In a candid question and answer session with Karina Bukhanov, MD, head of the division of breast imaging, Joint Department of Imaging, University Health Network, Mt Sinai Hospital and University Health Network, Toronto, the mammographer provides insight into the implications and operational impact of digital mammography on both patient care and the radiology department.
Bukhanov: The main differences are in the acquisition, storage, and display. So if we think of the analog mammogram, and I always give people the analogy of a camera, for instance, you develop the film and you get a picture. That paper holds the image, displays the image, and later on, when you put it in the photo album, the album stores it for you. Now, if we take a look at the digital camera, what we do with digital mammography is analogous. We separate each one of those functions: we electronically acquire the image, we electronically display the image, and we electronically store the image. And the ability to separate each of those functions allows us to manipulate each of those functions. So we are able to get the best out of each one of the steps that make up mammography.
Bukhanov: Superior. You get the sense when you are reviewing the images that you have examined the breast more thoroughly, and that is due, again, to the ability to manipulate the image. If we are looking at the film and part of the breast is too light and part is too dark, there is no way to improve that particular film: what you see is what you get. On a digital mammogram, because you are in front of a computer and in front of a monitor, you are able to change the contrast of the image. You can clearly see structures from the skin all the way back to the chest wall. By the time you are finished interpreting the mammogram, you are very confident that you have examined the entire breast very thoroughly.
Bukhanov: At our institution we do only soft copy. We do not print film, we never printed film. We went directly to soft-copy reporting, and it is, in fact, with soft-copy reporting that the full potential of digital mammography comes to light. If you are acquiring digitally but printing film, you are engaged in only half of the process, so in my opinion, you should not even bother. Only in reporting with soft copy, can you take advantage of the ability to manipulate, to electronically zoom to enhance the image, and to gain as much information out of the data as possible.
Bukhanov: It is a wider range, so we are able to see the tissues better. With film, for instance, you can see certain things incredibly well and others not as well. If part of the film is too light, you just can’t see through that area. Whereas the ability with digital mammography to change the level and the window allows you at one point, if your eye is looking at the skin, to look at the skin thoroughly and the rest of the mammogram doesn’t show up as well; then, when you finish with the skin, you just move along to the chest wall or whatever you are looking at and you concentrate on that area and window appropriately so that now you see that region as best you can. It allows you to optimize each part of the image.
Bukhanov: From the patient’s point of view, the main gain is in the time of the procedure. It is a lot faster to do the study. With analog, standard mammography, the patient has to wait while the film gets processed. So it takes a certain amount of time per image to process while the patient is waiting. At the end of this study, for instance, if one of the films is too dark or is too light, you have to take the patient back to the room and re-expose her. With digital acquisition that is no longer a problem. If the film is too light, then you can electronically make it darker. Or vice versa. So, from the patient’s point of view, the study is faster and much fewer retakes are necessary.
Bukhanov: We are still in a learning curve, right at the beginning of this technology. Our hope is that it will help with dense breasts. Our most difficult population in mammography is younger patients, patients who have dense breasts. Now with a lot of older people also taking estrogen replacement, we are seeing more and more dense breasts. In the old days, when women got older, the breast usually involutes, becoming predominantly fatty. Nowadays most people are on estrogen so at the age of 60 you basically have the breast of a 30 year old. And the problem with those breasts is that it is difficult for us to read those mammograms. The entire breast is white, cancers are white, and we have difficulty with white against a white background. With digital mammography, again, we are hoping that the ability to contrast the image will bring out those difficult-to-image or difficult-to-detect cancers. Our ultimate goal and hope is that we catch more and catch them earlier.
Bukhanov: From the patient perspective, it is new technology. It is different technology, and it requires reevaluation of the way we schedule and operate our practice. We are looking at a different process in which we would utilize this machine to its fullest capacity. We are restructuring right now, redesigning the work flow to maximize patient throughput, optimizing process for the patient and the radiologists. That is [necessary] to offset the cost of the machine: it is fairly expensive technology. [A potential for increased throughput] also is a benefit of this technology. We want to put through more patients so we can screen more individuals.
From the technology perspective, again, we are only at the beginning, but this technology will allow features such as computer-aided diagnosis. A lot of radiologists are starting to look at that, and it is equivalent to having a second pair of eyes look at a mammogram. I hit a button and the computer highlights areas that it deems abnormal. And then it is up to me to decide: “Yes, I agree; no, I don’t agree. Yes, I saw this; no, I didn’t see this. Maybe I should look at this more closely.”
Two, we are looking at telemedicine right now so the fact that we are able to acquire and store these images also allows us to send them electronically wherever we want. If somebody in a smaller town wants a second opinion, it is very easy these days for them to send me an image: I can take a look at it, call them on the phone, and tell them what I think. So that is a huge program. People are looking at tomosynthesis, the ability to assess lesions in the breast better with digital mammography. The equivalent in MRI is when we inject contrast to look at the vascularity of the tumor. People are starting to look at the same functions with digital mammography. We are early in a lot of these areas; we are just at the beginning, but the possibilities are definitely there.
Bukhanov: A typical study is eight megabytes, and the typical mammogram involves four exposures, so that is 32 megabytes per patient. We do about 50 cases a day. We store it in tape archives, but we also have short-term access on our PACS server, from 4 to 6 months. Then we dump it into the tape archives. If we need to request a study from the archive, it takes 5 to 10 minutes to recall those images.
Bukhanov: We are now reimbursed exactly the same for analog and digital mammography. In Canada, there is no movement or motion to change that right now. That probably will come; somebody will ask the government to change reimbursement, to have it reassessed. I would think reimbursement should be higher than for film just because it takes longer to read the examination and because there is so much more information available to you that you are really obliged to go through different windowing and display algorithms to evaluate each study. The length of time it takes is longer than on the analog system. Depending on the reader and the style of reporting, it can take from 20% more time to double the time. So logically, reimbursement should reflect that.
Bukhanov: You can definitely double the volume, that we have shown. We can do twice as many cases on a digital unit as opposed to an analog. Then there are savings in film costs. Right now we have darkrooms, we buy film, we process film, there are service costs associated with processing the film, there are chemical costs involved. It’s actually not a straightforward formula. You have to include all of that when you are calculating.
Bukhanov: Definitely there are patient benefits. Whether it is worth it or not is a different side of the equation, looking at reimbursement for the physician versus the benefit to the patient. There is definitely a huge benefit to the patient. Whether or not society deems the radiologist should get paid more for that or not, that is an ethical question. You have to decide what is worth what. How do you put a price on that, I do not know. I do not know if the price we have right now actually reflects what I do every day. If you ask me, I will say no. If you ask somebody else, they might say I am getting too much. That is a very appropriate question, I just don’t know that we have actually looked at that, or that we are at a stage with this new technology to be addressing such questions. We probably need more data, more information. When it comes to reimbursement, that is always a difficult fight with whoever the payor is.
Peter Pesavento is associate editor of Decisions in Axis Imaging News.