This paper presents a novel method to reduce the effects of interleaving motion artefacts in single-plane MR scanning of
the pelvic region without the need for k-space information. Interleaved image (or multipacket) acquisition is frequently
used to reduce cross-talk and scanning time during full pelvic MR scans. Patient motion during interleaved acquisition
can result in non-linear "staircase" imaging artefacts which are most visible on sagittal and coronal reconstructions.
These artefacts can affect the segmentation of organs, registration, and visualization. A fast method has been
implemented to replace artefact affected slices in a packet with interpolated slices based on Penney et al (2004) whose
method involves the registration of neighbouring slices to obtain correspondences, followed by linear interpolation of
voxel intensities along the displacement fields. This interpolation method has been applied to correct motion affected
MRI volumes by firstly creating a new volume where every axial slice from the artefact affected packet is removed and
replaced with an interpolated slice and then secondly for each of these slices, 2D non-rigid registration is used to register
each original axial slice back to its matching interpolated slice. Results show visible improvements in artefacts
particularly in sagittal and coronal image reconstructions, and should result in improved intensity based non-rigid
registration results between MR scans (for example for atlas based automatic segmentation). Further validation was
performed on simulated interleaving artefacts which were applied to an artefact free volume. Results obtained on
prostate cancer radiotherapy treatment planning contouring were inconclusive and require further investigation.
Increasing transmission of medical images across multiple user systems raises concerns for image security. Hiding watermark information in medical image data files is one solution for enhancing security and privacy protection of data. Medical image watermarking however is not a widely studied area, due partially to speculations on loss in viewer performance caused by degradation of image information. Such concerns are addressed if the amount of information lost due to watermarking can be kept at minimal levels and below visual perception thresholds. This paper describes experiments where three alternative visual quality metrics were used to assess the degradation caused by watermarking medical images. Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) medical images were watermarked using different methods: Block based Discrete Cosine Transform (DCT) and Discrete Wavelet Transform (DWT) with various embedding strengths. The visual degradation of each watermarking parameter setting was assessed using Peak Signal-to-Noise Ratio (PSNR), Structural Similarity Measure (SSIM) and Steerable Visual Difference Predictor (SVDP) numerical metrics. The suitability of each of the three numerical metrics for medical image watermarking visual quality assessment is noted. In addition, subjective test results from human observers are used to suggest visual degradation thresholds.
This paper investigates methods of processing mobility related static images to enhance the effectiveness of a visual prosthesis system. Eight images were processed into 50x50 pixel binary, greyscale, Sobel and Canny edge detected images. 10 subjects were asked 5 mobility related identification tasks for each (randomly ordered) image. Results indicate that edge detection may be useful at this resolution. However, there was not a significant difference found between the results achieved using the Canny and Sobel algorithms. These results support the development of an adaptive device. A mobility display framework has been proposed to assist in this development. Future work will focus on processing image sequences and the development of a visual prosthesis simulation device.