Application value of optimal energy imaging technique of monoenergetic dual-energy computed tomography in feeding arteries examination of rectal cancer

Abstract

Objective To explore the application value of optimal energy imaging technique of monoenergetic dual-energy computed tomography (DECT) in feeding arteries examination of rectal cancer. Methods The clinical data of 33 patients with rectal cancer who were admitted to the First Affiliated Hospital of Dalian Medical University from July 2012 to July 2014 were analyzed retrospectively. The polychromatic and monochromatic images of feeding arteries of tumors were reconstructed and evaluated using a subjective image quality score of 5-point scale by 2 observers. The consistency and scores of evaluation were analyzed by the κ test and Mann-Whitney U test. The CT value of feeding arteries of tumors and hip muscle, image noise and contrast to noise ratio (CNR) were measured and calculated by 2 observers, and were compared by the independent sample t test. The consistency of data between the 2 observers were measured by the intra-class correlation coefficients (ICC). Results Inferior mesenteric arteries were contributor of blood supply of tumors in all the 33 patients, including 4 cases with right inferior rectal artery as contributor of blood supply of tumors, 2 cases with bilateral inferior rectal artery. Among patients with abnormal blood vessels, there were 8 patients with left colic artery and sigmoid artery having common trunk, 4 patients with left colic artery originated from Inferior mesenteric artery, 1 patient with absence of left colic artery. The 0-, 1-, 2-, 3-, 4- score polychromatic image quality of feeding arteries of tumors were detected in 0, 13, 13, 5, 2 patients and 0, 11, 14, 6, 2 patients by 2 observers, respectively. The 0-, 1-, 2-, 3-, 4- score monochromatic image quality of feeding arteries of tumors were detected in 0, 0, 7, 7, 19 patients and 0, 0, 6, 9, 18 patients by 2 observers, respectively. Good interobserver agreement was found for the evaluation of subjective scores (κ=0.864, 0.897). The subjective scores of image quality of feeding arteries in the polychromatic images and in the monochromatic images were 1.9±0.9 and 3.4±0.8, with significant difference (Z=-5.21, P<0.05). The latter was superior to the former. The ICC values of the CT values of feeding arteries of tumor, hip muscle, image noise and CNR were 0.953, 0.907, 0.839, 0.964 and 0.966, 0.933, 0.952, 0.962 from the 2 observers, with a good consistency. The CT values of feeding arteries of tumor, gluteal muscles, image noise and CNR in the polychromatic images and in the monochromatic images were (234±52)HU and (412±83)HU, (57±9)HU and (71±15)HU, (21±3)HU and (31±6)HU, 9±3 and 11±4, respectively, with significant differences (t=-18.65, -4.44, -14.14, -6.55, P<0.05). The levels of monochromatic images of 33 patients were 51-61 keV, with a median of 55 keV. Conclusion The optimal energy imaging technique of monoenergetic DECT can improve the angiographic quality of feeding arteries in patients with rectal cancer. Key words: Rectal neoplasms; Arteries; Tomography, X-ray computed; Contrast noise ratio