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Table 1 Parameters relevant in characterizing historical radiographs

From: The skin dose of pelvic radiographs since 1896

Modern parameter

Old information (pre-1927)

Peak high-voltage (kVp)

Equivalent spark gap on functioning tube

Hardness X-rays according to penetrometer or half value layer in water

Electrical information on primary and secondary circuit

Tube current (mA)a

Average current, after 1904 often specified

Electrical information on primary and secondary circuit

Exposure time (min, s)a

Explicitly specified duration of exposure

Target (anode) material

Explicit or implicit: before 1912 platinum (Pt), then replacement by tungsten (W)

Filtration

Implicit: no filter added, i.e. tube envelope only. Later sometimes specified filter

Exposure geometry

Focus-plate or focus-patient distance, field size, type of study

Backscatter factor

kVp-info, filtration, object thickness, expo-geometry. Explicit BSF seldom & later

  1. aOften only product of tube current and exposure time was reported (unit: mA.min or mAs)