backMetrology in dosimetry for diagnostic radiology
You will find an overview of the “Metrological Aspects of Dosimetry in X‑ray Diagnostics” in an article on pp. 8 – 15 of PTB’s scientific journal “PTB‑Mitteilungen” 123 (2013), Issue 2
Dosimetry for computed tomography
Since multiphase CT scanners with a scanning width of more than 10 cm were introduced, the quantities used to date have faced heavy criticism. For this reason, dosimetry in computed tomography is one of the topics our research activities are currently focusing on.
Figure 2: For its research activities, Working Group 6.25 has its own GE Optima CT 660 ASIR type multislice CT scanner (above). Dose measurements are performed in an anthropomorphic phantom with detectors implanted at well-defined locations (below).
Dosimetry in mammography
In this field, developments have become very dynamic since the introduction of digital mammography. The focus is on the numerous types of X‑rays used that are created by combining anode materials of X‑ray tubes such as W, Rh and Mo with diverse filters such as Mo, Rh, Al, Ag, Pd or Ti. Here, research and development activities focus on generating reference radiations, on X‑ray spectrometry and on dosimetry. The results are necessary for the type examination of dosemeters for radiodiagnostics in accordance with the Measures and Verification Act.
Figure 3: Typical photon fluence spectra of mammography radiation qualities at a tube voltage of 28 kV and with different combinations of anode and filter materials. The spectra were recorded with a high-purity germanium detector.
Figure 4: 3D dose profile of a 28 kV mammography radiation quality (Mo anode with 60 μm Mo filter) at a distance of 1 m from the focus of the X-ray tube and with a nominal field size of 10 cm. The dose profile was recorded with a Hamamatsu C7942 type digital flat-panel detector. This detector has a 50 nm image sensor with 2400 × 2400 pixels which covers a surface of approximately 12 cm × 12 cm.