Cancer Research
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Management of Respiratory Motion Artefacts in 18F-fluorodeoxyglucose Positron Emission Tomography using an Amplitude-Based Optimal Respiratory Gating Algorithm
Chapters
Summary July 23rd, 2020
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.
Transcript
The deteriorating effects of respiratory motion artifacts in PET/CT imaging have long been well-recognized. Optimal respiratory gating is a method used to correct PET/CT images for these motion artifacts. Maintaining a sufficient image quality is problematic for most respiratory gating algorithms.
The optimal respiratory gating algorithm allows the user to maintain and define a sufficient image quality. Respiratory motion artifacts can significantly influence image quality and quantitative accuracy. Therefore, removal of these artifacts from PET images is important to improve diagnostic accuracy and the ability to monitor treatment responses.
Demonstrating the procedure will be Jurrian, a senior technologist at the Department of Radiology and Nuclear Medicine. Prior to administration of the radiotracer. It is important to measure the patient's blood glucose.
After explaining the preparation and imaging procedures to the patient, insert a peripheral venous cannula, into one of the antecubital veins of the patient, and attach a three-way stopcock system with a lure lock to a 20-milliliter syringe of saline. De-aerate the stopcock with saline and attach the stopcock to the venous cannula. Check the patency of the cannula with 10 milliliters of saline, and attach the syringe with the radiotracer to the three-way stopcock.
Then turn the valves of the three-way stopcock such that the direction of the fluid will flow from the syringe containing the radiotracer to the peripheral venous cannula. The syringe has been placed in a special tungsten shielded container. To administer the radiotracer, slowly depress the syringe plunger of the container.
When all of the tracer has been delivered. Turn the valves of the stopcock such that the syringe containing the saline is connected to the radiotracer syringe, and flush the syringe to capture any residual radiotracer within the syringe in the saline. Then turn the valves of the stopcock, and deliver the saline flush containing residual radiotracer to the patient.
After the last wash of radiotracer had been administered, remove the radiotracer syringe. And deliver 0.5 milligrams per kilogram of furosemide through the venous cannula. After the furosemide has been delivered, let the patient rest in a comfortable position for 50 minutes before asking the patient to void their bladder.
At 55 minutes, escort the patient to the scanner, and have the patient lie in the supine position with the arms up on the scanner bed. Use appropriate arm support to make the patient as comfortable as possible. And observe the patient's breathing pattern.
Secure the respiratory belt around the patient's thorax or upper abdomen with the sensor placed such that the abdominal wall excursion can be identified after visual inspection. Then use the hook and loop closing system to secure the belt around the patient, and check the scanner display to confirm that the respiratory signal remains within the bounds of the minimum and maximum range. At 60 minutes after registering the patient, select the whole body protocol on the scanner and click the optimal gated acquisition protocol.
Move the scanner table to the correct position for acquisition of the topogram. To initiate acquisition of the topogram, press the scanner start key on the scanner control box and click the left mouse button on the topogram to set the scan range. Then acquire a low-dose CT scan of the patient.
Next, set the PET bed position to be corrected for respiratory motion, and set the image recording time for the bed positions. When the acquisition parameters have been entered, press and hold the move key until the scanner bed has been moved back to the starting position, and press start again to initiate the PET scan. During the acquisition, regularly check the patient and the quality of the respiratory signal.
At the end of the scan, confirm that the respiratory signal has been acquired, and initiate the scan reconstruction. The use of optimal gating in PET images 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, optimal gating resulted in the detection of more pulmonary lesions, and hilar and mediastinal lymph nodes.
These differences can have an important impact on patient management, particularly in non-small cell lung cancer patients with early disease stages. An important advantage of the optimal respiratory gating algorithm is that image quality can be determined by the user. In this figure, two different optimally gated PET and non-gated PET images with different statistical quality can be observed.
While the statistical quality of the optimally gated PET image reconstructed with a duty cycle of 35%and the non gated equivalent image is kept constant. The trade-off between image noise and the amount of motion rejection from the pet images is determined by the duty cycle. Although image quality is maintained when using the optimal respiratory gating algorithm, appropriate positioning of the belt prior to scanning is important for acquiring a high quality respiratory signal.
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