Razi Muzaffar

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.

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.

Does 18F-FDG Uptake by Respiratory Muscles on PET/CT Correlate with Chronic Obstructive Pulmonary Disease?

18F-FDG muscle uptake is evident in some benign physiologic processes as seen in the respiratory muscles of patients with chronic obstructive pulmonary disease (COPD) and labored breathing. The purpose of this study was to correlate the presence of COPD with the patterns of 18F-FDG uptake by muscles as demonstrated by PET/CT scans. Methods: 18F-FDG PET/CT scans and pulmonary function tests (PFTs) were performed for 63 consecutive patients with newly diagnosed or highly suspected lung cancer. Presurgical pulmonary function tests by way of spirometry examinations were performed as the standard of care. Patients were grouped into those with normal spirometry findings and those with mild to very severe COPD. The guidelines of the Global Initiative for Chronic Obstructive Lung Disease were used for staging COPD and obstructive impairment. A nuclear medicine physician and 2 residents who did not know the COPD status retrospectively reviewed PET/CT scans and kept a log for cases of increased 18F-FDG uptake in the respiratory muscles (diaphragm, intercostal muscles, and scalene muscles). The χ2 test and Cramer V were used to evaluate the correlation between increased 18F-FDG uptake by muscles and the presence of COPD. Results: Sixty-three patients underwent both 18F-FDG PET/CT and PFT within 1 mo of each another without interval therapy. Of the 63 patients, 26 (41%) had no spirometric obstruction and 37 (59%) had spirometric obstruction. Of these, 30 (81%) had a previously established diagnosis of COPD (1 mild, 26 moderate, 9 severe, and 1 very severe). Excessive 18F-FDG uptake was seen in at least 2 of the 3 muscles (diaphragm and intercostal muscles) in 27 (73%) of the 37 patients with COPD and obstructive ventilatory impairment. The severity of COPD and obstruction showed a significant correlation with the presence of abnormal 18F-FDG uptake by any of the 3 muscle types, particularly when 2 groups of muscles were involved (Cramer V = 0.60, χ2 P < 0.001). Conclusion: Our study revealed a strong correlation between increased 18F-FDG uptake by respiratory muscles and the presence of COPD.

Ophthalmologic abnormalities on FDG-PET/CT: a pictorial essay

Abstract Positron emission tomography (PET) using [18F]-2-deoxy-d-glucose (FDG) diagnoses, stages, and restages many cancers and is often better than anatomic imaging alone. However, abnormalities within the orbit present a challenge in evaluation, mainly due to the subtle findings on PET/computed tomography (CT). In addition, this region is typically at the edge of the field of view for the standard base of skull to upper thigh FDG-PET/CT scans. The aim of this pictorial essay is to illustrate several subtle and apparent abnormalities within the orbit that can have a profound impact on patient management and follow-up.

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.

The Incremental Added Value of Including the Head in 18F-FDG PET/CT Imaging for Cancer Patients

Purpose: To assess the value of extending the routinely used base-of-skull (BOS) to upper-thigh field of view (FOV) to include the head on 18F-FDG PET/CT in cancer patients. Methods: We retrospectively reviewed 1000 consecutive top-of-head to foot PET/CT studies. Abnormalities above BOS were categorized as unsuspected or known and were correlated with pathology, MRI/CT, and clinical follow-up. Results: Of the 1000 patients, 102 (10.2%) had potentially significant findings above BOS. Of these, 70/102 (69%) were known and 32/102 (31%) were unsuspected. Of the patients with unsuspected findings, follow-up data was unavailable in 7/32 (22%) and abnormalities were confirmed in 25/32 (78%). Of the 25 confirmed unsuspected findings, 4/25 (16%) were false positives and 21/25 (84%) were true positives. Of these, 13/21 (62%) were confirmed metastatic, and 8/21 (38%) were benign. Unsuspected finding of brain metastasis changed the management in 11/13 (85%) and staging in 4/13 (31%). Conclusion: Including the head in PET/CT FOV incidentally detected clinically significant findings in 2.1% (21/1000) of patients. The detection of previously unsuspected metastasis had significant impact on patient management and provided more accurate staging.

Brown adipose tissue detected by PET/CT imaging is associated with less central obesity

Purpose This retrospective review was performed to determine whether patients with brown adipose tissue (BAT) detected by fluorine-18-fluorodeoxyglucose (18F-FDG) PET/computed tomography (CT) imaging have less central obesity than BMI-matched control patients without detectable BAT. Patients and methods Thirty-seven adult oncology patients with 18F-FDG BAT uptake were retrospectively identified from PET/CT studies from 2011 to 2013. The control cohort consisted of 74 adult oncology patients without detectable 18F-FDG BAT uptake matched for BMI/sex/season. Tissue fat content was estimated by CT density (Hounsfield units) with a subsequent noise removal step. Total fat and abdominal fat were calculated. An automated separation algorithm was utilized to determine the visceral fat and subcutaneous fat at the L4/L5 level. In addition, liver density was obtained from CT images. CT imaging was interpreted blinded to clinical information. Results There was no difference in total fat for the BAT cohort (34±15 l) compared with the controls (34±16 l) (P=0.96). The BAT cohort had lower abdominal fat to total fat ratio compared with the controls (0.28±0.05 vs. 0.31±0.08, respectively; P=0.01). The BAT cohort had a lower visceral fat/(visceral fat+subcutaneous fat) ratio compared with the controls (0.30±0.10 vs. 0.34±0.12, respectively; P=0.03). Patients with BAT had higher liver density, suggesting less liver fat, compared with the controls (51.3±7.5 vs. 47.1±7.0 HU, P=0.003). Conclusion The findings suggest that active BAT detected by 18F-FDG PET/CT is associated with less central obesity and liver fat. The presence of foci of BAT may be protective against features of the metabolic syndrome.

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.

Active Shingles Infection as Detected on 18F-FDG PET/CT

We present the case of a 56-year-old male with a history of recurrent follicular lymphoma undergoing chemotherapy with multiple 18F-FDG PET-CT studies at an outside facility. He developed a painful erythematous, pruritic rash in the left back requiring a visit to the emergency room. He was diagnosed and treated for Varicella zoster infection. He then presented to our imaging center 2 months later for a follow up 18F-FDG PET/CT study. Imaging demonstrated a cutaneous band of increased metabolic activity in the upper back following a dermatomal distribution. This was confirmed to be in the same area as the treated Varicella zoster eruption. A subsequent follow up 18F-FDG PET-CT scan 4 months later to confirm tumor resolution demonstrated the abnormal band of uptake in the back had resolved. This case illustrates the significance of being aware of this entity and to distinguish it from metastasis, especially in patients with a known history of malignancy.

Detection of Metastatic Disease in Cardiophrenic Lymph Nodes: FDG PET/CT Versus Contrast-Enhanced CT and Implications for Staging and Treatment of Disease

Objective: To determine whether FDG PET/CT was more sensitive than CT in detecting metastatic disease in the cardiophrenic space and whether the presence of disease in this location would change the staging and clinical management. Materials and Methods: About 1200 PET/CT scans were retrospectively reviewed over 20 months for the presence of FDG-avid cardiophrenic lymph nodes. The SUVmax was used to quantify the metabolic activity in each of the lymph nodes. The radiographic data was used for correlation. A retrospective review of diagnostic CT reports performed within a 1-month period of time of the PET/CT in the same subset of patients determined whether cardiophrenic lymph nodes were mentioned. Results: About 9 (0.8%) of the 1200 studies were found to have FDG-avid cardiophrenic lymph nodes (four males and five females with a mean age of 55 years; range 7–69, median 59). The mean SUVmax was 2.4 (range 1.2–7.9; median 1.9). Only three of the patients were found to have suspicious lymph nodes on CT. The presence of cardiophrenic lymph nodes had the potential to change the staging and/or management in three of the patients. Conclusion: PET/CT is more accurate in the detection of pathologic cardiophrenic lymph nodes than CT, especially when they are subcentimeter in size. When present, staging and/or management was potentially affected in 33%. Therefore, these nodes should be included in the TNM staging classification.