Sunday, October 20, 2013

Level of Detail

Way back at the beginning of my career, my first programming job was at Boeing working on flight simulator visual systems. That means the computer graphics system that produces the 3D images that the crew sees outside the window of a flight simulator. There can be many elements in a flight simulator scene but one that is almost always present is terrain.

The group in which I worked eventually built custom hardware for such a system. It filled a room and consumed several households' worth of power. These days, the smartphone in your pocket has many times the graphics capacity!

At the time, graphics capacity was limited. Terrain, and everything else in a computer graphics scene, is made up of polygons. The system can only draw so many polygons in the time available to render a scene. To produce the illusion of smooth motion, the system has to draw at least 15, and more typically 30, "scenes" (frames) per second.

One of the projects I worked on was called Level of Detail. When objects are farther away from the viewer, they can be drawn at a lower level of detail (fewer polygons) without the viewer noticing. The image above is a test image for a level of detail algorithm for terrain. The blue polygons are at full detail; the green polygons are twice as long on a side; and the red polygons are 4 times as long on a side as the blue. The stitching pattern is one of the artifacts I was trying to fix - the reason for it (z-buffer resolution) is too complicated to go into here.

The point is that information (polygon detail) became available as it was needed as the position of the viewer changed.

Why am I telling you this? Because I'm discovering that there is an art to being an oncologist, and "level of detail" is one important aspect of it.

Cancer doctors spare you the details at the beginning, and only give them to you as you need them.

Below are several examples from my follow-up appointment with Doctor Rad (the radiation oncologist) on Friday.

The first example concerns my teeth. Before treatment I was told to visit my dentist and get full x-rays and fluoride trays. I was supposed to use the fluoride trays nightly through treatment. I, like most people with my type of cancer and treatment, was not able to do so because of treatment-related mouth pain. The trays aggravated my gums mechanically, and the fluoride gel burned the damaged mouth tissue.

I figured I was protected by the fact I didn't put any food in my mouth for an extended period, so no sugars available to cause decay. Plus I was using the buffered saline rinse very frequently and that is supposed to provide a fair bit of protection of the teeth.

Doctor Rad brought up the fluoride during Friday's appointment. I thought it was only needed during treatment. I asked her how long I should use it?

"Well... I'm trying to find a way to break it to you... Forever."


The second surprise was a discussion of my beard. It is starting to grow again in a horizontal line just below my cheekbones. Doctor Rad told me Friday that it will likely never grow back on my neck. I've had beards off and on throughout my adult life. I guess I have had my last beard. Fortunately, it is not a huge part of my identity.

The third was the puffiness in my neck, which I knew was due to the lymph nodes recovering. She told me the puffiness is called lymphedema (logical name!). She told me I should at some point go to special physical therapy for it, where apparently I'll learn to massage my neck in such a way as to clear the edema.

After meeting with Doctor Rad we met with the nutritionist and the speech and swallow therapist. I can't remember if I mentioned this before: I also thought that the swallowing exercises were only to get me back to the point where I could eat. But last time we met with the nutritionist she told me that they recommend that I do the swallowing exercises for the rest of my life. The swallow therapist told me they have had patients come back as long as ten years after treatment with suddenly compromised swallowing because of scar tissue that formed that long after radiation.

So I have to establish two new daily habits that last the rest of my life: swallowing exercises and fluoride treatment. Plus some shorter-term work on my neck to relieve the lymphedema.

I didn't know I was going to emerge from cancer treatment with a bunch of life-long homework!

We also talked about taste and saliva. Doctor Rad seemed sure that both would improve. She thinks the bad taste issues I'm having at the moment might just be due to all the antibiotics I've taken in the past few months. My bacterial flora is certainly way out of whack. The nutritionist gave us the names of a couple of concentrated probiotic products that I can use to try to get good flora reestablished.

Doctor Rad was a little disappointed to hear that I had reverted to tube feeding. My next appointments are on November 5 and she recommended I use that as a goal and plan to remove my feeding tube that day. The nutritionist and swallow therapist think that's a little optimistic - they have safety criteria that say I should be eating by mouth with no issues for two weeks before removing the tube. The swallow therapist observed me drinking water and eating a cracker. I haven't noticed, but I clear my throat a lot while and after doing both. That's a sign that my swallow is not completely normal and there is some risk of aspirating food or liquid. They want to see that risk gone before removing the tube.

I had already decided that I was using the tube as a crutch and needed to get back to eating. Yesterday I managed to get all my calories through my mouth but it was a bit of a struggle. Nothing tastes "good". I have to force myself to keep eating and keep washing it down with a beverage, unless I'm eating soup with plenty of liquid in it.

Wonderful Wife looked up how to deal with eating challenges due to diminished taste and saliva. One suggestion she found was to distract oneself while eating by watching TV, reading or listening to music. I have been reading while eating and that does sometimes distract me enough that I get through a portion of whatever I'm eating without being aware of every mouthful. I'll have to also try music in headphones or TV. I won't be able to do that at every meal, though.

I need to try lots of different foods and see what works. Yesterday I had it in my mind that Japanese udon (noodle soup) would taste good. So we went to a Japanese restaurant for dinner (my first dinner out!) and I gave it a try. The tempura shrimp that came with the soup was good dipped in broth and soy sauce. The broth by itself tasted fishy. The fresh vegetables in the soup and the tempura vegetables tasted pretty bad, or perhaps it was the texture.

It's hard to think up foods that might work. I also need foods to be calorie-rich. The only foods we can come up with that are both wet and calorie-rich all contain dairy. I have nothing against dairy, but I can't eat it for every meal! I'm going to have to branch out and eat foods that are not wet, and just get used to washing drier foods down.

Eating is going to be my hardest long-term challenge. I guess I've probably made it clear by now: it really sucks for eating to be an unpleasant chore instead of something enjoyable.

Whenever I do get my feeding tube removed, the removal of the tube sounds interesting. The nurse practitioner will do it in the office. I read the instructions right after the tube was placed. They're pretty simple:

  1. Grasp firmly.
  2. Pull.

They just yank the thing out! On the stomach end of the tube there is a little hard plastic collar that is scored. When they pull on it, the scores give way and the collar collapses and the whole shebang comes out through the hole.

"It stings for a minute, " I'm told.

Something to look forward to.

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