Performance of Half-dose Chest Computed Tomography in Lung Malignancy Using an Iterative Reconstruction Technique / 고신대학교의과대학학술지

OBJECTIVES: The purpose of this study was to evaluate the performance of half-dose chest CT using an iterative reconstruction technique in patients with lung malignancies. METHODS: The Dual-source CT scans were obtained and half-dose datasets were reconstructed with 5 different strengths in 38 adults with lung malignancies. Two radiologists graded subjective image quality; noise, contrast and sharpness at the central/peripheral lung, mediastinum and chest wall of the reconstructed half-dose images, compared with those of standard-dose images, using a three-point scale. A lesion assessment; lesion conspicuity and diagnostic confidence, was also performed. The quantitative image noises; contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) were measured and compared with those of standard-dose images. RESULTS: The subjective image noise in the half-dose images was less than that of the standard-dose images. The contrast in strengths 2 to 5 was superior, the sharpness of the lung parenchyma in strengths 3 to 5 was inferior, and the CNR/SNR in all strengths were higher than those of standard-dose images (P < 0.05). The improvement of subjective image noise and contrast, the decrease in sharpness, were correlated with strength level (P < 0.05). The lesion conspicuity in half-dose images of strengths 4 and 5 was decreased. The diagnostic confidence of the half-dose images of all strengths was comparable to that of the standard-dose images (P < 0.05). CONCLUSIONS: Half-dose chest CT images using an iterative reconstruction technique show decreased image noise, increased contrast, and diagnostic confidence comparable to standard-dose images. Images reconstructed with strength 2 and 3 appear to be the optimal choice in clinical practice.

Head and Neck Tumors and Neck Node Metastasis: Comparison of Ga-67 Scan and CT Findings

PURPOSE: To assess relative diagnostic value of Ga-67 planar, Ga-67 SPECT, and CT images for detection of head and neck tumors and cervical lymph node metastasis. MATERIALS AND METHODS: Thirty eight patients of pathologically proven head and neck tumors including squamous cell carcinomas(n=32), malignant lymphomas(n=3), undifferentiated carcinomas(n=2), adenocarcinomas(n=l) were enrolled in this study. Ga-67 planar and SPECT images were obtained with intravenous injection of 5mCi of Ga-67 citrate. On the basis of 30 and 20 mm in the greatest diameter of cervical lymph nodes, we compared lesion detectability of Ga-67 planar, SPECT, and CT. RESULTS: Thirty eight cases of head and neck tumors were detected in 29 cases(76.3%) with Ga-67 planar image, 37 cases(97.3%) with Ga-67 SPECT, and 32 cases(84.2%) with CT. 25 of 32 squamous cell carcinomas were positive with Ga-67 planar image and all of 32 cases with Ga-67 SPECT. Both of two undifferentiated carcinomas were positive with Ga-67 planar and SPECT images. Two of three malignant lymphomas were positive with Ga-67 planar image and all of three with Ga-67 SPECT. Eight of nine tumors were negative with Ga-67 planar image and those were less than 30ram. One case of adenocarcinoma was negative with Ga-67 planar and SPECT images. Seven of nine lymph nodes greater than 30mm were positive with Ga-67 planar image and all of nine with Ga-67 SPECT. On the basis of 20mm in greatest diameter, 16 of 21 lymph nodes greater than 20 mm were positive with Ga-67 planar and SPECT images. CONCLUSION: CT providing better resolution than Ga-67 scan permitted analysis of size and location of metastatic cervical nodes, however primary tumors of oral cavity, vocal cord, and nasopharynx were often not detected on CT when metallic and motion artifacts were present, where Ga-67 SPECT was useful. Ga-67 SPECT enabled better anatomical localization than Ga-67 planar image and was useful in detection of lymph nodes greater than 30 mm.