Magnetic Resonance Spectroscopy as a diagnostic tool for Chronic Splanchnic Syndrome

Leersum, C.M. (2015) Magnetic Resonance Spectroscopy as a diagnostic tool for Chronic Splanchnic Syndrome.

Abstract:Stenosis or occlusion of the celiac artery (CA), the superior mesenteric artery (SMA) and/or the inferior mesenteric artery (IMA), most commonly caused by atherosclerosis, can lead to ischemia of the intestines. In this master thesis a new diagnostic tool to diagnose chronic splanchnic disease (CSD) and chronic splanchnic syndrome (CSS) is investigated for further development. Nowadays the diagnostic process encompasses first the anamneses. The symptoms of the classical triad are questioned; these three characteristic ischemic symptoms are postprandial pain, loss of weight, and epigastric bruit. Secondly, non-invasive as well as invasive diagnostic tools, have to be taken into account. All results are discussed with several specialists, a vessel surgeon, gastrointestinal surgeon, and radiologist, to complete the diagnostic process. This study is aimed to ease the diagnosis with a diagnostic tool that is beneficial for the patients and the physicians. The ‘new’ diagnosis should be less invasive, time consuming and usable at multiple locations as the complicated current diagnosis of CSD or CSS. Lactate is a potential marker for ischemia, because it is generated as the end product of anaerobic glycolysis. For the diagnosis of patient with CSD or CSS, the lactate concentration can be measured in the intestinal circulation, the portal vein. The main idea in this research line is to analyse portal flow Magnetic Resonance Spectroscopy (MRS) as a diagnostic tool to distinguish between CSD or CSS. MRS is a non-invasive and non-harmful technology to image the human body. In previous studies it seems that lactate was not detectable in a flowing solution with a velocity above 65 ml/min. This study will use another sequence with which it seems to be possible to measure lactate. Multiple experiments are performed to answer the following question: ‘Is it possible to measure physiological and pathological concentrations of lactate in the portal vein with the use of Magnetic Resonance Spectroscopy, to diagnose patients with Chronic Splanchnic Syndrome?’ This study contains seven different experiments. First, sequence determination, in which a suitable sequence is determined for the detection of lactate in volume flow velocities above 65 ml/min. This is possible with the preprogrammed [csi_fid_bir45_nodec_lowres] sequence, consisting of Chemical Shift Imaging (CSI) and B1-insensitive rotation (BIR). The goal in the second experiment is to detect lactate in a velocity above human blood flow, around 1000 ml/min. The velocity is stepwise increased and it seems that at a velocity of 1350 ml/min lactate is still detectable with MRS. A surface coil is used in the previous two parts, which is not suitable to measure a human body. In the third experiment different coils are used, after which it is concluded that an extended version of the portal vein phantom is necessary to use a body with spine coil combination. This combination is closest to real clinical settings and therefore desirable. The fourth experiment starts with the extended portal vein phantom. The tube mimicking the portal vein is situated in a box which mimics the human tissue. The height of the tube can be adjusted in this phantom, however, it is possible to detect lactate at almost all positions of the tube inside the body. All these experiments are performed with a 20 mM lactate concentration, which is at the high end of pathological lactate concentrations. In the fifth experiments, the lactate concentration is lowered stepwise from pathological to physiological lactate concentrations. Although it is shown that a 2.5 mM lactate concentration is still detected, this part of the research needs follow up. For example by repetition of the same experiment with the use of a newly prepared lactate solution and/or different dilution steps. The last two experiments of this thesis are to determine the possibility to measure lactate in a solution with other molecules. In the sixth part, lactate in fat emulsion, a lactate with lipids solution is prepared. This solution is used to see the influence of lipids on the lactate doublet in the spectrum acquired with MRS. It is know that lipids overlap the lactate peaks. However, it seems that it is possible to distinguish between lactate and lipids, for example with the use of a different program for data analysis or a different sequence. Further research is necessary to investigate the possibilities to distinguish the lactate doublet from the lipid peaks. The same applies for the last and seventh part of this study. Two measurements in healthy human test subjects are performed to see the capability of the CSI sequence to detect the portal vein and generate a spectrum. The portal vein is detectable and MRS can be performed in this portal vein, but it is not certain whether the lactate peak can be distinguished. In conclusion, it is possible to measure pathological lactate concentrations, ranging from 2.5 to 50 mM, in a flow model comparable to the human portal blood flow. MRS is a promising diagnostic tool to diagnose CSD or CSS, but some technical hurdles need to be overcome before clinical studies are started. The aim for further research should be to investigate the options to distinguish the lactate doublet from the overlapping lipid peaks. When this becomes possible and clinical studies can be performed, it can be discussed whether or not MRS is less invasive and time consuming technology for the diagnosis of intestinal ischemia.
Item Type:Essay (Master)
Faculty:TNW: Science and Technology
Subject:33 physics, 44 medicine
Programme:Technical Medicine MSc (60033)
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