Final Design

Final Design

This project’s motivation is to design an isolated lung chamber to replace the current method of imaging, thus enhancing the quality of images and making the imaging process easier. The chamber replaces the mouse’s body as a lung holder during imaging and grants the researcher access to all surfaces of the lung. When the mouse is ready for imaging, the lung and heart are removed from the mouse and placed into the chamber. The organs may be moved into any orientation that yields the best possible results. The final chamber consists of three main components: the lung reservoir, helper hands and a drainage system.

Final design with annotations showing theoverflow channels, helper hands and lung reservoir

Lung Reservoir

The purpose of the lung reservoir was to help hold the lung in place during imaging. It must be large enough to not to interfere with the microscope objective yet small enough to cradle the lung to help minimize its movement. Since the reservoir holds the lung, a very delicate organ, the shape and material composition of the reservoir must not damage the lung in any way. This was measured by observation; it would be clear if it was being damaged. Avoiding rigid shapes was used in the design process. The primary goal is to protect the lung and to produce the clearest images possible by minimizing the movement of the lung during imaging. The half cylinder dip was not only too big relative to the lung. The acrylic was hard to manufacture and the shape did not resemble the lung. The hemisphere design was the optimal shape because it supports the shape of the lung while keeping it lifted as opposed to sunken into the reservoir. The clamps were no longer necessary since there will not be culture medium in the chamber during imaging. Therefore, the only source of movement will come from the vibration in the tubes as saline solution pumps into the heart. To dampen this vibration, the tubes will be held in place by the helper hands.

Smooth, curved 3D printed reservoir that holds the lung

Helper Hands

The helper hands concept was originally intended to free up a doctor’s hand when working with tiny specimen by statically positioning tools for them. However, the flexibility of the design was found to be useful in tube placement. Tube orientation may be rigidly fixed and vibrations damped, preventing the specimen from moving during imaging. Additionally, there are slots or windows cut out on the sides of the chamber. This allows tools to be placed in a wider range of angles relative to the lung cradle for added adjustability.

Helper hands on the sides of the chamber

Draining Mechanism

Checking drainage seal on prototype (different helper hands)

The purpose of the drainage system is to relieve the lung reservoir of the culture medium that is present in the lung reservoir during microscope preparation. No fluid is to be present in the lung reservoir during imaging and any saline solution that leaks from the lung should be easily drained. The pump drain is problematic because an electrical system will make the device more complicated and expensive, causing budget concerns. Also, since the microscope and chamber will be completely enclosed it would be impossible to know when saline solution has leaked so the pump would have to be on at all times. The screw and spill design is a better option because it is a simpler system that only requires an O-ring seal. Once the seal is released using a special tool, all the fluid will spill into the reservoir. It is also easy to fabricate being made almost entirely of acrylic and 3D printed ABS plastic. The drain system uses gravity as an advantage, rather than having an external system to empty the lung reservoir of the culture medium and saline solution.

Twisting the cradle causes the reservoir to move up and down along a screw

Overflow channels lead to excess fluid reservoir at the bottom of the chamber

Project's Performance

The reservoir provides volume large enough to store all waste solution used during the imaging. The analysis of the reservoir volume versus the total solution volume is shown in the table below:

Individual component calculations

Final results of reservoir analysis

The analysis shows that the total solution volume is less than the reservoir volume, which means the reservoir will hold all solutions used during the imaging without problem. 

The chamber also holds solutions without leakage. During the preliminary testing, the chamber, with sealant applied, showed no sign of leakage. The chamber will be undergoing solution testing as part of the imaging simulation.

The final testing with actual imaging simulation will be conducted with sponsor at University of California Medical School, depending on the availability of the imaging room.