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The possibility of application of spiral brain computed tomography to traumatic brain injury
American Journal of Emergency Medicine 32 (2014) 1051–1054
Contents lists available at ScienceDirect
American Journal of Emergency Medicine journal homepage: www.elsevier.com/locate/ajem
Original Contribution
The possibility of application of spiral brain computed tomography to traumatic brain injury☆ Daesung Lim, MD a, Soo Hoon Lee, MD b,⁎, Dong Hoon Kim, MD, PhD b,⁎⁎, Dae Seub Choi, MD, PhD c, Hoon Pyo Hong, MD, PhD a, d, Changwoo Kang, MD b, Jin Hee Jeong, MD b, Seong Chun Kim, MD b, Tae-Sin Kang, MD b a
Department of Emergency Medicine, Kyung Hee University Medical Center, Seoul, Republic of Korea Department of Emergency Medicine, Gyeongsang National University Hospital, Jinju, Gyeongsangnam-Do, Republic of Korea c Department of Radiology, Gyeongsang National University Hospital, Jinju, Gyeongsangnam-Do, Republic of Korea d Department of Radiology, Kyung Hee University Medical Center, Seoul, Republic of Korea b
a r t i c l e
i n f o
Article history: Received 12 May 2014 Received in revised form 18 June 2014 Accepted 18 June 2014
a b s t r a c t Objectives: The spiral computed tomography (CT) with the advantage of low radiation dose, shorter test time required, and its multidimensional reconstruction is accepted as an essential diagnostic method for evaluating the degree of injury in severe trauma patients and establishment of therapeutic plans. However, conventional sequential CT is preferred for the evaluation of traumatic brain injury (TBI) over spiral CT due to image noise and artifact. We aimed to compare the diagnostic power of spiral facial CT for TBI to that of conventional sequential brain CT. Methods: We evaluated retrospectively the images of 315 traumatized patients who underwent both brain CT and facial CT simultaneously. The hemorrhagic traumatic brain injuries such as epidural hemorrhage, subdural hemorrhage, subarachnoid hemorrhage, and contusional hemorrhage were evaluated in both images. Statistics were performed using Cohen's κ to compare the agreement between 2 imaging modalities and sensitivity, specificity, positive predictive value, and negative predictive value of spiral facial CT to conventional sequential brain CT. Results: Almost perfect agreement was noted regarding hemorrhagic traumatic brain injuries between spiral facial CT and conventional sequential brain CT (Cohen's κ coefficient, 0.912). To conventional sequential brain CT, sensitivity, specificity, positive predictive value, and negative predictive value of spiral facial CT were 92.2%, 98.1%, 95.9%, and 96.3%, respectively. Conclusion: In TBI, the diagnostic power of spiral facial CT was equal to that of conventional sequential brain CT. Therefore, expanded spiral facial CT covering whole frontal lobe can be applied to evaluate TBI in the future. © 2014 Elsevier Inc. All rights reserved.
1. Introduction Management of complex, multiple-trauma patient in emergency setting is always a challenge, requiring numerous analyses and treatments within limited time. The golden time for severe trauma patient usually means the time from its onset to the time of hemostatic procedure or surgical treatment, which is set at 60 minutes in several studies [1-5]. Improved evaluation and management in emergency department (ED) are especially important in nations that have already ☆ Conflict of interest statement: All authors have no conflict of interest. ⁎ Correspondence to: SH Lee, Department of Emergency Medicine, Gyeongsang National University Hospital, Gangnam-Ro 79, Jinju, Gyeongsangnam-Do, Republic of Korea, 660-702. Tel.: +82 55 750 8975; fax: +82 55 757 0514. ⁎⁎ Correspondence to: DH Kim, Department of Emergency Medicine, Gyeongsang National University Hospital, Gangnam-Ro 79, Jinju, Gyeongsangnam-Do, Republic of Korea, 660-702. Tel.: +82 55 750 8281; fax: +82 55 757 0514. E-mail addresses: [email protected] (S.H. Lee), [email protected] (D.H. Kim). http://dx.doi.org/10.1016/j.ajem.2014.06.020 0735-6757/© 2014 Elsevier Inc. All rights reserved.
established basic emergency medical services [6]. However, the prompt surgical management or radiological interventions such as vascular embolization for hemostasis in severe trauma patients are often delayed for various reasons in these nations. The whole-body computed tomography (CT) is accepted as an essential diagnostic method for evaluating the degree of injury in severe trauma patients and establishment of therapeutic plans [7-9]. Imaging techniques for CT have continuously improved since its first invention in 1979, and currently, 64-channel multidetector CT is more widely used. The conventional sequential CT had several limitations including poor visualization of posterior fossa and bony artifact. On the other hand, the spiral CT had the advantage of shorter test time required and its multidimensional reconstruction providing 3-dimensional image, although there were some limitations such as decreased image clarity. Therefore, it is now used for anatomical evaluation of practically all body parts with the development of the technology [10,11]. Technical advancements of spiral imaging technique have remarkably reduced the time of CT evaluation and
1052
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could make CT into a criterion standard of evaluation even in the hemodynamically unstable patients regarded as the contraindication in the past. Recently, several emergency centers are now integrating the previously separated brain, facial, cervical, thoracic, and abdominal CT protocols together in efforts to minimize test time. However, still, most hospitals are using the conventional sequential imaging technique for brain CT, as there is notion that imaging technique for facial CT is unable to obtain clear image as the conventional technique due to image noise and artifacts generated from the skull. Recently, radiation exposure from CT is of particular concern. Although the issue is debatable, concern that even a single typical CT examination may confer a small but real risk of carcinogenesis is increasing [12,13]. The spiral CT has the advantage of low radiation dose in comparison with conventional CT. Average tube output of axial brain and face/orbit/ sinus protocol in GE Lightspeed VCT (General Electric Medical Systems, Milwaukee, WI, USA) used in this study was 51.1 mGy and 8.3 mGy in CT dose index, respectively. The objective of this study was to evaluate the diagnostic utility of facial CT in patients with head trauma by comparing the images of conventional sequential brain CT and spiral facial CT, respectively. Therefore, we hypothesized that, in patients with traumatic brain injury (TBI), the diagnostic power of spiral facial CT would be similar to that of conventional sequential brain CT.
(n = 56) older than 65 years. The proportion male patients was 71.7% (n = 226), and female patients, 28.3% (n = 89). Hemorrhage was identified in 32.4% (n = 102) of patients by conventional sequential brain CT. The concurrent positive result rate of facial CT was 92.2% (n = 94), whereas 7.8% (n = 8) were negative by facial CT. Negative result by brain CT was 67.6% (n = 213), whereas facial CT showed positive result in 1.9% (n = 4) from these brain CT negative patients (Table 1). Cohen's κ index between 2 techniques was 0.912, showing “almost perfect agreement.” The sensitivity, specificity, PPV, and NPV of facial CT based on result of brain CT were 92.2%, 98.1%, 95.9%, and 96.3%, respectively (Table 2). Among the 8 cases of brain CT and facial CT negative patients, 7 patients had frontal lobe hemorrhage, which is beyond the area covered by facial CT. Such 7 cases included 2 intracranial hemorrhages, 3 parafalcine subdural hematomas, and 2 subarachnoid hemorrhages. One case that had hemorrhage within the covered area of facial CT but interpreted as negative has small amount of subarachnoid hemorrhage. Of the 4 cases of brain CT–negative and facial CT–positive cases, 2 were a small amount subdural hematoma of the frontal lobe in proximity to the basal area. One case was later identified as false positive by follow-up brain and facial CT, whereas the other case with ambiguous facial CT image had no further evaluation.
2. Methods 4. Discussion During the period from January 1, 2013, to June 30, 2013, patients who visited the ED for head or facial trauma and were evaluated with brain CT and facial CT simultaneously were retrospectively reviewed of their medical charts. The protocol for head and/or facial trauma in our institution consists of conventional sequential brain CT followed by a spiral facial CT. The brain CT image is generated through conventional sequential imaging technique, taking images 5 mm apart starting from the basal section/plane of the brain following the long axis, tilted 20° to 40°. The spiral imaging technique takes images 2.5 mm apart, following the long axis tilted at 90°, spirally. All CT images from patients included in this study were generated by 64-channel multidetector CT (Lightspeed VCT), and the time difference of 2 tests was within 1 hour. Each study was usually completed within 5 minutes. The actual scan time of acquiring each image usually took less than 30 seconds. One team consisting of radiologist and emergency physician evaluated only conventional sequential brain CT without clinical information. The other team consisting of emergency radiologist and emergency physician evaluated only spiral facial CT without clinical information. The 2 test results were compared for agreement, and the cause of discrepancy was analyzed and summarized if discrepant. The test was classified as positive if epidural hemorrhage, subdural hemorrhage, subarachnoid hemorrhage, or contusional hemorrhage was visible from the images or was classified as negative. To evaluate the difference of resulting diagnosis of TBI between 2 techniques, the Cohen's κ index was used. The Cohen's κ index is a numerical representation of the agreement between 2 different tests, classified into 5 intervals: less than 0, 0.1 to 0.4, 0.41 to 0.6, 0.61 to 0.8, and greater than 0.81, interpreting below 0 as “no agreement” and above 0.81 as “almost perfect agreement.” Based on brain CT interpretation, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated. All statistical analyses were performed with the SPSS statistical package for Windows, version 19.0 (SPSS, Chicago, IL). The study was approved by the institutional review board of our hospital.
According to the study result, a high Cohen's κ index was found between conventional sequential and spiral image techniques. No statistical difference was found between 2 techniques in diagnosis of TBI. In addition, most hemorrhagic lesions seen on conventional sequential brain CT were mostly identifiable with facial CT obtained with spiral imaging technique, whereas small amount of basal hemorrhages, which were unidentified or ambiguous on brain CT, could be readily identified by facial CT. Although not included in this study, small pneumocephalus was only identified with spiral facial CT but not with conventional sequential brain CT. There were several previous studies that compared conventional and spiral imaging techniques. They concluded that the difference was minimal, but these studies were comparison of identifying normal structural discriminative powers and not hemorrhagic brain lesions. Two studies qualitatively compare first-generation spiral CT with conventional CT about their ability to identify physiologic brain structure [14,15]. Bahner et al [14] describe superiority of conventional brain CT in discrimination of nontraumatic brain lesions from normal brain tissue and qualitative aspects such as image noise and artifacts, therefore recommending spiral CT only when 3-dimensional reconstruction is necessary. Kuntz et al [15] state that 2 imaging techniques show no statistical difference in their ability to differentiate artificial contrast, gray mater, and white mater. These comparisons are limited by their comparison of ability to differentiate physiologic brain structure and qualitative comparison but not of differentiating pathologic lesions. A recent study by Reichelt et al [16] has found that conventional brain CT and spiral CT image by multidetector CT for multiple-trauma patients are not different in mechanical image quality and their ability to differentiate brain structures, announcing the possibility of clinically applying spiral CT imaging technique. Table 1 Cross-table between sequential brain CT and spiral facial CT
3. Results A total of 315 patients were included in the study. Their mean age was 45.1 ± 20.0 years, consisting of 8.9% (n = 28) younger than 16 years, 73.3% (n = 231) from 16 to younger than 65 years, and 17.8%
Sequential brain CT
Spiral facial CT
+ −
+
−
94 8
4 209
D. Lim et al. / American Journal of Emergency Medicine 32 (2014) 1051–1054
1053
Table 2 Statistical indices of spiral facial CT to sequential brain CT Variables
Results
Sensitivity Specificity PPV NPV
92.2% 98.1% 95.9% 96.3%
This study evaluates the possibility of application of spiral brain CT in TBI, which has not been established yet, with the advantage of directly comparing traumatic brain lesions and not the discriminative power of anatomical structures. Further reduction of test time is expected with the advancement of spiral CT through development of protocols integrating brain, facial, and cervical CT to evaluate complex, multiple-trauma patients. Furthermore, the spiral imaging technique has the several advantages of lower radiation dose, shorter test time, and multidimensional reconstruction providing 3-dimensional images in comparison with conventional sequential CT. In particular, the multidimensional reconstruction helps to detect and characterize for the evaluation of intracranial hemorrhage (ICH) compared with standard axial images alone. The advantages of reconstruction become clear for lesions that lie in the axial plane immediately adjacent to bony surfaces (the anterior cranial fossa, middle cranial fossa, and vertex). Coincidentally, these may also be locations that are at higher risk for injury in head trauma [17].
Fig. 2. Small epidural hematoma seen in spiral facial CT (B) missed in conventional brain CT (A).
This study, although not a prospective evaluation according to standardized protocols, has focused on the feature of facial CT covering nearly most brain mater except the frontal lobe and compared the diagnostic agreement of 2 techniques for hemorrhagic brain lesions. Fig. 1 is a case of pneumocephalus, although within the coverage of brain CT; brain CT result was negative and was only visible from facial CT. The case is an example showing the advantage of 2.5mm image interval of spiral facial CT over the conventional sequential brain CT with 5-mm image interval. Fig. 2 is a case of small amount right basal hemorrhage, which was also only visible from facial CT. The previous false-positive interpretation of facial CT can be attributable to lack of experience of evaluating brain parenchyma by facial CT in which reduction of false-positive interpretation is expected through establishment of positive interpretation criteria followed by clinical experience. There are several limitations in this study. First, patient selection was unstandardized as this study was performed retrospectively, which could include potential biases that were not explained in this study. Second, the object is limited on image; therefore, the patients were compared without regards to their clinical severity, and also, their surgical findings and follow-up results were not considered. Third, facial CT was not covering the whole brain parenchyma, as facial CT is not intended for such purposes, and the setting of coverage could differ from patient to patient. Lastly, the objective scale of the mechanical noise is not provided due to limitations of the instrument used in the institution. 5. Conclusion Fig. 1. Pneumocephalus in right frontal lobe. Equivocal finding in conventional brain CT (A) but clearly seen in spiral facial CT (B).
Spiral CT with relative advantages over conventional sequential CT has been limited of its utilization for brain CT imaging for few reasons.
1054
D. Lim et al. / American Journal of Emergency Medicine 32 (2014) 1051–1054
In this study of patients with TBI, the diagnostic power of spiral facial CT was equal to that of conventional sequential brain CT. Therefore, expanded spiral facial CT covering whole frontal lobe can be applied to evaluate hemorrhagic TBI in the future.
References [1] Weldon CB, Silberfein E, Chehardy PL, et al. ATLS training: a novel approach. Bull Am Coll Surg 2002;87(4):15–9. [2] Clarke JR, Trooskin SZ, Doshi PJ, et al. Time to laparotomy for intra-abdominal bleeding from trauma does affect survival for delays up to 90 minutes. J Trauma 2002;52(3):420–5. [3] Driscoll PA, Vincent CA. Variation in trauma resuscitation and its effect on patient outcome. Injury 1992;23(2):111–5. [4] Bouillon B, Kanz KG, Lackner CK, et al. The importance of Advanced Trauma Life Support (ATLS) in the emergency room (Die Bedeutung des Advanced Trauma Life Support (ATLS) im Schockraum). Unfallchirurg 2004;107(10):844–50. [5] Wurmb TE, Fruhwald P, Hopfner W, et al. Whole-body multislice computed tomography as the first line diagnostic tool in patients with multiple injuries: the focus on time. J Trauma 2009;66(3):658–65. [6] Mock CN, Jurkovich GJ, nii-Amon-Kotei D, et al. Trauma mortality patterns in three nations at different economic levels: implications for global trauma system development. J Trauma 1998;44(5):804–12 [discussion 12-4].
[7] Rieger M, Sparr H, Esterhammer R, et al. Modern CT diagnosis of acute thoracic and abdominal trauma (Moderne CT-Diagnostik des akuten Thorax- und Abdominaltraumas). Anaesthesist 2002;51(10):835–42. [8] Philipp MO, Kubin K, Hormann M, et al. Radiological emergency room management with emphasis on multidetector-row CT. Eur J Radiol 2003;48(1):2–4. [9] Low R, Duber C, Schweden F, et al. Whole body spiral CT in primary diagnosis of patients with multiple trauma in emergency situations (Ganzkorper-Spiral-CT zur Primardiagnostik polytraumatisierter Patienten unter Notfallbedingungen). Rofo 1997;166(5):382–8. [10] Hidajat N, Wolf M, Nunnemann A, et al. Survey of conventional and spiral CT doses. Radiology 2001;218(2):395–401. [11] Seifert H, Hagen T, Bartylla K, et al. Patient doses from standard and spiral CT of the head using a fast twin-beam system. Br J Radiol 1997;70(839):1139–45. [12] Smith-Bindman R, Lipson J, Marcus R, et al. Radiation dose associated with common computed tomography examinations and the associated lifetime attributable risk of cancer. Arch Intern Med 2009;169(22):2078–86. [13] Brenner DJ, Hall EJ. Computed tomography—an increasing source of radiation exposure. N Engl J Med 2007;357(22):2277–84. [14] Bahner ML, Reith W, Zuna I, et al. Spiral CT vs incremental CT: is spiral CT superior in imaging of the brain? Eur Radiol 1998;8(3):416–20. [15] Kuntz R, Skalej M, Stefanou A. Image quality of spiral CT versus conventional CT in routine brain imaging. Eur J Radiol 1998;26(3):235–40. [16] Reichelt A, Zeckey C, Hildebrand F, et al. Imaging of the brain in polytraumatized patients comparing 64-row spiral CT with incremental (sequential) CT. Eur J Radiol 2012;81(4):789–93. [17] Wei SC, Ulmer S, Lev MH, et al. Value of coronal reformations in the CT evaluation of acute head trauma. AJNR Am J Neuroradiol 2010;31(2):334–9.
Contents lists available at ScienceDirect
American Journal of Emergency Medicine journal homepage: www.elsevier.com/locate/ajem
Original Contribution
The possibility of application of spiral brain computed tomography to traumatic brain injury☆ Daesung Lim, MD a, Soo Hoon Lee, MD b,⁎, Dong Hoon Kim, MD, PhD b,⁎⁎, Dae Seub Choi, MD, PhD c, Hoon Pyo Hong, MD, PhD a, d, Changwoo Kang, MD b, Jin Hee Jeong, MD b, Seong Chun Kim, MD b, Tae-Sin Kang, MD b a
Department of Emergency Medicine, Kyung Hee University Medical Center, Seoul, Republic of Korea Department of Emergency Medicine, Gyeongsang National University Hospital, Jinju, Gyeongsangnam-Do, Republic of Korea c Department of Radiology, Gyeongsang National University Hospital, Jinju, Gyeongsangnam-Do, Republic of Korea d Department of Radiology, Kyung Hee University Medical Center, Seoul, Republic of Korea b
a r t i c l e
i n f o
Article history: Received 12 May 2014 Received in revised form 18 June 2014 Accepted 18 June 2014
a b s t r a c t Objectives: The spiral computed tomography (CT) with the advantage of low radiation dose, shorter test time required, and its multidimensional reconstruction is accepted as an essential diagnostic method for evaluating the degree of injury in severe trauma patients and establishment of therapeutic plans. However, conventional sequential CT is preferred for the evaluation of traumatic brain injury (TBI) over spiral CT due to image noise and artifact. We aimed to compare the diagnostic power of spiral facial CT for TBI to that of conventional sequential brain CT. Methods: We evaluated retrospectively the images of 315 traumatized patients who underwent both brain CT and facial CT simultaneously. The hemorrhagic traumatic brain injuries such as epidural hemorrhage, subdural hemorrhage, subarachnoid hemorrhage, and contusional hemorrhage were evaluated in both images. Statistics were performed using Cohen's κ to compare the agreement between 2 imaging modalities and sensitivity, specificity, positive predictive value, and negative predictive value of spiral facial CT to conventional sequential brain CT. Results: Almost perfect agreement was noted regarding hemorrhagic traumatic brain injuries between spiral facial CT and conventional sequential brain CT (Cohen's κ coefficient, 0.912). To conventional sequential brain CT, sensitivity, specificity, positive predictive value, and negative predictive value of spiral facial CT were 92.2%, 98.1%, 95.9%, and 96.3%, respectively. Conclusion: In TBI, the diagnostic power of spiral facial CT was equal to that of conventional sequential brain CT. Therefore, expanded spiral facial CT covering whole frontal lobe can be applied to evaluate TBI in the future. © 2014 Elsevier Inc. All rights reserved.
1. Introduction Management of complex, multiple-trauma patient in emergency setting is always a challenge, requiring numerous analyses and treatments within limited time. The golden time for severe trauma patient usually means the time from its onset to the time of hemostatic procedure or surgical treatment, which is set at 60 minutes in several studies [1-5]. Improved evaluation and management in emergency department (ED) are especially important in nations that have already ☆ Conflict of interest statement: All authors have no conflict of interest. ⁎ Correspondence to: SH Lee, Department of Emergency Medicine, Gyeongsang National University Hospital, Gangnam-Ro 79, Jinju, Gyeongsangnam-Do, Republic of Korea, 660-702. Tel.: +82 55 750 8975; fax: +82 55 757 0514. ⁎⁎ Correspondence to: DH Kim, Department of Emergency Medicine, Gyeongsang National University Hospital, Gangnam-Ro 79, Jinju, Gyeongsangnam-Do, Republic of Korea, 660-702. Tel.: +82 55 750 8281; fax: +82 55 757 0514. E-mail addresses: [email protected] (S.H. Lee), [email protected] (D.H. Kim). http://dx.doi.org/10.1016/j.ajem.2014.06.020 0735-6757/© 2014 Elsevier Inc. All rights reserved.
established basic emergency medical services [6]. However, the prompt surgical management or radiological interventions such as vascular embolization for hemostasis in severe trauma patients are often delayed for various reasons in these nations. The whole-body computed tomography (CT) is accepted as an essential diagnostic method for evaluating the degree of injury in severe trauma patients and establishment of therapeutic plans [7-9]. Imaging techniques for CT have continuously improved since its first invention in 1979, and currently, 64-channel multidetector CT is more widely used. The conventional sequential CT had several limitations including poor visualization of posterior fossa and bony artifact. On the other hand, the spiral CT had the advantage of shorter test time required and its multidimensional reconstruction providing 3-dimensional image, although there were some limitations such as decreased image clarity. Therefore, it is now used for anatomical evaluation of practically all body parts with the development of the technology [10,11]. Technical advancements of spiral imaging technique have remarkably reduced the time of CT evaluation and
1052
D. Lim et al. / American Journal of Emergency Medicine 32 (2014) 1051–1054
could make CT into a criterion standard of evaluation even in the hemodynamically unstable patients regarded as the contraindication in the past. Recently, several emergency centers are now integrating the previously separated brain, facial, cervical, thoracic, and abdominal CT protocols together in efforts to minimize test time. However, still, most hospitals are using the conventional sequential imaging technique for brain CT, as there is notion that imaging technique for facial CT is unable to obtain clear image as the conventional technique due to image noise and artifacts generated from the skull. Recently, radiation exposure from CT is of particular concern. Although the issue is debatable, concern that even a single typical CT examination may confer a small but real risk of carcinogenesis is increasing [12,13]. The spiral CT has the advantage of low radiation dose in comparison with conventional CT. Average tube output of axial brain and face/orbit/ sinus protocol in GE Lightspeed VCT (General Electric Medical Systems, Milwaukee, WI, USA) used in this study was 51.1 mGy and 8.3 mGy in CT dose index, respectively. The objective of this study was to evaluate the diagnostic utility of facial CT in patients with head trauma by comparing the images of conventional sequential brain CT and spiral facial CT, respectively. Therefore, we hypothesized that, in patients with traumatic brain injury (TBI), the diagnostic power of spiral facial CT would be similar to that of conventional sequential brain CT.
(n = 56) older than 65 years. The proportion male patients was 71.7% (n = 226), and female patients, 28.3% (n = 89). Hemorrhage was identified in 32.4% (n = 102) of patients by conventional sequential brain CT. The concurrent positive result rate of facial CT was 92.2% (n = 94), whereas 7.8% (n = 8) were negative by facial CT. Negative result by brain CT was 67.6% (n = 213), whereas facial CT showed positive result in 1.9% (n = 4) from these brain CT negative patients (Table 1). Cohen's κ index between 2 techniques was 0.912, showing “almost perfect agreement.” The sensitivity, specificity, PPV, and NPV of facial CT based on result of brain CT were 92.2%, 98.1%, 95.9%, and 96.3%, respectively (Table 2). Among the 8 cases of brain CT and facial CT negative patients, 7 patients had frontal lobe hemorrhage, which is beyond the area covered by facial CT. Such 7 cases included 2 intracranial hemorrhages, 3 parafalcine subdural hematomas, and 2 subarachnoid hemorrhages. One case that had hemorrhage within the covered area of facial CT but interpreted as negative has small amount of subarachnoid hemorrhage. Of the 4 cases of brain CT–negative and facial CT–positive cases, 2 were a small amount subdural hematoma of the frontal lobe in proximity to the basal area. One case was later identified as false positive by follow-up brain and facial CT, whereas the other case with ambiguous facial CT image had no further evaluation.
2. Methods 4. Discussion During the period from January 1, 2013, to June 30, 2013, patients who visited the ED for head or facial trauma and were evaluated with brain CT and facial CT simultaneously were retrospectively reviewed of their medical charts. The protocol for head and/or facial trauma in our institution consists of conventional sequential brain CT followed by a spiral facial CT. The brain CT image is generated through conventional sequential imaging technique, taking images 5 mm apart starting from the basal section/plane of the brain following the long axis, tilted 20° to 40°. The spiral imaging technique takes images 2.5 mm apart, following the long axis tilted at 90°, spirally. All CT images from patients included in this study were generated by 64-channel multidetector CT (Lightspeed VCT), and the time difference of 2 tests was within 1 hour. Each study was usually completed within 5 minutes. The actual scan time of acquiring each image usually took less than 30 seconds. One team consisting of radiologist and emergency physician evaluated only conventional sequential brain CT without clinical information. The other team consisting of emergency radiologist and emergency physician evaluated only spiral facial CT without clinical information. The 2 test results were compared for agreement, and the cause of discrepancy was analyzed and summarized if discrepant. The test was classified as positive if epidural hemorrhage, subdural hemorrhage, subarachnoid hemorrhage, or contusional hemorrhage was visible from the images or was classified as negative. To evaluate the difference of resulting diagnosis of TBI between 2 techniques, the Cohen's κ index was used. The Cohen's κ index is a numerical representation of the agreement between 2 different tests, classified into 5 intervals: less than 0, 0.1 to 0.4, 0.41 to 0.6, 0.61 to 0.8, and greater than 0.81, interpreting below 0 as “no agreement” and above 0.81 as “almost perfect agreement.” Based on brain CT interpretation, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated. All statistical analyses were performed with the SPSS statistical package for Windows, version 19.0 (SPSS, Chicago, IL). The study was approved by the institutional review board of our hospital.
According to the study result, a high Cohen's κ index was found between conventional sequential and spiral image techniques. No statistical difference was found between 2 techniques in diagnosis of TBI. In addition, most hemorrhagic lesions seen on conventional sequential brain CT were mostly identifiable with facial CT obtained with spiral imaging technique, whereas small amount of basal hemorrhages, which were unidentified or ambiguous on brain CT, could be readily identified by facial CT. Although not included in this study, small pneumocephalus was only identified with spiral facial CT but not with conventional sequential brain CT. There were several previous studies that compared conventional and spiral imaging techniques. They concluded that the difference was minimal, but these studies were comparison of identifying normal structural discriminative powers and not hemorrhagic brain lesions. Two studies qualitatively compare first-generation spiral CT with conventional CT about their ability to identify physiologic brain structure [14,15]. Bahner et al [14] describe superiority of conventional brain CT in discrimination of nontraumatic brain lesions from normal brain tissue and qualitative aspects such as image noise and artifacts, therefore recommending spiral CT only when 3-dimensional reconstruction is necessary. Kuntz et al [15] state that 2 imaging techniques show no statistical difference in their ability to differentiate artificial contrast, gray mater, and white mater. These comparisons are limited by their comparison of ability to differentiate physiologic brain structure and qualitative comparison but not of differentiating pathologic lesions. A recent study by Reichelt et al [16] has found that conventional brain CT and spiral CT image by multidetector CT for multiple-trauma patients are not different in mechanical image quality and their ability to differentiate brain structures, announcing the possibility of clinically applying spiral CT imaging technique. Table 1 Cross-table between sequential brain CT and spiral facial CT
3. Results A total of 315 patients were included in the study. Their mean age was 45.1 ± 20.0 years, consisting of 8.9% (n = 28) younger than 16 years, 73.3% (n = 231) from 16 to younger than 65 years, and 17.8%
Sequential brain CT
Spiral facial CT
+ −
+
−
94 8
4 209
D. Lim et al. / American Journal of Emergency Medicine 32 (2014) 1051–1054
1053
Table 2 Statistical indices of spiral facial CT to sequential brain CT Variables
Results
Sensitivity Specificity PPV NPV
92.2% 98.1% 95.9% 96.3%
This study evaluates the possibility of application of spiral brain CT in TBI, which has not been established yet, with the advantage of directly comparing traumatic brain lesions and not the discriminative power of anatomical structures. Further reduction of test time is expected with the advancement of spiral CT through development of protocols integrating brain, facial, and cervical CT to evaluate complex, multiple-trauma patients. Furthermore, the spiral imaging technique has the several advantages of lower radiation dose, shorter test time, and multidimensional reconstruction providing 3-dimensional images in comparison with conventional sequential CT. In particular, the multidimensional reconstruction helps to detect and characterize for the evaluation of intracranial hemorrhage (ICH) compared with standard axial images alone. The advantages of reconstruction become clear for lesions that lie in the axial plane immediately adjacent to bony surfaces (the anterior cranial fossa, middle cranial fossa, and vertex). Coincidentally, these may also be locations that are at higher risk for injury in head trauma [17].
Fig. 2. Small epidural hematoma seen in spiral facial CT (B) missed in conventional brain CT (A).
This study, although not a prospective evaluation according to standardized protocols, has focused on the feature of facial CT covering nearly most brain mater except the frontal lobe and compared the diagnostic agreement of 2 techniques for hemorrhagic brain lesions. Fig. 1 is a case of pneumocephalus, although within the coverage of brain CT; brain CT result was negative and was only visible from facial CT. The case is an example showing the advantage of 2.5mm image interval of spiral facial CT over the conventional sequential brain CT with 5-mm image interval. Fig. 2 is a case of small amount right basal hemorrhage, which was also only visible from facial CT. The previous false-positive interpretation of facial CT can be attributable to lack of experience of evaluating brain parenchyma by facial CT in which reduction of false-positive interpretation is expected through establishment of positive interpretation criteria followed by clinical experience. There are several limitations in this study. First, patient selection was unstandardized as this study was performed retrospectively, which could include potential biases that were not explained in this study. Second, the object is limited on image; therefore, the patients were compared without regards to their clinical severity, and also, their surgical findings and follow-up results were not considered. Third, facial CT was not covering the whole brain parenchyma, as facial CT is not intended for such purposes, and the setting of coverage could differ from patient to patient. Lastly, the objective scale of the mechanical noise is not provided due to limitations of the instrument used in the institution. 5. Conclusion Fig. 1. Pneumocephalus in right frontal lobe. Equivocal finding in conventional brain CT (A) but clearly seen in spiral facial CT (B).
Spiral CT with relative advantages over conventional sequential CT has been limited of its utilization for brain CT imaging for few reasons.
1054
D. Lim et al. / American Journal of Emergency Medicine 32 (2014) 1051–1054
In this study of patients with TBI, the diagnostic power of spiral facial CT was equal to that of conventional sequential brain CT. Therefore, expanded spiral facial CT covering whole frontal lobe can be applied to evaluate hemorrhagic TBI in the future.
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