Wavelet compression of low-dose chest CT data: Effect on lung nodule detection

PURPOSE: To assess the effect of using a lossy joint Photographic Experts Group standard for wavelet image compression, JPEG2000, on pulmonary nodule detection at low-dose computed tomography (CT). MATERIALS AND METHODS: One hundred sets of lung CT data ("cases") were compressed to 30:1, 20:1; and 10:1 levels by using a wavelet-based, JPEG2000 method, resulting in 400 test cases. Each case consisted of nine 1.25-mm sections that had been obtained with 20-40 mAs. Four thoracic radiologists independently interpreted the test case images: Performance was measured by using area under the receiver operating characteristic (ROC) curve (A(z)) and conventional sensitivity and specificity analyses. RESULTS: There were 51 cases with and 49 without lung nodules. Az values were respectively, for original and 10:1, 20:1, and 30;1 compressed images. A(z) values decreased significantly at 30:1 (P =.014) but riot at 10:1 compression, with a trend toward significant decrease at 20:1 (P=.051). Specificity values were unaffected by compression (>98.0% at all compression levels). Sensitivity values were 86.3% (176 of 204 test cases with nodules), 77.9./0 (159 of 204 cases); 76.5% (156 of 204 cases), and 70.1% (143 of 204 cases), respectively, for original and 10:1; 20:1, and 30:1 compressed images. analysis confirmed the significant effects of compression logistic regression model analysis P rate and nodule attenuation, size, and location on sensitivity (P <.05). CONCLUSION: While no reduction in nodule detection at 10:1 compression levels was demonstrated by using ROC analysis, a significant decrease in sensitivity was identified. Further investigation is needed before widespread use of image compression technology in low-dose chest CT can be recommended. (C) RSNA, 2003.