Gas mixing during transport typically does not cause problems for the read out of the stored spatial information as long as there is no mixing between the individual point-by-point experiments. The main advantage of this technique is that the encoding and detection regions can be independently optimized, the former for versatility of the encoding and the latter can be optimized for sensitivity. An increased sensitivity could be achieved VX-809 order using a coil that may be smaller than the actual sample leading to an improved filling factor and the detection field strength may be higher than in the sample region. This scheme allows for samples to be used that could not be measured sensitively in an NMR experiment,

such as a magnetic porous material. The mobile

phase can be encoded within this porous substance while the detection will be spatially removed from the material. Alternatively, detection methods that are not based on Faraday inductive detection may be employed to provide Enzalutamide cost higher sensitivity [113] and [114]. While remote detection does not contain a direct spectral or imaging dimension, the arrival of the encoded gas can be monitored transiently, thereby retrieving time-of-flight information in a direct dimension. This enables visualization of flow and diffusion through, for example, a porous rock sample [115] or through microfluidic devices [116] and [117]. The gas from various regions (and therefore the encoded information) may arrive at different times (of flight) as shown in Fig. 11. The 129Xe chemical shift can also be

utilized in remotely detected MRI to separate between different environments of the gas Dolichyl-phosphate-mannose-protein mannosyltransferase flowing through porous systems [118]. Perhaps most interesting for biomedical applications, is that the remote detection concept can be extended to MRI of dissolved xenon with detection after extraction from the liquid to the gas phase via membranes [119]. Remote detection of hp gases can also be utilized for relaxation measurements and may be particularly useful for field dependent relaxometry studies [120]. As a note of caution, remote detection suffers from the absence of a direct dimension (i.e. there is no frequency encoding) because the information has to be collected point by point. For instance, a 64 × 64 two-dimensional MR image requires a minimum of 4096 scans as opposed to 64 scans for directly detected MRI. On the other hand, time-of-flight information can be recorded transiently, which facilitates a different type of direct dimension than in conventional Fourier imaging techniques. Therefore continuous flow type of experiments are probably most practical for remote detection. Further, remote detection also requires that fluctuations in the gas delivery and spin polarization are kept at a minimum although calibration experiments can sometimes correct for such fluctuations [120].