Visualization of sources of scattered radiation from x-ray equipment used for interventional radiology

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1 Visualization of sources of scattered radiation from x-ray equipment used for interventional radiology Poster No.: C-1190 Congress: ECR 2011 Type: Scientific Exhibit Authors: K. Chida, T. Takahashi, D. Ito, M. Sakao, K. Satoh, Y. Miura, M. Zuguchi; Sendai/JP Keywords: Occupational / Environmental hazards, Radiation safety, Dosimetry, Angioplasty, Fluoroscopy, Digital radiography, Catheter arteriography, Radioprotection, Physics in radiology, Interventional vascular DOI: /ecr2011/C-1190 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 26

2 Purpose To clarify and visualize the sources of physician-received scattered radiation in interventional radiology (IR). To present the amount of sphysician-received cattered radiation from IR Xray equipment. To present the importance of radiation protection for the physician in IR. BACKGROUND: IR physicians are at a higher radiation risk compared to other medical professionals. Radiation protection for IR physicians is therefore an important issue [1-8]. In addition, radiation doses to the eyes frequently approach levels that put these physicians at a risk of developing cataracts (a deterministic effect) [9-11]. Therefore, we identified sources of scattered radiation from IR equipment using a pinhole camera. Fig. References: K. Chida; Radiological Technology, Tohoku University School of Health Sciences, Sendai, JAPAN Images for this section: Page 2 of 26

3 Fig. 1 Page 3 of 26

4 Methods and Materials Fig.: Pin-hole camera (handmade; the pin-hole is at the center of a surface camera; the diameter was approximately 0.3 mm). A 2-mm-thick lead (Pb) shield was outside the camera, except at the pin-hole. The camera height (the pin-hole to image receptor distance) was approximately 13 cm and the camera could hold a mm (8 10inch) image receptor. Two types of image receptors were used at the same time: an imaging plate (IP, containing photostimulable phosphors) and a single-emulsion film (film). Thus, these two image receptors were combined with pin-hole camera methods as the film/ip stack. References: K. Chida; Radiological Technology, Tohoku University School of Health Sciences, Sendai, JAPAN Visualization and quantification of physician-received scattered radiation in IR Xray equipment using a pin-hole camera method. (Fig.1 on page 6) Sources of scattered radiation from IR X-ray equipment were visualized using a pinhole camera (Fig.1 on page 6, handmade; the pin-hole is at the center of a surface Page 4 of 26

5 camera; the diameter was approximately 0.3 mm) with image receptors (imaging plate, IP, and single-emulsion film, film).(fig.2 on page 7) Handmade pin-hole camera for visualizing and quantifying the physician-received scattered radiation. (Fig.2 on page 7) These two image receptors (IP and film) were combined with pin-hole camera methods. (The film sits on the IP.) Image receptors were placed in the pin-hole camera in a darkroom. The film was used to detect visual images of X-ray equipment (photographic image), and the IP was used to detect physician-received scattered radiation (a radiographic image). The film was not suitable for detecting physician-received scattered radiation because the intensity of the scattered radiation was lower. The IP detected physician-received scattered radiation with much higher sensitivity. Additionally, the IP was not influenced by visible rays because the IP was behind the film, so that visible rays were shielded by the film on the IP. Geometry of the pin-hole camera and X-ray equipment.(fig.3 on page 8) The pin-hole camera was placed at a distance of 90 cm horizontally from a 20-cm-thick acrylic phantom center (i.e., the central radiation beam on the patient support table) at a height of 100 cm above the floor. X-ray exposure factors were as follows: 17 cm mode Image intensifier (I.I.), the source-to-i.i. distance was 100 cm, and posteroanterior (PA) view. The IPs were scanned with a computed radiology (CR) system using the high-sensitivity mode and the linear-scale mode in the IP readout parameters. Visual image of physician-received scattered radiation using the pin-hole camera method. Under-table X-ray tube system (Fig.4 on page 8) Page 5 of 26

6 (A) Photographic image (Fig.5 on page 9) We took pictures of X-ray equipment using the film. Exposure time with room light was approximately 1 min. (B) Radiographic image (Fig.6 on page 10) We assessed scattered radiation images using the IP and CR system in high-sensitivity readout mode. X-ray irradiation factors were as follows: digital cineangiography (15 f/s), tube voltage: 70 kv, duration time: 20 s. Combined (added) image (A+B) (Fig.7 on page 11) We added the photographic image obtained with the film and the radiographic image obtained with the IP to acquire a combined image of X-ray equipment and scattered radiation. Furthermore, black in the radiographic image was changed to red in the combined image, facilitating visualization. Thus, we could examine and identify the sources of physician-received scattered radiation from the phantom (incident surface), including the patient support table, and the exit port (surface cover) of the X-ray beam-collimating device. Images for this section: Page 6 of 26

7 Fig. 1: Pin-hole camera (handmade; the pin-hole is at the center of a surface camera; the diameter was approximately 0.3 mm). A 2-mm-thick lead (Pb) shield was outside the camera, except at the pin-hole. The camera height (the pin-hole to image receptor distance) was approximately 13 cm and the camera could hold a mm (8 10inch) image receptor. Two types of image receptors were used at the same time: an imaging plate (IP, containing photostimulable phosphors) and a single-emulsion film (film). Thus, these two image receptors were combined with pin-hole camera methods as the film/ip stack. Page 7 of 26

8 Fig. 2: Pin-hole camera (Sectional diagram). A 2-mm-thick lead (Pb) shield was outside the camera, except at the pin-hole. The camera height (the pin-hole to image receptor distance) was approximately 13 cm and the camera could hold a mm (8 10inch) image receptor. Two types of image receptors were used at the same time: an imaging plate (IP, containing photostimulable phosphors) and a single-emulsion film (film). Thus, these two image receptors were combined with pin-hole camera methods as the film/ip stack. Fig. 3: Geometry of the pin-hole camera and X-ray equipment Page 8 of 26

9 Fig. 4: Under-table X-ray tube system Page 9 of 26

10 Fig. 5: (A) Photographic image. We took pictures of X-ray equipment using the film. Exposure time with room light was approximately 1 min. Page 10 of 26

11 Fig. 6: (B) Radiographic image. We assessed scattered radiation images using the IP and CR system in high-sensitivity readout mode. X-ray irradiation factors were as follows: digital cineangiography (15 f/s), tube voltage: 70 kv, duration time: 20 s. Page 11 of 26

12 Fig. 7: Combined (added) image (A+B) (Fig.5+Fig.6). We added the photographic image obtained with the film and the radiographic image obtained with the IP to acquire a combined image of x-ray equipment and scattered radiation. Furthermore, black in the radiographic image was changed to red in the combined image, facilitating visualization. Thus, we could examine and identify the sources of physician-received scattered radiation from the phantom (incident surface), including the patient support table, and the exit port (surface cover) of the X-ray beam-collimating device. Page 12 of 26

13 Results Fig.: Visual image (combined image) of physician-received scattered radiation. (Black in the radiographic image was changed to red in the combined image, facilitating visualization.) Under-table X-ray tube system and the PA view using a 20-cm-thick acrylic phantom. We could examine and identify the sources of physician-received scattered radiation from the phantom (incident surface), including the patient support table, and the exit port (surface cover) of the X-ray beam-collimating device, but not the X-ray tube housing. The X-ray tube housing incorporates lead shielding that absorbs all X-rays except those emanating from the exit port. Thus, the lower part of a physician's body will receive high levels of scattered radiation when an under-table X-ray tube system is used. References: K. Chida; Radiological Technology, Tohoku University School of Health Sciences, Sendai, JAPAN Page 13 of 26

14 Visual image of physician-received scattered radiation (combined image, Fig.1 on page 16) (Under-table X-ray tube system and the PA view using a 20-cm-thick acrylic phantom.) Black in the radiographic image was changed to red in the combined image, facilitating visualization. We could examine and identify the sources of physician-received scattered radiation from the phantom (incident surface), including the patient support table, and the exit port (surface cover) of the X-ray beam-collimating device, but not the X-ray tube housing. The X-ray tube housing incorporates lead shielding that absorbs all X-rays except those emanating from the exit port. Thus, the lower part of a physician's body will receive high levels of scattered radiation when an under-table X-ray tube system is used. Patient (phantom, including the patient support table): Scatter radiation from the incident surface of the phantom is higher than that from other parts of the phantom because the surface of the phantom receives a higher dose, as the incident beam has not been attenuated. Cover of the X-ray beam-collimating device: Generally, the cover of the beam-collimating device is made of thin acrylic, and the percentage of attenuation in the cover is therefore very small. However, the distance between the cover of the beam-collimating device and the X-ray source is also very small; hence, the intensity of radiation exposure is high at the cover. Therefore, the amount of scattered radiation in the cover is high although the percentage attenuation at the cover is very small. Therefore, scatter from the exit port (surface cover) of the collimating device was significant. Over-table X-ray tube system (Fig.2 on page 17) Figure 3 on page 18 shows the scattered radiation (combined image) in an overtable X-ray tube system and the anteroposterior (AP) view using a phantom and pin-hole camera. Page 14 of 26

15 We could also visualize and identify the sources of physician-received scattered radiation from the phantom (incident surface) and exit port of the X-ray beam-collimating device (surface cover) in an over-table X-ray tube system (Fig.3 on page 18). Thus, with an over-table X-ray tube system, the upper part of the physician's body (e.g., the eyes) receives high doses of scattered radiation. In a lateral view, the physician dose when standing at the side of the X-ray tube was higher than that when standing at the side of the image receptor (i.e., I.I.). Stereoscopic image of scattered radiation (Under-table X-ray tube system, Fig.4 on page 20) Figure 5 on page 20 shows a stereo image of scattered radiation (combined image) in an under-table X-ray tube system and the PA view using a phantom and pin-hole camera. We obtained exposure with the pin-hole camera at two positions, separated by a few centimeters. With the three-dimensional effect (Fig.5 on page 20), we could identify the sources of physician-received scattered radiation from the phantom and exit port of the X-ray beamcollimating device (surface cover). Scattered radiation images in various angles and views We visualized the scattered radiation from IR X-ray equipment using a pin-hole camera and human phantom for various tube angles and views. Figures 6-10 show scattered radiation images (combined images) in the left anterior oblique (LAO) 45 view + caudocranial (Cranial) 20 on page 21, LAO50 view on page 22, LAO45 view + craniocaudal (Caudal) 30 on page 22, Cranial 30 view on page 22, and right anterior oblique (RAO) 30 view on page 23, respectively. We could visualize and identify the sources of physician-received scattered radiation from the human phantom (incident surface) and exit port of the X-ray beam-collimating device (surface cover) at various angles and views. These findings provide useful information on radiation protection for IR physicians, especially in percutaneous coronary intervention. Page 15 of 26

16 Fig.6. Scattered radiation image for LAO 45 + Cranial 20 on page 21 Fig.7. Scattered radiation image for LAO 50 on page 22 Fig.8. Scattered radiation image for LAO 45 + Caudal 30 on page 22 Fig.9. Scattered radiation image for Cranial 20 on page 22 Fig.10. Scattered radiation image for RAO 30 on page 23 Quantification of the scattered radiation using the pin-hole camera method We evaluated the amount of scattered radiation from IR X-ray equipment using a pin#hole camera. Figure 11 on page 23 shows scattered radiation image using the IP and CR system. (Under-table X-ray tube system and the PA view using a 20-cm-thick acrylic phantom.) Physician-received scattered radiation levels from the patient (represented by a phantom, including the table) and the surface cover (exit port) of the X-ray beam-collimating device were measured using pixel values of IPs from the image-analysis software provided with the CR system. The total pixel values of each part (phantom including the table and the beam-collimating device surface cover) in the circles were compared (Fig. 11 on page 23). As a result, the proportion of scattered radiation from the patient and exit port of the collimating device was approximately 50:50 in this case. Thus, the scatter from the exit port of the collimating device was not negligible. The proportion will depend on factors including the measurement location (position and height), X-ray tube angled-view, and X-ray output. Images for this section: Page 16 of 26

17 Fig. 1: Visual image (combined image) of physician-received scattered radiation. (Black in the radiographic image was changed to red in the combined image, facilitating visualization.) Under-table X-ray tube system and the PA view using a 20-cm-thick acrylic phantom. We could examine and identify the sources of physician-received scattered radiation from the phantom (incident surface), including the patient support table, and the exit port (surface cover) of the X-ray beam-collimating device, but not the X-ray tube housing. The X-ray tube housing incorporates lead shielding that absorbs all X-rays except those emanating from the exit port. Thus, the lower part of a physician's body will receive high levels of scattered radiation when an under-table X-ray tube system is used. Page 17 of 26

18 Fig. 2: Over-table X-ray tube system and the AP view using a phantom. Page 18 of 26

19 Fig. 3: Visual image (combined image) of physician-received scattered radiation for overtable X-ray tube system and the AP view using a phantom. (The black in the radiographic image was changed to red, facilitating visualization.) We could also visualize and identify the sources of physician-received scattered radiation from the phantom (incident surface) and exit port of the X-ray beam-collimating device (surface cover) in an over-table X-ray Page 19 of 26

20 tube system. Thus, with an over-table X-ray tube system, the upper part of the physician's body (e.g., the eyes) receives high doses of scattered radiation. Fig. 4: Under-table X-ray tube system and the PA view using a phantom. Page 20 of 26

21 Fig. 5: Stereoscopic image of scattered radiation. Visual image (combined image) of physician-received scattered radiation for under-table X-ray tube system and the PA view using a phantom. (The black in the radiographic image was changed to red, facilitating visualization.) We obtained exposure with the pin-hole camera at two positions, separated by a few centimeters. With the three-dimensional effect, we could identify the sources of physician-received scattered radiation from the phantom and exit port of the X-ray beamcollimating device (surface cover). Page 21 of 26

22 Fig. 6: Scattered radiation image for LAO 45 + Cranial 20. (The black in the radiographic image was changed to red, facilitating visualization.) We could visualize and identify the sources of physician-received scattered radiation from the phantom and exit port of the X-ray beam-collimating device (surface cover) in LAO45 + Cranial 20. Fig. 7: Scattered radiation image for LAO 50. (The black in the radiographic image was changed to red, facilitating visualization.) We could visualize and identify the sources of physician-received scattered radiation from the phantom and exit port of the X-ray beamcollimating device (surface cover). Fig. 8: Scattered radiation image for LAO 45 + Caudal 30 (The black in the radiographic image was changed to red, facilitating visualization.) We could visualize and identify the sources of physician-received scattered radiation from the phantom and exit port of the X-ray beam-collimating device (surface cover). Page 22 of 26

23 Fig. 9: Scattered radiation image for Cranial 30. (The black in the radiographic image was changed to red, facilitating visualization.) We could visualize and identify the sources of physician-received scattered radiation from the phantom and exit port of the X-ray beam-collimating device (surface cover). Fig. 10: Scattered radiation image for RAO 30. (The black in the radiographic image was changed to red, facilitating visualization.) We could visualize and identify the sources of physician-received scattered radiation from the phantom and exit port of the X-ray beamcollimating device (surface cover). Page 23 of 26

24 Fig. 11: Scattered radiation images using the IP and CR system. Under-table X-ray tube system and the PA view using a phantom. The total pixel values in the circles for each part (phantom including the table and the beam-collimating device surface cover) were compared. The proportion of scattered radiation (total pixel value) from the patient and exit port of the collimating device was approximately 50:50, although this will depend on the measurement conditions. Page 24 of 26

25 Conclusion We could examine and identify sources of physician-received scattered radiation in an IR X-ray system using a pin-hole camera method. Physicians are mainly exposed to two sources of scattered radiation: radiation reflected from the patient, including the patient support table, and radiation from the cover (exit port) of the X-ray beam-collimating device. The proportion of scattered radiation from the patient and the exit port of the collimating device was approximate 50%:50%. Thus, scatter from the exit port of the collimating device was not negligible. Physicians who stand close to the patient and the X-ray beam-collimating device, where scattered radiation is higher, show higher radiation doses. THerefore, radiation protection for the physician during IR procedures is an important problem. References 1. International Commission on Radiological Protection. ICRP publication 85: avoidance of radiation injuries from medical interventional procedures. Ann ICRP 2001; 30/2:Publication Balter S, et al. Fluoroscopically guided interventional procedures: a review of radiation effects on patients' skin and hair. Radiology ;254: Miller DL, et al. Clinical radiation management for fluoroscopically guided interventional procedures. Radiology ;257: Vano E, et al. Lens injuries induced by occupational exposure in nonoptimized interventional radiology laboratories. Br J Radiol 1998; 71, Williams JR. The interdependence of staff and patient doses in interventional radiology. Br J Radiol 1997; 70: Zuguchi M, et al. Usefulness of non-lead aprons in radiation protection for physicians performing interventional procedures. Radiat Prot Dosimetry 2008;131: Chida K, et al. Effect of radiation monitoring method and formula differences on estimated physician dose during percutaneous coronary intervention. Acta Radiol 2009;50: Chida K, et al. Radiation dose and radiation protection for patients and physicians during interventional procedure. J Radiat Res. 2010;51: Vano E, et al. Eye lens exposure to radiation in interventional suites: caution is warranted. Radiology 2008;248(3): Ainsbury EA, et al. Radiation cataractogenesis: a review of recent studies. Radiat Res. 2009;172: Vano E, et al. Radiation cataract risk in interventional cardiology personnel. Radiat Res. 2010;174: Page 25 of 26

26 Personal Information Correspondence: Koichi Chida, Ph.D, Department of Radiological Technology, Tohoku University School of Health Sciences, Seiryo 2-1, Aoba, Sendai , Japan. Page 26 of 26