Visual enhancement of laparoscopic partial nephrectomy with 3-charge coupled device camera: assessing intraoperative tissue perfusion and vascular anatomy by visible hemoglobin spectral response

Abstract

Purpose: We report the novel use of 3-charge coupled device camera technology to infer tissue oxygenation. The technique can aid surgeons to reliably differentiate vascular structures and noninvasively assess laparoscopic intraoperative changes in renal tissue perfusion during and after warm ischemia.

Materials and methods: We analyzed select digital video images from 10 laparoscopic partial nephrectomies for their individual 3-charge coupled device response. We enhanced surgical images by subtracting the red charge coupled device response from the blue response and overlaying the calculated image on the original image. Mean intensity values for regions of interest were compared and used to differentiate arterial and venous vasculature, and ischemic and nonischemic renal parenchyma.

Results: The 3-charge coupled device enhanced images clearly delineated the vessels in all cases. Arteries were indicated by an intense red color while veins were shown in blue. Differences in mean region of interest intensity values for arteries and veins were statistically significant (p >0.0001). Three-charge coupled device analysis of pre-clamp and post-clamp renal images revealed visible, dramatic color enhancement for ischemic vs nonischemic kidneys. Differences in the mean region of interest intensity values were also significant (p <0.05).

Conclusions: We present a simple use of conventional 3-charge coupled device camera technology in a way that may provide urological surgeons with the ability to reliably distinguish vascular structures during hilar dissection, and detect and monitor changes in renal tissue perfusion during and after warm ischemia.

Figure 1.

Reflected light in abdominal cavity is collected by laparoscope and separated into 3 individual responses by prisms, which diffract light into red, green and blue visible light regions, respectively. Wavelength filtered images are detected by 3 individual monochrome CCDs. Surgeon observes composite of 3 CCD responses on high definition monitor in operating room.

Figure 2.

Regions representing individual CCD responses (blue, green and red curves, respectively). Solid lines represent oxygenated (HbO₂) and deoxygenated (Hb) hemoglobin with absorbance maxima of 416, 541 and 577, and 430 and 556 nm, respectively.

Figure 3.

Original laparoscopic image with kidney clearly visible at right (A), and response detected by red (B) and blue (C) CCDs in grayscale. Calculated image created by subtracting blue from red CCD response (D) is shown as modified color scale. Red areas indicate regions with smallest CCD response difference, that is oxygenated, while blue areas indicate regions with greatest difference, that is deoxygenated. Calculated image was overlaid on original image to obtain enhanced image (E).

Figure 4.

Original image obtained and shown by laparoscopic tower reveals renal vein and 2 renal arteries (A). On enhanced image colored boxes indicating each ROI for which we calculated mean ROI intensity values, including 48.3 ± 1.3 (white boxes), 58.6 ± 6.1 (yellow boxes) and 66.9 ± 6.5 (green boxes) (B). Mean ROI intensity values in all 10 cases revealed clear distinction between venous and arterial vessels (p <0.0001) (C). Dotted line indicates arbitrary threshold value. a.u., arbitrary units.

Figure 5.

Boxes indicate ROIs (A and B). Mean ROI intensity values of baseline renal image before vessel clamping and ischemic kidney image after clamping was 83.30 ± 6.57 (A) and 27.42 ± 5.49 (B). Mean ROI intensity value measured after clamp was released was 76.42 ± 10.60 (C). a.u., arbitrary units.