Evaluation of the NMR-MOUSE as a new method for continuous functional monitoring of the small intestine during different perfusion states in a porcine model

Abstract

ObjectiveThe study aim was to evaluate a small low-field NMR (nuclear magnetic resonance) scanner, the NMR-MOUSE®, for detecting changes in intestinal diffusion under different (patho-) physiological perfusion states.MethodsLaparotomy was performed on 8 female landrace pigs (body weight 70±6 kg) and the feeding vessels of several intestinal loops were dissected. Successively, the intestinal loops were examined using O2C (oxygen to see, LEA Medizintechnik GmbH, Giessen, Germany) for microcirculatory monitoring and the NMR-MOUSE® for diffusion measurement (fast and slow components). On each loop the baseline measurement (physiological perfusion) was followed by one of the following main procedures: method 1 –ischemia; method 2 –flow reduction; method 3 –intraluminal glucose followed by ischemia; method 4 –intraluminal glucose followed by flow reduction. Additionally, standard perioperative monitoring (blood pressure, ECG, blood gas analyses) and histological assessment of intestinal biopsies was performed.ResultsThere was no statistical overall time and method effect in the NMR-MOUSE measurement (fast component: ptime = 0.6368, pmethod = 0.9766, slow component: ptime = 0.8216, pmethod = 0.7863). Yet, the fast component of the NMR-MOUSE measurement showed contrary trends during ischemia (increase) versus flow reduction (decrease). The slow-to-fast diffusion ratio shifted slightly towards slow diffusion during flow reduction. The O2C measurement showed a significant decrease of oxygen saturation and microcirculatory blood flow during ischemia and flow reduction (p < .0001). The local microcirculatory blood amount (rHb) showed a significant mucosal increase (pClamping(method 1) = 0.0007, pClamping(method 3) = 0.0119), but a serosal decrease (pClamping(method 1) = 0.0119, pClamping(method 3) = 0.0078) during ischemia. The histopathological damage was significantly higher with increasing experimental duration and at the end of methods 3 and 4 (p < .0001,Fisher-test).ConclusionMonitoring intestinal diffusion changes due to different perfusion states using the NMR-MOUSE is feasible under experimental conditions. Despite the lack of statistical significance, this technique reflects perfusion changes and therefore seems promising for the evaluation of different intestinal perfusion states in the future. Beforehand however, an optimization of this technology, including the optimization of the penetration depth, as well as further validation studies under physiological conditions and including older animals are required.

When the MOUSE leaves the house

“…2i) (Van Landeghem et al, 2012). With this sensor the time to acquire a depth profile into soft matter was reduced considerably, and it proved useful for in vivo applications like mapping human skin and monitoring perfusion states of the small intestine by diffusion maps (Keschenau et al, 2018).…”

“…Blümich and J. Anders: When the MOUSE leaves the house ratus (Varian, 2021;Woessner, 2001). The sensor to be inserted into the borehole of an oil well and operating in the earth's magnetic field eventually evolved into tube-shaped instruments housing permanent magnets as well as transmit and receive electronics to analyze the relaxation of 1 H NMR signals from particular regions localized in the borehole wall (Jackson et al, 1980;Kleinberg and Jackson, 2001). In his introduction to the 2016 book Mobile NMR and MRI , Eiichi Fukushima reviews the evolution of earthfield and mobile NMR with particular attention to these early developments (Fukushima, 2016).…”

Quantitative measurement of mammographic density in breast‐tissue explants using portable NMR: Precision and accuracy

“…32,35 In addition to breast imaging, the utility of pNMR and MRI for the measurement of compositional, structural, and functional characteristics of biological tissues has been demonstrated in a range of other prospective applications including the nervous system, [38][39][40][41] skin, [42][43][44][45][46] cardiovascular and respiratory system, 47-49 musculoskeletal system, [50][51][52][53][54][55][56] and other internal organs. [57][58][59][60] These studies have covered the measurements both in vitro 41,50,[52][53][54]56 and in vivo in test animals 38,51,58 and in humans. 42,44,61 This body of experimental results shows that portable MR techniques, including single-sided pNMR, hold significant promise as a clinical imaging modality that could complement the existing clinical MRI.…”

Oxygen saturation-dependent effects on blood transverse relaxation at low fields

“…Magnetic resonance systems that operate at lower fields than conventional scanners have been developed to achieve this goal [3,4]. MRI contrast mechanisms have also been applied in portable low field MR relaxometry devices, which may unlock new uses of magnetic resonance for point of care diagnosis and monitoring [5][6][7][8][9][10].…”