Management of Respiratory Motion Artefacts in 18F-fluorodeoxyglucose Positron Emission Tomography using an Amplitude-Based Optimal Respiratory Gating Algorithm

Summary

Amplitude-based optimal respiratory gating (ORG) effectively removes respiratory-induced motion blurring from clinical ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) images. Correction of FDG-PET images for these respiratory motion artefacts improves image quality, diagnostic and quantitative accuracy. Removal of respiratory motion artefacts is important for adequate clinical management of patients using PET.

Abstract

Positron emission tomography (PET) combined with X-ray computed tomography (CT) is an important molecular imaging platform that is required for accurate diagnosis and clinical staging of a variety of diseases. The advantage of PET imaging is the ability to visualize and quantify a myriad of biological processes in vivo with high sensitivity and accuracy. However, there are multiple factors that determine image quality and quantitative accuracy of PET images. One of the foremost factors influencing image quality in PET imaging of the thorax and upper abdomen is respiratory motion, resulting in respiration-induced motion blurring of anatomical structures. Correction of these artefacts is required for providing optimal image quality and quantitative accuracy of PET images.

Several respiratory gating techniques have been developed, typically relying on acquisition of a respiratory signal simultaneously with PET data. Based on the respiratory signal acquired, PET data is selected for reconstruction of a motion-free image. Although these methods have been shown to effectively remove respiratory motion artefacts from PET images, the performance is dependent on the quality of the respiratory signal being acquired. In this study, the use of an amplitude-based optimal respiratory gating (ORG) algorithm is discussed. In contrast to many other respiratory gating algorithms, ORG permits the user to have control over image quality versus the amount of rejected motion in the reconstructed PET images. This is achieved by calculating an optimal amplitude range based on the acquired surrogate signal and a user-specified duty cycle (the percentage of PET data used for image reconstruction). The optimal amplitude range is defined as the smallest amplitude range still containing the amount of PET data required for image reconstruction. It was shown that ORG results in effective removal of respiration-induced image blurring in PET imaging of the thorax and upper abdomen, resulting in improved image quality and quantitative accuracy.

Introduction

Positron Emission Tomography (PET) in combination with X-ray computed tomography (CT) is a widely accepted imaging tool in clinical practice for accurate diagnosis and clinical staging of a variety of diseases¹. The advantage of PET imaging is the ability to visualize and quantify a myriad of biological processes in vivo with high sensitivity and accuracy². This is achieved through intravenously administering a radioactively labelled compound, also known as a radiotracer, to the patient. Depending on the radiotracer being used, tissue characteristics such as glucose metabolism, cellular proliferation, degree of hypoxia, ....

Protocol

All procedures performed involving human participants were in accordance with the ethical standards of the internal review board (IRB) of the Radboud university medical center and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. The ORG algorithm is a vendor specific product and is available on the Siemens Biograph mCT PET/CT scanner family and newer PET/CT models.

1. Patient preparation

1. Patient anamnesis
   1. Check the patient’s name and date of birth. Inclusion criteria are similar to routine non-gated PET scanning. No additional in- or exclusion criteria are required.

Results

The use of ORG in PET results in an overall reduction of respiratory-induced blurring of the images. For example, in a clinical evaluation of patients with non-small cell lung cancer (NSCLC), ORG resulted in detection of more pulmonary lesions and hilar/mediastinal lymph nodes²⁰. This is readily demonstrated in Figure 8 and Figure 9, showing non-gated and ORG PET images of patients with NSCLC.

In particular, OR.......

Discussion

In the nuclear medicine community, the deteriorating effects of respiratory motion artefacts in PET imaging have been well-recognized for a long time. It has been shown in many studies that the blurring effect of respiratory motion artefacts can significantly influence image quantification and lesion detectability. Although several respiratory gating methods have been developed, respiratory gating is currently not widely being used in clinical practice. This is particularly due to a resulting variable image quality, unac.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Sensor Port, sensor, black box, wave deck, elastic band, load cell sensor (complete set)	anzai medical co.	respiratory gating system AZ-733V	http://www.anzai-med.co.jp/en/product/item/az733v