A 74-year-old man with progressive cough and radiographic evidence of a space occupying lesion in the lung underwent fludeoxyglucose F18* (18F FDG) PET•CT. The study for initial staging was performed on a Biograph™ mCT 64 PET•CT 1 hour following injection of 10 mCi of 18F FDG. A stop-and-go sequential bed acquisition was performed over 8 bed positions with a scan time of 1.5 min per bed position.
*Siemens' PETNET Solutions is a manufacturer of fludeoxyglucose F 18 injection (18F FDG). Indication and important safety information as approved by the US Food and Drug Administration can be found at the bottom of the page for 18F FDG, adult dose 5-10 mCi, administered by intravenous injection.
Scanner: Biograph mCT Flow** 64
Dose: 10 mCi (370/MBq) 18F FDG
Scan Delay: 60 min post injection
Parameters: 1.5 min/bed stop & go
2mm/sec;1 mm/sec & 1.5 mm/sec FlowMotion™
CT : 120kV, 45 eff mAs, 5 mm slice thickness
The PET•CT study demonstrated a large, hypermetabolic, right lower lobe tumor located in the upper posterior part with central necrotic zone as seen in the PET image (Figure 1). No well defined nodal metastases were visualized. The hilar uptake was interpreted as inflammatory changes.
Fig. 2: Comparison of post-therapy 18F FDG PET MIP images acquired with stop-and-go and FlowMotion. The FlowMotion image shows uniform edge-to-edge noise (arrows).
Fig. 3: Comparison of coronal thin MIP images of post-therapy 18F FDG PET performed with stop-and-go and FlowMotion acquisition. Coronal images show generalized increase in tracer uptake in the vertebral marrow with small focal cold areas (arrows).
Fig. 4: Comparison of sagittal images of stop-and-go and FlowMotion acquisition.
Fig. 5: CT and fused PET•CT images show focal cold areas in the vertebrae. CT images through T7 and T11 vertebrae show well circumscribed focal areas of lower density (white arrows) of vertebral spongy bone, which corresponds to the cold vertebral focal areas seen on PET and the fused PET•CT images. The pattern of hypodensity of CT and the cold areas within vertebral marrow seen on PET suggest that these lesions are vertebral body hemangiomas.
The patient was subjected to combined chemotherapy and radiation and, subsequently, underwent a follow-up 18F FDG PET•CT performed on Biograph mCT Flow™ (Figures 2-5). Immediately following the stop-and-go acquisition, a second PET acquisition using continuous FlowMotion scanning was performed. The table flow speed was 2 mm/sec in the head and neck area. The region of the thorax and upper abdomen was acquired with a slower 1.0 mm/sec acquisition speed since the lung was the primary area of interest. The rest of the body was acquired with a faster acquisition speed of 1.5 mm/sec.
Maximum intensity projection (MIP) images (Figure 2) show absence of significant tracer uptake in the right lung lesion, suggesting complete response to therapy. There are inflammatory changes in the right hilum. The generalized increase in uptake in the vertebral marrow and ribs suggest post-chemotherapy flare response. The increased noise at the edges of the image in stop-and-go acquisition (Figure 2 - black arrows) are absent in images acquired with FlowMotion technology, reflecting edge-to-edge sensitivity and end-plane image quality.
In view of the complete absence of residual tracer uptake in the lung lesion, the patient was labeled as tumor free and clinical follow-up was recommended.
The FlowMotion acquisition demonstrated the flexibility offered by this technology through freely selectable scan ranges with variable scan parameters in order to acquire higher count statistics in the organs of interest and to accelerate the scan in regions with little or no probability of clinical pathology. In this patient, the lung was scanned at a slower speed in order to generate higher counts in the region of interest, while the lower abdomen and extremities were scanned faster in order to optimize acquisition time. The freely selectable scan range avoids the limitations of the fixed-scan ranges of individual bed positions and requisite overlaps, allowing the appropriate scan speed for exactly determinable acquisition ranges as in this clinical example.
*Fludeoxyglucose F 18 Injection
INDICATIONS AND USAGE
Fludeoxyglucose F 18 injection (18F FDG) is indicated for positron emission tomography (PET) imaging in the following setting:
Oncology: For assessment of abnormal glucose metabolism to assist in the evaluation of malignancy in patients with known or suspected abnormalities found by other testing modalities, or in patients with an existing diagnosis of cancer.
IMPORTANT SAFETY INFORMATION
Radiation-emitting products, including fludeoxyglucose F 18 injection, may increase the risk for cancer, especially in pediatric patients. Use the smallest dose necessary for imaging and ensure safe handling to protect the patient and health care worker.
Blood Glucose Abnormalities
In the oncology and neurology setting, suboptimal imaging may occur in patients with inadequately regulated blood glucose levels. In these patients, consider medical therapy and laboratory testing to assure at least two days of normoglycemia prior to fludeoxyglucose F18 injection administration.
Hypersensitivity reactions with pruritus, edema and rash have been reported; have emergency resuscitation equipment and personnel immediately available.