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Tree nuts

The trees next to the house drop these large nut type things every other year that I’ve been told are pecans. This year the trees have dropped considerably more nuts than I’ve ever seen before.

Making things more interesting is that a bunch of them have split open and started sprouting, which is another thing I haven’t seen these things do (or noticed anyway).

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I planted some of them in some holes I dug around the yard, and the others I left on the ground where they sprouted. Since we won’t be here much longer, I won’t get to see what happens to them, but hopefully they end up sprouting into saplings and then into trees.

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BarcampCHS 2015

Another Barcamp Charleston is over with. The seventh Barcamp Charleston was a lot of fun. Significantly smaller than previous barcamps, but still a good time. There were also fewer presentations pitched this year as a result, but there were some pretty good ones.

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After the pitch sessions, I started the morning off hanging out with people in a BoF (Birds of a Feather) session. After that was my first presentation that I called Charleston Area Amateur Radio. Had a fairly decent sized group come to my talk where I talked a bit about the ham radio clubs in the area and the repeater networks around here that are available for use.

My session ended a bit early, and I was able to catch the Palmetto Scholars Academy kids working on their high altitude balloon launch demonstration. Their balloon didn’t go all that high, but they did a good job of explaining and demonstrating the process and requirements behind launching high altitude balloons.

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After the group photo and lunch was a session on graphs and graph theory by Denise Gosnell, one of the data scientists at Pokitdoc. Neat stuff. Kudos to Pokitdoc for being BarcampCHS sponsors and sending a great group of people to give some great presentations.

My second presentation of the day was a simple Ask a Medical Physicist session. Much to my surprise, I actually had a few (3) people show up, so it was just a very informal Q&A session where I gave a brief description of some of the things medical physicists do and answered any questions they had. It turned out to be a pretty decent session from my perspective.

The last two sessions I went to were on JSON and Clojure. They were both good sessions and I learned enough to dig a little more into them.

The crowd at this year’s Barcamp Charleston was a lot smaller than previous years, but there were a lot of new faces there. Hopefully they’ll spread the word and bring friends next year.

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Project idea: Half value layer comparisons

Two of the non-invasive meters I use at work can measure everything I need in a single shot: kV, exposure, exposure time, filtration, half value layer (HVL).

Even though the meters will calculate the HVL of the x-ray beam for me from one exposure, I still measure it with different thicknesses of aluminum and calculate the HVL. Just from first order impressions of using the meters over the years, I always felt that the HVL determined by the meter was never as accurate as doing the actual measurement.

It’s not anything I’ve ever tested or looked closely at though. With all the HVL data I have from the past few years, I can take a closer look at how the meter HVL and my calculated HVL compare. There’s at least a couple of years worth of HVL as a function of kV, so a plot of HVLmeter vs HVLcalc should give me a straight line with a slope of 1 if the meter HVL is useful.

I’ll need to go back to my spreadsheets and extract the meter derived HVLs and collect the corresponding measured HVL so it could be a while before I find a big enough chunk of free time to do that.

If it turns out the meter derived HVL is close to my calculated HVL, that means I could probably modify my data acquisition and do my testing with fewer exposures.

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International Day of Medical Physics 2015

November 7 (in addition to being BarcampCHS 7) is the third annual International Day of Medical Physics as well as being Marie Skłodowska Curie‘s birthday. The theme for this year’s IDMP is “Better Medical Physics = Better Cancer Care in Radiation Oncology“.

International Day of Medical Physics

Being a diagnostic medical physicist, I generally don’t have a lot of involvement in radiation oncology. The use of imaging in radiation therapy is growing though, so I have more occasions to work with my therapy physicist colleagues these days.

Diagnostic medical physicists like me stay busy doing a great many things, including:

  • equipment performance tests to make sure the imaging equipment is performing according to state/federal guidelines and manufacturer specifications
  • quality control/quality assurance
  • teaching residents and technologists the physics behind how the equipment works and how the images are generated
  • calculating radiation dose estimates
  • creating lead shielding plans for x-ray rooms
  • working with radiologists and technologists to optimize imaging protocols and techniques
  • working with field service engineers to diagnose equipment related problems
  • troubleshooting image artifacts
  • research
  • collaborating with radiologists and other physicians on research projects

You probably won’t see us if you need to get an x-ray or imaging study done, but we’re there working behind the scenes making sure the images look good while using a minimal amount of radiation.

Questions? Feel free to ask!

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Garmin StreetPilot 2610 guts

On the dissection table today is an old Garmin StreetPilot 26100 GPS unit. This is one I used in the car about 7 years ago, and then has been sitting in the console box since I got cell phoned.

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Undoing about 5 screws was all it took to separate the two halves of the GPS unit. A couple of ribbon cables and a wire connected the two halves.

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Disconnecting the ribbon cables and wire gets us a good look at the boards. The board on the back half of the unit contains the CF card slot, mini-USB port and connections for power and computer connection.

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The front half of the board is where all the interesting stuff is. Co-ax cables go from the patch antenna (top) and auxiliary antenna connector to the ICs that handle the GPS bits under the metal cover. Ribbon cables connect to the display, rear circuit board and the buttons at the front.

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The patch antenna showed some discolouration and scratches. Not sure if that was during manufacturing, or if the unit was previously disassembled.

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The patch antenna is soldered directly to the board and to the metal shield, so if I’m going to re-use it for something, I’ll have to cut it off. Removing the cover from this part shows a 32.735 MHz crystal and a bunch of other unidentified components.

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Underneath the other shielding section on the right side of the board is the brains of the unit, a 16/32 bit ARM core RISC microprocessor.

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Removing a few screws separates the main board from the display module. The other side of the main board contains a few more large ICs underneath a shielded area (128 Mb SDRAM, 512 Mb flash RAM, 16 Mb flash memory, Garmin BIOS ROM) and components associated with the display module.

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Moving on to the display module, bending out a few tabs allows it to be removed from its metal frame. The touch screen display module consists of the front glass, the LCD module, some plastic gratings/diffuser sheets and the backlight unit. It’s an interesting little module. The backlight unit consists of a U-shaped light that shines into a block of plastic. One side of the plastic has a matted finish to help diffuse the light.

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On top of the light are some plastic diffuser sheets that polarize, scatter and block some of the light.

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Finally comes the LCD unit. Seems to be a pretty run of the mill LCD.

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Not a whole lot of re-usable components in here. I’ll clip off the patch antenna for the junk bin and keep the buttons and mini-USB module. I might try to remove some of the larger components off the boards. Aside from that, the rest of it will probably end up in the electronics recycle box eventually.