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UW-Madison BME 300 - Facilitation of Neck Extension and Flexion During Fluoroscopic Examination of an Obtunded Patient

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Facilitation of Neck Extension and Flexion During Fluoroscopic Examination of an Obtunded Patient Team Members Alison Boumeester Allie Finney Kaitlin Brendel Megan Britson Peter Strohm Advisor Professor Walter Block Department of Biomedical Engineering Clients Victor Haughton, M.D. UW Department of Radiology Joshua Medow, M.D. UW Department of Neurological Surgery October 24th, 20072 Abstract In order to determine if an obtunded patient has suffered damage to the cervical spine, a flexion and extension motion about the neck +/-45 degrees is needed during the fluoroscopy examination. A device is necessary to aid in this movement as currently technicians manually provide the support the patient’s head during the procedure. A previous solution was designed using a linear actuator, but there were several issues. Three new approaches have been developed including two more linear actuator models and a motor and gear design. The motor and gear design is most favored as it meets the most requirements. Future work includes researching gears and dimensions as well as the materials that can be used in the final product. Problem Statement Diagnosing cervical spine injuries can be done using fluoroscopy. Fluoroscopy is a medical imaging method that captures a stream of images of internal body components while they are in motion. In the situation at hand, patients are unconscious, thus unable to communicate injuries or move their head. In order to determine if the patient has suffered damage to the upper spine, a hospital technician must flex and extend the neck +/-45 degrees during the fluoroscopy process. This action increases the chances of injuring the patient as well as exposes the technician to radiation. The goal is to develop a device that can rotate the head in the required movement during fluoroscopic examination. Motivation Victims of car accidents or other injuries are brought into the hospital, and depending on circumstances will be imaged to determine if they have any spinal injuries. This is often the case if the patient is unconscious and unable to provide feedback to the doctor about pain they are experiencing. If less than 72 hours has passed since the injury, an MRI scan can be performed to assess the fluid content3 and diagnose spine health. If this time window passes, a healthy spine can’t be distinguished from an injured spine, making MRI trivial. Fluoroscopic imaging of the neck in motion allows for the radiologist to observe how the vertebrae interact. Detecting abnormalities in movement may indicate injury. Radiologists performing this procedure are exposed to radiation as they manually flex and extend the head during imaging. This also involves a lack of precision and repeatability because flexion and extension won’t occur at the same rate each time. A device is needed that will flex and extend the patient’s neck at a consistent rate that takes into account safety concerns. Background Information Cervical Spine The cervical spine, as seen in Figure 1, is composed of seven vertebrae, from the base of the skull at C1, down to the vertebra prominens at C7. Found in the neck, these vertebrae facilitate movement such as extension and flexion. Most of the rotation occurs at the atlanto- occipital joint between C1 and the skull, although the entire neck has some degree of mobility. The neck contains critical nerves and blood vessels in addition to the spinal cord itself. To protect these vital structures, the vertebrae are secured into position by ligaments. In the event of an accident or other injury, these ligaments can be damaged, endangering the nerves and blood vessels. If the neck is not immobilized and or handled with care, there can be very serious consequences such as severing the spinal cord or damaging other nerve pathways (Eidelson, 2007). Figure 1: Cervical Spine4 Extension and Flexion The cervical spine is capable of extending and flexing in the sagittal plane of the body, see Figure 2. Extension is defined as when the head is brought back away from the chest, increasing the angle between the chest and cervical spine. Flexion is when the head is brought forward toward the chest, decreasing the angle between the cervical spine and chest. To best capture this movement and the vertebral interactions, a lateral view is best. The neck is capable of other types of movement, such as lateral rotation, but they are not of interest with this angle of imaging. Fluoroscopic Imaging A fluoroscopy machine, shown in Figure 3, takes x-ray images at a frequency of 30Hz and displays them as a video on a computer or television monitor. This real-time feedback on the area being imaged gives radiologists the opportunity to observe bone movement and angiography. Each snapshot taken exposes the patient to less radiation than a typical x-ray, but radiation exposure should always be kept to a minimum. Fluoroscopy machines generate x-rays by converting low voltage electricity to very high Figure 2: X-ray of Neck Flexion &Extension Figure 3: Fluoroscopy machine at UW Hospital5 voltage. This creates a beam of electrons that collides with a tungsten target that releases x-ray energy. Next, an x-ray tube concentrates the energy onto the body to be imaged (Roswell Radiology Associates, 2006). Depending on the mass attenuation coefficient of the tissues imaged, the beam is reflected or absorbed, and the machine analyzes this to create an image. These images are quickly processed and displayed on a screen to provide rapid feedback. Previous Work A prototype from last semester was capable of the full range of motion desired, but there were flaws that needed to be addressed. As seen in Figure 4 to the right, it was configured to hang over the end of the imaging table a full two feet, which could interfere with the fluoroscopy unit’s c-arm. The frame and actuator were prone to bending when the headboard was under load, which puts the safety of the patient at risk if structural failure ever occurred. Also, there was no simple way of attaching it to the table or to store it because of its awkward shape. Design Constraints Patient safety is the primary concern for this device. A majority of patients using the device will be comatose and thus will not be able to specify comfort levels. The device should ensure no further injury to the patient. Therefore, the device should move extend and flex the neck smoothly and


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UW-Madison BME 300 - Facilitation of Neck Extension and Flexion During Fluoroscopic Examination of an Obtunded Patient

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