Artificial intelligence in radiology


Artificial intelligence (AI) algorithms, particularly deep learning, have demonstrated remarkable progress in image-recognition tasks. Methods ranging from convolutional neural networks to variational autoencoders have found myriad applications in the medical image analysis field, propelling it forward at a rapid pace. Historically, in radiology practice, trained physicians visually assessed medical images for the detection, characterization and monitoring of diseases. AI methods excel at automatically recognizing complex patterns in imaging data and providing quantitative, rather than qualitative, assessments of radiographic characteristics. In this Opinion article, we establish a general understanding of AI methods, particularly those pertaining to image-based tasks. We explore how these methods could impact multiple facets of radiology, with a general focus on applications in oncology, and demonstrate ways in which these methods are advancing the field. Finally, we discuss the challenges facing clinical implementation and provide our perspective on how the domain could be advanced.

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Fig. 1: Artificial versus human intelligence.
Fig. 2: Artificial intelligence methods in medical imaging.
Fig. 3: Artificial intelligence impact areas within oncology imaging.


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The authors acknowledge financial support from the US National Institutes of Health (NIH-USA U24CA194354 and NIH-USA U01CA190234).

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A.H., C.P. and H.J.W.L.A. performed the literature survey, curated the content and general direction and wrote the manuscript. J.Q. and L.H.S. provided substantial contributions to discussions of the content. All authors contributed to reviewing and editing the manuscript before submission.

Correspondence to Hugo J. W. L. Aerts.

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Area under receiver operating characteristic curve

(AUC). A sensitivity versus specificity metric for measuring the performance of binary classifiers that can be extended to multi-class problems. The area under the curve is equal to the probability that a randomly chosen positive sample ranks above a randomly chosen negative one or is regarded to have a higher probability of being positive.

Artificial intelligence

(AI). A branch of computer science involved with the development of machines that are able to perform cognitive tasks that would normally require human intelligence.

Caption generation

The often automated generation of qualitative text describing an illustration or image and its contents.

Ground-glass opacity

(GGO). A visual feature of some subsolid pulmonary nodules that is characterized by focal areas of slightly increased attenuation on computed tomography. Underlying bronchial structures and vessels are often visually preserved (being even more recognizable owing to increased contrast), thus making the detection and diagnosis of such nodules somewhat challenging.

Health Insurance Portability and Accountability Act

(HIPAA). A US act that sets provisions for protecting and securing sensitive patient medical data.

Image registration

A process that involves aligning medical images either in terms of spatial or temporal characteristics, mostly intramodality and occasionally intermodality.

Imaging modalities

A multitude of imaging methods that are used to non-invasively generate visualizations of the human anatomy. Examples of these include computed tomography (CT), computed tomography angiography (CTA), magnetic resonance imaging (MRI), mammography, ultrasonography (echocardiography) and positron emission tomography (PET).


Within optimization problems, constantly adjusted parameters during run time need to be initialized to some value before the start of the process. Good initialization techniques aid models in converging faster and hence speed up the iteration process.

Machine learning

A branch of artificial intelligence and computer science that enables computers to learn without being explicitly programmed.

Multiparametric imaging

Medical imaging in which two or more parameters are used to visualize differences between healthy and diseased tissue. In multiparametric magnetic resonance imaging (MRI), these parameters include T2-weighted MRI, diffusion-weighted MRI and dynamic contrast-enhanced MRI, among others.

Predefined engineered features

A set of context-based human-crafted features designed to represent knowledge regarding a specific data space.

Probabilistic atlas

A single composite image formed by combining and registering pre-segmented images of multiple patients that thus contains knowledge on population variability.


A data-centric field investigating the clinical relevance of radiographic tissue characteristics automatically quantified from medical images.

Report generation

The communication of assessments and findings in both image and text formats among medical professionals.


The partitioning of images to produce boundary delineations of objects of interest. Such a boundary is defined by pixels and voxels (3D pixels) when performed in 2D and 3D, respectively.

Self-supervised learning

A type of supervised learning where labels are determined by the input data as opposed to being explicitly provided.

Supervised learning

A type of machine learning where functions are inferred from labelled training data. Example data pairs consist of the input together with its desired output or label.

Unsupervised learning

A type of machine learning where functions are inferred from training data without corresponding labels.


A collective term describing health-monitoring devices, smartwatches and fitness trackers that have recently been integrated into the health-care ecosystem as a means to remotely track vitals and adhere to treatment plans.

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Hosny, A., Parmar, C., Quackenbush, J. et al. Artificial intelligence in radiology. Nat Rev Cancer 18, 500–510 (2018). https://doi.org/10.1038/s41568-018-0016-5

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