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An optimized protocol for achieving high-quality contrast-enhanced MR angiography (CE MRA) was designed and evaluated. Time-intensity curves of the test bolus and main bolus were compared in 11 volunteers. To identify the acquisition zone sensitive to venous overprojection, sequential filling phantoms which consisted of 12 test tubes were developed and scanned. Using the parameters of the time-intensity curve which were consistent between the test and main boluses and the parameters of the sensitive acquisition zone in the pulse sequences, the protocol for calculation of scan delay time and acquisition time was optimized. The new protocol was verified by comparison of lower extremity CE MRAs acquired by traditional (scan delay time = peak enhancement time minus injection duration/2 + acquisition time/2; n = 12) and new (n = 23) protocols. The arterial and venous enhancing times of the time-intensity curves of the test and main boluses were statistically consistent (p < 0.01). The length of the sensitive acquisition zone was one-half the acquisition duration. With the parameters identified in the time-intensity curve and pulse sequence analyses, a new protocol was developed. For validation, the new protocol was able to study the smaller arteries such as the distal tibial arteries and branches of the femoral and iliac arteries (p < 0.01). Using the optimized protocol, higher-quality images were obtained than those acquired by traditional methods.

ObjectiveTo determine the optimal scan timing for contrast-enhanced magnetic resonance angiography and to evaluate a new timing method based on the arteriovenous circulation time.Materials and MethodsEighty-nine contrast-enhanced magnetic resonance angiographic examinations were performed mainly in the extremities. A 1.5T scanner with a 3-D turbo-FLASH sequence was used, and during each study, two consecutive arterial phases and one venous phase were acquired. Scan delay time was calculated from the time-intensity curve by the traditional (n = 48) and/or the new (n = 41) method. This latter was based on arteriovenous circulation time rather than peak arterial enhancement time, as used in the traditional method. The numbers of first-phase images showing a properly enhanced arterial phase were compared between the two methods.ResultsMean scan delay time was 5.4 sec longer with the new method than with the traditional. Properly enhanced first-phase images were found in 65% of cases (31/48) using the traditional timing method, and 95% (39/41) using the new method. When cases in which there was mismatch between the target vessel and the time-intensity curve acquisition site are excluded, erroneous acquisition occurred in seven cases with the traditional method, but in none with the new method.ConclusionThe calculation of scan delay time on the basis of arteriovenous circulation time provides better timing for arterial phase acquisition than the traditional method.

Transient global amnesia has been reported to be precipitated by intense emotion in adult patients. Transient global amnesia is uncommon in the pediatric age group. We report the unusual occurrence of this syndrome, apparently precipitated on two occasions by emotion, in an adolescent who had earlier in life suffered a left temporal and occipital lobe embolic infarction from congenital heart disease. Transient global amnesia following intense emotion may be a cause of some confusional states in children and adolescents.