Adult Tetralogy of Fallot: quantitative assessment of pulmonary perfusion with time-resolved three dimensional magnetic resonance angiography.

PURPOSE: To determine the potential role of dynamic temporally resolved three dimensional (3D) contrast-enhanced magnetic resonance angiography (MRA) for quantitative evaluation of pulmonary perfusion in adult patients with surgically treated Tetralogy of Fallot (ToF). MATERIALS AND METHODS: Institutional review board approval and written informed consent were obtained for this Health Insurance Portability and Accountability Act-compliant study. Thirty consecutive patients with surgically repaired ToF and 30 age-matched controls underwent breath-hold 3D time-resolved MRA (TR-MRA) and single-phase high-resolution 3D MRA of the thorax at 1.5 T. Two readers evaluated both datasets for image quality and findings. On TR-MRA datasets, regions-of-interest were placed over main pulmonary artery and lung fields obtaining signal intensity time curves. Using analytic software, time-to-peak (TTP), mean transit time (MTT), maximal signal intensity (MSI), maximum upslope of the curve (MUS), pulmonary blood volume (PBV), and pulmonary blood flow (PBF) were calculated. Pulmonary radionuclide scintigraphy was available for a subgroup of patients with ToF (n = 12). RESULTS: For ToF patients with unilateral pulmonary artery (PA) stenosis, TTP, and MTT were significantly longer, and MSI, MUS, PBV, and PBF were significantly lower in the ipsilateral lung compared with control subjects (P < 0.001 for all). There was no significant difference in TTP, MTT, MSI, MUS, PBV, and PBF between ToF patients without postsurgical stenotic residua and control subjects (P > 0.05 for all), nor between the mentioned perfusion indices for the contralateral lung in ToF patients with unilateral PA stenosis and control subjects (P > 0.05 for all). In ToF, patient with unilateral PA stenosis, analysis of contralateral-to-ipsilateral lung perfusion ratios on radionuclide scintigraphy and TR-MRA revealed significant correlation (r = 0.96). Bland-Altman plot showed a mean difference of 2.2% between the measured ratios (limits of agreement; -7.6%-12.0%). CONCLUSION: Time-resolved 3D contrast-enhanced MRA has potential for noninvasive and quantitative assessment of altered patterns of pulmonary perfusion in adult ToF, and may be a reliable technique for evaluation of postsurgical residua in these patients.

MR angiography at 3 T for assessment of the external carotid artery system.

OBJECTIVE: A number of clinical situations exist in which high-resolution depiction of the external carotid artery system is required, a task not previously addressed by MR angiography. The purpose of this study was to evaluate the extent to which high-spatial-resolution MR angiography at 3 T can be used to map the normal external carotid artery system. SUBJECTS AND METHODS: Twenty-three consenting adult patients were prospectively evaluated. Images acquired were evaluated by two independent observers, and each branch vessel was scored with regard to image quality, presence and grade of stenoses, and artifacts. Interobserver agreement regarding image quality and the presence and degree of stenosis was tested using the kappa coefficient. Differences in quality ratings between the two observers were assessed using the paired Student's t test. RESULTS: Of 828 vessels analyzed, 92.63% were designated of diagnostic quality with no significant difference between the observers' image quality scores (p = 0.63). Good agreement was determined regarding image quality achieved (kappa = 0.716). All examinations were free of artifact sufficient to interfere with confident interpretation. Excellent correlation was seen with regard to stenosis detection and grading (kappa = 0.857). Of the external carotid artery systems assessed, 82.6% showed conventional anatomic vascular branching. CONCLUSION: High-spatial-resolution, 3D contrast-enhanced MR angiography at 3 T using sagittal source data acquisition and an advanced acceleration factor of 6 allows high-quality (92.63% of arterial segments) visualization of the external carotid artery system, with complete head and neck vascular coverage.