| Objective：To assess the value of spectral CT imaging in differentiate malignantand benign serous cavity effusion on the basis of comprehensive analysis tools.Meterials and Methods：Review totally85patients with histopathological orlaboratory proven serous cavity effusion underwent spectral CT imaging from January2012to October2012, including14cases of benign serous effusion (including livercirrhosis, heart failure, inflammation and tuberculosis) and71cases of malignant serouseffusion (including gastrointestinal cancer, lung cancer, breast cancer, ovarian cancerand esophageal carcinoma). Using the spectral analysis software (GSI viewer), the meanCT value of140kVp images and monochromatic images(40～140) keV, effectiveatomic number(eff-Z) and fat (water), water (iodine), water (calcium) were measured.The difference of these spectral characteristic parameters was evaluated statistically byindependent-samples t test. Sensitivity, specificity and area under the ROC curve fordiagnosis of malignant serous cavity effusion using fat (water), water (iodine), water(calcium) concentration were obtained (SPSS17.0). The slope of spectral curve wasmeasured and evaluated statistically by independent-samples t test．According to theslope of spectral curve, the spectral curve was divided into2types：increment anddecrement curve, and the numbers of each type in benign group and malignant groupwere counted respectively. The difference of slope in the two groups were evaluatedstatistically by fisher’s exact test. The curve type of sensitivity and specificity, and areaunder the curve for the diagnosis of benign and malignant effusion were obtained bystatistical software. Approval for this retrospective HIPAA–compliant study wasobtained from the institutional review board.Results：1)The CT values on140kVp polychromatic images between benign and malignant didn’t show any statistically significant difference (p>0.05). There was statisticallysignificant difference between benign and malignant at low energy keV (40~60keV),and significant difference could be found at130~140keV, however, there was nostatistically significant differences of the CT value at70~120keV.2)The eff-Z ofbenign group (7.80±0.18) was higher than that of malignancy (7.32±0.20) withstatistical difference(t=8.52，P <0.01). The eff-Z distribution peaks of benign group(7.84±0.18) was higher than malignancy (7.32±0.19) with statistical difference(t=-9.05,p <0.01).3) The fat (water), water (iodine), water (calcium) of malignant effusions werehigher than that of benign effusion group which were220.51±187.92,1023.42±12.69,1026.04±12.69vs.-265.55±198.44,1011.91±7.40,1008.73±8.95, respectively withstatistical difference (p <0.01). With fat (water),water (iodine), water (calcium)concentration of104.34g/L,1024.22g/L and1028.44g/L, the sensitivity andspecificity of malignant effusions diagnosis were95.5%,86.4%,86.4%and92.6%,77.8%,92.6%and the area under the ROC curve were97.7%,79.8%,86.7%.4) Theslope of spectral curve of benign (0.17±0.21) was higher than that of malignancy(-0.20±0.26) with statistical difference (t=-7.75, P <0.01).5) About95.77%(68/71) ofmalignant serous effusions showed increament curve and100%(14/14) of benignserous effusions showed decreament curve with statistical difference (P <0.01). Thecharacter of the effusioncould be differentiated (benign from malignant or malignantform benign)with an overall sensitivity of85.7%and a specificity of98.6%, and thearea under the curve was92.1%.Conclusion：The nature of the serous cavity effusion was unable to be identified only by the CTvalues on conventional140kVp images. CT values at low energy keV (40~60keV)play an important role in identifying malignant and benign effusion. The spectral curvetype, eff-Z and concentration of the base material are different in two groups. Thespectral curve type has high sensitivity and specificity in differentiating benign andmalignant effusion.Comprehensive analysis of the HDCT provides a multi-parameterapproach for identifying benign and malignant serous cavity effusion. |
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