Nasopharyngeal carcinoma (NPC) is a tumor arising from the epithelial cells that cover the surface and line the nasopharynx. The concern about NPC in our studies is that it is more common in regions in East Asia and Africa, specifically Southeast Asia. Due to the high tendency for NPC to develop into metastatic dissemination, about 30- 60% of locally advanced patients will develop distant metastasis and die of disseminated disease. Thus this implies that apart from early diagnosis, it is also of paramount importance to locally monitor for the recurrence of NPC or the development of distant metastasis. Therefore, there is a need for a patient-operated, in-vivo surveillance system.
The approach for this project is that it has to be a remote surveillance system that is able to monitor the growth of the tumor in the nasopharyngeal region independently by the patient. The design requirements are as follows below:
1. The device must be made of medically approved materials that are mechanically strong enough to withstand 1 to 2 years of constant use. This is because the average time period for NPC surveillance spans to around 2 years.
2. The device must be durable so as to last the entire time period of use.
3. The device must house a camera module, which is rotatable to the minimum of 90 degrees, such that it can accurately pan throughout the entire nasopharynx region.
Additional aims were also realized in the device design as follows:
1. The device must be made in an economically feasible manner, such that it is able to reduce medical costs as much as possible.
2. The device outcome must be similar to any other method of NPC surveillance so that the quality of the monitoring system is not compromised.
3. The device must be patient-administered, meaning that the patient is able to deploy and use the device without the assistance of medical personnel. This is so as to decrease patient dependence on the healthcare system and also an attempt to decrease the burden on clinicians.
4. The device must be as safe and hassle-free to the patient as possible.
Results and Remarks
The first prototypical device comprises of the following components:
1. Camera Module
2. Arm Head and Hook
4. Wheel and Cover
The camera module houses a mini-camera, which will be able to obtain imaging output from within the nasopharyngeal region after its deployment into the nasal cavity. This housing contains two axles on either side, to enable the rotational mechanism. The camera module is then attached to the arm head, which clicks the axle of the camera into place.
The arm head also contains a hook, whose purpose is to ensure the stability of the device once deployed to the site of the vomer bone. The hook will allow the easy positioning of the camera module to the site and also increase the stability of the device during image capture. This decreases the possibilities of blurred imaging outputs.
The rotational mechanism is mainly powered by three components: (i) the camera module and axle, (ii) the arm, and (iii) the wheel. A thin piece of nylon wire is first threaded through the camera module, then threaded down the tunnels in the arm and finally around the wheel. The rotation mechanism works when the wheel is turned in either direction.
The results of the design verification experiments show that the maximum force required to fracture the Veroclear tip and head are 5.1N and 15.6N respectively. The maximum tensile strength of nylon is 262.4 MPa. The arm can bend to a maximum of 7.3 cm with a force of 15.3N before fracture. FEA shows that even under an exaggerated maximum loading of 100N, the device does not fracture.
The device is able to capture images from within the nasopharyngeal region from the mini camera. This was done by inserting the device through the nasal passageway of a phantom skull and the tumor is shown by the piece of BluTack.
The forces obtained for fracture and/or bending of the Veroclear arm are well beyond the acceptable range of forces as set by the acceptance criteria. This shows that the Veroclear arm passes the first stage of verification testing to determine is safety and suitability in this design. However, to add further to the safety of the device, it is aimed that the final device will be made of a much more mechanically strong material, which is also medically approved: 316L Stainless Steel. From the extrapolated calculations and research of 316L Stainless Steel through FEA, it can be concluded that 316L Stainless Steel is also a good, if not better choice of material for the manufacturing of this device due to its excellent mechanical strength and durability.
Video to be uploaded
Undergraduate Students: Neerajha Ram, Khor Jing An, Paul Ng, Ong Jun Shu, Anselina Goh
Advisor: Dr. Hongliang Ren
Awarded the MOST ELEGANT DESIGN INSTRUMENTATION AWARD at the BN3101 Presentations 2013.