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.
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.
Objective: Due to the recent increase in the availability of cone-beam CT (CBCT), delineation of blood vessels and intracranial stents using CBCT has been well-reported, but reports using 3D-rotational angiography (3D-RA) have been few. We evaluated delineation of carotid artery stents using 3D-RA with diluted contrast medium. Methods:We prepared simulated blood vessel phantoms covered by carotid artery stents different in material and shape. The phantoms were encapsulated with different concentration of contrast medium, and scanned using 3D-RA.The appropriate concentration of contrast medium was evaluated. Results:The appropriate concentrations of diluted contrast medium were 50-17% for the Carotid Wall Stent (Boston Scientific, Natick, MA, USA) and 20%-10% for PRECISE (Johnson & Johnson, Miami, FL, USA) and PROTÉGÉ (Covidien, Irvine, CA, USA). Conclusion:The appropriate concentration of contrast medium varied with carotid artery stent. By selecting an appropriate degree of dilution, the stent shape, plaque, intimal thickening, and vascular lumen in the stent can be visualized. Therefore, it is possible to evaluate vascular lumen after carotid artery stenting.
Background and purpose: Conventional angiographic assessment of collateral blood flow for internal carotid artery (ICA) or basilar artery (BA) occlusion requires contralateral ICA angiography and posterior circulation angiography. The angiography of other vessels may cause time delay for endovascular therapy (EVT) in acute ischemic stroke patients. In this study, we performed intra-aortic cone-beam CT (Ao-CBCT) for assessment of collateral blood flow and analyzed visualization of collateral flow and elapsed time in EVT compare with conventional angiographic assessment. Methods: From July 2010 to July 2014, patients with ICA or BA occlusion among fifty seven acute ischemic stroke patients treated by EVT were enrolled. The subjects were divided into 2 groups; conventional angiography (CA) group and Ao-CBCT group. Ao-CBCT images were acquired in 20 seconds rotational scan. Contrast medium was injected from ascending aorta with 1mL/s for a total of 30 seconds by use of a 4F or 6F catheter and an imaging delay of 10 seconds. We compared patient characteristics, visualization of collateral flow and time from groin puncture to injection from guiding catheter to treatment target vessel (“puncture to treatment” time). Results: Twelve patients in CA group and 4 patients in Ao-CBCT group were analyzed. There was no difference in age, sex, stroke subtypes and occlusion vessel between two groups. In CA group, in addition to target vessel angiography, 2 vessels angiography (interquartile range [IQR], 1-2) were performed. Three patients in CA group were performed Ao-CBCT simultaneously. Collateral blood flow from anterior/posterior communicating artery was equally visualized by both methods. Puncture to treatment time was significantly shorter in Ao-CBCT group than in CA group (21±13 vs. 51±18 minutes, p=0.0087). Conclusions: Ao-CBCT can visualize collateral blood flow in major vessel occlusion and shorten puncture to treatment time compare with conventional angiography.
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 (K a,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 K a,r and PSD, K a,r and right lens dose, and K a,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 K a,r .
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