Comparative analysis of F18-NaF PET/CT and Tc99m-MDP nuclear bone scans for detecting osseous metastases.

Objectives The utilization of sodium fluoride (NaF) in PET/CT bone scans is an example of continuing advancements in nuclear imaging to produce greater accuracy in patient diagnosis. 99mTc-Methylene diphosphonate (MDP) planar or SPECT nuclear bone scans are traditionally performed for evaluating osseous metastases in patients with known cancer. 18F-NaF PET/CT bone scans however, have proven to demonstrate superior accuracy in detecting lesions. This study evaluates the methods for detecting osseous metastases in nuclear bone imaging by comparing the sensitivity and specificity of planar and SPECT images with PET/CT scans.

Methods Forty-four patients with cancer underwent whole body bone planar scintigraphy and SPECT imaging of the axial skeleton as well as a PET/CT scan. Administration of 99mTc-MDP requires several hours of delay in order for soft tissue clearance and quality skeletal images to be obtained. In this study, after a 2-3 hours delay, planar bone scintigraphy and SPECT were performed. Due to high target-to-background ratio with rapid uptake and clearance of sodium fluoride, the PET/CT bone scan was performed 60-90 minutes after administration.

Results The standard dose for a 99mTc-MDP whole body bone scan produces an effective dose grater than 18F-NaF; however in correlation with CT, the effective dose is increased. After performing all three studies, the planar bone scintigraphy was 70% sensitive and 57% specific for identifying metastatic lesions. The multi-FOV SPECT images produced increased sensitivity and specificity values of 92% and 82% respectively. The PET/CT scans were 100% sensitive and 100% specific to metastatic lesion interpretations.

Conclusions This study demonstrates that PET/CT bone scans are highly sensitive and specific for identifying bone lesions in patients with known cancer. Although 99mTc-MDP whole body bone scintigraphy has proven to produce sufficient results with limited radiation to the patient, the evidence suggests that SPECT and more prominently PET/CT imaging are more diagnostically accurate.