Optimal scan time for fluorine-18 fluorodeoxyglucose positron emission tomography in breast cancer

Fluorine-18 fluorodeoxyglucose positron emission tomography (FDG PET) has p roven useful in the differentiation of various tumour entities, including b reast cancer. In patients with primary breast cancer we performed a 3-h ima ging protocol to examine possible improvements in tumour detectability and image contrast. Twenty-nine patients with primary breast cancer with a diam eter of greater than or equal to 2 cm that was demonstrated to be malignant by biopsy or surgery were injected with 370-740 MBq F-18-FDG and scanned i n the prone position. Data were acquired 0-40 min, 1.5 h and 3.0 h after in jection. After correction for measured attenuation, decay and scatter and i terative reconstruction, standardised uptake values (SUVs) and tumour-to-no n-tumour and tumour-to-organ ratios were calculated. Visual analysis was pe rformed using transverse, sagittal and coronal slices as well as 3D reproje ction images. Tumour-to-non-tumour and tumour-to-organ ratios were signific antly higher for the 3-h images than for the 1.5-h images. SUVs did not inc rease to the same extent. Lesion detectability was 83% in 1.5-h images comp ared to 93% in 3-h images. We conclude that tumour contrast in breast cance r is improved by starting the PET acquisition at 3 h p.i. rather than at 1. 5 h p.i.