One whole-body MRI could replace multiple cancer scans • Hacker News Board

Re: One whole-body MRI could replace multiple cancer scans

#81

Post by ChrisLomont » Mon, May 20, 2019, 7:30 PM UTC

DuskStar wrote: post #27

ChrisLomont wrote: post #25

Earlier quoted context omitted.

Because scans are not booked wall to wall every hour of every day. Needs more likely follow a poisson distribution with ample waits in between uses. To try and pack it that densely, with the large variation in how people show up at the hospital, would cause bottlenecks and loss of service. 20 a week is a more common number for most places. Here's actual data [1] measured on site. The usage is indeed around 50%, so th…

40% utilization means that it was in use for 67 hours per week. I don't think an MRI takes three hours. (In the case of the study listed, the utilization figures might be out of ~35 hours, which would make things different - but they also exclude scans scheduled in advance)

The link states "As a result, in our study the maximum hours per week on each scanner was limited to 35 h for the Vision (no hours on Tuesdays), 39 h for the Harmony, 32 h for the Sonata (no hours on Wednesdays) and 38 h for the Avanto."

Why guess 67 when you can look at the answer?

Re: One whole-body MRI could replace multiple cancer scans

#82

Post by [deleted] » Mon, May 20, 2019, 7:30 PM UTC

petschge wrote: post #55

chongli wrote: post #23

Earlier quoted context omitted.

This sounds to me like doing a full workup on blood chemistry. Individuals vary so much that you can get false positives. Wouldn't it be more useful as a baseline? Scan once and store it, then scan every few years and compare. If any of the "anomalies" has grown or new ones have appeared between scans, then they might be worth a second look?

Getting a baseline is harder than it sounds. In the case of blood chemistry that is caused by fluctuations due to time of day, time of month, season, what you recently ate and so one. In the case of MRI the problem is that internal organs shift to the point that it is impossible to automatically compare. And a experienced doctor comparing the scan millimeter for millimeter takes hours and would be very expensive. Eve…

[deleted]

Re: One whole-body MRI could replace multiple cancer scans

#83

Post by rolleiflex » Mon, May 20, 2019, 7:31 PM UTC

duxup wrote: post #69

petschge wrote: post #55

Earlier quoted context omitted.

Getting a baseline is harder than it sounds. In the case of blood chemistry that is caused by fluctuations due to time of day, time of month, season, what you recently ate and so one. In the case of MRI the problem is that internal organs shift to the point that it is impossible to automatically compare. And a experienced doctor comparing the scan millimeter for millimeter takes hours and would be very expensive. Eve…

> internal organs shift to the point that it is impossible to automatically compare I didn't even know that is a thing, I just sorta assumed they stayed put.

You are a wet squishy clump of really advanced bacteria trying their damned best to physically hold together, barely alive. Don’t expect much. Human politics is the literal definition of shipping the org chart.

Re: One whole-body MRI could replace multiple cancer scans

#84

Post by roywiggins » Mon, May 20, 2019, 7:31 PM UTC

ChrisLomont wrote: post #25

Someone1234 wrote: post #10

Earlier quoted context omitted.

Only 20 scans a week? A scan takes 30-60 minutes. So even if they only work 8 hour days and assume an hour for lunch/flex that's 35 scans per 5 day week. If they use it on weekends at all or run it for more than eight hours, that's just gravy. I'm not sure where you got the 20 scans a week number.

Because scans are not booked wall to wall every hour of every day. Needs more likely follow a poisson distribution with ample waits in between uses. To try and pack it that densely, with the large variation in how people show up at the hospital, would cause bottlenecks and loss of service. 20 a week is a more common number for most places. Here's actual data [1] measured on site. The usage is indeed around 50%, so th…

Utilization is less in a hospital, especially when you're measuring "active scanning time" and not all the time that you're really using a room. Hospitals also don't book scans so aggressively since someone might need a scan pronto- in an emergency, or near-emergency- and it can't be scheduled weeks in advance like you do in outpatient settings.

Complex cases where you need anesthesia, especially, may involve a lot of mucking about before and after the "active scanning" period, where the room is being used, but the scanner is not actively scanning anyone. Also, paediatrics cases.

Utilization is a lot higher in outpatient settings where you can line patients up and turn the room around in a few minutes.

Re: One whole-body MRI could replace multiple cancer scans

#85

Post by jmhmd » Mon, May 20, 2019, 7:32 PM UTC

SomaticPirate wrote: post #64

nknealk wrote: post #13

Many doctors hate full body scans. Every individual has a handful of anomalies which are almost always benign. They show up on full body scans and chasing them down comes with cost and patient risk. I have a hard time with reporting like this that doesn't quantify cost of biopsy on false-positives as well as cost of complications from examining false-positives. Source: worked in clinical research for 2 years.

But this is exactly what an “executive scan” is. I know several CEOs who get full body scans. Two of them caught early stage cancers and credit these scans with vastly improving their prognosis.

A counterpoint to these stories of early diagnosis is that not all cancers are equal, and there are some cancers which may not ever have affected the patient had they not been treated (or detected). Examples include some prostate and breast cancers. Autopsy studies have shown occult prostate cancer in about half of men > 70 years old who were asymptomatic and died of other causes.

Of course it is often impossible to know which cancer will or won't kill you, but it should be recognized that there is a risk to scanning oneself without a proper indication, for example, getting a prostatectomy for indolent prostate cancer and risking impotence.

Re: One whole-body MRI could replace multiple cancer scans

#86

Post by pbhjpbhj » Mon, May 20, 2019, 7:34 PM UTC

ChrisLomont wrote: post #25

Someone1234 wrote: post #10

Earlier quoted context omitted.

Only 20 scans a week? A scan takes 30-60 minutes. So even if they only work 8 hour days and assume an hour for lunch/flex that's 35 scans per 5 day week. If they use it on weekends at all or run it for more than eight hours, that's just gravy. I'm not sure where you got the 20 scans a week number.

Because scans are not booked wall to wall every hour of every day. Needs more likely follow a poisson distribution with ample waits in between uses. To try and pack it that densely, with the large variation in how people show up at the hospital, would cause bottlenecks and loss of service. 20 a week is a more common number for most places. Here's actual data [1] measured on site. The usage is indeed around 50%, so th…

>Because scans are not booked wall to wall every hour of every day. //

I had a scan in the UK, and this is exactly how it was done. Mine was actually in a mobile unit set up in a car park (for several months).

It took about 20mins and I was in the ante-room getting prepped as someone else was in the scanner, someone else was in the waiting room waiting to go next. At least a couple an hour and there were a couple of shifts of workers too (I asked).

As an aside the workers were all foreign, how fortunate we were/are and how sad for those countries to lose their talent to us.

Re: One whole-body MRI could replace multiple cancer scans

#87

Post by ChrisLomont » Mon, May 20, 2019, 7:38 PM UTC

snowwrestler wrote: post #38

ChrisLomont wrote: post #25

Earlier quoted context omitted.

Because scans are not booked wall to wall every hour of every day. Needs more likely follow a poisson distribution with ample waits in between uses. To try and pack it that densely, with the large variation in how people show up at the hospital, would cause bottlenecks and loss of service. 20 a week is a more common number for most places. Here's actual data [1] measured on site. The usage is indeed around 50%, so th…

This is data from a hospital. In the U.S. at least, a lot of MRI scans are done in outpatient centers, scheduled well in advance, and so utilization can be much higher. This would certainly be true of prophylactic scans.

The utilization could also be much lower. If not enough people need to sign up for each and every day, then it will not be full. It's extremely unlikely the needs in a region match the capacity anywhere near 100%. Such a tight capacity would result in many problems, so reasonable planning would have excess capacity to deal with busy seasons/holidays/weekends/etc.

Just like the hospital case, things like this likely follow a Poisson distribution, and it is therefore reasonable to assume similar usage patterns.

Have a link with data for your claim? I looked and found none.

Re: One whole-body MRI could replace multiple cancer scans

#88

Post by cheschire » Mon, May 20, 2019, 7:38 PM UTC

dillonmckay wrote: post #7

hammock wrote: post #6

Earlier quoted context omitted.

State of the art MRI machine costs $3 million up front. Would take 20 scans a week, every week, for 10 years to break even on that investment at $300 per scan. Not counting physician & staff time or cost of capital.

For reference, I recently went to an MRI ‘center’ and their business hours are 7:30am to 10pm 7 days a week. So, even charging $500 and booking every 30 minutes, payback on investment is much less than a year.

That sounds so ridiculous compared to Germany, where grocery stores aren’t even open 7 days a week.

Re: One whole-body MRI could replace multiple cancer scans

#89

Post by MegaButts » Mon, May 20, 2019, 7:40 PM UTC

arkades wrote: post #76

MegaButts wrote: post #57

Earlier quoted context omitted.

But doesn't this approach make it nigh impossible to catch people that don't fit the mold? It almost seems like it becomes a tautology, by not capturing the diseases in people you don't think have them, and only looking in people that you do think have them. And the only way to change the mold is for enough people to likely die that you reevaluate the model. I am not a doctor, but I cannot fathom why a doctor would e…

Well, that’s part of why there’s constant research into what risk factors / predictive factors are. These aren’t mutually exclusive activities. “Data” implies something neutral. Nothing about lab tests is neutral. Without contextual information and studies on how to -interpret- a finding, it’s just potentially terrifying noise. And terror usually results in action. Poorly informed action is often harmful. So... we ar…

I understand it is not a black-and-white situation, and that data is obviously not perfect. And I certainly am not advocating that doctors should order a gamut of tests unnecessarily. But if there is any doubt, how likely is the added data to harm more than help? And I firmly believe the doctor should not fight the patient on a test unless there is a strong reason not to (apart from an obvious medical disorder such as Munchausen syndrome it is hard for me to think of a reason).

If the added data is noise, it can easily be ignored. If it's not noise, then you're lucky to have it. And figuring out whether or not it is noise is important, but you can't do that without the data.

But again, I am not a doctor, and how much bandwidth they have and where their priorities lie is not something I intimately understand. However something that has become blindingly obvious to me is that most doctors do not have a firm grasp of statistics, and will advocate for new drugs when the actual test results are borderline statistically insignificant and easily explained away by confounding factors (most obviously the placebo effect). Sadly not all trials are double-blind, something else I do not understand.

Re: One whole-body MRI could replace multiple cancer scans

#90

Post by ChrisLomont » Mon, May 20, 2019, 7:41 PM UTC

lostlogin wrote: post #44

ChrisLomont wrote: post #25

Earlier quoted context omitted.

Because scans are not booked wall to wall every hour of every day. Needs more likely follow a poisson distribution with ample waits in between uses. To try and pack it that densely, with the large variation in how people show up at the hospital, would cause bottlenecks and loss of service. 20 a week is a more common number for most places. Here's actual data [1] measured on site. The usage is indeed around 50%, so th…

A lot has changed since 2011 but even back then the MR scanner should always have been full and the next patient should have been waiting outside. If a scanner is very early or late you call the next patients and alter scheduling. Anything else is a waste of time and money.

There's a reason we design roads, electric grids, food supply, and so on, to not perfectly match needs. It's impossible and foolish to assume constant rates of needs.

For the same reason, no hospital would assume MRI scanners are 100% in use all the time. You cannot schedule people needs that perfectly without fail, on holidays, summer versus winter, day and night, weekends versus Mondays, and so on.