BME Seminar Series: Justo Torres-Rodriguez, Michael Bush, & Ryan Somogye
"Patient specific prospective respiratory motion correction for efficient, free-breathing cardiovascular MRI"
Magnetic Resonance Imaging (MRI) has established itself as a safe and versatile imaging tool with a wide range of clinical applications. Due to relatively slow data acquisition, MRI is susceptible to motion-induced artifacts. These artifacts can lead to poor image quality, repeated scans, and decreased throughput and remain an obstacle to clinical utility. This problem is further amplified in cardiovascular magnetic resonance (CMR), where cardiac and respiratory motions coexist, and respiratory motion of the heart can range up to over 20 mm. Breath holding is commonly used to avoid respiratory effects; however, a significant fraction of patients cannot breath-hold. To allow free-breathing image acquisition, respiratory gated sequences have been developed to mitigate respiratory motion by “gating”, i.e., to restrict data acquisition to a narrow temporal window at end-expiration to capture all data during the same (or similar) phase of the respiratory cycle. Although these techniques can reduce the effects of respiratory motion, they typically reject 50% to 70% of acquired data, thereby increasing scan time by a factor of 2 to 3. To address these issues, we have developed a novel method for prospective motion correction in CMR, modeling the relationship between diaphragm position and the three-dimensional respiratory motion of the heart, and correcting for that motion in real time. Our patient-specific technique reduces in-plane and through-plane motions while maintaining 100% acquisition efficiency. PROCO has the potential to dramatically improve the efficiency and reliability of CMR by reducing acquisition time and mis registration across images acquired during free-breathing.
"Investigation of estimated pulsatile ocular blood flow variations in hemodynamically stable patients"
Perioperative visual loss (POVL) is a rare but catastrophic complication leaving the patient partially or completely blind following a non-ocular surgery. Risk factors have been identified with the highest occurrence rates in spinal, cardiac, and other lengthy procedures involving prone or steep Trendelenburg positioning. Ischemic optic neuropathy is associated with a majority of POVL outcomes, indicating a possible reduction in blood flow to the eye and nerve, however, the exact damage mechanism is not understood. This research focuses on characterizing variations in the ocular pressure waveform relative to variations in arterial and venous pressures during surgery to establish what is “normal” and what variations may indicate POVL onset.
"Fluid-structure nteraction simulations of the biomechanics of otitis media and the eustachian tube"
With an estimated $5.3 billion in treatment costs, Otitis media (OM,
any inflammation of the middle ear) is the most common disease for which children receive medical treatment in the US and the development of chronic OM is due to dysfunction of an upper respiratory airway, the Eustachian tube (ET). The anatomy of the ET is composed of a collapsible lumen, the surrounding mucosa and cartilaginous tissues as well as the tensor veli palatini and levator veli palatini muscles. Physiological function involves levator-induced anterior-posterior axial rotation (medial rotation) and tensor-assisted lumen dilation during swallowing to regulate pressures and fluid drainage from the middle ear to the nasopharynx. Although different factors precipitate the onset of OM, ET dysfunction (ETD) causes OM to persist long after the initial infection. It is not known what mechanical variables in the ET system are essential to its function and most methods that diagnose ETD are poorly understood and fail to identify therapeutic targets. Studies that attempt to
address these limitations have also failed to include important aspects of ET function, particularly the ET’s medial rotation.