ARRT - American Registry of Radiologic Technologists Spine and Pelvis Procedures Questions and Answers — Questions and Answers
Question 1: A patient is positioned for an AP axial projection of the sacrum. Which of the following describes the correct central ray (CR) orientation and centering point?
- 10 degrees caudad, centered to the ASIS
- 15 degrees cephalad, centered 2 inches superior to the pubic symphysis (Correct answer)
- Perpendicular, centered midway between the ASIS and pubic symphysis
- 25 degrees cephalad, centered to the iliac crest
Correct answer: 15 degrees cephalad, centered 2 inches superior to the pubic symphysis
For the AP axial projection of the sacrum, a 15-degree cephalic (upward) angle is required to project the pubic symphysis inferior to the sacrum, thus elongating the sacrum and opening the sacral foramina. The central ray should be directed to a point approximately 2 inches superior to the pubic symphysis.
Question 2: A radiograph of a lateral lumbar spine shows that the L5-S1 intervertebral joint space is not open. The patient was positioned with the midcoronal plane parallel to the image receptor. Which of the following modifications is MOST appropriate for a coned-down 'spot' view?
- Angle the CR 5-8 degrees cephalad
- Increase patient flexion at the knees and hips
- Angle the CR 5-8 degrees caudad (Correct answer)
- Position the patient in a 15-degree posterior oblique
Correct answer: Angle the CR 5-8 degrees caudad
When the L5-S1 joint space is not open on a true lateral lumbar spine image, it is often because the spine is not parallel to the image receptor due to the natural curve and pelvic tilt. A caudal (downward) angulation of 5-8 degrees (typically 5 for males, 8 for females) is necessary to align the central ray with the intervertebral joint space, effectively 'opening' it on the image.
Question 3: To properly visualize the right sacroiliac (SI) joint with minimal superimposition, which of the following positions should be performed?
- AP projection, left posterior oblique (LPO) (Correct answer)
- AP projection, right posterior oblique (RPO)
- PA projection, right anterior oblique (RAO)
- Lateral projection, right side down
Correct answer: AP projection, left posterior oblique (LPO)
For AP oblique projections of the SI joints, the joint of interest is the one that is elevated, or farthest from the image receptor. Therefore, to visualize the right SI joint, the patient should be placed in a left posterior oblique (LPO) position with a body rotation of approximately 25-30 degrees.
Question 4: A trauma patient requires an evaluation for a suspected pelvic ring fracture. The physician orders an AP axial 'outlet' projection (Taylor method). How should the technologist direct the central ray for a male patient?
- Perpendicular to the IR, centered 2 inches inferior to the ASIS
- 40 degrees caudad, centered to the level of the ASIS
- 15 degrees caudad, centered 2 inches superior to the pubic symphysis
- 20-35 degrees cephalad, centered 2 inches distal to the superior border of the pubic symphysis (Correct answer)
Correct answer: 20-35 degrees cephalad, centered 2 inches distal to the superior border of the pubic symphysis
The AP axial 'outlet' projection, or Taylor method, is designed to demonstrate the pubic and ischial rami without foreshortening. This is achieved by directing the central ray with a cephalic (upward) angle. For male patients, the angle is typically 20-35 degrees cephalad, centered to a point 2 inches distal to the superior border of the pubic symphysis.
Question 5: A scoliosis series including AP right and left bending projections (Ferguson method) is ordered. What is the primary purpose of performing these bending views?
- To assess the degree of vertebral rotation
- To measure the Cobb angle with maximal spinal flexion
- To differentiate between structural and functional scoliosis (Correct answer)
- To evaluate for spondylolisthesis associated with the curvature
Correct answer: To differentiate between structural and functional scoliosis
The Ferguson method, which involves AP projections with lateral bending, is specifically used to distinguish between structural and functional scoliosis. A structural curve is fixed and will show minimal correction on the bending films. A functional curve is compensatory and will straighten or reduce significantly when the patient bends toward the convex side of the curve.
Question 6: A radiograph of an AP pelvis is obtained on a patient who was positioned supine on the table with their legs extended. The image demonstrates significant foreshortening of the femoral necks. Which of the following positioning corrections is required for a repeat exposure?
- Externally rotate the feet and lower limbs 45 degrees
- Angle the central ray 15 degrees caudad
- Separate the heels and internally rotate the feet and lower limbs 15-20 degrees (Correct answer)
- Place a support under the patient's knees to flex them slightly
Correct answer: Separate the heels and internally rotate the feet and lower limbs 15-20 degrees
To place the femoral necks parallel to the image receptor and demonstrate them in their true anatomical profile, the lower limbs must be medially (internally) rotated 15-20 degrees. This maneuver overcomes the natural anteversion of the femoral necks. This is typically achieved by having the patient touch their big toes together or ensuring the heels are about 8-10 inches apart and the feet are rotated inward.
ARRT - American Registry of Radiologic Technologists Spine and Pelvis Procedures Questions and Answers
A patient is positioned for an AP axial projection of the sacrum.
Which of the following describes the correct central ray (CR) orientation and centering point?