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Rib fractures are a common and serious outcome of blunt thoracic trauma and their likelihood is greater in older individuals. Osteoporotic bone loss is a well-documented aging phenomenon with sex-specific characteristics, but within rib bones, neither baseline maps of regional thickness nor the rates of bone thinning with age have been quantified across whole ribs. This study presents such data from 4014 ribs of 240 adult subjects aged 20-90. A validated cortical bone mapping technique was applied to clinical computed tomography scans to obtain local rib cortical bone thickness measurements over the surfaces of ribs 2 through 11. Regression models to age and sex gave rates of cortex thinning in local zones and aggregated across whole ribs. The statistical parametric mapping provided these relationships regionally as a function of rib surface location. All models showed significant reductions in bone thickness with age (p 0.01). Average whole-rib thinning occurred at between 0.011 to 0.032 mm/decade (males) and 0.035 to 0.043 mm/decade (females), with sex and age accounting for up to 37% of population variability (R

Measurements of visceral adipose tissue cross-sectional area and radiation attenuation from computed tomography (CT) scans provide useful information about risk and mortality. However, scan protocols vary, encompassing differing vertebra levels and utilizing differing phases of contrast enhancement. Furthermore, fat measurements have been extracted from CT using different Hounsfield Unit (HU) ranges. To our knowledge, there have been no large studies of healthy cohorts that reported reference values for visceral fat area and radiation attenuation at multiple vertebra levels, for different contrast phases, and using different fat HU ranges. Two-phase CT scans from 1,677 healthy, adult kidney donors (age 18–65) between 1999 and 2017, previously studied to determine healthy reference values for skeletal muscle measures, were utilized. Visceral adipose tissue cross-sectional area (VFA) and radiation attenuation (VFRA) measures were quantified using axial slices at T10 through L4 vertebra levels. T-tests were used to compare males and females, while paired t-tests were conducted to determine the effect (magnitude and direction) of (a) contrast enhancement and (b) different fat HU ranges on each fat measure at each vertebra level. We report the means, standard deviations, and effect sizes of contrast enhancement and fat HU range. Male and female VFA and VFRA were significantly different at all vertebra levels in both contrast and non-contrast scans. Peak VFA was observed at L4 in females and L2 in males, while peak VFRA was observed at L1 in both females and males. In general, non-contrast scans showed significantly greater VFA and VFRA compared to contrast scans. The average paired difference due to contrast ranged from 1.6 to − 8% (VFA) and 3.2 to − 3.0% (VFRA) of the non-contrast value. HU range showed much greater differences in VFA and VFRA than contrast. The average paired differences due to HU range ranged from − 5.3 to 22.2% (VFA) and − 5.9 to 13.6% (VFRA) in non-contrast scans, and − 4.4 to 20.2% (VFA) and − 4.1 to 12.6% (VFRA) in contrast scans. The − 190 to − 30 HU range showed the largest differences in both VFA (10.8% to 22.2%) and VFRA (7.6% to 13.6%) compared to the reference range (− 205 to − 51 HU). Incidentally, we found that differences in lung inflation result in very large differences in visceral fat measures, particularly in the thoracic region. We assessed the independent effects of contrast presence and fat HU ranges on visceral fat cross-sectional area and mean radiation attenuation, finding significant differences particularly between different fat HU ranges. These results demonstrate that CT measurements of visceral fat area and radiation attenuation are strongly dependent upon contrast presence, fat HU range, sex, breath cycle, and vertebra level of measurement. We quantified contrast and non-contrast reference values separately for males and females, using different fat HU ranges, for lumbar and thoracic CT visceral fat measures at multiple vertebra levels in a healthy adult US population.

Background CT contrast media improves vessel visualization but can also confound calcification measurements. We evaluated variance in aorta attenuation from varied contrast-enhancement scans, and quantified expected plaque detection errors when thresholding for calcification. Methods We measured aorta attenuation (AoHU) in central vessel regions from 10K abdominal CT scans and report AoHU relationships to contrast phase (non-contrast, arterial, venous, delayed), demographic variables (age, sex, weight), body location, and scan slice thickness. We also report expected plaque segmentation false-negative errors (plaque pixels misidentified as non-plaque pixels) and false-positive errors (vessel pixels falsely identified as plaque), comparing a uniform thresholding approach and a dynamic approach based on local mean/SD aorta attenuation. Results Females had higher AoHU than males in contrast-enhanced scans by 65/22/20 HU for arterial/venous/delayed phases (p < 0.001) but not in non-contrast scans (p > 0.05). Weight was negatively correlated with AoHU by 2.3HU/10kg but other predictors explained only small portions of intra-cohort variance (R2 < 0.1 in contrast-enhanced scans). Average AoHU differed by contrast phase, but considerable overlap was seen between distributions. Increasing uniform plaque thresholds from 130HU to 200HU/300HU/400HU produces respective false-negative plaque content losses of 35%/60%/75% from all scans with corresponding false-positive errors in arterial-phase scans of 95%/60%/15%. Dynamic segmentation at 3SD above mean AoHU reduces false-positive errors to 0.13% and false-negative errors to 8%, 25%, and 70% in delayed, venous, and arterial scans, respectively. Conclusion CT contrast produces heterogeneous aortic enhancements not readily determined by demographic or scan protocol factors. Uniform CT thresholds for calcified plaques incur high rates of pixel classification errors in contrast-enhanced scans which can be minimized using dynamic thresholds based on local aorta attenuation. Care should be taken to address these errors and sex-based biases in baseline attenuation when designing automatic calcification detection algorithms intended for broad use in contrast-enhanced CTs.

Introduction: Cardiovascular disease remains the leading cause of death in the United States. Aortic calcification shows strong promise towards preventative screening efforts for cardiovascular risk in clinical and subclinical populations. While still relatively novel, granular distributions of aortic calcium in reference populations are absent from the literature. Methods: All participants of the Reference Analytic Morphomics Population, an approximation of vehicle occupants in the United States, with abdominal scans were considered for this analysis (n=4080). Analytic Morphomics was used to obtain vertebral-indexed anatomical measurements of the aorta and calcium characteristics (area, volume, density, and aortic wall obfuscation). Calcification was specifically identified as regions with a given morphology and pixel value three standard deviations above the defined central lumen zone. Results: Participant mean age was 33 (SD 22.6) and were mostly male (62.6%) due to the prevalence of males involved in trauma. Age and calcification distributions were right skewed among all vertebral levels and highest for the L3-L4 reference levels [~3% wall obfuscation (SD 10.5-11.3)]. Males demonstrated a progressive increase in total calcium volume from the 4 th decade of age, while females had comparatively smaller increases and a dramatic increase in total calcium after the 7 th decade. The largest increases in observed calcium volumes were observed in the 8 th decade for males (~2300 cm 3 ) and 7 th for females (~4500 cm 3 ). Conclusion: Aortic calcium prevalence was higher with reference to lower vertebral levels. Dramatic differential distributions of calcium were observed by age and sex.