Mustafa Altinyay

Impact of PET/CT in comparison with same day contrast enhanced CT in breast cancer management.

Purpose: To evaluate the impact of F-18 fluorodeoxyglucose (FDG) positron emission tomography with fused computerized tomography (PET/CT) in comparison with same day contrast enhanced CT (CE-CT) in breast cancer management. Method: Seventy studies in 49 breast cancer patients, 17 for initial and 53 for restaging disease were included. All patients underwent PET/CT for diagnostic purposes followed by CE-CT scans of selected body regions. PET/CT was started approximately 90 minutes following IV injection of 10–15 mCi of F-18 FDG on a GE Discovery PET/CT system. Oral contrast was given before F-18 FDG injection. The CE-CT was performed according to departmental protocol. Results: Out of a total of 257 lesions, 210 were concordant between PET/CT and CE-CT. There were 47 discordant lesions, which were verified by either biopsy (35) or follow-up (12 PET positive CE-CT negative lesions). PET/CT correctly identified 25 true positive (TP). CE-CT identified 2 TP lesions missed by PET/CT which were false negatives (FNs): one liver metastasis with necrosis, which was nonavid to FDG uptake because of necrosis and a second one missed on abdominal metastatic node, which did not change staging or treatment. PET/CT incorrectly identified 2 false positive lesions while CE-CT incorrectly identified 18 false positive. TP recurrence of the disease was found by PET/CT in 44% (15/34 pts), whereas 56% (19/34 pts) were free of disease. The CE-CT described progression of the disease in 1 true negative PET/CT study and no progression in 2 TP PET/CT studies. The sensitivity, specificity, accuracy, positive productive value, and negative productive value for PET/CT were 97.8%, 93.5%, 97.3%, 99.1%, 85% and for CE-CT were 87.6%, 42%, 82.1%, 91.6%, 31.7%. Conclusion: In this study, PET/CT played a more important role than CE-CT scans alone and provided an impact on the management of breast cancer patients.

FDG Dose Extravasations in PET/CT: Frequency and Impact on SUV Measurements

*Correspondence: Medhat M. Osman, Division of Nuclear Medicine, Department of Radiology, Saint Louis University, 3635 Vista Avenue, 2-DT, St. Louis, MO 63110, USA. e-mail: mosman@slu.edu Objectives: Positron emission tomography (PET)/CT with 18F-FDG has proven to be effective in detecting and assessing various types of cancers. However, due to cancer and/or its therapy, intravenous (IV) FDG injection may be problematic resulting in dose extravasations. In the most frequently used field of view (FOV), arms-up, and base of skull to upper thigh [limited whole body (LWB)], the injection site may not be routinely imaged. The purpose of this study was to evaluate the frequency of dose extravasations in FDG PET and the potential impact on standard uptake value (SUV) measurements. Methods:True whole body FDG PET/CT scans (including all extremities) of 400 patients were retrospectively reviewed. A log recorded cases of IV dose extravasations. When possible, SUVs were measured in two frequently used reference locations: mediastinum and liver. The SUVs were obtained in the same patients who had studies with and without FDG extravasations within an average of 3months without interval therapy. Results: Of the 400 scans, 42 (10.5%) had extravasations on the maximum intensity projections images. In scans with or without dose infiltration, FDG injection site was at or distal to the antecubital fossa in 97% of studies. Of those 42 cases, dose infiltration was within the LWB FOV in 29/42 (69%) and outside in the remaining 13/42 (31%). Of those 42 patients, 5 had repeat PET studies with no interval therapy. For those 5 patients, liver maximum SUV was 11.7% less in patients with infiltration than those without (2.22± 0.54 vs. 2.48± 0.6). Mediastinum SUVmax was 9.3% less in patients with infiltration than those without (1.72± 0.54 vs. 1.88± 0.49). Conclusion: We conclude dose extravasations were commonly encountered (10.5%) in PET/CT. However, it is underreported by at least 31% due to omitting injection site from the FOV. When present, extravasations may lead to underestimation of SUVmax. Therefore, it should not only be avoided but also reported in order to avoid false interpretations of the exam.

FDG PET/CT incidental diagnosis of a synchronous bladder cancer as a fourth malignancy in a patient with head and neck cancer.

A 74-year-old man with 40-year history of smoking and known history of chronic lymphocytic leukemia and cutaneous T-cell lymphoma underwent FDG PET/CT examination for a recent diagnosis of squamous cell carcinoma diagnosed from right frontal crown and left posterior ear skin biopsy. PET images revealed multiple FDG-avid lesions in the head and neck, highly suspicious for nodal metastases. Reviewing CT portion of PET/CT examination revealed a hyperattenuating density in the posterior bladder wall. This lesion was not noticed initially due to the intense physiologic bladder uptake. On lowering the intensity, this lesion showed intense FDG avidity on the PET portion of the examination. Cytoscopic biopsy revealed low-grade papillary urothelial cell carcinoma.

18F-FDG Hypermetabolism in Spinal Cord Schistosomiasis.

A 24-year-old Saudi man presented with progressive lower-back pain for 3 months followed by lower-limb weakness, numbness, and urinary retention. Cerebrospinal fluid examination revealed high-protein, elevated white blood cell count with lymphocyte predominance. MRI scan of the spine demonstrated heterogeneously enhancing longitudinal spinal cord lesion from T6 through T9. FDG-PET/CT demonstrated prominently hypermetabolic lesion in the spinal cord. He had laminectomy and spinal cord (intramedullary) biopsy. Pathology revealed Schistosoma mansoni ova.