Development of dual-energy subtraction digital chest photography

Development of dual-energy subtraction digital chest photography
Department of imaging diagnostics, Cancer Hospital, Peking Union Medical College, Chinese Emy of Medical Sciences, www.yxyxjs.com 'x % R! M0 e + O) N. J; Z8 ~ # H * Z & i8 [
Luo douqiang Shi Mulan Chen Da Wei Liu Jin Qi Xu Feng Yang Feng Chang Wu Ning Zhou chunwu Yu, Shen Hailong, Hailong, Hailong Wang, Medical Imaging Technology Forum, Medical Imaging Technology Network, website of professional imaging technology industry, medical imaging, medical imaging technology, medical imaging technology, radiology technology, X-ray technology, CT, B-ultrasound, color Doppler ultrasound, MRI, Dr, Cr, PACs, ect, pet, SPECT, TTM, RIS, computer photography, Digital Line photography, X-ray, X-ray, diagnostics, ultrasound, US, radiology, medical, DSA, 3D images, medical consumables, interventional equipment, film, medical software-J % ^ 4 D, E, _ & P # Y: ^ + | 'G

The concept of double-energy subtraction was proposed in 1925 and was applied to the clinic only in 1970s, for example, separation of Iodine contrast agent during angiography, hardening effect of high density objects in CT scans, and measurement of bone density, in 1980s, it basically started the application research in chest photography in sync with the math technology.
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Principle of dual-energy subtraction: 1x's5 o * {W; |
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Diagnostic X-ray films use a low-energy X-ray bundle. when it passes through the human body, it degrades mainly due to the Photoelectric Absorption Effect and the Compton scattering effect, the intensity of the photoelectric absorption effect is positively correlated with the atomic weight of the exposed substances. It is the main way for high-density substances such as calcium, bone, Iodine contrast agent to attenuation X-ray photon energy, the Compton scattering effect has nothing to do with the atomic weight of the substance, and has a functional relationship with the electronic density of the tissue, mainly occurs in soft tissue. The images obtained from conventional X-ray images contain the comprehensive information of the above two kinds of attenuation effects. The energy attenuation of X-ray photon by using bone and soft tissue in Two-energy subtraction films is different, and the difference in the Photoelectric Absorption Effect of substances with different atomic weights will be more strongly reflected in the changes in the attenuation intensity of X-ray bundles with different energy, the intensity of the Compton scattering effect is unrelated to the energy of the incident X-ray in a wide range. negligible characteristics are used to separate the information of the two effects, selective Removal of the attenuation information of the bone or soft tissue to produce the so-called tissue characteristic image that can reflect the chemical composition of the tissue-that is, the pure soft tissue image and the bone image.
Method for dual-energy subtraction: 4 Q # L1 ^ & A. R. D
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The dual-energy subtraction film can be achieved through two exposures and one exposure method.
(1) method 'x (Q3 H! P; B, J # B
Yi Yun, Shen Hailong, Hailong, Hailong Wang, Medical Imaging Technology Forum, Medical Imaging Technology Network, professional imaging technology industry website, medical imaging, medical imaging technology, medical imaging technology, radiation technology, x-ray technology, CT, B-ultrasound, color Doppler ultrasound, MRI, Dr, Cr, PACs, ect, pet, SPECT, TTM, RIS, computer photography, Digital Line photography, X-ray, x-ray, diagnostics, ultrasound, US, radiology, medical, DSA, 3D images, medical consumables, interventional equipment, film, medical software $ \ 7 V7 R8 N) a-_-J4 W
The two-shot method means to independently expose the subject using different X-ray ball tubes (kVp) to obtain two images or data, perform image subtraction or data separation and integration to generate the soft tissue density image, bone density image, and/or common chest X-ray. The used low-energy X-ray peak value is 60kvp ~ 85kvp and high-energy X-ray peak values: 120 kVp ~ Within the range of 140kvp. The Research of chest dual-energy subtraction films started with the two-shot method, although it was used in the film increase screen system and scan projection Film System (SPR) computed Radiography (CR) and digital radiography (DR), but most of them are only reports of the Nature of laboratory research and are basically not used in clinic, it is mainly because the time difference between two exposures is difficult to shorten to a satisfactory range, and it cannot effectively eliminate the false encoding between the two images caused by the motion displacement of the exposed objects between the two exposures. Until Direct Digital Radiography (DDR), revolution? XQ/I (gemedical systems, USA) was introduced because the time difference between two exposures can be reduced to 200 ms using a digital flat panel detector (DFP, the patient can complete the examination with one breath, which greatly reduces the error code. In addition, because the DFP can detect the quantum efficiency (detectable quantum efficiency, DQE), the energy separation efficiency is high, with a high degree of parallelism, the output energy of the ball canal can be reduced without sacrificing the quality. The output of low energy and high energy X-ray is 60 ~ 80kvp and 110 ~ 150kvp, and DFP directly converts the collected information into a visual image. The automatic post-processing speed is fast, and three images are obtained within several minutes-common digital chest X-ray, soft tissue image, and bone image, therefore, it can be used as a routine additional examination for chest X-ray. Www.yxyxjs.com * B $ ?! K7 J # H: X1 @
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(2) One-shot dual-energy subtraction film # G $] "} 5 J * g
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The method of one exposure is to separate the energy of the X-ray child output after the attenuation of the exposed object to obtain two images with different energy. This method was first proposed by speller in 1983 to eliminate the error code of the two exposure methods. They installed two sets of film increase screen systems in the special dark box, the two are separated by a copper filter plate. Films with lower energy are imaged at the front, while high energy X-ray filters are imaged at the back of the film to achieve energy separation. Barnes and Ishigaki respectively apply the one-shot method to various Cr chest photography systems, and use a double-layer image board to replace the dual-film photosensitive Screen System. The post-processing function of the information improves the image quality [13, 14]. Over the next 20 years, the application of one exposure method in DR chest x-ray machines has been continuously improved, and there are various versions of energy-sensitive detector arrays. Medical Imaging Technology Forum * x-o $ X & H-F! | _*'
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(3) Comparison between two exposures and one exposures
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The advantage of the two exposure methods is that the residual tissue of the image generated by the two-Energy Subtraction is good, the image signal-to-noise ratio is high, and, however, mistaken coding is the biggest weakness between two exposures due to respiration, heartbeat, and shift, in addition, the alternating output of high and low energy X-ray cables in a short period of time has high requirements on the ball tube, high loss, and increase in the patient's radiation. Although the one-shot method does not involve miscoding of images, the energy separation method is far less ideal than the two-shot method, the residual tissue of the image obtained is poorly compared, and the signal-to-noise ratio is low, although theoretically increasing exposure conditions can increase the intensity of energy separation and reduce the noise of quantum spots, when the exposure volume increases to a certain extent, the noise of the image board is no longer related to the exposure volume, in addition, if the exposure condition is too high, it will increase the noise caused by scattering. Some authors speculate that, if the signal-to-noise ratio of a dual-energy subtraction image is the same as that of the two exposures, the X-ray exposure needs to be increased by 16 times. Studies by physicists such as Ho show that, while other conditions are basically the same, the energy separation range of the 140kvp one-shot method is only 70/140 of the two-shot method of 50% kVp (21.6kv and 42.6kv respectively). The residual tissue contrast of the acquired subtract image is only about 50% of the contrast of the latter, the signal-to-noise ratio of an image is only 43% of that of the latter. Studies such as Barnes also produce similar data. Even so, for more than 20 years at the end of the last century, the academic focus of double energy subtraction technology was mostly on improving the method of one exposure. In recent years, because the DDR detector can directly convert the X-ray signal into a visible signal, and the speed is fast, the imaging and image removal rate is fast, there is no need to replace or use the overlapping image board between two exposures, which fundamentally solves the same weakness of two perfectly overlapped images that are difficult to generate when the two exposures are too long. In the future, the two exposure methods may be more widely used due to their inherent advantages.

(4) Others

In addition to the two exposure methods, some of them also put a metal filter board in the middle of two overlapping IP addresses, so that the quantum signals captured by the two IP addresses are different and two images are obtained, then perform the subtraction operation to obtain the subtraction image. Currently, I know that only Fuji CR has finished product technologies and commercial products.

Clinical significance of energy subtraction digital chest X-ray
(1) improve the sensitivity and accuracy of calcification Detection
As we all know, detecting calcification is one of the most reliable imaging signs for diagnosing benign pulmonary nodules. Calcification nodules appear on the Bone image with dual-energy subtraction, and disappear in whole or part of the soft tissue image; those without calcification are clearly displayed on the soft tissue image, and disappears on the Bone image. Kruger and other theoretical derivation and experiments prove that the bone image obtained by double energy Subtraction is not sensitive to soft tissue changes within a fairly thick range (at least 11.6, the sensitivity and accuracy of calcification detection are very high, and the calcium content above 125 mg/cm3 can be detected. Human body models such as Hickey show that the detection of calcium is related to the concentration of calcium. All nodules with a calcium content greater than 35 mg/cm2 can be identified on the image after reduction, its calcium concentration is linearly related to the Light Density on the subtraction image. It is believed that there is no calcification and it is very reliable to be measured by the naked eye on the subtraction image. In two consecutive reports such as Fraser, 8 and 3 of the 13 and 12 cases of pulmonary nodules detected by dual-energy subtraction chest X-ray were not able to determine whether there was calcification on conventional chest X-ray, two of them were subjected to chemical analysis of surgical removal specimens, and the obtained calcium content was very similar to the calculated calcium content measured on the dual-energy subtraction bone image. Studies such as kelcz show that dual-energy subtraction of chest X-ray can enable doctors to affirm or deny the confidence of pulmonary nodules containing calcification, greatly increasing the help for experienced patients. Medical Imaging Technology Forum # C1 w * R8 | (Q6 J: O * _; R
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(2) increase the detection rate of Pulmonary Nodules-a common home for medical imaging technicians! : ^ 0 _ (K. J: 'b8 v
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Chest X-ray is the basic imaging method for early detection of pulmonary nodules, but the false negative rate of conventional chest X-ray for single pulmonary nodules (SPNs) is as high as 18% ~ 32%, and no significant improvement in the last 30 years. Due to the removal of bone thoracic interference, the detection rate of pulmonary nodules is higher than that of normal chest X-ray, both the experimental model and the clinical case group study showed that the difference was statistically significant. Kelcz and others also observed that some small nodules located in the lung field that had no overlap with the ribs were less recognizable on the reduction of the soft tissue image than the conventional chest, it is considered that the contrast of residual soft tissue is reduced due to subtraction, prompting that you should pay attention to the combination with ordinary chest X-ray when reading the energy reduction film. Recent reports also pointed out that the detection rate of dual-energy subtraction chest X-ray is increased, especially when combined with computer-aided Diagnosis System (CAD, however, attention should be paid to the combination with conventional chest X-ray to reduce false positive. The authors also suggested that when detecting low-contrast pulmonary nodules (non-calcification density light nodules, dual-energy subtraction chest X-ray cannot replace conventional chest X-ray. Medical Imaging Technology Forum) L2 ^ # Q1 ~ 1 K, a "R: l

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It is also pointed out that dual-energy subtraction can be used to show the lesions of the thoracic spine and central airway, such as bone metastases, airway tumors, and the knife sheath-like trachea; identification of normal anatomy and improvement of chest X-ray imaging ability, such as skeletal thoracic malformed, normal bone island, type nodules caused by bone hyperplasia are helpful. Ishigaki and other reports that dual-energy subtraction films can increase information by 15% compared with normal chest X-rays. Some authors also used dual-energy subtraction film to quantify the calcium content to diagnose osteoporosis, detection of heart and lung metastasis calcification caused by late renal failure. 6 A4 e + n! Z # M6 s) '1 P7 S0 x $ \! O

Conclusion
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Dual-energy subtraction chest photography is a technology that has been continuously developed and improved over the past 20 years. In the past few years, it has begun to serve a wide range of clinical needs. In the past, a very limited number of clinical applications were reported using an exposure method, which revealed that dual-energy subtraction as an auxiliary means of chest X-ray can effectively improve the detection rate of small pulmonary nodules and increase the confidence in differential diagnosis. The updated and better DDR makes the two exposure Methods easy to implement and can improve the quality, and its clinical application prospects will be broader. However, the price-clinical benefit ratio and the complementary value of common chest X-ray or CT still need to be designed for a more comprehensive prospective clinical application study. , X. c't u (H8 a $ s

Appendix: images of this technology I saw at GE's booth at the 50 th National Medical Devices exhibition. It's really fresh. The Booth shows KUB (abdominal flat) this technique is used to remove the intestinal gas and stool of the abdominal cavity, so that the ureteric stones are clearly displayed.