Abstract:
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Purpose: The advent of very fast time resolved MRA has decreased the need for patients to perform long breath-holds, and allows for a very quick MR exam. MR perfusion information is also available in time resolved pulmonary MRA and has the advantage of not requiring identification of filling defects in very small vessels but instead relies on identification of larger microvascular perfusion defects. The purpose of our study was to compare the accuracy of high resolution MRA with parametric maps of pulmonary blood volume in patients being evaluated for pulmonary embolus.
Methods and Materials: Data from 10 patients who underwent a pulmonary MRA exam, and subsequently underwent pulmonary x-ray angiography was retrospectively reviewed by two readers. The MR examination was performed on a 1.5T GE scanner. Time resolved MRA was performed after injection of 15 ccs Gd-DTPA at 5ccs/sec. A 3D spoiled gradient echo sequence optimized for pulmonary perfusion: (TR=2.4, TE=1.7, 0.5NEX, 128X64 matrix, slice thickness 1.2cm (interpolated X 2), number of slices 12, time of acquisition 1.9seconds. A second injection of 15ccs of IV Gd-DTPA was then administered for a high resolution MRA examination. A 3D spoiled gradient echo sequence was employed optimized for high resolution MRA. Blood volume (positive integral under the curve) parametric mapping was performed for each patient. Analysis of the high resolution and time resolved MRA data was performed on a workstation. 2 readers separately analyzed the high resolution MRA, and the blood volume parametric map for each patient, and scored whether there was an embolus in the upper middle or lower lobes in the right and left lung. One x-ray angiographer reviewed the pulmonary angiograms and scored whether there was an embolus in the upper, middle or lower lobe of each lung.
Results: In 3/10 cases (30%) moderate respiratory artifact was present on the high resolution MRA images. All (100%) patients were able to complete high quality MR perfusion imaging, due to the high temporal resolution of the sequence. The accuracy of pulmonary blood volume mapping was 92% as compared to 71% for high resolution MRA.
Conclusion: High quality parametric maps of pulmonary blood volume measurements were able to be obtained reliably even in patients with difficulty holding there breath. Pulmonary blood volume mapping was more accurate than high resolution MRA in the identification of pulmonary embolus.
Goldman MD, J,
Comparison of Pulmonary Perfusion MRI and High-Resolution Pulmonary MRA in Evalution of Pulmonary Embolus. Radiological Society of North America 2003 Scientific Assembly and Annual Meeting, November 30 - December 5, 2003 ,Chicago IL.
http://archive.rsna.org/2003/3106814.html
