Consecutive patients admitted with ischemic stroke to Jikei University Hospital, Japan, between January 2016 and September 2017 were retrospectively enrolled in the study. The subtype of ischemic stroke was classified according to the TOAST (Trial of ORG 10172 in Acute Stroke Treatment) [10]. Stroke severity on admission was assessed using the National Institutes of Health Stroke Scale score [11]. After reviewing patients’ medical records, 108 patients with ischemic stroke in the middle cerebral artery territory identified on MRI within 24 hours of onset were enrolled in the study. Patients who did not undergo MRI upon admission or for whom imaging was not available were excluded from the study.

The JOIN (Allm, Tokyo, Japan) smartphone application enables teleradiology of medical images, including MRI, CT, ultrasonography, and angiography (Figure 1). Using JOIN, medical information can be shared immediately among the stroke team via SMS. Images from the initial MRI brain examination are sent immediately from the picture archiving and communication system (PACS) on the hospital server to each smartphone on which JOIN is installed. Users can enlarge and evaluate the images through a simple touch sequence on the screen of their smartphone.

All patients underwent routine 3D time-of-flight (TOF) MRA of the intracranial arteries and fluid-attenuated inversion recovery (FLAIR) of the brain on a 1.5T scanner (MAGNETOM Avanto and MAGNETOM Symphony). The imaging parameters were TOF MRA: repetition time (TR)/ echo time (TE) = 23/7.15 ms, flip angle = 20°, section thickness = 0.6 mm, matrix = 320 × 288, field-of-view (FOV) = 18 cm; FLAIR: TR/TE = 9000/94 ms, flip angle = 160°, section thickness = 5 mm, section gap = 1.5 mm, matrix = 256 × 256, FOV = 21 cm.

The image review process is shown in Figure 2. Prior to the review, 2 readers (TK and KS, Readers 1 and 2 with 8 years and 10 years of experience in vascular neurology, respectively) installed JOIN on a Jikei University Hospital iPhone (version 7; Apple). After they confirmed the operation of the application, a radiologist transmitted the MRA and FLAIR data to the application. Patient image sets were presented randomly, and the readers were blinded to all background and clinical information. Both readers evaluated all the images from all patients. After receiving the MRA and FLAIR images, the readers independently assessed them on the JOIN application for the presence or absence of intracranial arterial occlusion; in the case of LVO, the site of arterial occlusion was identified. In patients with acute stroke, it is important to check for hyperintense vessel sign (HVS) on FLAIR, which suggests the presence of LVO [12]. HVS occurs because of slow flow due to LVO but is not an indicator of infarction. Therefore, the 2 readers evaluated the MRA images for LVO and evaluated the FLAIR images for HVS. The arterial occlusion site was classified as internal carotid artery (ICA), the horizontal segment of the middle cerebral artery (M1), or insular or cortical segments of the middle cerebral artery (M2 or M3, respectively). The diagnosis accuracy of arterial occlusion was defined as interdevice variability between Smartphone-LVO and PC-LVO. We recorded the interpretation time (minutes), defined as the time between receiving the MRI data to completing the interpretation. We used 1 to 4 min to interpret times in segments of 0 to 1 min, 1 to 2 min, 2 to 3 min, and 3 to 4 min. The 2 readers evaluated all MRI data using the hospital desktop PC monitor in the same manner 2 weeks later.

Interdevice agreement for evaluating the presence of arterial occlusion was analyzed between Smartphone-LVO and PC-LVO via kappa statistics. Kappa scores for agreement were rated as follows: poor (<0.20), fair (0.21-0.40), moderate (0.41-0.60), favorable (0.61-0.80), almost perfect (0.81-1.0).

Wilcoxon signed-rank test was used to compare image interpretation times between Smartphone-LVO and PC-LVO.

P values <.05 indicated statistical significance. All analyses were performed using SPSS for Windows (version 22.0; BM-Armonk).

The Regional Ethics and Hospital Management Committee of the Jikei University School of Medicine approved the study (approval No. 29-197). The board waived the need for patient consent by giving patients from whom data had been collected the opportunity to opt-out of the study.

Table 1 lists the patient characteristics. We enrolled 108 patients with a median age of 69 years and a median NIHSS score of 4 upon admission, of whom 72 (66%) were male.

Interdevice agreement for evaluating the presence or absence of intracranial arterial occlusion was almost perfect between Smartphone-LVO and PC-LVO (Reader 1: κ=0.94, 95% CI 0.82-0.97; P<.001 and Reader 2: κ=0.89, 95% CI 0.77-0.92; P<.001; Table 2; Figure 3). Regarding detection of lesions in individual arteries, interdevice agreement was almost perfect for ICA and M1 occlusion (Tables 3 and 4; Figure 3). For analyzing M2 or M3 occlusion, interdevice agreement by Reader 1 was almost perfect (κ=0.89, 95% CI 0.77-0.93; P<.001,) and that by Reader 2 was favorable (κ=0.75, 95% CI 0.60-0.80 P<.001; Table 5; Figure 3).

Wilcoxon signed-rank test (2-tailed) revealed that the interpretation time was significantly longer for Smartphone-LVO than PC-LVO (Reader 1: z=–3.547; P<.001 and Reader 2: z=–2.921; P=.003). However, the median interpretation time was the same between Smartphone-LVO and PC-LVO for each reader (Reader 1: 2 min for each method and Reader 2: 1 min for each method; Table 6). The interpretation time difference between Smartphone-LVO and PC-LVO was less than 1 min in 98% of the patient data sets in our series (Figure 4).

The study results show that the smartphone application yielded an accurate diagnosis of anterior intracranial arterial occlusion in times similar to diagnoses completed using the hospital-based desktop PC monitor. Several studies have reported the use of smartphone applications for the management of stroke [4,13-15]; however, no study has reported their use for assessing LVO. To the best of our knowledge, this is the first article to examine interdevice agreement and compare interpretation times for MRA and HVS on FLAIR imaging between a smartphone application and a hospital desktop PC monitor.

The JOIN smartphone application shows promise for use in acute stroke management for several reasons. JOIN provides a platform for simultaneously sharing important clinical information among the entire stroke team via PACS, whether on duty or on call. Because the information shared within the team is secured, JOIN can seamlessly support intrahospital teleradiology for MT in the “drip and ship” acute stroke management model. Conventionally, after receiving a stroke call, the vascular neurologist must immediately access a desktop PC and log into the network and server before browsing images sent via PACS. The neurologist’s interpretation of the neuroimaging examinations is then shared over the telephone with one person in the stroke team. JOIN can substantially improve the speed of this process by reducing the time taken to evaluate neuroimaging, particularly in situations where the neurologist is not near a desktop PC or is not at the hospital at the time that treatment for hyperacute stroke is being decided. The utilization of the JOIN application should simplify and shorten the MT decision-making process.

Regarding the telestroke system, while peer-to-peer network protocols are standard, they are limited in that the sender communicates only with one receiver in the stroke team, much like a closed circuit loop. In contrast, the JOIN application enables multicasting communications from one sender to many receivers. The team leader pre-authorizes which stroke team members participate in the secure group chat, and all of the patient’s data are centralized to the group chat. The entire stroke team can then receive notifications of the stroke patient’s arrival, view neuroimaging examinations, and review the medical plan via JOIN. Thus, important information is shared immediately among all members. JOIN also enables messaging among the team and displays neuroimaging files at a high resolution. Because the decision-making process is tracked via messages displayed on JOIN, the application plays a role in avoiding errors. Thus, combining the conventional telestroke system with JOIN would be desirable for arranging hyperacute stroke care in a complex and time-sensitive environment.

Finally, the telestroke system, comprising the 3 components of teleconsultation (doctor to patient), teleconferencing, and teleradiology, is confronted with developmental challenges in Japan. It is difficult for hospitals in Japan to introduce the real-time interactive video conference systems required for tele-examination using a hub and spoke model because there is no legal or regulatory provision for doctors on the hub side regarding patient examinations or a provision for medical decisions [16]. In addition, the Japanese government only approves medical practice via conventional encounters with a unique patient in emergency settings. Therefore, teleconsultation is only allowed under strict conditions (ie, for monitoring chronic disease after a second visit). In contrast, teleradiology is commonly used in Japan because of national insurance coverage. The advantages of using JOIN for acute stroke care include its portability, quick accessibility of target neuroimages, and its financial viability. In the near future, the Japanese Stroke Association plans to expand their practical guidelines for telestroke to include ICT solutions, under which JOIN would be considered for use.

Our study has several limitations. First, the MRA images were evaluated by only 2 vascular neurologists, both of whom were experienced. In a future study, more evaluators should be used, including less experienced evaluators. Second, the study did not directly prove that the smartphone application was useful for early reperfusion therapy. Finally, the study only evaluated anterior circulation ischemic stroke; its applicability to posterior circulation ischemic stroke has yet to be investigated.

A smartphone application yielded an accurate diagnosis of anterior intracranial arterial occlusion in times similar to diagnoses completed using the hospital-based desktop PC monitor. It also enabled access to all patient information regardless of the user’s location. Thus, this system can play an important role in organizing the stroke team to manage patients with hyperacute ischemic stroke.

The authors declare that all supporting data are available within the article.