Preliminary experience with dynamic MR projection angiography in the evaluation of cervicocranial steno-occlusive disease

Dynamic MRA with four-dimensional time-resolved angiography using keyhole at 3 tesla in head and neck vascular lesions

Conventional MRA provides inadequate visualization of the dynamic features of blood flow in vascular lesions of the head and neck. Four-dimensional time-resolved angiography using keyhole (4D-TRAK) is a new technique of performing contrast-enhanced MRA. By combining parallel imaging with sensitivity encoding (SENSE) with the keyhole imaging technique and a high field strength (3 T) magnet, we have been able to obtain detailed hemodynamic information similar to that obtained via catheter angiography with digital subtraction (DSA), but without the risks associated with ionizing radiation exposure, iodizing contrast agents, or catheterization itself.

Dose optimization for dynamic time-resolved contrast-enhanced 3D MR angiography of pulmonary circulation

OBJECTIVE

The aim of this study was to optimize contrast media dose for assessment of pulmonary circulation with dynamic time-resolved contrast-enhanced 3D MR angiography. SUBJECTS AND METHODS. Twenty healthy volunteers (20-38 years old; mean [+/- SD], 27.2 +/- 4.5 years) were examined prospectively using turbo fast low-angle shot MR angiography (TR/TE, 2.4/1.04). Ten consecutive coronal 3D slabs with a frame rate of 3.2-sec duration were acquired during injection of contrast media at a rate of 4 mL/sec. Signal intensities were measured in various vessels and pulmonary parenchyma. Maximum signal-intensity enhancement (DeltaSI(max)) and time to peak enhancement were calculated. Depiction of pulmonary vessels and pulmonary parenchyma was scored according to an image quality score.

RESULTS

Central pulmonary arteries were well visualized at all tested doses. Segmental arteries, however, were blurry with 0.025 or 0.05 mmol/kg; image quality was improved at 0.1 mmol/kg of gadoterate meglumine (p < 0.05). Image quality did not further improve at 0.2 mmol/kg (p = not significant). Values for DeltaSI(max) in the pulmonary trunk were 38.9 +/- 9.7, 64.1 +/- 9.1, 79.7 +/- 12.2, and 96 +/- 6.0 at 0.025, 0.5, 0.1, and 0.2 mmol/kg of gadoterate meglumine, respectively. Pulmonary parenchyma showed almost no enhancement at 0.025 and 0.5 mmol/kg of gadoterate meglumine (DeltaSI(max) = 1.6 +/- 1.1 and 1.6 +/- 1.2, respectively), but better visualization was shown with 0.1 and 0.2 mmol/kg of gadoterate meglumine (DeltaSI(max) = 2.9 +/- 0.8 and 6.7 +/- 2.1, respectively). Time from peak enhancement in pulmonary arteries to peak enhancement in veins was independent of dose.

CONCLUSION

A dose of 0.1 mmol/kg of gadolinium chelate allows depiction of pulmonary arteries and qualitative assessment of pulmonary parenchyma. Thus, 0.1 mmol/kg can be recommended for dynamic contrast-enhanced 3D MR angiography.

Dynamic time-resolved contrast-enhanced two-dimensional MR projection angiography of the pulmonary circulation: standard technique and clinical applications

OBJECTIVE

Time-resolved pulmonary two-dimensional MR projection angiography is a fast acquisition technique that allows the generation of dynamic projection angiograms by a method similar to that used to generate digital subtraction angiograms. MR images are obtained after subtracting the mask defined at the beginning of the sequence from later images, thus generating time-resolved continuous projection angiograms that depict the passage of a bolus through the pulmonary circulation. This article describes the application of this novel technique in three patients with pathologic conditions not previously described with this modality and two control subjects.

CONCLUSION

The analysis of the findings on dynamic time-resolved contrast-enhanced two-dimensional MR projection angiography shows that this technique is useful not only in revealing morphologic changes associated with pulmonary disorders but also in following the passage of the bolus through the cardiopulmonary circulation. The latter capability allows qualitative detection of normal or abnormal pathways and thus is potentially of value in the assessment of several pulmonary disorders.

Color velocity imaging quantification in the detection of intracranial collateral flow

BACKGROUND AND PURPOSE

The development of intracranial collateral circulation is associated with a lower risk of stroke. A noninvasive technique that can reliably detect the presence of intracranial collaterals would be a valuable factor in the assessment of risk in patients with occlusive cerebrovascular disease.

METHODS

Color velocity imaging quantification was used to measure the blood flow volume of the common carotid and vertebral arteries in 40 patients with carotid occlusive disease. The blood flow volumes in these arteries were correlated with angiographic evidence of collaterals to establish the best cutoffs for detecting intracranial collateral circulation.

RESULTS

A blood flow volume of either > or =370 mL/min in the common carotid artery or > or =120 mL/min in the vertebral artery was indicative of the presence of intracranial collaterals. The sensitivity and specificity for the common carotid artery were 92.3% [95% confidence interval (CI), 62.1 to 99.6] and 92.1% (95% CI, 77.5 to 97.9), respectively. The sensitivity and specificity for the vertebral artery were 75.0% (95% CI, 35.6 to 95.5) and 87.5% (95% CI, 66.5 to 96.7), respectively.

CONCLUSIONS

Color velocity imaging quantification offers a noninvasive, accurate method for detecting the presence of intracranial collateral circulation and quantifying its magnitude. This technique would be a useful adjunct in screening or continuous monitoring of patients with severe carotid occlusive disease.