1. Lumbar Spine, Sacrum and Coccyx

2. Evaluation Criteria Structures shown Position/projection
Collimation/central ray
Exposure criteria
Acceptable and unacceptable lumbar spine images based on errors i.e.:
Motion
Collimation
Positioning
Exposure factors
Side markers and patient demographic information
Every time a radiographer completes an image, an evaluation must be made to determine whether the image is diagnostically optimal for the radiologist to provide an accurate diagnosis. A radiologist should NEVER have to return an image for repeat if proper evaluation of the image is done by the radiographer.
Here are five basic criteria for radiographic evaluations and critique. These should be used every time a radiographic image is performed.

3. Introduction <Image 1> The Lumbar Spine
The lower spine consists of five lumbar vertebrae, five fused sacral vertebrae ad three to five fused coccygeal vertebrae. The normal curvature of the lower spine changes from concave in the lumbar area to convex in the sacral region. The lumbar spine normally has a concave curvature. Abnormal accentuation of this curvature is called lordosis or swayback.
Each of the five lumbar vertebrae have identical processes. They possess no transverse foramen, as the cervical vertebrae do, or rib facets as the thoracic vertebrae do.
The Sacrum
The sacrum is a triangular-shaped bone consisting of five fused segments. The sacrum forms the posterior wall of the pelvis and its somewhat massive structure supports the pelvis and spine.
The Coccyx
The tiny coccyx is a triangular shaped bone that consists of approximately four fused vertebrae. Like the sacrum, the portion of the triangle pointing inferiorly is called the apex. It has two small transverse processes that project laterally from superior base of the coccyx.>

4. AP, Lateral and Oblique Lumbar Spine Basics
<Images 2-3>
Routine imaging of the lumbar spine includes: AP, both obliques, lateral, and spot lateral of L5-S1. Alternate imaging may consist of: axial AP L5-S1 junction, bending exams, hyperextension/hyperflexion, scoliosis series. As with the other imaging protocols, this video will concentrate on the routine images. The reason for performing lumbar imaging are trauma and degenerative diseases. Structures best demonstrated on the lumbar images include the vertebral bodies, transverse processes, pedicles, intervertebral disk spaces, spinous processes and intervertebral foramina.

5. AP, Lateral and Oblique Lumbar Spine Imaging Criteria
Technical Considerations
Regular IR
Grid
kVp range: 80-90
SID: 40 inches (100 cm)
AP, Obliques, Lateral:
IR size 14x17 inch (35 x 43 cm)
Spot Lateral L5-S1:
IR size 8x10 inch (18 x24 cm)
Patient Position
AP:
Supine with the MSP centered to the midline of the table
Arms are placed at the patient’s sides or high on the chest
Obliques:
Semi-supine
Both obliques are performed because each demonstrates structures in a slightly different perspective
Lateral:
Recumbent left lateral with knees and hips flexed for comfort
Arms are placed at right angles to the body with elbows flexed
Part Position
Flex the knees to place the small of the back in contact with the surface of the table and help reduce rotation
Place the spine at a 45 degree angle to the IR
Sagittal plane 1 to 2 inches (3-5 cm) medial to the elevated ASIS is centered to the IR
Place the long axis of the spine parallel to the IR
The sagittal plane should be parallel and the coronal plane perpendicular to the IR
The plane approximately 3 inches (8cm) anterior to the spinous processes should be centered to the IR
Central Ray (CR)
Perpendicular and centered at the level of the iliac crest
Patient Instructions
“Take a deep breath, let it all out. Don’t breathe or move.”
Evaluation Criteria
Image must include all lumbar vertebrae and part of the sacrum
Rotation, as evidenced by he asymmetrical appearance of the SI joints, pedicles, or transverse processes should not be observed
Transverse processes, pedicles, vertebral bodies and intervertebral disk spaces should be demonstrated
Spinous processes should be in the midline
Must include all lumbar vertebrae and part of the sacrum
Vertebral bodies, intervertebral disk spaces spinous processes and intervertebral foramina should be clearly demonstrated
The iliac crests and acetabula should be mostly superimposed, indicating minimal rotation
The RPO and LPO positions, the zygapophyseal joints on the side nearer the IR should be clearly opened
“Scotty dog” sign should be evident for all five lumbar vertebrae
Superior and inferior articulating processes, pedicles, laminae, pars interarticularis, vertebral bodies, and disk spaces should be demonstrated
Additional Information:
If the patient cannot be placed supine, the PA projection may be performed with the patient prone
PA will result in more magnification but may more clearly demonstrate the intervertebral disk spaces
Some departmental protocols require collimation to the edge of the transverse processes, whereas others prefer the collimators to be left open to view the entire abdomen
If a visible downward sag in the spine is present after placing the patient into a lateral position, a radiolucent sponge should be placed under the thoracolumbar area to make the spine parallel to the IR
To better open the intervertebral disk spaces, a 5 degree caudal angle may be used
If the patient is unable to lie on the left side, a right lateral may be substituted
A long radiolucent 45 degree sponge may be placed behind the spine to assist the patient in maintaining this position
If the patient cannot be placed supine, oblique PA projection may be performed with the patient semi prone (RAO/LAO).
Spine is centered to the midline of the IR by placing the CR 1 inch (3cm) to the left (for the RAO position) or right (for the LAO position) of the spinous processes.
Open zygapophyseal joint is the one farthest from the IR (this differs from the cervical and thoracic spine obliques)
Optimum visualization of the zygapophyseal joint between L5 and S1 may require a 30 degree patient angle
Click each button for more information about imaging the AP, lateral, and oblique lumbar spine.
Technical Considerations
Evaluation Criteria
Additional Information

6. Knowledge Check <Image 4 and 7> Label the following anatomy:
“Scotty Dog”, Pedicle, Inferior articular process, Pars interarticularis, Transverse process, Zygapophyseal joint, Superior articular process

7. Spot Lateral L5-SI Basics
<Images 8 and 10>
The fifth lumbar vertebra and the intervertebral disk between L5 and the sacrum are common sites of pathology and trauma. The region is often not well visualized on the lateral lumbar spine because it is much denser than the rest of the lumbar spine and lies at the end of the IR, causing the disk space to be closed by the diverging x-ray beam.

8. Spot Lateral L5-SI Imaging Criteria
Technical Considerations
Regular IR
Grid
kVp range:
SID: 40 inches (100 cm)
IR size 8x10 inch (18 x24 cm)
Patient Position
Recumbent left lateral with knees and hips flexed for comfort
Arms are placed at right angles to the body with elbows flexed
Part Position
Place the long axis of the spine parallel to the IR
Sagittal plane should be parallel and the coronal plane perpendicular to the IR
A plane 1 ½ inches (4cm) posterior to the midaxillary line should be centered to the IR
Central Ray (CR)
CR is directed at a 5 to 10 degree caudal angle to enter at the L5-S1 joint space
L5-S1 joint space is located halfway between the ASIS and the iliac crest and 2 inches (5cm) anterior to the palpated spinous processes
Patient Instructions
“Take a deep breath, let it all out. Don’t breathe or move.”
Evaluation Criteria:
L5-S1 joint space should be open on the image
Acetabula should be mostly superimposed
This indicates minimal rotation
Additional Information:
Angulation is not always necessary if the spine is placed parallel to the IR
Females may require an increased caudal angle to better open the joint space
To obtain a more uniform density, a lead strip may be placed on the table top behind the patient to limit scatter radiation
Sometimes a 5 degree cephalad angle may be required
Often an AP axial projection is needed to see this articulation
CR is directed at a 30 to 50 cephalad angle to enter at the level of the L5-S1 joint
Patient is supine with the MSP centered to the midline of the IR
Arms are placed at the patient’s sides or high on the chest the same as the AP Lumbar spine
Click each button for more information about XYZ
Technical Considerations
Evaluation Criteria
Additional Information

9. Knowledge Check
The axial AP projection of the L5-S1 junction requires what tube angulation?
10-15 degrees cephalad
10 to 15 degrees caudal
30-35 degrees cephalad
30 to 35 degrees caudal

10. Sacrum Basics <Images 12 and 13>
The most common rational for performing images of the sacrum is trauma. Structures best demonstrate include the ala, promontory, anterior sacral foramina and the L5-S1 joint space. Routine projections are the AP axial and lateral.

11. Sacrum Imaging Criteria
Incomplete sentence?
2 inches (5cm) anterior to the palpated sacral crest and 1 inch (3cm) below the A
Technical Considerations
Regular IR
Grid
kVp range: 80-90
SID: 40 inches (100 cm)
IR size 10 x 12 inch (24 x 30 cm)
Patient Position
AP axial:
Supine with arms placed at the patient’s side or high on the chest
Lateral:
Recumbent left lateral with knees and hips flexed for comfort
Arms are placed at right angles to the body with elbows flexed
Part Position
MSP is centered to the midline of the IR
Knees may be flexed to place the small of the back in contact with the surface of the table
This reduces rotation
Place the long axis of the spine parallel to the IR
The sagittal plane should be parallel and the coronal plane perpendicular to the IR
A plane 3 inches (8cm) posterior to the midaxillary line should be centered to the IR
Central Ray (CR)
CR is directed at a 15 degree cephalad angle
Entering at a level midway between the symphysis pubis and the ASIS
CR is directed perpendicular to the mid-sacrum
2 inches (5cm) anterior to the palpated sacral crest and 1 inch (3cm) below the ASIS
Patient Instructions
“Take a deep breath, let it all out. Don’t breathe or move.”
Evaluation Criteria:
Entire sacrum should be included on the image
Sacrum should appear more elongated than on an AP lumbar spine projection
Rotation, as evidenced by the asymmetrical appearance of the SI joints and ilia, should not be observed
Entire sacrum must be included
All or part of the L5-S1 joint space must be included
Iliac crests and acetabula should be most superimposed, indicating minimal rotation
Additional Information:
Injuries to the sacrum may prevent a patient from lying supine
An alternative PA projection can be performed with the patient lying prone and using a 15 degree caudal angle
This will create more magnification on the image
Because fecal shadows often overlie the sacrum, the bowel may require cleansing before the imaging is performed
To obtain a more uniform density, a lead strip may be placed on the table top behind the patient to limit scatter radiation
Close collimation is essential to limit scatter radiation
Click each button for more information about XYZ
Technical Considerations
Evaluation Criteria
Additional Information

12. Knowledge Check <Images 14-15) Label the following anatomy:
Body of L5, L5-S1 joint, Ilium, Sacrum, Left SI joint, Apex of sacrum, Sacral foramina, Sacral wing (ala), Superior articular process of the sacrum

13. Coccyx Basics <Images 16-17>
The most common indication for radiographic examination of the coccyx is trauma. There are two routine positions of the coccyx—the AP axial and the lateral. The coccyx is usually imaged as part of combined imaging of the sacrum.

14. Coccyx Criteria Click each button for more information about XYZ
Technical Considerations
Regular IR
Grid
kVp range: 75-80
SID: 40 inches (100 cm)
IR size 10 x 12 inch (24 x 30 cm)
Patient Position
AP axial:
Supine with the MSP centered to the midline of the IR
Supine with arms placed at the patient’s side or high on the chest
Lateral:
Recumbent left lateral with knees and hips flexed for comfort
Arms are placed at right angles to the body with elbows flexed
Part Position
MSP is centered to the midline of the IR
Knees may be flexed to place the small of the back in contact with the surface of the table
This reduces rotation
Place the long axis of the spine parallel to the IR
The sagittal plane should be parallel and the coronal plane perpendicular to the IR
A plane 5 inches (13cm) posterior to the midaxillary line should be centered to the IR
Central Ray (CR)
CR is directed at a 10 degree caudal angle
Entering at a level midway between the symphysis pubis and the ASIS
CR is directed perpendicular 1 inch (3cm) anterior to the palpated posterior coccyx
Patient Instructions
“Take a deep breath, let it all out. Don’t breathe or move.”
Evaluation Criteria:
Entire coccyx should be included on the image
Coccyx should appear more elongated than on an AP lumbar spine projection
Rotation, as evidenced by the asymmetrical appearance of the SI joints and ilia, should not be observed
Entire coccyx must be included plus a portion of the distal sacrum must be included on the image
Acetabula should be mostly superimposed, indicating minimal rotation
Additional Information:
Injuries to the coccyx may prevent a patient from lying supine
An alternative PA projection can be performed with the patient lying prone and using a 10 degree cephalad angle
This will create more magnification on the image
Because the rectal and bladder shadows overlie the coccyx, it is often desirable to have the patient void and defecate before the imaging examination
To obtain a more uniform density, a lead strip may be placed on the table top behind the patient to limit scatter radiation
Close collimation is essential to limit scatter radiation
Click each button for more information about XYZ
Technical Considerations
Evaluation Criteria
Additional Information

15. Knowledge Check
For the PA projection of the coccyx, how many degrees and in which direction is the CR directed?
15 degrees caudal
10 degrees caudal
15 degrees cephalad
10 degrees cephalad

16. Summary <Images 3, 12, 18>
As with all imaging procedures it is important that the routine imaging of the Lumbar Spine, Sacrum and Coccyx are priority in becoming proficient in the Radiographers quiver of imaging procedures. If the technologist is proficient in these positions/projections the alternative positions/projections are easier.