  Objective: This study introduces a novel method for defining virtual
resections in liver cancer surgery, aimed at enhancing the adaptability of
parenchyma-sparing resection (PSR) plans. By comparing these with traditional
anatomical resection (AR) plans, we explore the potential for optimization in
surgical planning. Methods: Leveraging contours and spline surface
approximations directly from the liver's surface, our method aligns closely
with actual surgical procedures, offering a more realistic representation of
curved resection paths. This technique, tested against 14 cases from the
OSLO-COMET study, incorporates surface deformation for versatile plan modeling,
comparing volumetric outcomes of PSR and AR. Results: The study highlights
significant benefits of PSR over AR, including reduced resected volume ($32.71
\pm 13.80$ ml for PSR vs. $249.53 \pm 135.23$ ml for AR, $p <0.0001$) and
higher remnant liver volume ($1922.77 \pm 442.86$ ml for PSR vs. $1716.87 \pm
403.00$ ml for AR, $p <0.0001$). PSR also showed a considerably higher remnant
percentage ($98.16 \pm 0.81%$) compared to AR ($87.40 \pm 6.49%$, $p <0.0001$).
Conclusion: The proposed approach is able to define virtual resections
accommodating a wide variety of resections (i.e., PSR and AR). Careful surgical
planning using virtual resections can optimize the resection strategy.
Significance: This study presents a novel computer-aided planning system for
liver surgery, demonstrating its efficacy and flexibility for definition of
virtual resections. Virtual surgery planning can be used for optimization of
resection strategies leading to increased preservation of healthy tissue.
