Currently, in routine patient care PET/CT scan protocols used on high sensitivity large field of-view (LAFOV) PET/CT systems are based on protocols that historically were developed for standard field-of-view (SAFOV) PET/CT systems with a much lower sensitivity profile. In the current SAFOV-based imaging protocols, the maximum delay between injection and actual scanning is limited by increasing noise (due to radioactive decay) resulting in bad image quality. A major advantage of later time-point imaging in general is, that the target-to background ratio improves. With the high-sensitive LAFOV PET/CT scanner later time-point imaging becomes possible, and higher tumour-to background ratios can be obtained. Specifically for the 18F-Fluoroesradiol tracer, used to image estrogen receptor positive tumors, high physiological uptake in the liver and intestines hampers the visualization and quantification of liver metastases and peritoneal metastases. The aim of this study is to evaluate whether late time point imaging with the 18F-Fluoroestradiol tracer on the LAFOV PET/CT improves visualization and quantification of liver metastases and peritoneal metastases.

Inclusion Criteria:

• Patients who are referred for PET/CT imaging with 18F-Fluoroestradiol will be included in this study.

Exclusion Criteria:

• Patients who are not able to lay down in supine position for up to one hour.