ABSTRACT
Respiratory motion is a major problem in cardiac MRI. In this work, the displacement of the heart relative to the diaphragm was investigated. A subject-specific nonlinear elliptical affine model has been developed to incorporate the effect of hysteresis in motion correction. Nine healthy volunteers participated in a study in which the diaphragm position and an image of the heart were acquired during each cardiac cycle, while breathing freely. The elliptical model was compared to a linear affine model, and the results show that the elliptical model performed significantly (P < 0.05) better than the linear model. Further, it has been established that the model can be constructed from 25 s of prescan data, which makes it feasible to perform a short prescan to construct the model, so that subject-specific prospective motion correction of the heart can be integrated into structural cardiac MRI sequences.
Subject(s)
Heart , Magnetic Resonance Imaging , Respiration , Adult , Humans , Middle Aged , Models, TheoreticalABSTRACT
BACKGROUND: Changes in the bone marrow microenvironment in myelofibrosis are triggered by a cytokine burst and consist of fibrosis, osteosclerosis, and angiogenesis. Sunitinib is a multitargeted small-molecule inhibitor of the receptor tyrosine kinases involved in cell proliferation and angiogenesis, including vascular endothelial growth factor receptors. PATIENTS AND METHODS: Fourteen patients with myelofibrosis were treated with sunitinib at a daily continuous dose of 37.5 mg orally. The median duration of sunitinib treatment was 5.2 months (range, 1-18 months). RESULTS: One patient (7%) showed a clinical improvement of anemia (increase in hemoglobin of 4 g/dL), with improvement in anemia-associated symptoms. The time to response was 6 months, and the benefit was sustained for 12 months. However, 8 patients (57%) experienced a total of 13 incidents of significant (grade 3-4) adverse events possibly related to sunitinib (fatigue, gastrointestinal disturbances, anemia, leukopenia, and thrombocytopenia were the most common). In 7 patients (50%), sunitinib was held, and subsequently the dose was reduced to 25 mg daily. Overall, 29% of patients withdrew from the study because of toxicity. CONCLUSION: Sunitinib therapy, as applied here, was not well-tolerated by patients with myelofibrosis, and the benefits were minimal. Our experience with sunitinib combined with previous experience with other antiangiogenic medications suggest that this class of drugs may have limited usefulness in myelofibrosis when used as a single-agent therapy.
