Low-dimensional-structure self-learning and thresholding: Regularization beyond compressed sensing for MRI Reconstruction

Mehmet Akçakaya, Tamer A. Basha, Beth Goddu, Lois A. Goepfert, Kraig V. Kissinger, Vahid Tarokh, Warren J. Manning, Reza Nezafat

Research output: Contribution to journalArticlepeer-review

119 Scopus citations


An improved image reconstruction method from undersampled k-space data, low-dimensional-structure self-learning and thresholding (LOST), which utilizes the structure from the underlying image is presented. A low-resolution image from the fully sampled k-space center is reconstructed to learn image patches of similar anatomical characteristics. These patches are arranged into "similarity clusters," which are subsequently processed for dealiasing and artifact removal, using underlying low-dimensional properties. The efficacy of the proposed method in scan time reduction was assessed in a pilot coronary MRI study. Initially, in a retrospective study on 10 healthy adult subjects, we evaluated retrospective undersampling and reconstruction using LOST, wavelet-based l1-norm minimization, and total variation compressed sensing. Quantitative measures of vessel sharpness and mean square error, and qualitative image scores were used to compare reconstruction for rates of 2, 3, and 4. Subsequently, in a prospective study, coronary MRI data were acquired using these rates, and LOST-reconstructed images were compared with an accelerated data acquisition using uniform undersampling and sensitivity encoding reconstruction. Subjective image quality and sharpness data indicate that LOST outperforms the alternative techniques for all rates. The prospective LOST yields images with superior quality compared with sensitivity encoding or l1-minimization compressed sensing. The proposed LOST technique greatly improves image reconstruction for accelerated coronary MRI acquisitions.

Original languageEnglish (US)
Pages (from-to)756-767
Number of pages12
JournalMagnetic resonance in medicine
Issue number3
StatePublished - Sep 2011


  • accelerated imaging
  • block matching
  • cardiac MR
  • compressed sensing
  • coronary MRI
  • image reconstruction
  • learning algorithm


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