(90)Y Radioembolization: Multimodality Imaging Pattern Approach with Angiographic Correlation for Optimized Target Therapy Delivery.

Primary and metastatic liver cancers are responsible for considerable morbidity and mortality, and many patients are not curable at presentation. Therefore, new therapies such as radioembolization with yttrium 90 ((90)Y)-labeled microspheres are an alternative method to treat patients with unresectable primary or secondary liver tumors. Patient selection, treatment technique, and early recognition of potential complications are the keys for successful patient outcomes. The activity of administered (90)Y microspheres depends on multiple variables, including the tumor burden, the volume of the liver lobe to be treated, the type of (90)Y microspheres, and the hepatopulmonary shunt fraction. Preprocedural planning relies on the results of cross-sectional imaging to determine the extent of disease, tumoral and nontumoral liver volumes, patency of the portal vein, and the degree of extrahepatic disease. A multidisciplinary approach that combines expertise in cross-sectional imaging, nuclear medicine, and flow dynamics is critical to adequately target malignant tissue. Preprocedural multimodality imaging, particularly combined single photon emission computed tomography (SPECT) and computed tomography (CT) imaging (SPECT/CT), may be used to identify nontarget imaging patterns that, if recognized, can potentially be corrected with either branch vessel embolization or catheter repositioning. Postprocedural multimodality imaging is also useful to confirm the appropriate delivery of (90)Y microspheres, enabling early identification of potential complications and the adequacy of microsphere distribution, thereby optimizing planning for subsequent therapies.

Normal patterns of 18F-FDG appendiceal uptake in children.

BACKGROUND: Prior to interpreting PET/CT, it is crucial to understand the normal biodistribution of fluorodeoxyglucose (FDG). It is also important to realize that the normal biodistribution can vary between adults and children. Although many studies have defined normal patterns of pediatric FDG uptake in structures like the thymus, brown fat and bone marrow, patterns of normal pediatric bowel activity, specifically uptake within the appendix, have not been well described. Active lymphoid tissue has increased FDG uptake when compared with inactive tissue. Since children have more active lymphoid tissue than adults, and because the appendix contains aggregated lymphoid tissue, we postulated that appendiceal uptake may be increased in pediatric patients. OBJECTIVE: To define the normal level of appendiceal FDG activity in children by evaluating a series of consecutive FDG PET/CT scans performed for other indications. MATERIALS AND METHODS: After obtaining IRB approval, we retrospectively reviewed 128 consecutive whole-body pediatric FDG PET/CT examinations obtained for a variety of clinical indications. CT scans on which the appendix could not be visualized were excluded from analysis. CT scans on which the appendix could be visualized were evaluated for underlying appendiceal pathology. Studies with appendiceal or periappendiceal pathology by CT criteria were excluded. A region of interest (ROI) was placed over a portion of each appendix and appendiceal maximum standardized uptake value (SUVmax) was calculated. If an adjacent loop of bowel activity interfered with accurate measurements of the appendix SUVmax, the scan was excluded from the analysis. A chart review was performed on patients with elevated appendiceal SUVmax values to ensure that the patients did not have clinical symptomatology suggestive of acute appendicitis. When the appendix or a portion of the appendix could be visualized and accurately measured, the SUVmax was determined. SUVmax of the appendix was compared to the SUVmax of normal liver and ratios were recorded. RESULTS: A total of 128 scans were reviewed, patient ages 1 month to 21 years (mean age: 11.6 years). Thirty-one scans were excluded because of inability to visualize the appendix on CT. No scans were excluded for appendiceal/periappendiceal pathology on CT or chart review. No scans had to be excluded for inability to obtain an accurate SUVmax measurement because measurements were calculated on portions of the appendix separate from adjacent bowel using small ROIs. Maximum appendiceal SUVs ranged from 0.5 to 9.4 (mean: 2.2) with an appendix-to-liver background ratio ranging from 0.3 to 3.1 (mean: 1.1). CONCLUSION: FDG uptake in the appendix is typically similar to that of background activity. However, slight variations in appendiceal FDG uptake do occur, which should not be misinterpreted as pathological.