Model-Based Registration of X-ray Mammograms and MR Images of the

Female Breast

N.V. Ruiter, T.O. Müller, R. Stotzka, H. Gemmeke,Forschungszentrum Karlsruhe, Germany

Motivation

• Locate lesion in complementary modality

MR image

X-ray mammogram

Registration: Find geometric correspondence

Support multimodal breast cancer diagnosis:

Registration Problem

• MR image:

• Volume image

• Undeformed breast

• Prone position

• X-ray mammography:

• 2D projection

• Large deformation

• Only one projection per deformation

Images not directly comparable !

Add information using a biomechanical model

X-ray mammogram

MR image

Process of Registration

Deformation process

Biomechanical model Deformed model

Projection of artificial MR image

Problems of Deformation Model• Large deformation of soft tissue

• Details of deformation process unknown:• Exact patient position

• 3D shape of breast

• Thickness of deformed breast

• Compression force

• Tissues of the breast:• Only large scale structures

resolved in MR image

• Material models in literature:• Inconclusive

• Not plausible for large deformation

Plate compression

L‘

Fatty tissue

Glandulartissue

Skin

Specification of Deformation Model• Adapt global parameters:

• Projection angle by non-linear scaling• Volume is preserved estimate thickness

• Finite Element Model• Large deformations (>>5%), (nearly) incompressible

materials

• Material model• Evaluation of models for breast tissue: Neo Hookean model,

homogeneous tissues

• Two step modeling of deformation1st step: Mammographic deformation 2nd step: Fine tuning using mammogram

Mammographicdeformation

Results with Clinical Datasets• Six clinical data sets:

Lesion position in X-ray mammograms and MR image known

• Smallest visible lesions in MR images: 5 mm

• X-ray MRI:• Mean center distance: 3.9 mm (1.6 – 6.4 mm)

• Mean volume overlap: 91%

• Prediction of lesion position

• MRI X-ray:

• Mean center distance: 4.3 mm (2.3 – 6 mm)

• Mean area overlap: 81%

Results with Clinical DatasetsMRI X-ray : craniocaudal example

X-ray mammogramDirect MR projection

MR projection after simulation

Center lesion distance 2.3 mm Lesion overlap 100%

24mm

Conclusions• Registration overcomes 3D deformation• Successful first evaluation:

Localization with approx. 5 mm deviation (smallest visible lesion)

Clinical evaluation

• Possible applications: • Support multimodal breast cancer diagnosis (also alternative 3D modalities)• Simulation of breast deformation

Thank you !