Post-operative pancreatic fistula is the most dreadful complication of pancreatic resections. Tissue perfusion is a recognized risk factor of fistula in gastrointestinal anastomosis, but has been poorly studied in case of pancreatic surgery. Organ perfusion can be estimated by several intraoperative optical imaging modalities, including exogenous fluorescence imaging with Indocyanine Green (ICG). A limitation of ICG fluorescence angiography is the lack of a quantitative analytic method. Our group has developed and validated a real-time computational imaging analysis of tissue perfusion, based on the slope of the time of fluorescence peak, defined fluorescence-based enhance reality (FLER). This consists in encoding tissue hemodynamics into a virtual perfusion cartography that is superimposed on intraoperative images in real time, in order to provide the perfusion information to surgeons. Another emerging technology is hyperspectral imaging (HSI), which combines a spectrometer and a camera. HSI obtains spectral tissue curves pixel by pixel in a wide wavelength range and can provide absolute values of concentration and/or oxygen saturation of hemoglobin. The aim of this study was to investigate the efficacy of both imaging modalities, FLER and HSI, to estimate pancreatic perfusion. Methods Twelve pigs were involved and randomly assigned to interventional group (n=6) and a control group (n =6). After a median laparotomy the pancreas was fully exposed. In the interventional group, under radiographic guidance, a segmental ischemia of the pancreas was induced by means of coil embolization in small splenic arterial branches, via a femoral artery approach. No ischemia was induced in the control group. HSI images were obtained using the TIVITA camera (Diaspective Vision, Germany). FLER was obtained after injecting 0.2 mg/kg of ICG and image processing using a dedicated software (ER PERFUSION, IRCAD, France). The augmented reality of color-coded images derived from both FLER and HSI were overlapped on the video image. Local capillary lactates (LCL) were sampled in different regions of interests (ROIs) of the pancreas. LCL were correlated to the absolute values provided by the imaging analyses (slope of time-to-peak and StO2, respectively for fluorescence and HSI). Results In all pigs from the interventional group, the segmental ischemic areas were successfully created. The mean slope was slower; the mean StO2 was lower; and mean LCL were lower in the ischemic zone than in the transition and vital zones. The scatter plot between the slope and StO2, the slope and LCL, and StO2 and LCL in all 12 pigs showed statistically significant correlation. In addition, LCL can be predicted from FLER and StO2. The prediction from HSI StO2 (median error: 0.67 mmol/L) is significantly more accurate than FLER (median error: 0.8 mmol/L) (P=0.02). Conclusions FLER and HSI, enable both to precisely quantify and visualize real-time perfusion of the pancreas in this porcine model of pancreas ischemia. HSI showed a greater accuracy in predicting the value of capillary local lactates when compared to quantitative exogenous fluorescence analysis.
The response of a fiber optic sensor [linearly chirped fiber Bragg grating (LCFBG)] to a linear thermal gradient applied on its sensing length (i.e., 1.5 cm) has been investigated. After these bench tests, we assessed their feasibility for temperature monitoring during thermal tumor treatment. In particular, we performed experiments during ex vivo laser ablation (LA) in pig liver and in vivo thermal ablation in animal models (pigs). We investigated the following: (i) the relationship between the full width at half maximum of the LCFBG spectrum and the temperature difference among the extremities of the LCFBG and (ii) the relationship between the mean spectrum wavelength and the mean temperature acting on the LCFBG sensing area. These relationships showed a linear trend during both bench tests and LA in animal models. Thermal sensitivity was significant although different values were found with regards to bench tests and animal experiments. The linear trend and significant sensitivity allow hypothesizing a future use of this kind of sensor to monitor both temperature gradient and mean temperature within a tissue undergoing thermal treatment.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.