Setting “Typical” Diagnostic Reference Levels for most common Computed Tomography guided Interventional procedures

Purpose: The new European Radiation Protection Law and International Radiation Protection Recommendation have stressed the need to monitor high radiation dose imaging examinations involving Computed Tomography (CT). There are no known diagnostic reference levels (DRLs) for CT-guided interventions. The scope of the study was to evaluate radiation doses and define typical DRLs. Material and Methods: The study was conducted in a tertiary referral hospital. The most frequent consecutive CT-guided procedures performed without use of fluoroscopy within a period of 17 months included biopsies (n=31), microwave ablations of malignant liver lesions (n=12), abscess drainages (n=45) and nephrostomies (n=15). A total of 103 CT-guided interventions performed by a single interventional radiologist (>20 years of experience) were reviewed. Using the CT DICOM data, all technical and dosimetric data were retrospectively collected for analysis. Results: There was a large variation in number of images (N) obtained and dose length product (DLP). N varied between patients depending on complexity of case. Limited dose comparison was possible due to actual absence of dosimetric data in the recent literature. Typical DLRs were established: 980, 790, 1380 and 850 mGy.cm for biopsy, drainage, ablation and nephrostomy respectively. Conclusions: Typical DLRs were established as per the latest International Commission on Radiological Protection report 135 definition for CT-guided interventional procedures without use of fluoroscopy. These could serve as a basis for in-house and/or national values. As results showed that complexity of clinical case greatly affects number of slices and thus radiation dose, the authors plan to further investigate how case complexity may affect radiation dose.