Thorax organ dose estimation in computed tomography based on patient CT data using Monte Carlo simulation

Background: this study presents patient specific and organ dose estimation in computed tomography [CT] imaging of thorax directly from patient CT image using Monte Carlo simulation. Patient's CT image is considered as the patient specific phantom and the best representative of patient physical index in order to calculate specific organ dose

Materials and Methods: EGSnrc /BEAMnrc Monte Carlo [MC] System was used for CT scanner simulation and DOSXYZnrc was used in order to produce patient specific phantom and irradiation of photons to phantom in step and shoot mode [axial mode]. In order to calculate patient thorax organ dose, patient CT image of thorax as voxelized phantom was divided to a 64x64x20 matrix and 6.25 x 6.25 x 6.25 mm[3] voxel size and this phantom was imported to DOSXYZnrc code. MC results in unit of Gy/particle were converted to absorbed dose in unit of mGy by a conversion factor [CF]. We calculated patient thorax organ dose in MC simulation from all irradiated slices, in 120 kV and 80 kV photon energies

Results: effective dose was obtained from organ dose and organ weighting factor. Esophagus and spinal cord received the lowest, and bone received the highest dose. In our study, effective dose in CT of thorax was 7.4 mSV and 1.8 mSv in 120 and 80 kV, respectively

Conclusion: the results of this study might be used to provide the actual patient organ dose in CT imaging and calculation of real effective dose based on organ dose

Patient effective dose evaluation for chest x-ray examination in three digital radiography centers

The radiation doses resulting from diagnostic X-ray examinations are routinely measured in terms of entrance surface dose [ESD] and effective dose [ED]. In this study, for the purpose of radiation protection, the radiation doses received from Digital chest X-ray examination were evaluated in terms of ESD and ED. The ED was calculated by using the MCNP Monte Carlo code and an adult hermaphrodite mathematical phantom. The effects of both operating high voltage and projection geometry on the effective dose were investigated. The absolute values of the ED were calculated for digital and conventional Posterior-Anterior [PA] and Lateral [LAT] projections of chest radiography. The results show ED for PA projection in digital chest radiography in some major hospitals is higher than National Diagnostic Reference Level [NDRL]. Therefore optimization process should be considered seriously at national level to reduce patient exposure in digital chest radiography in Iran

[Evaluating the applicability of post thyroidectomy drainage in the prevention of respiratory distress sencondary to hematoma formation of the surgical site]

Hematoma is a rare but potentially dangerous complication of thyroidectomy that can lead to airway obstruction and respiratory distress.The use of drain age tube for prevention of hematoma has met with reservations. In a randomaized controlled trial, thyroidectomized patients treated as groups with and without drains were assessed and compared with regard to hematoma formation, respiratory distress and duration of admission. 48 pts without drains [51.1% male, mean age 37 yrs] and 52 pts with drains [52% male, mean age 41.5 yrs] were studied. Two patients who had drainage tubes developed hematoma and respiratory distress [p<0.005]. There was no hematoma formation and respiratory distress in the group] without drains. Duration of hospitalization in the group without drain age tube was 2.9 days [SD 1.3 days], and in the group with drain age tube 4.1 days [SD 1.5 days] with a p>0.05