Bosch Asks: What’s a Medical Physicist?

Having watched all five seasons of the Amazon police drama Bosch, I was excited to find Season 6 arrive during the lockdown imposed on us due to the coronavirus pandemic. Ten minutes into the first episode and Bosch is called out to the Overlook at Lake Hollywood Park on a murder case. An abandoned 911 Porsche, an open boot and the victim: a medical physicist. In his usual downbeat manner, Bosch asks: “What’s a medical physicist?“

I knew a medical physicist once. He was the only one who went into that particular field of physics from the cohort on my physics degree. So I thought I would include a smattering of physics as I write my brief overview of this season’s Bosch.

First, though, I will say I am somewhat surprised that our relentless, veteran, LAPD super-detective, Hieronymus Bosch, doesn’t already know what a medical physicist is, because he does seem to know a little about a lot of things. Or maybe I’ve got that wrong and his knowledge really does only go from J to Z — and that’s jazz.

Anyway, Bosch is up in the hills with the Hollywood sign looming in the background and approaches the victim’s car. “Something heavy made these,” he says, as he ponders the imprints in the carpet in the trunk of the 911 made by something that’s no longer there.

Then he sees the body — a middle-aged man in smart-casual work clothes lying on a dirt track in the middle of nowhere, carrying a hospital swipe card and wearing some seriously funky jewellery for someone of that age and style of dress.

What are the bright orange coil rings the victim is wearing on the middle finger of each hand, Bosch is thinking — as are we.

They are radiation rings, or more precisely thermoluminescent dosimeters — devices used to monitor someone’s exposure to radiation.

How do thermoluminescent dosimeter rings work?

Click to skip this block and continue reading the article

Hands are expected to receive the highest dose of radiation during the preparation and handling of pharmaceutical radioactive material, so it is practical to wear a radiation exposure monitoring device as a ring.

The thermoluminescent dosimeter (TLD), whether worn as a ring or in any other form (a pin or a bracelet, for example) is a passive device. It contains a chip of thermoluminescent material, often lithium fluoride or calcium fluoride, doped with impurities in the crystal structure (ions such as magnesium, manganese or dysprosium, for example).

When exposed to ionizing radiation, electrons in the thermoluminescent material are excited to a higher energy state and get trapped there by the impurities.

When the material is subsequently heated, the electrons decay (via interactions with phonons in the crystal structure) to a lower energy state, emitting light at a frequency determined by the difference in energy between the upper and lower energy states.

The intensity of the light emitted is proportional to the amount of ionizing radiation measured by the detector in the ring. This allows the dose of ionizing radiation to which a person has been exposed to be monitored.

Our medical physicist victim, as we soon find out, was Stanley Kent who worked in a hospital nuclear medicine department and handled radioactive materials in the laboratory including caesium (cesium in the US) and iridium, being stored for use in cancer therapy amongst other things.

However, the last that the hospital’s CCTV sees of Kent is him wheeling a pig down the corridor. That’s a lead pig — a massively heavy and thick-walled lead container for transporting radioactive materials. Thirty two tiny vials of caesium, in fact, are in the pig — the lab’s entire inventory — the whole nine, as Bosch would say. That answers Bosch’s question as to what made the dents in the carpet in the trunk of Kent’s car.

The head of Kent’s department at the hospital tells Bosch that caesium is ‘old school’ and that no-one uses it in the hospital now. We must presume that Kent saw this as an opportunity (motive, even) for finding an alternative use for the redundant inventory.

The caesium being referred to is most likely caesium-137, one of the many radioactive isotopes of caesium. We only see small metal rods or tubes — the tubes aren’t the caesium, they contain a compound of caesium inside.

Back at Kent’s house, Bosch and his partner, Jerry “J Edgar”, are interviewing his questionably grieving widow who has just been untied from an apparent kidnapping linked to her husband’s smuggling activities and his own demise.

“This stuff, is it valuable?” Jerry asks. “No, it’s dangerous, extremely toxic…” she replies, with surprising knowledge of the properties of caesium. “If it gets in the wrong hands it…do you think that’s what they’re after?” she adds.

We get the feeling she already knows that to be the case.

We also get the feeling that her kidnapping isn’t quite what it seems and that maybe she is more involved in her husband’s seizing of the caesium than she is saying. It leads us to wonder whether she had anything to do with encouraging him to commit the crime that ended in his own demise.

What is caesium?

Caesium is a rare element, a silvery-gold alkali metal and one of the few which is liquid at or near room temperature. Although rare, it is still more abundant than some other common minerals like mercury, silver and tin.

Caesium occurs in nature as a salt compound, extracted from pollucite ore mined only in Canada, Zimbabwe and Australia.

Caesium is also produced as a fission waste by-product of nuclear reactors and weapons testing. When required for medical uses, caesium is produced commercially via different processes depending on the isotope of caesium required.

There are 40 known isotopes of caesium, ranging in mass number (neutrons + protons) from 112 to 151 and of these only one (caesium-133) is stable and the main isotope found in nature.

The other 39 isotopes are radioactive and decay with a half-life ranging from 2.3 million years to a fraction of a second – decaying to other isotopes of caesium or to isotopes of other elements (mainly barium and xenon).

Of those 39 radioactive caesium isotopes, caesium-137 and caesium-131 are both used in medical applications – but in very different situations.

Caesium-137 is used in irradiator devices to sterilize blood.

Caesium-131 is used in brachytherapy, a form of radiotherapy to treat certain cancers and tumours when a high dose of radiation is required to treat a very precise or not easily accessible area.

One of the ways caesium-131 is produced for use in medical applications is by irradiating barium with thermal neutrons.

Once produced, caesium-131 decays with a half-life of 9.7 days to xenon-131 via a process known as electron capture. Low-energy X-rays are emitted in the process and this is the ionizing radiation used in brachytherapy.

Caesium-137 for use in medical irradiators is produced by nuclear fission. Once produced, caesium-137 decays with a half-life of 30.17 years to a short-lived meta-stable state of barium-137 via a process known as beta decay, which in turn stabilises to a non-radioactive form of barium.

High energy gamma rays are emitted during the caesium-137 decay process and this is the form of ionizing radiation used in the medical irradiators — although not for much longer, because in 2015 the US Department of Energy announced plans to permanently eliminate the use of caesium irradiators by 2028.

One of the three FBI Agents who feature in the current season, vying for supremacy on this case over the LAPD and Bosch, describes what could happen if the caesium was released into the environment. “LAX, City Hall, Dodgers Stadium…unusable for 300 years,” he says. We sense the need to keep an eye on this agent — and not just because of his good looks.

Meanwhile, Bosch’s daughter finds out from her new medic boyfriend that a number of hospitals are, he thinks, being inundated with outbreaks of “ebola, measles and typhoid fever maybe.” I couldn’t work out why he said this or what happened to that thread in the story because it never surfaced again. But when I first heard it, I thought bish, bash, bosh that’s potentially three major epidemics and a radiological weapon all in the first half hour. It’s the whole nine coming our way as we watch this story unfold during our own coronavirus pandemic.

The entire situation is, at this point in time, understatedly described as “a bubbling cauldron of shit” by Bosch’s sometime adversary and marginally crooked Chief of Police, Irvin Irving.

Meanwhile, Bosch has done some digging around in Stanley Kent’s office and found some interesting papers.

Mrs Kent, it turns out, is herself a physicist but retired early on in her science career to live off the royalties she receives from a patented surgical sponge she invented as part of her PhD research at university. An X-ray detectable surgical sponge, in fact. And Mr Kent, our medical physicist, it turns out, had been receiving 50% of those royalties thanks to a clause in the couple’s prenuptial agreement that assigned the share to him so long as the marriage managed not to decay away before a certain number of years had elapsed.

Bosch’s expression as he hears this news suggests he may now have the grieving widow figured out. Although we could tell when she was interviewed after her alleged kidnapping that her demeanour was not entirely consistent with having just lost a beloved husband of many years.

The first thing she did after she had been found by Bosch and untied from her terrifying ordeal was to motion for her orange robe to be passed to her — from her closet, she said — an action not as trivial as it sounds.

The robe was the start of Mrs Kent’s downfall, because Bosch later notices in photographs, supposedly taken by her kidnappers that the orange robe is draped on the back of a chair, not in the closet, in what he now realises are staged images of her kidnapping.

To cut a long story short, Mrs Kent is accused of being complicit in her husband’s murder. She hires Honey “Money” Chandler to broker her a plea deal, which backfires in court when she is found to have been having an affair with the handsome FBI agent. The FBI agent in turn is found to have been involved in Kent’s demise and is shot by his FBI partner trying to abscond.

So Bosch solves the murder, but not before recovering the caesium and then ending up himself recovering in the hospital radiation contamination isolation unit.

There is, of course, a lot more to this season’s storyline than what I have described, including the undertones of the potential radiological threat and a group of sovereign citizens. You’ll need to watch all of Season 6 to appreciate this.

Many successful TV dramas have two main unrelated threads running all the way through the story and this season of Bosch is no exception. Throughout the ten episodes, Bosch is moonlighting with his ongoing investigation into the Daisy Clayton cold case (remember Bosch met her alcoholic mother on the pill trail in the latter part of Season 5). This cold case is solved in the last episode of Season 6.

We also have some lesser threads weaving in and out, including the surfacing of an old cassette tape recording of a younger Chief Irving that could scupper his plans of running for Mayor of LA.

We also have Bosch’s daughter’s internship supporting Honey Chandler’s latest litigation case, as well as the death of a veteran detective, an LAPD undercover cover being blown, and a departmental sexual harassment claim.

As I said before, the whole nine.

So that’s it for my overview of this season’s Bosch. And while Bosch may well have asked what’s a medical physicist, we’ll now ask Google: what’s an X-ray detectable surgical sponge?

If you liked this overview of Amazon’s police drama Bosch, take a look at my commentary on Amazon’s legal drama Goliath.

And finally…

So what exactly do medical physicists do?

As well as handling radioactive materials and specifying the important safety measures related to that, medical physicists are involved in clinical situations such as diagnosis, planning radiation treatment and analysing medical images, as well as consulting on specialist medical equipment and radiation facilities, and, for example, developing new equipment, research into new concepts for treatment and conducting the relevant clinical trials.

Here’s a link to a page on the website of The Royal Marsden Hospital in London, which provides a detailed overview of what medical physicists do.

Fair Use Notice: All images from Bosch shown in this article are credited to Amazon Studios and have been carefully chosen to support the commentary in this article. I believe this constitutes a ‘fair use’ of any such copyrighted material.