- Email: [email protected]
Impact of Mobile Phone Interference on Gamma Camera Performance
Journal of Medical Imaging and Radiation Sciences
Journal of Medical Imaging and Radiation Sciences xx (2018) 1-6
Journal de l’imagerie médicale et des sciences de la radiation
www.elsevier.com/locate/jmir
Clinical Perspective
Impact of Mobile Phone Interference on Gamma Camera Performance Melissa Dowling, BMed Rad Sc (Nucl Med) (Hons)a, Samantha O’Loughlin, BMed Rad Sc (Nucl Med) (Hons)b and Geoffrey M. Currie, BPharm, MMed Rad Sc (Nucl Med), MAppMngt (Health), MBA, PhDac* a
Faculty of Science, Charles Sturt University, Wagga Wagga, Australia b Regional Imaging Riverina, Wagga Wagga, Australia c Faculty of Health, Regis University, Boston, USA
ABSTRACT Introduction: Electromagnetic interference (EMI) due to a mobile phone device has been reported to produce a detrimental effect on the function of a gamma camera system. This effect provides evidentiary support of potential bans or restrictions regarding mobile phone use within a nuclear medicine department.
RESUM E Introduction : Il a ete indique que l’interference electromagnetique (EMI) causee par un telephone mobile pouvait produire un effet nuisible aufonctionnementd’unsystemedecameragamma.Ceteffetvientappuyer par des donnees probantes l’interdiction potentielle ou les restrictions a l’utilisation des telephones mobiles dans un service de medecine nucleaire.
Methodology: A 3G Apple iPhone 6 was tested against a thyroid phantom in four operating modes, in three positions. Testing was carried out on a Siemens E-Cam gamma camera and a GE Discovery 670 SPECT/ CT gamma camera. The protocols were standardized for operation on both systems with static images obtained for assessment. The static images were arithmetically assessed by means of subtraction from a baseline image, for results of potential EMI to be determined following comparison to the baseline image.
Methodologie : Un appareil Apple iPhone 6 3G a ete teste avec un fant^ome de thyro€ıde dans quatre modes de fonctionnement, en trois positions. Les essais ont ete menes sur une camera gamma Siemens E-Cam et une camera gamma de TEM/TDM GE Discovery 670. Les protocoles ont ete normalises pour le fonctionnement sur les deux systemes et des images statiques ont ete obtenues pour evaluation. Les images statiques ont ete evaluees arithmetiquement par soustraction a partir d’une image de reference, afin de determiner l’EMI potentielle apres comparaison avec l’image de reference.
Results: Initial assessment of static images acquired provided no abnormality between modes and positions. Following the application of arithmetic processes, the inferior right lobe presented with an increased ring of activity on activation of mobile signals regardless of position when tested on the Siemens E-Cam gamma camera. When compared to the GE Discovery 670 SPECT/CT gamma camera, these results did not appear to be present. This was confirmed numerically as a statistical significant difference was noted in count differences between the Siemens E-Cam and GE Discovery (P ¼ 0.0004). Conclusion: The function of a gamma camera has the potential to be influenced by EMI produced by mobile phone devices. Further investigation is warranted employing SPECT acquisition to assess the potential for amplification of errors.
Resultats : L’evaluation initiale des images statiques acquises n’a montre aucune anomalie entre les modes et les positions. Apres application des traitements arithmetiques, le lobe inferieur droit presentait une ceinture d’activite accrue au moment de l’activation du signal mobile sans egard a la position lors des tests sur la camera gamma Siemens E-Cam. En comparaison, ces resultats ne semblent pas appara^ıtre avec la camera gamma TEM/TDM GE Discovery 670, ce qui a ete confirme numeriquement, une difference statistiquement significative ayant ete notee dans les ecarts de compte entre les appareils Siemens E-Cam et GE Discovery (P¼0,0004). Conclusion : Le fonctionnement des cameras gamma peut potentiellement ^etre influence par l’EMI produite par les telephones mobiles. Des recherches plus poussees sont justifiees, en utilisant l’acquisition d’image par TEM pour evaluer le potentiel d’amplification des erreurs.
Keywords: EMI; mobile phone; interference; gamma camera
* Corresponding author. Geoffrey M. Currie, School of Dentistry and Health Sciences, Locked Bag 588, Charles Sturt University, Wagga, Wagga, NSW 2678, Australia. E-mail address: [email protected] (G.M. Currie). 1939-8654/$ - see front matter Ó 2018 Published by Elsevier Inc. on behalf of Canadian Association of Medical Radiation Technologists. https://doi.org/10.1016/j.jmir.2018.06.003
Introduction The use of mobile phones around medical devices has been reported to cause various degrees of interference, with the most serious effects occurring at distances of less than one meter. This interference is due to the electromagnetic interference (EMI) generated by mobile phones while operated as either transmitting or receiving devices. Although these previous occurrences are reported on medical equipment, only three studies have been conducted regarding their potential impact on the function of gamma cameras used within Nuclear Medicine departments with variable or nonreproducible results. The potential of mobile phone–induced EMI is an important issue regarding the quality of images that are produced. Data suggest that the closer a device (eg. phone) is to the gamma camera, the more likely it will cause an effect, in particular, count reduction [1–3]. With the increasing popularity of mobile phones, the chance of a device being left in a patient’s pocket during a scan is increased. Azizmohammadi et al [1] reported a case in which a mobile phone began ringing while in a patient’s pocket during a routine renal scan. They reported the production of abnormal bright dots observed in the frame corresponding to the ringing of the phone before returning to normal. Javadi et al [2] tested seven different models of mobile phones, all of which operated under global system mobile at 900 MHz, and were tested in standby, ringing, and while making a call. The results from this study demonstrated that different mobile phone models had different effects of EMI. Some models had significant effects on count density, while others had none; however, the only effects noted were during ringing of the phone (not standby). Pashazadeh et al [3] tested a GSM 900 MHz mobile device at different distances from a gamma camera, as well as different angles during a SPECT rotation. The results suggested that when mobile phones were operated under ringing conditions, they demonstrated a decrease in the overall count rate, compared to standby mode.
Figure 1. Schematic of thyroid phantom setup.
to test whether the resulting EMI resulted in an alteration of gamma camera performance. Specific objectives included to employ control conditions to evaluate phone impact in multiple modes in different positions relative to the object being imaged. A thyroid phantom was tested against an Apple iPhone 6 operating in multiple modes (standby, ringing, answer, and music), while located in three different positions. Planar imaging was performed using Siemens E-Cam SPECT gamma camera and General Electric (GE) Discovery 670 SPECT/ CT gamma camera. A summary of the scan parameters utilized throughout each study is included in table 1. System settings remained consistent throughout testing, utilizing low energy high resolution collimators with a 20% window centered on 140 keV for 99mTc. The three positions employed varied throughout the study based around the thyroid phantom. The phone was positioned supine directly on the detector against the superior aspect of the thyroid for position 1; supine directly posterior to the phantom for position 2; and elevated posteriorly by 10 cm behind the phantom for position 3; as illustrated in figure 1. For each of the 2 gamma camera configurations, a baseline static was obtained of the thyroid phantom. In position 1 (figure 2), a 1-minute static planar image was acquired for each of the following variations: the phone in standby mode, the phone continuously ringing, the phone during an answered call, and then the phone
Methods The aim of this investigation was to evaluate the function of the gamma camera during operation of a mobile phone and Table 1 Scan Parameters Used in Thyroid Phantom Acquisition Thyroid phantom
Matrix Zoom Pan x Pan y Detector Scan Time Dose Start Time
2
Siemens E-cam
GE Discovery 670
512 512 3.2 4 12 2 1 min 62.1MBq at 1640 1710
512 512 3.2 0 0 2 1 min 65.2MBq at 1626 1643
Figure 2. Position 1 set up on phone for Siemens E-Cam testing.
M. Dowling et al./Journal of Medical Imaging and Radiation Sciences
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(2018) 1-6
Figure 5. Siemens E-Cam baseline thyroid acquisition.
Figure 3. Position 2 set up on phone for Siemens E-Cam testing.
playing continuous music. This process was repeated after the phone had been relocated to positions 2 and 3, respectively (figure 3 and 4). Care was taken to ensure no movement of the phantom occurred between mobile positions and the resulted images (including subtraction) examined for evidence of motion. The statistical significance was calculated using Student’s t test for continuous data. The F test analysis of variances was used to determine statistically significant differences within grouped data. A P value less than 0.05 was considered significant. Results Figure 4. Position 3 set up on phone for Siemens E-Cam testing.
The thyroid phantom has three ‘‘cold’’ nodes located on both superior left and right poles, as well as one located on
Figure 6. Siemens E-Cam initial thyroid acquisitions.
M. Dowling et al./Journal of Medical Imaging and Radiation Sciences
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(2018) 1-6
3
Figure 7. GE Discovery baseline thyroid acquisition.
the right inferior pole. The final inferior left pole appears as a ‘‘hot’’ node. The thyroid is spilt down the isthmus with the right lobe demonstrating an increase of activity compared to the left. Initial visual inspection of all acquired images (modes of operation and positions) appears to maintain the same level of quality, uniformity, and resolution when compared to the baseline image (figures 5-8). Results following subtraction of each image from baseline demonstrated no artifact for standby mode in position 1 (figure 9); however, all other modes in position 1 and all modes, including standby in positions 2 and 3, created artifactual counts. This artifact is highlighted by the ring appearance around the inferior right nodule and some evidence of artifactual counts at other nodule sites (figure 9-11). Conversely, subtracted images acquired on the GE Discovery, demonstrated no post subtraction artifact in any position across all modes (figures 12-14).
Figure 9. Siemens E-Cam position 1 subtraction results.
Decay-corrected counts for each image were evaluated between baseline total counts and each position/mode to further quantitate the previous observations. There was no statistically significant variations between baseline total counts and any positions/mode combinations for images obtained on the GE Discovery (P ¼ 0.710). The mean difference between individual total counts for images and the baseline was 55.8 counts (95% confidence interval [CI]) 319 to 431), which supports the lack of statistically significant variation. There was, however, a statistically significant increase in counts noted from baseline to individual position/mode
Figure 8. GE Discovery initial thyroid acquisitions.
4
M. Dowling et al./Journal of Medical Imaging and Radiation Sciences
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(2018) 1-6
Figure 10. Siemens E-Cam position 2 subtraction results.
combinations (P ¼ 0.0005) with the mean difference (image minus baseline) of 1008.9 counts (95% CI 1384 to 633.8). A statistically significant difference was also noted in count differences (baseline minus each position/mode combination) between Siemens and GE (P ¼ 0.0004) (Figure 15). No statistical significant difference was noted in count differences (baseline minus images) based on grouped data of GE and Siemens based on position (P ¼ 0.847) or mode of operation (P ¼ 0.953). This observation remained true when observing the data for Siemens or GE results
Figure 11. Siemens E-Cam position 3 subtraction results.
Figure 12. GE Discovery position 1 subtraction results.
independently (rather than pooled) for Siemens P ¼ 0.360 and P ¼ 0.338, respectively, and for GE P ¼ 0.340 and P ¼ 0.623, respectively. Although no statistically significant differences were shown, as expected, ringing mode and position 2 created the greatest increase in artifactual counts. Discussion The use of mobile phone devices has increased dramatically increasing the occurrence and potential risk of EMI
Figure 13. GE Discovery position 2 subtraction results.
M. Dowling et al./Journal of Medical Imaging and Radiation Sciences
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(2018) 1-6
5
These observations were noted with planar imaging. Artifact in SPECT data may have a greater impact as errors are multiplied several orders of magnitude during the reconstruction process. It is recommended, therefore, that mobile phones are not left with a patient during scanning even if the phone is out of the field of view. Staff should be mindful of carrying a mobile phone and in particular using a mobile phone in close proximity to a gamma camera during data acquisition. It is also recommended that vendors are quizzed with respect to EMI shielding in their systems before purchase. A complete ban of mobile devices in a nuclear medicine department is not warranted. Instead, further investigation of the impact on SPECT data is recommended. Conclusion Mobile phones are capable of generating EMI sufficient, in all modes, to create artifactual count data on some gamma cameras. Caution is advised when mobile phone devices are to be used in immediate proximity to gamma camera during image acquisition. Figure 14. GE Discovery position 3 subtraction results.
Footnotes within the environment [4,5]. Unlike the initial case reported by Azizmohammadi et al [1], this study showed no initial observable effect with image quality, until affected at an arithmetic level (subtraction). These results also suggest that there is a potential difference between the applications of EMI shielding between manufacturers, gamma camera generation or, indeed, associated with hardware for hybrid capability. EMI shielding applied within gamma camera systems is housed around the photomultiplier tube components [6]. The photomultiplier tube are highly susceptible to environmental factors that include electromagnetic fields, which can affect and compromise their sensitivity [6]. Variations in the integrity and capability of this shielding between generations and manufacturers are likely to see varied responses to EMI.
Contributors: All authors contributed to the conception or design of the work, the acquisition, analysis, or interpretation of the data. All authors were involved in drafting and commenting on the paper and have approved the final version. Funding: This study did not receive any specific grant from funding agencies in the public, commercial, or notfor- profit sectors. Competing interests: All authors declare: no financial relationships with any organizations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work. Ethical approval: Not required.
References
Figure 15. Difference in counts between Siemens and GE. The diamonds represent the 95% CI of each mean (center line of diamond) and the horizontal line represents the overall mean. The circles are data points and self explanatory based on the X and Y axis headings.
6
[1] Azizmohammadi, Z., Baharfar, N., & Javadi, H., et al. (2011). Effect of mobile cell phone ringing on function of gamma camera. Clin Nucl Med 36, 1131. [2] Javadi, H., Azizmohammadi, Z., & Pashazadeh, M. A., et al. (2014). The electromagnetic interference of mobile phones on the function of a gamma camera. Clin Nucl Med 39, 232–236. [3] Pashazadeh, A. M., Dehkordi, F. J., Tanha, K., & Assadi, M. (2015). The effect of electromagnetic field generated by a mobile phone on the performance of a SPECT scanner. Clin Nucl Med 40(7), 545–547. [4] Choi, Y., Yoo, Y., Kim, J., & Kim, S. (2006). A comparison of the corrosion resistance of Cu–Ni–stainless steel multilayers used for EMI shielding. Surf Coat Technol 201(6), 3775–3782. [5] Pashazadeh, A. M., Aghajani, M., Nabipour, I., & Assadi, M. (2013). An update on mobile phones interference with medical devices. Radiat Prot Dosimetry 156, 401–406. [6] Flyckt, S., & Marmonier, C. (2002). Photomultiplier tubes principles & applications. France: Photonis. Retrieved from. http://www2.pv.infn.it/ wdebari/doc/Flyckt_Marmonier.pdf.
M. Dowling et al./Journal of Medical Imaging and Radiation Sciences
-
(2018) 1-6
Journal of Medical Imaging and Radiation Sciences xx (2018) 1-6
Journal de l’imagerie médicale et des sciences de la radiation
www.elsevier.com/locate/jmir
Clinical Perspective
Impact of Mobile Phone Interference on Gamma Camera Performance Melissa Dowling, BMed Rad Sc (Nucl Med) (Hons)a, Samantha O’Loughlin, BMed Rad Sc (Nucl Med) (Hons)b and Geoffrey M. Currie, BPharm, MMed Rad Sc (Nucl Med), MAppMngt (Health), MBA, PhDac* a
Faculty of Science, Charles Sturt University, Wagga Wagga, Australia b Regional Imaging Riverina, Wagga Wagga, Australia c Faculty of Health, Regis University, Boston, USA
ABSTRACT Introduction: Electromagnetic interference (EMI) due to a mobile phone device has been reported to produce a detrimental effect on the function of a gamma camera system. This effect provides evidentiary support of potential bans or restrictions regarding mobile phone use within a nuclear medicine department.
RESUM E Introduction : Il a ete indique que l’interference electromagnetique (EMI) causee par un telephone mobile pouvait produire un effet nuisible aufonctionnementd’unsystemedecameragamma.Ceteffetvientappuyer par des donnees probantes l’interdiction potentielle ou les restrictions a l’utilisation des telephones mobiles dans un service de medecine nucleaire.
Methodology: A 3G Apple iPhone 6 was tested against a thyroid phantom in four operating modes, in three positions. Testing was carried out on a Siemens E-Cam gamma camera and a GE Discovery 670 SPECT/ CT gamma camera. The protocols were standardized for operation on both systems with static images obtained for assessment. The static images were arithmetically assessed by means of subtraction from a baseline image, for results of potential EMI to be determined following comparison to the baseline image.
Methodologie : Un appareil Apple iPhone 6 3G a ete teste avec un fant^ome de thyro€ıde dans quatre modes de fonctionnement, en trois positions. Les essais ont ete menes sur une camera gamma Siemens E-Cam et une camera gamma de TEM/TDM GE Discovery 670. Les protocoles ont ete normalises pour le fonctionnement sur les deux systemes et des images statiques ont ete obtenues pour evaluation. Les images statiques ont ete evaluees arithmetiquement par soustraction a partir d’une image de reference, afin de determiner l’EMI potentielle apres comparaison avec l’image de reference.
Results: Initial assessment of static images acquired provided no abnormality between modes and positions. Following the application of arithmetic processes, the inferior right lobe presented with an increased ring of activity on activation of mobile signals regardless of position when tested on the Siemens E-Cam gamma camera. When compared to the GE Discovery 670 SPECT/CT gamma camera, these results did not appear to be present. This was confirmed numerically as a statistical significant difference was noted in count differences between the Siemens E-Cam and GE Discovery (P ¼ 0.0004). Conclusion: The function of a gamma camera has the potential to be influenced by EMI produced by mobile phone devices. Further investigation is warranted employing SPECT acquisition to assess the potential for amplification of errors.
Resultats : L’evaluation initiale des images statiques acquises n’a montre aucune anomalie entre les modes et les positions. Apres application des traitements arithmetiques, le lobe inferieur droit presentait une ceinture d’activite accrue au moment de l’activation du signal mobile sans egard a la position lors des tests sur la camera gamma Siemens E-Cam. En comparaison, ces resultats ne semblent pas appara^ıtre avec la camera gamma TEM/TDM GE Discovery 670, ce qui a ete confirme numeriquement, une difference statistiquement significative ayant ete notee dans les ecarts de compte entre les appareils Siemens E-Cam et GE Discovery (P¼0,0004). Conclusion : Le fonctionnement des cameras gamma peut potentiellement ^etre influence par l’EMI produite par les telephones mobiles. Des recherches plus poussees sont justifiees, en utilisant l’acquisition d’image par TEM pour evaluer le potentiel d’amplification des erreurs.
Keywords: EMI; mobile phone; interference; gamma camera
* Corresponding author. Geoffrey M. Currie, School of Dentistry and Health Sciences, Locked Bag 588, Charles Sturt University, Wagga, Wagga, NSW 2678, Australia. E-mail address: [email protected] (G.M. Currie). 1939-8654/$ - see front matter Ó 2018 Published by Elsevier Inc. on behalf of Canadian Association of Medical Radiation Technologists. https://doi.org/10.1016/j.jmir.2018.06.003
Introduction The use of mobile phones around medical devices has been reported to cause various degrees of interference, with the most serious effects occurring at distances of less than one meter. This interference is due to the electromagnetic interference (EMI) generated by mobile phones while operated as either transmitting or receiving devices. Although these previous occurrences are reported on medical equipment, only three studies have been conducted regarding their potential impact on the function of gamma cameras used within Nuclear Medicine departments with variable or nonreproducible results. The potential of mobile phone–induced EMI is an important issue regarding the quality of images that are produced. Data suggest that the closer a device (eg. phone) is to the gamma camera, the more likely it will cause an effect, in particular, count reduction [1–3]. With the increasing popularity of mobile phones, the chance of a device being left in a patient’s pocket during a scan is increased. Azizmohammadi et al [1] reported a case in which a mobile phone began ringing while in a patient’s pocket during a routine renal scan. They reported the production of abnormal bright dots observed in the frame corresponding to the ringing of the phone before returning to normal. Javadi et al [2] tested seven different models of mobile phones, all of which operated under global system mobile at 900 MHz, and were tested in standby, ringing, and while making a call. The results from this study demonstrated that different mobile phone models had different effects of EMI. Some models had significant effects on count density, while others had none; however, the only effects noted were during ringing of the phone (not standby). Pashazadeh et al [3] tested a GSM 900 MHz mobile device at different distances from a gamma camera, as well as different angles during a SPECT rotation. The results suggested that when mobile phones were operated under ringing conditions, they demonstrated a decrease in the overall count rate, compared to standby mode.
Figure 1. Schematic of thyroid phantom setup.
to test whether the resulting EMI resulted in an alteration of gamma camera performance. Specific objectives included to employ control conditions to evaluate phone impact in multiple modes in different positions relative to the object being imaged. A thyroid phantom was tested against an Apple iPhone 6 operating in multiple modes (standby, ringing, answer, and music), while located in three different positions. Planar imaging was performed using Siemens E-Cam SPECT gamma camera and General Electric (GE) Discovery 670 SPECT/ CT gamma camera. A summary of the scan parameters utilized throughout each study is included in table 1. System settings remained consistent throughout testing, utilizing low energy high resolution collimators with a 20% window centered on 140 keV for 99mTc. The three positions employed varied throughout the study based around the thyroid phantom. The phone was positioned supine directly on the detector against the superior aspect of the thyroid for position 1; supine directly posterior to the phantom for position 2; and elevated posteriorly by 10 cm behind the phantom for position 3; as illustrated in figure 1. For each of the 2 gamma camera configurations, a baseline static was obtained of the thyroid phantom. In position 1 (figure 2), a 1-minute static planar image was acquired for each of the following variations: the phone in standby mode, the phone continuously ringing, the phone during an answered call, and then the phone
Methods The aim of this investigation was to evaluate the function of the gamma camera during operation of a mobile phone and Table 1 Scan Parameters Used in Thyroid Phantom Acquisition Thyroid phantom
Matrix Zoom Pan x Pan y Detector Scan Time Dose Start Time
2
Siemens E-cam
GE Discovery 670
512 512 3.2 4 12 2 1 min 62.1MBq at 1640 1710
512 512 3.2 0 0 2 1 min 65.2MBq at 1626 1643
Figure 2. Position 1 set up on phone for Siemens E-Cam testing.
M. Dowling et al./Journal of Medical Imaging and Radiation Sciences
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(2018) 1-6
Figure 5. Siemens E-Cam baseline thyroid acquisition.
Figure 3. Position 2 set up on phone for Siemens E-Cam testing.
playing continuous music. This process was repeated after the phone had been relocated to positions 2 and 3, respectively (figure 3 and 4). Care was taken to ensure no movement of the phantom occurred between mobile positions and the resulted images (including subtraction) examined for evidence of motion. The statistical significance was calculated using Student’s t test for continuous data. The F test analysis of variances was used to determine statistically significant differences within grouped data. A P value less than 0.05 was considered significant. Results Figure 4. Position 3 set up on phone for Siemens E-Cam testing.
The thyroid phantom has three ‘‘cold’’ nodes located on both superior left and right poles, as well as one located on
Figure 6. Siemens E-Cam initial thyroid acquisitions.
M. Dowling et al./Journal of Medical Imaging and Radiation Sciences
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(2018) 1-6
3
Figure 7. GE Discovery baseline thyroid acquisition.
the right inferior pole. The final inferior left pole appears as a ‘‘hot’’ node. The thyroid is spilt down the isthmus with the right lobe demonstrating an increase of activity compared to the left. Initial visual inspection of all acquired images (modes of operation and positions) appears to maintain the same level of quality, uniformity, and resolution when compared to the baseline image (figures 5-8). Results following subtraction of each image from baseline demonstrated no artifact for standby mode in position 1 (figure 9); however, all other modes in position 1 and all modes, including standby in positions 2 and 3, created artifactual counts. This artifact is highlighted by the ring appearance around the inferior right nodule and some evidence of artifactual counts at other nodule sites (figure 9-11). Conversely, subtracted images acquired on the GE Discovery, demonstrated no post subtraction artifact in any position across all modes (figures 12-14).
Figure 9. Siemens E-Cam position 1 subtraction results.
Decay-corrected counts for each image were evaluated between baseline total counts and each position/mode to further quantitate the previous observations. There was no statistically significant variations between baseline total counts and any positions/mode combinations for images obtained on the GE Discovery (P ¼ 0.710). The mean difference between individual total counts for images and the baseline was 55.8 counts (95% confidence interval [CI]) 319 to 431), which supports the lack of statistically significant variation. There was, however, a statistically significant increase in counts noted from baseline to individual position/mode
Figure 8. GE Discovery initial thyroid acquisitions.
4
M. Dowling et al./Journal of Medical Imaging and Radiation Sciences
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(2018) 1-6
Figure 10. Siemens E-Cam position 2 subtraction results.
combinations (P ¼ 0.0005) with the mean difference (image minus baseline) of 1008.9 counts (95% CI 1384 to 633.8). A statistically significant difference was also noted in count differences (baseline minus each position/mode combination) between Siemens and GE (P ¼ 0.0004) (Figure 15). No statistical significant difference was noted in count differences (baseline minus images) based on grouped data of GE and Siemens based on position (P ¼ 0.847) or mode of operation (P ¼ 0.953). This observation remained true when observing the data for Siemens or GE results
Figure 11. Siemens E-Cam position 3 subtraction results.
Figure 12. GE Discovery position 1 subtraction results.
independently (rather than pooled) for Siemens P ¼ 0.360 and P ¼ 0.338, respectively, and for GE P ¼ 0.340 and P ¼ 0.623, respectively. Although no statistically significant differences were shown, as expected, ringing mode and position 2 created the greatest increase in artifactual counts. Discussion The use of mobile phone devices has increased dramatically increasing the occurrence and potential risk of EMI
Figure 13. GE Discovery position 2 subtraction results.
M. Dowling et al./Journal of Medical Imaging and Radiation Sciences
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(2018) 1-6
5
These observations were noted with planar imaging. Artifact in SPECT data may have a greater impact as errors are multiplied several orders of magnitude during the reconstruction process. It is recommended, therefore, that mobile phones are not left with a patient during scanning even if the phone is out of the field of view. Staff should be mindful of carrying a mobile phone and in particular using a mobile phone in close proximity to a gamma camera during data acquisition. It is also recommended that vendors are quizzed with respect to EMI shielding in their systems before purchase. A complete ban of mobile devices in a nuclear medicine department is not warranted. Instead, further investigation of the impact on SPECT data is recommended. Conclusion Mobile phones are capable of generating EMI sufficient, in all modes, to create artifactual count data on some gamma cameras. Caution is advised when mobile phone devices are to be used in immediate proximity to gamma camera during image acquisition. Figure 14. GE Discovery position 3 subtraction results.
Footnotes within the environment [4,5]. Unlike the initial case reported by Azizmohammadi et al [1], this study showed no initial observable effect with image quality, until affected at an arithmetic level (subtraction). These results also suggest that there is a potential difference between the applications of EMI shielding between manufacturers, gamma camera generation or, indeed, associated with hardware for hybrid capability. EMI shielding applied within gamma camera systems is housed around the photomultiplier tube components [6]. The photomultiplier tube are highly susceptible to environmental factors that include electromagnetic fields, which can affect and compromise their sensitivity [6]. Variations in the integrity and capability of this shielding between generations and manufacturers are likely to see varied responses to EMI.
Contributors: All authors contributed to the conception or design of the work, the acquisition, analysis, or interpretation of the data. All authors were involved in drafting and commenting on the paper and have approved the final version. Funding: This study did not receive any specific grant from funding agencies in the public, commercial, or notfor- profit sectors. Competing interests: All authors declare: no financial relationships with any organizations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work. Ethical approval: Not required.
References
Figure 15. Difference in counts between Siemens and GE. The diamonds represent the 95% CI of each mean (center line of diamond) and the horizontal line represents the overall mean. The circles are data points and self explanatory based on the X and Y axis headings.
6
[1] Azizmohammadi, Z., Baharfar, N., & Javadi, H., et al. (2011). Effect of mobile cell phone ringing on function of gamma camera. Clin Nucl Med 36, 1131. [2] Javadi, H., Azizmohammadi, Z., & Pashazadeh, M. A., et al. (2014). The electromagnetic interference of mobile phones on the function of a gamma camera. Clin Nucl Med 39, 232–236. [3] Pashazadeh, A. M., Dehkordi, F. J., Tanha, K., & Assadi, M. (2015). The effect of electromagnetic field generated by a mobile phone on the performance of a SPECT scanner. Clin Nucl Med 40(7), 545–547. [4] Choi, Y., Yoo, Y., Kim, J., & Kim, S. (2006). A comparison of the corrosion resistance of Cu–Ni–stainless steel multilayers used for EMI shielding. Surf Coat Technol 201(6), 3775–3782. [5] Pashazadeh, A. M., Aghajani, M., Nabipour, I., & Assadi, M. (2013). An update on mobile phones interference with medical devices. Radiat Prot Dosimetry 156, 401–406. [6] Flyckt, S., & Marmonier, C. (2002). Photomultiplier tubes principles & applications. France: Photonis. Retrieved from. http://www2.pv.infn.it/ wdebari/doc/Flyckt_Marmonier.pdf.
M. Dowling et al./Journal of Medical Imaging and Radiation Sciences
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(2018) 1-6