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Primary Salvage Survey of the Interference of Radiowaves Emitted by Smartphones on Medical Equipment

Takao, Hiroyuki; Yeh, Yu chih; Arita, Hiroyuki; Obatake, Takumi; Sakano, Teppei; Kurihara, Minoru; Matsuki, Akira; Ishibashi, Toshihiro; Murayama, Yuichi

doi: 10.1097/HP.0000000000000535
Notes
Open
SDC

Use of mobile phones has become a standard reality of everyday living for many people worldwide, including medical professionals, as data sharing has drastically helped to improve quality of care. This increase in the use of mobile phones within hospitals and medical facilities has raised concern regarding the influence of radio waves on medical equipment. Although comprehensive studies have examined the effects of electromagnetic interference from 2G wireless communication and personal digital cellular systems on medical equipment, similar studies on more recent wireless technologies such as Long Term Evolution, wideband code division multiple access, and high-speed uplink access have yet to be published. Numerous tests targeting current wireless technologies were conducted between December 2012 and March 2013 in an anechoic chamber, shielded from external radio signals, with a dipole antenna to assess the effects of smartphone interference on several types of medical equipment. The interference produced by electromagnetic waves across five frequency bands from four telecommunication standards was assessed on 49 components from 22 pieces of medical equipment. Of the 22 pieces of medical equipment tested, 13 experienced interference at maximum transmission power. In contrast, at minimum transmission power, the maximum interference distance varied from 2 to 5 cm for different wireless devices. Four machines were affected at the minimum transmission power, and the maximum interference distance at the maximum transmission power was 38 cm. Results show that the interference from smartphones on medical equipment is very controllable.

Supplemental digital content is available in the text.

*Department of Innovation for Medical Information Technology, Jikei University School of Medicine, Tokyo, Japan; †Division of Endovascular Neurosurgery and Neurosurgery, Jikei University School of Medicine, Tokyo, Japan.

Conflict of interest: Our academic institution received a research donation from NTT DOCOMO, Inc., that partially supported this work. Minoru Kurihara, Teppei Sakano, and Yu chih Yeh are full-time employees of Allm Inc. Corporation. Minoru Kurihara is a full-time employee of Medivation Co., Ltd. Hiroyuki Arita, Takumi Oobatake, and Akira Matsuki are full-time employees of NTT DOCOMO, INC.

For correspondence contact: Hiroyuki Takao, Department of Innovation for Medical Information Technology, and Division of Endovascular Neurosurgery, Department of Neurosurgery, Jikei University School of Medicine 3‐25‐8 Nishi-Shinbashi, Minato-ku, Tokyo 105‐8461, or email at takao@jikei.ac.jp.

(Manuscript accepted 29 March 2016)

Supplemental Digital Content is available in the HTML and PDF versions of this article on the journal’s Web site www.health-physics.com.

This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially.

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INTRODUCTION

AS THE use of mobile phones became widespread in the 1990s, concerns heightened regarding the effects of the radio waves emitted by these devices on nearby electronic equipment; in particular, interference with medical equipment. Several experimental surveys have been conducted examining various types of medical equipment deployed at healthcare facilities (CCAUE 1997; Tri et al. 2001, 2005, 2007; Morrissey et al. 2002; Shaw et al. 2004; Calcagnini et al. 2006; Ang et al. 2007; Dang et al. 2007; Hietanen and Sibakov 2007; van Lieshout et al. 2007; Hans and Kapadia 2008; Tang et al. 2009).

Comprehensive studies on the interference of the radio waves produced by mobile phones with medical equipment were conducted for 2G wireless communications and personal digital cellular systems, but similar studies on more recent wireless technologies such as Long Term Evolution (LTE), Wideband Code Division Multiple Access (W-CDMA), and High Speed Uplink Packet Access (HSUPA) have yet to be published.

In 1997, guidelines for the use of mobile phone handsets at medical facilities were established in Japan (CCAUE 1997). For personal digital cellular systems identified as having a sustained effect with a maximum interference extinction distance of 4 m, as reported in an experimental survey (CCAUE 1997), the guidelines restrict use in intensive care units (ICUs) and coronary care units, stipulating that their power must be turned off to prevent interference of their radio waves with medical equipment (Table 1). The guidelines thus ban the use of wireless paging devices, in place of which many medical centers introduced the personal handy-phone system (PHS).

Table 1

Table 1

Today, Internet connectivity is a standard function of new mobile phone handsets (i.e., smartphones) in addition to voice calling. The adoption of these more advanced mobile phones at medical facilities, where large amounts of data are handled on a daily basis, would enhance and expand healthcare services. As today’s approach to patient care tends to be based on the consultation of specialists in particular fields rather than a single doctor, the exchange of information and knowledge between professionals has become even more necessary. In some situations, like those encountered in the ICU or emergency room (ER), the patient's life may depend on a quick decision. In such cases, medical professionals should be able to access and share critical information anywhere and at any time, which is something made possible by using mobile phones. However, due to the aforementioned guidelines, many medical centers in Japan have not allowed these new services or technologies at sites of medical practice since the launch of the PHS and have limited the use of high-speed Internet communications via mobile phones.

Few survey data are available on electromagnetic interference with medical equipment caused by the radio waves from PHS, 3G, and 4G mobile phones after 2010 (Nagase et al. 2012). As such, electromagnetic interference testing was conducted with wireless terminals corresponding to the respective PHS, W-CDMA, HSUPA, and LTE communications systems to determine the impact of the radio waves emitted by mobile phones on medical equipment. This study does not include an assessment of the interference of Wi-Fi or Bluetooth signals on medical equipment, which would require a completely new approach focused on these transmissions.

The authors conducted surveys to assess the compatibility of mobile phone use in medical centers by analyzing and ascertaining the electromagnetic interference risks imposed by radio waves emitted from mobile phones on medical equipment.

The results of tests for electromagnetic interference from mobile phones reported here indicate that medical equipment used in hospitals and medical settings is unlikely to be adversely affected by mobile phones at distances ≥ 38 cm.

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MATERIALS AND METHODS

Selection of equipment

Two physicians and two medical engineers collaborated to select 22 different pieces of medical equipment for the present electromagnetic interference testing. Equipment was selected to include a representative variety of medical equipment for which electromagnetic interference may occur. The selected pieces of medical equipment are used in daily practice in hospitals and healthcare facilities, and interference with their operation could seriously affect a patient's wellbeing. The 22 selected pieces of medical equipment include 49 distinct main units and components, as detailed in Table 2.

Table 2

Table 2

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Testing conditions

Testing was conducted in an anechoic chamber, which blocks external radio waves and does not affect the radio waves produced internally. Thus, tests were conducted in an environment with no measureable influence from any other radio waves or equipment.

The tested telecommunication standards were those currently used in Japan: HSUPA, W-CDMA, LTE, and PHS. Fig. 1 shows an example of the measured signal waveforms. The peak-to-average power ratio (PAPR) varies depending on the standard adopted. For example, at a complementary cumulative distribution function of 0.01%, the measured PAPRs for LTE, HSUPA, and W-CDMA are 7.3, 4.7, and 3.3 dB, respectively.

Fig. 1

Fig. 1

A dipole antenna and a mobile phone were used as the emitters of the radio signals. The dipole antenna was used as the first step to determine which medical equipment was affected by interference. Subsequently, further tests were conducted using the mobile phone with the equipment for which interference with the dipole antenna was confirmed. According to a report from Japan’s Ministry of Internal Affairs and Communications, the gain of built-in antennas for mobile phones is 2 dB less than that of a dipole antenna (CCAUE 1997). Thus, the dipole antenna is more likely to affect medical equipment. Therefore, if no impact was detected from the dipole antenna, no testing was conducted with the mobile phone under the given test parameters for the dipole antenna and mobile phone (Table 3). When the source was scanned, the element of the half-wave dipole antenna or the long side of the mobile phone was set both perpendicular and parallel in turn to the long side of each face of a virtual cuboid that covered each piece of medical equipment. The electric field distribution around the mobile phones was measured with the back surface of the mobile phone set facing the medical equipment. In the case of the dipole antenna, the element of the antenna was placed parallel to the medical equipment.

Table 3

Table 3

The frequency bands used during testing were 3G (800 MHz, 1.7 GHz, and 2.0 GHz), LTE (800 MHz, 1.5 GHz, and 2.0 GHz), and PHS (1.9 GHz). Since there are no mobile phones that work with all of the above frequency bands, two different mobile phones were used for the test. One was selected for the 2‐GHz, 1.5‐GHz, and 800‐MHz tests, and another was selected for 1.7‐GHz tests.

Tests were conducted with the transmission power for each telecommunication standard set at the maximum value, where it is assumed that radio wave strength would be potentially the most detrimental to medical equipment. The maximum transmission powers were 250 mW for HSUPA and W-CDMA, and 200 mW for LTE. The electromagnetic interference characteristics were also considered for what is assumed to be a more common and lower transmission power: 10 mW. The transmission power of 10 mW was determined by referring to the Ministry of Internal Affairs and Communications in Japan: Report on research and study of effects of radio waves on medical equipment (MIC 2010). The PHS testing, however, employed 80 mW in all cases since the power for PHS is fixed.

The modulation scheme was selected according to the 3rd Generation Partnership Project (3GPP). The modulation scheme for HSUPA and W-CDMA was QPSK (Quadrature Phase Shift Keying) and π/4 DQPSK (Differential Quadrature Phase Shift Keying) for PHS. Regarding LTE, 64QAM (Quadrature Amplitude Modulation) and 16QAM were selected for the dipole antenna and mobile phone tests, respectively, assuming high-speed communication. The mobile phones used in this study cannot communicate with 64QAM.

With respect to the transmission mode, since medical equipment commonly includes control circuits based on biological rhythms such as pulse and respiration, two types of transmissions, intermittent (0.5‐s burst once per second) and continuous, were implemented under the premise that when signals are aligned close to biological rhythms that are applied to the medical equipment’s circuitry in the form of noise, there is a possibility of malfunction (Table 3).

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Test procedure

The International Electrotechnical Commission (IEC) 61000‐4‐3 describes a method for evaluating the electromagnetic interference for electrical devices including medical equipment (IEC 2010). This study was based on exposure to far-field radio waves; however, there are situations in which mobile phones can come into direct contact with medical equipment. In other words, the electric circuits of medical equipment and mobile phone antennas may directly interact through near electromagnetic field effects. Therefore, in this study, an evaluation scheme that is based on two methods was employed: the method used in the investigation conducted by EMCC and MIC (IEC 2010) and that described in the American National Standards Institute (ANSI) C63.18 (ANSI 1997). These methods provide a way to evaluate direct coupling in a near electromagnetic field. The medical equipment, except for floor standing equipment, was placed on an 80-cm high wooden table as described in ANSI C63.18 (ANSI 1997). Specifically, the procedure of the interference test, as shown in the flowchart (Fig. 2), was as follows. First, the radiation source was placed on top of the medical equipment, maintaining flush contact, and the radiation source was scanned over all test subject surfaces (left, front, right, rear, and top). If no electromagnetic interference was confirmed or if electromagnetic interference shifting to the next surface was confirmed, the most notable interference site, the results of the interference, and the produced effect (e.g., an alarm sound or noise crosstalk) were recorded. At the sites where effects due to interference were most notable, the reflective power, the change in the extent of the effect with a reduction in the transmission power, and the interference extinction power were recorded. Under maximum transmission power, the radiation source was distanced from the medical equipment, and the interference extinction distance was recorded. The authors measured the interference extinction distance at maximum transmission power and then the interference extinction distance at minimum transmission power. Identical tests were conducted for each surface.

Fig. 2

Fig. 2

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Assessment of electromagnetic interference effects

The categories listed in the “Report on research and study of effects of radio waves on medical equipment, etc.” published by the Ministry of Internal Affairs and Communications (MIC) in 2002 were used as indicators of the extent of the effect on medical practice when electromagnetic interference was confirmed (MIC 2010). The categories were determined from physical classifications of medical equipment hindrances and classifications of medical practice hindrances. Two physicians determined which phenomena resulting from electromagnetic interference belonged to which category. The physical classifications of medical equipment hindrances and classifications of medical practice hindrances were classified (Tables 4 and 5).

Table 4

Table 4

Table 5

Table 5

The method of determination and explanation for the classifications (categories) of medical equipment hindrance based on physical classifications of medical equipment hindrances and classifications of medical practice hindrances are explained (Tables 6 and 7). Category 1 indicates that no electromagnetic interference was confirmed for the medical equipment, while Categories 2–10 indicate electromagnetic interference occurring in increasing severity.

Table 6

Table 6

Table 7

Table 7

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RESULTS

Effects on medical equipment

The results of the electromagnetic interference testing conducted with a dipole antenna on the 22 pieces of medical equipment (49 components) revealed that 14 main components from 13 pieces of equipment exhibited some kind of electromagnetic interference effect (Table 8). All the affected pieces of equipment that required maintenance were restored to their normal state upon in situ maintenance of the unit. The interference extinction power and distance for the respective equipment were detailed (Supplemental Digital Content, Table 1, http://links.lww.com/HP/A68).

Table 8

Table 8

Four occurrences of interference were irreversible (8%), and one case (2%) was of Category 5 or higher with the possibility of exacerbation of the patient’s medical condition. This was confirmed to be Category 7 for “Artificial respirator C2.” For this model, however, an alarm and error display started following the initial electromagnetic interference; actual interruption of the artificial respirator operation occurred only if the transmission source (dipole) continued to be directed toward the C2. Thus, interruption of the artificial respirator operation was avoided when the source of the radiation was promptly removed from the C2's vicinity soon after the alarm and error display started.

In tests using an actual mobile phone, effects from electromagnetic interference were confirmed for six pieces of equipment, but no irreversible effects occurred.

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Interference extinction distance for different communications systems

The communication systems were compared at maximum transmission power output using the mobile phones based on the results of inspection of the electromagnetic interference generated by each system. PHS had weaker associated interference (Fig. 3) than any of the other systems, while LTE, HSUPA, and W-CDMA exhibited nearly the same interference. PHS also had a smaller result for the interference extinction distance than any of the other communication systems.

Fig. 3

Fig. 3

The interference extinction distances for the medical equipment per transmission power were confirmed with the respective interference extinction distances for the four transmission power settings at 10, 80, 200, and 250 mW (Figs. 3 and 4). At the maximum transmission power in the frequency band of 2 GHz, the longest interference extinction distance for all medical equipment tested in this study was measured for LTE to be 28 cm (transmission power: 200 mW; radiation source: dipole antenna; modulation scheme: 64QAM). The 2‐GHz band was commonly used in the LTE, HSUPA, and W-CDMA tests. For HSUPA, the longest interference extinction distance was 38 cm (transmission power: 250 mW; radiation source: dipole antenna; frequency: 2‐GHz band; modulation scheme: QPSK); for W-CDMA, it was 29 cm (transmission power: 250 mW; radiation source: dipole antenna; frequency: 2‐GHz band; modulation scheme: QPSK); and for PHS, it was 6 cm (transmission power: 80 mW; radiation source: dipole antenna; frequency: 1.9‐GHz band; modulation scheme: π/4 DQPSK). At maximum transmission power, the interference extinction distances for HSUPA and W-CDMA at 250 mW and LTE at 200 mW were nearly the same but slightly larger than that for PHS (80 mW). Nagase and colleagues reported that the difference in PAPRs between the LTE, HSUPA, and W-CDMA did not have a significant effect (Nagase et al. 2012).

Fig. 4

Fig. 4

Similarly, the maximum interference extinction distances at maximum transmission power for actual mobile phones using HSUPA, W-CDMA, and LTE were 10, 10, and 11 cm, respectively. At maximum transmission power, the electric field strength at 10 cm from the mobile phones was almost the same as the strength at 30 cm from the dipole antenna. The lengths also correspond approximately to the longest interference extinction distances for the mobile phones and dipole antenna, respectively. From these results, the relation between the electric field distribution and the interference extinction distance was confirmed.

At the minimum transmission power of 10 mW, the maximum interference extinction distances for HSUPA, W-CDMA, and LTE were 1, 2, and 2 cm, respectively. For PHS (80 mW), however, the result was the same as before at 6 cm, as the transmission power was the same.

At transmission powers of 80 and 10 mW, the interference extinction distances decreased tremendously compared with those at 250 and 200 mW. These results show that a change in transmission power has a large effect on the electromagnetic interference. In addition, it was revealed that when the transmission power of a mobile phone drops below that of PHS, the magnitude of the effect on medical equipment also becomes smaller than that for PHS. The transmission power of a mobile phone is varied according to a control signal from the base station with which it communicates. If the transmission power changes from 10 mW, the interference extinction distance may also change.

IEC 60601‐1‐2 specifies the recommended separation distance between mobile/PHS phone handsets and medical equipment (ECES 2007). Table 9 shows a comparison between the recommended separation distances in the frequency range used in this study and the longest interference extinction distances at each transmission power in this study. All interference extinction distances in this study were shorter than the recommended separation distances.

Table 9

Table 9

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Effects of different transmission modes on medical equipment

An inspection of the prominence of the electromagnetic interference generated for each transmission mode revealed that intermittent transmissions clearly caused more detrimental electromagnetic interference than continuous transmissions. The maximum interference distance during continuous transmission was 20 cm for the dipole antenna and 11 cm for a mobile phone, while the maximum interference distance during intermittent transmission was 38 cm for the dipole antenna and 15 cm for a mobile phone.

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Effects on medical equipment under the minimum radio wave conditions

According to the considered characteristics of electromagnetic interference under the reduced transmission power and restricted frequency band, testing proceeded under a frequency of 2 GHz and a power of 10 mW.

Four components from four different pieces of medical equipment experienced interference, or 8% of the total 49 components from the 22 pieces of equipment (Table 10).

Table 10

Table 10

The electromagnetic interference became considerably weaker when the conditions were restricted to 10 mW for the 2‐GHz band. Compared to the maximum transmission power across all frequency bands, the number of main components for which electromagnetic interference was confirmed dropped from 14 to 4; the maximum hindrance category dropped from 7 to 3. The maximum interference distance dropped from 38 cm to 2 cm.

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DISCUSSION

Effects of radio wave interference on medical equipment

Testing was conducted using the 2‐GHz frequency band and a power of 10 mW in order to consider the characteristics of electromagnetic interference under reduced transmission power and a restricted frequency band. According to the results, the effects of mobile phones on most daily medical practices are essentially nonexistent unless they are almost in contact with the medical equipment in question. However, in poor radio wave environments, the transmission power from mobile phones tends to increase to establish a sufficient connection with the base tower. One possible way to reduce the transmission power and frequency-band restrictions is to introduce indoor base stations, known as In-building Mobile Communication Systems (IMCSs) to medical centers. These are generally installed in ceilings away from medical equipment and have low radiofrequency emissions. Installation of an IMCS in poor radio wave environments reduces the distance between mobile phones and the communicating counterpart (the IMCS), resulting in a diminished propagation loss. Therefore, it is likely that a lower transmission power will be required in comparison to a scenario where no IMCSs are installed. This is due to a base station system whereby a control is applied that reduces the transmission power output whenever propagation loss is small. As described above, an IMCS may reduce the transmission power of mobile phones. However, if the propagation loss between mobile phones and the IMCS is large, or if there are many mobile phones in the same area, the transmission power required may reach the maximum power. If the distance between the mobile phones and the medical equipment is short, the effects of direct waves from the mobile phones can dominate over those of reflected waves. However, if the distance is longer, the opposite may be true. Future studies are required to clarify the relationship between the distance and the effect of reflected waves.

The current standards in Japan for medical equipment can be found in the “Guidelines on the Use of Radiocommunications Equipment such as Cellular Telephones and Safeguards for Electronic Medical Equipment” (CCAUE 1997) prepared in 1997 at the Electromagnetic Compatibility Conference. Subject equipment includes implanted pacemakers and general electrical medical equipment. The guidelines express in detail the prohibition of mobile phones in the operating room or ICU; the powering down of mobile phones in laboratories, consultation rooms, patient wards, and treatment rooms; and the use of mobile phones elsewhere, including solely in zones authorized by the medical institution. However, operative rules are not necessarily enforced by each medical institution. Moreover, since the establishment of the guidelines, efforts to lower outputs from mobile phones and enhance countermeasures to electromagnetic interference for medical equipment have been made. In 2002, MIC implemented electromagnetic interference testing within hospitals jointly with the Japan Federation of Medical Devices Associations and confirmed the appropriateness of the guidelines established at the Electromagnetic Compatibility Conference (CCAUE 1997). With respect to implanted medical equipment (pacemakers), the first edition of the Guidelines to Prevent Effects of Radio Waves from Types of Radio-using Equipment to Implanted Medical Equipment was presented in 2005. The recommended separation distance was 22 cm, which was reviewed and revised in January 2013 to 15 cm (MIC 2013).

For general medical equipment, however, only a few surveys have been completed since then. The details for general medical equipment should be reviewed in the same manner as those for implanted pacemakers.

As a result of the testing discussed here, it is highly likely that if the radio wave environments inside hospitals could be improved through the installation of IMCSs in locations with poor radio wave environments, the effect on general medical equipment can be significantly reduced. A mobile phone, for instance, must be almost in direct contact with ordinary medical equipment for any effects to occur at minimum transmission levels. In Japan, there have been no reports of electromagnetic interference from mobile phones that caused faults in medical equipment and consequently affected the condition of a patient. Therefore, it may be necessary to review the restrictions on mobile phone use in hospitals and medical facilities, including ICUs and ERs, due to the benefit of using such devices. If well regulated, the professional in charge would have immediate access to the knowledge and opinions of others, resulting in a great improvement in the quality of medical practice.

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Effects from continuous transmissions and intermittent transmissions

Nojima and Tarusawa (2002) noted that intermittent transmissions are more likely to affect medical equipment, as medical equipment frequently includes control circuits based on biological rhythms such as pulse and respiration. Hence, the present research indicates that the possibility of malfunction emerges when any signal closely aligned to a biological rhythm is applied as noise to the circuit of the medical equipment. Development of methods to prevent the interference between mobile phones and medical equipment is desired such that there are no effects on medical equipment even under intermittent transmissions.

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Limitations

Not all general medical equipment was tested. In fact, verification remains necessary for a variety of medical equipment in future work. Given the rapid advancement in mobile phone technology in recent years, the effects of electromagnetic interference on medical equipment should be examined at least once every 2 y.

Medical institutions are incidentally built with thicker walls than ordinary buildings due to the need for radiation shielding, containment of MRI magnetic fields, and other factors. Thus, many locations may have poor radio wave conditions, and these conditions influence the transmission power of mobile phones (Lonn et al. 2004). Such variations in transmission power can have a substantial effect, so the structure of the hospital building must be considered as a major factor in the issue of radio wave interference.

The maximum radiated power from the antennas of mobile phones is lower than 250 or 200 mW, but varies according to phone type. The electric field distribution around mobile phones also varies with phone type, and it is difficult to extrapolate accurately from the distribution around the mobile phones used in this study. However, a dipole antenna was used preliminarily in all tests. The radiated power from the dipole antenna was in the region of 200 to 250 mW; the conducted test using the dipole antenna is conservative compared to the test using mobile phones.

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Telemedicine

Telemedicine has been used in emergency departments to treat general patients (Brennan et al. 1998; Benger et al. 2004; Galli et al. 2008), stroke patients (Silva et al. 2012), and trauma patients (Latifi et al. 2007). Traub et al. (2013) used telemedicine to perform telemedical physician triage. The use of mobile phones, particularly videophones, could cut technology costs by an order of magnitude and expedite the setup, connection, and consultation processes (Gonzalez et al. 2011; Anderson et al. 2013).

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Improvement and equalization of medical practice quality through the use of telemedicine

Currently, nearly all hospitals in Japan have established a zone in which the use of mobile phones is permitted; however, the rapid reception of large volumes of medical data at any time and at any location could be a life-saving capability. For example, to improve the handling of strokes through earlier diagnosis and faster treatment, telemedicine was implemented in Japan that used a fixed videophone rather than a mobile phone (Saito et al. 2007); however, it has been stated in other reports that an improved survival rate can be achieved with remote imaging diagnosis via a mobile phone (Iguchi et al. 2011; Demaerschalk et al. 2012).

Telemedicine will hopefully overcome the geographical disparity among physicians by allowing the judgment of specialists to be sought easily. If a specialist could obtain medical data regardless of location through the use of a mobile phone, and subsequently administer or aid in healthcare, then standards of healthcare could be elevated worldwide. Therefore, in Japan, the established zonal system in medical centers whereby mobile phone use is prohibited in all but designated areas must be revised. Aziz and colleagues reported that no evidence exists for interference in a real hospital environment and that there are no reasons to prohibit the use of mobile phones within medical facilities (Aziz et al. 2003).

The effects of electromagnetic interference from mobile phones on general medical equipment, even those used in ICUs and ERs, are not absolutely irrelevant; however, they can essentially be considered as such according to the experimental results, except when the mobile phone is near (≤38 cm) or in direct contact with the medical equipment. With ample knowledge at hand with respect to the hindrances to general medical equipment, the use of mobile phones and other mobile communication systems should be increased to a level suitable for the modern information society, with an aim to improve the standards of healthcare.

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CONCLUSION

Depending on the equipment or radio wave conditions (radio wave environment), there is the possibility that mobile phones have an effect on general medical equipment. This research indicates that interference is not relevant if the mobile device is at least 38 cm away from the medical device, even in a bad cellphone network condition. This study also showed that the risk of interference can be further reduced by improving the cellphone network environment, resulting in lower radio transmissions by mobile devices. Thus, the range of mobile phone use should be expanded in medical facilities by establishing very few zones in which the use of mobile phones is prohibited or only restricting mobile phone use to areas more than 38 cm from medical equipment.

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Acknowledgments

We are very grateful to Satoshi Ishihara and Junji Higashiyama at the research laboratories of NTT DOCOMO, INC., for their valuable cooperation in our experiments. All research was conducted in the anechoic chamber at NTT DOCOMO R&D Center. All environment preparation and experiment annotation regarding the medical equipment and mobile phone research was conducted by Ishihara and Higashiyama.

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Keywords:

electromagnetic fields; exposure, radiofrequency; radiation, nonionizing; safety standards

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