Maximum intensity T-projection imaging for evaluation of patent foramen ovale

Background. Accurate diagnosis of patent foramen ovale [PFO] and grading of right-to-left shunts is often challenging. Interpretation of bubble studies may be difficult due to suboptimal image quality, high transition speed of the bubbles and inadequately performed Valsalva maneuver. We developed a new approach for simplified visualization and interpetation of bubble studies: Maximum Intensity T-Projection [MIP] Imaging.

Methods. MIP Imaging represents projection of all frames of an echocardiographic video onto one flattened image. Thus, all bubbles passing from right to left atrium are presented in one frame. The number of analyzed frames and cardiac cycles of the analyzed video can be modulated. We applied MIP Imaging to 122 echocardiographic examinations (75% of them were transesophageal), performed for detection of PFOs by injection of an intravenous bolus of bubbles during the studies. We evaluated feasibility and efficacy of MIP Imaging as a complementary tool for the diagnosis of PFO.

Results. Mean time needed for manual frame-by-frame analysis of video loops taken during bubble injection was 102±52sec. Producing and interpreting a MIP Image took less than 1 second. There was full agreement between conventional echocardiography and MIP Imaging in the diagnosis of PFO.

Conclusion. MIP Imaging is simple to perform, is much less time consuming then the classical method and it is at least as accurate as the classical method for detection of PFOs. MIP Imaging may be a useful complementary method for diagnosing PFOs and for significantly reducing the overall time necessary for reaching the diagnosis from echocardiographic bubble-studies.