4D-MRI for Radiotherapy of moving Tumours:
Latest developments, comparison to 4D-CT
J. Biederer
Vancouver, August 2, 2011
J. Biederer
Indications for Radiotherapy of Lung Cancer
primary radiotherapy in NCSLC
Oertel et al., Radiologe 2010;50:669–674
Haasbeek et al., Lung Cancer 2009;64,1–8
- stage III
- Pancoast tumour + stages I-II if surgery not possible
before surgery
- Pancoast tumour
after surgery
- pN2
- after incomplete resection (R1, R2)
J. Biederer
Improvements in Lung Cancer Radiotherapy
Improvements in LC radiotherapy
Increased demand of
appropriate multi-modality diagnostic imaging
J. Biederer
static CT
LC RT Planning:
4D-CT
Motion Adapted RT
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
J. Biederer
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
J. Biederer
Capturing respiratory Motion with CT
slow helical CT
integrating
iGTV over time
insp./exp. CT
breathing command
or external trigger
step-by-step cine CT
external signal
(belt)
low pitch helical CT
external signal
(belt)
prospective
techniques
retrospective
techniques
Capturing RM with CT: insp./exp. Scanning
J. Biederer
standard CT
Hintze et al., Exp. Rad. 2010, Kiel
static
breathing
Flash-CT
Flash-CT
Flash-CT
breathing
(trigger in.)
(trigger ex.)
J. Biederer
Capturing RM with CT: Step by step Cine CT
Step-by-Step (e.g. GE)
Detector width
Exp
Insp
Z
J. Biederer
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
J. Biederer
Capturing RM w/ CT: Low Pitch helical 4D-CT
Low Pitch helical CT (e.g. Siemens, Toshiba)
Exp
Insp
Z
J. Biederer
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
J. Biederer
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
J. Biederer
Capturing respiratory Motion with MRI
slow acquisition integrating
iGTV over time
MIP reconstruction
“navigator“ technique
prospective
techniques
triggered
acquisition
fast/ultrafast
time resolved display
of respiratory motion
retrospective
techniques
reassorting/binning
oversampled data
external signal (belt)
2D + t
3D + t = 4D
by external signal
by internal signal
(“self-navigated“)
J. Biederer
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;37:5914–5920
J. Biederer
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!
J. Biederer
Dynamic CE MRI: Navigator Motion Correction
A hybrid breathhold/Navigator-triggered approach
Hintze C, … Biederer J, … et al. RöFo 2010;182: 45-52
J. Biederer
Capturing RM with MRI: Retrospective Binning
3D-flash (GRE)
retrospective
(G. Remmert, DKFZ)
Remmert et al., Phys Med Biol 2007;18:N401-N405
J. Biederer
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
Weick S, Proc. 17th Sc. Meeting, ISMRM, 2009
J. Biederer
Capturing RM: Self-navigated 3D flash MRI
1) 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)
Lin W et al., Magn Reson Med 2008;60:1135–1146
J. Biederer
Capturing RM: Self-navigated radial MRI
1) 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
J. Biederer
Experimental Set up for 4D Imaging
Artificial
Thorax
4
5
3
2
1
LC RT:
J. Biederer
4D-CT
Comparison 4D-CT/4D-MRI/4D-CBCT
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: 919-926
Biederer J et al., JMRI 2010;32:1388–1397
J. Biederer
4D-CT vs. 4D-MRI for LC RT:
Comparison
J. Biederer
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