Seminars in Nuclear Medicine

Volume 54, Issue 5, September 2024, Pages 648-657
Seminars in Nuclear Medicine

Artificial Intelligence in Nuclear Cardiology: An Update and Future Trends

https://doi.org/10.1053/j.semnuclmed.2024.02.005Get rights and content
Myocardial perfusion imaging (MPI), using either single photon emission computed tomography (SPECT) or positron emission tomography (PET), is one of the most commonly ordered cardiac imaging tests, with prominent clinical roles for disease diagnosis and risk prediction. Artificial intelligence (AI) could potentially play a role in many steps along the typical MPI workflow, from image acquisition through to clinical reporting and risk estimation. AI can be utilized to improve image quality, reducing radiation exposure and image acquisition times. Once images are acquired, AI can help optimize motion correction and image registration during image reconstruction or provide direct image attenuation correction. Utilizing these image sets, AI can segment a number of anatomic features from associated computed tomographic imaging or even generate synthetic attenuation imaging. Lastly, AI may play an important role in disease diagnosis or risk prediction by combining the large number of potentially important clinical, stress, and imaging-related variables. This review will focus on the most recent developments in the field, providing clinicians and researchers with a timely update on the field. Additionally, it will discuss future trends including applications of AI during multiple points of the typical MPI workflow to maximize clinical utility and methods to maximize the information that can be obtained from hybrid imaging.

Introduction

Myocardial perfusion imaging (MPI) is one of the most commonly ordered cardiac imaging tests, with prominent clinical roles for disease diagnosis and risk prediction. The potential applications of artificial intelligence (AI) to MPI, by single photon emission computed tomography (SPECT) or positron emission tomography (PET), have been increasing exponentially.1 These algorithms could be applied at any point along the typical MPI workflow in order to improve the overall clinical utility, from image acquisition through to clinical reporting and risk estimation as shown in Figure 1. Given the rapidly expanding evidence base, it is difficult even for clinicians and researchers in the field to stay up to date with the latest applications of AI.
This review presents an updated perspective for clinicians and researchers, highlighting recently described approaches in the application of AI to MPI. We summarize recent AI approaches for image reconstruction which could be used to improve image quality or reduce radiation exposure as well as methods to provide correction for soft-tissue attenuation. We also discuss algorithms which leverage the vast array of clinical, stress, and imaging information available from MPI to predict the presence of obstructive coronary artery disease (CAD) and predict risk. We will focus on recent AI applications which can maximize clinical information. Finally, we will delve into the future prospects and directions for AI advancements in MPI obtained from available computed tomography (CT) imaging obtained with hybrid MPI.

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Section snippets

Improving Image Acquisition Times and Image Quality

AI algorithms are increasingly being utilized in image reconstruction to enhance image quality, which potentially allows for reduced radiation exposure or shorter acquisition times. For example, Ramon et al. denoised-dose SPECT MPI using stacked autoencoders trained to predict full-dose images from low-dose image reconstructions.2 In their analysis, images using 1/16th of the clinical dose de-noised with deep learning (DL) achieved similar quality to images using 1/8th dose de-noised with

Image Registration

All PET and many SPECT myocardial perfusion scans are acquired with CT for attenuation correction (AC).12 AC imaging improves the diagnostic accuracy of SPECT,13 but requires careful attention to image registration.14 AI could potentially be used to reduce the frequency or extent of image misregistration. Ko et al. trained a CNN-based algorithm to predict the offset between images compared to manually co-registered SPECT/CT.15 The algorithm (trained with 402 cases and tested using 100 cases)

AI-Derived Attenuation Correction

Soft-tissue attenuation is a universal issue in MPI, which can potentially be overcome by leveraging AI. In this regard, Chen et al. developed a DL network which incorporated gender, body mass index (BMI), images from 3 scatter windows and non-AC images to predict AC images.24 The predicted AC images from this comprehensive DL model more closely matched the actual AC images than predicted AC images from a U-Net model, with normalized mean square error of 2.01% vs 2.23%.24 Nguyen et al.

CAC Scoring

CT is increasingly acquired with MPI which provides an opportunity to extract additional anatomic information using AI which may complement the functional data from MPI. For example, coronary artery calcification (CAC) can be identified from computed tomography attenuation correction (CTAC) scans to improve risk classification.31 A few AI models have been developed which can automate this process,32, 33, 34 but CTAC scans are acquired with low radiation doses resulting in noisy images. Despite

Machine Learning

Several different AI approaches have been developed to classify MPI studies as abnormal or being associated with obstructive CAD. Machine learning (ML) is frequently utilized for this task since it can efficiently integrate the vast array of quantitative information available from MPI. However, ML can identify patients most likely to have abnormal myocardial perfusion using pre-test features for SPECT54 or PET,55 potentially allowing physicians to improve test selection for patients with very

Combining Clinical and Imaging Variables

One of the most important clinical roles for MPI is estimating cardiovascular risk, and AI may also play an important role in this regard. In one such study, a ML model was developed using MPI data from a single center (n = 2,619) for major adverse cardiovascular event (MACE) prediction.71 The ML model, trained and tested using 10-fold cross-validation, had higher AUC for MACE (0.81) compared to stress TPD (0.73), or ischemic TPD (0.71, P < 0.01 for both).71 Importantly, ∼20% of patients in the

Summary

AI has become an increasingly important tool, which can be applied throughout the average MPI process. Before the process even begins, AI may help improve test selection and identify patients for stress only imaging. Subsequently, AI can significantly improve image denoising and reconstruction, potentially allowing reduction in radiation exposure or scanning times. Once images have been reconstructed, AI can provide synthetic AC or be used to automatically segment a variety of anatomic

CRediT authorship contribution statement

Robert J.H. Miller: Conceptualization, Data curation, Formal analysis, Investigation, Writing – original draft, Writing – review & editing. Piotr J. Slomka: Conceptualization, Data curation, Formal analysis, Investigation, Supervision, Writing – original draft, Writing – review & editing.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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    Dr. Slomka participates in software royalties for QPS software at Cedars-Sinai Medical Center and has received research grant support from Siemens Medical Systems. Dr. Miller received research support and consulting fees from Pfizer.
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