Feasibility of ¹⁸F-FDG Dose Reductions in Breast Cancer PET/MRI

Abstract

The goal of this study was to determine the level of clinically acceptable F-FDG dose reduction in time-of-flight PET/MRI in patients with breast cancer. Twenty-six consecutive women with histologically proven breast cancer were analyzed (median age, 51 y; range, 34-83 y). Simulated dose-reduced PET images were generated by unlisting the list-mode data on PET/MRI. The acquired 20-min PET frame was reconstructed in 5 ways: a reconstruction of the first 2 min with 3 iterations and 28 subsets for reference, and reconstructions simulating 100%, 20%, 10%, and 5% of the original dose. General image quality and artifacts, image sharpness, image noise, and lesion detectability were analyzed using a 4-point scale. Qualitative parameters were compared using the nonparametric Friedman test for multiple samples and the Wilcoxon signed-rank test for paired samples. Different groups of independent samples were compared using the Mann-Whitney test. Overall, 355 lesions (71 lesions with 5 different reconstructions each) were evaluated. The 20-min reconstruction with 100% injected dose showed the best results in all categories. For general image quality and artifacts, image sharpness, and noise, the reconstructions with a simulated dose of 20% and 10% were significantly better than the 2-min reconstructions ( ≤ 0.001). Furthermore, 20%, 10%, and 5% reconstructions did not yield results different from those of the 2-min reconstruction for detectability of the primary lesion. For 10% of the injected dose, a calculated mean dose of 22.6 ± 5.5 MBq (range, 17.9-36.9 MBq) would have been applied, resulting in an estimated whole-body radiation burden of 0.5 ± 0.1 mSv (range, 0.4-0.7 mSv). Ten percent of the standard dose ofF-FDG (reduction of ≤90%) results in clinically acceptable PET image quality in time-of-flight PET/MRI. The calculated radiation exposure would be comparable to the effective dose of a single digital mammogram. A reduction of radiation burden to this level might justify partial-body examinations with PET/MRI for dedicated indications.

Convolutional neural networks for improving image quality with noisy PET data

“…For the qualitative evaluation, each observer read the total pool of 220 images, rating each on a 4-point scale according to 3 criteria: image noise, image sharpness, and general image quality-this scheme was similar to previously published criteria [30]. Additionally, for each patient full-count image, the observer selected locations of liver, lung, and blood pool (left ventricle or aorta) to be used subsequently for volume-of-interest (VOI) analyses, in which spherical VOIs, of radius 10 mm for liver and lung and 5 mm for blood pool, were defined and propagated throughout the reduced-count images for each patient.…”

Head-to-head comparison between digital and analog PET of human and phantom images when optimized for maximizing the signal-to-noise ratio from small lesions

“…A number of developments are currently being pursued for lowering the injected activities and/or PET recording times [29][30][31]. Recent studies have proposed appropriate regularization schemes to more effectively limit the increase in noise level [32,33].…”

Summary of the First ISMRM–SNMMI Workshop on PET/MRI: Applications and Limitations

“…Beyond MRI advances, new PET-detector technologies allowing for significantly reduced amounts of injected radiotracer offer considerably improved flexibility in acquisition time versus radiation burden (69,70). Sah et al, for example, demonstrated that the amount of injected radiotracer can be reduced to 5%-10% of the currently clinically accepted standard dose while maintaining image quality (71). However, that study evaluated breast lesions with favorably low background on PET.…”