Rationale and Objectives
This study aimed to evaluate the diagnostic performance of using a reformatted single-in-plane image reformation of the rib cage for the detection of rib fractures in computed tomography (CT) examinations, employing different levels of radiological experience.
Materials and Methods
We retrospectively evaluated 10 consecutive patients with and 10 patients without rib fractures, whose CT scans were reformatted to a single-in-plane image reformation of the rib cage. Eight readers (two radiologists, two residents in radiology, and four interns) independently evaluated the images for the presence of rib fractures using a reformatted single-in-plane image and a multi-planar image reformation. The time limit was 30 seconds for each read. A consensus of two radiologist readings was considered as the reference standard. Diagnostic performance (sensitivity, specificity, positive predictive value [PPV], and negative predictive value [NPV]) was assessed and evaluated per rib and per location (anterior, lateral, posterior). To determine the time limit, we prospectively analyzed the average time it took radiologists to assess the rib cage, in a bone window setting, in 50 routine CT examinations. McNemar test was used to compare the diagnostic performances.
Results
Single image reformation was successful in all 20 patients. The sensitivity, specificity, PPV, and NPV for the detection of rib fractures using the conventional multi-planar read were 77.5%, 99.2%, 89.9%, and 98.0% for radiologists; 46.3%, 99.7%, 92.5%, and 95.3% for residents; and 29.4%, 99.4%, 82.5%, and 93.9% for interns, respectively. Sensitivity, PPV, and NPV increased across all three groups of experience, using the reformatted single-in-plane image of the rib cage (radiologists: 85.0%, 98.6%, and 98.7%; residents: 80.0%, 92.8%, and 98.2%; interns: 66.9%, 89.9%, and 97.1%), whereas specificity did not change significantly (99.9%, 99.4%, and 99.3%). The diagnostic performance of the interns and residents was significantly better when evaluating the single-in-plane image reformations ( P < .01). The diagnostic performance of the radiologists was better when evaluating the single-in-plane image reformations; however, there was no significant difference (statistical power: 0.32).
Conclusions
The diagnostic performance for the detection of rib fractures, using CT images that have been reformatted to a single-in-plane image, improves for readers from different educational levels when the evaluation time is restricted to 30 seconds or less.
Introduction
Rib fractures occur in 40%–50% of severely injured patients or after blunt chest trauma . Depending on the number and the location of rib fractures, patients may develop respiratory failure , experience abdominal solid organ injury , and demonstrate a mortality rate of up to 6% . Therefore, it is important to accurately and quickly detect the location and type of fracture and the number of fractured ribs because this information can be an indication of the direction and severity of trauma and can indicate potential associated complications (eg respiratory failure) . More than 50% of rib fractures are missed on radiographs . In addition, 43% of initial computed tomography (CT) scan reports have incorrectly identified the number and location of rib fractures . The semicircular shape and angulation of ribs makes it difficult to identify rib fractures using standard transverse images. Coronal images do not improve the detection rates significantly . An aggravating circumstance is the fact that ribs often break as a buckle or incomplete fracture . Buckle fractures are the most frequently missed type of fracture, and the anterior arc is the location with the most missed fractures . But what are the reasons for these inadequate detection rates of rib fractures in CT? Undoubtedly, identifying these often subtle findings is time-consuming, and no dedicated standardized rib cage reformation, similar to sagittal spinal reformations in a bone window setting, is routinely used for the detection of rib fractures.
Therefore, the aim of this study is to evaluate the diagnostic performance for the detection of rib fractures in a CT examination using readings from both conventional multi-planar images and a reformatted single-in-plane image of the rib cage. We evaluated readers with different levels of radiological experience. The evaluation time was restricted to 30 seconds or less.
Materials and Methods
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Patient Population
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Imaging Technique
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Single-in-plane Image Reformation
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Reading Time
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Reference Standard
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Experimental Setup
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Statistical Analysis
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Results
Reading Time
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Reference Standard
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Diagnostic Performance of the Conventional Multi-planar Read
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Table 1
Diagnostic Performance for the Detection of Rib Fractures in CT Examinations (Per Rib Analysis) Using a Single-in-plane Image Reformation of the Rib Cage and Conventional Multi-planar Reformations, for Different Levels of Radiological Experience
Fractures Segmental Fractures Anterior Fractures Lateral Fractures Posterior Fractures Interns Residents Radiol. Interns Residents Radiol. Interns Residents Radiol. Interns Residents Radiol. Interns Residents Radiol. ( n = 4) ( n = 2) ( n = 2) ( n = 4) ( n = 2) ( n = 2) ( n = 4) ( n = 2) ( n = 2) ( n = 4) ( n = 2) ( n = 2) ( n = 4) ( n = 2) ( n = 2) Single-in-plane image read True positive_107_64__68__7__7__11__1__0__1 60 44 451__0__1 True negative_1748_875__879__1876__938__938__1899__954__955 1781 888 8851866__938__938 False positive_12_5__1__0__0__0__13__2__1 31 18 2110__0__0 False negative_53_16__12__37__15__11__7__4__3 48 10 943__22__21 Sensitivity_66.9%_80.0%__85.0%__15.9%__31.8%__50.0%__12.5%__0.0%__25.0% 55.6% 81.5% 83.3%2.3%__0.0%__4.5% Specificity_99.3%_99.4%__99.9%__100.0%__100.0%__100.0%__99.3%__99.8%__99.9% 98.3% 98.0% 97.7%99.5%__100.0%__100.0% PPV_89.9%_92.8%__98.6%__100.0%__100.0%__100.0%__7.1%__0.0%__50.0% 65.9% 71.0% 68.2%9.1%__0.0%__100.0% NPV_97.1%_98.2%__98.7%__98.1%__98.4%__98.8%__99.6%__99.6%__99.7% 97.4% 98.9% 99.0%97.7%__97.7%__97.8% Multi-planar read True positive_47_37__62__1__1__7__0__0__1 19 25 421__0__1 True negative_1750_877__873__1876__938__932__1898__956__953 1794 885 8841871__938__938 False positive_10_3__7__0__0__6__14__0__3 18 21 225__0__0 False negative_113_43__18__43__21__15__8__4__3 89 29 1243__22__21 Sensitivity_29.4%_46.3%__77.5%__2.3%__4.5%__31.8%__0.0%__0.0%__25.0% 17.6% 46.3% 77.8%2.3%__0.0%__4.5% Specificity_99.4%_99.7%__99.2%__100.0%__100.0%__99.4%__99.3%__100.0%__99.7% 99.0% 97.7% 97.6%99.7%__100.0%__100.0% PPV_82.5%_92.5%__89.9%__100.0%__100.0%__53.8%__0.0%__0.0%__25.0% 51.4% 54.3% 65.6%16.7%__0.0%__100.0% NPV_93.9%_95.3%__98.0%__97.8%__97.8%__98.4%__99.6%__99.6%__99.7% 95.3% 96.8% 98.7%97.8%__97.7%__97.8%
NPV, negative predictive value; PPV, positive predictive value; Radiol, radiologists; Segmental fracture, one rib is fractured in two or more places.
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Diagnostic Performance of the Single-in-plane Image Read
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Comparative Analysis
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Discussion
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Conclusions
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Acknowledgment
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