Estimated radiation dose according to the craniocaudal angle in cerebral digital subtraction angiography: Patient and phantom study.

BACKGROUND AND PURPOSE: Routine use of cranial angulation with 15-20 degrees, craniocaudal angled (CC) view, for cerebral digital subtraction angiography (DSA) helps minimize bone subtraction artifacts with less overlapping of the vessels, however, it may increase the radiation dose. We designed the phantom and patient studies to determine the effect of the angulation to the radiation dose and the feasibility of true posteroanterior angled (PA) view, in cerebral DSA. MATERIALS AND METHODS: In the phantom study, frontal DSA was simulated with variable angulations. In the patient study with thirty-one subjects, one internal carotid arteriogram was obtained with the CC view and the other, PA view in every patient. The dose-area product (DAP) and reference air-kerma (AK) were measured and compared between the angles. A qualitative analysis was performed to assess the diagnostic performance of the DSA over the angles. RESULTS: The phantom study confirmed that the greater craniocaudal angles caused higher radiation exposure. Especially, the radiation dose (AK) of the CC view was 5.4% higher than that of the PA view. In the patient study, the radiation dose of the PA view was significantly lower compared to the CC view (1.44 vs. 1.63 mGy, AK). In 4 patients, the dose particularly jumped when applying the CC view as the copper filter was automatically removed. The diagnostic ability of the DSA with the PA view tended to be higher without significance. CONCLUSIONS: In a daily routine cerebral angiography, a simple modification of the angle may help to minimize the radiation dose.

Feasibility of a silicone vascular phantom replicating real arterial contrast filling dynamics on cerebral angiography: An in-vitro pilot study.

Some cerebral arterial silicone phantoms have been used in preclinical evaluations. However, typical silicone-based phantoms are limited in their capacity to reproduce real contrast filling dynamics of the human cerebral artery. This study aimed to develop a cerebral arterial silicone phantom to analyze the feasibility of real contrast filling dynamics. The fluid circulation phantom system consisted of a cerebral arterial silicone phantom without or with additional devices, a pump, an injection system, a pressure-monitoring system, a constant-temperature bath, and a venous drainage container. Vascular resistance was reproduced with a plastic cistern only or a plastic cistern filled with a sponge pad. Three phantom groups were constructed as follows: a) the cerebral arterial silicone phantom used as the control group (type A), b) phantom with the incorporated plastic cistern (type B), and c) phantom with the incorporated plastic cistern filled with a sponge pad (type C). The contrast concentration-time curve patterns of the three groups obtained from digital subtraction angiography (DSA) were compared. Consequently, the DSA pattern of the type C phantom was the most similar to that obtained from the control group as the reference data, which showed the broadest full-width-at-half-maximum and the area under the curve values and the highest maximum contrast concentration. In conclusion, we could emulate the arterial contrast filling dynamics of clinical cerebral angiography by applying a small cistern filled with a sponge pad at the drainage side of the phantom.

Feasibility of ultra-low radiation dose digital subtraction angiography: Preliminary study in a simplified cerebral angiography phantom.

INTRODUCTION: The objective of this article is to evaluate the feasibility of cerebral digital subtraction angiography (DSA) using ultra-low radiation dose settings in a simplified cerebral angiography phantom. MATERIALS AND METHODS: We created a silicone phantom capable of producing a simplified cerebral DSA. A total of 18 DSA sets were obtained with gradual six-step reduction of the detector entrance dose (DED) from 1.82 to 0.08 µGy per frame, while standard, postprocessing algorithm (PPA) and copper filter (0.3 mm) with PPA (CwP) algorithm reconstruction protocols were applied. We quantitatively compared their signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) and qualitatively analyzed the images' qualities in terms of image sharpness, contrast, and noise as investigated by five observers. RESULTS: The SNR and CNR, which decreased with lowering of the DED in the standard protocol group, were significantly compensated by using the PPA. The values were approximately double in the PPA (11.5 ± 2.9) and CwP (11.0 ± 2.5) groups compared with the standard (5.4 ± 1.1) group in the DED of 0.24 µGy per frame as well as in the other values. The total scores of the observers according to the protocols showed a tendency to decrease as the DED lowered. On average, the PPA (96.3 ± 34.6) and CwP (91.3 ± 29.9) groups yielded higher results than the standard protocol (83.7 ± 46.7). CONCLUSION: Given that the current DED ranges from 1.82 to 3.60 µGy per frame for routine cerebral DSA, our results indicate that DED can be decreased to 15%-30% of the current dose level in vessels 2-4 mm in diameter if image-improvement algorithms are applied.

Increase in fluoroscopic radiation dose in successive sessions of multistage Onyx embolization of brain arteriovenous malformations compared with the first session.

BACKGROUND AND PURPOSE: Onyx embolization is a treatment for brain arteriovenous malformations (AVMs). However, multistage embolization usually involves the presence of radiodense Onyx cast from the previous sessions, which may influence the fluoroscopic radiation dose. We compared the fluoroscopic dose between the initial and final embolization sessions. MATERIALS AND METHOD: From January 2014 to September 2016, 18 patients underwent multistage Onyx embolization (more than twice) for brain AVMs. The total fluoroscopic duration (minutes), dose-area product (DAP, Gy×cm2), and cumulative air kerma (CAK, mGy) of both the frontal and lateral planes were obtained. We compared the frontal and lateral fluoroscopic dose rates (dose/time) of the final embolization session with those of the initial session. The relationship between the injected Onyx volume and radiation dose was tested. RESULTS: The initial and final procedures on the frontal plane showed significantly different fluoroscopic dose rates (DAP: initial 0.668 Gy×cm2/min, final 0.848 Gy×cm2/min, P=0.02; CAK: initial 12.7 mGy/min, final 23.1 mGy/min, P=0.007). Those on the lateral plane also showed a similar pattern (DAP: initial 0.365 Gy×cm2/min, final 0.519 Gy×cm2/min, P=0.03; CAK: initial 6.2 mGy/min, final 12.9 mGy/min, P=0.01). The correlation between the cumulative Onyx volume (vials) and radiation dose ratio of both planes showed an increasing trend (rho 0.4325-0.7053; P=0.0011-0.0730). CONCLUSION: Owing to the automatic exposure control function during fluoroscopy, successive Onyx embolization procedures increase the fluoroscopic radiation dose in multistage brain AVM embolization because of the presence of radiodense Onyx mass.

In Vitro Quantification of the Radiopacity of Onyx during Embolization.

PURPOSE: Onyx has been successfully applied in the treatment of various neurovascular lesions. However, some experience is required to get accustomed to its unpredictable fluoroscopic visibility during injection. This in vitro study aimed to evaluate the characteristics of radiopacity change in a simulated embolization procedure. MATERIALS AND METHODS: Using a bench-top Onyx injection experiment simulating a typical brain arteriovenous malformation embolization, nine cycles of casting modes (continuous injection) and plugging modes (injection with intermittent pauses) were performed. Radiodensity of Onyx droplets collected from the microcatheter tip and the distal head portion of the microcatheter were measured as time lapsed. Distribution of droplet radiodensity (radiodensity) and distribution of radiographic grade (grade) were analyzed and compared by repeated measurements. RESULTS: Within-group analysis revealed no significant radiodensity change with time (P>0.05). The radiodensity was significantly higher in the casting mode than in the plugging mode (P<0.01). The lateral radiograph of the microcatheter showed higher radiopacity (P<0.01) and better evenness (P<0.01) in the casting mode than in the plugging mode. A significant difference in microcatheter attenuation (both radiographic grade mean and SD; P<0.01) was noted between the two modes. Radiodensity had a significant influence on the radiopacity and radiopacity evenness of the microcatheter. CONCLUSION: The radiopacity of the Onyx can vary significantly over time because of early precipitation of tantalum powder. Radiopacity decreased significantly during plugging modes, characterized by pauses between injections.