Body Composition Laboratory Monash Medical Centre Dan Stroud
Body Composition Laboratory Monash Medical Centre Dan Stroud Anne-Marie, Melinda & Emma Boyd Strauss Mark Wahlqvist Kenneth Mc. Neill Max Thompson Daniel Borovnicar, all staff & John Shiells DBS 2001
Why Measure Body Composition? - Diabetes Osteoporosis Liver cancer & cirrhosis Growth hormone Cystic fibrosis Renal failure DBS 2001
Instrumentation – Direct & Indirect Height & Weight (BMI = W/H*H) Skinfolds Under-Water Weighing Bioimpedance Total Body Nitrogen (TBN) Total Body Potassium (TBK) Dual Energy X-ray Absorption (Dexa) Analysis of CT & MRI Slices DBS 2001
Total Body Nitrogen (TBN) Measured by prompt (IVNAA) i. e. In Vivo Neutron Activation Analysis + n 15 N + (10. 8 Me. V) 1 H + n 2 H + (2. 2 Me. V) 14 N Calibrate with urea solution Total Body Protein = 6. 25 x TBN TBCl can also be determined from TBN data DBS 2001
Total Body Nitrogen (TBN) DBS 2001
Measurement of Total Body Protein DBS MMC 2007
TBPr Lead Shielding & Collimator DBS MMC 2007
Large Na. I(Tl) Detector 10 x 40 cm DBS 2001
Electronics for TBPr DBS MMC 2007
Total Body Chloride (TBCl) Application - 95% of Cl is extra-cellular - Cl concentration varies , but is easily measured with blood sample - TBCl measures extra-cellular water DBS 2001
Total Body Potassium (TBK) Principle of Measurement 40 K - Radioactive Potassium 40 - Occurs naturally, 0. 012% abundance - Half life of 1. 3 x 109 y - Emits 1. 35 Me. V gamma Adult emits about 1500 gammas per sec Use Shadow Shield Detector - Large Na. I detectors (4 x 16 in) - shielding is 10 cm iron + some lead DBS 2001
Total Body Potassium (TBK) Counter DBS MMC 2007
Total Body Potassium (TBK) Application - 95% of K is intra-cellular - K is maintained at a constant concentration - TBK measures intra-cellular water - TBK estimates lean body & fat mass DBS 2001
DBS 2001
Osteoporosis • • • Bone mineral peaks in early 20’s Then we lose 1% per year Annual loss can be measured with Dexa After menopause, females lose 2% per year Many drug studies over past 20 y Drugs now available to help females stop or reverse the loss • DEXA also gives reliable estimates of fat and lean tissues
Dual Energy X-ray Absorptiometer (DEXA) • Measures bone density • 125 I used in earliest machines - single x-ray energy gave a single thickness - measured forearm in water tank • 154 Gd has 2 x-ray energies (44 & 100 ke. V) - gave bone thickness & soft tissue thickness • We have a Lunar DPX - first of the units with an x-ray tube - 3 cm of Al for filter - Na. I detector and pulse height analysis DBS 2001
Cystic Fibrosis (Daniel Borovnicar Ph. D. ) - 1 in 25 carry CF gene - 1 in 625 infants have CF - genetic fault relates to transport of Cl across cell membrane - study 23 prepubertal CF children from RCH - short stature as a group but not as individuals - TBN & TBCl are normal - water spaces are normal - bone mineral content is normal DBS 2001
On Display Tonight - Total Body Nitrogen facility (TBN) - Total Body Potassium facility (TBK) - Dual Energy X-ray Absorptiometer (DEXA) DBS 2001
The End
What is Body Composition? atomic (Heymsfield) molecular cellular tissue ----------in vivo in vitro ----------fat & lean fat, lean, water, glycogen, bone mineral nitrogen, potassium, chlorine water (intra- & extra-cellular) DBS 2001
Why Measure Body Composition? Diabetes & Arteriosclerosis (blocked arteries) - 50% of Australian population is overweight - 18% are obese (1995), i. e. BMI>30 - proportion is increasing - increase implies more diabetes & arteriosclerosis Other Diseases - Osteoporosis - Liver cancer & cirrhosis - Growth hormone - Cystic fibrosis - Renal failure DBS 2001
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