Evaluation of model-based deformation correction in image-guided liver surgery via tracked intraoperative ultrasound

Abstract

Soft-tissue deformation represents a significant error source in current surgical navigation systems used for open hepatic procedures. While numerous algorithms have been proposed to rectify the tissue deformation that is encountered during open liver surgery, clinical validation of the proposed methods has been limited to surface-based metrics, and subsurface validation has largely been performed via phantom experiments. The proposed method involves the analysis of two deformation-correction algorithms for open hepatic image-guided surgery systems via subsurface targets digitized with tracked intraoperative ultrasound (iUS). Intraoperative surface digitizations were acquired via a laser range scanner and an optically tracked stylus for the purposes of computing the physical-to-image space registration and for use in retrospective deformation-correction algorithms. Upon completion of surface digitization, the organ was interrogated with a tracked iUS transducer where the iUS images and corresponding tracked locations were recorded. Mean closest-point distances between the feature contours delineated in the iUS images and corresponding three-dimensional anatomical model generated from preoperative tomograms were computed to quantify the extent to which the deformation-correction algorithms improved registration accuracy. The results for six patients, including eight anatomical targets, indicate that deformation correction can facilitate reduction in target error of [Formula: see text].

Keywords: biomechanical modeling; clinical evaluation; image-guided surgery; open liver surgery; tracked ultrasound.

Fig. 1

(a) The tracked LRS device used for organ surface acquisition during the study. (b) The manual surface swabbing interface within the Explorer™ Liver navigation system highlighting a surface alignment generated from the stylus-based digitization. Note that the images shown were initially included in the works of Pheiffer et al. and Kingham et al.

Fig. 2

(a) The tracked adapter device in use during surgery during the organ interrogation with ultrasound and (b) a schematic of the adapter used to track an Aloka T-probe (UST-5713-T, Hitachi Aloka Medical Ltd., Wallingford, Connecticut) within the Explorer™ Liver navigation system. (c) A view of the OR during the use of the tracked iUS functionality within the Explorer™ Liver navigation system and (d) a screen capture of the Explorer™ Liver navigation system with iUS tracking in use during an ablation probe placement in an open hepatic procedure. Note that the oblique CT slice that corresponds with the tracked iUS plane is displayed in the lower right quadrant of the interface. These images were published in the work of Kingham et al.

Fig. 3

Visualization of the rigid registration alignment and texture map of the closest-point distances for the six patient cohort included in the current work. The figure panel labels of (a)–(f) indicate the results for patients 1 to 6, respectively. The six sets of data demonstrate the incidence of significant soft-tissue deformation in open IGLS and highlight the sparse nature of intraoperative liver surface digitization.

Fig. 4

Visualization of the tracked iUS image plane rendered within the 3-D models generated from the preoperative tomograms for patient 1. The raw iUS image captures used in the analysis are shown in panel (a) and panel (b) shows the highlighted anatomical feature (i.e., left portal vein confluence). The rigid registration transformation computed during the surgical procedure was used to generate the overlays in panels (c) and (d). Panel (c) shows a superior view of the rigid alignment and includes a rendering of the lesions (brown), hepatic vasculature (blue), portal vasculature (pink), and liver surface (gray). Panel (d) shows a zoomed superior view of the tracked iUS and portal vein structure. The deformed anatomical models and updated transform from the deformation-correction Algorithm 2 were used to generate the renderings in panels (e) and (f). Panel (e) shows a superior view of the deformation corrected alignment and includes a rendering of the lesions (brown), hepatic vasculature (blue), portal vasculature (pink), and liver surface (gray). Panel (f) shows a zoomed superior view of the tracked iUS and portal vein structure after deformation correction.

Fig. 5

Visualization of the tracked iUS image plane rendered within the 3-D models generated from the preoperative tomograms for patient 2. The raw iUS image captures used in the analysis are shown in panel (a) and panel (b) shows the highlighted anatomical feature (i.e., left portal vein confluence). The rigid registration transformation computed during the surgical procedure was used to generate the overlays in panels (c) and (d). Panel (c) shows an anterior view of the rigid alignment and includes a rendering of the lesion (brown), portal vasculature (pink), and liver surface (gray). Panel (d) shows a zoomed superior view of the tracked iUS and portal vein structure. The deformed anatomical models and updated transform from the deformation-correction Algorithm 2 were used to generate the renderings in panels (e) and (f). Panel (e) shows an anterior view of the deformation corrected alignment and includes a rendering of the lesion (brown), portal vasculature (pink), and liver surface (gray). Panel (f) shows a zoomed superior view of the tracked iUS and portal vein structure after deformation correction.

Fig. 6

Visualization of the tracked iUS image plane rendered within the 3-D models generated from the preoperative tomograms for patient 3. The raw iUS image captures used in the analysis are shown in panel (a) and panel (b) shows the highlighted anatomical feature (i.e., right hepatic vein). The rigid registration transformation computed during the surgical procedure was used to generate the overlays in panels (c) and (d). Panel (c) shows a superior view of the rigid alignment and includes a rendering of the lesion (brown), portal vasculature (pink), hepatic vasculature (blue), and liver surface (gray). Panel (d) shows a zoomed superior view of the tracked iUS and hepatic vein structure. The deformed anatomical models and updated transform from the deformation-correction Algorithm 2 were used to generate the renderings in panels (e) and (f). Panel (e) shows a superior view of the deformation corrected alignment and includes a rendering of the lesion (brown), portal vasculature (pink), hepatic vasculature (blue), and liver surface (gray). Panel (f) shows a zoomed superior view of the tracked iUS and hepatic vein structure after deformation correction.