Investigations on correlations between changes of optical tissue properties and NMR relaxation times

•Designed dual NMR/optical tissue phantoms mimicking simultaneously NMR relaxation times and optical tissue properties for tumor, white and grey matter tissue.•Dual NMR/optical tissue phantoms beneficial for iPDT research training and demonstration.•Promising first-step investigations on further dev...

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Published in:Photodiagnosis and photodynamic therapy 2024-02, Vol.45, p.103968-103968, Article 103968
Main Authors: Aumiller, Maximilian, Arazar, Asmerom, Sroka, Ronald, Dietrich, Olaf, Rühm, Adrian
Format: Article
Language:English
Subjects:
Absorption
Agar
Animals
Brain - diagnostic imaging
Humans
Interstitial photodynamic therapy
Magnetic Resonance Imaging
NMR relaxation times
Optical properties
Photochemotherapy - methods
Photosensitizing Agents
Scattering
Swine
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Summary:•Designed dual NMR/optical tissue phantoms mimicking simultaneously NMR relaxation times and optical tissue properties for tumor, white and grey matter tissue.•Dual NMR/optical tissue phantoms beneficial for iPDT research training and demonstration.•Promising first-step investigations on further developing iPDT treatment planning concepts based on local differences in optical properties evaluated from MRI.•Simultaneous prolongation of NMR relaxation times T1 and T2 indicates decreased optical tissue properties by water fraction in the tissue.•Differences in NMR relaxation time T2 at constant T1 may indicate differences in optical absorption due to different blood volume fractions. Accurate light dosimetry is a complex remaining challenge in interstitial photodynamic therapy (iPDT) for malignant gliomas. The light dosimetry should ideally be based on the tissue morphology and the individual optical tissue properties of each tissue type in the target region. First investigations are reported on using NMR information to estimate changes of individual optical tissue properties. Porcine brain tissue and optical tissue phantoms were investigated. To the porcine brain, supplements were added to simulate an edema or high blood content. The tissue phantoms were based on agar, Lipoveneous, ink, blood and gadobutrol (Gd-based MRI contrast agent). The concentrations of phantom ingredients and tissue additives are varied to compare concentration-dependent effects on optical and NMR properties. A 3-tesla whole-body MRI system was used to determine T1 and T2 relaxation times. Optical tissue properties, i.e., the spectrally resolved absorption and reduced scattering coefficient, were obtained using a single integrating sphere setup. The observed changes of NMR and optical properties were compared to each other. By adjusting the NMR relaxation times and optical tissue properties of the tissue phantoms to literature values, recipes for human brain tumor, white matter and grey matter tissue phantoms were obtained that mimic these brain tissues simultaneously in both properties. For porcine brain tissue, it was observed that with increasing water concentration in the tissue, both NMR-relaxation times increased, while µa decreased and µs’ increased at 635 nm. The addition of blood to porcine brain samples showed a constant T1, while T2 shortened and the absorption coefficient at 635 nm increased. In this investigation, by changing sample contents, notable changes of both NMR r
ISSN:1572-1000
1873-1597
DOI:10.1016/j.pdpdt.2024.103968