[Reduction of radiation dosage by using digital luminescence radiography on a hand phantom]

How much can the radiation dose be reduced for hand radiography by using digital luminescence radiography (DLR)?

A hand phantom (3M) with a cyst, two fractures and an "amputation" was digitally exposed in an anterior-posterior orientation using DLR (ADC-70, Agfa). The tube current time product (mAs) was reduced gradually while keeping the voltage constant. The surface entrance dose was measured by a Dosimax sensor (Wellhöfer). Five investigators evaluated the images for characteristics and critical features, pathological findings, visual resolution and contrast.

The surface entrance dose at 50 kV/5 mAs was 31 microGy. The images could be evaluated very well down to an average dose of 36% (11 microGy); sufficient images were obtained down to an average dose of 26% (8 microGy). The resolution of the line pairs was the same or reduced by 1 level depending on the investigator. Contrast was assessed as being very good to sufficient.

For the sufficient exclusion of a fracture the dose can be reduced to at least 39%, for the sufficient assessment of bony union and possible inflammatory changes to at least 42%, to position check and foreign body search to at least 23%. By DLR the following question-referred mAs-product at 50 kV are stated: fracture exclusion 2 mAs, bony union, arthritis and osteomyelitis 2.2 mAs, position check and foreign body search 1.25 mAs.