Targeting Accuracy under Model-to-Subject Misalignments in Model-Guided Cardiac Surgery

Abstract

Abstract. In image-guided interventions, anatomical models of organs are often generated from pre-operative images and further employed in planning and guiding therapeutic procedures. However, the accuracy of these models, along with their registration to the subject are crucial for successful therapy delivery. These factors are amplified when manipulating soft tissue undergoing large deformations, such as the heart. When used in guiding beating-heart procedures, pre-operative models may not be sufficient for guidance and they are often complemented with real-time, intra-operative cardiac imaging. Here we demonstrate via in vitro endocardial "therapy" that ultrasound-enhanced model-guided navigation provides sufficient guidance to preserve a clinically-desired targeting accuracy of under 3 mm independently of the model-to-subject misregistrations. These results emphasize the direct benefit of integrating real-time imaging within intra-operative visualization environments considering that modelto-subject misalignments are often encountered clinically.

Accuracy considerations in image-guided cardiac interventions: experience and lessons learned

“…While model-to patient misalignments are commonly encountered in cardiac interventions, the experiments confirmed that the real-time imaging component of the surgical guidance platform provided sufficient information to identify the correct intra-operative target location following model-assisted navigation, and compensate for the positioning error (Fig. 10), ultimately enabling consistent targeting within 1–1.5 mm [43]. …”

MRI Distortion Correction and Robot-to-MRI Scanner Registration for an MRI-Guided Robotic System

“…where α i ∈ R d are the centers for the basis functions in the Given the CT and MRI control point sets, {P, P }, the distortion correction requires computing an appropriate mapping function f (•) satisfying f (p i ) = p i for all 1 ≤ i ≤ N . This results in a system of N linear equations in N +M unknowns a i 's and b j 's (2). The additional unknowns due to the polynomials are eliminated by introducing the orthogonality conditions to ensure a unique solution [59]:…”

“…This image provides the background model. Then, the coils on top side of the pillars are activated by passing currents through coils 2 . Another multi-slice image is acquired using the same imaging sequence.…”

“…The clinicallydesired instrument to target accuracy may be defined as the maximum error that can be allowed during an intervention without putting the effect of the therapy in jeopardy or endangering the patient, where such tolerances are application specific [1]. For instance, in the case of an intracardiac ablation procedure a 3 mm instrument to target accuracy might be a clinically sufficient goal, given the ablation catheter can be manipulated with enough precision [2]. Thus, in order to achieve a clinically-desired accuracy, it is necessary to register the robot space to the scanner's image space.…”

On mixed reality environments for minimally invasive therapy guidance: Systems architecture, successes and challenges in their implementation from laboratory to clinic

“…Electromagnetic tracking systems (MTS), on the other hand, do not suffer from such limitations and allow the tracking of flexible instruments inside the body, such as a catheter tip [112], endoscope [103,113] or TEE transducer [114]. However, their performance may be limited by the presence of ferro-magnetic materials in the vicinity of the field generator, or inadequate placement of the “surgical field” within the tracking volume of the MTS.…”