Standard Operating Procedure: CT Imaging Protocol
| Document ID |
SOP-RAD-001 |
| Title |
Computed Tomography (CT) Imaging Protocol |
| Revision |
1.0 |
| Effective Date |
[DATE] |
| Author |
[AUTHOR] |
| Approved By |
[APPROVER] |
| Department |
Radiology/Diagnostic Imaging |
1. Purpose
To establish standardized procedures for performing computed tomography (CT) examinations to ensure patient safety, optimal image quality, and regulatory compliance with ACR, state, and federal requirements.
2. Scope
This procedure applies to all CT examinations including:
- Non-contrast CT studies
- Contrast-enhanced CT studies
- CT angiography (CTA)
- CT-guided procedures
- Emergency/trauma CT
3. Responsibilities
3.1 CT Technologist
- Screen patients for contraindications
- Position patient properly
- Select and execute protocols
- Assess image quality
- Monitor patient during examination
3.2 Radiologist
- Approve protocols
- Supervise contrast administration
- Interpret studies and generate reports
- Manage contrast reactions
3.3 Radiology Nurse (if applicable)
- Assess IV access
- Administer contrast
- Monitor for reactions
- Provide patient care
3.4 Medical Physicist
- Establish dose optimization protocols
- Perform quality control
- Monitor radiation exposure
4. Definitions
| Term |
Definition |
| CTDI |
CT Dose Index - measure of radiation output |
| DLP |
Dose Length Product - total dose metric |
| HU |
Hounsfield Units - density measurement |
| kVp |
Kilovoltage peak |
| mAs |
Milliampere-seconds |
| MPR |
Multiplanar reconstruction |
5. Equipment and Materials
- CT scanner (accredited)
- Power injector
- Contrast media (iodinated)
- IV supplies
- Emergency equipment and medications
- Shielding devices
- Patient monitoring equipment
6. Procedure
6.1 Pre-Examination
6.1.1 Order Verification
6.1.2 Patient Identification
- Verify using two identifiers
- Confirm exam matches order
- Review clinical history
6.1.3 Safety Screening
For all patients:
For contrast studies - additional screening:
| Risk Factor |
Check |
| Previous contrast reaction |
☐ Yes ☐ No |
| Allergies (iodine, shellfish) |
☐ Yes ☐ No |
| Kidney disease/elevated creatinine |
☐ Yes ☐ No |
| Diabetes (metformin use) |
☐ Yes ☐ No |
| Thyroid disease |
☐ Yes ☐ No |
| Multiple myeloma |
☐ Yes ☐ No |
| Age >70 years |
☐ Yes ☐ No |
| Dehydration |
☐ Yes ☐ No |
Renal Function Assessment:
| eGFR Level |
Risk |
Action |
| ≥60 |
Low risk |
Proceed |
| 45-59 |
Moderate risk |
Hydration, consider alternatives |
| 30-44 |
High risk |
Alternative imaging preferred, radiologist approval |
| <30 |
Very high risk |
Avoid unless emergent, nephrology consult |
6.1.4 Consent
- Explain procedure and risks
- Obtain informed consent for contrast (if applicable)
- Document consent
6.2 Patient Preparation
6.2.1 Preparation by Exam Type
| Exam Type |
Preparation Required |
| Head CT |
Remove metallic objects from head/neck |
| Chest CT |
Breathing instructions, arms above head |
| Abdomen/Pelvis CT |
Oral contrast (if ordered), full bladder (pelvic) |
| CT Angiography |
IV access, contrast protocol |
| CT Colonography |
Bowel preparation |
6.2.2 IV Access for Contrast
- Assess vein suitability
- 20-gauge or larger preferred for power injection
- Verify patency with saline flush
- Secure catheter properly
6.3 Patient Positioning
6.3.1 Standard Positions
| Body Part |
Position |
Gantry Entry |
| Head |
Supine, neutral |
Head first |
| Neck |
Supine, neck extended |
Head first |
| Chest |
Supine, arms up |
Head or feet first |
| Abdomen |
Supine, arms up |
Head first |
| Pelvis |
Supine, arms up |
Feet first |
| Extremity |
Per protocol |
Varies |
6.3.2 Positioning Considerations
- Center patient in gantry
- Use positioning aids as needed
- Apply shielding where appropriate
- Ensure patient comfort
- Remove all artifacts from scan field
6.4 Protocol Selection and Parameters
6.4.1 Dose Optimization Principles
- ALARA (As Low As Reasonably Achievable)
- Use automatic exposure control (AEC)
- Size-appropriate protocols
- Limit scan range to clinical question
6.4.2 Standard Protocol Parameters
| Protocol |
kVp |
mAs |
Slice Thickness |
Pitch |
| Head routine |
120 |
Auto |
5mm |
N/A (axial) |
| Chest routine |
120 |
Auto |
5mm/1.25mm |
1.0-1.5 |
| Abdomen routine |
120 |
Auto |
5mm/2.5mm |
1.0-1.5 |
| CT Angiography |
100-120 |
Auto |
0.625-1.25mm |
0.8-1.0 |
| Low-dose chest |
100-120 |
Reduced |
1.25mm |
1.0-1.5 |
6.4.3 Pediatric Considerations
- Reduce kVp and mAs based on weight/age
- Use pediatric-specific protocols
- Apply "Image Gently" principles
- Minimize number of phases
6.5 Contrast Administration
6.5.1 Contrast Selection
| Indication |
Contrast Type |
Concentration |
| Routine enhanced |
Low-osmolar |
300-350 mgI/mL |
| CT Angiography |
Low-osmolar |
350-370 mgI/mL |
| High-risk patients |
Iso-osmolar |
270-320 mgI/mL |
6.5.2 Contrast Volume and Rate
| Exam Type |
Volume |
Rate |
| Head with contrast |
100 mL |
1-2 mL/sec |
| Chest with contrast |
100-125 mL |
2-3 mL/sec |
| Abdomen with contrast |
100-150 mL |
2-3 mL/sec |
| CT Angiography |
75-125 mL |
4-5 mL/sec |
6.5.3 Timing Methods
- Fixed delay (empiric)
- Bolus tracking (threshold trigger)
- Test bolus (timing determination)
6.6 Image Acquisition
-
Scout/Topogram
- Acquire scout images
- Verify positioning and coverage
- Set scan range
-
Pre-Contrast (if applicable)
- Acquire non-contrast images
- Assess for baseline findings
-
Contrast Injection (if applicable)
- Verify IV patency
- Program injector parameters
- Monitor injection
-
Post-Contrast Acquisition
- Acquire at appropriate phase(s)
- Arterial: 25-35 seconds
- Portal venous: 60-70 seconds
- Delayed: 3-5 minutes (as needed)
-
Image Review
- Review images for quality
- Assess for artifacts
- Repeat if technically inadequate
6.7 Post-Examination
6.7.1 Patient Care After Contrast
- Monitor for 15-30 minutes
- Assess IV site
- Provide hydration instructions
- Advise on potential delayed reactions
- Metformin patients: follow institutional protocol
6.7.2 Documentation
- Complete FRM-RAD-001 CT Procedure Log
- Document dose metrics (CTDIvol, DLP)
- Record contrast details
- Note any adverse events
- Submit images to PACS
6.8 Image Post-Processing
| Reconstruction |
Application |
| Soft tissue |
Routine interpretation |
| Bone |
Skeletal evaluation |
| Lung |
Pulmonary parenchyma |
| 3D/MPR |
Vascular, complex anatomy |
| MIP |
Angiography |
7. Contrast Reaction Management
7.1 Reaction Classification
| Severity |
Symptoms |
Action |
| Mild |
Nausea, urticaria (limited), warmth |
Observe, treat symptoms |
| Moderate |
Extensive urticaria, bronchospasm, hypotension |
Medical treatment, monitor |
| Severe |
Anaphylaxis, cardiac arrest, seizure |
Emergency response, call code |
7.2 Emergency Equipment
Available in CT suite:
- Oxygen and suction
- Emergency medications (epinephrine, diphenhydramine, etc.)
- IV fluids
- Defibrillator/AED
- Crash cart
8. Radiation Safety
8.1 Dose Monitoring
- Record CTDIvol and DLP for each exam
- Compare to diagnostic reference levels
- Investigate outliers
8.2 Diagnostic Reference Levels
| Exam |
CTDIvol (mGy) |
DLP (mGy·cm) |
| Head |
60 |
1000 |
| Chest |
15 |
400 |
| Abdomen |
20 |
700 |
| Abdomen/Pelvis |
20 |
900 |
9. Quality Control
| Activity |
Frequency |
| Daily warm-up and calibration |
Daily |
| Water phantom QC |
Daily/Weekly |
| CT number accuracy |
Weekly |
| Spatial resolution |
Monthly |
| Physicist review |
Annually |
10. Documentation
- FRM-RAD-001 CT Procedure Log
- FRM-RAD-002 Contrast Administration Record
- FRM-RAD-003 Adverse Reaction Report
- Dose reports
- QC logs
11. References
- ACR Practice Parameter for CT
- ACR Manual on Contrast Media
- Image Gently Campaign
- AAPM CT Protocols
- State radiation regulations
Revision History
| Rev |
Date |
Description |
Author |
| 1.0 |
[DATE] |
Initial release |
[AUTHOR] |
