  Radiation dose is an important performance indicator of a dedicated breast CT
(DBCT). In this paper, the method of putting thermoluminescent dosimeters (TLD)
into a breast shaped PMMA phantom to study the dose distribution in breasts was
improved by using smaller TLDs and a new half-ellipsoid PMMA phantom. Then the
weighted CT dose index (CTDIw) was introduced to average glandular assessment
in DBCT for the first time and two measurement modes were proposed for
different sizes of breasts. The dose deviations caused by using cylindrical
phantoms were simulated using the Monte Carlo method and a set of correction
factors were calculated. The results of the confirmatory measurement with a
cylindrical phantom (11cm/8cm) show that CTDIw gives a relatively conservative
overestimate of the average glandular dose comparing to the results of Monte
Carlo simulation and TLDs measurement. But with better practicability and
stability, the CTDIw is suitable for dose evaluations in daily clinical
practice. Both of the TLDs and CTDIw measurements demonstrate that the
radiation dose of our DBCT system is lower than conventional two-view
mammography.
