Abstract
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Objectives 18F-choline is excreted in the urine, compromising the interpretation of the pelvic region. Dual-phase 18F-choline PET/CT (F-choline) may discriminate intra-prostatic uptake and suspected pelvic metastases. However, in busy clinics this may be a burden. We have assessed whether delayed imaging alone was accurate in detecting focal abnormalities seen within the prostate and in the pelvis on the early scan.
Methods 28 consecutive dual-phase F-choline studies in 27 patients (age 71.2+9.4 yr) with hormone refractory prostate carcinoma and rising PSA levels were retrospectively reviewed. A single field-of-view pelvic scan was performed immediately after injection, followed by delayed whole body images (84+15 min p/injection). Tracer uptake in the prostate and in the pelvic region was assessed separately on both sets of images.
Results 22 studies were abnormal and in 6 studies there were no pelvic abnormalities. On early images 11 patients had focal prostatic uptake (SUVmax 4.6+2.6), 6 patients had F-choline avid pelvic nodes (SUVmax 4.1+1.9) and 3 patients had F-choline avid skeletal (pelvic) lesions (SUVmax 9.4+5.9). All these findings persisted on delayed images. In addition 7 patients had F-choline avid inguinal nodes; in one patient (SUVmax 4.4) the uptake persisted on delayed images and in 6/7 patients with low grade activity (SUVmax 1.6+0.5) inguinal activity resolved on delayed images and appearances were consistent with reactive changes.
Conclusions Delayed F-choline images accurately detected all focal abnormalities seen on the early studies. With the exception of low grade uptake in reactive inguinal nodes, which resolved on delayed imaging, all findings were congruent on the early and delayed studies. Early findings did not contribute additional information, supporting the use of delayed imaging only in this population. With increasing utilization of F-choline in patients with prostate carcinoma further assessment in larger patient cohorts is required to determine the need for dual-phase imaging in these patients.