Intense focal F-18 FDG uptake in vocal cord associated with injection of calcium hydroxylapatite microspheres.

Lower F-18 fluorodeoxyglucose (FDG) uptake on PET/CT is generally expected on the side of a paralyzed vocal cord (VC). The contrary pattern of increased uptake can raise concern for metastasis or a primary VC malignancy. We present a case showing paradoxical development of intense FDG uptake in the paralyzed VC, unrelated to malignancy. History revealed injection of calcium hydroxylapatite microspheres for treatment of VC paralysis. This new synthetic material can stimulate local fibroblast activity and macrophage accumulation, leading to increased FDG uptake. The case illustrates the importance of obtaining accurate history before interpreting intense FDG uptake in a paralyzed VC.

Low-dose 18F-FDG PET/CT enterography: improving on CT enterography assessment of patients with Crohn disease.

UNLABELLED: The purpose of this study was to evaluate the diagnostic efficacy of low-dose, combined (18)F-FDG PET/CT enterography (PET/CTE), compared with CT enterography (CTE) alone, in the assessment of patients with Crohn disease. METHODS: Thirteen patients with Crohn disease were prospectively enrolled in this pilot study and underwent abdominal-pelvic (18)F-FDG PET/CTE using neutral oral and intravenous contrast medium. The effective dose from PET/CTE was 17.7 mSv for the first 4 patients and 8.31 mSv for the last 9 patients. Six patients underwent surgical resection of the bowel, and 7 patients underwent colonoscopy with biopsies within 27 d (mean, 12 d) of PET/CTE. PET/CTE and CTE images were each visually assessed for Crohn disease involvement in 54 bowel segments with pathology correlation. Extraintestinal findings were recorded. A CTE severity score, maximum standardized uptake value (SUVmax), SUVmax ratio, simplified endoscopic score, and clinical parameters were correlated with pathology inflammation grade, on a per-patient basis and on a per-bowel-segment basis, using Spearman correlation. RESULTS: In 3 (23.1%) of 13 patients, (18)F-FDG uptake using PET/CTE revealed active inflammation in a bowel segment not evident using CTE (n = 2) or revealed an enterocolic fistula missed with CTE (n = 1). Visual interpretation of both PET/CTE and CTE images detected the presence of disease in all bowel segments with more than mild inflammation (sensitivity, 100%; specificity, 89.7%; positive predictive value, 78.9%; and negative predictive value, 100%). Correlation to inflammation grade per patient was the strongest for the SUVmax ratio (0.735, P = 0.004) and SUVmax (0.67, P = 0.013), as compared with the CTE score (0.62, P = 0.024). Correlation with inflammation per bowel segment was higher for the CTE score (0.79, P < 0.0001) than the SUVmax ratio (0.62, P < 0.0001) or SUVmax (0.48, P < 0.0001). SUVmax correlated strongly with serum C-reactive protein (0.82, P = 0.023), but CTE score did not. CONCLUSION: Low-dose (18)F-FDG PET/CTE, compared with CTE, may improve the detection and grading of active inflammation in patients with Crohn disease. PET/CTE also may reveal clinically significant findings, such as enterocolic fistula, not evident on PET or CTE alone.

Improved discrimination of benign and malignant lesions on FDG PET/CT, using comparative activity ratios to brain, basal ganglia, or cerebellum.

PURPOSE: This study demonstrates a simple background correction method, which improves the discrimination of benign from malignant lesions on FDG PET-CT imaging, using activity ratios compared with brain, basal ganglia, or cerebellum. METHODS: Standardized uptake values (SUVs) and comparative activity ratios (CARs) were determined for FDG uptake in 92 lesions (39 benign and 53 malignant) in 49 patients. Reference tissues included cerebral cortex, basal ganglia, cerebellum, lung, liver, and aortic blood pool. Discriminant power for each CAR was evaluated as malignant-to-benign ratio of mean uptake and ratio of intermediate-likelihood lesions to total number of lesions. RESULTS: Uncorrected SUV varied widely for malignant and benign lesions, with considerable overlap. Ratio of mean uptake for malignant lesions versus benign lesions was lowest for uncorrected SUVAVG and SUVAVG/liver (1.92), and highest for SUVMAX/cerebral cortex (3.52). Lesions could be separated into very high (> 90%), very low (< 10%), and intermediate (> or = 10% and < or = 90%) likelihood of malignancy. The ratio of intermediate-likelihood lesions to the total number of lesions was greatest for SUVAVG (0.42) and lowest for SUVMAX/basal ganglia (0.22). CONCLUSIONS: Ability to discriminate malignant from benign lesions was enhanced by using CARs derived from cerebral cortex, basal ganglia, or cerebellum. Using a 3-tiered diagnostic schema, most lesions could be assigned to categories of very high or very low likelihood of malignancy, with a significant reduction in indeterminant lesions, compared with uncorrected SUV.

Molecular targeting with radionuclides: state of the science.

Inherent in the application of advances in biomedical science to nuclear medicine is the concept of molecular targeting: the in vivo concentration of labeled tracer by a gene, its transcribed DNA, or its protein product. This mechanism of localization has been and is being exploited for both nuclear imaging and radioisotopic therapy. Agents, such as antisense molecules, aptamers, antibodies, and antibody fragments, can be aimed at molecular targets. Tumor and nerve cell receptors provide such targets. So do certain cellular physiologic activities, including metabolism, hypoxia, proliferation, apoptosis, angiogenesis, response to infection, and multiple drug resistance. In this article we review the principles of molecular targeting based on radioisotopic methods and provide examples from the literature. We discuss applications to imaging and therapy and point out the hurdles that must be overcome in bringing molecular targeting to clinical reality.