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A phantom for the study of positional brain shift

Potts, Matthew 2020. A phantom for the study of positional brain shift. PhD Thesis, Cardiff University.
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Positional brain shift (PBS) is the term given to the displacement of the brain which occurs upon surgical reorientation of the head and presents as one of the many sources of targeting error in high precision neurosurgery. Due to the impracticality of imaging humans in non-standard positions, however, there is currently insufficient information for surgeons to utilize in order to mitigate against PBS in surgical planning. To better characterise PBS, a novel synthetic model (phantom) of the brain-skull system was developed, comprising hydrogel brain (inc. imaging beads) with water filled ventricle cavity, elastomer dural septa, water filled subarachnoid space, and plastic skull. This phantom was validated by simulating the supine to prone PBS event and mechanically tuning the phantom’s hydrogel brain such that the general magnitude of shift (measured through CT imaging) matched that reported in human MRI studies. Using this phantom, brain shift characterisation was performed for a discrete representation of the continuous spectrum of possible positional transitions in neurosurgery. Here, brain shift was measured across eight positional transitions at 44 locations within the brain. Eight novel PBS maps were produced as a result of this study, with mean brain shift ranging between 0.39 and 0.94 mm and the standard deviation of shift within each PBS map ranging between 0.12 and 0.44 mm. The greatest shift was found upon transition from the supine to elevated right decubitus position, with a shift of 2 mm being measured in the left parietal lobe. Importantly, it was found that, a) clinically significant brain shift took place across all transitions and, b) clinically significant variability took place between the brain shift patterns of individual transitions at the local level. Together these findings further highlight the need for the consideration of PBS in surgical planning and strongly suggest that versatile parametric software are likely needed to account for the variable shifting of neurosurgical targets. The developed phantom has allowed for novel insights into an event otherwise difficult to study in humans. With further developments, it is believed that the phantom can be used to study other similarly problematic events, such as trauma.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Engineering
Uncontrolled Keywords: Positional Brain Shift; Brain Deformation; Gravity; Brain Phantom; Head Phantom; Surgical Planning.
Date of First Compliant Deposit: 9 February 2021
Last Modified: 09 Feb 2021 17:13

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