Nghi Nguyen

Is there a common SUV threshold in oncological FDG PET/CT, at least for some common indications? A retrospective study

Abstract Purpose. We retrospectively compared the maximum standard uptake value (SUVmax) of FDG PET in four different sites to evaluate whether a common diagnostic SUVmax threshold may exist in these tumor locations. We further postulate that the SUVmax thresholds are higher in thoracic lesions than in extrathoracic lesions. Material and methods. N = 143 patients in four subgroups underwent a FDG PET/CT: a) 42 patients for solitary pulmonary nodules (SPNs) characterization with b) respective mediastinal lymph nodes (LNs), c) 65 patients for LN staging of head and neck cancer, and d) 36 cancer patients diagnosed with adrenal lesions. Receiver operating characteristics of SUVmax values were evaluated. Results. The SUVmax were statistically significantly greater in malignant than in benign lesions. For SPNs and mediastinal LNs, a SUVmax > 3.6 each resulted in a sensitivity of 81% and 87%, and a specificity of 94% and 89%. For cervical LNs and adrenal glands, a SUVmax > 2.2 each showed a sensitivity of 98% and 100%, and a specificity of 83% and 93%. Conclusion. A common SUVmax threshold did not exist in the four studied subgroups. The variable FDG uptake in SPNs and mediastinal LNs are associated with the high prevalence of inflammation/infection within the chest. Similar SUVmax thresholds however may exist for extrathoracic regions where the prevalence of inflammation/infection is low.

F-18 FDG PET/CT characterization of talc pleurodesis-induced pleural changes over time: a retrospective study.

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.

Spinal cord metastases from lung cancer: detection with F-18 FDG PET/CT.

Preoperative F-18 FDG PET/CT study in this 57-year-old woman showed an FDG avid lesion in the left upper lung without evidence of lymphadenopathy or distant metastasis. She underwent a left upper lobectomy in June 2005 revealing moderately poorly differentiated adenocarcinoma (pT3N0M0) and subsequent chemotherapy completed December 2005. Nine months later, a left parietal lobe metastatic lesion was surgically resected. A true whole body FDG PET/CT study in November 2006 for restaging demonstrated new FDG avid spinal cord foci, which were highly suspicious for spinal cord metastases; these lesions were confirmed by MRI. Clinically, the patient recently developed back pain without evidence of neurologic deficits.

18F-FDG PET/CT of Patients With Cancer: Comparison of Whole-Body and Limited Whole-Body Technique

OBJECTIVE Use of the routine field of view for whole-body (18)F-FDG PET/CT can lead to underestimation of the true extent of the disease because metastasis outside the typical base of skull to upper thigh field of view can be missed. The purpose of this study was to evaluate the incremental added value of true whole-body as opposed to this limited whole-body PET/CT of cancer patients. MATERIALS AND METHODS True whole-body FDG PET/CT, from the top of the skull to the bottom of the feet, was performed on 500 consecutively registered patients. A log was kept of cases of suspected malignancy outside the typical limited whole-body field of view. Suspected lesions in the brain, skull, and extremities were verified by correlation with surgical pathologic or clinical follow-up findings. RESULTS Fifty-nine of 500 patients had PET/CT findings suggestive of malignancy outside the limited whole-body field of view. Thirty-one of those patients had known or suspected malignancy outside the limited whole-body field of view at the time of the true whole-body study. Among the other 28 patients, follow-up data were not available for two, six had false-positive findings, and new cancerous involvement was confirmed in 20. Detection of malignancy outside the limited whole-body field of view resulted in a change in management in 65% and in staging in 55% of the 20 cases. CONCLUSION Our study showed that 20 of 500 (4.0%) of patients had previously unsuspected malignancy outside the typical limited whole-body field of view. Detection of such malignancy resulted in a change in management in 13 of 500 cases (2.6%). We propose that adopting a true whole-body field of view in the imaging of cancer patients may lead to more accurate staging and restaging than achieved with the routinely used limited whole-body field of view.

Extrapulmonary small cell sarcinoma: involvement of the brain without evidence of extracranial malignancy by serial PET/CT scans

BackgroundExtrapulmonary small cell carcinoma (EPSCC) involving the brain is a rare manifestation of an uncommon tumor type.Case presentationWe report a 59 year-old Caucasian female diagnosed with an EPSCC involving the left parietal lobe without detectable extracranial primary tumor followed by serial positron emission tomography/computed tomography (PET/CT) imaging. Histopathological examination at both initial presentation and recurrence revealed small cell carcinoma. Serial PET/CT scans of the entire body failed to reveal any extracranial [18F]2-fluoro-2-deoxy-D-glucose (FDG) avid lesions at either diagnosis or follow-up.ConclusionChemotherapy may show a transient response in the treatment of EPSCC. Further studies are needed to help identify optimal treatment strategies. Combination PET/CT technology may be a useful tool to monitor EPSCC and assess for an occult primary malignancy.

Incidental diagnosis of thrombus within an aneurysm on 18F-FDG PET/CT: frequency in 926 patients.

Our objective was to evaluate the incidence of aneurysm and the frequency of thrombus within an aneurysm on unenhanced 18F-FDG PET/CT studies. Methods: We reviewed 1,540 PET/CT scans from 926 patients. A log recorded whether each case of aneurysm had a suspected thrombus. The maximal standardized uptake value of the patent vessel was compared with the thrombus. Findings were confirmed using all available follow-up data. Results: Aneurysm was found incidentally in 16 (1.7%) of the 926 patients, with 15 occurring in the abdominal aorta and 1 in the internal jugular vein. Seven of these 16 patients had shown suggestions of thrombus on unenhanced PET/CT, and in all 7, thrombi were confirmed on contrast-enhanced CT. Conclusion: In 1.7% of patients, aneurysm was found incidentally on PET/CT, and thrombus was present in 44% of these cases.

Whole-Body 18F-FDG PET/CT: The Need for a Standardized Field of View—A Referring-Physician Aid

PET/CT fusion of anatomic and functional imaging modalities is in evolution, with rapid clinical dissemination. The imaged field of view (FOV) selected for whole-body PET/CT protocols is not standardized and varies by institution. Misuse of the term whole body, as well as the pressure to increase the number of daily studies by reducing scanning time, contributes to the lack of standardization. The purpose of this study was to evaluate variations in the FOV and arm positioning selected for whole-body PET/CT protocols at private, as well as academic, PET centers. Methods: Two hundred consecutive whole-body 18F-FDG PET/CT studies were retrospectively reviewed for FOV: 50 studies from a private stationary site, 50 studies from 2 separate private mobile sites (25 consecutive studies from each), and 100 studies from a stationary university site: 50 before and 50 after implementation of a true whole-body protocol covering the top of the head through the bottom of the feet. Data were categorized into 5 different anatomic scan lengths: base of skull to upper thigh, base of skull to mid thigh, top of head to upper thigh, top of head to mid thigh, and true whole-body. Studies were further categorized into 2 patient arm positions: up and down. Results: The private stationary and mobile sites had only 2 categories of anatomic scan lengths identified: base of skull to mid thigh, and top of head to upper thigh. At the university site, before implementation of a true whole-body protocol, the 5 different anatomic scan lengths were identified; after implementation, only the true whole-body scan length was identified. Patients’ arms in the private stationary sites were down 100% of the time. At the private mobile sites, patients’ arms were up 72% of the time and down 28% of the time. At the university site, patients’ arms were up 54% of the time and down 46% of the time. The same site, after implementation of a true whole-body protocol, had patients’ arms up 58% of the time and down 42% of the time. Overall, patients’ arms were up 46% of the time and down 54% of the time. Conclusion: The continued use of the term whole body is misleading because frequently it may not include the brain, skull, or significant portions of the upper and lower extremities. PET/CT anatomic scan length varied not only from one site to the next but also within individual sites. The Centers for Medicare and Medicaid Services have different current procedural terminology codes distinguishing between base of skull to upper thigh and true whole-body covering the top of the skull to the bottom of the feet, thus underscoring the need to standardize the terminology used in describing PET/CT scan length.

Decreased Blood Flow with Increased Metabolic Activity: A Novel Sign of Pancreatic Tumor Aggressiveness

To the Editor: Nghi Nguyen, Khalid Taalab, Medhat Osman. We read with great interest the recent article by Komar et al. ([1][1]), in which the authors evaluated blood flow (BF) using oxygen-15–labeled water and standardized uptake values (SUV) using 18F-fluorodeoxyglucose positron emission

Peritoneal Mouse as Detected on 18F-FDG PET-CT

We present the case of a 77-year-old male with a history of prostate cancer. Follow up PET-CT and contrast-enhanced CT demonstrated a small peritoneal loose body or “mouse” in the pelvis. This is an uncommon, benign, asymptomatic finding which is usually incidentally discovered. The significance of being aware of this entity is to distinguish it from metastasis, especially in patients with known abdominal and pelvic malignancies.

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.