Temporal Bone (eBook)

The Temporal Bone 2
Title Page 3
Copyright Page 4
Preface 5
Acknowledgments 7
Contents 9
Chapter 1 11
Imaging Technique 11
Imaging Microscopy 11
CT Microscopy 11
MR Microscopy 11
Clinical Imaging 12
Multidetector CT 12
High Field MR 12
Postprocessing 13
References 15
Chapter 2 16
Anatomy 16
Surface Anatomy 16
Skin Surface 16
Bone Surface 16
Bony External Auditory Canal and Tympanic Membrane 18
Middle Ear Space 18
The Auditory Ossicles 20
The Inner Ear 20
Reference 37
Chapter 3 38
Multiplanar Atlas 38
Temporal Bone Imaging: Historical Perspectives 38
The Axial Plane (in the Plane of the Lateral Semicircular Canal) 39
The Coronal Plane (Perpendicular to the Plane of the Lateral Semicircular Canal) 49
Pöschl Plane (Short Axis Plane of the Temporal Bone) 60
Stenvers Plane (Long Axis Plane of the Temporal Bone) 73
References 83
Chapter 4 85
Advanced Imaging Applications 85
References 106
Chapter 5 107
Imaging Microscopy of the Temporal Bone: An Anatomy Tutorial 107
Introduction 107
Temporal Bone Anatomy Tool 107
Virtual Endoscopy Video Player 107
Glossary 109
Index 116

"1 Imaging Technique (p. 1-2)

Imaging Microscopy

The gold standard for studying temporal bone anatomy has been histological sectioning by microtome following chemical fi xation and deossifi cation of the temporal bone specimen. This process introduces signifi cant artifacts visible even at low power magnifi cation. Although imaging microscopy cannot compete with histology at higher powers of magnifi cation (i.e., the cellular level), resolution at the 20–100 mm level is achievable, allowing study of the temporal bone without the aforementioned artifacts induced by fi xation and sectioning.

CT Microscopy

Computed tomography (CT) microscopy has been primarily used in the imaging of small animals in the research laboratory. There are several obvious advantages to imaging microscopy in the study of the temporal bone compared with standard microtomed histological preparations. MicroCT avoids signifi cant tissue destruction and artifacts introduced during the sectioning process such as fractures, soft tissue tears, fl uid, blood or bone dust in the pneumatized spaces, variable section thickness, and wrinkling, which can occur during the mounting process. Specimen preparation was critical to acquiring the best possible imaging dataset.

Despite a careful technique, we encountered small amounts of fl uid and bone dust in the middle ear space. Air–bone interfaces also caused some minor beam-hardening artifact. The temporal bone specimen used in this atlas was harvested from a male cadaver using the block technique, as described by Gulya [1]. The specimen had to be further reduced in size to a maximal diameter of 2.5 cm and to 4 cm in length in order to fi t properly in the microCT scanner.

The specimen was scanned without decalcifi cation or additional fi xation. The microCT scanning technique used to produce the images in this atlas has been previously described in the literature [2]. MicroCT scanning differs from clinical scanning in that the object is rotated between the tube and camera, which are stationary. The specimen is placed on a rotating stage, which turns 360° about its vertical axis in 0.5° increments. At each angle an X-ray exposure is recorded on the charge-coupled device (CCD) camera.

A single acquisition using a 20-mm slice thickness will cover approximately 2 cm of tissue. Our specimen was scanned in two acquisitions, each taking 8 h at 35 KV and 50 mAs. The two volume acquisitions were then combined using the Analyze 3-D voxel registration program, as described by Hanson et al. and Camp et al. [3, 4]. The fi rst image volume was padded with zerovalued voxels to enlarge the volume enough to contain the entire reassembled volume. The region of overlap between the two acquisitions was used to automatically register the second acquisition to the fi rst. Then, an appropriate “crossover” section was determined, and the whole volume assembled. The entire volume dataset consisted of 20 mm cubic voxels. "