Figure 5. Non-rigid registration applied to myocardial segmentation. In this example the myocardium has been manually delineated on each slice of the end-diastolic phase to define a surface. The end-diastolic image volume has been registered to the end-systolic volume to delineate the myocardium at end systole. Technical details: the images are short axis electrocardiogram triggered SSFP SENSE factor 2 images from a healthy volunteer collected on a Philips Intera 1.5 T scanner (Philips Medical Systems, Best, The Netherlands) at Guy's Hospital, London, UK. 20 cardiac phases were acquired with each volume consisting of 12–14 contiguous slices, collected in blocks of three, during up to five breath-holds. Registration was performed with vtknreg (available free from www.image-registration.com), which uses free-form deformations modelled with B-splines.