RadPy is based on plugins so that anyone can contribute their analysis code to the suite. Most physicists have software tools they have written to manage the data generated in their clinical practice. If the code I have written is any example, these tools are not very user friendly. They also are usually not tested by independent users. The goal of RadPy is to provide a usable framework to distribute and test these tools. By making the tools open source, they can be checked for bugs and the overall reliability of these programs should be increased.

Anyway, I’ve been holding off on posting while I went on a binge of RadPy coding. Originally, I wanted to post here at least three times a week. I probably will not come anywhere near that now, but I will still post items as they strike my fancy. They probably won’t be on a grand scale like the “What is Radiation Therapy?” series, though.

So if you are reading this, sorry about the extended absence. I hope you stick around for the new era of sporadic updates.

In testimony before an administrative law judge, the boy’s father, who during the scans was standing at the foot of the CT table to calm his son, recalled his growing concern as the scanning stretched on. “I said, ‘Stop this!’ ” Padre Roth recalled, noting that Knickerbocker finally stopped the scan only after he became angry.

Within a few hours, the child developed a bright red ring around his head from the massive overdose of radiation. Photographs of the left side of the boy’s face show a clear line extending from the infraorbital ridge backward through the ear and nape of the neck; a similar line extends from the infraorbital ridge through the ear on the right side.

In off-the-record comments, some state officials called it the worst case of radiation overdose of a child in the U.S.

How could something like this happen? Apparently the tech involved pressed the scan button 151 times, averaging 25 seconds between each press. Afterward, she could give no satisfactory explanation for the event. She gave various excuses including motion of the patient, mechanical failure and distraction by the parents. None of these are any excuse for intentionally irradiating a patient that many times. Her supervisor could only describe it as a “rogue act of insanity”.

The consequences were dire.

A report by the hospital’s medical physicist calculated that the boy’s absorbed radiation dose was 2.8 Gy (2,800 mSv) and possibly as high as 11 Gy (11,000 mSv). The dose the boy received compares to a range of 1.5-4.0 mSv for a normal pediatric CT study of the entire spine, according to pediatric imaging experts.

Using relevant material from the article “Estimated Risks of Radiation-Induced Fatal Cancer from Pediatric CT,” published in the American Journal of Roentgenology (February 2001, Vol. 176:2, pp. 289-296), a report by the hospital’s medical physicist concluded the child had a lifetime increased risk of a fatal cancer of 39%.

Hopefully the hearing will shed more light into what exactly went wrong. There should be a written procedure in place on how to respond to instances where the CT scanner behaves incorrectly. Often, however, scans like this are seen to be too routine to worry with a formal procedure. Technicians are expected to be able to adapt to unexpected events. If the technician does not have the necessary understanding of the system, though, the consequences can be catastrophic. In his book The Human Factor, Kim Vicente describes how a lack of understanding caused the Chernobyl accident.

The problem was that the plant designers hadn’t paid enough attention to the human factor – the operators were trained but the complexity of the reactor and the control panels nevertheless outstripped their ability to grasp what they were seeing. [The reactor operator] didn’t completely understand the effects his actions were going to have until it was too late – with devastating consequences.

As a friend of mine once told me, “the secret to life is being smarter than the machines you work with.”

Undoubtedly, the technician in this case will have her license revoked, and rightfully so. The fact that a scan that should have taken a few minutes instead took more than an hour was a warning sign that any reasonable person should have heeded. However, that won’t make the problem go away. If the CT console software is too complex for a trained technician to understand, then the software needs to be simplified or there need to be hard and fast guidelines as to when someone with a greater understanding needs to be called in.

In the face of the Mo-99 supply crisis, important diagnostic procedures often relating to life-threatening conditions such as heart disease and cancer are being postponed or cancelled because of the decreased volume of Tc-99m available to the nuclear medicine community. In addition, clinicians appear to be turning to older nuclear modalities with potentially less diagnostic certainty and more patient risk. Clinicians may also be foregoing nuclear medicine completely, opting for more invasive, more expensive, higher risk, surgical procedures. The nuclear medicine community seems widely affected by the supply crisis and appears to be adopting a variety of strategies to try to conserve the Mo-99 which is available.

The lack of controversy at the hearing is a good sign that hopefully indicates that the committee will report the bill to the whole House soon. On a personal note, I happened to be on an elevator yesterday when a courier was carrying a shipment of Tc-99m to a cardiologist’s office. I said to him, “I hear that you’re having a shortage of that.” “Yeah,” he replied, “in fact this is my last shipment of this. They’re having to switch over to Thallium.” As this presentation on the benefits of Tc-99m makes clear, that will result in poorer image quality and higher radiation dose for their cardiac imaging patients. It will take years for a domestic source of Mo-99 to become operational. We need to get the ball rolling right now.

What about the people who are cutting granite into counter shaped pieces, though? That is a different question altogether. One of the hazards of cutting any kind of material is dust inhalation. If the material is radioactive, it makes sense that the hazard could be significantly multiplied. The radon given off from a piece of granite might have a low enough concentration that not much of it is inhaled. However if the granite is in your lung already, the concentration would obviously be higher. Now one researcher claims that the risk from cutting granite is, in fact, significantly higher.

Craftsmen who cut granite for kitchen countertops can be at risk of radiation exposure thousands of times above the federal safety limit, according to new research.

The danger results from inhaling the airborne granite dust, which sometimes contains significant quantities of uranium and other dangerous isotopes, scientists say.

“What we found scared the daylights out of us,” said co-author Linda Kincaid, an industrial hygienist in Saratoga, Calif.

The study, “Implications of Granite Counter Top Construction and Uses,” raises concerns that the stone dust could be exposing America’s estimated 24,000 granite fabricators to elevated cancer risks, according to Kincaid. People living in homes with granite countertops face no health concerns from the dust, which is generated when the stone is cut.

Obviously, this research needs to be replicated and confirmed. It hasn’t been peer reviewed and published, only presented as a poster at a meeting of the Health Physics Society. It seems at least somewhat plausible. I would guess, though, that the hazard of breathing in the dust itself is higher than any risk from the radiation, and workshops already take measures to keep the amount of dust in the air down. The linked article states that most fabricators use water cutting techniques that minimize the amount of dust generated. Whether the radiation hazard is real or not, it looks like a good idea for all fabricators to adopt those techniques.

The Sarasota Herald Tribune is reporting that testing by three agencies, the Florida Department of Health, the U.S. Environmental Protection Agency and the Consumer Product Safety Commission, on drywall manufactured in China has found no traces of radioactivity. Why was it being tested in the first place? Apparently, there have been quite a few problems with Chinese drywall: foul smells, metal corrosion and even illnesses reported in people living in houses with it. A radioactive material called phosphogypsum was considered as a possible contaminant in the drywall, but the testing ruled this out.

Phosphogypsum is a byproduct left over from the process that creates fertilizer from phosphate ore. Phosphate ore contains trace amounts of uranium, and therefore its daughter product radium. When phosphate ore is chemically treated with sulfuric acid to create fertilizer, the radium is separated out with the phosphogypsum. As a Health Physics Society “Ask the Expert” answer makes clear, phosphate ore produced by marine deposits has a higher concentration of uranium, and therefore the phosphogypsum produced is too radioactive to use in construction materials. Since it cannot be used, the fertilizer industry has resorted to piling it into stacks. The wikipedia article states that there are 1 billion tons of radioactive phosphogypsum in stacks in Florida and that 30 million more tons are produced each year.

Chinese industries are not prohibited from using phosphogypsum, though. Was it reasonable to suspect that imported drywall laced with phosphogypsum was the culprit? An article in July from the Los Angeles Times found some evidence that phosphogypsum use was widespread in China. The radioactive La-Z-Boy story shows that radioactively contaminated materials can be imported into the US without discovery. However, in that case, the contamination was fairly low level. In order to corrode metal and cause acute illness in humans, a much higher level of radioactivity would be required.

In the United States, phosphogypsum cannot be used if its activity is greater than 370 becquerels/kg. Exposure to phosphogypsum with this activity is estimated to give a dose of 1 mSv/year. However, acute symptoms of radiation poisoning require a dose of around 500 mSv. Considering, that phosphogypsum has a maximum activity of around 1,300 becquerels/kg, even pure phosphogypsum would not come close to that. Of course, cancer can be induced at a much lower dose and therefore the drywall could still pose a significant health hazard. Therefore, it is reasonable to check the safety of the drywall even if the specific complaints listed above are unlikely to be caused by radiation.

In any event, the radioactivity in the drywall was found to be at background levels, and the more likely culprit might be sulfur compounds (which would explain the rotten egg smell described by some residents). But could other household objects be slowly killing you? Stay tuned for a special report that could save your life! (Well, not really. I just always wanted to say that.)

The third strategy is use substitute isotopes whenever possible. The article mentions several alternatives, such as thallium-201 for heart imaging studies. However, these alternatives can be more expensive and, as is the case with thallium-201, give the patient a higher dose of radiation. In addition, even if the alternatives cost the same, apparently Medicare is refusing to cover them. The Center for Medicare Services is considering changing its position, but no decision is expected for at least 6 months.

Meanwhile the American Medical Isotopes Production Act languishes in the House Committee on Energy and Commerce. Even if it passes, it will be several years before a domestic source of Mo-99 is viable. When the Petten reactor comes back up in a few weeks, it will only be in service for 6 months before it shuts down for maintenance for an additional 6 months. It’s looking more and more like this shortage is going to be more than a temporary inconvenience.

(Via the tireless John Jacobus. You can assume that for any post of mine, there is at least a 75% chance he was the one who brought it to my attention.)

For some reason, every dosimetrist likes to work with all of the lights turned off. So, if you didn’t take the opportunity yesterday, make sure to drag your dosimetrist out of their dark, dank dungeon and into the light and congratulate them on a job well done.

This week’s installment won a Grammy in 2007 for Best Pop Performance by a Duo or Group with Vocal. I can only imagine that the award category was so specific that this song was the only one nominated. In any event, you can find the Grammy award winning Black Eyed Peas with their Grammy award winning song, “My Humps”, here at YouTube (embedding disabled to protect the innocent).

Figure 1. A single 18 MV beam has a lower maximum dose than a 6 MV beam.

Figure 2. Parallel opposed beams.

Figure 3. Adding another beam directly opposed from the first limits the maximum dose.

Figure 4. Using higher energy beams will lower the dose to the normal tissue.

Figure 5. A four field beam arrangement.

So which arrangement is best? The answer is patient specific. Usually, simpler is better. The more fields there are, the longer it takes to treat the patient. As treatment time increases, the more likely it is that the patient or the patient’s internal anatomy will move and take the tumor away from the beam of radiation. When we get to patient immobilization, I will show some strategies we use to minimize this factor, but it can never be completely eliminated. Also, adding more beams may decrease the maximum dose, but it also exposes more normal tissue to radiation. Therefore, the answer is to use as few beams as it takes to treat the tumor effectively while sparing normal tissue. That answer is definitely vague, and this is where treatment planning becomes an art.

All clinics in the United States have full time staff members known as dosimetrists whose job it is to find the optimal beam arrangement for each patient. (Other countries have equivalent positions, but with different job titles). Obviously, this can be a very time consuming process. Fortunately, most types of cancer can be treated in a standardized fashion. For example, most lung tumors can be effectively treated with a parallel opposed set of beams. Breast cancer can often be treated with two tangent fields that treat the breast from either side. Sometimes, however, extra fields must be added to effectively treat lymph nodes that are at risk of disease.

A lot goes into treatment planning, and beam arrangement is just one part. In the next installments, I will discuss how blocking the beam affects the dose distribution and we will move from there into more advanced techniques.

Generally the Procurator Fiscal will receive notification of a person’s death and will investigate any which appear suspicious or where investigation is mandatory regardless of the suspicion of crime. Where the death appears to be due to a criminal act the Procurator Fiscal will initiate investigations by the police or other appropriate public authorities to enable the identification of suspects and associated evidence to enable him to prosecute the case in the Sheriff Court or for an Advocate Depute to prosecute in the High Court of Justiciary. However, if the circumstances give rise to investigation, or if the death occurred while the deceased was in lawful custody the Fiscal may choose to examine matters in greater detail. Where the circumstances justify it in the public interest, or where there is a statutory requirement the Fiscal will intimate his intention to prepare evidence for a Fatal Accident Inquiry.

If I am reading this correctly, it appears as if the inquiry could end in criminal charges being filed against the health care workers responsible.

Criminal charges for medical errors in radiation therapy are not unprecedented. Two medical physicists in Panama were sentenced to four years in prison after an error in treatment planning software overdosed 28 people, killing at least 18 of them. Also in Costa Rica, a physicist was sentenced to six years in prison after miscalibrating a Cobalt-60 unit, killing 30 people and injuring 59.

In this case, I believe criminal charges would be a gross overreaction. Leaving aside the question of whether Lisa died from her cancer or the overdose, the error occurred at a clinic that was woefully understaffed and under-equipped for the patient load they were expected to treat. According to this article from 2006, 5000 patients a year were given radiation treatments at the Beatson Oncology Clinic. That is an incredibly busy center. It accounted for almost half of all of the radiation treatments in Scotland. At the same time, a report from the Scottish government stated,

207. Using current recommendations from IPEM (Institute of Physics and Engineering in Medicine) an establishment of 58.5 WTE radiotherapy physicists is required for Scotland. The current establishment is 42.5 WTE, a shortfall of 16 WTE posts. Also 8 WTE posts were vacant as at December 2004 and therefore only 34.5 WTE were in post, less than 60% of the recommended level.

The final report on Lisa’s death acknowledged the role that understaffing played in the error.

When a horrible incident like this occurs, the first instinct is to find out who is to blame. In this instance, I believe that the blame lies in a system strained to the breaking point. Given that workload, it was only a matter of time before a grave error was made. Holding people criminally accountable who were only trying to do an impossible job would send a chilling note throughout the radiation therapy community. Needless to say, many will be watching the outcome of this inquiry, myself included.