Dr. Ayca Z. Kutlu Profile

Dr. Ayca Z. Kutlu

at Univ of Wisconsin-Madison

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Publications (3)

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Proceedings Article | 1 April 2024 Presentation + Paper

FEM deformable liver registration to facilitate CBCT guided histotripsy

Grace Minesinger, Paul Laeseke, Ayca Kutlu, Michael Speidel, Martin Wagner

Proceedings Volume 12925, 129251T (2024) https://doi.org/10.1117/12.3006515

KEYWORDS: Liver, Image segmentation, Cone beam computed tomography, Finite element methods, Image registration, Deformation, Motion models, Blood vessels

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Histotripsy is an emerging focal tumor therapy that utilizes focused ultrasound (US) to mechanically destroy tissue. Cone beam CT (CBCT) guidance has been developed to overcome limitations of diagnostic US for visualizing and targeting tumors. Existing workflow for CBCT-guided histotripsy utilizes targeting based on CBCT images acquired with the patient in position for treatment; therefore, treatment planning is currently performed intraprocedurally right before delivering therapy. To provide a framework for planning liver tumor treatments in advance, a biomechanical, nonrigid model is proposed to predict volumetric liver deformations between a pre-procedural diagnostic scan and the intraprocedural CBCT. In the proposed registration approach, the liver, gallbladder (GB), and hepatic blood vessels were segmented from CBCT images acquired at two different points of motion. Segmented structural surfaces were registered using a rigid iterative closest point algorithm followed by deformable registration (demons algorithm). These internal and external hepatic structural surface registrations were used as boundary conditions for a finite element model (FEM) to determine internal liver deformations. Four FEM models were constructed: the liver alone (L-FEM), liver and GB (LG-FEM), liver and vessels (LV-FEM), and liver, GB, and vessels (LGV-FEM). Registration accuracy was measured as the Euclidean distance between manually annotated vessel bifurcations. Bifurcation error was 3.5±3.5mm for LGV-FEM, a 52% improvement from L-FEM (7.4±6.1mm). Including vessels and GB in the model both individually reduced bifurcation error compared to corresponding models excluding those structures. FEM-based liver registration guided by internal and external hepatic structures is a feasible method to facilitate CBCT-guided histotripsy treatment planning.

Proceedings Article | 1 April 2024 Poster + Paper

Comparison of model-based iterative vs non-iterative 3D device reconstruction for continuous-sweep limited-angle fluoroscopy

Martin Wagner, Ayca Kutlu, Brian Davis, Paul Laeseke, Amish Raval, Michael Speidel

Proceedings Volume 12925, 129253U (2024) https://doi.org/10.1117/12.3006315

KEYWORDS: 3D modeling, Image segmentation, Reconstruction algorithms, Instrument modeling, 3D image reconstruction, Model based design, 3D equipment, Fluoroscopy, Cone beam computed tomography, 3D projection

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Continuous-sweep limited angle (CLA) fluoroscopy is a recently proposed method for live 3D catheter reconstruction using a single-plane C-arm that continuously rotates back-and-forth within a narrow angle during fluoroscopic image acquisition. This study compares the accuracy and computation time of two real-time 3D catheter reconstruction algorithms. The first approach, iterative model-based device reconstruction (MDR), optimizes the 3D location of 8 control points representing the catheter as a cubic spline. Optimization was performed by minimizing a cost function that describes the data consistency between reconstructed shape and 2D catheter segmentations in the current and previous fluoroscopic images. Alternatively, the second approach is a topology observing reconstruction (TOR) algorithm, which reduces the solution space by performing a graph-based analysis of the 3D vessel tree followed by an analytical minimization of a simplified cost function. Both approaches were evaluated in an experimental study where a microcatheter was navigated through a 3D printed vessel phantom. Accuracy was determined by comparing the reconstructed final catheter pose to a reference 3D cone beam CT scan. The root mean squared distance (RMSD) between reference and CLA reconstruction was considerably smaller for the TOR approach (1.88 ± 0.34mm) than for MDR (6.78 ± 4.4mm). Computation time was also shorter for TOR (0.34ms) compared to MDR (518.6ms) making it suitable for real-time reconstruction with clinically relevant frame rates. The clinical translation of CLA could improve procedure efficiency by providing an intuitive 3D visualization of the device within a vessel. Further work is needed to evaluate the approach in vivo in the presence of respiratory motion.

Proceedings Article | 7 April 2023 Presentation + Paper

A histotripsy targeting approach using a mobile C-arm

Martin Wagner, Paul Laeseke, Ayca Kutlu, Grace Minesinger, Sarvesh Periyasamy, Michael Speidel

Proceedings Volume 12463, 124630O (2023) https://doi.org/10.1117/12.2654002

KEYWORDS: Calibration, Cone beam computed tomography, Robotics, Transducers, Ultrasonography, Tumors, Pose estimation, 3D acquisition, Ultrasound transducers, Image segmentation

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Histotripsy is an emerging noninvasive, nonthermal, and nonionizing tumor treatment, which uses focused ultrasound to mechanically destroy tissue. Currently, targeting is performed using ultrasound imaging, which can be operator dependent. Additionally, many tumors cannot be seen or are poorly visualized on ultrasound due to obstructions, patient size, location, or echogenicity. In these cases, energy delivery for histotripsy treatment may still be possible if alternative targeting techniques are available. In this study, a mobile C-arm based targeting approach is presented, where a tumor can be selected on a 3D cone beam CT (CBCT) and automatically targeted using a histotripsy system with a robotic arm. To this end, a hand-eye calibration technique between a mobile C-arm and robotic arm was developed, where a CBCT and eight 2D x-ray acquisitions of a calibration phantom in different poses were acquired. The phantom poses in the CBCT coordinate system were estimated using a 2D/3D pose estimation approach and the corresponding robot end effector poses in the robot coordinate system were determined from the joint angles. A dual quaternion approach was then used to determine the relationship between C-arm and robot. During treatment, the histotripsy transducer can be aligned on a target using the calibrated robotic arm. Nine dual-modality soft-tissue mimicking phantoms were treated, and the resulting treatment zones were manually segmented from post-treatment CBCTs as reference. The average Euclidean distance between planned and actual treatment centers was 0.81 ± 0.45mm. This approach could considerably increase the number of patients that could benefit from histotripsy treatment, reduce operator dependency, and facilitate clinical translation of histotripsy.

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