Feasibility of image registration and intensity-modulated radiotherapy planning with hyperpolarized helium-3 magnetic resonance imaging for non-small-cell lung cancer

Purpose: To demonstrate the feasibility of registering hyperpolarized helium-3 magnetic resonance images (He-3-MRI) to X-ray computed tomography (CT) for functionally weighted intensity-modulated radiotherapy (IMRT) planning. Methods and Materials: Six patients with non-small-cell lung cancer underwent He-3 ventilation MRI, which was fused with radiotherapy planning CT using rigid registration. Registration accuracy was assessed using an overlap coefficient, calculated as the proportion of the segmented He-3-MR volume (V-MRI) that intersects the segmented CT lung volume expressed as a percentage of V-MRI. For each patient, an IMRT plan that minimized the volume of total lung receiving a dose >= 20 Gy (V-20) was compared with a plan that minimized the V-20, to well-ventilated lung defined by the registered He-3-MRI. Results: The He-3-MRI and CT were registered with sufficient accuracy to enable functionally guided IMRT planning (median overlap, 89%; range, 72-97%). In comparison with the total lung IMRT plans, IMRT constrained with He-3-MRI reduced the V-20, not only for the well-ventilated lung (median reduction, 3.1%; range, 0.4-5.1%; p = 0.028) but also for the total lung volume (median reduction, 1.6%; range, 0.2-3.7%; p = 0.028). Conclusions: Statistically significant improvements to IMRT plans are possible using functional information provided by He-3-MRI that has been registered to radiotherapy planning CT. (c) 2007 Elsevier Inc.