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Breast, General Radiology, Physics

Radiology Physics – Comparisons of Mammography and General Radiography

The test question writers at the American Board of Radiology seem to be obsessed with comparing mammography and general radiography. The below table should be high yield information for the ABR Core examination and certifying examination. In simple terms, mammography is lower energy, takes longer, generally uses different targets and filters, and is higher resolution. Those are the high points. Details below:

Parameter Mammography General Radiography
Energy (kVp) 25-35 50-120
Anode (target) Molybdenum, Rhodium Tungsten
Tube Current (mA) 100 mA 500 mA
Exposure time (ms) 1000 ms 50 ms
Receptor Air Kerma 100 microGy 5 microGy
Window Beryllium Glass (pyrex)
Focal spot Small (0.1 to 0.3 mm) Larger (0.6 to 1.2 mm)
Grid Ratio 5:1 10:1
Optic Density High Low
View box brightness 3000 cd/m2 1500 cd/m2

Other points to note are that the anode and filter can be changed depending on the density of the breast tissue. Always remember that for dense breasts, a rhodium anode/rhodium filter is a good combination because it results in a higher energy beam to penetrate the tissue, and you can NEVER combine a rhodium anode with a molybdenum filter! For more information on why that is, see the below figures. Their explanations can be found at Sprawls Educational Foundation. 

molymoly molyrho rhorho

In Mammography, never combine a rhodium anode with a molybdenum filter!

In Mammography, never combine a rhodium anode with a molybdenum filter!

About radiologypics

I am a radiology physician from California, USA.

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