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Morphomics Data Dictionary

Sven Holcombe, Binu Enchakalody, Peng Zhang, Stewart Wang

Overview

  • This page describes morphomics measures available for every chest/abdomen/pelvis scan in our CT database.
  • Most measures are taken "per vertebra" at each vertebral level visible in the CT scan, allowing morphomics to be reported as a function of body region.
  • A number of measures of muscle density are reported in Hounseld Units (HU), and often separated into Normal Density Muscle (NDM) and Low Density Muscle (LDM). The thresholds for these come from the paper: Goodpaster BH, Kelley DE, Wing RR, Meier A, Thaete FL. Effects of weight loss on regional fat distribution and insulin sensitivity in obesity. Diabetes. 1999;48(4):839-47.
  • The "lean psoas" is a mathematical combination of measures of psoas cross sectional area (mm2) and psoas density (in HU) inside the muscle boundary. The formula for lean psoas is then:
    This can be thought of as "normalizing a muscle's density between -85 HU (very fatty and low density) and +85 HU (very dense)". The values of ±85 were chosen by inspection of some of our sickest and healthiest individuals' data points.

Body Measures
(central plane depths)

Name Unit Meaning
VB2FASCIA mm Distance - front of vertebral body to fascia (central visceral size)
FASCIA2SKIN mm Linear distance from fascia to skin (central sub-cutaneous size)
SP2BACKSKIN mm Distance - posterior tip of spine to back skin (central back fat)

Body Measures
(shapes and sizes)

Name Unit Meaning
TOTALBODYAREA mm² Cross-sectional area of the body (area inside purple line)
FASCIAAREA mm² Cross-sectional area of the body (area inside yellow line)
BODYDEPTH mm Front-to-back body distance (aligned to body habitus)
BODYWIDTH mm Left-to-right body distance (aligned to body habitus)
FASCIAECCENTRICITY ratio Eccentricity of an ellipse having the same second-moments of the fascia region. (Ratio of major-axis length to the distance between ellipse foci). A circle has eccentricity of 0, while a line has eccentricity of 1.

Fat Measures

Name Unit Meaning
VISCERALFATAREA mm² Area inside fascia (yellow line) meeting fat density thresholds (-205 to 51 HU)
SUBCUTFATAREA mm² Area between skin and fascia meeting fat density thresholds (-205 to -51 HU)
SUBCUTFATHU HU Median pixel intensity of fat-intensity pixels (-205 to -51 HU) in the subcutaneous region. Not computed when fewer than 200 pixels of fat exist.
VISCERALFATHU HU Median pixel intensity of fat-intensity pixels (-205 to -51HU) inside the visceral cavity. Not computed when fewer than 200 pixels of fat exist.

Muscle
(psoas)

  • The psoas muscle is a core muscle running alongside the lumbar spine.
  • Muscle size and density (indicative of fatty infiltration) have shown to be good indicators of subject frailty
  • Psoas cross-section is sampled at the L4 vertebral level
Name Unit Meaning
TOTAL_PSOAS_AREA mm² Total area of the left/right psoas at L4 (region inside blue lines)
PSOAS_HU HU Average pixel intensity inside blue lines
WEIGHTED_LEAN_PSOAS HU*mm² PSOAS_HU normalized between -85 and +85, multiplied by TOTAL_PSOAS_AREA

Muscle
(dorsal muscle group)

Name Unit Meaning
studyid ID
vertebranumber ID
vertebraid ID
dmgvolofvb
DMG Volume within VB
mm³ Volume of the dorsal muscle group between this vertebra and its superior neighbor
dmgperimarea
DMG Boundary Area
mm² Cross sectional area of the DMG perimeter boundary. Boundary is built from triangl between spinal canal and left/right lateral seams, connected by nearest location to the posterior fascial envelope IRRESPECTIVE OF bone/muscle/air contents.
dmgldmarea
DMG Low Dens. Area
mm² Cross sectional area of the DMG falling in a low density muscle HU range (0 to 30)
dmgndmarea
DMG Normal Dens. Area
mm² Cross sectional area of the DMG falling in a normal density muscle HU range (31 to 100)
dmgperimmeanhu
DMG Mean HU
HU Mean pixel intensity within the DMG boundary.
dmgperimmedhu
DMG Median HU
HU Median pixel intensity within the DMG boundary.
dmgldmmeanhu
DMG Low Dens. Mean HU
HU Mean pixel intensity within Low Density Muscle (0 to 30) pixels inside the DMG boundary.
dmgldmmedhu
DMG Low Dens. Median HU
HU Median pixel intensity within Low Density Muscle (0 to 30) pixels inside the DMG boundary.
dmgndmmeanhu
DMG Normal Dens. Mean HU
HU Mean pixel intensity within Normal Density Muscle (31 to 100) pixels inside the DMG boundary.
dmgndmmedhu
DMG Normal Dens. Med HU
HU Median pixel intensity within Normal Density Muscle (31 to 100) pixels inside the DMG boundary.

Pelvis
(sizes)

Name Unit Meaning
DIST_WINGLATPT2WINGLATPT mm Distance across full pelvis (shown in orange)
DIST_ASISPT2ASISPT mm Distance across ASIS (where the seatbelt goes, shown blue)
DIST_LASISPT2PUBISPT mm Distance from pubis to ASIS (shown green)
ANG_LASIS_PUBIS_RASIS deg Angle between two green arrows
PHEIGHT mm Height of pelvis (vertical arrow, shown grey)

Spine Measures
(angles and sizes)

Name Unit Meaning
DIST_ANTPT2POSTPT mm Vertebral depth
DIST_INFSCPT2SUPSCPT mm Verteral height at the spinal canal
DIST_INFANTPT2SUPANTPT mm Vertebral height at the anterior of the body (inclusive of disc)
ANG_Y_WRT_INFVB deg Verteral angle (forward/backwards or flex./extension) with respect to the inferior vertebra (illustrated above)
ANG_X_WRT_INFVB deg Verteral angle (side-to-side) with respect to the inferior vertebra (not shown above, will be zero for a laterally symmetric spine)
ANG_Y_WRT_YZ deg Verteral "pose" (forward/backwards or flex./extension) with respect to the scanning table

Spine Measures
(cortical bone)

Name Unit Meaning
ANTCORTHMHU HU "Anterior Cortical Half-Maximum Hounsfield Unit" - HU level at half-max of the bone signal peak
ANTCORTFWBYHM HU*mm The "Full-width-multiplied-by-half-max" of the avg. cortical bone signal (Newman - 1998, Prevrhal - 1999)
ANTCORTFWBYHMSTD HU*mm Std. Dev. from all 60 "Full-width-by-half-max" measurements (at 1° increments in the 60° wedge)

Spine Measures
(trabecular bone)

Name Unit Meaning
BMDHUVBALIGNED HU Average pixel intensity (in CT Hounsfield Units) inside central bone core sample

Let's Collaborate

Morphomics is incredibly collaborative in nature, and its true power comes from bringing together experts and data from many fields to tackle important questions about human health and well-being.


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