Skull and Facial Anatomy PDF

1 Skull Anatomy: A review Composed of 22 separate bones divided into 2 groups Cranial bones- 8 Facial bones – 14 Cranial bones further subdivided into Skull Anatomy: A review Calvaria Floor...

1 Skull Anatomy: A review Composed of 22 separate bones divided into 2 groups Cranial bones- 8 Facial bones – 14 Cranial bones further subdivided into Skull Anatomy: A review Calvaria Floor Lateral aspect of skull Anterior aspect of the skull  2 Facial bones Anatomy: A review Anterior aspect of facial bones Lateral aspect of facial bones  3 Lateral aspect of Mandible Anterior aspect of Mandible  4 Orbits Each is composed of seven bones: Frontal Sphenoid Ethmoid Maxilla Zygoma Lacrimal Palatine  5 Paranasal Sinuses Anatomy: A review  6 Skull topography (Landmarks) Be able to locate the following landmarks: Glabella Inner canthus Outer canthus Nasion Infraorbital margin Acanthion Gonion Mental point EAM Auricular point Top of ear attachment (TEA)  7 A. Glabella B. Nasion C. Infraorbital line D. Alar E. Acanthion F. Angle of the mouth G. Mental point H. Angle mandible I. External acoustic meatus J. Outer canthus eye K. Supra orbital margin  8 Radiographic Reference Lines Orbitomeatal line (OML) From outer canthus to EAM Infraorbital line (IOML) From infraorbital margin to EAM Glabellomeatal line (GML) From glabella to EAM Interpupillary line (IPL) Perpendicular line between pupils of eyes Acanthiomeatal line (AML) From acanthion to EAM Mentomeatal line (MML) From meatal point (center of chin) to EAM  9 Facial lines A. Supraorbital margin B. Interpupillary line C. Infraorbital margin D. Median sagittal plane E. Orbitomeatal baseline (OMBL)  10 General body position Patient may be examined in recumbent (table) or upright positions.  11 General body position is especially important in asthenic, hyposthenic and hypersthenic body types. Hyposthenic/asthenic patients usually need support at chest to elevate cervical spine (C-spine). Helps prevent downward tilt of MSP. Hypersthenic patients require radiolucent support at head. Helps prevent upward tilt of MSP.  12 Hyposthenic/Asthenic Hypersthenic patients Orbito- Meatal line (OML) patients Outer canthus of the eye to tragus of the ear 13  14 Essential projections: Cranium PA or PA axial (Caldwell method) PA axial (Haas method) AP axial AP axial (Towne method) Lateral Right and left lateral positions Dorsal decubitus position Submento vertical (SMV) For cranial base Anteroposterior (AP) Posteroanterior (PA)  15 PA or PA axial (Caldwell method) Pathology demonstrated: Fracture, tumor, metastasis, Paget disease IR 10 X 12 inch( 24X30 cm) Grids For digital IR use lead masking 70-80 kV range  16 Patient positioning Patient seated erect or prone Center the midsagittal plane of the body to the midline of the grid device Part position Forehead and nose resting on table or upright Bucky OML perpendicular to IR plane MSP perpendicular to IR CR 15 degree caudal degree to film center 90 degree to film center for PA projection Exits at the Nasion Collimate – Adjust to 10X12 Inches (24X30 cm) Lead shields  17 Evaluation criteria ID: date: side marker all clearly visible. Evidence of proper collimation. Entire cranium without rotation or tilt, demonstrated by: - Equal distances from lateral borders of skull to lateral borders of orbits on both sides - Symmetric petrous ridges MSP of cranium aligned with long axis of collimated field. PA projection shows orbits filled by petrous ridges. PA axial (Caldwell) demonstrates petrous pyramids lying in the lower third of the orbit. Entire cranial perimeter showing three distinct tables of squamous bone. Penetration of frontal bone with appropriate brightness at lateral borders of skull.  18 PA axial (Haas method) Pathology demonstrated: Fracture, tumor, metastasis, Paget disease IR 10 X 12 inch( 24X30 cm) Grids For digital IR use lead masking 70-80 kV range  19 Patient positioning Posture Prone or seated upright MSP centered to midline Shoulders in same horizontal plane Part position Forehead and nose on table MSP perpendicular OML perpendicular to IR CR Directed cephalad at 25-degree angle to OML Enters at a point 1½ inches (3.8 cm) below external occipital protuberance Exits 1½ inches (3.8 cm) superior to the Nasion Collimate – Adjust to 10X12 Inches(24X30 cm) Lead shields  20 Evaluation criteria ID: date: side marker all clearly visible Evidence of proper collimation Entire cranium, without rotation or tilt, evidenced by: Equal distances from lateral borders of skull to lateral margins of foramen magnum on both sides Symmetric petrous pyramids MSP of cranium aligned with long axis of collimated field Dorsum sellae and posterior clinoid processes visible within foramen magnum Penetration of occipital bone with appropriate brightness at lateral borders of skull  21 AP or AP axial projection Note: Provides similar but magnified image when patient cannot be positioned for PA or PA axial projection.  22 Patient positioning Patient and part position Supine MSP centered to midline MSP and OML perpendicular to IR CR Perpendicular for AP 15 degrees cephalad for AP axial projection Both should enter the Nasion Collimated field 10 x 12 inches (24 x 30 cm)  23 Evaluation criteria ID: date: side marker all clearly visible Evidence of proper collimation Entire cranium without rotation or tilt, demonstrated by: Equal distances from lateral borders of skull to lateral borders of orbits on both sides Symmetric petrous ridges MSP of cranium aligned with long axis of collimated field ▪ AP projection shows orbits filled by petrous ridges ▪ AP axial demonstrates petrous pyramids lying in lower third of orbit Entire cranial perimeter showing three distinct tables of squamous bone Penetration of frontal bone with appropriate brightness at lateral borders of skull  24 AP axial (Towne method) Pathology demonstrated: Fracture, tumor, metastasis, Paget disease IR 10 X 12 inch( 24X30 cm) Grids For digital IR use lead masking 70-80 kV range  25 Patient positioning Part position Supine or seated erect MSP centered to midline MSP perpendicular OML or IOML perpendicular CR Directed through foramen magnum Caudal 30 degrees with the OML Caudal 37 degrees with the IOML Collimate – Adjust to 10x12 Inches (24x30 cm) Lead shields 26  27 Evaluation criteria ID: date: side marker all clearly visible Evidence of proper collimation Entire cranium, without rotation or tilt, demonstrated by: Equal distances from lateral borders of skull to lateral margins of foramen magnum on both sides Symmetric petrous pyramids MSP of cranium aligned with long axis of collimated field Dorsum sellae and posterior clinoid processes visible within foramen magnum Penetration of occipital bone with appropriate brightness at lateral borders of skull 28  29 Lateral projection Pathology demonstrated: Fracture, tumor, metastasis, Paget disease IR 10 X 12 inch( 24X30 cm) Grids For digital IR use lead masking 70-80 kV range  30 Patient positioning Upright or recumbent anterior oblique CR Horizontal or 90 degree to film center CR Enters 2 inches (5 cm) superior to EAM Part position MSP of head parallel to image receptor (IR) IPL perpendicular IOML parallel to transverse axis of cassette Collimate – Adjust to 10X12 Inches(24X30 cm) Lead shields  31 Evaluation criteria ID: date: side marker all clearly visible Evidence of proper collimation Entire cranium without rotation or tilt, demonstrated by: Superimposed orbital roofs and greater wings of sphenoid Superimposed mastoid regions and EAM Superimposed TMJs Sella turcica in profile Radiographic penetration of parietal region No overlap of cervical spine by mandible  32 Lateral projection (Patient in supine position) Pathology demonstrated: Fracture, tumor, metastasis, Paget disease IR 10 X 12 inch( 24X30 cm) Grid For digital IR use lead masking 70-80 kV range  33 Patient positioning Supine or recumbent posterior oblique position CR Perpendicular to center of IR CR Enters 2 inches (5 cm) superior to EAM Part position Elevate head on radiolucent support to place MSP parallel and IPL perpendicular Turn head toward side of interest Collimate – Adjust to 10X12 Inches(24X30 cm) Lead shields  34 Evaluation criteria ID: date: side marker all clearly visible Evidence of proper collimation Entire cranium without rotation or tilt, demonstrated by: Superimposed orbital roofs and greater wings of sphenoid Superimposed mastoid regions and EAM Superimposed TMJs Sella turcica in profile Radiographic penetration of parietal region No overlap of cervical spine by mandible  35 Lateral decubitus projection Pathology demonstrated: Trauma for Fracture IR 10 X 12 inch( 24X30 cm) Grid For digital IR use lead masking 70-80 KV range  36 Patient positioning Dorsal Decubitus CR Horizontal and perpendicular to center of IR CR Enters 2 inches (5 cm) superior to EAM Part position Elevate head on radiolucent support to center to vertical IR MSP of head vertical IPL perpendicular to IR IOML parallel to transverse axis of cassette Collimate – Adjust to 10X12 Inches(24X30 cm) Lead shields  37 Evaluation criteria ID: date: side marker all clearly visible Evidence of proper collimation Entire cranium without rotation or tilt, demonstrated by: Superimposed orbital roofs and greater wings of sphenoid Superimposed mastoid regions and EAM Superimposed TMJs Sella turcica in profile Radiographic penetration of parietal region No overlap of cervical spine by mandible  38 SMV projection Pathology demonstrated: Fracture, tumor, metastasis, Paget disease IR 10 X 12 inch( 24X30 cm) Grid For digital IR use lead masking 75-90 kV range  39 Patient and part positioning Patient position Seated upright or supine Torso elevated if supine Part position MSP centered to midline IOML parallel with IR MSP perpendicular to IR CR Through sella turcica perpendicular to IOML Enters MSP of throat between angles of mandible Passes through a point ¾ inch (1.9 cm) anterior to level of EAM Center IR to CR ▪ Collimate – Adjust to 10X12 Inches(24X30 cm) ▪ Lead shields  40 Evaluation criteria ID: date: side marker all clearly visible Entire cranium, without tilt, evidenced by: Equal distances from lateral borders of skull to mandibular condyles on both sides Symmetric petrosae IOML is parallel to IR (full neck extension), evidenced by: Mental protuberance superimposed over anterior frontal bone Mandibular condyles anterior to petrosae Brightness and contrast sufficient to demonstrate cranial base anatomy  1 Essential projections of the facial bones: Lateral projection Parietoachanthial- occioitomental (waters) PA/PA axial (Caldwell method) Parietoachanthial (waters)- alternative Lateral projection (Nasal bone) SMV projection (Zygomatic arches) PA- Mandibular Rami (Mandible) Axiolateral and axiolateral oblique- (Mandible) Axiolateral oblique (TMJs)  2 Lateral projection Pathology demonstrated: Fracture, tumor, metastasis IR 10 X 12 inch (24x30 cm) or 8x10 inches (18x24 cm) Grids For digital IR use lead masking 70-80 kV range  3 Patient positioning Upright or recumbent anterior oblique CR: Perpendicular to IR center Enters patient on lateral surface of zygomatic bone halfway between outer canthus and external acoustic meatus (EAM) Part position MSP of head parallel to image receptor (IR) IPL perpendicular to image receptor (IR) IOML perpendicular to front edge of IR Collimate – Adjust to 10 x 12 inch ( 24x30 cm) or 8x10 inches (18x24 cm) Lead shields  4 Evaluation criteria ID: date: side marker all clearly visible Evidence of proper collimation All facial bones in their entirety, with the zygomatic bone in the center No rotation or tilt of the facial bones, evidenced by Almost perfectly superimposed mandibular rami Superimposed orbital roofs Sella turcica in profile Brightness and contrast demonstrates soft tissue and bony trabecular detail  5 Parietoachanthial- occioitomental (waters) Pathology demonstrated: Fracture, tumor, metastasis IR 10 x 12 inch( 24x30 cm) or 8x10 inches (18x24 cm) Grids For digital IR use lead masking 70-80 kV range  6 Patient and part positioning Patient position Prone or seated upright Center MSP to midline of upright Bucky Part position Rest head on tip of extended chin OML to form 37-degree angle with plane of IR Mentomeatal line (MML) perpendicular to IR MSP perpendicular to IR Center IR to level of acanthion Collimate – Adjust to 10 x 12 inch ( 24x30 cm) or 8x10 inches (18x24 cm) Lead shields  7 Evaluation criteria ID: date: side marker all clearly visible. Evidence of proper collimation. Entire orbits and facial bones. Anatomy demonstrated: IOMs, maxillae, nasal septum, zygomatic bones, zygomatic arches, and anterior nasal spine. No rotation or tilt, evidenced by: Distances between the lateral borders of the skull and the orbits equal on each side MSP of head aligned with long axis of collimated field Petrous ridges projected immediately below maxillary sinuses. Brightness and contrast demonstrates soft tissue and bony trabecular detail  8 PA/PA axial (Caldwell method) Pathology demonstrated: Fracture, tumor, metastasis, Paget disease IR 10 X 12 inch ( 24x30 cm) or 8x10 inches (18x24 cm). Grids. ▪ For digital IR use lead masking. ▪ 70-80 kV range.  9 Patient positioning Patient seated erect or prone Center the midsagittal plane of the body to the midline of the grid device Part position Forehead and nose resting on table or upright Bucky OML perpendicular to IR plane MSP perpendicular to IR CR 15 degree caudal to film center 90 degree to film center for PA projection Exits at the Nasion Collimate – Adjust to 10 x 12 inch ( 24x30 cm) Lead shields  10 Evaluation criteria ID: date: side marker all clearly visible. Evidence of proper collimation. Entire cranium without rotation or tilt, demonstrated by: - Equal distances from lateral borders of skull to lateral borders of orbits on both sides - Symmetric petrous ridges MSP of cranium aligned with long axis of collimated field. PA projection shows orbits filled by petrous ridges. PA axial (Caldwell) demonstrates petrous pyramids lying in the lower third of the orbit. Entire cranial perimeter showing three distinct tables of squamous bone. Penetration of frontal bone with appropriate brightness at lateral borders of skull.  11 Parietoachanthial (waters)- alternative Pathology demonstrated: Fracture, tumor, metastasis, Paget disease IR 10 x 12 inch ( 24x30 cm) or 8x10 inches (18x24 cm). Grids. ▪ For digital IR use lead masking. ▪ 70-80 kV range.  12 Patient and part positioning Patient position Supine MSP centered to midline of grid Part position Extend chin and neck to place OML at a 37-degree angle with the plane of the IR. MML almost perpendicular to IR plane. MSP perpendicular to IR plane. CR Perpendicular to IR to enter acanthion. Collimate – Adjust to 10x12 inch ( 24x30 cm)or 8x10 inches (18X24 cm) Lead shields  13 Evaluation criteria ID: date: side marker all clearly visible. Evidence of proper collimation. Entire orbits and facial bones. No rotation or tilt, evidenced by: Distances between lateral borders of the skull and orbits equal on each side. MSP of head aligned with long axis of collimated field. Petrous ridges projected below maxillary sinuses. Brightness and contrast demonstrates soft tissue and bony trabecular detail.  14 Lateral projection – Nasal bone ▪ Pathology demonstrated: Fracture ▪ IR: 8x10 inches (18x24 cm) ▪ No Grids (Out Bucky) ▪ For digital IR use lead masking ▪ 60-65 kV range  15 Patient and part positioning Patient position Upright or recumbent anterior oblique. MSP of head horizontal and parallel to the IR. Part position MSP parallel with tabletop IPL perpendicular to tabletop IOML is parallel with transverse axis of IR CR Perpendicular to bridge of nose Enters at a point ½ inch (1.3 cm) distal to nasion Collimated field 3 x 3 inches (8 x 8 cm) Field should extend from the glabella to the acanthion and ½ inch beyond the tip of the nose Lead shields  16 Evaluation criteria ID: date: side marker all clearly visible. Evidence of proper collimation. Nasofrontal suture Nasal bones, anterior nasal spine and frontonasal suture. Nasal bone No rotation of nasal bones and soft tissue. Brightness and contrast Anterior nasal demonstrates soft tissue and spine of maxilla bony trabecular detail.  17 SMV projection – Zygomatic arches ▪ Pathology demonstrated: Fracture ▪ IR: 10 x 12 inch ( 24x30 cm) ▪ Grids ▪ For digital IR use lead masking ▪ 75-90 kV range  18 Patient and part positioning Patient position Seated upright or supine If supine, elevate thorax Part position Hyperextend neck to place IOML parallel with IR plane Rest head on vertex MSP perpendicular to IR plane CR Perpendicular to IOML CR enters MSP of throat at level 1 inch (2.5 cm) posterior to outer canthi Collimate – Adjust to 10x12 inches (24x30 cm) Lead shields  19 Evaluation criteria ID: date: side marker all clearly visible Evidence of proper collimation Zygomatic arches free from overlying structures No rotation or tilt of head, evidenced by Zygomatic arches symmetric and without foreshortening Brightness and contrast demonstrate soft tissue and bony trabecular detail  20 Essential projections: Mandible PA- Mandibular Rami Axiolateral and axiolateral oblique- mandible Axiolateral oblique TMJs Kindly refer to the link below for a video on positioning: https://www.youtube.com/watch?v=Xx3DJe9DHto  21 PA- Mandibular Rami ▪ Pathology demonstrated: Fracture ▪ IR 8x10 inches (18x24 cm) ▪ Grids ▪ For digital IR use lead masking ▪ 70-80 kV range  22 Patient positioning Patient position Prone or seated upright facing vertical Bucky Part position Rest patients forehead and nose on IR OML perpendicular to the IR plane. MSP perpendicular to IR plane. CR Perpendicular to IR to exit Acanthion Collimate- adjust to 8x10 inches (18x24 cm) Lead shields.  23 Evaluation criteria ID: date: side marker all clearly visible Evidence of proper collimation Entire mandible No rotation or tilt, evidenced by: Mandibular body and rami symmetric on each side MSP of head aligned with long axis of collimated field Brightness and contrast sufficient to demonstrate soft tissues and bony trabecular detail  24 Axiolateral and axiolateral oblique- mandible ▪ Pathology demonstrated: Fracture ▪ IR 8x10 Inches (18x24 cm) ▪ Grids ▪ For digital IR use lead masking ▪ 70-80 kV range  25 Patient and part positioning Position for Ramus Patient position Seated upright in anterior oblique position Semiprone or semisupine Part position Lateral with IPL perpendicular to IR Mouth closed with teeth together Extend neck to place mandibular body parallel with transverse axis of IR Position for Body Adjust rotation of head to place area of interest parallel to IR Ramus = patient’s head in true lateral Body = rotate patient’s head 30 degrees toward IR Symphysis = rotate patient’s head 45 degrees toward IR CR Angled 25 degrees cephalad to pass directly through the mandibular region of interest ▪ Collimate – Adjust to 8X10 Inches(18X24 cm) Position for Symphysis ▪ Lead shields  26 Evaluation criteria ID: date: side marker all clearly visible Evidence of proper collimation Ramus and body No overlap of ramus by opposite side of mandible No elongation or foreshortening of ramus or body No superimposition of ramus by C-spine  27 Axiolateral oblique TMJs ▪ Pathology demonstrated: Fracture, dislocation ▪ IR 8X10 Inches(18X24 cm) ▪ Grids ▪ For digital IR use lead masking ▪ 70-80 kV range  28 Patient and part positioning Patient Position Semiprone or seated upright One exposure made with mouth closed and, if possible, another with mouth open Part Position Center a point (TMJ closer to IR)) ½ inch (1.3 cm) anterior to EAM to IR Rest cheek against grid device Rotate MSP of the patients body 15 degrees toward IR MSP of the head is parallel to IR plane IPL perpendicular to IR plane Acanthiomeatal line (AML) parallel with transverse axis of IR CR Angled 15 degrees caudad Exits through TMJ closer to IR Enters approximately 1½ inch (3.8 cm) superior to and ½ inch (1.3 cm) anterior upside EAM ▪ Collimate – Adjust to 8x10 Inches(18x24 cm) ▪ Lead shields  29 Evaluation criteria ID: date: side marker all clearly visible Evidence of proper collimation TMJ Condyle lying in mandibular fossa in closed-mouth position Condyle lying inferior to articular tubercle in open- mouth position, if normal. Right TMJ Left TMJ  1 Paranasal Sinuses-Essential projections Lateral Posteroanterior (PA) axial (Caldwell method) Parietoacanthial- Occipitomental(OM) (Waters method) Parietoacanthial- Occipitomental(OM) (Waters method) open-mouth modification  2 Technical considerations Density is most critical to demonstrate pathology Upright position necessary to demonstrate fluid levels Central ray (CR) should remain horizontal Shielding must be used on pregnant patients and pediatric patients Proper collimation critical in reducing scatter radiation and patient dose  3 Lateral projection Pathology demonstrated: Sinusitis, polyp, tumor, fracture IR 8x10 inches (18x24 cm) Grids For digital IR use lead masking 70-80 kV range  4 Patient and part positioning Patient position Seated erect in anterior oblique position Part position Midsagittal plane (MSP) of head parallel with IR plane Interpupillary line (IPL) perpendicular to IR plane Infraorbitomeatal line (IOML) perpendicular to front edge of IR CR Horizontal and perpendicular to IR Enters ½ to 1 inch (1.3 to 2.5 cm) posterior to outer canthus ▪ Collimate – Adjust to 8X10 Inches(18X24 cm) ▪ Lead shields  5 Evaluation criteria ID: date: side marker all clearly visible. Evidence of proper collimation; close beam restriction to sinus area. All four sinus groups -- the sphenoidal sinus is best demonstrated. Anteroposterior (AP) and superoinferior (SI) dimensions of the paranasal sinuses. Thickness of the frontal bone. Details of side closer to the image receptor (IR). No rotation or tilt of sinus anatomy, as evidenced by: Sella turcica in profile Superimposed orbital roofs Superimposed mandibular rami Brightness and contrast sufficient to visualize air- fluid levels, if present.  6 PA axial (Caldwell Method) Pathology demonstrated: Sinusitis, polyp, tumor, fracture IR 8x10 inches (18x24 cm) Grids For digital IR use lead masking 70-85 kV range Alternative: OML 15° to CR (if Bucky cannot be tilted)  7 Patient and part positioning Angled Grid Technique Patient position Seated upright facing Bucky MSP centered to midline Part position Tilt vertical Bucky down 15 degrees. Rest patient’s forehead and nose on device Center The Nasion to IR MSP and orbitomeatal line (OML) perpendicular to IR plane CR Horizontal and perpendicular to IR Center CR to exit at the Nasion ▪ Collimate – Adjust to 8x10 inches (18x24 cm) ▪ Lead shields Alternative: OML 15° to CR Kindly refer to video below for the positioning technique: (if Bucky cannot be tilted) https://youtu.be/TlhGr5GsrZg  8 Evaluation criteria ID: date: side marker all clearly visible Evidence of proper collimation Entire orbits and facial bones It demonstrates ✓ Frontal sinus above frontonasal suture ✓ Anterior ethmoid air cells ✓ Sphenoid sinuses seen through nasal fossa below or between ethmoids. ✓ Petrous pyramids in lower third of orbits. No rotation or tilt, evidenced by: Equal distances from lateral borders of skull to lateral borders of orbits on both sides Symmetric petrous ridges lying in lower third of orbit MSP of head aligned with long axis of collimated field Penetration of frontal bone with appropriate brightness at lateral borders of skull, which shows the facial bones  MEDICAL IMAGING DIVISION 9 Parietoacanthial- occipitomental (OM) (waters Method) Pathology demonstrated: Sinusitis, polyp, tumor, fracture IR 8x10 inches (18x24 cm) Grids For digital IR use lead masking 70-80 kV range  MEDICAL IMAGING DIVISION 10 Patient and part positioning Patient position Prone or seated upright Center MSP to midline of upright Bucky Part position Rest head on tip of extended chin Place orbitomeatal line (OML) to form 37-degree angle with plane of IR Mentomeatal line (MML) perpendicular to IR MSP perpendicular to IR Center IR to level of acanthion CR Horizontal and perpendicular to IR Center CR to exit at the Acanthion. Collimate – Adjust to 10 x 12 inch (24x30 cm) or 8x10 inches (18x24 cm) Lead shields  MEDICAL IMAGING DIVISION 11 Evaluation criteria ID: date: side marker all clearly visible Evidence of proper collimation with close beam restriction to the sinus area It demonstrates: Maxillary sinuses Petrous pyramids lying inferior to maxillary floor Frontal and ethmoid sinuses are distorted. OML in proper position (sufficient neck extension), as evidenced by: Petrous pyramids lying immediately inferior to the floor of the maxillary sinuses No rotation or tilt, indicated by: Equal distance between the lateral border of the skull and the lateral border of the orbit on both sides Orbits and maxillary sinuses symmetric on each side MSP of head aligned with long axis of collimated field Brightness and contrast sufficient to visualize air- fluid levels, if present  MEDICAL IMAGING DIVISION 12 Parietoacanthial-Occipitomental (OM) Projection (Open-Mouth Waters Method) Pathology demonstrated: Sinusitis, polyp, tumor, fracture IR 8x10 inches (18x24 cm) Grids For digital IR use lead masking 70-80 KV range  MEDICAL IMAGING DIVISION 13 Patient and part positioning Patient position Seated erect facing Bucky MSP centered to midline Part position Hyperextend neck to place OML at 37-degree angle from IR plane MSP and MML perpendicular to IR plane Open mouth wide while holding position CR Horizontal and perpendicular to IR Center CR to exit at the Acanthion. ▪ Collimate –8X10 inches (18x24 cm) ▪ Lead shields  14 Evaluation criteria ID: date: side marker all clearly visible Evidence of proper collimation with close beam restriction to sinus area It demonstrates: Sphenoid sinuses projected through open mouth Maxillary sinuses OML in proper position (sufficient neck extension), as evidenced by: Petrous pyramids lying immediately inferior to the floor of the maxillary sinuses No rotation or tilt, indicated by: Equal distance between the lateral border of the skull and the lateral border of the orbit on both sides Orbits and maxillary sinuses symmetric on each side MSP of head aligned with long axis of collimated field Brightness and contrast sufficient to visualize air-fluid levels, if present