# Soft X-ray Microscopy Techniques for Medical and Biological Imaging at TwinMic--[PERSON]
## 3 Results
### Compressive Sensing  
Even though compressive sensing XRF can be applied to any kind of sample, it appears to be particularly useful for biological/medical samples, where the specimens are often of irregular shapes or discontinuous by nature (such as cell or alveolar structures in lungs) and with chemical elements of interest located in specific limited areas. On the other hand, for such kind of samples, in order to collect statistically significant data, it may be necessary to scan large areas (millimeters wide) or several samples/patients. In this section, we thus present two examples that allow us to appreciate the benefits of the compressive sensing approach in biology and medicine. The first example applies to a specific field of growing interest in biomedical research due to recent and pressing concerns over viruses and pathogens, especially in relation to pandemics and the climate crisis [87; 88]. In particular, the study of insects, and more widely, of other arthropods and invertebrates, can bring fundamental insights when dealing with pathogens causing diseases potentially harmful or fatal for humans [89]. Insects are indeed often vector/carriers for the transmission of known pathogens and might also foster the spread of novel virulence factors into existing ones [90; 91]. Moreover, many invertebrates possess highly specific virus-host interactions and immune responses, as well as a variety of regulatory mechanisms either to eliminate toxic compounds from their cells, or to balance the uptake of specific elements and intracellular sequestration [92]. The TwinMic setup, combined with compressive sensing acquisition, allows for a more efficient STXM-LEXRF analysis for insect systems, providing both the scan of the entire specimen and the spatial distributions of elements with micrometric resolution. The example in Figure 9 shows results of a study on Rhodrius prolixus that may be of significance for vector control studies, particularly toward the control of the Chagas Disease [80; 93]. LEXRF maps allow the study of tissue/organ-specific accumulation patterns, as well as element distributions in various insect's life stages, which may have significant implications for toxicology and medicine. More generally, this kind of information can help in understanding insect-virus interactions and the modality of transmission with vertebrates. This case exemplifies how compressive sensing can vastly improve time-effective acquisition, which is very advantageous for the scanning of large areas or a large sample set. Indeed, by acquiring the XRF signal only in the areas with an absorption signal below a specific threshold, only 21% of the total area was mapped without losing essential information, allowing one to save around 79% of the total time required with a standard LEXRF rectangular mapping. The absorption threshold was defined by acquiring a low-resolution STXM scan with step size of 5 \(\upmu\)m. The overall complete STXM scan (Figure 9) coupled with selective LEXRF mapping (Figure 10) lasted 42 h.  
The distributions of C, O, Na, Mg, Al, and Fe are shown in Figure 10, which can be correlated to the insect morphological features shown in Figure 9[80]. The second example of compressive sensing LEXRF concerns the research field of imaging combined with element localization in extended organs, such as arteries and aortic arch [81]. XRF has been shown to be a powerful tool to investigate aortic systems in connection to several medical treatments and diseases, e.g., atherosclerotic plaques [94; 95] radiotherapy and chemotherapy treatments [96] or calcification effects [37; 97]. Moreover, the same technique can reveal interesting connections between the distribution of specific elements and physical and mechanical properties of aortic media, as presented in the work of [PERSON] and coauthors [98].