Artifacts in MR Imaging due to ventilation tubes.

Purpose: MR examinations may be necessary in patients under artificial vent ilation. Possible imaging artifacts originating from ventilation tubing mad e from silicone are demonstrated. Materials and Methods: In silicone carboh ydrate residues are bound to silicon atoms. In silicone gels they give stro ng signals in MR imaging. MR signals from more solid silicone rubber are on ly possible if the carbohydrate residues in the molecular chain retain a su fficient mobility. To investigate whether silicone tubes give signals in MR images, different tubes for ventilation made from silicone and polyester w ere examined at 1.5T (Gyroscan ACS NT, Powertrak 6000 gradients) with MR im aging and spectroscopy (MRS: PRESS, TE=20ms; relaxation time measurements: MIXED sequence; imaging: FFE [gradient echo] and TSE sequences). Results. U sing short TE (less than or equal to4 ms), tubes and sockets made from sili cone could be imaged with FFE and SE sequences. An SE sequence with a short TE=4 ms provided a sufficient signal intensity to depict the tube clearly besides brain tissue of a volunteer. When foldover occured, the signal of t he tube was projected onto the brain tissue. MR spectra confirmed that the image signal originated from the carbohydrate residues of the silicone mole cule chains, not from residual water in the tube wall material. T-2 determi nations indicate a multiexponential relaxation including a large component with a short TE (less than or equal to 15 ms). Tubes made from a polyester elastomere did not show up in MR images. Conclusion: In MR images acquired with very short echo times silicone in ventilation tubes may produce signif icant artifacts.