EVOLUTION OF BONE DENSITOMETRYNOVEL DXA USESNOVEL DXA USES

M h 8th 2012March 8th, 2012ISCD 2012: Los Angeles, CA

Mark PunyanityaBiomedical Engineer

TYPES OF FATSubcutaneous Adipose Tissue (SAT)

S b t f t f d d th th ki

Apple shape vs. Pear shape

Subcutaneous fat found underneath the skin, which may cause dimpling and cellulite

Fat accumulated in the lower body (the pear shape) is subcutaneous

Above the waist p )

Visceral Adipose Tissue (VAT)

Below the waist

Also known as, intra-abdominal fat, belly fat, beer belly, central adiposity

Visceral fat pads all internal vital organs such asVisceral fat pads all internal vital organs such as stomach, kidney, heart and also pancreas

Fat in the abdominal area (the apple shape) is largely visceral

Apple shape•More visceral fat•Higher risk of weight‐related health problems

Pear shape•Less visceral fat•Lower risk of weight‐related health problems

S GSK d i i l Metabolically activeSource: GSK education material

http://www.alli.co.uk/How‐alli‐works/How‐visceral‐fat‐works/

VISCERAL ADIPOSE TISSUE (VAT)

• VAT (fat in and around abdominal organs) has been shown to be a risk factor for allshown to be a risk factor for all cause mortality in men1

• VAT is a unique pathogenic fat• VAT is a unique, pathogenic fat depot2 associated with metabolic risk factors (triglycerides cholesterol(triglycerides, cholesterol, fasting glucose, hypertension) and CVD

1Kuk JL, et al Visceral fat is an independent predictor of all-cause mortality in men. Obesity. 2006;14(2):336-41.

2Fox CS, et al Abdominal visceral and subcutaneous adiposeFox CS, et al Abdominal visceral and subcutaneous adipose tissue compartments: association with metabolic risk factors in the Framingham Heart Study. Circulation. 2007 Jul 3;116(1):39-48.

VISCERAL FAT AND METABOLIC RISK

Key PointsKey Points Recent study of more than 3000

participants drawn from the Framingham Heart Study showed

SAT and VAT are correlated with metabolic risk factors

VAT more strongly associated withVAT more strongly associated with an adverse metabolic risk profile

GR = 4.7/SD (Females)

G /S ( ) GR = 4.2/SD (Males)

.

Fox CS et al. (2007) Circulation 116 39-48

VisceralAdiposeTissue

ResidualTissue

Compartment

SubcutaneousAdiposeTiss e CompartmentTissue

WHOLE BODY MRI ANALYSISWHOLE-BODY MRI ANALYSIS

VisceralAdiposeTissue

SubcutaneousAdiposeTissue

MuscleTissue

ResidualTiss e

Tissue

TissueCompartment

VisceralVisceralAdiposeTissue

MuscleTissue

Subcutaneous

Resid al

SubcutaneousAdiposeTissue

ResidualTissue

Compartment

RELIABILITY MEASURE FOR MRIRELIABILITY MEASURE FOR MRIICC CVICC CV

Skeletal Muscle 0.99 2-5%Subcutaneous AT 0.99 2-5%Vi l ATVisceral AT 0.95 2-5%Intermuscular AT 0 97 5-8%0.97 5 8%

SENSITIVITY MEASURE FOR MRIMRI Baseline SD of Individual Group

SENSITIVITY MEASURE FOR MRI

(kg)ase e

(mean)S o

changes(1 year)

d dua95% CI

G oup95% CI(N=20)

SM 18 6 0 40 0 82 0 19SM 18.6 0.40 0.82 0.19TAT 26.8 1.00 2.06 0.47SAT 24 0 0 90 1 85 0 43SAT 24.0 0.90 1.85 0.43VAT 1.9 0.20 0.41 0.09IMAT 1 08 0 10 0 21 0 05IMAT 1.08 0.10 0.21 0.05

MRI AnalysisMRI Analysis•Tissues were segmented by trained technicians using 

MRI AnalysisMRI Analysis

commercially available image analysis software. •Analysis time: 24 hours for ysubcutaneous adipose tissue, skeletal muscle, Visceral adipose tissue, p ,Bone+organ, Intramuscular adipose tissue, lung.

‐Shen W., et al., Curr Opin Clin Nutr Metab Care.‐2006;8:595‐601

The % difference between Vgap and Vtrue was generally smaller with the decrease of gap size

2 cm gap 3 cm gap 4 cm gap 5 cm gap

generally smaller with the decrease of gap size

Acquisitiontime

40-50 minutes 35-40 minutes 30 minutes 25 minutes

Analysis 12 hours 8 hours 6.5 hours 5 hoursa ys stime

8 ou s 6 5 ou s 5 ou s

SM 0.30%±0.43%*

0.41%±0.35%*

0.59%±0.63%*

1.04%±0.77%*

SAT 0.26%±0.23%*

0.53%±0.45%*

0.59%±0.49%*

0.85%±0.86%*

VAT 3.14%±2.99%*

5.23%±6.01%*

8.14%±8.15%*

9.70%±8.58%*

IMAT 3.06%±2.41%*

4.75%±4.48%*

6.93%±7.30%*

9.55%±8.77%* Studies will require 2 % more subjects if every 5 cm protocol is used in 5 to 17 

year old subjects and 8‐10 % more subjects in 5 to 10 year old prepubertal hild f i l t th ti t l i ichildren for equivalent power as the continuous every‐cm protocol in measuring VAT and IMAT.

‐ Shen W., et al., Int J Pediatric Obesity. 2010

Pearson correlations between VAT volume and Pearson correlations between VAT volume and

Correlation Coefficients

VAT areas for individual transverse slicesVAT areas for individual transverse slices

Correlation Coefficients

-10 cm -5 cm L4-L5 + 5 cm + 10 cm + 15 cm

Men Abdominal VAT 0.843 0.899 0.951 0.966 0.924

Abdominopelvic VAT 0.857 0.889 0.919 0.950 0.961 0.917

Women Abdominal VAT 0.908 0.929 0.972 0.961 0.822

Abdominopelvic VAT 0.856 0.930 0.936 0.964 0.951 0.821

‐ Shen W et al., Am J Clin Nutr 2004;80:271‐8

Group Glu Insulin TG HDL SBP DBPMen (n= 283)

Abdominal VAT .211 .505 .361 -.242 .312 .318Abdominopelvic VAT .217 .522 .356 -.255 .309 .316-5 cm .186 .389** .272** -.194 .244** .264

L4-L5 .193 .384** .276** -.162** .277 .266**+5 cm .187 .458** .354 -.235 .307 .306+10 cm .210 .520 .401* -.271* .306 .31310 cm .210 .520 .401 .271 .306 .313+15 cm .201 .522 .332 -.238 .295 .313

Women (n = 411)

Abdominal VAT .218 .569 .397 -.383 -.054 .104Abdominopelvic VAT 222 558 398 - 385 - 051 110Abdominopelvic VAT .222 .558 .398 .385 .051 .110-5 cm .192 .547 .386 -.386 -.072 .069L4-L5 .161** .569 .369 -.350** -.054 .139+5 cm 219 562 392 - 392 - 060 076+5 cm .219 .562 .392 -.392 -.060 .076 +10 cm .230 .514** .385 -.348** -.062 .083+15 cm .220 .467** .305** -.299** .013 .118

***, significantly higher (P < 0.05) than abdominal VAT; **, significantly lower (P < 0.05) than abdominal VAT.

‐Shen W., et al., Int J Obesity, 2007,31:763‐9

How CoreScan works

• Key Differentiator: Separates out SAT and VAT

1. Start with total fat iDXA distinguishes between fat, lean and bone through dual

energy measurementsenergy measurements Excellent image resolution helps enable accurate tissue

characterization

2. Calculate SAT Utilize iDXA to measure SAT layer thickness at sides of

android region CoreScan maps the total SAT layer around android region

3. Total fat – SAT = VATSAT inner wall

SAT outer wall

CoreScan: Reproducible

• Defined region of measurement ‐ Android

• Automated definition of region – based off• Automated definition of region – based off 

bone landmarks on the body

• Consistent method of acquisition

CoreScan: ReproducibleAndroid Region

Standard region of interest for iDXA body compositionpBase of the ROI located at top of pelvisHeight (H) = 20% of distance from top of pelvis to base of skullpelvis to base of skull Android region contains high proportion of visceral fatRelatively little bone in android region

CoreScan: Accuracy

• Validated in clinical trial*

• High degree of correlation with CT

• On average difference between iDXA• On average difference between iDXA 

and CT ~60g

• 95% of subjects were within a range of 

16‐96cm3 difference between measuring 

CT image of visceral fat from subject (42 year old male; BMI = 26.2 kg/m2)

I f D S ji K lwith CT and iDXA

Image courtesy of Dr. Sanjiv Kaul

* Kaul et al. Dual X‐Ray Absorptiometry for Quantification of Visceral Adipose Tissue. Advance online publication 26 January 2012.

CoreScan: AccuracyAnalysis on OHSU DataAnalysis on OHSU Data

OHSU CT vs. iDXA VAT VolumeAll Subjects

Gender r2 SEE

All Subjects

4000

5000

m³)

Excellent Correlation*

Gender r SEEFemales 0.960 190.5Males 0.953 221.6 2000

3000

AT

Volu

me

(cm

Combined 0.958 209.41000

CT

VA0

0 1000 2000 3000 4000 5000

iDXA VAT Volume (cm³)data ID

* Kaul et al. Dual X‐Ray Absorptiometry for Quantification of Visceral Adipose Tissue. Advance online publication 26 January 2012.

SUMMARYSUMMARY• Further studies are needed to determine• Further studies are needed to determine

whether VF estimation offers incremental value to other more standard measures ofvalue to other more standard measures of metabolic and cardiovascular risk in patientspatients.

VISCERAL ADIPOSE TISSUEVISCERAL ADIPOSE TISSUE

VISCERAL ADIPOSE TISSUE (VAT)VISCERAL ADIPOSE TISSUE (VAT)ROI DEFINITIONROI DEFINITION

Regions are automatically placed by the software•Outer region extends across entire abdomenOuter region extends across entire abdomen•Middle region extends across visceral cavity including abdominal wall•Inside region extends across visceral cavity just inside abdominal•Inside region extends across visceral cavity just inside abdominal wall

DXA VAT vs. VAT by CTy

i l i•Linear Relation•High Correlation•Low SEE vs. CT VAT by an Expert Reader

Micklesfield et al, Dual-Energy X-Ray Performs as Well as Clinical Computed Tomography for the Measurement of Visceral Fat, Advance online publication 12 January 2012

CONCLUSIONCONCLUSION• If these findings are supported by similar• If these findings are supported by similar

results in other populations, DXA-VAT may become a useful alternative to CTmay become a useful alternative to CT and MRI for the estimation of VAT in both clinical and research settingsclinical and research settings.

SUMMARY OF NEWBODY COMPOSITION FEATURES

The new VAT Application, reference values, andreporting enhancements should be helpful in thep g pevaluation of a wide variety of abnormalities involving fatmass, lean mass, and bone, for establishing entrycriteria into clinical trials and for other clinical researchcriteria into clinical trials, and for other clinical, research,and epidemiological uses.

Mark PunyanityaBi di l E iBiomedical EngineerDirector, Image Reading Center

Phone: (646) 736-2487Email: mark@imagereadingcenter.comWeb: www imagereadingcenter comWeb: www.imagereadingcenter.com