Abstract
BACKGROUND
PET/MRI has a high potential in oncology imaging, especially for tumor indications where high soft tissue contrast is crucial such as genitourinary tumors. One of the challenges for PET/MRI acquisition is handling of metal implants. In addition to conventional methods, more innovative techniques have been developed to reduce artifacts caused by those implants such as the selective multiacquisition variable-image combination (MAVRIC-SL). The aim of this study is to perform a quantitative and qualitative assessment of metal artifact reduction in $^{68}$Ga-PSMA-11 PET/MRI for prostate cancer patients with hip joint replacement using a selective MAVRIC-SL sequence for the whole pelvis.
METHODS
We retrospectively analyzed data of 20 men with 37 metal hip implants diagnosed with PCA, staged or restaged by $^{68}$Ga-PSMA-11 PET/MRI from June 2016 to December 2017. Each signal cancellation per side or metal implant was analyzed on the reference sequence LAVA-FLEX, as well as T1-weighted fast spin echo (T1w-FSE) sequence and MAVRIC-SL. Two independent reviewers reported on a four-point scale whether abnormal pelvic $^{68}$Ga-PSMA-11 uptake could be assigned to an anatomical structure in the tested sequences.
RESULTS
The smallest averaged signal void was observed on MAVRIC-SL sequences with a mean artifact size of 26.17 cm$^{2}$ (range 12.63 to 42.93 cm$^{2}$, p < 0.001). The best image quality regarding anatomical assignment of pathological PSMA uptakes in the pelvis by two independent readers was noted for MAVRIC-SL sequences, followed by T1w-FSE with excellent interreader agreement.
CONCLUSIONS
MAVRIC-SL sequence allows better image quality in the surrounding of hip implants by reducing MR signal voids and increasing so the accuracy of anatomical assignment of pathological $^{68}$Ga-PSMA-11 uptake in the pelvis over LAVA-FLEX and T1w-FSE sequences.
Kudura, Ken