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Ljungberg, Maria, et al.
(författare)
31P MR spectroscopy to evaluate the efficacy of hepatic artery embolization in the treatment of neuroendocrine liver metastases.
2012
Ingår i: Acta radiologica (Stockholm, Sweden : 1987). - : SAGE Publications. - 1600-0455 .- 0284-1851. ; 53:10, s. 1118-1126
Tidskriftsartikel (refereegranskat) abstract
BackgroundIt is common to treat patients with metastatic disease from gastrointestinal neuroendocrine (NE) tumors with surgical reduction to prolong survival. This can be combined with hepatic arterial embolization (HAE) and medical treatment to reduce hormonal symptoms. Today there are no rapid and reliable methods to evaluate the efficacy of HAE in the treatment of neuroendocrine liver metastasis.PurposeTo investigate metabolic changes in hepatic metastases of NE tumors following HAE, and to establish if there are any early spectral patterns that might indicate therapeutic efficacy based on in vivo (31)P MRS data.Material and MethodsVolume selective (31)P MRS was used to study 11 patients with disseminated NE tumors with regional lymph nodes and bilobar liver metastases. Measurements were performed before and 1 and 3 days after HAE.ResultsNon-responders had significantly higher PME/Pi and αNTP/ΣNTP ratios than the responders before HAE (P < 0.05). Three days after HAE, non-responders still had significantly higher αNTP/ΣNTP than the responders did (P < 0.05). We also observed trends for increased PME ratios 3 days after HAE, decreased ATP-levels, and liberated Pi in responders.ConclusionThis (31)P-MRS study showed significant differences in PME/Pi and αNTP/ΣP ratios between responders and non-responders on the day before HAE, which is an interesting finding that may reflect intrinsic properties of the tumor tissue. We also observed trends for cell membrane renewal and increased energy consumption in responders after HAE. These results demonstrate potentials for (31)P-MRS to predict individual responsiveness prior to HAE.
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Montelius, Mikael, 1979, et al.
(författare)
Optimal ROI Size for IVIM Imaging parameter determination
2012
Ingår i: European Society for Magnetic Resonance in Medicine and Biology (ESMRMB), Oct 4-6 2012, Lisbon/PT.
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)
Tumour size measurement in a mouse model using high resolution MRI.
2012
Ingår i: BMC medical imaging. - : Springer Science and Business Media LLC. - 1471-2342. ; 12:1
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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Carlsson, Åsa, 1978, et al.
(författare)
Degraded water suppression in small volume ¹H MRS due to localised shimming.
2011
Ingår i: Magma (New York, N.Y.). - : Springer Science and Business Media LLC. - 0968-5243. ; 24:2, s. 97-107
Tidskriftsartikel (refereegranskat) abstract
High quality, artifact free, ¹H MRS require a homogeneous magnetic field over the volume of interest (VOI) and an effective global water suppression (WS). However, the shim coils act globally and, hence, affect the resonance frequency over the entire object, making the frequency selective WS spatially selective. Unsuppressed water signal may cause spurious echo artifacts. Aim: Study and visualise the effect localised shimming has on WS.
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