1. Nuclear imaging for prostate cancer: What’s new?
Dr. Debra Freeman
July 25, 2017

2. Disclosures Employed by CyberKnife Centers of Tampa Bay
Active board member of the CyberKnife Coalition (CKC)
Co-director of the Registry for Prostate Cancer Radiosurgery

3. The basics of nuclear imaging
A radioisotope is attached to an inert molecule to create a radiotracer
Step 1
Radiotracer is injected into the patient
Gamma rays are emitted as the radiotracer decays
Step 2
Emissions are measured using a gamma detector
Measurements are summed and reformatted to create visible images
Step 3

5. Hospitals generally use two types of gamma emission detectors:
Single photon emission scanner (SPECT)
Positron emission tomography scanner (PET/CT)

6. SPE(CT) scans

8. Standard whole body bone scan
Technetium-99 (radioisotope) is attached to methylene disphosphonate (inert molecule) to create the radiotracer
Radiotracer is injected and taken up at sites of bone rebuilding (osteoblastic) activity
Images are acquired using 2-D gamma camera or 3-D SPECT scanner
78-80% sensitivity for detection of bone metastases from prostate cancer

9. Normal scan
Bone metastases

10. ProstaScint scan
Indium-11 (radioisotope) attached to prostate specific membrane antigen (PSMA)-a prostate cell surface protein
Radiotracer is absorbed primarily in soft tissues
Overall accuracy of approx. 68% for detection of recurrent disease
Better if fused with CT or MRI scans

11. ProstaScint scan
CT scan
Fused study

12. PET/CT scans

14. F-18 FDG-PET
Fluorine-18 (radioisotope) is attached to 2-deoxy-2-fluoro-D-glucose to create radiotracer
Actively dividing cells, like cancer cells, take up more glucose than normal cells
False positive results: inflammation
infection
False negative results: slow growing tumors*
small lesions (<5mm)
hyperglycemia

16. FDG-PET for prostate cancer
Limited use for detection and initial staging of primary prostate cancer
More useful for detection of aggressive disease, evaluation of metastatic disease and response to therapy

17. 18-F NaF PET bone scan
Fluorine-18 (radioisotope) attached to sodium fluoride to create the radiotracer
18-F NaF is a highly sensitive radiotracer for skeletal metastases
Emission data acquired with positron emission tomography (same detector as FDG-PET)
More sensitive than Tc-99 bone scan for early detection of bone metastases

19. 18-F fluciclovine (Axumin) PET scan
Fluorine-18 (radioisotope) attached to an amino acid analog of L-leucine, creating the radiotracer (Axumin)
Levels of many amino acids are increased within prostate cancer cells, as compared to normal tissues
Gamma emissions detected using positron emission tomography (again , same scanner as FDG-PET)
Axumin may be superior other radiotracers for detection of recurrent disease in the setting of PSA failure

21. Other radiotracers being studied for prostate cancer imaging
Carbon-11 (radioisotope) attached to choline
Carbon-11 attached to acetate (metabolized into acetyl-CoA)
F-18 attached to fluoro-dihydrotesterone (FDHT)

22. The future… PET/MRI fusion scans
GE and Siemens already have scanners in production
Functional MRI
Androgen receptor PET scans