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Table 4 R value according to the interaction between low and high energy X-ray beams and the atomic number (Z) and mass (A) of each tissue element

From: Official position of the Brazilian Association of Bone Assessment and Metabolism (ABRASSO) on the evaluation of body composition by densitometry: part I (technical aspects)—general concepts, indications, acquisition, and analysis

Element

Z

A

40 keV

70 keV

R value

H

1

1.008

0.3458

0.3175

1.0891

C

6

12

0.2047

0.1678

1.2199

N

7

14

0.2246

0.1722

1.3043

O

8

16

0.2533

0.1788

1.4167

Na

11

23

0.3851

0.2022

1.9045

Mg

12

24.3

0.4704

0.2244

2.0963

P

15

31

0.7784

0.2839

2.7418

S

16

32.1

0.9507

0.3258

2.9180

Cl

17

35.5

1.100

0.3491

3.1510

K

19

39.1

1.484

0.4297

3.4536

Ca

20

40.1

1.792

0.5059

3.5422