Cited by 2,529Numerical methods in inverse problemsMedical Imaging Techniques and ApplicationsImage and Signal Denoising Methods

The DOI matches its Crossref record; 74 of the 83 references it cites were found in a registry or an index; none of the 13 sources its claims cite is checked for support yet.

Deep Convolutional Neural Network for Inverse Problems in Imaging

Open access
Jin, Kyong Hwan, McCann, Michael T., Froustey, Emmanuel, Unser, Michael·2017·IEEE Transactions on Image Processing

Abstract

In this paper, we propose a novel deep convolutional neural network (CNN)-based algorithm for solving ill-posed inverse problems. Regularized iterative algorithms have emerged as the standard approach to ill-posed inverse problems in the past few decades. These methods produce excellent results, but can be challenging to deploy in practice due to factors including the high computational cost of the forward and adjoint operators and the difficulty of hyperparameter selection. The starting point of this paper is the observation that unrolled iterative methods have the form of a CNN (filtering followed by pointwise nonlinearity) when the normal operator (H*H, where H* is the adjoint of the forward imaging operator, H) of the forward model is a convolution. Based on this observation, we propose using direct inversion followed by a CNN to solve normal-convolutional inverse problems. The direct inversion encapsulates the physical model of the system, but leads to artifacts when the problem is ill posed; the CNN combines multiresolution decomposition and residual learning in order to learn to remove these artifacts while preserving image structure. We demonstrate the performance of the proposed network in sparse-view reconstruction (down to 50 views) on parallel beam X-ray computed tomography in synthetic phantoms as well as in real experimental sinograms. The proposed network outperforms total variation-regularized iterative reconstruction for the more realistic phantoms and requires less than a second to reconstruct a 512 × 512 image on the GPU.

Overview

AI snapshot

Written from the paper’s full text.

TL;DR

The paper proposes FBPConvNet, a deep CNN that takes a filtered back projection (FBP) reconstruction as input and learns to remove artifacts for inverse problems whose normal operator is a convolution, demonstrated on sparse-view X-ray CT. It reports competitive or better SNR than TV-regularized iterative reconstruction on realistic synthetic and real CT datasets, with sub-second GPU reconstruction.

Key findings

  • FBPConvNet outperformed TV-regularized iterative reconstruction on the biomedical synthetic dataset: at 143 views, SNR was 36.15 dB vs. 31.92 dB for TV; at 50 views, 28.83 dB vs. 25.20 dB.
  • On the real experimental CT dataset, FBPConvNet also had higher SNR than TV: 11.34 dB vs. 8.25 dB at 145 views, and 8.85 dB vs. 7.25 dB at 14× subsampling (table lists 51 views).
  • On the ellipsoidal synthetic dataset, TV outperformed FBPConvNet: 29.48 dB vs. 28.96 dB at 143 views, and 27.69 dB vs. 23.84 dB at 50 views; the paper attributes this to TV being optimal for piecewise-constant phantoms.
  • Reconstruction speed was about 200 ms for FBP plus 200–300 ms for the CNN on GPU for a 512 × 512 image, versus around 7 minutes for iterative reconstruction; the abstract states less than one second total.

Methods

  • Design: FBPConvNet applies discretized FBP to measurements, then a CNN based on U-net with multilevel decomposition, multichannel filtering, and residual learning via a skip connection; zero-padding is used and the final layer reduces 64 channels to a single output image. Training pairs low-view FBP images with full-view FBP images as input and output.
  • Data: three datasets—ellipsoid synthetic (500 images, sinograms 729 × 1,000), biomedical synthetic (500 real in-vivo CT images from the Mayo Clinic Low-dose Grand Challenge, sinograms 729 × 1,000), and experimental real CT (377 sinograms from the TOMCAT beamline, each 1,493 × 721, from rat brain z-slices). Synthetic data used 475 training and 25 test images; real data used 327 training and 25 test images with a 25-slice gap. Subsampling was ×7 and ×20 for synthetic (143 and 50 views) and ×5 and ×14 for real (145 and 52 views).
  • Analysis: SNR was the quantitative metric; FBP, TV-regularized iterative reconstruction [13], and FBPConvNet were compared. Training used MatConvNet, a Titan Black GPU, about 15 hours for 101 iterations, learning rate decreasing from 0.01 to 0.001, batch size 1, momentum 0.99, gradient clipping at 10⁻², and flip-flop augmentation. TV parameters were selected by golden-section search to optimize performance on the training set.

Limitations

  • Stated: the method lacks transfer between datasets; a network trained on ×7 subsampled sinograms retained artifacts when applied to ×20 subsampled sinograms, and different dimensions or subsampling factors require retraining.
  • Stated: the work focuses on X-ray CT; adapting to MRI or diffraction tomography is expected to be non-trivial experimentally, requiring large training sets and a high-quality iterative reconstruction for comparison, and complex-valued data would need a CNN architecture that correctly handles complex values.
  • Evident/acknowledged: TV outperformed FBPConvNet on the ellipsoidal piecewise-constant phantom, which the paper says is reasonable because TV regularization should be optimal there; the paper also notes TV parameters were tuned on the training set rather than learned from data, and the correct way to learn such parameters remains open.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1109/tip.2017.2713099

Cites

74 of 74 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Verification

Claims the paper makes

0 of 13 cited sources checked · 0 supported · 0 flagged

Show all 34 claims

  • It may state two separate claims as one. 20
  • Probably not a substantial claim. 8
28 of 28
  • The paper relies on this without support.

    High-view FBP reconstructions can serve as ground truth for training and evaluation.

    “We compute its FBP (standard high quality reconstruction) and take this as the ground truth.”
  • The paper relies on this without support.

    A twenty times reduction in the number of views corresponds to a twenty times reduction in the radiation dose received by the patient.

    “a twenty times reduction in the number of views corresponds to a twenty times reduction in the radiation dose received by the patient.”
  • The paper relies on this without support.

    The training and test sets for the synthetic datasets are disjoint.

    “In case of synthetic data, the total number of training images is 475. The number of test images is 25.”
3 of 3

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Experimental 14-fold case is reported as both 51 and 52 views

    Minor

    The data-preparation text says the 14-fold subsampling yields 52 views, but Table III labels that case as 51 views.

  • Experimental result is described as 20-fold rather than 14-fold downsampling

    Minor

    The discussion of Fig. 8 calls it a twenty-times downsampling case, whereas the experimental data-preparation text identifies the corresponding 52-view case as 14-fold downsampling.

2 of 2

Citations

Cites

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9 of the 83 references couldn’t be matched to a known paper.

Research works printed but not linked: 1

  1. epperson, 2013, Creation of fully sampled mr data repository for compressed sensing of the knee, Proc SMRT Conf

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Metadata

Authors
Jin, K. H., McCann, M. T., Froustey, E., & Unser, M.
Affiliations
  • École Polytechnique Fédérale de Lausanne (CH)
  • Dassault Aviation (France) (FR)
Venue
IEEE Transactions on Image Processing
Published
2017-09
Volume
26
Issue
9
Pages
4509-4522
ISSN
  • 1057-7149 (ISSN-L)
  • 1941-0042
OpenAlex
W2574952845
Cited by
2,529
References
83
Citations by year
2026: 184 · 2025: 280 · 2024: 291 · 2023: 318 · 2022: 317 · 2021: 383 · 2020: 326 · 2019: 277 · 2018: 128 · 2017: 23
FWCI
228.23
Type
journal article
Language
en
Open access
Locations
  • IEEE Transactions on Image Processing (publishedVersion)
  • PubMed (publishedVersion)
  • arXiv (Cornell University) (submittedVersion)
  • DORA PSI (Paul Scherrer Institute) (submittedVersion)
  • Infoscience (Ecole Polytechnique Fédérale de Lausanne) (submittedVersion)
  • Infoscience (Ecole Polytechnique Fédérale de Lausanne) (submittedVersion, cc-by-nc-nd)
  • arXiv (Cornell University)
Funders
  • H2020 European Research Council (the European Research Council under Grant 692726 ()
  • Centre dImagerie BioMedicale
  • EPFL Fellows fellowship program co-funded by Marie Curie from the EuropeanUnions Horizon 2020 Framework Programme for Research and Innovation (665667)
Topics
  • Physical Sciences › Mathematics › Mathematical Physics › Numerical methods in inverse problems
  • Health Sciences › Medicine › Radiology, Nuclear Medicine and Imaging › Medical Imaging Techniques and Applications
  • Physical Sciences › Computer Science › Computer Vision and Pattern Recognition › Image and Signal Denoising Methods
Keywords
deep convolutional neural networks, ill-posed inverse problems, direct inversion, artifact removal, multiresolution decomposition, residual learning, sparse-view reconstruction, total variation regularization, image reconstruction

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