Hepatic 18F-FDG Uptake Measurements on PET/MR: Impact of Volume of Interest Location on Repeatability.

Background: To investigate same day 18F-FDG (Fluorodeoxyglucose) PET (Positron Emission Tomography)/MR (Magnetic Resonance) test-retest repeatability of Standardized Uptake Value measurements normalized for body weight (SUV) and lean body mass (SUL) in different locations in the liver. Methods: This prospective study was IRB approved with written informed consent obtained. 35 patients (20 women and 15 men, 61 ± 11.2 years) that performed a whole-body 18F-FDG PET/MR followed by liver-dedicated contrast-enhanced 18F-FDG PET/MR were included. SUV/L max, mean, and peak were measured inferior to, superior to, and at the right portal vein and in the left lobe of the liver. The coefficient of variation (CV) and intraclass correlation coefficient (ICC) were calculated and Bland-Altman plots were obtained. Results: The variability for SUV/L's measurements was lowest inferior to the portal vein (<9.2%) followed by measurements performed at the level of the portal vein (<14.6%). Conclusion: The area inferior to the portal vein is the most reliable location for hepatic 18F-FDG uptake measurements on PET/MR.

18F-FDG-PET/CT Pulmonary Infiltrates in Non-Hodgkin Lymphoma Patients Treated with Combined Immunochemotherapy: Incidence and Clinical Characteristics.

BACKGROUND: Pulmonary infiltrates (PIs) detected in patients with non-Hodgkin lymphoma (NHL) may present a diagnostic challenge due to their wide differential diagnosis, including infection, pulmonary lymphoma and immunochemotherapy-associated pulmonary toxicity. OBJECTIVES: To characterize therapy-associated PIs by positron emission tomography/computed tomography (PET/CT) imaging. METHODS: We conducted a historical analysis of fluorodeoxyglucose-PET/CT (18F-FDG-PET/CT) PIs in NHL patients treated with combined immunochemotherapy including rituximab. Incidence of PIs, radiological features, patients' characteristics, underlying NHL type, rituximab/chemotherapy dosing schedules, and symptoms were recorded. Therapy-associated PIs were defined as new or worsening PIs appearing after treatment onset, without evidence of active pulmonary lymphoma or infection. RESULTS: Among 80 patients who met the pre-specified criteria, therapy-associated PIs were identified in 17 (21%), 6 of whom had accompanying symptoms. Increased FDG uptake was observed in nine, and PI resolution in six. The incidence of PIs was higher in females and in patients with aggressive lymphoma, at advanced stages, and in those who had received treatment consisting of a combination of rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisolone every 14 days (R-CHOP-14). CONCLUSIONS: This characterization of therapy-associated PIs may support the clinician managing NHL patients. Further prospective studies are needed to establish the role of each therapeutic component and the natural history of this phenomenon.

FDG PET/CT early dynamic blood flow and late standardized uptake value determination in hepatocellular carcinoma.

PURPOSE: To prospectively determine whether fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) early dynamic blood flow estimates could be used to discriminate hepatocellular carcinoma (HCC) from background liver and to characterize HCC in patients with and those without angioinvasion; and to evaluate the association between blood flow measures at FDG PET/CT with metabolism in HCCs. MATERIALS AND METHODS: Institutional review board approval and written informed consent were obtained for this prospective study. Twenty-one consecutive patients (mean age, 65 years) with 30 established HCCs (mean size, 5.5 cm; seven lesions in five patients with angioinvasion) underwent a blood flow study with an FDG dynamic scan divided into 18 sequences of 5 seconds each and a standard PET/CT scan. On the dynamic study, three independent operators obtained volumes of interest (VOIs) for which three blood flow estimates were calculated (hepatic perfusion index [HPI], time to peak [TTP], and peak intensity [PI]). On the late study, a VOI was placed on the fused scan for each HCC, and maximum standardized uptake value (SUV(max)) was obtained. By using a mixed-effects model analysis, comparison of blood flow estimates between HCC with and that without angioinvasion and background liver was performed. The association between blood flow estimates and SUV(max) was also assessed. RESULTS: HPI and TTP showed better performance than did SUV(max) for discriminating HCC and background liver (areas under receiver operating characteristic curve: 0.96, 0.95, and 0.83, respectively; P < .05). HPI was higher in HCC in patients with angioinvasion (0.91 ± 0.15 [standard deviation]) than in those without angioinvasion (0.80 ± 0.18; P = .03). There was no difference in SUV(max) between HCC in patients with and those without angioinvasion (7.8 ± 2.9 vs 6.3 ± 3.4; P = .85). No clear association was found between HPI, PI, or TTP and SUV(max) (P = .49, .77, and .91, respectively). CONCLUSION: Early dynamic blood flow FDG PET/CT may be used to help discriminate and characterize HCC tumors.

Accessory spleen-like masses in oncology patients: Are they always benign?

AIM: To assess retrospectively the significance of accessory spleen-like mass (ASLM) in oncology patients undergoing positron emission tomography/computed tomography (PET/CT). METHODS: The results of PET/CT of 913 patients (278 lymphoma; 635 solid tumors) were reviewed. The number, size, location and attenuation of all ASLMs, and spleen attenuation, were recorded. ASLM fluorodeoxyglucose uptake was graded as normal (less than or equal to that in the liver) or representative of malignancy (more than in the liver). Follow-up PET/CT in patients with ASLM was reviewed when available. ASLM size and attenuation for spleen and ASLM were compared by unpaired Student's t test. The χ(2) and Fisher's exact tests were used to compare ASLM frequency and uptake for lymphomatous and solid tumors, respectively. RESULTS: ASLM frequency was 14.8%, with 152 ASLMs found in 135 patients. Mean attenuation was lower in ASLM compared with spleen by enhanced and non-enhanced CT (80.7 ± 20.4 HU vs 92.0 ± 14.4 HU, P < 0.0011 and 42.3 ± 9.0 HU vs 51.5 ± 6.3 HU, P < 0.0001, respectively). ASLM incidence was higher in lymphoma patients (56/278, 20.1%) than in those with solid tumors (56/278, 20.1% vs 79/635, 12.4%, P = 0.0036). Pathological uptake was found in four (7.1%) lymphoma patients but not in any patients with a solid tumor (P = 0.028) and it upstaged one patient with lymphoma. Follow-up PET/CT within 3-16 mo was available in 54% of patients with ASLM. Lesion regression was noted in all four pathological ASLMs on follow-up PET/CT after chemotherapy. CONCLUSION: In patients with lymphoma, ASLM can represent malignancy, and thus further characterization with PET/CT might be warranted. Patients with neoplasia other than ASLM can be confidently diagnosed with accessory spleen.

PET/CT enterography in Crohn disease: correlation of disease activity on CT enterography with 18F-FDG uptake.

UNLABELLED: We combined (18)F-FDG PET and CT enterography in a single examination and compared the level of (18)F-FDG uptake measured by maximal standardized uptake value (SUVmax) with the CT enterography patterns of disease activity found in patients with Crohn disease (CD). METHODS: Twenty-eight patients (mean age, 37.5 y; 11 male and 17 female) suspected of having active CD underwent PET/CT enterography. Abnormal bowel segments recognized on CT enterography were graded qualitatively for the presence of perienteric fat infiltration, the comb sign, and intramural attenuation and by quantitative measurements of mural enhancement (Hounsfield units) and thickness (mm). Also, for each patient, normal segments of the ileum and colon were noted, and CT enterography measurements of thickness and enhancement were obtained. For segments detected on CT enterography, a volume of interest was placed on the fused (18)F-FDG PET scan, and the SUVmax was obtained. RESULTS: Of the 28 patients with suspected active CD, 22 had 85 abnormal segments and 6 had no abnormal segments. SUVmax was significantly higher in the abnormal segments than in the normal segments (5.0 +/- 2.5 [95% confidence interval, 4.5-5.5] and 2.1 +/- 0.69 [95% confidence interval, 1.9-2.2], respectively; P < 0.0001). A good correlation was found between SUVmax with CT enterography measurements of mural thickness and enhancement (P < 0.00001). There was a significant difference in SUVmax between the 3 levels of disease activity found by intramural attenuation, perienteric fat infiltration, and the comb sign on CT enterography. SUVmax was significantly higher when there were intense CT enterography findings of active disease (P < 0.001). CONCLUSION: SUVmax assessment may allow an objective, reliable indication of the grade and severity of inflammation activity in abnormal segments of the bowel detected by CT enterography.

The metabolic spectrum of venous thrombotic disorders found on PET/CT.

OBJECTIVE: Thrombotic disorders detected on PET/CT are usually incidental findings and may change the treatment strategy and patient's disease prognosis. The purpose of this article is to present the spectrum of venous thrombotic disorders found on PET/CT. CONCLUSION: The division of thrombotic disorders into metabolically nonactive and active thrombus may be helpful for differential diagnosis of underlying diseases causing thrombus formation. IV contrast media administration during PET/CT makes it possible to visualize the thrombus itself and helps to distinguish between benign and malignant metabolically active thrombus.

Spectrum of focal benign musculoskeletal 18F-FDG uptake at PET/CT of the shoulder and pelvis.

OBJECTIVE: The purpose of this article is to illustrate the spectrum of common benign intraarticular and extraarticular disorders associated with focal (18)F-FDG uptake in the shoulder and pelvic areas in oncology patients referred for PET/CT. CONCLUSION: A wide spectrum of benign musculoskeletal disorders associated with focal FDG uptake may be detected in cancer patients. This incidental uptake usually does not seem to be a clinically significant finding, but it can affect quality of life.