Showing posts with label Radiation Treatments. Show all posts
Showing posts with label Radiation Treatments. Show all posts

8.12.2019

Proctitis





Turns out I've had some bleeding and when I met with the Dr last week, he ordered it 

 I have proctitis as a result of the radiation that I had 2 1/2 years ago. It's a damaged section of my bowel. It's not severe. If it gets worse, I may need further treatments 

 Picture from today. I'm home and all is well

On drinking the prep: (Not my picture ... I only drank ⅔)


More: The doctor called it radiation proctopathy

The Doctor




APC

hematochezia

Note to self: MyChart message center 



Posted by Jim Peet at 8/12/2019 09:46:00 PM 0 comments

Labels: , , , ,

12.15.2017

The Strange Case of the Killer Therac-25






Killed By A Machine: The Therac-25


Excerpt:

The Therac-25 went into service in 1983. For several years and thousands of patients there were no problems. On June 3, 1985, a woman was being treated for breast cancer. She had been prescribed 200 Radiation Absorbed Dose (rad) in the form of a 10 MeV electron beam. The patient felt a tremendous heat when the machine powered up. It wasn’t known at the time, but she had been burned by somewhere between 10,000 and 20,000 rad. The patient lived, but lost her left breast and the use of her left arm due to the radiation.

On July 26, a second patient was burned at The Ontario Cancer Foundation in Hamilton, Ontario, Canada. This patient died in November of that year. Autopsy ruled that the death was due to a particularly aggressive cervical cancer. Had she lived however, she would have needed a complete hip replacement to correct the damage caused by the Therac-25.

In December of 1985, a third woman was burned by a Therac-25 installed in Yakima, Washington. She developed a striped burn pattern on her hip which closely matched the beam blocking strips on the Therac-25. This patient lived, but eventually needed skin grafts to close the wounds caused by radiation burns.

On March 21, 1986, a patient in Tyler, Texas was scheduled to receive his 9th Therac-25 treatment. He was prescribed 180 rads to a small tumor on his back. When the machine turned on, he felt heat and pain, which was unexpected as radiation therapy is usually a painless process. The Therac-25 itself also started buzzing in an unusual way. The patient began to get up off the treatment table when he was hit by a second pulse of radiation. This time he did get up and began banging on the door for help. He received a massive overdose. He was hospitalized for radiation sickness, and died 5 months later.

On April 11th, 1986, a second accident occurred in Tyler, Texas. This time the patient was being treated for skin cancer on his ear. The same operator was running the machine as in the March 21st accident. When therapy started, the patient saw a bright light, and heard eggs frying. He said it felt like his face was on fire. The patient died three weeks later due to radiation burns on the right temporal lobe of his brain and brain stem.

The final overdose occurred much later, this time at Yakima Valley hospital in January, 1987. This patient later died due to his injuries.

After each incident, the local hospital physicist would call AECL and the medical regulation bureau in their respective countries. At first AECL denied that the Therac-25 was capable of delivering an overdose of radiation. The machine had so many safeguards in place that it frequently threw error codes and paused treatment, giving less than the prescribed amount of radiation. After the Ontario incident, it was clear that something was wrong. The only way that kind of overdose could be delivered is if the turntable was in the wrong position. If the scanning magnets or X-ray target were not in position, the patient would be hit with a laser-like beam of radiation.

AECL carefully ran test after test and could not reproduce the error. The only possible cause they could come up with was a temporary failure in the three microswitches which determined the turntable’s position. The microswitch circuit was re-designed such that the failure of any one microswitch could be detected by the computer. This modification was quickly added and was in place for the rest of the accidents.

If this story has a hero, it’s [Fritz Hager], the staff physicist at the East Texas Cancer Center in Tyler, Texas. After the second incident at his facility, he was determined to get to the bottom of the problem. In both cases, the Therac-25 displayed a “Malfunction 54” message. The message was not mentioned in the manuals. AECL explained that Malfunction 54 meant that the Therac-25’s computer could not determine if there a underdose OR overdose of radiation.

The same radiotherapy technician had been involved in both incidents, so [Fritz] brought her back into the control room to attempt to recreate the problem. The two “locked the doors” NASA style, working into the night and through the weekend trying to reproduce the problem. With the technician running the machine, the two were able to pinpoint the issue. The VT-100 console used to enter Therac-25 prescriptions allowed cursor movement via cursor up and down keys. If the user selected X-ray mode, the machine would begin setting up the machine for high-powered X-rays. This process took about 8 seconds. If the user switched to Electron mode within those 8 seconds, the turntable would not switch over to the correct position, leaving the turntable in an unknown state.

It’s important to note that all the testing to this date had been performed slowly and carefully, as one would expect. Due to the nature of this bug, that sort of testing would never have identified the culprit. It took someone who was familiar with the machine – who worked with the data entry system every day, before the error was found. [Fritz] practiced, and was eventually able to produce Malfunction-54 himself at will. Even with this smoking gun, it took several phone calls and faxes of detailed instructions before AECL was able to obtain the same behavior on their lab machine. [Frank Borger], staff physicist for a cancer center in Chicago proved that the bug also existed in the Therac-20’s software. By performing [Fritz’s] procedure on his older machine, he received similar error, and a fuse in the machine would blow. The fuse was part of a hardware interlock which had been removed in the Therac-25.

As the investigations and lawsuits progressed, the software for the Therac-25 was placed under scrutiny. The Therac-25’s PDP-11 was programmed completely in assembly language. Not only the application, but the underlying executive, which took the place of an operating system. The computer was tasked with handling real-time control of the machine, both its normal operation and safety systems. Today this sort of job could be handled by a microcontroller or two, with a PC running a GUI front end.

AECL never publicly released the source code, but several experts including [Nancy Leveson] did obtain access for the investigation. What they found was shocking. The software appeared to have been written by a programmer with little experience coding for real-time systems. There were few comments, and no proof that any timing analysis had been performed. According to AECL, a single programmer had written the software based upon the Therac-6 and 20 code. However, this programmer no longer worked for the company, and could not be found.
Comment: Good Wiki article

Posted by Jim Peet at 12/15/2017 05:10:00 PM 0 comments

Labels: ,

11.09.2017

39 Radiation Treatments


Beginning a week from today, the 39 radiation treatments will commence: Weekdays only with 3 holidays off. 

I had the targeting CAT scan today. They molded a custom form for my feet and legs and I have three "dot" tattoos at my hip level that the machine can triangulate on for targeting. 

It all starts next week at Methodist Hospital in Saint Louis Park. Each radiation treatment is just about 15 minutes, but I have travel, checkin, dressing down etc., so I think each day may be about 2 hours. 

Kathee will go with me with the exception of two days a week when she babysits our grandkids. Thanks for your prayers for me. 

If all goes well, blood work in late January will show the cancer to be in remission. 

I hope to keep a normal schedule but the doctor tells me I may be extra tired. 

I am going to try to witness to one person everyday. Today I gave a gospel of John to a receptionist. So perhaps pray that God would enable this opportunity as well. 


Date
Day
Time
16-Nov
Thursday
Completed
17-Nov
Friday
Completed
20-Nov
Monday
Completed
21-Nov
Tuesday
Completed
22-Nov
Wednesdayy
Completed
23-Nov
Thursday
Thanksgiving
24-Nov
Friday
Completed
27-Nov
Monday
Completed
28-Nov
Tuesday
Completed
29-Nov
Wednesdayy
Completed
30-Nov
Thursday
Completed
1-Dec
Friday
Machine Down
4-Dec
Monday
Completed
5-Dec
Tuesday
Completed
6-Dec
Wednesdayy
Completed
7-Dec
Thursday
Completed
8-Dec
Friday
Completed
11-Dec
Monday
Completed
12-Dec
Tuesday
Completed
13-Dec
Wednesdayy
Completed
14-Dec
Thursday
Completed
15-Dec
Friday
Completed
18-Dec
Monday
Completed
19-Dec
Tuesday
Completed
20-Dec
Wednesdayy
Completed
21-Dec
Thursday
Completed
22-Dec
Friday
Completed
25-Dec
Monday
Christmas
26-Dec
Tuesday
Completed
27-Dec
Wednesdayy
Completed
28-Dec
Thursday
Completed
29-Dec
Friday
Completed
1-Jan
Monday
New Years
2-Jan
Tuesday
Completed
3-Jan
Wednesdayy
Completed
4-Jan
Thursday
Completed
5-Jan
Friday
Completed
8-Jan
Monday
Completed
9-Jan
Tuesday
Completed
10-Jan
Wednesdayy
Completed
11-Jan
Thursday
Completed
12-Jan
Friday
Completed
15-Jan
Monday
Completed

The delivery device is a Varian TrueBeam












Update:

Posted by Jim Peet at 11/09/2017 12:19:00 PM 56 comments

Labels: ,

Subscribe to: Comments (Atom)