Utility of 18F-FDG uptake in various regions of Waldeyer's ring to differentiate benign from malignant lesions in the midline roof of the nasopharynx.

PURPOSE: Lymphoid hyperplasia is not uncommon in the midline roof of the nasopharynx. Most nasopharyngeal carcinoma patients present with primary tumors in the midline of the nasopharynx. The aim of this study was to evaluate the efficacy of 2-[fluorine-18] fluoro-2-deoxy-D-glucose ((18)F-FDG) PET/computed tomography (CT) to differentiate between benign and malignant lesions in the midline roof of the nasopharynx. MATERIALS AND METHODS: The data from the (18)F-FDG PET/CT images of 4846 participants were analyzed. Visual uptake, the lesions' standard uptake values (SUVs), and any abnormalities on the PET/CT images were evaluated. RESULTS: Sixty-six individuals with benign lesions and 25 with nasopharyngeal carcinoma were included in the analysis. The participants with benign and malignant lesions displayed increased (18)F-FDG uptake (SUV; mean±SD) in the midline roof of the nasopharynx (4.16±1.92 and 6.65±2.81, respectively), with SUVs significantly differing between the two types of lesions (P<0.001). An associated increased (18)F-FDG uptake in Waldeyer's ring and the salivary glands occurred in benign but not in malignant lesions. The ratio of uptake in the midline roof of the nasopharynx and the palatine tonsil in the benign lesions (0.92±0.42) was significantly lower than that in the malignant lesions (1.76±0.93) (P<0.001). CONCLUSION: The analysis of the intensity and patterns of (18)F-FDG uptake in various regions of Waldeyer's ring provides a feasible modality for the differentiation between benign lesions and malignant nasopharyngeal midline roof lesions.

The significance of alteration 2-[fluorine-18]fluoro-2-deoxy-(D)-glucose uptake in the liver and skeletal muscles of patients with hyperthyroidism.

RATIONALE AND OBJECTIVES: Hyperthyroidism leads to an enhanced demand for glucose. The hypothesis of the study is that 2-[fluorine-18]fluoro-2-deoxy-d-glucose (FDG) positron emission tomography (PET) can demonstrate the alteration of systemic glucose metabolism in hyperthyroidism patients by measuring the FDG standard uptake value (SUV) in liver and skeletal muscle. MATERIALS AND METHODS: Forty-eight active hyperthyroidism patients and 30 control participants were recruited for the study. The intensity of FDG uptake in the liver and thigh muscles was graded subjectively, comprising three groups: group I, higher FDG uptake in the liver; group II, equal FDG uptake in the liver and muscles; and group III, higher FDG uptake in the muscles. Ten subjects with FDG PET scans at hyperthyroid and euthyroid status were analyzed. Serum levels of thyroxine (T4) and triiodothyronine (T3) correlated to the SUVs of the liver and muscles. RESULTS: Forty-one patients (41/48, 85.4%) showed symmetrically increased FDG uptake in the muscles (22 in group I, 9 in group II, and 17 in group III). Group I patients were significantly older than group II (P = .02) and group III (P = .001) patients. The correlation coefficient between the serum T3, T4, and SUV levels in the muscles was significant (r = 0.47-0.77, P < .01), particularly in liver and muscle FDG uptake between hyperthyroid and euthyroid states. In the 30 control subjects, there was normal physiological FDG uptake in the liver and muscles. CONCLUSION: In PET scans showing a pattern of decreased liver and increased skeletal muscle FDG uptake in hyperthyroidism patients, this change of FDG distribution is correspondence to the severity of hyperthyroidism status.

The frequency and spectrum of thymus 2-[fluorine-18] fluoro-2-deoxy-D-glucose uptake patterns in hyperthyroidism patients.

RATIONALE AND OBJECTIVES: Thymic hyperplasia is associated with hyperthyroidism. Increased thymus 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) uptake in hyperthyroidism patients has been reported. The aim of this study was to analyze the FDG positron emission tomography (PET) thymus uptake spectrum in patients with active hyperthyroidism with correlation with serum hormones. MATERIALS AND METHODS: The prospective study included FDG PET scans from 65 hyperthyroidism patients and 30 subjects with euthyroid status as control group. The intensity of FDG uptake in thyroid and thymus regions was graded subjectively on a five-point scale and semi-quantitatively by measuring standard uptake value (SUV). Correlation coefficient between thymus SUV and serum thyroxine, triiodothyronine, thyrotropin, thyroid peroxidase antibodies (TPO Ab), thyrotropin receptor autoantibody (TR Ab), and thymulin were analyzed. RESULTS: Among 65 hyperthyroidism patients, 30 (46.2%) and 39 (60%) patients showed thyroid and thymus FDG uptake, respectively. The frequency of thymus uptake FDG was high in patients younger than age 40 (28/31, 90.3%). The patterns of the thymic FDG uptake include inverted V or triangular, separated triangular, united nontriangular, unilateral right or left extension, and focal midline. Focal midline FDG uptake was the most common pattern (15/39, 38.5%). None of the control group showed thymus FDG uptake. The correlation coefficient between the FDG uptake SUV levels in thymus and serum hormones, thyrotropin, TPO Ab, TR Ab, and thymulin levels were all low (P > .05). CONCLUSIONS: In FDG PET scan, thymus activity was common in hyperthyroidism patients; this should not be misdiagnosed as a malignancy in patients exhibiting weight loss.

Use of laxative-augmented contrast medium in the evaluation of colorectal foci at FDG PET.

PURPOSE: To compare the diagnostic accuracy of fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET) in the detection of colon lesions with that of delayed PET/computed tomography (CT) performed after the administration of a laxative-augmented contrast medium. MATERIALS AND METHODS: All patients gave written informed consent according to the guidelines issued by the institutional review board. In a prospective study performed from November 2005 to December 2006, images obtained in 847 patients were reviewed by two physicians in consensus. Colorectal FDG uptake on initial PET images that exceeded background FDG accumulation was graded as minimal, equivocal, or positive. When the initial PET scan revealed a colorectal region of increased uptake, either oral or anal laxative-augmented contrast medium was administered on the basis of the site of colorectal FDG focus and delayed PET/CT was performed. Initial PET findings were reevaluated and revised when necessary. Comparison was performed on a per-patient basis. Findings at histopathologic analysis and clinical follow-up served as the reference standard. The accuracy of PET was compared with that of PET/CT by using the McNemar test. RESULTS: Colorectal FDG foci were seen on initial images in 137 patients. Uptake on the initial images was reported as minimal in 14 patients, equivocal in 68, and positive in 55. With use of a laxative-augmented contrast medium and delayed PET/CT, the proportions of equivocal and positive results decreased by 84% (57 of 68 patients) and 58% (18 of 31 patients), respectively. The accuracy of delayed PET/CT in the depiction of colorectal cancer was greater than that of initial PET (93.4% [128 of 137 patients] vs 71.5% [98 of 137 patients], respectively; P < .01). CONCLUSION: Delayed PET/CT with laxative-augmented contrast medium is more accurate than initial PET alone in the detection of colorectal cancer. This approach has promise as a tool for guiding decisions about how to treat patients with colorectal FDG foci. SUPPLEMENTAL MATERIAL: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.11101193/-/DC1.

Utility of 18F-FDG PET/CT uptake patterns in Waldeyer's ring for differentiating benign from malignant lesions in lateral pharyngeal recess of nasopharynx.

UNLABELLED: Focally increased (18)F-FDG uptake in the lateral pharyngeal recess (LPR) of the nasopharynx due to a benign or malignant lesion is not an uncommon finding on PET images. The aim of this study was to evaluate whether, on PET/CT images, (18)F-FDG uptake occurs with characteristic patterns and intensities in various regions of Waldeyer's ring that can improve our ability to differentiate benign from malignant lesions. METHODS: Data generated from the (18)F-FDG PET/CT images of 1,628 subjects in our cancer-screening program were analyzed. Increased uptake in the LPR was observed in 80 subjects (4.9%) presenting with benign lesions, including 53 subjects without and 27 subjects with symptoms of upper airway discomfort. In addition, 30 healthy controls and 21 patients with newly diagnosed nasopharyngeal carcinoma were recruited for this study. Visual uptake, measurements of the lesions' standardized uptake value (SUV), and any abnormalities on PET/CT were evaluated. The receiver-operating-characteristic curve and area under the curve were applied to evaluate the discriminating power. RESULTS: Increased (18)F-FDG uptake (SUV, mean +/- SD) was found in the LPR, with a statistically significant (P < 0.001) difference between benign lesions (3.0 +/- 1.16) and malignant lesions (7.03 +/- 3.83). However, associated increased uptake exclusively in the palatine tonsil, lingual tonsil, and submandibular gland was found in both asymptomatic and symptomatic subjects. The ratio of LPR uptake to palatine tonsil uptake (N/P ratio) in benign lesions (0.81 +/- 0.37) was significantly (P < 0.001) lower than that in malignant lesions (2.30 +/- 1.62). Higher incidences of asymmetric (18)F-FDG LPR uptake, cervical lymph node uptake, and asymmetric wall thickening of the LPR on CT were observed in patients with nasopharyngeal carcinoma. When an SUV of less than 3.9 and an N/P ratio of less than 1.5 were used as cutoff points in subjects showing the combination of symmetric uptake in the LPR and normal or symmetric wall thickening, and detectable lymph node uptake, the area under the curve for benign lesions on PET/CT was 0.932 +/- 0.042 (95% confidence interval, 0.86-0.98), with a sensitivity of 90.4% and a specificity of 93.8%. CONCLUSION: The intensity and patterns of (18)F-FDG uptake in various regions of Waldeyer's ring along with CT scan findings provide a feasible modality to differentiate benign from malignant nasopharyngeal lesions.

The significance of FDG uptake in bilateral thyroid glands.

AIM: To evaluate the significance of bilateral fluorodeoxyglucose (FDG) uptake in the thyroid glands. METHODS: Bilateral thyroid FDG uptake, defined as visualization of thyroid glands, was found in 66 (3.4%) of 1925 subjects who underwent our FDG PET cancer-screening program. Additionally, 16 of the 41 patients with Graves' disease and hyperthyroidism (GD(H)) and six of the 20 subjects with Graves' disease and euthyroidism (GD(E)), who had FDG uptake in thyroid glands, were enrolled in this study. RESULTS: Among the 66 subjects, 22 were normal variant, 39 subjects had chronic thyroiditis (35 subjects presented with diffuse goitre and four with multinodular goitre), and five subjects had multinodular goitre (MNG) without chronic thyroiditis. Fourteen of 22 (63.6%) of the subjects with the normal variant had a visual uptake intensity less than that of the liver, while 30 of 39 (76.9%) of the subjects with chronic thyroiditis and 14 of 22 (63.6%) of the subjects with Graves' disease had visual uptake intensity greater than or equal to liver uptake. Two of the five subjects with MNG with focally intense uptake were proven to have thyroid carcinoma. Bilateral loser uptake in thyroids associated with thymus and symmetrical skeletal muscle uptake were found in GD(H). The standard uptake value (SUV) (mean+/-SD) in subjects with chronic thyroiditis (2.76+/-1.24) were higher, while those with GD(H) (1.59+/-0.36) were lower than that of the normal variant (1.99+/-0.63). Subjects with hypothyroidism (3.04+/-1.39) had higher SUV levels than those subjects with euthyroidism (2.44+/-1.11). In addition, patients with GD(H) had lower levels than those with GD(E) (2.0+/-0.38). CONCLUSION: (1) Bilateral thyroidal uptake of FDG can be found in normal variants and subjects with various thyroid disorders, showing varieties of uptake patterns. (2) Diffuse intense uptake and higher SUV levels are a clue to a diagnosis of chronic thyroiditis, especially for those with hypothyroidism. (3) Focally intense uptake suggests the possibility of a thyroid carcinoma. (4) Sparse uptake associated with the thymus and symmetrical skeletal muscle uptake and lower SUV level raise the possibility of Graves' disease with hyperthyroidism.