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New PET/CT scanners may offer safer imaging in children

Primarily, researchers are studying whether these new scanners can help reduce the use of sedation in children by acquiring images faster, as well as reducing their exposure to radiation by allowing a lower dose of the radiotracer F-18 FDG. necessary for imaging.


To that end, a group at Cincinnati Children’s Hospital Medical Center in Ohio explored the impact of shorter whole-body F-18 FDG PET/CT imaging acquisition times in children and young adults diagnosed with cancer.


“We know that by decreasing [bed] position time, we can potentially reduce the need for sedation, which is a special consideration for childcare,” said radiology researcher Dr. Vilnius Alves.


Current clinical standard of care images for whole body PET/CT are typically acquired in pediatric patients in 90 seconds per bed position. Since a number of bed positions are required, PET/CT scans can take up to 30 minutes of table time.


This can cause patient discomfort and anxiety, as well as poor image quality due to patient movement. Thus, clinicians may have to sedate pediatric patients, which can have negative side effects.


Faster scan times


In this study, Alves and colleagues used a computational method established in previous studies to reprocess raw data from 90-second images acquired from 27 pediatric patients with tumors using one of the latest PET scanners digital whole body on the market (Discovery MI Gen 2, GE Health).


The researchers trained the scanner’s “count rates” (the number of emissions of the radioactive isotope F-18 recorded per second by the scanner) to simulate decreasing acquisition times at 60, 55, 50, 45 , 40 and 30 seconds. per bed position.


A total of 189 images were generated and independently assessed in random order by three pediatric radiologists experienced in pediatric nuclear medicine. Clinicians scored each image based on visibility of lesions, visibility of normal structures, and overall image quality.


Results showed that compared to acquisition times of 90 seconds, significant differences were observed in lesion visibility scores at 40 seconds or less, for visibility of normal structures and overall image quality at 45 seconds or less, and image noise at 55 seconds or less, says Alves.


Ultimately, an acquisition time of 60 seconds per bed position showed no significant impact on image quality, which could have a significant impact on the clinical care of pediatric patients. -he declares.


“Moving forward, we believe that prospective studies are now needed to define the lowest threshold for acquisition time or dose among different vendors and specific populations,” Alves concluded.


Sufficient image quality


In another study proposed during the session, a Chinese group from Sun Yat-Sen University Cancer Center in Guangzhou explored the effects of digital whole-body PET/CT (uExplorer, United Imaging) on ​​image quality and lesion detectability in pediatric cancer patients using half-dose F-18 FDG.


Presenter Dr. Wanqi Chen and colleagues studied outcomes in 100 pediatric oncology patients who underwent whole body PET/CT using a half dose of 1.85 megabecquerels per kilogram (MBq/kg) of F- 18 FDG between May and December 2021. Patients underwent imaging with acquisition times of 600 seconds or 20 minutes.


The group then generated low-dose whole-body PET/CT images and divided them into groups of 300 seconds, 180 seconds, 60 seconds, 40 seconds, and 20 seconds by truncating the PET data in list mode to stimulate low-dose images. F-18 FDG activity dose between 0.06 and 0.93 MBq/kg.



Imaging of an 11-year-old child with neuroblastoma, with the maximum intensity projection (MIP) of the half dose image and the coronal view and axial images of the serial dose reduction image generated by a reduced number. Overall image quality ratings from G600 to G20 were 5, 5, 4, 3, 3, and 2 points. The lesion was even identifiable reduced at a dose of 1/60. Image courtesy of Dr. Wanqi Chen.



The team found that image quality scores in the generated 20-second full-body PET/CT images were significantly lower, but sufficient subjective image quality and lesion visibility could be maintained in the other pictures.


Specifically, the study authors determined that images generated with an acquisition time of 60 seconds with a dose reduction of 0.185 F-18 FDG MBq/kg identified 100% of cancerous lesions in patients , Chen explained.


“Whole-body PET/CT with half dose of F-18 FDG achieved good performance in pediatric oncology patients, ensuring sufficient image quality and lesion visibility,” Chen concluded.



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