ORIGINAL ARTICLE F-18 FDG PET/CT Characterization of Talc Pleurodesis-Induced Pleural Changes Over Time A Retrospective Study Nghi C. Nguyen, MD, PhD,* Isaac Tran, CNMT,* Christopher N. Hueser, DO,† Dana Oliver, ASCP,‡ Hussein R. Farghaly, MD,* and Medhat M. Osman, MD, PhD* Purpose: The current study characterized pleural changes induced by talc pleurodesis (TP), based on serial positron emission tomography/computer- tomography (PET/CT) with F-18 fluorodeoxyglucose (FDG). Materials and Methods: A total of 8 cancer patients who had both TP and PET/CT and no evidence of active pleural involvement after TP were retrospectively evaluated. Maximum standard uptake values, maximum Hounsfield units (HU), and thickness were followed over time. Results: The 8 patients had 25 PET/CT scans performed in an average of 22 months after TP. An increased FDG uptake was associated with an increase in pleural thickness within 5 months after TP, and both parameters showed statistical significance as compared with findings before TP. After 5 months of TP, the standard uptake value appeared to persist or increase further, and the pleural thickening stabilized. The formation of calcification was a slow process and might lag behind the changes in FDG metabolism and pleural thickness. The HU did not change significantly once pleural calcification had been formed. Conclusions: Knowledge of aforementioned pleural changes may help differentiate TP induced pleural inflammation from pleural malignancy and to avoid false-positive interpretation of FDG PET/CT exams. Key Words: Talc pleurodesis, pleural changes, F-18 FDG PET/CT (Clin Nucl Med 2009;34: 886 – 890) T alc pleurodesis (TP) is a technique used in the treatment of patients with persistent pleural effusions or pneumothorax. In addition, TP is frequently used in managing malignant effusions and has a success rate of greater than 90%. 1–3 TP is performed by instillation of talc into the pleural cavity (chemical pleurodesis). The effectiveness of the TP derives from the pleuritis produced by chemical irritation, which results ultimately in pleural fibrosis. 4 Computed tomography (CT) and F-18 fluorodeoxyglucose positron emission tomography (F-18 FDG-PET) are imaging modalities that play a critical role in the detection and staging of cancers. 5 Dual PET/CT imaging fuses anatomic with functional images and can provide more accurate clinical data for tumor characterization. 6 PET with F-18 FDG might not be able to distinguish between malignant and benign inflammatory processes. 7 For example, TP may result in intense FDG uptake in thickened pleura, therefore, is a potential for false positive interpretation. 7,8 There have been only case reports in the literature about post-TP changes using fused PET/CT. 8,9 The purpose of the current retrospective study was to monitor and characterize the TP-induced pleural changes by a dual PET/CT scanner. MATERIALS AND METHODS Patients A review of PET/CT reports between June 2004 and March 2007 identified 10 patients with cancer and a history of TP who underwent PET/CT scans for staging and restaging at our institution. Their medical records including time of TP, cancer type, tumor staging, treatment modality, and pleural biopsies were retrospec- tively reviewed. Of the 10 patients, 2 patients (stage IV infiltrating ductal breast carcinoma, stage III malignant mesothelioma) were excluded from this study because they showed evidence of recurrent or persistent pleural malignancy by biopsy or clinical follow-up. The remaining 8 patients (male 4; female 4; median age 57) included in the current study did not show evidence of pleural malignancy based on imaging modalities including diagnostic CT and PET/CT scans as well as clinical follow-up for at least 6 months after their last PET/CT exams. The study was approved by the Human Research Committee of our institution. PET/CT Scanning The patients fasted at least 4 hours before the PET/CT examination and received an intravenous injection of about 5.18 MBq/kg (0.14 mCi/kg) of F-18 FDG, with a maximum of 444 MBq (12 mCi). Blood glucose concentration was 200 mg/dL immedi- ately before the tracer injection in all studied cases. Upon comple- tion of the 45 to 60 minitues of uptake phase, the PET/CT scans were acquired during normal breathing (18 scans on the Gemini from July 2004 to August 2006, 7 scans on the Gemini TF from September 2006 until September 2007, Philips Medical Systems, Cleveland, OH) and with an axial co-scan range of 193 cm enabling a head-to-toe imaging in 1 sweep. The CT scan of the PET/CT scanner consisted of a 16-slice (Gemini) or 64-slice (Gemini TF) multidetector helical CT and was performed before the PET scan. Parameters were as follows: 120 to 140 kv and 33–100 mAs, 0.5 second per CT rotation, pitch of 0.9 and 512  512 matrix. CT data were used for image fusion and the generation of the CT transmission map. No oral or intravenous contrast was used. PET data were acquired for 18 to 22 bed positions. PET scans were acquired at 1.5 to 3.0 minutes per bed position depending on the patient’s weight with a 50% overlap. Processing consisted of the 3D Row Action Maximum Likelihood Algorithm method. 10 Image Analysis The PET/CT images were evaluated on the Extended Bril- liance workstation (Philips Medical Systems, Philips Medical Sys- tems, Cleveland, OH). Two representative pleural lesions with the highest metabolic activity (locations 1 and 2) were determined by Received for publication January 13, 2009; revision accepted May 27, 2009. From the *Division of Nuclear Medicine, Department of Radiology, St. Louis University, St. Louis, MO; †Division of Hematology and Oncology, Depart- ment of Internal Medicine, St. Louis University, St. Louis, MO; and ‡Cancer Center, St. Louis University, St. Louis, MO. Reprints: Nghi C. Nguyen, MD, PhD, Division of Nuclear Medicine, Department of Radiology, School of Medicine, 3635 Vista Ave (at S. Grand), St. Louis, MO 63110. E-mail: nguyenn@.slu.edu. Copyright © 2009 by Lippincott Williams & Wilkins ISSN: 0363-9762/09/3412-0886 Clinical Nuclear Medicine • Volume 34, Number 12, December 2009 886 | www.nuclearmed.com