Utility of 68Ga-DOTATATE PET-MRI for Gamma Knife® stereotactic radiosurgery treatment planning for meningioma.

OBJECTIVES: To investigate the impact of adding 68Ga-DOTATATE PET/MRI to standard MRI for target volume delineation in Gamma Knife® stereotactic radiosurgery (GKSRS) for meningioma. METHODS: Seventeen patients with 18 lesions undergoing GKSRS for WHO grade 1 meningioma were enrolled in a prospective study. All patients underwent pre-treatment 68Ga-DOTATATE PET/MRI examination in addition to standard procedures. Five clinicians independently contoured the gross tumour volume (GTV) based on standard MRI (GTVMRI) and PET/MRI (GTVPET/MRI) on separate occasions. Interobserver agreement was evaluated using Cohen's Kappa statistic (CKS), Dice similarity coefficient (DC), and Hausdorff distance (HD). Statistical analysis was performed with paired t-test and Wilcoxon signed rank test. RESULTS: The addition of PET/MRI significantly increased GTV contour volume (mean GTVPET/MRI 3.59 cm3 versus mean GTVMRI 3.18 cm3, P = .008). Using the treating clinician's pre-treatment GTVMRI as the reference, median CKS (87.2 vs 77.5, P = .006) and DC (87.2 vs 77.4, P = .006) were significantly lower, and median HD (25.2 vs 31.0, P = .001) was significantly higher with the addition of PET/MRI. No significant difference was observed in interobserver contouring reproducibility between GTVMRI and GTVPET/MRI. CONCLUSION: The addition of 68Ga-DOTATATE PET/MRI for target volume delineation in GKSRS for meningioma is associated with an increase in GTV volume and greater interobserver variation. PET/MRI did not affect interobserver contouring reproducibility. ADVANCES IN KNOWLEDGE: This study provides novel insights into the impact of 68Ga-DOTATATE PET/MRI on GTV delineation and interobserver agreement in meningioma GKSRS, highlighting its potential for improving GKSRS treatment accuracy.

Discrepancies between positron emission tomography/magnetic resonance imaging and positron emission tomography/computed tomography in a cohort of oncological patients.

INTRODUCTION: This study aims to evaluate discrepant findings between positron emission tomography/magnetic resonance imaging (PET/MRI) and positron emission tomography/computed tomography (PET/CT) in a cohort of oncological patients and to undertake a phantom study to assess the potential for extended PET acquisitions to lead to false-positive findings on PET/MRI. METHODS: Discrepant findings from a series of 106 patients undergoing same-day 18 F-fluorodeoxyglucose (FDG)-PET/CT and PET/MRI were reviewed. Phantom studies explored the potential for PET acquisition time to contribute to discrepancy. RESULTS: There were 14 discrepant cases, 5 (35.7%) of which related to PET/MRI acquisitions that had been extended to 10 min. Three of these five cases proved to be falsely positive. Phantom studies showed greater contrast recovery and signal to noise ratio for 10-min PET/MRI acquisitions compared to 2-min acquisitions using PET/CT. There were no discrepancies when PET/CT showed disseminated disease (P = 0.036). CONCLUSIONS: Extended PET/MRI acquisitions used to accommodate multiple MRI sequences may be associated with false-positive findings compared to PET/CT. PET/MRI is more likely to have incremental value when the prior probability for disseminated disease is low.

Evaluation of a matched filter resolution recovery reconstruction algorithm for SPECT-CT imaging.

AIM: The aim of our study was to assess improvements in spatial resolution and noise control from the application of the Astonish resolution recovery algorithm for single photon emission computed tomography imaging. Secondary aims were to compare acquisitions made with low-energy general purpose collimators with those obtained using low-energy high-resolution collimators in this context and evaluate the potential of a finer matrix to improve image quality further. MATERIALS AND METHODS: A Tc-filled Jaszczak phantom with hot spheres was used to assess contrast and noise. A National Electrical Manufacturers Association triple line source single photon emission computed tomography resolution phantom was used to measure spatial resolution. Acquisitions were made using both low-energy high-resolution and low-energy general purpose collimators. RESULTS: Compared with standard ordered subsets expectation maximization reconstructions, the resolution recovery algorithm resulted in a higher spatial resolution (8 vs. 14 mm full-width at half-maximum) leading to reduced partial volume effects in the smaller Jaszczak spheres. Higher image contrast was achieved alongside lower levels of noise. An edge enhancement artefact was observed in the resolution recovery corrected images. An overestimate of the target-to-background activity was also observed for the larger spheres. CONCLUSION: The use of such an algorithm results in images characterized by increased spatial resolution and reduced noise. However, small sources of the order of 2-3 cm can be significantly overenhanced.