Data-driven bulk patient motion detection and correction in prostate PET/MRI

Ziel/Aim PSMA PET/MRI has made a clinical impact on prostate cancer (PCa) assessment, including a biopsy planning protocol used to target PCa lesions and aid ultrasound in the ensuing biopsy. Bulk patient motion can spontaneously occur during lengthy imaging scans and may thus introduce artefacts in the final PET image leading to reduced spatial resolution that could explain some biopsy mismatches for presumably very small lesions. The aim of this study was hence to detect and correct for bulk patient motion in a prostate biopsy planning PET/MR protocol.

Methodik/Methods Ten PCa patients injected with 320 ± 20 MBq of F-18-PSMA were scanned 15 min in a single bed position in the PET/MR scanner. A technique based on centre-of-mass (CoM) tracking was used to detect axial motion from the single-slice rebinned sinograms with a time resolution of 250 ms. Upon filtering the CoM signal for noise and respiration artefacts, axial shifts were detected and divided into rapid and tardy motion. The entire PET raw data were accordingly divided into motion frames, separately reconstructed and co-registered, thus generating a motion-corrected PET image. SUV_mean was computed from the lesions before and after motion correction.

Ergebnisse/Results Six patient scans featured rapid or tardy movements. On average, 3.5 ± 1.5 frames were considered for each patient, resulting in mean frame duration of 3.75 min (minimum was 3 min to ensure a sufficiently high SNR). A mean SUV change of 12 % was found, going as high up as 21 % in one patient scan. Maximal detected axial displacement was 1.3 mm.

Schlussfolgerungen/Conclusions Patient bulk motion is common in prostate PET examinations and can affect PET quantitation and final representation of lesion size and location. To better evaluate the full scope of bulk patient motion in prostate PET/MRI, further work including transversal motion assessment is in progress.

Publication History

Article published online:
08 April 2021