Changes of [18F]FDG-PET/CT quantitative parameters in tumor lesions by the Bayesian penalized-likelihood PET reconstruction algorithm and its influencing factors.

BACKGROUND: To compare the changes in quantitative parameters and the size and degree of 18F-fluorodeoxyglucose ([18F]FDG) uptake of malignant tumor lesions between Bayesian penalized-likelihood (BPL) and non-BPL reconstruction algorithms. METHODS: Positron emission tomography/computed tomography images of 86 malignant tumor lesions were reconstructed using the algorithms of ordered subset expectation maximization (OSEM), OSEM + time of flight (TOF), OSEM + TOF + point spread function (PSF), and BPL. [18F]FDG parameters of maximum standardized uptake value (SUVmax), SUVmean, metabolic tumor volume (MTV), total lesion glycolysis (TLG), and signal-to-background ratio (SBR) of these lesions were measured. Quantitative parameters between the different reconstruction algorithms were compared, and correlations between parameter variation and lesion size or the degree of [18F]FDG uptake were analyzed. RESULTS: After BPL reconstruction, SUVmax, SUVmean, and SBR were significantly increased, MTV was significantly decreased. The difference values of %ΔSUVmax, %ΔSUVmean, %ΔSBR, and the absolute value of %ΔMTV between BPL and OSEM + TOF were 40.00%, 38.50%, 33.60%, and 33.20%, respectively, which were significantly higher than those between BPL and OSEM + TOF + PSF. Similar results were observed in the comparison of OSEM and OSEM + TOF + PSF with BPL. The %ΔSUVmax, %ΔSUVmean, and %ΔSBR were all significantly negatively correlated with the size and degree of [18F]FDG uptake in the lesions, whereas significant positive correlations were observed for %ΔMTV and %ΔTLG. CONCLUSION: The BPL reconstruction algorithm significantly increased SUVmax, SUVmean, and SBR and decreased MTV of tumor lesions, especially in small or relatively hypometabolic lesions.

[Optimization of scan protocol in pulmonary angiography of second generation dual source computed tomography].

OBJECTIVE: To explore the scan protocol of second generation dual source computed tomography (CT) for CT pulmonary angiogram (CTPA) in patients with suspected pulmonary embolism and determine the proper volume of contrast medium. METHODS: A total of 120 patients undergoing CTPA were recruited. All examinations were performed on a second generation dual source CT. The scan delay was determined with the test bolus technique. Four contrast volume protocols were designed, namely groups A, B, C and D respectively (n = 30 each). For CTPA scan of groups A, B, C and D, 35, 40, 45 and 50 ml contrast medium were injected at an injection rate of 4 ml/s, followed by a saline chaser of 55, 50, 45 and 40 ml respectively. Attenuation profiles of different vascular segments (subclavian vein, vena cava, left atrium, pulmonary trunk, S1 artery, S10 artery) were measured to evaluate the timing techniques. The image quality and artifact of iodine map were analyzed by two radiologists for comparisons. RESULTS: The percentage of pulmonary arteries exceeding optimal attenuation (> 200 HU) showed that groups of B, C and D were higher than group A (93% - 100% vs 80% - 90%). The image quality of group A was lower than the others (P < 0.05) while the other groups showed no significant difference. The artifacts of iodine map of group A were much fewer than the others (P < 0.05) and group D was much more than the other groups (P < 0.05). Groups B and C had a score of 4.13 and 3.67 respectively without significant difference (P = 0.091). CONCLUSION: With the aids of test bolus technique and proper injection protocol (40 ml contrast medium followed by 50 ml saline), the high quality image and low volume of iodine can be realized with second generation dual source CT for CTPA.

[Localization of upper airway stricture by CT scan in patients with obstructive sleep apnea syndrome during drug-induced sleeping].

OBJECTIVE: To evaluate the feasibility of multi-slice spiral CT scan to localize upper airway stricture in patients with obstructive sleep apnea syndrome (OSAS) during drug-induced sleeping. METHODS: One hundred and fourteen patients diagnosed as OSAS by polysomnography were included in the study. Multi-slice spiral CT scan covering upper airway was performed at the end of inspiration and clear upper airway images were obtained in waking. After injecting 5 mg of midazolam intravenously slowly in 109 patients, CT scan was performed at apnea and clear upper airway images were obtained in sleeping. Cross-section area and minimal diameter of airway were measured and the parameters were compared under those two states. Upper airway was displayed intuitionisticly by using post-processing techniques. RESULTS: One hundred and nine patients with OSAS finished the examination with a success rate of 100 %. Airway obstruction at retropalatal level was observed in 62 patients, among whom 26 were associated with airway obstruction at retroglossal level, 27 with narrower airway at retroglossal level in sleeping compared with that in waking, and 9 with no significant change of the airway at retroglossal level after sleeping. Narrower airway at retropalatal level in sleeping compared with that in waking was observed in 40 patients, among whom 20 were associated with narrower airway at retroglossal level in sleeping compared with that in waking, 10 with complete airway obstruction at retroglossal level in sleeping, and 7 with no significant change of the airway at both retropalatal and retroglossal levels before and after sleeping. Minimal mean cross-section area of airway at retropalatal level was (72.60 +/-45.15)mm(2) in waking and (8.26 +/-18.16)mm(2) in sleeping; and minimal mean cross-section area of airway at retroglossal level was (133.21 +/-120.36)mm(2)in waking and (16.73 +/-30.21)mm(2) in sleeping (P <0.01). Minimal mean diameter of airway at retropalatal level was (6.91 +/-2.23) mm in waking and (1.18 +/-2.14) mm in sleeping; and minimal mean diameter of airway at retroglossal level was (8.68 +/-4.32) mm in waking and (1.68 +/-2.22) mm in sleeping (P <0.01). CONCLUSION: Multi-slice spiral CT with post-processing techniques can display the shape of the upper airway in patients with OSAS in sleeping, and can localize the upper airway stricture and assess its range accurately.

Perivascular epithelioid cell tumor of the liver: a report of two cases and review of the literature.

Perivascular epithelioid cell tumor (PEComa) is a rare tumor which arises from mesenchymal tissues. It is predominant in the uterus, but very rare in the liver. To the best of our knowledge, less than 5 cases of PEComa of the liver have been reported. Herein we present two pathologically proven cases of PEComa of the liver, retrospectively analyze their clinical and imaging features, and review the literature.

[A report of 12 cases of primary pulmonary cryptococcosis].

OBJECTIVE: The purpose of this study was to analyze the chest CT findings of immunocompetent patients with primary pulmonary cryptococcosis and to evaluate the utility of CT-guided percutaneous biopsy in the diagnosis. METHODS: Chest CT scans of 12 immunocompetent patients with biopsy-proven primary pulmonary cryptococcosis were analyzed for the number of lesions, morphologic characteristics, distribution of parenchymal abnormalities, and the presence of lymphadenopathy and pleural effusion. Lung specimens were obtained by CT guided percutaneous biopsy (n = 9) and/or surgical resection (n = 7). A pulmonary pathologist reviewed the specimens. RESULTS: The main manifestations were classified into two patterns. Localized multiple mixed lesions (nodules and/or masses and/or consolidation) were found in 67% (8/12) of the cases, and single nodules were found in 33% (4/12). Associated findings included air bronchograms (n = 9), cavity (n = 2), and CT halo sign (n = 4). Lung specimens were obtained by CT guided percutaneous biopsy in 9 cases, of which 7 (78%) were confirmed by pathology. Seven cases recovered after treatment with fluconazole, but cryptococcal meningitis occurred in 1 case 5 month after single excision. CONCLUSIONS: Chest CT findings of primary pulmonary cryptococcosis in immunocompetent patients have a predominant pattern of localized multiple mixed lesions. CT guided percutaneous biopsy is helpful in confirming the diagnosis. Fluconazole is effective in the treatment of pulmonary cryptococcosis in these patients.