1. Context

I am Yassine Bouchareb, clinical scientist in image fusion working full time on the multi-modality medical image fusion project. This project is run within the Department of Medical Physics and Bioengineering of University College of London Hospitals by Prof. Roland Blackwell (Head of the department) and the Institute of Nuclear Medicine, University College London by Prof. Peter Ell (Director of the institute).
Several Radiologists are involved in this project: Liz Prvulovich, consultant physician in Nuclear Medicine, Nicholas Hyde a maxillofacial surgeon at the Maxillo Facial Unit and Rolf Jager, consultant Neuroradiologist at University College London Hospitals Trust and Reader in Neuroradiology at the Institute of Neurology, National Hospital, Queen Square.

2. Objective

The first aim of the project is to implement an image fusion application for ontological studies using images acquired using the GE "Advanced" full ring PET scanner in the Department of Nuclear Medicine and images acquired using the Large Bore Picker "Acqsim" CT scanner used for simulation in the Radiotherapy Department. The fusion application will be delivered for clinical use for radiotherapy treatment planning. Further application for MRI-PET fusion are being investigated.

3. Progress & Results

The Image Fusion Project is based on the use of the rigid body multi-modality image fusion software developed at Guys Hospital for research purposes. This fusion technique is voxel intensity based and uses mutual information as a similarity measure for registering images. This software is actually installed and running on the sun workstation "chaabi" dedicated to this project. The project was started by working on CT and PET data. Some preliminary results (click here to see the presentation) for the chest scans CT/PET were presented at the UK PET physics group on 10th May (see figure 1).
 

Figure1. CT axial slice, a PETemission slice, superimposition of CT/PET images
   before registration and the fused images from left to right.

Six datasets for Chest patients have been processed so far, and there is still great interest in recruiting more Brain, Chest and Head & Neck studies from Radiotherapy to increase the range of clinical applications covered, and a more accurate evaluation of our fusion technique.
Recently 12 Head & Neck patients with both MRI and PET scans have been processed in order to test the ability of the fusion application to show how accurate are these fused images (see figure 2a and 2b).
 

Figure2a. MRI T1 (left) and PET (right) images from a Head and Neck patient.
Figure2b. MRI/PET fused images from images above.

The fusion results for these Head and Neck patients are interesting from a clinical point of view, however, these results show some limitations of the actual MRI acquisition protocol in addition to the type of deformations that are likely to be present in this region.
To overcome these limitations, the practical ways to proceed for the MR imaging protocol for Head and Neck studies were discussed in the group. A specific MRI acquisition protocol for image fusion will be considered for the future tumour patients candidates for the fusion process. This protocol is currently under test.
The MRI protocol should include T1 transverse slices spaced at 3 mm through the region of interest (bottom of the brain to the top of shoulders). The time implications of including the T1 scan in the protocol will be studied as well.
In the future, the use of MR images acquired with an appropriate acquisition protocol for image fusion is expected to increase further the value of this fusion technique.

4. The Image Fusion Group
 
Medical physics

Dave Plummer,  d.plummer@medphys.ucl.ac.uk
Cliff Ruff, c.ruff@medphys.ucl.ac.uk
Yassine Bouchareb, y.bouchareb@medphys.ucl.ac.uk
Nuclear Medicine
Peter Ell,  p.ell@nucmed.ucl.ac.uk
Liz Prvulovich,  l.prvulovich@nucmed.ucl.ac.uk
Glyn Davies,  g.davies@nucmed.ucl.ac.uk
Dimitris Visvikis, d.visvikis@nucmed.ucl.ac.uk
Wendy Waddington, w.waddington@nucmed.ucl.ac.uk
Radiotherapy
Anna Cassoni, anna.cassoni@uclh.org
Derek DeSouza,  d.desouza@medphys.ucl.ac.uk
Caroline Doolan, caroline.doolan@uclh.org
Neuroradiology
Rolf Jager,  r.jager@ion.ucl.ac.uk
Maxillo Facial Unit
Nicholas Hyde, Nicholas.Hyde@stgeorges.nhs.uk