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Dan Leotta

Senior Engineer

Email

leotta@uw.edu

Phone

206-616-6787

Education

B.S. Bioengineering, Syracuse University, 1982

M.S. Electrical Engineering, Massachusetts Institute of Technology, 1985

Ph.D. Bioengineering, University of Washington, 1998

Publications

2000-present and while at APL-UW

Measurement of transcranial Doppler insonation angles from three-dimensional reconstructions of CT angiography scans

Leotta, D.F., M. Anderson, A. Straccia, R.E. Zierler, A. Aliseda, F.H. Sheehan, and D. Sharma, "Measurement of transcranial Doppler insonation angles from three-dimensional reconstructions of CT angiography scans," J. Clin. Monit. Comput., EOR, doi:10.1007/s10877-024-01187-6, 2024.

More Info

16 Aug 2024

Blood velocities measured by Transcranial Doppler (TCD) are dependent on the angle between the incident ultrasound beam and the direction of blood flow (known as the Doppler angle). However, when TCD examinations are performed without imaging the Doppler angle for each vessel segment is not known. We have measured Doppler angles in the basal cerebral arteries examined with TCD using three-dimensional (3D) vessel models generated from computed tomography angiography (CTA) scans. This approach produces angle statistics that are not accessible during non-imaging TCD studies. We created 3D models of the basal cerebral arteries for 24 vasospasm patients. Standard acoustic windows were mapped to the specific anatomy of each patient. Virtual ultrasound transmit beams were generated that originated from the acoustic window and intersected the centerline of each arterial segment. Doppler angle measurements were calculated and compiled for each vessel segment. Doppler angles were smallest for the middle cerebral artery M1 segment (median 24.6°) and ophthalmic artery (median 25.0°), and largest for the anterior cerebral artery A2 segment (median 76.4°) and posterior cerebral artery P2 segment (median 75.8°). The ophthalmic artery had the highest proportion of Doppler angles that were less than 60° (99%) while the anterior cerebral artery A2 segment had the lowest proportion of Doppler angles that were less than 60° (10%). These angle measurements indicate the expected deviation between measured and true velocities in the cerebral arteries, highlighting specific segments that may be prone to underestimation of velocity.

A novel 4D volumetric M-mode ultrasound scanning technique for evaluation of intravascular volume and hemodynamic parameters

Patel, S., E. Kao, X. Wang, K. Ringgold, J. Thiel, N. White, S. Aarabi, and D.F. Leotta, "A novel 4D volumetric M-mode ultrasound scanning technique for evaluation of intravascular volume and hemodynamic parameters," WFUMB Ultrasound Open, 2, doi:10.1016/j.wfumbo.2024.100058, 2024.

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25 Jul 2024

Introduction: We use a novel 4-dimensional (4D) volumetric M-mode (VMM) ultrasound (US) technique to assess intravascular volume by monitoring the inferior vena cava (IVC). The VMM method expands the spatial coverage of standard M-mode scanning (depth vs time) by including lateral image direction and adds transducer tilt to cover the region surrounding the IVC. Current ultrasound methods for volume assessment suffer from intra- and inter-operator variability. The VMM technique aims to address these limitations, aiding in early detection of hypovolemia/hemorrhage and guiding resuscitation.
Methods/technical approach: The 4D VMM technique was used on animals that underwent a swine hemorrhagic shock protocol with fluid resuscitation. 2D ultrasound images obtained were formatted in a 3D volume to capture changes over time in vessel size with respiration and volume status. Planes were then extracted from the 3D volume at multiple lateral locations to find and track the IVC. The vessel walls were manually traced on vertical planes (depth vs. time) to determine mean IVC diameter and IVC collapsibility at each measurement time point in the shock/resuscitation protocol. Planes at constant depth (lateral vs. time) were selected to extract respiratory and cardiac cycle data.
Results: Mean IVC diameter in the baseline phase was significantly greater than in the hemorrhage phase (p = 0.020). There was no significant different in mean IVC diameter between baseline and resuscitation (p = 0.064) or hemorrhage and resuscitation phases (p = 0.531). There was no statistically significant difference in mean collapsibility or ΔIVC diameter between protocol phases. The 4D VMM technique effectively measured heart and respiratory rates, consistent with monitored vitals.
Conclusion: 4D VMM identified IVC changes corresponding to blood loss and resuscitation during hemorrhagic shock as well as heart/respiratory rates. This innovative approach holds promise in reducing operator variability and providing actionable information during treatment of shock.

Numerical modeling of flow in the cerebral vasculature: Understanding changes in collateral flow directions in the Circle of Willis for a cohort of vasospasm patients through image-based computational fluid dynamics

Straccia, A., and 9 others including D. Leotta, "Numerical modeling of flow in the cerebral vasculature: Understanding changes in collateral flow directions in the Circle of Willis for a cohort of vasospasm patients through image-based computational fluid dynamics," Ann. Biomed. Eng., EOR, doi:10.1007/s10439-024-03533-w, 2024.

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17 May 2024

The Circle of Willis (CoW) is a ring-like network of blood vessels that perfuses the brain. Flow in the collateral pathways that connect major arterial inputs in the CoW change dynamically in response to vessel narrowing or occlusion. Vasospasm is an involuntary constriction of blood vessels following subarachnoid hemorrhage (SAH), which can lead to stroke. This study investigated interactions between localization of vasospasm in the CoW, vasospasm severity, anatomical variations, and changes in collateral flow directions. Patient-specific computational fluid dynamics (CFD) simulations were created for 25 vasospasm patients. Computed tomographic angiography scans were segmented capturing the anatomical variation and stenosis due to vasospasm. Transcranial Doppler ultrasound measurements of velocity were used to define boundary conditions. Digital subtraction angiography was analyzed to determine the directions and magnitudes of collateral flows as well as vasospasm severity in each vessel. Percent changes in resistance and viscous dissipation were analyzed to quantify vasospasm severity and localization of vasospasm in a specific region of the CoW. Angiographic severity correlated well with percent changes in resistance and viscous dissipation across all cerebral vessels. Changes in flow direction were observed in collateral pathways of some patients with localized vasospasm, while no significant changes in flow direction were observed in others. CFD simulations can be leveraged to quantify the localization and severity of vasospasm in SAH patients. These factors as well as anatomical variation may lead to changes in collateral flow directions. Future work could relate localization and vasospasm severity to clinical outcomes like the development of infarct.

More Publications

Inventions

Fenestration template for endovascular repair of aortic aneurysms

Patent Number: 9,811,613

Dan Leotta, Benjamin Starnes

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Patent

7 Nov 2017

To provide simple yet accurate stent graft fenestration, a patient-specific fenestration template is used as a guide for graft fenestration. To generate the fenestration template, a patient's medical imaging data such as CT scan data may be used to generate a 3-D digital model of an aorta lumen of the patient. The aorta lumen may encompass one or more branch vessels, which may be indicated on the 3-D digital model. Based on the 3-D digital model or a segment thereof, the fenestration template may be generated, for example, using 3-D printing technology. The fenestration template may include one or more holes or openings that correspond to the one or more branch vessels. To fenestrate a stent graft, the fenestration template is coupled to the stent graft so that the holes or openings on the fenestration template indicate the fenestration locations.

Fenestration template for endovascular repair of aortic aneurysms

Patent Number: 9,305,123

Dan Leotta, Benjamin Starnes

More Info

Patent

5 Apr 2016

To provide simple yet accurate stent graft fenestration, a patient-specific fenestration template is used as a guide for graft fenestration. To generate the fenestration template, a patient's medical imaging data such as CT scan data may be used to generate a 3-D digital model of an aorta lumen of the patient. The aorta lumen may encompass one or more branch vessels, which may be indicated on the 3-D digital model. Based on the 3-D digital model or a segment thereof, the fenestration template may be generated, for example, using 3-D printing technology. The fenestration template may include one or more holes or openings that correspond to the one or more branch vessels. To fenestrate a stent graft, the fenestration template is coupled to the stent graft so that the holes or openings on the fenestration template indicate the fenestration locations.

Acoustics Air-Sea Interaction & Remote Sensing Center for Environmental & Information Systems Center for Industrial & Medical Ultrasound Electronic & Photonic Systems Ocean Engineering Ocean Physics Polar Science Center
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