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- Montelius, Mikael, 1979, et al.
(författare)
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Optimal ROI Size for IVIM Imaging parameter determination
- 2012
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Ingår i: European Society for Magnetic Resonance in Medicine and Biology (ESMRMB), Oct 4-6 2012, Lisbon/PT.
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Konferensbidrag (refereegranskat)abstract
- The use of multiple b-values in diffusion weighted (DW) imaging allows calculation of the tissue molecular diffusion parameter D, the perfusion-related diffusion parameter D* and the perfusion fraction f, by applying the intravoxel incoherent motion (IVIM) model (Le Bihan 1988). Region of interest (ROI) based signal analysis is a widely used approach, where the normalized average ROI signal is plotted vs. b-value, and the acquired signal decay curve is fitted to a bi-exponential model in order to extract D, D* and f. However, the use of this approach requires consideration regarding the ROI area used for signal averaging, since a too small area would lead to uncertainties in the parameter determination, e.g. due to noise and patient motion. Likewise, a too large area increases the likelihood of including unwanted large vessels in the ROI, which confounds the interpretation of the perfusion fraction parameter. Better knowledge on how to choose the ROI size could lead to better and more reproducible estimations of D, D* and f; important parameters in e.g. tumor therapy response assessment. In this work we investigated the variability of these parameters due to the use of different ROI areas in liver IVIM experiments, and thereby empirically determined an optimal area for signal averaging.
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- Montelius, Mikael, 1979, et al.
(författare)
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Optimal ROI Size for Parameter Determination in IVIM Imaging
- 2012
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Ingår i: European Association of Nuclear Medicine (EANM), October 27 - 31, 2012, Milan/ITALY.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Successful delivery of therapy agents to tumor cells depends on tumor tissue perfusion and diffusion. Assessment of these parameters prior to and during treatment would facilitate decision-making regarding e.g. treatment strategy. The intravoxel incoherent motion (IVIM) model (Le Bihan 1988) applied to multi b-value diffusion weighted MRI offers non-invasive quantification of tissue diffusion (D), perfusion-related pseudo diffusion (D*) and perfusion fraction (f). However, the quantification is highly affected by the size of the analyzed region of interest (ROI). In this work, the optimal ROI size for quantification of D, D* and f was determined.
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- Montelius, Mikael, 1979, et al.
(författare)
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Tumour size measurement in a mouse model using high resolution MRI.
- 2012
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Ingår i: BMC medical imaging. - : Springer Science and Business Media LLC. - 1471-2342. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- ABSTRACT: BACKGROUND: Animal models are frequently used to assess new treatment methods in cancer research. MRI offers a non-invasive in vivo monitoring of tumour tissue and thus allows longitudinal measurements of treatment effects, without the need for large cohorts of animals. Tumour size is an important biomarker of the disease development, but to our knowledge, MRI based size measurements have not yet been verified for small tumours (102-101g). The aim of this study was to assess the accuracy of MRI based tumour size measurements in small tumours on mice. METHODS: 2D and 3D T2-weighted RARE images of tumour bearing mice were acquired in vivo using a 7 T dedicated animal MR system. For the 3D images the acquired image resolution was varied. The images were exported to a PC workstation where the tumour mass was determined assuming a density of 1 g/cm3, using an in-house developed tool for segmentation and delineation. The resulting data were compared to the weight of the resected tumours after sacrifice of the animal using regression analysis. RESULTS: Strong correlations were demonstrated between MRI-and necropsy determined masses. In general, 3D acquisition was not a prerequisite for high accuracy. However, it was slightly more accurate than 2D when small (<0.2 g) tumours were assessed for inter-and intraobserver variation. In 3D images, the voxel sizes could be increased from 1603um3 to 2403um3 without affecting the results significantly, thus reducing acquisition time substantially. CONCLUSIONS: 2D MRI was sufficient for accurate tumour size measurement, except for small tumours (<0.2g) where 3D acquisition was necessary to reduce interobserver variation. Acquisition times between 15 and 50 minutes, depending on tumour size, were sufficient for accurate tumour volume measurement. Hence, it is possible to include further MR investigations of the tumour, such as tissue perfusion, diffusion or metabolic composition in the same MR session.
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