Imaging acquisition display performance: an evaluation and discussion of performance metrics and procedures.

When The Joint Commission updated its Requirements for Diagnostic Imaging Services for hospitals and ambulatory care facilities on July 1, 2015, among the new requirements was an annual performance evaluation for acquisition workstation displays. The purpose of this work was to evaluate a large cohort of acquisition displays used in a clinical environment and compare the results with existing performance standards provided by the American College of Radiology (ACR) and the American Association of Physicists in Medicine (AAPM). Measurements of the minimum luminance, maximum luminance, and luminance uniformity, were performed on 42 acquisition displays across multiple imaging modalities. The mean values, standard deviations, and ranges were calculated for these metrics. Additionally, visual evaluations of contrast, spatial resolution, and distortion were performed using either the Society of Motion Pictures and Television Engineers test pattern or the TG-18-QC test pattern. Finally, an evaluation of local nonuniformities was performed using either a uniform white display or the TG-18-UN80 test pattern. Displays tested were flat panel, liquid crystal displays that ranged from less than 1 to up to 10 years of use and had been built by a wide variety of manufacturers. The mean values for Lmin and Lmax for the displays tested were 0.28 ± 0.13 cd/m2 and 135.07 ± 33.35 cd/m2, respectively. The mean maximum luminance deviation for both ultrasound and non-ultrasound displays was 12.61% ± 4.85% and 14.47% ± 5.36%, respectively. Visual evaluation of display performance varied depending on several factors including brightness and contrast settings and the test pattern used for image quality assessment. This work provides a snapshot of the performance of 42 acquisition displays across several imaging modalities in clinical use at a large medical center. Comparison with existing performance standards reveals that changes in display technology and the move from cathode ray tube displays to flat panel displays may have rendered some of the tests inappropriate for modern use.

The design and fabrication of two portal vein flow phantoms by different methods.

PURPOSE: This study outlines the design and fabrication techniques for two portal vein flow phantoms. METHODS: A materials study was performed as a precursor to this phantom fabrication effort and the desired material properties are restated for continuity. A three-dimensional portal vein pattern was created from the Visual Human database. The portal vein pattern was used to fabricate two flow phantoms by different methods with identical interior surface geometry using computer aided design software tools and rapid prototyping techniques. One portal flow phantom was fabricated within a solid block of clear silicone for use on a table with Ultrasound or within medical imaging systems such as MRI, CT, PET, or SPECT. The other portal flow phantom was fabricated as a thin walled tubular latex structure for use in water tanks with Ultrasound imaging. Both phantoms were evaluated for usability and durability. RESULTS: Both phantoms were fabricated successfully and passed durability criteria for flow testing in the next project phase. CONCLUSIONS: The fabrication methods and materials employed for the study yielded durable portal vein phantoms.

An investigation of industrial molding compounds for use in 3D ultrasound, MRI, and CT imaging phantoms.

PURPOSE: This study investigated the ultrasound, MRI, and CT imaging characteristics of several industrial casting and molding compounds as a precursor to the future development of durable and anatomically correct flow phantoms. METHODS: A set of usability and performance criteria was established for a proposed phantom design capable of supporting liquid flow during imaging. A literature search was conducted to identify the materials and methods previously used in phantom fabrication. A database of human tissue and casting material properties was compiled to facilitate the selection of appropriate materials for testing. Several industrial casting materials were selected, procured, and used to fabricate test samples that were imaged with ultrasound, MRI, and CT. RESULTS: Five silicones and one polyurethane were selected for testing. Samples of all materials were successfully fabricated. All imaging modalities were able to discriminate between the materials tested. Ultrasound testing showed that three of the silicones could be imaged to a depth of at least 2.5 cm (1 in.). The RP-6400 polyurethane exhibited excellent contrast and edge detail for MRI phantoms and appears to be an excellent water reference for CT applications. The 10T and 27T silicones appear to be usable water references for MRI imaging. CONCLUSIONS: Based on study data and the stated selection criteria, the P-4 silicone provided sufficient material contrast to water and edge detail for use across all imaging modalities with the benefits of availability, low cost, dimensional stability, nontoxic, nonflammable, durable, cleanable, and optical clarity. The physical and imaging differences of the materials documented in this study may be useful for other applications.

A metabolically healthy obese phenotype in hispanic participants in the IRAS family study.

OBJECTIVE: Some obese individuals appear to be protected from developing type 2 diabetes mellitus and cardiovascular disease (CVD). This has led to characterizing body size phenotypes based on cardiometabolic risk factors specifically as obese or overweight, and as metabolically healthy (MH) or metabolically abnormal (MA) based upon blood pressure, lipids, glucose homeostasis, and inflammatory parameters. The aim of this study was to measure the prevalence of and describe fat distribution across these phenotypes in a minority population. DESIGN AND METHODS: Hispanic participants (N = 1054) in the IRAS Family Study were categorized into different body size phenotypes. Computed tomography (CT) abdominal scans were evaluated for measures of nonalcoholic fatty liver disease (NAFLD) and abdominal fat distribution. Statistical models adjusting for familial relationships were estimated. RESULTS: Seventy percent (70%) of the Hispanic cohort was overweight (32%) or obese (38%). Forty-one percent (n = 138) of overweight participants and 19% (n = 74) of obese participants met criteria for MH. Adjusted analyses showed the MH phenotype was associated with lower visceral adipose tissue (VAT) and higher liver density (indicating lower fat content) in obese participants (p = 0.0005 and p = 0.0002, respectively), and lower VAT but not liver density in overweight participants (p = 0.008 and p = 0.162, respectively) compared to their MA counterparts. Odds of NAFLD were reduced in MH obese (OR = 0.34, p = 0.0007) compared to MA obese. VAT did not differ between MH obese or overweight and normal weight groups. CONCLUSIONS: These findings suggest that lower levels of visceral and liver fat, despite overall increased total body fat, may be a defining feature of MH obesity in Hispanic Americans.

Selective protection against extremes in childhood body size, abdominal fat deposition, and fat patterning in breastfed children.

OBJECTIVE: To determine whether the effect of breastfeeding on childhood measures of adiposity differs across percentiles of childhood body mass index (BMI), subcutaneous (SAT) and visceral (VAT) adipose tissue deposition, ratio of subcutaneous to triceps skinfold (STR), and intramyocellular lipid accumulation (IMCL). DESIGN: Retrospective cohort. SETTING: Denver, Colorado. PARTICIPANTS: Four hundred forty-two children and adolescents aged 6 to 13 years participating in the Exploring Perinatal Outcomes Among Children study (EPOCH) with material recall of infant diet. MAIN EXPOSURE: Adequate (≥6 breast milk-months) vs low (<6 breast milk-months) neonatal breastfeeding status. MAIN OUTCOME MEASURES: Mean and percentile differences in BMI, SAT, VAT, STR, and IMCL between children who had adequate compared with low levels of breastfeeding. RESULTS: No significant differences in mean levels of childhood adiposity levels between adequate and low breastfeeding status were detected using linear regression models. However, in quantile regression models, adequate breastfeeding was associated with lower levels of adiposity levels for those in the upper percentiles (>60th percentile for VAT, 85th and 95th percentiles for BMI, and 95th percentiles for SAT and STR) and a null effect for those at the 50th percentile or lower. These effects were independent of sociodemographic, perinatal, and current lifestyle factors. We found no relationship between breastfeeding and IMCL at any percentile of the distribution. CONCLUSIONS: Rather than shifting the entire distribution of adiposity-related measures in childhood, breastfeeding selectively protects against extremes in body size and fat deposition, reinforcing the American Academy of Pediatrics recommendation for 6 months of exclusive breastfeeding as the optimal infant diet.

Fat infiltration of muscle, diabetes, and clinical fracture risk in older adults.

CONTEXT: Older adults with type 2 diabetes are at higher risk for fracture compared with nondiabetic adults after adjustment for their higher bone mineral density. Infiltration of muscle by fat predicts increased risk of hip fracture. OBJECTIVE: We investigated whether fat infiltration of muscle, which is greater in diabetic adults, is associated with all clinical fracture and whether it accounts for the increased fracture risk in those with diabetes. DESIGN, SETTING, AND PARTICIPANTS: Data were analyzed from the Health, Aging, and Body Composition Study, a cohort of community-dwelling adults aged 70-79 yr. Glucose metabolism status and x-ray attenuation of thigh muscle were determined at baseline for 2762 participants. MAIN OUTCOME MEASURES: During a mean 8.2 ± 2.3 yr follow-up, 331 participants reported at least one clinical fracture. RESULTS: Fat infiltration of muscle was higher in those with diabetes or impaired glucose metabolism than in those with normal glucose metabolism (P < 0.001). Fat infiltration of muscle was independently associated with a 19% increased risk of incident clinical fracture (multivariate hazard ratio = 1.19; 95% confidence interval = 1.04-1.36); this association did not differ across glucose metabolism groups (P for interaction = 0.65). As previously reported, diabetes was associated with a greater fracture risk compared with normal glucose metabolism (hazard ratio = 1.42; 95% confidence interval = 1.07-1.89) after adjustment for bone mineral density, but further adjustment for fat infiltration of muscle did not attenuate this association. CONCLUSIONS: Fat infiltration of muscle predicts clinical fracture in older adults. Although fat infiltration of muscle is higher among those with diabetes, it does not account for their increased fracture risk.

Correlates and heritability of nonalcoholic fatty liver disease in a minority cohort.

Nonalcoholic fatty liver disease (NAFLD) is associated with obesity and insulin resistance. The condition disproportionately affects Hispanic Americans. The aims of this study were to examine the risk factors and heritability of NAFLD in 795 Hispanic American and 347 African-American adults participating in the Insulin Resistance Atherosclerosis Study (IRAS) Family Study. Computed tomography (CT) scans of the abdomen were evaluated centrally for measures of liver-spleen (LS) density ratio and abdominal fat distribution. Other measures included insulin sensitivity (SI) calculated from a frequently sampled intravenous glucose tolerance test and various laboratory measures. Statistical models which adjust for familial relationships were estimated separately for the two ethnic groups. Heritability was calculated using a variance components approach. The mean age of the cohort was 49 years (range 22-84); 66% were female. NAFLD (LS ratio<1) was more common in Hispanic Americans (24%) than African Americans (10%). NAFLD was independently associated with SI and visceral adipose tissue (VAT) area in both ethnic groups, although the proportion of explained variance was considerably higher in the Hispanic models. Adiponectin contributed significantly in the African-American models whereas triglycerides (TGs) and plasminogen activator inhibitor 1 (PAI-1) contributed only in the Hispanic models. Liver density was modestly heritable in both ethnic groups (h2 approximately 0.35). In summary, the prevalence of NAFLD was twofold greater in Hispanic than African Americans. Certain correlates of NAFLD were similar between the ethnic groups, whereas others were distinct. NAFLD was modestly heritable. These findings suggest that NAFLD may have a differing environmental and/or genetic basis in these ethnic groups.

Effects of maintained weight loss on sleep dynamics and neck morphology in severely obese adults.

The goals of the study were to determine if moderate weight loss in severely obese adults resulted in (i) reduction in apnea/hypopnea index (AHI), (ii) improved pharyngeal patency, (iii) reduced total body oxygen consumption (VO(2)) and carbon dioxide production (VCO(2)) during sleep, and (iv) improved sleep quality. The main outcome was the change in AHI from before to after weight loss. Fourteen severely obese (BMI > 40 kg/m(2)) patients (3 males, 11 females) completed a highly controlled weight reduction program which included 3 months of weight loss and 3 months of weight maintenance. At baseline and postweight loss, patients underwent pulmonary function testing, polysomnography, and magnetic resonance imaging (MRI) to assess neck morphology. Weight decreased from 134 +/-6.6 kg to 118 +/- 6.1 kg (mean +/- s.e.m.; F = 113.763, P < 0.0001). There was a significant reduction in the AHI between baseline and postweight loss (subject, F = 11.11, P = 0.007). Moreover, patients with worse sleep-disordered breathing (SDB) at baseline had the greatest improvements in AHI (group, F = 9.00, P = 0.005). Reductions in VO(2) (285 +/- 12 to 234 +/-16 ml/min; F = 24.85, P < 0.0001) and VCO(2) (231 +/- 9 to 186 +/- 12 ml/min; F = 27.74, P < 0.0001) were also observed, and pulmonary function testing showed improvements in spirometry parameters. Sleep studies revealed improved minimum oxygen saturation (minSaO(2)) (83.4 +/- 61.9% to 89.1 +/- 1.2%; F = 7.59, P = 0.016), and mean SaO(2) (90.4 +/- 1.1% to 93.8 +/- 1.0%; F = 6.89, P = 0.022), and a significant increase in the number of arousals (8.1 +/- 1.4 at baseline, to 17.1 +/- 3.0 after weight loss; F = 18.13, P = 0.001). In severely obese patients, even moderate weight loss (approximately 10%) boasts substantial benefit in terms of the severity of SDB and sleep dynamics.

Virtual anatomy: an anatomist's playground.

Virtual anatomy presents significant advantages over the reality of a cadaver as it can provide different views and perspectives, portability, longevity, standardization, diversity and most importantly the opportunity to learn the anatomy of the living human body instead of the corpse. Virtual anatomy is the life-like appearance of visible anatomy, a good example of which is the evolution of the Visible Human. Racial and statistical diversity is already developing as the population of photographic "Visible Humans" is now at least 10. Virtual anatomy should include additional diversity and therefore, consideration should be given to the preparation of more visible anatomy that will better support the virtual integration of all areas of physiology, kinematics, pathology and pathophysiology, development and evolution. Integration of anatomists with mathematicians, computer scientists, information scientists, physiologists, pathologists and clinicians (and LIST other basic scientist) is needed in order to facilitate this development. As this unfolds it is proposed, or challenged, that anatomists should maintain their position of responsibility for building anatomy as the foundation for all medical and healthcare education. In order to maintain that position they must understand and participate in this development and enjoy the rewards of teaching more visually empowering, functional, and clinical anatomy. The trip is a long one and is only about to begin but the train is leaving. Are you on board?

Insulin sensitivity, body fat distribution, and family diabetes history: the IRAS Family Study.

OBJECTIVE: Markers of insulin resistance are often apparent in nondiabetic relatives of subjects with type 2 diabetes. Whether diabetes family history (FH) also predicts visceral fat accumulation and, if so, whether the increased insulin resistance in relatives of diabetic subjects occurs independently of visceral fat accumulation are not known. RESEARCH METHODS AND PROCEDURES: To examine this issue, we studied the relationship of diabetes FH with insulin sensitivity and fat measures, measured by minimal model analysis and computed tomography, respectively, in families participating in the Insulin Resistance Atherosclerosis (IRAS) Family Study. FH scores were based on the diabetes status of the participants' parents and older siblings. RESULTS: FH scores were significantly correlated with reduced insulin sensitivity (p < 0.05) and increased subcutaneous (p < 0.05) and visceral (p < 0.05, San Antonio only) fat in families from San Antonio and Los Angeles but not in the leaner Hispanic families from San Luis Valley. There was no evidence for a stronger association of FH score with visceral fat accumulation than with subcutaneous fat or insulin resistance. DISCUSSION: The absence of an association between FH score and insulin resistance/fat accumulation in San Luis Valley is consistent with the idea that the expression of transmitted diabetes genes may be suppressed in leaner, more physically active populations.

Insulin sensitivity, insulin secretion, and abdominal fat: the Insulin Resistance Atherosclerosis Study (IRAS) Family Study.

The relationship between insulin sensitivity and overall obesity is well established. However, there remains debate as to which of the fat depots, visceral abdominal tissue (VAT) or subcutaneous abdominal tissue (SAT), is of greater importance. Also, the relationship between fat distribution and insulin secretion is largely unknown. We studied SI, acute insulin response (AIR), and disposition index (DI), as obtained by minimal model analysis, in 999 Hispanic and 458 African-American men and women as part of the Insulin Resistance Atherosclerosis Study (IRAS) Family Study. VAT and SAT were measured from computed tomography scans performed at the L4/L5 vertebral region. A mixed-model approach was used to determine the relationship between each of the glucose homeostasis measures (SI, AIR, and DI) versus abdominal fat measures. Mean values were as follows: age, 41 years; SI, 1.98 10(-4).min(-1).microU(-1).ml(-1); AIR, 840 pmol.ml(-1).min(-1); BMI, 28.5 kg/m2; VAT, 100 cm2; and SAT, 333 cm2. SAT, VAT, and their joint interaction were each inversely and significantly associated with SI, adjusting for age, sex, ethnicity, and BMI. SAT, but not VAT, was positively associated with AIR, except when additionally adjusting for SI, in which case VAT was inversely associated with AIR. VAT and the joint interaction of VAT and SAT were inversely associated with DI. The fat measures explained 27% of the model R2 for SI, 16% for AIR, and 16% for DI. Thus, fat distribution is an important determinant of both insulin resistance and insulin secretion.