Improved reproducibility for myocardial ASL: Impact of physiological and acquisition parameters

PURPOSE: To investigate and mitigate the influence of physiological and acquisition-related parameters on myocardial blood flow (MBF) measurements obtained with myocardial Arterial Spin Labeling (myoASL). METHODS: A Flow-sensitive Alternating Inversion Recovery (FAIR) myoASL sequence with bSSFP and spoiled GRE (spGRE) readout is investigated for MBF quantification. Bloch-equation simulations and phantom experiments were performed to evaluate how variations in acquisition flip angle (FA), acquisition matrix size (AMS), heart rate (HR) and blood T 1 $${\mathrm{T}}_1$$ relaxation time ( T 1 , B $${\mathrm{T}}_{1,B}$$ ) affect quantification of myoASL-MBF. In vivo myoASL-images were acquired in nine healthy subjects. A corrected MBF quantification approach was proposed based on subject-specific T 1 , B $${\mathrm{T}}_{1,B}$$ values and, for spGRE imaging, subtracting an additional saturation-prepared baseline from the original baseline signal. RESULTS: Simulated and phantom experiments showed a strong dependence on AMS and FA ( R 2 $${R}^2$$ >0.73), which was eliminated in simulations and alleviated in phantom experiments using the proposed saturation-baseline correction in spGRE. Only a very mild HR dependence ( R 2 $${R}^2$$ >0.59) was observed which was reduced when calculating MBF with individual T 1 , B $${\mathrm{T}}_{1,B}$$ . For corrected spGRE, in vivo mean global spGRE-MBF ranged from 0.54 to 2.59 mL/g/min and was in agreement with previously reported values. Compared to uncorrected spGRE, the intra-subject variability within a measurement (0.60 mL/g/min), between measurements (0.45 mL/g/min), as well as the inter-subject variability (1.29 mL/g/min) were improved by up to 40% and were comparable with conventional bSSFP. CONCLUSION: Our results show that physiological and acquisition-related factors can lead to spurious changes in myoASL-MBF if not accounted for. Using individual T 1 , B $${\mathrm{T}}_{1,B}$$ and a saturation-baseline can reduce these variations in spGRE and improve reproducibility of FAIR-myoASL against acquisition parameters

Improved reproducibility for myocardial ASL: Impact of physiological and acquisition parameters

Purpose To investigate and mitigate the influence of physiological and acquisition‐related parameters on myocardial blood flow (MBF) measurements obtained with myocardial Arterial Spin Labeling (myoASL). Methods A Flow‐sensitive Alternating Inversion Recovery (FAIR) myoASL sequence with bSSFP and spoiled GRE (spGRE) readout is investigated for MBF quantification. Bloch‐equation simulations and phantom experiments were performed to evaluate how variations in acquisition flip angle (FA), acquisition matrix size (AMS), heart rate (HR) and blood relaxation time () affect quantification of myoASL‐MBF. In vivo myoASL‐images were acquired in nine healthy subjects. A corrected MBF quantification approach was proposed based on subject‐specific values and, for spGRE imaging, subtracting an additional saturation‐prepared baseline from the original baseline signal. Results Simulated and phantom experiments showed a strong dependence on AMS and FA (>0.73), which was eliminated in simulations and alleviated in phantom experiments using the proposed saturation‐baseline correction in spGRE. Only a very mild HR dependence (>0.59) was observed which was reduced when calculating MBF with individual . For corrected spGRE, in vivo mean global spGRE‐MBF ranged from 0.54 to 2.59 mL/g/min and was in agreement with previously reported values. Compared to uncorrected spGRE, the intra‐subject variability within a measurement (0.60 mL/g/min), between measurements (0.45 mL/g/min), as well as the inter‐subject variability (1.29 mL/g/min) were improved by up to 40% and were comparable with conventional bSSFP. Conclusion Our results show that physiological and acquisition‐related factors can lead to spurious changes in myoASL‐MBF if not accounted for. Using individual and a saturation‐baseline can reduce these variations in spGRE and improve reproducibility of FAIR‐myoASL against acquisition parameters

Participatory Approaches to Research and Development in the Southeast Asian Uplands: Potential and Challenges

International audienceParticipatory approaches have been discussed as alternatives to and complementary elements of more conventional research on sustainable land use and rural development in upland areas of Southeast Asia. Following a brief overview of the history of participatory approaches (Sect. 9.1), this chapter discusses the potential and limitations of applying Participatory Rural Appraisal (PRA) tools to field research practice in Vietnam (Sect. 9.2) and of involving stakeholders in priority setting, modeling and environmental valuation in the Southeast Asian uplands (Sect. 9.3). Section 9.4 scrutinizes the use of the Payments for Environmental Services (PES) tool, which aims to actively engage smallholder farmers in preserving fragile mountain ecosystems in Southeast Asia by rewarding them in cash or in kind. Section 9.5 provides an example of a successful multi-stakeholder knowledge and innovation partnership in northern Thailand – in the form of a litchi processing and marketing network formed among Hmong villagers, an approach which uses a promising action-research approach towards building sustainable rural livelihoods among ethnic minority groups