Multislice CT fluoroscopy: technical principles, clinical applications and dosimetry.

Purpose: The aim of this study is describing fluoroscopic techniques with multislice CT during interventional procedures. We emphasize the technical principles of the multislice CT fluoroscopy and the relative advantages in clinical application, in comparison to single slice fluoroCT and conventional CT guided procedures. Other topics are dosimetry and patient's and operator's radioprotection.

Materials And Methods: We describe our experience in 60 cases of interventional procedures performed with CT fluoroscopy array for the TOSHIBA AQUILION-MULTI TSX-101A scanner that allows a real-time 3 slices simultaneous representation of the target: middle target slice, superior and inferior slices. Thirty nine biopsies, 5 abscess drainage, 12 shoulder arthrocentesis previous to arthro-MR and 4 hepatic neoplasm ablations have been performed during the last 9 months. For each procedure questionnaires have been used to evaluate: target organs, scan parameters, fluoroscopy techniques (continuous or spot) and total time of fluoroCT. Basing on these data and on the measurements made on a body phantom we calculated patient's and operator's radiation dose rate.

Results And Discussion: The real-time simultaneous representation of the middle target slice and the adjacent superior and inferior slices has always allowed an immediate identification of the needle tip and direction. The use of a needle holder has been determined by the needle type, the fluoroscopy technique (continuous or spot), the type of interventional procedure and the target. In our experience freehand spot fluoroscopy approach was easier, faster and with less radiation dose rate. 24 seconds were the mean fluoroscopy time for all different CT fluoroscopy modalities and procedures. The mean absorbed equivalent dose rate to patient's skin was 5300 microSv/s while the dose to operator's body and hand was respectively 0.3 microSv/s and 30 microSv/s.

Conclusions: Multislice CT fluoroscopy, specially if performed by spot technique, leads to an acceptable radiation dose rate to patient and operator, is user friendly and guides interventional procedures with rapidity.