In vivo MRS for the assessment of mouse colon using a dedicated endorectal coil: initial findings

Abstract

Inflammatory bowel disease is a common group of inflammation conditions that can affect the colon and the rectum. These pathologies require a careful follow-up of patients to prevent the development of colorectal cancer. Currently, conventional endoscopy is used to depict alterations of the intestinal walls, and biopsies are performed on suspicious lesions for further analysis (histology). MRS enables the in vivo analysis of biochemical content of tissues (i.e. without removing any samples). Combined with dedicated endorectal coils (ERCs), MRS provides new ways of characterizing alterations of tissues. An MRS in vivo protocol was specifically set up on healthy mice and on mice chemically treated to induce colitis. Acquisitions were performed on a 4.7 T system using a linear volume birdcage coil for the transmission of the B magnetic field, and a dedicated ERC was used for signal reception. Colon-wall complex, lumen and visceral fat were assessed on healthy and treated mice with voxel sizes ranging from 0.125 μL to 2 μL while keeping acquisition times below 3 min. The acquired spectra show various biochemical contents such as α- and β-methylene but also glycerol backbone and diacyl. Choline was detected in tumoral regions. Visceral fat regions display a high lipid content with no water, whereas colon-wall complex exhibits both high lipid and high water contents. To the best of our knowledge, this is the first time that in vivo MRS using an ERC has been performed in the assessment of colon walls and surrounding structures. It provides keys for the in vivo characterization of small local suspicious lesions and offers complementary solutions to biopsies.

Comparison of MRI‐derived vs. traditional estimations of fatty acid composition from MR spectroscopy signals

“…Lipid MRS is a simple and fast tool to analyze metabolic modification when quantifying fatty acid: it could be advantageous in the follow‐up of the lipid composition modification in adipose tissues in weight gain or weight loss phases, in the evaluation of fat surrounding a tumor or in inflammatory tissue . However, the fatty acid composition modifications could be very small in comparison with the measurement uncertainties related to the current methods.…”

Feasibility and characterization of a safe susceptibility‐matched endorectal coil for MR spectroscopy

“…Besides, compared with the SNR obtained with a 32‐channel torso coil, which is often used in the examination of the abdomen and rectal wall 34,35 for rectal cancer staging, the SNR of the endorectal coil is significantly superior within a radius of 3.5 cm, corresponding to the targeted region of interest. This would be relevant for in vivo MRI and even more so in MRS 14 where in vivo metabolite concentrations are lower than in the phantom used. Hence, the extra SNR could be used to either reduce the voxel size or to reduce the acquisition time.…”

“…For instance, MRS provides relevant information on the metabolism of prostate cancer by locating and measuring levels of citrate, choline, creatine and polyamines 12,13 . The use of endorectal coils improve SNR and give access to higher spatial and temporal resolution that may also be useful for diagnosing and monitoring inflammatory bowel disease 14 . Clinical PECs are either flexible coils surrounded by a balloon inflated with air intended to prevent coil migration and unfold the loop coil (eg, Medrad Prostate eCoil from Medrad or PMS Endo Coil Intera from Invivo) or rigid coils whose migration is prevented by a rigid arm (eg, Sentinelle Endo Coil Array System from Hologic).…”

Optical Link as an Alternative for MRI Receive Coils: Toward a Passive Approach

“…Involving arrays of surface coils with many elements, which is the trend in MR coils currently [4,5], this solution is of significant weight. Moreover, cable traps are so cumbersome that they still would not enable proper insertion of endoluminal coils to the area of interest during most cases of digestive tract exploration [6,7]. Great efforts have been made to reduce the size and weight of baluns.…”