title: Spectral CT with monochromatic imaging and metal artifacts reduction software for artifacts reduction of ¹²⁵I radioactive seeds in liver brachytherapy.
abstract: OBJECTIVE
  To investigate the optimal monochromatic energy for artifacts reduction from (125)I seeds as well as image improvement in the vicinity of seeds on monochromatic images with and without metal artifacts reduction software (MARS) and to compare this with traditional 120-kVp images, so as to evaluate the application value of gemstone spectral imaging for reducing artifacts from (125)I seeds in liver brachytherapy.
  
  
  METHODS
  A total of 45 tumors from 25 patients treated with (125)I seed brachytherapy in the liver were enrolled in this study. Multiphasic spectral computed tomography (CT) scanning was performed for each patient. After a delay time of 15 s of portal vein phase, a traditional 120-kVp scan was performed, focusing on several planes of (125)I seeds only. The artifact index (AI) in the vicinity of seeds and the standard deviation (SD) of the CT density of region of interest in the outside liver parenchyma were calculated. Artifact appearance was evaluated and classified on reconstructed monochromatic S and 120-kVp images. Image quality in the vicinity of seeds of three data sets were evaluated using a 1-5 scale scoring method. The Friedman rank-sum test was used to estimate the scoring results of image quality.
  
  
  RESULTS
  The greatest noise in monochromatic images was found at 40 keV (SD = 27.38, AI = 206.40). The optimal monochromatic energy was found at 75 keV, which provided almost the least image noise (SD = 10.01) and good performance in artifact reduction (AI = 102.73). Image noise and AI reduction at 75 keV was decreased by 63.44 and 50.23%, compared with at 40 keV. Near-field thick artifacts were obvious in all 45 lesions, in 120-kVp images, and 75-keV images, but basically reduced in 75 keV MARS images and artifacts completely invisible in 7 lesions. The number of diagnosable images (score ≥3) was significantly more in the 75-keV MARS group (28/45), and the 75-keV group (22/45) than in the 120-kVp group (11/45) (p < 0.0167 for both). Compared with 120-kVp images alone, 75-keV images plus 75-keV MARS images can increase tumor visibility around seeds and increase the proportion of diagnostic images to 84.4% (38/45).
  
  
  CONCLUSIONS
  Spectral CT producing 75-keV MARS images could substantially reduce near-field thick artifacts caused by (125)I seeds and improve image quality, even to a state of being completely free from artifacts. Spectral CT imaging (with and without MARS) can provide more accurate CT images for estimating efficacy after (125)I seed brachytherapy in the liver.
authors.affiliation: State Key Laboratory of Oncology in South China, Department of Medical Imaging and Minimally Invasive Interventional Center, Sun Yat-sen University Cancer Center, 651 Dongfeng Road East, Guangzhou, Guangdong, 510060, People's Republic of China.
authors.forename: Qiuxia
authors.initials: Q
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Oncology in South China, Department of Medical Imaging and Minimally Invasive Interventional Center, Sun Yat-sen University Cancer Center, 651 Dongfeng Road East, Guangzhou, Guangdong, 510060, People's Republic of China.
authors.forename: Sheng
authors.initials: S
authors.lastname: Peng
authors.affiliation: State Key Laboratory of Oncology in South China, Department of Medical Imaging and Minimally Invasive Interventional Center, Sun Yat-sen University Cancer Center, 651 Dongfeng Road East, Guangzhou, Guangdong, 510060, People's Republic of China.
authors.forename: Jing
authors.initials: J
authors.lastname: Wu
authors.affiliation: State Key Laboratory of Oncology in South China, Department of Medical Imaging and Minimally Invasive Interventional Center, Sun Yat-sen University Cancer Center, 651 Dongfeng Road East, Guangzhou, Guangdong, 510060, People's Republic of China.
authors.forename: Xiaohua
authors.initials: X
authors.lastname: Ban
authors.affiliation: State Key Laboratory of Oncology in South China, Department of Medical Imaging and Minimally Invasive Interventional Center, Sun Yat-sen University Cancer Center, 651 Dongfeng Road East, Guangzhou, Guangdong, 510060, People's Republic of China.
authors.forename: Mingyan
authors.initials: M
authors.lastname: He
authors.affiliation: State Key Laboratory of Oncology in South China, Department of Medical Imaging and Minimally Invasive Interventional Center, Sun Yat-sen University Cancer Center, 651 Dongfeng Road East, Guangzhou, Guangdong, 510060, People's Republic of China.
authors.forename: Chuanmiao
authors.initials: C
authors.lastname: Xie
authors.affiliation: State Key Laboratory of Oncology in South China, Department of Medical Imaging and Minimally Invasive Interventional Center, Sun Yat-sen University Cancer Center, 651 Dongfeng Road East, Guangzhou, Guangdong, 510060, People's Republic of China. yangqx@sysucc.org.cn.
authors.forename: Rong
authors.initials: R
authors.lastname: Zhang
mesh_terms: D000328:Adult; D000368:Aged; D016477:Artifacts; D001918:Brachytherapy / Q000379:methods*; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes / Q000008:administration & dosage*; D008099:Liver / Q000000981:diagnostic imaging; D008113:Liver Neoplasms / Q000532:radiotherapy*; D008297:Male; D008670:Metals; D008875:Middle Aged; D011856:Radiographic Image Enhancement / Q000379:methods; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D012984:Software; D014057:Tomography, X-Ray Computed
chemical_list: D007457:Iodine Radioisotopes; D008670:Metals
keywords: 125I seed brachytherapy; Artifacts reduction; Metal artifacts reduction software; Monochromatic imaging; Spectral computed tomography