Image Quality Characteristics of Handheld Display Devices for Medical Imaging

Abstract

Handheld devices such as mobile phones and tablet computers have become widespread with thousands of available software applications. Recently, handhelds are being proposed as part of medical imaging solutions, especially in emergency medicine, where immediate consultation is required. However, handheld devices differ significantly from medical workstation displays in terms of display characteristics. Moreover, the characteristics vary significantly among device types. We investigate the image quality characteristics of various handheld devices with respect to luminance response, spatial resolution, spatial noise, and reflectance. We show that the luminance characteristics of the handheld displays are different from those of workstation displays complying with grayscale standard target response suggesting that luminance calibration might be needed. Our results also demonstrate that the spatial characteristics of handhelds can surpass those of medical workstation displays particularly for recent generation devices. While a 5 mega-pixel monochrome workstation display has horizontal and vertical modulation transfer factors of 0.52 and 0.47 at the Nyquist frequency, the handheld displays released after 2011 can have values higher than 0.63 at the respective Nyquist frequencies. The noise power spectra for workstation displays are higher than 1.2×10−5 mm2 at 1 mm−1, while handheld displays have values lower than 3.7×10−6 mm2. Reflectance measurements on some of the handheld displays are consistent with measurements for workstation displays with, in some cases, low specular and diffuse reflectance coefficients. The variability of the characterization results among devices due to the different technological features indicates that image quality varies greatly among handheld display devices.

Image-based teleconsultation using smartphones or tablets: qualitative assessment of medical experts

“…17 The computer screen's spatial resolution was lower than that of the handheld devices and this may be one of the reasons why it received a lower quality rating. However, spatial resolution is just one of the technical features that come into play when looking at display quality 18 and its importance may depend on the type of image. 19 The large variations found within each image category and more so between the clinical photographs of the type not studied thus far (burns and dermatological) might enhance the importance of protocols for image capture in those specialties.…”

“…The experiment was also conducted in realistic lightning conditions so as to represent an environment as similar as possible to what experts experience in real-life consultation. Further, as the display characteristics (spatial resolution, noise and reflectance) of handheld devices have already been assessed technically, 18 the subjective user approach we adopted felt most relevant.…”

Pitfalls in photographing radiological images from computer screens

“…For example, many computer monitors exhibit viewing angle‐dependent reductions in luminance and contrast ratio, 3 which render images susceptible to artefact, particularly when viewed at close range 4 . Moreover, mobile phone screens do not meet the technical requirements of a medical imaging display device 5 …”

“…4 Moreover, mobile phone screens do not meet the technical requirements of a medical imaging display device. 5 "spatial variations in image brightness can dramatically affect image interpretation, with potentially disastrous results"…”

Radiological interpretation of images displayed on tablet computers: a systematic review

“…6 Whilst both primary and secondary liquid crystal display (LCD) devices can be calibrated to the GSDF, it is not possible to calibrate a tablet computer, which may potentially compromise accuracy. 7 Despite the inability to calibrate the display, high levels of diagnostic accuracy have been reported when using tablet computers. [8][9][10] Hence, there is contradictory information to inform practice on the use of tablet computers for radiological interpretation.…”