C OMPUTED T OMOGRAPHY II – RAD 473 Prepared By: Ala’a Ali Tayem Abed

SINUSES CT SCAN

Screening Sinus CT  CT of the sinuses primarily is used to: 1. Detect the presence of inflammatory diseases. 2. Plan for surgery by defining anatomy or giving further information about tumors of the nasal cavity and sinuses. 3. Evaluate sinuses that are filled with fluid or thickened sinus membranes. 4. Help diagnose sinusitis.  Scout image: Patient is placed supine. The alignment of the scan is perpendicular to the hard palate. The scan is set up to start posterior to the sphenoid sinus and continued anteriorly through the frontal sinuses and anterior face.  Contrast: 100cc Omnipaque 300 IV, R/O sinus or nasal cavity tumor  kVp / Effective mAs / Rotation time (sec) 120 / 130 / 0.75  FOV : 180 mm.  Thickness : 3 mm.  Resolution : high.  Bone Window: WC : 200, WW : 2000  Soft Tissue Window: WC : 50, WW : 350  Submit images in bone and soft tissue algorithm, ALL 3 PLANES at 2mm x 2mm.

Sagittal reconstructions (through all sinuses) Coronal reconstructions (back of sphenoid sinus through nose) Scan Coverage: Maxillary teeth through frontal sinuses Ethmoid Sinus Sphenoid Sinus Maxillary Sinus

CT axial view shows a well-defined expansile lesion (black arrow) with sclerotic margin ( red arrow), scattered amorphous calcification and teeth within the lesion (yellow arrow). CT coronal view shows an expansile lesion in the right maxilla exhibiting features of calcification, presence of teeth displaced due to the lesion (black arrow) and involving the floor of the maxillary sinus. A computed tomography sagittal view of a front sinus active ossifying fibroma.

Axial image with arrow pointing to air-fluid level in maxillary sinus in acute sinusitis. Note the slightly bubbly appearing fluid. Axial image demonstrating additional case of acute sinusitis with arrows pointing to air-fluid levels in the Ethmoid and sphenoid sinuses Coronal image with arrow pointing to right maxillary sinus mucus retention cyst (MRC). Coronal image with arrow pointing to maxillary sinus polyp. Often on imaging a polyp and mucus retention cyst cannot be differentiated

TEMPORAL BONE CT SCAN

Temporal Bone CT  Temporal bone CTs, also known as mastoid bone CTs are typically ordered to evaluate the outer ear, bones of the ear and inner ear structures for infection, tumor, injury or congenital or acquired hearing disorders.  Axial scout image: The patient is placed supine. The alignment of the plane is parallel to the Orbitomeatal line. This is set up to start at the top of the anterior arch of C1, and scan superiorly to the roof of the mastoid air cells.  Coronal scout image: The patient is placed prone with the neck hyperextended. The alignment of the plane is perpendicular to the Orbitomeatal line. This is set up to start at the posterior edge of the mastoid air cells and go anteriorly to the mid-portion of the TMJ.  kVp / Effective mAs / Rotation time (sec): 120 / 160 / 1.0  FOV : 100 mm.  Res: Ultra high bone algorithm.  Thickness : 1 mm.  Bone Window: WC: 400, WW: 4000  Soft Tissue Window: WC: 50, WW: 350  Submit images in bone and soft tissue algorithm.

Scan Coverage: Above Petrous ridges to tip of mastoids Mandibular condyle External auditory canals Mastoid air cells Clivus Ossicles

Temporal Bone Fracture

The eardrum is thickened. A small amount of soft tissue (arrow) is visible between the scutum and the ossicular chain but no erosion is present. This favors the diagnosis of chronic otitis media.

Cochlear Implantation

Temporal Bone Tumor

CT scan of the head demonstrating a large hyperdense mass in the right CP angle, solid arrow, (Schwannoma). Right acoustic neuroma (schwannoma).

FACIAL BONE CT SCAN

Facial Bones CT (also use for mandible protocol)  A CT of the Facial Bones is an exam that takes very thin slice (2-3.5mm) images of the facial bone structure, including the jaw, nose, eye sockets and cheek bones. These images are helpful in the diagnosis of facial trauma and malformations.  Axial scout image: Patient is placed supine. The scan is set up to start below the mandible and continue superiorly through the frontal sinuses. The alignment is with the plane of a line from the center of the orbit though the external auditory canal, called the Orbitomeatal line.  Coronal scout image: Patient is placed prone, with the neck hyperextended. The scan is set up to start posterior to the sphenoid sinus and continued anteriorly through the frontal sinuses and anterior face.  FOV : 180 mm.  Thickness : 3 mm.  Resolution : high.  Bone Window: WC : 200, WW : 2000  Soft Tissue Window: WC : 50, WW : 350  Submit images in bone and soft tissue algorithm.

Coronal reconstructions external auditory canals through nasal bones Sagittal reconstructions through Zygomatic arches Scan Coverage: Maxillary teeth through frontal sinuses; If mandibular trauma, begin below mandible

Nasal Bone Fracture

three-dimensional (3-D) model made from a CT scan showing a broken (fractured) cheekbone that extends into the gum of the mouth. 3-dimensional reconstruction of the fracture under the eye- socket on the left side of the image.

ORBIT CT SCAN

Orbit CT  A CT of the Orbits is an exam that takes very thin slice images of the eyes and orbital socket at three different angles. This allows for the diagnosis of a range of conditions such as injury, disease and congenital defects.  Axial scout image: Patient is placed supine. The scan is set up to start at the hard palate and continue superiorly through the orbits. The alignment is with the plane of a line from the center of the orbit though the external auditory canal, called the Orbitomeatal line.  Coronal scout image: Patient is placed prone, with the neck hyperextended. The scan is set up to start posterior to the sphenoid sinus and continued anteriorly through the frontal sinuses and anterior face. If a contrasted study is required, Common Histories: Cannot have MR;R/O infection/abscess; assess orbital tumor; R/O lacrimal gland pathology; optic atrophy…. 60 cc of contrast is given prior to the coronal scans, and the other 60 cc is given prior to the axial scan.  kVp / Effective mAs / Rotation time (sec) 120 / 170 / 0.75  FOV : 180 mm.  Thickness : 3mm.  Resolution : high.  Bone Window: WC : 200, WW : 2000  Soft Tissue Window: WC : 50, WW : 350  Submit images in bone and soft tissue algorithm.

Scan Coverage: Mid maxillary sinus to frontal sinuses. Coronal reconstructions Sagittal reconstructions

Orbit CT – Soft Tissue Window (Axial Plane)

Orbit CT – Bone Window (Axial and Coronal Plane)

Orbit CT – Soft Tissue Window (Coronal Plane)

Orbit CT – Bone Window (Sagittal Plane) Orbit CT – Soft Tissue Window (Sagittal Plane)

ORBIT CT (with contrast)

Right orbital blow-out fracture on CT-scan; coronal reformat Axial CT scan of a patient with thyroid eye disease. Several of the elements of this disease are evident on this image: 1) exophthalmos or protrusion of the eye ball from the orbit, and 2) enlargement of the extraocular muscles, including the medial rectus (mr). Also seen are some less common variations of sinus anatomy. Specifically, a posterior Ethmoid cell (EC) has extended into the sphenoid bone to pneumatize the area around the optic nerve.

The axial CT scan (right) shows air in the orbit and a mild proptosis. Orbital swelling and proptosis from vigorous sneezing. Air escaped into the orbit through a "reverse" medial blow-out fracture of the lamina papyracea, resulting in orbital emphysema. Unilateral subconjunctival fat prolapse. Precontrast axial CT scan shows the herniated fat at the superotemporal aspect of the right epibulbar area (arrow). The prolapsed fat is continuous with the intraconal fat and lies between the lateral wall of the eyeball medially and the lateral rectus muscle and the lacrimal gland laterally.

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