Comparison of different spectral cameras for image-guided organ transplantation

Abstract

Significance: Hyperspectral and multispectral imaging (HMSI) in medical applications provides information about the physiology, morphology, and composition of tissues and organs. The use of these technologies enables the evaluation of biological objects and can potentially be applied as an objective assessment tool for medical professionals.

Aim: Our study investigates HMSI systems for their usability in medical applications.

Approach: Four HMSI systems (one hyperspectral pushbroom camera and three multispectral snapshot cameras) were examined and a spectrometer was used as a reference system, which was initially validated with a standardized color chart. The spectral accuracy of the cameras reproducing chemical properties of different biological objects (porcine blood, physiological porcine tissue, and pathological porcine tissue) was analyzed using the Pearson correlation coefficient.

Results: All the HMSI cameras examined were able to provide the characteristic spectral properties of blood and tissues. A pushbroom camera and two snapshot systems achieve Pearson coefficients of at least 0.97 compared to the ground truth, indicating a very high positive correlation. Only one snapshot camera performs moderately to high positive correlation (0.59 to 0.85).

Conclusion: The knowledge of the suitability of HMSI cameras for accurate measurement of chemical properties of biological objects offers a good opportunity for the selection of the optimal imaging tool for specific medical applications, such as organ transplantation.

Keywords: blood analysis; hyperspectral imaging; image-guided surgery; multispectral imaging; organ analysis; spectral camera comparison.

Fig. 1

The setup is shown during (a) calibration and (b) as sketch with the complete equipment: (1) pushbroom camera setup, 41-bands setup with (2) $4\times 4$-VIS camera and (3) $5\times 5$-NIR camera, (4) $3\times 3$-VIS camera setup, (5) six illumination spots, (6) spectrometer, (7) tissue sample, (8) heating unit, (9) thermometer, (10) cursor, and (11) perfusion machine for blood measurements.

Fig. 4

Spatially resolved HMSI images of the heart of the third pig model. (a) Multispectral $4\times 4$ VIS camera; (b) multispectral $5\times 5$ NIR camera; and (c) Multispectral $3\times 3$ VIS camera. One spectral band of the snapshot sensor data for (a) $\lambda =530\mathrm{nm}$, (b) $\lambda =746\mathrm{nm}$, and (c) $\lambda =515\mathrm{nm}$. (d) The intensity distribution of the TIVITA Tissue pushbroom camera image at $\lambda =750\mathrm{nm}$.

Fig. 2

Five different analyzed color tiles of the Color Checker Board. The continuous lines are measured with a spectometer in this study and the dashed lines are published reference measurements.^,

Fig. 3

Two color tiles, with defined colors (a) light skin and (b) magenta, analyzed with all four described setups. The two curves per imaging setup correspond to the two selected ROIs in each captured image.

Fig. 5

The spectral reflectance behaviors for all four analyzed organs averaged over all measurements presented of (a) spectrometer ground truth data, (b) hyperspectral pushbroom camera, (c) multispectral 41-band setup, and (d) multispectral $3\times 3$ camera.

Fig. 6

For the porcine heart measurements, all curves acquired by the different spectral cameras—(a) hyperspectral pushbroom camera, (b) 41-bands setup, and (c) $3\times 3$-VIS camera—match the behavior of the reference spectrometer data (dashed lines). For each of the three camera acquisition methods, two ROIs are selected, reconstructed, and averaged over the three measurements. The resulting two ROIs are presented here.

Fig. 7

Porcine brain measurements of all three pigs both two selected ROIs are averaged to one spectral curve.

Fig. 8

Porcine lung measurements of the third pig at two different selected ROIs. These spectral curves are representative for the other two pigs as well.

Fig. 9

Porcine kidney measurements of (a) healthy kidney tissue from the second pig and (b) kidney with a superficial cyst from the first pig, both averaged over both measured ROIs. The spectral curves in (a) are representative for the other two pigs as well, which are omitted for readability. In (b), the spectrometer data of the healthy kidney of the first pig are plotted for comparability.

Fig. 10

Blood measurements of all three camera setups. For each setup, the two ROIs average over the three measurements are presented.