Real-time computerized video enhancement for minimally invasive fetoscopic surgery

Background:The only definitive treatment for twin-to-twin transfusion syndrome is minimally invasive fetoscopic surgery for the selective coagulation of placental blood vessels.Fetoscopic surgery is a technically challenging operation,mainly due to the poor visibility conditions in the uterine environment.We present the design of an algorithm for the computerized enhancement of fetoscopic video and show that the enhanced video increases the ability of human users to identify blood vessels within fetoscopic video rapidly and accurately.Methods:A computer algorithm for the enhancement of fetoscopic video frames was created.First,optical fiber artifacts were removed via a modification of unsharp masking.Second,image contrast was increased via Contrast Limited Adaptive Histogram Equalization(CLAHE).Third,the effect of contrast enhancements on stationary features was removed by normalizing to a windowed mean of the video frames.Fourth,color information was reincorporated by combining the mean-normalized result with the unnormalized contrast enhanced image using the soft light blending algorithm.Medical trainees(n?16)were recruited into a study to validate the algorithm.Subjects were shown enhanced or unenhanced fetoscopic video frames on a screen and were asked to identify whether a randomly placed marker fell on a blood vessel or on background.The accuracy of their responses was recorded.Results:On the subset of images where subjects had the lowest mean accuracy in identifying the placement of the marker,subjects performed better when viewing video frames enhanced by the computer(accuracy 74.27%;SE 0.97)than when viewing unenhanced video frames(accuracy 63.78%;SE 2.79).This result was statistically significant(p<0.01).Conclusion:Real-time computerized enhancement of fetoscopic video has the potential to ease the readability of video in poor lighting conditions,thus providing a benefit to the surgeon intraoperatively.

Predicting Infiltrative Hepatocellular Carcinoma Patient Outcome Post-TACE:MR Bias Field Correction Effect on 3D-quantitative Image Analysis

Background and Aims:To investigate the impact of MR bias field correction on response determination and survival prediction using volumetric tumor enhancement analysis in patients with infiltrative hepatocellular carcinoma,after transcatheter arterial chemoembolization(TACE).Methods:This study included 101 patients treated with conventional or drug-eluting beads TACE between the years of 2001 and 2013.Semi-automated 3D quantification software was used to segment and calculate the enhancing tumor volume(ETV)of the liver with and without bias-field correction on multi-phasic contrast-enhanced MRI before and 1-month after initial TACE.ETV(expressed as cm3)at baseline imaging and the relative change in ETV(as%change,ETV%)before and after TACE were used to predict response and survival,respectively.Statistical survival analyses included Kaplan-Meier curve generation and Cox proportional hazards modeling.Q statistics were calculated and used to identify the best cut-off value for ETV to separate responders and non-responders(ETV cm3).The difference in survival was evaluated between responders and non-responders using Kaplan-Meier and Cox models.Results:MR bias field correction correlated with improved response calculation from baseline MR as well as survival after TACE;using a 415 cm3 cut-off for ETV at baseline(hazard ratio:2.00,95%confidence interval:1.23-3.26,p=0.01)resulted in significantly improved response prediction(median survival in patients with baseline ETV<415 cm3:19.66 months vs.≥415 cm3:9.21 months,p<0.001,log-rank test).A≥41%relative decrease in ETV(hazard ratio:0.58,95%confidence interval:0.37-0.93,p=0.02)was significant in predicting survival(ETV≥41%:19.20 months vs.ETV<41%:8.71 months,p=0.008,log-rank test).Without MR bias field correction,response from baseline ETV could be predicted but survival after TACE could not.Conclusions:MR bias field correction improves both response assessment and accuracy of survival prediction using whole liver tumor enhancement analysis from baseline MR after initial TACE in patients with infiltrative hepatocellular carcinoma.