- Email: [email protected]
Clinical mammography at the SYRMEP beam line
ARTICLE IN PRESS
Nuclear Instruments and Methods in Physics Research A 572 (2007) 237–240 www.elsevier.com/locate/nima
Clinical mammography at the SYRMEP beam line E. Castellia,, F. Arfellia, D. Dreossia, R. Longoa, T. Rokvica,e, M.A. Covab, E. Quaiab, M. Tonuttib, F. Zanconatib, A. Abramic, V. Chendac, R.H. Menkc, E. Quaic, G. Trombac, P. Bregantd, F. de Guarrinid a Department of Physics, University and INFN, Trieste, Italy Department of Radiology, University and Hospital, Trieste, Italy c ELETTRA, Trieste, Italy d Health Physics, Hospital, Trieste, Italy e Faculty of Physics, University, Belgrade, Serbia and Montenegro
b
Available online 29 November 2006
Abstract The synchrotron radiation (SR) clinical mammography, using as detector a commercial screen-film system, is a further crucial step of the SYRMEP (Synchrotron Radiation for Medical Physics) Project. In March and April of this year, mammographic examinations on nine patients have been carried out with X-rays from ELETTRA, the SR laboratory in Trieste, Italy. The facility for Phase Contrast (PhC) SR mammography is now operative in patient mode and is used for patient examinations, producing breast images in different projections. The entire procedure is automated and is able to achieve the correct exposure on the film taking into consideration the requested limits on the applied dose, as a function of the thickness and glandularity of the breast. The SR mammography shows a higher spatial resolution and contrast detail visibility, in comparison with the conventional analog or digital mammography, with a comparable or lower dose. In some cases of these first nine patients, the radiologists have clarified the ambiguity of the previous examinations. These preliminary results are encouraging and a complete evaluation of the clinical impact of the new method is in progress. r 2006 Elsevier B.V. All rights reserved. PACS: 87.59.Ek; 29.20.Lq Keywords: Clinical mammography; Synchrotron radiation; Phase contrast
1. Introduction: the SYRMEP story The proposal to build a SR facility, later named ELETTRA, was launched during the 71st Annual National Congress of the Italian Physical Society, in October 1985 at Trieste, Italy. Several meetings—generally held at the International Centre for Theoretical Physics (ICTP) in Trieste—immediately focused on the issue of which beam lines had to be developed [1]. The SYRMEP Project, for the construction of a medical beam line, already foreseeing the final phase of ‘‘in vivo’’ mammographic examinations, was presented in 1991 at a meeting of the Program Advisory Committee of the Sincrotrone Trieste SCpA Corresponding author. Tel.: +39 040 558 3369; fax: +39 040 558 3350.
E-mail address: [email protected] (E. Castelli). 0168-9002/$ - see front matter r 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2006.10.295
(ST), the company devoted to the construction of the ELETTRA laboratory. The project approval was subject to the fulfillment of two conditions: finding the necessary funds and starting with the ‘‘in vitro’’ phase, in order to verify the effectiveness of the proposed technique. ELETTRA began its operations in 1993, and in the same year the construction of SYRMEP beam line started off. The University of Trieste was the major source of funding, with a significant contribution of ST; in addition, the National Institute of Nuclear Physics (INFN) supported the development of a new digital detection system. The ‘‘in vitro’’ experimentation was started in 1996 and the results of this preliminary phase were very promising. In 1998 international scientific committees of ST approved the next steps of ‘‘in vivo’’, i.e. with patients, experimentation, provided that the availability of funds was granted. In the
ARTICLE IN PRESS 238
E. Castelli et al. / Nuclear Instruments and Methods in Physics Research A 572 (2007) 237–240
following year the Fondazione CRTrieste financially supported the project, formally called ‘‘Synchrotron X-ray mammography: clinical experimentation’’. Experiments on patients are envisaged; therefore the University of Trieste, the local Hospital and ST signed a 5 years agreement. The INFN continues to support the digital detection system, also in view of possible development in the field of tomo-mammographic experiments. In the year 2000 the beam line modification phase started by designing the patient room with the mobile patient support, the room for medical and technical radiologists, and the control system to comply with all the required safety regulations. In July 2004 the Ethical Committee of the local Hospital authorized the experimentation on patients and in March 2005 an Italian ministerial agency tested out, with positive feedback, the general safety control system; in September a renewed agreement of the three contracting bodies defined the performances to be attained and the responsibilities of the persons involved in the experimentation. Eventually, in January 2006, the Ministry of Health gave the ultimate approval. The scientific results of the SYRMEP collaboration, particularly in the field of development of the silicon detector, were always presented at the Pisa Meetings, starting with the sixth one, in 1994 [2–6]. The total budget for the various parts of the project has been of 2.4 millions euros, without taking the expenses for personnel into account. This budget accounts for the construction of the original beam line [7] and for the upgrading to the clinical mammography system, which leaves the availability of an experimental room for the usual SR experimental activities, when the patient modality is not active.
2. The beam line layout for ‘‘in vivo’’ mammography The upgrading of the original beam line SYRMEP in view of experimentation with patients is shortly discussed in Ref. [8], and in the relevant references therein. A more detailed description of the new equipment can be found in Ref. [9], where in particular the features of the high precision ionization chambers and the patient scanning stage are presented. The new ionization chambers allow the evaluation of the dose delivered to the patient on-line, i.e. during the examination itself. Since the laminar SR beam is fixed, planar images are obtained by scanning with high precision, the patient prone on the support, through the beam. An important aspect to point out here is the very peculiar geometrical set-up of SR mammography in comparison with the standard one carried out by conventional clinical units. In this latter case source, compressed breast and detector are fixed; the source-to-breast distance is of 65 cm and the screen-film cassette is practically in contact with the breast, at 70 cm from the source. The dimensions of the detector are of 18 cm 24 cm; in the
18 cm direction the full compressed breast is seen with an angle of 18/70 ¼ 0.26 radians. With the PhC SR mammography at the SYRMEP beam line the source is fixed, but the breast and the screen-film detector are simultaneously scanned in the vertical direction, in which the beam is 4 mm high; the source-tobreast distance is of 30 m and the breast-to-detector distance is of 2 m. Thus the vertical angle is in this case of 0.004/32 ¼ 0.00013 radians, very different from the previous 0.26. The focal spot sizes is of 300 300 mm2 (or 100 100 mm2 in case some degree of magnification is applied) for a conventional mammography unit, while at SYRMEP is of 1000 100 mm2 in the horizontal and vertical directions, respectively. Although a certain degree of phase contrast is currently achievable also with state-of-the-art micro focal sources [10], the use of a 3rd generation SR source clearly makes these effects much more intense and easier to detect. The results of the next sections show in fact that the availability of such SR high intensity laminar beams of nearly monochromatic and parallel X-rays, allows highlighting the PhC features also in thick objects, like the breast. 3. The ‘‘in vitro’’ digital mammography During the preparatory phase, ‘‘in vitro’’ experiments have been carried out both with digital and analog detectors. A discussion on the results obtained with a detection system developed by the SYRMEP collaboration in the field of the morphological breast imaging can be found in Ref. [11]. It consists of a silicon micro-strip detector equipped with a low noise read-out electronics working in single photon counting mode. The ‘‘edge on’’ configuration defines the pixel structure, achieving moreover high conversion efficiency. Mammographic phantoms and ‘‘in vitro’’ full breast samples have been investigated: with the SR PhC digital mammography it is possible to obtain images with high contrast and good spatial resolution; the doses delivered to the breast tissues during the acquisition are significantly lower than those of a conventional mammography. All these results have been obtained in the experimental station of the original beam line. Afterwards the beam line layout has been modified in order to realize the clinical facility, with the medical radiologist room and the patient examination hall. In this last year, breast samples from mastectomy surgery have been studied using the complete final set-up in order to test the overall control system as well as the security and image quality protocols; in this starting phase the detector is a commercial screen-film mammographic system. Moreover surgical breast specimens from total mastectomy in 4 patients were imaged both by conventional mammography and SR PhC mammography in 1 projection (craniocaudal). Fig. 1 shows a detail of one of these last samples obtained at 18 keV and the comparison with the clinical image on a hospital analog mammographic unit. The increased image
ARTICLE IN PRESS E. Castelli et al. / Nuclear Instruments and Methods in Physics Research A 572 (2007) 237–240
239
fluence. Small size and small contrast imply high dose for good image quality. Since the breast is one of the most radiosensitive organs, the risk of cancer induced by X-ray exposure has to be minimized. Increasing image quality without increasing the dose is therefore one of the primary goals in mammography. The SR implies a practically monochromatic X-ray laminar beam and the PhC imaging; therefore high contrast and spatial resolution can be a priori obtained with dose reduction [12]. For this clinical trial a limited number of volunteer patients has to be selected by radiologists, after routine examinations, on the basis of BI-RADS classification [13]; according to the research program approved by the local Ethical Committee, the recruitment of at least 70 patients to be evaluated by SR PhC mammography is foreseen during the next year. As starting point, 9 female patients, 3 in March and 6 in April 2006, with indeterminate findings at clinical mammography (suspicious opacity not referred to the breast parenchyma, asymmetrical appearance of the two breasts), and not clarified by ultrasound, were examined by digital mammography and SR mammography in 2 projections (oblique and craniocaudal). In SR mammography, patients were examined in a prone position with compressed breast, while the images were obtained by scanning the breast vertically in front of a stationary monochromatic laminar beam. The detector, a commercial mammographic screenfilm system, was about 2 m from the breast, at the correct distance to optimize the so-called phase contrast effects. 5. Results
Fig. 1. Radiological image from a mastectomy acquired: (a) with a conventional screen-film system at a mammography unit of the hospital; and (b) with the SR setup in phase contrast geometry at the SYRMEP beam line of the SR facility ELETTRA. More details are apparent in (b) image.
quality for diagnostical purposes, without dose increment, is apparent. 4. The ‘‘in vivo’’ mammography In the medical community there is a general agreement that an early diagnosis of breast cancer has beneficial consequences on successful prognosis: an early detection saves lives. Early diagnosis of breast cancer implies the detection of microcalcifications (high contrast, small size details) and nodules (low contrast details). Image visibility depends upon object size, object contrast and photon
As far as the physics is concerned, the ‘‘in vivo’’ phase contrast images acquired at the clinical facility match the quality obtained in the previous ‘‘in vitro’’ SR experimental conditions. Moreover the average dose delivered in the SR PhC mammographic examinations is comparable or lower than those used in clinical practice with conventional units. From the clinical side, two independent medical doctors, scoring the conspicuity of the breast parenchyma over background, the depiction of lesion margins and the microcalcification visibility, evaluated the images on film for SR mammography at the SYRMEP beam line and the on-screen for digital mammography, with the GE Senographe 2000D unit of the hospital. The different parameters were better depicted by the SR mammography both in the surgical specimens and patient breasts. In some cases of these first 9 patients, the radiologists have clarified the ambiguity of the previous examinations (digital conventional clinical mammography and/or ultrasound). These preliminary results are encouraging and a complete evaluation of the clinical impact of the new method is in progress. Moreover on the digital detector development side, in collaboration with the Paul Scherrer Institut, Villigen, Switzerland a silicon microstrip laminar detector (Hamamatsu), in ‘‘edge-on’’ geometrical configuration [6],
ARTICLE IN PRESS 240
E. Castelli et al. / Nuclear Instruments and Methods in Physics Research A 572 (2007) 237–240
equipped with single photon counting electronics Mythen II [14], has been successfully tested at the SYRMEP beam line. 6. Conclusions and perspectives This preliminary experience with SR mammography produced high-quality images of the breast both in surgical specimens and humans. The SR PhC technique may therefore improve the overall image quality of clinical mammography. In order to reach a final assessment on the potentiality of the method, a good statistics is of course necessary: the recruitment of over 100 patients to be evaluated by SR PhC mammography is foreseen during the next year. The main goal of the SYRMEP collaboration is to optimize the quality of radiological examinations operating both on the source and on the detector side [15]. Therefore the next step of the project will involve the introduction of conventional and custom digital detectors. This will allow the exploitation of all the advantages pointed out during the long R&D activity of the SYRMEP collaboration in the field of the ‘‘in vitro’’ SR PhC digital mammography. Taking into account the preliminary good results of the custom detector [14], a new proposal has been presented to INFN in order to build a detection system suited to perform ‘‘digital’’ mammographic examinations on patients.
References [1] L. Dalla Palma, E. Castelli, Report from the working group on medical physics, Proceedings of the Workshop on Scientific and Technological Application of Synchrotron Radiation, ICTP, Trieste, 1987, p. 98. [2] F. Arfelli, et al., Nucl. Instr. Meth. A 360 (1995) 283. [3] F. Arfelli, et al., Nucl. Instr. Meth. A 409 (1998) 351. [4] F. Arfelli, et al., Nucl. Instr. Meth. A 409 (1998) 529. [5] M. Prest, et al., Nucl. Instr. Meth. A 461 (2001) 435. [6] A. Bergamaschi, et al., Nucl. Instr. Meth. A 518 (2004) 415. [7] F. Arfelli, et al., Radiology 215 (2000) 286. [8] A. Abrami, et al., Nucl. Instr. Meth. A 548 (2005) 221. [9] F. Arfelli, et al., Synchrotron radiation mammography: clinical experimentation, to be published in AIP Conference Proceedings of the Ninth international Conference on Synchrotron Radiation Instrumentation (SRI 2006), May 28–June 3, 2006, Daegu, Korea. [10] A. Olivo, R. Speller, Phys. Med. Biol. 51 (2006) 3015. [11] R. Longo, et al., Nucl. Instr. Meth. A 497 (2003) 9. [12] F. Arfelli, et al., Phys. Med. Biol. 43 (1998) 2845. [13] American College of Radiology. Illustrated Breast Imaging Reporting and Data System (BI-RADS), 4th ed, Reston VA, ACR, 2003. [14] A. Bergamaschi, B. Schmitt, Paul Scherrer Institut, Villigen, Switzerland, private commuication. [15] E. Castelli, Medical application planned at Elettra: SYRMEP project (Synchrotron Radiation for Medical Physics), in: E. Burattini, A. Balerna (Eds.), Proceedings of the International School of Physics ‘‘Enrico Fermi’’, Course CXXVIII (1994), IOS Press, Amsterdam, 1996, p. 379.
Nuclear Instruments and Methods in Physics Research A 572 (2007) 237–240 www.elsevier.com/locate/nima
Clinical mammography at the SYRMEP beam line E. Castellia,, F. Arfellia, D. Dreossia, R. Longoa, T. Rokvica,e, M.A. Covab, E. Quaiab, M. Tonuttib, F. Zanconatib, A. Abramic, V. Chendac, R.H. Menkc, E. Quaic, G. Trombac, P. Bregantd, F. de Guarrinid a Department of Physics, University and INFN, Trieste, Italy Department of Radiology, University and Hospital, Trieste, Italy c ELETTRA, Trieste, Italy d Health Physics, Hospital, Trieste, Italy e Faculty of Physics, University, Belgrade, Serbia and Montenegro
b
Available online 29 November 2006
Abstract The synchrotron radiation (SR) clinical mammography, using as detector a commercial screen-film system, is a further crucial step of the SYRMEP (Synchrotron Radiation for Medical Physics) Project. In March and April of this year, mammographic examinations on nine patients have been carried out with X-rays from ELETTRA, the SR laboratory in Trieste, Italy. The facility for Phase Contrast (PhC) SR mammography is now operative in patient mode and is used for patient examinations, producing breast images in different projections. The entire procedure is automated and is able to achieve the correct exposure on the film taking into consideration the requested limits on the applied dose, as a function of the thickness and glandularity of the breast. The SR mammography shows a higher spatial resolution and contrast detail visibility, in comparison with the conventional analog or digital mammography, with a comparable or lower dose. In some cases of these first nine patients, the radiologists have clarified the ambiguity of the previous examinations. These preliminary results are encouraging and a complete evaluation of the clinical impact of the new method is in progress. r 2006 Elsevier B.V. All rights reserved. PACS: 87.59.Ek; 29.20.Lq Keywords: Clinical mammography; Synchrotron radiation; Phase contrast
1. Introduction: the SYRMEP story The proposal to build a SR facility, later named ELETTRA, was launched during the 71st Annual National Congress of the Italian Physical Society, in October 1985 at Trieste, Italy. Several meetings—generally held at the International Centre for Theoretical Physics (ICTP) in Trieste—immediately focused on the issue of which beam lines had to be developed [1]. The SYRMEP Project, for the construction of a medical beam line, already foreseeing the final phase of ‘‘in vivo’’ mammographic examinations, was presented in 1991 at a meeting of the Program Advisory Committee of the Sincrotrone Trieste SCpA Corresponding author. Tel.: +39 040 558 3369; fax: +39 040 558 3350.
E-mail address: [email protected] (E. Castelli). 0168-9002/$ - see front matter r 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2006.10.295
(ST), the company devoted to the construction of the ELETTRA laboratory. The project approval was subject to the fulfillment of two conditions: finding the necessary funds and starting with the ‘‘in vitro’’ phase, in order to verify the effectiveness of the proposed technique. ELETTRA began its operations in 1993, and in the same year the construction of SYRMEP beam line started off. The University of Trieste was the major source of funding, with a significant contribution of ST; in addition, the National Institute of Nuclear Physics (INFN) supported the development of a new digital detection system. The ‘‘in vitro’’ experimentation was started in 1996 and the results of this preliminary phase were very promising. In 1998 international scientific committees of ST approved the next steps of ‘‘in vivo’’, i.e. with patients, experimentation, provided that the availability of funds was granted. In the
ARTICLE IN PRESS 238
E. Castelli et al. / Nuclear Instruments and Methods in Physics Research A 572 (2007) 237–240
following year the Fondazione CRTrieste financially supported the project, formally called ‘‘Synchrotron X-ray mammography: clinical experimentation’’. Experiments on patients are envisaged; therefore the University of Trieste, the local Hospital and ST signed a 5 years agreement. The INFN continues to support the digital detection system, also in view of possible development in the field of tomo-mammographic experiments. In the year 2000 the beam line modification phase started by designing the patient room with the mobile patient support, the room for medical and technical radiologists, and the control system to comply with all the required safety regulations. In July 2004 the Ethical Committee of the local Hospital authorized the experimentation on patients and in March 2005 an Italian ministerial agency tested out, with positive feedback, the general safety control system; in September a renewed agreement of the three contracting bodies defined the performances to be attained and the responsibilities of the persons involved in the experimentation. Eventually, in January 2006, the Ministry of Health gave the ultimate approval. The scientific results of the SYRMEP collaboration, particularly in the field of development of the silicon detector, were always presented at the Pisa Meetings, starting with the sixth one, in 1994 [2–6]. The total budget for the various parts of the project has been of 2.4 millions euros, without taking the expenses for personnel into account. This budget accounts for the construction of the original beam line [7] and for the upgrading to the clinical mammography system, which leaves the availability of an experimental room for the usual SR experimental activities, when the patient modality is not active.
2. The beam line layout for ‘‘in vivo’’ mammography The upgrading of the original beam line SYRMEP in view of experimentation with patients is shortly discussed in Ref. [8], and in the relevant references therein. A more detailed description of the new equipment can be found in Ref. [9], where in particular the features of the high precision ionization chambers and the patient scanning stage are presented. The new ionization chambers allow the evaluation of the dose delivered to the patient on-line, i.e. during the examination itself. Since the laminar SR beam is fixed, planar images are obtained by scanning with high precision, the patient prone on the support, through the beam. An important aspect to point out here is the very peculiar geometrical set-up of SR mammography in comparison with the standard one carried out by conventional clinical units. In this latter case source, compressed breast and detector are fixed; the source-to-breast distance is of 65 cm and the screen-film cassette is practically in contact with the breast, at 70 cm from the source. The dimensions of the detector are of 18 cm 24 cm; in the
18 cm direction the full compressed breast is seen with an angle of 18/70 ¼ 0.26 radians. With the PhC SR mammography at the SYRMEP beam line the source is fixed, but the breast and the screen-film detector are simultaneously scanned in the vertical direction, in which the beam is 4 mm high; the source-tobreast distance is of 30 m and the breast-to-detector distance is of 2 m. Thus the vertical angle is in this case of 0.004/32 ¼ 0.00013 radians, very different from the previous 0.26. The focal spot sizes is of 300 300 mm2 (or 100 100 mm2 in case some degree of magnification is applied) for a conventional mammography unit, while at SYRMEP is of 1000 100 mm2 in the horizontal and vertical directions, respectively. Although a certain degree of phase contrast is currently achievable also with state-of-the-art micro focal sources [10], the use of a 3rd generation SR source clearly makes these effects much more intense and easier to detect. The results of the next sections show in fact that the availability of such SR high intensity laminar beams of nearly monochromatic and parallel X-rays, allows highlighting the PhC features also in thick objects, like the breast. 3. The ‘‘in vitro’’ digital mammography During the preparatory phase, ‘‘in vitro’’ experiments have been carried out both with digital and analog detectors. A discussion on the results obtained with a detection system developed by the SYRMEP collaboration in the field of the morphological breast imaging can be found in Ref. [11]. It consists of a silicon micro-strip detector equipped with a low noise read-out electronics working in single photon counting mode. The ‘‘edge on’’ configuration defines the pixel structure, achieving moreover high conversion efficiency. Mammographic phantoms and ‘‘in vitro’’ full breast samples have been investigated: with the SR PhC digital mammography it is possible to obtain images with high contrast and good spatial resolution; the doses delivered to the breast tissues during the acquisition are significantly lower than those of a conventional mammography. All these results have been obtained in the experimental station of the original beam line. Afterwards the beam line layout has been modified in order to realize the clinical facility, with the medical radiologist room and the patient examination hall. In this last year, breast samples from mastectomy surgery have been studied using the complete final set-up in order to test the overall control system as well as the security and image quality protocols; in this starting phase the detector is a commercial screen-film mammographic system. Moreover surgical breast specimens from total mastectomy in 4 patients were imaged both by conventional mammography and SR PhC mammography in 1 projection (craniocaudal). Fig. 1 shows a detail of one of these last samples obtained at 18 keV and the comparison with the clinical image on a hospital analog mammographic unit. The increased image
ARTICLE IN PRESS E. Castelli et al. / Nuclear Instruments and Methods in Physics Research A 572 (2007) 237–240
239
fluence. Small size and small contrast imply high dose for good image quality. Since the breast is one of the most radiosensitive organs, the risk of cancer induced by X-ray exposure has to be minimized. Increasing image quality without increasing the dose is therefore one of the primary goals in mammography. The SR implies a practically monochromatic X-ray laminar beam and the PhC imaging; therefore high contrast and spatial resolution can be a priori obtained with dose reduction [12]. For this clinical trial a limited number of volunteer patients has to be selected by radiologists, after routine examinations, on the basis of BI-RADS classification [13]; according to the research program approved by the local Ethical Committee, the recruitment of at least 70 patients to be evaluated by SR PhC mammography is foreseen during the next year. As starting point, 9 female patients, 3 in March and 6 in April 2006, with indeterminate findings at clinical mammography (suspicious opacity not referred to the breast parenchyma, asymmetrical appearance of the two breasts), and not clarified by ultrasound, were examined by digital mammography and SR mammography in 2 projections (oblique and craniocaudal). In SR mammography, patients were examined in a prone position with compressed breast, while the images were obtained by scanning the breast vertically in front of a stationary monochromatic laminar beam. The detector, a commercial mammographic screenfilm system, was about 2 m from the breast, at the correct distance to optimize the so-called phase contrast effects. 5. Results
Fig. 1. Radiological image from a mastectomy acquired: (a) with a conventional screen-film system at a mammography unit of the hospital; and (b) with the SR setup in phase contrast geometry at the SYRMEP beam line of the SR facility ELETTRA. More details are apparent in (b) image.
quality for diagnostical purposes, without dose increment, is apparent. 4. The ‘‘in vivo’’ mammography In the medical community there is a general agreement that an early diagnosis of breast cancer has beneficial consequences on successful prognosis: an early detection saves lives. Early diagnosis of breast cancer implies the detection of microcalcifications (high contrast, small size details) and nodules (low contrast details). Image visibility depends upon object size, object contrast and photon
As far as the physics is concerned, the ‘‘in vivo’’ phase contrast images acquired at the clinical facility match the quality obtained in the previous ‘‘in vitro’’ SR experimental conditions. Moreover the average dose delivered in the SR PhC mammographic examinations is comparable or lower than those used in clinical practice with conventional units. From the clinical side, two independent medical doctors, scoring the conspicuity of the breast parenchyma over background, the depiction of lesion margins and the microcalcification visibility, evaluated the images on film for SR mammography at the SYRMEP beam line and the on-screen for digital mammography, with the GE Senographe 2000D unit of the hospital. The different parameters were better depicted by the SR mammography both in the surgical specimens and patient breasts. In some cases of these first 9 patients, the radiologists have clarified the ambiguity of the previous examinations (digital conventional clinical mammography and/or ultrasound). These preliminary results are encouraging and a complete evaluation of the clinical impact of the new method is in progress. Moreover on the digital detector development side, in collaboration with the Paul Scherrer Institut, Villigen, Switzerland a silicon microstrip laminar detector (Hamamatsu), in ‘‘edge-on’’ geometrical configuration [6],
ARTICLE IN PRESS 240
E. Castelli et al. / Nuclear Instruments and Methods in Physics Research A 572 (2007) 237–240
equipped with single photon counting electronics Mythen II [14], has been successfully tested at the SYRMEP beam line. 6. Conclusions and perspectives This preliminary experience with SR mammography produced high-quality images of the breast both in surgical specimens and humans. The SR PhC technique may therefore improve the overall image quality of clinical mammography. In order to reach a final assessment on the potentiality of the method, a good statistics is of course necessary: the recruitment of over 100 patients to be evaluated by SR PhC mammography is foreseen during the next year. The main goal of the SYRMEP collaboration is to optimize the quality of radiological examinations operating both on the source and on the detector side [15]. Therefore the next step of the project will involve the introduction of conventional and custom digital detectors. This will allow the exploitation of all the advantages pointed out during the long R&D activity of the SYRMEP collaboration in the field of the ‘‘in vitro’’ SR PhC digital mammography. Taking into account the preliminary good results of the custom detector [14], a new proposal has been presented to INFN in order to build a detection system suited to perform ‘‘digital’’ mammographic examinations on patients.
References [1] L. Dalla Palma, E. Castelli, Report from the working group on medical physics, Proceedings of the Workshop on Scientific and Technological Application of Synchrotron Radiation, ICTP, Trieste, 1987, p. 98. [2] F. Arfelli, et al., Nucl. Instr. Meth. A 360 (1995) 283. [3] F. Arfelli, et al., Nucl. Instr. Meth. A 409 (1998) 351. [4] F. Arfelli, et al., Nucl. Instr. Meth. A 409 (1998) 529. [5] M. Prest, et al., Nucl. Instr. Meth. A 461 (2001) 435. [6] A. Bergamaschi, et al., Nucl. Instr. Meth. A 518 (2004) 415. [7] F. Arfelli, et al., Radiology 215 (2000) 286. [8] A. Abrami, et al., Nucl. Instr. Meth. A 548 (2005) 221. [9] F. Arfelli, et al., Synchrotron radiation mammography: clinical experimentation, to be published in AIP Conference Proceedings of the Ninth international Conference on Synchrotron Radiation Instrumentation (SRI 2006), May 28–June 3, 2006, Daegu, Korea. [10] A. Olivo, R. Speller, Phys. Med. Biol. 51 (2006) 3015. [11] R. Longo, et al., Nucl. Instr. Meth. A 497 (2003) 9. [12] F. Arfelli, et al., Phys. Med. Biol. 43 (1998) 2845. [13] American College of Radiology. Illustrated Breast Imaging Reporting and Data System (BI-RADS), 4th ed, Reston VA, ACR, 2003. [14] A. Bergamaschi, B. Schmitt, Paul Scherrer Institut, Villigen, Switzerland, private commuication. [15] E. Castelli, Medical application planned at Elettra: SYRMEP project (Synchrotron Radiation for Medical Physics), in: E. Burattini, A. Balerna (Eds.), Proceedings of the International School of Physics ‘‘Enrico Fermi’’, Course CXXVIII (1994), IOS Press, Amsterdam, 1996, p. 379.