Neck Extender/ Flexor to Facilitate Fluoroscopic ExaminationTeam MembersTasha BenkovichKaitlin BrendelAmy LenzVince MiAdvisorBill Murphy, Ph.D.ClientVictor Haughton, M.D.UW Department of RadiologyMarch 9, 2008AbstractIn order to quantitatively diagnose cervical spinal instability in accident victims, patients are monitored with fluoroscopy as the neck is flexed and extended. To facilitate this fluoroscopic examination, a remotely controlled, motor driven device that mimics the natural motion of flexion and extension in the cervical spine is needed. The device is designed to be used during a fluoroscopy examination in place of manual movement and support given by a technician. Therefore, components of the device must not absorb the lateral x-ray beam used in fluoroscopy. Three designs to fulfill specified requirements are described and categorized by the type of mechanism: motor, gear and worm-box attached to the fluoroscopic table; motor and tracking gear independent of the table; and motor and linear actuator. Currently, the table independent gear tracking system is considered the best solution because it allows the headboard to rotate at the correct axis of the cervical spine. Future work includes selecting from motor and gear suppliers and identifying the optimal carbon fiber or other radiotranslucent materials to be used to construct the final prototype. Problem StatementIdentifying traumatic cervical spinal instability, due to an occult fracture or ligamentous injury of the cervical spine, can be accomplished through a dynamic fluoroscopic examination. The fluoroscopy machine takes a real-time stream of images while the patient’s neck is in motion. The disadvantages of the current fluoroscopic examination include: technicians and other medical staff currently are required to support and rotate the patient’s head manually in extension and flexion thereby exposing them to 2Figure 1: Diagram of the cervical spine, vertebrae C1 through C7radiation, achieving the desired slow, constant movement of the cervical spine at a constant speed is difficult, and positioning the fluoroscopic monitor exactly while moving the neck manually may be difficult. The goal for this semester is to design a device, suitable for manufacture, and capable of rotating the cervical spine at its axis in flexion and extension during this fluoroscopic procedure. MotivationCurrently, practices of imaging comatose patients pose risks to not only the accident victim but also the hospital staff. Radiographs and CT do not detect all spinal fractures. MRI does not detect spinal ligament damage reliably, especially more than 72 hours after injury. Therefore the current examinations do not reliably detect all traumatic causes for spinal instability. Thus, a fluoroscopy examination is needed to observe how the vertebrae respond to movement. A mechanical device is essential to provide steady, controlled, quantitative movement of the cervical spine and also to minimize radiation exposure to staff. Background InformationCervical SpineThe cervical spine is composed of seven vertebrae, from the base of the skull at C1, down to the vertebra prominens of C7. The disks and the facet joint between these vertebrae facilitate movement such as extension and flexion. Most of the 3Figure 2: Extension and flexion of cervical spine (from left to right).rotation in the cervical spine 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).Extension and FlexionThe cervical spine is capable of extending and flexing in the sagittal plane of the body. Extension is defined as the movement of the head away from the chest, increasing the angle between the chest and cervical spine. Flexion is the movement of the head forward toward the chest, decreasing the angle between the cervical spine and chest. In order to best image this movement and the vertebral interactions, the procedure uses a lateral view along the coronal plane. 4Figure 3: Fluoroscopy machine in UW-Hospital where procedure takes placeFluoroscopic ImagingA fluoroscopy machine 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 of the imaged area gives the radiologists the opportunity to observe bone movement and angiography. Each image exposes a 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 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 (Rosewell Radiology Associates, 2006). Depending on the mass attenuation coefficient of the tissues imaged, the beam is reflected or absorbed. X-rays are detected by means of a specialized screen. The output from the screen is used to create an image. The images are quickly processed and displayed on a screen to provide rapid feedback to the staff on any changes in the area being observed.5Figure 4: Prototype created from fall 2007Figure 5: Prototype modeled on SolidworksPrevious WorkPast design groups have attempted to design a neck rotator; however, all of the designs that have been created have faults. In the last semester, a device was created that consisted of an inclined backboard and a rotating headboard. The headboard included a translating head-stabilizer which moved forward and back during rotation of the headboard. The headboard was rotated by a gear and motor system. There was a 4 inch diameter gear that was cut at an angle of 120 degrees and secured to the headboard. This gear was rotated by a smaller spur gear that had a 1 inch diameter. This spur gear was attached to the shaft of the motor, which was powered by a 12 Volt DC battery.In tests of this device , several problems were discovered. The device was difficult
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