Although robot-assisted coronary artery bypass grafting (RA-CABG) has gained more acceptance worldwide, its success still depends on the surgeon’s experience and expertise, and the conversion rate to full sternotomy is in the order of 15%–25%. One of the reasons for conversion is poor pre-operative planning, which is based solely on pre-operative computed tomography(CT)images. In this paper, the authors propose a technique to estimate the global peri-operative displacement of the heart and to predict the intra-operative target vessel location, validated via both anin vitro and a clinical study.Methods:
As the peri-operative heart migration during RA-CABG has never been reported in the literatures, a simplein vitro validation study was conducted using a heart phantom. To mimic the clinical workflow, a pre-operative CT as well as peri-operative ultrasoundimages at three different stages in the procedure (Stage0—following intubation; Stage1—following lung deflation; and Stage2—following thoracic insufflation) were acquired during the experiment. Following image acquisition, a rigid-body registration using iterative closest point algorithm with the robust estimator was employed to map the pre-operative stage to each of the peri-operative ones, to estimate the heart migration and predict the peri-operative target vessel location. Moreover, a clinical validation of this technique was conducted using offline patient data, where a Monte Carlo simulation was used to overcome the limitations arising due to the invisibility of the target vessel in the peri-operative ultrasoundimages.Results:
For thein vitro study, the computed target registration error (TRE) at Stage0, Stage1, and Stage2 was 2.1, 3.3, and 2.6 mm, respectively. According to the offline clinical validation study, the maximum TRE at the left anterior descending (LAD) coronary artery was 4.1 mm at Stage0, 5.1 mm at Stage1, and 3.4 mm at Stage2.Conclusions
: The authors proposed a method to measure and validate peri-operative shifts of the heart during RA-CABG.In vitro and clinical validation studies were conducted and yielded a TRE in the order of 5 mm for all cases. As the desired clinical accuracy imposed by this procedure is on the order of one intercostal space (10–15 mm), our technique suits the clinical requirements. The authors therefore believe this technique has the potential to improve the pre-operative planning by updating peri-operative migration patterns of the heart and, consequently, will lead to reduced conversion to conventional open thoracic procedures.
II.A. Clinical procedure workflow
II.B. Estimating peri-operative heart migration
II.B.1. Predicting target vessel location
II.B.2. Pre- to intra-operative landmark-based registration
II.C. In vitro experimental validation
II.C.1. Experimental apparatus
II.C.2. Image acquisition
II.C.3. Computing LAD target registration error
II.D. Clinical Validation
II.D.1. Assessing target vessel location
III.A. In vitro experimental result
III.B. Clinical validation results
III.C. Simulation study result
IV.A. In vitro experiment
IV.B. Clinical validation
IV.C. Future challenges
- Medical imaging
- Computed tomography
- Multivariate analysis
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