The next Imaging and Optical Physics seminar will take place at 11:00 am - 12:30 pm, Tuesday, 10 July 2018, at Geoff Opat Seminar Room, room 660, School of Physics, the University of Melbourne, cnr Swanston St and Tin Alley. 

Agenda for Imaging and Optical Physics seminar (10 July 2018)

11:00 am - 11:30 am. Dr Imants Svalbe (Monash University)

Title of the talk: Families of spectrally flat arrays as masks for discrete imaging

Abstract: Methods are presented to construct image-sized binary or grey-level discrete arrays that exhibit perfect periodic auto-correlation and low cross-correlation. Here the Finite Radon Transform is the key tool used in the design of each array. These arrays find use as sampling masks for image formation and acquisition. They have found application: for example in compressed sensing for MRI, where real spatial domain data is sub-sampled in the Fourier domain, in thinned antennae arrays of transmit and receiver elements with narrow beam and low side-lobe patterns (in radar and astronomy) and in bucket imaging, where the intensity of 'random' subsets of rays are transmitted through an object and pooled for low-dose tomography. Large families of such arrays are constructed where each array samples with equal amplitude sensitivity across all Fourier frequencies. Each array within a family appears to be very similar, but each is structured to have minimal overlap with all of the other family members.

11:30 am – 12 noon. Ms Linda Croton (Monash University)

Title of the talk: Imaging the Brain In Situ with Phase-Contrast CT

Abstract: Phase-contrast X-ray imaging (PCXI) is an emerging modality that exploits the differing refractive indices of materials to create additional image contrast. When used in conjunction with computed tomography (CT), PCXI can produce images with greatly increased contrast resolution with respect to standard attenuation CT. This means that soft tissue boundaries that are typically not well resolved, such as those between the grey and white matter in the brain, can be visualized clearly. The brain poses unique problems for PCXI-CT, since it is fully encased in the highly-attenuating skull. Damage or defects in the imaging system and other physical effects result in inaccurate estimates of the attenuation gradient across high-contrast boundaries, causing distinct streak artifacts that can overwhelm the parts of the image that contain underlying tissues. In addition, ring artifacts caused by variations in X-ray beam intensity and detector response are more difficult to remove due to the roughly circular symmetry of the skull. I will present the first PCXI-CT of a brain in situ and the challenges faced for further image improvement. I will also present a new, simple ring artefact removal algorithm that requires no prior knowledge of the sample and that is highly effective, particularly in the presence of strongly absorbing features.

12 noon – 12:30 pm. Other topics of interest and discussion