Physical Sciences of Imaging in the Biomedical Sciences CDT
Completed in 2016 and progressed into a clinical scientist training position.
Thesis project - "Functional Near Infrared Spectroscopy (fNIRS) and High Density Diffuse Optical Tomography (HD-DOT) of the human brain to assess traumatic brain injury"
Dr Hamid Dehghani, School of Computer Science
Dr Sam Lucas, School of Sport, Exercise and Rehabilitation Sciences
Mr Antonio Belli, Institute of Inflammation and Ageing
Summary: The aim of this project is to develop a near infrared imaging probe, protocol and reconstruction algorithm to provide near real-time measurements of cerebral oxygenation level in patients with traumatic brain injury (TBI).
Currently standard procedure for trauma patients, recommended by NICE and other bodies, is Permissive Hypotensive Resuscitation (PHR). PHR is used to increase blood pressure in order to maintain blood flow to vital organs. A notable exception to this is in the event of TBI, which makes up 50% of all trauma cases. This is due to fears of an ischaemic insult to the brain where permanent damage can occur within just 15 minutes. This is very controversial, as the brain processes an intrinsic mechanism that works to maintain adequate perfusion during changes in blood pressure. However the initial roadside suspicion of TBI, frequently confounded by alcohol or shock, later turns out to be incorrect. This means that in major trauma, some real or putative TBI victims are unnecessarily denied PHR and therefore risk secondary haemorrhage, lung injury or tissue oedema, whilst others suffer ischaemic brain damage. The successful implementation of near infrared monitoring would provide a cheap, safe and non-invasive means of assessing brain oxygenation of trauma victims in the short and long term.
There are NIRS systems available for functional monitoring of brain oxygenation levels; however they have not been deemed sufficient to provide a 'gold standard' form on assessment. There is a wireless dual wavelength NIRS system which has the size and portability required however it lacks the quantitative information provided by some of the more complex tomographic systems. The goal of this project is to re-engineer this technology; making it portable, rugged and fast system, in order to guide pre-hospital resuscitation and then assess resuscitation efficacy. This would include the move to using a small scale HD-DOT probe which through overlapping measurements and a finite element model (FEM) based reconstruction will provide increased accuracy in the reconstruction of oxygenation values without contamination from surface signal which is common in NIRS instruments. FEM reconstruction accuracy can also be improved with the use of a brain atlas or a patient specific head model (in the case of long term monitoring). Then by optimising reconstruction methods and reducing dataset sizes through non collocated sources, the overall reconstruction time could be reduced to allow effective and faster monitoring of patients. The use of light emitting diodes (LEDs) and silicon photodiodes (SPDs) will greatly reduce the cost of the probes meaning that there is the option to have disposable probes for field trauma monitoring.