• 1 dps = 1 Bq = 27 pCi
• 1 R = one roentgen = 2.58E-4 C/kg
  • this is exposure ( exposure = ability of X-rays or Gamma-rays to cause ionization in air )( coulombs of charge generated per kg )
    
  • one roentgen of x-rays in the range 0.1 - 3.0 MeV produces 0.96 rad in tissue
  • typically measured as roentgens/hour at 1 meter from the source
• 1 Gy = 100 rad
  • this is dose ( dose = absorbed energy per unit mass )
  • 1 rad = 100 ergs per gram of material
  • 1 Gy = 1E4 ergs per g = 1E-3 J per g
• 1 Sv = 100 rem
  • dose equivalent = (absorbed dose) * (quality factor) * (dose distribution factor) * (any other fudge factor)
  • rem = rad * stuff
  • Sv = Gy * stuff

mass attenuation length
mean free path = m.f.p. = 1/(u/density) g/cm**2
1/m.f.p. = u/density cm**2/g
m.f.p. = 10 for Pb
density = 11.35 for Pb
i=I*e(-thickness*density/m.f.p.)
LN(i/I) = -thickness*density/m.f.p.
for i/I = 0.1
-2.303 = -thickness*density/m.f.p.
2.3 = thickness*1.135
thickness = 0.49cm  ( for Pb )

• 1 gram/cc = 2.54 mg/cm**2/mil