3 Methodology 3.1 DEXA Scans of Tissue Phantoms Samples of lean and fat tissue were sourced from lamb carcases and used to create mixtures of the following fat:muscle ratio's:0:100,25:75,50:50,75:25,or 100:0.These samples were then ground and homogenised,after which subsamples were taken for the determination of chemical fat and lean percentage,and percent dry matter,as reported in Error!Reference source not found.below Table 1.Dry matter,chemical fat and chemical lean percentage of mixtures of fat and lean. Fat:Lean ratio Percent Dry Matter Chemical Fat Chemical Lean 100:0 26.6 88.0 12.0 75:25 36.3 60.6 39.4 50:50 53.4 40.0 60.0 25:75 70.2 18.3 81.7 0:100 91.4 6.2 93.8 These mixtures were then used to create calibration blocks of 3 different uniform sizes using custom built moulds which were 10mm,80mm,or 160mm thick.Thus 3 calibration blocks were created for each of the 5 fat:lean mixtures,with thicknesses of 10mm,80mm,or 160mm.X-Ray images were then generated of the phantoms.This entire process was repeated 3 times using 3 sets of 3 calibration blocks. Prior to carrying out image analysis,sections within each image were selected which corresponded to the calibration tissue.The corresponding pixels within the low and high energy images were then used to calculate an R-value for these pixels according to the following formula: (R=In(ILow/AirAtten)/In(IHigh/AirAtten)); Where: lLow represents the pixel value in the low energy image(ZnSe Photodiode) h represents the pixel value in the high energy image(Csl Photodiode) AirAen represents the pixel value corresponding to the un-attenuated photons(lo)in the white part of each image. Equation 1-R-value calculation The R-values for the pixels of each calibration block were then averaged to give a single R Value representing that block.This data was represented graphically relative to the corresponding chemical fat for that block. Page 8 of 44Page 8 of 44 3 Methodology 3.1 DEXA Scans of Tissue Phantoms Samples of lean and fat tissue were sourced from lamb carcases and used to create mixtures of the following fat:muscle ratio’s: 0:100, 25:75, 50:50, 75:25, or 100:0. These samples were then ground and homogenised, after which subsamples were taken for the determination of chemical fat and lean percentage, and percent dry matter, as reported in Error! Reference source not found. below. Table 1. Dry matter, chemical fat and chemical lean percentage of mixtures of fat and lean. Fat:Lean ratio Percent Dry Matter Chemical Fat % Chemical Lean % 100:0 26.6 88.0 12.0 75:25 36.3 60.6 39.4 50:50 53.4 40.0 60.0 25:75 70.2 18.3 81.7 0:100 91.4 6.2 93.8 These mixtures were then used to create calibration blocks of 3 different uniform sizes using custom built moulds which were 10mm, 80mm, or 160mm thick. Thus 3 calibration blocks were created for each of the 5 fat:lean mixtures, with thicknesses of 10mm, 80mm, or 160mm. X-Ray images were then generated of the phantoms. This entire process was repeated 3 times using 3 sets of 3 calibration blocks. Prior to carrying out image analysis, sections within each image were selected which corresponded to the calibration tissue. The corresponding pixels within the low and high energy images were then used to calculate an R-value for these pixels according to the following formula: (R = ln(ILow/AirAtten) / ln(IHigh/AirAtten)); Where: ILow represents the pixel value in the low energy image (ZnSe Photodiode) IHigh represents the pixel value in the high energy image (CsI Photodiode) AirAtten represents the pixel value corresponding to the un-attenuated photons (I0) in the white part of each image. Equation 1 - R-value calculation The R-values for the pixels of each calibration block were then averaged to give a single R Value representing that block. This data was represented graphically relative to the corresponding chemical fat % for that block