gms | German Medical Science

Fragestellung: Fluoroscopy-guided minimally invasive transverse placement of cannulated iliosacral screws (ISS) through S1 and/or S2 is an established technique to stabilize fractures of the posterior pelvic ring. Usually, three standard views (lateral (LV), outlet (OLV) and inlet (ILV)) are used. However, this technique may be associated with a considerable amount of radiation exposure. It was the aim of this experimental study to evaluate LV, OLV and ILV regarding effective dose and organ doses.

Methodik: An anthropomorphic cross sectional dosimetry phantom, representing the body of a male human (173cm/73kg), was equipped with metal oxide semiconductor field effect transistors in different organ locations such as red bone marrow, liver, stomach, colon, gonads and bladder to measure radiation exposure. LV, OLV and ILV of the phantom were obtained with a mobile C-arm with three minutes of irradiation for each view. The acquisition protocol was repeated three times to adjust the variability. This data was used to calculate the effective dose and the organ doses according to the guidelines of the International Commission on Radiological Protection (ICRP).

Ergebnisse und Schlussfolgerung: The effective dose was the lowest for LV (0.46 mSv/min) with about the double and fourfold amount of that for OLV (0.95 mSv/min) and ILV (1.85 mSv/min), respectively. For LV, the highest organ dose was found in colon (0.119 mSv/min), followed by red bone marrow (0.090 mSv/min). For OLV, colon (0.507 mSv/min) was also the most affected organ, followed by bladder (0.135 mSv/min). Regarding ILV, stomach showed the highest organ dose (0.918 mSv/min) and colon was also considerably affected (0.321 mSv/min).

Usually, the correct starting point of the guide wire is determined on LV. ILV and OLV are then alternately applied for a proper visualisation of the advancing guide wire. Based on our study, one should consider to advance the guide wire as far as possible exclusively guided by an exact LV to reduce irradiation with the guide wire aimed strictly in line with the central beam of LV. ILV and OLV may be used sparingly to confirm the correct wire position and to determine proper screw length. However, if the radiological anatomy of LV is considered not to be sufficient enough for a safe advancement of the guide wire, OLV and ILV may have to be used more often to improve safety despite higher radiation exposure.