Toolkits

Patient Exam Cameras - Technology Overview

Video has long been a staple of telehealth systems.  Videoconferencing cameras, dedicated specialty scopes, handheld examination cameras, and recorded video files in store-and-forward systems have been used with great success for years.  This toolkit looks specifically at devices that serve as handheld examination cameras. 

Examination cameras can be a highly effective tool, supporting live and still imaging of wounds, dermatological conditions, neurological exams, physical therapy evaluations, and more.  Many questions exist about what makes an effective patient exam camera, especially in light of the high costs of telehealth-oriented exam cameras.  This overview will discuss fundamentals of video imaging and video connections, how video cameras work in conjunction with both live and store-and-forward telehealth systems, and how the telehealth-specific cameras compare against camcorder or point-and-shoot cameras

 

 Defining the Terms

Various terms are used in the video camera market, and figuring out exactly what they mean can be a little challenging.  Knowing what is meant by patient exam camera as opposed to camcorder, high-definition instead of standard-definition, 720p and 1080i, composite, component – the list goes on – can be very useful in determining which device is appropriate for an organization’s needs:

Devices

Devices that are being included under the broad category of “exam cameras” have a video output that can be routed into either a live videoconferencing or store-and-forward system and a form factor that comfortably fits in one hand.  Within this group there are several terms used to talk about devices with similar functionality – patient exam cameras, general exam cameras, camcorders, handicams, handhelds, cameras, point-and-shoots, security cameras, home monitor cameras, or lipstick cams.  These more-specific terms really relate to four primary categories of camera.

Patient Exam Cameras

Devices that fall under the category of patient exam cameras have a few distinct features, including built-in lighting that surrounds the lens, the ability to “freeze” or “pause” the video, an inability to save images directly to the camera, and a minimalistic interface.  Only two devices are currently on the market as dedicated patient exam cameras.  These are the GlobalMedia’s TotalExam Medical Exam Camera and AMD’s 2500 General Exam Camera.  Both of these devices also share another common element, beyond the video functions – a price of several thousand dollars.  This one feature often drives organizations to consider other categories of camera.

Camcorders

One of the first areas that people turn to when looking at options for the more expensive exam cameras are devices that are marketed as camcorders.  These devices have a video output, either internal or removable storage media, the ability to record video and photos, and, increasingly, the option for high-definition video output.  These devices fall within the consumer market, and, as such, include a wide range of functions and features, levels of quality, and prices.  The camcorder market is large, a fact that can make selecting the appropriate device challenging. 

Digital Cameras

The line between camcorder and digital camera continues to grow increasingly blurred.  As camcorders have gradually picked up the ability to record photos, digital cameras have proven to be rather capable of recording video.  Many point-and-shoot digital cameras provide a live video output through special cables, as well as the ability to record images and video to storage media.  As with camcorders, the digital camera market falls into the consumer category, resulting in devices that have a wide variety of functions and features, all performing similar tasks with various levels of success.

Security Cameras

A variety of very simple video camera devices are on the market that advertise a set of standard video outputs, excellent performance in low-light situations, and a very low price.  They do not have the ability to record directly to any built-in or removable storage media.  Much of the advertised lowlight performance comes from infrared LEDs, which do not produce visible light and, when used, typically switch the video signal to black-and-white.  These security cameras are a consumer-oriented product, and may be advertised as security cameras, home monitoring cameras, baby monitoring devices, or night-vision cameras.

Video Technology

A collection of terms are used to describe the functions and features of video devices.  Product specifications, especially in the consumer market, include a lot of numbers and letters that are meaningless without some context.  High-definition, standard-definition, frame rate, scanning modes, megapixels, and aspect ratios are often presented as significant, but are rarely given a larger context to explain why.

Pixels and Megapixels

A pixel is a single point in an electronic representation of a digitized image.  Pixels are used in monitors and screens, as well as the sensors in imaging devices like digital camcorders and cameras.  A megapixel is one million pixels.  An image or sensor that is 1000 pixels tall by 1000 pixels wide will equal a single megapixel.  Digital cameras often produce images that are over 6 megapixels (3000 by 2000 pixels).

High-Definition and Standard-Definition

Once only found in the domain of professional videographers and home cinemas, high-definition is increasingly advertised on camcorders and digital cameras.  Standard-definition video images are 640 pixels wide by 480 pixels high.  Two of the frequently used numbers around high-definition are 720 or 1080, each of which are “high definition” resolutions.  Both numbers refer to the height of the video image, in pixels.  The horizontal resolutions are 1280 and 1920, respectively (1280x720 and 1920x1080)

To put these numbers into context, consider how many megapixels each of these displays consist of.  A 640x480 pixel image has a total area of just over 300,000 pixels, or less than one third of one megapixel.  1280x720 is just under one megapixel, while 1920x1080 is just over two megapixels.

Frame Rate and Scanning Mode

Videos consist of still images played back at a high rate.  The eye interprets the rapidly-changing snapshots as motion.  Many camcorders support recording content at a range of speeds, typically offering 30 and 60 frames per second (fps) at a minimum, with options for 24, 25, 50, 72 fps.  On their own, these numbers do not carry too much significance for clinical purposes.

The scanning mode defines how the still images that make up a video signal are generated.  Interlaced video scans alternating horizontal lines on one frame, and then scans the other horizontal lines on the second frame.  When played back at a high speed, these images appear smooth due to persistence of vision.  When paused, however, a still frame will appear jagged, with easily seen horizontal lines.  Devices that include “i” after the frame rate are referring to an interlaced recording mode.  Examples include 50i and 60i.

Progressive scanning captures the entire image on every frame, which avoids the problem of horizontal lines that can occur when capturing interlaced video.  Examples include 24p and 30p.

To tie all of this together, a camera that captures 720p30 is recording an image that is 720 pixels tall 30 times every second, and capturing the entire image on each frame.  1080i60 is capturing a larger image every 1/60 of a second, but is doing so by capturing an alternating set of lines on each frame (540 odd lines, then 540 even lines).

Note that the problem with clearly-visible horizontal lines does not apply to monitors or screens that use interlacing.  An example would be a 1080i screen.  These devices are refreshing the screen by “painting” the pixels on in alternating lines, with the odd lines painted in one frame and the even pines painted on the second frame.  If the video that is being played on a screen is frozen, the screen will continually paint at the high frame rate.  It is also important to note that there is no requirement to use an interlaced monitor to play interlaced video, or a progressive monitor to play progressive video.

Aspect Ratio

The ratio of a screen’s width to height defines its aspect ratio.  If looking at standard-definition video, the aspect ratio os 4:3 (640:480), while high-definition video is 16:9 (1290:720).  High-definition video signals are also referred to as wide screen, due to their greater ratio in comparison with standard-definition video.

Aspect ratios are not a concern when playing high-definition video signals on a high-definition screen, or standard-definition video on a standard-definition screen.  Problems can arise when playing a high-definition video on a standard-definition display (the wider screen is compressed to fit the narrower display, resulting in a tall, skinny video image), or vice versa.

Connections and Converters

The previous set of definitions looked at all of the different formats in which video can be recorded and displayed.  A standard set of pieces help to tie all of the devices together, allowing video signals to be sent to displays.

Standard-Definition Connectors

S-Video and Composite cables and ports can be used to send standard-definition video signals.

High-Definition Connectors

HDMI and Component cables and ports can be used to send high-definition video signals.

Standard-Definition to High-Definition Down-Converters

Down-converters allow high-definition signals to be transmitted to and displayed on standard-definition displays and devices.  These often accept an HDMI or Component input, and offer both an S-Video and Composite output.  This down-conversion may cause the aspect ratio of a video signal to change, resulting in video images that appear to be taller and thinner.  These devices require external DC power.

High-Definition to Standard-Definition Up-Converters

Up converters take a standard-definition signal and transforms it into a high-definition signal, such as HDMI and Component.  These devices may cause aspect ratios of video signals to change, resulting in video images that appear to be shorter and wider.  There is no increase in actual resolution of the video images; the images are simply enlarged to fill the screen, resulting in a “pixilated” or blocky image.  These devices require external DC power.

Standard-Definition Connectors

A variety of standard-definition connectors exist, including “gender-changing” attachments that help connect S-Video or Composite cables and devices.  Another very useful device is the S-Video-to-Composite converter, which allows a Composite cable to be attached to an S-Video system and vice versa.  The converter often requires the use of a gender changer, as well.  These attachments do not require power.

High-Definition Converters

Component video sources can be turned into HDMI signals, and HDMI into Component, through the use of a powered converter.  These devices are not especially useful in the context of patient exam cameras, but may be desired if converting a signal from a camcorder or digital camera for playback on a high-definition TV or monitor.

 How Exam Cameras Work

Video Imaging Basics

Light reflects off of surfaces at various wavelengths, resulting in our perception of color and shape, light and dark.  Digital video cameras capture this same reflected light through a lens, which focuses the light onto a light-sensitive sensor.  This sensor translates the scene that is being captured into a set of pixels, each with a red, green, and blue value.  That data is then sent to a monitor or other display, at which point it is rendered into what we see as an image.

Video cameras capture light and transmit it at various speeds, often sending a new image 30 times every second.  As mentioned in some of the above definitions, the frame rate and scanning modes may result in slightly different signals and images, but the basic concept of a stream of rapidly-changing still images holds as the basis behind digital video.

This data is made available in a variety of formats on different devices, allowing it to be sent to other viewing platforms, such as videoconferencing units, monitors, capture cards, and internal memory.

The Devices

Exam cameras can come in a variety of functions and formats, with different strengths and weaknesses.  Many organizations have an interest in learning how various video devices might work in a telehealth environment.

Patient Exam Cameras

These devices do not record video, instead serving as a sort of “pass through” for video signals.  Telehealth-specific patient exam cameras only have standard-definition outputs.  The video signals are streamed live through s-video connectors.  When the “freeze” or “still” button is pushed, the devices will pause the live video signal and send out the paused image.  Pushing the pause button again resumes the live video feed.

The option to freeze an image can be useful in a variety of situations, especially when reviewing an image over video conferencing equipment.  Being able to pause the video allows for an image to be reviewed without requiring the patient and camera operator to hold perfectly still.

The onboard light, which surrounds the lens on both models of patient exam camera, helps provide balanced lighting across the subject, even when very near to the surface being imaged.  This is a very useful feature when attempting to image dermatological conditions, the eye, and intraoral surfaces.

While there are differences in how focusing is performed, both models of patient exam camera offer manual focusing options, which can make it easier to ensure that the proper area of the subject is in focus.

Camcorders

Whether using tape-based camcorders, or those with internal storage media, camcorders allow for images and video to be captured and stored, while also providing an output that allows for transmitting of video data.

Camcorders function in slightly different ways, depending in part on the storage media that is used.  Tape-based systems write to a magnetic tape, often in an 8mm digital video cassette.  The digitized video signal is written directly to the tape as recording occurs, transmitting the data gathered by the sensor to a physical medium.  These models do not easily support recording and reviewing video, as they require rewinding to the appropriate section before beginning playback.  Note that some of these models do support using a memory card in addition to the video tapes, allowing for photos and videos to be accessed more easily.

Devices that operate with internal hard drives or flash-based memory allow for videos and photos to be recorded from the sensor.  As each video and photo is stored as a distinct file, there is no need to rewind to the start of a video clip; all a user needs to do is select the video or image and it will be displayed on the monitor or video output.

High-definition video output is often handled with an HDMI cable.  A frustratingly-high percentage of camcorder manufacturers utilize a proprietary HDMI port on their devices, necessitating the purchase of a separate cable to work with and HDMI monitor.  It is important to note that videoconferencing systems do not support high-definition auxiliary inputs at this time, meaning that HDMI inputs will likely not be especially useful if attempting to integrate a camcorder into a videoconferencing system.  Vidyo does have an HDMI input, allowing an HDMI camcorder to be connected in lieu of their normal VTC camera.

Standard-definition video output is often an option on camcorders, as the devices typically support an A/V output that utilizes an S-Video or Composite connector.  This is the connector that most systems will use if attempting to integrate with a VTC system or a framegrabber in a store-and-forward system.

Focusing is usually automatic in camcorders, which can be problematic if attempting to focus on very specific areas of a subject.  That said, the automatic focus is often very good, and does work in many situations.  Some camcorders offer touch-screen focusing, allowing a user to press on the LCD viewfinder, which then causes the camcorder to set the focus to where the user touched.  Some of the higher-end camcorders also support manual focusing, though this is not as easily accessed in camcorders as it is on patient exam cameras.

Three major issues arise in the use of camcorders, as well as digital cameras.

The first problem is that a live video cannot be paused as it can be in a patient exam camera.  To be able to transmit a still image, a photo or video must be recorded, then the user must enter video or photo playback mode, and transmit the image on the output.  For most devices, this will add two to four additional steps when attempting to show a static image.

The second problem is related to the storing of images and videos.  Patient data is captured by the device, and may be stored for long periods of time.  A process needs to be put in place to ensure that patient data is properly protected, and to ensure that it is not stored in a way that is a HIPAA risk for the organization.

The third problem ties into the lack of good lighting on most of these devices.  While some units do include built-in lights, they are typically underpowered if they are video lights, overpowered if using as a flash in macro situations, and often off to one side, causing heavy shadowing in many macro situations.  However, some of these cameras have excellent low-light performance, reducing the need to have a flash in some scenarios.  Some camcorders perform better if an auxiliary light is used during a patient exam, such as a small flashlight or external lamp.

One thing that camcorders offer than patient exam cameras cannot is tied to recording video and images.  The storage of photos and videos, while potentially a risk if poorly handled, can provide some benefits during image review.  One of the largest of these is that an image, once captured, can be often be zoomed in on, allowing the higher resolution sensors on some cameras to be used more fully.  A standard-definition sensor on a patient exam camera will only capture and transmit a standard-definition image (640 x 480 pixels).  Camcorders, with their sensors that may support high-resolution still images (up to 14 megapixels in some cases), allow a user to zoom in and show higher levels of detail in their recordings.

Additionally, the storage media on camcorders can typically be accessed via a USB cable or memory card reader, allowing high-resolution images and recorded videos to be saved and transferred to others by way of store-and-forward system.

Point-and-Shoot Cameras

As with camcorders, point-and-shoot cameras support the capture of still images and video.  These devices will typically have limited internal memory, necessitating the use of removable media.  Some digital cameras provide either an A/V or HDMI output, allowing for live video and recorded media to be sent to other systems. 

Digital cameras do not all operate in the same way, especially when it comes to transmitting live video.  It is important to test a digital camera to make sure that it has live video if intending to use it as an exam camera for live videoconferencing.

The photos and videos are recorded and played back in ways that are similar to camcorders.  The same problems exist, with the addition of a problem in how focusing is handled.  Digital cameras often require the shutter to be pressed partway down to engage autofocus, which makes moving the camera around during a live videoconference more difficult; the user must refocus the camera often.  Additionally, point-and-shoot cameras can be somewhat finicky when focusing in macro mode, making it challenging to get good focus.

One of the largest benefits to point-and-shoot digital cameras is the very high still-image resolution.  This high resolution allows for the user to zoom in on very small details when in playback mode.

Security Cameras

The low-light performance of security cameras, combined with their simplicity, may make them appear to be a price-effective option to patient exam cameras.  Security cameras, as mentioned above, simply pass video through a standard-definition video output.  As with patient exam cameras, they do not support onboard recording, serving instead to pass a video signal through to another device.

Security cameras are highly “automatic”, meaning that they have autofocus and autobrightness controls.  There is no ability to manually focus these devices, which makes getting a clear image challenging, especially when combined with their relatively poor macro functionality.

The Modalities

Videoconferencing

Patient exam cameras can be outstanding auxiliary video devices for videoconferencing systems, allowing for a video camera to be moved around a patient, as opposed to moving the patient around in front of a fixed videoconferencing platform.  In live videoconferencing, the patient exam camera’s output is run into the VTC hardware’s input (usually labeled as a VCR input).

As different cameras have different outputs, and different videoconferencing systems have different inputs, it is necessary to make sure that the devices can talk to one another.  Converters are often needed, typically to switch the s-video output to a composite input or vice versa.  Patient exam cameras have the most straightforward connections to videoconferencing systems, as this is usually the only conversion that is needed to work with a VTC unit.

Converting from high-definition to standard-definition can be a problem for some digital cameras and camcorders.  High-definition video signals are in a widescreen format, while standard-definition inputs are in the 4:3 aspect ratio.  Converting HDMI straight to standard-definition can alter the appearance of images and video.  It is recommended that organizations use the A/V output and a standard-definition cable to connect camcorders and digital cameras to videoconferencing units.

Some camcorders and digital cameras need additional configuration to their settings, often under an aspect-ratio menu heading.  Switch the device output to the 4:3 aspect ratio when connecting to most videoconferencing systems.

Desktop videoconferencing adds an additional challenge when attempting to integrate with exam cameras, but also provides users with the option of providing live video of a patient without requiring a hardware-based codec.  It is possible to use a USB-based video converter, which will take a video input and make it appear as a USB camera device.  Depending on the desktop videoconferencing application that is used, and the converter that is used, it is possible to select the converter as the video device for a video conference, thereby allowing the exam cam to appear in place of the normal USB webcam.

Store-and-Forward

Systems that allow asynchronous transmission of image and video data may interact with exam cameras in different ways.  Some systems will utilize frame grabbers for acquiring stills and videos from a standard-definition input, while others will read directly from devices through a USB connection or memory card reader, allowing recorded files to be transmitted as a part of an asynchronous encounter. 

Patient exam cameras, older camcorders that utilize digital video tapes, and security cameras will all require frame grabbers for transferring videos or images to a store-and-forward system.  Newer camcorders and digital cameras, using an A/V cable to connect to the frame grabber, may also interact with store-and-forward systems in this way.  The use of converters and proper aspect ratios will hold true for frame grabbers, which capture contents via a composite or s-video input. 

The format becomes less of an issue when taking images and videos directly from stored media, as there is no need to convert the files into standard definition.  The strength of camcorders and point-and-shoot cameras come out at this point, as high-definition videos and images that are many megapixels in size can be sent in full resolution via the store-and-forward systems.

Conclusion

Discussions around exam cameras often turns to an acknowledgement of the current leaders in the telehealth market – AMD and GlobalMedia – while at the same time asking if there are other, less-expensive alternatives on the market.  Camcorders and digital cameras (and, to a limited extend, security cameras) provide a different approach to handheld examination cameras.  With each device there are costs and benefits; making a decision on which device to implement depends on an organizations needs, users, and personal assessment of the quality and functionality of the various devices.

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