ABSTRACT
Objective:To investigate the value of low-energy virtual monoenergetic image (VMI) at 45 keV in visualizing the primary tumor and T staging of hypopharyngeal squamous cell carcinoma.Methods:The clinical and imaging data of 58 patients with hypopharyngeal squamous cell carcinoma from April 2018 to January 2020 at Eye & ENT Hospital, Fudan University were analyzed retrospectively. All the patients underwent a venous phase contrast-enhanced dual-source dual-energy CT scan before treatment. The VMI at 45 keV and standard linearly blended image (30% 80 kV+70% 140 kV) were acquired from dual-energy post-processing software. One senior radiologist and one junior radiologist independently assessed the visibility of the tumor on the 45 keV VMI and standard linearly blended image using a 5-point Likert rating scale. Furthermore, the senior radiologist assessed the visibility of the tumor at each subsite (piriform fossa, posterior pharyngeal wall, postcricoid region) and determined the invasion depth of the tumor (extension to esophagus, invasion to strip muscles and prevertebral muscles) and performed the T staging of the primary tumor using the two sets of images blindly. The accuracy of T staging was calculated, using pathological T staging (surgical cases) or clinical T staging (non-surgical cases) as the gold standard. The image scores of the two sets of images were compared using Wilcoxon rank sum test. McNemar-Bowker test was used to compare the accuracy of T staging using the two sets of images.Results:The overall image scores of the 45 keV VMI and standard linearly blended image from the senior radiologist were 3.5 (3, 4) and 3 (2, 3) respectively ( Z=-7.03, P<0.001), and the scores from the junior radiologist were 3 (3, 4) and 2 (2, 3) ( Z=-6.93, P<0.001). The scores of the 45 keV VMI were significantly higher than those of the standard linearly blended image in visualizing tumors in the piriform fossa, posterior pharyngeal wall, and postcricoid region, as well as in detecting invasion to the strip muscles ( P<0.05). There was no significant difference in the scores of the two sets of images in determining whether the tumor extended to esophagus or invaded prevertebral muscles ( P>0.05). Referring to pathological and clinical T stage, the accuracy of T staging determined by the 45 keV VMI and standard linearly blended image was 87.9% (51/58) and 81.0% (47/58) respectively, and the difference was not significant (χ 2=3.33, P=0.189). Conclusions:The 45 keV VMI is superior to the standard linearly blended image in visualizing tumors and detecting invasion to the strip muscles of hypopharynx squamous cell carcinoma. However, the accuracy of determining T staging using 45 keV VMI is slightly improved than that of standard linearly blended image, and the difference is not statistically significant. In determining whether the tumor extends to esophagus or invades prevertebral muscles, 45 keV VMI shows no significant advantage over standard linearly blended image.
ABSTRACT
Virtual monochromatic images (VMI) that reconstructed on dual-energy computed tomography (DECT) have further application prospects in radiotherapy, and there is still a lack of clinical dose verification. In this study, GE Revolution CT scanner was used to perform conventional imaging and gemstone spectral imaging on the simulated head and body phantom. The CT images were imported to radiotherapy treatment planning system (TPS), and the same treatment plans were transplanted to compare the CT value and the dose distribution. The results show that the VMI can be imported into TPS for CT value-relative electron density conversion and dose calculation. Compared to conventional images, the VMI varies from 70 to 140 keV, has little difference in dose distribution of 6 MV photon treatment plan.
Subject(s)
Electrons , Phantoms, Imaging , Tomography Scanners, X-Ray Computed , Tomography, X-Ray ComputedABSTRACT
Abstract Objective: To determine whether dual-energy computed tomography (DECT) of the chest can be performed at a reduced radiation dose, with an emphasis on images generated with post-processing techniques. Materials and Methods: In 21 patients undergoing DECT of the chest in a dual-source scanner, an additional image series was acquired at a reduced radiation dose. Four thoracic radiologists assessed both image series for image quality, normal thoracic structures, as well as pulmonary and mediastinal abnormalities, on virtual monochromatic images at 40 keV and 60 keV. Data were analyzed with Student's t-test, kappa statistics, analysis of variance, and the Wilcoxon signed-rank test. Results: The overall image quality of 60 keV virtual monochromatic images at a reduced radiation dose was considered optimal in all patients, and no abnormalities were missed. Contrast enhancement and lesion detection performance were comparable between reduced-dose images at 40 keV and standard-of-care images at 60 keV. The intraobserver and interobserver agreement were both good. The mean volumetric CT dose index (CTDIvol), size-specific dose estimate (SSDE), dose-length product (DLP), and effective dose (ED) for reduced-dose DECT were 3.0 ± 0.6 mGy, 4.0 ± 0.6 mGy, 107 ± 30 mGy.cm, and 1.5 ± 0.4 mSv, respectively. Conclusion: DECT of the chest can be performed at a reduced radiation dose (CTDIvol < 3 mGy) without loss of diagnostic information.
Resumo Objetivo: Verificar se a tomografia computadorizada de dupla energia (TCDE) do tórax pode ser realizada com baixas doses de radiação, com ênfase em imagens pós-processadas. Materiais e Métodos: Em 21 pacientes submetidos a DECT do tórax foi adicionada uma série de imagens adquiridas com baixas doses de radiação. Quatro radiologistas com especialidade em tórax avaliaram a qualidade, visualização de estruturas torácicas normais e também anormalidades pulmonares e mediastinais das imagens monocromáticas de baixa energia (40 e 60 keV). Os dados foram analisados utilizando t-test, estatística kappa, análise de variância e teste Wilcoxon. Resultados: A qualidade das imagens monocromáticas de baixa energia (60 keV) com doses reduzidas foi considerada ótima para todos os pacientes e nenhuma anormalidade no tórax foi perdida. O realce pelo contraste e a performance de detecção de lesões foram similares nas imagens com radiação reduzida e com radiação padrão. Boa concordância intra-avaliadores e interavaliadores foi observada. A média dos parâmetros CTDIvol, SSDE, DLP e ED para TCDE de baixa dose foram 3,0 ± 0,6 mGy, 4,0 ± 0,6 mGy, 107 ± 30 mGy.cm e 1,5 ± 0,4 mSv, respectivamente. Conclusão: TCDE do tórax pode ser realizada com baixas doses de radiação (CTDIvol < 3 mGy), sem perder informações diagnósticas.
ABSTRACT
Objective To evaluate the clinical value of spectral CT monochromatic imaging in improvement of imaging quality of bronchial arteries.Methods We retrospevtively analyzed the chest CT images in 38 patients who underwent the contrast-enhanced spectral CT.These images included a set of 140 kVp polychromatic images and default 70 keV monochromatic images.Using a standard Gemstone Spectral Imaging (GSI)viewer at an advanced workstation (AW4.6),an optimal energy level (in keV)for obtai-ning the best CNR of the bronchial artery could be automatically obtained.The SNR,CNR and objective imaging quality score for these 3 imaging sets (140 kVp,70 keV and optimal energy level)were obtained and compared with one-way ANOVA .Results The optimal energy levels for obtaining the best CNR were (62.58±2.74)keV.The SNR of the 140 kVp polychromatic images,70 keV monochromatic images,and the optimal keV monochromatic images were 1 6.44±5.85,20.96 ±8.32 and 24.91 ±9.91,the CNR were 13.30±5.45,1 7.25±6.97 and 20.67±8.62,and the subjective imaging quality scores were 1.97 ±0.82,3.24±0.75 and 4.47±0.60,respectively,exhibiting significant differences among groups (F =10.1 7,10.1 7 and 1 1 1.12,P <0.00).The optimal monochromatic group was superior to the 70 keV group and the 140 kVp mixed-energy group.Conclusion Monochromatic images at approximately 62 keV in dual-energy spectral CTA yields the best CNR and highest diagnostic confidence for imaging bronchial ar-teries,which may improve imaging quality for imaging bronchial arteries.