Q2. What future works have the authors mentioned in the paper "Optical techniques for 3d surface reconstruction in computer-assisted laparoscopic surgery" ?
In the following paragraphs, the authors summarize some of the key areas of future development required to move the new technologies from the laboratory into the hospital with the ultimate goal of improving patient care: Robustness. The study, which will be published in the near future, concluded that none of the state-of-the-art reconstruction methods yielded accurate reconstruction results under all conditions. To advance future research in 3D reconstruction, standardized data repositories need to be established and shared for comparison of the different techniques. As accuracy requirements expand further, with targets for therapy becoming smaller due to improved image resolution and new forms of treatment, and surgery continuing to move toward minimally invasive interventions, the demand for image-guided systems can be expected to further increase in the future ( Cleary and Peters, 2010 ).
Q3. What are the stages of the disparity map?
To compute the disparity map, computational stereo algorithms can typically be broken down into four stages as described by (Scharstein and Szeliski, 2002): cost computation, cost aggregation, disparity computation and optimization, and disparity refinement.
Q4. Why is the SNR in endoscopic ToF images very low?
Due to the challenge in transmitting enough light to the tissue, the SNR in endoscopic ToF images and thus the measurement precision in camera direction (Lange, 2000) is very low.
Q5. What are the major challenges to be addressed in the context of laparoscopic surgery?
Major challenges to be addressed in the context of laparoscopic surgery further include scattered light, multi-path reflexions and tissue penetration.
Q6. Why is the number of medical applications expected to increase?
Due to the potential for realizing extremely compact ToF devices, it can be expected that the number of medical applications in the coming years will increase.
Q7. What are the challenging scenarios for obtaining reference data?
The most challenging scenarios for obtaining reference data are cadaver, in vivo and wet lab experiments, which are mostly presented to qualitatively demonstrate practical feasibility (Richa et al., 2008a,b; Noonan et al., 2009; Stoyanov et al., 2010).
Q8. What are the two biophotonic modalities that illustrate this potential?
Two biophotonic modalities that illustrate this potential and are used clinically are multispectral imaging and confocal laser endomicroscopy (CLE).
Q9. What is the main method used for measuring the run-time of emitted light?
There are two main approaches currently employed for measuring the run-time of emitted light (Lange, 2000): Pulsed modulation is the most obvious method,because it directly measures the ToF of an emitted pulse of light.
Q10. What is the effect of light scattering on the camera lens?
The light scattering effect is caused by multiple light reflexions between the camera lens and its sensor and causes a depth underestimation over the affected pixels (Foix et al., 2011).
Q11. What is the main reason for the lack of real-time performance?
Despite acceptable performance, lag remains an issue, and this is compounded by other computational tasks such as registration or biomechanical modelling, which are currently not real-time in general.
Q12. What is the importance of careful validation in the clinic?
Careful validation, both in controlled environments as well as in clinical scenarios, is crucial for establishing a new system in the clinic (Jannin et al., 2002, 2006).
Q13. How can the authors combine the camera parameters in one matrix?
All projection parameters can be combined in one matrix P and are usually obtained in a pre-operative calibration procedure using calibration objects with precisely known geometry (Zhang, 2000).
Q14. What is the tradeoff between 3D reconstruction accuracy and reconstruction quality?
Because reconstruction accuracy increases with the length of the baseline, there is a tradeoff between compactness and reconstruction quality.
Q15. How can the authors compensate for the error?
The remaining error can then be compensated by determining the calibration parameters as a function of measured distance and amplitude, either in a coupled or in a decoupled approach (Lindner et al., 2010).
Q16. What are the current methods for estimating the surface of a 3D organ?
Current methods for estimating the surface of tissue are either not real-time (CT, MRI, laser range scanners) and fail to capture tissue deformation, are not practical to introduce into the operating room, or are experimental systems under evaluation (e.g. structured light).
Q17. How is the system adapted to low-resolution stereo fibre image guides?
The system was has been adapted to low-resolution stereo fibre image guides (10,000 fibres) (Noonan et al., 2009)and demonstrated reconstruction accuracy of less than 3 mm on phantom data.