 Fusion Image Sets, 9 Patient Summaries Contour tumour volumes Complete Survey 54 Image Sets Volumes Analyzed for: Difference in Mean Volumes Max/Min Ratio, X/Y/Z Observers repeated contours on CT and Fusion for Intraobserver Δ Minimum 2 week delay between contouring on image sets

14. RESULTS

15. ResultsMean Contoured Tumour Volume By Patient CT volumes were 20% larger then fusion volumes

16. ResultsContoured Tumour Volumes Oncologists included more NORMAL TISSUE if unsure of volume on CT vs. MRI • This accounted for larger overall CT volumes CT Fusion

17. ResultsContoured Tumour Volumes Fusion CT • CT contours not always inclusive of MRI signal changes • GROSS TUMOUR EXCLUDED

18. Interobserver VariationMaximum Variation Ratio Compare Max/Min Contoured Volume for each patient between observers • More Interobserver Variation with CT

19. Interobserver VariationMaximum Variation Ratio CT Fusion • Volumes contoured with Fusion more consistent between observers

20. Intraobserver VariationMaximum Variation Ratio Compare Max/Min Contoured Volume for each patient within observers • More Intraobserver Variation with CT

21. ResultsContoured Tumour Volumes • Contoured Tumour Volumes (GTV) • Mean CTvolumes by pt were larger then Fusion volumes • Mean CT gross tumour volumes for each patient were 1.2 times larger (range 0.90-1.56) then CT/MRI fusion images • p=0.04 • Interobserver Variation (Maximum Variation Ratio) • CT 3.72 (range 1.19- 9.0) • Fusion 1.72 (range 1.16-3.07) • Less interobserver variation with fusion p=0.001 • IntraobserverVariation (Maximum Variation Ratio) • CT 1.41 (range 1.03-1.72) • Fusion 1.10 (range 1.01-1.27) • Less intraobserver variation with fusion p=0.02

22. ResultsSurvey • 10 question survey completed by Radiation Oncologists and Radiation Therapists involved in sarcoma planning after completing planning • Radiation Oncologists unanimously felt better able to delineate tumour from normal tissue with fusion • Radiation therapists felt fusion aided in their ability to prepare images (contour critical structures) in preparation for planning by Radiation Oncologists

23. Conclusions A Role for Fusion in Sarcoma Planning? • One of first studies to formally evaluate use fusion for planning sarcomas • Results justify use of fusion • Fusion allows Radiation Oncologists to define smaller more accurate volumes which may: • decrease dose to normal tissues • Improve tumour coverage • Fusion increases consistency and reproducibility of treatment planning Results show the optimal modality for planning sarcoma is CT-MRI Fusion to ensure gross disease appropriately represented

24. Thank you • CTOS Abstract Review Committee • BCCA Musculoskeletal Tumour Group • Dr. C. Candish • Dr. K. Goddard • Dr. C. Grafton • Dr. L. Weir • Dr. C. Keogh (Radiology) • C. Marlowe, K. Dahle, C. Mengerink (Radiation Therapy) • V. Morovan (Statistics) “Imaging Matters”

25. Questions?

26. Supplementary Slides

27. ResultsCT with Bowel Contrast CT with Contrast MRI

28. ResultsCT with IV Contrast CT with Contrast MRI

29. ResultsImaging and Registration MRI slices 5mm

30. ResultsContoured Tumour Volumes CT Fuse

31. ResultsContoured Tumour Volumes PTV’s CT Fuse

32. Results Underestimate Tumour Extent

33. ResultsContoured Tumour Volumes

34. ResultsGross Tumour Volumes by Observer

35. ResultsGross Tumour Volume By Patient

36. ResultsMean Gross Tumour Volume By Patient • CT volumes 1.2 times larger then fusion, p=0.04

37. ResultsMean PTV By Patient

38. ResultsMeasuring Variation

39. ResultsMEAN X,Y,Z Variation Standard Deviation smaller for fusion all directions All dimensions smaller for Fusion (sup/inf most significant)

40. ResultsVariation Superior to Inferior

41. ResultsMedial and Lateral Variation

42. ResultsCompletion Survey Survey completed for each image set at completion of contouring (N=88) Linear Analog Rating Scale Rate the general quality of this CT (fusion) image set? (1 – poor, 5-meets expectations, 10 – exceeds expectations) • CT score 4.9, Fusion 6.7 • Both image sets were “acceptable” for contouring Rate the quality of this CT (fusion) image set for delineating: (1- can not delineate to 10 –exceeds expectations) a. Tumor volume • CT 4.0, Fusion 7.8 b. Critical Structures • CT 4.2, Fusion 7.4 Indicates Subjectively “Better" Delineation of Tumour and Critical Structures with Fusion

43. ResultsRadiation Oncologists Completion Survey Using a linear analog scale (poor to exceeds expectations) rate the quality of this CT (fusion) image set for delineating: Tumour Volumes • CT 4.0, Fusion 7.8 • Normal Tissues • CT 4.2, Fusion 7.4 Fuse Fuse CT CT poor meets expectations exceeds poor meets expectations exceeds Improved Delineation of Tumour and Normal Structures with Fusion

44. ResultsRadiation Therapists Opinions 8 question survey for Radiation therapists (n=4) involved in sarcoma fusions • Average time for fusion • 35.5 minutes • Usefulness of Fusion for delineating normal structures • Extremely useful • Difficulty of Performing Fusions compared to other sites • Slightly more difficult, (extremities the most difficult) • Important factors in image fusion • Tumour location, MRI quality, time available • IMMOBILIZATION and Position

45. ConclusionsA Role for Fusion in Sarcoma Planning? • CT/MRI fusion is valuable to the planning process for sarcoma • Contoured Tumour Volumes • More normal tissue included in the target volumes with CT • Disease excluded on CT • Volume Variation • More consistency in contours with Fusion • Completion Survey • Radiation Oncologists and Therapists felt fusion was valuable