The proposed physiology-based FDG PET/CT criteria in reducing false-positive results in advanced head and neck cancer after chemoradiotherapy.

BACKGROUND: Distinguishing benign complications after concurrent chemoradiotherapy (CCRT) from a local residual tumor in advanced head and neck squamous cell carcinoma (HNSCC) remains a clinical challenge. In this study, we propose criteria when considering physiological uptake patterns on F-18-fluorodeoxyglucose (FDG) PET/CT in patients with advanced HNSCC after CCRT. METHODS: We retrospectively reviewed FDG PET/CT images of 62 patients with advanced HNSCC, which were taken within 16 weeks following CCRT. Visual interpretation criteria were rated by three nuclear medicine physicians, independently, according to the uptake patterns of the primary site. The Cohen k coefficient was calculated to assess inter-reader agreement. The histology of the primary site within a 1 month of the PET/CT study was used as the gold standard for sensitivity, specificity, positive predictive value and negative predictive value. RESULTS: PET/CT was arranged at a median interval of 10.5 weeks (range 4-16 weeks) after CCRT, and the pathologic residual rate was 55.7% at the primary site. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of identifying residual disease were 91.1%, 50.0%, 68.9%, 82.3%, and 72.6%, respectively, by the previously established criteria, and 88.2%, 92.9%, 93.8%, 86.7%, and 90.3%, respectively, by our physiology-based criteria. Our visual rating criteria corrected 12 of 14 (84.6%) false-positive results from the established criteria, while two more false-negative cases identified with our criteria were proven to be small residual tumors. CONCLUSIONS: By incorporating physiological changes following CCRT, our visual rating criteria improved the accuracy of the currently used FDG PET/CT visual rating system, especially the number of false-positive cases with advanced HNSCC after CCRT.

The efficacy of 18F-FDG PET/CT and 67Ga SPECT/CT in diagnosing fever of unknown origin.

OBJECTIVE: Fever of unknown origin (FUO) is a diagnostic challenge. This study aimed to assess the efficacy of fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) and gallium-67 single-photon emission computed tomography/computed tomography (67Ga SPECT/CT) in diagnosing FUO. METHODS: A total of 68 patients with FUO underwent 18F-FDG PET/CT and 67Ga SPECT/CT from January 2013 through May 2016. Images were read independently. The imaging results were compared with the final diagnosis and categorized as helpful for diagnosis or non-contributory to diagnosis in the clinical setting. Associations between categorical variables were evaluated with the chi-square test or Fisher's exact test. RESULTS: Ten of the 68 patients were excluded. An infectious underlying disease was found in 23 patients. A malignant disorder was the cause of FUO in 10 patients. Non-infectious inflammatory disease was found in 11 patients. Adrenal insufficiency was the cause of FUO in two patients. The cause of FUO was not found for 12 patients. A high false-positive rate of 44% (7/16) was observed for 18F-FDG PET/CT, while a high false-negative rate of 55% (23/42) was observed for 67Ga SPECT/CT. 18F-FDG PET/CT studies depicted all 67Ga-avid lesions. The sensitivity (79% vs. 45%) and clinical contribution (72% vs. 55%) of 18F-FDG PET/CT in diagnosing FUO were significantly higher than those of 67Ga SPECT/CT (p<0.05). CONCLUSIONS: On the basis of this study, the diagnostic performance of 18F-FDG PET/CT is superior to 67Ga SPECT/CT in the work-up of patients with FUO. With its rapid results and superior sensitivity, 18F-FDG PET/CT may replace 67Ga SPECT/CT where this technique is available.

Revisiting morphine-augmented hepatobiliary imaging for diagnosing acute cholecystitis: the potential pitfall of high false positive rate.

PURPOSE: The aim of this retrospective study was to investigate the efficacy of morphine-augmented hepatobiliary imaging (MAHBI) for diagnosing acute cholecystitis (AC). METHODS: Sixty-eight patients (Male:Female = 36:32, age = 54 ± 17 years) referred for diagnosis of AC by 30-min post-morphine MAHBI after the standard 1-h imaging were recruited. Non-visualization of gallbladder on 30-min post-morphine images by visual analysis was considered positive. Final diagnosis of pathological examination for all patients was used as the gold standard. RESULTS: There was significant correlation of AC and MAHBI (p < 0.05). There were 45 true positive (TP), 19 false positive (FP), 4 true negative (TN), and no false negative (FN) cases using gallbladder visualization by 30-min post-morphine as the criteria, with a high false positive rate of 83%. The sensitivity, specificity, accuracy, positive and negative predictive values of MAHBI in detecting AC were 100%, 17%, 72%, 70%, and 100%, respectively. CONCLUSIONS: MAHBI is sensitive but may not specific for diagnosing AC due to the potential pitfall of high false positive rate. Correlation with other clinical findings is recommended for optimal patient management.

A comparative study of fused FDG PET/MRI, PET/CT, MRI, and CT imaging for assessing surrounding tissue invasion of advanced buccal squamous cell carcinoma.

PURPOSE: This study aimed to evaluate the diagnostic value of fused fluorodeoxyglucose positron emission tomography and magnetic resonance imaging (PET/MRI) compared with PET/computed tomography (CT), MRI, and CT in assessing surrounding tissue invasion of advanced buccal squamous cell carcinoma (BSCC). MATERIALS AND METHODS: PET/CT and MRI were performed in 17 consecutive patients with suspected masticator space invasion of BSCC from CT images. Attenuation-corrected PET and head and neck MRI datasets were registered. For pathologic correlation, 4 regions of interest were examined, including the maxilla, mandible, pterygoid, and masseter muscle. The tumor maximal diameter, measured by different imaging modalities, was correlated with pathology results. RESULTS: All PET/MRI fusions were verified as well matched using specific anatomic criteria. For pathology results, 1 patient had inflammation only, 1 had spindle cell cancer, and 15 had squamous cell cancer. Of 64 regions of interest, 20 (31.3%) harbored tumor invasion. The likelihood ratio was highest in fused PET/MRI (42.56) compared with PET/CT (25.02), MRI (22.94), and CT (8.6; all P < 0.05). The sensitivity and specificity of fused PET/MRI were also highest among the 4 modalities (90.0%/90.9%, 80.0%/84.1%, 80.0%/79.5%, and 55.0%/81.8%, respectively). The level of confidence was higher in fused PET/MRI or MRI than in PET/CT or CT (85.9%, 85.9%, 70.3%, 73.4%, respectively). The maximal lesion size was 3.0 to 6.0 cm in the pathology specimen. Regression analysis showed better agreement between fused PET/MRI and pathology results. CONCLUSIONS: Fused PET/MRI is more reliable for focal invasion assessment and tumor size delineation in advanced BSCC compared with PET/CT, MRI, and CT. PET/CT has the lowest confidence level, which may limit its use in the clinical setting.

Tc99m-sestamibi thigh SPECT/CT images for noninvasive assessment of skeletal muscle injury in carbon monoxide intoxication with clinical and pathological correlation.

PURPOSE: Muscle weakness has been repeatedly reported in patients with carbon monoxide (CO) intoxication. In animal models, CO intoxication has been linked with mitochondrial electron transport dysfunction. The objectives of the present study were to use Tc-99m sestamibi thigh single-photon emission computed tomography/computed tomography (SPECT/CT) to evaluate the mitochondrial status in patients with CO intoxication, correlate this with clinical parameters, and compare with age-matched controls. MATERIAL AND METHODS: A total of 25 patients with delayed sequelae after CO intoxication (range: 1-60 months) and 17 sex- and age-matched healthy volunteers underwent Tc-99m sestamibi thigh SPECT/CT. Cognitive evaluation and muscle power according to medical research council (MRC) grading were collected. Both visual scoring from planar images and automatic volumetric analysis were used to rate the Tc-99m sestamibi uptake level. RESULTS: The visual scores showed that 14 patients (56.0%) were scored as moderate-to-severe decrement. Volumetric analysis showed that a significant Tc99m-sestamibi uptake decrement was found in the CO intoxication group as compared with the controls, and 16 patients (64.0%) had uptakes below 1 standard deviation of the control group. In the CO group, the muscle power but not the cognitive evaluation correlated with Tc-99m sestamibi uptake in muscles. The decrement of muscle Tc99m-sestamibi uptake was related to mitochondria swelling, increased mitochondrial numbers, and type II muscle atrophy in 1 patient. CONCLUSIONS: In this study, we demonstrated that patients with CO intoxication sustained defective mitochondrial metabolism in skeletal muscles as revealed by a decrement in Tc-99m sestamibi uptake either by visual or semiquantification of thigh SPECT/CT. Tc-99m sestamibi scanning provided noninvasive measurement of mitochondrial injury in muscles after CO intoxication and the correlation with clinical parameters was good.

Appropriate time for post-therapeutic I-131 whole body scan.

Iodine metabolism and kinetics in thyroid carcinoma cells may be different from that in normal thyroid tissue. The optimal time for performing post-therapeutic scans to detect metastatic lesions is still controversial.We retrospectively analyzed the images of 239 patients who received I-131 therapy at our hospital from January 2006 to May 2008. The therapeutic dose ranged from 1.1 GBq (30 mCi) to 7.4 GBq (200 mCi) and the patients received 3 sequential whole body scans on the third to fourth day, fifth to sixth day, and 10th-11th day after I-131 administration. We scored the I-131 avid lesions by visual assessment into 3 grades: 2=clearly visible; 1=visible; and 0=not visible. We also compared the thyroglobulin levels and FDG uptake among the lesions with probably different kinetics of iodine metabolism.In this study, there was a trend of decreasing visualization of lesions in the sequential images. Twenty-eight percent of lymph node metastases, 17% of lung metastases, and 16% of bone metastases were missed on the late images on 10-11th day. On the other hand, only 5% of the remnants were missed. The ratio of early washout was different between remnants and metastatic lesions. The serum thyroglobulin levels and FDG uptake did not correlate with early washout of the I-131 avid lesions. We concluded that earlier imaging is necessary for detection of metastatic lesions.