PubMed · 9798575
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R Lord. 1998. Central venous cannulation.. https://pubmed.ncbi.nlm.nih.gov/9798575/
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The incorporation of RF coils into the tips of intravascular devices has been shown to enable the localization of catheters and guidewires under MR guidance. Furthermore, such coils can be used for endoluminal imaging. The long cable required to connect the coil with the scanner input inadvertently acts as a dipole antenna which picks up RF energy from the body coil during transmit. Currents are induced on the cable which can lead to localized heating of surrounding tissue. Cables of various lengths were measured to determine if a resonance in the heating as a function of cable length could be found. Coaxial chokes with a length of lambda/4 were added to coaxial cables to reduce the amplitude of the currents induced on the cable shield. A 0.7-mm diameter triaxial cable, small enough to fit into a standard intravascular device, was developed and measured both with and without a coaxial choke. It is demonstrated that resonant heating does occur and that it can be significantly reduced by avoiding a resonant length of cable and by including coaxial chokes on the cable.
BACKGROUND: Central catheters in neonatological intensive care patients are used for the prolonged application of medication or parenteral infusions. Dislocations and septic and thromboembolic complications may occur. CONTROL OF POSITION: Radiologically, the correct position of the catheter must be proven. Dislocations or complications associated with central catheters must be diagnosed. For catheter monitoring plain film radiographs are the first line of investigation; however, sonography may be of additional assistance. Angiographic techniques should only be performed when conventional noninvasive methods do not supply satisfactory results. Special knowledge is necessary for monitoring catheters that are set via the umbilical artery or vein. The radiological applications for catheter monitoring in the neonate intensive care unit are discussed in this article.