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Comparative study of DTS and CT in the skeletal trauma imaging diagnosis evaluation and radiation dose
European Journal of Radiology 82 (2013) e76–e80
Contents lists available at SciVerse ScienceDirect
European Journal of Radiology journal homepage: www.elsevier.com/locate/ejrad
Comparative study of DTS and CT in the skeletal trauma imaging diagnosis evaluation and radiation dose Wei Xia ∗ , Xiao-rui Yin 1 , Jing-Tao Wu 1 , Hai-tao Wu Clinical Medical College, Yangzhou University, Subei People’s Hospital of Jiangsu Province, Yangzhou 225001, China
a r t i c l e
i n f o
Article history: Received 2 July 2012 Received in revised form 19 September 2012 Accepted 21 September 2012 Keywords: Digital tomosynthesis Tomography Radiation dose Fracture
a b s t r a c t Purpose: To compare the differences between CT (Computed tomography) and DTS (digital tomosynthesis) in the X-ray radiation dose, and to analyze the sensitivity and specificity of each examination to check the suspected fractures and dislocations cases. Methods: From May 2010 to February 2012, 46 patients suspected with fractures and/or dislocations were prospectively enrolled to do the CT and DTS examination on the basis of the results of DR examination. Patients were considered ineligible if they were pregnant or lactating (female subjects only). The Yangzhou Regional Ethical Review Board in Jiangsu province, China approved this study. All 46 patients signed the informed consent. To contrast radiation dose between CT and DTS group of the patients and make statistical analysis. Two experienced experts assess the image quality by I–III grade and make statistical analysis. Draw the ROC of reader A and B according to the golden standard of clinical diagnosis. Results: The average effective dose of CT Group is 5.46 msv, while average effective dose of DTS group is 0.07 msv.There is significant statistical difference (t = 22.89, p < 0.01) between them. Calculate and compare the area under the ROC curve of reader A and B. The area of reader A by CT and DTS is 0.999 ± 0.005, 0.973 ± 0.022. The area of reader B is 0.961 ± 0.026, 0.944 ± 0.032. Both of them perform z test, and P > 0.05. There is no significant difference. Assess the uniformity of two readers with Kappa test. The Kappa value of reader A and B is respectively 0.757 and 0.783. When the value is greater than 0.75, two readers’ uniformity is considered well. The two readers’ sensitivity and specificity in diagnosing hidden skeletal trauma with CT and DTS are respectively 97.06% (reader A), 96.97% (reader B); 91.67% (reader A), 84.62% (reader B). Use the 2 test to them, then get the same result: P > 0.05. There is no statistical significant. Conclusion: Radiation dose of VolumnRAD DTS only account for 1.5% of CT, but its image can meet the requirements for clinical diagnosis. When fracture and/or dislocation is suspected with DR, VolumnRAD DTS can be recommended firstly as further checks. © 2012 Elsevier Ireland Ltd. All rights reserved.
1. Introduction Digital radiograph is the preferred examination to diagnose fracture and dislocation currently. Its virtue resides in its less radiation, economic, convenient and high spatial resolution image [1,2]. But DR can only manifest composite imaging, the fracture, dislocation and normal anatomical tissue are not easy to display because of anatomical structure overlapping. For this reason sometimes the symptom is severe while diagnosis result is ambiguous or negative patients need to be performed with CT, whose radiation dose is worthy of our noticeable especially such as women, children and physique weaker person [3,4]. Digital tomosynthesis fusion technology is that the X-ray tube gets scanned objects multiple angle projection data in a low dose exposure [5–7] after its exposure in
∗ Corresponding author. Tel.: +86 13805279355. E-mail address: [email protected] (W. Xia). 1 Both authors contributed equally to this work. 0720-048X/$ – see front matter © 2012 Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ejrad.2012.09.008
the track, through the computer reconstruction of arbitrary dimension, highly arbitrary image [8]. DTS can conquer overlapping and have obvious advantages in the diagnosis of fracture and dislocation especially in deep and complicate part [9]. In this paper, our aim is to study X-ray radiation dose differences of CT and DTS in skeletal system and analysis the image quality, sensitivity and specificity of two methods of concealed fracture, dislocation cases. 2. Materials and methods 1. Clinical materials: From May 2010 to February 2012, 46 patients suspected with fractures and/or dislocations were prospectively enrolled to do the CT and DTS examination on the basis of the results of DR examination. Patients were considered ineligible if they were pregnant or lactating (female subjects only). The Yangzhou Regional Ethical Review Board in Jiangsu province, China approved this study, all 46 patients signed the informed consent. These patients including 29 men and 17 women were divided into CT and DTS group. Median age was 38 years (range
W. Xia et al. / European Journal of Radiology 82 (2013) e76–e80
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Table 1 CT and DTS radiation dose statistics. Inspection site Limbs Head Atlantoaxial joint Spine Pelvis
Number 28 4 8 4 2
CTDlvol (mGy)
CT(DLP) (mGy cm)
23.68 23.68 23.68 23.68 23.68
456 445 388 517 620
Table 2 Radiation dose statistical analysis table of group CT and DTS. Check method
CT(DLP) DTS (total dose) The value of P
Radiation dosage average value
Effective dose average value
390.11 mGy cm 4.65 mGy P < 0.01
5.46 msv 0.07 msv P < 0.01
DTS/CT (%)
± ± ± ± ±
DTS (mGy)
154 152 136 130 40
4.1 4.7 5.5 6.6 7.3
± ± ± ± ±
CT ED (msv)
0.8 0.5 0.6 0.4 0.4
6.4 6.2 5.4 7.2 8.7
± ± ± ± ±
3–72). Among them 28 cases were suspected limb fracture, 4 cases were suspected nasal bone fracture, 4 cases were suspected spinal fractures, 2 cases were suspected pelvic fractures, 8 cases were suspected atlantoaxial joint semidislacation by DR. All the patients were informed consent. 2. Scanning technical parameters: (1) CT scans were performed on CT (General Electric Medical Systems, 16 Lightspeed VCT), 120 KV, 240 mA, pitch 0.984:1, rotary speed of 0.8 s/turn, thickness of 5 mm. (2) In group DTS GE Discovery XR650DTS was used. The distance from ball tube to bed surface is l00 cm. According to client site in patients with different exposure conditions, use 60–75 KVp, AEC (automatic exposure control) automatic exposure, 0–5 cm from the bed to the center to take 50 mm of the upper and lower range scan, Matrix for 1024 × 1024 of the image, image reconstruction slice thickness is 5 mm and 1 mm. 3. Radiation dose calculation: detailed record X-ray dose parameters of CT and DTS. Including the DTS: [total dose (mGy)]; CT: CTDlvol [CT dose index (mGy)], DLP [dose length product (mGy cm)], ED [effective dose (mSv)], ED = DLP × K, K represent conversion factors. k coefficient for this article is 0.014 provided by GE company. To calculate the average CT DLP value and average DTS total dose. 4. Image analysis: (1) Two skilled radiologists evaluate the DTS and CT imaging by double-blind method and grade them into five level: (I) there is no fracture or dislocation definitely; (II) there is high probability with no fracture or dislocation l; (III) uncertain diagnostic result. (IV) There is high probability with fracture or dislocation. (V) It is definite with fracture or dislocation. It is regarded as positive when the grade is larger than 3 and negative when the
DTS ED (msv) 0.06 0.07 0.08 0.09 0.10
± ± ± ± ±
0.01 0.01 0.01 0.01 0.01
Table 3 The CT and DTS in subtle fractures and dislocation of disease of the sensitivity and specificity. Reader
Groups
TP
FP
TN
FN
Sensitivity
Specificity
A A
CT DTS
33 31
1 2
11 11
1 2
B B
CT DTS
32 31
2 3
11 11
1 1
97.06% 93.94% P > 0.05 96.97% 96.87% P > 0.05
91.67% 84.62% P > 0.05 84.62% 78.57% P > 0.05
1.36%
Notes: [CT(DLP) and DTS(total dose) paired samples t test, t = 22.89 P < 0.01].
2.2 2.1 1.9 1.8 0.6
Notes: TP: true positive, FP: false positive, TN: true negative, FN: false negative.
grade is less than 3. To make ROC curves according to the data in the table by taking the clinical findings as the gold standard, which can show intuitively the difference of the sensitivity and specificity of the two methods in hidden fracture, dislocation diagnosis. 5 Diagnostic criteria: The final diagnosis is determined by clinical data of patients and the follow-up result, including: surgical operation record, MRI examination, clinical follow-up records etc. 6 Statistical processing: Using the SPSS 18 statistical software package for statistical analysis, and doing statistical analysis on radiation dose with paired t test. To draw the ROC curve of reader A and B who respectively analyze the lesion imaging on CT and DTS by using MedCalc 9.2 software and setting the final clinical results as the golden standard. Two inspection’s accuracy calculates the area under the curve, which is expressed by AZ . Using z test to the area difference under the curves by two methods. It is statistically significant if P < 0.05. Kappa test is used to check consistency of assessment of two readers. There is good consistency if Kappa ≥ 0.75, general if 0.75 ≥ Kappa ≥ 0.4, poor if Kappa ≤ 0.4. To check the sensitivity and specificity of two methods with paired 2 test. There was statistically significant if P < 0.05. 3. Results 1. Radiation dose comparison To do the statistical analysis on CT and DTS radiation dose (Table 1) and use paired sample t test, t = 22.89, P < 0.01 for CT (DLP)
Fig. 1. The ROC curve of the radiographic evaluation of CT and DTS for hidden fracture and dislocation.
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Fig. 2. The image analyses of concealment fracture and dislocation from DR, CT, DTS. A1–3: from the same case, A1 is scanned by DR, which cannot clearly show the fracture line below intercondylar eminence. A2 is scanned by CT, which can clearly show the fracture line below intercondylar eminence. A3 is scanned by DTS, which can clearly show the fracture line below intercondylar eminence. B1–3: from the same case. B1 is scanned by DR, which cannot clearly show the fracture line of nasal bone. B2 is scanned by CT, which can clearly show the fracture line of nasal bone. B3 is scanned by CT, which can clearly show the fracture line of nasal bone. C1–3: are from the same case. C1 is scanned by DR, but this patient can show us the articulatio atlantoepistrophica because of the pain. C2 is scanned by CT, which can clearly show the relocation of the articulatio atlantoepistrophica. C3 is scanned by DTS, which can clearly show the relocation of the articulatio atlantoepistrophica.
and DTS (total dose) (Table 2). The radiation quantity differences of two methods are statistically significant. 2 CT and DTS image assessment and analysis (1) There were 35 positive cases, 11 negative cases among 46 patients according to the clinical final diagnosis (golden standard). Using the ROC curve to display the radiological evaluation of Reader A and B on the two examinations: CT and DTS area of reader A under the curve was respectively 0.999 + 0.005 and 0.973 + 0.022. z test was used to check it, P > 0.05, no statistically significant; CT and DTS area of reader B under the curve was respectively 0.961 + 0.026 and 0.944 + 0.032. z test was used to check it, P > 0.05, no statistical significance (Fig. 1). (2) Using the Kappa test to evaluate consistency in subtle fractures and dislocation of reader A and B for CT and DTS, the Kappa
value was 0.912. If the Kappa value > 0.75, it means the consistency of two readers is very good. (3) Read A and B for CT and DTS in subtle fractures and dislocations disease sensitivity respectively 97.06%, 93.94% (reader A); 96.97%, 96.87 (reader B); specificity 91.67%, 84.62% (reader A); 84.62%, 78.57% (reader B). The sensitivity and specificity of Reader A and B for CT and DTS in subtle fractures and dislocation of diseases were tested by 2 . All P > 0.05, no statistically significant (Table 3). 4. Conclusion and discussions 1. DR is currently the preferred exam of bone and joint trauma imaging. But some conceal fracture and dislocation of the patients often cannot be checked clearly with DR. This is because
W. Xia et al. / European Journal of Radiology 82 (2013) e76–e80
DR imaging is the projection of various tissues and structures of the body in the plane. We often encountered these situations that the organization and structure of region of interest overlap with others. It may result missed diagnosis and misdiagnosis. Then further exam will be performed in order to avoid missed diagnosis and misdiagnosis. And CT is always the first choice. With the development of science and technology, many new types of CT such as 128 rows of dual-source CT, Dual source CT, Light Speed CT750 HD, GE HDCT are emerged quickly. With the popular application of CT, these new equipment add more radiation dose as well as bring more excellent image quality. The more radiation dose People are subjected with, the bigger the potential harm will be. Thus lowering the doses of radiation has got more and more experts’ attentions [10]. How to use the minimum radiation dose to satisfy requirement of diagnosis has become the key research task of radiology department currently. 2. Conventional tomography plays an important role in previous radiography. But because of its complicated operation, time-consuming, laborious and once imaging just for a level photography [11], especially with the CT and MSCT appearing, tomography gradually withdrew from the historical stage. Digital tomography fusion (digital tomosynthesis, referred to as DTS) is a new technology. It receives the multiple angle projection data after once low dose exposure of the tube from the track gets scanned objects, through the computer reconstruction of arbitrary dimension, highly arbitrary image. The principle is that the tube and the detector being parallel to the patients with synchronous reverse movement, a series of projection data are collected, relying on computer processing workstation, using a filtered back projection algorithm, matrix inversion, transposition and recombination, laminated reset processing algorithm and fuzzy processing [12,13], and reconstruct the examination part of any coronary dimensions of clear digital image, also can adjust the posture for sagittal images. Conventional backprojection tomography often produces reconstructions obscured by substantial tomographic blur. Matrix inversion tomosynthesis (MITS) uses both linear systems theory and a priori knowledge of the imaging geometry, to make it easier to distinguish between true structure and overlying tomographic blur. 3. This paper is focused on studying the differences between DTS and CT in the radiation dose and the iconography diagnosis of hidden fracture and dislocation. The DTS used in the present study, the X-ray tube performed a vertical continuous movement from −15◦ to +15◦ around the standard orthogonal posteroanterior position. The DTS used in the present study collects 30–50 projection images, each with a radiation dose corresponding to an effective dose to a standard patient of approximately about 2 Sv. Thus, the resulting total average effective dose is 0.07 mSv. However, it only approximately accounts for 1.5% of CT examination (5.46 mSv). The proportions of ROC curve (Table 1), which represent the iconography diagnosis credibility by DTS and CT to diagnose hidden fracture and dislocation, are 0.961 ± 0.026, 0.944 ± 0.032 (Reader A), 0.999 ± 0.005, 0.973 ± 0.022 (Reader B). Verifying by z test, P > 0.05, there is no statistics meaning. The sensitivities of CT and DTS of diagnosing hidden fracture and dislocation are 91.67%, 84.62% (Reader A), 84.62%, 78.57% (Reader B). And verifying by 2 test, P > 0.05, so there is no statistics meaning (Table 3). All of those tell us that the radiation dose of DTS falls considerably compared with CT, but the iconography diagnosis credibility of hidden fracture and dislocation is just the same with CT. From the images (Fig. 2) analysis of DTS and CT, we can test fracture and dislocation clearly, which cannot view clearly by DR. So by the researches of this paper we confirm that DTS can clearly display the internal, deep structure and surrounding tissues relationship of these check parts in skeletal system [14], thus DTS can replace CT for the further check of the
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DR suspected fractures and dislocations cases. Recently, there are foreign researches reported that DTS has a higher sensitivity in checking out breast suspicious nodules [15,16], chest suspicious nodules [17], belly stone and so on [18]. Therefore DTS examinations need our further researches and explorations. 4. The writer summarizes the advantages and disadvantages of DTS by daily experiences. The advantages of DTS comparing with CT: (1) convenience: if the fracture and dislocation are suspected, the doctors can do DTS instantly without moving the patients after the examination of DR. (2) Lower radiation dose. The radiation dose of DTS is only 1.5% of that in CT, and lower than 5% [5–7] that is reported by some references. (3) Economy. The price of CT is often around 500 Yuan. But the price of DTS is just around 160 Yuan. The differences of price are so big. (4) Higher image spatial resolution. Image spatial resolution of DTS is higher than that of CT, besides this DTS can show the bone anatomic structure more direct than CT, through DTS, we are able to get more details. 5. The disadvantages of DTS compared with CT. (1) DTS can only take the sagittal view and coronal view, most of DTS cannot get axial view. (2) The image density resolution of DTS is not as good as CT, which cannot measure the mean density. (3) DTS cannot perform three-dimensional reconstruction [19,20]. In conclusion, DTS as a new digital tomography technique, has a prominent superiority compared with CT. In the aspect of bone trauma iconography, CT and DTS have their own strong points. So DTS can be the prime extension and complement of regular X scanning in bone trauma iconography to take its advantages of lower radiation dose, convenience and economy.
Conflict of interest We declare that we have no conflict of interest.
References [1] Chotas HG, Dobbins JT, Ravin CE. Principles of digital radiography with large, electronically readable detectors. A review of the basic. Radiology 1999;210(2):595–9. [2] Hamers S, Freyschmidt J. Digital radiography with an electronic flat panel detector. First experience in skeletal diagnostics. Medicamundi 1998;42(1):2–6. [3] Verdun FR, Gutierrez D, Vader JP, et al. CT radiation dose in children: a survey to establish age-based diagnostic reference levels in Switzerland. European Radiology 2008;18(9), 1980, 1986. [4] Lee CH, Coo JM, Ye HJ, et al. Radiation dose modulation techniques in the multidetector CT era: from basics to practice. Radiographics 2008;28(5), 145l-1459. [5] Fuji K, Aoyama T, Koyama S, et al. Comparative evaluation of organ and effective dose for pediatric patients with those for adults an chest and abdominal CT examinations. British Journal of Radiology 2007;80(956):657–67. [6] Vikgren J, Zachrisson S, Svalkvist A, et al. Comparison of chest tomosynthesis and chest radiography for detection of pulmonary nodules: human observer study of clinical cases. Radiology 2008;249:1034–41. [7] Dobbins JT, Mc Adams HP, Song JW, et al. Digital tomosynthesis of the chest for lung nodule detection: interim sensitivity results from an ongoing NIHsponsored trial. Medical Physics 2008;35:2554–7. [8] Haruhiko M, Toshiyuki Y, Mori T, et al. Optimizing parameters for flat-panel detector digital tomosynthesis. Radiographics 2010;30:549–62. [9] Tian J, Gong WX, Zhang DX, et al. The application of digital tomosynthesis in diagnosis of occult bone fracture. Chinese Journal of Radiology 2011;5(June (6)):566–8 [in Chinese]. [10] Nickoloff EL, Alderson PO. Radiation exposures to patients from CT: reality, public perception and policy. American Journal of Roentqenology 2001;176: 285–7. [11] Grant DG. Tomosynthesis: a three-dimensional radiographic imaging technique. IEEE Transactions on Biomedical Engineering 1972;19(1):20–8. [12] Dobbins 3rd JT, Godfrey DJ. Digital X-ray tomosynthesis: current state of the art and clinical potential. Physics in Medicine and Biology 2003;48:R65–106. [13] McAdams HP, Samei E, Dobbins 3rd JT, et al. Recent advances in chest radiography. Radiology 2006;241:663. [14] Mermuys K, Vanslambrouck K, Goubau J, Steyaert L, Casselman JW. Use of digital tomosynthesis: case report of a suspected scaphoid fracture and technique. Skeletal Radiology 2008;37:569–72.
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[15] Hakim CM, Chough DM, Ganott MA, et al. Digital breast tomosynthesis in the diagnostic environment: a subjective side-by-side review. American Journal of Roentqenology 2010;195(2):W172–6. [16] Helvie MA. Digital mammography imaging: breast tomosynthesis and advanced applications. Radiologic Clinics of North America 2010;48(5): 917–29. [17] Santoro J, Kriminski S, Lovelock DM, et al. Evaluation of respiration-correlated digital tomosynthesis in lung. Medical Physics 2010;37(March (3)):1237–45.
[18] Zachrisson S, Vikgren J, Svalkvist A, et al. Effect of clinical experience of chest tomosynthesis on detection of pulmonary nodules. Acta Radiologica 2009;50:884–91. [19] Revel MP, Lefort C, Bissery A, et al. Pulmonary nodules: preliminary experience with three-dimensional evaluation. Radiology 2004;231: 459–66. [20] Kostis WJ, Yankelevitz DF, Reeves AP, et al. Small pulmonary nodules: reproducibility of three-dimensional volumetric measurement and estimation of time to follow-up CT. Radiology 2004;231: 446–52.
Contents lists available at SciVerse ScienceDirect
European Journal of Radiology journal homepage: www.elsevier.com/locate/ejrad
Comparative study of DTS and CT in the skeletal trauma imaging diagnosis evaluation and radiation dose Wei Xia ∗ , Xiao-rui Yin 1 , Jing-Tao Wu 1 , Hai-tao Wu Clinical Medical College, Yangzhou University, Subei People’s Hospital of Jiangsu Province, Yangzhou 225001, China
a r t i c l e
i n f o
Article history: Received 2 July 2012 Received in revised form 19 September 2012 Accepted 21 September 2012 Keywords: Digital tomosynthesis Tomography Radiation dose Fracture
a b s t r a c t Purpose: To compare the differences between CT (Computed tomography) and DTS (digital tomosynthesis) in the X-ray radiation dose, and to analyze the sensitivity and specificity of each examination to check the suspected fractures and dislocations cases. Methods: From May 2010 to February 2012, 46 patients suspected with fractures and/or dislocations were prospectively enrolled to do the CT and DTS examination on the basis of the results of DR examination. Patients were considered ineligible if they were pregnant or lactating (female subjects only). The Yangzhou Regional Ethical Review Board in Jiangsu province, China approved this study. All 46 patients signed the informed consent. To contrast radiation dose between CT and DTS group of the patients and make statistical analysis. Two experienced experts assess the image quality by I–III grade and make statistical analysis. Draw the ROC of reader A and B according to the golden standard of clinical diagnosis. Results: The average effective dose of CT Group is 5.46 msv, while average effective dose of DTS group is 0.07 msv.There is significant statistical difference (t = 22.89, p < 0.01) between them. Calculate and compare the area under the ROC curve of reader A and B. The area of reader A by CT and DTS is 0.999 ± 0.005, 0.973 ± 0.022. The area of reader B is 0.961 ± 0.026, 0.944 ± 0.032. Both of them perform z test, and P > 0.05. There is no significant difference. Assess the uniformity of two readers with Kappa test. The Kappa value of reader A and B is respectively 0.757 and 0.783. When the value is greater than 0.75, two readers’ uniformity is considered well. The two readers’ sensitivity and specificity in diagnosing hidden skeletal trauma with CT and DTS are respectively 97.06% (reader A), 96.97% (reader B); 91.67% (reader A), 84.62% (reader B). Use the 2 test to them, then get the same result: P > 0.05. There is no statistical significant. Conclusion: Radiation dose of VolumnRAD DTS only account for 1.5% of CT, but its image can meet the requirements for clinical diagnosis. When fracture and/or dislocation is suspected with DR, VolumnRAD DTS can be recommended firstly as further checks. © 2012 Elsevier Ireland Ltd. All rights reserved.
1. Introduction Digital radiograph is the preferred examination to diagnose fracture and dislocation currently. Its virtue resides in its less radiation, economic, convenient and high spatial resolution image [1,2]. But DR can only manifest composite imaging, the fracture, dislocation and normal anatomical tissue are not easy to display because of anatomical structure overlapping. For this reason sometimes the symptom is severe while diagnosis result is ambiguous or negative patients need to be performed with CT, whose radiation dose is worthy of our noticeable especially such as women, children and physique weaker person [3,4]. Digital tomosynthesis fusion technology is that the X-ray tube gets scanned objects multiple angle projection data in a low dose exposure [5–7] after its exposure in
∗ Corresponding author. Tel.: +86 13805279355. E-mail address: [email protected] (W. Xia). 1 Both authors contributed equally to this work. 0720-048X/$ – see front matter © 2012 Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ejrad.2012.09.008
the track, through the computer reconstruction of arbitrary dimension, highly arbitrary image [8]. DTS can conquer overlapping and have obvious advantages in the diagnosis of fracture and dislocation especially in deep and complicate part [9]. In this paper, our aim is to study X-ray radiation dose differences of CT and DTS in skeletal system and analysis the image quality, sensitivity and specificity of two methods of concealed fracture, dislocation cases. 2. Materials and methods 1. Clinical materials: From May 2010 to February 2012, 46 patients suspected with fractures and/or dislocations were prospectively enrolled to do the CT and DTS examination on the basis of the results of DR examination. Patients were considered ineligible if they were pregnant or lactating (female subjects only). The Yangzhou Regional Ethical Review Board in Jiangsu province, China approved this study, all 46 patients signed the informed consent. These patients including 29 men and 17 women were divided into CT and DTS group. Median age was 38 years (range
W. Xia et al. / European Journal of Radiology 82 (2013) e76–e80
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Table 1 CT and DTS radiation dose statistics. Inspection site Limbs Head Atlantoaxial joint Spine Pelvis
Number 28 4 8 4 2
CTDlvol (mGy)
CT(DLP) (mGy cm)
23.68 23.68 23.68 23.68 23.68
456 445 388 517 620
Table 2 Radiation dose statistical analysis table of group CT and DTS. Check method
CT(DLP) DTS (total dose) The value of P
Radiation dosage average value
Effective dose average value
390.11 mGy cm 4.65 mGy P < 0.01
5.46 msv 0.07 msv P < 0.01
DTS/CT (%)
± ± ± ± ±
DTS (mGy)
154 152 136 130 40
4.1 4.7 5.5 6.6 7.3
± ± ± ± ±
CT ED (msv)
0.8 0.5 0.6 0.4 0.4
6.4 6.2 5.4 7.2 8.7
± ± ± ± ±
3–72). Among them 28 cases were suspected limb fracture, 4 cases were suspected nasal bone fracture, 4 cases were suspected spinal fractures, 2 cases were suspected pelvic fractures, 8 cases were suspected atlantoaxial joint semidislacation by DR. All the patients were informed consent. 2. Scanning technical parameters: (1) CT scans were performed on CT (General Electric Medical Systems, 16 Lightspeed VCT), 120 KV, 240 mA, pitch 0.984:1, rotary speed of 0.8 s/turn, thickness of 5 mm. (2) In group DTS GE Discovery XR650DTS was used. The distance from ball tube to bed surface is l00 cm. According to client site in patients with different exposure conditions, use 60–75 KVp, AEC (automatic exposure control) automatic exposure, 0–5 cm from the bed to the center to take 50 mm of the upper and lower range scan, Matrix for 1024 × 1024 of the image, image reconstruction slice thickness is 5 mm and 1 mm. 3. Radiation dose calculation: detailed record X-ray dose parameters of CT and DTS. Including the DTS: [total dose (mGy)]; CT: CTDlvol [CT dose index (mGy)], DLP [dose length product (mGy cm)], ED [effective dose (mSv)], ED = DLP × K, K represent conversion factors. k coefficient for this article is 0.014 provided by GE company. To calculate the average CT DLP value and average DTS total dose. 4. Image analysis: (1) Two skilled radiologists evaluate the DTS and CT imaging by double-blind method and grade them into five level: (I) there is no fracture or dislocation definitely; (II) there is high probability with no fracture or dislocation l; (III) uncertain diagnostic result. (IV) There is high probability with fracture or dislocation. (V) It is definite with fracture or dislocation. It is regarded as positive when the grade is larger than 3 and negative when the
DTS ED (msv) 0.06 0.07 0.08 0.09 0.10
± ± ± ± ±
0.01 0.01 0.01 0.01 0.01
Table 3 The CT and DTS in subtle fractures and dislocation of disease of the sensitivity and specificity. Reader
Groups
TP
FP
TN
FN
Sensitivity
Specificity
A A
CT DTS
33 31
1 2
11 11
1 2
B B
CT DTS
32 31
2 3
11 11
1 1
97.06% 93.94% P > 0.05 96.97% 96.87% P > 0.05
91.67% 84.62% P > 0.05 84.62% 78.57% P > 0.05
1.36%
Notes: [CT(DLP) and DTS(total dose) paired samples t test, t = 22.89 P < 0.01].
2.2 2.1 1.9 1.8 0.6
Notes: TP: true positive, FP: false positive, TN: true negative, FN: false negative.
grade is less than 3. To make ROC curves according to the data in the table by taking the clinical findings as the gold standard, which can show intuitively the difference of the sensitivity and specificity of the two methods in hidden fracture, dislocation diagnosis. 5 Diagnostic criteria: The final diagnosis is determined by clinical data of patients and the follow-up result, including: surgical operation record, MRI examination, clinical follow-up records etc. 6 Statistical processing: Using the SPSS 18 statistical software package for statistical analysis, and doing statistical analysis on radiation dose with paired t test. To draw the ROC curve of reader A and B who respectively analyze the lesion imaging on CT and DTS by using MedCalc 9.2 software and setting the final clinical results as the golden standard. Two inspection’s accuracy calculates the area under the curve, which is expressed by AZ . Using z test to the area difference under the curves by two methods. It is statistically significant if P < 0.05. Kappa test is used to check consistency of assessment of two readers. There is good consistency if Kappa ≥ 0.75, general if 0.75 ≥ Kappa ≥ 0.4, poor if Kappa ≤ 0.4. To check the sensitivity and specificity of two methods with paired 2 test. There was statistically significant if P < 0.05. 3. Results 1. Radiation dose comparison To do the statistical analysis on CT and DTS radiation dose (Table 1) and use paired sample t test, t = 22.89, P < 0.01 for CT (DLP)
Fig. 1. The ROC curve of the radiographic evaluation of CT and DTS for hidden fracture and dislocation.
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Fig. 2. The image analyses of concealment fracture and dislocation from DR, CT, DTS. A1–3: from the same case, A1 is scanned by DR, which cannot clearly show the fracture line below intercondylar eminence. A2 is scanned by CT, which can clearly show the fracture line below intercondylar eminence. A3 is scanned by DTS, which can clearly show the fracture line below intercondylar eminence. B1–3: from the same case. B1 is scanned by DR, which cannot clearly show the fracture line of nasal bone. B2 is scanned by CT, which can clearly show the fracture line of nasal bone. B3 is scanned by CT, which can clearly show the fracture line of nasal bone. C1–3: are from the same case. C1 is scanned by DR, but this patient can show us the articulatio atlantoepistrophica because of the pain. C2 is scanned by CT, which can clearly show the relocation of the articulatio atlantoepistrophica. C3 is scanned by DTS, which can clearly show the relocation of the articulatio atlantoepistrophica.
and DTS (total dose) (Table 2). The radiation quantity differences of two methods are statistically significant. 2 CT and DTS image assessment and analysis (1) There were 35 positive cases, 11 negative cases among 46 patients according to the clinical final diagnosis (golden standard). Using the ROC curve to display the radiological evaluation of Reader A and B on the two examinations: CT and DTS area of reader A under the curve was respectively 0.999 + 0.005 and 0.973 + 0.022. z test was used to check it, P > 0.05, no statistically significant; CT and DTS area of reader B under the curve was respectively 0.961 + 0.026 and 0.944 + 0.032. z test was used to check it, P > 0.05, no statistical significance (Fig. 1). (2) Using the Kappa test to evaluate consistency in subtle fractures and dislocation of reader A and B for CT and DTS, the Kappa
value was 0.912. If the Kappa value > 0.75, it means the consistency of two readers is very good. (3) Read A and B for CT and DTS in subtle fractures and dislocations disease sensitivity respectively 97.06%, 93.94% (reader A); 96.97%, 96.87 (reader B); specificity 91.67%, 84.62% (reader A); 84.62%, 78.57% (reader B). The sensitivity and specificity of Reader A and B for CT and DTS in subtle fractures and dislocation of diseases were tested by 2 . All P > 0.05, no statistically significant (Table 3). 4. Conclusion and discussions 1. DR is currently the preferred exam of bone and joint trauma imaging. But some conceal fracture and dislocation of the patients often cannot be checked clearly with DR. This is because
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DR imaging is the projection of various tissues and structures of the body in the plane. We often encountered these situations that the organization and structure of region of interest overlap with others. It may result missed diagnosis and misdiagnosis. Then further exam will be performed in order to avoid missed diagnosis and misdiagnosis. And CT is always the first choice. With the development of science and technology, many new types of CT such as 128 rows of dual-source CT, Dual source CT, Light Speed CT750 HD, GE HDCT are emerged quickly. With the popular application of CT, these new equipment add more radiation dose as well as bring more excellent image quality. The more radiation dose People are subjected with, the bigger the potential harm will be. Thus lowering the doses of radiation has got more and more experts’ attentions [10]. How to use the minimum radiation dose to satisfy requirement of diagnosis has become the key research task of radiology department currently. 2. Conventional tomography plays an important role in previous radiography. But because of its complicated operation, time-consuming, laborious and once imaging just for a level photography [11], especially with the CT and MSCT appearing, tomography gradually withdrew from the historical stage. Digital tomography fusion (digital tomosynthesis, referred to as DTS) is a new technology. It receives the multiple angle projection data after once low dose exposure of the tube from the track gets scanned objects, through the computer reconstruction of arbitrary dimension, highly arbitrary image. The principle is that the tube and the detector being parallel to the patients with synchronous reverse movement, a series of projection data are collected, relying on computer processing workstation, using a filtered back projection algorithm, matrix inversion, transposition and recombination, laminated reset processing algorithm and fuzzy processing [12,13], and reconstruct the examination part of any coronary dimensions of clear digital image, also can adjust the posture for sagittal images. Conventional backprojection tomography often produces reconstructions obscured by substantial tomographic blur. Matrix inversion tomosynthesis (MITS) uses both linear systems theory and a priori knowledge of the imaging geometry, to make it easier to distinguish between true structure and overlying tomographic blur. 3. This paper is focused on studying the differences between DTS and CT in the radiation dose and the iconography diagnosis of hidden fracture and dislocation. The DTS used in the present study, the X-ray tube performed a vertical continuous movement from −15◦ to +15◦ around the standard orthogonal posteroanterior position. The DTS used in the present study collects 30–50 projection images, each with a radiation dose corresponding to an effective dose to a standard patient of approximately about 2 Sv. Thus, the resulting total average effective dose is 0.07 mSv. However, it only approximately accounts for 1.5% of CT examination (5.46 mSv). The proportions of ROC curve (Table 1), which represent the iconography diagnosis credibility by DTS and CT to diagnose hidden fracture and dislocation, are 0.961 ± 0.026, 0.944 ± 0.032 (Reader A), 0.999 ± 0.005, 0.973 ± 0.022 (Reader B). Verifying by z test, P > 0.05, there is no statistics meaning. The sensitivities of CT and DTS of diagnosing hidden fracture and dislocation are 91.67%, 84.62% (Reader A), 84.62%, 78.57% (Reader B). And verifying by 2 test, P > 0.05, so there is no statistics meaning (Table 3). All of those tell us that the radiation dose of DTS falls considerably compared with CT, but the iconography diagnosis credibility of hidden fracture and dislocation is just the same with CT. From the images (Fig. 2) analysis of DTS and CT, we can test fracture and dislocation clearly, which cannot view clearly by DR. So by the researches of this paper we confirm that DTS can clearly display the internal, deep structure and surrounding tissues relationship of these check parts in skeletal system [14], thus DTS can replace CT for the further check of the
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DR suspected fractures and dislocations cases. Recently, there are foreign researches reported that DTS has a higher sensitivity in checking out breast suspicious nodules [15,16], chest suspicious nodules [17], belly stone and so on [18]. Therefore DTS examinations need our further researches and explorations. 4. The writer summarizes the advantages and disadvantages of DTS by daily experiences. The advantages of DTS comparing with CT: (1) convenience: if the fracture and dislocation are suspected, the doctors can do DTS instantly without moving the patients after the examination of DR. (2) Lower radiation dose. The radiation dose of DTS is only 1.5% of that in CT, and lower than 5% [5–7] that is reported by some references. (3) Economy. The price of CT is often around 500 Yuan. But the price of DTS is just around 160 Yuan. The differences of price are so big. (4) Higher image spatial resolution. Image spatial resolution of DTS is higher than that of CT, besides this DTS can show the bone anatomic structure more direct than CT, through DTS, we are able to get more details. 5. The disadvantages of DTS compared with CT. (1) DTS can only take the sagittal view and coronal view, most of DTS cannot get axial view. (2) The image density resolution of DTS is not as good as CT, which cannot measure the mean density. (3) DTS cannot perform three-dimensional reconstruction [19,20]. In conclusion, DTS as a new digital tomography technique, has a prominent superiority compared with CT. In the aspect of bone trauma iconography, CT and DTS have their own strong points. So DTS can be the prime extension and complement of regular X scanning in bone trauma iconography to take its advantages of lower radiation dose, convenience and economy.
Conflict of interest We declare that we have no conflict of interest.
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