INSTITUTE OF PHYSICS PUBLISHING HYSICS IN MEDICINE AND BIOLOGY hys.Med.Biol.52(2007)419-427 10.1088/0031-9155/52/2008 Evaluation of x-ray diffraction enhanced imaging in the diagnosis of breast cancer Chenglin Liu., Xiaohui Yan, Xinyi Zhang. 3, Wentao Yang+ Weijun Peng, Daren Shi, Peiping Zhu, Wanxia Huang and SyicharoKey Radation Rese arch enter, Physis aepatmens a pace pe res lbo at cy Physics Department of Yancheng Teachers'College, Yancheng 224002, People's Republic of 3 Shanghai Research Center of Acupuncture and Meridian, Pudong, Shanghai 201203, People's Republic of chin 4 Cancer Hospital, Medical Center of Fudan University, Shanghai 200032, People's Republic of Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of E-mail: xy-zhang@fudan.edu. Received 8 March 2006, in final form 20 August 2006 Published 29 December 2006 Online at stacks. iop. org/PMB/52/419 The significance of the x-ray diffraction enhanced imaging(DEI) technique in the diagnosis of breast cancer and its feasibility in clinical medical imaging are evaluated. Different massive specimens including normal breast tissues, benign breast tumour tissues and malignant breast tumour tissues are imaged with the DEl method. The images are recorded respectively by CCD or x-ray film at different positions of the rocking curve and processed with a pixel- by-pixel algorithm. The characteristics of the DEl images about the normal and diseased tissues are compared. The rocking curves of a double-cryst diffractometer with various tissues are also studied. The differences in del images and their rocking curves are evaluated for early diagnosis of breast (Some figures in this article are in colour only in the electronic version) 1. Introduction Breast diseases are common for women and breast cancer is a dangerous killer(bothorel et al 1997). Early diagnosis and treatment are the best ways to reduce the hazard. Current procedures for the diagnosis of breast cancer mainly include self-examination, mammography (Feig 2002, Freedman et al 2003, Humphrey et al 2002), ultrasonography(US)(Shankar 0031-9155/07/020419+09S3000 2007 1OP Publishing Ltd Printed in the UK
INSTITUTE OF PHYSICS PUBLISHING PHYSICS IN MEDICINE AND BIOLOGY Phys. Med. Biol. 52 (2007) 419–427 doi:10.1088/0031-9155/52/2/008 Evaluation of x-ray diffraction enhanced imaging in the diagnosis of breast cancer Chenglin Liu1,2, Xiaohui Yan1 , Xinyi Zhang1,3, Wentao Yang4 , Weijun Peng4 , Daren Shi4 , Peiping Zhu5 , Wanxia Huang5 and Qingxi Yuan5 1 Synchrotron Radiation Research Center, Physics Department, Surface Physics Laboratory (National Key Laboratory) of Fudan University, Shanghai 200433, People’s Republic of China 2 Physics Department of Yancheng Teachers’ College, Yancheng 224002, People’s Republic of China 3 Shanghai Research Center of Acupuncture and Meridian, Pudong, Shanghai 201203, People’s Republic of China 4 Cancer Hospital, Medical Center of Fudan University, Shanghai 200032, People’s Republic of China 5 Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100039, People’s Republic of China E-mail: xy-zhang@fudan.edu.cn Received 8 March 2006, in final form 20 August 2006 Published 29 December 2006 Online at stacks.iop.org/PMB/52/419 Abstract The significance of the x-ray diffraction enhanced imaging (DEI) technique in the diagnosis of breast cancer and its feasibility in clinical medical imaging are evaluated. Different massive specimens including normal breast tissues, benign breast tumour tissues and malignant breast tumour tissues are imaged with the DEI method. The images are recorded respectively by CCD or x-ray film at different positions of the rocking curve and processed with a pixelby-pixel algorithm. The characteristics of the DEI images about the normal and diseased tissues are compared. The rocking curves of a double-crystal diffractometer with various tissues are also studied. The differences in DEI images and their rocking curves are evaluated for early diagnosis of breast cancers. (Some figures in this article are in colour only in the electronic version) 1. Introduction Breast diseases are common for women and breast cancer is a dangerous killer (Bothorel et al 1997). Early diagnosis and treatment are the best ways to reduce the hazard. Current procedures for the diagnosis of breast cancer mainly include self-examination, mammography (Feig 2002, Freedman et al 2003, Humphrey et al 2002), ultrasonography (US) (Shankar 0031-9155/07/020419+09$30.00 © 2007 IOP Publishing Ltd Printed in the UK 419
C Liu et al et al 1993)and magnetic resonance imaging(MRI(Orel et al 1997). Mammography is currently recognized as the gold standard for the early detection of breast cancer because it requires lower radiation doses, though the rate of false negatives is still as high as 10 per cent (Wilkinson et al 2005). Recently, some new techniques, such as digital mammography, computer aided diagnosis, synchrotron mammography and digital tomosynthesis have been developed to optimize image quality and improve the diagnostic capabilities( Giammarile and Bremond 2004, Niklason et al 1997). The synchrotron radiation, which is electromagnetic by charged particles moving with a speed very close to light speed in a circular orbit, was first found in 1947 and then widely used in different fields, including material science, biology, medicine(Margaritondo and Meuli 2003, Suortti and Thomlinson 2003), etc. Images obtained by using synchrotron radiation with higher spatial resolution and better contrast( Fiedler et al 2003)are superior to those with a conventional x-ray source. With synchrotron radiation, some microstructures inside organic tissues can be shown, which are often missed with conventional techniques Since the middle of the 1990s, x-ray phase-contrast imaging techniques, which can clearly show the microstructure of biological soft tissues under low radiation dose, have been quickly developed (Lewis et al 2002). Diffraction enhanced imaging (DED, whose contrast comes from the absorption, the refractive gradient and the small-angle scattering rejection(usually called extinction), is one of them(Hasnah et al 2002, Zhong et al 2000). The DEl method enhances the sharpness and clarity of the soft tissue image relative to the traditional method due to the combination of more contrast mechanisms(Menk 1999). In recent years, DEI has shown some latent applications in early diagnosis(Lewis 2004). The spatial resolution of DEl images is higher than that of B-mode ultrasound, MRI or CT(computer tomography), and reaches the order of micrometres (Liu et al 2005). The combination of DEl and ct (also called DEI-CT)makes medical images of tumours extraordinarily similar to pathological histology ( Fiedler et al 2004). Moreover, due to the high intensity of synchrotron radiation, only a short exposure time(see below) is needed. Therefore, synchrotron radiation based DEl has a low risk of complications due to the radiation exposure which is obviously an advantage in the early diagnosis of cancer. 6. In this paper, we compared various DEI images of the tissues for the normal breast, benign breast tumour and malignant breast tumour along with their rocking curves to distinguish the microstructures inside those tissues, and we also discussed the merits of this technique for medical applications 2. Materials and methods The specimens were prepared in the Cancer Hospital, Medical Center of Fudan University. We selected 13 of them, including four cases of normal breast tissue, four cases of benign breast tumour tissue and five cases of breast cancer tissue. Both the diseased tissues and the healthy ones were taken from mastectomy sufferers. The main part of each cancer tissue included a great mass of cancer nests, and the normal tissue was taken from a distance of about 2 cm beside the tumour. These specimens were cut into small pieces of 10 x9 mm with a thickness of approximately 2 mm and fixed in 10% buffered formalin. The DEl experiments have been carried out at the topography end station of the 4WiA beamline of the Beijing Synchrotron Radiation Facility(BSRF). The energy of the monochromatic x-rays was 9 keV with an incident angle of 12.7, and the maximum size of the light spot was approximately 12 x 10 mm" at the position of specimen. The analyser was fixed at the axis so it could be tuned to get the different positions of the rocking curve. The DEl images were recorded using a CCD with 1300 x 1030 pixels(X-ray Fast Digital Imager
420 C Liu et al et al 1993) and magnetic resonance imaging (MRI) (Orel et al 1997). Mammography is currently recognized as the gold standard for the early detection of breast cancer because it requires lower radiation doses, though the rate of false negatives is still as high as 10 per cent (Wilkinson et al 2005). Recently, some new techniques, such as digital mammography, computer aided diagnosis, synchrotron mammography and digital tomosynthesis have been developed to optimize image quality and improve the diagnostic capabilities (Giammarile and Bremond 2004, Niklason et al 1997). The synchrotron radiation, which is electromagnetic radiation emitted by charged particles moving with a speed very close to light speed in a circular orbit, was first found in 1947 and then widely used in different fields, including material science, biology, medicine (Margaritondo and Meuli 2003, Suortti and Thomlinson 2003), etc. Images obtained by using synchrotron radiation with higher spatial resolution and better contrast (Fiedler et al 2003) are superior to those with a conventional x-ray source. With synchrotron radiation, some microstructures inside organic tissues can be shown, which are often missed with conventional techniques. Since the middle of the 1990s, x-ray phase-contrast imaging techniques, which can clearly show the microstructure of biological soft tissues under low radiation dose, have been quickly developed (Lewis et al 2002). Diffraction enhanced imaging (DEI), whose contrast comes from the absorption, the refractive gradient and the small-angle scattering rejection (usually called extinction), is one of them (Hasnah et al 2002, Zhong et al 2000). The DEI method enhances the sharpness and clarity of the soft tissue image relative to the traditional method due to the combination of more contrast mechanisms (Menk 1999). In recent years, DEI has shown some latent applications in early diagnosis (Lewis 2004). The spatial resolution of DEI images is higher than that of B-mode ultrasound, MRI or CT (computer tomography), and reaches the order of micrometres (Liu et al 2005). The combination of DEI and CT (also called DEI-CT) makes medical images of tumours extraordinarily similar to pathological histology (Fiedler et al 2004). Moreover, due to the high intensity of synchrotron radiation, only a short exposure time (see below) is needed. Therefore, synchrotron radiation based DEI has a low risk of complications due to the radiation exposure which is obviously an advantage in the early diagnosis of cancer. In this paper, we compared various DEI images of the tissues for the normal breast, benign breast tumour and malignant breast tumour along with their rocking curves to distinguish the microstructures inside those tissues, and we also discussed the merits of this technique for medical applications. 2. Materials and methods The specimens were prepared in the Cancer Hospital, Medical Center of Fudan University. We selected 13 of them, including four cases of normal breast tissue, four cases of benign breast tumour tissue and five cases of breast cancer tissue. Both the diseased tissues and the healthy ones were taken from mastectomy sufferers. The main part of each cancer tissue included a great mass of cancer nests, and the normal tissue was taken from a distance of about 2 cm beside the tumour. These specimens were cut into small pieces of 10 × 9 mm with a thickness of approximately 2 mm and fixed in 10% buffered formalin. The DEI experiments have been carried out at the topography end station of the 4W1A beamline of the Beijing Synchrotron Radiation Facility (BSRF). The energy of the monochromatic x-rays was 9 keV with an incident angle of 12.7◦, and the maximum size of the light spot was approximately 12 × 10 mm2 at the position of specimen. The analyser was fixed at the axis so it could be tuned to get the different positions of the rocking curve. The DEI images were recorded using a CCD with 1300 × 1030 pixels (X-ray Fast Digital Imager
Evaluation of x-ray diffraction enhanced imaging in the diagnosis of breast cancer 18 mm system, Photonic-science Ltd, UK) or industrial x-ray film(Fuji IX80)behind the analyser crystal. The spatial resolutions of the CCD and x-ray film(pixel sizes)were 10.9 um nd 2.3 um, respectively. The distance between the specimen and CCd detector was about I m. The photon flux incident onto the specimens is proportional to the beam current. Hence we can use the product of beam current multiplied by the exposure time as the exposure dose. In our experiments the exposure dose was controlled as a constant, whose average values were about 26.4 mA s and 360 mA s for the CCD and x-ray film, respectively. The beam current was normally between 50 and 100 mA and the exposure time ranged from less than 1 s to several second For the DEl setup in the bse, two Si (111) crystals are equipped. One serves as a monochrometer and the other one serves as the analyser. These two crystals formed a double-crystal diffractometer. The rocking curve, which is the relationship between the reflected intensity and deflection angle of the analyser, can be obtained by tuning the analyser ontinuously to different angles related to the Bragg angle of Si(111). The variation of the rocking curve with different breast tissues has been carefully studied When the Ccd is used as the detector three kinds of images can be obtained. The first one is recorded at the peak position of the rocking curve, which is usually called the peak image. The other two images are taken when the analyser is tuned to the FWHM full-width of half-maximum) positions on the either side of the rocking curve. These two images contain the same absorption and little scattering information but opposite refraction information. When these two images are added pixel by pixel, the refraction information will be eliminated, thus we can obtain an image called the apparent absorption image because of the pure absorption contrast(but with weak extinction). When two images are subtracted pixel by pixel, the so-called refraction image can be obtained, in which not only the refraction but also the absorption contrast is included. And consequently the edge effect will be greatl enhanced. This image processing is very easy because only a simple pixel-by-pixel algorithm is needed In addition, we also recorded the images by x-ray films and read them out through an optical microscope. In this case two different imaging setups were used. One is to place the x-ray film about 1 cm behind the sample without using the analyser crystal, and record the image, which is called absorption image, resembling conventional mammography. The other setup is to place the x-ray film just behind the analyser crystal which is in the top position of its rocking curve, and obtain the peak image. These images will display some microstructures of various tissues after they are read out by the optical microscope 3. Result In our DEl experiments, we obtained various images from those tissues. The various normal tissue (or benign or malignant tumour tissue) cases had similar characteristics in their DEl images. Therefore, only one set of DEI images from each case is shown here. We compared these images to evaluate the significance of the DEl method and show the differences between the normal, benign and malignant tissues The peak image recorded by CCD of these three different kinds of tissues, normal benign tumour and malignant tumour, are shown in figure 1. They contain the information of absorption and small-angle scattering rejection(extinction). The apparent absorption images (figure 2) and the refraction images(figure 3)are obtained by the simple pixel-by-pixel algorithm( Chapman et al 1997)using two images obtained as the analyser is tuned to either side of the FWHM positions, i.e. the low-angle position and the high-angle position of the ocking curve, as mentioned above. The refraction image is extraordinarily sensitive to the
Evaluation of x-ray diffraction enhanced imaging in the diagnosis of breast cancer 421 18 mm system, Photonic-science Ltd, UK) or industrial x-ray film (Fuji IX80) behind the analyser crystal. The spatial resolutions of the CCD and x-ray film (pixel sizes) were 10.9 µm and 2.3 µm, respectively. The distance between the specimen and CCD detector was about 1 m. The photon flux incident onto the specimens is proportional to the beam current. Hence we can use the product of beam current multiplied by the exposure time as the exposure dose. In our experiments the exposure dose was controlled as a constant, whose average values were about 26.4 mA s and 360 mA s for the CCD and x-ray film, respectively. The beam current was normally between 50 and 100 mA and the exposure time ranged from less than 1 s to several seconds. For the DEI setup in the BSRF, two Si (1 1 1) crystals are equipped. One serves as a monochrometer and the other one serves as the analyser. These two crystals formed a double-crystal diffractometer. The rocking curve, which is the relationship between the reflected intensity and deflection angle of the analyser, can be obtained by tuning the analyser continuously to different angles related to the Bragg angle of Si (1 1 1). The variation of the rocking curve with different breast tissues has been carefully studied. When the CCD is used as the detector, three kinds of images can be obtained. The first one is recorded at the peak position of the rocking curve, which is usually called the peak image. The other two images are taken when the analyser is tuned to the FWHM (full-width of half-maximum) positions on the either side of the rocking curve. These two images contain the same absorption and little scattering information but opposite refraction information. When these two images are added pixel by pixel, the refraction information will be eliminated, thus we can obtain an image called the apparent absorption image because of the pure absorption contrast (but with weak extinction). When two images are subtracted pixel by pixel, the so-called refraction image can be obtained, in which not only the refraction but also the absorption contrast is included. And consequently the edge effect will be greatly enhanced. This image processing is very easy because only a simple pixel-by-pixel algorithm is needed. In addition, we also recorded the images by x-ray films and read them out through an optical microscope. In this case two different imaging setups were used. One is to place the x-ray film about 1 cm behind the sample without using the analyser crystal, and record the image, which is called absorption image, resembling conventional mammography. The other setup is to place the x-ray film just behind the analyser crystal which is in the top position of its rocking curve, and obtain the peak image. These images will display some microstructures of various tissues after they are read out by the optical microscope. 3. Results In our DEI experiments, we obtained various images from those tissues. The various normal tissue (or benign or malignant tumour tissue) cases had similar characteristics in their DEI images. Therefore, only one set of DEI images from each case is shown here. We compared these images to evaluate the significance of the DEI method and show the differences between the normal, benign and malignant tissues. The peak image recorded by CCD of these three different kinds of tissues, normal, benign tumour and malignant tumour, are shown in figure 1. They contain the information of absorption and small-angle scattering rejection (extinction). The apparent absorption images (figure 2) and the refraction images (figure 3) are obtained by the simple pixel-by-pixel algorithm (Chapman et al 1997) using two images obtained as the analyser is tuned to either side of the FWHM positions, i.e. the low-angle position and the high-angle position of the rocking curve, as mentioned above. The refraction image is extraordinarily sensitive to the
C Figure 1. Peak images which are recorded by CCD at the peak position of rocking curves of different breast tissues (A)normal. (B) benign tumour, and (C) malignant tumour). Figure 2. Apparent absorption images of different breast tissues. These images are obtained by adding two raw images pixel by pixel. The raw images are recorded by CCD when the analyser is tuned to either side of the FWHM positions.(A)normal, (B)benign tumour, and ( C)malignant Figure 3. Refraction images of different breast tissues. These images raw images by pixel by pixel. The raw images are recorded by CCD when the analyser is tuned to either side of the FWHM positions.(A)normal, (B)benign tumour, and(C)malignant variation of the refractive index of the sample. A few microstructures of tissues can be seen in those images. Especially, there are evidently differences in the calcification between the normal tissues, benign and malignant tumour tissues(see discussion section below). In order to compare diffraction enhanced imaging with the conventional radiographs, x-ray films were used as the detector. The peak images were recorded by x-ray films as shown in figure 4. The absorption images are shown in figure 5, and as we mentioned earlier, in this case the analyser crystal was not used. The contrast of the absorption images is lower than that of the peak images due to the strong scattering which will reduce the image's quality When the peak images are magnified by the optical microscope, some microstructures can be clearly seen. For example, we can see bundles which consist of fibres of about 30 um in diameter(denoted by the black arrow) and some reticulate structures(by the white arrow) in figure 6(A). Some small cavities are shown by arrows in figure 6(B). In the same way, the
422 C Liu et al (A) (B) (C) Figure 1. Peak images which are recorded by CCD at the peak position of rocking curves of different breast tissues (A) normal, (B) benign tumour, and (C) malignant tumour). (A) (B) (C) Figure 2. Apparent absorption images of different breast tissues. These images are obtained by adding two raw images pixel by pixel. The raw images are recorded by CCD when the analyser is tuned to either side of the FWHM positions. (A) normal, (B) benign tumour, and (C) malignant tumour). (A) (B) (C) Figure 3. Refraction images of different breast tissues. These images are obtained by subtracting two raw images by pixel by pixel. The raw images are recorded by CCD when the analyser is tuned to either side of the FWHM positions. (A) normal, (B) benign tumour, and (C) malignant tumour). variation of the refractive index of the sample. A few microstructures of tissues can be seen in those images. Especially, there are evidently differences in the calcification between the normal tissues, benign and malignant tumour tissues (see discussion section below). In order to compare diffraction enhanced imaging with the conventional radiographs, x-ray films were used as the detector. The peak images were recorded by x-ray films as shown in figure 4. The absorption images are shown in figure 5, and as we mentioned earlier, in this case the analyser crystal was not used. The contrast of the absorption images is lower than that of the peak images due to the strong scattering which will reduce the image’s quality. When the peak images are magnified by the optical microscope, some microstructures can be clearly seen. For example, we can see bundles which consist of fibres of about 30 µm in diameter (denoted by the black arrow) and some reticulate structures (by the white arrow) in figure 6(A). Some small cavities are shown by arrows in figure 6(B). In the same way, the
Evaluation of x-ray diffraction enhanced imaging in the diagnosis of breast cancer Figure 4. Peak images which are recorded by x-ray films at the peak position of rocking curves of different breast tissues(A)normal, (B)benign tumour, and(C)malignant tumour) Figure 5. Absorption images which are recorded by x-ray films of different breast tissues (A)normal. (B)benign tumour, and (C)malignant tumour). Figure 6. Peak images of various breast tissues recorded by industrial x-ray films at the peak position of the rocking curve and magnified by an optical microscope. These images can show the microstructures of various breast tissues(A) normal, (B)benign and(C) malignant irregular conglomeration(pointed out by the white arrow) and the expanded duct(by the black arrow) can be also observed, as shown in figure 6(C) On the other hand, the rocking curve can also show the differences of various tissues in the DEl method. Figure 7 shows the rocking curves of the double-crystal diffractometer itself with different breast tissues. Comparing these rocking curves, the diversities of peak displacement and FWHM are not obvious. However, the intensity and integrated intensity of reflectivity can show definite differences. These values for each case and their average values are collected in table 1 4. Discussion 4.1. Peak image, apparent absorption image and refraction image There are three kinds of images which can be used in the diagnosis of breast tumours. These images are peak images, apparent absorption images and refraction images. The peak image
Evaluation of x-ray diffraction enhanced imaging in the diagnosis of breast cancer 423 (A) (B) (C) Figure 4. Peak images which are recorded by x-ray films at the peak position of rocking curves of different breast tissues (A) normal, (B) benign tumour, and (C) malignant tumour). (A) (B) (C) Figure 5. Absorption images which are recorded by x-ray films of different breast tissues (A) normal, (B) benign tumour, and (C) malignant tumour). (A) (B) (C) Figure 6. Peak images of various breast tissues recorded by industrial x-ray films at the peak position of the rocking curve and magnified by an optical microscope. These images can show the microstructures of various breast tissues (A) normal, (B) benign tumour, and (C) malignant tumour). irregular conglomeration (pointed out by the white arrow) and the expanded duct (by the black arrow) can be also observed, as shown in figure 6(C). On the other hand, the rocking curve can also show the differences of various tissues in the DEI method. Figure 7 shows the rocking curves of the double-crystal diffractometer itself with different breast tissues. Comparing these rocking curves, the diversities of peak displacement and FWHM are not obvious. However, the intensity and integrated intensity of reflectivity can show definite differences. These values for each case and their average values are collected in table 1. 4. Discussion 4.1. Peak image, apparent absorption image and refraction image There are three kinds of images which can be used in the diagnosis of breast tumours. These images are peak images, apparent absorption images and refraction images. The peak image
24 C si(111) 如 04 Rotation Angle(second Figure 7. Rocking curves of the double-crystal diffractometer including various breast tissues taken with the 9 keV x-ray. There are obvious differences between these rocking curves taken with or without various tissues Table 1. The peak displacement, reflected intensity and FWHM of the rocking curve of the double-crystal diffractometer with different breast tissues and 9 keV x-ray. Peak displacement (s) FWHM (s) Reflected intensity Double-crystal 0.00 Normal breast 0.381 (9.00±006)0.33200.43±0.07) ouble-crystal 0.2 Benign breast -0.2 0.498 tumour tissue (-0.15±0.08) 917(9.16±0.08)0.763(0.66±0.09) double-crystal -0.2 -0.2 0.633 cancer 0.594 (0.00±0.16 9.14(8.97±0.07)0.413(0.50±0.10)449 diffractometer 0.2 8.96 0.678 Data in parentheses are the average values. can provide the absorption and extinction information. Its contrast will not be seriously affected by the scattering because those scatters are out of the rocking curve, which is the extinction effect. In other words, the small-angle scattering is rejected from the peak images The contrast of peak images can be enhanced by virtue of the extinction effect. Therefore, some new structures will be seen in the peak images. For example, the fibril of normal breast tissue with a diameter of about 30 um( see figure 1(A), the benign tumour with a sharp edge(see figure 1(B))and the sheets of calcifications(formed by calcified spots of tens of micrometres)of malignant breast tissue(see figure I(C) are shown in those peak image
424 C Liu et al Figure 7. Rocking curves of the double-crystal diffractometer including various breast tissues taken with the 9 keV x-ray. There are obvious differences between these rocking curves taken with or without various tissues. Table 1. The peak displacement, reflected intensity and FWHM of the rocking curve of the double-crystal diffractometer with different breast tissues and 9 keV x-ray. Integrated Peak displacement (s) FWHM (s) Reflected intensity intensity Double-crystal 0.00 8.37 1.00 8.37 diffractometer Normal breast 0.2 8.96 0.381 tissue + 0.2 (0.25 ± 0.08)a 8.97 (9.00 ± 0.06) 0.332 (0.43 ± 0.07) 3.87 double-crystal 0.2 9.13 0.522 diffractometer 0.4 8.96 0.477 Benign breast −0.2 9.18 0.498 tumour tissue + 0.0 (−0.15 ± 0.08) 9.17 (9.16 ± 0.08) 0.763 (0.66 ± 0.09) 6.05 double-crystal −0.2 9.00 0.734 diffractometer −0.2 9.30 0.633 Breast cancer 0.2 8.80 0.594 tissue + 0.0 8.97 0.392 double-crystal −0.2 (0.00 ± 0.16) 9.14 (8.97 ± 0.07) 0.413 (0.50 ± 0.10) 4.49 diffractometer 0.2 8.97 0.567 −0.2 8.96 0.678 a Data in parentheses are the average values. can provide the absorption and extinction information. Its contrast will not be seriously affected by the scattering because those scatters are out of the rocking curve, which is the extinction effect. In other words, the small-angle scattering is rejected from the peak images. The contrast of peak images can be enhanced by virtue of the extinction effect. Therefore, some new structures will be seen in the peak images. For example, the fibril of normal breast tissue with a diameter of about 30 µm (see figure 1(A)), the benign tumour with a sharp edge (see figure 1(B)) and the sheets of calcifications (formed by calcified spots of tens of micrometres) of malignant breast tissue (see figure 1(C)) are shown in those peak images
Evaluation of x-ray diffraction enhanced imaging in the diagnosis of breast cancer The apparent absorption images shown in figure 2 are similar to the conventional x-ray image and there are no advantages in distinguishing the microstructure of soft tissues. Its clarity is worse than that of the peak image because it contains a weak small-angle scattering signal besides absorption. Nevertheless, some structures can still be found in apparent absorption images. For example, the boundaries of the breast gland and the reticulate structure are clearly seen in normal breast tissues as shown in figure 2(A). As for the benign tumour, the boundary of the tumour is not obvious because the density of benign tumour is similar to the environmental tissue(see figure 2(B). A few calcifications can be distinctly seen in figure 2(C) from the breast cancer tissues Some typical refraction images of various breast tissues are shown in figure 3. In igure 3(A), the boundary of the fat, the fibril and the gland of normal breast tissue can be seen clearly. For benign tumours, the ellipsoidal and sheet-like masses of tumours are shown in figure 3(B). The fibre bundle of tens of micrometres in diameter and two 1 to 2 millimetre sized masses can be seen, for breast cancer the calcification is the most familiar symptom. Some circinal or anomalous trigonal or linear calcifications of breast cancer are shown in figure 3(C). The size of these calcifications ranges from 50 to 200 micrometres, respectively. The linear calcification, which is assembled from many calcified spots and distributed along the breast duct, is the most important diagnostic standard. Accordingly, there are important values of the DEl method in diagnosing breast cancer because some linear or branched calcifications can be clearly seen in refraction images. They are so valuable that ye can directly see the inside structure of soft tissues without the need of large numbers of pathology slices and thus much diagnosing work with optical microscopes can be avoided The refraction image contains abundant structural information; therefore we can use it to distinguish benign and malignant breast tumours. 4.2. Peak image and absorption image recorded by x-ray films X-ray films are used instead of CCDs to record the image because the spatial resolution of x-ray film is higher than that of the CCD. If the x-ray film is placed directly behind the sample without the analyser crystal, the recorded image is called the synchrotron based absorption image. It strongly resembles mammography, and contains a large number of scattering signals The quality of such absorption images(see figure 5)is superior to those obtained from medical x-ray tubes due to the high intensity of the synchrotron radiation, but their contrast cannot be improved because there is no extinction contrast in these images. As a result, the fine structure of normal tissue does not emerge, the edge of benign tumour is blurry, and the profile of calcifications is not that obvious and or peak images recorded by the x-ray film placed behind the analyser crystal, the clarity and contrast can be improved. Some microstructures of various tissues which do not display in the absorption images can be seen. Similar to the peak images from CCD(see figure 1), fibre reticulation of normal breast tissue. fibre bundles of benign breast tumour and linear calcification can be seen in the peak images recorded by the x-ray films(see figure 4) 4.3. Peak image read by the optical microscope The clarity of images can be further improved if the peak images recorded by the industrial x-ray film are read out by an optical microscope. Some microstructures in breast tissues can be seen in these images. For normal breast tissues, their fibres of about 30 um in diameter are enlaced into bundles(denoted by the black arrow in figure 6(A)) and form the reticulate structures(by the white arrow in figure 6(A). There are small bright spots which
Evaluation of x-ray diffraction enhanced imaging in the diagnosis of breast cancer 425 The apparent absorption images shown in figure 2 are similar to the conventional x-ray image and there are no advantages in distinguishing the microstructure of soft tissues. Its clarity is worse than that of the peak image because it contains a weak small-angle scattering signal besides absorption. Nevertheless, some structures can still be found in apparent absorption images. For example, the boundaries of the breast gland and the reticulate structure are clearly seen in normal breast tissues as shown in figure 2(A). As for the benign tumour, the boundary of the tumour is not obvious because the density of benign tumour is similar to the environmental tissue (see figure 2(B)). A few calcifications can be distinctly seen in figure 2(C) from the breast cancer tissues. Some typical refraction images of various breast tissues are shown in figure 3. In figure 3(A), the boundary of the fat, the fibril and the gland of normal breast tissue can be seen clearly. For benign tumours, the ellipsoidal and sheet-like masses of tumours are shown in figure 3(B). The fibre bundle of tens of micrometres in diameter and two 1 to 2 millimetre sized masses can be seen. For breast cancer the calcification is the most familiar symptom. Some circinal or anomalous trigonal or linear calcifications of breast cancer are shown in figure 3(C). The size of these calcifications ranges from 50 to 200 micrometres, respectively. The linear calcification, which is assembled from many calcified spots and distributed along the breast duct, is the most important diagnostic standard. Accordingly, there are important values of the DEI method in diagnosing breast cancer because some linear or branched calcifications can be clearly seen in refraction images. They are so valuable that we can directly see the inside structure of soft tissues without the need of large numbers of pathology slices and thus much diagnosing work with optical microscopes can be avoided. The refraction image contains abundant structural information; therefore we can use it to distinguish benign and malignant breast tumours. 4.2. Peak image and absorption image recorded by x-ray films X-ray films are used instead of CCDs to record the image because the spatial resolution of x-ray film is higher than that of the CCD. If the x-ray film is placed directly behind the sample without the analyser crystal, the recorded image is called the synchrotron based absorption image. It strongly resembles mammography, and contains a large number of scattering signals. The quality of such absorption images (see figure 5) is superior to those obtained from medical x-ray tubes due to the high intensity of the synchrotron radiation, but their contrast cannot be improved because there is no extinction contrast in these images. As a result, the fine structure of normal tissue does not emerge, the edge of benign tumour is blurry, and the profile of calcifications is not that obvious. For peak images recorded by the x-ray film placed behind the analyser crystal, the clarity and contrast can be improved. Some microstructures of various tissues which do not display in the absorption images can be seen. Similar to the peak images from CCD (see figure 1), fibre reticulation of normal breast tissue, fibre bundles of benign breast tumour and linear calcification can be seen in the peak images recorded by the x-ray films (see figure 4). 4.3. Peak image read by the optical microscope The clarity of images can be further improved if the peak images recorded by the industrial x-ray film are read out by an optical microscope. Some microstructures in breast tissues can be seen in these images. For normal breast tissues, their fibres of about 30 µm in diameter are enlaced into bundles (denoted by the black arrow in figure 6(A)) and form the reticulate structures (by the white arrow in figure 6(A)). There are small bright spots which
C are calcifications in the normal breast tissues because of calcium salt deposited in the ageing breast tissue. The fibres of benign tumour breast tissue are in disorder and make up anomaly masses(see figure 6(B), which means the high density tumour tissues get together and form anomalous conglomerations. The sizes of the conglomerations are different and have a random distribution. For those specimens tested in this work, the maximum one is about 2 mm and the minimum one is 0.5 mm. The cavity formed due to liquid degeneration appears obviously in figure 6(B), denoted by the white arrow. Their average size is 0.5 mm. There are some microstructures found in the malignant tumour, such as fibre fortification(see figure 6(C) These fortifications result from uniform or asymmetric encroachment of the malignant cell along the breast duct. At the same time the calcifications also distribute along the fibre fortification and form the stick or Y-shaped assembly as shown in figure 6(C). In addition some breast ducts are expanded(the black arrow in figure 6(C). These irregular structures and pecial symptoms of the tissue can play very important roles in distinguishing the malignant Id benign tumours. 4.4. Rocking curve The rocking curve which can be used to study the dynamic processes of x-ray diffraction is related to the absorption, the extinction, the mosaic domain in crystals, and so on. In DEl experiments, the shape of the rocking curve is decided by the analyser Si(111crystal and the experimental specimen(see figure 7). As listed in table 1, the peak remains in the same position but in general the sample affects the broadening of the rocking curve and also the d intensity. Due to the differences between the absorption and refraction of the specimens, the DEl images let us see various microstructures clearly. The integrated intensities of the rocking curve are obviously different for different kinds of breast tissues, although its peak position nd the width stay almost unchanged. The difference of integrated intensity mainly results from the differences in absorption of breast tissues under test. Because of the compactness and the relatively high density of healthy tissues, the integrated intensity for normal breast tissue is the lowest, which reflects a strong absorption. For the tumour tissues, the formation of cavities in benign tumours will increase the transmittance and result in a growth of the integrated intensity of the rocking curve. In contrast the assembling of calcified spots in the progression to cancer of diseased tissue will increase the absorption and then lead to a fall of the rocking curve. This general trend is in accordance with our earlier work in which the infrared absorption of healthy or diseased human tissues was studied (Liu et al 2006). we found that the IR absorption spectrum varies from abundantly featured to faint from normal breast tissue to benign tumours: while it develops from a relatively smooth spectrum to a much more complicated one in progressing to cancer of the diseased tissue. The reason for these changes is the variation of the absorption of different breast tissues in the IR region. However, the change of integrated intensity of rocking curves among different breast tissues is due to their different absorptions in the x-ray region. 5. Conclusions DEl images can disclose the inside microstructures of various breast tissues without the need of large numbers of pathology slices. The refraction images can show the microstructures of normal, benign and malignant breast tissues with the best clarity and highest contrast in all kinds of DEl images. The peak images have higher contrast than the apparent absorption images and can show microstructures inside the breast tissues as well. there are more
426 C Liu et al are calcifications in the normal breast tissues because of calcium salt deposited in the ageing breast tissue. The fibres of benign tumour breast tissue are in disorder and make up anomaly masses (see figure 6(B)), which means the high density tumour tissues get together and form anomalous conglomerations. The sizes of the conglomerations are different and have a random distribution. For those specimens tested in this work, the maximum one is about 2 mm and the minimum one is 0.5 mm. The cavity formed due to liquid degeneration appears obviously in figure 6(B), denoted by the white arrow. Their average size is 0.5 mm. There are some microstructures found in the malignant tumour, such as fibre fortification (see figure 6(C)). These fortifications result from uniform or asymmetric encroachment of the malignant cell along the breast duct. At the same time, the calcifications also distribute along the fibre fortification and form the stick or Y-shaped assembly as shown in figure 6(C). In addition, some breast ducts are expanded (the black arrow in figure 6(C)). These irregular structures and special symptoms of the tissue can play very important roles in distinguishing the malignant and benign tumours. 4.4. Rocking curve The rocking curve which can be used to study the dynamic processes of x-ray diffraction is related to the absorption, the extinction, the mosaic domain in crystals, and so on. In DEI experiments, the shape of the rocking curve is decided by the analyser Si (1 1 1) crystal and the experimental specimen (see figure 7). As listed in table 1, the peak remains in the same position but in general the sample affects the broadening of the rocking curve and also the integrated intensity. Due to the differences between the absorption and refraction of the specimens, the DEI images let us see various microstructures clearly. The integrated intensities of the rocking curve are obviously different for different kinds of breast tissues, although its peak position and the width stay almost unchanged. The difference of integrated intensity mainly results from the differences in absorption of breast tissues under test. Because of the compactness and the relatively high density of healthy tissues, the integrated intensity for normal breast tissue is the lowest, which reflects a strong absorption. For the tumour tissues, the formation of cavities in benign tumours will increase the transmittance and result in a growth of the integrated intensity of the rocking curve. In contrast the assembling of calcified spots in the progression to cancer of diseased tissue will increase the absorption and then lead to a fall of the rocking curve. This general trend is in accordance with our earlier work in which the infrared absorption of healthy or diseased human tissues was studied (Liu et al 2006). We found that the IR absorption spectrum varies from abundantly featured to faint from normal breast tissue to benign tumours; while it develops from a relatively smooth spectrum to a much more complicated one in progressing to cancer of the diseased tissue. The reason for these changes is the variation of the absorption of different breast tissues in the IR region. However, the change of integrated intensity of rocking curves among different breast tissues is due to their different absorptions in the x-ray region. 5. Conclusions DEI images can disclose the inside microstructures of various breast tissues without the need of large numbers of pathology slices. The refraction images can show the microstructures of normal, benign and malignant breast tissues with the best clarity and highest contrast in all kinds of DEI images. The peak images have higher contrast than the apparent absorption images and can show microstructures inside the breast tissues as well. There are more
Evaluation of x-ray diffraction enhanced imaging in the diagnosis of breast cancer abundant microstructures in the peak images recorded by x-ray films and magnified by optical microscope, but this image processing procedure is not as convenient as using CCDs The differences of the integrated intensity of rocking curves are also a possible way to distinguish normal, benign or malignant breast tissues. The DEl method could be valuable in the diagnosis of breast cancers in their early stage. To our knowledge, so far only breast useltiy specimens have been imaged with DEL, not the whole in vivo tissue. While DEI may be useful in characterizing breast tissue specimens, it is not yet useful in detecting breast cancer Acknowledgments This work was supported by the National Natural Science Foundation of China(no. 10105002) nd National Basic Research Programme of China(no. 2005CB523306 References Bothorel S, Meunier BB and Muller s A 1997 Fuzzy logic based approach for semilogical analysis of microcalcification oman D. Thomlinson W. Johnston R E. Washburn D, Pisano ayers D 1997 Diffraction enhanced x-ray imaging Phys Med Biol. 42 2015-25 Giammarile F and Bremond A 2004 Diagnostic of breast cancer: what do clinicians expect from PEM Nuc/ Instrum Methods Phys Res. A 52783-6 Feig SA 2002 Effect of service screening mammography on population mortality from breast carcinoma Cancer 451-7 Fiedler S, Bravin A, Keyrilainen J, Femandez M, Suortti P, Thomlinson W, Tenhunen M, Virkkunen Pand Karjalainen- Lindsberg M-L 2004 Imaging lobular breast carcinoma: comparison of synchrotron radiation DEI-CT technique Fiedler S, Pagot E, Cloetens P, Bravin A, Baruchel J, Hartwig J, Coan P, Salicru B and Thomlinson W2003 Evaluation of the phase contrast techniques: diffraction enhanced imaging and propagation Proc. SPIE 5030 266-73 breast conservation in breast carcinoma patients age 40 years and older Cancer 98918-25 Hasnah MO, Zhong Z, Oltulu O, Pisano E, Johnston R E, Sayers D, Thomlinson W and Chapman D 2002 Diffraction enhanced imaging contrast mechanisms in breast specimens Med. Phys. 29 2216-21 Humphrey LL, Helfand M, Chan B K S and Woolf S H 2002 Breast cancer screening: a summary of the evidence for the U.S. preventive services task force Ann Intern. Med. 137 347-60 Lewis R A et al 2002 Diffraction enhanced imaging: improved contrast, lower dose x-ray imaging Proc. SPIE 4682286-97 Lewis R A 2004 Medical phase contrast x-ray imaging: current status and future prospects Phys Med. Biol. 493573-83 Liu C L, Zhang Y, Zhang X Y, Yang WT, Peng wJ, Shi D R, Zhu PP, Tian Y L and Huang wx 2005 X-rays diffraction enhanced imaging of uterine leiomyomas Med. Sci Monit. 11 MT33-38 Liu C L, Zhang Y, Yan X H, Zhang X Y, Li X, Yang WT and Shi DR 2006 Infrared absorption of human breast tissues in vitro Lumin. 119-200132-6 Margaritondo G and Meuli R 2003 Synchrotron radiation in radiology: novel x-rays sources Eur Radiol. 13 2633-4 Menk R H 1999 Interference imaging and its application to material and medical imaging Nucl. Phys. B 78 604-9 Niklason L T et al 1997 Digital tomosynthesis in breast imaging Radiology 205 399-406 Orel S G. Mendonca M H, Reynolds C, Schnall M D, Solin L J and Sullivan 1997 MR imaging of ductal carcinoma in situ Radiology 202 413-20 Shankar PM. Reid J M, Ortega H, Piccoli C Wand Goldberg B B 1993 Use of non-Rayleigh statistics for identification of tumors in ultrasonic B-scans of the breast IEEE Trans. Med Imaging 12 687-92 Suortti P and Thomlinson W 2003 Medical application of synchrotron radiation Phys Med Biol. 48R1-35 Wilkinson SJ, Rogers K D, Hall C J, Lewis R A, Round A, Pinder S E, Boggis C and Hufton A 2005 Small angle diffraction imaging for disease diagnosis Nuc/ Instrum. Methods Phys Res. A 548 135-9 Zhong Z, Thomlinson w, Chapman D and Sayers D 2000 Implementation of diffraction enhanced imaging xperiments: at the NSLS and ASP Nucl. Instrum. Methods Phys Res 450 556-68
Evaluation of x-ray diffraction enhanced imaging in the diagnosis of breast cancer 427 abundant microstructures in the peak images recorded by x-ray films and magnified by optical microscope, but this image processing procedure is not as convenient as using CCDs. The differences of the integrated intensity of rocking curves are also a possible way to distinguish normal, benign or malignant breast tissues. The DEI method could be valuable in the diagnosis of breast cancers in their early stage. To our knowledge, so far only breast tissue specimens have been imaged with DEI, not the whole in vivo tissue. While DEI may be useful in characterizing breast tissue specimens, it is not yet useful in detecting breast cancer in asymptomatic women. Acknowledgments This work was supported by the National Natural Science Foundation of China (no. 10105002) and National Basic Research Programme of China (no. 2005CB523306). References Bothorel S, Meunier B B and Muller S A 1997 Fuzzy logic based approach for semilogical analysis of microcalcification in mammographic images Int. J. Intell. Syst. 12 819–48 Chapman D, Thomlinson W, Johnston R E, Washburn D, Pisano E, Gmur N, Zhong Z, Menk R, Arfelli F and Sayers D 1997 Diffraction enhanced x-ray imaging Phys. Med. Biol. 42 2015–25 Giammarile F and Bremond A 2004 Diagnostic of breast cancer: what do clinicians expect from PEM Nucl. Instrum. Methods Phys. Res. A 527 83–6 Feig S A 2002 Effect of service screening mammography on population mortality from breast carcinoma Cancer 95 451–7 Fiedler S, Bravin A, Keyrilainen J, Fernandez M, Suortti P, Thomlinson W, Tenhunen M, Virkkunen P and KarjalainenLindsberg M-L 2004 Imaging lobular breast carcinoma: comparison of synchrotron radiation DEI-CT technique with clinical CT, mammography and histology Phys. Med. Biol. 49 175–88 Fiedler S, Pagot E, Cloetens P, Bravin A, Baruchel J, Hartwig J, Coan P, Salicru B and Thomlinson W 2003 Evaluation of the phase contrast techniques: diffraction enhanced imaging and propagation Proc. SPIE 5030 266–73 Freedman G M et al 2003 Routine mammography is associated with earlier stage disease and greater eligibility for breast conservation in breast carcinoma patients age 40 years and older Cancer 98 918–25 Hasnah M O, Zhong Z, Oltulu O, Pisano E, Johnston R E, Sayers D, Thomlinson W and Chapman D 2002 Diffraction enhanced imaging contrast mechanisms in breast cancer specimens Med. Phys. 29 2216–21 Humphrey L L, Helfand M, Chan B K S and Woolf S H 2002 Breast cancer screening: a summary of the evidence for the U.S. preventive services task force Ann. Intern. Med. 137 347–60 Lewis R A et al 2002 Diffraction enhanced imaging: improved contrast, lower dose x-ray imaging Proc. SPIE 4682 286–97 Lewis R A 2004 Medical phase contrast x-ray imaging: current status and future prospects Phys. Med. Biol. 49 3573–83 Liu C L, Zhang Y, Zhang X Y, Yang W T, Peng W J, Shi D R, Zhu P P, Tian Y L and Huang W X 2005 X-rays diffraction enhanced imaging of uterine leiomyomas Med. Sci. Monit. 11 MT33–38 Liu C L, Zhang Y, Yan X H, Zhang X Y, Li C X, Yang W T and Shi D R 2006 Infrared absorption of human breast tissues in vitro J. Lumin. 119–200 132–6 Margaritondo G and Meuli R 2003 Synchrotron radiation in radiology: novel x-rays sources Eur. Radiol. 13 2633–41 Menk R H 1999 Interference imaging and its application to material and medical imaging Nucl. Phys. B 78 604–9 Niklason L T et al 1997 Digital tomosynthesis in breast imaging Radiology 205 399–406 Orel S G, Mendonca M H, Reynolds C, Schnall M D, Solin L J and Sullivan 1997 MR imaging of ductal carcinoma in situ Radiology 202 413–20 Shankar P M, Reid J M, Ortega H, Piccoli C W and Goldberg B B 1993 Use of non-Rayleigh statistics for identification of tumors in ultrasonic B-scans of the breast IEEE Trans. Med. Imaging 12 687–92 Suortti P and Thomlinson W 2003 Medical application of synchrotron radiation Phys. Med. Biol. 48 R1–35 Wilkinson S J, Rogers K D, Hall C J, Lewis R A, Round A, Pinder S E, Boggis C and Hufton A 2005 Small angle diffraction imaging for disease diagnosis Nucl. Instrum. Methods Phys. Res. A 548 135–9 Zhong Z, Thomlinson W, Chapman D and Sayers D 2000 Implementation of diffraction enhanced imaging experiments: at the NSLS and ASP Nucl. Instrum. Methods Phys. Res. 450 556–68
