Surgical Management of Facial Trauma, An Issue of Otolaryngologic Clinics (eBook)

Kofi Derek O. Boahene, Anthony E. Brissett (Autoren)

eBook Download: EPUB

2013 | 1. Auflage
220 Seiten
Elsevier Health Sciences (Verlag)
978-0-323-22732-2 (ISBN)

Infos

Techniques on facial reconstruction are presented with videos demonstrating many of the procedures. Topics include: 3D imaging and modeling for treatment planning in facial trauma; Intraoperative Use of CT Imaging; Contemporary management of traumatic fractures of the frontal sinus; Surgical treatment of traumatic injuries of the cranial base; Surgical management of complex mid facial fractures; Current management of condylar and subcondylar fractures; Management of Pediatric mandible fractures; Management of dental injuries associated with maxillomandibular trauma; Injuries of the eye and periorbital structures; Managing the facial nerve after trauma; Reconstruction of the avulsed auricle after trauma; Secondary repair of acquired enophthalmos; Secondary management of telecanthus; Improving post traumatic facial scars; Potential application of Face transplantation in massive traumatic tissue loss; Potential application of autologous free tissue transfer in massive traumatic tissue loss. Guest Editors leading this publication are Kofi Boahene of Johns Hopkins, whose practice and teaching encompasses corrective surgery for congenital facial defects, cleft lip and palate repair, craniofacial surgery, minimally invasive and endoscopic skull base surgery, microsurgery, reconstruction of cancer patients and extensive post-traumatic deformities, among others and Anthony Brissett of Baylor University, whose research and teaching include craniofacial surgery and wound healing, among other reconstructive and cosmetic surgeries.

Textauszug

Intraoperative Use of CT Imaging

E. Bradley Strong, MD∗ and Travis T. Tollefson, MD, MPH,     Department of Otolaryngology-Head and Neck Surgery, University of California Davis Medical Center, 2521 Stockton Boulevard, Suite 7200, Sacramento, CA 95817, USA

∗Corresponding author. Email: [e-mail]

This article presents an overview of intraoperative computed tomography for maxillofacial reconstructive surgery. It reviews the current literature and offers guidelines and techniques for the use of intraoperative imaging.

Keywords

Computed tomography

Intraoperative imaging

Maxillofacial trauma

Cone beam CT

Fan beam CT

Intraoperative CT

Facial fracture

Key points

• Intraoperative computed tomography likely has a role in complex congenital, traumatic, and/or oncologic facial deformities.

• There is low level support for this hypothesis in the literature.

• Although many surgeons think intraoperative imaging is beneficial in complex cases, high-quality prospective outcomes research will be required to determine the appropriate indications for the use of intraoperative computed tomography.

Introduction

In 1895 Wilhelm Rontgen discovered electron beam radiation and coined the term “x-ray.” In 1903 William Coolidge developed the x-ray tube, which was further refined and is in clinical use today. Plain radiographs are the fundamental tools used for diagnosis and treatment of long bone fractures. Preoperative radiographs are used for diagnosis and treatment. Intraoperative and postoperative radiographs are routinely obtained to assure adequate reduction and appropriate implant positioning.

Before the advent of computed tomography (CT), plain radiographs were also the modality of choice for the diagnosis and treatment planning of maxillofacial injuries. However, intraoperative and postoperative radiographs were not routinely used. Studies evaluating the efficacy of postoperative plain radiographs have not found them to be beneficial,1–4 most likely due to the limited resolution of plain radiographs in determining the accuracy of fracture reduction and implant placement, as well as the potential risk associated with radiation exposure to the vital structures of the head and neck.

The development of CT is credited to Godfrey Hounsfield and Allan Cormack in 1972. The specificity, sensitivity, and resolution of CT in midfacial fractures is significantly greater than plain radiographs5,6 and greater than or equal to that of panorex images for the mandible.7 Since its clinical introduction, CT has revolutionized head and neck diagnostic imaging and has become the gold standard for diagnosis and treatment planning of maxillofacial injuries.

With the increased availability of CT in the 1990s, some surgeons began to use CT for postoperative confirmation of fracture reduction and implant positioning. The more recent addition of portable scanners has brought the question of intraoperative imaging to the forefront. The few studies, which have looked at the efficacy of intraoperative CT scans for maxillofacial trauma, have been supportive of the technique.8–11 However the question of efficacy remains unanswered. Is intraoperative and postoperative CT imaging beneficial for maxillofacial reconstructive surgery? Although currently there are no answers to this question, this article reviews the current literature, discusses the different CT modalities that are available, and presents the authors’ clinical experience with the use of intraoperative CT for maxillofacial trauma and reconstruction.

Technology

X-ray CT can be divided into 2 different modalities, computed axial tomography (CAT) and digital volume tomography (DVT). Computed axial tomography scanners are also called “fan beam” scanners because of the “fan” shape of the x-ray photons that are emitted. These scanners are composed of an x-ray tube, a collimator to shape the beam, and a series of detector arrays opposite to the x-ray tube, all contained within a circular gantry. As the patient passes though the gantry, the x-ray tube moves in a circle around the patient. The x-ray beam is variably absorbed by the tissues, and the density differences are then recorded by a sensor array (Fig. 1). Information is then presented as a series of axial slices: one slice per sensor. Current CT scanners typically obtain between 64 and 256 slices per rotation. DVT scanners are also called “cone beam” scanners because of the “cone” shape of the x-ray photons that are emitted. Unlike fan beam scanners, there is no collimator, only a source and a sensor. The sensor is a generally a “flat panel” screen that records the pattern of tissue absorption (Fig. 2). There is no collimator; therefore, the tissue density differences are recorded as a volume of data that can be sliced in any dimension without significant image degradation (Fig. 3). Subsequent descriptions in this article use the terms “fan beam CT” and “cone beam DVT” to reference these 2 different technologies. The term “CT” will be used to describe the general modality of x-ray CT.

Fig. 1 The components of a fan beam CT scanner.

Fig. 2 The components of a cone beam DVT scanner.

Fig. 3 Three-dimensional reconstruction of a mandible from a cone beam DVT scanner (A). Note that the data are recorded as a 3-dimensional volume, but can be sliced in any plane to obtain 2-dimensional structural representations (B).

Radiation Dose

The effective radiation doses associated with traditional fan beam CT scans of the maxillofacial region are low, ranging from 600 to 800 microsieverts. Some comparative numbers include background radiation, 8 microsieverts (24 h); lateral cephalogram, 6 microsieverts; dental series, 171 microsieverts. However, recent studies have brought into question the long-term risk of radiation exposure related to CT scans.12,13 Although cone beam DVT generates less patient dosage (40–80 microseiverts) than fan beam CT,14 a comparison between the 2 techniques raises some complex issues. First, there is no universally accepted common dose metric to compare the 2 techniques. Also, direct comparison of the modalities is complicated by the lack of equivalent image quality (particularly soft tissue resolution).15 Finally, because cone beam DVT systems usually operate with an automated exposure system, control of patient dosage can be more difficult than with fan beam CT.16

Contrast Resolution/Image Quality

The image quality and contrast resolution of traditional fan beam CT is superior to cone beam DVT because the cone beam DVT does not have a collimator (resulting in greater x-ray scatter) and the characteristic of the flat panel detector.17 However, cone beam DVT provides near equivalent bony resolution (Fig. 4).

Fig. 4 (A) An axial slice of a head CT taken from a fan beam CT scanner. Note the soft tissues of the brain and orbit are demarcated. (B) An axial slice of a head CT taken from a cone beam DVT scanner. Note that the soft tissues of the brain and orbit are poorly defined. However bone resolution is similar.

Configuration and Portability

Fan beam CT scanners have a circular “closed gantry” structure, which the patient passes through. There are stationary, in hospital scanners, and portable configurations (Fig. 5). Cone beam DVT scanners vary in configuration, but typically have an open gantry format that looks very similar to a c-arm (Fig. 6). There are also hybrid configurations that are open to position the patient and closed to scan (Fig. 7). Stationary cone beam DVT scanners exist (ex. interventional angiography), but they are beyond the scope of this article.

Fig. 5 Portable fan beam CT scanner.

Fig. 6 Physical configuration of an open gantry fan beam DVT scanner with a flat panel sensor. (Courtesy of Ziehm Imaging, Inc, Nuremberg, Germany; with permission.)

Fig. 7 Physical configuration of a “hybrid”-type fan beam CT scanner. The gantry is open to position the patient and closed to scan (inset). Note the c-arm drape (central image) that is passed over the patient and bed to maintain patient sterility.

Field of View

Fan beam CT scanners typically obtain data as the patient moves through the gantry on a motorized bed, allowing an essentially “unlimited” field of view...

Produkt-Details

• Erscheint lt. Verlag: 1.12.2013
• Sprache: englisch
• Themenwelt: Medizin / Pharmazie ► Medizinische Fachgebiete ► Chirurgie
• Themenwelt: Medizin / Pharmazie ► Medizinische Fachgebiete ► HNO-Heilkunde
• Themenwelt: Medizinische Fachgebiete ► Innere Medizin ► Pneumologie
• ISBN-10: 0-323-22732-5 / 0323227325
• ISBN-13: 978-0-323-22732-2 / 9780323227322