A 54-year-old female patient with history of adenocarcinoma of the left breast, treated with mastectomy with axillary clearance, underwent Fludeoxyglucose F 18 (18F FDG) PET•CT for follow up. The patient complained of right-side weakness for which she underwent a CT scan of the brain that showed a suspicious space-occupying lesion in the left basal ganglial region. PET•CT was recommended to evaluate for metastases. A PET•CT study was performed 1 hour following IV administration of 8 mCi of 18F FDG. FlowMotion™ acquisition was utilized with variable table speed (Figure 1) in order to perform a slower acquisition for the brain (0.4 mm) to generate high count statistics, which enables high-quality reconstruction at the higher matrix required for the brain. The thorax and abdomen,including the pelvis, was acquired at a slightly higher speed of 1 mm/s, which enabled high-quality PET acquisition for standard matrix reconstruction. The acquisition for zone 3, which comprised the thighs, was accelerated at 2.0 mm/s in
order to complete the acquisition without time penalty, since the thighs were not very clinically relevant.
Whole-body PET images show mild non-specific 18F FDG PET•CT uptake in the region of the surgical clips in the left axilla (Figure 1) and a significant amount of physiological uptake in brown fat in the bilateral axilla, mediastinum and para-spinal regions of the neck as well as the supraclavicular regions and thorax. There is a large photopenic hypodense lesion in the spleen suggestive of a benign splenic cyst (Figure 2). There is also 18F FDG PET•CT uptake in the left para-renal brown fat.
PET images of the brain demonstrated a hypermetabolic mass in the left basal ganglia that corresponds to the lesion seen on CT, suggestive of brain metastases. The PET brain acquisition was also reconstructed using a 400x400 matrix, due to the higher count statistics enabled by slower table speed acquisition of the brain region, made possible with FlowMotion technology. Higher matrix reconstructions (Figure 3) show sharper delineation of the basal ganglial metastases compared to a 200x200 matrix reconstruction. The central necrotic area within the basal ganglial metastases (arrow) is more sharply delineated with Hi-Rez reconstruction, along with the delineation of the superior extension of the metastatic lesion (arrow). Higher matrix acquisition of the brain requires high count statistics for high reconstruction quality, which is enabled by the slower table speed during the FlowMotion acquisition of the brain. Careful analysis of Hi-Rez brain PET images also showed relative hypometabolism in the left frontal region and the right cerebellar hemisphere, which is typical of crossed-cerebellar diaschisis (Figure 4). Crossed-cerebellar diaschisis is a reversible, matched reduction in blood flow and metabolism in the contralateral cerebellum in patients with supratentorial
lesions, including acute cerebral infarction or tumor. This phenomenon is secondary to the interruption of the corticopontocerebellar tract by the lesion, such as the basal ganglial metastases in this case. Higher matrix reconstructions are instrumental for proper demonstration of the mild hypometabolism in the right cerebellar hemisphere.
In view of the high physiological uptake of FDG in the brain, detection of small brain metastases with PET•CT requires high lesion contrast and higher matrix reconstruction in order to differentiate small hypermetabolic lesions from the surrounding cortex. Higher matrix Hi-Rez reconstruction (400x400 matrix) requires high count statistics in order to generate highquality reconstructions without excess noise. The slow table speed of 0.4 mm enabled by FlowMotion technology permits such high count statistics acquisition for the brain with unprecendented flexibility, without compromising overall acquisition time, as well as not requiring a separate dedicated brain acquisition.
Value of FlowMotion Technology
This study illustrates the clinical importance of higher matrix reconstruction for improved visualization of brain lesions such as metastases. FlowMotion technology enables very flexible ranges for slow table speed acquisition for higher count statistics,which enables high-quality reconstructions with a 400x400 matrix. This matrix provides for sharper delineation of small intracerebral lesions with higher lesion to background ratio due to lower partial volume effects. In situations where only the brain requires a Hi-Rez reconstruction, FlowMotion enables only the brain to be scanned slowly for higher count statistics with normal or faster scanning for the rest of the body as part of the integrated whole-body PET•CT acquisition. This flexibility ensures patient-specific acquisition for adequate image quality and resolution without undue time penalty.
Scanner: Biograph mCT Flow™**
Scan dose: 8 mCi 18F FDG
CT: 100kV 53 eff mAs
PET: FlowMotion variable speed acquisition
*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.
Full prescribing information for Fludeoxyglucose F 18 Injection
Fludeoxyglucose F 18 injection is manufactured by Siemens' PETNET Solutions, 810 Innovation Drive, Knoxville, TN 39732
** Biograph mCT Flow is not commercially available in all countries. Due to regulatory reasons its future availability cannot be guaranteed. Please contact your local Siemens organization for further details.
The statements by Siemens customers described herein are based on results that were achieved in the customer’s unique setting. Since there is no “typical” hospital and many variable exist (e.g., hospital size, case mix, level of IT adoption) there can be no guarantee that other customers will achieve the same results.