Category: Sciency things

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Peeping into the brain

BrainMaps.org is totally cool. 50 TB of images of the brains of 12 different animals (so far). You can zoom in to see microscopic structures with a resolution of just under 0.5μm per pixel. One of their recent papers in NeuroImage describes the technique they used to acquire and assemble the images. Pretty cool stuff.

BrainMaps.org is an interactive zoomable high-resolution digital brain atlas and virtual microscope that is based on over 15 million megapixels of scanned images of serial sections of both primate and non-primate brains and that is integrated with a high-speed database for querying and retrieving data about brain structure and function over the internet. Currently featured are complete brain atlas datasets for various species, including Macaca mulatta, Chlorocebus aethiops, Felis catus, Mus musculus, Rattus norvegicus, and Tyto alba.

Found via ScienceDaily

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Scary new radiation symbol

New radiation symbolThere’s a new radiation symbol that’s been introduced by the ISO and IAEA which is meant to alert people that whatever they see this symbol on is a potentially lethal source of radiation. The rationale behind developing the new symbol is that while the old symbol marked the presence of radiation, it didn’t provide any indication as to how dangerous the source might be. The new symbol with the addition of the skull and cross bones should definitely indicate to everyone that the source marked by the symbol is dangerous.
From the IAEA press release:

With radiating waves, a skull and crossbones and a running person, a new ionizing radiation warning symbol is being introduced to supplement the traditional international symbol for radiation, the three cornered trefoil.

The new symbol is aimed at alerting anyone, anywhere to the potential dangers of being close to a large source of ionizing radiation, the result of a five-year project conducted in 11 countries around the world. The symbol was tested with different population groups – mixed ages, varying educational backgrounds, male and female – to ensure that its message of “danger – stay away” was crystal clear and understood by all.

Radiation symbolIt’s a decidedly scarier looking symbol than the classic yellow/magenta radiation symbol (right), which is probably a good thing considering the class of radioactive materials the new symbol is meant to warn people about. The new symbol is meant to be used on what the IAEA classifies as Category 1, 2 or 3 sources. These are the kinds of sources that nobody really wants to be around when they’re shielded (although perfectly safe to be around when properly shielded), and definitely not when they’re unshielded. Category 1 sources include RTG sources, irradiators used in sterilizers and teletherapy sources. They contain activities in the TBq (tera-Becquerel) or MCi (mega-Curie) amounts. Even brief exposure to these sources would probably be fatal in a matter of days or weeks. Category 2 sources cover industrial radiography sources and usually have activities in the high GBq (a few hundred Ci) range. Certainly less lethal, but still not something you want to be around for any length of time. Category 3 sources include calibration sources and sources for gauges and well logging.and have activities in the low GBq (a few Ci) range.

Fortunately, I will never have to see the new symbol because the activities I’m around are in the MBq (mCi) range. And if I ever do see the new symbol, I’m definitely not sticking around.

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On the way to Pluto

The New Horizons probe destined for Pluto is hurtling towards Jupiter now for an additional speed boost. On the way, the science instruments will be getting a bit of testing making observations of Jupiter and its moons. Should be a good workout for the system.

After the probe’s encounter with Jupiter, it will be speeding off towards Pluto at a pretty good clip of 52 000 mph (nearly 84 000 km/h or 23 km/s). That will make it the fastest probe sent out to date. Even at that speed it won’t reach Pluto for another 8 years though. You can follow the probe’s trajectory here.

Neat stuff. It will be cool to see what kind of things we’ll learn about Pluto in 8 years time.

Found at Slashdot.

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The perils of procrastinating

So it seems a group of people at Ottawa Hospital in Ontario has just had a paper published in JNMT that covers pretty much the same material I worked on and just submitted to the same journal. My contact at GSK told me it was something they also sponsored (like my project), but wasn’t aware they had submitted it for publication.

Trying to get my hands on a copy of the article so I can read it and see what they looked at. Fortunately they come up with the same conclusions and results I did. From the abstract it seems like some of the things they investigated were different from what I looked at, so hopefully it’s different enough from mine that the reviewers decide it’s still worthy of publication.


My abstract:

Objective: Residence time measurements obtained by serial whole body conjugate view imaging are commonly used in patient specific dosimetry for radioimmunotherapy (RIT) applications. In order to determine the effect of collimator selection on residence time measurements for 131I, the accuracy of 131I half-life measurements using multiple gamma camera and collimator combinations was investigated. Method: Serial anterior and posterior whole body images were acquired over a period of 15 days using 4 different gamma cameras with medium and/or high energy collimators. Background corrected geometric mean counts from the images were fitted to a mono-exponential curve to determine the half-life of 131I for the different gamma camera/collimator combinations. Results: An average half-life of 8.15 days with a standard deviation (SD) of 0.07 days was obtained from all camera/collimator combinations. A half life of 8.12 days (SD 0.11 d) was obtained for the high energy collimators, and 8.18 d (SD 0.04 d) for the medium energy collimators. These values are all very close to the 8.02 day 131I physical half-life and were not found to be statistically different (p=0.44). Similar results were also obtained for the measured half-life for single head gamma camera configurations (mean half life 8.15 d, SD 0.12 d). The therapeutic 131I-tositumomab dose resulting from the differences in measured half-life ranged between 2.58–2.6 GBq (69.8–70.4 mCi). Conclusion: There is no significant difference in 131I half-life and residence time measurements made using medium or high energy collimators in dual head or single head imaging configurations.

Their abstract:

131I-Tositumomab has been used in treating patients with non-Hodgkin’s lymphoma. It is generally recommended that high-energy collimators be used to image patients before they receive 131I-tositumomab therapy, to determine the effective half-life for therapeutic dose and gross biodistribution. Because many nuclear medicine departments do not possess high-energy collimators, this study was designed to assess the suitability of using medium-energy collimators. The effect of scanning speed was also investigated, in an attempt to optimize the acquisition time. Methods: Measurements were taken using an elliptic anthropomorphic torso phantom and an organ-scanning phantom fitted with fillable spheres (1-5 cm in diameter) and organ inserts. Three phantom studies were performed with differing initial 131I concentrations in the organs, the spheres, and the thoracic and abdominal chambers. Images were acquired with both high-energy and medium-energy collimators and at acquisition speeds of 20 and 100 cm/min. The half-life for each combination (study/collimator/speed) was calculated from a linear fit of the data. The contrast of the tumor sphere was assessed using 2 identical regions, placed on and beside the sphere, and averaged over several time points. Biodistribution and image quality were visually assessed by 2 independent observers. Results: Measured half-life values and visual assessment of biodistribution showed no significant difference between the 2 collimators (P = 0.32) or acquisition speeds (P = 0.85). A significant difference in the contrast of the tumor spheres was observed between the 2 collimators (P < 0.01) but not between acquisition speeds. Visual assessment of the images showed increased noise on the image acquired at 100 cm/min, although this noise did not affect lesion detectability. Conclusion: Measured half-life is not significantly different between the 2 collimators; hence, calculation of the residence time would be nearly the same. Medium-energy collimators can be used to accurately calculate the 131I-tositumomab therapeutic dose and detect alterations in biodistribution.

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Package irradiation

I’ve been doing a little bit of liason work between one of the clinical research coordinators at work and K & S Associates. Someone decided to check out the radiation exposure patients were getting from a particular CT study and ordered some TLD chips for the measurement. Had they consulted us first, we’d have told them it probably wasn’t the best way to get the dosimetry data, but they’d already ordered them.

So calibration chips were irradiated with a measured amount of radiation, and the rest were attached to patients who were then scanned. Then they were sent back for reading.

Normally a report is issued back in a couple of days, but this time there were some strange results. The charge readings K & S were getting were rather low (not surprising considering the amount of exposure they were getting) and somewhat inconsistent. TLD’s normally aren’t used for this kind of application either, so the charge stored on the chips was pretty close to the low end of their ability to read reliably. Normally these TLD chips are used to measure therapy doses, which are several orders of magnitude higher than what they would have been exposed to for this project.

So in the course of investigating the discrepancies, and several phone calls to me to confirm the calibration conditions, the tech at K & S learned that both UPS and FedEx have started running all the packages they handle through an x-ray scanner (one of those DHS screening things I’m sure).

The dose to the packages is far from trivial either. The K & S guy figured the TLD chips got anywhere from 0.5 to 1 cGy (50-100 mrad), which is about the radiation you’d get from 3 or 4 chest x-rays. With the TLD exposures the K & S are used to seeing, this amount of radiation is pretty negligible, but relative to the exposures we were using it’s pretty honkin’ big and can definitely skew the results in a big way.

For most packages this is hardly anything to be worried about, but for radiosensitive things like TLD chips and film it can be problematic. Photographic film, likely a non-issue, although perhaps some minor fogging possible.

Bottom line, if you’re shipping anything radiosensitive or photosensitive, UPS/FedEx might not be the best choices.