| Magnetic susceptibility is an intrinsic physical quantity which can be used to represent the magnetized degree of organization in the strong magnetic field.In recent years,quantitative analysis of the susceptibility of human body has become a new hot spot of MR imaging.Since its unique relation to the actual physical tissue magnetic properties,quantitative susceptibility mapping(QSM)could provide special contrast which is more efficient than other MR techniques.Especially in some brain diseases and disorders,such as Alzheimer's disease,Thalassemia and Parkinson's disease,it works as a powerful auxiliary tool in the diagnosis.The QSM methods under the classical frame decompose the main problem into three subproblems,and solve them independently.But this decomposition does not conform to the causes of problems,which causes a negative influence of the reconstruction accuracy,higher parameter sensitivity and more error accumulation.In this paper,two new single-step reconstruction methods are proposed:the first one,based on harmonic function property,inherits and develops classical methods which efficiently reduces accumulated errors;the second one,under a new reconstruction frame,artfully skips the phase pretreatment by inversing total field directly.Benefited from the right prior,it gets a excellent result in just 3-4 iterations.In terms of algorithm theory,there is a progressive relationship between two methods.It's a complete change of the classical frame,which proposes a new end-to-end frame to get better results.Not only that,due to the advantage of the new model,the second method could well reconstruct the brain with trauma and lesion,which other methods are helpless.We also introduce an advanced solution of weighted L0 norm regularization,aimed at accelerating the convergence of the whole algorithm.All the results of the experiment verify the new method improves the reconstruction accuracy,provides artifact-free results and promotes clinical applications. |
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