This document provides information about CT procedures for the lower limbs, including the hip, knee, and ankle joints. It describes patient preparation, positioning, scanning protocols, and reconstruction parameters for CT imaging of each area. Key anatomical structures are identified for the hip, knee, and ankle joints. Indications for lower limb CT include evaluation of tumors, fractures, infections, and joint abnormalities.
3. WHY Lower Extremity CT
Computed tomography (CT) is used for evaluation of tumors, metastatic
lesions, infection, fractures and other problems.
Magnetic resonance imaging (MRI) is the first-line choice for imaging of
many conditions, but CT may be used in these cases if MRI is
contraindicated or unable to be performed
4. • Evaluation of suspicious mass/ tumor (unconfirmed cancer
diagnosis
Initial evaluation of suspicious mass/tumor , which has been
nondiagnostic after x ray and ultrasound
Suspected tumor size increase or recurrence based on a sign,
symptom, imaging study or abnormal lab value
5. Evaluation of Known Cancer
Initial staging of known cancer in the lower extremity.
Follow-up of known cancer of patient undergoing active treatment within the past year.
Known cancer with suspected lower extremity metastasis based on a sign, symptom, imaging
study or abnormal lab value.Initial staging of known cancer in the lower extremity.
Follow-up of known cancer of patient undergoing active treatment within the past year.
Known cancer with suspected lower extremity metastasis based on a sign, symptom, imaging
study or abnormal lab value.
6. For evaluation of known or suspected fracture and/or injury:
Further evaluation of an abnormality or non-diagnostic findings on prior imaging.
Suspected fracture when imaging is negative or equivocal.
Determine position of known fracture fragments/dislocation.
7. For evaluation of persistent pain, initial imaging (e.g. x-ray) has been
performed and MRI is contraindicated or cannot be performed:
Chronic (lasting 3 months or greater) pain and/or persistent tendonitis
unresponsive to conservative treatment*, which include - medical
therapy (may include physical therapy or chiropractic treatments)
8. Pre-operative evaluation.
Post-operative/procedural evaluation:
When imaging, physical, or laboratory findings indicate joint infection,
delayed or non-healing, or other surgical/procedural complications.
A follow-up study may be needed to help evaluate a patient’s progress
after treatment, procedure, intervention, or surgery. Documentation
requires a medical reason that clearly indicates why additional imaging is
needed for the type and area(s) requested.
9. • For evaluation of known or suspected infection or inflammatory disease (e.g.
osteomyelitis)
• For evaluation of suspected (AVN) avascular necrosis (e.g., aseptic necrosis,
Legg-Calve-Perthes disease in children) and MRI is contraindicated or cannot be
performed
• For evaluation of suspected or known Auto Immune Disease, (e.g. Rheumatoid
arthritis)
• Abnormal bone scan and radiograph is non-diagnostic or requires further
evaluation.
• For evaluation of leg length discrepancy when physical deformities of the lower
extremities would prevent standard modalities such as x-rays or a Scanogram
from being performed.
• CT arthrogram and MRI is contraindicated or cannot be performed.
• To assess status of osteochondral abnormalities including osteochondral
fractures, osteochondritis dissecans, treated osteochondral defects where
physical or imaging findings suggest its presence and MRI is contraindicated or
cannot be performed.
51. CT Procedure of Hip
Computed tomography is primarily used to evaluate acute trauma,
e.g., acetabular fracture or hip dislocation. It can detect
intraarticular fragments and associated articular surface fractures
and it is useful in surgical planning.
52. Additional Indications Specific to Hip CT
For any evaluation of patient with hip prosthesis or other implanted metallic
hardware where prosthetic loosening or dysfunction is suspected on physical
examination or imaging.
For evaluation of total hip arthroplasty patients with suspected loosening
and/or wear or osteolysis or assessment of bone stock is needed.
For evaluation of suspected slipped capital femoral epiphysis with non-
diagnostic or equivocal imaging and MRI is contraindicated or cannot be
performed.
Suspected labral tear of the hip with signs of clicking and pain with hip
motion especially with hip flexion, internal rotation and adduction which can
also be associated with locking and giving way sensations of the hip on
ambulation and MRI is contraindicated or cannot be performed.
53. Patient preperation
Remove any non-fixed metal prosthesis, jewelry or zippers that
might interfere with the region to be scanned.
- Discuss the procedure with the patient. The patient must not
move during any part of the scanning.
-
54. Patient Position
and Posture
• Patient laying supine with legs extended.
• Legs in natural alignment with neutral rotation.
• No un-natural tilt or lift of the pelvis.
• Arms folded upward away from the pelvis
• Position the patient to maximize comfort and minimize motion.
• Only true axial slices are allowed: no oblique or reformatted images and no gantry tilt
55. Hip Joint/ Proximal femurProtocol
Positioning patient supine, with feet first
Scouts AP and Lat
Scan Type Helical
Start Location Just Above SI Joint
End Location Approx 4cm below Lesser trochanter
DFOV ~ 30 cm ( Include Skin Surface )
Acqusition Detector Width * Number of detector in row= coverage
Reconstruction ( Slice Thickness/ Interval ) 1.25mm/ 0.625 mm
Pitch 0.5
Kvp 120
mA 200
56. Clinical indications that may necessitate IV contrast include infection
or tumor. When IV contrast is ordered, 80 mL of LOCM
is injected at 3 mL/s and scanning begins after 40 seconds.
Algorithm Bone
Window Width 2000
Window level 500
Algorithm Standard
Window width 350
Window level 50
57. A. Axial MPR can be programmed from an AP scout. B. Coronal MPR can be
programmed from an axial image and should follow the long axis of the femoral neck.
C. Sagittal MPR can be programmed from an axial image and should be perpendicular to the
coronal MPR plane.
59. 1. Acetabulum (anterior column)
2. Acetabulum
3.Femoral head
4. Acetabulum posterior column
5. Hip Joint
6. Illiopsoas mUscle
7. Sarotrius M
8.Gluteus Minimus M
9. Gletues Medius M
10. Gluteal Maximus Muscle
11. Bladder
12. Rectus Femoris
60. 1. Femoral head
2. Iliopsoas m.
3. Femoral neck
4. Rectus femoris m.
5. Tensor fascia lata m.
6. Greater trochanter
7. Ischium/Ischial tuberosity
8. Obturator internus m.
9. Pubis
10. Pectineus m.
11. Gluteus maximus m.
12. Sartorius m.
61. Adductor brevis m.
2. Rectus femoris m.
3. Vastus intermedius m.
4. Femur
5. Pubis, inferior ramus
6. Obturator externus m.
7. Iliopsoas m.
8. Femur, lesser trochanter
9. Gluteus maximus m.
10. Sartorius m.
11. Tensor fascia lata m.
12. Vastus lateralis m
65. Meniscus:Ameniscus(me-NIS-kus;a crescent;plural,menisci) isa pad
offibrocartilage betweenopposing boneswithinasynovial joint.
Meniscus:A meniscus (me-NIS-kus; a crescent; plural,
menisci) is a pad offibrocartilage between opposing
bones within a synovial joint.
70. Bursa: bursa is a small, thin, fluid-filled pocket that forms in
connective tissue outside of a joint capsule. It contains synovial
fluid and is lined by a synovial membrane.Bursae often form
where a tendon or ligament rubs against other tissues.
Suprapatellar
Infrapatellar
prepatellar
87. Additional indications specific for KNEE CT and MRI is
contraindicated or cannot be performed:
Accompanied by blood in the joint (hemarthrosis) demonstrated by aspiration.
Presence of a joint effusion.
Accompanied by physical findings of a meniscal injury determined by physical
examination tests (McMurray’s, Apley’s) or significant laxity on varus or valgus stress
tests.
Accompanied by physical findings of anterior cruciate ligament (ACL) or posterior
cruciate ligament (PCL) ligamental injury determined by the drawer test or the
Lachman test.
88. Patient preperation
Remove any non-fixed metal prosthesis, jewelry or zippers that
might interfere with the region to be scanned.
- Discuss the procedure with the patient. The patient must not
move during any part of the scanning.
-
89. Patient Position
and Posture
• Patient laying supine with legs extended.
• Legs in natural alignment with neutral rotation.
• No un-natural tilt or lift of the pelvis.
• Arms folded upward away from the pelvis
• Position the patient to maximize comfort and minimize motion.
• Only true axial slices are allowed: no oblique or reformatted images and no gantry tilt
90. KNEE/ TIBIAL PLATEAU
Positioning Patient Supine with feet first , Legs Flat on table
Scouts Ap and Lateral
Scan Type Helical
Start Location Just Above Patella
End Location Just below fibular Head
DFOV ~ 20cm ( adjust to include Skin Surface : affected knee only )
SFOV large Body
Acquisition Detector Width * Number of detector in row= coverage
Reconstruction ( Slice thickness/ interval ) 1.25mm/0.625 mm
Pitch 0.5
Kvp/ mA 120
91. Reconstruction 1
Algorithm Bone Plus
Window Width 2000
Window level 500
Reconstruction 2
Algorithm Standard
Window Width 350
Window level 50
92. MPR: Bone AlgorithmSlice Thickness/ Interval : 2mm/2mm
Planes: Axial, coronal, sagittal
A. Axial MPR can be programmed from an AP scout and should be parallel to the tibial plateau.
B. Coronal MPR can be programmed from an axial image and should be parallel to the femoral condyles.
C. Sagittal MPR can be programmed from an axial image and should be perpendicular to the coronal
MPR.
103. Ankle/ Distal Tibia
Positioning Patient Supine with feet first , Legs Flat on table, use foot
holder
Scouts Ap and Lateral
Scan Type Helical
Start Location Just Above ankle joint
End Location Through calcaneus
DFOV ~ 16 cm ( adjust to include Skin Surface )
SFOV large Body
Acquisition Detector Width * Number of detector in row= coverage
Reconstruction ( Slice thickness/ interval ) 0.625mm/0.3 mm
Pitch 0.562
Kvp/ mA 120
104. Reconstruction 1
Algorithm Bone Plus
Window Width 2000
Window level 500
Reconstruction 2
Algorithm Standard
Window Width 350
Window level 50
105. MPR: Bone Algorithm
A. Axial MPR can be programmed from an AP scout parallel to the top of the talus.
B. Coronal MPR can be programmed from an axial image at the level of the distal tibia.
C. Sagittal MPR can be programmed from an axial image at the level of the distal tibia. They are perpendicular to the coronal MPR
plane.
Slice Thickness/ Interval : 2mm/2mm
Planes: Axial, coronal, sagittal