MR vessel-encoded arterial spin labeling with the placement of metallic items to visualize the territorial blood flow after extracranial-intracranial bypass surgery: a proof-of-concept study.

BACKGROUND: Depiction of bypass blood flow in patients who received extracranial-intracranial (EC-IC) bypass surgery is important for patient care. PURPOSE: To develop a vessel-encoded arterial spin labeling (VE-ASL) method using surgical staples as a magnetic resonance (MR)-conditional product in patients who received EC-IC bypass surgery. MATERIAL AND METHODS: Pseudo-continuous labeling was used for VE-ASL acquisition with a 3-T MR unit. First, an experimental study was conducted to determine the appropriate number of surgical staples to obtain a spatially sufficient saturation effect. Thereafter, four healthy normal volunteers underwent a VE-ASL study to confirm the sufficiency of the saturation effect to the right or left common carotid artery. Finally, VE-ASL scanning was performed in seven patients after EC-IC bypass surgery to confirm the ability of VE-ASL to visualize the territorial bypass perfusion. All qualitative evaluation was performed by two neuroradiologists using a 3-point grading system (2 = good, 1 = moderate, 0 = poor). RESULTS: A quantity of 200 staples was found to be appropriate for VE-ASL scanning. In healthy volunteers, one neuroradiologist rated the images of all four cases as good, while the other rated three cases as good and one case as moderate. For the seven patients after EC-IC bypass surgery, one neuroradiologist rated all seven cases as good, and the other rated six cases as good and one case as moderate. CONCLUSION: VE-ASL using surgical staples might be useful for the evaluation of territorial bypass perfusion in patients after EC-IC bypass surgery.

Delivering the diluted contrast agent with saline via a spiral flow tube improves arterial enhancement for contrast enhancement of magnetic resonance angiography of the neck: A retrospective study.

A contrast agent can be pushed by a saline solution more effectively through a spiral flow tube than through a conventional T-shaped tube in contrast-enhanced magnetic resonance angiography (CEMRA). To compare the degree of contrast enhancement and signal stability in the carotid artery by using CEMRA between a spiral flow tube and a T-shaped tube.A total of 100 patients were analyzed in this retrospective study. The first 50 patients underwent CEMRA of the carotid artery with the T-shaped tube, while the last 50 patients used the spiral flow tube. Gadoterate meglumine was diluted with saline to make a total volume of 20 mL. Injection was performed with a bolus rate of 2.5 mL/s for 8 seconds. Five regions of interest (ROIs) were placed on the contrast-enhanced area in each carotid artery and the signal intensity (SI) in the ROI was used for the analysis. The ROIs on the brain stem were also placed and the average SI in this ROI was used as a reference signal. The enhancement of the artery (Eartery) was calculated as a normalized signal using the following equation: Eartery = SI in the ROI of the carotid bifurcation/SI in the ROI of the brain stem. Signal homogeneity in the contrast-enhanced area (SHenhance) was assessed by calculating the coefficient of variation from the SI in the 5 ROIs. The value of SHenhance and Eartery between the data obtained from the spiral flow tube and the T-shaped tube were compared. P-values <.05 were considered significant.We found a significant difference in SHenhance between the data obtained from the spiral flow tube (0.20 ±â€Š0.060) and the T-shaped tube (0.24 ±â€Š0.056) (P = .001). The Eartery values significantly increased by 15% (spiral flow tube, median 14.1 with interquartile range [IQR] 11.8-15.4 vs T-shaped tube, median 12.3 IQR 11.3-14.0, P = .02) using the spiral flow tube.These findings suggest that, by using the Spiral flow tube, the homogeneity of the contrast-enhanced signal intensity in the carotid artery was significantly improved without decreasing the signal intensity in CEMRA.

Improvement of the diagnostic accuracy of MRA with subtraction technique in cerebral vasospasm.

PURPOSE: Vasospasm has been considered the most severe acute complication after subarachnoid hemorrhage (SAH). MRA is not considered ideal for detecting cerebral vasospasm because of background including the hemorrhage. The aim of this study is to evaluate the efficacy of Subtraction MRA (SMRA) by comparing it to that of conventional MRA (CMRA) for diagnosis of cerebral vasospasm. METHODS: Arteries were assigned to one of three categories based on the degree of MRA diagnostic quality of vasospasm (quality score): 0, bad … 2, good. Furthermore each artery was assigned to one of four categories based on the degree of vasospasm severity (SV score): 0, no vasospasm … 3, severe. The value of the difference between DSA-SV score and MRA-SV score was defined as the DIF score. CMRA and SMRA were compared for each arterial region with regard to quality score and DIF score. RESULTS: The average CMRA and SMRA quality score were 1.46 and 1.79; the difference was statistically significant. The average CMRA and SMRA DIF score were 1.08 and .60; the difference was statistically significant. CONCLUSIONS: Diagnosis of cerebral vasospasm is more accurate by SMRA than by CMRA. The advantages are its noninvasive nature and its ability to detect cerebral vasospasm.

[Examination of scan parameters that influence image quality in three-dimensional rotational angiography(3D-RA)].

Because the imaging qualities of three-dimensional rotational angiography(3D-RA)are influenced by various imaging parameters, it is difficult to obtain high-quality images from 3D-RA. In this study, we compared two methods of 3D-RA, the propeller rotation technique(PRT)and the roll rotation technique(RRT)by changing image intensifier(I.I.)sizes(5, 7 and 9 inches)using a test chart and handmade phantom. The results of this study demonstrated that one of the factors determining the image quality of 3D-RA was spatial resolution. Therefore, it was important to choose an optimum I.I. size that was similar in size to collimating the region of interest(ROI)in clinical use. Another factor influencing image quality was radiographic condition, especially the setting of tube voltage. This factor was indispensable in obtaining good image contrast, but the use of high-voltage exposure was one of the reasons for lower image contrast. Therefore, if image contrast was insufficient, the image qualities of 3D-RA became worse with increasing tube voltage because the tube voltage in this study was automatically changed according to scanning method and I.I. size. In addition, because the spatial resolution of PRT was similar to that of RRT, we thought it better to use PRT because the data acquisition time(scan time)of this technique was 4 seconds shorter than that of RRT, whereas, if PRT was used, it was necessary to set a suitable rate of injection of contrast medium because the setting of the tube voltage of PRT was 10 kV higher than that of RRT. In conclusion, to improve the image qualities of 3D-RA, we considered it necessary to obtain sufficient image contrast not influenced by high tube voltage and to choose an optimum I.I. size suitable for the spatial resolution of ROI.