Safety and efficacy of histotripsy delivery through overlying gas-filled small bowel in an ex vivo swine model.

PURPOSE: To evaluate the safety and efficacy of performing histotripsy through overlying gas-filled bowel in an ex vivo swine model. METHODS: An ex vivo model was created to simulate histotripsy treatment of solid organs through gas-filled bowel. Spherical 2.5 cm histotripsy treatments were performed in agar phantoms for each of five treatment groups: 1) control with no overlying bowel (n = 6), 2) bowel 0 cm above phantom (n = 6), 3) bowel 1 cm above phantom (n = 6), 4) bowel 2 cm above phantom (n = 6), and 5) bowel 0 cm above the phantom with increased treatment amplitude (n = 6). Bowel was inspected for gross and microscopic damage, and treatment zones were measured. A ray-tracing simulation estimated the percentage of therapeutic beam path blockage by bowel in each scenario. RESULTS: All histotripsy treatments through partial blockage were successful (24/24). No visible or microscopic damage was observed to intervening bowel. Partial blockage resulted in a small increase in treatment volume compared to controls (p = 0.002 and p = 0.036 for groups with bowel 0 cm above the phantom, p > 0.3 for bowel 1 cm and 2 cm above the phantom). Gas-filled bowel was estimated to have blocked 49.6%, 35.0%, and 27.3% of the therapeutic beam at 0, 1, and 2 cm, respectively. CONCLUSION: Histotripsy has the potential to be applied through partial gas blockage of the therapeutic beam path, as shown by this ex vivo small bowel model. Further work in an in vivo survival model appears indicated.

Percutaneous CT-Guided Abdominal and Pelvic Biopsies: Comparison of an Electromagnetic Navigation System and CT Fluoroscopy.

PURPOSE: To compare electromagnetic navigation (EMN) with computed tomography (CT) fluoroscopy for guiding percutaneous biopsies in the abdomen and pelvis. MATERIALS AND METHODS: A retrospective matched-cohort design was used to compare biopsies in the abdomen and pelvis performed with EMN (consecutive cases, n = 50; CT-Navigation; Imactis, Saint-Martin-d'Hères, France) with those performed with CT fluoroscopy (n = 100). Cases were matched 1:2 (EMN:CT fluoroscopy) for target organ and lesion size (±10 mm). RESULTS: The population was well-matched (age, 65 vs 65 years; target size, 2.0 vs 2.1 cm; skin-to-target distance, 11.4 vs 10.7 cm; P > .05, EMN vs CT fluoroscopy, respectively). Technical success (98% vs 100%), diagnostic yield (98% vs 95%), adverse events (2% vs 5%), and procedure time (33 minutes vs 31 minutes) were not statistically different (P > .05). Operator radiation dose was less with EMN than with CT fluoroscopy (0.04 vs 1.2 µGy; P < .001), but patient dose was greater (30.1 vs 9.6 mSv; P < .001) owing to more helical scans during EMN guidance (3.9 vs 2.1; P < .001). CT fluoroscopy was performed with a mean of 29.7 tap scans per case. In 3 (3%) cases, CT fluoroscopy was performed with gantry tilt, and the mean angle out of plane for EMN cases was 13.4°. CONCLUSIONS: Percutaneous biopsies guided by EMN and CT fluoroscopy were closely matched for technical success, diagnostic yield, procedure time, and adverse events in a matched cohort of patients. EMN cases were more likely to be performed outside of the gantry plane. Radiation dose to the operator was higher with CT fluoroscopy, and patient radiation dose was higher with EMN. Further study with a wider array of procedures and anatomic locations is warranted.

Monitoring Microwave Ablation of Ex Vivo Bovine Liver Using Ultrasonic Attenuation Imaging.

Thermal ablation of soft tissue changes the tissue microstructure and, consequently, induces changes in its acoustic properties. Although B-mode ultrasound provides high-resolution and high-frame-rate images of ablative therapeutic procedures, it is not particularly effective at delineating boundaries of ablated regions because of poor contrast in echogenicity between ablated and surrounding normal tissue. Quantitative ultrasound techniques can provide quantitative estimates of acoustic properties, such as backscatter and attenuation coefficients, and differentiate ablated and unablated regions more effectively, with the potential for monitoring minimally invasive thermal therapies. In this study, a previously introduced attenuation estimation method was used to create quantitative attenuation coefficient maps for 11 microwave ablation procedures performed on refrigerated ex vivo bovine liver. The attenuation images correlate well with the pathologic images of the ablated region. The mean attenuation coefficient for regions of interest drawn inside and outside the ablated zones were 0.9 (±0.2) and 0.45 (±0.15) dB/cm/MHz, respectively. These estimates agree with reported values in the literature and establish the usefulness of non-invasive attenuation imaging for monitoring therapeutic procedures in the liver.

Brightness, contrast, and color balance of digital versus film retinal images in the age-related eye disease study 2.

PURPOSE: To analyze brightness, contrast, and color balance of digital versus film retinal images in a multicenter clinical trial, to propose a model image from exemplars, and to optimize both image types for evaluation of age-related macular degeneration (AMD). METHODS: The Age-Related Eye Disease Study 2 (AREDS2) is enrolling subjects from 90 clinics, with three quarters of them using digital and one quarter using film cameras. Image brightness (B), contrast (C), and color balance (CB) were measured with three-color luminance histograms. First, the exemplars (film and digital) from expert groups were analyzed, and an AMD-oriented model was constructed. Second, the impact of B/C/CB on the appearance of typical AMD abnormalities was analyzed. Third, B/C/CB in AREDS2 images were compared between film (156 eyes) and digital (605 eyes), and against the model. Fourth, suboptimal images were enhanced by adjusting B/C/CB to bring them into accord with model parameters. RESULTS: Exemplar images had similar brightness, contrast, and color balance, supporting an image model. Varying a specimen image through a wide range of B/C/CB revealed greatest contrast of drusen and pigment abnormalities against normal retinal pigment epithelium with the model parameters. AREDS2 digital images were more variable than film, with lower correspondence to our model. Ten percent of digital were too dim and 19% too bright (oversaturated), versus 1% and 4% of film, respectively. On average, digital had lower green channel contrast (giving less retinal detail) than film. Overly red color balance (weaker green) was observed in 23% of digital versus 8% of film. About half of digital (but fewer film) images required enhancement before AMD grading. After optimization of both image types, AREDS2 image quality was judged as good as that in AREDS (all film). CONCLUSIONS: A histogram-based model, derived from exemplars, provides a pragmatic guide for image analysis and enhancement. In AREDS2, the best digital images matched the best film. Overall, however, digital provided lower contrast of retinal detail. Digital images taken with higher G-to-R ratio showed better brightness and contrast management. Optimization of images in the multicenter study helps standardize documentation of AMD (ClinicalTrials.gov NCT00345176).

A framework to contain a spatially distributed model of the degradation of solid waste in landfills.

This paper describes the concept and development of a generic spatially distributed numerical model that can contain and link sub-models of landfill processes in order to simulate solid waste degradation and gas generation in landfills. The model has been designed to simulate anaerobic degradation of solid waste saturated in leachate, and to reflect the effect on degradation of the control of both the flow and chemistry of the leachate in the pore space of the solids. The model can accommodate different profiles of waste constituents and therefore has the potential to simulate the effects of pre-treatment techniques such as shredding and inoculation. Components of the model simulate the transport of leachate and gases, and the consolidation of the solid waste. The results of some prototype calculations are presented.