Enhanced surgical imaging: laparoscopic vessel identification and assessment of tissue oxygenation

Abstract

Background: Inherent to minimally invasive procedures are loss of tactile feedback and loss of three-dimensional assessment. Tasks such as vessel identification and dissection are not trivial for the inexperienced laparoscopic surgeon. Advanced surgical imaging, such as 3-charge-coupled device (3-CCD) image enhancement, can be used to assist with these more challenging tasks and, in addition, offers a method to noninvasively monitor tissue oxygenation during operations.

Study design: In this study, 3-CCD image enhancement is used for identification of vessels in 25 laparoscopic donor and partial nephrectomy patients. The algorithm is then applied to two laparoscopic nephrectomy patients involving multiple renal arteries. We also use the 3-CCD camera to qualitatively monitor renal parenchymal oxygenation during 10 laparoscopic donor nephrectomies (LDNs).

Results: The mean region of interest (ROI) intensity values obtained for the renal artery and vein (68.40 +/- 8.44 and 45.96 +/- 8.65, respectively) are used to calculate a threshold intensity value (59.00) that allows for objective vessel differentiation. In addition, we examined the renal parenchyma during LDNs. Mean ROI intensity values were calculated for the renal parenchyma at two distinct time points: before vessel stapling (nonischemic) and just before extraction from the abdomen (ischemic). The nonischemic mean ROI intensity values are statistically different from the ischemic mean ROI intensity values (p < 0.05), even with short ischemia times.

Conclusions: We have developed a technique, 3-CCD image enhancement, for identification of vasculature and monitoring of parenchymal oxygenation. This technique requires no additional laparoscopic operating room equipment and has real-time video capability.

Figure 1

A) Original laparoscopic image extracted from video footage of surgery. The stapler is at the base of the artery and the vein is immediately to the right of the artery. B) Grayscale tagged image file format (TIFF) of the red CCD response. C) Grayscale TIFF of the blue CCD response. D) Calculated image (red CCD response minus blue CCD response). The vein and artery are indicated by yellow dashed lines. E) The enhanced image consisting of the calculated image overlaid onto the original laparoscopic image.

Figure 2

Visible absorbance spectra of oxygenated and deoxygenated hemoglobin (HbO₂ and Hb, respectively) with overlaid estimated individual CCD responses (red, green and blue, from top to bottom).

Figure 3

Mean ROI intensity values for arteries and veins in 15 nephrectomy cases (LDNs and LPNs). A dashed threshold to distinguish arteries and veins is drawn at 59.00. The bars indicate one standard deviation, σ.

Figure 4

A) Laparoscopic image of renal vessels extracted from video footage of a partial nephrectomy. Note the presence of multiple arteries. B) The enhanced 3-CCD image of the vein and arteries. Note, the vein is clearly shaded in blue and the arteries in red. C) Laparoscopic image of renal vessels extracted from video footage of a donor nephrectomy. In this case, multiple renal arteries are also present. D) The enhanced 3-CCD image clearly depicts the vein in blue and the arteries in red. For both cases, ROIs used for mean intensity value calculations are indicated by white, yellow, and green rectangles (vein, left artery, and right artery, respectively).

Figure 5

Mean ROI intensity values calculated for the renal parenchyma prior to vessel clamping (black) and after vessel clamping (gray) for each LDN case. The single asterisk (*) is displayed for p ≤ 0.05, while a double asterisk (**) is shown for p ≤ 0.01.