Development of CBCT-based prostate setup correction strategies and impact of rectal distension.

BACKGROUND: Cone-beam computed tomography (CBCT) image-guided radiotherapy (IGRT) systems are widely used tools to verify and correct the target position before each fraction, allowing to maximize treatment accuracy and precision. In this study, we evaluate automatic three-dimensional intensity-based rigid registration (RR) methods for prostate setup correction using CBCT scans and study the impact of rectal distension on registration quality. METHODS: We retrospectively analyzed 115 CBCT scans of 10 prostate patients. CT-to-CBCT registration was performed using (a) global RR, (b) bony RR, or (c) bony RR refined by a local prostate RR using the CT clinical target volume (CTV) expanded with 1-to-20-mm varying margins. After propagation of the manual CT contours, automatic CBCT contours were generated. For evaluation, a radiation oncologist manually delineated the CTV on the CBCT scans. The propagated and manual CBCT contours were compared using the Dice similarity and a measure based on the bidirectional local distance (BLD). We also conducted a blind visual assessment of the quality of the propagated segmentations. Moreover, we automatically quantified rectal distension between the CT and CBCT scans without using the manual CBCT contours and we investigated its correlation with the registration failures. To improve the registration quality, the air in the rectum was replaced with soft tissue using a filter. The results with and without filtering were compared. RESULTS: The statistical analysis of the Dice coefficients and the BLD values resulted in highly significant differences (p<10(-6)) for the 5-mm and 8-mm local RRs vs the global, bony and 1-mm local RRs. The 8-mm local RR provided the best compromise between accuracy and robustness (Dice median of 0.814 and 97% of success with filtering the air in the rectum). We observed that all failures were due to high rectal distension. Moreover, the visual assessment confirmed the superiority of the 8-mm local RR over the bony RR. CONCLUSION: The most successful CT-to-CBCT RR method proved to be the 8-mm local RR. We have shown the correlation between its registration failures and rectal distension. Furthermore, we have provided a simple (easily applicable in routine) and automatic method to quantify rectal distension and to predict registration failure using only the manual CT contours

Comparison of prasugrel and clopidogrel used as antiplatelet medication for endovascular treatment of unruptured intracranial aneurysms: A meta-analysis

BACKGROUND: Clopidogrel is routinely used to decrease ischemic complications during neurointerventional procedures. However, the efficacy may be limited by antiplatelet resistance. PURPOSE: Our aim was to analyze the efficacy of prasugrel compared with clopidogrel in the cerebrovascular field. DATA SOURCES: A systematic search of 2 large databases was performed for studies published from 2000 to 2018. STUDY SELECTION: According to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, we included studies reporting treatment-related outcomes of patients undergoing neurointerventional procedures under prasugrel, and studies comparing prasugrel and clopidogrel. DATA ANALYSIS: Random-effects meta-analysis was used to pool the overall rate of complications, ischemic and hemorrhagic events, and influence of the dose of prasugrel. DATA SYNTHESIS: In the 7 included studies, 682 and 672 unruptured intracranial aneurysms were treated under prasugrel (cases) and clopidogrel (controls), respectively. Low-dose (20 mg/5 mg; loading and maintenance doses) prasugrel compared with the standard dose of clopidogrel (300 mg/75 mg) showed a significant reduction in the complication rate (OR 0.36; 95% CI, 0.17–74, P .006; I2 0%). Overall, the ischemic complication rate was significantly higher in the clopidogrel group (40/672 6%; 95% CI, 3%–13%; I2 83% versus 16/682 2%; 95% CI, 1%–5%; I2 73%; P .03). Low and high loading doses of prasugrel were associated with 0.6% (5/535; 95% CI, 0.1%–1.6%; I2 0%) and 9.3% (13/147; 95% CI, 0.2%–18%; I2 60%) intraperiprocedural hemorrhages, respectively (P .001), whereas low and high maintenance doses of prasugrel were associated with 0% (0/433) and 0.9% (2/249; 95% CI, 0.3%–2%; I2 0%) delayed hemorrhagic events, respectively (P .001). LIMITATIONS: Retrospective series and heterogeneous endovascular treatments were limitations. CONCLUSIONS: In our study, low-dose prasugrel compared with clopidogrel premedication was associated with an effective reduction of the ischemic events with an acceptable rate of hemorrhagic complications

Unsupervised texture segmentation using active contours driven by the chernoff gradient flow

We present a new unsupervised segmentation of textural images based on integration of a texture descriptor in the formulation of active contour. The proposed texture descriptor intrinsically describes the geometry of textural regions using the shape operator defined in Beltrami framework. We use the Chernoff distance to define an active contours model which discriminates textures by maximizing the distance between the probability density functions which leads to distinguish textural objects of interest and background described by texture descriptor. We prove the existence of a solution to the new formulated active contours based segmentation model and we propose a fast and easy algorithm based on the dual formulation of the Total Variation norm. Finally, we show results on challenging images to illustrate accurate segmentations that are possible

Fast Unsupervised Texture Segmentation Using Active Contours Model Driven by Bhattacharyya Gradient Flow

We present a new unsupervised segmentation based active contours model and texture descriptor. The proposed texture descriptor intrinsically describes the geometry of textural regions using the shape operator defined in Beltrami framework. We use Bhattacharyya distance to discriminate textures by maximizing distance between the probability density functions which leads to distinguish textural objects of interest and background. We propose a fast Bregman split implementation of our segmentation algorithm based on the dual formulation of the Total Variation norm. Finally, we show results on some challenging images to illustrate segmentations that are possible

Automatic prostate segmentation in cone-beam computed tomography images using rigid registration.

We propose to evaluate automatic three-dimensional gray-value rigid registration (RR) methods for prostate localization on cone-beam computed tomography (CBCT) scans. In total, 103 CBCT scans of 9 prostate patients have been analyzed. Each one was registered to the planning CT scan using different methods: (a) global RR, (b) pelvis bone structure RR, (c) bone RR refined by local soft-tissue RR using the CT clinical target volume (CTV) expanded with a 1, 3, 5, 8, 10, 12, 15 or 20-mm margin. To evaluate results, a radiation oncologist was asked to manually delineate the CTV on the CBCT scans. The Dice coefficients between each automatic CBCT segmentation - derived from the transformation of the manual CT segmentation - and the manual CBCT segmentation were calculated. Global or bone CT/CBCT RR has been shown to yield insufficient results in average. Local RR with an 8-mm margin around the CTV after bone RR was found to be the best candidate for systematically significantly improving prostate localization

Application of Active Contour Models in Medical Image Segmentation

Abstract: Recent developments on medical imaging techniques have brought a completely new research field on image processing. The principal aim is to improve medical diagnosis through segmented images. Techniques have been developed to help for identifying specific structures within a magnetic resonance image: MRI. The Active Contour methods, these methods are adaptable to the desired features in the image. In our work, we describe two classes of active contour models and discussing application aspects in medical imaging area

Antiplatelet Therapy in Patients with Aneurysmal SAH: Impact on Delayed Cerebral Ischemia and Clinical Outcome. A Meta-Analysis

International audienceBackground and purpose: Delayed cerebral ischemia strongly impacts clinical outcome after aneurysmal SAH. The effect of antiplatelet therapy on delayed cerebral ischemia has been described with heterogeneous results. Our aim was to analyze the efficacy of antiplatelet therapy on delayed cerebral ischemia and clinical outcome in patients with SAH.Data sources: A systematic search of 3 databases was performed for studies published from 1990 to 2019.Study selection: According to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, we included studies comparing the rates of delayed cerebral ischemia and clinical outcomes among patients with SAH with and without antiplatelet therapy.Data analysis: Random-effects meta-analysis was used to pool the following: delayed cerebral ischemia, mortality, and good outcome rates.Data synthesis: Including 7 studies, 1060 and 1762 patients with SAH were endovascularly or surgically treated with (cases) and without (controls) antiplatelet therapy, respectively. Overall, antiplatelet therapy did not significantly decrease delayed cerebral ischemia rates compared with the control group (219/1060 versus 485/1762, OR = 0.781; 95% CI, 0.46-1.31; P = .33). Among patients treated endovascularly, there was a trend toward lower delayed cerebral ischemia rates after antiplatelet therapy (157/778 versus 413/1410, OR = 0.552; 95% CI, 0.273-1.115; P = .06). Long-term (>2 weeks) antiplatelet therapy tended to be associated with a lower incidence of delayed cerebral ischemia (63/438 versus 96/353, OR = 0.379; 95% CI, 0.12-1.2; P = .06). The good-outcome rate was significantly higher (803/1144 versus 1175/1775, OR = 1.368; 95% CI, 1.117-1.676; P = .002) and the mortality rate was significantly lower (79/672 versus 97/571, OR = 0.656; 95% CI, 0.47-0.91; P = .01) among the antiplatelet therapy group.Limitations: Heterogeneity was high for most outcomes.Conclusions: Overall, the incidence of delayed cerebral ischemia seems not to be significantly reduced among the antiplatelet therapy group. However, delayed cerebral ischemia tended to be lower among subjects with both long-term antiplatelet therapy and endovascular treatment and antiplatelet administration. Poor outcome and mortality rates were significantly reduced among the antiplatelet therapy group

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