Enhanced Visualization of Lytic Sacral Metastases with Biograph mMR in a Patient with Breast Cancer

The combination of PET and MR identify early metastatic lesions.

Ciprian Catana, MD, PhD and Alexander R. Guimaraes, MD, PhD

Case study data provided by Athinoula A. Martinos Center for Biomedical Imaging, Radiology Department, Massachusetts General Hospital, Boston, Mass., USA

 |  2012-10-28

History
A 67-year-old woman presented with left side breast cancer for staging workup. A fludeoxyglucose F 18* (18F FDG) PET•MR study was performed on the Siemens Biograph mMR™. A 99mTc MDP bone scan performed prior to the Biograph mMR study was reported as normal.

 

*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.

 

Examination Protocol
Scanner: Biograph mCT
Scan mode: 20 mCi 18F FDG injection
Scan time:150 minutes post-injection delay (during which time the patient was scanned on a PET•MR system)
Scan area: 4-minute/bed PET acquisition with simultaneous MR acquisition-T2 fat sat

 

Diagnosis
Maximum intensity projection (MIP) of PET (Figure 1) data show a hypermetabolic primary breast tumor with bony metastases in the scapula, vertebrae, rib and pelvis. Coronal images of MRI, PET and fused PET•MR demonstrate focal hyperintensities in the T2 fat-suppressed MR image in the right scapula, ribs, lower thoracic and mid-lumbar vertebrae, as well as multiple lesions in the sacrum. PET shows corresponding areas of hypermetabolism typical of skeletal metastases.

However, a small focal hyperintensity in the lower part of the right ala of the sacrum seen on MRI did not show a corresponding increase in 18F FDG uptake (orange arrow on MR image in Figure 2). This was suggestive of bony metastases without a corresponding increase in glucose metabolism—possibly an early lesion involving only marrow changes or a lytic lesion. A CT study of the pelvis and lumbar vertebrae was performed subsequently. The CT coronal and axial slices at the level of the sacrum do not show specific changes corresponding to the area of hyperintensity in the lower right ala of the sacrum seen on the coronal MR image.

 

Comments
The combination of hyperintense marrow changes on fat suppressed T2- weighted MR images combined with glucose hyper-metabolism seen on 18F FDG PET has the potential of improving the detectability of early or lytic skeletal metastases. In early skeletal metastases, marrow changes may be detected on MR and with 18F FDG PET in some cases, but bony lysis or sclerosis may not be sufficient to be visible on stand-alone CT. In such situations, PET•CT or PET•MR acquisition can show improved sensitivity. In this patient, 18F FDG PET was positive for early skeletal metastases, while the 99mTc MDP bone scan was negative since the metastatic lesions may have been very early with predominantly marrow involvement. The hyperintense lesion in the lower right ala of the sacrum seen on MR, but without a corresponding increase in 18F FDG uptake along with the absence of significant lytic change on CT, may be related to a very early metastatic lesion within the marrow without sufficient tumor burden yet to be visualized on 18F FDG PET.
 

* 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 Risks
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.

Adverse Reactions
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

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 variables exist (e.g., hospital size, case mix, level of IT adoption) there can be no guarantee that other customers will achieve the same results.