MPRI and IUCF cyclotron tour

Midwest Proton Radiotherapy Institute (MPRI) is the radiation treatment facility that consumes protons generated by Indiana University Cyclotron Facility (IUCF) for the treatment of cancer.
About once per month, they provide free tours to the public of both facilities. Since there are relatively few proton treatment centers operating in the United States, (currently 7 I think), and we're stuck here for a few months, I was interested to go behind the scenes and get a better understanding of how the facility works. This past Saturday, my father-in-law and I were able to attend one of these tours.

This is the clinic side of MPRI. Each treatment morning we come in and meet with a pediatric nurse, radiation oncologist, anesthesiologist, and several technicians.

The gantry rooms are behind a winding hallway, designed to keep stray neutrons from escaping and exposing the staff to excess radiation. There are several cameras on the wall and control stations behind leaded-glass, like you find in a normal x-ray facility or dentist office.

This is one of the 2 gantry rooms. The treatment table is mounted on a robotic arm like what is used in the automotive industry and can move every which way. The 2 little squares on the white wall are retractable x-ray units used to validate positioning prior to each treatment. Everything is computer controlled so that the exact same position is replicated each day, for 31 days.

This is the business end of the proton beam. It's designed to rotate 360 degrees around the patient. During the tour, one of the physicists described how they take into account the distance between it and the patient, because as the protons pass through air, they slow down a bit. They are able to calculate the point at which radiation stops within the body to a tolerance of about 1 millimeter.

This cube of water is called a shadowbox and is used for calibration of the proton beam. The ability to treat to the depth of each tumor (and not beyond) is unique to proton radiation. This is one way they can measure how far the proton's will go, by measuring how far they pass through water. Inside the box, technicians move sensors around which detect the protons. Once everything lines up the way they expect, they can use these measurements to extrapolate how far the beam would pass through different types of body tissue.

This is one of many neutron detectors in each room. In a brief discussion with the director of operations, he was saying that proton's are easily controlled (because of their positive charge) by magnets. However, it's the neutron's (neutral charge) they worry about. He described them as like the leaves blowing around your yard, and the shape of the treatment rooms were designed specifically to keep them from exiting into the hallways.

This device helps shape the proton beam to the precise outline of each tumor. The top part is made of brass, and shapes the X and Y axis (left-right, top-bottom). Below the brass piece is a custom shape of acrylic, which slows down the protons at a faster rate than air. This shapes the Z axis (front-back) or depth of the proton beam. Each one is custom designed for each patient.

This is the machine shop where each device is made. They use brass for shaping the beam and acrylic for the depth. Anything associated directly to a patients treatment is called Tier 1 Material.

This is the control room for the cyclotron, which is manned 24/7 with an operator. MPRI typically treats patients from 7am to about 7pm (sometimes later into the evening), but the beam is usually on all the time, and various maintannce and calibration activities happen when patients are not being treated. Above the control panel are varous space mission badges that IUCF assisted with. Typically, anything electronic that goes into outer-space gets radiated first, to determine how it would work outside the earths' atmosphere.

IUCF writes all their own software, and even had an electric bill tally. They had spent $83,000 so far this month.

This is a close up of their control panel; was funny to see it running on Redhat:)

This is one of 2 cyclotrons at the facility. This one is the main cyclotron unit. They take hydrogen gas, excite it with microwaves to split off the positive protons and send them inside the first one. Once inside, they keep alternating the magnetic field which accelerates the protons to about 2/3rds the speed of light.

Once protons accelerate faster and faster, they spin out in ever widening arcs. At 102 inches in diameter, the protons can exit the cyclotron into the beam pipe.

This is the path the proton beam travels to each patent's treatment room. Every few feet there are vacuum pumps and magnets. The pumps continually remove all air from the beam pipe and the magnets continually refocus the proton beam into a pencil size shape. At each treatment room, there's a final "kicker" magnet that can redirect the positively charged proton beam into the treatment room. Treatments only last 30-60 seconds for each dose, after which the "kicker" beam redirects proton's back into the pipe.