Summary
Objectives: We survey recent developments in medical Information Extraction (IE) as reported
in the literature from the past three years. Our focus is on the fundamental methodological
paradigm shift from standard Machine Learning (ML) techniques to Deep Neural Networks
(DNNs). We describe applications of this new paradigm concentrating on two basic IE
tasks, named entity recognition and relation extraction, for two selected semantic
classes—diseases and drugs (or medications)—and relations between them.
Methods: For the time period from 2017 to early 2020, we searched for relevant publications
from three major scientific communities: medicine and medical informatics, natural
language processing, as well as neural networks and artificial intelligence.
Results: In the past decade, the field of Natural Language Processing (NLP) has undergone
a profound methodological shift from symbolic to distributed representations based
on the paradigm of Deep Learning (DL). Meanwhile, this trend is, although with some
delay, also reflected in the medical NLP community. In the reporting period, overwhelming
experimental evidence has been gathered, as illustrated in this survey for medical
IE, that DL-based approaches outperform non-DL ones by often large margins. Still,
small-sized and access-limited corpora create intrinsic problems for data-greedy DL
as do special linguistic phenomena of medical sublanguages that have to be overcome
by adaptive learning strategies.
Conclusions: The paradigm shift from (feature-engineered) ML to DNNs changes the fundamental
methodological rules of the game for medical NLP. This change is by no means restricted
to medical IE but should also deeply influence other areas of medical informatics,
either NLP- or non-NLP-based.
Keywords
Neural networks - deep learning - natural language processing - information extraction
- named entity recognition - relation extraction