Radiation exposure of the radiologist's eye lens during CT-guided interventions.

BACKGROUND: In the past decade the number of computed tomography (CT)-guided procedures performed by interventional radiologists have increased, leading to a significantly higher radiation exposure of the interventionalist's eye lens. Because of growing concern that there is a stochastic effect for the development of lens opacification, eye lens dose reduction for operators and patients should be of maximal interest. PURPOSE: To determine the interventionalist's equivalent eye lens dose during CT-guided interventions and to relate the results to the maximum of the recommended equivalent dose limit. MATERIAL AND METHODS: During 89 CT-guided interventions (e.g. biopsies, drainage procedures, etc.) measurements of eye lens' radiation doses were obtained from a dedicated dosimeter system for scattered radiation. The sensor of the personal dosimeter system was clipped onto the side of the lead glasses which was located nearest to the CT gantry. After the procedure, radiation dose (µSv), dose rate (µSv/min) and the total exposure time (s) were recorded. RESULTS: For all 89 interventions, the median total exposure lens dose was 3.3 µSv (range, 0.03-218.9 µSv) for a median exposure time of 26.2 s (range, 1.1-94.0 s). The median dose rate was 13.9 µSv/min (range, 1.1-335.5 µSv/min). CONCLUSION: Estimating 50-200 CT-guided interventions per year performed by one interventionalist, the median dose of the eye lens of the interventional radiologist does not exceed the maximum of the ICRP-recommended equivalent eye lens dose limit of 20 mSv per year.

Effective dose of CT- and fluoroscopy-guided perineural/epidural injections of the lumbar spine: a comparative study.

The objective of this study was to compare the effective radiation dose of perineural and epidural injections of the lumbar spine under computed tomography (CT) or fluoroscopic guidance with respect to dose-reduced protocols. We assessed the radiation dose with an Alderson Rando phantom at the lumbar segment L4/5 using 29 thermoluminescence dosimeters. Based on our clinical experience, 4-10 CT scans and 1-min fluoroscopy are appropriate. Effective doses were calculated for CT for a routine lumbar spine protocol and for maximum dose reduction; as well as for fluoroscopy in a continuous and a pulsed mode (3-15 pulses/s). Effective doses under CT guidance were 1.51 mSv for 4 scans and 3.53 mSv for 10 scans using a standard protocol and 0.22 mSv and 0.43 mSv for the low-dose protocol. In continuous mode, the effective doses ranged from 0.43 to 1.25 mSv for 1-3 min of fluoroscopy. Using 1 min of pulsed fluoroscopy, the effective dose was less than 0.1 mSv for 3 pulses/s. A consequent low-dose CT protocol reduces the effective dose compared to a standard lumbar spine protocol by more than 85%. The latter dose might be expected when applying about 1 min of continuous fluoroscopy for guidance. A pulsed mode further reduces the effective dose of fluoroscopy by 80-90%.

Effective doses in standard protocols for multi-slice CT scanning.

The purpose of this study was to assess the radiation exposure of patients in several standard protocols in multi-slice CT (MSCT). Scanning protocols for neck, chest, abdomen, and spine were examined on a Somatom Plus 4 Volume Zoom MSCT (Siemens, Erlangen, Germany) with changing slice collimation (4x1, 4x2.5, and 4x5 mm), and pitch factors (1, 1.5, and 2). Effective doses were calculated from LiF-TLD measurements at several organ sites using an Alderson-Rando phantom and compared with calculations using the weighted CTDI. Effective dose for MSCT of the neck was 2.8 mSv. For different protocols for MSCT of the chest, 7.5-12.9 mSv were found. In abdominal MSCT protocols, effective dose varied between 12.4 and 16.1 mSv. The MSCT of the spine may lead to 12 mSv. An excellent correlation between the effective dose as determined by LiF-TLD and the calculated effective dose using the weighted CTDI could be demonstrated; however, a difference of up to 30% (mean 14.3%) was noted. Standard protocols for MSCT as measured in this study showed effective doses of up to16 mSv. Phantom measurement data show a good correlation to estimations using the weighted CTDI.

Radiation exposure during cardiac CT: effective doses at multi-detector row CT and electron-beam CT.

PURPOSE: To measure the effective radiation doses delivered at electron-beam computed tomography (CT) and multi-detector row spiral CT of coronary arteries and to compare these doses with those delivered at catheter coronary angiography. MATERIALS AND METHODS: An anthropomorphic phantom equipped with 66 thermoluminescent dosimeters was imaged at cardiac CT. Four protocols for unenhanced coronary artery calcium scoring were simulated: one with electron-beam CT and three with multi-detector row CT. Four similar protocols for coronary CT angiography were simulated. All multi-detector row spiral CT protocols were performed with retrospective electrocardiographic triggering. Biplane catheter coronary angiography also was simulated. Radiation doses to organs were measured, and effective doses were calculated according to guidelines published in International Commission on Radiological Protection Publication 60. RESULTS: Coronary artery calcium scoring with electron-beam CT yielded effective radiation doses of 1.0 and 1.3 mSv for male and female patients, respectively. The radiation doses at calcium scoring with multi-detector row CT were 1.5-5.2 mSv for male patients and 1.8-6.2 mSv for female patients. Electron-beam CT coronary angiography yielded effective doses of 1.5 and 2.0 mSv for male and female patients, respectively. The highest effective doses were delivered at multi-detector row CT angiography: 6.7-10.9 mSv for male patients and 8.1-13.0 mSv for female patients. Catheter coronary angiography yielded effective doses of 2.1 and 2.5 mSv for male and female patients, respectively. CONCLUSION: Higher radiation doses are delivered at multi-detector row cardiac CT compared with the doses delivered at electron-beam CT and catheter coronary angiography.