Usefulness of low dose chest CT for initial evaluation of blunt chest trauma

Abstract

We aimed to compare the diagnostic performance and inter-observer consistency between low dose chest CT (LDCT) and standard dose chest CT (SDCT) in the patients with blunt chest trauma.A total of 69 patients who met criteria indicative of blunt chest trauma (77% of male; age range, 16-85) were enrolled. All patients underwent LDCT without intravenous (IV) contrast and SDCT with IV contrast using parameters as following: LDCT, 40 mAs with automatic tube current modulation (ATCM) and 100 kVp (BMI <25, n = 51) or 120 kVp (BMI>25, n = 18); SDCT, 180 mAs with ATCM and 120 kVp. Transverse, coronal, sagittal images were reconstructed with 3-mm slice thickness without gap and provided for evaluation of 3 observers. Reference standard images (transverse, coronal, sagittal) were reconstructed using SDCT data with 1-mm slice thickness without gap. Reference standard was established by 2 experienced thoracic radiologists by consensus. Three observers independently evaluated each data set of LDCT and SDCT.Multiple-reader receiver operating characteristic analysis for comparing areas under the ROC curves demonstrated that there was no significant difference of diagnostic performance between LDCT and SDCT for the diagnosis of pulmonary injury, skeletal trauma, mediastinal injury, and chest wall injury (P > 0.05). The intraclass correlation coefficient was measured for inter-observer consistency and revealed that there was good inter-observer consistency in each examination of LDCT and SDCT for evaluation of blunt chest injury (0.8601-1.000). Aortic and upper abdominal injury could not be appropriately compared as LDCT was performed without using contrast materials and this was limitation of this study.The effective radiation dose of LDCT (average DLP = 1.52 mSv⋅mGy cm) was significantly lower than those of SDCT (7.21 mSv mGy cm).There is a great potential benefit to use of LDCT for initial evaluation of blunt chest trauma because LDCT could maintain diagnostic image quality as SDCT and provide significant radiation dose reduction. A further study of LDCT with IV contrast for evaluation of aortic and upper abdominal injury is needed.

Figure 1

A 43-year-old man who had a driver traffic accident. All observers could detect small amount of left pneumothorax (arrows) on the axial 3-mm image of (A) SDCT (120 kVp and 180 mAs with ATCM) with 3–4 confidence. However, only 1 observer identified pneumothorax on the 3-mm axial image of (B) LDCT (100 kVp and 40 mAs with ATCM) with confidence 3. ATCM = automatic tube current modulation, LDCT = low dose chest CT, SDCT = standard dose chest CT.

Figure 2

A 54-year-old woman who had blunt chest trauma from driver accident. All 3 observers identified this sternal fracture (arrows) on 3-mm axial and coronal images of both (A) LDCT (100 kVp and 40 mAs with ATCM) and (B) SDCT (120 kVp and 180 mAs with ATCM) with confidence 4 (definite fracture). ATCM = automatic tube current modulation, LDCT = low dose chest CT, SDCT = standard dose chest CT.

Figure 3

A 48-year-old man who had fallen from 3-m height. Axial 3-mm image of (A) LDCT (100 kVp and 40 mAs with ATCM) and (B) SDCT (120 kVp and 180 mAs with ATCM) shows fracture of left 1st rib (arrows). Although there is more artifact at the image of LDCT, all observers could identify rib fracture. ATCM = automatic tube current modulation, LDCT = low dose chest CT, SDCT = standard dose chest CT.