Postoperative Imaging After Lobectomy: Predicting the Displacement and Change in Orientation of Nonresected Lung Nodules.

OBJECTIVES: The objective of this study was to determine the effect of a lobectomy to the location and orientation of nonresected lung nodule and its corresponding airway. METHODS: We reviewed preoperative and postoperative computed tomography of patients who underwent lobectomies and have a separate nonresected nodule in the ipsilateral lung. Displacement of the nonresected nodule and angulation of its corresponding segmental bronchus were measured. RESULTS: Fifty nodules from 40 patients (30 females, 10 male; mean ± SD age, 67 ± 7 years) were assessed. Nodules are displaced clockwise after right upper, right middle, and left lower lobectomies and counterclockwise after right lower and left upper lobectomies. Displacement of the remaining nodules was greater in the craniocaudal plane, followed by anteroposterior and transverses planes (mean, 3.7, 2.5, and 1.9 cm, respectively). CONCLUSIONS: Remaining ipsilateral nodules and their associated segmental airways are displaced in a predictable fashion after lobectomy. This may help in the assessment of follow-up imaging.

Thoracic Skeletal Muscle Is Associated With Adverse Outcomes After Lobectomy for Lung Cancer.

BACKGROUND: Assessment of risk associated with lung cancer resection is primarily based on evaluation of cardiopulmonary function and remains imprecise. We investigated the relationship between thoracic muscle and early outcomes after lobectomy. METHODS: Cross-sectional area of skeletal muscle was measured at the level of the fifth thoracic vertebra on computed tomography in 135 consecutive patients before lobectomy for lung cancer. Patients were stratified into low and high muscle groups using the sex-specific muscle median. Primary outcome was a composite of any postoperative complication as per The Society of Thoracic Surgeons General Thoracic Surgical Database. Secondary outcomes included postoperative respiratory complications, postoperative intensive care unit admission, hospital length of stay, and hospital readmission within 30 days of hospital discharge. The χ2 test, adjusted multivariable regression analysis, and likelihood ratio test were performed. RESULTS: Patients with low muscle were significantly more likely to have any postoperative complication and respiratory postoperative complications. Although postoperative intensive care unit admission was similar for low muscle and high muscle groups, low muscle patients had longer hospital length of stay and a higher rate of hospital readmission. Adjusted multivariable regression revealed the independent association of thoracic muscle with all outcomes. The likelihood ratio test suggested that thoracic muscle adds predictive capability to information captured by preoperative pulmonary function testing. CONCLUSIONS: Low thoracic muscle is independently associated with increased postoperative complications and health care utilization among patients undergoing lobectomy for lung cancer. Evaluation of thoracic muscle may enhance risk prediction models.

Quantifying the effect of slice thickness, intravenous contrast and tube current on muscle segmentation: Implications for body composition analysis.

OBJECTIVES: To quantify the effect of IV contrast, tube current and slice thickness on skeletal muscle cross-sectional area (CSA) and density (SMD) on routine CT. METHODS: CSA and SMD were computed on 216 axial CT images obtained at the L3 level in 72 patients with variations in IV contrast, slice thickness and tube current. Intra-patient mean difference (MD), 95 % CI and limits of agreement were calculated using the Bland-Altman approach. Inter- and intra-analyst agreement was evaluated. RESULTS: IV contrast significantly increased CSA by 1.88 % (MD 2.33 cm2; 95 % CI 1.76-2.89) and SMD by 5.99 % (p<0.0001). Five mm slice thickness significantly increased mean CSA by 1.11 % compared to 2 mm images (1.32 cm2; 0.78-1.85) and significantly decreased SMD by 11.64 % (p<0.0001). Low tube current significantly decreased mean CSA by 4.79 % (6.44 cm2; 3.78-9.10) and significantly increased SMD by 46.46 % (p<0.0001). Inter- and intra-analyst agreement was excellent. CONCLUSIONS: IV contrast, slice thickness and tube current significantly affect CSA and SMD. Investigators designing and analysing clinical trials using CT for body composition analysis should report CT acquisition parameters and consider the effect of slice thickness, IV contrast and tube current on myometric data. KEY POINTS: • Intravenous contrast, slice thickness and tube current significantly affect myometric data. • Image acquisition parameter variations may obscure intrapatient muscle differences on serial measurements. • Investigators using CT for body composition analysis should report CT acquisition parameters.

Lumbar skeletal muscle index derived from routine computed tomography exams predict adverse post-extubation outcomes in critically ill patients.

PURPOSE: To evaluate the effect of a skeletal muscle index derived from a routine CT image at the level of vertebral body L3 (L3SMI) on outcomes of extubated patients in the surgical intensive care unit. MATERIALS AND METHODS: 231 patients of a prospective observational trial (NCT01967056) who had undergone CT within 5days of extubation were included. L3SMI was computed using semi-automated segmentation. Primary outcomes were pneumonia within 30days of extubation, adverse discharge disposition and 30-day mortality. Secondary outcomes included re-intubation within 72h, total hospital costs, ICU length of stay (LOS), post-extubation LOS and total hospital LOS. Outcomes were analyzed using multivariable regression models with a priori-defined covariates height, gender, age, APACHE II score and Charlson Comorbidity Index. RESULTS: L3SMI was an independent predictor of pneumonia (aOR 0.96; 95% CI 0.941-0.986; P=0.002), adverse discharge disposition (aOR 0.98; 95% CI 0.957-0.999; P=0.044) and 30-day mortality (aOR 0.94; 95% CI 0.890-0.995; P=0.033). L3SMI was significantly lower in re-intubated patients (P=0.024). Secondary analyses suggest that L3SMI is associated with total hospital costs (P=0.043) and LOS post-extubation (P=0.048). CONCLUSION: The lumbar skeletal muscle index, derived from routine abdominal CT, is an objective prognostic tool at the time of extubation.

Biases and reconciliation in estimates of linkage disequilibrium in the human genome.

Genetic association studies of common disease often rely on linkage disequilibrium (LD) along the human genome and in the population under study. Although understanding the characteristics of this correlation has been the focus of many large-scale surveys (culminating in genomewide haplotype maps), the results of different studies have yielded wide-ranging estimates. Since understanding these differences (and whether they can be reconciled) has important implications for whole-genome association studies, in this article we dissect biases in these estimations that are due to known aspects of study design and analytic methodology. In particular, we document in the empirical data that the long-known complicating effects of allele frequency, marker density, and sample size largely reconcile all large-scale surveys. Two exceptions are an underappraisal of redundancy among single-nucleotide polymorphisms (SNPs) when evaluation is limited to short regions (as in candidate-gene resequencing studies) and an inflation in the extent of LD in HapMap phase I, which is likely due to oversampling of specific haplotypes in the creation of the public SNP map. Understanding these factors can guide the understanding of empirical LD surveys and has implications for genetic association studies.