New SMRT President appointed

Profile photo of Shawna facing camera and smiling
NIF Facility Fellow and Florey Chief Radiographer, Shawna Farquharson. Photo attributed to S. Farquharson

NIF Facility Fellow Shawna Farquharson is leading the way to empower, connect, educate and inform MRI Radiographers and Technologists worldwide. Following their 2019 Annual Meeting, the Society for MR Radiographers & Technologists (SMRT), a Section of the International Society for Magnetic Resonance in Medicine (ISMRM), appointed Shawna Farquharson as its new President of SMRT. SMRT is the leading non-profit organisation that provides an international forum for education, information and research in magnetic resonance for radiographers and technologists throughout the world.

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Magnetic Lymphatic Mapping in Pigs

Working Towards a New Gold Standard for Cancer Care

 

The lymphatic system is one of the key mechanisms for metastatic spread, whereby cancer cells that have disseminated from a primary tumour are taken up into lymphatic vessels and transported to other locations in the body, beginning with the lymph nodes. Conventionally, surgeons map the lymphatic flow from a tumour site into the first draining nodes – known as sentinel lymph nodes – using a Tc99m radiocolloid. Drainage pathways of tracers may be imaged before surgery with gamma cameras (lymphoscintigraphy), and individual nodes detected during surgery with handheld gamma probes. These sentinel nodes are the ‘canary in the coal mine’ and can offer valuable information to help stage the disease and determine the most appropriate treatment options, so it is ideal for removing just these nodes while leaving uninvolved nodes intact.

While this technique is successfully and routinely applied to breast cancer and melanoma, accuracy is limited in cancers where the nodes are in close proximity to the primary tumour or other nodes, such as cancers of the head and neck. Without an accurate method to identify sentinel nodes in oral cancer, extensive dissection of all nodes in the neck region is routinely performed to ensure any potential draining nodes are harvested, yet approximately 75 % of patients undergoing neck dissection are exposed to the complications and morbidity of this invasive procedure without clinical benefit.

Dr Aidan Cousins and Dr Giri Krishnan have been working as part of a collaborative project between the University of South Australia and the University of Adelaide to demonstrate a novel, high-resolution technique for lymphatic mapping using magnetic nanoparticle-based tracers. Studies conducted at the South Australian Health and Medical Research Institute (SAHMRI) involve the injection of the magnetic tracer to the oral cavity of female Large White pigs, which are then scanned with a 3.0T Siemens MRI located at the large animal research and imaging facility (LARIF) NIF Node. Post-injection scans give Dr Cousins and Dr Krishnan detailed anatomical information of the drainage patterns of the tracer, which is then used to plan the surgery. During surgery, a handheld magnetometer probe developed by Dr Cousins is used, along with MRI data and visual identification, to pinpoint the draining nodes of interest from other, uninvolved nodes.

Two men looking at a screen in front of an MRI

Dr Cousins with Raj Perumal (LARIF) examining an MRI scan of a pig following injection of the magnetic tracer

The results of this experiment showed the magnetic alternative to be adept for mapping lymphatic drainage in complex environments. Triangulating the location draining nodes with high precision before surgery was made possible by the high-resolution soft-tissue detail afforded by the 3.0T MRI. During surgery, the handheld probe was able to identify all draining nodes by way of detecting their magnetic ‘signature’. This final confirmation of draining nodes is analogous to the use of handheld gamma probes but has the distinct advantage of pin-point resolution, meaning nodes can be in very close (touching) proximity to each other and it is still possible to differentiate between the individual nodes’ magnetic signals. This spatial resolution is currently unmatched by any other probe technology commercially available and is key to the application of sentinel node mapping in complex cancers.

Photo of the high-resolution magnetometer probe developed by Dr Cousins

 

Results from this study are being used to design a world-first clinical trial applying magnetic tracers and a high-resolution probe to human patients with cancer of the oral cavity.

 

This story was contributed by SAHMRI. For further inquiries, please contact Mr Raj Perumal

Exploration of the deep foot muscles at ultra-high field

The arches of the human foot are unique structures that are important for functions like walking and running. The deep intrinsic muscles of the foot, such as the adductor halluces and interossei, are thought to play key roles in arch control; yet little is known about how they are controlled during functional tasks. The traditional measurement techniques can only provide information regarding muscle size, which is inadequate to evaluate the force-generating capacity of the muscles, assess the process of force generation by the muscles, and understand the involvement of the neural drive sent by the body to the muscles to regulate force production.

 

Using the 7T human MRI at the Centre for Advanced Imaging, a research study is currently investigating the muscle architecture of the adductor halluces and interossei. This research aims to quantify the force-generating capacities of these deep-foot muscles by measuring their MRI muscle volumes, estimate their force production by shear wave Elastography and measure their neural drive by using Electromyography.

black and white MRI images showing a cross-section of the foot with deep foot muscles outlined in colour

Deep foot muscles outlined in two cross-sections of a structural MRI scan obtained at ultra-high field: abductor halluces (green), abductor digiti minimi (pink), flexor digitorium brevis (magenta), quadrature plantae (cyan) and extensor digitorium brevis (yellow). With thanks to Dr Natalie Collins, University of Queensland

 

MRI images are obtained from male and female volunteers with no lower limb pain or injury. To date, structural MR images of deep foot muscles have been obtained using T1 VIBE 3D Transverse Oblique sequence and MRI muscle volumes have been measured. In future, diffusion tensor imaging will be performed to measure apparent diffusion coefficient and fractional anisotropy of the deep foot muscles.

 

This story was contributed by the University of Queensland, with acknowedgements to Dr Natalie Collins of the School of Health and Rehabilitation Sciences, Health and Behavioural Sciences, University of Queensland.

For further information, please contact Dr Tonima Ali.

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