Va s c u l a r a n d I n t e r ve n t i o n a l R a d i o l o g y • Te c h n i c a l I n n ov a t i o n Gailloud Radiation Reduction for Fluoroscopically Guided Procedures
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Vascular and Interventional Radiology Technical Innovation
A Large Display Is a Powerful Tool to Reduce Radiation Exposure During Single-Plane Fluoroscopically Guided Procedures Philippe Gailloud1 Gailloud P
OBJECTIVE. Magnification is a well-known, but often overlooked, factor impacting radiation exposure. Modern angiography units are commonly offered with single large monitors that allow multiple configurations, including wide display setting in addition to standard display setting similar to a classic arrangement of multiple monitors. CONCLUSION. By reducing the need for magnification, the wide display mode of large angiography monitors is a simple but extremely efficient tool to decrease radiation exposure to patients and care providers during single-plane procedures.
A
Keywords: angiography, radiation protection, technique DOI:10.2214/AJR.14.13246 Received June 30, 2014; accepted after revision September 1, 2014. P. Gailloud is a consultant to Codman and Penumbra and recipient of research grants from Siemens Medical. 1 Department of Radiology, Division of Interventional Neuroradiology, The Johns Hopkins Hospital, 1800 E Orleans St, Bloomberg 7218, Baltimore, MD 21287. Address correspondence to P. Gailloud ([email protected]).
WEB This is a web exclusive article. AJR 2015; 204:W483–W485 0361–803X/15/2044–W483 © American Roentgen Ray Society
lthough proper training and experience remain key elements in keeping the radiation exposure as low as possible during angiographic procedures, adjunct methods can play an important role in reducing the doses delivered to patients and care providers. These methods include using low-dose protocols for both standard and 3D acquisitions (e.g., reduced dose per frame, variable or low frame rate), limiting the number of angiographic sequences acquired, minimizing the fluoroscopy time and pulse rate, using collimation, and optimizing the patientto-detector distance [1–3]. A well-known, but often overlooked, factor with a significant impact on radiation exposure is the use of magnification [4–7]. Modern angiography units are now commonly offered with a single large monitor that allows multiple viewing configurations, including wide display setting in addition to standard display setting similar to a classic arrangement of multiple monitors (Fig. 1). This article reports a simple experiment that emphasizes the role that single large monitors can play as a dose reduction tool during single-plane procedures by eliminating or reducing the need for magnification. Experiment The experiment was performed using a standard radiographic abdominal and pelvic phantom in a biplane angiography suite (Artis Zee, Siemens Healthcare) equipped with a single 56-inch (142-cm) configurable monitor and 30 × 40 inch
(76 × 102 cm) flat-panel detectors. The two monitor configurations tested were the standard and wide display setting (Fig. 1). A 10-second fixed subtracted radiographic sequence was performed with a variable frame rate setting (4 seconds at 2 frames/s and 6 seconds at 1 frame/s for a total of 14 images per acquisition). The sequence was repeated with and without collimation using each of the following six available input field sizes: zoom 0, 48 cm; zoom 1, 42 cm; zoom 2, 32 cm; zoom 3, 22 cm; zoom 4, 16 cm; and zoom 5, 11 cm (Fig. 2). Fluoroscopy was not performed. The reference point air Kerma (in milligrays) associated with each acquisition was recorded from the report automatically generated by the equipment. The displayed size of the acquired images (i.e., the image seen by the operator during angiography) were compared by measuring the displayed length of a 1-cm gradation of the radiographic ruler (in centimeters) directly on the monitor at each magnification factor in both the standard and wide configurations.
Results The displayed length of a 1-cm gradation of the ruler measured on the monitor showed that the size shift between the standard and wide configurations in the tested equipment was equivalent to 2 zoom factors (Table 1). For example, the measured length of a 1-cm gradation was 3.1 cm using either the 42cm input field size (zoom 1) with the wide display setting or the 22-cm input field size (zoom 3) with the standard display setting. In other words, a visually equivalent image—in terms of the perceived size on the monitor—
AJR:204, April 2015 W483
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Gailloud could be produced using the wide display setting with a twofold decrease in magnification (Fig. 3). With regard to radiation exposure, the reference point air Kerma increased significantly with each increase in magnification. An increase in magnification from zoom 1 to zoom 5 yielded an increase in reference point air Kerma of approximately 520% without collimation and 425% with collimation (Table 1). At an identical magnification, the reference point air Kerma was slightly higher with collimation than without collimation. There was no measured difference between the 48- and 42cm input field sizes (zoom 0 and zoom 1, respectively) because the transition in the tested equipment is an electronic manipulation of the image rather than a true radiographic zoom. Discussion The best strategy with regard to magnification and dose reduction when performing single-plane angiography is to choose a low magnification factor with optimal collimation. However, this option is not practical with standard-size monitors because the structures being investigated become too small to be
Assist A Live A
Assist B Live B
Reference A
Live B Live A
Reference B
Assist A A
B
Fig. 1—Two configurations of single large monitor (56 inches [142 cm]) used in this study. A, Standard setting is typical configuration used during biplane angiography; it may be considered representative of arrangement with multiple monitors (six or eight monitors). Screen size for each panel is slightly bigger with partitions of single monitor than with multiple monitors. A and B refer to two projections. B, Wide setting takes advantage of customizability of single large monitor to enlarge one projection. A and B refer to two projections.
comfortably seen by the operator. This drawback is easily avoided by using a large monitor with a wide display setting, a configuration that offers similar working image sizes at lower magnification factors. Hence, the use of a large monitor is one of the simplest and most powerful methods available to angiographers to reduce radiation exposure without a detectable loss of imaging quality during single-plane angiography procedures. For example, performing angiography in a wide display mode with a zoom factor of 1 (42-cm input field size) rather than at a zoom factor of 3 (22-cm input field size) in a standard display
mode can result in a 50–60% dose reduction depending on whether collimation is used. A similar strategy can be applied to biplane procedures during which one plane is less important than the other—for example, during cerebral aneurysm coiling using one optimal projection. Most large monitors offer variable configuration options with multiple panel sizes and arrangements that can be tailored to specific operators and procedures. The screen size in the standard display setting used in this study is slightly larger than the screen size in a classic arrangement of multiple monitors. Our experiment
TABLE 1: Effect of Magnification on Radiation Exposure Input Field Size (Zoom)
Size of 1-cm Gradation Measured Directly on Monitor (cm)
Reference Point Air Kerma With No Wide Display Setting Standard Display Setting Collimation (mGy)
Relative Increase in Reference Point Air Kerma (%)
Reference Point Air Relative Increase in Kerma With Reference Point Air Collimation (mGy) Kerma (%)
48 cm (0)
2.5
1.3
0.6
100
0.8
42 cm (1)
3.1
1.5
0.6
100
0.8
100 100
32 cm (2)
4.3
2.2
0.9
150
1.1
138
22 cm (3)
6.1
3.1
1.6
267
1.6
200
16 cm (4)
8.7
4.3
2.1
350
2.4
300
11 cm (5)
12.2
6.1
3.1
517
3.4
425
Fig. 2—Examples of noncollimated (left) and collimated (right) radiography images of phantom at 42-cm input field size (zoom 1). Edge of radiopaque ruler was used as landmark to keep degree of collimation identical at various magnification levels evaluated. Scale: centimeters.
W484
AJR:204, April 2015
Downloaded from www.ajronline.org by NYU Langone Med Ctr-Sch of Med on 04/23/15 from IP address 128.122.253.212. Copyright ARRS. For personal use only; all rights reserved
Radiation Reduction for Fluoroscopically Guided Procedures plicable dose reduction method. The potential advantage of the simple technique described here needs to be confirmed by a study quantifying the gain in radiation protection achieved in patients and the impact on clinical image quality. Although no image degradation was subjectively noticeable between the wide and standard display settings in this preliminary evaluation, a formal assessment of the image quality using line-pair or contrast resolution phantoms was not performed.
A
Conclusion More than just a pragmatic or esthetic addition to the angiography suite, recently introduced single large angiography monitors are a simple but extremely efficient tool to decrease radiation exposure to patients and care providers. The dose reduction role of large monitors with customizable configurations can be adapted to various clinical situations and operators’ preferences. References
B Fig. 3—Imaging of phantom at two magnification levels: 22-cm input field size (zoom 3) and 42-cm input field size (zoom 1). A, Radiography images of phantom shown in standard display setting using 22-cm input field size (zoom 3); this magnification factor offers reasonable image size for spinal angiography. Scale: centimeters. B, Radiography images of phantom shown in wide display setting using 42-cm input field size (zoom 1). Note that size and quality of images are comparable to images shown in A in spite of magnification level being set two zoom levels lower. Scale: centimeters.
was performed on a single angiography unit with a single large monitor to have directly comparable doses, but the exposure reduction may be even more significant when compared with an angiography unit with multiple monitors. Centers that have multiple angiography suites with different types of monitors
should try adapting their daily schedule to get optimal radiation reduction benefits— for example, by prioritizing the use of suites equipped with a large display for singleplane procedures. This brief investigation using a phantom aims to raise awareness about an easily ap-
1. Pearl MS, Torok C, Wang J, Wyse E, Mahesh M, Gailloud P. Practical techniques for reducing radiation exposure during cerebral angiography procedures. J Neurointerv Surg 2014 Jan 31 [Epub ahead of print] 2. Pearl MS, Torok CM, Messina SA, et al. Reducing radiation dose while maintaining diagnostic image quality of cerebral three-dimensional digital subtraction angiography: an in vivo study in swine. J Neurointerv Surg 2014; 6:672–676 3. Pearl MS, Torok C, Katz Z, et al. Diagnostic quality and accuracy of low dose 3D-DSA protocols in the evaluation of intracranial aneurysms. J Neurointerv Surg 2014 Apr 8 [Epub ahead of print] 4. Mahesh M. Fluoroscopy: patient radiation exposure issues. RadioGraphics 2001; 21:1033–1045 5. Miller DL, Balter S, Noonan PT, Georgia JD. Minimizing radiation-induced skin injury in interventional radiology procedures. Radiology 2002; 225:329–336 6. Stecker MS, Balter S, Towbin RB, et al.; SIR Safety and Health Committee; CIRSE Standards of Practice Committee. Guidelines for patient radiation dose management. J Vasc Interv Radiol 2009; 20(suppl 7):S263–S273 7. Miller DL, Balter S, Schueler BA, Wagner LK, Strauss KJ, Vañó E. Clinical radiation management for fluoroscopically guided interventional procedures. Radiology 2010; 257:321–332
AJR:204, April 2015 W485
Downloaded from www.ajronline.org by NYU Langone Med Ctr-Sch of Med on 04/23/15 from IP address 128.122.253.212. Copyright ARRS. For personal use only; all rights reserved
Vascular and Interventional Radiology Technical Innovation
A Large Display Is a Powerful Tool to Reduce Radiation Exposure During Single-Plane Fluoroscopically Guided Procedures Philippe Gailloud1 Gailloud P
OBJECTIVE. Magnification is a well-known, but often overlooked, factor impacting radiation exposure. Modern angiography units are commonly offered with single large monitors that allow multiple configurations, including wide display setting in addition to standard display setting similar to a classic arrangement of multiple monitors. CONCLUSION. By reducing the need for magnification, the wide display mode of large angiography monitors is a simple but extremely efficient tool to decrease radiation exposure to patients and care providers during single-plane procedures.
A
Keywords: angiography, radiation protection, technique DOI:10.2214/AJR.14.13246 Received June 30, 2014; accepted after revision September 1, 2014. P. Gailloud is a consultant to Codman and Penumbra and recipient of research grants from Siemens Medical. 1 Department of Radiology, Division of Interventional Neuroradiology, The Johns Hopkins Hospital, 1800 E Orleans St, Bloomberg 7218, Baltimore, MD 21287. Address correspondence to P. Gailloud ([email protected]).
WEB This is a web exclusive article. AJR 2015; 204:W483–W485 0361–803X/15/2044–W483 © American Roentgen Ray Society
lthough proper training and experience remain key elements in keeping the radiation exposure as low as possible during angiographic procedures, adjunct methods can play an important role in reducing the doses delivered to patients and care providers. These methods include using low-dose protocols for both standard and 3D acquisitions (e.g., reduced dose per frame, variable or low frame rate), limiting the number of angiographic sequences acquired, minimizing the fluoroscopy time and pulse rate, using collimation, and optimizing the patientto-detector distance [1–3]. A well-known, but often overlooked, factor with a significant impact on radiation exposure is the use of magnification [4–7]. Modern angiography units are now commonly offered with a single large monitor that allows multiple viewing configurations, including wide display setting in addition to standard display setting similar to a classic arrangement of multiple monitors (Fig. 1). This article reports a simple experiment that emphasizes the role that single large monitors can play as a dose reduction tool during single-plane procedures by eliminating or reducing the need for magnification. Experiment The experiment was performed using a standard radiographic abdominal and pelvic phantom in a biplane angiography suite (Artis Zee, Siemens Healthcare) equipped with a single 56-inch (142-cm) configurable monitor and 30 × 40 inch
(76 × 102 cm) flat-panel detectors. The two monitor configurations tested were the standard and wide display setting (Fig. 1). A 10-second fixed subtracted radiographic sequence was performed with a variable frame rate setting (4 seconds at 2 frames/s and 6 seconds at 1 frame/s for a total of 14 images per acquisition). The sequence was repeated with and without collimation using each of the following six available input field sizes: zoom 0, 48 cm; zoom 1, 42 cm; zoom 2, 32 cm; zoom 3, 22 cm; zoom 4, 16 cm; and zoom 5, 11 cm (Fig. 2). Fluoroscopy was not performed. The reference point air Kerma (in milligrays) associated with each acquisition was recorded from the report automatically generated by the equipment. The displayed size of the acquired images (i.e., the image seen by the operator during angiography) were compared by measuring the displayed length of a 1-cm gradation of the radiographic ruler (in centimeters) directly on the monitor at each magnification factor in both the standard and wide configurations.
Results The displayed length of a 1-cm gradation of the ruler measured on the monitor showed that the size shift between the standard and wide configurations in the tested equipment was equivalent to 2 zoom factors (Table 1). For example, the measured length of a 1-cm gradation was 3.1 cm using either the 42cm input field size (zoom 1) with the wide display setting or the 22-cm input field size (zoom 3) with the standard display setting. In other words, a visually equivalent image—in terms of the perceived size on the monitor—
AJR:204, April 2015 W483
Downloaded from www.ajronline.org by NYU Langone Med Ctr-Sch of Med on 04/23/15 from IP address 128.122.253.212. Copyright ARRS. For personal use only; all rights reserved
Gailloud could be produced using the wide display setting with a twofold decrease in magnification (Fig. 3). With regard to radiation exposure, the reference point air Kerma increased significantly with each increase in magnification. An increase in magnification from zoom 1 to zoom 5 yielded an increase in reference point air Kerma of approximately 520% without collimation and 425% with collimation (Table 1). At an identical magnification, the reference point air Kerma was slightly higher with collimation than without collimation. There was no measured difference between the 48- and 42cm input field sizes (zoom 0 and zoom 1, respectively) because the transition in the tested equipment is an electronic manipulation of the image rather than a true radiographic zoom. Discussion The best strategy with regard to magnification and dose reduction when performing single-plane angiography is to choose a low magnification factor with optimal collimation. However, this option is not practical with standard-size monitors because the structures being investigated become too small to be
Assist A Live A
Assist B Live B
Reference A
Live B Live A
Reference B
Assist A A
B
Fig. 1—Two configurations of single large monitor (56 inches [142 cm]) used in this study. A, Standard setting is typical configuration used during biplane angiography; it may be considered representative of arrangement with multiple monitors (six or eight monitors). Screen size for each panel is slightly bigger with partitions of single monitor than with multiple monitors. A and B refer to two projections. B, Wide setting takes advantage of customizability of single large monitor to enlarge one projection. A and B refer to two projections.
comfortably seen by the operator. This drawback is easily avoided by using a large monitor with a wide display setting, a configuration that offers similar working image sizes at lower magnification factors. Hence, the use of a large monitor is one of the simplest and most powerful methods available to angiographers to reduce radiation exposure without a detectable loss of imaging quality during single-plane angiography procedures. For example, performing angiography in a wide display mode with a zoom factor of 1 (42-cm input field size) rather than at a zoom factor of 3 (22-cm input field size) in a standard display
mode can result in a 50–60% dose reduction depending on whether collimation is used. A similar strategy can be applied to biplane procedures during which one plane is less important than the other—for example, during cerebral aneurysm coiling using one optimal projection. Most large monitors offer variable configuration options with multiple panel sizes and arrangements that can be tailored to specific operators and procedures. The screen size in the standard display setting used in this study is slightly larger than the screen size in a classic arrangement of multiple monitors. Our experiment
TABLE 1: Effect of Magnification on Radiation Exposure Input Field Size (Zoom)
Size of 1-cm Gradation Measured Directly on Monitor (cm)
Reference Point Air Kerma With No Wide Display Setting Standard Display Setting Collimation (mGy)
Relative Increase in Reference Point Air Kerma (%)
Reference Point Air Relative Increase in Kerma With Reference Point Air Collimation (mGy) Kerma (%)
48 cm (0)
2.5
1.3
0.6
100
0.8
42 cm (1)
3.1
1.5
0.6
100
0.8
100 100
32 cm (2)
4.3
2.2
0.9
150
1.1
138
22 cm (3)
6.1
3.1
1.6
267
1.6
200
16 cm (4)
8.7
4.3
2.1
350
2.4
300
11 cm (5)
12.2
6.1
3.1
517
3.4
425
Fig. 2—Examples of noncollimated (left) and collimated (right) radiography images of phantom at 42-cm input field size (zoom 1). Edge of radiopaque ruler was used as landmark to keep degree of collimation identical at various magnification levels evaluated. Scale: centimeters.
W484
AJR:204, April 2015
Downloaded from www.ajronline.org by NYU Langone Med Ctr-Sch of Med on 04/23/15 from IP address 128.122.253.212. Copyright ARRS. For personal use only; all rights reserved
Radiation Reduction for Fluoroscopically Guided Procedures plicable dose reduction method. The potential advantage of the simple technique described here needs to be confirmed by a study quantifying the gain in radiation protection achieved in patients and the impact on clinical image quality. Although no image degradation was subjectively noticeable between the wide and standard display settings in this preliminary evaluation, a formal assessment of the image quality using line-pair or contrast resolution phantoms was not performed.
A
Conclusion More than just a pragmatic or esthetic addition to the angiography suite, recently introduced single large angiography monitors are a simple but extremely efficient tool to decrease radiation exposure to patients and care providers. The dose reduction role of large monitors with customizable configurations can be adapted to various clinical situations and operators’ preferences. References
B Fig. 3—Imaging of phantom at two magnification levels: 22-cm input field size (zoom 3) and 42-cm input field size (zoom 1). A, Radiography images of phantom shown in standard display setting using 22-cm input field size (zoom 3); this magnification factor offers reasonable image size for spinal angiography. Scale: centimeters. B, Radiography images of phantom shown in wide display setting using 42-cm input field size (zoom 1). Note that size and quality of images are comparable to images shown in A in spite of magnification level being set two zoom levels lower. Scale: centimeters.
was performed on a single angiography unit with a single large monitor to have directly comparable doses, but the exposure reduction may be even more significant when compared with an angiography unit with multiple monitors. Centers that have multiple angiography suites with different types of monitors
should try adapting their daily schedule to get optimal radiation reduction benefits— for example, by prioritizing the use of suites equipped with a large display for singleplane procedures. This brief investigation using a phantom aims to raise awareness about an easily ap-
1. Pearl MS, Torok C, Wang J, Wyse E, Mahesh M, Gailloud P. Practical techniques for reducing radiation exposure during cerebral angiography procedures. J Neurointerv Surg 2014 Jan 31 [Epub ahead of print] 2. Pearl MS, Torok CM, Messina SA, et al. Reducing radiation dose while maintaining diagnostic image quality of cerebral three-dimensional digital subtraction angiography: an in vivo study in swine. J Neurointerv Surg 2014; 6:672–676 3. Pearl MS, Torok C, Katz Z, et al. Diagnostic quality and accuracy of low dose 3D-DSA protocols in the evaluation of intracranial aneurysms. J Neurointerv Surg 2014 Apr 8 [Epub ahead of print] 4. Mahesh M. Fluoroscopy: patient radiation exposure issues. RadioGraphics 2001; 21:1033–1045 5. Miller DL, Balter S, Noonan PT, Georgia JD. Minimizing radiation-induced skin injury in interventional radiology procedures. Radiology 2002; 225:329–336 6. Stecker MS, Balter S, Towbin RB, et al.; SIR Safety and Health Committee; CIRSE Standards of Practice Committee. Guidelines for patient radiation dose management. J Vasc Interv Radiol 2009; 20(suppl 7):S263–S273 7. Miller DL, Balter S, Schueler BA, Wagner LK, Strauss KJ, Vañó E. Clinical radiation management for fluoroscopically guided interventional procedures. Radiology 2010; 257:321–332
AJR:204, April 2015 W485
