Cardiac Imaging

Left-to-Right Cardiac Shunts: Comparison of Measurements Obtained with MR Velocity Mapping and with Radionuclide Angiography

Abstract

PURPOSE: To investigate the agreement between two noninvasive methods, magnetic resonance (MR) velocity mapping and first-pass radionuclide angiography, to quantify the pulmonary-to-systemic blood flow ratio (QP/QS) in adults, adolescents, and children with left-to-right cardiac shunts.

MATERIALS AND METHODS: The accuracy and precision of MR velocity mapping were studied in 12 control subjects (six men, six women) and in a phantom. MR velocity mapping and radionuclide angiography were performed on the same day in 24 patients (16 adults, two adolescents, six children; five male patients, 19 female patients).

RESULTS: The mean error in QP/QS at MR velocity mapping in phantom experiments was −1% ± 1 (mean ± SD). In control subjects, QP/QS at MR velocity mapping was 1.03 ± 0.03, and the cardiac index was 3.1 L/min/m² ± 0.2 and 3.2 L/min/m² ± 0.3 for women and men, respectively. In patients, QP/QS at radionuclide angiography was 14% ± 13, higher than at MR velocity mapping. Interobserver variability was four times higher for radionuclide angiography compared with MR velocity mapping, 0% ± 16 versus 0% ± 4 (n = 12). The difference between repeated MR flow measurements in the same vessel was −1% ± 5 (n = 36).

CONCLUSION: The data suggest that MR velocity mapping is accurate and precise for measurements of shunt size over the whole range of possible QP/QS values.

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Published in print: May 1999

Vol. 211, No. 2

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