Evaluation of Peak Skin Doses and Lens Doses during Interventional Neuroradiology Using a Direct Measurement System.

Objective: In interventional neuroradiology (INR), the evaluation of the peak skin dose (PSD) and lens dose is important because the patient radiation dose increases in cases in which the procedure is more difficult and complex. This study evaluated the radiation doses during INR procedures using a direct measurement system. Methods: Radiation dose measurements during INR were performed in 332 patients with unruptured aneurysm (URAN), dural arteriovenous fistula (DAVF), and arteriovenous malformation (AVM). The PSD and bilateral lens doses were analyzed for each disease. The Pearson correlation test was used to determine whether the PSD and lens doses were linearly related to the reference air kerma (Ka,r). Results: In all cases, the PSD and right and left lens doses were 2.36 ± 1.28 Gy, 114.2 ± 54.6 mGy, and 189.8 ± 160.3 mGy, respectively. The PSD and lens doses of the DAVF and AVM cases were significantly higher than those of the URAN case. The Pearson correlation test revealed statistically significant positive correlations between Ka,r and PSD, Ka,r and right lens dose, and Ka,r and left lens dose. Conclusion: The characteristics of radiation dose in INR were clarified. Owing to the concern of increased radiation doses exceeding the threshold values in DAVF and AVM cases, protection from radiation is required. Simple regression analysis revealed the possibility of precisely predicting PSD using Ka,r.

ESTIMATION OF PATIENT LENS DOSE ASSOCIATED WITH C-ARM CONE-BEAM COMPUTED TOMOGRAPHY USAGE DURING INTERVENTIONAL NEURORADIOLOGY.

The purpose of this study was to investigate the dose distribution and lens doses associated with C-arm cone-beam computed tomography (CBCT), using a head phantom, and to estimate the contribution ratio of C-arm CBCT to each patient's lens dose during interventional neuroradiology ('lens dose ratio') in 109 clinical cases. In the phantom study, the peak skin doses and respective right and left lens doses of C-arm CBCT were as follows: 63.0 ± 1.9 mGy, 19.7 ± 1.4 mGy and 21.9 ± 0.8 mGy in whole brain C-arm CBCT and 39.2 ± 1.4 mGy, 4.7 ± 0.9 mGy and 3.6 ± 0.3 mGy in high-resolution C-arm CBCT. In the clinical study, the lens dose ratios were 25.4 ± 8.7% in the right lens and 19.1 ± 9.8% in the left lens. This study shows that, on average, ~25% of patients' total lens dose was contributed by C-arm CBCT.

Intra-arterial Contrasted Cone-beam Computed Tomography Assessment of Vessels Distal from Occluded Site in Acute Ischemic Stroke with Major Vessel Occlusion.

Characterization of vessels distal from occluded site is important when considering endovascular revascularization therapy (EVT) for acute ischemic stroke. The goal of this study was to assess the clinical value of intra-arterial contrasted high-resolution cone-beam computed tomography from the ascending aorta (Ao-CBCT) for visualization of the vessels distal from occluded site. Acute ischemic stroke patients with large vessel occlusion who were to undergo EVT were evaluated. In EVT, digital subtraction angiography (DSA) and Ao-CBCT were performed with local anesthesia. Ao-CBCT images were acquired in a 20-second rotational scan. Contrast medium was injected (1 mL/s for a total of 30 seconds using a 4-Fr catheter and an imaging delay of 10 seconds) from the ascending aorta. We assessed the image quality of Ao-CBCT and compared the visualization of the vessels distal from occluded site among magnetic resonance angiography (MRA), DSA and Ao-CBCT. We analyzed 14 patients (mean age, 66 years; three female patients). Stroke subtypes were cardiogenic (n = 6), atherothrombotic (n = 5) and others/unknown (n = 3). Occluded sites were middle cerebral artery (MCA) M1 (n = 8), MCA M2 (n = 2), internal carotid artery (ICA) (n = 2), MCA M4 (n = 1) and basilar artery (BA) (n = 1). All obtained Ao-CBCT images successfully characterized the vessels distal from occluded site, and 11 images (79%) were excellent. In all cases, Ao-CBCT images could depict distal vessels with more detail when compared with MRA and DSA. Ao-CBCT is an efficient method to obtain detailed information regarding vessels distal from occluded site when compared with conventional examination methods.

[Estimation of Maximum Entrance Skin Dose during Cerebral Angiography].

Using radio-photoluminescence glass dosimeter, we measured the entrance skin dose (ESD) in 46 cases and analyzed the correlations between maximum ESD and angiographic parameters [total fluoroscopic time (TFT); number of digital subtraction angiography (DSA) frames, air kerma at the interventional reference point (AK), and dose-area product (DAP)] to estimate the maximum ESD in real time. Mean (± standard deviation) maximum ESD, dose of the right lens, and dose of the left lens were 431.2 ± 135.8 mGy, 33.6 ± 15.5 mGy, and 58.5 ± 35.0 mGy, respectively. Correlation coefficients (r) between maximum ESD and TFT, number of DSA frames, AK, and DAP were r=0.379 (P<0.01), r=0.702 (P<0.001), r=0.825 (P<0.001), and r=0.709 (P<0.001), respectively. AK was identified as the most useful parameter for real-time prediction of maximum ESD. This study should contribute to the development of new diagnostic reference levels in our country.