Pelvimetry by digital radiography and its dosimetry

Sonography is firmly established in obstetrics as the method of choice for the localization of fetus and placenta. However, for the determination of pelvic dimensions sonography does not suffice. Thus, for a few strictly selected indications conventional x-ray pelvimetry is used. This has the disadvantage of the relatively high radiation dose for the fetus and the maternal gonads. Since the introduction of digital radiography, there is the alternative of digital pelvimetry. We performed dosimetry comparing digital and conventional radiography with the new high amplifying screens (Quanta III, Dupont) using an ionization dosimeter and a wax phantom. The radiation dose of digital radiography was 24 mu Gy. This corresponds to about 15% of a comparable conventional exposure (177 mu Gy). A further advantage of digital radiography is a standardized and rapid exposure technique; furthermore pelvic dimensions can be measured directly. The disadvantages are the poorer spacial resolution and poor image quality in obese patients. Digital radiography because of its lower radiation dose is suitable for pelvimetry for special indications.