Interactive two-dimensional fresh blood imaging: a feasibility study

Magnetic resonance angiography using fresh blood imaging in oral and maxillofacial regions

The present paper provides general dentists with an introduction to the clinical applications and significance of magnetic resonance angiography (MRA) in the oral and maxillofacial regions. Specifically, the method and characteristics of MRA are first explained using the relevant MR sequences. Next, clinical applications to the oral and maxillofacial regions, such as identification of hemangiomas and surrounding vessels by MRA, are discussed. Moreover, the clinical significance of MRA for other regions is presented to elucidate future clinical applications of MRA in the oral and maxillofacial regions.

Magnetic resonance angiography with fresh blood imaging for identification of hemangiomas and blood vessels around hemangiomas in oral and maxillofacial regions

OBJECTIVES

To evaluate fresh blood imaging (FBI), a magnetic resonance imaging technique that does not use contrast, for identifying hemangiomas and feeding arteries in the oral and maxillofacial regions.

STUDY DESIGN

For 16 patients with hemangiomas, FBI visualizations of hemangiomas and feeding arteries in the oral and maxillofacial regions were compared with those from 3-dimensional (3D) phase-contrast magnetic resonance angiography (PC-MRA). Comparisons were based on the conspicuities of blood vessels and the 3D relationships of hemangiomas with the surrounding blood vessels.

RESULTS

The conspicuity of hemangiomas, feeding arteries, and blood vessels were significantly better with FBI than with PC-MRA. After differentiating arteries from veins, 3D visualizations of hemangiomas and arteries or veins could be performed with FBI.

CONCLUSIONS

FBI is a useful method in oral and maxillofacial regions for identifying the relationships between hemangiomas and the surrounding arteries or veins.

Fresh blood imaging of the peripheral vasculature: an emerging unenhanced MR technique

OBJECTIVE

There is an increasing demand for MR angiography (MRA) techniques that do not require the administration of exogenous contrast material. Fresh blood imaging utilizes an ECG-gated fast spin-echo sequence to acquire images in both the systolic and diastolic phases of the cardiac cycle. Fast systolic arterial flow is differentiated from slower diastolic flow and a subtraction technique is used to produce angiographic images. We describe the technical aspects of performing lower extremity MRA and illustrate some sample cases.

CONCLUSION

Fresh blood imaging is an emerging unenhanced MRA technique that has recently become commercially available. Early clinical trials appear promising and it is anticipated that fresh blood imaging will become invaluable, particularly in patients with impaired renal function. Technical refinements are still required to perfect this novel MR application, particularly for the assessment of distal calf and pedal vessels and for the evaluation of patients with arrhythmias and those with impaired cardiac function.

[A fundamental study of non-contrast enhanced MR angiography using ECG gated-3D fast spin echo at 3.0 T]

Contrast-enhanced magnetic resonance angiography (CE-MRA) is frequently performed in body and extremity studies because of its superior ability to detect the vascular stenosis. However, nephrotoxicity of the contrast medium has been emphasized in recent years. Non-contrast MRA using the three-dimensional electrocardiogram-synchronized fast spin echo method (FBI, NATIVE and TRANCE) is recommended as a substitute for CE-MRA. There are a few reports in the literature that evaluate the detectability of vascular stenosis using non-contrast MRA on 3.0 T MRI. The purpose of this study was to evaluate the detectability of vascular stenosis using non-contrast MRA at 3.0 T with an original vascular phantom. The vascular phantom consisted of silicon tubes. 30% and 70% stenosis of luminal diameter were made. Each silicon tube connected a pump producing a pulsatile flow. A flowing material to was used in this study to show the similarity of the intensity to blood on MRI. MRA without a contrast medium (NATIVE sequence) were performed in the vascular phantom by changing the image matrix, static magnetic field strength and flow velocity. In addition, the NATIVE sequence was used with or without flow compensation. Vascular stenosis was quantitatively estimated by measurement of the signal intensities in non-contrast MRA images. MRA with NATIVE sequence demonstrated an accurate estimation of 30% vascular stenosis at slow flow velocity. However, 30% stenosis was overestimated in cases of high flow velocity. Estimation was improved by using a flow compensation sequence. 70% stenosis was overestimated on MRA with NATIVE sequence. Estimation of 70% stenosis was improved by using a flow compensation sequence. Accurate estimation of vascular stenosis in MRA with a NATIVE sequence is improved by using the flow compensation technique. MRA with NATIVE sequence is considered to be a promising method for the evaluation of patients with severe renal dysfunction as a substitute for CT angiography or CE-MRA.