Analog Angle Blog

Your Radiography AFE Killed My Light-box Business

I was at the doctor's office a few weeks ago, and as you'd expect, there was a row of those standard light boxes (see Figure 1) hanging along the office walls. But then I realized that all of them, except one, were covered with announcements, bulletins, and personal notes. In other words, these once-critical units were no longer needed; they had served their purpose, but their purpose had come to its end (although one light box was left clean and clear; I suppose it was for “just in case” situations).

Figure 1

Figure 1

We've all seen the ubiquitous visual cliché in movies and TV with a doctor putting the X-ray film onto a light box, to clearly explain to others the ailment (or cause of death), and so advance the plot line. But just as conventional cameras using film have been demolished by digital photography, the film-based X-ray is going the way of corded phones and the dial tone.

Why go digital? Assuming the costs are comparable to film-based X-rays, and meet the medically mandated imaging performance, digital X-ray imaging has multiple tangible advantages: no consumables (film and processing kits); no environmental (chemical) issues; instantaneous availability; lower X-ray exposure; potential for further processing to enhance images and reduce artifacts; images are easy to store, retrieve, and share; no re-filing, misplaced or lost films; and reduced need for physical storage space.

All this is possible largely due to the components and ICs, especially high-performance, highly integrated analog front ends (AFEs) which have become available in the past few years. In addition to the X-ray detector array at the very front end, and the video display at the user end, there's the signal-processing chain of the analog/digital (A/D) converter, processor (usually dedicated FPGAs), and memory, all supported by a sophisticated and complex power-management subsystem, of course. With highly integrated technology, all this can be packed in a modest, portable, battery-powered box — a real plus for mobility (bring it to the patient not vice versa) and use in remote or hostile situations.

The A/D converters take the weak signal from the detector array (comprised of photodiodes and transistors, somewhat similar to a CCD sensor) which can be configured as a single line array or a two-dimensional flat panel, depending on the machine and applications. While they do not need to operate at those blazing RF speeds and bandwidths, they must provide samples at a fairly high rate and resolution, and with very low nonlinearity (which affects gray-scale performance).

[Note : These systems also require D/A converters for various control functions, but the technical requirements are much less stringent.]

Although the specific numbers depend on the system front-end architecture and how the images are processed, a starting point for the converter is resolution of 12 to 18 bits, sampling times of several hundred nsec or less (>2 Msps), dynamic range of >100 dB, high-speed data transfer, and multichannel operation to save space and power. The required sampling rate may be somewhat higher or lower depending if the X-ray system is intended for static imaging (broken bones) versus dynamic imaging (cardiovascular studies).

Leading A/D converter vendors such as Analog Devices, Texas Instruments, and Maxim (to cite just a few) have targeted the digital X-ray market with devices which have the appropriate combination of specifications in key parameters which are unique to this application. This is achieved by packing multichannel front ends and converters into small, low-power devices with performance, which meets the complex and stringent application requirements.

I don't envy the situation of vendors of those traditional light boxes, but there's no holding back the technology in these cases — and digital imaging will only get better, as the components and algorithms (yes, it takes those, as well) get better. The integrated, application-specific AFE has done them in, just as the image sensor and ASIC has killed the venerable film-based camera for snapshots and professional picture-taking.

Are there any other historically long-lasting and significant technologies which integrated AFEs have “destroyed?” Even more intriguing: are there any applications where you don’t see that happening, at least for a long while?

9 comments on “Your Radiography AFE Killed My Light-box Business

  1. RedDerek
    February 7, 2014

    Back in the mid-90's, I worked for a semiconductor company. I have to go back through my notes, but one of my customers were highly involved with the development of this product. They used high voltage digital ICs to read the panel (my involvement). Beyond this point, I am sure there was analog component to obtain the grey scale component of the panel.

    One of the challenges they had was packaging. They had to bulk up the panel in order to fit the current x-ray film trays. I am sure that is all gone by the way-side now.

    As an applications engineer, it was fun helping the developing technologies to market. Other products I worked with back then were plasma displays, vacuum florescent displays, and several other high-voltage display applications such as eInk's for the Sony eBook.

    I could like up some blogs as to how these displays operate – on a simple level. I just have to make sure I do not provide any trade secrets in the process. (I still respect my customers from years ago.)

  2. Victor Lorenzo
    February 8, 2014

    Just like radiography imaging has beneficed from advances in analog and digital integration, ultrasound imaging has also been subjected to dramatic changes in the last few years. The following three could somehow represent three integration levels in diagnostic equipments (combison 310, Sonosite-Fujifilm Edge(R) ultrasound machine and GE Handlhelp VScan):

  3. samicksha
    February 9, 2014

    As more and more applications reaching cloud with demand of creating most of things online, the medical devices are required to transform into digital. I visted a very old hospital near my home they have Uni-matic 325 but their interest was to convert same machine to digital rather than investing in new machine.

  4. Victor Lorenzo
    February 9, 2014

    Interesting project, @Samicksha. Having the possibility to integrate a sensor like GE's FlashPad (part of GE's Discovery 565 RX Ray) would probably be feasible.

  5. Davidled
    February 13, 2014

    I think that medical Imaging processing requires a high resolution. It sounds like all display may be similar to concept of Oscilloscope display panel.

  6. eafpres
    February 20, 2014

    Strangely enough, MRIs, which seem almost inherently digital, were connected with what must have been a bunch of specialized hardware and software to generate “flims”.  Like many of us as we grow older, I've had to submit to various kinds of imaging.  Some years ago a problem called for an MRI of my neck.  The neurologist who ordered the MRI requested that I get the films so he could view them on a lightbox in the exam room at his office.  Years past and another specialist wanted a new MRI of the same area of my skeleton.  The new guy wanted me to bring the CDR from the imaging lab.  Coincidently I went to the same imaging lab as I had before.  When I asked them for the CDR they said “sure, and we'll put your previous one on there too”.  When I sat with the doctor, he popped in the disc and was able to bring up the same images four years apart side by side on a computer monitor.  An 8th grader could have diagnosed the additional degradation in the area of interest.

    While in principal the same thing could be done with films, it is more accurate doing it with digital images, which can be panned and zoomed and compared.

  7. eafpres
    February 20, 2014

    Many, many years ago I was working a project that involved a chemical reaction to generate an electronically excited state of a gas molecule.  The concentration of the excited state could be determined by measuring IR photons that were emitted when 2 excited molecules collided, in a process called quenching.  We used cryogenically cooled solid state detectors to measure the emission from a flowing gas stream in real time.

    It turns out that some visible photons may be generated if the quenching takes place in a different process.  We wanted to “see” what was going on in the reactor section, not just what came out the final back end.  The solution?  We used a very nice Nikon film camera that had the option to electrically trigger the shutter, and had a motor drive to advance the film.  Using ASA 1000 film and shooting images with the lab completely darkened, we could get good images and watch different areas of the reactor (it was made of glass).  We used a time-delay relay to set the speed at which images were captured, and a computer to track the relay at the same time as we collected data off the IR detector.  We could then later match up the images with the other data in time.

    Nowadays high speed high resolution digital cameras could do this, and much better IR detectors that don't require a liquid nitrogen bath would be used as well.  As this work was for the government, I imagine that beautiful Nikon was eventually “surplused”.

  8. anthony.nima
    February 20, 2014

    @DaeJ: Yes it does require high resolution since it needs clear clarification and sharp edges in a very visible manner. Mainly it requires because of the nature of the industry. Its all about dealing with sensitive data so things should be clear 

  9. PCR
    February 22, 2014

    Yes Samicksha they have to move to digital for sure in order to compete in the competitive business environment in long run. 

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