Development of a 3D Learning Resource of the Pterygopalatine Fossa Using Cone Beam Computed Tomography For Dental Students By Ryan James Casper A THESIS Submitted to the Faculty of the Graduate School in partial fulfillment of the requirements for the Degree of Master of Science in the Department of Oral Biology Omaha, Nebraska April 25th 2012 Abstract The pterygopalatine fossa is a pyramidal shaped fossa located between the infratemporal fossa and the nasal cavity. The major contents include the maxillary division of the trigeminal nerve, the pterygopalatine ganglion, and branches of the 3rd part of the maxillary artery. The fossa is very difficult for students to visualize in textbooks and the gross laboratory. The increasing use of cone beam computed tomography (CBCT) in dentistry has increased the ability of dental clinicians to visualize anatomical structures in multiple dimensions. The purpose of this study was to develop a 3D learning resource of the pterygopalatine fossa using CBCT for dental students. Anonymized CBCT files were selected from a series of patients with normal anatomy. All of the scans had been performed at 0.3 mm resolution and were reconstructed using Osirix version 3.9.2 in axial, coronal, and sagittal planes. Digital images of a dry skull specimen and cadaveric dissection of the pterygopalatine fossa were collected using a Canon Powershot ELPH 100 HS. Final Cut version 10.0 was used to create a multimedia learning resource. A multimedia learning resource for the pterygopalatine fossa was created using CBCT videos, CBCT images, cadaver photographs, and skull photographs. The CBCT videos and images incorporated axial, sagittal, and coronal planes of the pterygopalatine fossa. Labeled and unlabeled cadaver and dry skull specimen photographs were utilized. Audio was integrated to explain the clinical relevance of the anatomy of the pterygopalatine fossa. This learning resource provides dental students a tool to augment their understanding of the anatomy of the pterygopalatine fossa. iii Acknowledgements I would like to thank my mentor, Dr. Neil Norton. He has offered support and guidance throughout this project, and has also demonstrated what it takes to be an incredible educator. I would also like to thank Dr. Margaret Jergenson. She offered her knowledge to me when needed and spares no effort in educating her students. These two professors have developed in me a deeper respect for academics. I would like to thank the Department of Oral Biology and the School of Dentistry for providing the resources and material needed for me to complete my studies and this project. Lastly, I must thank my wife Natalie. She has an amazing amount of belief in me and that inspires me to want to succeed. Natalie has instilled in me the attitude of never giving up and never giving less than your best. She has incredible amount of passion for life, she is an unbelievable mother to our children, and she is an astonishing wife. I cannot thank her enough. iv Table of Contents I. Introduction 1 A. Overview & Purpose 1 B. Cone Beam Computed Tomography 2 C. Osseous Anatomy 7 D. Pterygopalatine Fossa Borders 8 E. Foramina/Fissures and Communications 10 F. Nervous Supply 16 G. Vasculature 22 H. Computer-Assisted Learning 25 II. Materials and Methods 27 A. CBCT 27 B. Dry Skull Specimens 27 C. Dissection 27 D. Software 28 III. Results and Discussion 29 IV. Conclusions 30 V. Citations 31 List of Figures Figure 1: Pterygopalatine Fossa shown between the infratemporal fossa and the nasal cavity. 1 Figure 2: 3rd generation CT. 2 Figure 3: 4th generation CT for dental use. 2 Figure 4: Shows the z-axis. 3 Figure 5: Cross-sectional CT slice. 3 Figure 6: 3rd generation CT that has detectors and an x-ray tube rotating within the gantry. 4 Figure 7: 4th generation CT that has stationary detectors and an x-ray tube that rotates. 4 v Figure 8: X-ray tube and power supply from which it is receiving voltage to send out the x-ray beam. 5 Figure 9: Compares the shape of the x-ray beam for 3rd and 4th generation CT scanners. 5 Figure 10: Orbital and sphenoidal processes of the perpendicular plate of the palatine bone. 8 Figure 11: Anterior, posterior, and medial borders, of the PPF. 9 Figure 12: Superior aspect of superior border of the PPF 9 Figure 13: Pyramidal process fusing with the pterygoid plates. 9 Figure 14: A cube representing the PPF. 10 Figure 15: CBCT axial image of pterygomaxillary fissure. 11 Figure 16: Dry skull specimen of the lateral opening of the PPF. 11 Figure 17: CBCT sagittal image of the foramen rotundum. 12 Figure 18: CBCT axial image of the foramen rotundum. 12 Figure 19: Disarticulated sphenoid bone labeling the three posterior openings of the PPF. 12 Figure 20: Superior view of a skull identifying the foramen rotundum. 12 Figure 21: CBCT axial image of the pterygoid canal and pharyngeal canal. 13 Figure 22: Inferior view of the skull demonstrating the pterygoid canal. 13 Figure 23: CBCT sagittal image of the palatine canal dividing into the greater and lesser palatine canal. 14 Figure 24: Dissection photo of the palatine canal traveling from the PPF to the palate. 14 Figure 25: CBCT sagittal image of the superior communication of the PPF. 15 Figure 26: Dry skull specimen of the inferior orbital fissure. 15 vi Figure 27: Medial aspect of a skull, illustrating the sphenopalatine foramen. 16 Figure 28: Represents a lateral view of the sphenopalatine foramen on a skull. 16 Figure 29: CBCT axial image of the sphenopalatine foramen. 16 Figure 30: CBCT image of the PPF communicating with the nasal cavity. 16 Figure 31: Maxillary division of the trigeminal nerve and 3rd part of the maxillry artery. 17 Figure 32: Trigeminal ganglion in the middle cranial fossa. 18 Figure 33: Medial view demonstrating the pterygopalatine ganglion. 19 Figure 34: Nasopalatine nerve traveling anteroinferiorly over the nasal septum. 21 Figure 35: Maxillary artery traveling through the infratemporal foss. 23 Figure 36: Illustration of the sphenopalatine artery. 25 vii I. Introduction A. Overview & Purpose The pterygopalatine fossa (PPF) is a pyramidal shaped fossa located between the infratemporal fossa and the nasal cavity (Figure 1). The major contents include the maxillary division of the trigeminal nerve, the pterygopalatine ganglion, and branches of the 3rd part of the maxillary artery. Within this space there are also seven different foramina/fissures that allow passage for these nerves and arteries to communicate with surrounding areas. Studying this space can be difficult, especially when using a skull to attempt to visualize where this space is located and the passage of the nerves and vessels. The purpose of this study was to create a multimedia resource using a combination of cone beam computed tomography (CBCT), cadaver pictures, and dry skull specimen pictures to aid in the study of the pterygopalatine fossa for dental students. Figure 1: Pterygopalatine Fossa shown between the infratemporal fossa and the nasal cavity. 1 B. Cone Beam Computed Tomography Computed Tomography (CT) scanning was first developed in 1967 and has continued to advance with the continued development of newer sensors and computers (Sukovic, 2003). There are two main types of CT that are used, fan beam CT (Figure 2), and CBCT (Figure 3) (MacDonald, 1995). Figure 2: Fan beam CT for medical use. Figure 3: CBCT for dental use. CT scanning provides 3-D imaging that is generated by gathering slices of images that are collected from rows of detectors. These images are stacked on each other to construct a 3-D outcome (Dawood, 2009). A single CT slice will show the portion of the anatomy at the level of the slice, which represents a plane within the body. The thickness of the plane is the z-axis (Figure 4). The thickness of a slice can be varied and once it is set, it limits the x-ray beam to scan the selected volume only. CT slices are further sectioned into an x-axis and a y-axis, making a two dimensional square, known as a pixel. When the z-axis is taken into consideration, a cube is made, and this is known as a voxel (Figure 5). Each individual pixel will be used to generate a 3-D image (Romans, 1995). 2 Figure 4: Illustration of the z-axis, which is Figure 5: Represents a cross-sectional CT the thickness of a CT slice (Romans, L. E. slice that may be stacked to create a 3-D (1995). Introduction to computed image (Romans, L. E. (1995). Introduction tomography. Baltimore: Williams & to computed tomography. Baltimore: Wilkins. Used with the permission of Williams & Wilkins. Used with the publisher.) permission of publisher.) To produce an image, a generator and gantry are required. A generator simply produces voltage that is transmitted to the x-ray tube (Figure 8). The gantry is the part of the CT system that holds the x-ray tube, which will move in a circular path within the gantry. The x-ray tube will emit x-ray energy, which will pass through the body and will be recorded by detectors. An x-ray beam releases protons that are absorbed by the detector. When the protons are absorbed, the detector generates light, which is converted into electric current that presents data to produce an image (Romans, 1995). Figure 6 illustrates a fan beam CT that has detectors and an x-ray tube rotating within the gantry. Whereas figure 7 shows a CBCT that has stationary detectors placed around the entire gantry and an x-ray tube that rotates. The problem with fan beam CT is that there is a high x-ray dose required, the machines are large, generally expensive, and they are typically found only in a hospital setting (Dawood, 2009).