Abstract Archives of the RSNA, 2011
MRI Triggering by a Cardiotocograph at 1.5 T for Future Fetal Cardiac Function Investigation
Scientific Informal (Poster) Presentations
Presented on November 30, 2011
Presented as part of LL-CAS-WE: Cardiac
Jin Yamamura MD, Presenter: Nothing to Disclose
Bjoern Schoennagel, Abstract Co-Author: Nothing to Disclose
Chressen Catharina Much, Abstract Co-Author: Nothing to Disclose
Roland Fischer Dipl Phys, Abstract Co-Author: Nothing to Disclose
Kurt Hecher MD, Abstract Co-Author: Nothing to Disclose
Gerhard B. Adam MD, Abstract Co-Author: Nothing to Disclose
Ulrike Wedegaertner MD, Abstract Co-Author: Nothing to Disclose
To perform cardiac MR imaging of the fetal heart in utero using a Doppler ultrasound probe of a standard cardiotocograph (CTG) as a triggering device and to compare the images with those from pulse-wave (PW) triggering.
All magnetically perturbing components of the CTG's ultrasound transducer were replaced by non-magnetic materials. The CTG signal was protected against the electro-magnetic interference between the 65 MHz MR signal. MRI measurements were performed on 4 pregnant ewes carrying singleton fetuses. The fetuses were chronically instrumented with a carotid catheter to measure the fetal heart frequency for the PW triggering. The fetal heart rate (FetHR) was recorded by newly developed MR compatible ultrasound transducer of the CTG. Retrospective fetal cardiac PW and CTG gating was used on a 1.5 T MRI. GRAPPA retrogated Cine-MRI sequence was used in short axis, four and two chamber view. Skin exposure to local heat generation by eddy currents and RF energy absorption in the shielded ultrasound probe and its cable were tested by two adult subjects and was measured by using a MRI compatible thermometer.
After removing all perturbing components the artifacts of the probe itself were reduced. For both techniques, an adequate quantitative measurement was possible. Left-ventricular functions of the fetuses were measured form the short axis as well as from the four chamber views to assess the temporal left ventricular stroke volume and ejection fraction. The resulting ventricular filling rate patterns are very similar indicating that the CTG is registering the fetal heart beat with the same precision as the reference PW trigger. The thickness of the septum and the LV wall were 0.9 cm and 0.8 cm in diastole and 1.0 cm und 1.3 cm in systole, respectively, in both techniques and no differences could be measured. No local temperature increase was sensed during cardiac function assessment using the CTG and the PW- trigger.
The newly developed MR compatible cardiotocograph with its ultrasound transducer allowed a sufficient cardiac triggering of the fetal heart without artifacts. The so obtained cardiac MR images were comparable and as sufficient as pulse wave triggered MR images.
Not only can the newly developed device used as triggering device for fetal cardiac MRI in utero, but also for monitoring the fetus during fetal MRI itself.
MRI Triggering by a Cardiotocograph at 1.5 T for Future Fetal Cardiac Function Investigation. Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11034644.html