Tuesday, March 27, 2012

The Man with X-Ray Eyes

Let me take a moment to deal with the vexed subject of Doctor Who, his two hearts and chest x-rays. I assume that people in all professions have difficulties watching representations of their jobs on film or television. That's certainly the case with me and on screen doctors. It is, of course, great fun watching them make schoolboy errors or spouting techno-babble, and there are few things I like more than making a diagnosis before my television counterparts.

There are three basic errors that seem to be almost universal. The first is the inappropriate use of head mirrors which is best dealt with by my American colleague Scott in his blog. The second is wearing stethoscopes back to front which I might blog about another time. And the third is displaying chest x-rays the wrong way round, which will bring us to Doctor Who. First let's look at a normal chest x-ray and the structures visible. Here is a nice labelled example.
The heart is a big solid lump of muscle and does show up with the low dose of x-rays used to image the chest. You will notice that the left lung is shown on the right of the picture and that most of the heart is on the same side. Chest x-rays are always looked at like this so that what you are seeing corresponds with the front of the patient as you look at them. Now the one thing that isn't shown on the above image is the side marker. It is quite important to know that you have the x-ray film the right way round so the radiographers who take the pictures put a radio-opaque label on the film before pressing the magic button. You can see the side marker in this image.
Having a side marker is crucial in diagnosing a rare condition called Dextrocardia where the heart (and possibly other internal organs) are on the opposite side. Here is an x-ray showing Dextrocardia and notice the side marker.
But of course these side markers can cause confusion and when actors are called upon to put a chest x-ray up on a light box they usually assume that right means right and so put the film up with the R marker on the right hand side. The most infamous example is the title sequence for the medical comedy Scrubs.

Apparently so many medics complained about this that eventually Scrubs included a joke about it and had a character correct the error.

So last night I was watching Paul McGann as the Eighth Doctor in the 1996 TV movie. The film starts with Sylvester McCoy's Seventh Doctor being shot and the struggles of the emergency room physicians to save him before he apparently dies only to later regenerate while in the mortuary fridge. Now as we all know Time Lords from Gallifrey have two hearts and lots of other physiological differences from humans. The Doctor's chest x-ray is put up on a light box and the on-screen medics notice that this shows two hearts and put this down to something they call a "double exposure". This is just medical techno-babble that doesn't really mean anything. But let us examine the x-ray as shown in the film.
Here we can see a single heart shadow which is on the right hand side so either the emergency room medics have put the film up the wrong way round or the Doctor has Dextrocardia (I suspect the former). Then there are the two white shadows in the middle of the lung fields that the screen doctors call hearts. They are the wrong shape and in the wrong place. They look more like hilar shadows which would indicate a whole different set of problems for the Doctor.

I posted a brief comment about this on my Facebook page last night and Brian from British Invaders asked if the scene from Spearhead in Space was any better. This was the story which introduced Jon Pertwee as the Third Doctor in 1970. Interestingly this also showed the Doctor recovering from his regeneration in a hospital. Once again he has a chest x-ray which is supposed to show his two hearts, this time the screen doctor assumes that someone in the x-ray department is playing a joke on him and goes off to remonstrate with them leaving a nurse (and us) to look at this x-ray.
This looks like an artist's impression of a chest x-ray and the staggering thing about it to medical eyes is that it shows no hearts at all! The two dark circles at the top of the chest cavity are what the Spearhead doctor thinks are hearts but again they are wrongly placed, sized and coloured. They should be white shadows where the x-rays have not penetrated to the photographic film. So the simple answer to Brian's question is that the props department and the actors in Spearhead in Space were no better with x-rays than their technologically advanced, but equally incompetent, successors in the 1996 TV movie.

All they need is to have a real medical doctor on set to put them right about all this stuff. It would only take a few minutes and I could spend the rest of my time blogging about it!

No comments:

Post a Comment