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Purpose: A segmented inversion-recovery module combined with the 2D ultrashort echo time radial technique is proposed that allows accurate pixel level T(1) mapping of mouse lung in vivo., Methods: Numerical simulations were performed to estimate T(1) measurement accuracy and precision versus flip angle and signal-to-noise ratio. Phantom measurements were used for protocol validation, where the segmented inversion-recovery ultrashort echo-time sequence was compared with the reference technique (inversion-recovery rapid acquisition with refocused echoes). The in vivo experiments were carried out on free-breathing C57 mice (n = 10), breathing first air and then oxygen., Results: The simulations demonstrated the high potential of the technique for accurate and precise T(1) assessment. Phantom experiments showed good agreement for T(1) values measured with segmented inversion-recovery ultrashort echo-time and the reference technique. The in vivo experiment demonstrated the utility of the technique in oxygen-enhanced assessment, where small T(1) changes were detected with high precision., Conclusion: Segmented inversion-recovery ultrashort echo-time provides accurate, high resolution T(1) mapping of the lung parenchyma., (Copyright © 2013 Wiley Periodicals, Inc.)

Tissue microcirculation can be quantified by a deconvolution analysis of concentration-time curves measured by dynamic contrast-enhanced magnetic resonance imaging. However, deconvolution is an ill-posed problem, which requires regularization of the solutions. In this work, four algebraic deconvolution/regularization methods were evaluated: truncated singular value decomposition and generalized Tikhonov regularization (GTR) in combination with the L-curve criterion, a modified LCC (GTR-MLCC), and a response function model that takes a-priori knowledge into account. To this end, dynamic contrast-enhanced magnetic resonance imaging data sets were simulated by an established physiologically reference model for different signal-to-noise ratios and measured on a 1.5-T system in the lung of 10 healthy volunteers and 20 patients. Analysis of both the simulated and measured dynamic contrast-enhanced magnetic resonance imaging datasets revealed that GTR in combination with the L-curve criterion does not yield reliable and clinically useful results. The three other deconvolution/regularization algorithms resulted in almost identical microcirculatory parameter estimates for signal-to-noise ratios > 10. At low signal-to-noise ratios levels (<10) typically occurring in pathological lung regions, GTR in combination with a modified L-curve criterion approximates the true response function much more accurately than truncated singular value decomposition and GTR in combination with response function model with a difference in accuracy of up to 76%. In conclusion, GTR in combination with a modified L-curve criterion is recommended for the deconvolution of dynamic contrast-enhanced magnetic resonance imaging curves measured in the lung parenchyma of patients with highly heterogeneous signal-to-noise ratios., (Copyright © 2012 Wiley Periodicals, Inc.)

In preclinical research, allergic asthma is investigated in rats sensitised with the antigen ovalbumin (OVA), followed by a challenge with aerosolised OVA to induce an inflammatory reaction of the lower airways. This causes diffuse, nonfocal ventilation defects that lead to heterogeneously distributed signal intensities in hyperpolarised (HP) (3)He MR images, which are difficult to assess directly by diagnostic grading or volumetry. Texture analysis can characterise these changes and does not require segmentation of the lung structures prior to the analysis. The aim of this work was to evaluate a texture analysis approach to quantify changes in lung ventilation in HP (3)He MRI of OVA-challenged rats. OVA-challenged animals were treated with two different compound doses to evaluate the sensitivity of the texture analysis. Four groups were investigated using HP (3)He MRI at 4.7 T: controls, vehicle-treated, and low- and high-dose budesonide-treated rats. In addition, broncho-alveolar lavage was performed and the eosinophil cell count was used as a biological reference marker. First-order texture, geometrical features and features based on second-order statistics using run-length and grey-level co-occurrence matrices were calculated. In addition, wavelet transforms were applied to compute first-order statistics on multiple scales. The texture analysis was able to show significant differences between the control and untreated vehicle groups as well as between the vehicle and treatment groups. This is in agreement with the findings of the eosinophil cell counts, which were used as a marker for the severity of inflammation. However, not all features used in the different texture analysis methods could differentiate between the treatment groups. In conclusion, texture analysis can be used to quantify changes in lung ventilation as measured with HP (3)He MRI after therapeutic intervention with budesonide., (Copyright © 2011 John Wiley & Sons, Ltd.)