Differential Imaging of Liver Tumors before and after Microwave Ablation with Electrode Displacement Elastography.

Liver cancer is a leading cause of cancer-related deaths; however, primary treatment options such as surgical resection and liver transplant may not be viable for many patients. Minimally invasive image-guided microwave ablation (MWA) provides a locally effective treatment option for these patients with an impact comparable to that of surgery for both cancer-specific and overall survival. MWA efficacy is correlated with accurate image guidance; however, conventional modalities such as B-mode ultrasound and computed tomography have limitations. Alternatively, ultrasound elastography has been used to demarcate post-ablation zones, yet has limitations for pre-ablation visualization because of variability in strain contrast between cancer types. This study attempted to characterize both pre-ablation tumors and post-ablation zones using electrode displacement elastography (EDE) for 13 patients with hepatocellular carcinoma or liver metastasis. Typically, MWA ablation margins of 0.5-1.0 cm are desired, which are strongly correlated with treatment efficacy. Our results revealed an average estimated ablation margin inner quartile range of 0.54-1.21 cm with a median value of 0.84 cm. These treatment margins lie within or above the targeted ablative margin, indicating the potential to use EDE for differentiating index tumors and ablated zones during clinical ablations. We also obtained a high correlation between corresponding segmented cross-sectional areas from contrast-enhanced computed tomography, the current clinical gold standard, when compared with EDE strain images, with r2 values of 0.97 and 0.98 for pre- and post-ablation regions.

Comparison of Displacement Tracking Algorithms for in Vivo Electrode Displacement Elastography.

Hepatocellular carcinoma and liver metastases are common hepatic malignancies presenting with high mortality rates. Minimally invasive microwave ablation (MWA) yields high success rates similar to surgical resection. However, MWA procedures require accurate image guidance during the procedure and for post-procedure assessments. Ultrasound electrode displacement elastography (EDE) has demonstrated utility for non-ionizing imaging of regions of thermal necrosis created with MWA in the ablation suite. Three strategies for displacement vector tracking and strain tensor estimation, namely coupled subsample displacement estimation (CSDE), a multilevel 2-D normalized cross-correlation method, and quality-guided displacement tracking (QGDT) have previously shown accurate estimations for EDE. This paper reports on a qualitative and quantitative comparison of these three algorithms over 79 patients after an MWA procedure. Qualitatively, CSDE presents sharply delineated, clean ablated regions with low noise except for the distal boundary of the ablated region. Multilevel and QGDT contain more visible noise artifacts, but delineation is seen over the entire ablated region. Quantitative comparison indicates CSDE with more consistent mean and standard deviations of region of interest within the mass of strain tensor magnitudes and higher contrast, while Multilevel and QGDT provide higher CNR. This fact along with highest success rates of 89% and 79% on axial and lateral strain tensor images for visualization of thermal necrosis using the Multilevel approach leads to it being the best choice in a clinical setting. All methods, however, provide consistent and reproducible delineation for EDE in the ablation suite.

Diagnostic radiology resident compliance with recommended health guidelines: effect of resident work environment.

RATIONALE AND OBJECTIVES: To determine diagnostic radiology resident compliance with recommended health guidelines for physical activity, body weight, diet, related health indicators, and the effects of the resident work environment on compliance. MATERIALS AND METHODS: A request was electronically mailed to members of the Association of Program Directors in Radiology and the Association of Program Coordinators in Radiology in May 2007 and again in June 2007, asking members to forward to their radiology residents an invitation to complete an online health survey. Frequency counts and Fisher's exact test, respectively, were used to summarize results and to determine statistically significant relationships between survey variables. RESULTS: A total of 811 radiology residents completed the survey, representing 18% of 4,412 diagnostic radiology residents. Five hundred forty-five (67.2%) of 811 were male and 264 (32.6%) female. Two hundred ten (25.9%) were first-year, 239 (29.5%) second-year, 201 (24.8%) third-year, and 161 (19.9%) fourth-year residents. Three hundred two (37.2%) engaged in recommended guidelines for physical activity and < or =465 (57.3%) complied with each of multiple federal dietary guidelines (excluding alcohol intake). Up to 329 (40.6%) residents did not know whether they were in compliance with various dietary guidelines. A total of 426 (52.5%) residents reported working > or =60 hours/week, which significantly correlated with less physical activity (P = .013). CONCLUSION: A substantial number of residents are out of compliance with federal guidelines for physical activity and diet and are not knowledgeable about their personal dietary intake. Long work hours are related to a lack of physical activity. Radiology programs may be able to influence resident health practices by modifying work hours and the working environment, encouraging healthy dietary intake and physical activity, and instituting campaigns to inform residents and faculty about health guidelines and available wellness programs.

Post-Procedure Evaluation of Microwave Ablations of Hepatocellular Carcinomas Using Electrode Displacement Elastography.

Microwave ablation has been used clinically as an alternative to surgical resection. However, lack of real-time imaging to assess treated regions may compromise treatment outcomes. We previously introduced electrode displacement elastography (EDE) for strain imaging and verified its feasibility in vivo on porcine animal models. In this study, we evaluated EDE on 44 patients diagnosed with hepatocellular carcinoma, treated using microwave ablation. The ablated region was identified on EDE images for 40 of the 44 patients. Ablation areas averaged 13.38 ± 4.99 cm2 on EDE, compared with 7.61 ± 3.21 cm2 on B-mode imaging. Contrast and contrast-to-noise ratios obtained with EDE were 232% and 98%, respectively, significantly higher than values measured on B-mode images (p < 0.001). This study indicates that EDE is feasible in patients and provides improved visualization of the ablation zone compared with B-mode ultrasound.