4D-MRI for Radiotherapy of moving Tumours: Latest developments, comparison to 4D-CT. J. Biederer Vancouver, August 2, 2011

Transcription

1 4D-MRI for Radiotherapy of moving Tumours: Latest developments, comparison to 4D-CT Vancouver, August 2, 2011

2 Indications for Radiotherapy of Lung Cancer primary radiotherapy in NCSLC - stage III Oertel et al., Radiologe 2010;50: Haasbeek et al., Lung Cancer 2009;64,1 8 - Pancoast tumour + stages I-II if surgery not possible before surgery - Pancoast tumour after surgery -pn2 - after incomplete resection (R1, R2)

3 Improvements in Lung Cancer Radiotherapy Improvements in LC radiotherapy Increased demand of appropriate multi-modality diagnostic imaging

4 LC RT Planning: Motion Adapted RT static CT 4D-CT 4D-CT 4D-CT Beam ON plan under assumption of tu. displacement detection of tu. displacement plan in knowledge of tu. displacement gating for tu. position

5 LC RT Planning: Motion Adapted RT ex. PTV2 w/ motion compensation PTV1 w/ ideal motion adaption in. PTV2 - PTV1= IPPT individual potential to preserve tissue

6 Capturing respiratory Motion with CT prospective techniques slow helical CT insp./exp. CT integrating igtv over time breathing command or external trigger step-by-step cine CT external signal (belt) retrospective techniques low pitch helical CT external signal (belt)

7 Capturing RM with CT: insp./exp. Scanning standard CT Flash-CT Flash-CT Flash-CT static breathing breathing (trigger in.) (trigger ex.) Hintze et al., Exp. Rad. 2010, Kiel

8 Capturing RM with CT: Step by step Cine CT Step-by-Step (e.g. GE) Detector width Exp Insp Z

9 Capturing RM with CT: Step by step Cine CT Advantages robust against changes of respiration frequency no overranging at z-limits respiration triggering easy Disadvantages Z-coverage incomplete w. changes of respiration depth every single position waists 180 rotation

10 Capturing RM w/ CT: Low Pitch helical 4D-CT Low Pitch helical CT (e.g. Siemens, Toshiba) Exp Insp Z

11 Capturing RM w/ CT: Low Pitch helical 4D-CT Advantages more effective use of projections changes in respiration frequency better tolerated Disadvantages Z-coverage incomplete with changes of respiration depth (use lowest pitch cave dose and imaging time) overranging at z-limits

12 4D MRI as an Alternative? - if soft tissue contrast in CT is poor (e.g. liver) - if minimizing radiation dose is important - if multiple respiratory cycles have to be covered

13 Capturing respiratory Motion with MRI slow acquisition integrating igtv over time MIP reconstruction prospective techniques triggered acquisition navigator technique external signal (belt) fast/ultrafast time resolved display of respiratory motion 2D + t 3D + t = 4D retrospective techniques reassorting/binning oversampled data by external signal by internal signal ( self-navigated )

14 Capturing RM with MRI: Integrating igtv/t - acquisition of 2D-SS-GRE (TrueFISP) at 3/s - MIP of non-assorted images ( slice stacking ) - volume/area agree with step-by-step 4D-CT Adamson et al., Med Phys 2010;37:

15 Capturing respiratory Motion with MRI Hypothesis: Robustness against respiratory motion is achieved with the same technology that would produce 4D image data correlated with respiratory motion!

16 Dynamic CE MRI: Navigator Motion Correction A hybrid breathhold/navigator-triggered approach Hintze C, Biederer J, et al. RöFo 2010;182: 45-52

17 Capturing RM with MRI: Retrospective Binning 3D-flash (GRE) retrospective (G. Remmert, DKFZ) Remmert et al., Phys Med Biol 2007;18:N401-N405

18 The Future: self navigated 4D-MRI Evolution of self-navigated MRI Respiration belt Navigator technique self-navigated MRI: 3D flash self-navigated MRI: Radial/KWIC

19 Capturing RM: Self-navigated 3D flash MRI Weick S, Proc. 17 th Sc. Meeting, ISMRM, ) 3D flash free breathing 2) quasi-random k-space ordering 3) non-spatially encoded DC signals from k-space center > determination of respiratory cycle 4) grouping of acquisitions for respiratory phase > expiration or multiple phases (S. Weick et al., Würzburg)

20 Capturing RM: Self-navigated radial MRI Lin W et al., Magn Reson Med 2008;60: ) radial data acquisition 2) signal from k-space center > determination of respiratory cycle 3) grouping of views for respiratory phase > expiration or multiple phases 4) further improvements of image quality autofocusing - 3D image correlation - K-space-weighted image contrast (KWIC) - principal component analysis

21 Experimental Set up for 4D Imaging 4 5 Artificial Thorax 3 2 1

22 LC RT: Comparison 4D-CT/4D-MRI/4D-CBCT 4D-CT 4D-Cone beam CT 4D-MRI - 4D-MRI and CBCT overestimate lesion size - 4D-MRI and CBCT underestimate displacement - 4D-MRI and CBCT with less reproducibility Biederer J et al. (2007), RSNA 2007, ISMRM 2007 Biederer J et al., Int J Radiat Oncol Biol Phys. 2009;73:

23 4D-CT vs. 4D-MRI for LC RT: Comparison Biederer J et al., JMRI 2010;32:

24 4D MRI for LC RT: Perspectives - might replace 4D-CT for RT planning in the future - ideal for selection of patients - will profit from faster acquisition schemes TWIST 4D MRI 2.5 vol/s Courtesy of J. Dinkel, DKFZ