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 CancerO

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primary radiotherapy in NCSLC

- 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 LC radiotherapy

Increased demand of

appropriate multi-modality diagnostic imaging

Improvements in Lung Cancer Radiotherapy

J. Biederer

static CT

plan underassumption of

tu. displacement

4D-CT

detectionof

tu. displacement

plan inknowledge of

tu. displacement

4D-CT 4D-CT

Beam ON

gatingfor

tu. position

LC RT Planning: Motion Adapted RT

J. Biederer

ex.

in.

LC RT Planning: Motion Adapted RT

PTV2 w/ motion compensation

PTV1 w/ ideal motion adaption

PTV2 - PTV1= IPPT

individual potential to preserve tissue

J. Biederer

step-by-step cine CT

Capturing respiratory Motion with CT

slow helical CT

prospective

techniques

retrospective

techniqueslow pitch helical CT

external signal(belt)

integratingiGTV over time

external signal(belt)

insp./exp. CTbreathing commandor external trigger

J. Biederer Capturing RM with CT: insp./exp. ScanningH

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standard CT

static breathing

Flash-CT Flash-CT

(trigger ex.)

Flash-CT

(trigger in.)breathing

J. Biederer

ZZ

Detector widthDetector widthExp InspExp Insp

Step-by-Step (e.g. GE)Step-by-Step (e.g. GE)

Capturing RM with CT: Step by step Cine CT

J. Biederer

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

Capturing RM with CT: Step by step Cine CT

J. Biederer

ZZ

Low Pitch helical CT (e.g. Siemens, Toshiba)Low Pitch helical CT (e.g. Siemens, Toshiba)

Exp InspExp Insp

Capturing RM w/ CT: Low Pitch helical 4D-CT

J. Biederer

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

Capturing RM w/ CT: Low Pitch helical 4D-CT

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

fast/ultrafasttime resolved displayof respiratory motion

2D + t

3D + t = 4D

slow acquisition integratingiGTV over time

triggeredacquisition

prospective

techniques

by external signal

MIP reconstruction

Capturing respiratory Motion with MRI

by internal signal(“self-navigated“)

retrospective

techniques

reassorting/binningoversampled data

“navigator“ technique

external signal (belt)

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

Hypothesis: Robustness against respiratory motion …

… is achieved with the same technology that would produce

4D image data correlated with respiratory motion!

Capturing respiratory Motion with MRI

J. Biederer

A hybrid breathhold/Navigator-triggered approach

Hintze C, … Biederer J, … et al. RöFo 2010;182: 45-52

Dynamic CE MRI: Navigator Motion Correction

J. Biederer

3D-flash (GRE) retrospective(G. Remmert, DKFZ)

Capturing RM with MRI: Retrospective Binning

Remmert et al., Phys Med Biol 2007;18:N401-N405

J. Biederer

“Evolution“ of self-navigated MRI

Respiration belt

Navigator technique

self-navigated MRI: 3D flash

self-navigated MRI: Radial/KWIC

The Future: self navigated 4D-MRI

J. Biederer

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)

Capturing RM: Self-navigated 3D flash MRIW

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J. Biederer

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

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Capturing RM: Self-navigated radial MRI

J. Biederer

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Experimental Set up for 4D Imaging

J. Biederer

Biederer J et al. (2007), RSNA 2007, ISMRM 2007Biederer J et al., Int J Radiat Oncol Biol Phys. 2009;73: 919-926

LC RT: Comparison 4D-CT/4D-MRI/4D-CBCT

- 4D-MRI and CBCT overestimate lesion size

- 4D-MRI and CBCT underestimate displacement

- 4D-MRI and CBCT with less reproducibility

4D-MRI4D-CT 4D-Cone beam CT

J. Biederer 4D-CT vs. 4D-MRI for LC RT: ComparisonBi

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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/sCourtesy of J. Dinkel, DKFZ