The hex Phantom Karin Bryskhe, 1 Daniel Topgaard, 2 1 CR Development, Lund, Sweden 2 Lund University, Lund, Sweden Purpose. Multidimensional diffusion MRI is used to determine the microstructure in tissue. The microscopic fractional anisotropy 1 (μFA) describes the cell shape 2 and has the potential to characterize tumors and enable grading and follow-up of treatment. When new contrasts based on microstructural imaging are used, it is of great importance to calibrate the scanner and validate that the system and data processing pipeline are set up so that μFA can be quantified accurately and precisely. Methods. For this purpose we have designed a phantom with μFA equal to the theoretical maximum value 1. The phantom comprises a mixture of inexpensive and reasonably harmless chemicals, namely water, isooctane (gasoline), and the detergent AOT. In the temperature range 10- 25 °C, this mixture forms a liquid crystal with hexagonally packed water channels in a continuous matrix of liquid isooctane, and the detergent located in the interface between the water and the isooctane. 3 The water channels have a diameter of a few nanometers and lengths approaching macroscopic dimensions. With inspiration from the hexagonal nanostructure, we propose the name “Hex Phantom”. Results. Because of the low solubility of the water in the isooctane, water diffusion is constrained to follow the paths of the narrow channels, giving a value of μFA equal to 1. The phantom has so far been applied for measurements on a microimaging system, 4,5 see figure 1, and a clinical scanner at Hvidovre Hospital, Denmark. Conclusions. We suggest the Hex Phantom as the “gold standard” for μFA. Whenever a protocol for measuring μFA has been modified or implemented on a new MR scanner, the Hex Phantom should be used for validation purposes. Funding Source. Swedish Research Council (VR) and the Swedish Foundation for Strategic Research (SSF). References 1. S. Lasič, F. Szczepankiewicz, S. Eriksson, M. Nilsson and D. Topgaard, Front. Physics, 2014, 2, 11. 2. F. Szczepankiewicz, S. Lasič, D. van Westen, P. C. Sundgren, E. Englund, C.-F. Westin, F. Ståhlberg, J. Lätt, D. Topgaard and M. Nilsson, Neuroimage, 2015, 104, 241. 3. B. Jönsson, B. Lindman, K. Holmberg and B. Kronberg, Surfactants and polymers in aqueous solution, John Wiley & Sons Ltd, Chichester, 1998. 4. J. P. de Almeida Martins and D. Topgaard, Phys. Rev. Lett., 2016, 116, 087601. 5. D. Topgaard, Phys. Chem. Chem. Phys., 2016, 18, 8545. oriented random order tensor, S! microscopic diffusion tensor, D voxel-average diffusion tensor, 〈D〉 Figure 1. Microimaging results for the Hex Phantom. The tensors are mapped with an in-plane spatial resolution of 0.3 mm. The linear microscopic diffusion tensors correspond to μFA = 1. (Adapted with permission from ref. [5].)

The hex Phantom - EUROMAR 2016program.euromar2016.org/abstracts/613.pdf · · 2016-06-10The hex Phantom Karin Bryskhe,1 Daniel Topgaard,2 ... results for the Hex Phantom. The tensors

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The hex Phantom

Karin Bryskhe,1 Daniel Topgaard,2

1CR Development, Lund, Sweden 2Lund University, Lund, Sweden

Purpose. Multidimensional diffusion MRI is used to determine the microstructure in tissue. The microscopic fractional anisotropy1 (µFA) describes the cell shape2 and has the potential to characterize tumors and enable grading and follow-up of treatment. When new contrasts based on microstructural imaging are used, it is of great importance to calibrate the scanner and validate that the system and data processing pipeline are set up so that µFA can be quantified accurately and precisely.

Methods. For this purpose we have designed a phantom with µFA equal to the theoretical maximum value 1. The phantom comprises a mixture of inexpensive and reasonably harmless chemicals, namely water, isooctane (gasoline), and the detergent AOT. In the temperature range 10-25 °C, this mixture forms a liquid crystal with hexagonally packed water channels in a continuous matrix of liquid isooctane, and the detergent located in the interface between the water and the isooctane.3 The water channels have a diameter of a few nanometers and lengths approaching macroscopic dimensions. With inspiration from the hexagonal nanostructure, we propose the name “Hex Phantom”.

Results. Because of the low solubility of the water in the isooctane, water diffusion is constrained to follow the paths of the narrow channels, giving a value of µFA equal to 1. The phantom has so far been applied for measurements on a microimaging system,4,5 see figure 1, and a clinical scanner at Hvidovre Hospital, Denmark.

Conclusions. We suggest the Hex Phantom as the “gold standard” for µFA. Whenever a protocol for measuring µFA has been modified or implemented on a new MR scanner, the Hex Phantom should be used for validation purposes.

Funding Source. Swedish Research Council (VR) and the Swedish Foundation for Strategic Research (SSF).

References 1. S. Lasič, F. Szczepankiewicz, S. Eriksson, M. Nilsson and D. Topgaard, Front. Physics, 2014, 2, 11. 2. F. Szczepankiewicz, S. Lasič, D. van Westen, P. C. Sundgren, E. Englund, C.-F. Westin, F. Ståhlberg, J. Lätt,

D. Topgaard and M. Nilsson, Neuroimage, 2015, 104, 241. 3. B. Jönsson, B. Lindman, K. Holmberg and B. Kronberg, Surfactants and polymers in aqueous solution, John

Wiley & Sons Ltd, Chichester, 1998. 4. J. P. de Almeida Martins and D. Topgaard, Phys. Rev. Lett., 2016, 116, 087601. 5. D. Topgaard, Phys. Chem. Chem. Phys., 2016, 18, 8545.

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order tensor, S! microscopic diffusion tensor, Dvoxel-average diffusion tensor, 〈D〉

Figure 1. Microimaging results for the Hex Phantom. The tensors are mapped with an in-plane spatial resolution of 0.3 mm. The linear microscopic diffusion tensors correspond to µFA = 1. (Adapted with permission from ref. [5].)