Top Ten Tips for Buying Digital Video Colposcopes
Many of our clients ask us what to look out for when buying the latest colposcopes, the truth is it varies depending on the use, some users need high quality images on zoom, others flexibility to connect to different systems or portability.
Here are some ideas on some of the technical features that you should consider when buying a new digital video colposcope, which should help you to decide which option is best for you.
The Traditional Binocular Style Colposcopes
Generally there are 2 main types of mainstream colposcope, the traditional binocular style and digital video colposcope.
The traditional colposcopes are better for ‘live’ view, that’s to say a 3D natural view through the eyepiece via the human eye. The setback is that many of these scopes are not digitalised and cannot ‘save’ the images for later use. They do not have the direct connection to a hospital network necessary to save images directly into a folder or onto a patient record on the hospital patient management record system.*
The latest Digital Video colposcopes combine digital imaging and connectivity with the functions necessary to perform a colposcopy, they vary in shape and size but normally resemble a sci-fi ‘ray gun’ with the lens at the front and the functions at the back, with a handle for the user to hold below.
This article will largely deal with the digital video colposcope and what features to take into consideration when buying.
Some Small Technical Details – Digital Imaging and the Digital Video Colposcope
Digital imaging is the capture of a live visual (thing, object, person, scene etc), using digital technology to process, compress and store. A digital video colposcope is a smaller unit with a handle, easily moved into place and easy to point and record. Digital Video Colposcopes are designed for digital systems such as image capture systems and have many features you would find on a digital camera such as autofocus and zoom.
How does digital imaging work?
The easiest way to describe how this process works is to imagine that inside the colposcope there are electronic sensors and these sensors convert normal light (similar to the old SLR FILM cameras) into a digital representation and process this to create a stream of data using the camera technology.
This data can be ‘input’ into a system and thus converts the object being captured from the camera into a digital file which can be drawn/commented on or simply saved to, stored and viewed from a hospital patient record.
The advantages are huge, firstly this information can be manipulated, compressed and stored into different databases to be shown on different types of machine or computer. The data can also be analysed for certain patterns to help with diagnosis. The data can last for much longer than physical images and the quality stays the same.
The question is, with all the current technology available, how do you pick the right colposcope for your requirements, how, for example, are the needs of a SARC (Sexual Abuse Referral Centre) different from a colposcopy clinic.
Key features compared – here’s what to ask your supplier
The 10 key features of an image capture ‘device’ to take into consideration are the following:
1. The Base and Support of the Colposcope
There are normally two different types of base:
- The ‘swing arm’ version includes a (very heavy) base that compensates for the weight of the camera when fully extended, the camera can then ‘stretch’ across on an arm and can be positioned into a wide variety of spaces.
- The smaller shaft type base is much lighter and easier to position, normally made of sturdy plastic or aluminium with adjustable height and angle of the camera.
The swing arm base is more flexible in positioning and can reach many areas the shaft based cameras cannot. The shaft base is much more portable and easy to move quickly and easily, useful for moving to different locations, the swing arm is very heavy and difficult to move
2. Digital Image Sensor
Normally this is the difference between two types of sensor, the Metal Oxide Sensor (such as CMOS) or Charged Coupled Device (CCD). These days modern cameras use CMOS and this has been the industry standard for some time. CCD is still widely used but normally present in lower quality scopes and cameras.
3. Image Compression
This is how the original data stream captured from the colposcope is compressed to a manageable sized file, this is more relevant to the capture system attached to the camera but still important to consider especially in systems that include some form of software with the scope.
Normally the output files have the .jpeg, .tiff or .gif extension (last part of the file that tells the computer which program to use to open the image), these are the safer options, other formats may mean very large files or lower quality.
4. Image Resharpen – Zoom, Autofocus etc
The ability of the colposcope to automatically lock onto the image in the lens and adjust the focus to present the user with the perfectly sharp picture.
Zoom requirements depend on the challenge in hand, for example, a SARC centre does not need to zoom to the same extent as a colposcopy clinic because their needs are less on the minute details and more on the injuries sustained, therefore getting good colour reproduction is more important in this case.
Most good colposcopes should be capable of 40x (40 times the actual size of the subject in the lens) and include autofocus. When viewing a demonstration ask the rep to demonstrate the quality of the video and check using a picture with solid lines as follows:
- Make sure the lens has nothing behind it and that there is a space of a few metres with a white of pastel coloured wall
- Introduce a picture or an object with clear lines in front of the lens at the working distance of the colposcope, this is normally around 25cm-35cm
- Make sure the camera adjusts quickly to the image and that the image is clear
- Do the same at different magnifications, the camera should have minimal noise (higher magnifications will always have some noise)
This should give you a good idea of the quality at the magnification you are happy to work at, it will also give you a good idea of the quality of the image on the capture system that the supplier is going to provide you.
5. Colour processing
The ability of the camera to present an accurate representation of the subtleties of the colours of the subject. This is very important especially in SARC centres where evidence must be easy to determine and where colour and contrast make a huge difference to the quality of the image.
For higher quality colour reproduction make sure the camera has high colour rendering, lower renders are less life-like and more difficult to see contrasts
6. SD or HD output
The output, again, depends on the job in hand, it may not be necessary to implement HD (High Definition) if low quality images are sufficient. HD adds the benefit of better colour quality, less pixelated pictures and less ‘noise’.
The size of captured images (if the system is able to capture in HD) will vary, HD images and video captured files are generally much larger. This may fill up a hard drive much quicker on a local machine or may be slower to save across a network. For these issues it’s best to check with your IT department on network speeds, or, if a standalone capture machine is purchased as a part of the full system, ensure that the hard drive is a good size to be able to store the images.
When referring to industry standards, we normally speak about ‘resolution’, with a pixel height being the reference. So, for example, with colposcopes, a Standard Definition pixel height would be around 480, High Definition pixel height can be 720 or full HD (higher quality HD) is 1080.
7. TVL or TV Lines
This refers to the number of TV lines in the video, the higher the number the better quality the image/video. TVL should be taken into consideration with resolution above and the size of the viewing screen (the larger the screen, the more blurred it will be, therefore the more lines the better).
Standard specifications denote that 500-650 TVL is standard definition, anything over 700 is HD quality
8. Frame Rate
The frame rate determines the number of frames per second that the viewer sees when playing a video back, the higher the frame rate, the more frames get sent to the capture machine and the smoother the video looks.
Measurement: Above 30 is normally the minimum in most cases, any less that than and the video quality can look poor.
9. Light source
It is very important to have a good light source with clear light for the subject. These days, most light sources use LED technology, this means a cleaner light but also much longer lifespan. LEDs can last for over 50,000 hours, this is considerable when you compare to a incandescent (800-2000 hours) or Halogen (2000-4000 hours)
It’s important to have a number of filters on the camera for specific tasks, these are normally provided using buttons on the user side of the colposcope.
The following buttons should be available on your colposcope:
Green filter – these allow colposcopy professionals to add acetic acid to the cervix this highlights areas such as veins and helps to avoid cutting into blood vessels during procedures
White filter – this allows the user to calibrate the camera colours. Holding a white piece of paper in front of the camera and pressing the white balance effectively resets the colours when they are looking washed out or inaccurate.
We hope this article has given you an idea of what to look out for when choosing your colposcope.
Please send us your comments below, if there is a med-tech question you have that relates to medical imaging in any of the ‘oscopies’ or forensic image capture, please forward on and we will be happy to respond.
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*NB It is however possible to buy add-ons that enable this feature, but this adds to the cost of the scope.For more information on how this is possible, please click HERE for details of MaynBridge, which effectively adds a ‘go-between (or bridge) to add this function to analogue systems like traditional, binocular style colposcopes.