Final Design

      So what will the Patient Setup System look like in the UCSD Health Radiology suite?

The entire system as it sits on the existing Varian treatment table. The carbon fiber tray houses a custom foam and air bladder mattress, and the custom SideLok indexing 

mechanism firmly secures the entire device to the CT and LINAC machine's treatment tables.

The Patient Support System for Adaptive Palliative Radiotherapy and Computerized Tomography is comprised of a foam and pressurized air bladder mattress, which is inserted into a carbon fiber tray for ease of maneuverability and storage. The foam and air bladder mattress is inserted into a urethane mattress cover to maintain waterproofing and anti-microbial properties. This cover can be removed for cleaning purposes. An off-board pressure device and associated plumbing will be attached to inflate the mattress, at which point technicians can reduce the pressure of the bladders if needed, as per patient's desire. Placing the device in the same place each time is critical for repeat-ability of radiation treatments and subsequent CT imaging scans. To meet this requirement, we developed the SideLok, shown in green in the figure above. These will slot into half-moon shaped feature indexes on the treatment tables. Technicians can note their position in each patients chart, and ensure the device is placed securely in the same place each time. 

Expanded System View

The expanded system view shows clearly how all our device's elements will stack onto the existing firm treatment table to provide a comfortable patient  support system. The placement of the gel head donut and the foam knee positioners can be moved and placed by hand with ease by the technician depending on the patient's needs (ankle positioner can be used if needed). A cut-away view of the zipper urethane mattress cover shows how all the foam and air bladder assembly will be inserted inside. All pressurization tubing will be removed from the device when a pressure has been attained.  

How will the device attach to the existing table?

Our device will attach to the existing treatment tables with an in-house developed SideLok mechanism that will slot into halfmoon shaped features on the existing treatment table.

See above and below how the SideLok will interface with the carbon fiber treatment table, by slotting into existing half-moon shaped indices on the Diacor and Varian treatment tables.

See How Our Air Bladders Meet the Challenge of Supporting Intense Pressure Points of Varying Intensity

The patient's weight creates areas of high pressure, which translate to the origins of discomfort when oxygenating blood flow is inhibited (while lying down for treatment). 

Our air bladder panel provides critical support while maintaining radio-translucency, thereby preserving treatment quality and accuracy. A series of welds and one way valves in the pressure plumbing system allow the air bladders to stay inflated in crucial areas such as under the lumbar of the patient. This will stop patients "bottoming out" the device and touching a hard surface while lying down for treatment. Our gel head donut will support other areas of high pressure such as the back of the head.

The air bladder panel shown above, where cross-hatched lines represent welds in the urethane fabric panels. These welds provide compartments to restrict the air's motion, and prevent over inflation and elevation of the air bladder panel. Keeping the profile slim and supportive allows us to meet the difficult geometric constraints of the CT scanner tunnel with our device. 

See above the gel head donut and its traditional use on the surface of a restraint device 

Device Performance

The critical aspects of the design such as achieving patient comfort for a 20 minute radiotherapy session and preserving patient safety were heavily dependent on the foam selection. The foam was qualified by performing a radiation signal attenuation test, and a surface dose test. Having an easily ionizable material close to a patients skin can cause a build up of charge on neighboring electrons. This charge accumulation harbored in a material close to a patient's skin can cause severe burns and a decrease in potency of the treatment at the target site. The foam options were first selected based on their ability to provide comfort, and then all these options were tested at the Dept. of Radiation Medicine at the Moore's Cancer Center at UCSD Health. Below is a graphic detailing the outcome of the device's performance. 

This led us to select two of the foams that were below the dotted red line. The red line indicates the permissible level of increase in surface radiation as defined by the system currently in use. We decided to choose the J_Mem (purple bar) and the J_2" (orange bar) foams as these offered superior supporting qualities but also fell below the ceiling set by the currently used "black support pad." 

We then performed a comfort test with volunteers, who were asked to lie on the device for 20 minutes, and then rate their comfort on a scale of 1 to 5 (where 1 was defined as lying on a flat, hard surface, and 5 was defined as lying on a high quality mattress, such as a tempur-pedic or sleep number). The results of this test are shown below.