The ability to control high-intensity focused ultrasound (HIFU) thermal ablation using echo decorrelation imaging feedback was evaluated in ex vivo bovine liver. Sonications were automatically ceased when the minimum cumulative echo decorrelation within the region of interest exceeded an ablation control threshold, determined from preliminary experiments as -2.7 (log-scaled decorrelation per millisecond), corresponding to 90% specificity for local ablation prediction. Controlled HIFU thermal ablation experiments were compared with uncontrolled experiments employing two, five or nine sonication cycles. Means and standard errors of the lesion width, area and depth, as well as receiver operating characteristic curves testing ablation prediction performance, were computed for each group. Controlled trials exhibited significantly smaller average lesion area, width and treatment time than five-cycle or nine-cycle uncontrolled trials and also had significantly greater prediction capability than two-cycle uncontrolled trials. These results suggest echo decorrelation imaging is an effective approach to real-time HIFU ablation control.

Feasibility of controlling bulk ultrasound (US) thermal ablation using echo decorrelation imaging was investigated in ex vivo bovine liver. The first of two ablation and control procedures used a sequence of constant-intensity sonication cycles, ceased when the minimum echo decorrelation within a control region of interest (ROI) exceeded a predetermined threshold. The second procedure used a variable-intensity sonication sequence, with spatially averaged decorrelation as the stopping criterion. US exposures and echo decorrelation imaging were performed by a linear image-ablate array. Based on preliminary experiments, control ROIs and thresholds for the minimum-decorrelation and average-decorrelation criteria were specified. Controlled trials for the minimum-decorrelation and average-decorrelation criteria were compared with uncontrolled trials employing 9 or 18 cycles of matching sonication sequences. Lesion dimensions, treatment times, ablation rates, and areas under receiver operating characteristic curves were statistically compared. Successfully controlled trials using both criteria required significantly shorter treatment times than corresponding 18-cycle treatments, with better ablation prediction performance than uncontrolled 9-cycle and 18-cycle treatments. Either control approach resulted in greater ablation rate than corresponding 9-cycle or 18-cycle uncontrolled approaches. A post hoc analysis studied the effect of exchanging control criteria between the two series of controlled experiments. For either group, the average time needed to exceed the alternative decorrelation threshold approximately matched the average duration of successfully controlled experimental trials. These results indicate that either approach, using minimum-decorrelation or average-decorrelation criteria, is feasible for control of bulk US ablation. In addition, use of a variable-intensity sonication sequence for bulk US thermal ablation can result in larger ablated regions compared to constant-intensity sonication sequences.

Colletotrichum spp. is an emerging pathogen which causes a variety of human infections. Only a few cases of Colletotrichum keratitis have been reported from India. We are reporting three cases of keratitis which were caused by three different species of Colletotrichum. Two of the three patients had a history of trauma and of a previous treatment with topical antibiotics.A direct microscopic examination of the corneas of all the three patients revealed fungal elements and Colletotrichum spp. grew in the culture. Two patients responded to topical anti -fungal therapy and the ulcer regressed, while the third patient failed to respond .The third patient was referred to a higher specialty centre for Keratoplasty.

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The utility of echo decorrelation imaging feedback for real-time control of in vivo ultrasound thermal ablation was assessed in rabbit liver with VX2 tumor. High-intensity focused ultrasound (HIFU) and unfocused (bulk) ablation were performed using 5 MHz linear image-ablate arrays. Treatments comprised up to nine lower-power sonications, followed by up to nine higher-power sonications, ceasing when the average cumulative echo decorrelation within a control region of interest exceeded a predefined threshold (− 2.3, log10-scaled echo decorrelation per millisecond, corresponding to 90% specificity for tumor ablation prediction in previous in vivo experiments). This threshold was exceeded in all cases for both HIFU (N = 12) and bulk (N = 8) ablation. Controlled HIFU trials achieved a significantly higher average ablation rate compared to comparable ablation trials without image-based control, reported previously. Both controlled HIFU and bulk ablation trials required significantly less treatment time than these previous uncontrolled trials. Prediction of local liver and VX2 tumor ablation using echo decorrelation was tested using receiver operator characteristic curve analysis, showing prediction capability statistically equivalent to uncontrolled trials. Compared to uncontrolled trials, controlled trials resulted in smaller thermal ablation regions and higher contrast between echo decorrelation in treated vs. untreated regions. These results indicate that control using echo decorrelation imaging may reduce treatment duration and increase treatment reliability for in vivo thermal ablation.