PhD Candidate!

After doing my qualifier presentation back in May, I discovered there was another step before I could become a PhD Candidate.

The proposal presentation is supposed to demonstrate to the committee that my research is going on the right track and I’m actually capable of doing the work. Mine took the form of an NIH format grant proposal and a presentation to my committee.

Today I gave my presentation, and my committee saw fit to pass me, so now I can call myself a PhD Candidate!

This is good…I think.

Now the rest of the work begins.

A new portable x-ray unit

A new Carestream DRX Revolution Nano portable x-ray unit arrived at work this week. Normally the arrival of a new portable x-ray unit wouldn’t be a terribly notable event, but the size of the unit and label on the tube head intrigued me.

It’s a pretty compact unit (about the size of a shopping cart), weighing in at just over 100 kg. The x-ray tube is considerably smaller than a normal x-ray tube. I was told by the service engineer that the x-ray tube uses carbon nanotubes for the cathode. I had read about this technology a few years ago, but wasn’t aware that it was being used commercially. This is the first application I’ve heard of in the medical imaging world.

The machine is quiet during the exposures, without the normal sound of an x-ray tube anode spinning up, so I suspect this is a tube with a stationary anode.

The Nano turns out to be a pretty low power unit, even for a portable unit. The x-ray technique maxes out at 110 kV and 12.5 mAs. At 60 and 80 kV, the maximum mAs was 20 and 16 respectively. Not entirely sure if this was just a soft limit based on the imaging protocol I selected, or a hard limit. I still need to go through the documentation and the technical specifications for the unit.

Radiation output in mGy/mAs was pretty similar to a conventional x-ray tube (compared to a Shimadzu portable unit in the graph below).

Radiation output (mGy/mAs) graph
Radiation output for the Carestream Nano (orange diamond) and Shimadzu portable ( blue square)

Exposure times for the Nano were quite a bit longer though, so the tube obviously operates at a considerably lower tube current than a conventional x-ray tube. Pretty clear from the exposure rate graph below that while the mGy/mAs is similar, the Nano tube is spitting out much less radiation.

Exposure rate (mGy/s) graph
Exposure rate (mGy/s) for the Carestream Nano (orange diamond) and the Shimadzu portable (blue square). Multiple values at 80 kV are exposures at different mAs settings.

Crunching a few numbers, I found that the tube current for the Nano goes between 30 – 60 mA, about 1/4 of what I might expect for a regular portable x-ray unit, but about what I’d expect for something with a stationary anode.

kV/mA graph
mA range at different kV settings for the Nano (orange diamond) and Shimadzu portable (blue square)

As far as the kV and exposure rate wave form goes, it’s about as perfect as I’ve ever seen from any x-ray tube. Excuse the small size of the graph. The software for my meter started spitting out tiny images into my spreadsheets instead of the big ones it used to, and I haven’t figured out how to fix it yet.

kV and exposure rate wave forms for the Nano
Exposure rate (green) and kV (red) wave forms from the Nano

It’s a pretty neat little unit. Should be pretty decent for imaging babies and small kids (unless they’re very squirmy), but probably a bit under powered for imaging anything larger than a toddler. I predict the addition of at another more conventional portable x-ray unit a few months down the road.

After Dorian

Hurricane Dorian started making itself felt yesterday and slowly came closer overnight. The weather radio blared out a flash flood warning at 0430 that woke me up this morning so that I wouldn’t miss too much of Dorian’s approach.

Through the rest of the day, Dorian crawled by, skimming the SC coast and bringing some steady but not torrential rains, and a lot of wind at the house. The 24 hours or so of sustained winds with Dorian seemed to cause more problems than water this time, although there was still plenty of flooding going on. Twitter was full of reports of downed trees and branches, and power outages.

The generator transfer switch we had installed last year got it’s first non-testing use today. Power went out at the house around noon, unlike a lot of other areas where power went out early in the morning.

Around 4PM, I decided the refrigerator and freezer had been without power long enough so I got the generator set up out in the driveway, connected it to the transfer switch, and fired up the generator. Switched over the refrigerator, freezer, smoke detectors, and kitchen island (so I could run my laptop) to the generator and flipped each of them on. Everything came on like it should have. So much easier than running extension cords everywhere like we did for Florence.

The big black switches down the middle of the transfer switch switches each circuit between mains power and the generator. The white switches along the sides are off/on switches for each circuit. Fire up the generator, switch the desired circuit from line to generator, and flip the switch to on. Circuit is on generator power now. Easy peasy. I also decided each switch needed labels to make it easier to tell what circuits we wanted to switch over to the generator.

Generator transfer switch

The power came on about an hour later, so I didn’t have to be on generator power for too long fortunately (generator is loud!). Good test of getting the generator deployed and testing the transfer switch. I left the generator and power cord out for a little while longer in case power dropped out again, but it stayed on so everything got put back away for next time.

The only problem I ran into was that we had let a bunch of stuff pile up in front of the transfer switch, so I had to move a few things out of the way. A pretty minor problem, but something to avoid doing for the future.

Prepping for Dorian

All eyes are on Hurricane Dorian right now. At the moment, it’s pretty much stalled out over the western Bahamas battering the islands as a Category 4/5 storm. Everybody on the east coast from Florida to North Carolina is waiting to see when Dorian will make the turn to the northwest.

The NHC’s three day forecast track for Dorian has been pretty accurate except for when it went between the Eastern Caribbean Islands and Puerto Rico. With this track record, I’m feeling pretty good about our preparations.