CT-guided interventional procedures without CT fluoroscopy assistance: patient effective dose and absorbed dose considerations.

OBJECTIVE

The purpose of this study was to determine patient effective dose (E) and peak absorbed dose to the skin of the patient from various CT-guided interventional procedures performed without CT fluoroscopy assistance.

MATERIALS AND METHODS

In total, 49 interventions were retrospectively studied: 14 biopsies, 14 radiofrequency ablations, 14 abscess drainages, and seven nephrostomies. CT images were acquired from the department's PACS system and reviewed to record the scan parameters of each slice. Entrance surface dose and E were estimated using the Impactscan database and the related Monte Carlo conversion coefficients.

RESULTS

Median values of E for biopsies, radiofrequency ablations, abscess drainages, and nephrostomies were 23, 35.3, 16.2, and 11.5 mSv, respectively. Respective ranges were 5.8-46.6, 18.4-57.2, 10.9-31.5, and 5.1-32.7 mSv. The corresponding median values and ranges for the peak absorbed dose were 281, 557, 155, and 145 mGy and 133-982, 147-699, 94-315, and 75-297 mGy. The diagnostic scans obtained before the interventions were responsible for 63%, 33% 40%, and 51% of E, respectively. The largest contribution to the peak absorbed dose was due to positioning of the tissue acquisition biopsy gun in biopsies (48%), the radiofrequency needle in ablations (57%), and the catheter in abscess drainages (41%) and nephrostomies (49%).

CONCLUSION

For the CT interventions studied, and especially for biopsies and radiofrequency ablations, patient effective doses were considerably high. Maximum peak absorbed dose observed was about 1 Gy, considerably lower than the threshold for deterministic effects (2 Gy).