American Journal of Roentgenology Abdominal Imaging

[Abdominal Imaging] Abdominal Manifestations of Extranodal Lymphoma: Spectrum of Imaging Findings

Lee, W.-K., Lau, E. W. F., Duddalwar, V. A., Stanley, A. J., Ho, Y. Y. — 2008-06-18

OBJECTIVE. The purpose of this article is to illustrate the spectrum of appearances of extranodal lymphoma in the abdomen using cross-sectional imaging techniques.

CONCLUSION. Extranodal lymphoma in the abdomen can mimic other neoplastic or inflammatory conditions. Although a definitive diagnosis is possible only with biopsy, it is important to consider extranodal lymphoma in the presence of certain imaging appearances in the appropriate clinical setting for the correct diagnosis, accurate staging, and optimal management.

[Abdominal Imaging] Local Tumor Progression After Radiofrequency Ablation of Liver Tumors: Analysis of Morphologic Pattern and Site of Recurrence

Kei, S. K., Rhim, H., Choi, D., Lee, W. J., Lim, H. K., Kim, Y.-s. — 2008-05-20

OBJECTIVE. The purpose of our study was to assess the morphologic pattern and exact site of local tumor progression with relation to various risk factors after radiofrequency ablation of liver tumors.

CONCLUSION. Local tumor progression after radiofrequency ablation shows mostly the peripheral nodular type. The site of local tumor progression shows a higher concordance rate with insufficient ablative margin than contiguous vessel and subcapsular location.

[Abdominal Imaging] Artifacts in Slab Average-Intensity-Projection Images Reformatted from JPEG 2000 Compressed Thin-Section Abdominal CT Data Sets

Kim, B., Lee, K. H., Kim, K. J., Mantiuk, R., Kim, H.-r., Kim, Y. H. — 2008-05-20

OBJECTIVE. The objective of our study was to assess the effects of compressing source thin-section abdominal CT images on final transverse average-intensity-projection (AIP) images.

MATERIALS AND METHODS. At reversible, 4:1, 6:1, 8:1, 10:1, and 15:1 Joint Photographic Experts Group (JPEG) 2000 compressions, we compared the artifacts in 20 matching compressed thin sections (0.67 mm), compressed thick sections (5 mm), and AIP images (5 mm) reformatted from the compressed thin sections. The artifacts were quantitatively measured with peak signal-to-noise ratio (PSNR) and a perceptual quality metric (High Dynamic Range Visual Difference Predictor [HDR-VDP]). By comparing the compressed and original images, three radiologists independently graded the artifacts as 0 (none, indistinguishable), 1 (barely perceptible), 2 (subtle), or 3 (significant). Friedman tests and exact tests for paired proportions were used.

RESULTS. At irreversible compressions, the artifacts tended to increase in the order of AIP, thick-section, and thin-section images in terms of PSNR (p < 0.0001), HDR-VDP (p < 0.0001), and the readers' grading (p < 0.01 at 6:1 or higher compressions). At 6:1 and 8:1, distinguishable pairs (grades 1-3) tended to increase in the order of AIP, thick-section, and thin-section images. Visually lossless threshold for the compression varied between images but decreased in the order of AIP, thick-section, and thin-section images (p < 0.0001).

CONCLUSION. Compression artifacts in thin sections are significantly attenuated in AIP images. On the premise that thin sections are typically reviewed using an AIP technique, it is justifiable to compress them to a compression level currently accepted for thick sections.